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DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

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Claude Code v2.1.166

fallbackModel setting in settings.json

What

The fallback model list can now be set in settings.json as an array, not only via --fallback-model on the command line.

Usage
# Via CLI (comma-separated, as before)
claude --fallback-model sonnet,haiku

# Via settings.json (new — array form)
# In ~/.claude/settings.json or project .claude/settings.json:
# { "fallbackModel": ["sonnet", "haiku"] }
Details
  • Accepts model name aliases such as "sonnet", "haiku", or "default" (which expands to the current default model)
  • CLI --fallback-model takes precedence over the setting
  • The setting is also available in managed settings for enterprise deployments
  • Models that are not recognized or not available in the current context are silently skipped
Evidence

New fallbackModel schema field (search for 'Fallback model(s) tried in order when the primary model is overloaded or unavailable')

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

See this entry in the whole of v2.1.166 →