# Review Code > Perform a thorough code review of the current branch or a GitHub PR by number. - Skill: `nvidia-nemo-datadesigner/review-code` (Agent Skill) - Install (CLI): `npx skillmds@latest add nvidia-nemo-datadesigner/review-code` - Raw SKILL.md: https://api.skillmd.com/api/skills/nvidia-nemo-datadesigner/review-code/raw - Safety review: pending - Works with: Claude Code, Claude.ai, OpenAI Codex - Category: Coding & Dev Tools - Author: NVIDIA-NeMo (https://skillmd.com/u/nvidia-nemo-datadesigner) - Updated: 2026-09-10 - Page: https://skillmd.com/skills/nvidia-nemo-datadesigner/review-code --- # Review Code Changes Perform a comprehensive code review of either the current branch or a specific GitHub pull request. ## Arguments `$ARGUMENTS` determines the review mode: **PR mode** — first argument is a number: - `366` — review PR #366 - `366 focus on the API changes` — review PR #366 with a focus area **Branch mode** — no number, or only instructions: - *(empty)* — review current branch against `main` - `compare against develop` — review against a different base - `focus on the API changes` — review current branch with a focus area Additional instructions work in both modes: - `be strict about type annotations` - `skip style nits` ## Step 1: Gather Changes ### If PR mode (argument starts with a number) Run these commands in parallel using `gh`: 1. **PR details**: `gh pr view --json title,body,author,baseRefName,headRefName,state,additions,deletions,changedFiles,commits,url` 2. **PR diff**: `gh pr diff ` 3. **PR files**: `gh pr diff --name-only` 4. **PR commits**: `gh pr view --json commits --jq '.commits[].messageHeadline'` 5. **Existing inline review comments**: `gh api repos/{owner}/{repo}/pulls//comments --paginate --jq '.[].body'` 5b. **Existing PR-level reviews** (top-level review bodies from "Review changes"): `gh api repos/{owner}/{repo}/pulls//reviews --paginate --jq '.[].body'` 6. **Repo info**: `gh repo view --json nameWithOwner -q '.nameWithOwner'` Then get the PR branch locally for full file access. Prefer a **worktree** so your current branch and uncommitted work are untouched: ```bash git fetch origin pull//head:pr- --force git worktree add /tmp/review- pr- # Cleanup when done: git worktree remove /tmp/review- && git branch -D pr- ``` If worktrees aren't suitable, you can use `gh pr checkout ` (this switches your current branch — only if you have no uncommitted work). Run the rest of the review from `/tmp/review-`. If checkout isn't possible (e.g., external fork), use `gh api` to fetch file contents: ```bash gh api repos/{owner}/{repo}/contents/{path}?ref={head-branch} --jq '.content' | base64 --decode ``` **Important checks:** - If the PR number doesn't exist, inform the user - If the PR is merged or closed, note the state but proceed (useful for post-merge audits) - If the PR is a draft, note it — review may be on incomplete work - For very large diffs (>3000 lines), fetch and read changed files individually instead of relying solely on the diff ### If Branch mode (no number) First, fetch the base branch to ensure the remote ref is current: 0. **Fetch base**: `git fetch origin ` Then run these commands in parallel: 1. **Current branch**: `git branch --show-current` 2. **Commits on branch**: `git log origin/..HEAD --oneline` 3. **File changes summary**: `git diff --stat origin/..HEAD` 4. **Full diff**: `git diff origin/..HEAD` 5. **Uncommitted changes**: `git status --porcelain` 6. **Merge base**: `git merge-base origin/ HEAD` Where `` is `main` unless overridden in arguments. **Important checks:** - If no commits ahead of base, inform the user there's nothing to review - If uncommitted changes exist, note them but review committed changes only - For very large diffs (>3000 lines), read changed files individually instead of relying solely on the diff ## Step 2: Load Project Guidelines Read the following files at the repository root to load the project's standards and conventions: - **`AGENTS.md`** — architecture, layering, core design principles, structural invariants - **`STYLEGUIDE.md`** — code style rules (formatting, naming, imports, type annotations), design principles (DRY, KISS, YAGNI, SOLID), common pitfalls, lazy loading and `TYPE_CHECKING` patterns - **`DEVELOPMENT.md`** — testing patterns and expectations **Documentation sources (load when the changeset touches matching areas):** - **`architecture/*.md`** — subsystem maps aligned with `packages/` (e.g. `engine/mcp/` ↔ `architecture/mcp.md`). Use to verify the PR does not leave recorded architecture false relative to new behavior. - **`fern/versions/latest/pages/`** — published user-facing documentation. Cross-check when public API, CLI behavior, or config surface changes would affect what readers are told. Use these guidelines as the baseline for the entire review. Project-specific rules take precedence over general best practices. ## Step 3: Understand the Scope Before diving into details, build a mental model: 1. **Read the PR description** (PR mode) or commit messages to understand the stated intent 2. **Read each commit message** to understand the progression of changes 3. **Group changed files** by module/package to identify which areas are affected 4. **Identify the primary goal** (feature, refactor, bugfix, etc.) 5. **Note cross-cutting concerns** (e.g., a rename that touches many files vs. substantive logic changes) 6. **Check existing feedback** (PR mode): inspect both inline comments (Step 1, item 5) and PR-level review bodies (Step 1, item 5b) so you don't duplicate feedback already given 7. **Classify the contract impact**: note whether the change introduces or modifies supported public symbols or exports, config or model schemas, serialized formats, extension/plugin boundaries, or builder APIs. If none apply, skip items 8-10 and continue to Step 3.5. 