find-mismatch

name	find-mismatch
effort	high
description	Systematic code review focusing on bugs that break at runtime (contract mismatches, logic/async errors, serialization, styling) and JS/TS static analysis via fallow.
disable-model-invocation	true

Find Mismatch

Walk through every file. Focus only on runtime failures/bugs. Do NOT report style, formatting, performance suggestions, docs/tests, or "consider using X".

1. Process

1. JS/TS (Pre-check): Run static analysis.
   • Check if installed: fallow --version.
   • Install globally if missing: npm install -g fallow.
   • Execute audit: fallow audit --format json --quiet.
   • Filter findings by git status: git diff --staged --name-only.
   • If staged: auto-apply safe fixes, re-run audit to verify.
   • If unstaged: report-only (no modification).
2. Review Checklist: Apply checklist to all changes.
3. Report: Format findings using the specified template.

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2. Checklist Categories

1. Cross-Boundary Contracts

• Calling mismatch: Check RPC, HTTP, IPC, event name/subject match receiver.
• Param names/types: userId vs user_id, string vs number, flat vs wrapped.
• Return type: Field accesses (result.field) must match return signature.

2. Serialization & Deserialization

• Casing: snake_case in DB/backend vs camelCase in JSON/frontend.
• Optionals: Field expected by receiver but optional in producer.
• Enums/discriminators: Discriminant fields (type, kind) and variants match.
• Base64: Double-encoding layers.

3. Logic Bugs

• Double counting: Counters incremented both in loop/branch and outside.
• Off-by-one: Index, pagination bounds (page <= total vs page < total).
• Conditions: Redundant/dead flags, unreachable statements, shadowed variables.

4. Property & Method Access

• Null derefs: Method calls or array index access (items[0].name) without null/length checks.
• Optional chaining: Stop check too early (e.g. user?.address.street still crashes if address is null).
• This context: Callback bindings in classes.

5. Async & Concurrency

• Race conditions: Shared mutable states, parallel filesystem accesses without coordination.
• Missing await: Promise ignored, silent errors.
• Leaks: File/DB/network connections not closed in error paths.

6. CSS & Styling

• HSL variables: Raw HSL components (0 0% 100%) instead of functional format (hsl(0 0% 100%)) fail in Tailwind v4 (unlike v3).
• Inline themes: Circular references, selector mismatch (class vs data-theme).

7. Placeholder & Stub Code

• Unused declarations/files/dependencies, TODO comments, empty catch blocks.

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3. Language-Specific Pitfalls

• Python: Hallucinated library methods (pandas, numpy, requests), sync/asyncio confusion, mutable default arguments (def f(x=[])), silent indentation drops.
• JS/TS: Backend (Node) vs Frontend (Browser) API mix-ups, any abuse, type-only import mismatches, barrel file false positives (exported but unused in production, used in tests/libraries).
• C++: Raw vs smart pointer mix-ups, missing standard library header #include, uninitialized variables, buffer overflows.
• Rust: Borrow checker lifetime overcomplication, unwrap() on None/Err, locking across .await yield points.
• Java / .NET: Hallucinated annotations/attributes, LINQ N+1 queries, Entity Framework model snapshot drift / missing migrations (check model changes under Entities/ against Migrations/).
• Go: WaitGroup/Channel deadlocks, unexported struct fields in JSON, defer in loop, map concurrent access.
• PHP: Loose type comparisons (== vs ===), array vs object access, key undefined.

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4. Fallow Finding Mapping & Fixes

Fallow Type	Checklist Category	Auto-Fix Action
unused_exports	Placeholder & Stub	Remove export (if used locally) or entire declaration.
unused_files	Placeholder & Stub	Delete file (check dynamic imports first).
unused_dependencies	Placeholder & Stub	Remove dependency from package.json.
circular_dependencies	Cross-Boundary	Defer to manual review (causes init bugs).
complexity/duplication	Logic Bugs	Defer to manual review.

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5. Output Format

Include ## Review Summary header (only if JS/TS project):

## Review Summary
- **Manual review bugs found**: N
- **Fallow auto-fixed**: N findings (staged files only)
- **Fallow non-auto-fixable**: N findings
- **Fallow verdict**: pass / fail

Format individual findings (add [fallow] tag for fallow-sourced bugs):

## Bug #1
- **File**: <path>:<line>
- **Category**: <category>
- **What's wrong**: <description>
- **Runtime effect**: <effect>
- **Fix**: <code>