Claude Sonnet 4.5 Now Available in Cline

TL;DR

• Claude Sonnet 4.5 is now available in Cline with 200k context window at Sonnet 4 pricing ($3/$15 per million tokens)
• The model writes its own documentation, works test-first, and maintains state across sessions — changing how you structure long-running tasks
• Update Cline and select claude-sonnet-4.5 to start using it today

What Dropped

Anthropic's Claude Sonnet 4.5 is live in Cline. Same pricing as Sonnet 4, same 200k context window, but a fundamentally different approach to how it tackles software development. The model automatically creates documentation files, builds test suites before implementation, and maintains its own state across context boundaries.

The Dev Angle

Sonnet 4.5 treats the filesystem as external memory. Without prompting, it generates CHANGELOG.md, SUMMARY.md, and progress.txt files as it works. It creates structured test files (like tests.json) and init.sh scripts before touching implementation code. This test-first pattern means the model can work on complex features across an entire context window, save its state, then pick up in a fresh session by reading its own progress notes and test results.

The model is noticeably more terse than previous versions — it skips commentary, jumps to implementation, and only speaks when it needs clarification. This terseness pairs naturally with Cline's Auto Compact feature. When Auto Compact compresses conversation history to continue past context limits, Sonnet 4.5 excels at creating concise, accurate summaries. The result is smooth continuity across context windows without the context pollution that derails other models.

For practical use: be explicit about intent. Say "implement these changes" rather than "suggest changes." The model precisely follows instructions. For complex tasks, let it set up comprehensive tests first — it's designed to work that way. Trust its state tracking across sessions; you don't need to re-explain requirements or remind it of context.

Should You Care?

If you're running multi-session projects in Cline, this is a direct upgrade. Same cost as Sonnet 4, better continuity, and a model that's built for how Cline actually works. The test-first approach and documentation habits reduce the friction of context switching — something that's been a real pain point for long-running tasks.

If you're on Sonnet 4 and happy with it, there's no urgency. But if you've hit context limits on complex features or struggled with session continuity, Sonnet 4.5 addresses those specific problems. The 200k context window is identical, so you're not getting more raw capacity — you're getting smarter use of the capacity you have.

Update Cline and select claude-sonnet-4.5 from the model dropdown to start using it.

Source: Cline