null-as-error-cc

name	null-as-error-cc
description	Audit an Effect codebase for silent error swallowing -- catchAll patterns that collapse errors into sentinel values (null, [], false, void) in the success channel. Runs a scanner script, spawns a read-only auditor, and produces a classified report. NOT for: non-Effect projects, React/frontend code, plain TypeScript without Effect.
allowed-tools	["Read","Glob","Grep","Bash","Agent"]

null-as-error

Detect silent error swallowing in Effect codebases. The antipattern: catchAll(() => Effect.succeed(null)) collapses real errors (disk full, permissions) into sentinel values (null, [], false) that callers cannot distinguish from normal absence.

Project context

• effect_posture: !~/.claude/skills/null-as-error-cc/scripts/probe-effect.sh

Workflow

Phase 1 -- Gate on Effect

If the probe above shows effect="false", stop immediately:

This project does not use Effect. The null-as-error scanner targets Effect-specific patterns (catchAll, Effect.succeed, Effect.ignore). Nothing to scan.

Phase 2 -- Run scanner

Execute the scanner script. The user may provide a scope (directory path) as an argument; default to src/.

bun ~/.claude/skills/null-as-error-cc/scripts/scan.ts [scope] --json

Capture the JSON output. If meta.hitsFound is 0:

No silent error swallowing patterns found in [scope]. Clean.

Stop here.

Phase 3 -- Semantic analysis

The scanner found hits. Spawn the auditor subagent to classify each one:

Agent({
  subagent_type: "null-as-error-auditor",
  prompt: <see below>
})

The auditor task prompt must include:

• The full scanner JSON output
• Reference file paths for the auditor to read:
  • ~/.claude/skills/null-as-error-cc/references/patterns.md
  • ~/.claude/skills/null-as-error-cc/references/fixes.md
  • ~/.claude/skills/null-as-error-cc/references/guardrails.md

Phase 4 -- Report

Synthesize the auditor's findings into a final report:

## Silent Error Swallowing Audit

### Summary
- Scanned: N files in [scope]
- Found: N occurrences
- Breakdown: X errors, Y warnings, Z info, W suppressed

### Findings

#### [ERROR] ...
#### [WARNING] ...
#### [INFO] ...
#### [SUPPRESSED] ...

### Summary Table
| Function | File | Severity | Sentinel | Fix | Blast Radius |
|----------|------|----------|----------|-----|--------------|

Reference navigation

Question	Load
Detection patterns and severity rules	references/patterns.md
Fix strategies and decision tree	references/fixes.md
False-positive prevention	references/guardrails.md
Auditor agent definition	~/.claude/agents/null-as-error-auditor.md