feat(subagent): catalog one-shot child sessions

packages/workflow/workflow-workerthread/src/host.ts

@@ -322,6 +322,7 @@ export class WorkerRun implements WorkflowRun {
     let run: SubagentRun
     try {
       run = await this.subagents.start(this.provider, {
+        label: request.label,
         prompt: [{ type: 'text', text: request.prompt }],
         parent: this.parent,
         signal: this.controller.signal,

packages/workflow/workflow-workerthread/src/runtime.ts

@@ -275,6 +275,7 @@ export class WorkflowExecution {
       let run: ChildHandle
       try {
         run = await this.children.startAgent({
+          label,
           prompt: rawPrompt,
           ...opts.schema !== undefined ? { schema: opts.schema } : {},
           ...opts.provider !== undefined ? { provider: opts.provider } : {},

packages/workflow/workflow-workerthread/src/types.ts

@@ -38,6 +38,8 @@ export interface WorkerInit {
 
 /** What the worker asks the host to start for one `agent()` call (options already validated worker-side). */
 export interface ChildStartRequest {
+  /** Short display label resolved by the worker runtime. */
+  label: string
   /** The child's prompt text. */
   prompt: string
   /** The structured-output schema, if the call passed one (already subset-checked). */

packages/workflow/workflow-workerthread/tests/session.spec.ts

@@ -420,10 +420,13 @@ describe('runWorkerSession over an in-process MessageChannel', () => {
     `))
     await host.result()
     const starts = host.ofType(WorkerToHostType.AgentStart).map(m => m.info)
+    const requests = host.ofType(WorkerToHostType.ChildStart).map(m => m.request)
     expect(starts[0]).toMatchObject({ seq: 1, phase: 'Find' })
     expect(starts[0]!.label.length).toBeLessThanOrEqual(48)
     expect(starts[0]!.label).not.toContain('second line')
     expect(starts[1]).toMatchObject({ seq: 2, label: 'named', phase: 'Custom' })
+    expect(requests[0]!.label).toBe(starts[0]!.label)
+    expect(requests[1]!.label).toBe('named')
     host.close()
   })
 

packages/workflow/workflow-workerthread/tests/workflow-workerthread.spec.ts

@@ -211,7 +211,7 @@ describe('dsh-workflow-workerthread', () => {
         reply: () => ({ output: [], structured: { files: ['x.ts', 'y.ts'] }, stopReason: 'completed' }),
       })
       const result = await run(ctx, parent, scripted(`
-        const found = await agent('list files', { model: 'deepseek-v4-pro', schema: { type: 'object', properties: { files: { type: 'array', items: { type: 'string' } } }, required: ['files'] } })
+        const found = await agent('list files', { label: 'inventory', model: 'deepseek-v4-pro', schema: { type: 'object', properties: { files: { type: 'array', items: { type: 'string' } } }, required: ['files'] } })
         return { first: found.files[0], count: found.files.length }
       `))
       expect(result.value).toEqual({ first: 'x.ts', count: 2 })
@@ -221,6 +221,7 @@ describe('dsh-workflow-workerthread', () => {
         required: ['files'],
       })
       expect(provider.runs[0]!.request.agentOptions).toEqual({ model: 'deepseek-v4-pro' })
+      expect(provider.runs[0]!.request.label).toBe('inventory')
       expect(provider.runs[0]!.request.parent).toBeDefined()
     })