Claude Coding Best Practices 2025: Master AI-Powered Development with Sonnet 4.5

Executive Summary

Why Claude for Coding in 2025

Claude Sonnet 4.5: The Numbers

Benchmark Performance:

• SWE-bench Verified: 77.2% (highest ever, vs 50% for GPT-4)
• HumanEval: 92.3% (industry-leading)
• Coding Tasks: Outperforms all competitors in autonomous coding

Real-World Impact:

• 15x faster prototype development vs manual coding
• 80% reduction in boilerplate code writing
• 3x faster debugging with AI-assisted error analysis

When Claude Excels:

• Full-stack web development
• Code refactoring and optimization
• Bug fixing and debugging
• API integration
• Test generation
• Documentation writing

When to Use Alternatives:

• Ultra-low-latency autocomplete (use GitHub Copilot)
• Simple code snippets (use ChatGPT)
• Specialized domains (genomics, quantum → GPT-4)

The 10 Essential Claude Coding Best Practices

1. Create a CLAUDE.md File (Your Project's Permanent Brain)

What It Is: A Markdown file at your project root containing permanent instructions for Claude.

Why It Matters: Without it, you'll repeat context every conversation. With it, Claude "remembers" your project structure, style, and commands automatically.

What to Include:

Example CLAUDE.md:

# Project: E-commerce Platform

## Tech Stack
- Frontend: Next.js 15, React 19, TypeScript, TailwindCSS
- Backend: Node.js, Express, PostgreSQL
- Testing: Jest, Playwright

## Code Style
- Use functional components with hooks (no class components)
- Single quotes for strings
- Trailing commas always
- Max line length: 100 characters
- Use ES6+ features (arrow functions, destructuring, spread)

## Common Commands
- `npm run dev` - Start development server
- `npm run build` - Build for production
- `npm test` - Run Jest unit tests
- `npm run test:e2e` - Run Playwright E2E tests

## Key Files
- `src/app/` - Next.js app router pages
- `src/components/` - Reusable React components
- `src/lib/` - Utility functions and helpers
- `src/db/schema.ts` - Database schema (Drizzle ORM)

## Architecture Patterns
- Use Server Actions for server-side data mutations
- Use Server Components by default, Client Components only when needed
- Keep API routes thin, business logic in separate modules
- Use Zod for runtime validation

## Testing Guidelines
- Write tests AFTER implementing features (not TDD)
- Test user-facing behavior, not implementation details
- Mock external API calls
- Aim for 80%+ coverage on critical paths

## Important Notes
- This project uses App Router (not Pages Router)
- Drizzle ORM for database (not Prisma)
- Biome for linting/formatting (not ESLint/Prettier)

Pro Tip: Create multiple CLAUDE.md files:

• /CLAUDE.md - General project instructions
• /frontend/CLAUDE.md - Frontend-specific (component patterns, styling)
• /backend/CLAUDE.md - Backend-specific (API design, database)

ROI: Saves 10-20 minutes per session by eliminating repetitive context-setting.

2. Use Extended Thinking Modes for Complex Problems

What It Is: Special keywords that allocate more "thinking budget" before Claude responds.

The Thinking Hierarchy:

1. "think" - Standard thinking (~2-5 seconds)
2. "think hard" - Moderate thinking (~10-20 seconds)
3. "think harder" - Deep thinking (~30-60 seconds)
4. "ultrathink" - Maximum thinking (~2-3 minutes)

When to Use Each Level:

Standard ("think"):

• Simple code generation
• Straightforward bug fixes
• Documentation writing

Example:

Think about the best way to implement user authentication using Next.js Server Actions.

Moderate ("think hard"):

• Architectural decisions
• Complex refactoring
• Performance optimization
• Test strategy

Example:

Think hard about how to architect a real-time chat feature with:
- 1000+ concurrent users
- Message persistence
- Read receipts
- Typing indicators
- Minimal server cost

Don't write code yet. Give me the architecture first.

Deep ("think harder"):

• System design
• Critical bug hunts
• Security analysis
• Algorithm optimization

Example:

Think harder about this performance issue:
Our API endpoint takes 3 seconds to respond. 
[Paste code and database schema]

Analyze all potential bottlenecks and rank solutions by impact.

Maximum ("ultrathink"):

• Novel problems with no clear solution
• Debugging cryptic issues
• Multi-system integration design

Example:

Ultrathink: We need to migrate 10 million user records from MongoDB to PostgreSQL 
with zero downtime and no data loss. 

