[BUG] stop-hook-git-check.sh false-positives on SSH-signed commits (%G?=N), creating an unbreakable Stop-hook loop

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

Environment

• Claude Code on the web (Anthropic-managed cloud session, research preview)
• Hook: ~/.claude/stop-hook-git-check.sh (provisioned by the web launcher via ~/.claude/launcher-settings.json)
• Signing config in the session: gpg.format=ssh, commit.gpgsign=true,

user.signingkey=~/.ssh/commit_signing_key.pub, gpg.ssh.program=/tmp/code-sign

Summary

The Stop hook flags validly signed commits as "Unverified" and enters an
infinite loop: it fires on every turn, and the remedy it prescribes
(git commit --amend --no-edit --reset-author) can never satisfy it. The only
escape is pushing the branch.

Root cause

stop-hook-git-check.sh line ~54:

unverifiable=$(git log --format='%h %G? %ce' "$upstream..HEAD" \
| awk '$2 == "N" || $3 != "noreply@anthropic.com"')

The comment above it (lines ~51–52) assumes that signed-but-locally-unverifiable
commits report %G? of U/B/E, so treating N as "unsigned" is claimed to
be a reliable presence check. That assumption is false in this environment.

In the web session, SSH-signed commits report %G? = N, identical to
unsigned, because local verification is impossible:

• gpg.ssh.allowedSignersFile is not configured, and
• the public key file ~/.ssh/commit_signing_key.pub is empty (0 bytes), and
• the signer /tmp/code-sign is sign-only (error: ... only SSH-style signing (-Y sign) is supported).

So git can't verify, prints
error: gpg.ssh.allowedSignersFile needs to be configured and exist, and
reports N. The commits are genuinely signed — git cat-file commit HEAD shows a
gpgsig -----BEGIN SSH SIGNATURE----- header and committer ... <noreply@anthropic.com>.

Actual

Signed commits are flagged identically to unsigned ones; the amend remedy is a
no-op against the check; the hook loops every turn until the branch is pushed
(which empties origin/<branch>..HEAD and is the only thing that silences it).

Suggested fixes (any one)

1. Detect signature presence without relying on %G? — e.g. check for a

gpgsig header directly (git cat-file commit <sha> / git log --format=%GK),
so a real signature isn't read as N.

1. Provision gpg.ssh.allowedSignersFile from the signing public key so %G?

can actually verify — but note the key file is currently empty, so that needs
fixing too.

1. When local verification is known-unavailable in this runtime, skip the

signature branch and rely only on committer-email + unpushed checks.

Impact

Wasted turns/tokens on a remedy that cannot work, and a confusing UX: the user is
repeatedly told their (correctly signed) commits are unverified.

What Should Happen?

Expected

A commit that carries a valid signature and committer noreply@anthropic.com
should NOT be flagged, and the amend remedy should clear the warning.

Error Messages/Logs

# ── Claude Code on the web — cloud session ──────────────────────────────────
# Repo: kleer001/book_loom   Branch: claude/book-loom-critique-rewrite-hbv7l4

# 1) Signing IS configured and active (SSH signing, web-provisioned):
$ git config --get-regexp '^(commit\.gpgsign|gpg\.|user\.signingkey)'
user.signingkey /home/claude/.ssh/commit_signing_key.pub
gpg.format ssh
gpg.ssh.program /tmp/code-sign
commit.gpgsign true

# 2) The signing PUBLIC KEY file is EMPTY (0 bytes), and the signer is sign-only:
$ ls -la "$(git config user.signingkey)"
-rw-r--r-- 1 claude claude 0 Mar 31 13:31 /home/claude/.ssh/commit_signing_key.pub
$ ls -la /tmp/code-sign
lrwxrwxrwx 1 root root 35 /tmp/code-sign -> /opt/env-runner/environment-manager

# 3) allowedSignersFile is UNSET, so local verification is impossible:
$ git config gpg.ssh.allowedSignersFile
$ echo $?
1

# 4) The commits ARE genuinely signed — note the gpgsig SSH header & committer:
$ git cat-file commit HEAD | head -6
tree dcfa8a69ce4546c4934b8db5a2020068c446bd0b
parent 814891bb69130e05fd94d7626b0dad7aebffa232
author Claude <noreply@anthropic.com> 1781716009 +0000
committer Claude <noreply@anthropic.com> 1781716009 +0000
gpgsig -----BEGIN SSH SIGNATURE-----
 U1NIU0lHAAAAAQAAADMAAAALc3NoLWVkMjU1MTkAAAAg...

