Best practices for Claude Code changedbest-practices

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# Best practices for Claude Code

> Tips and patterns for getting the most out of Claude Code, from configuring your environment to scaling across parallel sessions.

Claude Code is an agentic coding environment. Unlike a chatbot that answers questions and waits, Claude Code can read your files, run commands, make changes, and autonomously work through problems while you watch, redirect, or step away entirely.

This changes how you work. Instead of writing code yourself and asking Claude to review it, you describe what you want and Claude figures out how to build it. Claude explores, plans, and implements.

But this autonomy still comes with a learning curve. Claude works within certain constraints you need to understand.

This guide covers patterns that have proven effective across Anthropic's internal teams and for engineers using Claude Code across various codebases, languages, and environments. For how the agentic loop works under the hood, see [How Claude Code works](/docs/en/how-claude-code-works).

***

Most best practices are based on one constraint: Claude's context window fills up fast, and performance degrades as it fills.

Claude's context window holds your entire conversation, including every message, every file Claude reads, and every command output. However, this can fill up fast. A single debugging session or codebase exploration might generate and consume tens of thousands of tokens.

This matters since LLM performance degrades as context fills. When the context window is getting full, Claude may start "forgetting" earlier instructions or making more mistakes. The context window is the most important resource to manage. To see how a session fills up in practice, [watch an interactive walkthrough](/docs/en/context-window) of what loads at startup and what each file read costs. Track context usage continuously with a [custom status line](/docs/en/statusline), and see [Reduce token usage](/docs/en/costs#reduce-token-usage) for strategies on reducing token usage.

***

## Give Claude a way to verify its work

<Tip>
  Give Claude a check it can run: tests, a build, a screenshot to compare. It's the difference between a session you watch and one you walk away from.
</Tip>

Claude stops when the work looks done. Without a check it can run, "looks done" is the only signal available, and you become the verification loop: every mistake waits for you to notice it. Give Claude something that produces a pass or fail, and the loop closes on its own. Claude does the work, runs the check, reads the result, and iterates until the check passes.

The check is anything that returns a signal Claude can read in the conversation: a test suite, a build exit code, a linter, a script that diffs output against a fixture, or a [browser screenshot](/docs/en/chrome) compared against a design.

| Strategy                              | Before                                                  | After                                                                                                                                                                                                   |
| ------------------------------------- | ------------------------------------------------------- | ------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Provide verification criteria**     | *"implement a function that validates email addresses"* | *"write a validateEmail function. example test cases: [[email protected]](mailto:[email protected]) is true, invalid is false, [[email protected]](mailto:[email protected]) is false. run the tests after implementing"* |
| **Verify UI changes visually**        | *"make the dashboard look better"*                      | *"\[paste screenshot] implement this design. take a screenshot of the result and compare it to the original. list differences and fix them"*                                                            |
| **Address root causes, not symptoms** | *"the build is failing"*                                | *"the build fails with this error: \[paste error]. fix it and verify the build succeeds. address the root cause, don't suppress the error"*                                                             |

Once the check exists, decide how hard it gates the stop:

* **In one prompt**: ask Claude to run the check and iterate in the same message, as in the table above.
* **Across a session**: set the check as a [`/goal` condition](/docs/en/goal). A separate evaluator re-checks it after every turn and Claude keeps working until it holds.
* **As a deterministic gate**: a [Stop hook](/docs/en/hooks#stop) runs your check as a script and blocks the turn from ending until it passes. Claude Code overrides the hook and ends the turn after 8 consecutive blocks.
* **By a second opinion**: a [verification subagent](/docs/en/sub-agents) or a [dynamic workflow](/docs/en/workflows) that checks its own findings has a fresh model try to refute the result, so the agent doing the work isn't the one grading it.

Each step trades setup for attention. The prompt version works on any task today. The `/goal` and Stop hook versions are what let an unattended run finish correctly without you.

Have Claude show evidence rather than asserting success: the test output, the command it ran and what it returned, or a screenshot of the result. Reviewing evidence is faster than re-running the verification yourself, and it works for sessions you weren't watching.

