feat: ACP thread-bound agents (#23580)

* docs: add ACP thread-bound agents plan doc

* docs: expand ACP implementation specification

* feat(acp): route ACP sessions through core dispatch and lifecycle cleanup

* feat(acp): add /acp commands and Discord spawn gate

* ACP: add acpx runtime plugin backend

* fix(subagents): defer transient lifecycle errors before announce

* Agents: harden ACP sessions_spawn and tighten spawn guidance

* Agents: require explicit ACP target for runtime spawns

* docs: expand ACP control-plane implementation plan

* ACP: harden metadata seeding and spawn guidance

* ACP: centralize runtime control-plane manager and fail-closed dispatch

* ACP: harden runtime manager and unify spawn helpers

* Commands: route ACP sessions through ACP runtime in agent command

* ACP: require persisted metadata for runtime spawns

* Sessions: preserve ACP metadata when updating entries

* Plugins: harden ACP backend registry across loaders

* ACPX: make availability probe compatible with adapters

* E2E: add manual Discord ACP plain-language smoke script

* ACPX: preserve streamed spacing across Discord delivery

* Docs: add ACP Discord streaming strategy

* ACP: harden Discord stream buffering for thread replies

* ACP: reuse shared block reply pipeline for projector

* ACP: unify streaming config and adopt coalesceIdleMs

* Docs: add temporary ACP production hardening plan

* Docs: trim temporary ACP hardening plan goals

* Docs: gate ACP thread controls by backend capabilities

* ACP: add capability-gated runtime controls and /acp operator commands

* Docs: remove temporary ACP hardening plan

* ACP: fix spawn target validation and close cache cleanup

* ACP: harden runtime dispatch and recovery paths

* ACP: split ACP command/runtime internals and centralize policy

* ACP: harden runtime lifecycle, validation, and observability

* ACP: surface runtime and backend session IDs in thread bindings

* docs: add temp plan for binding-service migration

* ACP: migrate thread binding flows to SessionBindingService

* ACP: address review feedback and preserve prompt wording

* ACPX plugin: pin runtime dependency and prefer bundled CLI

* Discord: complete binding-service migration cleanup and restore ACP plan

* Docs: add standalone ACP agents guide

* ACP: route harness intents to thread-bound ACP sessions

* ACP: fix spawn thread routing and queue-owner stall

* ACP: harden startup reconciliation and command bypass handling

* ACP: fix dispatch bypass type narrowing

* ACP: align runtime metadata to agentSessionId

* ACP: normalize session identifier handling and labels

* ACP: mark thread banner session ids provisional until first reply

* ACP: stabilize session identity mapping and startup reconciliation

* ACP: add resolved session-id notices and cwd in thread intros

* Discord: prefix thread meta notices consistently

* Discord: unify ACP/thread meta notices with gear prefix

* Discord: split thread persona naming from meta formatting

* Extensions: bump acpx plugin dependency to 0.1.9

* Agents: gate ACP prompt guidance behind acp.enabled

* Docs: remove temp experiment plan docs

* Docs: scope streaming plan to holy grail refactor

* Docs: refactor ACP agents guide for human-first flow

* Docs/Skill: add ACP feature-flag guidance and direct acpx telephone-game flow

* Docs/Skill: add OpenCode and Pi to ACP harness lists

* Docs/Skill: align ACP harness list with current acpx registry

* Dev/Test: move ACP plain-language smoke script and mark as keep

* Docs/Skill: reorder ACP harness lists with Pi first

* ACP: split control-plane manager into core/types/utils modules

* Docs: refresh ACP thread-bound agents plan

* ACP: extract dispatch lane and split manager domains

* ACP: centralize binding context and remove reverse deps

