diff --git a/sidecar/src/Aryx.AgentHost/Contracts/ProtocolModels.cs b/sidecar/src/Aryx.AgentHost/Contracts/ProtocolModels.cs
index 9717122..ef53f4b 100644
--- a/sidecar/src/Aryx.AgentHost/Contracts/ProtocolModels.cs
+++ b/sidecar/src/Aryx.AgentHost/Contracts/ProtocolModels.cs
@@ -138,6 +138,8 @@ public sealed class WorkflowEdgeDto
     public EdgeConditionDto? Condition { get; init; }
     public string? Label { get; init; }
     public FanOutConfigDto? FanOutConfig { get; init; }
+    public bool? IsLoop { get; init; }
+    public int? MaxIterations { get; init; }
 }
 
 public sealed class WorkflowGraphDto
diff --git a/sidecar/src/Aryx.AgentHost/Services/WorkflowConditionEvaluator.cs b/sidecar/src/Aryx.AgentHost/Services/WorkflowConditionEvaluator.cs
new file mode 100644
index 0000000..846d80c
--- /dev/null
+++ b/sidecar/src/Aryx.AgentHost/Services/WorkflowConditionEvaluator.cs
@@ -0,0 +1,432 @@
+using System.Collections;
+using System.Globalization;
+using System.Reflection;
+using System.Text.Json;
+using System.Text.RegularExpressions;
+using Aryx.AgentHost.Contracts;
+
+namespace Aryx.AgentHost.Services;
+
+internal static class WorkflowConditionEvaluator
+{
+    private static readonly HashSet<string> SupportedConditionTypes = new(StringComparer.OrdinalIgnoreCase)
+    {
+        "always",
+        "message-type",
+        "expression",
+        "property",
+    };
+
+    private static readonly HashSet<string> SupportedOperators = new(StringComparer.OrdinalIgnoreCase)
+    {
+        "equals",
+        "not-equals",
+        "contains",
+        "gt",
+        "lt",
+        "regex",
+    };
+
+    private static readonly Regex ComparisonExpression = new(
+        @"^(?<path>[A-Za-z_][A-Za-z0-9_\.]*)\s*(?<operator>==|!=|>|<|contains|matches)\s*(?<value>""(?:[^""\\]|\\.)*""|'(?:[^'\\]|\\.)*'|-?\d+(?:\.\d+)?|true|false)$",
+        RegexOptions.Compiled | RegexOptions.CultureInvariant | RegexOptions.IgnoreCase);
+
+    internal static bool IsSupportedConditionType(string? type)
+        => !string.IsNullOrWhiteSpace(type) && SupportedConditionTypes.Contains(type);
+
+    internal static bool IsSupportedOperator(string? @operator)
+        => !string.IsNullOrWhiteSpace(@operator) && SupportedOperators.Contains(@operator);
+
+    internal static bool IsSupportedExpression(string? expression)
+    {
+        if (string.IsNullOrWhiteSpace(expression))
+        {
+            return false;
+        }
+
+        string trimmed = expression.Trim();
+        if (string.Equals(trimmed, "true", StringComparison.OrdinalIgnoreCase)
+            || string.Equals(trimmed, "false", StringComparison.OrdinalIgnoreCase))
+        {
+            return true;
+        }
+
+        string? delimiter = trimmed.Contains("&&", StringComparison.Ordinal) ? "&&" : null;
+        if (delimiter is null && trimmed.Contains("||", StringComparison.Ordinal))
+        {
+            delimiter = "||";
+        }
+
+        if (delimiter is null)
+        {
+            return ComparisonExpression.IsMatch(trimmed);
+        }
+
+        return trimmed
+            .Split(delimiter, StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)
+            .All(segment => ComparisonExpression.IsMatch(segment));
+    }
+
+    internal static Func<object?, bool>? Compile(WorkflowEdgeDto edge)
+    {
+        ArgumentNullException.ThrowIfNull(edge);
+
+        Func<object?, bool>? baseCondition = edge.Condition is null
+            ? null
+            : CompileCondition(edge.Condition);
+
+        if (edge.IsLoop != true)
+        {
+            return baseCondition;
+        }
+
+        int maxIterations = edge.MaxIterations ?? 0;
+        int successfulIterations = 0;
+        return payload =>
+        {
+            if (successfulIterations >= maxIterations)
+            {
+                return false;
+            }
+
+            if (baseCondition is not null && !baseCondition(payload))
+            {
+                return false;
+            }
+
+            successfulIterations++;
+            return true;
+        };
+    }
+
+    internal static bool Evaluate(EdgeConditionDto condition, object? payload)
+    {
+        ArgumentNullException.ThrowIfNull(condition);
+        return CompileCondition(condition)?.Invoke(payload) ?? true;
+    }
+
+    private static Func<object?, bool>? CompileCondition(EdgeConditionDto condition)
+    {
+        if (string.IsNullOrWhiteSpace(condition.Type)
+            || string.Equals(condition.Type, "always", StringComparison.OrdinalIgnoreCase))
+        {
+            return null;
+        }
+
+        if (string.Equals(condition.Type, "message-type", StringComparison.OrdinalIgnoreCase))
+        {
+            string expectedTypeName = condition.TypeName?.Trim() ?? string.Empty;
+            return payload =>
+            {
+                if (payload is null || string.IsNullOrWhiteSpace(expectedTypeName))
+                {
+                    return false;
+                }
+
+                Type payloadType = payload.GetType();
+                return string.Equals(payloadType.Name, expectedTypeName, StringComparison.OrdinalIgnoreCase)
+                    || string.Equals(payloadType.FullName, expectedTypeName, StringComparison.OrdinalIgnoreCase);
+            };
+        }
+
+        if (string.Equals(condition.Type, "property", StringComparison.OrdinalIgnoreCase))
+        {
+            string combinator = string.Equals(condition.Combinator, "or", StringComparison.OrdinalIgnoreCase) ? "or" : "and";
+            return payload =>
+            {
+                IReadOnlyList<bool> results = condition.Rules
+                    .Select(rule => EvaluateRule(rule, payload))
+                    .ToArray();
+
+                if (results.Count == 0)
+                {
+                    return false;
+                }
+
+                return string.Equals(combinator, "or", StringComparison.OrdinalIgnoreCase)
+                    ? results.Any(result => result)
+                    : results.All(result => result);
+            };
+        }
+
+        if (string.Equals(condition.Type, "expression", StringComparison.OrdinalIgnoreCase))
+        {
+            return payload => EvaluateExpression(condition.Expression, payload);
+        }
+
+        throw new NotSupportedException($"Condition type \"{condition.Type}\" is not supported.");
+    }
+
+    private static bool EvaluateExpression(string? expression, object? payload)
+    {
+        string trimmed = expression?.Trim() ?? string.Empty;
+        if (string.Equals(trimmed, "true", StringComparison.OrdinalIgnoreCase))
+        {
+            return true;
+        }
+
