[ptr727]

Summary

Fixes a finding raised on promotion #3715. GNU env accepts a unique abbreviation of a long option, so a constructed env --ch=/srv/other GIT_DIR=.git git push origin main runs git in /srv/other. The write guard read --ch as a no-op and resolved the push's repository from the working directory.

• An env option the guard does not recognize, long or short, now leaves the directory a push runs in unnamed for requirement 4. _push_repo and the bare-push branch reader take None in place of the working directory, the value env -C "$D" already produces, so requirement 4 fails closed only for main, master, and develop, as Read a Push's Remote and Branch in the Repository Git Uses in the Write Guard #3709 and Read env's Directory and Environment Options in the Write Guard #3722 treat a shape they cannot resolve. An absolute --git-dir, git's own -C, or an absolute cd in a wrapper body still names the repository. A GIT_DIR behind such an option is not read for the repository, since the option may abbreviate --unset. Prefix matching was decided against.
• Each unrecognized option may or may not take the next word, and a value it takes may be an -S string, which reaches an abbreviated --split-string. _launches reads every combination of up to four of those choices. A reading past the first adds commands only and changes no shell state, and a subshell restores the body's undetermined state with its directory.
• A push naming no refspec or HEAD behind such an option, whose branch nothing else names, reads it as if the option were absent. So it is never weaker than before and never newly blocks a feature-branch push.
• --null, --debug, and the GNU signal options are now listed, so they keep reading as no-ops. -0, -v, -i and the value letters keep their behavior.
• Requirement 6 keeps judging the working directory. The extra readings can only add a deny there, for example env --chd /path/wt git commit run from a primary checkout.
• host-setup/agent-safety/README.md states the new reading in its lexer paragraph, in requirement 4, and in requirement 6.

Verification

• Reproduced first with classify on two constructed scratch checkouts, origins alpha/x and beta/y, with a stubbed live-rules lookup requiring a pull request on beta/y's main. Before the fix --ch=<b>, --chd <b>, and -X <b> pushes to main were allowed. After it they are denied, and feature-branch pushes stay allowed.
• New self-test cases cover --ch=<dir>, --chd <dir>, an unknown short letter, two unrecognized options of different arity, an abbreviated split string, an unknown option ahead of sh -c, a subshell in the body, absolute -C/--git-dir/body cd re-anchoring, a URL remote, bare and HEAD pushes, GH_REPO not leaking from a speculative reading, each recognized option unchanged, and allow on feature/x. Each new repository and branch row fails with its fix reverted.
• gh-write-guard.py --selftest passes. Pinned ruff format and check, mypy, tests/test_guard_size.py, and the prose gate pass.
• Seven local strict-review passes, the last raising nothing.

Dropped findings

• gh-write-guard.py _env_option, style: reading an unknown short letter as unrecognized was named as over-hardening. The decided fix for Read an Unrecognized env Option as an Undetermined Repository in the Write Guard #3725 names short options explicitly.

Pre-existing findings, not filed

• gh-write-guard.py _bare_push_branch, pre-existing: its leading_cd and moved parameters answer no caller, since every caller passes None and False. One caller is in host-setup/agent-safety/claude/test_install.py, outside this change.

Closes on promotion: #3725

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[ptr727]

A recorded local strict-review pass covers head 2ce9fbd42dc1af6efe5d5894f7d4f896616479b7, the content this pull request carries at that commit against develop, and it recorded 6 findings.

[Copilot]

🟡 Changes recommended

Outstanding critical and moderate findings leave subshell state and split-string write detection incorrect, while branch-case tests do not prove repository resolution.

4 open issues

• Detect commands in abbreviated split-string options · New
• Restore the undetermined flag after subshells · New
• Make branch tests verify repository resolution · New
• Describe the unresolved directory, not repository · New

What changed in this PR

This pull request hardens the write guard against unrecognized GNU env options that may alter directory or command resolution.

Changes:

• Tracks unknown options and evaluates bounded possible argument consumption.
• Adds recognized GNU env flags and expands push-resolution tests.
• Documents undetermined-directory behavior and requirement 4 semantics.

Unresolved correctness issues remain around subshell state restoration and split-string option abbreviations.

File	Summary
host-setup/​agent-safety/​README.md	Documents how unrecognized env options affect directory resolution and requirement 4.
host-setup/​agent-safety/​claude/​gh-write-guard.py	Updates env parsing, uncertainty propagation, push resolution, and related self-tests.

This pull request requires changes.

_{Review effort: Lite}

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 82.02%. Comparing base (8d71126) to head (6746e61).

Additional details and impacted files

@@           Coverage Diff            @@
##           develop    #3727   +/-   ##
========================================
  Coverage    82.02%   82.02%           
========================================
  Files           27       27           
  Lines         9275     9275           
========================================
  Hits          7608     7608           
  Misses        1667     1667           

Flag	Coverage Δ
python-3.13	82.02% <ø> (ø)

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[ptr727]

A recorded local strict-review pass covers head f26d9085085ecb16daa18f191f504358a3427f97, the content this pull request carries at that commit against develop, and it recorded 2 findings.

[ptr727]

A recorded local strict-review pass covers head 6746e6186b3562fc1b05e3f32dd551fc1e8a2392, the content this pull request carries at that commit against develop, and it recorded 0 findings.