***

## Explore first, then plan, then code

<Tip>
  Separate research and planning from implementation to avoid solving the wrong problem.
</Tip>

Letting Claude jump straight to coding can produce code that solves the wrong problem. Use [plan mode](/docs/en/permission-modes#analyze-before-you-edit-with-plan-mode) to separate exploration from execution.

The recommended workflow has four phases:

<Steps>
  <Step title="Explore">
    Enter plan mode by pressing `Shift+Tab` until the status bar shows `⏸ plan mode on`, or start the session with `claude --permission-mode plan`. Claude reads files and answers questions without making changes.

    ```txt title="claude (plan mode)" wrap theme={null}
    read /src/auth and understand how we handle sessions and login.
    also look at how we manage environment variables for secrets.
    ```
  </Step>

  <Step title="Plan">
    Ask Claude to create a detailed implementation plan.

    ```txt title="claude (plan mode)" wrap theme={null}
    I want to add Google OAuth. What files need to change?
    What's the session flow? Create a plan.
    ```

    Press `Ctrl+G` to open the plan in your text editor for direct editing before Claude proceeds.
  </Step>

  <Step title="Implement">
    Switch out of plan mode by approving the plan or pressing `Shift+Tab`, then let Claude code, verifying against its plan.

    ```txt title="claude (default mode)" wrap theme={null}
    implement the OAuth flow from your plan. write tests for the
    callback handler, run the test suite and fix any failures.
    ```
  </Step>

  <Step title="Commit">
    Ask Claude to commit with a descriptive message and create a PR.

    ```txt title="claude (default mode)" wrap theme={null}
    commit with a descriptive message and open a PR
    ```
  </Step>
</Steps>

<Callout>
  Plan mode is useful, but also adds overhead.

  For tasks where the scope is clear and the fix is small (like fixing a typo, adding a log line, or renaming a variable) ask Claude to do it directly.

  Planning is most useful when you're uncertain about the approach, when the change modifies multiple files, or when you're unfamiliar with the code being modified. If you could describe the diff in one sentence, skip the plan.
</Callout>

***

## Provide specific context in your prompts

<Tip>
  The more precise your instructions, the fewer corrections you'll need.
</Tip>

Claude can infer intent, but it can't read your mind. Reference specific files, mention constraints, and point to example patterns.

| Strategy                                                                                         | Before                                               | After                                                                                                                                                                                                                                                                                                                                                            |
| ------------------------------------------------------------------------------------------------ | ---------------------------------------------------- | ---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------- |
| **Scope the task.** Specify which file, what scenario, and testing preferences.                  | *"add tests for foo.py"*                             | *"write a test for foo.py covering the edge case where the user is logged out. avoid mocks."*                                                                                                                                                                                                                                                                    |
| **Point to sources.** Direct Claude to the source that can answer a question.                    | *"why does ExecutionFactory have such a weird api?"* | *"look through ExecutionFactory's git history and summarize how its api came to be"*                                                                                                                                                                                                                                                                             |
| **Reference existing patterns.** Point Claude to patterns in your codebase.                      | *"add a calendar widget"*                            | *"look at how existing widgets are implemented on the home page to understand the patterns. HotDogWidget.php is a good example. follow the pattern to implement a new calendar widget that lets the user select a month and paginate forwards/backwards to pick a year. build from scratch without libraries other than the ones already used in the codebase."* |
| **Describe the symptom.** Provide the symptom, the likely location, and what "fixed" looks like. | *"fix the login bug"*                                | *"users report that login fails after session timeout. check the auth flow in src/auth/, especially token refresh. write a failing test that reproduces the issue, then fix it"*                                                                                                                                                                                 |

Vague prompts can be useful when you're exploring and can afford to course-correct. A prompt like `"what would you improve in this file?"` can surface things you wouldn't have thought to ask about.

### Provide rich content

<Tip>
  Use `@` to reference files, paste screenshots/images, or pipe data directly.
</Tip>

You can provide rich data to Claude in several ways:

* **Reference files with `@`** instead of describing where code lives. Claude reads the file before responding.
* **Paste images directly**. Copy/paste or drag and drop images into the prompt.
* **Give URLs** for documentation and API references. Use `/permissions` to allowlist frequently-used domains.
* **Pipe in data** by running `cat error.log | claude` to send file contents directly.
* **Let Claude fetch what it needs**. Tell Claude to pull context itself using Bash commands, MCP tools, or by reading files.

