merge: integrate master into session-log-v4

packages/api/session-controller/src/agent.ts

@@ -58,7 +58,7 @@ export class ApiSessionPresetConflict extends Error {
 }
 
 /** Failures produced while resolving one ordinary Session identity to its live Agent. */
-export type ApiSessionAgentError = RemoteError<'session/not-found' | 'session/agent-busy' | 'gateway/internal'>
+export type ApiSessionAgentError = RemoteError<'session/not-found' | 'session/agent-busy' | 'session/writer-held' | 'gateway/internal'>
 
 /** Result of resolving one ordinary Session identity to its live Agent. */
 export type ApiSessionAgentResult =
@@ -215,6 +215,9 @@ export class ApiSessionAgentController {
       if (racedSession !== undefined && hasApiSessionSubagentOwner(this.ctx, racedSession, undefined)) {
         return { error: apiSessionSubagentOwnershipError(sessionId) }
       }
+      if (error instanceof Error && error.name === 'SessionAlreadyOwnedError') {
+        return { error: new RemoteError('session/writer-held', error.message, { sessionId }) }
+      }
       return {
         error: new RemoteError(
           'gateway/internal',

packages/api/session-controller/src/types.ts

@@ -194,6 +194,7 @@ declare module '@deepseek-ai/dsh-typert-protocol' {
       readonly existingCwd?: string
     }
     'session/projections-unavailable': Record<string, never>
+    'session/writer-held': { readonly sessionId: SessionId }
     'session/agent-busy': { readonly reason: string }
     'session/invalid-time-zone': { readonly value: string }
     'session/workspace-attach-failed': { readonly sessionId: SessionId; readonly workspaceId: string }