codex change model bug

Resolved 💬 2 comments Opened Apr 21, 2026 by zhm19940813 Closed Apr 26, 2026

What version of Codex CLI is running?

0.121.0

What subscription do you have?

ChatGPT Plus

Which model were you using?

gtp-5.4

What platform is your computer?

_No response_

What terminal emulator and version are you using (if applicable)?

_No response_

What issue are you seeing?

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<body>
<h3 data-section-id="64jxzd" data-start="471" data-end="531">🐞 Bug: Codex TUI prewarm maps gpt-5.4 → gpt-5.4-t (404)</h3>
<p data-start="533" data-end="548"><strong data-start="533" data-end="548">Environment</strong></p>
<ul data-start="549" data-end="644">
<li data-section-id="14zstlg" data-start="549" data-end="578">
OS: WSL (Ubuntu on Windows)
</li>
<li data-section-id="108v3o3" data-start="579" data-end="599">
Codex CLI: 0.121.0
</li>
<li data-section-id="4bzuz8" data-start="600" data-end="620">
Install: npm (nvm)
</li>
<li data-section-id="1hc7bbo" data-start="621" data-end="644">
Account: ChatGPT Plus
</li>
</ul>
<hr data-start="646" data-end="649">
<p data-start="651" data-end="666"><strong data-start="651" data-end="666">Description</strong></p>
<p data-start="668" data-end="694">When using Codex TUI with:</p>
<pre class="overflow-visible! px-0!" data-start="696" data-end="725"><div class="relative w-full mt-4 mb-1"><div class=""><div class="relative"><div class="h-full min-h-0 min-w-0"><div class="h-full min-h-0 min-w-0"><div class="border border-token-border-light border-radius-3xl corner-superellipse/1.1 rounded-3xl"><div class="h-full w-full border-radius-3xl bg-token-bg-elevated-secondary corner-superellipse/1.1 overflow-clip rounded-3xl lxnfua_clipPathFallback"><div class="pointer-events-none absolute inset-x-4 top-12 bottom-4"><div class="pointer-events-none sticky z-40 shrink-0 z-1!"><div class="sticky bg-token-border-light"></div></div></div><div class="relative"><div class=""><div class="relative z-0 flex max-w-full"><div id="code-block-viewer" dir="ltr" class="q9tKkq_viewer cm-editor z-10 light:cm-light dark:cm-light flex h-full w-full flex-col items-stretch ͼ5 ͼj"><div class="cm-scroller"><div class="cm-content q9tKkq_readonly"><span>model = "gpt-5.4"</span></div></div></div></div></div></div></div></div></div></div><div class=""><div class=""></div></div></div></div></div></pre>
<p data-start="727" data-end="765">the session fails during startup with:</p>
<pre class="overflow-visible! px-0!" data-start="767" data-end="833"><div class="relative w-full mt-4 mb-1"><div class=""><div class="relative"><div class="h-full min-h-0 min-w-0"><div class="h-full min-h-0 min-w-0"><div class="border border-token-border-light border-radius-3xl corner-superellipse/1.1 rounded-3xl"><div class="h-full w-full border-radius-3xl bg-token-bg-elevated-secondary corner-superellipse/1.1 overflow-clip rounded-3xl lxnfua_clipPathFallback"><div class="pointer-events-none absolute end-1.5 top-1 z-2 md:end-2 md:top-1"></div><div class="relative"><div class="pe-11 pt-3"><div class="relative z-0 flex max-w-full"><div id="code-block-viewer" dir="ltr" class="q9tKkq_viewer cm-editor z-10 light:cm-light dark:cm-light flex h-full w-full flex-col items-stretch ͼ5 ͼj"><div class="cm-scroller"><div class="cm-content q9tKkq_readonly"><span>Unexpected status 404 Not Found: Model not found gpt-5.4-t</span></div></div></div></div></div></div></div></div></div></div><div class=""><div class=""></div></div></div></div></div></pre>
<hr data-start="835" data-end="838">
<p data-start="840" data-end="859"><strong data-start="840" data-end="859">Key Observation</strong></p>
<ul data-start="861" data-end="1055">
<li data-section-id="1qub33b" data-start="861" data-end="887">
My config uses <code data-start="878" data-end="887">gpt-5.4</code>
</li>
<li data-section-id="j4dfvi" data-start="888" data-end="968">
Codex internally rewrites it to <code data-start="922" data-end="933">gpt-5.4-t</code> during <strong data-start="941" data-end="968">session_startup_prewarm</strong>
</li>
<li data-section-id="53hfmz" data-start="969" data-end="1013">
<code data-start="971" data-end="982">gpt-5.4-t</code> is not a valid public model ID
</li>
<li data-section-id="1ro88mt" data-start="1014" data-end="1055">
Failure happens before actual inference
</li>
</ul>
<hr data-start="1057" data-end="1060">
<p data-start="1062" data-end="1070"><strong data-start="1062" data-end="1070">Logs</strong></p>
<pre class="overflow-visible! px-0!" data-start="1072" data-end="1215"><div class="relative w-full mt-4 mb-1"><div class=""><div class="relative"><div class="h-full min-h-0 min-w-0"><div class="h-full min-h-0 min-w-0"><div class="border border-token-border-light border-radius-3xl corner-superellipse/1.1 rounded-3xl"><div class="h-full w-full border-radius-3xl bg-token-bg-elevated-secondary corner-superellipse/1.1 overflow-clip rounded-3xl lxnfua_clipPathFallback"><div class="pointer-events-none absolute end-1.5 top-1 z-2 md:end-2 md:top-1"></div><div class="relative"><div class="pe-11 pt-3"><div class="relative z-0 flex max-w-full"><div id="code-block-viewer" dir="ltr" class="q9tKkq_viewer cm-editor z-10 light:cm-light dark:cm-light flex h-full w-full flex-col items-stretch ͼ5 ͼj"><div class="cm-scroller"><div class="cm-content q9tKkq_readonly"><span>codex_core::session_startup_prewarm:</span><br><span>startup websocket prewarm setup failed:</span><br><span>unexpected status 404 Not Found: Model not found gpt-5.4-t</span></div></div></div></div></div></div></div></div></div></div><div class=""><div class=""></div></div></div></div></div></pre>
<hr data-start="1217" data-end="1220">
<p data-start="1222" data-end="1234"><strong data-start="1222" data-end="1234">Behavior</strong></p>
<div class="TyagGW_tableContainer"><div tabindex="-1" class="group TyagGW_tableWrapper flex flex-col-reverse w-fit">
Model | Result
-- | --
gpt-5.3-codex | ✅ works
gpt-5.4-mini | ✅ works
gpt-5.4 | ❌ fails (rewritten to gpt-5.4-t)

