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/auto-reply/reply/reply-payloads.ts

@@ -2,6 +2,7 @@ import { isMessagingToolDuplicate } from "../../agents/pi-embedded-helpers.js";
 import type { MessagingToolSend } from "../../agents/pi-embedded-runner.js";
 import type { ReplyToMode } from "../../config/types.js";
 import { normalizeTargetForProvider } from "../../infra/outbound/target-normalization.js";
+import { normalizeOptionalAccountId } from "../../routing/account-id.js";
 import type { OriginatingChannelType } from "../templating.js";
 import type { ReplyPayload } from "../types.js";
 import { extractReplyToTag } from "./reply-tags.js";
@@ -120,11 +121,6 @@ export function filterMessagingToolMediaDuplicates(params: {
   });
 }
 
-function normalizeAccountId(value?: string): string | undefined {
-  const trimmed = value?.trim();
-  return trimmed ? trimmed.toLowerCase() : undefined;
-}
-
 export function shouldSuppressMessagingToolReplies(params: {
   messageProvider?: string;
   messagingToolSentTargets?: MessagingToolSend[];
@@ -139,7 +135,7 @@ export function shouldSuppressMessagingToolReplies(params: {
   if (!originTarget) {
     return false;
   }
-  const originAccount = normalizeAccountId(params.accountId);
+  const originAccount = normalizeOptionalAccountId(params.accountId);
   const sentTargets = params.messagingToolSentTargets ?? [];
   if (sentTargets.length === 0) {
     return false;
@@ -155,7 +151,7 @@ export function shouldSuppressMessagingToolReplies(params: {
     if (!targetKey) {
       return false;
     }
-    const targetAccount = normalizeAccountId(target.accountId);
+    const targetAccount = normalizeOptionalAccountId(target.accountId);
     if (originAccount && targetAccount && originAccount !== targetAccount) {
       return false;
     }