refactor: remove legacy patterns system, unify on workflows

Remove the entire patterns domain model, IPC channels, sidecar services,
renderer components, and tests. Sessions now bind exclusively to workflows
via workflowId. Builtin workflows replace builtin patterns.

Backend:
- Make AgentNodeConfig standalone (no longer extends PatternAgentDefinition)
- Add WorkflowOrchestrationMode and WorkflowExecutionDefinition
- Create builtin workflows (single-agent, sequential, concurrent, handoff, group-chat)
- Rewrite session model config helpers for workflow-only
- Remove pattern IPC channels, handlers, and preload bindings
- Merge createSession/createWorkflowSession into single method
- Remove sidecar PatternGraphResolver, PatternValidator, pattern DTOs
- Add workspace migration for legacy sessions (patternId -> workflowId)

Frontend:
- Delete PatternEditor, pattern-graph components, patternGraph lib
- Delete NewSessionModal (session creation uses workflows directly)
- Remove PatternsSection from SettingsPanel
- Update App.tsx, ChatPane, ActivityPanel, Sidebar, RunTimeline,
  AgentConfigFields, InlinePills, sessionActivity to use workflow types
- Delete pattern.ts domain module

78 files changed across backend and frontend.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

sidecar/src/Aryx.AgentHost/Contracts/ProtocolModels.cs

@@ -3,18 +3,7 @@ using System.Text.Json.Serialization;
 
 namespace Aryx.AgentHost.Contracts;
 
-public sealed class PatternAgentDefinitionDto
-{
-    public string Id { get; init; } = string.Empty;
-    public string Name { get; init; } = string.Empty;
-    public string Description { get; init; } = string.Empty;
-    public string Instructions { get; init; } = string.Empty;
-    public string Model { get; init; } = string.Empty;
-    public string? ReasoningEffort { get; init; }
-    public PatternAgentCopilotConfigDto? Copilot { get; init; }
-}
-
-public sealed class PatternAgentCopilotConfigDto
+public sealed class WorkflowAgentCopilotConfigDto
 {
     public IReadOnlyList<RunTurnCustomAgentConfigDto> CustomAgents { get; init; } = [];
     public string? Agent { get; init; }
@@ -23,50 +12,6 @@ public sealed class PatternAgentCopilotConfigDto
     public RunTurnInfiniteSessionsConfigDto? InfiniteSessions { get; init; }
 }
 
-public sealed class PatternGraphPositionDto
-{
-    public double X { get; init; }
-    public double Y { get; init; }
-}
-
-public sealed class PatternGraphNodeDto
-{
-    public string Id { get; init; } = string.Empty;
-    public string Kind { get; init; } = string.Empty;
-    public PatternGraphPositionDto Position { get; init; } = new();
-    public string? AgentId { get; init; }
-    public int? Order { get; init; }
-}
-
-public sealed class PatternGraphEdgeDto
-{
-    public string Id { get; init; } = string.Empty;
-    public string Source { get; init; } = string.Empty;
-    public string Target { get; init; } = string.Empty;
-}
-
-public sealed class PatternGraphDto
-{
-    public IReadOnlyList<PatternGraphNodeDto> Nodes { get; init; } = [];
-    public IReadOnlyList<PatternGraphEdgeDto> Edges { get; init; } = [];
-}
-
-public sealed class PatternDefinitionDto
-{
-    public string Id { get; init; } = string.Empty;
-    public string Name { get; init; } = string.Empty;
-    public string Description { get; init; } = string.Empty;
-    public string Mode { get; init; } = string.Empty;
-    public string Availability { get; init; } = "available";
-    public string? UnavailabilityReason { get; init; }
-    public int MaxIterations { get; init; }
-    public ApprovalPolicyDto? ApprovalPolicy { get; init; }
-    public IReadOnlyList<PatternAgentDefinitionDto> Agents { get; init; } = [];
-    public PatternGraphDto? Graph { get; init; }
-    public string CreatedAt { get; init; } = string.Empty;
-    public string UpdatedAt { get; init; } = string.Empty;
-}
-
 public sealed class WorkflowPositionDto
 {
     public double X { get; init; }
@@ -84,7 +29,7 @@ public sealed class WorkflowNodeConfigDto
     public string Instructions { get; init; } = string.Empty;
     public string Model { get; init; } = string.Empty;
     public string? ReasoningEffort { get; init; }
-    public PatternAgentCopilotConfigDto? Copilot { get; init; }
+    public WorkflowAgentCopilotConfigDto? Copilot { get; init; }
     public string? WorkspaceAgentId { get; init; }
     public string? Implementation { get; init; }
     public string? FunctionRef { get; init; }
@@ -170,6 +115,7 @@ public sealed class WorkflowSettingsDto
 {
     public WorkflowCheckpointSettingsDto Checkpointing { get; init; } = new();
     public string ExecutionMode { get; init; } = "off-thread";
+    public string? OrchestrationMode { get; init; }
     public int? MaxIterations { get; init; }
     public ApprovalPolicyDto? ApprovalPolicy { get; init; }
     public IReadOnlyList<WorkflowStateScopeDto> StateScopes { get; init; } = [];
@@ -220,13 +166,6 @@ public sealed class ChatMessageAttachmentDto
     public string? DisplayName { get; init; }
 }
 
-public sealed class PatternValidationIssueDto
-{
-    public string Level { get; init; } = "error";
-    public string? Field { get; init; }
-    public string Message { get; init; } = string.Empty;
-}
-
 public sealed class WorkflowValidationIssueDto
 {
     public string Level { get; init; } = "error";
@@ -303,11 +242,6 @@ public class SidecarCommandEnvelope
 
 public sealed class DescribeCapabilitiesCommandDto : SidecarCommandEnvelope;
 
-public sealed class ValidatePatternCommandDto : SidecarCommandEnvelope
-{
-    public PatternDefinitionDto Pattern { get; init; } = new();
-}
-
 public sealed class ValidateWorkflowCommandDto : SidecarCommandEnvelope
 {
     public WorkflowDefinitionDto Workflow { get; init; } = new();
@@ -322,8 +256,7 @@ public sealed class RunTurnCommandDto : SidecarCommandEnvelope
     public string Mode { get; init; } = "interactive";
     public string MessageMode { get; init; } = "enqueue";
     public string? ProjectInstructions { get; init; }
-    public PatternDefinitionDto Pattern { get; init; } = new();
-    public WorkflowDefinitionDto? Workflow { get; init; }
+    public WorkflowDefinitionDto Workflow { get; init; } = new();
     public IReadOnlyList<WorkflowDefinitionDto> WorkflowLibrary { get; init; } = [];
     public IReadOnlyList<ChatMessageDto> Messages { get; init; } = [];
     public RunTurnPromptInvocationDto? PromptInvocation { get; init; }
@@ -464,11 +397,6 @@ public sealed class CapabilitiesEventDto : SidecarEventDto
     public SidecarCapabilitiesDto Capabilities { get; init; } = new();
 }
 
-public sealed class PatternValidationEventDto : SidecarEventDto
-{
-    public IReadOnlyList<PatternValidationIssueDto> Issues { get; init; } = [];
-}
-
 public sealed class WorkflowValidationEventDto : SidecarEventDto
 {
     public IReadOnlyList<WorkflowValidationIssueDto> Issues { get; init; } = [];

sidecar/src/Aryx.AgentHost/Services/AgentIdentityResolver.cs

@@ -10,14 +10,14 @@ internal static class AgentIdentityResolver
     private const string GenericAssistantIdentifier = "assistant";
 
     public static bool TryResolveKnownAgentIdentity(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         string? agentIdentifier,
         out AgentIdentity agent)
     {
         agent = default;
 
-        PatternAgentDefinitionDto? match = FindKnownAgent(pattern, agentIdentifier)
-            ?? ResolveSingleAgentAssistantAlias(pattern, agentIdentifier);
+        WorkflowNodeDto? match = FindKnownAgent(workflow, agentIdentifier)
+            ?? ResolveSingleAgentAssistantAlias(workflow, agentIdentifier);
         if (match is null)
         {
             return false;
@@ -28,12 +28,12 @@ internal static class AgentIdentityResolver
     }
 
     public static bool TryResolveObservedAgentIdentity(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         string? agentIdentifier,
         AgentIdentity? fallbackAgent,
         out AgentIdentity agent)
     {
-        if (TryResolveKnownAgentIdentity(pattern, agentIdentifier, out agent))
+        if (TryResolveKnownAgentIdentity(workflow, agentIdentifier, out agent))
         {
             return true;
         }
@@ -49,13 +49,13 @@ internal static class AgentIdentityResolver
     }
 
     public static AgentIdentity ResolveAgentIdentity(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         string? agentId,
         string? agentName)
     {
-        PatternAgentDefinitionDto? match = FindKnownAgent(pattern, agentId)
-            ?? FindKnownAgent(pattern, agentName)
-            ?? ResolveSingleAgentAssistantAlias(pattern, agentId, agentName);
+        WorkflowNodeDto? match = FindKnownAgent(workflow, agentId)
+            ?? FindKnownAgent(workflow, agentName)
+            ?? ResolveSingleAgentAssistantAlias(workflow, agentId, agentName);
 
         return match is not null
             ? ToAgentIdentity(match)
@@ -63,16 +63,16 @@ internal static class AgentIdentityResolver
     }
 
     public static string ResolveDisplayAuthorName(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         string? primaryIdentifier,
         string? fallbackIdentifier = null)
     {
-        if (TryResolveKnownAgentIdentity(pattern, primaryIdentifier, out AgentIdentity primaryAgent))
+        if (TryResolveKnownAgentIdentity(workflow, primaryIdentifier, out AgentIdentity primaryAgent))
         {
             return primaryAgent.AgentName;
         }
 
-        if (TryResolveKnownAgentIdentity(pattern, fallbackIdentifier, out AgentIdentity fallbackAgent))
+        if (TryResolveKnownAgentIdentity(workflow, fallbackIdentifier, out AgentIdentity fallbackAgent))
         {
             return fallbackAgent.AgentName;
         }
@@ -98,26 +98,23 @@ internal static class AgentIdentityResolver
             StringComparison.Ordinal);
     }
 
-    private static PatternAgentDefinitionDto? ResolveSingleAgentAssistantAlias(
-        PatternDefinitionDto pattern,
+    private static WorkflowNodeDto? ResolveSingleAgentAssistantAlias(
+        WorkflowDefinitionDto workflow,
         params string?[] agentIdentifiers)
     {
-        return pattern.Agents.Count == 1 && agentIdentifiers.Any(IsGenericAssistantIdentifier)
-            ? pattern.Agents[0]
+        IReadOnlyList<WorkflowNodeDto> agentNodes = workflow.GetAgentNodes();
+        return agentNodes.Count == 1 && agentIdentifiers.Any(IsGenericAssistantIdentifier)
+            ? agentNodes[0]
             : null;
     }
 
-    private static PatternAgentDefinitionDto? FindKnownAgent(PatternDefinitionDto pattern, string? candidate)
+    private static WorkflowNodeDto? FindKnownAgent(WorkflowDefinitionDto workflow, string? candidate)
     {
-        return pattern.Agents.FirstOrDefault(agent => MatchesAgent(agent, candidate));
+        return workflow.GetAgentNodes().FirstOrDefault(agent => MatchesAgent(agent, candidate));
     }
 
-    private static AgentIdentity ToAgentIdentity(PatternAgentDefinitionDto agent)
-    {
-        return new AgentIdentity(
-            agent.Id,
-            string.IsNullOrWhiteSpace(agent.Name) ? agent.Id : agent.Name);
-    }
+    private static AgentIdentity ToAgentIdentity(WorkflowNodeDto agent)
+        => new(agent.GetAgentId(), agent.GetAgentName());
 
     private static AgentIdentity CreateFallbackIdentity(string? agentId, string? agentName)
     {
@@ -131,22 +128,24 @@ internal static class AgentIdentityResolver
         return new AgentIdentity(resolvedAgentId, resolvedAgentName);
     }
 
-    private static bool MatchesAgent(PatternAgentDefinitionDto agent, string? candidate)
+    private static bool MatchesAgent(WorkflowNodeDto agent, string? candidate)
     {
         if (string.IsNullOrWhiteSpace(candidate))
         {
             return false;
         }
 
-        if (string.Equals(agent.Id, candidate, StringComparison.OrdinalIgnoreCase)
-            || string.Equals(agent.Name, candidate, StringComparison.OrdinalIgnoreCase))
+        string agentId = agent.GetAgentId();
+        string agentName = agent.GetAgentName();
+        if (string.Equals(agentId, candidate, StringComparison.OrdinalIgnoreCase)
+            || string.Equals(agentName, candidate, StringComparison.OrdinalIgnoreCase))
         {
             return true;
         }
 
         string normalizedCandidate = NormalizeComparisonKey(candidate);
-        string normalizedId = NormalizeComparisonKey(agent.Id);
-        string normalizedName = NormalizeComparisonKey(agent.Name);
+        string normalizedId = NormalizeComparisonKey(agentId);
+        string normalizedName = NormalizeComparisonKey(agentName);
         if (normalizedCandidate.Length == 0)
         {
             return false;

sidecar/src/Aryx.AgentHost/Services/AgentInstructionComposer.cs

@@ -5,15 +5,15 @@ namespace Aryx.AgentHost.Services;
 internal static class AgentInstructionComposer
 {
     public static string Compose(
-        PatternDefinitionDto pattern,
-        PatternAgentDefinitionDto agent,
+        WorkflowDefinitionDto workflow,
+        WorkflowNodeDto agentNode,
         int agentIndex,
         string workspaceKind = "project",
         string interactionMode = "interactive",
         string? projectInstructions = null,
         RunTurnPromptInvocationDto? promptInvocation = null)
     {
-        string baseInstructions = agent.Instructions.Trim();
+        string baseInstructions = agentNode.Config.Instructions.Trim();
         string repositoryInstructions = projectInstructions?.Trim() ?? string.Empty;
         string promptInvocationInstructions = FormatPromptInvocation(promptInvocation);
         string workspaceGuidance = string.Equals(workspaceKind, "scratchpad", StringComparison.OrdinalIgnoreCase)
@@ -34,7 +34,7 @@ internal static class AgentInstructionComposer
               """
             : string.Empty;
 
-        if (string.Equals(pattern.Mode, "group-chat", StringComparison.OrdinalIgnoreCase))
+        if (string.Equals(workflow.Settings.OrchestrationMode, "group-chat", StringComparison.OrdinalIgnoreCase))
         {
             string groupChatGuidance = agentIndex == 0
                 ? """

sidecar/src/Aryx.AgentHost/Services/CopilotAgentBundle.cs

@@ -1,10 +1,9 @@
-using System.Threading;
-using GitHub.Copilot.SDK;
+using System.Linq;
 using Aryx.AgentHost.Contracts;
+using GitHub.Copilot.SDK;
 using Microsoft.Agents.AI;
 using Microsoft.Agents.AI.GitHub.Copilot;
 using Microsoft.Agents.AI.Workflows;
-using Microsoft.Agents.AI.Workflows.Specialized;
 using Microsoft.Extensions.AI;
 
 namespace Aryx.AgentHost.Services;
@@ -32,9 +31,9 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
 
     public static async Task<CopilotAgentBundle> CreateAsync(
         RunTurnCommandDto command,
-        Func<PatternAgentDefinitionDto, PermissionRequest, PermissionInvocation, Task<PermissionRequestResult>> onPermissionRequest,
-        Func<PatternAgentDefinitionDto, UserInputRequest, UserInputInvocation, Task<UserInputResponse>> onUserInputRequest,
-        Action<PatternAgentDefinitionDto, SessionEvent>? onSessionEvent,
+        Func<WorkflowNodeDto, PermissionRequest, PermissionInvocation, Task<PermissionRequestResult>> onPermissionRequest,
+        Func<WorkflowNodeDto, UserInputRequest, UserInputInvocation, Task<UserInputResponse>> onUserInputRequest,
+        Action<WorkflowNodeDto, SessionEvent>? onSessionEvent,
         CancellationToken cancellationToken)
     {
         List<IAsyncDisposable> disposables = [];
@@ -53,7 +52,8 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
             disposables.Add(toolingBundle);
         }
 
-        foreach ((PatternAgentDefinitionDto definition, int agentIndex) in command.Pattern.Agents.Select((definition, index) => (definition, index)))
+        IReadOnlyList<WorkflowNodeDto> agentNodes = command.Workflow.GetAgentNodes();
+        foreach ((WorkflowNodeDto definition, int agentIndex) in agentNodes.Select((definition, index) => (definition, index)))
         {
             CopilotClient client = new(clientOptions);
             await client.StartAsync(cancellationToken).ConfigureAwait(false);
@@ -75,9 +75,9 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
                 client,
                 sessionConfig,
                 ownsClient: true,
-                id: definition.Id,
-                name: definition.Name,
-                description: definition.Description);
+                id: definition.GetAgentId(),
+                name: definition.GetAgentName(),
+                description: NormalizeOptionalString(definition.Config.Description));
 
             agents.Add(agent);
             disposables.Add(agent);
@@ -90,7 +90,7 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
 
     internal static SessionConfig CreateSessionConfig(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto definition,
+        WorkflowNodeDto definition,
         int agentIndex,
         PermissionRequestHandler? onPermissionRequest = null,
         UserInputHandler? onUserInputRequest = null,
@@ -98,16 +98,14 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
         ResolvedHookSet? configuredHooks = null,
         IHookCommandRunner? hookCommandRunner = null)
     {
-        // Let the Copilot SDK allocate session IDs. Explicit custom SessionId values currently
-        // cause turns to complete without assistant output, even for simple single-agent prompts.
         return new SessionConfig
         {
-            Model = definition.Model,
-            ReasoningEffort = definition.ReasoningEffort,
+            Model = definition.Config.Model,
+            ReasoningEffort = definition.Config.ReasoningEffort,
             SystemMessage = new SystemMessageConfig
             {
                 Content = AgentInstructionComposer.Compose(
-                    command.Pattern,
+                    command.Workflow,
                     definition,
                     agentIndex,
                     command.WorkspaceKind,
@@ -121,11 +119,11 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
             Hooks = CopilotSessionHooks.Create(command, definition, configuredHooks, hookCommandRunner),
             OnEvent = onSessionEvent,
             Streaming = true,
-            CustomAgents = CreateCustomAgents(definition.Copilot?.CustomAgents),
-            Agent = ResolveEffectiveAgent(definition.Copilot?.Agent, command.PromptInvocation),
-            SkillDirectories = CreateStringList(definition.Copilot?.SkillDirectories),
-            DisabledSkills = CreateStringList(definition.Copilot?.DisabledSkills),
-            InfiniteSessions = CreateInfiniteSessions(definition.Copilot?.InfiniteSessions),
+            CustomAgents = CreateCustomAgents(definition.Config.Copilot?.CustomAgents),
+            Agent = ResolveEffectiveAgent(definition.Config.Copilot?.Agent, command.PromptInvocation),
+            SkillDirectories = CreateStringList(definition.Config.Copilot?.SkillDirectories),
+            DisabledSkills = CreateStringList(definition.Config.Copilot?.DisabledSkills),
+            InfiniteSessions = CreateInfiniteSessions(definition.Config.Copilot?.InfiniteSessions),
         };
     }
 
@@ -205,6 +203,34 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
         };
     }
 
