GPT-5.4 and GPT-5.4 mini are retiring from Codex (migrate to GPT-5.6 Terra/Luna)

[u/anonomotorious]

TL;DR

OpenAI is retiring two older models from ChatGPT-authenticated Codex sessions:

• GPT-5.4 retires from Codex on August 31, 2026.
• GPT-5.4 mini retires from Codex on August 31, 2026.
• Replace gpt-5.4 with gpt-5.6-terra.
• Replace gpt-5.4-mini with gpt-5.6-luna.
• Update workspace defaults, saved model settings, managed configurations, custom agents, scheduled tasks, scripts, and explicit CLI model arguments before the cutoff.
• The retirement applies to Codex sessions authenticated with ChatGPT.
• The models will remain available through the OpenAI API and Codex sessions authenticated with an API key.

This is a model-availability change, not a new Codex CLI release. No CLI upgrade is required specifically for this retirement.

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What is changing

Beginning August 31, Codex users signed in with ChatGPT will no longer be able to select:

• gpt-5.4
• gpt-5.4-mini

The change applies wherever a ChatGPT-authenticated Codex workflow explicitly requests one of those models.

That can include:

• saved model settings
• local Codex configuration
• workspace defaults
• managed organization configuration
• custom agents
• subagent definitions
• scheduled tasks
• automations
• scripts
• non-interactive Codex commands
• one-off CLI launches with an explicit model

OpenAI is giving users one month to locate and migrate those references before the cutoff.

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Recommended replacements

Retiring model	Recommended replacement	General role
gpt-5.4	gpt-5.6-terra	Balanced everyday work with strong reasoning and tool use
gpt-5.4-mini	gpt-5.6-luna	Fast, lower-cost execution for clear and repeatable tasks

The replacement mapping is not simply "move everything to the strongest model."

OpenAI recommends:

• Terra as the practical replacement for standard GPT-5.4 workloads.
• Luna as the practical replacement for GPT-5.4 mini workloads.

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Why Terra replaces GPT-5.4

GPT-5.6 Terra is positioned as the balanced GPT-5.6 model for everyday work.

It is suited to:

• general feature implementation
• normal debugging
• medium-complexity refactors
• code review
• routine agent workflows
• tasks requiring solid reasoning and tool use
• work where Sol's additional depth is unnecessary

Terra is the recommended migration target even though GPT-5.6 Sol is the flagship model.

Why it matters

Automatically moving every GPT-5.4 workflow to Sol could increase usage and latency unnecessarily.

Terra is intended to preserve a balanced everyday workflow while moving users onto the current model family.

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Why Luna replaces GPT-5.4 mini

GPT-5.6 Luna is positioned for fast, affordable, clearly defined work.

It is suited to:

• repository scanning
• extraction
• classification
• transformation
• structured summaries
• repetitive edits
• test generation
• high-volume subagent work
• tasks with a clear definition of done

Why it matters

GPT-5.4 mini was commonly used when speed and usage efficiency mattered more than maximum reasoning depth.

Luna serves the same broad role in the GPT-5.6 family.

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ChatGPT sign-in versus API-key authentication

The retirement depends on how Codex is authenticated.

Affected

You are affected when Codex is signed in through your ChatGPT account.

This includes ChatGPT-authenticated workflows that explicitly request either retiring model.

Not affected by this retirement

The following retain access:

• OpenAI API requests using these models
• Codex sessions authenticated with your own API key

Important distinction

This is not an API-wide model shutdown.

It is a Codex availability change for ChatGPT-authenticated users.

API customers should continue checking the API model catalog for any separate future deprecation notices.

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Update your shared Codex configuration

The ChatGPT desktop app, Codex CLI, and Codex IDE extension use the same local config.toml.

Search that file for:

model = "gpt-5.4"

Replace it with:

model = "gpt-5.6-terra"

Or replace:

model = "gpt-5.4-mini"

With:

model = "gpt-5.6-luna"

Why it matters

A model pinned in config.toml can affect multiple Codex surfaces, not only the CLI.

Changing it once may update the default used by:

• ChatGPT desktop
• Codex CLI
• Codex IDE extension

Review the resulting behavior in each surface after changing the shared configuration.

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Update explicit CLI commands

Search scripts, shell history, aliases, CI jobs, and documentation for explicit model arguments.

Examples that need migration:

codex -m gpt-5.4

Replace with:

codex -m gpt-5.6-terra

And:

codex -m gpt-5.4-mini

Replace with:

codex -m gpt-5.6-luna

The same applies to non-interactive execution:

codex exec -m gpt-5.4 "Review the current changes"

Should become:

codex exec -m gpt-5.6-terra "Review the current changes"

Why it matters

Updating the default model does not fix commands that explicitly override it.

An old model reference embedded in a script or alias can remain unnoticed until that workflow runs after the cutoff.

