fix(resume): recover cleanly after Pi exits

backend/src/app.ts

@@ -20,6 +20,7 @@ export interface BuildAppDeps {
   listModels?: ListModelsFn;
   getSettings?: () => Settings;
   readiness?: ReadinessManager;
+  hub?: SseHub;
 }
 
 export function buildApp(config: AppConfig, deps?: BuildAppDeps): FastifyInstance {
@@ -39,7 +40,7 @@ export function buildApp(config: AppConfig, deps?: BuildAppDeps): FastifyInstanc
     dataRoot: config.dataRoot,
   });
   const mgr = deps?.mgr ?? new PiProcessManager(config, deps?.spawnFn ? { spawnFn: deps.spawnFn } : undefined);
-  const hub = new SseHub();
+  const hub = deps?.hub ?? new SseHub();
   const readiness = deps?.readiness ?? new ReadinessManager(
     tht as ThtRunner,
     Math.round(config.ollamaEnsureTimeoutMs / 1000),

backend/src/bridge/session-bridge.ts

@@ -33,7 +33,7 @@ export class SessionBridge {
         m.message?.role === "assistant" &&
         m.message?.stopReason === "error"
       ) {
-        this.state = "failed";
+        this.markFailed();
         this.fan({
           type: "info",
           level: "error",
@@ -69,6 +69,9 @@ export class SessionBridge {
 
   beginTurn(): void { this.state = "running"; }
 
+  /** Record a backend-detected failure; callers own any sanitized client message. */
+  markFailed(): void { this.state = "failed"; }
+
   onClientEvent(cb: (e: ClientEvent) => void): void { this.cbs.add(cb); }
 
   /** Eventi generati dal backend stesso (es. exit inatteso del child Pi), non da Pi. */

backend/src/pi/pi-process-manager.ts

@@ -103,6 +103,7 @@ export class PiProcessManager {
     child.on("exit", (code) => {
       console.error(`[pi:${sessionId}] exited code=${code ?? "?"} mapped=${this.runtimes.get(sessionId) === rt}`);
       if (this.runtimes.get(sessionId) === rt) {
+        rt.bridge.markFailed();
         this.runtimes.delete(sessionId);
         rt.bridge.emitClientEvent({
           type: "info",

backend/src/routes/sessions.ts

@@ -106,8 +106,6 @@ export function sessionRoutes(
       if (state === "running" || state === "waiting") {
         return reply.code(200).send({ id, alreadyActive: true });
       }
-      d.mgr.teardown(id);
-      d.hub.clear(id);
     }
     const manifest = (await d.tht.sessionShow(id, d.getSettings().workspace)) as { status?: string; archived?: boolean } | null;
     if (manifest?.status === "finalized" || manifest?.archived) {
@@ -124,6 +122,8 @@ export function sessionRoutes(
       author: getUser(req).id,
       mode: "resume" as const,
     };
+    if (existing) d.mgr.teardown(id);
+    d.hub.clear(id);
     await d.tht.reopenSession(id, settings.workspace);
     const rt = d.mgr.createFor(id, options);
     bindRuntime(id, rt);