+    internal static AIAgentHostOptions CreateAgentHostOptions()
+    {
+        return new AIAgentHostOptions
+        {
+            EmitAgentUpdateEvents = null,
+            EmitAgentResponseEvents = false,
+            InterceptUserInputRequests = false,
+            InterceptUnterminatedFunctionCalls = false,
+            ReassignOtherAgentsAsUsers = true,
+            ForwardIncomingMessages = true,
+        };
+    }
+
+    internal static HandoffsWorkflowBuilder CreateHandoffWorkflowBuilder(AIAgent entryAgent)
+    {
+        return AgentWorkflowBuilder.CreateHandoffBuilderWith(entryAgent)
+            .WithToolCallFilteringBehavior(HandoffToolCallFilteringBehavior.HandoffOnly)
+            .WithHandoffInstructions(HandoffWorkflowGuidance.CreateWorkflowInstructions());
+    }
+
+    public async ValueTask DisposeAsync()
+    {
+        foreach (IAsyncDisposable disposable in _disposables)
+        {
+            await disposable.DisposeAsync().ConfigureAwait(false);
+        }
+    }
+
     private static List<string>? CreateStringList(IReadOnlyList<string>? values)
     {
         return values is { Count: > 0 }
@@ -277,221 +303,4 @@ internal sealed class CopilotAgentBundle : IAsyncDisposable
     {
         return string.IsNullOrWhiteSpace(value) ? null : value.Trim();
     }
-
-    public Workflow BuildWorkflow(PatternDefinitionDto pattern)
-    {
-        return pattern.Mode switch
-        {
-            "single" => BuildSequentialWorkflow(pattern),
-            "sequential" => BuildSequentialWorkflow(pattern),
-            "concurrent" => BuildConcurrentWorkflow(pattern),
-            "handoff" => BuildHandoffWorkflow(pattern),
-            "group-chat" => BuildGroupChatWorkflow(pattern),
-            "magentic" => throw new NotSupportedException(
-                pattern.UnavailabilityReason
-                ?? "Magentic orchestration is not yet supported in the .NET Agent Framework."),
-            _ => throw new NotSupportedException($"Unsupported orchestration mode '{pattern.Mode}'."),
-        };
-    }
-
-    public async ValueTask DisposeAsync()
-    {
-        foreach (IAsyncDisposable disposable in _disposables)
-        {
-            await disposable.DisposeAsync().ConfigureAwait(false);
-        }
-    }
-
-    private Workflow BuildHandoffWorkflow(PatternDefinitionDto pattern)
-    {
-        Dictionary<string, AIAgent> agentMap = BuildAgentMap(pattern);
-        Dictionary<string, PatternAgentDefinitionDto> definitionMap = pattern.Agents.ToDictionary(
-            definition => definition.Id,
-            definition => definition,
-            StringComparer.Ordinal);
-        PatternHandoffTopology topology = PatternGraphResolver.ResolveHandoff(pattern);
-        string entryAgentId = agentMap.ContainsKey(topology.EntryAgentId)
-            ? topology.EntryAgentId
-            : pattern.Agents.FirstOrDefault()?.Id ?? topology.EntryAgentId;
-        AIAgent entryAgent = agentMap.GetValueOrDefault(entryAgentId) ?? Agents[0];
-
-        HandoffsWorkflowBuilder builder = CreateHandoffWorkflowBuilder(entryAgent);
-
-        foreach (PatternHandoffRoute route in topology.Routes)
-        {
-            if (!agentMap.TryGetValue(route.SourceAgentId, out AIAgent? sourceAgent)
-                || !agentMap.TryGetValue(route.TargetAgentId, out AIAgent? targetAgent)
-                || !definitionMap.TryGetValue(route.TargetAgentId, out PatternAgentDefinitionDto? targetDefinition))
-            {
-                continue;
-            }
-
-            string handoffReason = string.Equals(
-                route.TargetAgentId,
-                topology.EntryAgentId,
-                StringComparison.Ordinal)
-                ? HandoffWorkflowGuidance.CreateReturnReason(targetDefinition)
-                : HandoffWorkflowGuidance.CreateForwardReason(targetDefinition);
-
-            builder = builder.WithHandoff(
-                sourceAgent,
-                targetAgent,
-                handoffReason);
-        }
-
-        return builder.Build();
-    }
-
-    internal static AIAgentHostOptions CreateAgentHostOptions()
-    {
-        return new AIAgentHostOptions
-        {
-            // Aryx controls per-turn streaming with TurnToken(emitEvents: true), so keep this
-            // null to preserve that behavior while making the host defaults explicit in code.
-            EmitAgentUpdateEvents = null,
-            // Aryx already projects streamed transcript state itself; enabling this would add
-            // extra response events that need separate reconciliation first.
-            EmitAgentResponseEvents = false,
-            InterceptUserInputRequests = false,
-            InterceptUnterminatedFunctionCalls = false,
-            ReassignOtherAgentsAsUsers = true,
-            ForwardIncomingMessages = true,
-        };
-    }
-
-    internal static HandoffsWorkflowBuilder CreateHandoffWorkflowBuilder(AIAgent entryAgent)
-    {
-        return AgentWorkflowBuilder.CreateHandoffBuilderWith(entryAgent)
-            // Preserve normal tool-call history across handoffs while still hiding the
-            // workflow's handoff plumbing. Make this explicit so AF default changes
-            // cannot silently alter Aryx handoff behavior.
-            .WithToolCallFilteringBehavior(HandoffToolCallFilteringBehavior.HandoffOnly)
-            .WithHandoffInstructions(HandoffWorkflowGuidance.CreateWorkflowInstructions());
-    }
-
-    private Workflow BuildSequentialWorkflow(PatternDefinitionDto pattern)
-    {
-        IReadOnlyList<AIAgent> agents = ResolveOrderedAgents(pattern);
-        List<ExecutorBinding> agentExecutors = agents
-            .Select(CreateAgentExecutorBinding)
-            .ToList();
-
-        ExecutorBinding previous = agentExecutors[0];
-        WorkflowBuilder builder = new(previous);
-
-        foreach (ExecutorBinding next in agentExecutors.Skip(1))
-        {
-            builder.AddEdge(previous, next);
-            previous = next;
-        }
-
-        WorkflowOutputMessagesExecutor end = new();
-        builder = builder.AddEdge(previous, end).WithOutputFrom(end);
-
-        if (pattern.Name is not null)
-        {
-            builder = builder.WithName(pattern.Name);
-        }
-
-        return builder.Build();
-    }
-
-    private Workflow BuildConcurrentWorkflow(PatternDefinitionDto pattern)
-    {
-        IReadOnlyList<AIAgent> agents = ResolveOrderedAgents(pattern);
-        ChatForwardingExecutor start = new("Start");
-        WorkflowBuilder builder = new(start);
-
-        ExecutorBinding[] agentExecutors = agents
-            .Select(CreateAgentExecutorBinding)
-            .ToArray();
-        ExecutorBinding[] accumulators = agentExecutors
-            .Select(executor => CreateAggregateMessagesExecutorBinding($"Batcher/{executor.Id}"))
-            .ToArray();
-
-        builder.AddFanOutEdge(start, agentExecutors);
-
-        for (int index = 0; index < agentExecutors.Length; index++)
-        {
-            builder.AddEdge(agentExecutors[index], accumulators[index]);
-        }
-
-        Func<string, string, ValueTask<WorkflowConcurrentEndExecutor>> endFactory =
-            (_, __) => new(new WorkflowConcurrentEndExecutor(agentExecutors.Length, AggregateConcurrentResults));
-        ExecutorBinding end = endFactory.BindExecutor(WorkflowConcurrentEndExecutor.ExecutorId);
-
-        builder.AddFanInBarrierEdge(accumulators, end);
-        builder = builder.WithOutputFrom(end);
-
-        if (pattern.Name is not null)
-        {
-            builder = builder.WithName(pattern.Name);
-        }
-
-        return builder.Build();
-    }
-
-    private Workflow BuildGroupChatWorkflow(PatternDefinitionDto pattern)
-    {
-        int maximumIterations = pattern.MaxIterations <= 0 ? 5 : pattern.MaxIterations;
-        AIAgent[] agents = ResolveOrderedAgents(pattern).ToArray();
-        Dictionary<AIAgent, ExecutorBinding> agentMap = agents.ToDictionary(
-            agent => agent,
-            CreateAgentExecutorBinding);
-
-        Func<string, string, ValueTask<WorkflowRoundRobinGroupChatHost>> groupChatHostFactory =
-            (id, _) => new(new WorkflowRoundRobinGroupChatHost(
-                id,
-                agents,
-                agentMap,
-                maximumIterations));
-
-        ExecutorBinding host = groupChatHostFactory.BindExecutor("GroupChatHost");
-        WorkflowBuilder builder = new(host);
-
-        foreach (ExecutorBinding participant in agentMap.Values)
-        {
-            builder
-                .AddEdge(host, participant)
-                .AddEdge(participant, host);
-        }
-
-        return builder.WithOutputFrom(host).Build();
-    }
-
-    private static ExecutorBinding CreateAgentExecutorBinding(AIAgent agent)
-        => agent.BindAsExecutor(CreateAgentHostOptions());
-
-    private static ExecutorBinding CreateAggregateMessagesExecutorBinding(string id)
-    {
-        Func<string, string, ValueTask<WorkflowAggregateTurnMessagesExecutor>> factory =
-            (_, __) => new(new WorkflowAggregateTurnMessagesExecutor(id));
-        return factory.BindExecutor(id);
-    }
-
-    private static List<ChatMessage> AggregateConcurrentResults(IList<List<ChatMessage>> lists)
-        => [.. from list in lists where list.Count > 0 select list.Last()];
-
-    private IReadOnlyList<AIAgent> ResolveOrderedAgents(PatternDefinitionDto pattern)
-    {
-        Dictionary<string, AIAgent> agentMap = BuildAgentMap(pattern);
-        List<AIAgent> orderedAgents = PatternGraphResolver.ResolveOrderedAgentIds(pattern)
-            .Select(agentId => agentMap.TryGetValue(agentId, out AIAgent? agent) ? agent : null)
-            .Where(agent => agent is not null)
-            .Cast<AIAgent>()
-            .ToList();
-
-        return orderedAgents.Count == Agents.Count ? orderedAgents : Agents;
-    }
-
-    private Dictionary<string, AIAgent> BuildAgentMap(PatternDefinitionDto pattern)
-    {
-        Dictionary<string, AIAgent> agentMap = new(StringComparer.Ordinal);
-        foreach ((PatternAgentDefinitionDto definition, AIAgent agent) in pattern.Agents.Zip(Agents))
-        {
-            agentMap[definition.Id] = agent;
-        }
-
-        return agentMap;
-    }
 }

sidecar/src/Aryx.AgentHost/Services/CopilotApprovalCoordinator.cs

@@ -67,7 +67,7 @@ internal sealed class CopilotApprovalCoordinator
 
     public async Task<PermissionRequestResult> RequestApprovalAsync(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         PermissionRequest request,
         PermissionInvocation invocation,
         IReadOnlyDictionary<string, string> toolNamesByCallId,
@@ -88,7 +88,7 @@ internal sealed class CopilotApprovalCoordinator
 
     public async Task<PermissionRequestResult> RequestApprovalAsync(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         PermissionRequest request,
         PermissionInvocation invocation,
         IReadOnlyDictionary<string, string> toolNamesByCallId,
@@ -108,7 +108,7 @@ internal sealed class CopilotApprovalCoordinator
         }
 
         if (IsToolApprovedForRequest(command.RequestId, approvalCacheKey)
-            || !RequiresToolCallApproval(command.Pattern.ApprovalPolicy, agent.Id, toolName, autoApprovedToolName, mcpServerApprovalKey))
+            || !RequiresToolCallApproval(command.Workflow.Settings.ApprovalPolicy, agent.GetAgentId(), toolName, autoApprovedToolName, mcpServerApprovalKey))
         {
             return CreateApprovalResult(PermissionRequestResultKind.Approved);
         }
@@ -149,7 +149,7 @@ internal sealed class CopilotApprovalCoordinator
 
     internal static ApprovalRequestedEventDto BuildPermissionApprovalEvent(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         PermissionRequest request,
         PermissionInvocation invocation,
         string approvalId,
@@ -157,7 +157,8 @@ internal sealed class CopilotApprovalCoordinator
     {
         string permissionKind = ResolvePermissionKind(request, command.Tooling?.McpServers);
 
-        string agentName = string.IsNullOrWhiteSpace(agent.Name) ? agent.Id : agent.Name;
+        string agentId = agent.GetAgentId();
+        string agentName = agent.GetAgentName();
         string? sessionId = NormalizeOptionalString(invocation.SessionId);
         string? normalizedToolName = NormalizeOptionalString(toolName);
         string? requestedUrl = request is PermissionRequestUrl urlRequest
@@ -191,7 +192,7 @@ internal sealed class CopilotApprovalCoordinator
             SessionId = command.SessionId,
             ApprovalId = approvalId,
             ApprovalKind = ToolCallApprovalKind,
-            AgentId = NormalizeOptionalString(agent.Id),
+            AgentId = NormalizeOptionalString(agentId),
             AgentName = NormalizeOptionalString(agentName),
             ToolName = normalizedToolName,
             PermissionKind = permissionKind,
@@ -203,7 +204,7 @@ internal sealed class CopilotApprovalCoordinator
 
     internal static AgentActivityEventDto? BuildToolCallFileChangeActivity(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         PermissionRequest request,
         string? toolName)
     {
@@ -218,14 +219,15 @@ internal sealed class CopilotApprovalCoordinator
             return null;
         }
 
-        string agentName = string.IsNullOrWhiteSpace(agent.Name) ? agent.Id : agent.Name;
+        string agentId = agent.GetAgentId();
+        string agentName = agent.GetAgentName();
         return new AgentActivityEventDto
         {
             Type = "agent-activity",
             RequestId = command.RequestId,
             SessionId = command.SessionId,
             ActivityType = ToolCallingActivityType,
-            AgentId = NormalizeOptionalString(agent.Id),
+            AgentId = NormalizeOptionalString(agentId),
             AgentName = NormalizeOptionalString(agentName),
             ToolName = NormalizeOptionalString(toolName),
             ToolCallId = NormalizeOptionalString(write.ToolCallId),

sidecar/src/Aryx.AgentHost/Services/CopilotExitPlanModeCoordinator.cs

@@ -11,7 +11,7 @@ internal sealed class CopilotExitPlanModeCoordinator
 
     public ExitPlanModeRequestedEventDto RecordExitPlanModeRequest(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         ExitPlanModeRequestedEvent request)
     {
         ArgumentNullException.ThrowIfNull(command);
@@ -33,7 +33,7 @@ internal sealed class CopilotExitPlanModeCoordinator
 
     internal static ExitPlanModeRequestedEventDto BuildExitPlanModeRequestedEvent(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         ExitPlanModeRequestedEvent request)
     {
         ArgumentNullException.ThrowIfNull(command);
@@ -45,8 +45,8 @@ internal sealed class CopilotExitPlanModeCoordinator
 
         string exitPlanId = NormalizeOptionalString(requestData.RequestId)
             ?? throw new InvalidOperationException("Exit plan mode request ID is required.");
-        string? normalizedAgentId = NormalizeOptionalString(agent.Id);
-        string? normalizedAgentName = NormalizeOptionalString(agent.Name) ?? normalizedAgentId;
+        string? normalizedAgentId = NormalizeOptionalString(agent.GetAgentId());
+        string? normalizedAgentName = NormalizeOptionalString(agent.GetAgentName()) ?? normalizedAgentId;
 
         return new ExitPlanModeRequestedEventDto
         {

sidecar/src/Aryx.AgentHost/Services/CopilotMcpOAuthCoordinator.cs

@@ -7,7 +7,7 @@ internal sealed class CopilotMcpOAuthCoordinator
 {
     public McpOauthRequiredEventDto BuildMcpOauthRequiredEvent(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         McpOauthRequiredEvent request)
     {
         ArgumentNullException.ThrowIfNull(command);
@@ -19,8 +19,8 @@ internal sealed class CopilotMcpOAuthCoordinator
 
         string oauthRequestId = NormalizeOptionalString(requestData.RequestId)
             ?? throw new InvalidOperationException("MCP OAuth request ID is required.");
-        string? normalizedAgentId = NormalizeOptionalString(agent.Id);
-        string? normalizedAgentName = NormalizeOptionalString(agent.Name) ?? normalizedAgentId;
+        string? normalizedAgentId = NormalizeOptionalString(agent.GetAgentId());
+        string? normalizedAgentName = NormalizeOptionalString(agent.GetAgentName()) ?? normalizedAgentId;
 
         return new McpOauthRequiredEventDto
         {

sidecar/src/Aryx.AgentHost/Services/CopilotSessionHooks.cs

@@ -40,7 +40,7 @@ internal static class CopilotSessionHooks
 
     public static SessionHooks Create(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agentDefinition,
+        WorkflowNodeDto agentDefinition,
         ResolvedHookSet? configuredHooks = null,
         IHookCommandRunner? hookCommandRunner = null)
     {
@@ -62,7 +62,7 @@ internal static class CopilotSessionHooks
 
     private static async Task<PreToolUseHookOutput?> CreatePreToolUseOutputAsync(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agentDefinition,
+        WorkflowNodeDto agentDefinition,
         ResolvedHookSet configuredHooks,
         IHookCommandRunner hookCommandRunner,
         PreToolUseHookInput input)
@@ -236,7 +236,7 @@ internal static class CopilotSessionHooks
 
     private static PreToolUseHookOutput CreateApprovalPolicyOutput(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agentDefinition,
+        WorkflowNodeDto agentDefinition,
         PreToolUseHookInput input)
     {
         string? toolName = Normalize(input.ToolName);
@@ -254,8 +254,8 @@ internal static class CopilotSessionHooks
             command.Tooling?.McpServers);
 
         bool requiresApproval = CopilotApprovalCoordinator.RequiresToolCallApproval(
-            command.Pattern.ApprovalPolicy,
-            agentDefinition.Id,
+            command.Workflow.Settings.ApprovalPolicy,
+            agentDefinition.GetAgentId(),
             toolName,
             autoApprovedToolName,
             mcpServerApprovalKey);

sidecar/src/Aryx.AgentHost/Services/CopilotTurnExecutionState.cs

@@ -65,12 +65,12 @@ internal sealed class CopilotTurnExecutionState
         }
     }
 
-    public void ObserveSessionEvent(PatternAgentDefinitionDto agentDefinition, SessionEvent sessionEvent)
+    public void ObserveSessionEvent(WorkflowNodeDto agentDefinition, SessionEvent sessionEvent)
     {
         AgentIdentity agent = AgentIdentityResolver.ResolveAgentIdentity(
-            _command.Pattern,
-            agentDefinition.Id,
-            agentDefinition.Name);
+            _command.Workflow,
+            agentDefinition.GetAgentId(),
+            agentDefinition.GetAgentName());
 
         switch (sessionEvent)
         {

sidecar/src/Aryx.AgentHost/Services/CopilotUserInputCoordinator.cs

@@ -32,7 +32,7 @@ internal sealed class CopilotUserInputCoordinator
 
     public async Task<UserInputResponse> RequestUserInputAsync(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         UserInputRequest request,
         UserInputInvocation invocation,
         Func<UserInputRequestedEventDto, Task> onUserInput,
@@ -46,8 +46,8 @@ internal sealed class CopilotUserInputCoordinator
 
         return await RequestUserInputCoreAsync(
             command,
-            agent.Id,
-            agent.Name,
+            agent.GetAgentId(),
+            agent.GetAgentName(),
             request,
             onUserInput,
             cancellationToken).ConfigureAwait(false);
@@ -74,7 +74,7 @@ internal sealed class CopilotUserInputCoordinator
 
     internal static UserInputRequestedEventDto BuildUserInputRequestedEvent(
         RunTurnCommandDto command,
-        PatternAgentDefinitionDto agent,
+        WorkflowNodeDto agent,
         UserInputRequest request,
         string userInputId)
     {
@@ -82,8 +82,8 @@ internal sealed class CopilotUserInputCoordinator
         ArgumentNullException.ThrowIfNull(agent);
         ArgumentNullException.ThrowIfNull(request);
 
-        string? normalizedAgentId = NormalizeOptionalString(agent.Id);
-        string? normalizedAgentName = NormalizeOptionalString(agent.Name) ?? normalizedAgentId;
+        string? normalizedAgentId = NormalizeOptionalString(agent.GetAgentId());
+        string? normalizedAgentName = NormalizeOptionalString(agent.GetAgentName()) ?? normalizedAgentId;
 
         return new UserInputRequestedEventDto
         {

sidecar/src/Aryx.AgentHost/Services/CopilotWorkflowRunner.cs

@@ -14,7 +14,6 @@ namespace Aryx.AgentHost.Services;
 public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
 {
     private const string HandoffFunctionPrefix = "handoff_to_";
-    private readonly PatternValidator _patternValidator;
     private readonly WorkflowValidator _workflowValidator;
     private readonly WorkflowRunner _workflowRunner = new();
     private readonly CopilotApprovalCoordinator _approvalCoordinator = new();
@@ -22,9 +21,8 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
     private readonly CopilotMcpOAuthCoordinator _mcpOAuthCoordinator = new();
     private readonly CopilotExitPlanModeCoordinator _exitPlanModeCoordinator = new();
 
-    public CopilotWorkflowRunner(PatternValidator patternValidator, WorkflowValidator? workflowValidator = null)
+    public CopilotWorkflowRunner(WorkflowValidator? workflowValidator = null)
     {
-        _patternValidator = patternValidator;
         _workflowValidator = workflowValidator ?? new WorkflowValidator();
     }
 
@@ -38,9 +36,8 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
         Func<ExitPlanModeRequestedEventDto, Task> onExitPlanMode,
         CancellationToken cancellationToken)
     {
-        string? validationError = command.Workflow is null
-            ? _patternValidator.Validate(command.Pattern).FirstOrDefault()?.Message
-            : _workflowValidator.Validate(command.Workflow, command.WorkflowLibrary).FirstOrDefault()?.Message;
+        string? validationError = _workflowValidator.Validate(command.Workflow, command.WorkflowLibrary)
+            .FirstOrDefault()?.Message;
         if (validationError is not null)
         {
             throw new InvalidOperationException(validationError);
@@ -87,9 +84,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
                 },
                 runCancellation.Token);
             ConfigureHookLifecycleEventSuppression(state, bundle);
-            Workflow workflow = command.Workflow is null
-                ? bundle.BuildWorkflow(command.Pattern)
-                : _workflowRunner.BuildWorkflow(command.Workflow, command.Pattern, bundle.Agents, command.WorkflowLibrary);
+            Workflow workflow = _workflowRunner.BuildWorkflow(command.Workflow, bundle.Agents, command.WorkflowLibrary);
             List<ChatMessage> inputMessages = command.Messages.Select(WorkflowTranscriptProjector.ToChatMessage).ToList();
             WorkflowTranscriptProjector.AttachMessageMode(inputMessages, command.MessageMode);
 
@@ -166,12 +161,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
     internal static bool ShouldEnableWorkflowCheckpointing(RunTurnCommandDto command)
     {
         ArgumentNullException.ThrowIfNull(command);
-        if (command.Workflow is not null)
-        {
-            return command.Workflow.Settings.Checkpointing.Enabled;
-        }
-
-        return string.Equals(command.Pattern.Mode, "handoff", StringComparison.OrdinalIgnoreCase);
+        return command.Workflow.Settings.Checkpointing.Enabled;
     }
 
     internal static string GetCheckpointStorePath(RunTurnCommandDto command)
@@ -210,7 +200,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
     {
         ArgumentNullException.ThrowIfNull(command);
 
-        string executionMode = command.Workflow?.Settings.ExecutionMode?.Trim() ?? "off-thread";
+        string executionMode = command.Workflow.Settings.ExecutionMode?.Trim() ?? "off-thread";
         InProcessExecutionEnvironment environment = string.Equals(
             executionMode,
             "lockstep",
@@ -300,7 +290,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
         if (evt is ExecutorInvokedEvent invoked)
         {
             if (AgentIdentityResolver.TryResolveKnownAgentIdentity(
-                command.Pattern,
+                command.Workflow,
                 invoked.ExecutorId,
                 out AgentIdentity invokedAgent))
             {
@@ -357,7 +347,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
         if (evt is ExecutorCompletedEvent completed)
         {
             if (AgentIdentityResolver.TryResolveObservedAgentIdentity(
-                command.Pattern,
+                command.Workflow,
                 completed.ExecutorId,
                 state.ActiveAgent,
                 out AgentIdentity completedAgent))
@@ -471,7 +461,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
             authorName = observedMessageAgent.AgentName;
         }
         else if (AgentIdentityResolver.TryResolveObservedAgentIdentity(
-            command.Pattern,
+            command.Workflow,
             update.ExecutorId,
             state.ActiveAgent,
             out AgentIdentity resolvedUpdateAgent))
@@ -594,7 +584,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
             case ExecutorFailedEvent executorFailed:
             {
                 AgentIdentity? agent = AgentIdentityResolver.TryResolveObservedAgentIdentity(
-                    command.Pattern,
+                    command.Workflow,
                     executorFailed.ExecutorId,
                     state.ActiveAgent,
                     out AgentIdentity resolvedAgent)
@@ -754,7 +744,7 @@ public sealed class CopilotWorkflowRunner : ITurnWorkflowRunner
 
     private static void TraceHandoff(RunTurnCommandDto command, string message)
     {
-        if (!string.Equals(command.Pattern.Mode, "handoff", StringComparison.OrdinalIgnoreCase))
+        if (!command.Workflow.IsOrchestrationMode("handoff"))
         {
             return;
         }

sidecar/src/Aryx.AgentHost/Services/HandoffWorkflowGuidance.cs

@@ -21,17 +21,17 @@ internal static class HandoffWorkflowGuidance
                """;
     }
 
-    public static string CreateForwardReason(PatternAgentDefinitionDto target)
+    public static string CreateForwardReason(WorkflowNodeDto target)
     {
-        string specialty = string.IsNullOrWhiteSpace(target.Description)
-            ? target.Name
-            : target.Description.TrimEnd('.');
+        string specialty = string.IsNullOrWhiteSpace(target.Config.Description)
+            ? target.GetAgentName()
+            : target.Config.Description.TrimEnd('.');
 