+        if (string.Equals(trimmed, "false", StringComparison.OrdinalIgnoreCase))
+        {
+            return false;
+        }
+
+        if (trimmed.Contains("&&", StringComparison.Ordinal))
+        {
+            return trimmed
+                .Split("&&", StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)
+                .All(segment => EvaluateExpression(segment, payload));
+        }
+
+        if (trimmed.Contains("||", StringComparison.Ordinal))
+        {
+            return trimmed
+                .Split("||", StringSplitOptions.TrimEntries | StringSplitOptions.RemoveEmptyEntries)
+                .Any(segment => EvaluateExpression(segment, payload));
+        }
+
+        Match match = ComparisonExpression.Match(trimmed);
+        if (!match.Success)
+        {
+            return false;
+        }
+
+        string path = match.Groups["path"].Value;
+        string @operator = match.Groups["operator"].Value switch
+        {
+            "==" => "equals",
+            "!=" => "not-equals",
+            ">" => "gt",
+            "<" => "lt",
+            "matches" => "regex",
+            _ => match.Groups["operator"].Value,
+        };
+
+        string rawValue = match.Groups["value"].Value;
+        string value = UnwrapLiteral(rawValue);
+        return EvaluateRule(
+            new WorkflowConditionRuleDto
+            {
+                PropertyPath = path,
+                Operator = @operator,
+                Value = value,
+            },
+            payload);
+    }
+
+    private static bool EvaluateRule(WorkflowConditionRuleDto rule, object? payload)
+    {
+        if (payload is null || string.IsNullOrWhiteSpace(rule.PropertyPath))
+        {
+            return false;
+        }
+
+        if (!TryResolvePropertyPath(payload, rule.PropertyPath, out object? actualValue))
+        {
+            return false;
+        }
+
+        return rule.Operator switch
+        {
+            "equals" => AreEqual(actualValue, rule.Value),
+            "not-equals" => !AreEqual(actualValue, rule.Value),
+            "contains" => ContainsValue(actualValue, rule.Value),
+            "gt" => CompareAsNumberOrString(actualValue, rule.Value) > 0,
+            "lt" => CompareAsNumberOrString(actualValue, rule.Value) < 0,
+            "regex" => Regex.IsMatch(CoerceToString(actualValue), rule.Value, RegexOptions.CultureInvariant),
+            _ => false,
+        };
+    }
+
+    private static bool TryResolvePropertyPath(object payload, string propertyPath, out object? value)
+    {
+        object? current = payload;
+        foreach (string segment in propertyPath.Split('.', StringSplitOptions.RemoveEmptyEntries | StringSplitOptions.TrimEntries))
+        {
+            if (!TryResolvePropertySegment(current, segment, out current))
+            {
+                value = null;
+                return false;
+            }
+        }
+
+        value = current;
+        return true;
+    }
+
+    private static bool TryResolvePropertySegment(object? current, string segment, out object? value)
+    {
+        value = null;
+        if (current is null)
+        {
+            return false;
+        }
+
+        if (current is JsonElement jsonElement)
+        {
+            if (jsonElement.ValueKind == JsonValueKind.Object)
+            {
+                foreach (JsonProperty jsonProperty in jsonElement.EnumerateObject())
+                {
+                    if (string.Equals(jsonProperty.Name, segment, StringComparison.OrdinalIgnoreCase))
+                    {
+                        value = jsonProperty.Value;
+                        return true;
+                    }
+                }
+            }
+
+            return false;
+        }
+
+        if (current is IDictionary dictionary)
+        {
+            foreach (DictionaryEntry entry in dictionary)
+            {
+                if (entry.Key is string key && string.Equals(key, segment, StringComparison.OrdinalIgnoreCase))
+                {
+                    value = entry.Value;
+                    return true;
+                }
+            }
+        }
+
+        Type type = current.GetType();
+        PropertyInfo? property = type.GetProperties(BindingFlags.Instance | BindingFlags.Public)
+            .FirstOrDefault(candidate => string.Equals(candidate.Name, segment, StringComparison.OrdinalIgnoreCase));
+        if (property is not null)
+        {
+            value = property.GetValue(current);
+            return true;
+        }
+
+        return false;
+    }
+
+    private static bool AreEqual(object? actualValue, string expectedValue)
+    {
+        if (actualValue is null)
+        {
+            return false;
+        }
+
+        if (TryConvertToDecimal(actualValue, out decimal actualDecimal)
+            && decimal.TryParse(expectedValue, NumberStyles.Float, CultureInfo.InvariantCulture, out decimal expectedDecimal))
+        {
+            return actualDecimal == expectedDecimal;
+        }
+
+        return string.Equals(CoerceToString(actualValue), expectedValue, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static bool ContainsValue(object? actualValue, string expectedValue)
+    {
+        if (actualValue is null)
+        {
+            return false;
+        }
+
+        if (actualValue is string actualString)
+        {
+            return actualString.Contains(expectedValue, StringComparison.OrdinalIgnoreCase);
+        }
+
+        if (actualValue is IEnumerable enumerable)
+        {
+            foreach (object? item in enumerable)
+            {
+                if (string.Equals(CoerceToString(item), expectedValue, StringComparison.OrdinalIgnoreCase))
+                {
+                    return true;
+                }
+            }
+        }
+
+        return CoerceToString(actualValue).Contains(expectedValue, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static int CompareAsNumberOrString(object? actualValue, string expectedValue)
+    {
+        if (actualValue is null)
+        {
+            return -1;
+        }
+
+        if (TryConvertToDecimal(actualValue, out decimal actualDecimal)
+            && decimal.TryParse(expectedValue, NumberStyles.Float, CultureInfo.InvariantCulture, out decimal expectedDecimal))
+        {
+            return actualDecimal.CompareTo(expectedDecimal);
+        }
+
+        return string.Compare(CoerceToString(actualValue), expectedValue, StringComparison.OrdinalIgnoreCase);
+    }
+
+    private static bool TryConvertToDecimal(object? value, out decimal result)
+    {
+        switch (value)
+        {
+            case byte byteValue:
+                result = byteValue;
+                return true;
+            case short shortValue:
