Compatibility

• Status: Beta

• Beta header: compact-2026-01-12

• ZDR: eligible (excludes Covered Models)

• Supported models: claude-fable-5-1, claude-mythos-5-1, claude-fable-5, claude-mythos-5, claude-mythos-preview, claude-opus-5, claude-opus-4-8, claude-opus-4-7, claude-opus-4-6, claude-sonnet-5, claude-sonnet-4-6

• Platforms: Claude API (beta), Claude Platform on AWS (beta), Amazon Bedrock (beta), Google Cloud (beta), Microsoft Foundry (beta)

  Server-side compaction is the recommended strategy for managing context in long-running conversations and agentic workflows. It handles context management automatically, without client-side summarization code.

Compaction extends the effective context length for long-running conversations and tasks by automatically summarizing older context when approaching the context window limit. It also keeps the active context small: as a conversation grows, response quality degrades, so compaction replaces older content with a concise summary.

For a deeper look at why long contexts degrade and how compaction helps, see Effective context engineering.

This is ideal for:

• Chat-based, multi-turn conversations where you want users to use one chat for a long period of time
• Task-oriented prompts that require a lot of follow-up work (often tool use) that might exceed the context window