What
The fallbacks request parameter, which lets the server retry a refused request against another model, is now documented as available on the Claude API and Claude Platform on AWS. It was previously Claude-API-only with AWS support described as still being validated.
Details
- Bedrock, Vertex and Foundry are still excluded and keep the client-side middleware instead.
- A new row in the platform-availability table names both beta headers:
server-side-fallback-2026-07-01for the"default"form andserver-side-fallback-2026-06-01for the array form.
Evidence
available on the Claude API and Claude Platform on AWS
Strings lifted out of the shipped bundle, so the claim above can be checked against them.
Names in the bundlefallbacks
The entry above is what we published on the day. These lines were added later, as Anthropic's own pages caught up, and they sit beside the original rather than replacing it.
Confirmed since
Anthropic's documentation has since written up fallbacks, on Deploy managed settings.
`allowedHttpHookUrls` and `httpHookAllowedEnvVars` merge across settings files, so entries in your user, project, or local settings still apply while the managed list is empty. The fallbacks for those two keys and for `allowedChannelPlugin…managed-settings see the edit
One source agreesOne thing we can check says the same as this entry.
Anthropic's documentation agrees
Anthropic's documentation has since written up fallbacks, on Deploy managed settings.