Under the hoodTier: how much it should matter to you
1Useful: my rating, 1 to 5
2Signal: worth watching, 1 to 5
ElsewhereArea: what it touches
Internal ChangesKind: in v2.1.309,
Internal ChangesSection of the release
Unclear It is not clear whether setting ANTHROPIC_BEDROCK_BASE_URL still turns eager input streaming off.
What
ANTHROPIC_BEDROCK_BASE_URL is the environment variable that points Claude Code at a custom Amazon Bedrock endpoint, such as an LLM gateway. Two places that used to read it directly now call a helper function instead:
The check that decides whether Bedrock is using its default endpoint. Before, it tested whether ANTHROPIC_BEDROCK_BASE_URL was unset. The Vertex, Mantle and Google Cloud cases still check their own environment variables.
The check for eager input streaming on Bedrock (sending a tool's input as it is produced, controlled by eagerInputStreaming.bedrock). Before, it also required ANTHROPIC_BEDROCK_BASE_URL to be unset. The Vertex branch still checks ANTHROPIC_VERTEX_BASE_URL.
Why
The members do not show what the helper looks at, so whether a custom Bedrock URL is still treated the same way depends on it. If you reach Bedrock through a gateway or custom endpoint, watch for differences in default-endpoint behaviour and in tool-input streaming.
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 sinceAnthropic's documentation has since written up ANTHROPIC_VERTEX_BASE_URL, on Connect Claude Code to an LLM gateway.> export ANTHROPIC_VERTEX_BASE_URL=https://llm-gateway.example.com/vertexllm-gateway-connectsee the edit
Confirmed sinceAnthropic's documentation has since written up ANTHROPIC_BEDROCK_BASE_URL, on Connect Claude Code to an LLM gateway.> export ANTHROPIC_BEDROCK_BASE_URL=https://llm-gateway.example.com/bedrockllm-gateway-connectsee the edit
How sure we are
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubtIt is not clear whether setting `ANTHROPIC_BEDROCK_BASE_URL` still turns eager input streaming off.
Anthropic's documentation agreesAnthropic's documentation has since written up ANTHROPIC_BEDROCK_BASE_URL, on Connect Claude Code to an LLM gateway.
Anthropic's release notes agreeFixed fine-grained tool streaming staying off on Amazon Bedrock when ANTHROPIC_BEDROCK_BASE_URL is set to the default…