-        return $"Hand off when the request primarily concerns {specialty}. Once handed off, let {target.Name} own the substantive response.";
+        return $"Hand off when the request primarily concerns {specialty}. Once handed off, let {target.GetAgentName()} own the substantive response.";
     }
 
-    public static string CreateReturnReason(PatternAgentDefinitionDto triageAgent)
+    public static string CreateReturnReason(WorkflowNodeDto triageAgent)
     {
-        return $"Hand off back to {triageAgent.Name} only when the task needs re-routing, cross-specialist coordination, or is outside your specialty.";
+        return $"Hand off back to {triageAgent.GetAgentName()} only when the task needs re-routing, cross-specialist coordination, or is outside your specialty.";
     }
 }

sidecar/src/Aryx.AgentHost/Services/PatternGraphResolver.cs

@@ -1,345 +0,0 @@
-using Aryx.AgentHost.Contracts;
-
-namespace Aryx.AgentHost.Services;
-
-internal sealed record PatternHandoffRoute(string SourceAgentId, string TargetAgentId);
-
-internal sealed record PatternHandoffTopology(string EntryAgentId, IReadOnlyList<PatternHandoffRoute> Routes);
-
-internal static class PatternGraphResolver
-{
-    private const string UserInputKind = "user-input";
-    private const string UserOutputKind = "user-output";
-    private const string AgentKind = "agent";
-    private const string DistributorKind = "distributor";
-    private const string CollectorKind = "collector";
-    private const string OrchestratorKind = "orchestrator";
-
-    private static readonly StringComparer Comparer = StringComparer.OrdinalIgnoreCase;
-
-    public static PatternGraphDto Resolve(PatternDefinitionDto pattern)
-        => pattern.Graph ?? CreateDefault(pattern);
-
-    public static IReadOnlyList<string> ResolveOrderedAgentIds(PatternDefinitionDto pattern)
-    {
-        PatternGraphDto graph = Resolve(pattern);
-
-        return pattern.Mode switch
-        {
-            "single" or "sequential" or "magentic" => ResolveLinearAgentIds(pattern, graph),
-            "concurrent" or "group-chat" or "handoff" => ResolveAgentOrder(pattern, graph),
-            _ => pattern.Agents.Select(agent => agent.Id).ToList()
-        };
-    }
-
-    public static PatternHandoffTopology ResolveHandoff(PatternDefinitionDto pattern)
-    {
-        return TryResolveHandoff(pattern, Resolve(pattern))
-            ?? TryResolveHandoff(pattern, CreateDefault(pattern))
-            ?? new PatternHandoffTopology(
-                pattern.Agents.FirstOrDefault()?.Id ?? string.Empty,
-                []);
-    }
-
-    public static PatternGraphDto CreateDefault(PatternDefinitionDto pattern)
-    {
-        return pattern.Mode switch
-        {
-            "single" or "sequential" or "magentic" => CreateLinearGraph(pattern.Agents),
-            "concurrent" => CreateConcurrentGraph(pattern.Agents),
-            "handoff" => CreateHandoffGraph(pattern.Agents),
-            "group-chat" => CreateGroupChatGraph(pattern.Agents),
-            _ => CreateLinearGraph(pattern.Agents)
-        };
-    }
-
-    private static IReadOnlyList<string> ResolveLinearAgentIds(PatternDefinitionDto pattern, PatternGraphDto graph)
-    {
-        PatternGraphNodeDto? inputNode = GetNodeByKind(graph, UserInputKind);
-        PatternGraphNodeDto? outputNode = GetNodeByKind(graph, UserOutputKind);
-        if (inputNode is null || outputNode is null)
-        {
-            return pattern.Agents.Select(agent => agent.Id).ToList();
-        }
-
-        Dictionary<string, PatternGraphNodeDto> nodesById = graph.Nodes.ToDictionary(node => node.Id, node => node);
-        Dictionary<string, List<PatternGraphEdgeDto>> outgoing = BuildOutgoingLookup(graph);
-        List<string> orderedAgentIds = [];
-        HashSet<string> visitedNodeIds = [];
-        string currentNodeId = inputNode.Id;
-
-        while (visitedNodeIds.Add(currentNodeId))
-        {
-            if (!outgoing.TryGetValue(currentNodeId, out List<PatternGraphEdgeDto>? edges) || edges.Count != 1)
-            {
-                break;
-            }
-
-            string nextNodeId = edges[0].Target;
-            if (!nodesById.TryGetValue(nextNodeId, out PatternGraphNodeDto? nextNode))
-            {
-                break;
-            }
-
-            if (Comparer.Equals(nextNode.Id, outputNode.Id))
-            {
-                break;
-            }
-
-            if (Comparer.Equals(nextNode.Kind, AgentKind) && !string.IsNullOrWhiteSpace(nextNode.AgentId))
-            {
-                orderedAgentIds.Add(nextNode.AgentId);
-            }
-
-            currentNodeId = nextNodeId;
-        }
-
-        return orderedAgentIds.Count == pattern.Agents.Count
-            ? orderedAgentIds
-            : pattern.Agents.Select(agent => agent.Id).ToList();
-    }
-
-    private static IReadOnlyList<string> ResolveAgentOrder(PatternDefinitionDto pattern, PatternGraphDto graph)
-    {
-        Dictionary<string, int> fallbackOrder = pattern.Agents
-            .Select((agent, index) => new { agent.Id, Index = index })
-            .ToDictionary(item => item.Id, item => item.Index);
-
-        List<string> orderedAgentIds = graph.Nodes
-            .Where(node => Comparer.Equals(node.Kind, AgentKind) && !string.IsNullOrWhiteSpace(node.AgentId))
-            .OrderBy(node => node.Order ?? int.MaxValue)
-            .ThenBy(node => fallbackOrder.GetValueOrDefault(node.AgentId!, int.MaxValue))
-            .Select(node => node.AgentId!)
-            .Distinct()
-            .ToList();
-
-        return orderedAgentIds.Count == pattern.Agents.Count
-            ? orderedAgentIds
-            : pattern.Agents.Select(agent => agent.Id).ToList();
-    }
-
-    private static PatternHandoffTopology? TryResolveHandoff(PatternDefinitionDto pattern, PatternGraphDto graph)
-    {
-        Dictionary<string, PatternGraphNodeDto> nodesById = graph.Nodes.ToDictionary(node => node.Id, node => node);
-        PatternGraphNodeDto? inputNode = GetNodeByKind(graph, UserInputKind);
-        string? entryAgentId = null;
-
-        if (inputNode is not null)
-        {
-            entryAgentId = graph.Edges
-                .Where(edge => Comparer.Equals(edge.Source, inputNode.Id))
-                .Select(edge => nodesById.TryGetValue(edge.Target, out PatternGraphNodeDto? targetNode)
-                    ? targetNode.AgentId
-                    : null)
-                .FirstOrDefault(agentId => !string.IsNullOrWhiteSpace(agentId));
-        }
-
-        List<PatternHandoffRoute> routes = graph.Edges
-            .Select(edge => (SourceNode: nodesById.GetValueOrDefault(edge.Source), TargetNode: nodesById.GetValueOrDefault(edge.Target)))
-            .Where(item =>
-                item.SourceNode is not null
-                && item.TargetNode is not null
-                && Comparer.Equals(item.SourceNode.Kind, AgentKind)
-                && Comparer.Equals(item.TargetNode.Kind, AgentKind)
-                && !string.IsNullOrWhiteSpace(item.SourceNode.AgentId)
-                && !string.IsNullOrWhiteSpace(item.TargetNode.AgentId))
-            .Select(item => new PatternHandoffRoute(item.SourceNode!.AgentId!, item.TargetNode!.AgentId!))
-            .Distinct()
-            .ToList();
-
-        if (string.IsNullOrWhiteSpace(entryAgentId) || routes.Count == 0)
-        {
-            return null;
-        }
-
-        return new PatternHandoffTopology(entryAgentId!, routes);
-    }
-
-    private static Dictionary<string, List<PatternGraphEdgeDto>> BuildOutgoingLookup(PatternGraphDto graph)
-    {
-        Dictionary<string, List<PatternGraphEdgeDto>> lookup = new(StringComparer.Ordinal);
-        foreach (PatternGraphNodeDto node in graph.Nodes)
-        {
-            lookup[node.Id] = [];
-        }
-
-        foreach (PatternGraphEdgeDto edge in graph.Edges)
-        {
-            if (!lookup.TryGetValue(edge.Source, out List<PatternGraphEdgeDto>? edges))
-            {
-                edges = [];
-                lookup[edge.Source] = edges;
-            }
-
-            edges.Add(edge);
-        }
-
-        return lookup;
-    }
-
-    private static PatternGraphNodeDto? GetNodeByKind(PatternGraphDto graph, string kind)
-        => graph.Nodes.FirstOrDefault(node => Comparer.Equals(node.Kind, kind));
-
-    private static PatternGraphDto CreateLinearGraph(IReadOnlyList<PatternAgentDefinitionDto> agents)
-    {
-        PatternGraphNodeDto inputNode = CreateSystemNode("system-user-input", UserInputKind, 0, 0);
-        PatternGraphNodeDto outputNode = CreateSystemNode("system-user-output", UserOutputKind, 220 * Math.Max(agents.Count + 1, 2), 0);
-        List<PatternGraphNodeDto> agentNodes = agents
-            .Select((agent, index) => CreateAgentNode(agent, index, 220 * (index + 1), 0))
-            .ToList();
-        List<PatternGraphEdgeDto> edges = [];
-        List<string> path = [inputNode.Id, .. agentNodes.Select(node => node.Id), outputNode.Id];
-        for (int index = 0; index < path.Count - 1; index += 1)
-        {
-            edges.Add(CreateEdge(path[index], path[index + 1]));
-        }
-
-        return new PatternGraphDto
-        {
-            Nodes = [inputNode, .. agentNodes, outputNode],
-            Edges = edges
-        };
-    }
-
-    private static PatternGraphDto CreateConcurrentGraph(IReadOnlyList<PatternAgentDefinitionDto> agents)
-    {
-        PatternGraphNodeDto inputNode = CreateSystemNode("system-user-input", UserInputKind, 0, 0);
-        PatternGraphNodeDto distributorNode = CreateSystemNode("system-distributor", DistributorKind, 190, 0);
-        PatternGraphNodeDto collectorNode = CreateSystemNode("system-collector", CollectorKind, 650, 0);
-        PatternGraphNodeDto outputNode = CreateSystemNode("system-user-output", UserOutputKind, 860, 0);
-        List<PatternGraphNodeDto> agentNodes = agents
-            .Select((agent, index) => CreateAgentNode(agent, index, 430, SpreadY(index, Math.Max(agents.Count, 1), 170)))
-            .ToList();
-
-        return new PatternGraphDto
-        {
-            Nodes = [inputNode, distributorNode, .. agentNodes, collectorNode, outputNode],
-            Edges =
-            [
-                CreateEdge(inputNode.Id, distributorNode.Id),
-                .. agentNodes.Select(node => CreateEdge(distributorNode.Id, node.Id)),
-                .. agentNodes.Select(node => CreateEdge(node.Id, collectorNode.Id)),
-                CreateEdge(collectorNode.Id, outputNode.Id)
-            ]
-        };
-    }
-
-    private static PatternGraphDto CreateHandoffGraph(IReadOnlyList<PatternAgentDefinitionDto> agents)
-    {
-        PatternGraphNodeDto inputNode = CreateSystemNode("system-user-input", UserInputKind, 0, 0);
-        PatternGraphNodeDto outputNode = CreateSystemNode("system-user-output", UserOutputKind, 860, 0);
-        PatternAgentDefinitionDto? entryAgent = agents.FirstOrDefault();
-        PatternGraphNodeDto? entryNode = entryAgent is null
-            ? null
-            : CreateAgentNode(entryAgent, 0, 220, 0);
-        List<PatternGraphNodeDto> specialistNodes = agents
-            .Skip(1)
-            .Select((agent, index) => CreateAgentNode(agent, index + 1, 540, SpreadY(index, Math.Max(agents.Count - 1, 1), 220)))
-            .ToList();
-
-        List<PatternGraphEdgeDto> edges = [];
-        if (entryNode is not null)
-        {
-            edges.Add(CreateEdge(inputNode.Id, entryNode.Id));
-            edges.Add(CreateEdge(entryNode.Id, outputNode.Id));
-
-            foreach (PatternGraphNodeDto specialistNode in specialistNodes)
-            {
-                edges.Add(CreateEdge(entryNode.Id, specialistNode.Id));
-                edges.Add(CreateEdge(specialistNode.Id, entryNode.Id));
-                edges.Add(CreateEdge(specialistNode.Id, outputNode.Id));
-            }
-        }
-
-        List<PatternGraphNodeDto> nodes = [inputNode];
-        if (entryNode is not null)
-        {
-            nodes.Add(entryNode);
-        }
-        nodes.AddRange(specialistNodes);
-        nodes.Add(outputNode);
-
-        return new PatternGraphDto
-        {
-            Nodes = nodes,
-            Edges = edges
-        };
-    }
-
-    private static PatternGraphDto CreateGroupChatGraph(IReadOnlyList<PatternAgentDefinitionDto> agents)
-    {
-        PatternGraphNodeDto inputNode = CreateSystemNode("system-user-input", UserInputKind, 0, 0);
-        PatternGraphNodeDto orchestratorNode = CreateSystemNode("system-orchestrator", OrchestratorKind, 250, 0);
-        PatternGraphNodeDto outputNode = CreateSystemNode("system-user-output", UserOutputKind, 900, 0);
-        const double centerX = 560;
-        const double centerY = 0;
-        const double radiusX = 190;
-        const double radiusY = 170;
-
-        List<PatternGraphNodeDto> agentNodes = agents
-            .Select((agent, index) =>
-            {
-                double angle = agents.Count <= 1
-                    ? 0
-                    : (Math.PI * 2 * index) / agents.Count - (Math.PI / 2);
-                return CreateAgentNode(
-                    agent,
-                    index,
-                    Math.Round(centerX + Math.Cos(angle) * radiusX),
-                    Math.Round(centerY + Math.Sin(angle) * radiusY));
-            })
-            .ToList();
-
-        return new PatternGraphDto
-        {
-            Nodes = [inputNode, orchestratorNode, .. agentNodes, outputNode],
-            Edges =
-            [
-                CreateEdge(inputNode.Id, orchestratorNode.Id),
-                .. agentNodes.SelectMany(node => new[]
-                {
-                    CreateEdge(orchestratorNode.Id, node.Id),
-                    CreateEdge(node.Id, orchestratorNode.Id)
-                }),
-                CreateEdge(orchestratorNode.Id, outputNode.Id)
-            ]
-        };
-    }
-
-    private static PatternGraphNodeDto CreateSystemNode(string id, string kind, double x, double y)
-        => new()
-        {
-            Id = id,
-            Kind = kind,
-            Position = new PatternGraphPositionDto
-            {
-                X = x,
-                Y = y
-            }
-        };
-
-    private static PatternGraphNodeDto CreateAgentNode(PatternAgentDefinitionDto agent, int order, double x, double y)
-        => new()
-        {
-            Id = $"agent-node-{agent.Id}",
-            Kind = AgentKind,
-            AgentId = agent.Id,
-            Order = order,
-            Position = new PatternGraphPositionDto
-            {
-                X = x,
-                Y = y
-            }
-        };
-
-    private static PatternGraphEdgeDto CreateEdge(string source, string target)
-        => new()
-        {
-            Id = $"edge-{source}-to-{target}",
-            Source = source,
-            Target = target
-        };
-
-    private static double SpreadY(int index, int count, double gap)
-        => (index - ((count - 1) / 2d)) * gap;
-}

