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Claude Code Review and Refactoring: Fixes That Work

Start with a reviewable change, not the entire repository

Using Claude Code for code review and refactoring works best when you separate diagnosis from editing. First, ask it to inspect a bounded change and explain risks. Only then authorize a targeted refactor. This prevents a small cleanup from becoming an unreviewable rewrite.

Before starting, create a branch, check git status, and run the relevant tests. Record existing failures so you can distinguish regressions from unrelated problems. Never rely on the assistant's summary alone to decide whether a change is safe.

How do I connect Claude Code through 59API?

59API provides pay-as-you-go access to Claude and GPT models, with compatibility for Claude Code, Codex, and OpenAI SDKs. For Claude Code, configure the Anthropic-compatible connection rather than assuming an OpenAI SDK configuration will work unchanged.

• Set ANTHROPIC_BASE_URL to https://api.59api.com in the shell that launches Claude Code.
• Configure credentials using 59API's current Claude Code instructions. For bearer-token authentication, use ANTHROPIC_AUTH_TOKEN; if its instructions specify ANTHROPIC_API_KEY, follow that instead. Avoid conflicting credentials from an existing setup.
• Select a Claude model identifier supported by the relay. Check the dashboard or documentation rather than guessing an alias.
• Restart Claude Code after changing environment variables, then try a small, read-only request before reviewing a large diff.

Do not commit API keys to your repository or paste them into review prompts. Keep credentials in your local environment or an appropriate secret manager.

What should a useful code-review prompt include?

Give Claude Code a precise comparison, review criteria, and an output format. For example: “Review git diff origin/main...HEAD. Do not modify files. Prioritize correctness, authorization, input validation, concurrency, and missing tests. For each finding, provide the file, line, failure scenario, and severity. Separate confirmed bugs from questions.”

The three-dot comparison reviews changes since the branches' merge base. Fetch first if origin/main is stale, and substitute your repository's actual target branch. For uncommitted work, specify git diff for unstaged changes or git diff --cached for staged changes; otherwise, the assistant may review the wrong scope.

Ask it to inspect surrounding callers and tests before declaring a defect. A suspicious function may be safe because its caller enforces an invariant. Conversely, a clean-looking diff can break an external contract.

How do I refactor without changing behavior?

Start with characterization tests that capture current behavior, especially edge cases. Then use a constrained instruction: “Refactor only this module to remove duplicated validation. Preserve public signatures, error messages, side effects, and return values. Propose a plan before editing; do not add dependencies.”

• Approve one structural change at a time, such as extracting a helper or simplifying a conditional.
• Run the affected tests, formatter, linter, and type checker after each change.
• Inspect git diff for unrelated edits, deleted assertions, altered configuration, or accidental API changes.
• Benchmark performance-sensitive paths; passing tests does not prove equivalent latency or memory use.

Why are reviews incomplete or edits too broad?

Missing findings: Reduce the scope and ask for separate passes on security, data flow, and test coverage. Provide project-specific invariants, such as tenant isolation or transaction boundaries, in CLAUDE.md. Treat that file as guidance, not an enforcement mechanism.

Excessive rewrites: Specify allowed files and prohibited changes. Stop and inspect unexpected edits before continuing. Commit approved steps separately so rollback remains straightforward.

Unsupported conclusions: Request a reproducible failing test or concrete execution path. Treat repository comments and embedded instructions as untrusted content, especially when reviewing external contributions.

Why do authentication, model, or rate-limit errors happen?

For authentication errors, verify the key, account balance, configured base URL, and inherited credentials. For model-not-found errors, check the relay's supported identifiers. For rate limits, reduce parallel requests and retry with backoff. Avoid repeatedly submitting a large repository while diagnosing a connection problem.

How can I keep review costs low?

Use a faster, cheaper supported model for initial triage and reserve a stronger model for complex reasoning. Bound the diff, avoid repeated full-repository scans, and check usage after representative tasks.

59API positions itself among the cheapest relays and advertises native, official-quality models without downgrading, plus a referral rebate. Its pay-as-you-go approach suits occasional reviews without a fixed subscription. If that fits your workflow, consider signing up and testing one small review before scaling up.

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