Hey, this is a known bug in the CLI model selector. When one model name is a prefix of another like “GPT-5.4” vs “GPT-5.4 1M”, the selector re-filters the list instead of confirming your selection.
Workaround: try typing /model gpt-5.4 with a trailing space, then press Enter right away. It’s not perfect, but it avoids the re-filtering.
For the High and Extra High options, they’re available in the parameterized picker by pressing Tab on the “GPT-5.4” line, which opens the quality tier picker. The UX there is honestly not obvious.
The team knows about the bug. There’s no ETA yet, but your report helps with prioritization. Related thread for context: CLI model selector is buggy for gpt-5.*-High