Fast mode toggle missing for Opus 5.5 in the Claude Code model selector (catalog has no fast_mode for claude-opus-5-5 on cc/ccd/ccr)

Summary

In the Claude Desktop Code tab, the model menu shows a Fast mode toggle for Opus 5 but not for Opus 5.5. Fast mode works on Opus 5.5 once it is switched on through another route, so the missing toggle appears to be a gap in the model catalog rather than a model limitation.

Evidence

The published model catalog (https://downloads.claude.ai/model-catalog/v1/catalog.json, version 1000, issued 2026-09-23T02:58:17Z) gives claude-opus-5 a fast_mode toggle block on the Claude Code surfaces and gives claude-opus-5-5 none:

{"id": "claude-opus-5-5", "section": "main", "fast_mode": null}
{"id": "claude-opus-5", "section": "overflow", "fast_mode": {"type": "toggle", "name": "Fast mode", "options": [{"id": "fast", "name": "Enable fast mode", "selector_label": "Fast"}, {"id": "off", "name": "Off"}]}}

It is the same on cc, ccd and ccr. On chat and cowork, both models carry "supports_fast_mode": true.

To reproduce:

curl -s https://downloads.claude.ai/model-catalog/v1/catalog.json | jq '.surfaces.ccd.model_selector_config[0].models[] | select(.id | startswith("claude-opus-5")) | {id, fast_mode}'

Other signs that Opus 5.5 is meant to support fast mode:

• The fast mode docs list Opus 5.5 as supported, alongside Opus 5 and Opus 4.8.
• The model table bundled in Claude Code 2.1.280 includes fast_mode among the capabilities of claude-opus-5-5.
• A Code-tab session on claude-opus-5-5 reports fast mode state on with no disabled reason after fast mode is enabled for it programmatically.

Expected

The Code tab model menu shows the Fast mode toggle for Opus 5.5, as it does for Opus 5 and as Chat does for both.

Actual

No toggle for Opus 5.5 in the Code tab. /fast is no alternative: in the desktop Code tab it answers "Fast mode is not available in the Agent SDK" on every model, so the menu toggle is the only UI route.

Environment

• Claude Desktop 2.2553.13 (Linux, Fedora 44)
• Claude Code 2.1.280
• The toggle comes from the server-side catalog, so this should not be platform-specific.