What
A warning is emitted when requesting the 1M context beta ([1m] model suffix) on Vertex for models that do not support it.
Details
- The check fires at startup when the resolved gateway configuration includes a vertex upstream that serves
claude-sonnet-4-5orclaude-sonnet-4models (identified internally assonnet45/sonnet40). - If the gateway config sets
auto_include_builtin_models: true, the built-inclaude-sonnet-4-5model is automatically added to the warning list even when no explicit upstream model mapping covers it. - The emitted message names the specific model IDs that triggered it:
"vertex upstream serves <model-list>: Sonnet 4.5/Sonnet 4 do not support 1M context on Vertex — requests with the context-1m beta (the [1m] model suffix) for these models will be rejected with a 400. Vertex 1M lineup: Opus 4.6+/Sonnet 4.6." - Emitted as a
warn-level log viagu("warn", …)during gateway config validation; does not block startup or abort the request. - Only vertex-provider upstreams are checked; other providers (bedrock, foundry, etc.) are unaffected by this warning.
Evidence
Vertex 1M limitation notice (search for "Sonnet 4.5/Sonnet 4 do not support 1M context on Vertex", u5c, auto_include_builtin_models)
Strings lifted out of the shipped bundle, so the claim above can be checked against them.