Adds a tier-2 pre-commit hook that auto-unstages sandbox-only files
from any tier-2 commit, preventing the leak that hit master in
00e5a3f2 (the offender commit that was just selectively reverted
in fab2e55b). The hook is paired with a config file that lists the
forbidden paths as substring patterns.
Design:
- Hook reads conductor/tier2/githooks/forbidden-files.txt (one
substring pattern per line; # comments and blanks ignored)
- For each staged file, checks if any pattern is a substring of
the path. If a match is found, the file is auto-unstaged via
`git rm --cached --force` (force is required when the index
has content that differs from BOTH HEAD and the working tree)
- Hook always exits 0 — it removes the leak rather than blocking
the commit. A hard reject would leave tier-2 stuck mid-flow
(tier-2 cannot run `git restore --staged`, which is banned by
the sandbox permission rules)
- The hook's config file lives at the project root so it ships
with the clone. setup_tier2_clone.ps1 will install the hook
in a follow-up commit; existing clones need to re-run setup
to get the hook
Forbidden patterns (substring matches):
- .opencode/agents/tier2-autonomous (sandbox agent prompt)
- .opencode/commands/tier-2-auto-execute (sandbox slash command)
- opencode.json (MCP path / default_agent / model override)
- mcp_paths.toml (extra_dirs cleared in clone)
Patterns are SPECIFIC (not prefix-based) so they do not match
the legitimate interactive tier-2 tech-lead prompt at
.opencode/agents/tier2-tech-lead.md.
Tests (tests/test_tier2_pre_commit_hook.py, 12 cases):
- Empty staged set: git's standard "nothing to commit" error
- Allowed files: commit succeeds normally
- Each forbidden file (agent, command, opencode.json,
mcp_paths.toml) staged: auto-unstaged, commit proceeds
- Mixed staged set: only forbidden are unstaged
- Hook silent when no leaks detected
- Hook warns (stderr) when unstaging
- Config-driven: replacing forbidden-files.txt changes the
denylist without modifying the hook
- Paths with spaces: handled correctly via git diff -z
Defense-in-depth context:
- Layer 1: OpenCode permission system (denies direct edits to
these files from the tier2-autonomous agent)
- Layer 2 (this commit): pre-commit hook (removes the leak at
the commit boundary)
- Layer 3 (follow-up commit): scripts/audit_tier2_leaks.py
(scans working tree, CI gate)
