Desktop app: model picker has no 1M Opus option and overrides saved [1m] default with 200k

Environment

• Claude Code: 2.1.233
• Claude desktop app: 1.30096.5.0 (Microsoft Store package), Windows 11 Pro 10.0.26200
• Settings: ~/.claude/settings.json contains "model": "claude-opus-4-6[1m]". No project/local settings or ANTHROPIC_MODEL env var override the model.

Expected

New chats in the desktop app start with the saved default model, including its [1m] context-window variant (1,000,000 tokens). The model picker offers a way to select the 1M variant of Opus.

Actual

• New chats where "Opus 4.6" is selected in the desktop app's model picker start with a 200k context window. The picker selection overrides the [1m] default saved in settings.
• The picker has no 1M entry for Opus. The only 1M entry served to the app (additionalModelOptionsCache in ~/.claude.json) is claude-fable-5[1m].
• Running /model claude-opus-4-6[1m] inside a session works and gives the 1M window, so account access to the 1M variant is not the issue.

Verification that settings resolution itself works

A headless session started from the CLI with no model flag honors the setting:

claude -p "Reply with only the word OK" --output-format json

returns modelUsage with "claude-opus-4-6[1m]": { ..., "contextWindow": 1000000, ... }.

So the [1m] default is resolved correctly by the CLI core; only the desktop app's new-chat/model-picker path loses it.

Suggested fix

Either expose the [1m] variants in the desktop app model picker, or make a plain picker selection (e.g. "Opus 4.6") preserve the [1m] suffix of the saved default instead of silently downgrading to 200k.

Related (closed, inverse symptom): #53780.