8. **Inventory the changed contract**: list each changed contract element—including symbols, schema fields, serialized representations, extension entry points, and builder operations—and record its exposure, stability commitment, and expected callers or consumers 9. **Map invariant ownership**: identify where each new rule is parsed, normalized, validated, resolved, and compiled so duplicated checks and unclear responsibility are visible before the detailed review 10. **Find the closest existing analogue**: compare the complete neighboring API surface—not just individual names—for builder vocabulary, type precision, export strategy, errors, and contract clarity ## Step 3.5: Structural Impact (if available) Check for a pre-computed structural impact analysis at `/tmp/structural-impact-.md`. This file is produced by `graphify` AST extraction and contains: - **Risk level** (LOW/MEDIUM/HIGH) based on god nodes touched, import violations, and cluster spread - **Core abstractions modified** - the most-connected entities in the codebase (high blast radius if changed) - **Import direction violations** - cross-package edges that violate the layering rule (interface -> engine -> config) - **High-connectivity changes** - entities with many dependents - **Cross-package dependencies** - edges crossing package boundaries If the file exists, read it and use it to calibrate your review: - **HIGH risk**: apply extra scrutiny in Pass 2 (Design & Architecture). Verify backward compatibility for god nodes. Check that cross-package changes don't break existing callers. - **Import violations**: flag real dependency direction issues (not just inferred edges) as at least Warnings. Use Critical when the violation breaks packaging or establishes a foundational public boundary in the wrong layer. - **LOW risk**: the structural analysis confirms a localized change. You can focus more on correctness (Pass 1), but still perform the mandatory public-contract checks below when applicable. If the file does not exist (e.g. local branch review), skip this step. ## Step 4: Review Each Changed File (Multi-Pass) Perform **at least 2-3 passes** over the changed files. Each pass has a different focus — this catches issues that a single read-through would miss. **Scope rule: Only flag issues introduced or modified by this changeset.** Read the full file for context, but do not report pre-existing patterns, style issues, or design choices that were already present before this branch/PR. If existing code was merely moved without modification, don't flag it. The goal is to review what the author changed, not audit the entire file. ### Pass 1: Correctness & Logic Read each changed file in full (not just the diff), but evaluate only the **new or modified code**: - Logic errors, off-by-one, wrong operator, inverted condition - Missing edge case handling (None, empty collections, boundary values) - Truthy/falsy checks on values where 0, empty string, or None is valid (e.g. `if index:` when index can be 0) - Defensive `getattr(obj, attr, fallback)` or `.get()` on Pydantic models where the field always exists with a default - Silent behavior changes for existing users that aren't called out in the PR description - Race conditions or concurrency issues - Resource leaks (unclosed files, connections, missing cleanup) - Incorrect error handling (swallowed exceptions, wrong exception type) - Input validation at boundaries (user input, API responses, file I/O) - Graceful degradation on failure ### Pass 2: Design, Architecture & API Re-read the changed files with a focus on **structure and design of the new/modified code**: - Does the change fit the existing architecture and patterns? - Are new abstractions at the right level? (too abstract / too concrete) - Single responsibility — does each new function, class, and module do one coherent job? - If one module owns distinct phases such as authored config, resolution, compilation, and validation, would splitting those responsibilities make ownership and future changes clearer? - Are new dependencies flowing in the right direction? - Could this introduce circular imports or unnecessary coupling? - Does every symbol live in the module that owns it? Treat a leading-underscore helper imported by sibling modules as a signal to inspect ownership and package-export intent. Package-private sharing can be legitimate when the defining module owns the helper and it remains intentionally unexported. - Are helpers scoped to their actual consumers? Logic used only to validate or construct one class usually belongs on that class instead of in module-level generic machinery. - Are re-exports intentional and sourced from the defining module rather than incidental import chains? - Is there one canonical public entry point per operation, or do class methods plus module-level