Requirements:
- Users must not experience service interruption
- Data consistency guaranteed
- Rollback plan needed
- Must complete in 2 weeks

Design the complete migration strategy.

Pro Tip: Always start with "think hard" or higher for non-trivial problems. The upfront time investment pays off with better solutions.

3. Plan Before Coding (The Two-Step Approach)

The Problem: Jumping straight to code often leads to suboptimal solutions or missed edge cases.

The Solution: Two-step workflow

Step 1: Get the Plan

Prompt Template:

Think hard about [problem description].

Requirements:
- [Requirement 1]
- [Requirement 2]
- [Requirement 3]

DO NOT WRITE ANY CODE YET. 

Give me:
1. Proposed approach
2. Potential challenges
3. Edge cases to consider
4. Alternative solutions
5. Recommended solution with justification

Example:

Think hard about implementing a rate limiter for our API.

Requirements:
- 100 requests per minute per user
- Must work across multiple server instances
- Low latency overhead (<5ms)
- Should handle burst traffic gracefully

DO NOT WRITE ANY CODE YET.

Give me:
1. Proposed approach
2. Potential challenges
3. Edge cases
4. Alternatives
5. Recommendation

Step 2: Execute the Plan

Once you've reviewed and approved the plan:

Great plan. Let's implement approach #2 (Redis-based sliding window).

Write the code for:
1. Rate limiter middleware
2. Redis connection setup
3. Unit tests
4. Integration with existing Express app

Follow the CLAUDE.md code style.

Why This Works:

• Saves time: Fewer iterations fixing wrong approaches
• Better solutions: Claude considers alternatives upfront
• Learning: You understand the "why" behind code decisions

ROI: 30-50% reduction in refactoring time.

4. Provide Rich Context (Images, Files, URLs)

The More Context, The Better: Claude excels when given comprehensive information.

Context Types:

A. Screenshots/Diagrams

• Paste error screenshots directly
• Include UI mockups for frontend work
• Share architecture diagrams
• Show database schemas

Example:

[Paste screenshot of error]

This error appears when users try to checkout. 
Debug this issue in the payment flow.

B. Tab-Completion for Files

• Type partial filename + Tab to autocomplete
• Reference multiple files easily
• Claude reads file contents automatically

Example:

Review @src/app/checkout/page.tsx and @src/lib/stripe.ts for the payment bug

C. URLs for External Context

• Paste documentation URLs
• Link to GitHub issues
• Share Stack Overflow threads

Example:

Implement authentication following this guide:
https://next-auth.js.org/getting-started/example

Adapt it for our Next.js 15 App Router setup.

Pro Tip: For large codebases, use /summarize to generate a project summary Claude can reference throughout the session.

5. Use Permissions Management Wisely

The Problem: Constant permission prompts break flow.

The Nuclear Option:

claude --dangerously-skip-permissions

What It Does: Disables all permission prompts (like Cursor's old "yolo mode").

When to Use:

• Trusted projects
• Rapid prototyping
• Personal projects

When NOT to Use:

• Shared/open-source projects
• Production code you haven't reviewed
• Projects with sensitive data

Alternative (Granular Control):

claude --allow-read="src/**" --allow-write="src/**" --deny-write="node_modules/**"

Best Practice: Start with default permissions, enable --dangerously-skip-permissions only for trusted rapid iteration sessions.

6. Clear Context Frequently

The Problem: Long conversations accumulate irrelevant context, slowing responses and wasting tokens.

The Solution: Use /clear liberally

When to Clear:

• New feature: Starting a different task
• After completing a task: Finished debugging, moving to next feature
• Context shift: Switching from frontend to backend work
• Before major decisions: Ensure Claude isn't biased by stale context

Example Workflow:

[Work on login feature for 20 minutes]
/clear

[Start work on dashboard]
I'm now working on the dashboard. Forget everything from the login conversation.

Read @src/app/dashboard/page.tsx and suggest performance optimizations.

Pro Tip: If you need to preserve specific context, copy important snippets to your next prompt after /clear.

ROI: 20-30% faster response times, reduced token costs.

7. Create Custom Slash Commands

What They Are: Reusable prompt templates stored as Markdown files.

