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/config/schema.help.ts

@@ -153,6 +153,28 @@ export const FIELD_HELP: Record<string, string> = {
     "Use this legacy ElevenLabs API key for Talk mode only during migration, and keep secrets in env-backed storage. Prefer talk.providers.elevenlabs.apiKey (fallback: ELEVENLABS_API_KEY).",
   "talk.interruptOnSpeech":
     "If true (default), stop assistant speech when the user starts speaking in Talk mode. Keep enabled for conversational turn-taking.",
+  acp: "ACP runtime controls for enabling dispatch, selecting backends, constraining allowed agent targets, and tuning streamed turn projection behavior.",
+  "acp.enabled":
+    "Global ACP feature gate. Keep disabled unless ACP runtime + policy are configured.",
+  "acp.dispatch.enabled":
+    "Independent dispatch gate for ACP session turns. Disable to keep ACP commands available while blocking ACP turn execution.",
+  "acp.backend":
+    "Default ACP runtime backend id (for example: acpx). Must match a registered ACP runtime plugin backend.",
+  "acp.defaultAgent":
+    "Fallback ACP target agent id used when ACP spawns do not specify an explicit target.",
+  "acp.allowedAgents":
+    "Allowlist of ACP target agent ids permitted for ACP runtime sessions. Empty means no additional allowlist restriction.",
+  "acp.maxConcurrentSessions":
+    "Maximum concurrently active ACP sessions across this gateway process.",
+  "acp.stream": "ACP streaming projection controls for chunk sizing and coalescer flush timing.",
+  "acp.stream.coalesceIdleMs":
+    "Coalescer idle flush window in milliseconds for ACP streamed text before block replies are emitted.",
+  "acp.stream.maxChunkChars":
+    "Maximum chunk size for ACP streamed block projection before splitting into multiple block replies.",
+  "acp.runtime.ttlMinutes":
+    "Idle runtime TTL in minutes for ACP session workers before eligible cleanup.",
+  "acp.runtime.installCommand":
+    "Optional operator install/setup command shown by `/acp install` and `/acp doctor` when ACP backend wiring is missing.",
   "agents.list.*.skills":
     "Optional allowlist of skills for this agent (omit = all skills; empty = no skills).",
   "agents.list[].skills":
@@ -1364,6 +1386,8 @@ export const FIELD_HELP: Record<string, string> = {
     "Auto-unfocus TTL in hours for Discord thread-bound sessions (/focus and spawned thread sessions). Set 0 to disable (default: 24). Overrides session.threadBindings.ttlHours when set.",
   "channels.discord.threadBindings.spawnSubagentSessions":
     "Allow subagent spawns with thread=true to auto-create and bind Discord threads (default: false; opt-in). Set true to enable thread-bound subagent spawns for this account/channel.",
+  "channels.discord.threadBindings.spawnAcpSessions":
+    "Allow /acp spawn to auto-create and bind Discord threads for ACP sessions (default: false; opt-in). Set true to enable thread-bound ACP spawns for this account/channel.",
   "channels.discord.ui.components.accentColor":
     "Accent color for Discord component containers (hex). Set per account via channels.discord.accounts.<id>.ui.components.accentColor.",
   "channels.discord.voice.enabled":