2 minute read

Summary

Subagents are useful, but they should not become the default. Use them only when parallelism or specialization creates a real benefit.

The point is not that several agents automatically do better work. The point is to separate independent questions or tasks, then integrate their results into one judgment.

Document Information

  • Written on: 2026-04-23
  • Verification date: 2026-04-23
  • Document type: analysis
  • Test environment: No execution test. This is an operating judgment guide based on official OpenAI Codex documentation.
  • Tested version: OpenAI Codex documentation checked on 2026-04-23

Problem Definition

Complex work makes parallel agents tempting. But parallel work also creates cost and integration burden. If agents edit the same files or the integration standard is unclear, parallelism can increase risk.

This post explains when to use Codex subagents and when to stay with a single flow.

Verified Facts

According to official documentation, Codex can spawn specialized agents in parallel and collect their results into one response. Source: OpenAI, Subagents

According to official documentation, Codex only spawns subagents when explicitly asked, and subagent workflows consume more tokens than comparable single-agent runs. Source: OpenAI, Subagents

According to official documentation, Codex ships with built-in default, worker, and explorer agents, and custom agents can be defined. Source: OpenAI, Subagents

According to official documentation, subagents inherit the parent session’s sandbox policy and approval settings. Source: OpenAI, Subagents

Directly Reproduced Results

No direct reproduction was performed. This post does not measure speed or quality across subagent runs. It turns documented behavior into usage criteria.

Interpretation / Opinion

I use subagents when:

  • Several independent codebase exploration questions exist.
  • Review angles are clearly separated, such as security, performance, tests, and maintainability.
  • Implementation ownership can be split by file or module.
  • A parallel investigation can run while the main flow continues.
  • Someone can integrate the results and own the final decision.

I prefer a single flow when:

  • The next step depends strongly on one result.
  • Multiple agents would edit the same files.
  • The problem definition is still vague.
  • Sequential reasoning matters more than parallelism.
  • There is no integration standard.

Delegation template:

Split this investigation into subagents.

- Agent A: inspect only security risks in the auth flow. Do not edit files.
- Agent B: inspect missing tests and regression risk. Do not edit files.
- Agent C: inspect possible performance bottlenecks. Do not edit files.

Wait for all results, deduplicate them, and summarize by priority.

Opinion: the value of subagents comes from boundaries, not count. Without role boundaries, file ownership, and integration criteria, parallelism becomes noise.

Limits and Exceptions

Subagent availability and visibility can vary by Codex client. As of the 2026-04-23 documentation check, subagent activity is surfaced in the Codex app and CLI, while IDE extension visibility is described as coming soon.

Subagents do not remove verification responsibility. The final change still needs review, tests, and diff inspection.

References

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