sidecar/src/Aryx.AgentHost/Services/PatternValidator.cs

@@ -1,573 +0,0 @@
-using Aryx.AgentHost.Contracts;
-
-namespace Aryx.AgentHost.Services;
-
-public sealed class PatternValidator
-{
-    private static readonly StringComparer Comparer = StringComparer.OrdinalIgnoreCase;
-
-    public IReadOnlyList<PatternValidationIssueDto> Validate(PatternDefinitionDto pattern)
-    {
-        List<PatternValidationIssueDto> issues = [];
-
-        if (string.IsNullOrWhiteSpace(pattern.Name))
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "name",
-                Message = "Pattern name is required.",
-            });
-        }
-
-        if (string.Equals(pattern.Availability, "unavailable", StringComparison.OrdinalIgnoreCase))
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "availability",
-                Message = pattern.UnavailabilityReason ?? "This orchestration mode is currently unavailable.",
-            });
-        }
-
-        if (pattern.Agents.Count == 0)
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "agents",
-                Message = "At least one agent is required.",
-            });
-        }
-
-        if (string.Equals(pattern.Mode, "single", StringComparison.OrdinalIgnoreCase) && pattern.Agents.Count != 1)
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "agents",
-                Message = "Single-agent chat requires exactly one agent.",
-            });
-        }
-
-        if (string.Equals(pattern.Mode, "handoff", StringComparison.OrdinalIgnoreCase) && pattern.Agents.Count < 2)
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "agents",
-                Message = "Handoff orchestration requires at least two agents.",
-            });
-        }
-
-        if (string.Equals(pattern.Mode, "group-chat", StringComparison.OrdinalIgnoreCase) && pattern.Agents.Count < 2)
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "agents",
-                Message = "Group chat requires at least two agents.",
-            });
-        }
-
-        if (string.Equals(pattern.Mode, "magentic", StringComparison.OrdinalIgnoreCase))
-        {
-            issues.Add(new PatternValidationIssueDto
-            {
-                Field = "mode",
-                Message = pattern.UnavailabilityReason
-                    ?? "Magentic orchestration is currently documented as unsupported in the .NET Agent Framework.",
-            });
-        }
-
-        foreach (PatternAgentDefinitionDto agent in pattern.Agents)
-        {
-            if (string.IsNullOrWhiteSpace(agent.Name))
-            {
-                issues.Add(new PatternValidationIssueDto
-                {
-                    Field = "agents.name",
-                    Message = "Every agent needs a name.",
-                });
-            }
-
-            if (string.IsNullOrWhiteSpace(agent.Model))
-            {
-                issues.Add(new PatternValidationIssueDto
-                {
-                    Field = "agents.model",
-                    Message = $"Agent \"{agent.Name}\" requires a model identifier.",
-                });
-            }
-        }
-
-        ValidateGraph(pattern, PatternGraphResolver.Resolve(pattern), issues);
-        return issues;
-    }
-
-    private static void ValidateGraph(
-        PatternDefinitionDto pattern,
-        PatternGraphDto graph,
-        List<PatternValidationIssueDto> issues)
-    {
-        if (graph.Nodes.Count == 0)
-        {
-            AddGraphIssue(issues, "Pattern graph must include nodes.");
-            return;
-        }
-
-        HashSet<string> nodeIds = new(StringComparer.Ordinal);
-        HashSet<string> edgeIds = new(StringComparer.Ordinal);
-        HashSet<string> agentIds = pattern.Agents.Select(agent => agent.Id).ToHashSet(StringComparer.Ordinal);
-        HashSet<string> seenAgentIds = new(StringComparer.Ordinal);
-        HashSet<int> seenAgentOrders = [];
-        Dictionary<string, PatternGraphNodeDto> nodesById = new(StringComparer.Ordinal);
-
-        foreach (PatternGraphNodeDto node in graph.Nodes)
-        {
-            if (!nodeIds.Add(node.Id))
-            {
-                AddGraphIssue(issues, $"Pattern graph contains duplicate node \"{node.Id}\".");
-            }
-
-            nodesById[node.Id] = node;
-
-            if (Comparer.Equals(node.Kind, "agent"))
-            {
-                if (string.IsNullOrWhiteSpace(node.AgentId) || !agentIds.Contains(node.AgentId))
-                {
-                    AddGraphIssue(issues, $"Agent node \"{node.Id}\" must reference a known agent.");
-                }
-
-                if (!string.IsNullOrWhiteSpace(node.AgentId) && !seenAgentIds.Add(node.AgentId))
-                {
-                    AddGraphIssue(issues, $"Pattern graph contains multiple nodes for agent \"{node.AgentId}\".");
-                }
-
-                if (!node.Order.HasValue)
-                {
-                    AddGraphIssue(issues, $"Agent node \"{node.Id}\" must define an order.");
-                }
-                else if (!seenAgentOrders.Add(node.Order.Value))
-                {
-                    AddGraphIssue(issues, $"Pattern graph contains duplicate agent order \"{node.Order.Value}\".");
-                }
-            }
-            else if (!string.IsNullOrWhiteSpace(node.AgentId))
-            {
-                AddGraphIssue(issues, $"System node \"{node.Id}\" cannot reference an agent.");
-            }
-        }
-
-        foreach (PatternAgentDefinitionDto agent in pattern.Agents)
-        {
-            if (!seenAgentIds.Contains(agent.Id))
-            {
-                AddGraphIssue(issues, $"Pattern graph is missing node metadata for agent \"{agent.Id}\".");
-            }
-        }
-
-        foreach (PatternGraphEdgeDto edge in graph.Edges)
-        {
-            if (!edgeIds.Add(edge.Id))
-            {
-                AddGraphIssue(issues, $"Pattern graph contains duplicate edge \"{edge.Id}\".");
-            }
-
-            if (!nodesById.ContainsKey(edge.Source) || !nodesById.ContainsKey(edge.Target))
-            {
-                AddGraphIssue(issues, $"Pattern graph edge \"{edge.Id}\" must connect known nodes.");
-            }
-        }
-
-        switch (pattern.Mode)
-        {
-            case "single":
-            case "sequential":
-            case "magentic":
-                ValidateLinearGraph(pattern, graph, issues);
-                break;
-            case "concurrent":
-                ValidateConcurrentGraph(pattern, graph, issues);
-                break;
-            case "handoff":
-                ValidateHandoffGraph(graph, issues);
-                break;
-            case "group-chat":
-                ValidateGroupChatGraph(pattern, graph, issues);
-                break;
-        }
-    }
-
-    private static void ValidateLinearGraph(
-        PatternDefinitionDto pattern,
-        PatternGraphDto graph,
-        List<PatternValidationIssueDto> issues)
-    {
-        ValidateSystemNodeCounts(graph, ["user-input", "user-output"], issues);
-        PatternGraphNodeDto? inputNode = GetNodeByKind(graph, "user-input");
-        PatternGraphNodeDto? outputNode = GetNodeByKind(graph, "user-output");
-        if (inputNode is null || outputNode is null)
-        {
-            return;
-        }
-
-        Dictionary<string, List<PatternGraphEdgeDto>> incoming = BuildIncomingLookup(graph);
-        Dictionary<string, List<PatternGraphEdgeDto>> outgoing = BuildOutgoingLookup(graph);
-        List<PatternGraphNodeDto> agentNodes = GetAgentNodes(graph);
-
-        if (graph.Edges.Count != pattern.Agents.Count + 1)
-        {
-            AddGraphIssue(issues, "Linear orchestration graphs must be a single path from user input through every agent to user output.");
-        }
-
-        if (incoming.GetValueOrDefault(inputNode.Id, []).Count != 0 || outgoing.GetValueOrDefault(inputNode.Id, []).Count != 1)
-        {
-            AddGraphIssue(issues, "User input must start exactly one path.");
-        }
-
-        if (incoming.GetValueOrDefault(outputNode.Id, []).Count != 1 || outgoing.GetValueOrDefault(outputNode.Id, []).Count != 0)
-        {
-            AddGraphIssue(issues, "User output must terminate exactly one path.");
-        }
-
-        foreach (PatternGraphNodeDto node in agentNodes)
-        {
-            if (incoming.GetValueOrDefault(node.Id, []).Count != 1 || outgoing.GetValueOrDefault(node.Id, []).Count != 1)
-            {
-                AddGraphIssue(issues, "Each agent in a linear orchestration must have exactly one incoming and one outgoing edge.");
-                break;
-            }
-        }
-
-        HashSet<string> visited = new(StringComparer.Ordinal);
-        string currentNodeId = inputNode.Id;
-        while (visited.Add(currentNodeId))
-        {
-            List<PatternGraphEdgeDto> nextEdges = outgoing.GetValueOrDefault(currentNodeId, []);
-            if (nextEdges.Count == 0)
-            {
-                break;
-            }
-
-            if (nextEdges.Count != 1)
-            {
-                AddGraphIssue(issues, "Linear orchestration nodes may only branch to one next step.");
-                break;
-            }
-
-            currentNodeId = nextEdges[0].Target;
-            if (Comparer.Equals(currentNodeId, outputNode.Id))
-            {
-                visited.Add(currentNodeId);
-                break;
-            }
-        }
-
-        HashSet<string> expectedVisited = new(StringComparer.Ordinal)
-        {
-            inputNode.Id,
-            outputNode.Id
-        };
-        foreach (PatternGraphNodeDto node in agentNodes)
-        {
-            expectedVisited.Add(node.Id);
-        }
-
-        if (!expectedVisited.SetEquals(visited))
-        {
-            AddGraphIssue(issues, "Linear orchestration graphs must visit every agent exactly once.");
-        }
-    }
-
-    private static void ValidateConcurrentGraph(
-        PatternDefinitionDto pattern,
-        PatternGraphDto graph,
-        List<PatternValidationIssueDto> issues)
-    {
-        ValidateSystemNodeCounts(graph, ["user-input", "distributor", "collector", "user-output"], issues);
-        PatternGraphNodeDto? inputNode = GetNodeByKind(graph, "user-input");
-        PatternGraphNodeDto? distributorNode = GetNodeByKind(graph, "distributor");
-        PatternGraphNodeDto? collectorNode = GetNodeByKind(graph, "collector");
-        PatternGraphNodeDto? outputNode = GetNodeByKind(graph, "user-output");
-        if (inputNode is null || distributorNode is null || collectorNode is null || outputNode is null)
-        {
-            return;
-        }
-
-        Dictionary<string, List<PatternGraphEdgeDto>> incoming = BuildIncomingLookup(graph);
-        Dictionary<string, List<PatternGraphEdgeDto>> outgoing = BuildOutgoingLookup(graph);
-        List<PatternGraphNodeDto> agentNodes = GetAgentNodes(graph);
-        HashSet<string> distributorTargets = outgoing.GetValueOrDefault(distributorNode.Id, []).Select(edge => edge.Target).ToHashSet(StringComparer.Ordinal);
-        HashSet<string> collectorSources = incoming.GetValueOrDefault(collectorNode.Id, []).Select(edge => edge.Source).ToHashSet(StringComparer.Ordinal);
-
-        if (graph.Edges.Count != pattern.Agents.Count * 2 + 2)
-        {
-            AddGraphIssue(issues, "Concurrent orchestration graphs must fan out from the distributor and fan back into the collector.");
-        }
-
-        if (incoming.GetValueOrDefault(inputNode.Id, []).Count != 0 || outgoing.GetValueOrDefault(inputNode.Id, []).Count != 1)
-        {
-            AddGraphIssue(issues, "User input must connect only to the distributor.");
-        }
-
-        if (incoming.GetValueOrDefault(distributorNode.Id, []).Count != 1)
-        {
-            AddGraphIssue(issues, "Distributor must receive exactly one edge from user input.");
-        }
-
-        if (outgoing.GetValueOrDefault(collectorNode.Id, []).Count != 1 || incoming.GetValueOrDefault(outputNode.Id, []).Count != 1)
-        {
-            AddGraphIssue(issues, "Collector must forward exactly one edge to user output.");
-        }
-
-        foreach (PatternGraphNodeDto agentNode in agentNodes)
-        {
-            if (!distributorTargets.Contains(agentNode.Id))
-            {
-                AddGraphIssue(issues, $"Distributor must connect to agent \"{agentNode.AgentId}\".");
-            }
-
-            if (!collectorSources.Contains(agentNode.Id))
-            {
-                AddGraphIssue(issues, $"Agent \"{agentNode.AgentId}\" must connect to the collector.");
-            }
-        }
-    }
-
-    private static void ValidateHandoffGraph(
-        PatternGraphDto graph,
-        List<PatternValidationIssueDto> issues)
-    {
-        ValidateSystemNodeCounts(graph, ["user-input", "user-output"], issues);
-        PatternGraphNodeDto? inputNode = GetNodeByKind(graph, "user-input");
-        PatternGraphNodeDto? outputNode = GetNodeByKind(graph, "user-output");
-        if (inputNode is null || outputNode is null)
-        {
-            return;
-        }
-
-        Dictionary<string, List<PatternGraphEdgeDto>> incoming = BuildIncomingLookup(graph);
-        Dictionary<string, List<PatternGraphEdgeDto>> outgoing = BuildOutgoingLookup(graph);
-        List<PatternGraphNodeDto> agentNodes = GetAgentNodes(graph);
-        HashSet<string> agentNodeIds = agentNodes.Select(node => node.Id).ToHashSet(StringComparer.Ordinal);
-        List<PatternGraphEdgeDto> entryEdges = outgoing.GetValueOrDefault(inputNode.Id, []);
-        List<PatternGraphEdgeDto> completionEdges = incoming.GetValueOrDefault(outputNode.Id, []);
-
-        if (entryEdges.Count != 1)
-        {
-            AddGraphIssue(issues, "Handoff graphs must connect user input to exactly one entry agent.");
-            return;
-        }
-
-        if (!agentNodeIds.Contains(entryEdges[0].Target))
-        {
-            AddGraphIssue(issues, "Handoff entry edges must target an agent node.");
-        }
-
-        if (completionEdges.Count == 0)
-        {
-            AddGraphIssue(issues, "Handoff graphs must allow at least one agent to complete back to user output.");
-        }
-
-        bool hasAgentToAgentRoute = false;
-        foreach (PatternGraphEdgeDto edge in graph.Edges)
-        {
-            if (Comparer.Equals(edge.Source, inputNode.Id))
-            {
-                continue;
-            }
-
-            if (Comparer.Equals(edge.Target, outputNode.Id))
-            {
-                if (!agentNodeIds.Contains(edge.Source))
-                {
-                    AddGraphIssue(issues, "Only agent nodes may complete to user output.");
-                }
-                continue;
-            }
-
-            if (!agentNodeIds.Contains(edge.Source) || !agentNodeIds.Contains(edge.Target))
-            {
-                AddGraphIssue(issues, "Handoff routes may only connect agents to agents or agents to user output.");
-                continue;
-            }
-
-            if (Comparer.Equals(edge.Source, edge.Target))
-            {
-                AddGraphIssue(issues, "Handoff routes cannot target the same agent node.");
-            }
-
-            hasAgentToAgentRoute = true;
-        }
-
-        if (!hasAgentToAgentRoute && agentNodes.Count > 1)
-        {
-            AddGraphIssue(issues, "Handoff graphs must include at least one agent-to-agent handoff route.");
-        }
-
-        HashSet<string> reachable = new(StringComparer.Ordinal);
-        Stack<string> stack = new Stack<string>([entryEdges[0].Target]);
-        while (stack.Count > 0)
-        {
-            string nodeId = stack.Pop();
-            if (!reachable.Add(nodeId))
-            {
-                continue;
-            }
-
-            foreach (PatternGraphEdgeDto edge in outgoing.GetValueOrDefault(nodeId, []))
-            {
-                if (agentNodeIds.Contains(edge.Target) && !reachable.Contains(edge.Target))
-                {
-                    stack.Push(edge.Target);
-                }
-            }
-        }
-
-        foreach (PatternGraphNodeDto agentNode in agentNodes)
-        {
-            if (!reachable.Contains(agentNode.Id))
-            {
-                AddGraphIssue(issues, $"Handoff entry agent must be able to reach \"{agentNode.AgentId}\".");
-            }
-        }
-
-        if (incoming.GetValueOrDefault(inputNode.Id, []).Count != 0 || outgoing.GetValueOrDefault(outputNode.Id, []).Count != 0)
-        {
-            AddGraphIssue(issues, "User input cannot have incoming edges and user output cannot have outgoing edges.");
-        }
-    }
-
-    private static void ValidateGroupChatGraph(
-        PatternDefinitionDto pattern,
-        PatternGraphDto graph,
-        List<PatternValidationIssueDto> issues)
-    {
-        ValidateSystemNodeCounts(graph, ["user-input", "orchestrator", "user-output"], issues);
-        PatternGraphNodeDto? inputNode = GetNodeByKind(graph, "user-input");
-        PatternGraphNodeDto? orchestratorNode = GetNodeByKind(graph, "orchestrator");
-        PatternGraphNodeDto? outputNode = GetNodeByKind(graph, "user-output");
-        if (inputNode is null || orchestratorNode is null || outputNode is null)
-        {
-            return;
-        }
-
-        Dictionary<string, List<PatternGraphEdgeDto>> incoming = BuildIncomingLookup(graph);
-        Dictionary<string, List<PatternGraphEdgeDto>> outgoing = BuildOutgoingLookup(graph);
-        List<PatternGraphNodeDto> agentNodes = GetAgentNodes(graph);
-        HashSet<string> orchestratorTargets = outgoing.GetValueOrDefault(orchestratorNode.Id, []).Select(edge => edge.Target).ToHashSet(StringComparer.Ordinal);
-        HashSet<string> orchestratorSources = incoming.GetValueOrDefault(orchestratorNode.Id, []).Select(edge => edge.Source).ToHashSet(StringComparer.Ordinal);
-
-        if (graph.Edges.Count != pattern.Agents.Count * 2 + 2)
-        {
-            AddGraphIssue(issues, "Group chat graphs must connect the orchestrator to every participant and then back to user output.");
-        }
-
-        if (outgoing.GetValueOrDefault(inputNode.Id, []).Any(edge => !Comparer.Equals(edge.Target, orchestratorNode.Id)))
-        {
-            AddGraphIssue(issues, "User input must only connect to the orchestrator.");
-        }
-
-        if (!outgoing.GetValueOrDefault(orchestratorNode.Id, []).Any(edge => Comparer.Equals(edge.Target, outputNode.Id)))
-        {
-            AddGraphIssue(issues, "Group chat orchestrator must connect to user output.");
-        }
-
-        foreach (PatternGraphNodeDto agentNode in agentNodes)
-        {
-            if (!orchestratorTargets.Contains(agentNode.Id))
-            {
-                AddGraphIssue(issues, $"Orchestrator must connect to agent \"{agentNode.AgentId}\".");
-            }
-
-            if (!orchestratorSources.Contains(agentNode.Id))
-            {
-                AddGraphIssue(issues, $"Agent \"{agentNode.AgentId}\" must connect back to the orchestrator.");
-            }
-        }
-    }
-
-    private static void ValidateSystemNodeCounts(
-        PatternGraphDto graph,
-        IReadOnlyList<string> expectedKinds,
-        List<PatternValidationIssueDto> issues)
-    {
-        Dictionary<string, int> counts = graph.Nodes
-            .GroupBy(node => node.Kind, Comparer)
-            .ToDictionary(group => group.Key, group => group.Count(), Comparer);
-        HashSet<string> expected = expectedKinds.ToHashSet(Comparer);
-
-        foreach (string kind in expectedKinds)
-        {
-            if (counts.GetValueOrDefault(kind, 0) != 1)
-            {
-                AddGraphIssue(issues, $"Pattern graph must include exactly one \"{kind}\" node.");
-            }
-        }
-
-        foreach ((string kind, int count) in counts)
-        {
-            if (Comparer.Equals(kind, "agent"))
-            {
-                continue;
-            }
-
-            if (!expected.Contains(kind) && count > 0)
-            {
-                AddGraphIssue(issues, $"Pattern graph does not allow \"{kind}\" nodes in this mode.");
-            }
-        }
-    }
-
-    private static PatternGraphNodeDto? GetNodeByKind(PatternGraphDto graph, string kind)
-        => graph.Nodes.FirstOrDefault(node => Comparer.Equals(node.Kind, kind));
-
-    private static List<PatternGraphNodeDto> GetAgentNodes(PatternGraphDto graph)
-        => graph.Nodes.Where(node => Comparer.Equals(node.Kind, "agent")).ToList();
-
-    private static Dictionary<string, List<PatternGraphEdgeDto>> BuildIncomingLookup(PatternGraphDto graph)
-    {
-        Dictionary<string, List<PatternGraphEdgeDto>> incoming = new(StringComparer.Ordinal);
-        foreach (PatternGraphNodeDto node in graph.Nodes)
-        {
-            incoming[node.Id] = [];
-        }
-
-        foreach (PatternGraphEdgeDto edge in graph.Edges)
-        {
-            if (!incoming.TryGetValue(edge.Target, out List<PatternGraphEdgeDto>? edges))
-            {
-                edges = [];
-                incoming[edge.Target] = edges;
-            }
-
-            edges.Add(edge);
-        }
-
-        return incoming;
-    }
-
-    private static Dictionary<string, List<PatternGraphEdgeDto>> BuildOutgoingLookup(PatternGraphDto graph)
-    {
-        Dictionary<string, List<PatternGraphEdgeDto>> outgoing = new(StringComparer.Ordinal);
-        foreach (PatternGraphNodeDto node in graph.Nodes)
-        {
-            outgoing[node.Id] = [];
-        }
-
-        foreach (PatternGraphEdgeDto edge in graph.Edges)
-        {
-            if (!outgoing.TryGetValue(edge.Source, out List<PatternGraphEdgeDto>? edges))
-            {
-                edges = [];
-                outgoing[edge.Source] = edges;
-            }
-
-            edges.Add(edge);
-        }
-
-        return outgoing;
-    }
-
-    private static void AddGraphIssue(List<PatternValidationIssueDto> issues, string message)
-        => issues.Add(new PatternValidationIssueDto
-        {
-            Field = "graph",
-            Message = message,
-        });
-}

sidecar/src/Aryx.AgentHost/Services/SidecarProtocolHost.cs

@@ -10,7 +10,6 @@ namespace Aryx.AgentHost.Services;
 public sealed class SidecarProtocolHost
 {
     private const string DescribeCapabilitiesCommandType = "describe-capabilities";
-    private const string ValidatePatternCommandType = "validate-pattern";
     private const string ValidateWorkflowCommandType = "validate-workflow";
     private const string RunTurnCommandType = "run-turn";
     private const string CancelTurnCommandType = "cancel-turn";
@@ -42,7 +41,6 @@ public sealed class SidecarProtocolHost
     ];
 
     private readonly Func<CancellationToken, Task<SidecarCapabilitiesDto>> _capabilitiesProvider;
-    private readonly PatternValidator _patternValidator;
     private readonly WorkflowValidator _workflowValidator;
     private readonly ITurnWorkflowRunner _workflowRunner;
     private readonly ICopilotSessionManager _sessionManager;
@@ -55,29 +53,26 @@ public sealed class SidecarProtocolHost
         new(StringComparer.Ordinal);
 
     public SidecarProtocolHost()
-        : this(new PatternValidator(), new WorkflowValidator())
+        : this(new WorkflowValidator())
     {
     }
 
     public SidecarProtocolHost(
-        PatternValidator patternValidator,
         ITurnWorkflowRunner? workflowRunner = null,
         Func<CancellationToken, Task<SidecarCapabilitiesDto>>? capabilitiesProvider = null,
         ICopilotSessionManager? sessionManager = null)
-        : this(patternValidator, new WorkflowValidator(), workflowRunner, capabilitiesProvider, sessionManager)
+        : this(new WorkflowValidator(), workflowRunner, capabilitiesProvider, sessionManager)
     {
     }
 
     public SidecarProtocolHost(
-        PatternValidator patternValidator,
         WorkflowValidator workflowValidator,
         ITurnWorkflowRunner? workflowRunner = null,
         Func<CancellationToken, Task<SidecarCapabilitiesDto>>? capabilitiesProvider = null,
         ICopilotSessionManager? sessionManager = null)
     {
-        _patternValidator = patternValidator;
         _workflowValidator = workflowValidator;
-        _workflowRunner = workflowRunner ?? new CopilotWorkflowRunner(_patternValidator, _workflowValidator);
+        _workflowRunner = workflowRunner ?? new CopilotWorkflowRunner(_workflowValidator);
         _capabilitiesProvider = capabilitiesProvider ?? BuildCapabilitiesAsync;
         _sessionManager = sessionManager ?? new CopilotSessionManager();
         _jsonOptions = JsonSerialization.CreateWebOptions();
@@ -86,7 +81,6 @@ public sealed class SidecarProtocolHost
         _commandHandlers = new Dictionary<string, Func<CommandContext, Task>>(StringComparer.Ordinal)
         {
             [DescribeCapabilitiesCommandType] = HandleDescribeCapabilitiesAsync,
-            [ValidatePatternCommandType] = HandleValidatePatternAsync,
             [ValidateWorkflowCommandType] = HandleValidateWorkflowAsync,
             [RunTurnCommandType] = HandleRunTurnAsync,
             [CancelTurnCommandType] = HandleCancelTurnAsync,
@@ -182,18 +176,6 @@ public sealed class SidecarProtocolHost
         }, context.CancellationToken).ConfigureAwait(false);
     }
 
-    private async Task HandleValidatePatternAsync(CommandContext context)
-    {
-        ValidatePatternCommandDto command = DeserializeCommand<ValidatePatternCommandDto>(context);
-
-        await WriteAsync(context.Output, new PatternValidationEventDto
-        {
-            Type = "pattern-validation",
-            RequestId = context.Envelope.RequestId,
-            Issues = _patternValidator.Validate(command.Pattern),
-        }, context.CancellationToken).ConfigureAwait(false);
-    }
-
     private async Task HandleValidateWorkflowAsync(CommandContext context)
     {
         ValidateWorkflowCommandDto command = DeserializeCommand<ValidateWorkflowCommandDto>(context);

sidecar/src/Aryx.AgentHost/Services/WorkflowDefinitionExtensions.cs

@@ -0,0 +1,54 @@
+using Aryx.AgentHost.Contracts;
+
+namespace Aryx.AgentHost.Services;
+
+internal static class WorkflowDefinitionExtensions
+{
+    public static IReadOnlyList<WorkflowNodeDto> GetAgentNodes(this WorkflowDefinitionDto workflow)
+    {
+        ArgumentNullException.ThrowIfNull(workflow);
+
+        return workflow.Graph.Nodes
+            .Where(IsAgentNode)
+            .ToList();
+    }
+
+    public static bool IsAgentNode(this WorkflowNodeDto node)
+    {
+        ArgumentNullException.ThrowIfNull(node);
+        return string.Equals(node.Kind, "agent", StringComparison.OrdinalIgnoreCase);
+    }
+
+    public static string GetAgentId(this WorkflowNodeDto node)
+    {
+        ArgumentNullException.ThrowIfNull(node);
+        return !string.IsNullOrWhiteSpace(node.Config.Id) ? node.Config.Id : node.Id;
+    }
+
+    public static string GetAgentName(this WorkflowNodeDto node)
+    {
+        ArgumentNullException.ThrowIfNull(node);
+        return FirstNonBlank(node.Config.Name, node.Label, node.Id) ?? "agent";
+    }
+
+    public static bool IsOrchestrationMode(this WorkflowDefinitionDto workflow, string mode)
+    {
+        ArgumentNullException.ThrowIfNull(workflow);
+        ArgumentException.ThrowIfNullOrWhiteSpace(mode);
+
+        return string.Equals(workflow.Settings.OrchestrationMode, mode, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static string? FirstNonBlank(params string?[] values)
+    {
+        foreach (string? value in values)
+        {
+            if (!string.IsNullOrWhiteSpace(value))
+            {
+                return value.Trim();
+            }
+        }
+
+        return null;
+    }
+}

sidecar/src/Aryx.AgentHost/Services/WorkflowRequestInfoInterpreter.cs

@@ -20,7 +20,7 @@ internal static class WorkflowRequestInfoInterpreter
         AgentIdentity? activeAgent,
         ConcurrentDictionary<string, string> toolNamesByCallId)
     {
-        RequestInterpretation interpretation = InterpretRequest(command.Pattern, requestInfo);
+        RequestInterpretation interpretation = InterpretRequest(command.Workflow, requestInfo);
         return interpretation switch
         {
             HandoffRequestInterpretation handoff =>
@@ -35,8 +35,8 @@ internal static class WorkflowRequestInfoInterpreter
         RunTurnCommandDto command,
         RequestInfoEvent requestInfo)
     {
-        return string.Equals(command.Pattern.Mode, "handoff", StringComparison.OrdinalIgnoreCase)
-            && InterpretRequest(command.Pattern, requestInfo) is UnknownRequestInterpretation;
+        return command.Workflow.IsOrchestrationMode("handoff")
+            && InterpretRequest(command.Workflow, requestInfo) is UnknownRequestInterpretation;
     }
 
     private static AgentActivityEventDto CreateHandoffActivity(
@@ -95,10 +95,10 @@ internal static class WorkflowRequestInfoInterpreter
     }
 
     private static RequestInterpretation InterpretRequest(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         RequestInfoEvent requestInfo)
     {
-        if (TryGetHandoffTarget(pattern, requestInfo, out AgentIdentity handoffAgent))
+        if (TryGetHandoffTarget(workflow, requestInfo, out AgentIdentity handoffAgent))
         {
             return new HandoffRequestInterpretation(handoffAgent);
         }
@@ -109,7 +109,7 @@ internal static class WorkflowRequestInfoInterpreter
     }
 
     private static bool TryGetHandoffTarget(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         RequestInfoEvent requestInfo,
         out AgentIdentity agent)
     {
@@ -128,7 +128,7 @@ internal static class WorkflowRequestInfoInterpreter
         }
 
         agent = AgentIdentityResolver.ResolveAgentIdentity(
-            pattern,
+            workflow,
             target.Id,
             target.Name);
         return !string.IsNullOrWhiteSpace(agent.AgentName);

sidecar/src/Aryx.AgentHost/Services/WorkflowRunner.cs

@@ -8,12 +8,10 @@ internal sealed class WorkflowRunner
 {
     public Workflow BuildWorkflow(
         WorkflowDefinitionDto workflowDefinition,
-        PatternDefinitionDto patternDefinition,
         IReadOnlyList<AIAgent> agents,
         IReadOnlyList<WorkflowDefinitionDto>? workflowLibrary = null)
     {
         ArgumentNullException.ThrowIfNull(workflowDefinition);
-        ArgumentNullException.ThrowIfNull(patternDefinition);
         ArgumentNullException.ThrowIfNull(agents);
 
