Code Review Skill for Claude

Code Review Skill

Perform structured, objective code reviews for Flutter/Dart projects following a repeatable checklist.

When to Use

Use this skill when:

• Asked to review a pull request, merge request, or branch.
• Evaluating changed, added, or deleted files for correctness and quality.
• Auditing a diff before merging.
• Checking whether new code meets project standards.

Review Workflow

Step 1 — Validate branch and merge target

• Confirm the current branch is a feature, bugfix, or PR/MR branch — not the project's primary branch (e.g. main, master, develop).
• Verify the branch is up-to-date with the target branch (no unresolved conflicts).
• Identify the target branch for the merge.

Checkpoint: If the branch is behind the target, flag it before proceeding.

Step 2 — Discover changes

• List all changed, added, and deleted files.
• For each change, look up the commit title and review how connected components are implemented.
• Analyze the change: is it clear *why* the change was made? If not, dig into the connected methods and files until it is. When you report, name which connected files/methods you analyzed and why — this shows the change was understood, not assumed.
• Never assume a change is correct without investigating the implementation.
• If a change remains unclear after investigation, note this explicitly in the report.

Step 3 — Review each file

Iterate through each changed file. For every file, verify the following:

| Area | What to verify |

|---|---|

| Understand the change | Why was it made? Review connected methods/files; note which ones you analyzed and why |

| Location | File is in the correct directory |

| Naming | File name follows project naming conventions |

| Responsibility | The file's responsibility is clear; reason for change is understandable |

| Readability | Variable, function, and class names are descriptive and consistent |

| Logic & correctness | No logic errors or missing edge cases |

| Code smells | Scan for the smells in Code Smells Reference below |

| Maintainability | Code is modular; no unnecessary duplication |

| Error handling | Errors and exceptions are handled appropriately |

| Security | No input validation gaps; no secrets committed to code |

| Performance | No obvious inefficiencies (e.g., unnecessary rebuilds, O(n^2) loops on large lists) |

| SOLID principles | Adherence assessed without forcing unnecessary boilerplate or over-abstraction |

| Flutter/Dart/<your-state-management-package> patterns | Match against the project's loaded guidelines and conventions |

| Documentation | Public APIs, complex logic, and new modules are documented |

| Test coverage | New or changed logic has sufficient tests (see Step 4) |

| Style | Code matches the project's style guide and linting rules |

| Existing code | If the new changes look fine, also review surrounding existing (unchanged) code for smells and suggest refactors where relevant |

For generated files (e.g., *.g.dart, *.freezed.dart): confirm they are up-to-date and not manually modified.

> Scope discipline: Your job is not to comment on every change — it's to find errors and concrete improvement areas and comment on those. Don't manufacture comments where the code is fine.

Flutter-specific checks

*(Note: The following is just an example using Bloc/Cubit; apply similar principles to Riverpod, Provider, or your chosen state management package.)*

// BAD — rebuilds entire tree on every state change
BlocBuilder<MyCubit, MyState>(
  builder: (context, state) => EntireScreen(state: state),
);

// GOOD — scope rebuilds to the widget that actually changes
BlocSelector<MyCubit, MyState, String>(
  selector: (state) => state.title,
  builder: (context, title) => Text(title),
);

• Verify Key usage on dynamically generated widgets.
• Check that dispose() is called for controllers, streams, and animation controllers.
• Confirm const constructors are used where possible.

Code Smells Reference

For each file, check for common code smells. Use refactoring.guru/refactoring/smells for definitions and suggested refactorings.

| Category | Smells |

|---|---|

| Bloaters | Long Method, Large Class, Primitive Obsession, Long Parameter List, Data Clumps |

| Object-Orientation Abusers | Alternative Classes with Different Interfaces, Refused Bequest, Temporary Field, Switch Statements |

| Change Preventers | Divergent Change, Parallel Inheritance Hierarchies, Shotgun Surgery |

| Dispensables | Comments (redundant), Duplicate Code, Data Class, Dead Code, Lazy Class, Speculative Generality |

| Couplers | Feature Envy, Inappropriate Intimacy, Incomplete Library Class, Message Chains, Middle Man |

Step 4 — Evaluate the overall change set

• Verify the change set is focused and scoped to its stated purpose — no unrelated changes.
• Check that the PR/MR description accurately reflects the changes.

Test coverage

Verify test coverage explicitly — this is easy to skip and easy to fake, so be deliberate:

• For any new logic or significant change, search for the corresponding test file(s) and confirm tests actually exist.
• Check that tests cover the changed functionality including edge cases, not just the happy path.
• Evaluate whether tests could actually fail against real code, or only verify mocked behavior (a test that asserts a mock returns what the mock was told to return proves nothing).
• If tests are missing or insufficient, comment on the lack of coverage — don't let it pass silently.

Step 5 — Verify CI and tests

• Ensure all tests pass in CI.
• Check for new analyzer warnings or lint violations.
• Fetch official documentation when unsure about best practices for a package.

Checkpoint: If CI is red or tests are missing for new logic, flag as a blocking issue.

Wrap-Up

After the per-file pass, decide the outcome:

• If everything looks good and no changes are needed: post an overall conclusion comment summarizing what the MR is about (what was done) plus any observations, and approve the MR.
• If the new changes are clean but you spotted smells in existing code: include those as optional refactor suggestions rather than blockers.
• If issues were found: summarize the key concerns clearly so the author knows what to address first.

Feedback Standards

• Be objective and reasonable — avoid automatic praise or flattery.
• Take a devil's advocate approach: give honest, thoughtful feedback.
• Provide clear, constructive suggestions for every issue found.
• Include requests for clarification for anything unclear.
• Classify each finding by severity: suggestion, minor, or major.

Output Format

By default, provide the review as a chat response — a structured response covering each file:

• Summary — what changed and why.
• Issues — each with severity (suggestion / minor / major) and a concrete fix suggestion.
• Questions — specific clarification requests per file.
• Verdict — one of: Approved, Approved with suggestions, or Changes requested.

> Posting comments online (opt-in only). After presenting the chat review, ask the user whether they'd prefer you to also post these comments online on the PR/MR — so the team can see them, review them, and reply. Only post online if the user explicitly says yes. Never post to the platform on your own initiative.

>

> When the user does opt in, post issues as inline comments anchored to the right file and line (use proper position fields), with the conclusion/key-concerns as a top-level review comment and an approval when warranted. This requires a review-bot access token for the platform (GitHub/GitLab); if one isn't configured, let the user know and ask them to set it up before posting.

>

> Token safety. The token is a secret. You may check whether it exists and report its length to confirm it's configured, but never read, echo, log, print, or otherwise reveal the token value — not in chat, not in a file, not in a commit. Pass it to curl only by referencing the env var (e.g. $GITLAB_TOKEN), never by inlining the literal value, and avoid curl -v/--verbose (it prints the auth header). This is enforced by a PreToolUse hook (scripts/protect-token.sh) that blocks any Bash command which would expose the value. See the "Handling the token safely" section in each reference file for the safe existence/length check.

>

> The hook fires in both the Claude Code CLI and the Agent SDK. (SDK apps that set settingSources/setting_sources explicitly must include "project" for skill hooks to load; it's included by default.)

>

> For platform-specific API details, curl formats, and approval steps, follow:

> - GitLab → references/gitlab-posting.md (uses the GITLAB_TOKEN env var)

> - GitHub → references/github-posting.md (uses the GITHUB_TOKEN env var)