semgrep

name

semgrep

description

Run the pinned Semgrep CLI to statically measure security issues (taint/injection, hardcoded secrets, OWASP Top Ten) on changed files, and interpret the SARIF output. Use ONLY when the user explicitly asks to "run semgrep", "static-analysis the diff", scan for injection/secrets, or interpret a Semgrep SARIF report. Do NOT auto-activate on generic "review my code" — the 4-agent battery and Biome cover that. CI is the authoritative gate; this skill is the local/agent interface.

Semgrep (static analysis, on-demand)

Semgrep deterministically measures injection sinks, taint flows, and hardcoded secrets — the property the security-auditor agent reasons about but cannot measure. It is a complement to the review battery, not a replacement. The CI semgrep job (.github/workflows/ci.yml) is authoritative and uploads SARIF to the code-scanning tab; this skill is the local/agent interface.

Invocation — pinned only

Semgrep is pinned to 1.169.0. Run through the repo wrapper, never a bare global call:

pnpm lint:semgrep                       # scan app/ lib/ components/ scripts/, write semgrep.sarif
node scripts/run-semgrep.mjs <paths>    # scan specific paths
node scripts/run-semgrep.mjs --error --sarif out.sarif <paths>

Local install (optional — CI is authoritative): pip install semgrep==1.169.0. If Semgrep is not installed, the wrapper exits 2 with an install hint; defer to CI.

Rulesets

• Vendored, content-pinned (.semgrep/owasp-top-ten.yml, .semgrep/secrets.yml) — the security-load-bearing rules. Edit these files to change behavior; they are the source of truth, immune to registry-side drift.
• Registry-latest packs (p/typescript, p/react, p/nextjs) — framework lint, lower stakes. The Semgrep CLI has no pack version-pinning syntax, so these fetch the latest registry rules (mutable); findings may drift between runs. Drift is accepted for the framework packs (documented in the ADR), which is why the security-load-bearing rules are instead vendored + content-pinned in .semgrep/.

Interpreting SARIF

• runs[].results[] — each is one finding. level (error/warning), ruleId, message.text, and locations[].physicalLocation (file + line).
• Zero results in --error mode → wrapper exits 0. Any result → exits 1.
• Triage a finding as real → fix the code; false positive → add a justified // nosemgrep: <rule-id> — <reason> at the site (never a blanket disable).

Hard rules

• Never disable a rule globally to clear a finding. Fix the code or justify per-line.
• Never edit fixtures under tests/fixtures/semgrep/ to dodge a finding — they are the wrapper's test ground truth.
• The CI job is currently non-blocking (continue-on-error: true). Do not promote it to blocking without a measured FP-rate baseline recorded in DECISIONS.md.