+                result = shortValue;
+                return true;
+            case int intValue:
+                result = intValue;
+                return true;
+            case long longValue:
+                result = longValue;
+                return true;
+            case float floatValue:
+                result = (decimal)floatValue;
+                return true;
+            case double doubleValue:
+                result = (decimal)doubleValue;
+                return true;
+            case decimal decimalValue:
+                result = decimalValue;
+                return true;
+            case JsonElement jsonElement when jsonElement.ValueKind == JsonValueKind.Number && jsonElement.TryGetDecimal(out decimal jsonDecimal):
+                result = jsonDecimal;
+                return true;
+            default:
+                return decimal.TryParse(
+                    CoerceToString(value),
+                    NumberStyles.Float,
+                    CultureInfo.InvariantCulture,
+                    out result);
+        }
+    }
+
+    private static string CoerceToString(object? value)
+    {
+        if (value is null)
+        {
+            return string.Empty;
+        }
+
+        if (value is JsonElement jsonElement)
+        {
+            return jsonElement.ValueKind switch
+            {
+                JsonValueKind.String => jsonElement.GetString() ?? string.Empty,
+                JsonValueKind.True => bool.TrueString,
+                JsonValueKind.False => bool.FalseString,
+                _ => jsonElement.ToString(),
+            };
+        }
+
+        return Convert.ToString(value, CultureInfo.InvariantCulture) ?? string.Empty;
+    }
+
+    private static string UnwrapLiteral(string rawValue)
+    {
+        if (rawValue.Length >= 2
+            && ((rawValue.StartsWith('"') && rawValue.EndsWith('"'))
+                || (rawValue.StartsWith('\'') && rawValue.EndsWith('\''))))
+        {
+            return rawValue[1..^1];
+        }
+
+        return rawValue;
+    }
+}
diff --git a/sidecar/src/Aryx.AgentHost/Services/WorkflowRunner.cs b/sidecar/src/Aryx.AgentHost/Services/WorkflowRunner.cs
index a89cf67..d69b32e 100644
--- a/sidecar/src/Aryx.AgentHost/Services/WorkflowRunner.cs
+++ b/sidecar/src/Aryx.AgentHost/Services/WorkflowRunner.cs
@@ -36,16 +36,41 @@ internal sealed class WorkflowRunner
         foreach (WorkflowEdgeDto edge in workflowDefinition.Graph.Edges.Where(edge =>
                      string.Equals(edge.Kind, "direct", StringComparison.OrdinalIgnoreCase)))
         {
-            builder.AddEdge(bindings[edge.Source], bindings[edge.Target]);
+            Func<object?, bool>? condition = WorkflowConditionEvaluator.Compile(edge);
+            if (condition is null)
+            {
+                builder.AddEdge(bindings[edge.Source], bindings[edge.Target]);
+            }
+            else
+            {
+                builder.AddEdge<object>(bindings[edge.Source], bindings[edge.Target], condition);
+            }
         }
 
         foreach (IGrouping<string, WorkflowEdgeDto> fanOutGroup in workflowDefinition.Graph.Edges
                      .Where(edge => string.Equals(edge.Kind, "fan-out", StringComparison.OrdinalIgnoreCase))
                      .GroupBy(edge => edge.Source, StringComparer.Ordinal))
         {
-            builder.AddFanOutEdge(
+            WorkflowEdgeDto[] fanOutEdges = fanOutGroup.ToArray();
+            ExecutorBinding[] targets = fanOutEdges.Select(edge => bindings[edge.Target]).ToArray();
+            Func<object?, bool>?[] compiledConditions = fanOutEdges
+                .Select(WorkflowConditionEvaluator.Compile)
+                .ToArray();
+            bool hasConditionalRouting = fanOutEdges.Any(edge => edge.Condition is not null);
+            if (!hasConditionalRouting)
+            {
+                builder.AddFanOutEdge(bindings[fanOutGroup.Key], targets);
+                continue;
+            }
+
+            builder.AddFanOutEdge<object>(
                 bindings[fanOutGroup.Key],
-                fanOutGroup.Select(edge => bindings[edge.Target]).ToArray());
+                targets,
+                (payload, _) => fanOutEdges
+                    .Select((edge, index) => (edge, index))
+                    .Where(pair => compiledConditions[pair.index]?.Invoke(payload) ?? true)
+                    .Select(pair => pair.index)
+                    .ToArray());
         }
 
         foreach (IGrouping<string, WorkflowEdgeDto> fanInGroup in workflowDefinition.Graph.Edges
diff --git a/sidecar/src/Aryx.AgentHost/Services/WorkflowValidator.cs b/sidecar/src/Aryx.AgentHost/Services/WorkflowValidator.cs
index 4e69801..9e359cb 100644
--- a/sidecar/src/Aryx.AgentHost/Services/WorkflowValidator.cs
+++ b/sidecar/src/Aryx.AgentHost/Services/WorkflowValidator.cs
@@ -135,6 +135,8 @@ public sealed class WorkflowValidator
             incomingCounts[edge.Target] = incomingCounts.TryGetValue(edge.Target, out int incoming)
                 ? incoming + 1
                 : 1;
+
+            ValidateEdgeCondition(edge, issues);
         }
 
         List<WorkflowNodeDto> startNodes = workflow.Graph.Nodes
@@ -250,9 +252,219 @@ public sealed class WorkflowValidator
             });
         }
 
+        if (workflow.Settings.MaxIterations is int workflowMaxIterations
+            && (workflowMaxIterations < 1 || workflowMaxIterations > 100))
+        {
+            issues.Add(new WorkflowValidationIssueDto
+            {
+                Field = "settings.maxIterations",
+                Message = "Workflow maxIterations must be between 1 and 100.",
+            });
+        }
+
+        foreach (WorkflowEdgeDto edge in workflow.Graph.Edges)
+        {
+            bool participatesInCycle = IsLoopEdge(workflow.Graph, edge);
+            if (!participatesInCycle)
+            {
+                if (edge.IsLoop == true)
+                {
+                    issues.Add(new WorkflowValidationIssueDto
+                    {
+                        Level = "warning",
+                        Field = "graph.edges.isLoop",
+                        EdgeId = edge.Id,
+                        Message = "This edge is marked as a loop but does not currently form a cycle.",
+                    });
+                }
+
+                continue;
+            }
+
+            if (!string.Equals(edge.Kind, "direct", StringComparison.OrdinalIgnoreCase))
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.kind",
+                    EdgeId = edge.Id,
+                    Message = "Loop edges currently support only direct edges.",
+                });
+            }
+
