A long task fills the model's context with files, search results, test logs, and dead ends. The useful conclusions compete with all that raw material. When the window gets crowded, the model has less room to reason and may need a summary that drops detail.
A subagent starts with a fresh context and one scoped job. The parent, called the orchestrator, gets back a short result instead of every file and failed search the worker saw.
Follow the blue work out and the gold findings back. One finding fails verification before the parent uses it.
The economics
Four workers can finish four independent jobs at the same time, but you still pay for every token all four use. The parent keeps more context space because it stores the plan and four short results instead of the full reading history.
Watch where the raw reading lives, then check how much space the decision-maker keeps.
One agent
Orchestrated
A worker has no conversation history unless the parent supplies it. A useful assignment names the scope, the expected result, and what the worker must not change. A vague prompt often buys a second round trip.
Try the decision
Choose for each job, then compare your reason with the reveal.
The patterns
Four shapes cover most subagent work.
Fan-out
Independent parts run in parallel, such as one worker per module in an audit. The parent chooses boundaries that keep workers from touching the same files.
Pipeline
Each item moves through stages such as find, fix, and check. One item can be in review while another is still being found.
Judge and jury
A fresh worker tries to disprove each finding. The parent keeps claims that survive an independent check.
Loop until dry
For a search with unknown size, send new finder waves until repeated waves return nothing new.
What goes wrong
- Workers collide. Give them separate files or isolated workspaces.
- The parent trusts raw claims. Verify findings before they drive a decision.
- The parent rereads everything. That fills the context you were trying to protect.
- A small task gets split. Coordination adds cost without a gain.
When to reach for it
Use orchestration when the reading will crowd one window, when independent parts can run at the same time, or when a decision needs an independent check. Keep small, sequential work in one context.
Reasoning effort controls how much one agent thinks. Orchestration controls how work spreads across agents. A mechanical worker can run at low effort while the verifier uses more.
- Workers protect the parent's context by returning short results.
- Parallel work can finish sooner while using more total tokens.
- Split independent work and verify claims before integration.