fix(native-chat): a chat the user closed while its agent started is not a failed start

A still-starting child the user's close cut counted as a failed start, since only 'user-stop' was excluded: a start-failure row, and queued messages rejected as a provider failure. Whether an ending fails its start is now one exhaustive switch, shared by the failed-start read and the delivery loop's handover: a user's stop or close never does; an exit, a failed attach and the host's own stops still do.

src/main/native-chat/agent-session-wire/structured-agent-session-delivery-loop.ts

@@ -26,7 +26,10 @@ import {
   oldestQueuedSubmission,
   recordStructuredAgentSessionStartFailure
 } from './structured-agent-session-start-failure-row'
-import { failedProviderChildStart } from './structured-agent-session-provider-child'
+import {
+  childEndFailsItsStart,
+  failedProviderChildStart
+} from './structured-agent-session-provider-child'
 import { handOverSubmission } from './structured-agent-session-turns'
 
 export type StructuredAgentSessionDeliveryLoopDeps = {
@@ -171,9 +174,9 @@ export class StructuredAgentSessionDeliveryLoop {
     if (!awaitedChild || (awaitedChild.phase === 'starting' && startFailure !== null)) {
       // The child waited on is gone, replaced by another, or settled its start without proving it.
       const ended = awaitedChild ? undefined : session.lastEndedChild
-      // A user's Stop is not a failure: the next step starts, or waits on, a child for what is
-      // queued. A host stop is: its cause is why the start did not land.
-      if (ended?.cause === 'user-stop') {
+      // A user's Stop or close is not a failure: the next step starts, or waits on, a child for
+      // what is queued. A host stop is: its cause is why the start did not land.
+      if (ended && !childEndFailsItsStart(ended.cause)) {
         return 'continue'
       }
       return this.fail(sessionId, {

src/main/native-chat/agent-session-wire/structured-agent-session-provider-child-record.test.ts

@@ -672,6 +672,22 @@ describe('how a stopped child ends the start its loop was waiting on', () => {
     expect(statusRows()).toEqual([])
   })
 
+  it('records no failure when the user closed the chat while its child started', async () => {
+    // The close's stop alone: a close that aborts after it leaves the conversation indexed.
+    const second = await stoppedWhileStarting(() =>
+      host['serialize'](SESSION, () =>
+        stopStructuredAgentSessionAgentUnderSerialize(host['lifetimeContext'](), SESSION, {
+          cause: 'user-close'
+        })
+      )
+    )
+
+    await settleLoop()
+    expect(conversation()?.lastEndedChild).toMatchObject({ cause: 'user-close' })
+    expect(submission(second)?.dispatchState).not.toBe('rejected')
+    expect(statusRows()).toEqual([])
+  })
+
   it('fails the start after a host stop, with the stop as the reason (R2)', async () => {
     const reason = 'Claude never finished starting, so Orca stopped it.'
     const second = await stoppedWhileStarting(() =>

src/main/native-chat/agent-session-wire/structured-agent-session-provider-child.ts

@@ -8,6 +8,7 @@
 import type { AgentSessionRecordStore } from '../../runtime/agent-session-record-store'
 import type { AgentSessionJournal } from '../agent-session-journal/journal-store'
 import type {
+  StructuredAgentSessionChildEndCause,
   StructuredAgentSessionEndedChild,
   StructuredAgentSessionHostSession,
   StructuredAgentSessionProviderChild,
@@ -64,7 +65,22 @@ export function failedProviderChildStart(
   session: Pick<ChildBearer, 'child' | 'lastEndedChild'>
 ): StructuredAgentSessionEndedChild | null {
   const ended = session.lastEndedChild
-  return !session.child && ended?.duringStartup && ended.cause !== 'user-stop' ? ended : null
+  return !session.child && ended?.duringStartup && childEndFailsItsStart(ended.cause) ? ended : null
+}
+
+/** Whether a child that ended this way, still starting, failed its start. A stop the user aimed at
+ *  this chat is their cancellation, never a failure; a host's own stop is why the start did not land. */
+export function childEndFailsItsStart(cause: StructuredAgentSessionChildEndCause): boolean {
+  switch (cause) {
+    case 'user-stop':
+    case 'user-close':
+      return false
+    case 'exit':
+    case 'attach-failed':
+    case 'host-stop':
+    case 'evict':
+      return true
+  }
 }
 
 function matchingChild(