Feature request: dedicated model setting to pin "btw" (aside) messages to Haiku
Open 💬 0 comments Opened Jun 11, 2026 by wenodev
Feature description
btw aside messages (quick side questions that don't interrupt the main task) currently appear to be handled by the small/fast model mechanism, but there is no documented, explicit way to control which model handles them.
Request
Provide a dedicated setting to pin the model used for btw/aside responses, e.g.:
- a settings.json key such as
btwModel, or - an environment variable such as
CLAUDE_CODE_BTW_MODEL
so users can guarantee asides always run on a fast/cheap model (e.g. claude-haiku-4-5) regardless of the main conversation model.
Why
- Asides are typically lightweight questions where Haiku-level latency/cost is the right trade-off.
ANTHROPIC_DEFAULT_HAIKU_MODELcontrols the fast model for background operations in general, but the docs (model-config) do not explicitly state thatbtwmessages follow it, so there is no way to guarantee the model used for asides.
Workaround today
Setting ANTHROPIC_DEFAULT_HAIKU_MODEL in settings.json env — but its effect on btw specifically is undocumented.
Environment
- Platform: macOS (darwin)
- Claude Code CLI