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/types.base.ts

@@ -84,6 +84,19 @@ export type SessionResetByTypeConfig = {
   thread?: SessionResetConfig;
 };
 
+export type SessionThreadBindingsConfig = {
+  /**
+   * Master switch for thread-bound session routing features.
+   * Channel/provider keys can override this default.
+   */
+  enabled?: boolean;
+  /**
+   * Auto-unfocus TTL for thread-bound sessions (hours).
+   * Set to 0 to disable. Default: 24.
+   */
+  ttlHours?: number;
+};
+
 export type SessionConfig = {
   scope?: SessionScope;
   /** DM session scoping (default: "main"). */
@@ -105,6 +118,8 @@ export type SessionConfig = {
     /** Max ping-pong turns between requester/target (0–5). Default: 5. */
     maxPingPongTurns?: number;
   };
+  /** Shared defaults for thread-bound session routing across channels/providers. */
+  threadBindings?: SessionThreadBindingsConfig;
   /** Automatic session store maintenance (pruning, capping, file rotation). */
   maintenance?: SessionMaintenanceConfig;
 };