* Infra: unify system message formatting

* ACP: centralize error boundaries and session id rendering

* ACP: enforce init concurrency cap and strict meta clear

* Tests: fix ACP dispatch binding mock typing

* Tests: fix Discord thread-binding mock drift and ACP request id

* ACP: gate slash bypass and persist cleared overrides

* ACPX: await pre-abort cancel before runTurn return

* Extension: pin acpx runtime dependency to 0.1.11

* Docs: add pinned acpx install strategy for ACP extension

* Extensions/acpx: enforce strict local pinned startup

* Extensions/acpx: tighten acp-router install guidance

* ACPX: retry runtime test temp-dir cleanup

* Extensions/acpx: require proactive ACPX repair for thread spawns

* Extensions/acpx: require restart offer after acpx reinstall

* extensions/acpx: remove workspace protocol devDependency

* extensions/acpx: bump pinned acpx to 0.1.13

* extensions/acpx: sync lockfile after dependency bump

* ACPX: make runtime spawn Windows-safe

* fix: align doctor-config-flow repair tests with default-account migration (#23580) (thanks @osolmaz)

src/channels/thread-bindings-messages.ts

@@ -0,0 +1,84 @@
+import { prefixSystemMessage } from "../infra/system-message.js";
+
+const DEFAULT_THREAD_BINDING_FAREWELL_TEXT =
+  "Session ended. Messages here will no longer be routed.";
+
+function normalizeThreadBindingMessageTtlMs(raw: unknown): number {
+  if (typeof raw !== "number" || !Number.isFinite(raw)) {
+    return 0;
+  }
+  const ttlMs = Math.floor(raw);
+  if (ttlMs < 0) {
+    return 0;
+  }
+  return ttlMs;
+}
+
+export function formatThreadBindingTtlLabel(ttlMs: number): string {
+  if (ttlMs <= 0) {
+    return "disabled";
+  }
+  if (ttlMs < 60_000) {
+    return "<1m";
+  }
+  const totalMinutes = Math.floor(ttlMs / 60_000);
+  if (totalMinutes % 60 === 0) {
+    return `${Math.floor(totalMinutes / 60)}h`;
+  }
+  return `${totalMinutes}m`;
+}
+
+export function resolveThreadBindingThreadName(params: {
+  agentId?: string;
+  label?: string;
+}): string {
+  const label = params.label?.trim();
+  const base = label || params.agentId?.trim() || "agent";
+  const raw = `🤖 ${base}`.replace(/\s+/g, " ").trim();
+  return raw.slice(0, 100);
+}
+
+export function resolveThreadBindingIntroText(params: {
+  agentId?: string;
+  label?: string;
+  sessionTtlMs?: number;
+  sessionCwd?: string;
+  sessionDetails?: string[];
+}): string {
+  const label = params.label?.trim();
+  const base = label || params.agentId?.trim() || "agent";
+  const normalized = base.replace(/\s+/g, " ").trim().slice(0, 100) || "agent";
+  const ttlMs = normalizeThreadBindingMessageTtlMs(params.sessionTtlMs);
+  const cwd = params.sessionCwd?.trim();
+  const details = (params.sessionDetails ?? [])
+    .map((entry) => entry.trim())
+    .filter((entry) => entry.length > 0);
+  if (cwd) {
+    details.unshift(`cwd: ${cwd}`);
+  }
+  const intro =
+    ttlMs > 0
+      ? `${normalized} session active (auto-unfocus in ${formatThreadBindingTtlLabel(ttlMs)}). Messages here go directly to this session.`
+      : `${normalized} session active. Messages here go directly to this session.`;
+  if (details.length === 0) {
+    return prefixSystemMessage(intro);
+  }
+  return prefixSystemMessage(`${intro}\n${details.join("\n")}`);
+}
+
+export function resolveThreadBindingFarewellText(params: {
+  reason?: string;
+  farewellText?: string;
+  sessionTtlMs: number;
+}): string {
+  const custom = params.farewellText?.trim();
+  if (custom) {
+    return prefixSystemMessage(custom);
+  }
+  if (params.reason === "ttl-expired") {
+    return prefixSystemMessage(
+      `Session ended automatically after ${formatThreadBindingTtlLabel(params.sessionTtlMs)}. Messages here will no longer be routed.`,
+    );
+  }
+  return prefixSystemMessage(DEFAULT_THREAD_BINDING_FAREWELL_TEXT);
+}