concepts/subagents.md Codex Docs, 2026-03-17 00:33 UTC → 2026-04-16 00:46 UTC

1# Subagents1# Subagents

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3Codex can run subagent workflows by spawning specialized agents in parallel so3Codex can run subagent workflows by spawning specialized agents in parallel so

4they can explore, execute, or analyze work concurrently.4they can explore, tackle, or analyze work concurrently.

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6This page explains the core concepts and tradeoffs. For setup, agent configuration, and examples, see [Subagents](https://developers.openai.com/codex/subagents).6This page explains the core concepts and tradeoffs. For setup, agent configuration, and examples, see [Subagents](https://developers.openai.com/codex/subagents).

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66If you don't pin a model or `model_reasoning_effort`, Codex can choose a setup66If you don't pin a model or `model_reasoning_effort`, Codex can choose a setup

67that balances intelligence, speed, and price for the task. It may favor67that balances intelligence, speed, and price for the task. It may favor

68`gpt-5.3-codex-spark` for fast scans or a higher-effort `gpt-5.4`68`gpt-5.4-mini` for fast scans or a higher-effort `gpt-5.4`

69configuration for harder reasoning. When you want finer control, steer that69configuration for more demanding reasoning. When you want finer control, steer that

70choice in your prompt or set `model` and `model_reasoning_effort` directly in70choice in your prompt or set `model` and `model_reasoning_effort` directly in

71the agent file.71the agent file.

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73For most tasks in Codex, start with `gpt-5.4`. Use `gpt-5.3-codex-spark` when73For most tasks in Codex, start with `gpt-5.4`. Use `gpt-5.4-mini` when you

74you want a faster option for lighter subagent work.74want a faster, lower-cost option for lighter subagent work. If you have

75ChatGPT Pro and want near-instant text-only iteration, `gpt-5.3-codex-spark`

76remains available in research preview.

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76### Model choice78### Model choice

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78- **`gpt-5.4`**: Start here for most agents. It combines strong coding, reasoning, tool use, and broader workflows. The main agent and agents that coordinate ambiguous or multi-step work fit here.80- **`gpt-5.4`**: Start here for most agents. It combines strong coding, reasoning, tool use, and broader workflows. The main agent and agents that coordinate ambiguous or multi-step work fit here.

79- **`gpt-5.3-codex-spark`**: Use for agents that favor speed over depth, such as exploration, read-heavy scans, or quick summarization tasks. It works well for parallel workers that return distilled results to the main agent.81- **`gpt-5.4-mini`**: Use for agents that favor speed and efficiency over depth, such as exploration, read-heavy scans, large-file review, or processing supporting documents. It works well for parallel workers that return distilled results to the main agent.

82- **`gpt-5.3-codex-spark`**: If you have ChatGPT Pro, use this research preview model for near-instant, text-only iteration when latency matters more than broader capability.

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81### Reasoning effort (`model_reasoning_effort`)84### Reasoning effort (`model_reasoning_effort`)

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