+            if (edge.IsLoop != true)
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.isLoop",
+                    EdgeId = edge.Id,
+                    Message = "Edges that participate in a cycle must be explicitly marked as loops.",
+                });
+            }
+
+            if (edge.Condition is null || string.Equals(edge.Condition.Type, "always", StringComparison.OrdinalIgnoreCase))
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.condition",
+                    EdgeId = edge.Id,
+                    Message = "Loop edges require a non-default condition so the loop can terminate.",
+                });
+            }
+
+            if (edge.MaxIterations is null || edge.MaxIterations < 1)
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.maxIterations",
+                    EdgeId = edge.Id,
+                    Message = "Loop edges require a maxIterations value of at least 1.",
+                });
+            }
+
+            HashSet<string> componentNodes = CollectStronglyConnectedNodes(workflow.Graph, edge.Source);
+            bool hasExitPath = workflow.Graph.Edges.Any(candidate =>
+                componentNodes.Contains(candidate.Source) && !componentNodes.Contains(candidate.Target));
+            if (!hasExitPath)
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges",
+                    EdgeId = edge.Id,
+                    Message = "Loop cycles must include an exit path to a node outside the loop.",
+                });
+            }
+        }
+
         return issues;
     }
 
+    private static void ValidateEdgeCondition(WorkflowEdgeDto edge, List<WorkflowValidationIssueDto> issues)
+    {
+        if (edge.Condition is null)
+        {
+            return;
+        }
+
+        if (string.Equals(edge.Kind, "fan-in", StringComparison.OrdinalIgnoreCase))
+        {
+            issues.Add(new WorkflowValidationIssueDto
+            {
+                Field = "graph.edges.condition",
+                EdgeId = edge.Id,
+                Message = "Fan-in edges do not support conditions.",
+            });
+        }
+
+        if (!WorkflowConditionEvaluator.IsSupportedConditionType(edge.Condition.Type))
+        {
+            issues.Add(new WorkflowValidationIssueDto
+            {
+                Field = "graph.edges.condition.type",
+                EdgeId = edge.Id,
+                Message = $"Condition type \"{edge.Condition.Type}\" is not supported.",
+            });
+            return;
+        }
+
+        if (string.Equals(edge.Condition.Type, "message-type", StringComparison.OrdinalIgnoreCase)
+            && string.IsNullOrWhiteSpace(edge.Condition.TypeName))
+        {
+            issues.Add(new WorkflowValidationIssueDto
+            {
+                Field = "graph.edges.condition.typeName",
+                EdgeId = edge.Id,
+                Message = "Message-type conditions require a type name.",
+            });
+        }
+
+        if (string.Equals(edge.Condition.Type, "expression", StringComparison.OrdinalIgnoreCase))
+        {
+            if (string.IsNullOrWhiteSpace(edge.Condition.Expression))
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.condition.expression",
+                    EdgeId = edge.Id,
+                    Message = "Expression conditions require a non-empty expression.",
+                });
+            }
+            else if (!WorkflowConditionEvaluator.IsSupportedExpression(edge.Condition.Expression))
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.condition.expression",
+                    EdgeId = edge.Id,
+                    Message = "Expression conditions currently support simple comparisons using ==, !=, >, <, contains, matches, optionally combined with && or ||.",
+                });
+            }
+        }
+
+        if (string.Equals(edge.Condition.Type, "property", StringComparison.OrdinalIgnoreCase))
+        {
+            if (edge.Condition.Rules.Count == 0)
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.condition.rules",
+                    EdgeId = edge.Id,
+                    Message = "Property conditions require at least one rule.",
+                });
+            }
+
+            if (!string.IsNullOrWhiteSpace(edge.Condition.Combinator)
+                && !string.Equals(edge.Condition.Combinator, "and", StringComparison.OrdinalIgnoreCase)
+                && !string.Equals(edge.Condition.Combinator, "or", StringComparison.OrdinalIgnoreCase))
+            {
+                issues.Add(new WorkflowValidationIssueDto
+                {
+                    Field = "graph.edges.condition.combinator",
+                    EdgeId = edge.Id,
+                    Message = "Property conditions must use the \"and\" or \"or\" combinator.",
+                });
+            }
+
+            foreach (WorkflowConditionRuleDto rule in edge.Condition.Rules)
+            {
+                if (string.IsNullOrWhiteSpace(rule.PropertyPath))
+                {
+                    issues.Add(new WorkflowValidationIssueDto
+                    {
+                        Field = "graph.edges.condition.rules.propertyPath",
+                        EdgeId = edge.Id,
+                        Message = "Property condition rules require a property path.",
+                    });
+                }
+
+                if (!WorkflowConditionEvaluator.IsSupportedOperator(rule.Operator))
+                {
+                    issues.Add(new WorkflowValidationIssueDto
+                    {
+                        Field = "graph.edges.condition.rules.operator",
+                        EdgeId = edge.Id,
+                        Message = $"Property condition operator \"{rule.Operator}\" is not supported.",
+                    });
+                }
+
+                if (string.Equals(rule.Operator, "regex", StringComparison.OrdinalIgnoreCase))
+                {
+                    try
+                    {
+                        _ = new System.Text.RegularExpressions.Regex(rule.Value);
+                    }
+                    catch (ArgumentException)
+                    {
+                        issues.Add(new WorkflowValidationIssueDto
+                        {
+                            Field = "graph.edges.condition.rules.value",
+                            EdgeId = edge.Id,
+                            Message = $"Regex pattern \"{rule.Value}\" is invalid.",
+                        });
+                    }
+                }
+            }
+        }
+    }
+
     private static bool HasPathToAnyEnd(
         string startNodeId,
         WorkflowGraphDto graph,
@@ -289,4 +501,64 @@ public sealed class WorkflowValidator
 
