feat: add scratchpad chat model controls

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

src/shared/contracts/channels.ts

@@ -6,6 +6,7 @@ export const ipcChannels = {
   deletePattern: 'patterns:delete',
   createSession: 'sessions:create',
   sendSessionMessage: 'sessions:send-message',
+  updateScratchpadSessionConfig: 'sessions:update-scratchpad-config',
   selectProject: 'selection:project',
   selectPattern: 'selection:pattern',
   selectSession: 'selection:session',

src/shared/contracts/ipc.ts

@@ -1,4 +1,4 @@
-import type { PatternDefinition } from '@shared/domain/pattern';
+import type { PatternDefinition, ReasoningEffort } from '@shared/domain/pattern';
 import type { ProjectRecord } from '@shared/domain/project';
 import type { SessionEventRecord } from '@shared/domain/event';
 import type { WorkspaceState } from '@shared/domain/workspace';
@@ -17,6 +17,12 @@ export interface SendSessionMessageInput {
   content: string;
 }
 
+export interface UpdateScratchpadSessionConfigInput {
+  sessionId: string;
+  model: string;
+  reasoningEffort: ReasoningEffort;
+}
+
 export interface ElectronApi {
   loadWorkspace(): Promise<WorkspaceState>;
   addProject(): Promise<WorkspaceState>;
@@ -25,6 +31,7 @@ export interface ElectronApi {
   deletePattern(patternId: string): Promise<WorkspaceState>;
   createSession(input: CreateSessionInput): Promise<WorkspaceState>;
   sendSessionMessage(input: SendSessionMessageInput): Promise<void>;
+  updateScratchpadSessionConfig(input: UpdateScratchpadSessionConfigInput): Promise<WorkspaceState>;
   selectProject(projectId?: string): Promise<WorkspaceState>;
   selectPattern(patternId?: string): Promise<WorkspaceState>;
   selectSession(sessionId?: string): Promise<WorkspaceState>;

src/shared/domain/pattern.ts

@@ -11,6 +11,13 @@ export type OrchestrationMode =
 export type PatternAvailability = 'available' | 'preview' | 'unavailable';
 export type ReasoningEffort = 'low' | 'medium' | 'high' | 'xhigh';
 
+export const reasoningEffortOptions: ReadonlyArray<{ value: ReasoningEffort; label: string }> = [
+  { value: 'low', label: 'Low' },
+  { value: 'medium', label: 'Medium' },
+  { value: 'high', label: 'High' },
+  { value: 'xhigh', label: 'Maximum' },
+];
+
 export interface PatternAgentDefinition {
   id: string;
   name: string;
@@ -45,6 +52,12 @@ const defaultModels = {
   gpt53: 'gpt-5.3-codex',
 } as const;
 
+const reasoningEffortSet = new Set<ReasoningEffort>(reasoningEffortOptions.map((option) => option.value));
+
+export function isReasoningEffort(value: string | undefined): value is ReasoningEffort {
+  return value !== undefined && reasoningEffortSet.has(value as ReasoningEffort);
+}
+
 export function createBuiltinPatterns(timestamp: string): PatternDefinition[] {
   return [
     {

src/shared/domain/session.ts

@@ -1,6 +1,13 @@
+import type { PatternDefinition, ReasoningEffort } from '@shared/domain/pattern';
+
 export type ChatRole = 'system' | 'user' | 'assistant';
 export type SessionStatus = 'idle' | 'running' | 'error';
 
+export interface ScratchpadSessionConfig {
+  model: string;
+  reasoningEffort?: ReasoningEffort;
+}
+
 export interface ChatMessageRecord {
   id: string;
   role: ChatRole;
@@ -20,4 +27,58 @@ export interface SessionRecord {
   status: SessionStatus;
   messages: ChatMessageRecord[];
   lastError?: string;
+  scratchpadConfig?: ScratchpadSessionConfig;
+}
+
+export function createScratchpadSessionConfig(
+  pattern: PatternDefinition,
+): ScratchpadSessionConfig | undefined {
+  const primaryAgent = pattern.agents[0];
+  if (!primaryAgent) {
+    return undefined;
+  }
+
+  return {
+    model: primaryAgent.model,
+    reasoningEffort: primaryAgent.reasoningEffort,
+  };
+}
+
+export function resolveScratchpadSessionConfig(
+  session: SessionRecord,
+  pattern: PatternDefinition,
+): ScratchpadSessionConfig | undefined {
+  const defaults = createScratchpadSessionConfig(pattern);
+  if (!defaults) {
+    return undefined;
+  }
+
+  const overrideModel = session.scratchpadConfig?.model.trim();
+  return {
+    model: overrideModel || defaults.model,
+    reasoningEffort: session.scratchpadConfig?.reasoningEffort ?? defaults.reasoningEffort,
+  };
+}
+
+export function applyScratchpadSessionConfig(
+  pattern: PatternDefinition,
+  session: SessionRecord,
+): PatternDefinition {
+  const config = resolveScratchpadSessionConfig(session, pattern);
+  const primaryAgent = pattern.agents[0];
+  if (!config || !primaryAgent) {
+    return pattern;
+  }
+
+  return {
+    ...pattern,
+    agents: [
+      {
+        ...primaryAgent,
+        model: config.model,
+        reasoningEffort: config.reasoningEffort,
+      },
+      ...pattern.agents.slice(1),
+    ],
+  };
 }