Context isolation means running noisy intermediate work (file reads, searches, tool output) somewhere other than the main conversation, so only the conclusion comes back. In Claude Code, a subagent is the mechanism.
What it protects
Every exchange and tool result uses up the main context window (the finite amount of text the model can hold at once). A large investigation can fill it with material that is no longer useful; moving that exploration into a separate context keeps the main one clear.1
What it costs
The parent loses visibility into how the conclusion was reached and into anything discovered but left out of the summary.1 Two consequences follow in the course:
- The result must be specified in advance, including obstacles, or the main thread has to rediscover them. See Delegation contract.1
- Chains of dependent steps lose information at each handoff, so they belong in one context. See When to delegate.1
A side benefit: fresh context
A reviewer subagent starts without the conversation history that produced the code, so it can review more critically than the main conversation that helped write it.1
Related
- Progressive disclosure: saving context by not loading material until needed.
- Source: Introduction to Claude Code Subagents