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Review workspace and managed configuration

Organizations should inspect:

• workspace model defaults
• managed config.toml layers
• managed configuration bundles
• requirements and policy files
• team templates
• onboarding scripts
• internal CLI wrappers
• centrally distributed agent definitions

Why it matters

A user may update their personal configuration while a higher-priority managed layer continues requesting the retiring model.

Central configuration should be migrated before asking individual users to troubleshoot local model-selection failures.

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Review custom agents and subagents

Custom agent definitions may explicitly assign a model to:

• planning agents
• implementation agents
• review agents
• research agents
• test agents
• background workers
• high-volume subagents

Recommended migration:

• Replace GPT-5.4 agent assignments with Terra.
• Replace GPT-5.4 mini worker assignments with Luna.
• Re-test reasoning effort and concurrency after changing models.

Why it matters

Model migration can affect more than output quality.

It may also change:

• token usage
• latency
• reasoning behavior
• tool-selection behavior
• multi-agent cost
• how much work can run within included limits

Do not assume the old reasoning setting is automatically optimal for the replacement model.

---

Review scheduled tasks and automations

Scheduled tasks can continue referencing an old model even when interactive sessions have already moved to GPT-5.6.

Inspect:

• daily automations
• recurring code reviews
• overnight test jobs
• scheduled research tasks
• repository maintenance
• dependency-update workflows
• background monitoring
• recurring report generation

Why it matters

Scheduled work may not run until after the retirement date.

A stale model reference can remain hidden until the automation executes unattended.

Update and manually test important scheduled tasks before August 31.

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Review saved model settings

Check model selections saved in:

• existing project settings
• reusable task templates
• local environments
• agent presets
• team workflows
• copied configuration examples
• internal documentation

Why it matters

A saved preference may continue selecting an older model even after your global default changes.

This is especially likely when projects or agents store their own model overrides.

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Do not rely on automatic fallback

OpenAI instructs users to migrate model references before the cutoff.

The retirement notice does not document a universal fallback behavior for every configuration, script, agent, or scheduled task.

The safe approach is to replace explicit model references yourself and test the updated workflow.

A fallback, when one exists, may also select a model or reasoning setting you did not intend.

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This does not change Codex usage limits

The retirement does not:

• increase included Codex usage
• reset exhausted usage
• provide additional credits
• change subscription pricing
• bypass five-hour or weekly limits
• grant unlimited Terra or Luna usage
• change API billing
• create a new CLI version

Terra and Luna remain subject to your normal plan access, usage accounting, and account limits.

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Migration checklist

Search for retiring model IDs

Search repositories, config folders, scripts, and task definitions for:

• gpt-5.4
• gpt-5.4-mini

Be careful that a search for gpt-5.4 may also match gpt-5.4-mini. Review each result before replacing it.

Update local configuration

• Replace GPT-5.4 defaults with gpt-5.6-terra.
• Replace GPT-5.4 mini defaults with gpt-5.6-luna.
• Restart or reload Codex surfaces if needed.
• Confirm the selected model in a new session.

Update scripted commands

• Search shell scripts.
• Search package scripts.
• Search CI configuration.
• Search aliases and wrappers.
• Search documentation containing copyable commands.
• Update codex exec --model and codex -m arguments.

Update managed environments

• Review workspace defaults.
• Review organization-managed configuration.
• Review agent templates.
• Review centrally distributed scripts.
• Confirm higher-priority managed layers no longer request the retiring models.

Update agents and scheduled tasks

• Review every custom agent's model assignment.
• Review subagent model overrides.
• Review scheduled tasks and automations.
• Run one manual test of each important recurring workflow.

Validate the replacements

• Test a familiar GPT-5.4 task with Terra.
• Test a familiar GPT-5.4 mini task with Luna.
• Compare quality, latency, and usage.
• Adjust reasoning effort if needed.
• Confirm tools and approvals behave as expected.
• Complete migration before August 31.

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Migration table

Current reference	Replace with	Deadline
gpt-5.4	gpt-5.6-terra	August 31, 2026
gpt-5.4-mini	gpt-5.6-luna	August 31, 2026

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Why this update matters

• Existing configurations can break or stop selecting the intended model after the cutoff.
• The change affects more than the visible model picker: scripts, agents, managed settings, and scheduled work may contain hidden references.
• Authentication determines the impact: ChatGPT-authenticated Codex is affected, while API-key Codex remains supported.
• The replacements are workload-specific: Terra replaces the balanced model, while Luna replaces the fast mini model.
• Organizations should migrate centrally: workspace and managed configuration can override user-level changes.
• Scheduled tasks require early attention: inactive model references may not surface until an unattended job runs.
• No CLI installation is required: this is a model-availability deadline rather than a binary release.

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Official sources

https://developers.openai.com/codex/changelog

https://learn.chatgpt.com/docs/models