***

## Configure your environment

A few setup steps make Claude Code significantly more effective across all your sessions. For a full overview of extension features and when to use each one, see [Extend Claude Code](/docs/en/features-overview).

### Write an effective CLAUDE.md

<Tip>
  Run `/init` to generate a starter CLAUDE.md file based on your current project structure, then refine over time.
</Tip>

CLAUDE.md is a special file that Claude reads at the start of every conversation. Include Bash commands, code style, and workflow rules. This gives Claude persistent context it can't infer from code alone.

The `/init` command analyzes your codebase to detect build systems, test frameworks, and code patterns, giving you a solid foundation to refine.

There's no required format for CLAUDE.md files, but keep it short and human-readable. For example:

```markdown CLAUDE.md theme={null}
# Code style
- Use ES modules (import/export) syntax, not CommonJS (require)
- Destructure imports when possible (eg. import { foo } from 'bar')

# Workflow
- Be sure to typecheck when you're done making a series of code changes
- Prefer running single tests, and not the whole test suite, for performance
```

Run `/context` to confirm Claude loaded the file. CLAUDE.md is loaded every session, so only include things that apply broadly. For domain knowledge or workflows that are only relevant sometimes, use [skills](/docs/en/skills) instead. Claude loads them on demand without bloating every conversation.

Keep it concise. For each line, ask: *"Would removing this cause Claude to make mistakes?"* If not, cut it. Bloated CLAUDE.md files cause Claude to ignore your actual instructions!

| ✅ Include                                            | ❌ Exclude                                          |
| ---------------------------------------------------- | -------------------------------------------------- |
| Bash commands Claude can't guess                     | Anything Claude can figure out by reading code     |
| Code style rules that differ from defaults           | Standard language conventions Claude already knows |
| Testing instructions and preferred test runners      | Detailed API documentation (link to docs instead)  |
| Repository etiquette (branch naming, PR conventions) | Information that changes frequently                |
| Architectural decisions specific to your project     | Long explanations or tutorials                     |
| Developer environment quirks (required env vars)     | File-by-file descriptions of the codebase          |
| Common gotchas or non-obvious behaviors              | Self-evident practices like "write clean code"     |

If Claude keeps doing something you don't want despite having a rule against it, the file is probably too long and the rule is getting lost. If Claude asks you questions that are answered in CLAUDE.md, the phrasing might be ambiguous. Treat CLAUDE.md like code: review it when things go wrong, prune it regularly, and test changes by observing whether Claude's behavior actually shifts.

You can tune instructions by adding emphasis (e.g., "IMPORTANT" or "YOU MUST") to improve adherence. Check CLAUDE.md into git so your team can contribute. The file compounds in value over time.

CLAUDE.md files can import additional files using `@path/to/import` syntax:

```markdown CLAUDE.md theme={null}
See @README.md for project overview and @package.json for available npm commands.

# Additional Instructions
- Git workflow: @docs/git-instructions.md
- Personal overrides: @~/.claude/my-project-instructions.md
```

You can place CLAUDE.md files in several locations:

* **Home folder (`~/.claude/CLAUDE.md`)**: applies to all Claude sessions
* **Project root (`./CLAUDE.md`)**: check into git to share with your team
* **Project root (`./CLAUDE.local.md`)**: personal project-specific notes; add this file to your `.gitignore` so it isn't shared with your team
* **Parent directories**: useful for monorepos where both `root/CLAUDE.md` and `root/foo/CLAUDE.md` are pulled in automatically
* **Child directories**: Claude pulls in child CLAUDE.md files on demand when it reads a file in those directories

### Configure permissions

<Tip>
  Use [auto mode](/docs/en/permission-modes#eliminate-prompts-with-auto-mode) to let a classifier handle approvals, `/permissions` to allowlist specific commands, or `/sandbox` for OS-level isolation. Each reduces interruptions while keeping you in control.
</Tip>

By default, Claude Code requests permission for actions that might modify your system: file writes, Bash commands, MCP tools, etc. This is safe but tedious. After the tenth approval you're not really reviewing anymore, you're just clicking through. There are three ways to reduce these interruptions:

