{"version":"2.1.267","anchor":"model-capability-lookup-can-now-explicitly-force-fast-model","canonical_anchor":"new-claude-code-model-capabilities-env-var-to-override-model","heading":"Model capability flags can now be explicitly forced on or off","tier":"use","area":"Model Capabilities","url":"https:\/\/changelogs.core-directive.com\/v\/2.1.267\/e\/model-capability-lookup-can-now-explicitly-force-fast-model","release_url":"https:\/\/changelogs.core-directive.com\/v\/2.1.267","markdown":"### Model capability flags can now be explicitly forced on or off\n\nClaude Code's per-model capability checks now honor explicit true\/false overrides, including via a new CLAUDE_CODE_MODEL_CAPABILITIES env var\n\n**What**\n\n- The shared model-capability gate helper (`dm`, formerly `Rm`) now distinguishes an explicit `false` result from an undefined\/unset one. Previously only a falsy or undefined answer fell through to the same \"no answer\" fallback; now an explicit `false` immediately disables the feature.\n\n- This affects checks such as `mid_conv_system`, `adaptive_thinking`, `rejects_disabled_thinking`, `context_management`, `fast_mode`, `lean_prompt`, `thrifty_sonic`, `mid_conv_tool_change`, and `refusal_fallback`, which now short-circuit to \"off\" as soon as the gate explicitly says `false`, instead of falling back to matching on model-name strings like `opus-4-8` or `claude-mythos-5`.\n\n- The `fable_5_mitigations` gate similarly now respects an explicit `false` for the `claude-mythos-5` model, where before mitigations were always applied for that model regardless of the gate value.\n\n- A new `CLAUDE_CODE_MODEL_CAPABILITIES` environment variable lets you override these capability flags directly, as a semicolon-separated list of rules in the form `modelPattern=flag1,-flag2,...`, with a trailing `*` wildcard supported when matching model IDs.\n\n**Why** Makes model-specific behavior more predictable: capability gates can now definitively turn a feature off rather than silently falling back to guesswork based on the model's name, and the new env var gives a direct way to override these flags.\n\n- Area: Model Capabilities\n- Tier: Use it now\n- Useful: 5\/5\n- Signal: 4\/5"}