Fix: drain context stdout before process.exit (#573)

process.exit after a queued write truncated boot output on a backpressured pipe. Await the write callback, then close the fetch dispatcher.

AI assistance: implemented with Cursor Grok 4.6.

Co-authored-by: Cursor <cursoragent@cursor.com>

skill/scripts/context.mjs

@@ -1023,6 +1023,17 @@ async function destroyFetchDispatcher() {
   }
 }
 
+// Drain the boot payload before process.exit(): a live pipe that has not
+// flushed yet is truncated when Node tears down (issue #573 review). Then
+// close fetch so Windows teardown does not abort on the keep-alive socket.
+async function finishCli(output) {
+  await new Promise((resolve) => {
+    process.stdout.write(output, () => resolve());
+  });
+  await destroyFetchDispatcher();
+  process.exit(0);
+}
+
 // Two instructions used to sit in one directive: ask, and "if they agree, run
 // it". Nothing gated the second on an answer, and the same sentence said to
 // continue without waiting, so a run that could never establish agreement was
@@ -1169,9 +1180,7 @@ async function cli() {
     appendImageToolsDirective(parts);
     appendStalenessDirective(parts, ctx, cliOptions);
     if (updateDirective) parts.push(updateDirective);
-    process.stdout.write(parts.join('\n\n---\n\n') + '\n');
-    await destroyFetchDispatcher();
-    process.exit(0);
+    await finishCli(parts.join('\n\n---\n\n') + '\n');
   }
   const parts = [`# PRODUCT.md\n\n${ctx.product.trim()}`];
   if (ctx.hasDesign) {
@@ -1217,9 +1226,7 @@ async function cli() {
     }
   }
   if (updateDirective) parts.push(updateDirective);
-  process.stdout.write(parts.join('\n\n---\n\n') + '\n');
-  await destroyFetchDispatcher();
-  process.exit(0);
+  await finishCli(parts.join('\n\n---\n\n') + '\n');
 }
 
 function parseCliOptions(args) {

tests/context.test.mjs

@@ -1060,6 +1060,27 @@ describe('context.mjs CLI', () => {
     assert.match(res.stdout, /detect\.mjs --json <changed targets>/);
   });
 
+  it('drains stdout before exit when the parent pipe is paused', async () => {
+    const MARKER = 'END_MARKER_573';
+    write('PRODUCT.md', `# Acme\n\n${'x'.repeat(256 * 1024)}\n\n${MARKER}\n`);
+    const child = spawn(process.execPath, [SCRIPT_PATH], {
+      cwd: scratch,
+      env: { ...process.env, IMPECCABLE_NO_UPDATE_CHECK: '1', IMPECCABLE_NO_STALENESS_CHECK: '1' },
+    });
+    let stdout = '';
+    child.stdout.on('data', (chunk) => { stdout += chunk; });
+    child.stdout.pause();
+    const resume = setTimeout(() => child.stdout.resume(), 100);
+    const status = await new Promise((resolve, reject) => {
+      child.on('error', reject);
+      child.on('close', resolve);
+    });
+    clearTimeout(resume);
+    assert.equal(status, 0);
+    assert.match(stdout, /END_MARKER_573/);
+    assert.match(stdout, /RESOLVED_CONTEXT:/);
+  });
+
   // The build-path preference rides the unified config beside hook and
   // detector settings. The local file wins because whether a machine can
   // generate images is a property of that machine, not of the committed