Default Terra Sub-Agent Configuration for Codex Multi-Agent V2

One-sentence takeaway

Restricting Multi-Agent V2 to a maximum of 4 concurrent threads, setting Terra with high reasoning effort as the sub-agent default, and delegating the "when to delegate" logic to AGENTS.md or the root prompt serves as a reusable starting point for quota and capacity control.

Suitable use cases

• Suitable tasks: Codex CLI Multi-Agent V2, parallelizable and bounded engineering subtasks.

• Unsuitable tasks: Serial modifications heavily dependent on shared state, production tasks without concurrency or write isolation configured.

• Applicable model versions: GPT-5.6 Terra; the original post also notes that model and reasoning levels can be overridden on a per-bounded-task basis.

• Applicable clients, agents, or APIs: Codex CLI 0.145.0 and versions supporting Multi-Agent V2 (the original post cites Codex Releases).

• Recommended reasoning tiers and parameters: Sub-agent default high; up to 4 concurrent threads; max_depth = 1 retained solely for V1 compatibility.

Copy-ready content

The original post disclosed configuration intent and fields rather than a complete config.toml. It can be mapped into the following checklist based on the current Codex version:

Multi-Agent V2: Enabled
Expose per-generation model override and reasoning override
Max concurrent threads: 4
Sub-agent default model: GPT-5.6 Terra
Sub-agent default reasoning: high
Preserve interrupt context
max_depth = 1 (V1 compatibility only, not used as V2 delegation depth control)
Root Agent / AGENTS.md determines model and reasoning overrides during delegation

How to use

1. Enable V2 in a Codex CLI version that supports Multi-Agent V2.

2. Set the default sub-agent model to Terra, default effort to high, and set the concurrency limit to 4.

3. Do not rely on max_depth to control V2 delegation depth; clearly define delegation conditions in AGENTS.md or the root prompt.

4. Override the model/reasoning level as needed for bounded tasks, and preserve interrupt context.

5. Monitor quotas, failure retries, concurrency conflicts, and subtask artifacts before adjusting the limits.

Boundaries

• The original post did not disclose the full configuration file, hardware, task suite, run counts, or quota consumption, so these settings cannot be claimed as an optimal solution.

• "Controlling capacity via configuration and delegating timing via instructions" reflects the author's personal experience rather than an official Codex guarantee.

• Specific field names and available models should be based on the current CLI version; avoid blindly copying non-existent configuration keys.