wrappers expose redundant APIs? - Does each business invariant have one authoritative owner, with complementary boundary checks allowed when representation or trust level changes and without independently redefining the rule? - Are new or modified public signatures clear and minimal? - Do generic helpers and `TypeVar`s eliminate enough real duplication to justify their cognitive cost, and are their names consistent with those already used in the changed module? - Are return types precise (not overly broad like `Any`)? - Could the new API be misused easily? Is it hard to use incorrectly? - Are breaking changes to existing interfaces intentional and documented? - Dead code left behind after refactors - Scalability: in-memory operations that could OOM on large datasets - Raw exceptions leaking instead of being normalized to project error types (see AGENTS.md / interface errors) - Obvious inefficiencies introduced by this change (N+1 queries, repeated computation, unnecessary copies) - Appropriate data structures for the access pattern **Public interface inventory (mandatory when Step 3 identifies contract impact):** Review every item in the Step 3 inventory individually, using the invariant map and neighboring analogue built there. Do not infer that a coherent-looking module implies a coherent public API. - Does each name identify the value's actual role or lifecycle when callers need that distinction? - Does each parameter or field name match the concrete value it contains rather than an earlier or later representation? - Are public Python inputs expressed with concrete config/model classes where those classes already define the contract? Broad `Mapping[str, object]`, `dict[str, Any]`, or `**kwargs` inputs add normalization branches and weaken discoverability unless accepting arbitrary mappings is an explicit requirement. - Does the API vocabulary match neighboring builders and established cardinality? For example, repeatable collection operations should follow the existing `add_*` convention, while `with_*` should retain its established singleton/configuration meaning. - Is every exported symbol meant to become a compatibility commitment? Keep implementation bases, compiler internals, and shared utilities private unless external callers need them. - Are exceptions named and located at the right subsystem boundary? Avoid generic names that become ambiguous when imported, and prefer the project's canonical error hierarchy over parallel local taxonomies. - Can callers determine parameter semantics, accepted representations, return values, lifecycle transitions, and raised project errors from the public contract itself? Flag ambiguous or incomplete API design separately from project-standard docstring coverage. **Boundary and representation checks:** - Treat plugin-owned or opaque payloads as opaque. Core code may validate a stable envelope it owns, but should not infer extension semantics from familiar-looking keys or current built-in payload shapes. - Test the boundary with an unfamiliar future extension value. If valid unknown fields or plugin payloads are rejected, stripped, or reinterpreted, the abstraction is not actually extensible. - At exception boundaries, inspect the public error and how actionable detail is preserved. Use a safe chained cause when it will not expose sensitive provider data; otherwise put sanitized detail on the public error and suppress the raw cause with `raise ... from None` according to boundary policy. **Documentation alignment (same pass — scoped, not a full docs audit):** When **code** under `packages/` changes behavior, structure, or public contracts in a way that a maintainer would reasonably describe in `architecture/` or Fern docs: 1. Identify the closest **`architecture/.md`** (and any obvious `fern/versions/latest/pages/` pages) for that subsystem. 2. If the PR **also edits** those docs, sanity-check that the edits match the code. 3. If the PR **does not** edit docs but the change **contradicts** what `architecture/` or Fern docs currently assert, flag it (**Warnings** if contributors rely on that text; **Suggestions** if impact is narrow). Suggest updating the same PR or an explicit follow-up issue. 4. **Skip** this check for pure refactors with no observable behavior change, typo-only PRs, or changes already limited to documentation. The local **`search-docs`** skill can help locate Fern docs pages by topic when the right file is not obvious. ### Pass 3: Standards, Testing & Polish Final pass focused on **project conventions and test quality for new/modified code only**: **Testing:** - Are new code paths covered by tests? - Do new tests verify behavior, not implementation details? (Flag tests that only verify plumbing — e.g. "mock was called" — without exercising actual behavior.) - Duplicate test setup across tests that should use fixtures or `@pytest.mark.parametrize` - Prefer flat test functions over test classes unless grouping is meaningful - Are edge cases tested? - Are mocks/stubs used appropriately (at boundaries, not deep internals)? - Do new test names clearly describe what they verify? - For new public contracts, do tests exercise direct supported construction as well as builder/factory paths, lifecycle transitions, malformed boundary input, and an unfamiliar extension/plugin case where applicable? - For