refactor(acp): simplify pass — wire exit-hook, drop dead idle timer

Post-implementation /simplify cleanup. Registers the plan-specified
process.on('exit', killAllProcesses) safety hook in index.ts (was missing —
closes an orphan-subprocess gap on hard exit). Removes the unwired idle-timer
(engine StuckTaskDetector + dispose()/registry teardown is authoritative per
KTD4a) and its tests. Fixes a stale dispositionFor doc comment, removes a
redundant identifier re-normalization in the event bridge, and clarifies why
the FusionCategory type keeps git_write/task_agent_mutation. Behavior-
preserving; 177 tests green.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

plugins/fusion-plugin-acp-runtime/src/__tests__/process-manager.test.ts

@@ -10,7 +10,6 @@ import {
   forceKill,
   spawnAgent,
   activeProcessCount,
-  createIdleTimer,
 } from "../process-manager.js";
 
 const spawned: ChildProcess[] = [];
@@ -160,24 +159,3 @@ describe("spawnAgent", () => {
   });
 });
 
-describe("createIdleTimer", () => {
-  it("fires onIdle after the interval and reset re-arms", async () => {
-    let fired = 0;
-    const timer = createIdleTimer(30, () => {
-      fired += 1;
-    });
-    await new Promise((r) => setTimeout(r, 50));
-    expect(fired).toBe(1);
-    timer.clear();
-  });
-
-  it("clear prevents firing", async () => {
-    let fired = 0;
-    const timer = createIdleTimer(20, () => {
-      fired += 1;
-    });
-    timer.clear();
-    await new Promise((r) => setTimeout(r, 40));
-    expect(fired).toBe(0);
-  });
-});

plugins/fusion-plugin-acp-runtime/src/control-handler.ts

@@ -98,11 +98,10 @@ function buildResponse(sel: {
 }
 
 /**
- * Read the per-category disposition from the live policy (exempt → allow).
- *
- * Exported so the fs-capabilities write path (U7) can reuse the exact same
- * per-category gate-reading logic for `file_write_delete` instead of duplicating
- * it (and risking drift from the U5 security floor).
+ * Read the raw per-category disposition from the live policy (exempt → allow),
+ * before the Risk S1 acknowledgement escalation. Callers that gate untrusted
+ * actions should use `effectiveDisposition` (which applies the escalation); this
+ * is the unescalated primitive it builds on.
  */
 export function dispositionFor(
   category: FusionCategory | "exempt",

plugins/fusion-plugin-acp-runtime/src/event-bridge.ts

@@ -207,7 +207,8 @@ export function createEventBridge(callbacks: AcpCallbacks): EventBridge {
     // them (a partial update may only set status/output).
     if (update.title != null) tracked.title = safeTitle(update.title);
     if (update.kind != null) tracked.kind = update.kind;
-    setTracked(update.toolCallId, tracked);
+    // `id` is already bounded above; setTracked re-keys with the same value.
+    setTracked(id, tracked);
 
     const status = update.status;
     if (status !== "completed" && status !== "failed") {

plugins/fusion-plugin-acp-runtime/src/index.ts

@@ -2,6 +2,12 @@ import { definePlugin } from "@fusion/plugin-sdk";
 import type { FusionPlugin, PluginRuntimeFactory, PluginRuntimeManifestMetadata } from "@fusion/plugin-sdk";
 import { resolveCliSettings } from "./cli-spawn.js";
 import { AcpRuntimeAdapter } from "./runtime-adapter.js";
+import { killAllProcesses } from "./process-manager.js";
+
+// Reap any live agent subprocesses on hard process exit so none are orphaned
+// (KTD4 — the registry SIGKILL is the authoritative no-orphan guarantee). Scoped
+// to tracked agent subprocesses only; never touches other processes/ports.
+process.on("exit", killAllProcesses);
 
 export const ACP_RUNTIME_ID = "acp";
 const ACP_RUNTIME_VERSION = "0.1.0";

plugins/fusion-plugin-acp-runtime/src/process-manager.ts

@@ -152,38 +152,3 @@ export function captureStderr(child: ChildProcess): () => string {
   });
   return () => buffer;
 }
-
-// --- inactivity timer (KTD4: high ceiling, engine is the authority) --------
-
-/** Default idle ceiling. The engine's StuckTaskDetector is authoritative. */
-export const DEFAULT_IDLE_CEILING_MS = 30 * 60_000;
-
-export interface IdleTimer {
-  reset(): void;
-  clear(): void;
-}
-
-/**
- * Create an inactivity timer that fires `onIdle` after `ms` of no `reset()`.
- * The default ceiling is intentionally high (KTD4) — this is a backstop, not
- * the primary aborter.
- */
-export function createIdleTimer(ms: number, onIdle: () => void): IdleTimer {
-  let handle: NodeJS.Timeout | undefined;
-  const arm = () => {
-    handle = setTimeout(onIdle, ms);
-    // Don't keep the event loop alive solely for the backstop timer.
-    handle.unref?.();
-  };
-  arm();
-  return {
-    reset() {
-      if (handle) clearTimeout(handle);
-      arm();
-    },
-    clear() {
-      if (handle) clearTimeout(handle);
-      handle = undefined;
-    },
-  };
-}

plugins/fusion-plugin-acp-runtime/src/types.ts

@@ -24,8 +24,16 @@ export interface AcpCallbacks {
 export type GateDisposition = "allow" | "block" | "require-approval";
 
 /**
- * Fusion action-gate categories the ACP `toolCall.kind` is classified into
- * (KTD3a). `"exempt"` is implicit (read-only / benign) and always allows.
+ * Fusion action-gate categories — the full policy-rule keyspace, used to read
+ * `permissionPolicy.rules[category]`. `"exempt"` is implicit (read-only / benign)
+ * and always allows.
+ *
+ * Note: ACP's `ToolKind` has no git/task discriminator, so `classifyToolKind`
+ * only ever produces `file_write_delete` / `command_execution` / `network_api`
+ * (+ exempt). `git_write` and `task_agent_mutation` remain part of the category
+ * type because the policy rules are keyed by all categories — git writes in
+ * particular route through `file_write_delete` gating PLUS the path-jail's hard
+ * `.git/**` reject (KTD6a), not a dedicated `git_write` classification.
  */
 export type FusionCategory =
   | "git_write"