Setup:

Step 1: Create commands folder

mkdir -p .claude/commands

Step 2: Create command file (e.g., .claude/commands/review-pr.md):

---
description: Review this pull request for code quality and bugs
---

Review this pull request:

{{input}}

Check for:
1. Code style consistency (per CLAUDE.md)
2. Potential bugs or edge cases
3. Performance concerns
4. Security vulnerabilities
5. Test coverage

Provide:
- Overall assessment (approve/request changes)
- Specific issues with line numbers
- Suggested improvements

Step 3: Use the command:

/review-pr

[Paste PR diff or GitHub URL]

More Example Commands:

.claude/commands/generate-tests.md:

---
description: Generate comprehensive unit tests for a file
---

Generate Jest unit tests for:

{{input}}

Requirements:
- Test all public functions
- Cover edge cases
- Mock external dependencies
- Follow AAA pattern (Arrange, Act, Assert)
- Aim for 90%+ coverage

.claude/commands/explain-code.md:

---
description: Explain code in detail for documentation
---

Explain this code as if documenting it for a new team member:

{{input}}

Include:
1. High-level purpose
2. Key logic flow
3. Important edge cases handled
4. Potential gotchas
5. Suggested improvements (if any)

Pro Tip: Build a library of 10-15 commands for your most common tasks. Saves 5-10 minutes per use.

8. Maintain Small, Iterative Changes

The Anti-Pattern: Asking Claude to build an entire feature in one go.

Problem: Large changes are harder to review, more likely to have bugs, and harder to roll back if wrong.

The Solution: Break work into small, testable iterations.

Example (Large Change - BAD):

Build a complete user profile system with:
- Profile page
- Edit functionality
- Avatar upload
- Bio editing
- Privacy settings
- Friend list
- Activity feed

Example (Iterative - GOOD):

Iteration 1:

Create a basic profile page that displays:
- User name
- Email
- Join date

Use our existing user data model. Just the UI, no editing yet.

Iteration 2:

Add an "Edit Profile" button that opens a modal form.
Just the UI structure, no save functionality yet.

Iteration 3:

Implement the save functionality using Next.js Server Actions.
Update the user's name and email.

Iteration 4:

Add avatar upload using our existing S3 integration.
Show upload progress and handle errors.

[And so on...]

Benefits:

• Each iteration is testable immediately
• Easier to spot bugs early
• Can pivot if requirements change
• Clearer git history

Rule of Thumb: Each Claude request should produce <200 lines of new code.

9. Use Artifacts for Interactive Code

What They Are: Claude's feature for generating standalone, runnable code snippets.

When to Use:

• Quick UI prototypes (React components)
• Algorithm visualization
• Data processing scripts
• Config file generation

How to Trigger:

Example 1: React Component:

Create an interactive React component that displays a bar chart 
of sales data with hover tooltips. 

Use artifacts so I can see it live.

Example 2: Algorithm Visualization:

Create a visual demonstration of the quicksort algorithm with step-by-step animation.

Use artifacts so I can run it immediately.

Example 3: Config Generator:

Generate an interactive form that lets me configure Tailwind settings, 
then outputs a tailwind.config.js file.

Use artifacts.

Pro Tip: Artifacts are great for stakeholder demos. Generate a quick prototype, share the artifact link with your team for immediate feedback.

10. Leverage the Files API for Large Codebases

The Problem: Pasting entire files hits context limits and is cumbersome.

The Solution: Use Claude's Files API

How It Works:

Step 1: Upload project files:

claude --upload src/app/**/*.tsx

Step 2: Reference in prompts:

Analyze the authentication flow across all uploaded files.
Identify security vulnerabilities.

Advanced: Persistent File Context:

# Upload and cache files for 1 hour
claude --upload --cache src/**/*.ts

Use Cases:

• Large refactoring across multiple files
• Codebase-wide analysis
• Consistency checks (naming, patterns)
• Dependency audits

ROI: Essential for projects with 50+ files. Saves hours vs manual file pasting.

Advanced Techniques for Power Users

A. Chaining Requests for Complex Tasks

Technique: Break complex tasks into a series of dependent requests.

Example: Full Feature Implementation

Request 1 (Planning):

Think hard about implementing "forgot password" functionality.

Outline:
1. User flow
2. Required API endpoints
3. Database changes needed
4. Email templates
5. Security considerations

No code yet.

Request 2 (Database):

Based on that plan, create the database migration for password reset tokens.

Use Drizzle ORM (per CLAUDE.md).

Request 3 (API):

Now implement the `/api/auth/forgot-password` endpoint.

It should:
- Generate a secure reset token
- Store in database with 1-hour expiration
- Send reset email
- Handle errors gracefully

Request 4 (Frontend):

Create the forgot password form component.

Use our existing form components (in @src/components/ui/form.tsx).
Submit to the API we just created.

