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Managing the Context Window

Claude Code operates within a context window whose size depends on your model and plan. As of v2.1.139, Opus 4.7 supports a 1M token context window by default on Max, Team, and Enterprise plans. Sonnet and Haiku have smaller windows. How you manage that window directly affects response quality, speed, and cost. This guide covers strategies for keeping context focused and knowing when to start fresh.

How Context Works

Every message you send, every file Claude reads, and every tool result occupies tokens in the context window. With the 1M token limit, you can sustain much longer sessions than before -- reading dozens of files, making multi-file changes, and iterating extensively without hitting the ceiling. However, as the conversation grows, older messages get compressed automatically. Understanding this lifecycle helps you work more effectively:

  1. Fresh context — Early in a conversation, Claude has full access to everything discussed.
  2. Active window — With Opus 4.7 on Max/Team/Enterprise, the 1M token window lets you work through large features, multi-file refactors, and extended debugging sessions in a single conversation. Smaller models hit compression sooner.
  3. Compression — As the window fills, the system summarizes older messages to make room.
  4. Degradation — After heavy compression, nuance from earlier exchanges may be lost.

The /compact Command

Use /compact to manually trigger context compression. With the 1M token window, you no longer need to compact aggressively -- but it remains valuable for cost control and keeping Claude focused. Compact when:

  • You have finished one subtask and are moving to another (reduces cost of subsequent messages)
  • The conversation has accumulated a lot of tool output you no longer need
  • You notice responses slowing down or becoming less accurate
  • You want to reduce token spend even though you have not hit the limit

You can also pass a prompt to /compact to guide what gets preserved:

/compact focus on the database migration work

This tells the compressor to prioritize retaining information about database migrations while aggressively summarizing everything else.

Scoping Tasks Narrowly

The single most effective context management strategy is keeping tasks small. Instead of asking Claude to "refactor the entire authentication system," break it into focused requests:

  • "Refactor the password hashing in auth/hash.ts"
  • "Update the session middleware to use the new token format"
  • "Add tests for the refreshToken endpoint"

Each focused task uses less context, produces better results, and is easier to review.

Using Subagents to Protect Context

When you need to explore the codebase or research a question, subagents run in their own context window. The main conversation only receives a summary of their findings. This is valuable when:

  • Exploring unfamiliar code — A subagent can read dozens of files without polluting your main context.
  • Running broad searches — Grep and glob results from a subagent stay contained.
  • Parallel investigation — Multiple subagents can research different aspects simultaneously.

Claude Code automatically uses subagents for deep exploration tasks. You can encourage this by framing requests as research:

Find all the places where we handle authentication errors and summarize the patterns used.

What 1M Tokens Gets You (Opus 4.7 on Max/Team/Enterprise)

To put the Opus 4.7 context limit in perspective:

Content Approximate tokens
One source file (~200 lines) ~2,000
10 source files ~20,000
A 50-message conversation with tool use ~100,000-200,000
A full-day pair programming session ~400,000-600,000
Reading an entire medium codebase (500 files) ~1,000,000

With Opus on Max/Team/Enterprise, most development sessions -- even long ones -- will stay well within the 1M limit. You can comfortably read entire modules, iterate on complex features, and run multiple test-fix cycles without running out of room. On Sonnet or Haiku, context management remains important since these models have smaller windows.

When to Start Fresh

Start a new conversation when:

  • You are switching to a completely unrelated task
  • The conversation has gone through multiple rounds of compression
  • Claude starts "forgetting" decisions made earlier in the conversation
  • You want to reset cost accumulation (each message in a long session sends the full context)

There is no penalty for starting fresh. Claude reads your CLAUDE.md and project files at the start of every conversation, so project context is always available.

Practical Tips

  • Front-load important information. Put critical constraints and requirements in your first message or in CLAUDE.md so they survive compression.
  • Use CLAUDE.md for durable context. Anything Claude needs to remember across conversations belongs in CLAUDE.md, not in chat.
  • Avoid pasting large files into chat. Let Claude read files with tools instead — the content can be compressed more effectively than inline text.
  • Review what Claude remembers. If you suspect context loss, ask "What do you remember about X?" to check before continuing.
  • One concern per conversation. Mixing bug fixes, feature work, and refactoring in one session wastes context on task-switching overhead.

How Context Compression Works

When the context window approaches its limit, the system automatically:

  1. Identifies older message pairs (your message + Claude's response)
  2. Summarizes them into compact representations
  3. Replaces the originals with summaries
  4. Preserves the most recent messages in full

The compression is lossy — specific code snippets, exact line numbers, and nuanced decisions may be simplified. This is why keeping tasks focused matters: less to compress means less information lost.

See Also