Anthropic's Claude Sonnet 4.5 is Live in Cline

Claude Sonnet 4.5 by Anthropic is now available in Cline. With a 200k context window at the same $3/$15 pricing as Sonnet 4, this update doubles down on reliability, terseness, and stateful project memory — and Cline is the ideal environment to unlock it.

The model writes its own documentation

Without prompting, Sonnet 4.5 creates CHANGELOG.md, SUMMARY.md, and progress.txt files. It treats the filesystem as memory, describing architecture and decisions in real time. This documentation isn’t filler — it’s how the model maintains continuity across multi-session builds.

Because Cline executes through structured diffs, those files act as live context anchors: when the model resumes a session, it reads its own notes, inspects git history, and continues implementation without re-prompting.

It works test-first

Sonnet 4.5’s new discipline shows up in how it codes: fewer words, more commits. The model writes tests first — often in tests.json or as scaffold scripts like init.sh — then implements the feature. Inside Cline, that means each diff is backed by a passing test suite before it lands in the repo. Long-running refactors or multi-file tasks now survive across sessions without losing track of state.

Why this pairs with Auto Compact

Cline’s Auto Compact feature compresses conversation history to keep huge contexts coherent. Sonnet 4.5’s built-in summarization instincts make that process nearly seamless. It writes accurate summaries, maintains external state files, and avoids “context pollution,” giving you continuity over multi-day or multi-window builds.

Getting the Most from Sonnet 4.5

• Be direct. Commands like “implement these changes” trigger execution; vague phrasing just invites suggestions.
• Let it scaffold tests. Cline will automatically capture and apply the test-first workflow.
• Trust its memory. Between Cline’s compression and Sonnet’s self-written state, you rarely need to restate requirements.

The model is available now in Cline as claude-sonnet-4.5. 200k context window, same pricing as Sonnet 4 at $3 per million input tokens and $15 per million output tokens.

Ready to experience a model that focuses on shipping code? Update Cline and select Sonnet 4.5 today. Share your experiences with complex, multi-session projects on Reddit or Discord.