         Dictionary<string, WorkflowDefinitionDto> workflowLibraryMap = workflowLibrary?
@@ -22,9 +20,10 @@ internal sealed class WorkflowRunner
             .ToDictionary(group => group.Key, group => group.Last(), StringComparer.Ordinal)
             ?? new Dictionary<string, WorkflowDefinitionDto>(StringComparer.Ordinal);
 
-        Dictionary<string, AIAgent> agentMap = patternDefinition.Agents
-            .Zip(agents, (definition, agent) => (definition.Id, agent))
-            .ToDictionary(pair => pair.Id, pair => pair.agent, StringComparer.Ordinal);
+        List<string> agentIds = ResolveAgentIds(workflowDefinition, workflowLibraryMap);
+        Dictionary<string, AIAgent> agentMap = agentIds
+            .Zip(agents, (agentId, agent) => (agentId, agent))
+            .ToDictionary(pair => pair.agentId, pair => pair.agent, StringComparer.Ordinal);
 
         return BuildWorkflow(workflowDefinition, agentMap, workflowLibraryMap);
     }
@@ -222,6 +221,47 @@ internal sealed class WorkflowRunner
     private static string? NormalizeOptionalString(string? value)
         => string.IsNullOrWhiteSpace(value) ? null : value.Trim();
 
+    private static List<string> ResolveAgentIds(
+        WorkflowDefinitionDto workflowDefinition,
+        IReadOnlyDictionary<string, WorkflowDefinitionDto> workflowLibrary)
+    {
+        List<string> agentIds = [];
+        CollectAgentIds(workflowDefinition, workflowLibrary, agentIds, new HashSet<string>(StringComparer.Ordinal));
+        return agentIds;
+    }
+
+    private static void CollectAgentIds(
+        WorkflowDefinitionDto workflowDefinition,
+        IReadOnlyDictionary<string, WorkflowDefinitionDto> workflowLibrary,
+        List<string> agentIds,
+        ISet<string> visitedWorkflowIds)
+    {
+        string workflowKey = string.IsNullOrWhiteSpace(workflowDefinition.Id)
+            ? Guid.NewGuid().ToString("N")
+            : workflowDefinition.Id;
+        if (!visitedWorkflowIds.Add(workflowKey))
+        {
+            return;
+        }
+
+        foreach (WorkflowNodeDto node in workflowDefinition.Graph.Nodes)
+        {
+            if (string.Equals(node.Kind, "agent", StringComparison.OrdinalIgnoreCase))
+            {
+                agentIds.Add(!string.IsNullOrWhiteSpace(node.Config.Id) ? node.Config.Id : node.Id);
+                continue;
+            }
+
+            if (!string.Equals(node.Kind, "sub-workflow", StringComparison.OrdinalIgnoreCase))
+            {
+                continue;
+            }
+
+            WorkflowDefinitionDto subWorkflow = ResolveSubWorkflowDefinition(node, workflowLibrary);
+            CollectAgentIds(subWorkflow, workflowLibrary, agentIds, visitedWorkflowIds);
+        }
+    }
+
     private sealed record WorkflowNodeRoute(
         ExecutorBinding Entry,
         ExecutorBinding Exit,

sidecar/src/Aryx.AgentHost/Services/WorkflowTranscriptProjector.cs

@@ -73,7 +73,7 @@ internal static class WorkflowTranscriptProjector
         List<ChatMessageDto> projectedMessages = [];
         int fallbackOutputIndex = 0;
         string createdAt = DateTimeOffset.UtcNow.ToString("O");
-        List<TranscriptSegment> preparedSegments = PrepareSegmentsForProjection(command.Pattern, segments);
+        List<TranscriptSegment> preparedSegments = PrepareSegmentsForProjection(command.Workflow, segments);
         List<TranscriptSegment> remainingSegments = preparedSegments.ToList();
         List<ChatMessage> assistantMessages = newMessages.Where(message => message.Role != ChatRole.User).ToList();
 
@@ -84,7 +84,7 @@ internal static class WorkflowTranscriptProjector
                 message,
                 remainingSegments,
                 assistantMessages.Count - messageIndex,
-                command.Pattern,
+                command.Workflow,
                 fallbackAgent);
             string content = ResolveProjectedContent(message, matchedSegment);
             if (string.IsNullOrWhiteSpace(content))
@@ -133,7 +133,7 @@ internal static class WorkflowTranscriptProjector
                 ?? $"{command.RequestId}-final-{fallbackOutputIndex}",
             Role = message.Role == ChatRole.System ? "system" : "assistant",
             AuthorName = ResolveProjectedAuthorName(
-                command.Pattern,
+                command.Workflow,
                 message.AuthorName,
                 matchedSegment?.AuthorName,
                 fallbackAgent),
@@ -180,17 +180,17 @@ internal static class WorkflowTranscriptProjector
         {
             Id = segment.MessageId,
             Role = "assistant",
-            AuthorName = AgentIdentityResolver.ResolveDisplayAuthorName(command.Pattern, segment.AuthorName),
+            AuthorName = AgentIdentityResolver.ResolveDisplayAuthorName(command.Workflow, segment.AuthorName),
             Content = segment.Content,
             CreatedAt = createdAt,
         };
     }
 
     private static List<TranscriptSegment> PrepareSegmentsForProjection(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         IReadOnlyList<TranscriptSegment> segments)
     {
-        if (!string.Equals(pattern.Mode, "concurrent", StringComparison.Ordinal)
+        if (!workflow.IsOrchestrationMode("concurrent")
             || segments.Count <= 1)
         {
             return segments.ToList();
@@ -205,7 +205,7 @@ internal static class WorkflowTranscriptProjector
         for (int index = 0; index < segments.Count; index++)
         {
             TranscriptSegment segment = segments[index];
-            string authorKey = AgentIdentityResolver.ResolveDisplayAuthorName(pattern, segment.AuthorName);
+            string authorKey = AgentIdentityResolver.ResolveDisplayAuthorName(workflow, segment.AuthorName);
             latestSegmentByAuthor[authorKey] = (segment, index);
         }
 
@@ -219,7 +219,7 @@ internal static class WorkflowTranscriptProjector
         ChatMessage message,
         IReadOnlyList<TranscriptSegment> remainingSegments,
         int remainingMessageCount,
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         AgentIdentity? fallbackAgent)
     {
         if (remainingSegments.Count == 0)
@@ -231,7 +231,7 @@ internal static class WorkflowTranscriptProjector
         if (messageText is not null)
         {
             string resolvedAuthorName = ResolveProjectedAuthorName(
-                pattern,
+                workflow,
                 message.AuthorName,
                 fallbackIdentifier: null,
                 fallbackAgent);
@@ -240,7 +240,7 @@ internal static class WorkflowTranscriptProjector
                     remainingSegments,
                     segment => string.Equals(segment.Content, messageText, StringComparison.Ordinal)
                         && string.Equals(
-                            AgentIdentityResolver.ResolveDisplayAuthorName(pattern, segment.AuthorName),
+                            AgentIdentityResolver.ResolveDisplayAuthorName(workflow, segment.AuthorName),
                             resolvedAuthorName,
                             StringComparison.Ordinal),
                     out TranscriptSegment authorMatchedSegment))
@@ -264,7 +264,7 @@ internal static class WorkflowTranscriptProjector
                 && TryFindLastSegment(
                     remainingSegments,
                     segment => string.Equals(
-                        AgentIdentityResolver.ResolveDisplayAuthorName(pattern, segment.AuthorName),
+                        AgentIdentityResolver.ResolveDisplayAuthorName(workflow, segment.AuthorName),
                         fallbackAgent.Value.AgentName,
                         StringComparison.Ordinal),
                     out TranscriptSegment fallbackMatchedSegment))
@@ -382,7 +382,7 @@ internal static class WorkflowTranscriptProjector
     }
 
     private static string ResolveProjectedAuthorName(
-        PatternDefinitionDto pattern,
+        WorkflowDefinitionDto workflow,
         string? primaryIdentifier,
         string? fallbackIdentifier,
         AgentIdentity? fallbackAgent)
@@ -399,16 +399,17 @@ internal static class WorkflowTranscriptProjector
             return fallbackAgent.Value.AgentName;
         }
 
-        if (pattern.Agents.Count == 1
+        IReadOnlyList<WorkflowNodeDto> agentNodes = workflow.GetAgentNodes();
+        if (agentNodes.Count == 1
             && string.IsNullOrWhiteSpace(primaryIdentifier)
             && string.IsNullOrWhiteSpace(fallbackIdentifier))
         {
-            PatternAgentDefinitionDto singleAgent = pattern.Agents[0];
-            return AgentIdentityResolver.ResolveDisplayAuthorName(pattern, singleAgent.Id, singleAgent.Name);
+            WorkflowNodeDto singleAgent = agentNodes[0];
+            return AgentIdentityResolver.ResolveDisplayAuthorName(workflow, singleAgent.GetAgentId(), singleAgent.GetAgentName());
         }
 
         return AgentIdentityResolver.ResolveDisplayAuthorName(
-            pattern,
+            workflow,
             primaryIdentifier,
             fallbackIdentifier);
     }

sidecar/tests/Aryx.AgentHost.Tests/AgentIdentityResolverTests.cs

@@ -8,14 +8,14 @@ public sealed class AgentIdentityResolverTests
     [Fact]
     public void TryResolveKnownAgentIdentity_MatchesRuntimeExecutorIdentifier()
     {
-        PatternDefinitionDto pattern = CreatePattern(
+        WorkflowDefinitionDto workflow = CreateWorkflow(
         [
-            CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
-            CreateAgent(id: "agent-concurrent-product", name: "Product"),
+            CreateAgent("agent-concurrent-architect", "Architect"),
+            CreateAgent("agent-concurrent-product", "Product"),
         ]);
 
         bool resolved = AgentIdentityResolver.TryResolveKnownAgentIdentity(
-            pattern,
+            workflow,
             "Architect_agent_concurrent_architect",
             out AgentIdentity agent);
 
@@ -27,14 +27,14 @@ public sealed class AgentIdentityResolverTests
     [Fact]
     public void TryResolveKnownAgentIdentity_MatchesSanitizedNameAndId()
     {
-        PatternDefinitionDto pattern = CreatePattern(
+        WorkflowDefinitionDto workflow = CreateWorkflow(
         [
-            CreateAgent(id: "agent-single-primary", name: "Primary Agent"),
+            CreateAgent("agent-single-primary", "Primary Agent"),
         ],
-        mode: "single");
+        orchestrationMode: "single");
 
         bool resolved = AgentIdentityResolver.TryResolveKnownAgentIdentity(
-            pattern,
+            workflow,
             "Primary_Agent_agent_single_primary",
             out AgentIdentity agent);
 
@@ -46,14 +46,14 @@ public sealed class AgentIdentityResolverTests
     [Fact]
     public void TryResolveKnownAgentIdentity_MapsAssistantToSingleAgent()
     {
-        PatternDefinitionDto pattern = CreatePattern(
+        WorkflowDefinitionDto workflow = CreateWorkflow(
         [
-            CreateAgent(id: "agent-single-primary", name: "Primary Agent"),
+            CreateAgent("agent-single-primary", "Primary Agent"),
         ],
-        mode: "single");
+        orchestrationMode: "single");
 
         bool resolved = AgentIdentityResolver.TryResolveKnownAgentIdentity(
-            pattern,
+            workflow,
             "assistant",
             out AgentIdentity agent);
 
@@ -63,16 +63,16 @@ public sealed class AgentIdentityResolverTests
     }
 
     [Fact]
-    public void TryResolveKnownAgentIdentity_DoesNotGuessAssistantForMultiAgentPattern()
+    public void TryResolveKnownAgentIdentity_DoesNotGuessAssistantForMultiAgentWorkflow()
     {
-        PatternDefinitionDto pattern = CreatePattern(
+        WorkflowDefinitionDto workflow = CreateWorkflow(
         [
-            CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
-            CreateAgent(id: "agent-concurrent-product", name: "Product"),
+            CreateAgent("agent-concurrent-architect", "Architect"),
+            CreateAgent("agent-concurrent-product", "Product"),
         ]);
 
         bool resolved = AgentIdentityResolver.TryResolveKnownAgentIdentity(
-            pattern,
+            workflow,
             "assistant",
             out _);
 
@@ -82,14 +82,14 @@ public sealed class AgentIdentityResolverTests
     [Fact]
     public void ResolveDisplayAuthorName_UsesCanonicalAgentName()
     {
-        PatternDefinitionDto pattern = CreatePattern(
+        WorkflowDefinitionDto workflow = CreateWorkflow(
         [
-            CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"),
+            CreateAgent("agent-concurrent-implementer", "Implementer"),
         ],
-        mode: "single");
+        orchestrationMode: "single");
 
         string authorName = AgentIdentityResolver.ResolveDisplayAuthorName(
-            pattern,
+            workflow,
             "Implementer_agent_concurrent_implementer");
 
         Assert.Equal("Implementer", authorName);
@@ -98,14 +98,14 @@ public sealed class AgentIdentityResolverTests
     [Fact]
     public void TryResolveObservedAgentIdentity_UsesFallbackAgentForGenericAssistant()
     {
-        PatternDefinitionDto pattern = CreatePattern(
+        WorkflowDefinitionDto workflow = CreateWorkflow(
         [
-            CreateAgent(id: "agent-handoff-ux", name: "UX Specialist"),
-            CreateAgent(id: "agent-handoff-runtime", name: "Runtime Specialist"),
+            CreateAgent("agent-handoff-ux", "UX Specialist"),
+            CreateAgent("agent-handoff-runtime", "Runtime Specialist"),
         ]);
 
         bool resolved = AgentIdentityResolver.TryResolveObservedAgentIdentity(
-            pattern,
+            workflow,
             "assistant",
             new AgentIdentity("agent-handoff-ux", "UX Specialist"),
             out AgentIdentity agent);
@@ -115,28 +115,43 @@ public sealed class AgentIdentityResolverTests
         Assert.Equal("UX Specialist", agent.AgentName);
     }
 
-    private static PatternDefinitionDto CreatePattern(
-        IReadOnlyList<PatternAgentDefinitionDto> agents,
-        string mode = "concurrent")
+    private static WorkflowDefinitionDto CreateWorkflow(
+        IReadOnlyList<WorkflowNodeDto> agents,
+        string orchestrationMode = "concurrent")
     {
-        return new PatternDefinitionDto
+        return new WorkflowDefinitionDto
         {
-            Id = $"{mode}-pattern",
-            Name = "Pattern",
-            Mode = mode,
-            Availability = "available",
-            Agents = agents,
+            Id = $"{orchestrationMode}-workflow",
+            Name = "Workflow",
+            Graph = new WorkflowGraphDto
+            {
+                Nodes =
+                [
+                    .. agents,
+                ],
+            },
+            Settings = new WorkflowSettingsDto
+            {
+                OrchestrationMode = orchestrationMode,
+            },
         };
     }
 
-    private static PatternAgentDefinitionDto CreateAgent(string id, string name)
+    private static WorkflowNodeDto CreateAgent(string id, string name)
     {
-        return new PatternAgentDefinitionDto
+        return new WorkflowNodeDto
         {
             Id = id,
-            Name = name,
-            Model = "gpt-5.4",
-            Instructions = "Help with the request.",
+            Kind = "agent",
+            Label = name,
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = id,
+                Name = name,
+                Model = "gpt-5.4",
+                Instructions = "Help with the request.",
+            },
         };
     }
 }

sidecar/tests/Aryx.AgentHost.Tests/AgentInstructionComposerTests.cs

@@ -8,19 +8,10 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_LeavesNonHandoffInstructionsUnchanged()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-sequential",
-            Name = "Sequential",
-            Mode = "sequential",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto agent = CreateAgent(
-            id: "agent-reviewer",
-            name: "Reviewer",
-            instructions: "Review the proposal.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("sequential");
+        WorkflowNodeDto agent = CreateAgent("agent-reviewer", "Reviewer", "Review the proposal.");
 
-        string instructions = AgentInstructionComposer.Compose(pattern, agent, agentIndex: 0);
+        string instructions = AgentInstructionComposer.Compose(workflow, agent, agentIndex: 0);
 
         Assert.Equal("Review the proposal.", instructions);
     }
@@ -28,24 +19,12 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_StrengthensGroupChatCollaborationRoles()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-group-chat",
-            Name = "Group Chat",
-            Mode = "group-chat",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto writer = CreateAgent(
-            id: "agent-group-writer",
-            name: "Writer",
-            instructions: "Draft an answer.");
-        PatternAgentDefinitionDto reviewer = CreateAgent(
-            id: "agent-group-reviewer",
-            name: "Reviewer",
-            instructions: "Review the draft.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("group-chat");
+        WorkflowNodeDto writer = CreateAgent("agent-group-writer", "Writer", "Draft an answer.");
+        WorkflowNodeDto reviewer = CreateAgent("agent-group-reviewer", "Reviewer", "Review the draft.");
 
-        string writerInstructions = AgentInstructionComposer.Compose(pattern, writer, agentIndex: 0);
-        string reviewerInstructions = AgentInstructionComposer.Compose(pattern, reviewer, agentIndex: 1);
+        string writerInstructions = AgentInstructionComposer.Compose(workflow, writer, agentIndex: 0);
+        string reviewerInstructions = AgentInstructionComposer.Compose(workflow, reviewer, agentIndex: 1);
 
         Assert.Contains("collaborative multi-turn group chat", writerInstructions, StringComparison.OrdinalIgnoreCase);
         Assert.Contains("refine your earlier draft", writerInstructions, StringComparison.OrdinalIgnoreCase);
@@ -56,19 +35,13 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_LeavesHandoffTriagePromptFocusedOnAgentInstructions()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-handoff",
-            Name = "Handoff",
-            Mode = "handoff",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto triage = CreateAgent(
-            id: "agent-handoff-triage",
-            name: "Triage",
-            instructions: "You triage requests and must hand them off to the most appropriate specialist.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("handoff");
+        WorkflowNodeDto triage = CreateAgent(
+            "agent-handoff-triage",
+            "Triage",
+            "You triage requests and must hand them off to the most appropriate specialist.");
 
-        string instructions = AgentInstructionComposer.Compose(pattern, triage, agentIndex: 0);
+        string instructions = AgentInstructionComposer.Compose(workflow, triage, agentIndex: 0);
 
         Assert.Equal("You triage requests and must hand them off to the most appropriate specialist.", instructions);
         Assert.DoesNotContain("routing", instructions, StringComparison.OrdinalIgnoreCase);
@@ -78,19 +51,13 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_LeavesHandoffSpecialistPromptFocusedOnAgentInstructions()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-handoff",
-            Name = "Handoff",
-            Mode = "handoff",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto specialist = CreateAgent(
-            id: "agent-handoff-ux",
-            name: "UX Specialist",
-            instructions: "You focus on navigation, UX, and interaction details.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("handoff");
+        WorkflowNodeDto specialist = CreateAgent(
+            "agent-handoff-ux",
+            "UX Specialist",
+            "You focus on navigation, UX, and interaction details.");
 
-        string instructions = AgentInstructionComposer.Compose(pattern, specialist, agentIndex: 1);
+        string instructions = AgentInstructionComposer.Compose(workflow, specialist, agentIndex: 1);
 
         Assert.Equal("You focus on navigation, UX, and interaction details.", instructions);
         Assert.DoesNotContain("triage agent", instructions, StringComparison.OrdinalIgnoreCase);
@@ -100,20 +67,11 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_AddsScratchpadGuidanceForProjectlessQaSessions()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-single",
-            Name = "Single",
-            Mode = "single",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto agent = CreateAgent(
-            id: "agent-primary",
-            name: "Primary Agent",
-            instructions: "You are a helpful assistant.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("single");
+        WorkflowNodeDto agent = CreateAgent("agent-primary", "Primary Agent", "You are a helpful assistant.");
 
         string instructions = AgentInstructionComposer.Compose(
-            pattern,
+            workflow,
             agent,
             agentIndex: 0,
             workspaceKind: "scratchpad");
@@ -127,20 +85,11 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_AddsPlanModeGuidanceWhenRequested()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-single",
-            Name = "Single",
-            Mode = "single",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto agent = CreateAgent(
-            id: "agent-primary",
-            name: "Primary Agent",
-            instructions: "You are a helpful assistant.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("single");
+        WorkflowNodeDto agent = CreateAgent("agent-primary", "Primary Agent", "You are a helpful assistant.");
 
         string instructions = AgentInstructionComposer.Compose(
-            pattern,
+            workflow,
             agent,
             agentIndex: 0,
             interactionMode: "plan");
@@ -154,20 +103,11 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_InsertsProjectInstructionsBetweenBaseAndRuntimeGuidance()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-single",
-            Name = "Single",
-            Mode = "single",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto agent = CreateAgent(
-            id: "agent-primary",
-            name: "Primary Agent",
-            instructions: "You are a helpful assistant.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("single");
+        WorkflowNodeDto agent = CreateAgent("agent-primary", "Primary Agent", "You are a helpful assistant.");
 
         string instructions = AgentInstructionComposer.Compose(
-            pattern,
+            workflow,
             agent,
             agentIndex: 0,
             workspaceKind: "scratchpad",
@@ -187,20 +127,11 @@ public sealed class AgentInstructionComposerTests
     [Fact]
     public void Compose_AppendsPromptInvocationAsATaskDirective()
     {
-        PatternDefinitionDto pattern = new()
-        {
-            Id = "pattern-single",
-            Name = "Single",
-            Mode = "single",
-            Availability = "available",
-        };
-        PatternAgentDefinitionDto agent = CreateAgent(
-            id: "agent-primary",
-            name: "Primary Agent",
-            instructions: "You are a helpful assistant.");
+        WorkflowDefinitionDto workflow = CreateWorkflow("single");
+        WorkflowNodeDto agent = CreateAgent("agent-primary", "Primary Agent", "You are a helpful assistant.");
 
         string instructions = AgentInstructionComposer.Compose(
-            pattern,
+            workflow,
             agent,
             agentIndex: 0,
             promptInvocation: new RunTurnPromptInvocationDto
@@ -228,14 +159,34 @@ public sealed class AgentInstructionComposerTests
             StringComparison.Ordinal);
     }
 
