fix: address CodeRabbit review issues for PR #582

- precompact-session-digest.cjs: spawn detached child process instead of
  require()-ing runner in-process. The runner uses setImmediate internally
  which kept the event loop alive and caused the hook to block (wait for
  the 9 s safety timeout) instead of being fire-and-forget. Context is
  forwarded via AIOX_HOOK_CONTEXT env var to the inline Node script.

- synapse-engine.cjs: replace process.exitCode = 0 with process.exit(0)
  in the timeout callback. process.exitCode alone does not terminate the
  process when active handles remain (e.g. stdout backpressure), defeating
  the 5 s hard limit that protects Claude Code from a blocking hook.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: oalanicolas

.claude/hooks/precompact-session-digest.cjs

@@ -85,8 +85,23 @@ async function main() {
     provider: 'claude',
   };
 
-  const { onPreCompact } = require(runnerPath);
-  await onPreCompact(context);
+  // Spawn a detached child process so the digest is fire-and-forget.
+  // Using require() in-process keeps the event loop alive (setImmediate inside
+  // the runner), causing the hook to block until the 9 s safety timeout.
+  // The child receives context via AIOX_HOOK_CONTEXT env var and calls
+  // onPreCompact() exported by the runner module.
+  const { spawn } = require('child_process');
+  const inlineScript = [
+    `const ctx = JSON.parse(process.env.AIOX_HOOK_CONTEXT || '{}');`,
+    `const { onPreCompact } = require(${JSON.stringify(runnerPath)});`,
+    `onPreCompact(ctx).catch(() => {});`,
+  ].join('\n');
+  const child = spawn(process.execPath, ['-e', inlineScript], {
+    detached: true,
+    stdio: 'ignore',
+    env: { ...process.env, AIOX_HOOK_CONTEXT: JSON.stringify(context) },
+  });
+  child.unref();
 }
 
 /** Entry point runner — sets safety timeout and executes main(). */

.claude/hooks/synapse-engine.cjs

@@ -90,7 +90,10 @@ async function main() {
 /** Entry point runner — lets Node exit naturally after stdout flush. */
 function run() {
   const timer = setTimeout(() => {
-    process.exitCode = 0;
+    // process.exitCode alone won't terminate the process if active handles
+    // remain (e.g. stdout backpressure). Use process.exit() to enforce the
+    // 5 s hard limit and guarantee the hook never blocks Claude Code.
+    process.exit(0);
   }, HOOK_TIMEOUT_MS);
   timer.unref();
   main()