Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx skills add synthesisengineering/synthesis-skills --skill synthesis-git-hooksgit clone --depth 1 https://github.com/synthesisengineering/synthesis-skillsWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/synthesisengineering/synthesis-skills/synthesis-git-hooks)<a href="https://agentmods.dev/skills/synthesisengineering/synthesis-skills/synthesis-git-hooks"><img src="https://agentmods.dev/badge/skills/synthesisengineering/synthesis-skills/synthesis-git-hooks/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/synthesisengineering/synthesis-skills/synthesis-git-hooks"><img src="https://agentmods.dev/badge/skills/synthesisengineering/synthesis-skills/synthesis-git-hooks.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- NVIDIA SkillSpector warn
SkillSpector: 2 findings, up to high
These are SkillSpector’s own severities. On a checked sample its high-severity flags on skills were ~96% false positives — a documented command, a public API, a “never do X” rule — so we show them as a caution to read, not a verdict. Why →
- high Tool Misuse · line 168 Tool parameters are crafted to achieve unintended or unsafe behavior. Parameter abuse can bypass intended safety checks (e.g. shell=True, --force, dangerous glob patterns).Fix: Validate all tool parameters against an allowlist. Reject dangerous parameter values (shell=True, --force, -rf /) and use safe defaults.
- medium Rogue Agent · line 50 Skill establishes unauthorized persistence across sessions via cron jobs, startup scripts, or state files. Session persistence allows an attacker to maintain access beyond the current interaction.Fix: Remove any persistence mechanisms (cron jobs, startup scripts, state files). Skills should not maintain state across sessions without explicit user consent.
What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00171 | $0.03615 |
| Opus 5 | $0.00086 | $0.01808 |
| Sonnet 5 | $0.00034 | $0.00723 |
| Haiku 4.5 | $0.00017 | $0.00362 |
Grade A, and why
synthesis-git-hooks scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 5d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 236 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Synthesis Git Hooks
A YAML-driven pre-commit policy engine. Part of the synthesis-engineering operational layer — deterministic enforcement that catches credential leaks and exposure-sensitive content at the commit boundary, before the diff persists.
The engine is a Bash boundary plus standard-library Python sidecars. The policy
is data — a YAML file at ~/.synthesis/git-hook-config.yaml that anyone
adopting synthesis engineering fills in with personal-remote patterns, client
names, internal URLs, and optionally a coordination-board path.
v2.4.0 — Coordination claims at the commit boundary
When coordination_board is configured, pre-commit invokes
synthesis-project-management's check-staged before content scanning or a
repo-local hook. It refuses unless the selected active session owns the exact
worktree and branch and every staged source/destination path is covered by the
session's claims. SYNTHESIS_COORDINATION_SESSION supplies the committing
session when the active-project pointer does not. A deliberate outside-claim
exception requires SYNTHESIS_COORDINATION_OVERRIDE_REASON; the checker
atomically records it on the board before the commit proceeds. Missing runtime,
board, lease refresh, selector, or index evidence fails closed.
The hook accepts only passed-inside-claim and recorded-override, requires the
outcome and outside-path list to match their hash-bound receipt fields, and
revalidates the board and index before continuing. A coordination refusal is
reported separately from content-policy-engine unavailability.
Repositories remain usable when coordination is not adopted: omitting
coordination_board does not block, and each hook invocation explicitly says
that this control is absent. The credential and exposure scanners still run.
v2.3.0 — Portable drift-source resolution
v2.3.0 (2026-08-03) removes the doctor's hardcoded personal checkout path.
The drift check's source now resolves portably: $SYNTHESIS_GIT_HOOKS_SOURCE
when set (authoritative — an empty value skips the check deliberately; an
invalid value is a doctor problem, fail closed), else the running script's
own directory when it is not itself an installed engine copy (repo
checkouts, worktrees, client plugin caches), else the documented locations
the ecosystem's own installers create (direct-copy skill installs, the
shared installer's cached clone). A source must carry all three engine
files to qualify, and the doctor names the resolved source in its output.
The v2.4.0 installer also persists its absolute source directory beside the
installed engine. Later direct doctor runs use that pointer before documented
fallback locations; an invalid or missing pointed source is a doctor failure.
What ships with it
10 files beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
- agents/openai.yaml 251 B
- references/per-repo-overrides.md 4.4 KB
- references/threat-model.md 4.6 KB
- references/tier-classification.md 4.2 KB
- scripts/_load_config.py 43 KB runs code
- scripts/commit-msg 3.9 KB
- scripts/git-hook-config.example.yaml 7.4 KB
- scripts/install.sh 4.1 KB runs code
- scripts/pre-commit 17 KB
- scripts/test_pre_commit.py 34 KB runs code
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 5d ago Changed 415d42a6c5d7
- 8d ago First seen · 236 lines · 171 tokens per session scan A 19da5339c6d2
synthesis-git-hooks is a skill published in the GitHub repository synthesisengineering/synthesis-skills (18 stars, last pushed yesterday), licensed Apache-2.0. It adds 171 tokens to every session and 3,615 once invoked, about $0.0009 per session on Opus 5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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