-    private static PatternAgentDefinitionDto CreateAgent(string id, string name, string instructions)
+    private static WorkflowDefinitionDto CreateWorkflow(string orchestrationMode)
     {
-        return new PatternAgentDefinitionDto
+        return new WorkflowDefinitionDto
+        {
+            Id = $"{orchestrationMode}-workflow",
+            Name = "Workflow",
+            Settings = new WorkflowSettingsDto
+            {
+                OrchestrationMode = orchestrationMode,
+            },
+        };
+    }
+
+    private static WorkflowNodeDto CreateAgent(string id, string name, string instructions)
+    {
+        return new WorkflowNodeDto
         {
             Id = id,
-            Name = name,
-            Instructions = instructions,
-            Model = "gpt-5.4",
+            Kind = "agent",
+            Label = name,
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = id,
+                Name = name,
+                Instructions = instructions,
+                Model = "gpt-5.4",
+            },
         };
     }
 }

sidecar/tests/Aryx.AgentHost.Tests/CopilotAgentBundleTests.cs

@@ -158,34 +158,17 @@ public sealed class CopilotAgentBundleTests
         Assert.Equal(HandoffWorkflowGuidance.CreateWorkflowInstructions(), builder.HandoffInstructions);
     }
 
-    [Theory]
-    [InlineData("single", 1)]
-    [InlineData("sequential", 2)]
-    [InlineData("concurrent", 2)]
-    [InlineData("group-chat", 2)]
-    public void BuildWorkflow_ExplicitlyConfiguresAgentHostOptions(string mode, int agentCount)
+    [Fact]
+    public void CreateAgentHostOptions_UsesExpectedAryxDefaults()
     {
-        CopilotAgentBundle bundle = new(CreateAgents(agentCount), hasConfiguredHooks: false);
-        PatternDefinitionDto pattern = CreatePattern(mode, agentCount);
+        AIAgentHostOptions options = CopilotAgentBundle.CreateAgentHostOptions();
 
-        Workflow workflow = bundle.BuildWorkflow(pattern);
-
-        AIAgentBinding[] bindings = workflow.ReflectExecutors().Values
-            .OfType<AIAgentBinding>()
-            .ToArray();
-
-        Assert.Equal(agentCount, bindings.Length);
-
-        foreach (AIAgentBinding binding in bindings)
-        {
-            AIAgentHostOptions options = Assert.IsType<AIAgentHostOptions>(binding.Options);
-            Assert.Null(options.EmitAgentUpdateEvents);
-            Assert.False(options.EmitAgentResponseEvents);
-            Assert.False(options.InterceptUserInputRequests);
-            Assert.False(options.InterceptUnterminatedFunctionCalls);
-            Assert.True(options.ReassignOtherAgentsAsUsers);
-            Assert.True(options.ForwardIncomingMessages);
-        }
+        Assert.Null(options.EmitAgentUpdateEvents);
+        Assert.False(options.EmitAgentResponseEvents);
+        Assert.False(options.InterceptUserInputRequests);
+        Assert.False(options.InterceptUnterminatedFunctionCalls);
+        Assert.True(options.ReassignOtherAgentsAsUsers);
+        Assert.True(options.ForwardIncomingMessages);
     }
 
     [Fact]
@@ -387,28 +370,12 @@ public sealed class CopilotAgentBundleTests
             ProjectPath = @"C:\workspace\project",
             WorkspaceKind = "project",
             Mode = "interactive",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
-                    },
-                ],
-            },
+            Workflow = CreateWorkflow("single", 1),
         };
 
         SessionConfig sessionConfig = CopilotAgentBundle.CreateSessionConfig(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             agentIndex: 0);
 
         Assert.Null(sessionConfig.SessionId);
@@ -427,28 +394,12 @@ public sealed class CopilotAgentBundleTests
             WorkspaceKind = "project",
             Mode = "interactive",
             ProjectInstructions = "Follow repository guidance.",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
-                    },
-                ],
-            },
+            Workflow = CreateWorkflow("single", 1),
         };
 
         SessionConfig sessionConfig = CopilotAgentBundle.CreateSessionConfig(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             agentIndex: 0);
 
         Assert.Equal("Help.\n\nFollow repository guidance.", sessionConfig.SystemMessage?.Content);
@@ -471,28 +422,12 @@ public sealed class CopilotAgentBundleTests
                 Agent = "designer",
                 ResolvedPrompt = "Review the docs for missing steps.",
             },
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
-                    },
-                ],
-            },
+            Workflow = CreateWorkflow("single", 1),
         };
 
         SessionConfig sessionConfig = CopilotAgentBundle.CreateSessionConfig(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             agentIndex: 0);
 
         Assert.Equal("designer", sessionConfig.Agent);
@@ -516,28 +451,12 @@ public sealed class CopilotAgentBundleTests
                 ResolvedPrompt = "Review the docs for missing steps.",
                 Tools = ["view"],
             },
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
-                    },
-                ],
-            },
+            Workflow = CreateWorkflow("single", 1),
         };
 
         SessionConfig sessionConfig = CopilotAgentBundle.CreateSessionConfig(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             agentIndex: 0);
 
         Assert.Equal("agent", sessionConfig.Agent);
@@ -550,13 +469,10 @@ public sealed class CopilotAgentBundleTests
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                ApprovalPolicy = new ApprovalPolicyDto
+            Workflow = CreateWorkflow(
+                "single",
+                1,
+                new ApprovalPolicyDto
                 {
                     Rules =
                     [
@@ -566,21 +482,10 @@ public sealed class CopilotAgentBundleTests
                             AgentIds = ["agent-1"],
                         },
                     ],
-                },
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
-                    },
-                ],
-            },
+                }),
         };
 
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0]);
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0]);
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
             {
@@ -630,25 +535,41 @@ public sealed class CopilotAgentBundleTests
             .Select(index => (AIAgent)CreateChatClientAgent($"agent-{index}", $"Agent {index}"))
             .ToArray();
 
-    private static PatternDefinitionDto CreatePattern(string mode, int agentCount)
+    private static WorkflowDefinitionDto CreateWorkflow(
+        string mode,
+        int agentCount,
+        ApprovalPolicyDto? approvalPolicy = null)
     {
-        return new PatternDefinitionDto
+        return new WorkflowDefinitionDto
         {
-            Id = $"pattern-{mode}",
-            Name = $"Pattern {mode}",
-            Mode = mode,
-            Availability = "available",
-            Agents =
-            [
-                .. Enumerable.Range(1, agentCount).Select(index => new PatternAgentDefinitionDto
-                {
-                    Id = $"agent-{index}",
-                    Name = $"Agent {index}",
-                    Description = $"Agent {index} description.",
-                    Instructions = $"Agent {index} instructions.",
-                    Model = "gpt-5.4",
-                }),
-            ],
+            Id = $"workflow-{mode}",
+            Name = $"Workflow {mode}",
+            Graph = new WorkflowGraphDto
+            {
+                Nodes =
+                [
+                    .. Enumerable.Range(1, agentCount).Select(index => new WorkflowNodeDto
+                    {
+                        Id = $"agent-{index}",
+                        Kind = "agent",
+                        Label = $"Agent {index}",
+                        Config = new WorkflowNodeConfigDto
+                        {
+                            Kind = "agent",
+                            Id = $"agent-{index}",
+                            Name = $"Agent {index}",
+                            Description = $"Agent {index} description.",
+                            Instructions = "Help.",
+                            Model = "gpt-5.4",
+                        },
+                    }),
+                ],
+            },
+            Settings = new WorkflowSettingsDto
+            {
+                OrchestrationMode = mode,
+                ApprovalPolicy = approvalPolicy,
+            },
         };
     }
 
@@ -697,3 +618,4 @@ public sealed class CopilotAgentBundleTests
         }
     }
 }
+

sidecar/tests/Aryx.AgentHost.Tests/CopilotExitPlanModeCoordinatorTests.cs

@@ -14,7 +14,7 @@ public sealed class CopilotExitPlanModeCoordinatorTests
 
         ExitPlanModeRequestedEventDto exitPlanEvent = coordinator.RecordExitPlanModeRequest(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new ExitPlanModeRequestedEvent
             {
                 Data = new ExitPlanModeRequestedData
@@ -50,23 +50,36 @@ public sealed class CopilotExitPlanModeCoordinatorTests
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-1",
-                Name = "Plan Mode Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help with the request.",
-                    },
-                ],
+                Id = "workflow-1",
+                Name = "Plan Mode Workflow",
+                Graph = new WorkflowGraphDto
+                {
+                    Nodes =
+                    [
+                        new WorkflowNodeDto
+                        {
+                            Id = "agent-1",
+                            Kind = "agent",
+                            Label = "Primary",
+                            Config = new WorkflowNodeConfigDto
+                            {
+                                Kind = "agent",
+                                Id = "agent-1",
+                                Name = "Primary",
+                                Model = "gpt-5.4",
+                                Instructions = "Help with the request.",
+                            },
+                        },
+                    ],
+                },
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = "single",
+                },
             },
         };
     }
 }
+

sidecar/tests/Aryx.AgentHost.Tests/CopilotMcpOAuthCoordinatorTests.cs

@@ -14,7 +14,7 @@ public sealed class CopilotMcpOAuthCoordinatorTests
 
         McpOauthRequiredEventDto oauthEvent = coordinator.BuildMcpOauthRequiredEvent(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new McpOauthRequiredEvent
             {
                 Data = new McpOauthRequiredData
@@ -49,23 +49,36 @@ public sealed class CopilotMcpOAuthCoordinatorTests
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-1",
-                Name = "MCP OAuth Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help with the request.",
-                    },
-                ],
+                Id = "workflow-1",
+                Name = "MCP OAuth Workflow",
+                Graph = new WorkflowGraphDto
+                {
+                    Nodes =
+                    [
+                        new WorkflowNodeDto
+                        {
+                            Id = "agent-1",
+                            Kind = "agent",
+                            Label = "Primary",
+                            Config = new WorkflowNodeConfigDto
+                            {
+                                Kind = "agent",
+                                Id = "agent-1",
+                                Name = "Primary",
+                                Model = "gpt-5.4",
+                                Instructions = "Help with the request.",
+                            },
+                        },
+                    ],
+                },
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = "single",
+                },
             },
         };
     }
 }
+

sidecar/tests/Aryx.AgentHost.Tests/CopilotSessionHooksTests.cs

@@ -23,7 +23,7 @@ public sealed class CopilotSessionHooksTests
             ],
         };
 
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], configuredHooks, runner);
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], configuredHooks, runner);
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -64,7 +64,7 @@ public sealed class CopilotSessionHooksTests
             ],
         };
 
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], configuredHooks, runner);
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], configuredHooks, runner);
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -93,7 +93,7 @@ public sealed class CopilotSessionHooksTests
             ],
         };
 
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], configuredHooks, runner);
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], configuredHooks, runner);
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -123,7 +123,7 @@ public sealed class CopilotSessionHooksTests
     public async Task Create_PreToolUseAutoAllowsInternalOrchestrationTools(string toolName)
     {
         RunTurnCommandDto command = CreateCommandWithToolApproval();
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -139,7 +139,7 @@ public sealed class CopilotSessionHooksTests
     public async Task Create_PreToolUseKeepsStoreMemoryUnderApprovalPolicy()
     {
         RunTurnCommandDto command = CreateCommandWithToolApproval();
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -159,7 +159,7 @@ public sealed class CopilotSessionHooksTests
     public async Task Create_PreToolUseAutoAllowsWhenCategoryIsApproved(string toolName, string category)
     {
         RunTurnCommandDto command = CreateCommandWithAutoApprovedCategory(category);
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -177,7 +177,7 @@ public sealed class CopilotSessionHooksTests
         RunTurnCommandDto command = CreateCommandWithConfiguredMcpServers(
             ["icm-mcp"],
             ["mcp_server:icm-mcp"]);
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -193,7 +193,7 @@ public sealed class CopilotSessionHooksTests
     public async Task Create_PreToolUseRequiresApprovalWhenMcpServerIsNotApproved()
     {
         RunTurnCommandDto command = CreateCommandWithConfiguredMcpServers(["icm-mcp"]);
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -219,7 +219,7 @@ public sealed class CopilotSessionHooksTests
             ErrorOccurred = [CreateHookCommand("error-hook")],
         };
 
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], configuredHooks, runner);
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], configuredHooks, runner);
 
         await hooks.OnSessionStart!(
             new SessionStartHookInput
@@ -293,7 +293,7 @@ public sealed class CopilotSessionHooksTests
     public async Task Create_WithoutConfiguredFileHooksPreservesExistingApprovalBehavior()
     {
         RunTurnCommandDto command = CreateCommandWithoutApprovalRules();
-        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Pattern.Agents[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
+        SessionHooks hooks = CopilotSessionHooks.Create(command, command.Workflow.GetAgentNodes()[0], ResolvedHookSet.Empty, new RecordingHookCommandRunner());
 
         PreToolUseHookOutput? decision = await hooks.OnPreToolUse!(
             new PreToolUseHookInput
@@ -312,34 +312,17 @@ public sealed class CopilotSessionHooksTests
             RequestId = "turn-1",
             SessionId = "session-1",
             ProjectPath = @"C:\workspace\project",
-            Pattern = new PatternDefinitionDto
+            Workflow = CreateWorkflow(new ApprovalPolicyDto
             {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                ApprovalPolicy = new ApprovalPolicyDto
-                {
-                    Rules =
-                    [
-                        new ApprovalCheckpointRuleDto
-                        {
-                            Kind = "tool-call",
-                            AgentIds = ["agent-1"],
-                        },
-                    ],
-                },
-                Agents =
+                Rules =
                 [
-                    new PatternAgentDefinitionDto
+                    new ApprovalCheckpointRuleDto
                     {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
+                        Kind = "tool-call",
+                        AgentIds = ["agent-1"],
                     },
                 ],
-            },
+            }),
         };
     }
 
@@ -351,15 +334,7 @@ public sealed class CopilotSessionHooksTests
             RequestId = command.RequestId,
             SessionId = command.SessionId,
             ProjectPath = command.ProjectPath,
-            Pattern = new PatternDefinitionDto
-            {
-                Id = command.Pattern.Id,
-                Name = command.Pattern.Name,
-                Mode = command.Pattern.Mode,
-                Availability = command.Pattern.Availability,
-                ApprovalPolicy = new ApprovalPolicyDto(),
-                Agents = command.Pattern.Agents,
-            },
+            Workflow = CreateWorkflow(new ApprovalPolicyDto()),
         };
     }
 
@@ -370,35 +345,18 @@ public sealed class CopilotSessionHooksTests
             RequestId = "turn-1",
             SessionId = "session-1",
             ProjectPath = @"C:\workspace\project",
-            Pattern = new PatternDefinitionDto
+            Workflow = CreateWorkflow(new ApprovalPolicyDto
             {
-                Id = "pattern-1",
-                Name = "Pattern",
-                Mode = "single",
-                Availability = "available",
-                ApprovalPolicy = new ApprovalPolicyDto
-                {
-                    Rules =
-                    [
-                        new ApprovalCheckpointRuleDto
-                        {
-                            Kind = "tool-call",
-                            AgentIds = ["agent-1"],
-                        },
-                    ],
-                    AutoApprovedToolNames = [category],
-                },
-                Agents =
+                Rules =
                 [
-                    new PatternAgentDefinitionDto
+                    new ApprovalCheckpointRuleDto
                     {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help.",
+                        Kind = "tool-call",
+                        AgentIds = ["agent-1"],
                     },
                 ],
-            },
+                AutoApprovedToolNames = [category],
+            }),
         };
     }
 
@@ -416,18 +374,44 @@ public sealed class CopilotSessionHooksTests
             {
                 McpServers = [.. serverNames.Select(CreateMcpServerConfig)],
             },
-            Pattern = new PatternDefinitionDto
+            Workflow = CreateWorkflow(new ApprovalPolicyDto
             {
-                Id = command.Pattern.Id,
-                Name = command.Pattern.Name,
-                Mode = command.Pattern.Mode,
-                Availability = command.Pattern.Availability,
-                ApprovalPolicy = new ApprovalPolicyDto
-                {
-                    Rules = command.Pattern.ApprovalPolicy?.Rules ?? [],
-                    AutoApprovedToolNames = autoApprovedToolNames ?? [],
-                },
-                Agents = command.Pattern.Agents,
+                Rules = command.Workflow.Settings.ApprovalPolicy?.Rules ?? [],
+                AutoApprovedToolNames = autoApprovedToolNames ?? [],
+            }),
+        };
+    }
+
+    private static WorkflowDefinitionDto CreateWorkflow(ApprovalPolicyDto approvalPolicy)
+    {
+        return new WorkflowDefinitionDto
+        {
+            Id = "workflow-1",
+            Name = "Workflow",
+            Graph = new WorkflowGraphDto
+            {
+                Nodes =
+                [
+                    new WorkflowNodeDto
+                    {
+                        Id = "agent-1",
+                        Kind = "agent",
+                        Label = "Primary",
+                        Config = new WorkflowNodeConfigDto
+                        {
+                            Kind = "agent",
+                            Id = "agent-1",
+                            Name = "Primary",
+                            Model = "gpt-5.4",
+                            Instructions = "Help.",
+                        },
+                    },
+                ],
+            },
+            Settings = new WorkflowSettingsDto
+            {
+                OrchestrationMode = "single",
+                ApprovalPolicy = approvalPolicy,
             },
         };
     }
@@ -477,3 +461,4 @@ public sealed class CopilotSessionHooksTests
         string InputJson,
         string ProjectPath);
 }
+

sidecar/tests/Aryx.AgentHost.Tests/CopilotTurnExecutionStateTests.cs

@@ -14,7 +14,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new McpOauthRequiredEvent
             {
                 Data = new McpOauthRequiredData
@@ -37,7 +37,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -66,7 +66,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """{"type":"tool.execution_start","data":{"toolCallId":"tool-call-1","toolName":"view"},"id":"33333333-3333-3333-3333-333333333333","timestamp":"2026-03-27T00:00:00Z"}"""));
 
@@ -85,7 +85,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """{"type":"tool.execution_start","data":{"toolCallId":"tool-call-1","toolName":"handoff_to_specialist"},"id":"1ce9d1dc-68f1-4df5-9728-f97017233279","timestamp":"2026-03-27T00:00:00Z"}"""));
 
@@ -101,7 +101,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -142,7 +142,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -158,7 +158,7 @@ public sealed class CopilotTurnExecutionStateTests
         _ = state.DrainPendingEvents();
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -172,7 +172,7 @@ public sealed class CopilotTurnExecutionStateTests
                 }
                 """));
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -207,7 +207,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -231,7 +231,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -267,7 +267,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -298,7 +298,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -356,7 +356,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -386,7 +386,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -417,7 +417,7 @@ public sealed class CopilotTurnExecutionStateTests
         RunTurnCommandDto command = CreateCommand();
         CopilotTurnExecutionState state = new(command);
 
-        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookStartEvent());
+        state.ObserveSessionEvent(command.Workflow.GetAgentNodes()[0], CreateHookStartEvent());
 
         HookLifecycleEventDto evt = Assert.Single(state.DrainPendingEvents().OfType<HookLifecycleEventDto>());
         Assert.Equal("start", evt.Phase);
@@ -432,7 +432,7 @@ public sealed class CopilotTurnExecutionStateTests
         RunTurnCommandDto command = CreateCommand();
         CopilotTurnExecutionState state = new(command);
 
-        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookEndEvent());
+        state.ObserveSessionEvent(command.Workflow.GetAgentNodes()[0], CreateHookEndEvent());
 
         HookLifecycleEventDto evt = Assert.Single(state.DrainPendingEvents().OfType<HookLifecycleEventDto>());
         Assert.Equal("end", evt.Phase);
@@ -450,8 +450,8 @@ public sealed class CopilotTurnExecutionStateTests
             SuppressHookLifecycleEvents = true,
         };
 
-        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookStartEvent());
-        state.ObserveSessionEvent(command.Pattern.Agents[0], CreateHookEndEvent());
+        state.ObserveSessionEvent(command.Workflow.GetAgentNodes()[0], CreateHookStartEvent());
+        state.ObserveSessionEvent(command.Workflow.GetAgentNodes()[0], CreateHookEndEvent());
 
         Assert.Empty(state.DrainPendingEvents());
     }
@@ -463,7 +463,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -526,7 +526,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -561,7 +561,7 @@ public sealed class CopilotTurnExecutionStateTests
         CopilotTurnExecutionState state = new(command);
 
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -624,7 +624,7 @@ public sealed class CopilotTurnExecutionStateTests
 
         // Simulate assistant message with tool requests → triggers reclassification
         state.ObserveSessionEvent(
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             SessionEvent.FromJson(
                 """
                 {
@@ -672,23 +672,36 @@ public sealed class CopilotTurnExecutionStateTests
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-1",
-                Name = "MCP OAuth Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    new PatternAgentDefinitionDto
-                    {
-                        Id = "agent-1",
-                        Name = "Primary",
-                        Model = "gpt-5.4",
-                        Instructions = "Help with the request.",
-                    },
-                ],
+                Id = "workflow-1",
+                Name = "Execution State Workflow",
+                Graph = new WorkflowGraphDto
+                {
+                    Nodes =
+                    [
+                        new WorkflowNodeDto
+                        {
+                            Id = "agent-1",
+                            Kind = "agent",
+                            Label = "Primary",
+                            Config = new WorkflowNodeConfigDto
+                            {
+                                Kind = "agent",
+                                Id = "agent-1",
+                                Name = "Primary",
+                                Model = "gpt-5.4",
+                                Instructions = "Help with the request.",
+                            },
+                        },
+                    ],
+                },
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = "single",
+                },
             },
         };
     }
 }
+

sidecar/tests/Aryx.AgentHost.Tests/CopilotUserInputCoordinatorTests.cs

@@ -15,7 +15,7 @@ public sealed class CopilotUserInputCoordinatorTests
 
         Task<UserInputResponse> pending = coordinator.RequestUserInputAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new UserInputRequest
             {
                 Question = "How should I proceed?",
@@ -76,33 +76,40 @@ public sealed class CopilotUserInputCoordinatorTests
         Assert.Contains("is not pending", error.Message);
     }
 
