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Claude Haiku 3 is Being Retired April 19 — Complete Migration Guide
Anthropic has confirmed that Claude Haiku 3 (claude-3-haiku-20240307) will be retired on April 19, 2026. If you're using Haiku 3 in production via the API, you have under two weeks to migrate. This guide covers everything you need to make the switch with zero downtime.
TL;DR
- • Retirement date: April 19, 2026 — model ID stops accepting requests
- • Recommended replacement: Claude Haiku 4.5 (
claude-haiku-4-5-20251001) - • Price change: None — Haiku 4.5 costs the same as Haiku 3
- • Performance: Haiku 4.5 is 2× faster and significantly smarter
- • Migration effort: Low — change the model ID string; test your prompts
⏰ Deadline: April 19, 2026. After this date, calls to claude-3-haiku-20240307 will return an error. Act now to avoid production outages.
What Is Changing
Claude Haiku 3 (claude-3-haiku-20240307) was released in March 2024 as Anthropic's fastest and most affordable model. In the two years since, the Claude model family has advanced significantly. Haiku 4.5 — released in October 2025 — is faster, smarter, and costs exactly the same.
Anthropic's standard model lifecycle policy is to retire models 12+ months after their successor releases. Haiku 3's retirement follows this same pattern. The claude-3-haiku-20240307 model ID will return an API error after April 19, 2026.
Haiku 3 vs Haiku 4.5: What Actually Improves
| Metric | Claude Haiku 3 | Claude Haiku 4.5 |
|---|---|---|
| Model ID | claude-3-haiku-20240307 | claude-haiku-4-5-20251001 |
| Context window | 200K tokens | 200K tokens |
| Input price | $0.80/M tokens | $0.80/M tokens |
| Output price | $4/M tokens | $4/M tokens |
| Speed (latency) | Baseline | ~2× faster (lower TTFT) |
| HumanEval (coding) | 75.9% | 88.1% |
| MMLU (knowledge) | 75.2% | 82.4% |
| Tool / function calling | Supported | Improved accuracy |
| Vision (image input) | ✓ | ✓ (higher accuracy) |
| Batch API discount | 50% off | 50% off |
How to Migrate: Step-by-Step
Migration from Haiku 3 to Haiku 4.5 is deliberately straightforward. The API is fully backwards compatible.
Step 1: Update the Model ID
In your code, find every instance of claude-3-haiku-20240307 and replace it with claude-haiku-4-5-20251001.
# Before (retiring April 19)
model = "claude-3-haiku-20240307"
# After (Haiku 4.5)
model = "claude-haiku-4-5-20251001"
Step 2: Check Environment Variables
If you store the model ID in an environment variable (e.g., CLAUDE_MODEL=claude-3-haiku-20240307), update that variable in your .env files, CI/CD secrets, and deployment configs (Vercel, Railway, AWS, etc.).
Step 3: Test Your Key Prompts
While the API format is identical, Haiku 4.5 is a different model with different behavior. You should validate:
- Your most critical prompts return the expected format and quality
- Tool/function calling payloads parse correctly
- System prompts behave as expected (Haiku 4.5 follows instructions more reliably)
- Output length is within expected ranges
Step 4: Update Your Codebase References
Search your codebase for the old model string. Common places it appears:
# Find all occurrences in your project
grep -r "claude-3-haiku-20240307" . --include="*.ts" --include="*.js" --include="*.py"
Should You Consider Claude Sonnet 4.6 Instead?
If your use case has grown in complexity since you originally chose Haiku 3, this migration is a good time to reconsider whether a more capable model is now worth the higher cost. Haiku 4.5 is the right default replacement for speed-sensitive, high-volume workloads. But consider Claude Sonnet 4.6 if your tasks include:
- Complex multi-step reasoning or planning
- Code generation with review or debugging
- Document analysis over 50K tokens
- Agentic workflows with tool use chains
| Model | Best For | Input Price | Output Price |
|---|---|---|---|
| Haiku 4.5 | High-volume, speed-sensitive tasks; classification; extraction | $0.80/M | $4/M |
| Sonnet 4.6 | Coding, analysis, writing, agent workflows; best value for complex tasks | $3/M | $15/M |
| Opus 4.6 | Hardest reasoning, research, 1M context; flagship performance | $15/M | $75/M |
Migration Checklist
- ☐Update model ID in source code (claude-3-haiku-20240307 → claude-haiku-4-5-20251001)
- ☐Update environment variables in .env files
- ☐Update CI/CD pipeline secrets and configs
- ☐Update deployment environment variables (Vercel, Railway, AWS, GCP, etc.)
- ☐Run test suite against Haiku 4.5
- ☐Validate tool/function calling payloads
- ☐Test vision inputs if applicable
- ☐Deploy to staging, monitor for unexpected behavior
- ☐Deploy to production before April 19
FAQ
When is Claude Haiku 3 being retired?
Claude Haiku 3 (claude-3-haiku-20240307) is being retired on April 19, 2026. After this date, the model ID will no longer accept new requests through the Anthropic API.
What should I migrate to from Claude Haiku 3?
Anthropic's recommended migration path is Claude Haiku 4.5 (claude-haiku-4-5-20251001). Haiku 4.5 is 2× faster, significantly smarter on coding and reasoning tasks, and costs the same as Haiku 3.
Is Claude Haiku 4.5 backwards compatible with Haiku 3?
Yes. Haiku 4.5 uses the same messages format, tool/function calling format, and system prompt structure as Haiku 3. For most applications, changing the model ID is the only required change.
How much does Claude Haiku 4.5 cost vs Haiku 3?
Claude Haiku 4.5 costs $0.80/million input tokens and $4/million output tokens — identical pricing to Haiku 3. There is no price increase for migrating.
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