ACTION REQUIRED · API USERS
Claude API Deadlines — What to Migrate Before It Breaks
One Claude model retires next: Sonnet 4.5 on November 30, 2026. Here's the plain-English checklist: what's breaking, what to swap it to, and what you can ignore.
Last checked: October 23, 2026, against Anthropic's model deprecations page.
⚠ Skip this page if you only use Claude in claude.ai or the desktop or mobile apps.
These are Claude API changes. If you're a knowledge worker using Claude in the apps, you don't need to do anything. Send this page to your dev team instead.
Do you need to read this?
- Yes — if you have code that calls the Claude API (backend services, scripts, agents, integrations).
- Yes — if you use Claude through Microsoft Foundry, Claude Platform on AWS, or Google Cloud (Anthropic managed). Amazon Bedrock and Google-managed Google Cloud set their own retirement dates; check theirs.
- No — if you only use Claude in claude.ai or the desktop or mobile apps.
- No — if someone else on your team owns your Claude API integration.
Deadlines at a glance
Monday, November 30, 2026 Nov 30, 2026
Sonnet 4.5 retires
Anthropic deprecated Sonnet 4.5 on September 30, 2026. After November 30, requests to it fail.
claude-sonnet-4-5-20250929
claude-sonnet-5-5
Deprecation guide →
Now, API version 2026-10-21 Parameters
temperature, top_p and top_k are gone
In API version 2026-10-21, requests that set them return a 400 error. On earlier versions, setting them to a non-default value already errors on Claude 4.7 and later models. Remove them and steer with your prompt instead.
Anthropic's migration notes →
Already retired: Opus 4.1 retired August 5, 2026. Sonnet 4 and Opus 4 retired June 15, 2026. Calls to them fail now.
The 5-minute migration checklist
- Search every repo and config for
claude-sonnet-4-5-20250929, and for temperature, top_p and top_k.
- For each hit: swap the model ID to
claude-sonnet-5-5, and delete the parameters.
- Run your existing eval suite or golden test cases against the new model in staging.
- Pay attention to output formatting diffs — especially prompts that depend on specific token counts or structured JSON.
- Roll canary traffic to 10% for 24 hours, watch error rates and output quality, then promote to 100%.
- Document the swap in your team's runbook so the next deprecation is faster.
What you don't need to do
If you're only using Claude in claude.ai or the desktop or mobile apps: nothing.
One more thing
Anthropic gives at least 60 days' notice before retiring a publicly released model. We'll keep this page current.