</div></div>
<hr data-start="1375" data-end="1378">
<p data-start="1380" data-end="1396"><strong data-start="1380" data-end="1396">What I tried</strong></p>
<ul data-start="1398" data-end="1472">
<li data-section-id="bki5tj" data-start="1398" data-end="1427">
Full reinstall of codex CLI
</li>
<li data-section-id="v2p6vz" data-start="1428" data-end="1446">
Deleted ~/.codex
</li>
<li data-section-id="1dkr8vl" data-start="1447" data-end="1457">
Re-login
</li>
<li data-section-id="1zj8xz" data-start="1458" data-end="1472">
Clean config
</li>
</ul>
<p data-start="1474" data-end="1489">Issue persists.</p>
<hr data-start="1491" data-end="1494">
<p data-start="1496" data-end="1510"><strong data-start="1496" data-end="1510">Conclusion</strong></p>
<p data-start="1512" data-end="1586">This appears to be a <strong data-start="1533" data-end="1579">TUI prewarm / websocket initialization bug</strong> where:</p>
<pre class="overflow-visible! px-0!" data-start="1588" data-end="1625"><div class="relative w-full mt-4 mb-1"><div class=""><div class="relative"><div class="h-full min-h-0 min-w-0"><div class="h-full min-h-0 min-w-0"><div class="border border-token-border-light border-radius-3xl corner-superellipse/1.1 rounded-3xl"><div class="h-full w-full border-radius-3xl bg-token-bg-elevated-secondary corner-superellipse/1.1 overflow-clip rounded-3xl lxnfua_clipPathFallback"><div class="pointer-events-none absolute end-1.5 top-1 z-2 md:end-2 md:top-1"></div><div class="relative"><div class="pe-11 pt-3"><div class="relative z-0 flex max-w-full"><div id="code-block-viewer" dir="ltr" class="q9tKkq_viewer cm-editor z-10 light:cm-light dark:cm-light flex h-full w-full flex-col items-stretch ͼ5 ͼj"><div class="cm-scroller"><div class="cm-content q9tKkq_readonly"><span>gpt-5.4 → gpt-5.4-t (invalid)</span></div></div></div></div></div></div></div></div></div></div><div class=""><div class=""></div></div></div></div></div></pre>
<hr data-start="1627" data-end="1630">
<p data-start="1632" data-end="1646"><strong data-start="1632" data-end="1646">Workaround</strong></p>
<ul data-start="1648" data-end="1703">
<li data-section-id="1gni5on" data-start="1648" data-end="1687">
Use <code data-start="1654" data-end="1668">gpt-5.4-mini</code> or <code data-start="1672" data-end="1687">gpt-5.3-codex</code>
</li>
<li data-section-id="1cwxv6f" data-start="1688" data-end="1703">
Or bypass TUI</li></ul>
</body>
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What steps can reproduce the bug?

change model

What is the expected behavior?

_No response_

Additional information

_No response_

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