feat: thread-bound subagents on Discord (#21805)

* docs: thread-bound subagents plan

* docs: add exact thread-bound subagent implementation touchpoints

* Docs: prioritize auto thread-bound subagent flow

* Docs: add ACP harness thread-binding extensions

* Discord: add thread-bound session routing and auto-bind spawn flow

* Subagents: add focus commands and ACP/session binding lifecycle hooks

* Tests: cover thread bindings, focus commands, and ACP unbind hooks

* Docs: add plugin-hook appendix for thread-bound subagents

* Plugins: add subagent lifecycle hook events

* Core: emit subagent lifecycle hooks and decouple Discord bindings

* Discord: handle subagent bind lifecycle via plugin hooks

* Subagents: unify completion finalizer and split registry modules

* Add subagent lifecycle events module

* Hooks: fix subagent ended context key

* Discord: share thread bindings across ESM and Jiti

* Subagents: add persistent sessions_spawn mode for thread-bound sessions

* Subagents: clarify thread intro and persistent completion copy

* test(subagents): stabilize sessions_spawn lifecycle cleanup assertions

* Discord: add thread-bound session TTL with auto-unfocus

* Subagents: fail session spawns when thread bind fails

* Subagents: cover thread session failure cleanup paths

* Session: add thread binding TTL config and /session ttl controls

* Tests: align discord reaction expectations

* Agent: persist sessionFile for keyed subagent sessions

* Discord: normalize imports after conflict resolution

* Sessions: centralize sessionFile resolve/persist helper

* Discord: harden thread-bound subagent session routing

* Rebase: resolve upstream/main conflicts

* Subagents: move thread binding into hooks and split bindings modules

* Docs: add channel-agnostic subagent routing hook plan

* Agents: decouple subagent routing from Discord

* Discord: refactor thread-bound subagent flows

* Subagents: prevent duplicate end hooks and orphaned failed sessions

* Refactor: split subagent command and provider phases

* Subagents: honor hook delivery target overrides

* Discord: add thread binding kill switches and refresh plan doc

* Discord: fix thread bind channel resolution

* Routing: centralize account id normalization

* Discord: clean up thread bindings on startup failures

* Discord: add startup cleanup regression tests

* Docs: add long-term thread-bound subagent architecture

* Docs: split session binding plan and dedupe thread-bound doc

* Subagents: add channel-agnostic session binding routing

* Subagents: stabilize announce completion routing tests

* Subagents: cover multi-bound completion routing

* Subagents: suppress lifecycle hooks on failed thread bind

* tests: fix discord provider mock typing regressions

* docs/protocol: sync slash command aliases and delete param models

* fix: add changelog entry for Discord thread-bound subagents (#21805) (thanks @onutc)

---------

Co-authored-by: Shadow <hi@shadowing.dev>

src/config/sessions/transcript.ts

@@ -2,8 +2,9 @@ import fs from "node:fs";
 import path from "node:path";
 import { CURRENT_SESSION_VERSION, SessionManager } from "@mariozechner/pi-coding-agent";
 import { emitSessionTranscriptUpdate } from "../../sessions/transcript-events.js";
-import { resolveDefaultSessionStorePath, resolveSessionFilePath } from "./paths.js";
-import { loadSessionStore, updateSessionStore } from "./store.js";
+import { resolveDefaultSessionStorePath } from "./paths.js";
+import { resolveAndPersistSessionFile } from "./session-file.js";
+import { loadSessionStore } from "./store.js";
 import type { SessionEntry } from "./types.js";
 
 function stripQuery(value: string): string {
@@ -108,10 +109,16 @@ export async function appendAssistantMessageToSessionTranscript(params: {
 
   let sessionFile: string;
   try {
-    sessionFile = resolveSessionFilePath(entry.sessionId, entry, {
+    const resolvedSessionFile = await resolveAndPersistSessionFile({
+      sessionId: entry.sessionId,
+      sessionKey,
+      sessionStore: store,
+      storePath,
+      sessionEntry: entry,
       agentId: params.agentId,
       sessionsDir: path.dirname(storePath),
     });
+    sessionFile = resolvedSessionFile.sessionFile;
   } catch (err) {
     return {
       ok: false,
@@ -146,19 +153,6 @@ export async function appendAssistantMessageToSessionTranscript(params: {
     timestamp: Date.now(),
   });
 
-  if (!entry.sessionFile || entry.sessionFile !== sessionFile) {
-    await updateSessionStore(
-      storePath,
-      (current) => {
-        current[sessionKey] = {
-          ...entry,
-          sessionFile,
-        };
-      },
-      { activeSessionKey: sessionKey },
-    );
-  }
-
   emitSessionTranscriptUpdate(sessionFile);
   return { ok: true, sessionFile };
 }