Speed

You can increase model speed in Codex in exchange for higher usage.

Fast mode

Fast mode speeds up supported models, including GPT-6.1 Sol, GPT-6 Astra, GPT-6 Sol, and GPT-6 Luna, where available. For GPT-5.6 and GPT-5.5, the speed increase is 1.5x.

Use /fast in the CLI to toggle Fast mode. Use /statusline to show it in the footer. You can also persist the default with service_tier = "fast" plus [features].fast_mode = true in config.toml. Fast mode is available in the ChatGPT desktop app, Codex CLI, and IDE extension when you sign in with ChatGPT.

For supported models, Fast mode uses included subscription limits at 2.5x the Standard rate. Purchased credits and Enterprise pay-as-you-go usage are billed at 2x the Standard rate. These billing multipliers don’t describe speed increases.

Ultrafast mode

GPT-6 Astra Ultrafast generates tokens up to 8x faster than GPT-6 Astra in Standard mode in Codex. This comparison measures token generation speed, not billing rates or overall task completion time.

Ultrafast is available in Codex and ChatGPT Work on Pro $500 and eligible Enterprise and Edu plans. On Pro $500, Ultrafast uses your included usage first, then your available credits after that allowance runs out.

For GPT-6 Astra, Ultrafast uses included subscription limits at 8x the Standard rate. Purchased credits and Enterprise pay-as-you-go usage are billed at 6x the Standard rate. These billing multipliers don’t describe speed increases. Enterprise billing remains subject to the workspace’s agreement.

For Enterprise workspaces, Ultrafast is off by default. Workspace owners can enable access for selected users or the workspace through workspace permissions. Existing per-user spend controls apply to eligible Ultrafast usage.

Availability and billing details

Supported models

GPT-6 Astra, GPT-6 Sol, and GPT-6 Luna support Fast mode where available. GPT-6.1 Sol supports Standard and Fast where available. Access depends on your plan, client, workspace settings, and rollout. See Models for model availability and Pricing for token rates.

Ultrafast plan and workspace requirements

• Eligible Enterprise workspaces use credit-based or USD usage-based agreements. Usage is billed according to the workspace’s agreement.
• Eligible Edu plans use credits. Legacy Enterprise plans that rely on rate limits instead of usage-based billing aren’t supported.

Other self-serve plans don’t have access to Ultrafast at launch, even with purchased credits.

Ultrafast isn’t available to workspaces that require inference residency outside the United States. A workspace’s location alone doesn’t determine eligibility.

API billing

With an API key, Codex uses API token pricing instead, and ChatGPT credit multipliers don’t apply.

For API availability, request configuration, and pricing, see Ultrafast mode in the API.

Retirement and migration

GPT-5.5 retires from ChatGPT, ChatGPT Work, and Codex on all plans on October 14, 2026. The OpenAI API isn’t affected.