semgrep

semgrep is a skill for Claude Code from CraftOS-dev/CraftBot. It costs 95 tokens per session (2,330 once invoked), scanned A, original, MIT.

A workflow for scanning a codebase with Semgrep, a tool that checks source code for known security and bug patterns. It can run broad or high-confidence scans and produce SARIF results, a standard format for tool findings.

In plain words
What is it for?
Use it to scan supported codebases, detect languages automatically, check for security vulnerabilities, and prepare results for review or CI pipelines.
Why use it?
It helps locate security issues across a project while reducing scan telemetry and combining findings into one report.

Skill for Claude Code

Written for Claude Code: allowed-tools in frontmatter. Also seen: mentions subagents; names the AskUserQuestion tool.

Install

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.

agentmods
npx agentmods add skills/craftos-dev/craftbot/semgrep
Any agent
npx skills add CraftOS-dev/CraftBot --skill semgrep
Clone the repo
git clone --depth 1 https://github.com/CraftOS-dev/CraftBot

Made for: Claude Code.

Wrote 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.

agentmods badge for semgrep

README.md
[![agentmods](https://agentmods.dev/badge/skills/craftos-dev/craftbot/semgrep.svg)](https://agentmods.dev/skills/craftos-dev/craftbot/semgrep)
Your own site
<a href="https://agentmods.dev/skills/craftos-dev/craftbot/semgrep"><img src="https://agentmods.dev/badge/skills/craftos-dev/craftbot/semgrep.svg" alt="Measured on agentmods" height="20"></a>
Per session 95 Skills are progressive disclosure: only the name and description are preloaded; the body loads when the skill is used.
When invoked 2,330 The whole file, excluding the scripts and references it only reads on demand.
Security scan A 0 findings. Scan, not verified.
Origin original No closer match found in the catalogue.
Token cost

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.

ModelPer sessionOnce invoked
Fable 5.1 $0.00095 $0.02330
Opus 5 $0.00048 $0.01165
Sonnet 5 $0.00019 $0.00466
Haiku 4.5 $0.00010 $0.00233

Measured 2d ago against content hash 092472caba4d, method: parsed. Prices are Anthropic first-party input rates as of 2026-09-06, from the pricing page.

Security

Grade A, and why

semgrep 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.

The scan reads SKILL.md. This mod also ships 1 executable file (scripts/merge_sarif.py), listed below but not scanned — reading those needs a real analyzer, not pattern matching.

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.

Origin

Copies of this mod

3 near-identical copies found in the catalogue:

  • semgrep — 100% identical, 10 lines differ
  • semgrep — 100% identical, 10 lines differ
  • semgrep — 100% identical, 0 lines differ
skills/semgrep/SKILL.md · 205 lines

How it starts

The opening of the file, as written. The whole thing — 205 lines — stays where its author put it; the contents beside it link to each section on GitHub.

Semgrep Security Scan

Run a Semgrep scan with automatic language detection, parallel execution via Task subagents, and merged SARIF output.

Essential Principles

  1. Always use --metrics=off — Semgrep sends telemetry by default; --config auto also phones home. Every semgrep command must include --metrics=off to prevent data leakage during security audits.
  2. User must approve the scan plan (Step 3 is a hard gate) — The original "scan this codebase" request is NOT approval. Present exact rulesets, target, engine, and mode; wait for explicit "yes"/"proceed" before spawning scanners.
  3. Third-party rulesets are required, not optional — Trail of Bits, 0xdea, and Decurity rules catch vulnerabilities absent from the official registry. Include them whenever the detected language matches.
  4. Spawn all scan Tasks in a single message — Parallel execution is the core performance advantage. Never spawn Tasks sequentially; always emit all Task tool calls in one response.
  5. Always check for Semgrep Pro before scanning — Pro enables cross-file taint tracking and catches ~250% more true positives. Skipping the check means silently missing critical inter-file vulnerabilities.

When to Use

  • Security audit of a codebase
  • Finding vulnerabilities before code review
  • Scanning for known bug patterns
  • First-pass static analysis

When NOT to Use

  • Binary analysis → Use binary analysis tools
  • Already have Semgrep CI configured → Use existing pipeline
  • Need cross-file analysis but no Pro license → Consider CodeQL as alternative
  • Creating custom Semgrep rules → Use semgrep-rule-creator skill
  • Porting existing rules to other languages → Use semgrep-rule-variant-creator skill

Output Directory

All scan results, SARIF files, and temporary data are stored in a single output directory.

  • If the user specifies an output directory in their prompt, use it as OUTPUT_DIR.
  • If not specified, default to ./static_analysis_semgrep_1. If that already exists, increment to _2, _3, etc.

Read the full file on GitHub · 205 lines

Files

What ships with it

5 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.

Changes

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.

  1. 2d ago First seen · 205 lines · 95 tokens per session scan A 092472caba4d

Subscribe to this mod's changes

semgrep is a skill published in the GitHub repository CraftOS-dev/CraftBot (380 stars, last pushed 3d ago), licensed MIT. It adds 95 tokens to every session and 2,330 once invoked, about $0.0005 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 2026-09-03.

Related

Other skills, from other repositories

development-estimation

Use when estimating time, effort, cost, or complexity for features, projects, refactors, and bug backlogs. Produces defensible estimates via triage, decomposition, risk handling, and confidence intervals, with clear assumptions and validation steps.

frumu-ai/tandem · 53 tokens

systematic-debugging

Use when debugging a failing test, build error, or runtime issue that isn't immediately obvious. Guides a 4-phase root cause analysis instead of random fix attempts.

open-metadata/OpenMetadata · 37 tokens

diagnose

Trace from a reproduced symptom to the source code that causes it. Pin the specific file and approximate line, rate confidence in the cause and clarity of the fix independently, and always propose a concrete fix.

emdash-cms/emdash · 43 tokens

cwv-optimizer

Diagnose and fix Core Web Vitals issues on AEM Edge Delivery Services pages. Goes deeper than generic CWV advice by understanding EDS-specific performance patterns including the 100KB LCP budget, E-L-D loading phases, block rendering behavior, and third-party script impact. Produces specific fixes for LCP, CLS, and…

adobe/skills · 112 tokens

trace

Dispatch trace subagent to investigate unknown issues — reproduces, traces, and reports root cause for fix handoff.

automagik-dev/genie · 25 tokens

triaging-web-analytics-support

Triage web analytics support tickets end to end: enumerate open tickets from the in-app conversations product and their Zendesk mirrors, classify each into a diagnostic shape (frontend crash, "two numbers don't match", traffic count drop, tracker not loading / undercounting vs a competitor, ad-platform integration…

PostHog/posthog · 151 tokens