* **Auto mode**: a separate classifier model reviews commands and blocks only what looks risky: scope escalation, unknown infrastructure, or hostile-content-driven actions. Best when you trust the general direction of a task but don't want to click through every step
* **Permission allowlists**: permit specific tools you know are safe, like `npm run lint` or `git commit`
* **Sandboxing**: enable OS-level isolation that restricts filesystem and network access, allowing Claude to work more freely within defined boundaries

Read more about [permission modes](/docs/en/permission-modes), [permission rules](/docs/en/permissions), and [sandboxing](/docs/en/sandboxing).

### Use CLI tools

<Tip>
  Tell Claude Code to use CLI tools like `gh`, `aws`, `gcloud`, and `sentry-cli` when interacting with external services.
</Tip>

CLI tools are the most context-efficient way to interact with external services. If you use GitHub, install the `gh` CLI. Claude knows how to use it for creating issues, opening pull requests, and reading comments. Without `gh`, Claude can still use the GitHub API, but unauthenticated requests often hit rate limits.

Claude is also effective at learning CLI tools it doesn't already know. Try prompts like `Use 'foo-cli-tool --help' to learn about foo tool, then use it to solve A, B, C.`

### Connect MCP servers

<Tip>
  Run `claude mcp add` with a server name and URL or command to connect external tools like Notion, Figma, or your database. For example: `claude mcp add --transport http notion https://mcp.notion.com/mcp`.
</Tip>

With [MCP servers](/docs/en/mcp), you can ask Claude to implement features from issue trackers, query databases, analyze monitoring data, integrate designs from Figma, and automate workflows.

### Set up hooks

<Tip>
  Use hooks for actions that must happen every time with zero exceptions.
</Tip>

[Hooks](/docs/en/hooks-guide) run scripts automatically at specific points in Claude's workflow. Unlike CLAUDE.md instructions which are advisory, hooks are deterministic and guarantee the action happens.

Claude can write hooks for you. Try prompts like *"Write a hook that runs eslint after every file edit"* or *"Write a hook that blocks writes to the migrations folder."* Edit `.claude/settings.json` directly to configure hooks by hand, and run `/hooks` to browse what's configured.

### Create skills

<Tip>
  Create `SKILL.md` files in `.claude/skills/` to give Claude domain knowledge and reusable workflows.
</Tip>

[Skills](/docs/en/skills) extend Claude's knowledge with information specific to your project, team, or domain. Claude applies them automatically when relevant, or you can invoke them directly with `/skill-name`.

Create a skill by adding a directory with a `SKILL.md` to `.claude/skills/`:

```markdown .claude/skills/api-conventions/SKILL.md theme={null}
---
name: api-conventions
description: REST API design conventions for our services
---
# API Conventions
- Use kebab-case for URL paths
- Use camelCase for JSON properties
- Always include pagination for list endpoints
- Version APIs in the URL path (/v1/, /v2/)
```

Skills can also define repeatable workflows you invoke directly:

```markdown .claude/skills/fix-issue/SKILL.md theme={null}
---
name: fix-issue
description: Fix a GitHub issue
disable-model-invocation: true
---
Analyze and fix the GitHub issue: $ARGUMENTS.

1. Use `gh issue view` to get the issue details
2. Understand the problem described in the issue
3. Search the codebase for relevant files
4. Implement the necessary changes to fix the issue
5. Write and run tests to verify the fix
6. Ensure code passes linting and type checking
7. Create a descriptive commit message
8. Push and create a PR
```

Run `/fix-issue 1234` to invoke it. Use `disable-model-invocation: true` for workflows with side effects that you want to trigger manually.

### Create custom subagents

<Tip>
  Define specialized assistants in `.claude/agents/` that Claude can delegate to for isolated tasks.
</Tip>

[Subagents](/docs/en/sub-agents) run in their own context with their own set of allowed tools. They're useful for tasks that read many files or need specialized focus without cluttering your main conversation.

```markdown .claude/agents/security-reviewer.md theme={null}

Cut at 300 lines. The page has the rest.

No line in this hunk matches that.