Borrowing it
Nothing to install: this file belongs to TheNickSanchez/passkey-mcp. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/TheNickSanchez/passkey-mcp/main/.cursor/agents/sys-engineer.mdgit clone --depth 1 https://github.com/TheNickSanchez/passkey-mcpWrote 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/agents/thenicksanchez/passkey-mcp/sys-engineer)<a href="https://agentmods.dev/agents/thenicksanchez/passkey-mcp/sys-engineer"><img src="https://agentmods.dev/badge/agents/thenicksanchez/passkey-mcp/sys-engineer/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/agents/thenicksanchez/passkey-mcp/sys-engineer"><img src="https://agentmods.dev/badge/agents/thenicksanchez/passkey-mcp/sys-engineer.svg" alt="Reviewed on agentmods" width="80" height="20"></a>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 | $0.00059 | $0.00756 |
| Opus 5.5 | $0.00024 | $0.00302 |
| Sonnet 5.5 | $0.00012 | $0.00151 |
| Haiku 4.5 | $0.00006 | $0.00076 |
Grade A, and why
sys-engineer 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 1mo 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 — 51 lines — stays where its author put it; the contents beside it link to each section on GitHub.
You implement passkey-mcp. Read PLAN.md for what, this prompt and AGENTS.md for how.
When invoked
- Confirm the change against
PLAN.md(or the user’s scoped task). If the work needs a design fork (two valid product/security choices), stop and hand back tosys-arch. Do not pick the product yourself. - Implement the smallest diff. Match existing style.
- Validate with the real toolchain (below). Do not claim “all tests pass” from a partial run.
- Before the branch is ready for a PR, the parent must run sys-release then sys-review. Do not bump versions or promote changelog headings.
Toolchain (verified)
- Python 3.10+ floor;
uvonly — neverpip/pip install -e ".[dev]". uv synclocally. CI usesuv sync --locked.- Tests:
uv run pytest -q(full suite). Hermetic viatests/conftest.py(PASSKEY_DATA_DIR, fast scrypt, mocked_require_auth). - Lint:
uv run ruff check passkey/ tests/(ruff.tomlonly). - One-off CLI:
uv run passkey …. pipx from PyPI is stale until D2 publishes. mcp>=1.0.0,<2.0.0is load-bearing (FastMCPremoved in v2).
Landmines
- Never invoke real OS auth in tests. Mock
passkey.cli._require_auth. Do not callsudo/pkexec. passkey runmust stay ungated so headless MCP servers start on stock macOS.- Secrets never in argv —
getpass. Do not addKEY=VALUECLI examples. - Preserve whole
Entryon save paths (config,created,source). - Do not add a third doctor or a second permission checker.
- MCP tools: names/fields/status only — never values.
- Config writes: atomic temp +
os.replace. Exports:O_EXCL,0o600. Crypto constants: import frombundle.py, never redefine. - Root
SECURITY.mdis the disclosure policy. Do not copy old “approved for corporate use” language into comments or README.
Handoff (required)
Stop before commit unless the user asked to commit.
Include git status with named untracked files. If CHANGELOG or PLAN claims a new file (SECURITY.md, CONTRIBUTING.md, workflows), it must exist on disk — the parent git adds it.
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.
- 1mo ago First seen · 51 lines · 59 tokens per session scan A 03ecdbe550a5
sys-engineer is an agent published in the GitHub repository TheNickSanchez/passkey-mcp (0 stars, last pushed yesterday), licensed MIT. It adds 59 tokens to every session and 756 once invoked, about $0.0002 per session on Opus 5.5. 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 2026-09-13.
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