diff --git a/.changeset/687-agy-print-timeout.md b/.changeset/687-agy-print-timeout.md
new file mode 100644
index 000000000..ea9f4eb48
--- /dev/null
+++ b/.changeset/687-agy-print-timeout.md
@@ -0,0 +1,5 @@
+---
+type: Fixed
+pr: 689
+---
+**`/gsd-review --agy` no longer hangs the whole review on large prompts.** On a big, file-path-rich prompt Antigravity's `agy -p` agentic Cascade can loop on its `code_search`/grep steps and never converge. The invocation now passes agy's own `--print-timeout` flag (its native print-mode cap) so a stalled run self-terminates through the tool's own mechanism; on a non-zero exit any partial output is discarded so the existing transcript fallback / "review failed" stub take over.
diff --git a/gsd-core/workflows/review.md b/gsd-core/workflows/review.md
index 58edb986c..123da933c 100644
--- a/gsd-core/workflows/review.md
+++ b/gsd-core/workflows/review.md
@@ -350,8 +350,19 @@ if [ -f "$_AGY_CACHE" ]; then
   fi
 fi
 
-# Step 1 — primary invocation: stdout works on macOS, Linux, and WSL
-agy -p "$(cat /tmp/gsd-review-prompt-{phase}.md)" 2>/dev/null > /tmp/gsd-review-antigravity-{phase}.md
+# Step 1 — primary invocation: stdout works on macOS, Linux, and WSL.
+# Bound the run with agy's OWN `--print-timeout` (issue #687). On a large,
+# file-path-rich prompt agy's agentic Cascade can loop on its code_search/grep
+# steps and never converge; `--print-timeout` is agy's native cap for print mode
+# (defaults to 5m — see maintainer note above), so we pass it explicitly to let a
+# stalled run self-terminate through the tool's own mechanism. A non-zero exit
+# (timeout or crash) discards any partial output so the Step 2 transcript fallback
+# / Step 3 stub take over.
+agy --print-timeout 300s -p "$(cat /tmp/gsd-review-prompt-{phase}.md)" 2>/dev/null > /tmp/gsd-review-antigravity-{phase}.md
+_AGY_RC=$?
+if [ "$_AGY_RC" -ne 0 ]; then
+  : > /tmp/gsd-review-antigravity-{phase}.md
+fi
 
 # Step 2 — transcript fallback: catches Windows agy -p stdout bug (and any future stdout-silent edge cases).
 # Reads only lines appended AFTER the pre-flight watermark. If agy failed before writing a new response,
diff --git a/tests/bug-687-agy-timeout.test.cjs b/tests/bug-687-agy-timeout.test.cjs
new file mode 100644
index 000000000..e75711d67
--- /dev/null
+++ b/tests/bug-687-agy-timeout.test.cjs
@@ -0,0 +1,45 @@
+// allow-test-rule: source-text-is-the-product
+// review.md is a workflow file whose deployed text IS the runtime contract; the
+// agy -p invocation cannot be run in CI, so we assert on its content (issue #687).
+'use strict';
+
+const { describe, test } = require('node:test');
+const assert = require('node:assert/strict');
+const fs = require('node:fs');
+const path = require('node:path');
+
+const reviewPath = path.resolve(__dirname, '..', 'gsd-core', 'workflows', 'review.md');
+const read = () => fs.readFileSync(reviewPath, 'utf-8');
+
+describe('bug #687: agy print mode must be bounded via its native --print-timeout', () => {
+  test('invokes agy with its own --print-timeout flag (not an external killer)', () => {
+    assert.match(read(), /agy --print-timeout \d+s? -p "\$\(cat/,
+      'review.md must cap agy through `agy --print-timeout <N> -p …` (the tool\'s own mechanism)');
+  });
+
+  test('discards partial output on non-zero exit so the fallback fires', () => {
+    const c = read();
+    assert.match(c, /_AGY_RC.*-ne 0/, 'review.md must check the agy exit code');
+    assert.match(c, /: > \/tmp\/gsd-review-antigravity-/,
+      'review.md must truncate the output file when agy timed out / failed');
+  });
+
+  test('agy is bounded only by its own --print-timeout, not an external process killer', () => {
+    const c = read();
+    // Print-mode reviewers invoke the tool directly; agy must self-terminate via
+    // --print-timeout, never via an external SIGKILL/timeout binary wrapped around it.
+    assert.doesNotMatch(c, /-s KILL/, 'must not SIGKILL agy from the outside');
+    // Any external timeout binary wrapping agy — `timeout 300s agy …`,
+    // `gtimeout 300 agy …`, `timeout -s KILL 300 agy …`. The lookbehind keeps
+    // agy's own `--print-timeout` flag from tripping it.
+    assert.doesNotMatch(c, /(?<!print-)\bg?timeout[ \t]+[^\n]*\bagy\b/,
+      'must not wrap agy in an external timeout binary — use its --print-timeout flag');
+    assert.doesNotMatch(c, /kill -9 "\$_AGY/, 'must not use a kill -9 watchdog on agy');
+  });
+
+  test('no unguarded bare "agy -p" invocation remains at line start', () => {
+    // A bare `agy -p "$(cat …)"` with no cap was the original hang.
+    assert.doesNotMatch(read(), /^agy -p "\$\(cat/m,
+      'review.md must not invoke agy -p without --print-timeout');
+  });
+});