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 agentmods add skills/google/mantis/mantis-reviewnpx skills add google/mantis --skill mantis-reviewgit clone --depth 1 https://github.com/google/mantisWhat 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 | $0.00038 | $0.06345 |
| Opus 5 | $0.00019 | $0.03173 |
| Sonnet 5 | $0.00008 | $0.01269 |
| Haiku 4.5 | $0.00004 | $0.00634 |
Grade A, and why
mantis-review 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 2d 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 — 438 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Reviewer (/mantis-review)
System Goal
Independent Validator. Reviews consolidated findings against active source code to verify validity and filter out noise and false positives.
Command Definition
- Command:
/mantis-review - Description: Independently reviews findings and filters out false positives.
Input/Output Contract
- Reads:
workspace/findings/(finding JSON files, including each finding's optionaldiscovery_commitprovenance stamp).workspace/.mantis_state.json(current looppass_number; and, when present,active_snapshot={root, snapshot_id, snapshot_pinned}for snapshot provenance).- Invocation args when passed by the orchestrator:
--snapshot_root,--snapshot_id,--state_root(and, rarely,--target_root). - Target source code files at the
code_pathspaths/lines, read under the resolvedCODE_ROOT(the pinned snapshot root — see Instructions Step 0 / Block A), never the live tree when a snapshot is pinned.
- Writes:
- Updates findings on disk in-place (sets
"status","reasoning","repro_hints","triage_checklist", and appends history). - Writes helper script
workspace/helpers/append_review.py.
- Updates findings on disk in-place (sets
- Preconditions:
workspace/findings/exists with finding files.- Target source code files exist.
- Idempotency Guarantee:
- Modifies finding files in-place using the helper script
append_review.py, which MUST carry# MANTIS_HELPER_VERSION = 2as its first line; regenerate the helper if that marker is absent or a different integer (see Instructions step 5). - Idempotency key is (pass_number, snapshot). Before (re)writing a
finding, scan its
historyarray:- SNAPSHOT MODE OFF (neither
--snapshot_idwas passed NOR isactive_snapshotreadable in state): SKIP the review update iff a"stage": "reviewer"entry already exists for the currentpass_number(byte-for-byte today's behavior). - SNAPSHOT MODE ON: SKIP the review update iff a
"stage": "reviewer"entry exists whosepass_numberequals the current pass AND whosesnapshotequalsSNAPSHOT_ID. A reviewer entry that lackssnapshot(legacy) or carries a differentsnapshotcounts as UNKNOWN → RE-REVIEW (do NOT skip), so a finding reviewed under the old skill is re-grounded against the current pinned snapshot.
- SNAPSHOT MODE OFF (neither
- Modifies finding files in-place using the helper script
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.
- 2d ago First seen · 438 lines · 38 tokens per session scan A 3c0a274abc31
mantis-review is a skill published in the GitHub repository google/mantis (853 stars, last pushed 5d ago), licensed Apache-2.0. It adds 38 tokens to every session and 6,345 once invoked, about $0.0002 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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