         return false;
     }
+
+    private static bool CanReachNode(
+        WorkflowGraphDto graph,
+        string startNodeId,
+        string targetNodeId,
+        string? excludedEdgeId = null)
+    {
+        if (string.Equals(startNodeId, targetNodeId, StringComparison.Ordinal))
+        {
+            return true;
+        }
+
+        Dictionary<string, List<string>> outgoing = graph.Edges
+            .Where(edge => !string.Equals(edge.Id, excludedEdgeId, StringComparison.Ordinal))
+            .GroupBy(edge => edge.Source, StringComparer.Ordinal)
+            .ToDictionary(
+                group => group.Key,
+                group => group.Select(edge => edge.Target).ToList(),
+                StringComparer.Ordinal);
+
+        Queue<string> queue = new([startNodeId]);
+        HashSet<string> visited = new(StringComparer.Ordinal);
+        while (queue.Count > 0)
+        {
+            string current = queue.Dequeue();
+            if (!visited.Add(current))
+            {
+                continue;
+            }
+
+            foreach (string target in outgoing.GetValueOrDefault(current, []))
+            {
+                if (string.Equals(target, targetNodeId, StringComparison.Ordinal))
+                {
+                    return true;
+                }
+
+                queue.Enqueue(target);
+            }
+        }
+
+        return false;
+    }
+
+    private static bool IsLoopEdge(WorkflowGraphDto graph, WorkflowEdgeDto edge)
+        => CanReachNode(graph, edge.Target, edge.Source, edge.Id);
+
+    private static HashSet<string> CollectStronglyConnectedNodes(WorkflowGraphDto graph, string nodeId)
+    {
+        HashSet<string> connected = new(StringComparer.Ordinal);
+        foreach (WorkflowNodeDto candidate in graph.Nodes)
+        {
+            if (CanReachNode(graph, nodeId, candidate.Id) && CanReachNode(graph, candidate.Id, nodeId))
+            {
+                connected.Add(candidate.Id);
+            }
+        }
+
+        return connected;
+    }
 }
diff --git a/sidecar/tests/Aryx.AgentHost.Tests/WorkflowConditionEvaluatorTests.cs b/sidecar/tests/Aryx.AgentHost.Tests/WorkflowConditionEvaluatorTests.cs
new file mode 100644
index 0000000..e91ae55
--- /dev/null
+++ b/sidecar/tests/Aryx.AgentHost.Tests/WorkflowConditionEvaluatorTests.cs
@@ -0,0 +1,80 @@
+using Aryx.AgentHost.Contracts;
+using Aryx.AgentHost.Services;
+
+namespace Aryx.AgentHost.Tests;
+
+public sealed class WorkflowConditionEvaluatorTests
+{
+    [Fact]
+    public void Evaluate_PropertyCondition_MatchesPayload()
+    {
+        EdgeConditionDto condition = new()
+        {
+            Type = "property",
+            Combinator = "and",
+            Rules =
+            [
+                new WorkflowConditionRuleDto
+                {
+                    PropertyPath = "Role",
+                    Operator = "equals",
+                    Value = "user",
+                },
+            ],
+        };
+
+        bool matched = WorkflowConditionEvaluator.Evaluate(condition, new TestPayload("user", 1, "hello"));
+
+        Assert.True(matched);
+    }
+
+    [Fact]
+    public void Evaluate_ExpressionCondition_MatchesPayload()
+    {
+        EdgeConditionDto condition = new()
+        {
+            Type = "expression",
+            Expression = "Iteration < 3 && Role == \"user\"",
+        };
+
+        bool matched = WorkflowConditionEvaluator.Evaluate(condition, new TestPayload("user", 2, "hello"));
+
+        Assert.True(matched);
+    }
+
+    [Fact]
+    public void Compile_LoopCondition_StopsAfterMaxIterations()
+    {
+        WorkflowEdgeDto edge = new()
+        {
+            Id = "edge-loop",
+            Source = "agent",
+            Target = "agent",
+            Kind = "direct",
+            IsLoop = true,
+            MaxIterations = 2,
+            Condition = new EdgeConditionDto
+            {
+                Type = "property",
+                Rules =
+                [
+                    new WorkflowConditionRuleDto
+                    {
+                        PropertyPath = "Iteration",
+                        Operator = "lt",
+                        Value = "10",
+                    },
+                ],
+            },
+        };
+
+        Func<object?, bool>? compiled = WorkflowConditionEvaluator.Compile(edge);
+
+        Assert.NotNull(compiled);
+        Assert.True(compiled!(new TestPayload("user", 1, "hello")));
+        Assert.True(compiled(new TestPayload("user", 2, "hello")));
+        Assert.False(compiled(new TestPayload("user", 3, "hello")));
+    }
+
+    private sealed record TestPayload(string Role, int Iteration, string Content);
+}
diff --git a/sidecar/tests/Aryx.AgentHost.Tests/WorkflowValidatorTests.cs b/sidecar/tests/Aryx.AgentHost.Tests/WorkflowValidatorTests.cs
new file mode 100644
index 0000000..4936c6c
--- /dev/null
+++ b/sidecar/tests/Aryx.AgentHost.Tests/WorkflowValidatorTests.cs
@@ -0,0 +1,187 @@
+using Aryx.AgentHost.Contracts;
+using Aryx.AgentHost.Services;
+
+namespace Aryx.AgentHost.Tests;
+
+public sealed class WorkflowValidatorTests
+{
+    private readonly WorkflowValidator _validator = new();
+
+    [Fact]
+    public void Validate_RejectsInvalidConditionOperator()
+    {
+        WorkflowDefinitionDto workflow = CreateWorkflow();
+        workflow = new WorkflowDefinitionDto
+        {
+            Id = workflow.Id,
+            Name = workflow.Name,
+            Settings = workflow.Settings,
+            Graph = new WorkflowGraphDto
+            {
+                Nodes = workflow.Graph.Nodes,
+                Edges =
+                [
+                    new WorkflowEdgeDto
+                    {
+                        Id = "edge-start-agent",
+                        Source = "start",
+                        Target = "agent",
+                        Kind = "direct",
+                        Condition = new EdgeConditionDto
+                        {
+                            Type = "property",
+                            Rules =
+                            [
+                                new WorkflowConditionRuleDto
+                                {
+                                    PropertyPath = "Role",
+                                    Operator = "bad-op",
+                                    Value = "user",
+                                },
+                            ],
+                        },
+                    },
+                    workflow.Graph.Edges[1],
+                ],
+            },
+        };
+
+        IReadOnlyList<WorkflowValidationIssueDto> issues = _validator.Validate(workflow);
+
+        Assert.Contains(issues, issue => issue.Field == "graph.edges.condition.rules.operator");