-    private static PatternAgentDefinitionDto CreateAgent(string id, string name)
-    {
-        return new PatternAgentDefinitionDto
-        {
-            Id = id,
-            Name = name,
-            Model = "gpt-5.4",
-            Instructions = "Help with the request.",
-        };
-    }
-
     private static RunTurnCommandDto CreateUserInputCommand()
     {
         return new RunTurnCommandDto
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-1",
-                Name = "User Input Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent("agent-1", "Primary"),
-                ],
+                Id = "workflow-1",
+                Name = "User Input Workflow",
+                Graph = new WorkflowGraphDto
+                {
+                    Nodes =
+                    [
+                        new WorkflowNodeDto
+                        {
+                            Id = "agent-1",
+                            Kind = "agent",
+                            Label = "Primary",
+                            Config = new WorkflowNodeConfigDto
+                            {
+                                Kind = "agent",
+                                Id = "agent-1",
+                                Name = "Primary",
+                                Model = "gpt-5.4",
+                                Instructions = "Help with the request.",
+                            },
+                        },
+                    ],
+                },
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = "single",
+                },
             },
         };
     }

sidecar/tests/Aryx.AgentHost.Tests/CopilotWorkflowRunnerTests.cs

@@ -95,23 +95,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_FallsBackToStreamingSegmentsWhenWorkflowOutputIsMissing()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-concurrent",
-                Name = "Concurrent Brainstorm",
-                Mode = "concurrent",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
-                    CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "concurrent",
+            CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
+            CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -140,22 +127,9 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_CanonicalizesWorkflowOutputAuthorNames()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-single",
-                Name = "Single Agent",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-single-primary", name: "Primary Agent"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "single",
+            CreateAgent(id: "agent-single-primary", name: "Primary Agent"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -178,22 +152,9 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_UsesFinalAssistantPayloadWhenStreamingTextIsMissing()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-single",
-                Name = "Single Agent",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-single-primary", name: "Primary Agent"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "single",
+            CreateAgent(id: "agent-single-primary", name: "Primary Agent"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -222,24 +183,11 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_PreservesSequentialConversationHistory()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-sequential",
-                Name = "Sequential Trio Review",
-                Mode = "sequential",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-sequential-analyst", name: "Analyst"),
-                    CreateAgent(id: "agent-sequential-builder", name: "Builder"),
-                    CreateAgent(id: "agent-sequential-reviewer", name: "Reviewer"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "sequential",
+            CreateAgent(id: "agent-sequential-analyst", name: "Analyst"),
+            CreateAgent(id: "agent-sequential-builder", name: "Builder"),
+            CreateAgent(id: "agent-sequential-reviewer", name: "Reviewer"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -272,24 +220,11 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_PreservesConcurrentAggregatedResponses()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-concurrent",
-                Name = "Concurrent Brainstorm",
-                Mode = "concurrent",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
-                    CreateAgent(id: "agent-concurrent-product", name: "Product"),
-                    CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "concurrent",
+            CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
+            CreateAgent(id: "agent-concurrent-product", name: "Product"),
+            CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -310,24 +245,11 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_ConcurrentUsesLastStreamedMessagePerAgentForGenericOutput()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-concurrent",
-                Name = "Concurrent Brainstorm",
-                Mode = "concurrent",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
-                    CreateAgent(id: "agent-concurrent-product", name: "Product"),
-                    CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "concurrent",
+            CreateAgent(id: "agent-concurrent-architect", name: "Architect"),
+            CreateAgent(id: "agent-concurrent-product", name: "Product"),
+            CreateAgent(id: "agent-concurrent-implementer", name: "Implementer"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -379,23 +301,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_PreservesGroupChatConversationHistory()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-group-chat",
-                Name = "Collaborative Group Chat",
-                Mode = "group-chat",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-group-writer", name: "Writer"),
-                    CreateAgent(id: "agent-group-reviewer", name: "Reviewer"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "group-chat",
+            CreateAgent(id: "agent-group-writer", name: "Writer"),
+            CreateAgent(id: "agent-group-reviewer", name: "Reviewer"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -428,23 +337,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_FallsBackToPositionWhenOutputTextDiffers()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-group-chat",
-                Name = "Collaborative Group Chat",
-                Mode = "group-chat",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-group-writer", name: "Writer"),
-                    CreateAgent(id: "agent-group-reviewer", name: "Reviewer"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "group-chat",
+            CreateAgent(id: "agent-group-writer", name: "Writer"),
+            CreateAgent(id: "agent-group-reviewer", name: "Reviewer"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -482,23 +378,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_UsesFallbackAgentForGenericAssistantOutput()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-handoff",
-                Name = "Handoff Support Flow",
-                Mode = "handoff",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-handoff-triage", name: "Triage"),
-                    CreateAgent(id: "agent-handoff-ux", name: "UX Specialist"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "handoff",
+            CreateAgent(id: "agent-handoff-triage", name: "Triage"),
+            CreateAgent(id: "agent-handoff-ux", name: "UX Specialist"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -519,23 +402,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_PrefersContentMatchedStreamingSegmentOverPosition()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-handoff",
-                Name = "Handoff Support Flow",
-                Mode = "handoff",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-handoff-triage", name: "Triage"),
-                    CreateAgent(id: "agent-handoff-runtime", name: "Runtime Specialist"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "handoff",
+            CreateAgent(id: "agent-handoff-triage", name: "Triage"),
+            CreateAgent(id: "agent-handoff-runtime", name: "Runtime Specialist"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -560,23 +430,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_UsesFallbackAgentForSingleGenericAssistantOutputWithMultipleSegments()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-handoff",
-                Name = "Handoff Support Flow",
-                Mode = "handoff",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-handoff-triage", name: "Triage"),
-                    CreateAgent(id: "agent-handoff-runtime", name: "Runtime Specialist"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "handoff",
+            CreateAgent(id: "agent-handoff-triage", name: "Triage"),
+            CreateAgent(id: "agent-handoff-runtime", name: "Runtime Specialist"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -601,23 +458,10 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public void ProjectCompletedMessages_DropsBlankAssistantOutputMessages()
     {
-        RunTurnCommandDto command = new()
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-handoff",
-                Name = "Handoff Support Flow",
-                Mode = "handoff",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(id: "agent-handoff-triage", name: "Triage"),
-                    CreateAgent(id: "agent-handoff-ux", name: "UX Specialist"),
-                ],
-            },
-        };
+        RunTurnCommandDto command = CreateCommand(
+            "handoff",
+            CreateAgent(id: "agent-handoff-triage", name: "Triage"),
+            CreateAgent(id: "agent-handoff-ux", name: "UX Specialist"));
 
         IReadOnlyList<ChatMessageDto> messages = WorkflowTranscriptProjector.ProjectCompletedMessages(
             command,
@@ -835,7 +679,7 @@ public sealed class CopilotWorkflowRunnerTests
     [Fact]
     public async Task RunTurnAsync_RequestPortWorkflowUsesUserInputBridge()
     {
-        CopilotWorkflowRunner runner = new(new PatternValidator());
+        CopilotWorkflowRunner runner = new(new WorkflowValidator());
         List<UserInputRequestedEventDto> requests = [];
 
         IReadOnlyList<ChatMessageDto> messages = await runner.RunTurnAsync(
@@ -927,6 +771,25 @@ public sealed class CopilotWorkflowRunnerTests
     public async Task HandleWorkflowEventAsync_EmitsWorkflowCheckpointSavedEvent()
     {
         RunTurnCommandDto command = CreateHandoffCommand();
+        command = new RunTurnCommandDto
+        {
+            RequestId = command.RequestId,
+            SessionId = command.SessionId,
+            Workflow = new WorkflowDefinitionDto
+            {
+                Id = command.Workflow.Id,
+                Name = command.Workflow.Name,
+                Graph = command.Workflow.Graph,
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = command.Workflow.Settings.OrchestrationMode,
+                    Checkpointing = new WorkflowCheckpointSettingsDto
+                    {
+                        Enabled = true,
+                    },
+                },
+            },
+        };
         CopilotTurnExecutionState state = new(command);
         List<WorkflowCheckpointSavedEventDto> checkpoints = [];
 
@@ -1831,7 +1694,7 @@ public sealed class CopilotWorkflowRunnerTests
 
         Task<PermissionRequestResult> pending = coordinator.RequestApprovalAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new PermissionRequestCustomTool
             {
                 Kind = "custom tool",
@@ -1875,7 +1738,7 @@ public sealed class CopilotWorkflowRunnerTests
 
         Task<PermissionRequestResult> pending = coordinator.RequestApprovalAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new PermissionRequestWrite
             {
                 Kind = "write",
@@ -1938,7 +1801,7 @@ public sealed class CopilotWorkflowRunnerTests
 
         PermissionRequestResult result = await coordinator.RequestApprovalAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new PermissionRequestCustomTool
             {
                 Kind = "custom tool",
@@ -1972,7 +1835,7 @@ public sealed class CopilotWorkflowRunnerTests
 
         PermissionRequestResult result = await coordinator.RequestApprovalAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new PermissionRequestHook
             {
                 Kind = "hook",
@@ -2007,7 +1870,7 @@ public sealed class CopilotWorkflowRunnerTests
 
         Task<PermissionRequestResult> firstPending = coordinator.RequestApprovalAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new PermissionRequestRead
             {
                 Kind = "read",
@@ -2048,7 +1911,7 @@ public sealed class CopilotWorkflowRunnerTests
         bool sawSecondApproval = false;
         PermissionRequestResult secondResult = await coordinator.RequestApprovalAsync(
             command,
-            command.Pattern.Agents[0],
+            command.Workflow.GetAgentNodes()[0],
             new PermissionRequestRead
             {
                 Kind = "read",
@@ -2084,7 +1947,7 @@ public sealed class CopilotWorkflowRunnerTests
 
         Task<PermissionRequestResult> firstPending = coordinator.RequestApprovalAsync(
             firstCommand,
-            firstCommand.Pattern.Agents[0],
+            firstCommand.Workflow.GetAgentNodes()[0],
             new PermissionRequestRead
             {
                 Kind = "read",
@@ -2124,7 +1987,7 @@ public sealed class CopilotWorkflowRunnerTests
         RunTurnCommandDto secondCommand = CreateApprovalCommand(requestId: "turn-2");
         Task<PermissionRequestResult> secondPending = coordinator.RequestApprovalAsync(
             secondCommand,
-            secondCommand.Pattern.Agents[0],
+            secondCommand.Workflow.GetAgentNodes()[0],
             new PermissionRequestRead
             {
                 Kind = "read",
@@ -2179,38 +2042,56 @@ public sealed class CopilotWorkflowRunnerTests
         Assert.Contains("is not pending", error.Message);
     }
 
-    private static PatternAgentDefinitionDto CreateAgent(string id, string name)
+    private static WorkflowNodeDto CreateAgent(string id, string name)
     {
-        return new PatternAgentDefinitionDto
+        return new WorkflowNodeDto
         {
             Id = id,
-            Name = name,
-            Model = "gpt-5.4",
-            Instructions = "Help with the request.",
+            Kind = "agent",
+            Label = name,
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = id,
+                Name = name,
+                Model = "gpt-5.4",
+                Instructions = "Help with the request.",
+            },
         };
     }
 
-    private static RunTurnCommandDto CreateHandoffCommand()
+    private static RunTurnCommandDto CreateCommand(
+        string orchestrationMode,
+        params WorkflowNodeDto[] agents)
     {
         return new RunTurnCommandDto
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-handoff",
-                Name = "Handoff Flow",
-                Mode = "handoff",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent("agent-handoff-triage", "Triage"),
-                    CreateAgent("agent-handoff-ux", "UX Specialist"),
-                ],
+                Id = $"workflow-{orchestrationMode}",
+                Name = $"Workflow {orchestrationMode}",
+                Graph = new WorkflowGraphDto
+                {
+                    Nodes = [.. agents],
+                },
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = orchestrationMode,
+                },
             },
         };
     }
 
+    private static RunTurnCommandDto CreateHandoffCommand()
+    {
+        return CreateCommand(
+            "handoff",
+            CreateAgent("agent-handoff-triage", "Triage"),
+            CreateAgent("agent-handoff-ux", "UX Specialist"));
+    }
+
     private static RequestInfoEvent CreateRequestInfoEvent(object payload)
     {
         RequestPort port = RequestPort.Create<object, object>("test-port");
@@ -2253,30 +2134,35 @@ public sealed class CopilotWorkflowRunnerTests
                 {
                     McpServers = [.. mcpServers],
                 },
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-1",
-                Name = "Approval Pattern",
-                Mode = "single",
-                Availability = "available",
-                ApprovalPolicy = new ApprovalPolicyDto
+                Id = "workflow-1",
+                Name = "Approval Workflow",
+                Graph = new WorkflowGraphDto
                 {
-                    Rules =
+                    Nodes =
                     [
-                        new ApprovalCheckpointRuleDto
-                        {
-                            Kind = "tool-call",
-                            AgentIds = ["agent-1"],
-                        },
+                        CreateAgent("agent-1", "Primary"),
                     ],
-                    AutoApprovedToolNames = autoApprovedToolNames is null
-                        ? ["web_fetch"]
-                        : [.. autoApprovedToolNames],
                 },
-                Agents =
-                [
-                    CreateAgent("agent-1", "Primary"),
-                ],
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = "single",
+                    ApprovalPolicy = new ApprovalPolicyDto
+                    {
+                        Rules =
+                        [
+                            new ApprovalCheckpointRuleDto
+                            {
+                                Kind = "tool-call",
+                                AgentIds = ["agent-1"],
+                            },
+                        ],
+                        AutoApprovedToolNames = autoApprovedToolNames is null
+                            ? ["web_fetch"]
+                            : [.. autoApprovedToolNames],
+                    },
+                },
             },
         };
     }
@@ -2288,14 +2174,6 @@ public sealed class CopilotWorkflowRunnerTests
             RequestId = "turn-request-port",
             SessionId = "session-request-port",
             ProjectPath = "c:\\workspace\\personal\\projects\\aryx.worktrees\\copilot-powerful-vulture",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-request-port",
-                Name = "Request Port Pattern",
-                Mode = "single",
-                Availability = "available",
-                Agents = [],
-            },
             Messages =
             [
                 new ChatMessageDto
@@ -2407,3 +2285,4 @@ public sealed class CopilotWorkflowRunnerTests
         }
     }
 }
+

sidecar/tests/Aryx.AgentHost.Tests/HandoffWorkflowGuidanceTests.cs

@@ -23,13 +23,20 @@ public sealed class HandoffWorkflowGuidanceTests
     [Fact]
     public void CreateForwardReason_UsesTargetSpecialtyAndOwnership()
     {
-        PatternAgentDefinitionDto specialist = new()
+        WorkflowNodeDto specialist = new()
         {
             Id = "agent-handoff-ux",
-            Name = "UX Specialist",
-            Description = "Handles user experience questions.",
-            Instructions = "Focus on UX.",
-            Model = "claude-opus-4.5",
+            Kind = "agent",
+            Label = "UX Specialist",
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = "agent-handoff-ux",
+                Name = "UX Specialist",
+                Description = "Handles user experience questions.",
+                Instructions = "Focus on UX.",
+                Model = "claude-opus-4.5",
+            },
         };
 
         string reason = HandoffWorkflowGuidance.CreateForwardReason(specialist);
@@ -42,13 +49,20 @@ public sealed class HandoffWorkflowGuidanceTests
     [Fact]
     public void CreateReturnReason_RestrictsReturnToReroutingCases()
     {
-        PatternAgentDefinitionDto triage = new()
+        WorkflowNodeDto triage = new()
         {
             Id = "agent-handoff-triage",
-            Name = "Triage",
-            Description = "Routes the request to the right specialist.",
-            Instructions = "Triages requests.",
-            Model = "gpt-5.4",
+            Kind = "agent",
+            Label = "Triage",
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = "agent-handoff-triage",
+                Name = "Triage",
+                Description = "Routes the request to the right specialist.",
+                Instructions = "Triages requests.",
+                Model = "gpt-5.4",
+            },
         };
 
         string reason = HandoffWorkflowGuidance.CreateReturnReason(triage);

sidecar/tests/Aryx.AgentHost.Tests/PatternGraphResolverTests.cs

@@ -1,127 +0,0 @@
-using Aryx.AgentHost.Contracts;
-using Aryx.AgentHost.Services;
-
-namespace Aryx.AgentHost.Tests;
-
-public sealed class PatternGraphResolverTests
-{
-    [Fact]
-    public void ResolveOrderedAgentIds_UsesSequentialGraphPath()
-    {
-        PatternDefinitionDto pattern = CreatePattern(
-            "sequential",
-            [
-                CreateAgent("agent-1", "Analyst"),
-                CreateAgent("agent-2", "Builder"),
-                CreateAgent("agent-3", "Reviewer"),
-            ],
-            new PatternGraphDto
-            {
-                Nodes =
-                [
-                    CreateSystemNode("system-user-input", "user-input"),
-                    CreateAgentNode("agent-1", 0),
-                    CreateAgentNode("agent-2", 1),
-                    CreateAgentNode("agent-3", 2),
-                    CreateSystemNode("system-user-output", "user-output"),
-                ],
-                Edges =
-                [
-                    CreateEdge("system-user-input", "agent-node-agent-3"),
-                    CreateEdge("agent-node-agent-3", "agent-node-agent-1"),
-                    CreateEdge("agent-node-agent-1", "agent-node-agent-2"),
-                    CreateEdge("agent-node-agent-2", "system-user-output"),
-                ],
-            });
-
-        IReadOnlyList<string> orderedAgentIds = PatternGraphResolver.ResolveOrderedAgentIds(pattern);
-
-        Assert.Equal(["agent-3", "agent-1", "agent-2"], orderedAgentIds);
-    }
-
-    [Fact]
-    public void ResolveHandoff_UsesExplicitEntryAndRoutes()
-    {
-        PatternDefinitionDto pattern = CreatePattern(
-            "handoff",
-            [
-                CreateAgent("agent-1", "Triage"),
-                CreateAgent("agent-2", "UX"),
-                CreateAgent("agent-3", "Runtime"),
-            ],
-            new PatternGraphDto
-            {
-                Nodes =
-                [
-                    CreateSystemNode("system-user-input", "user-input"),
-                    CreateSystemNode("system-user-output", "user-output"),
-                    CreateAgentNode("agent-1", 0),
-                    CreateAgentNode("agent-2", 1),
-                    CreateAgentNode("agent-3", 2),
-                ],
-                Edges =
-                [
-                    CreateEdge("system-user-input", "agent-node-agent-3"),
-                    CreateEdge("agent-node-agent-3", "agent-node-agent-2"),
-                    CreateEdge("agent-node-agent-2", "agent-node-agent-1"),
-                    CreateEdge("agent-node-agent-2", "system-user-output"),
-                ],
-            });
-
-        PatternHandoffTopology topology = PatternGraphResolver.ResolveHandoff(pattern);
-
-        Assert.Equal("agent-3", topology.EntryAgentId);
-        Assert.Contains(new PatternHandoffRoute("agent-3", "agent-2"), topology.Routes);
-        Assert.Contains(new PatternHandoffRoute("agent-2", "agent-1"), topology.Routes);
-        Assert.DoesNotContain(new PatternHandoffRoute("agent-1", "agent-2"), topology.Routes);
-    }
-
-    private static PatternDefinitionDto CreatePattern(
-        string mode,
-        IReadOnlyList<PatternAgentDefinitionDto> agents,
-        PatternGraphDto graph)
-        => new()
-        {
-            Id = $"{mode}-pattern",
-            Name = "Pattern",
-            Mode = mode,
-            Availability = "available",
-            Agents = agents,
-            Graph = graph,
-        };
-
-    private static PatternAgentDefinitionDto CreateAgent(string id, string name)
-        => new()
-        {
-            Id = id,
-            Name = name,
-            Model = "gpt-5.4",
-            Instructions = "Help with the user's request.",
-        };
-
-    private static PatternGraphNodeDto CreateSystemNode(string id, string kind)
-        => new()
-        {
-            Id = id,
-            Kind = kind,
-            Position = new PatternGraphPositionDto(),
-        };
-
-    private static PatternGraphNodeDto CreateAgentNode(string agentId, int order)
-        => new()
-        {
-            Id = $"agent-node-{agentId}",
-            Kind = "agent",
-            AgentId = agentId,
-            Order = order,
-            Position = new PatternGraphPositionDto(),
-        };
-
-    private static PatternGraphEdgeDto CreateEdge(string source, string target)
-        => new()
-        {
-            Id = $"edge-{source}-to-{target}",
-            Source = source,
-            Target = target,
-        };
-}

sidecar/tests/Aryx.AgentHost.Tests/SidecarProtocolHostTests.cs

@@ -62,52 +62,6 @@ public sealed class SidecarProtocolHostTests
             });
     }
 
-    [Fact]
-    public async Task ValidatePatternCommand_ReturnsIssuesAndCompletion()
-    {
-        IReadOnlyList<JsonElement> events = await RunHostAsync(new ValidatePatternCommandDto
-        {
-            Type = "validate-pattern",
-            RequestId = "validate-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "single-pattern",
-                Name = "",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(),
-                    CreateAgent(id: "agent-2", name: "Reviewer", model: ""),
-                ],
-            },
-        });
-
-        Assert.Collection(
-            events,
-            validationEvent =>
-            {
-                Assert.Equal("pattern-validation", validationEvent.GetProperty("type").GetString());
-                Assert.Equal("validate-1", validationEvent.GetProperty("requestId").GetString());
-
-                JsonElement[] issues = validationEvent.GetProperty("issues").EnumerateArray().ToArray();
-                Assert.Contains(issues, issue =>
-                    issue.GetProperty("field").GetString() == "name"
-                    && issue.GetProperty("message").GetString() == "Pattern name is required.");
-                Assert.Contains(issues, issue =>
-                    issue.GetProperty("field").GetString() == "agents"
-                    && issue.GetProperty("message").GetString() == "Single-agent chat requires exactly one agent.");
-                Assert.Contains(issues, issue =>
-                    issue.GetProperty("field").GetString() == "agents.model"
-                    && issue.GetProperty("message").GetString() == "Agent \"Reviewer\" requires a model identifier.");
-            },
-            completionEvent =>
-            {
-                Assert.Equal("command-complete", completionEvent.GetProperty("type").GetString());
-                Assert.Equal("validate-1", completionEvent.GetProperty("requestId").GetString());
-            });
-    }
-
     [Fact]
     public async Task ValidateWorkflowCommand_ReturnsIssuesAndCompletion()
     {
@@ -182,7 +136,7 @@ public sealed class SidecarProtocolHostTests
     public async Task RunTurnCommand_ReturnsActivityEventsAndCompletion()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await onActivity(new AgentActivityEventDto
@@ -230,37 +184,7 @@ public sealed class SidecarProtocolHostTests
                 ];
             }));
 
-        IReadOnlyList<JsonElement> events = await RunHostAsync(
-            new RunTurnCommandDto
-            {
-                Type = "run-turn",
-                RequestId = "turn-1",
-                SessionId = "session-1",
-                ProjectPath = "C:\\workspace\\project",
-                Pattern = new PatternDefinitionDto
-                {
-                    Id = "pattern-1",
-                    Name = "Single Agent",
-                    Mode = "single",
-                    Availability = "available",
-                    Agents =
-                    [
-                        CreateAgent(name: "Primary"),
-                    ],
-                },
-                Messages =
-                [
-                    new ChatMessageDto
-                    {
-                        Id = "user-1",
-                        Role = "user",
-                        AuthorName = "You",
-                        Content = "Hello",
-                        CreatedAt = "2026-01-01T00:00:00.0000000Z",
-                    },
-                ],
-            },
-            host);
+        IReadOnlyList<JsonElement> events = await RunHostAsync(CreateRunTurnCommand(), host);
 
