What
When you use Claude through Amazon Bedrock or Google Vertex AI and have not pinned a specific model, Claude Code checks which models your account can use and falls back to another if needed. Before, it kept a single cached yes-or-no answer. Now:
- Each model gets its own recorded result: refused, denied, temporary or accessible, and each result expires.
- Models that refused are remembered.
- A candidate model is confirmed with a fresh live check before it is used.
- A version check can mark a model as unavailable.
- Saved results are tied to the endpoint address and to whether authentication is skipped, so changing either does not reuse old results.
None of this runs when CLAUDE_CODE_PROVIDER_MANAGED_BY_HOST is set.
Why
If you use Bedrock or Vertex AI, you should see fewer false "model unavailable" fallbacks and fewer repeated checks.
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How long each remembered result lasts, and exactly what you will see differently, is not stated.