+    }
+
+    [Fact]
+    public void Validate_RejectsLoopWithoutMetadata()
+    {
+        WorkflowDefinitionDto workflow = CreateWorkflow();
+        workflow = new WorkflowDefinitionDto
+        {
+            Id = workflow.Id,
+            Name = workflow.Name,
+            Settings = workflow.Settings,
+            Graph = new WorkflowGraphDto
+            {
+                Nodes = workflow.Graph.Nodes,
+                Edges =
+                [
+                    .. workflow.Graph.Edges,
+                    new WorkflowEdgeDto
+                    {
+                        Id = "edge-loop",
+                        Source = "agent",
+                        Target = "agent",
+                        Kind = "direct",
+                    },
+                ],
+            },
+        };
+
+        IReadOnlyList<WorkflowValidationIssueDto> issues = _validator.Validate(workflow);
+
+        Assert.Contains(issues, issue => issue.Field == "graph.edges.isLoop");
+        Assert.Contains(issues, issue => issue.Field == "graph.edges.condition");
+        Assert.Contains(issues, issue => issue.Field == "graph.edges.maxIterations");
+    }
+
+    [Fact]
+    public void Validate_AcceptsLoopWithExitPathConditionAndCap()
+    {
+        WorkflowDefinitionDto workflow = CreateWorkflow();
+        workflow = new WorkflowDefinitionDto
+        {
+            Id = workflow.Id,
+            Name = workflow.Name,
+            Settings = workflow.Settings,
+            Graph = new WorkflowGraphDto
+            {
+                Nodes = workflow.Graph.Nodes,
+                Edges =
+                [
+                    .. workflow.Graph.Edges,
+                    new WorkflowEdgeDto
+                    {
+                        Id = "edge-loop",
+                        Source = "agent",
+                        Target = "agent",
+                        Kind = "direct",
+                        IsLoop = true,
+                        MaxIterations = 3,
+                        Condition = new EdgeConditionDto
+                        {
+                            Type = "expression",
+                            Expression = "Iteration < 3",
+                        },
+                    },
+                ],
+            },
+        };
+
+        IReadOnlyList<WorkflowValidationIssueDto> issues = _validator.Validate(workflow);
+
+        Assert.DoesNotContain(issues, issue => issue.Level == "error");
+    }
+
+    private static WorkflowDefinitionDto CreateWorkflow()
+    {
+        return new WorkflowDefinitionDto
+        {
+            Id = "workflow-1",
+            Name = "Loop Workflow",
+            Graph = new WorkflowGraphDto
+            {
+                Nodes =
+                [
+                    new WorkflowNodeDto
+                    {
+                        Id = "start",
+                        Kind = "start",
+                        Label = "Start",
+                        Config = new WorkflowNodeConfigDto { Kind = "start" },
+                    },
+                    new WorkflowNodeDto
+                    {
+                        Id = "agent",
+                        Kind = "agent",
+                        Label = "Agent",
+                        Config = new WorkflowNodeConfigDto
+                        {
+                            Kind = "agent",
+                            Id = "agent",
+                            Name = "Agent",
+                            Model = "gpt-5.4",
+                        },
+                    },
+                    new WorkflowNodeDto
+                    {
+                        Id = "end",
+                        Kind = "end",
+                        Label = "End",
+                        Config = new WorkflowNodeConfigDto { Kind = "end" },
+                    },
+                ],
+                Edges =
+                [
+                    new WorkflowEdgeDto
+                    {
+                        Id = "edge-start-agent",
+                        Source = "start",
+                        Target = "agent",
+                        Kind = "direct",
+                    },
+                    new WorkflowEdgeDto
+                    {
+                        Id = "edge-agent-end",
+                        Source = "agent",
+                        Target = "end",
+                        Kind = "direct",
+                    },
+                ],
+            },
+            Settings = new WorkflowSettingsDto
+            {
+                Checkpointing = new WorkflowCheckpointSettingsDto(),
+            },
+        };
+    }
+}
diff --git a/src/shared/domain/workflow.ts b/src/shared/domain/workflow.ts
index fec609e..34b393a 100644
--- a/src/shared/domain/workflow.ts
+++ b/src/shared/domain/workflow.ts
@@ -131,6 +131,8 @@ export interface WorkflowEdge {
   condition?: EdgeCondition;
   label?: string;
   fanOutConfig?: FanOutConfig;
+  isLoop?: boolean;
+  maxIterations?: number;
 }
 
 export interface WorkflowGraph {
@@ -236,6 +238,41 @@ function normalizeNodeConfig(kind: WorkflowNodeKind, config?: Partial<WorkflowNo
   }
 }
 
+function normalizeConditionRule(rule: WorkflowConditionRule): WorkflowConditionRule {
+  return {
+    propertyPath: rule.propertyPath.trim(),
+    operator: rule.operator,
+    value: rule.value.trim(),
+  };
+}
+
+function normalizeEdgeCondition(condition?: EdgeCondition): EdgeCondition | undefined {
+  if (!condition) {
+    return undefined;
+  }
+
+  switch (condition.type) {
+    case 'always':
+      return { type: 'always' };
+    case 'message-type':
+      return {
+        type: 'message-type',
+        typeName: condition.typeName.trim(),
+      };
+    case 'expression':
+      return {
+        type: 'expression',
+        expression: condition.expression.trim(),
+      };
+    case 'property':
+      return {
+        type: 'property',
+        combinator: condition.combinator === 'or' ? 'or' : 'and',
+        rules: condition.rules.map(normalizeConditionRule),
+      };
+  }
+}
+
 export function normalizeWorkflowDefinition(workflow: WorkflowDefinition): WorkflowDefinition {
   return {
     ...workflow,
@@ -256,7 +293,13 @@ export function normalizeWorkflowDefinition(workflow: WorkflowDefinition): Workf
         source: edge.source.trim(),
         target: edge.target.trim(),
         kind: edge.kind,
+        condition: normalizeEdgeCondition(edge.condition),
         label: normalizeOptionalString(edge.label),
+        isLoop: edge.isLoop === true ? true : undefined,
+        maxIterations:
+          typeof edge.maxIterations === 'number' && edge.maxIterations > 0
