Vulnetix Secure Code Write Skill

Use when

• About to write authentication, crypto, SQL, deserialization, file-handling, or template code.
• Coaching a junior on a new security-sensitive feature.
• Pair-programming a security-sensitive change with a reviewer who wants to surface rules upfront.
• Reviewing a PR and want the rule digest the author should have seen.
• Cross-referencing the SAST rules that would fail BEFORE writing the code that triggers them.

Don't use for

• Actually scanning code — use sast-scan.
• Generic security advice — this skill is rule-grounded, not narrative.
• Educating non-developer audiences — the rule digest is engineer-targeted.

Conventions

Follows skills/_lib/contract.md. In short: use the vulnetix_* MCP tools when the agent has them and the CLI otherwise — both shape their own output, so there is no jq step any more. Independent calls go out as concurrent Bash tool calls in one message. One trailing suggestion, not a playbook. See the contract for surface selection, output style and memory writes.

A coach, not a scanner. Use this when about to author auth, crypto, SQL, deserialization, file-handling, or templating code — surfaces the rules a reviewer would check, before you write the buggy version.

Step 1: Load capabilities + decide topic

Read .vulnetix/capabilities.yaml. Determine language from derived.primary_package_manager or the file extension of $ARGUMENTS.

If $ARGUMENTS is a topic keyword (auth, crypto, sql, xss, deser, file, template), use it directly. Else infer from file content (Read the file, look for keywords).

Step 2: Pull rule digest

vulnetix scan --list-default-rules -o json | jq '[.rules[] | select(.tags | contains([$topic]))]' --arg topic "$TOPIC"

Plus CWE intel:

vulnetix vdb cwe list --keyword "$TOPIC" -V v2 -o json

Step 3: Render coach

Secure-code coach: <topic> in <language>

Top rules to honor:
1. <rule-id>: <one-line summary>  (CWE-XXX)
2. ...

Common pitfalls:
- ...

Snippets that pass / fail:
PASS:
<code>

FAIL:
<code>

Tailor snippets to the detected language.

Step 4: Optional inline check

If the user is editing a file, offer:

Run `sast-scan --paths <file>` after I finish to confirm.

No memory writes

Coaching only.

Edge cases & gotchas

• Topic detection from file content uses keyword heuristics — be explicit (--topic crypto) if working with mixed-concern code.
• Rule digest is vulnetix scan --list-default-rules filtered by tag; the rule set updates with the CLI release, not per-org policy.
• PASS/FAIL snippets are language-tailored from derived.primary_package_manager. JVM-stack repos with both Java and Kotlin may get snippets in only one.
• vdb cwe <id> -V v2 returns CWE-specific defensive guidance — use it for educational follow-up, not as the rule source.
• No memory writes — this is read-only coaching.
• For green-field projects without a lockfile, the language detection falls back to --topic; pass explicitly.