normalized exceptions, do tests assert the stable public error and verify that actionable detail is preserved through either a safe chained cause or sanitized public-error detail without leaking provider secrets? **Project Standards (from AGENTS.md and STYLEGUIDE.md) — apply to new/modified code only:** Verify the items below on lines introduced or changed by this branch. Refer to `AGENTS.md` and `STYLEGUIDE.md` loaded in Step 2 for details and examples. - License headers: if present, they should be correct (wrong year or format → suggest `make update-license-headers`; don't treat as critical if CI enforces this) - `from __future__ import annotations` in new files - Type annotations on new/modified functions, methods, and class attributes - Modern type syntax (`list[str]`, `str | None` — not `List[str]`, `Optional[str]`) - Absolute imports only (no relative imports) - Lazy loading for heavy third-party imports via `lazy_heavy_imports` + `TYPE_CHECKING` - Naming: snake_case functions starting with a verb, PascalCase classes, UPPER_SNAKE_CASE constants - Public API classes and functions have Google-style docstrings; private helpers need them only when their logic is non-obvious - No vacuous comments — comments only for non-obvious intent - Public before private ordering in new classes - Design principles: DRY (extract on third occurrence), KISS (flat over clever), YAGNI (no speculative abstractions) - Common pitfalls: no mutable default arguments, no unused imports, simplify where possible ## Step 5: Run Linter Run the linter on all changed files (requires local checkout). Use the venv directly to avoid sandbox permission issues in some environments (e.g. Claude Code): ```bash .venv/bin/ruff check .venv/bin/ruff format --check ``` > **Note**: This runs ruff only on the changed files for speed. For a full project-wide check, use `make check-all` or `uv run ruff check` (and `ruff format --check`) without file arguments. For new or substantially expanded production modules, also use complexity rules as an exploratory signal: ```bash .venv/bin/ruff check --select C901,PLR0912,PLR0913,PLR0915 ``` Do not report a metric violation by itself. Use it to identify functions or modules that need a closer cohesion, responsibility, and maintainability review, then report the concrete design problem if one exists. Expect broad signals in config- or builder-heavy modules; pursue a violation only when it coincides with a concrete cohesion or ownership concern. If the branch isn't checked out locally (e.g., external fork in PR mode), skip this step and note it in the review. ## Tone Write as a supportive teammate, not a gatekeeper. The goal is to help the author ship great code, not to prove you found problems. - **Be cordial and collaborative.** Use "we" language and frame genuine alternatives as questions or suggestions ("Could we …?", "What do you think about …?", "Nice approach — one thought: …"). State confirmed merge blockers directly. - **Assume good intent.** If something looks off, ask before assuming it's wrong — the author may have context you don't. - **Lead with what's good.** Acknowledge effort and smart decisions before raising concerns. - **Keep it conversational.** Avoid stiff, formal phrasing. Write the way you'd talk to a colleague at a whiteboard. - **Be direct, not blunt.** Clearly state what needs to change and why, but without harsh or commanding language ("This must be fixed" → "This could bite us in production — worth addressing before merge"). ## Step 6: Produce the Review Write the review as **GitHub-flavored Markdown** ready to post as a PR comment. Save it to a temporary file outside the repository (e.g. `/tmp/review-.md`) so it doesn't pollute `git status`. Do not commit this file; treat it as ephemeral. Use the template below exactly — omit a severity section if it has no findings, include Open Questions only with **Needs discussion**, and omit Residual Risk when empty, but keep all other sections. --- Open with a brief, genuine thank-you to the author (e.g. "Thanks for putting this together, @author!" or "Nice work on this one, @author — here are my thoughts."). Keep it to one sentence; don't over-do it. Do NOT add a top-level title like "## Code Review" — the comment speaks for itself. ### Summary 1-2 sentence description of what the changes accomplish. In PR mode, note whether the implementation matches the stated intent in the PR description. ### Findings Group findings by severity. Omit any severity section that has no findings. Format each finding as a heading + bullet list — do NOT use numbered lists: ``` **`path/to/file.py:42` — Short title** - **What**: Concise description of the issue. - **Why**: Why it matters. - **Suggestion**: Concrete fix or improvement (with code snippet when helpful). ``` Separate each finding with a blank line. Use bold file-and-title as a heading line, then bullet points for What/Why/Suggestion. Never use numbered lists (`1.`, `2.