+            ? Math.round(edge.maxIterations)
+            : undefined,
       })),
     },
     settings: {
@@ -372,9 +415,10 @@ function hasPathToEnd(startNodeId: string, graph: WorkflowGraph, endNodeIds: Set
   const visited = new Set<string>();
   while (queue.length > 0) {
     const nodeId = queue.shift()!;
-    if (!visited.add(nodeId)) {
+    if (visited.has(nodeId)) {
       continue;
     }
+    visited.add(nodeId);
     if (endNodeIds.has(nodeId)) {
       return true;
     }
@@ -386,6 +430,184 @@ function hasPathToEnd(startNodeId: string, graph: WorkflowGraph, endNodeIds: Set
   return false;
 }
 
+function buildOutgoingEdges(graph: WorkflowGraph, excludedEdgeId?: string): Map<string, WorkflowEdge[]> {
+  const outgoing = new Map<string, WorkflowEdge[]>();
+  for (const edge of graph.edges) {
+    if (edge.id === excludedEdgeId) {
+      continue;
+    }
+
+    const current = outgoing.get(edge.source);
+    if (current) {
+      current.push(edge);
+    } else {
+      outgoing.set(edge.source, [edge]);
+    }
+  }
+
+  return outgoing;
+}
+
+function canReachNode(graph: WorkflowGraph, startNodeId: string, targetNodeId: string, excludedEdgeId?: string): boolean {
+  if (startNodeId === targetNodeId) {
+    return true;
+  }
+
+  const outgoing = buildOutgoingEdges(graph, excludedEdgeId);
+  const queue = [startNodeId];
+  const visited = new Set<string>();
+  while (queue.length > 0) {
+    const nodeId = queue.shift()!;
+    if (visited.has(nodeId)) {
+      continue;
+    }
+    visited.add(nodeId);
+
+    for (const edge of outgoing.get(nodeId) ?? []) {
+      if (edge.target === targetNodeId) {
+        return true;
+      }
+
+      queue.push(edge.target);
+    }
+  }
+
+  return false;
+}
+
+function collectStronglyConnectedNodes(graph: WorkflowGraph, nodeId: string): Set<string> {
+  const connected = new Set<string>();
+  for (const candidate of graph.nodes) {
+    if (canReachNode(graph, nodeId, candidate.id) && canReachNode(graph, candidate.id, nodeId)) {
+      connected.add(candidate.id);
+    }
+  }
+
+  return connected;
+}
+
+function isLoopEdge(graph: WorkflowGraph, edge: WorkflowEdge): boolean {
+  return canReachNode(graph, edge.target, edge.source, edge.id);
+}
+
+function isSupportedExpressionCondition(expression: string): boolean {
+  const trimmed = expression.trim();
+  if (!trimmed) {
+    return false;
+  }
+
+  if (trimmed === 'true' || trimmed === 'false') {
+    return true;
+  }
+
+  const comparisonPattern =
+    /^[A-Za-z_][A-Za-z0-9_.]*\s*(==|!=|>|<|contains|matches)\s*(?:"(?:[^"\\]|\\.)*"|'(?:[^'\\]|\\.)*'|-?\d+(?:\.\d+)?|true|false)$/;
+  const logicalOperator = trimmed.includes('&&') ? '&&' : trimmed.includes('||') ? '||' : undefined;
+  if (!logicalOperator) {
+    return comparisonPattern.test(trimmed);
+  }
+
+  return trimmed
+    .split(logicalOperator)
+    .map((segment) => segment.trim())
+    .every((segment) => comparisonPattern.test(segment));
+}
+
+function validateEdgeCondition(edge: WorkflowEdge, issues: WorkflowValidationIssue[]): void {
+  const condition = edge.condition;
+  if (!condition) {
+    return;
+  }
+
+  switch (condition.type) {
+    case 'always':
+      return;
+    case 'message-type':
+      if (!condition.typeName.trim()) {
+        addIssue(issues, {
+          level: 'error',
+          field: 'graph.edges.condition.typeName',
+          edgeId: edge.id,
+          message: 'Message-type conditions require a type name.',
+        });
+      }
+      return;
+    case 'expression':
+      if (!condition.expression.trim()) {
+        addIssue(issues, {
+          level: 'error',
+          field: 'graph.edges.condition.expression',
+          edgeId: edge.id,
+          message: 'Expression conditions require a non-empty expression.',
+        });
+        return;
+      }
+
+      if (!isSupportedExpressionCondition(condition.expression)) {
+        addIssue(issues, {
+          level: 'error',
+          field: 'graph.edges.condition.expression',
+          edgeId: edge.id,
+          message:
+            'Expression conditions currently support simple comparisons using ==, !=, >, <, contains, matches, optionally combined with && or ||.',
+        });
+      }
+      return;
+    case 'property': {
+      if (condition.rules.length === 0) {
+        addIssue(issues, {
+          level: 'error',
+          field: 'graph.edges.condition.rules',
+          edgeId: edge.id,
+          message: 'Property conditions require at least one rule.',
+        });
+      }
+
+      if (condition.combinator && condition.combinator !== 'and' && condition.combinator !== 'or') {
+        addIssue(issues, {
+          level: 'error',
+          field: 'graph.edges.condition.combinator',
+          edgeId: edge.id,
+          message: 'Property conditions must use the "and" or "or" combinator.',
+        });
+      }
+
+      for (const rule of condition.rules) {
+        if (!rule.propertyPath.trim()) {
+          addIssue(issues, {
+            level: 'error',
+            field: 'graph.edges.condition.rules.propertyPath',
+            edgeId: edge.id,
+            message: 'Property condition rules require a property path.',
+          });
+        }
+
+        if (!['equals', 'not-equals', 'contains', 'gt', 'lt', 'regex'].includes(rule.operator)) {
+          addIssue(issues, {
+            level: 'error',
+            field: 'graph.edges.condition.rules.operator',
+            edgeId: edge.id,
+            message: `Property condition operator "${rule.operator}" is not supported.`,
+          });
+        }
+
+        if (rule.operator === 'regex') {
+          try {
+            new RegExp(rule.value);
+          } catch {
+            addIssue(issues, {
+              level: 'error',
+              field: 'graph.edges.condition.rules.value',
+              edgeId: edge.id,
+              message: `Regex pattern "${rule.value}" is invalid.`,
+            });
+          }
+        }
+      }
+    }
+  }
+}
+
 export function validateWorkflowDefinition(workflow: WorkflowDefinition): WorkflowValidationIssue[] {
   const normalized = normalizeWorkflowDefinition(workflow);
   const issues: WorkflowValidationIssue[] = [];
@@ -464,7 +686,6 @@ export function validateWorkflowDefinition(workflow: WorkflowDefinition): Workfl
       }
     }
   }
-
   for (const edge of normalized.graph.edges) {
     if (!edge.id) {
       addIssue(issues, { level: 'error', field: 'graph.edges.id', message: 'Workflow edges must have an ID.' });
@@ -490,8 +711,18 @@ export function validateWorkflowDefinition(workflow: WorkflowDefinition): Workfl
 
     outgoingCounts.set(edge.source, (outgoingCounts.get(edge.source) ?? 0) + 1);
