diff --git a/apps/desktop/CLAUDE.md b/apps/desktop/CLAUDE.md
index b08711c1..8f9d11a6 100644
--- a/apps/desktop/CLAUDE.md
+++ b/apps/desktop/CLAUDE.md
@@ -177,11 +177,17 @@ Gateway section remains.
   all five agent CLIs, writing through the first-party `importSession` into the
   same in-process DB.
 - **Fixed port (differs from the gateway):** `127.0.0.1:4820`
-  (`AGENT_MONITOR_PORT` in `src/shared/contracts.ts`). It MUST be fixed — the
-  hook handler POSTs to `127.0.0.1:${CLAUDE_DASHBOARD_PORT||4820}`, baked into
-  `~/.claude/settings.json` at install time, so 4820 means hooks need zero
-  per-hook env. 4820 is outside `PORT_PROBE_ORDER`, so it never collides with
-  the gateway. (FEA-1500 tracks migrating this transport later.)
+  (`AGENT_MONITOR_PORT` in `src/shared/contracts.ts`). It MUST be fixed —
+  `~/.claude/settings.json` pins only the Electron-as-Node command pointing at the
+  userData `hook-handler.js` copy; that copied handler owns the
+  `CLAUDE_DASHBOARD_PORT || 4820` fallback, the route, and the payload envelope, so
+  hooks need zero per-hook env. 4820 is outside `PORT_PROBE_ORDER`, so it never
+  collides with the gateway. The route + envelope must stay backward-compatible
+  across handler/receiver changes — a persisted handler copy refreshes only
+  best-effort on boot, and `/api/hooks/event` is served by **both** the legacy
+  sidecar (default mode) and the in-process listener (design-system mode). This
+  loopback-HTTP transport is the accepted permanent design; a unix-socket
+  alternative was considered and declined (FEA-1500, obsoleted).
 - **Durable DB:** `app.getPath("userData")/agent-dashboard.sqlite` (schema in
   `src/main/database/schema.ts`), Node's built-in `node:sqlite`. Persisted
   collector caches live under `<userData>/agent-monitor/`.
diff --git a/apps/desktop/package.json b/apps/desktop/package.json
index 78e45ff4..da64bdcc 100644
--- a/apps/desktop/package.json
+++ b/apps/desktop/package.json
@@ -1,6 +1,6 @@
 {
   "name": "desktop",
-  "version": "0.15.113",
+  "version": "0.15.114",
   "description": "ClosedLoop Desktop",
   "author": "ClosedLoop AI <support@closedloop.ai>",
   "private": true,
diff --git a/apps/desktop/resources/hooks/codex-hook-handler.js b/apps/desktop/resources/hooks/codex-hook-handler.js
index 56077c40..36d804be 100644
--- a/apps/desktop/resources/hooks/codex-hook-handler.js
+++ b/apps/desktop/resources/hooks/codex-hook-handler.js
@@ -10,7 +10,10 @@
  * Zero-dependency, plain CommonJS, fail-silent — a hook must never block a Codex
  * turn. Codex calls this once per lifecycle event (SessionStart, UserPromptSubmit,
  * PreToolUse, PostToolUse, Stop) with the event name as the single argv arg. The
- * port + path + payload envelope are a backward-compatible contract (FEA-1500).
+ * port + route + payload envelope must stay backward-compatible: this handler is
+ * a persisted userData copy that settings keep invoking and that refreshes only
+ * best-effort on boot, so do not make breaking changes to /api/hooks/codex/event
+ * without keeping the 4820 receiver (AgentHookListener) backward-compatible.
  *
  * Part of FEA-1444 (opt-in Codex hook ingestion).
  */
diff --git a/apps/desktop/resources/hooks/hook-handler.js b/apps/desktop/resources/hooks/hook-handler.js
index 3f564bfa..05ee9b28 100644
--- a/apps/desktop/resources/hooks/hook-handler.js
+++ b/apps/desktop/resources/hooks/hook-handler.js
@@ -12,8 +12,13 @@
  *
  * Zero-dependency, plain CommonJS, fail-silent: it runs via the Electron binary
  * as Node (ELECTRON_RUN_AS_NODE) from a userData copy, and must NEVER block or
- * fail a Claude turn. The port + path + payload envelope are a backward-compatible
- * contract baked into ~/.claude/settings.json (see FEA-1500); do not change them.
+ * fail a Claude turn. The port + route + payload envelope must stay
+ * backward-compatible with BOTH receivers of /api/hooks/event: the legacy
+ * AgentMonitorSidecar (default Agent Monitor mode) and the in-process
+ * AgentHookListener (design-system mode). This handler is a persisted userData
+ * copy that settings.json keeps invoking and that refreshes only best-effort on
+ * boot, so do not make breaking route/envelope changes without keeping the
+ * receivers backward-compatible.
  */
 
 const http = require("http");
diff --git a/apps/desktop/src/main/agent-monitor-listener.ts b/apps/desktop/src/main/agent-monitor-listener.ts
index f40f1b52..22f6b3ef 100644
--- a/apps/desktop/src/main/agent-monitor-listener.ts
+++ b/apps/desktop/src/main/agent-monitor-listener.ts
@@ -6,13 +6,24 @@ import { AGENT_MONITOR_PORT } from "../shared/contracts.js";
 import { isSessionInSandbox } from "./agent-session-sync-service.js";
 import type { createLifecycle, HookData } from "./database/lifecycle.js";
 
-// CLOSEDLOOP-TICKET FEA-1500: remove legacy HTTP hook listener on 4820 after
-// transport migration (FEA-1497 breaking-change discipline contract #1). The hook
-// commands baked into ~/.claude/settings.json and ~/.codex/hooks.json POST to
-// 127.0.0.1:4820/api/hooks/event; this in-process listener replaces the vendor
-// sidecar that previously owned that port. The contract (port, path, payload
-// envelope) MUST stay backward-compatible until all installs self-heal to a
-// lighter transport.
+// Fixed-port hook transport (127.0.0.1:4820). The first-party hook handlers
+// (resources/hooks/hook-handler.js, codex-hook-handler.js) POST the
+// `{ hook_type, data }` envelope to /api/hooks/event (Codex:
+// /api/hooks/codex/event). This in-process listener serves that route in
+// design-system mode; in default mode the legacy AgentMonitorSidecar serves the
+// same route, so /api/hooks/event has two receivers across modes.
+//
+// COMPATIBILITY REQUIREMENT — the route + payload envelope must stay
+// backward-compatible; do NOT treat it as freely changeable. The handler is a
+// persisted userData copy that Claude/Codex settings keep invoking;
+// refreshHandlerCopy() only refreshes it best-effort on boot (failures are
+// caught and logged), so a stale copy can outlive an app upgrade. Any route or
+// envelope change therefore needs backward-compatible receiver support until all
+// persisted handler copies are known refreshed.
+//
+// 4820 is fixed and outside PORT_PROBE_ORDER so hooks need zero per-hook env.
+// This loopback-HTTP transport is the accepted permanent design; a unix-socket
+// alternative was considered and declined (FEA-1500, obsoleted).
 
 const HOST = "127.0.0.1";
 const MAX_BODY_BYTES = 8 * 1024 * 1024; // hook payloads (incl. large tool_input) cap