google/mantis is a modular set of security-review skills that coding agents use to find, reproduce, and patch software vulnerabilities. It is for adapting automated security testing to application, infrastructure, machine-learning, hardware, and firmware projects, with expert review required for results. The catalogue skills and instruction provide the workflow for using Mantis with coding agents.
Getting it into your agent
It runs from inside its repository, so the clone comes first — what it calls does not travel with the file alone.
git clone --depth 1 https://github.com/google/mantisnpx agentmods add skills/google/mantis/mantis-structural-indexWrote 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/google/mantis/mantis-structural-index)<a href="https://agentmods.dev/skills/google/mantis/mantis-structural-index"><img src="https://agentmods.dev/badge/skills/google/mantis/mantis-structural-index/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/google/mantis/mantis-structural-index"><img src="https://agentmods.dev/badge/skills/google/mantis/mantis-structural-index.svg" alt="Reviewed on agentmods" width="80" height="20"></a>- Socket pass
- Snyk pass
- NVIDIA SkillSpector pass
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 | $0.00055 | $0.08881 |
| Opus 5.5 | $0.00022 | $0.03552 |
| Sonnet 5.5 | $0.00011 | $0.01776 |
| Haiku 4.5 | $0.00006 | $0.00888 |
Grade A, and why
mantis-structural-index 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 — 747 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Structural Code Index Builder
This is an optional first-class stage in the Pass Lifecycle Contract. It
runs immediately after the snapshot is pinned (Block D), before the first
code-reading analysis stage (summarize/architecture). It only needs CODE_ROOT
+ SNAPSHOT_ID and must not depend on architecture/KB.
System Goal
Structural Code Index Builder. Builds a content-addressed semantic-unit index
from source code using capability-based per-partition backend selection,
degrading gracefully to grep. Provides find_callers(symbol),
get_function_boundary(file, line), and call-site awareness to improve LLM
reasoning quality during discovery — supplementing (never replacing) grep-based
call-site discovery with structural data. The index is composed from independent
semantic compilation units, persisted as a manifest + SQLite catalog, and
exposed through a bounded query helper.
Command Definition
- Command:
/mantis-structural-index - Description: Build a content-addressed semantic-unit index from source
code under
CODE_ROOT. - Arguments (optional; supplied by the orchestrator, consumed by Block A):
--snapshot_root/--snapshot_id/--state_root. All absent → MODE-OFF/legacy mode (reads source from the current directory, writes index to./workspace/kb/structural_index/).
Input/Output Contract
- Reads:
workspace/.mantis_state.json(to readactive_snapshotfor provenance checking and snapshot-aware rebuild logic).workspace/kb/structural_index/manifest.json(to checksnapshot_idfor reuse-on-match idempotency — primary check).workspace/kb/structural_index.jsonl(backward-compat provenance check if manifest absent).workspace/kb/structural_index/units/(content-addressed cache for incremental unit reuse).workspace/kb/structural_index/native/and sidecarprovenance.jsonfiles (prebuilt index attachments and metadata manifests).- CODE_ROOT source files (via generated helper script — the script parses all
source files under
CODE_ROOT).
- Writes:
workspace/kb/structural_index/manifest.json(STATE-RELATIVE — atomic commit point, written LAST).workspace/kb/structural_index/catalog.sqlite(STATE-RELATIVE — query-optimized serving store).workspace/kb/structural_index/units/(STATE-RELATIVE — content-addressed immutable unit outputs).workspace/kb/structural_index/shards/(STATE-RELATIVE — partitioned serving data for large corpora).workspace/kb/structural_index/native/(STATE-RELATIVE — prebuilt index attachments: SCIP, Kythe, LSIF).workspace/kb/structural_index/tmp/(STATE-RELATIVE — temporary objects during build).workspace/kb/structural_index.jsonl(STATE-RELATIVE — compatibility pointer; full export below threshold).workspace/helpers/build_structural_index.py(STATE-RELATIVE — the builder helper script).workspace/helpers/query_structural_index.py(STATE-RELATIVE — the query helper script).
- Preconditions:
- Source files must exist under
CODE_ROOT. IfCODE_ROOTis not resolved (MODE-OFF and no readableactive_snapshot), build against the current directory withsnapshot_idset to"unknown". Do NOT skip — this is the standalone-efficiency case.
- Source files must exist under
- Inert until wired: This skill returns an empty index until a caller
invokes it (the harness,
mantis-plan, ormantis-researcher). It never fails — it simply returns an empty index if tools are unavailable or source cannot be parsed. - Idempotency Guarantee:
- Read-only on
CODE_ROOT. Writes only to STATE-RELATIVE paths. Re-running with the sameCODE_ROOTandSNAPSHOT_IDreuses the existing index (manifestsnapshot_idmatch) rather than rebuilding — except in MODE-OFF, where it always rebuilds. Individual semantic units are reused across snapshots when their content-addressed cache keys match (incremental rebuild).
- Read-only on
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 · 747 lines · 55 tokens per session scan A 5a65e5589084
mantis-structural-index is a skill published in the GitHub repository google/mantis (2,525 stars, last pushed today), licensed Apache-2.0. It adds 55 tokens to every session and 8,881 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 2026-08-30.
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