     incomingCounts.set(edge.target, (incomingCounts.get(edge.target) ?? 0) + 1);
-  }
 
+    if (edge.kind === 'fan-in' && edge.condition) {
+      addIssue(issues, {
+        level: 'error',
+        field: 'graph.edges.condition',
+        edgeId: edge.id,
+        message: 'Fan-in edges do not support conditions.',
+      });
+    }
+
+    validateEdgeCondition(edge, issues);
+  }
   const startNodes = normalized.graph.nodes.filter((node) => node.kind === 'start');
   const endNodes = normalized.graph.nodes.filter((node) => node.kind === 'end');
   const agentNodes = normalized.graph.nodes.filter((node) => node.kind === 'agent');
@@ -592,7 +823,6 @@ export function validateWorkflowDefinition(workflow: WorkflowDefinition): Workfl
       });
     }
   }
-
   const startNode = startNodes[0];
   if (startNode && endNodes.length > 0 && !hasPathToEnd(startNode.id, normalized.graph, new Set(endNodes.map((node) => node.id)))) {
     addIssue(issues, {
@@ -601,6 +831,81 @@ export function validateWorkflowDefinition(workflow: WorkflowDefinition): Workfl
       message: 'Workflow graph must include a path from the start node to at least one end node.',
     });
   }
+  if (
+    normalized.settings.maxIterations !== undefined
+    && (normalized.settings.maxIterations < 1 || normalized.settings.maxIterations > 100)
+  ) {
+    addIssue(issues, {
+      level: 'error',
+      field: 'settings.maxIterations',
+      message: 'Workflow maxIterations must be between 1 and 100.',
+    });
+  }
+
+  for (const edge of normalized.graph.edges) {
+    const loopEdge = isLoopEdge(normalized.graph, edge);
+
+    if (loopEdge && edge.kind !== 'direct') {
+      addIssue(issues, {
+        level: 'error',
+        field: 'graph.edges.kind',
+        edgeId: edge.id,
+        message: 'Loop edges currently support only direct edges.',
+      });
+    }
+
+    if (loopEdge && !edge.isLoop) {
+      addIssue(issues, {
+        level: 'error',
+        field: 'graph.edges.isLoop',
+        edgeId: edge.id,
+        message: 'Edges that participate in a cycle must be explicitly marked as loops.',
+      });
+    }
+
+    if (!loopEdge && edge.isLoop) {
+      addIssue(issues, {
+        level: 'warning',
+        field: 'graph.edges.isLoop',
+        edgeId: edge.id,
+        message: 'This edge is marked as a loop but does not currently form a cycle.',
+      });
+    }
+
+    if (!loopEdge) {
+      continue;
+    }
+
+    if (!edge.condition || edge.condition.type === 'always') {
+      addIssue(issues, {
+        level: 'error',
+        field: 'graph.edges.condition',
+        edgeId: edge.id,
+        message: 'Loop edges require a non-default condition so the loop can terminate.',
+      });
+    }
+
+    if (edge.maxIterations === undefined || edge.maxIterations < 1) {
+      addIssue(issues, {
+        level: 'error',
+        field: 'graph.edges.maxIterations',
+        edgeId: edge.id,
+        message: 'Loop edges require a maxIterations value of at least 1.',
+      });
+    }
+
+    const loopComponent = collectStronglyConnectedNodes(normalized.graph, edge.source);
+    const hasExitPath = normalized.graph.edges.some((candidate) =>
+      loopComponent.has(candidate.source) && !loopComponent.has(candidate.target));
+    if (!hasExitPath) {
+      addIssue(issues, {
+        level: 'error',
+        field: 'graph.edges',
+        edgeId: edge.id,
+        message: 'Loop cycles must include an exit path to a node outside the loop.',
+      });
+    }
+  }
 
   return issues;
 }
diff --git a/tests/shared/workflow.test.ts b/tests/shared/workflow.test.ts
index cb59366..3b48aab 100644
--- a/tests/shared/workflow.test.ts
+++ b/tests/shared/workflow.test.ts
@@ -92,4 +92,98 @@ describe('workflow validation', () => {
     expect(pattern.agents[0]?.name).toBe('Primary Agent');
     expect(pattern.graph?.nodes.map((node) => node.kind)).toEqual(['user-input', 'agent', 'user-output']);
   });
+
+  test('accepts simple property and expression conditions', () => {
+    const workflow = createWorkflow();
+    workflow.graph.edges[0] = {
+      ...workflow.graph.edges[0]!,
+      condition: {
+        type: 'property',
+        combinator: 'and',
+        rules: [
+          {
+            propertyPath: 'role',
+            operator: 'equals',
+            value: 'user',
+          },
+        ],
+      },
+    };
+    workflow.graph.edges[1] = {
+      ...workflow.graph.edges[1]!,
+      condition: {
+        type: 'expression',
+        expression: 'role == "assistant" || role == "user"',
+      },
+    };
+
+    expect(validateWorkflowDefinition(workflow)).toEqual([]);
+  });
+
+  test('rejects invalid condition operators and expressions', () => {
+    const workflow = createWorkflow();
+    workflow.graph.edges[0] = {
+      ...workflow.graph.edges[0]!,
+      condition: {
+        type: 'property',
+        rules: [
+          {
+            propertyPath: 'role',
+            operator: 'bad-op' as 'equals',
+            value: 'user',
+          },
+        ],
+      },
+    };
+    workflow.graph.edges[1] = {
+      ...workflow.graph.edges[1]!,
+      condition: {
+        type: 'expression',
+        expression: 'role ~= "user"',
+      },
+    };
+
+    const issues = validateWorkflowDefinition(workflow);
+    expect(issues.some((issue) => issue.field === 'graph.edges.condition.rules.operator')).toBe(true);
+    expect(issues.some((issue) => issue.field === 'graph.edges.condition.expression')).toBe(true);
+  });
+
+  test('rejects unmarked loop edges and requires termination metadata', () => {
+    const workflow = createWorkflow();
+    workflow.graph.edges.push({
+      id: 'edge-agent-loop',
+      source: 'agent-primary',
+      target: 'agent-primary',
+      kind: 'direct',
+    });
+
+    const issues = validateWorkflowDefinition(workflow);
+    expect(issues.some((issue) => issue.field === 'graph.edges.isLoop')).toBe(true);
+    expect(issues.some((issue) => issue.field === 'graph.edges.condition')).toBe(true);
+    expect(issues.some((issue) => issue.field === 'graph.edges.maxIterations')).toBe(true);
+  });
+
+  test('accepts loop edges with condition, cap, and exit path', () => {
+    const workflow = createWorkflow();
+    workflow.graph.edges.push({
+      id: 'edge-agent-loop',
+      source: 'agent-primary',
+      target: 'agent-primary',
+      kind: 'direct',
+      isLoop: true,
+      maxIterations: 3,
+      condition: {
+        type: 'property',
+        rules: [
+          {
+            propertyPath: 'iteration',
+            operator: 'lt',
+            value: '3',
+          },
+        ],
+      },
+    });
+
+    expect(validateWorkflowDefinition(workflow)).toEqual([]);
+  });
 });