Codex Says "Model not found gpt-5.6-sol"? Triage It Safely

If Codex returns 404 Not Found: Model not found gpt-5.6-sol, switch the affected task to a model that the current picker offers and keep your local project intact. Do not reinstall Codex, delete .codex, clear model metadata, or change authentication just to chase a 404. A July 29 incident affected users on current clients across multiple regions and one reporter said it recovered without a local repair.

First read the complete error. Codex has used similar wording for at least four different conditions: a transient 404, a client that is too old, an account or workspace that does not yet have Sol, and a usage allowance that has reset access temporarily. The status code and exact message determine the next step.

Quick Decision Table

OpenAI's current guidance lists Codex CLI 0.144.0 and ChatGPT desktop app 26.707.30751 as the minimum versions for GPT-5.6. It also says Sol availability depends on plan, rollout, and managed-workspace settings. A version check can rule out an old client, but it cannot repair a backend 404 on a current client.

Prerequisites

Before troubleshooting:

• save or commit important project work outside the chat;

• copy the full error, request ID, timestamp, Codex version, and selected model;

• note whether the failure affects one model or every model;

• keep credentials, transcript contents, local paths, and full diagnostics private;

• avoid changing configuration while an outage is still plausible.

This guide is for Codex Desktop, the Codex IDE extension, and Codex CLI when the selected model is unavailable. It is not a guide for API projects that use their own API key, Azure deployment name, or third-party model provider.

Step 1: Preserve the Error Before Retrying

Copy the complete line, not only Model not found. Record these fields:

timestamp:
Codex surface and version:
operating system:
selected model:
HTTP status:
exact error message:
request ID:
other models working: yes/no

Expected result: you can tell a 404 from a 400 and can compare the failing model with another model on the same account. Do not post the full task, diagnostics bundle, or authentication files in a public issue.

Step 2: Test an Offered Fallback, Not a Hidden Model ID

Open a new empty task and select a model that Codex currently shows in its picker. Send a harmless prompt such as:

Reply with MODEL_OK and do not call tools

Expected result: the fallback returns MODEL_OK. If another offered model works while Sol returns the July 29-style 404, your project, basic authentication, and general Codex connection are probably not the immediate failure boundary. Continue work on the fallback or wait. Do not repeatedly force gpt-5.6-sol with -m when the picker no longer offers it.

If every offered model fails, stop treating this as a Sol-only problem. Check the OpenAI status page and use the exact error to investigate authentication, connectivity, or a broader service incident.

Step 3: Verify Which Codex Installation Is Running

For Codex CLI, run read-only checks first.

On macOS or Linux:

command -v codex
codex --version
codex doctor

On Windows PowerShell:

Get-Command codex -All | Select-Object Source,Version
codex --version
codex doctor

Expected result: one intended installation is first on PATH, the running version is identified, and codex doctor reports the installation owner and any supported update action. If several binaries appear, update the installation that actually owns the first path instead of installing a second copy.

If the running client is below OpenAI's published minimum, fully close Codex and update it through the same package manager, app store, or managed software channel that installed it. Restart the shell or desktop app, then repeat the version check.

If the client meets the minimum and the exact error is still a 404, another reinstall is not a useful next test. The July 29 report reproduced on Codex CLI 0.146.0, above the documented minimum.

Step 4: Check Plan, Account, and Workspace Policy

OpenAI currently documents these Codex choices:

• Free and Go: GPT-5.6 Terra;

• Plus, Pro, Business, and Enterprise: Sol, Terra, and Luna;

• managed Business and Enterprise workspaces: model availability can also depend on administrator settings.

Confirm that Codex is signed in to the account you intended to use. If it belongs to a managed workspace, ask an administrator whether Sol is enabled for your role. If the picker does not show Sol, do not treat a manually typed model ID as proof of entitlement or availability.

OpenAI also says a model can become temporarily unavailable after its allowance is reached. If the product shows a reset time, use another offered model or wait for that time. See Aident's Codex usage-spike diagnostic guide before assuming a missing model is a billing failure.

