When Not to Use Subagents
Subagents are not universally beneficial. Delegation carries its own cost, and without a benefit that exceeds it the result is worse than not delegating.
The Cost of Delegating
| Cost | Description |
|---|---|
| Writing the instruction | Stating purpose, input, completion condition, and output format |
| Summarizing assumptions | Extracting the needed parts from the main context |
| Merging the result | Interpreting what comes back on the main side |
| Round-trip time | Waiting from launch to result |
For short work, this cost exceeds the work itself.
Three Poor Fits
1. Work That Finishes in One or Two Steps
Counting the lines in a file does not need delegation. Writing the instruction takes longer than doing it.
2. Work That Requires Shared Fine-Grained Context
Design decisions, where the approach firms up gradually through conversation, resist delegation. Summarizing the assumptions already drops the nuance the decision depends on.
# A poor fit for delegation
"Between these two designs, which do you think is better?"
→ the evidence is spread across the whole conversation, and summarizing loses the point3. Work Where Responsibility Becomes Unclear
Assigning the same scope to several subagents makes it impossible to decide which result to adopt. Keep assigned scopes non-overlapping.
Avoid Nesting
A subagent calling another subagent summarizes at each level, drifting further from the original intent.
Main → subagent (first summarization) → its subagent (second summarization)
→ the original intent arrives through two rounds of compressionKeep delegation to one level as a rule. When more is needed, split the steps on the main side as orchestration instead.
The Deciding Question
Ask whether the benefit of context isolation exceeds the cost of delegating.
| Situation | Decision |
|---|---|
| Heavy reading, only the conclusion needed | Delegate |
| An independent check is wanted | Delegate |
| Finishes in a few steps | Do not delegate |
| The approach forms through conversation | Do not delegate |
Summary
- Delegation costs instruction writing, assumption summarizing, and result merging
- Short work and context-dependent work are poor fits
- Overlapping scopes make it impossible to choose which result to adopt
- Nesting dilutes intent, so keep delegation to one level