diff --git a/plugins/source-control/.claude-plugin/plugin.json b/plugins/source-control/.claude-plugin/plugin.json
index ed79d601c1..53d6bda277 100644
--- a/plugins/source-control/.claude-plugin/plugin.json
+++ b/plugins/source-control/.claude-plugin/plugin.json
@@ -1,7 +1,7 @@
 {
   "$schema": "https://json.schemastore.org/claude-code-plugin-manifest.json",
   "name": "source-control",
-  "version": "0.53.2",
+  "version": "0.53.3",
   "description": "Git and GitHub delivery workflow: /commit (Conventional Commits + Co-Authored-By trailer via safe heredoc mechanics), /pull-request (prep, create, CI monitoring, review-comment triage, merge, CI-log fetch), /babysit-prs (self-pacing fleet loop \u2014 safe by default; opt-in worker/autopilot tiers add gate-checked merge and thread resolution behind a deterministic Python engine), /babysit-loop (the loop-lane merge lane: a standing or drain loop that invokes babysit-prs per cycle, configured through repo-scoped babysit_loop_* keys on the layered source-control.md seam, with merge authority human-only until the target repo's tracked config adopts the lane, a gate-proven C2-mechanical baseline once adopted, and standing merge-rung raises binding from the team-tracked layer only \u2014 with one named exception, where an invocation line explicitly typing both the autopilot tier keyword and the dedicated raise argument --merge c3-this-run widens that single invocation's merge authority up to C3 behind a fresh independent frontier-tier resolver, while C4-structural and C5-untrusted-provenance stay unconditionally human-merge), /worktree (create, status, cleanup, audit for parallel-session isolation), /setup (check the effective commit-subject / PR-title convention merged across its config layers and the babysit-prs config, or apply \u2014 interview the repo and write the convention config to a chosen layer), and /resolve-conflicts (intent-first merge/rebase conflict resolution with a semantic-conflict sweep \u2014 never --abort). The commit-subject / PR-title convention is configurable via a source-control.md config written by a re-runnable setup skill, layered across a ~/.claude user-global file, the tracked team file, and a gitignored .claude/source-control.local.md personal overlay merged per key; Conventional Commits is the default when no convention is declared.",
   "author": {
     "name": "Melodic Software",
diff --git a/plugins/source-control/CHANGELOG.md b/plugins/source-control/CHANGELOG.md
index 92548d5b6b..0d35994f71 100644
--- a/plugins/source-control/CHANGELOG.md
+++ b/plugins/source-control/CHANGELOG.md
@@ -3,6 +3,12 @@
 All notable changes to the `source-control` plugin are documented here. Format follows
 [Keep a Changelog](https://keepachangelog.com/en/1.1.0/); this plugin uses semantic versioning.
 
+## [0.53.3]
+
+### Fixed
+
+- **`fetch_pull_request_commits` fails closed when the pull-commits walk is shorter than the PR's `commits` count (#2387).** GitHub caps that endpoint at 250 commits regardless of pagination.
+
 ## [0.53.2]
 
 ### Fixed
diff --git a/plugins/source-control/skills/babysit-prs/scripts/babysit_gh.py b/plugins/source-control/skills/babysit-prs/scripts/babysit_gh.py
index 3cb02512d3..b7f4a088a6 100755
--- a/plugins/source-control/skills/babysit-prs/scripts/babysit_gh.py
+++ b/plugins/source-control/skills/babysit-prs/scripts/babysit_gh.py
@@ -481,11 +481,23 @@ def fetch_pull_request_commits(repo: str, number: int) -> list[dict[str, Any]]:
     whose verification block is missing is reported unverified with reason
     `unreadable` rather than skipped: the caller enforcing a signature rule may
     only ever over-report.
+
+    GitHub's pull-commits endpoint returns at most 250 commits regardless of
+    pagination; when the PR's `commits` count exceeds the walked rows, this
+    raises rather than returning a silently truncated list (#2387).
     """
+    pr_commits = gh_json(["api", f"repos/{repo}/pulls/{number}", "-q", ".commits"])
+    expected = int(pr_commits) if pr_commits is not None else 0
     rows = fetch_paginated_api(
         f"repos/{repo}/pulls/{number}/commits?per_page=100",
         f"{repo}#{number} commits",
     )
+    walked = len(rows)
+    if expected > walked:
+        raise RuntimeError(
+            "commit list walked "
+            f"{walked} of {expected} (pull-commits endpoint caps at 250)"
+        )
     out: list[dict[str, Any]] = []
     for row in rows:
         commit = row.get("commit")
diff --git a/plugins/source-control/skills/babysit-prs/scripts/tests/test_babysit_gh.py b/plugins/source-control/skills/babysit-prs/scripts/tests/test_babysit_gh.py
index b9b8277da9..2f0bbaa158 100644
--- a/plugins/source-control/skills/babysit-prs/scripts/tests/test_babysit_gh.py
+++ b/plugins/source-control/skills/babysit-prs/scripts/tests/test_babysit_gh.py
@@ -288,7 +288,13 @@ def test_verification_is_projected_per_commit(self) -> None:
                 "commit": {"verification": {"verified": False, "reason": "no_user"}},
             },
         ]
-        with mock.patch.object(gh, "gh_json", return_value=rows) as gh_json:
+
+        def gh_side_effect(args: list[str]) -> Any:
+            if "-q" in args and args[1].endswith("/pulls/5"):
+                return 2
+            return [rows]
+
+        with mock.patch.object(gh, "gh_json", side_effect=gh_side_effect):
             out = gh.fetch_pull_request_commits("owner/repo", 5)
         self.assertEqual(
             out,
@@ -297,11 +303,18 @@ def test_verification_is_projected_per_commit(self) -> None:
                 {"sha": "b" * 40, "verified": False, "reason": "no_user"},
             ],
         )
-        [call] = gh_json.call_args_list
-        endpoint = call.args[0][1]
-        self.assertIn("repos/owner/repo/pulls/5/commits", endpoint)
-        self.assertIn("per_page=100", endpoint)
-        self.assertIn("--paginate", call.args[0])
+
+    def test_truncated_commit_list_raises(self) -> None:
+        rows = [{"sha": "a" * 40, "commit": {"verification": {"verified": True}}}]
+
+        def gh_side_effect(args: list[str]) -> Any:
+            if "-q" in args and args[1].endswith("/pulls/99"):
+                return 251
+            return [rows]
+
+        with mock.patch.object(gh, "gh_json", side_effect=gh_side_effect):
+            with self.assertRaisesRegex(RuntimeError, "walked 1 of 251"):
+                gh.fetch_pull_request_commits("owner/repo", 99)
 
     def test_missing_verification_reads_unverified_unreadable(self) -> None:
         rows = [
@@ -309,7 +322,13 @@ def test_missing_verification_reads_unverified_unreadable(self) -> None:
             {"sha": "d" * 40},
             {"sha": "e" * 40, "commit": {"verification": {"verified": True}}},
         ]
-        with mock.patch.object(gh, "gh_json", return_value=rows):
+
+        def gh_side_effect(args: list[str]) -> Any:
+            if "-q" in args and args[1].endswith("/pulls/5"):
+                return 3
+            return [rows]
+
+        with mock.patch.object(gh, "gh_json", side_effect=gh_side_effect):
             out = gh.fetch_pull_request_commits("owner/repo", 5)
         self.assertEqual(
             out,