1M Token Context - Claude Code

The 1M token context window lets Claude Code hold roughly a full mid-size codebase plus history in a single session - no compaction, no chunking.

What it does

Supported Opus and Sonnet models on qualifying plans offer up to a one-million-token context window. That's enough for a large repository's source, a long conversation history, and tool output without losing earlier turns. Compaction still exists as a safety net but rarely fires during normal work.

When to use it

• Large codebases you'd otherwise have to chunk.
• Long debugging sessions with lots of file reads.
• Tasks that require tying together evidence from many files at once.
• Agent runs where compaction loss would hurt correctness.

Gotchas

• More context costs more per turn, even with caching. Watch your spend on marathon sessions.
• Availability depends on your plan and the selected model. Check /status if you're unsure.
• Just because the window is big doesn't mean you should fill it. Focused reads still outperform broad ones.

Official docs: https://code.claude.com/docs/en/model-config.md#extended-context