Backend Code Review

Backend Code Review

When to use this skill

Use this skill whenever the user asks to review, analyze, or improve backend code (e.g., .py) under the api/ directory. Supports the following review modes:

• Pending-change review: when the user asks to review current changes (inspect staged/working-tree files slated for commit to get the changes).
• Code snippets review: when the user pastes code snippets (e.g., a function/class/module excerpt) into the chat and asks for a review.
• File-focused review: when the user points to specific files and asks for a review of those files (one file or a small, explicit set of files, e.g., api/..., api/app.py).

Do NOT use this skill when:

• The request is about frontend code or UI (e.g., .tsx, .ts, .js, web/).
• The user is not asking for a review/analysis/improvement of backend code.
• The scope is not under api/ (unless the user explicitly asks to review backend-related changes outside api/).

Rationalizations to Reject

When reviewing, explicitly reject these shortcuts:

• "The tests pass, so the code is correct" — tests don't cover all security and edge-case scenarios
• "This pattern is used elsewhere in the codebase" — widespread usage doesn't make a pattern correct; it may mean the bug is systemic
• "It's an internal endpoint / internal service" — internal code runs with real privileges on real data
• "It's just a minor fix" — every change to auth, session, or data layer needs full scrutiny
• "The ORM protects against SQL injection" — only if used correctly; raw queries or .execute() with string formatting are still vulnerable

Quality Thresholds

Before delivering the review, verify:

• Every finding cites a specific File:Line reference
• Every Critical finding includes a concrete fix example (not just a description)
• Security findings include an exploitation scenario, not just "this could be vulnerable"
• No vague language ("probably", "might", "could potentially be an issue")

How to use this skill

Follow these steps when using this skill:

1. Identify the review mode (pending-change vs snippet vs file-focused) based on the user’s input. Keep the scope tight: review only what the user provided or explicitly referenced.
2. Follow the rules defined in Checklist to perform the review. If no Checklist rule matches, apply General Review Rules as a fallback to perform the best-effort review.
3. Compose the final output strictly follow the Required Output Format.

Notes when using this skill:

• Always include actionable fixes or suggestions (including possible code snippets).
• Use best-effort File:Line references when a file path and line numbers are available; otherwise, use the most specific identifier you can.

Checklist

• db schema design: if the review scope includes code/files under api/models/ or api/migrations/, follow references/db-schema-rule.md to perform the review
• architecture: if the review scope involves controller/service/core-domain/libs/model layering, dependency direction, or moving responsibilities across modules, follow references/architecture-rule.md to perform the review
• repositories abstraction: if the review scope contains table/model operations (e.g., select(...), session.execute(...), joins, CRUD) and is not under api/repositories, api/core/repositories, or api/extensions/*/repositories/, follow references/repositories-rule.md to perform the review
• sqlalchemy patterns: if the review scope involves SQLAlchemy session/query usage, db transaction/crud usage, or raw SQL usage, follow references/sqlalchemy-rule.md to perform the review

General Review Rules

1. Security Review

Check for:

• SQL injection vulnerabilities
• Server-Side Request Forgery (SSRF)
• Command injection
• Insecure deserialization
• Hardcoded secrets/credentials
• Improper authentication/authorization
• Insecure direct object references

2. Performance Review

Check for:

• N+1 queries
• Missing database indexes
• Memory leaks
• Blocking operations in async code
• Missing caching opportunities

3. Code Quality Review

Check for:

• Code forward compatibility
• Code duplication (DRY violations)
• Functions doing too much (SRP violations)
• Deep nesting / complex conditionals
• Magic numbers/strings
• Poor naming
• Missing error handling
• Incomplete type coverage

4. Testing Review

Check for:

• Missing test coverage for new code
• Tests that don't test behavior
• Flaky test patterns
• Missing edge cases

Required Output Format

When this skill invoked, the response must exactly follow one of the two templates:

Template A (any findings)

# Code Review Summary

Found <X> critical issues need to be fixed:

## 🔴 Critical (Must Fix)

### 1. <brief description of the issue>

FilePath: <path> line <line>
<relevant code snippet or pointer>

#### Explanation

<detailed explanation and references of the issue>

#### Suggested Fix

1. <brief description of suggested fix>
2. <code example> (optional, omit if not applicable)

---
... (repeat for each critical issue) ...

Found <Y> suggestions for improvement:

## 🟡 Suggestions (Should Consider)

### 1. <brief description of the suggestion>

FilePath: <path> line <line>
<relevant code snippet or pointer>

#### Explanation

<detailed explanation and references of the suggestion>

#### Suggested Fix

1. <brief description of suggested fix>
2. <code example> (optional, omit if not applicable)

---
... (repeat for each suggestion) ...

Found <Z> optional nits:

## 🟢 Nits (Optional)
### 1. <brief description of the nit>

FilePath: <path> line <line>
<relevant code snippet or pointer>

#### Explanation

<explanation and references of the optional nit>

#### Suggested Fix

- <minor suggestions>

---
... (repeat for each nits) ...

## ✅ What's Good

- <Positive feedback on good patterns>

• If there are no critical issues or suggestions or option nits or good points, just omit that section.
• If the issue number is more than 10, summarize as "Found 10+ critical issues/suggestions/optional nits" and only output the first 10 items.
• Don't compress the blank lines between sections; keep them as-is for readability.
• If there is any issue requires code changes, append a brief follow-up question to ask whether the user wants to apply the fix(es) after the structured output. For example: "Would you like me to use the Suggested fix(es) to address these issues?"

Template B (no issues)

## Code Review Summary
✅ No issues found.