Step 5: Separate a Transient 404 From a Persistent Access Error

The July 29 issue began at 06:11 UTC and quickly collected independent reports from TLV, NRT, HKG, VNO, FRA, GRU, LAX, ICN, and SJC Cloudflare regions. Reporters said GPT-5.5 or Terra still worked. At 07:04 UTC, one user reported that the problem had resolved. That pattern supports a transient service or routing failure for that incident, not a local cache fix.

By contrast, July 9 reports used a 400 response saying Sol was not supported with a ChatGPT account or required a newer client. Those reports coincided with the product rollout and persisted for some accounts after reinstalling or clearing local metadata. Use the error class, date, account, and available picker options together. Do not apply a workaround from one failure class to another.

Step 6: Report Persistent Failures With Bounded Evidence

If the exact error survives a reasonable wait, the status page is clear, the client is current, and the model should be available to the account, add evidence to the matching OpenAI Codex issue or contact support.

Include:

• error timestamp and time zone;

• Codex surface and version;

• operating system;

• ChatGPT plan and managed-workspace status;

• exact status code and sanitized message;

• request ID and Cloudflare region suffix, if returned;

• whether a model from the current picker works;

• whether the failure occurs in a new empty task.

Do not include auth.json, API keys, cookies, complete codex doctor output, private repository paths, or transcript files. A short comparison is more useful than a destructive reinstall history.

Common Mistakes

Why This Triage Order Works

The exact server response is the highest-signal evidence. A clean fallback test separates one model from a total Codex outage. Version and installation checks address the only client-side gate OpenAI documents without creating a second installation. Plan and workspace checks explain legitimate absence, while a bounded wait handles a transient incident without destroying local state.

The structure follows the useful lesson from Aident's Ollama networking guide: name the exact symptom, run safe checks, show expected results, distinguish look-alike failures, and explain why each boundary matters.

Verify One Remote Action With Aident Loadout

Once an offered Codex model works, verify that one remote integration is available independently of the model incident. Install or update Aident Loadout with this prompt:

Follow https://aident.ai/SETUP.md

Then run:

aident account auth status
aident vault vault --action status
aident capabilities search \
  --queries '["find one connected read-only GitHub Action that searches issues"]' \
  --types '["action"]'

Inspect the chosen schema before execution:

aident capabilities get --name "<canonical-action-name>"

Success means Aident is authenticated, Vault can identify connected integrations, and the current read-only Action contract is available without pasting a provider key into the replacement Codex task. This does not restore Sol; it proves the external tool boundary still works while the model layer changes.

Use Aident Loadout to verify one read-only Action. Measure success as one inspected live schema, zero pasted provider secrets, and zero repository changes.

Sources

• GPT-5.6 in ChatGPT, OpenAI Help Center, updated July 2026

• BLOCKER - Model not found gpt-5.6-sol, OpenAI Codex issue, opened July 29, 2026

• Unexpected status 404 Not Found: Model not found gpt-5.6-sol, OpenAI Codex issue, opened July 29, 2026

• Unable to use gpt-5.6-sol with ChatGPT Plus, OpenAI Codex issue, opened July 9, 2026

• Linux Codex CLI cannot use GPT-5.6 models while macOS works, OpenAI Codex issue, opened July 9, 2026

• The gpt-5.6-sol model is not supported with a ChatGPT account, OpenAI Codex issue, opened July 18, 2026

• Can't see GPT-5.6 Sol in Codex or Work, r/codex, posted July 10, 2026

• GPT-5.6 Sol and Codex release discussion, r/codex, posted July 9, 2026

• Codex just got better for developers, OpenAI, published July 14, 2026

• OpenAI service status, accessed July 29, 2026

• Aident setup instructions, accessed July 29, 2026

Refresh this guide when OpenAI changes GPT-5.6 plan availability or minimum versions, documents a supported model-catalog refresh, or closes the July 29 model-routing reports with a confirmed cause.