# 5) But because verification can't run, git reports %G? = N (== "no signature"),
#    identical to an unsigned commit. THIS is what the hook keys on:
$ git log --format='%h %G? %ce %s' -3
error: gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification
error: gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification
7a929d1 N noreply@anthropic.com Refine reloom spec: input formats, ingest, and the Mandate workflow
814891b N noreply@anthropic.com Add spec for inverting book_loom into a critique-and-rewrite pipeline

$ git verify-commit HEAD
error: gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification

$ git show --show-signature -s HEAD | head -3
error: gpg.ssh.allowedSignersFile needs to be configured and exist for ssh signature verification
commit 7a929d1602a79451a197e11072a599365664a185
No signature        # ← signed commit reported as "No signature"

# 6) The Stop hook (~/.claude/stop-hook-git-check.sh, line ~54) does:
#      git log --format='%h %G? %ce' "$upstream..HEAD" | awk '$2=="N" || $3!="noreply@anthropic.com"'
#    and emits (exit 2), every single turn:
[~/.claude/stop-hook-git-check.sh]: There are commit(s) on branch
'claude/book-loom-critique-rewrite-hbv7l4' that GitHub will show as Unverified
(missing signature, or committer email is not noreply@anthropic.com):
7a929d1 N noreply@anthropic.com
814891b N noreply@anthropic.com
Please run 'git config user.email noreply@anthropic.com && git config user.name Claude',
then 'git commit --amend --no-edit --reset-author' ...

# 7) The prescribed remedy does NOT help: amend re-signs the same way, %G? is still N.
#    The check is unsatisfiable for unpushed commits → fires on every turn (token burn).

# 8) The ONLY thing that silences it: push, so the scanned range empties.
$ git rev-list "origin/$(git branch --show-current)..HEAD" --count
0     # after pushing, upstream..HEAD is empty → hook finally exits 0

Steps to Reproduce

Steps to reproduce

1. In a web session, make a commit (it is auto-signed; committer = noreply@anthropic.com).
2. End the turn → Stop hook reports the commit as Unverified.
3. Run the prescribed git commit --amend --no-edit --reset-author (or the rebase --exec variant).
4. End the turn again → the same commit is reported again. Loop repeats indefinitely.

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.170

Claude Code Version

2.1.179

Platform

Anthropic API

Operating System

Other

Terminal/Shell

Other

Additional Information

Actual

Signed commits are flagged identically to unsigned; the amend remedy is a no-op; the hook loops every turn until the branch is pushed.

Suggested fixes (any one)

1. Detect signature presence without %G? — e.g. check for a gpgsig header (git cat-file commit <sha> / git log --format=%GK).
2. Provision gpg.ssh.allowedSignersFile (and a non-empty pubkey) so %G? can actually verify.
3. When local verification is known-unavailable in the runtime, skip the signature branch and rely on the committer-email + unpushed checks only.

Workaround

Push the branch — origin/<branch>..HEAD empties and the hook goes silent; no --amend needed. Commits show Verified on GitHub regardless.

Related

• #7711 (commit-signing feature request, closed not planned — but the web runtime does sign now; the verification check is what's broken)
• Same loop class as #55754 / #58348 / #3573 / #10205, distinct root cause (%G?=N on validly SSH-signed commits with no local verification).

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Disclosure: This report — including the reproduction log and root-cause analysis — was drafted by Claude Code (Opus 4.8) running in the affected web session, at the reporter's direction. Commands and outputs in the log were executed live in that session.