`) for findings or their sub-items. #### Critical — Let's fix these before merge > Issues that would cause bugs, data loss, security vulnerabilities, or broken functionality; also foundational flaws in a new or materially changed public, serialized, or extension contract that should block merge because correcting them after release would require a breaking compatibility change. #### Warnings — Worth addressing > Significant design issues that are not foundational compatibility blockers, missing error handling, test gaps, or violations of project standards that could cause problems later. #### Suggestions — Take it or leave it > Style improvements, minor simplifications, or optional enhancements that would improve code quality. ### What Looks Good Call out 2-3 things done well (good abstractions, thorough tests, clean refactoring, etc.). Be genuine — positive feedback is part of a good review and helps the author know what to keep doing. ### Open Questions (Needs discussion only) State the material question, why it affects compatibility or merge readiness, and the team decision needed. ### Residual Risk (optional) Note validation gaps or lower-impact uncertainty that do not change merge readiness. If a risk is concrete enough to require action before merge, report it as a finding instead. ### Verdict Choose the verdict that matches the **highest severity confirmed finding** in the review. If there are no confirmed Critical or Warning findings but a design question material to compatibility or merge readiness cannot be resolved without team input, use **Needs discussion**. - **Ship it** — No findings. Ready to merge as-is. - **Ship it (with nits)** — Only Suggestions (see above — style improvements, simplifications, or optional enhancements). Nothing blocking. - **Needs changes** — Any Critical or Warning findings. List the items that must be addressed before merge. - **Needs discussion** — No confirmed Critical or Warning findings, but an architectural or design question material to compatibility or merge readiness needs team input before a decision can be made. A confirmed foundational contract flaw is Critical and requires **Needs changes**. Reserve **Needs discussion** for material uncertainty that requires team input. Lower-impact uncertainty belongs in **Residual Risk** and does not preclude **Ship it** or **Ship it (with nits)**. ### Signature (PR mode only) When the review will be posted as a PR comment, end with a signature line so readers can distinguish agent-generated reviews from human ones: ``` --- *This review was generated by an AI assistant.* ``` In branch mode (local only), omit the signature. --- ## Step 7: Post the Review (PR mode only) In PR mode, display the review to the user and note the temp file path (`/tmp/review-.md`). Then ask if they'd like you to post it as a PR comment. Only run the command after the user confirms: ```bash gh pr comment --body-file /tmp/review-.md ``` In branch mode, skip this step — display the review to the user and note the temp file path. --- ## Review Principles - **Only flag what's new**: Report issues introduced by this changeset — not pre-existing patterns or style in untouched code, unless explicitly asked by the user - **Be specific**: "This could return None on line 42 when `items` is empty" not "handle edge cases better" - **Suggest, don't just criticize**: Always pair a problem with a concrete suggestion - **Distinguish severity honestly**: Don't inflate cosmetic naming or internal refactors into blockers. Do treat foundational public-contract design as Critical when merging would create a hard-to-reverse compatibility commitment. - **Consider intent**: Review what the author was trying to do, not what you would have done differently - **Batch related issues**: If the same pattern appears in multiple places, note it once and list all locations - **Read the full file**: Diff-only reviews miss context — always read the surrounding code, but only flag new issues - **Don't repeat existing feedback**: In PR mode, check both inline comments and PR-level review bodies and skip issues already raised **Do not flag (focus on what CI won't catch):** - Issues that are supposed to be caught by CI (linter, typechecker, formatter) — mention "run `make check-all`" if relevant, but don't list every style nit - Pre-existing issues on unmodified lines - Pedantic nits that don't affect correctness or maintainability - Missing docstrings on private helpers when their purpose is clear, or prose-only comment/docstring nits that do not affect correctness or understanding; public API docstrings remain required by `STYLEGUIDE.md` - Intentional functionality or API changes that are clearly documented, unless the new design introduces a concrete correctness, extensibility, or compatibility risk, or a maintainability risk that would require a breaking change to correct ## Edge Cases - **No changes**: Inform user there's nothing to review - **PR not found**: Inform user the PR number doesn't exist - **Merged/closed PR**: Note the state, proceed with review anyway - **Draft PR**: Note it's a draft; review may be on incomplete work - **External fork**: Can't checkout locally — use `gh api` to fetch file contents and skip the linter step - **Huge changeset** (>50 files): Summarize by module first, then review the most critical files in detail; ask user if they want the full file-by-file review - **Only renames/moves**: Note that changes are structural and focus on verifying nothing broke - **Only test changes**: Focus review on test quality, coverage, and correctness of assertions - **Only config/docs changes**: Adjust review to focus on accuracy and completeness rather than code quality