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Handbook›Codex Command Master›Cmd. /model
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Cmd. /model

Switch among GPT-6 Astra, GPT-5.6 Sol, Terra, Luna, and supported reasoning effort levels.

Key takeaways

  • Switch among GPT-6 Astra, GPT-5.6 Sol, Terra, Luna, and supported reasoning effort levels.
  • Check the input surface and availability before using the examples below.

Purpose

Switch among GPT-6 Astra, GPT-5.6 Sol, Terra, Luna, and supported reasoning effort levels.

/model

Availability

FieldValue
Input surfaceRunning CLI prompt
KindBuilt-in
StatusCurrent reference
Aliases—
Documented minimumNot specified
Reviewed against2026-09-22 · Codex CLI 0.155.1

The installed command menu and account or organization settings determine availability.

Examples

/model

When to use it

  1. Select GPT-6 Astra with high~max reasoning before the hardest and longest work.
  2. Select Astra or GPT-5.6 Sol before architecture, browser, security, or review work.
  3. Use Terra for daily implementation and Luna for explicit repeated edits.
  4. Run /status afterward to confirm the model, reasoning, and approval policy.

Choosing related commands

CommandDifferenceChoose It When
/modelChanges model and reasoningQuality, cost, or latency posture must change
/fastChanges speed/service tierThe model is correct but response priority should change
/statusShows current policyYou need to verify the selection

Effects and persistence

Uses the selected model for subsequent requests. Access, reasoning settings, and pricing depend on the chosen model.

/model chooses the active model and, in supported flows, reasoning effort for the current Codex session.

GPT-6 Astra at a Glance

ItemValue
Model IDgpt-6-astra
Minimum CLI0.153.0 (bundled default from 0.153.4 when no model is configured)
Context / output1,050,000 / 128,000 tokens
API pricing (per 1M)$10 input · $1 cached input · $50 output
Knowledge cutoffApril 30, 2026
Reasoninglow, medium, high, xhigh, max
model = "gpt-6-astra"
model_reasoning_effort = "high"

The 0.153.4 default change applies only to sessions without an explicit model in config.toml, so teams that pin a standard should adopt Astra deliberately. Astra also appears in the Amazon Bedrock Mantle and Runtime pickers from 0.153.3.

Current Selection Notes

  • Top model and hardest work: GPT-6 Astra (gpt-6-astra)
  • Hardest GPT-5.6 work: GPT-5.6 Sol
  • Balanced daily engineering: GPT-5.6 Terra
  • Clear repeated or cost-sensitive work: GPT-5.6 Luna
  • Pro text-only research preview: GPT-5.3-Codex-Spark
  • Previous generation: GPT-5.5 for compatibility or regression comparison
  • Retired: GPT-5.4 and GPT-5.4 mini left ChatGPT-sign-in Codex on 2026-08-31
  • Remove from new defaults: gpt-5.2 and gpt-5.3-codex for ChatGPT sign-in

Check permissions before adopting Astra

OpenAI classifies Astra as its first model to reach the Critical cybersecurity capability level under the Preparedness Framework. Narrow /permissions, sandboxing, and auto-approval scope before putting it behind broad automation.

Authentication boundary

The August 31 retirement applied to Codex with ChatGPT sign-in. Verify OpenAI API and API-key Codex availability separately in the provider catalog.

Cautions

  • Use the account's /model picker for exact IDs and reasoning levels.
  • Bound concurrency, write scope, and credits before using Ultra delegation.
  • Codex Cloud tasks currently use a fixed default model.
  • Pair high-risk model choices with /permissions and human review.

Official sources

  • Developer Commands
  • Models
  • Changelog

Complete command list · Verification scope · History for this command

Related docs

Models and Reasoning

Advanced Codex Usage · Choose GPT-6 Astra, GPT-5.6 Sol, Terra, Luna, and reasoning levels by task risk, cost, and latency.

Verification

Advanced Codex Usage · A checklist for validating advanced Codex team operations.

Cmd. /effort

Claude Code Command Master · Set or inspect model-specific reasoning effort.

Advanced Codex Usage

An advanced operations and extension guide for teams standardizing Codex usage.

Cmd. /fast

Turn Fast mode on or off, or report its status, to change the service tier without changing reasoning effort.

Cmd. /review

Ask Codex to review the current working tree.

Cmd. /fast

Turn Fast mode on or off, or report its status, to change the service tier without changing reasoning effort.

On this page

PurposeAvailabilityExamplesWhen to use itChoosing related commandsEffects and persistenceGPT-6 Astra at a GlanceCurrent Selection NotesCautionsOfficial sources