Scan Skill

Overview

Deterministic check engine that runs grep patterns and structural analysis against backend code. Accepts a scope argument (file path, directory path, or cwd) and a dimensions argument (comma-separated dimension list or "all") to control which checks execute.

This skill performs purely mechanical detection — it matches known patterns, counts structural violations, and reports findings with exact file locations. It does not make qualitative judgments about architecture or design. Other skills (like axiom:critique) handle subjective assessment and invoke scan when they need deterministic evidence.

See @skills/scan/references/check-catalog.md for scan-specific execution guidance including ordering, batching, and exclusions.

Triggers

Activate this skill when:

• User says "scan code", "check patterns", "run checks", or "detect anti-patterns"
• User runs /axiom:scan
• Another axiom skill requests deterministic pattern detection
• User wants mechanical verification of known code smells

Do not activate this skill when:

• User wants qualitative architecture review — use axiom:critique instead
• User wants a full quality audit — use axiom:audit instead
• User needs subjective design feedback rather than pattern matching

Process

Step 1: Load Check Catalog

Load the canonical check definitions from @skills/backend-quality/references/deterministic-checks.md. This file defines every grep pattern, structural check, and their associated dimensions and severities.

Step 2: Load Project-Specific Checks (Optional)

If .axiom/checks.md exists in the project root, load additional project-specific check definitions. These follow the same format as the canonical catalog and are merged into the check set. If the file does not exist, silently skip this step.

Step 3: Filter by Requested Dimensions

Apply the dimensions argument to filter the merged check set:

• If dimensions is "all" or omitted, run every check in the catalog
• If dimensions is a comma-separated list (e.g., "topology,observability"), only run checks tagged with those dimensions
• Invalid dimension names produce an actionable error message listing valid dimensions

Step 4: Execute Checks

For each check in the filtered set, run the grep or structural pattern against the resolved scope:

• Execute grep patterns using the exact expressions from the catalog
• Run structural analysis checks (file counts, nesting depth, import graphs)
• Collect all matches with file path, line number, and matched content
• Record checks that produced zero matches as passing

Step 5: Format Findings

Format each match as a finding per @skills/backend-quality/references/findings-format.md. Every finding produced by this skill is marked deterministic: true to distinguish mechanical detections from qualitative assessments.

Step 6: Group and Output

Output findings grouped by dimension, then by severity (HIGH, MEDIUM, LOW) within each dimension. Include:

• Total checks run and total findings
• Per-dimension summary with finding counts
• Individual findings with file location, matched pattern, and remediation hint

Error Handling

• Invalid patterns: If a grep pattern from the catalog fails to compile or execute, report the specific pattern and error message. Do not silently skip — the user needs to know which check is broken so they can fix the catalog entry.
• Empty scope: If the resolved scope contains no files to scan (empty directory, nonexistent path), return a "nothing to scan" message with the resolved path. Do not treat this as a failure.
• Missing .axiom/checks.md: Silently skip project-specific check loading. This file is optional and its absence is expected for projects that have not customized their check set.
• Permission errors: If a file cannot be read due to permissions, log the file path and continue scanning remaining files.

Output Format

All findings use the standard format from @skills/backend-quality/references/findings-format.md with one addition: every finding includes deterministic: true to signal that it was produced by mechanical pattern matching, not qualitative judgment.

dimension: observability
severity: MEDIUM
deterministic: true
file: src/handlers/query.ts
line: 42
pattern: readEvents
match: "const items = await readEvents(stream)"
remediation: "Move raw event reads out of query handlers — use a read model projection instead"

Anti-Patterns