Claude Code changelog

Claude Code makes Haiku 5.5 the default Haiku model

Claude Code 2.1.293 added Claude Haiku 5.5 as the default Haiku model on the Anthropic API.

Claude Code makes Sonnet 5.5 the default Sonnet model

Claude Code 2.1.284 added Claude Sonnet 5.5 as the default Sonnet model on the Anthropic API.

Claude Code defaults to Opus 5.5, including on Pro plans

Claude Code 2.1.280 made Opus 5.5 the default Opus model and changed the default on Pro and Team Standard plans from Sonnet to Opus.

Who is affected:

Claude Code users on Pro and Team Standard plans, whose usage limits may now be consumed by Opus.

What to do:

Use /model to pick Sonnet if you want to stretch usage limits.

Claude Code makes Fable 5.1 the default Fable model

Claude Code 2.1.257 added Claude Fable 5.1 as the default Fable model with a 1M context window at $10 / $50 per million tokens.

Who is affected:

Claude Code users on the fable alias.

What to do:

Update Claude Code. Fable 5.1 needs version 2.1.255 or later.

Claude Code default model for seat-based Enterprise switches to Opus 5

Claude Code 2.1.251 changed the default model for seat-based Enterprise subscriptions to Opus 5, matching other premium plans.

Who is affected:

Claude Code users on seat-based Enterprise plans.

What to do:

Pick a model with /model if you want a different default.

Claude Code removes todo tools on newer models

Claude Code 2.1.233 removed the TodoWrite and task-tracking tools on Opus 4.8, Sonnet 5, Fable 5, Mythos 5 and newer models. An environment variable brings them back.

Who is affected:

Claude Code hooks, scripts or SDK apps that depend on TodoWrite or TaskCreate.

What to do:

Set CLAUDE_CODE_ENABLE_TODO_TOOLS=1 if you rely on those tools.

Claude Code makes Opus 5 the default Opus model

Claude Code 2.1.219 added Claude Opus 5 as the default Opus model and removed Opus 4.7 from fast mode. Anthropic also made Opus 5 the default model on Claude Max.

Who is affected:

Claude Code users on the opus alias or the Max plan.

What to do:

Pin claude-opus-4-8 with /model if you need the previous model.

Claude Sonnet 5 becomes the default model in Claude Code

Claude Code 2.1.197 made Claude Sonnet 5 the default model, with a native 1M token context window.

Who is affected:

Claude Code users who had not picked a model.

What to do:

Update to Claude Code 2.1.197 or later. Use /model to pick a different default.

Claude Code Max users default to fast mode on Opus 4.8

In Claude Code, Max plan users now default to fast mode when using Claude Opus 4.8.

Who is affected:

Claude Code users on the Max plan.

What to do:

Run /fast to turn fast mode off if you prefer standard speed.