         Assert.Collection(
             events,
@@ -306,7 +230,7 @@ public sealed class SidecarProtocolHostTests
     public async Task RunTurnCommand_ReturnsWorkflowDiagnosticEventsAndCompletion()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await onActivity(new WorkflowDiagnosticEventDto
@@ -327,25 +251,7 @@ public sealed class SidecarProtocolHostTests
             }));
 
         IReadOnlyList<JsonElement> events = await RunHostAsync(
-            new RunTurnCommandDto
-            {
-                Type = "run-turn",
-                RequestId = "turn-diagnostic",
-                SessionId = "session-1",
-                ProjectPath = "C:\\workspace\\project",
-                Pattern = new PatternDefinitionDto
-                {
-                    Id = "pattern-1",
-                    Name = "Single Agent",
-                    Mode = "single",
-                    Availability = "available",
-                    Agents =
-                    [
-                        CreateAgent(name: "Primary"),
-                    ],
-                },
-                Messages = [],
-            },
+            CreateRunTurnCommand(requestId: "turn-diagnostic", messages: []),
             host);
 
         Assert.Collection(
@@ -378,7 +284,7 @@ public sealed class SidecarProtocolHostTests
     {
         string? capturedMode = null;
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 capturedMode = command.Mode;
@@ -386,25 +292,7 @@ public sealed class SidecarProtocolHostTests
             }));
 
         await RunHostAsync(
-            new RunTurnCommandDto
-            {
-                Type = "run-turn",
-                RequestId = "turn-plan",
-                SessionId = "session-1",
-                ProjectPath = "C:\\workspace\\project",
-                Mode = "plan",
-                Pattern = new PatternDefinitionDto
-                {
-                    Id = "pattern-1",
-                    Name = "Single Agent",
-                    Mode = "single",
-                    Availability = "available",
-                    Agents =
-                    [
-                        CreateAgent(name: "Primary"),
-                    ],
-                },
-            },
+            CreateRunTurnCommand(requestId: "turn-plan", interactionMode: "plan"),
             host);
 
         Assert.Equal("plan", capturedMode);
@@ -414,7 +302,7 @@ public sealed class SidecarProtocolHostTests
     public async Task RunTurnCommand_ReturnsApprovalEvents()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await onApproval(new ApprovalRequestedEventDto
@@ -441,24 +329,7 @@ public sealed class SidecarProtocolHostTests
             }));
 
         IReadOnlyList<JsonElement> events = await RunHostAsync(
-            new RunTurnCommandDto
-            {
-                Type = "run-turn",
-                RequestId = "turn-approval",
-                SessionId = "session-1",
-                ProjectPath = "C:\\workspace\\project",
-                Pattern = new PatternDefinitionDto
-                {
-                    Id = "pattern-1",
-                    Name = "Single Agent",
-                    Mode = "single",
-                    Availability = "available",
-                    Agents =
-                    [
-                        CreateAgent(name: "Primary"),
-                    ],
-                },
-            },
+            CreateRunTurnCommand(requestId: "turn-approval"),
             host);
 
         Assert.Collection(
@@ -492,7 +363,7 @@ public sealed class SidecarProtocolHostTests
     public async Task RunTurnCommand_ReturnsUserInputEvents()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await onUserInput(new UserInputRequestedEventDto
@@ -512,24 +383,7 @@ public sealed class SidecarProtocolHostTests
             }));
 
         IReadOnlyList<JsonElement> events = await RunHostAsync(
-            new RunTurnCommandDto
-            {
-                Type = "run-turn",
-                RequestId = "turn-user-input",
-                SessionId = "session-1",
-                ProjectPath = "C:\\workspace\\project",
-                Pattern = new PatternDefinitionDto
-                {
-                    Id = "pattern-1",
-                    Name = "Single Agent",
-                    Mode = "single",
-                    Availability = "available",
-                    Agents =
-                    [
-                        CreateAgent(name: "Primary"),
-                    ],
-                },
-            },
+            CreateRunTurnCommand(requestId: "turn-user-input"),
             host);
 
         Assert.Collection(
@@ -565,7 +419,7 @@ public sealed class SidecarProtocolHostTests
     public async Task RunTurnCommand_ReturnsMcpOauthRequiredEvents()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await onMcpOAuthRequired(new McpOauthRequiredEventDto
@@ -623,7 +477,7 @@ public sealed class SidecarProtocolHostTests
     public async Task RunTurnCommand_ReturnsExitPlanModeEvents()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await onExitPlanMode(new ExitPlanModeRequestedEventDto
@@ -644,25 +498,7 @@ public sealed class SidecarProtocolHostTests
             }));
 
         IReadOnlyList<JsonElement> events = await RunHostAsync(
-            new RunTurnCommandDto
-            {
-                Type = "run-turn",
-                RequestId = "turn-plan-mode",
-                SessionId = "session-1",
-                ProjectPath = "C:\\workspace\\project",
-                Mode = "plan",
-                Pattern = new PatternDefinitionDto
-                {
-                    Id = "pattern-1",
-                    Name = "Single Agent",
-                    Mode = "single",
-                    Availability = "available",
-                    Agents =
-                    [
-                        CreateAgent(name: "Primary"),
-                    ],
-                },
-            },
+            CreateRunTurnCommand(requestId: "turn-plan-mode", interactionMode: "plan"),
             host);
 
         Assert.Collection(
@@ -698,7 +534,7 @@ public sealed class SidecarProtocolHostTests
     public async Task CancelTurnCommand_CancelsInProgressTurnAndCompletesBothCommands()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) =>
             {
                 await Task.Delay(Timeout.Infinite, cancellationToken);
@@ -746,7 +582,7 @@ public sealed class SidecarProtocolHostTests
     public async Task CancelTurnCommand_AfterTurnCompletion_IsNoOp()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) => []));
 
         await RunHostAsync(CreateRunTurnCommand(requestId: "turn-completed"), host);
@@ -768,7 +604,7 @@ public sealed class SidecarProtocolHostTests
     {
         ResolveApprovalCommandDto? captured = null;
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(
                 handler: async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) => [],
                 resolveApprovalHandler: (command, cancellationToken) =>
@@ -801,7 +637,7 @@ public sealed class SidecarProtocolHostTests
     {
         ResolveUserInputCommandDto? captured = null;
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             new FakeWorkflowRunner(
                 handler: async (command, onDelta, onActivity, onApproval, onUserInput, onMcpOAuthRequired, onExitPlanMode, cancellationToken) => [],
                 resolveUserInputHandler: (command, cancellationToken) =>
@@ -925,7 +761,7 @@ public sealed class SidecarProtocolHostTests
     public async Task ListSessionsCommand_ReturnsSessionsListedEvent()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             sessionManager: new FakeSessionManager
             {
                 Sessions =
@@ -972,7 +808,7 @@ public sealed class SidecarProtocolHostTests
             ],
         };
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             sessionManager: sessionManager);
 
         IReadOnlyList<JsonElement> events = await RunHostAsync(
@@ -995,7 +831,7 @@ public sealed class SidecarProtocolHostTests
     public async Task GetQuotaCommand_ReturnsQuotaResultEvent()
     {
         SidecarProtocolHost host = new(
-            new PatternValidator(),
+            new WorkflowValidator(),
             sessionManager: new FakeSessionManager
             {
                 QuotaSnapshots = new Dictionary<string, QuotaSnapshotDto>(StringComparer.Ordinal)
@@ -1037,7 +873,7 @@ public sealed class SidecarProtocolHostTests
             await Task.Delay(Timeout.InfiniteTimeSpan, cancellationToken);
             return [];
         });
-        SidecarProtocolHost host = new(new PatternValidator(), runner);
+        SidecarProtocolHost host = new(new WorkflowValidator(), runner);
 
         IReadOnlyList<JsonElement> events = await RunHostAsync(
         [
@@ -1098,7 +934,7 @@ public sealed class SidecarProtocolHostTests
     private static SidecarProtocolHost CreateHostForTests()
     {
         return new SidecarProtocolHost(
-            new PatternValidator(),
+            new WorkflowValidator(),
             capabilitiesProvider: _ => Task.FromResult(new SidecarCapabilitiesDto
             {
                 Modes = new Dictionary<string, SidecarModeCapabilityDto>(StringComparer.OrdinalIgnoreCase)
@@ -1176,24 +1012,35 @@ public sealed class SidecarProtocolHostTests
         return events;
     }
 
-    private static PatternAgentDefinitionDto CreateAgent(
+    private static WorkflowNodeDto CreateAgent(
         string id = "agent-1",
         string name = "Primary",
         string model = "gpt-5.4",
         string instructions = "Help with the user's request.")
     {
-        return new PatternAgentDefinitionDto
+        return new WorkflowNodeDto
         {
             Id = id,
-            Name = name,
-            Model = model,
-            Instructions = instructions,
+            Kind = "agent",
+            Label = name,
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = id,
+                Name = name,
+                Model = model,
+                Instructions = instructions,
+            },
         };
     }
 
     private static RunTurnCommandDto CreateRunTurnCommand(
         string requestId = "turn-1",
-        string sessionId = "session-1")
+        string sessionId = "session-1",
+        string mode = "single",
+        string interactionMode = "interactive",
+        IReadOnlyList<WorkflowNodeDto>? agents = null,
+        IReadOnlyList<ChatMessageDto>? messages = null)
     {
         return new RunTurnCommandDto
         {
@@ -1201,18 +1048,9 @@ public sealed class SidecarProtocolHostTests
             RequestId = requestId,
             SessionId = sessionId,
             ProjectPath = "C:\\workspace\\project",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-1",
-                Name = "Single Agent",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent(name: "Primary"),
-                ],
-            },
-            Messages =
+            Mode = interactionMode,
+            Workflow = CreateWorkflow(mode, agents),
+            Messages = messages ??
             [
                 new ChatMessageDto
                 {
@@ -1226,6 +1064,25 @@ public sealed class SidecarProtocolHostTests
         };
     }
 
+    private static WorkflowDefinitionDto CreateWorkflow(
+        string mode = "single",
+        IReadOnlyList<WorkflowNodeDto>? agents = null)
+    {
+        return new WorkflowDefinitionDto
+        {
+            Id = $"workflow-{mode}",
+            Name = "Single Agent",
+            Graph = new WorkflowGraphDto
+            {
+                Nodes = [.. agents ?? [CreateAgent(name: "Primary")]],
+            },
+            Settings = new WorkflowSettingsDto
+            {
+                OrchestrationMode = mode,
+            },
+        };
+    }
+
     private sealed class FakeWorkflowRunner : ITurnWorkflowRunner
     {
         private readonly Func<
@@ -1325,3 +1182,4 @@ public sealed class SidecarProtocolHostTests
         }
     }
 }
+

sidecar/tests/Aryx.AgentHost.Tests/UnitTest1.cs

@@ -1,169 +0,0 @@
-using Aryx.AgentHost.Contracts;
-using Aryx.AgentHost.Services;
-
-namespace Aryx.AgentHost.Tests;
-
-public sealed class PatternValidatorTests
-{
-    private readonly PatternValidator _validator = new();
-
-    [Fact]
-    public void SingleAgentPattern_WithExactlyOneAgent_IsValid()
-    {
-        IReadOnlyList<PatternValidationIssueDto> issues = _validator.Validate(
-            CreatePattern(
-                "single",
-                [CreateAgent()]));
-
-        Assert.Empty(issues);
-    }
-
-    [Fact]
-    public void HandoffPattern_WithSingleAgent_IsReportedAsInvalid()
-    {
-        IReadOnlyList<PatternValidationIssueDto> issues = _validator.Validate(
-            CreatePattern(
-                "handoff",
-                [CreateAgent()]));
-
-        Assert.Contains(issues, issue =>
-            issue.Field == "agents"
-            && issue.Message == "Handoff orchestration requires at least two agents.");
-    }
-
-    [Fact]
-    public void AgentWithoutModel_IsReportedAsInvalid()
-    {
-        IReadOnlyList<PatternValidationIssueDto> issues = _validator.Validate(
-            CreatePattern(
-                "sequential",
-                [
-                    CreateAgent(model: ""),
-                    CreateAgent(id: "agent-2", name: "Reviewer"),
-                ]));
-
-        Assert.Contains(issues, issue =>
-            issue.Field == "agents.model"
-            && issue.Message == "Agent \"Primary\" requires a model identifier.");
-    }
-
-    [Fact]
-    public void MagenticPattern_IsReportedAsUnavailable()
-    {
-        IReadOnlyList<PatternValidationIssueDto> issues = _validator.Validate(
-            CreatePattern(
-                "magentic",
-                [
-                    CreateAgent(id: "agent-1", name: "Planner", instructions: "Plan the task."),
-                    CreateAgent(
-                        id: "agent-2",
-                        name: "Specialist",
-                        model: "claude-opus-4.5",
-                        instructions: "Complete the task."),
-                ],
-                availability: "unavailable",
-                unavailabilityReason: "Unsupported in C#.",
-                name: "Magentic"));
-
-        Assert.Contains(issues, issue =>
-            issue.Field == "availability"
-            && issue.Message.Contains("Unsupported", StringComparison.OrdinalIgnoreCase));
-        Assert.Contains(issues, issue =>
-            issue.Field == "mode"
-            && issue.Message.Contains("Unsupported", StringComparison.OrdinalIgnoreCase));
-    }
-
-    [Fact]
-    public void SequentialPattern_WithBranchedGraph_IsReportedAsInvalid()
-    {
-        IReadOnlyList<PatternValidationIssueDto> issues = _validator.Validate(
-            CreatePattern(
-                "sequential",
-                [
-                    CreateAgent(id: "agent-1", name: "Analyst"),
-                    CreateAgent(id: "agent-2", name: "Builder"),
-                ],
-                graph: new PatternGraphDto
-                {
-                    Nodes =
-                    [
-                        CreateSystemNode("system-user-input", "user-input"),
-                        CreateAgentNode("agent-1", 0),
-                        CreateAgentNode("agent-2", 1),
-                        CreateSystemNode("system-user-output", "user-output"),
-                    ],
-                    Edges =
-                    [
-                        CreateEdge("system-user-input", "agent-node-agent-1"),
-                        CreateEdge("system-user-input", "agent-node-agent-2"),
-                        CreateEdge("agent-node-agent-1", "agent-node-agent-2"),
-                        CreateEdge("agent-node-agent-2", "system-user-output"),
-                    ],
-                }));
-
-        Assert.Contains(issues, issue =>
-            issue.Field == "graph"
-            && issue.Message.Contains("single path", StringComparison.OrdinalIgnoreCase));
-    }
-
-    private static PatternDefinitionDto CreatePattern(
-        string mode,
-        IReadOnlyList<PatternAgentDefinitionDto> agents,
-        string availability = "available",
-        string? unavailabilityReason = null,
-        string name = "Pattern",
-        PatternGraphDto? graph = null)
-    {
-        return new PatternDefinitionDto
-        {
-            Id = $"{mode}-pattern",
-            Name = name,
-            Mode = mode,
-            Availability = availability,
-            UnavailabilityReason = unavailabilityReason,
-            Agents = agents,
-            Graph = graph,
-        };
-    }
-
-    private static PatternAgentDefinitionDto CreateAgent(
-        string id = "agent-1",
-        string name = "Primary",
-        string model = "gpt-5.4",
-        string instructions = "Help with the user's request.")
-    {
-        return new PatternAgentDefinitionDto
-        {
-            Id = id,
-            Name = name,
-            Model = model,
-            Instructions = instructions,
-        };
-    }
-
-    private static PatternGraphNodeDto CreateSystemNode(string id, string kind)
-        => new()
-        {
-            Id = id,
-            Kind = kind,
-            Position = new PatternGraphPositionDto(),
-        };
-
-    private static PatternGraphNodeDto CreateAgentNode(string agentId, int order)
-        => new()
-        {
-            Id = $"agent-node-{agentId}",
-            Kind = "agent",
-            AgentId = agentId,
-            Order = order,
-            Position = new PatternGraphPositionDto(),
-        };
-
-    private static PatternGraphEdgeDto CreateEdge(string source, string target)
-        => new()
-        {
-            Id = $"edge-{source}-to-{target}",
-            Source = source,
-            Target = target,
-        };
-}

sidecar/tests/Aryx.AgentHost.Tests/WorkflowRequestInfoInterpreterTests.cs

@@ -186,54 +186,52 @@ public sealed class WorkflowRequestInfoInterpreterTests
     }
 
     private static RunTurnCommandDto CreateSingleAgentCommand()
-    {
-        return new RunTurnCommandDto
-        {
-            RequestId = "turn-1",
-            SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
-            {
-                Id = "pattern-single",
-                Name = "Single Agent",
-                Mode = "single",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent("agent-1", "Primary"),
-                ],
-            },
-        };
-    }
+        => CreateCommand("single", [CreateAgent("agent-1", "Primary")]);
 
     private static RunTurnCommandDto CreateHandoffCommand()
+        => CreateCommand("handoff",
+        [
+            CreateAgent("agent-handoff-triage", "Triage"),
+            CreateAgent("agent-handoff-ux", "UX Specialist"),
+        ]);
+
+    private static RunTurnCommandDto CreateCommand(string orchestrationMode, IReadOnlyList<WorkflowNodeDto> agents)
     {
         return new RunTurnCommandDto
         {
             RequestId = "turn-1",
             SessionId = "session-1",
-            Pattern = new PatternDefinitionDto
+            Workflow = new WorkflowDefinitionDto
             {
-                Id = "pattern-handoff",
-                Name = "Handoff Flow",
-                Mode = "handoff",
-                Availability = "available",
-                Agents =
-                [
-                    CreateAgent("agent-handoff-triage", "Triage"),
-                    CreateAgent("agent-handoff-ux", "UX Specialist"),
-                ],
+                Id = $"{orchestrationMode}-workflow",
+                Name = "Workflow",
+                Graph = new WorkflowGraphDto
+                {
+                    Nodes = [.. agents],
+                },
+                Settings = new WorkflowSettingsDto
+                {
+                    OrchestrationMode = orchestrationMode,
+                },
             },
         };
     }
 
-    private static PatternAgentDefinitionDto CreateAgent(string id, string name)
+    private static WorkflowNodeDto CreateAgent(string id, string name)
     {
-        return new PatternAgentDefinitionDto
+        return new WorkflowNodeDto
         {
             Id = id,
-            Name = name,
-            Model = "gpt-5.4",
-            Instructions = "Help with the request.",
+            Kind = "agent",
+            Label = name,
+            Config = new WorkflowNodeConfigDto
+            {
+                Kind = "agent",
+                Id = id,
+                Name = name,
+                Model = "gpt-5.4",
+                Instructions = "Help with the request.",
+            },
         };
     }
 

sidecar/tests/Aryx.AgentHost.Tests/WorkflowRunnerTests.cs

@@ -15,7 +15,6 @@ public sealed class WorkflowRunnerTests
         WorkflowRunner runner = new();
         Workflow workflow = runner.BuildWorkflow(
             CreateSubworkflowParent(inlineWorkflow: CreateAgentWorkflow("child-inline", "agent-child")),
-            CreatePattern("agent-child"),
             [CreateChatClientAgent("agent-child", "Child Agent")]);
 
         ProtocolDescriptor descriptor = await workflow.DescribeProtocolAsync();
@@ -30,7 +29,6 @@ public sealed class WorkflowRunnerTests
         WorkflowDefinitionDto childWorkflow = CreateAgentWorkflow("child-ref", "agent-child");
         Workflow workflow = runner.BuildWorkflow(
             CreateSubworkflowParent(workflowId: childWorkflow.Id),
-            CreatePattern("agent-child"),
             [CreateChatClientAgent("agent-child", "Child Agent")],
             [childWorkflow]);
 
@@ -46,7 +44,6 @@ public sealed class WorkflowRunnerTests
 
         InvalidOperationException error = Assert.Throws<InvalidOperationException>(() => runner.BuildWorkflow(
             CreateSubworkflowParent(workflowId: "missing-child"),
-            CreatePattern("agent-child"),
             [CreateChatClientAgent("agent-child", "Child Agent")],
             []));
 
@@ -65,7 +62,6 @@ public sealed class WorkflowRunnerTests
                     Kind = "code-executor",
                     Implementation = "return-text:done",
                 }),
-            CreateEmptyPattern(),
             []);
 
         List<ChatMessage> output = await RunWorkflowToOutputAsync(workflow);
@@ -81,7 +77,6 @@ public sealed class WorkflowRunnerTests
         WorkflowRunner runner = new();
         Workflow workflow = runner.BuildWorkflow(
             CreateStatefulFunctionWorkflow(),
-            CreateEmptyPattern(),
             []);
 
         List<ChatMessage> output = await RunWorkflowToOutputAsync(workflow);
@@ -105,7 +100,6 @@ public sealed class WorkflowRunnerTests
                     ResponseType = "string",
                     Prompt = "Approve the workflow?",
                 }),
-            CreateEmptyPattern(),
             []);
 
         ChatMessage[] input =
@@ -153,33 +147,11 @@ public sealed class WorkflowRunnerTests
                     Kind = "function-executor",
                     FunctionRef = "missing-function",
                 }),
-            CreateEmptyPattern(),
             []));
 
         Assert.Contains("unsupported functionRef", error.Message, StringComparison.OrdinalIgnoreCase);
     }
 
-    private static PatternDefinitionDto CreatePattern(string agentId)
-    {
-        return new PatternDefinitionDto
-        {
-            Id = "pattern-1",
-            Name = "Workflow Pattern",
-            Mode = "single",
-            Availability = "available",
-            Agents =
-            [
-                new PatternAgentDefinitionDto
-                {
-                    Id = agentId,
-                    Name = "Child Agent",
-                    Instructions = "Help with the request.",
-                    Model = "gpt-5.4",
-                },
-            ],
-        };
-    }
-
     private static WorkflowDefinitionDto CreateAgentWorkflow(string id, string agentId)
     {
         return new WorkflowDefinitionDto
@@ -243,18 +215,6 @@ public sealed class WorkflowRunnerTests
         };
     }
 
-    private static PatternDefinitionDto CreateEmptyPattern()
-    {
-        return new PatternDefinitionDto
-        {
-            Id = "pattern-empty",
-            Name = "Workflow Pattern",
-            Mode = "single",
-            Availability = "available",
-            Agents = [],
-        };
-    }
-
     private static WorkflowDefinitionDto CreateSubworkflowParent(
         string? workflowId = null,
         WorkflowDefinitionDto? inlineWorkflow = null)