Request 5 (Tests):

Generate tests for the forgot password flow:
- Unit tests for the API endpoint
- E2E test for the complete user flow

Why This Works: Each step builds on the previous, with opportunities to review and correct course.

B. Error-Driven Development

Technique: Let errors guide refinement.

Workflow:

1. Generate initial code:

Create a function to parse CSV files and insert into PostgreSQL.

2. Run code, hit error:

Error: CSV has unexpected columns

[Paste error and sample CSV]

Fix the parser to handle dynamic columns.

3. Iterate until working:

Now getting: "Database connection timeout"

[Paste error]

Add connection pooling and retry logic.

Why It Works: Real errors provide specific, concrete feedback Claude can act on.

C. Comparative Code Reviews

Technique: Have Claude compare your code to best practices or alternative implementations.

Example:

Here's my current implementation:

[Paste code]

Compare this to industry best practices for [task].

Provide:
1. What I did well
2. What could be improved
3. Alternative approaches
4. Security/performance concerns

Use Cases:

• Learning new patterns
• Code review before PR
• Optimization opportunities

D. Progressive Enhancement

Technique: Start basic, incrementally add features.

Example (Building an API):

Version 1: Basic CRUD Version 2: Add input validation Version 3: Add authentication Version 4: Add rate limiting Version 5: Add caching Version 6: Add comprehensive error handling

Each version works, just with progressive sophistication.

Common Mistakes & How to Avoid Them

Mistake 1: Not Using CLAUDE.md

Problem: Repeating project context every session.

Fix: Create comprehensive CLAUDE.md on day 1. Update it as project evolves.

Mistake 2: Asking for Too Much at Once

Problem: "Build a complete e-commerce platform" → overwhelming, buggy output.

Fix: Break into 50+ small tasks. Build iteratively.

Mistake 3: Not Reviewing Code

Problem: Blindly accepting Claude's code without understanding it.

Fix: Always review generated code. Ask Claude to explain unclear parts.

Example:

Explain line 47-52 of this code. Why use reduce() instead of a for loop here?

Mistake 4: Ignoring Extended Thinking

Problem: Using default thinking for complex problems → suboptimal solutions.

Fix: Use "think hard" or higher for any non-trivial task.

Mistake 5: Not Clearing Context

Problem: 1-hour conversation with 10 different topics → slow, confused responses.

Fix: /clear every time you switch tasks.

Mistake 6: Vague Prompts

Bad: "Make this code better"

Good:

Refactor this code for:
1. Better readability (add descriptive variable names)
2. Performance (reduce O(n²) to O(n))
3. Error handling (wrap in try-catch)
4. Type safety (add TypeScript types)

Follow CLAUDE.md code style.

Claude Coding Workflow Template

Daily Development Session:

1. Session Start (5 mins)

# Open Claude Code
claude

# Review CLAUDE.md to refresh context
cat CLAUDE.md

2. Feature Planning (10 mins)

Think hard about implementing [feature].

[Describe requirements]

DO NOT CODE YET. Give me the plan.

3. Iterative Implementation (60-120 mins)

Let's implement step 1 of the plan: [specific step]

[Implement, test, refine]

/clear

Now step 2: [next step]

[Repeat]

4. Code Review (15 mins)

Review all code we wrote today for:
- Bugs
- Performance issues
- Security concerns
- Test coverage gaps

Suggest improvements.

5. Documentation (10 mins)

Generate inline code comments for complex functions we added today.

Also update the README with new features.

Conclusion

Claude Sonnet 4.5 is the world's best coding AI, but only if you use it right. Master these 10 practices:

1. ✅ Create comprehensive CLAUDE.md
2. ✅ Use extended thinking ("think hard") for complex tasks
3. ✅ Plan before coding (two-step approach)
4. ✅ Provide rich context (images, files, URLs)
5. ✅ Manage permissions appropriately
6. ✅ Clear context frequently
7. ✅ Create custom slash commands
8. ✅ Make small, iterative changes
9. ✅ Use artifacts for interactive code
10. ✅ Leverage Files API for large codebases

Your Next Steps:

1. Create your project's CLAUDE.md today
2. Try "think hard" on your next complex problem
3. Build one custom slash command for a common task

The 80/20 Rule: CLAUDE.md + extended thinking + small iterations = 80% of productivity gains.

Guide Updated: 2025-10-14 | Claude Version: Sonnet 4.5 | SWE-bench Score: 77.2% (世界最高)