gptel-bedrock: AWS_BEARER_TOKEN_BEDROCK support

[leezu]

AWS has introduced Bearer token based authentication for Bedrock https://docs.aws.amazon.com/bedrock/latest/userguide/api-keys.html Bearer token based authentication only requires the Authorization: Bearer header and does not need the sigv4 signing and thus removes the current dependency of the Bedrock backend on curl >= 8.9.

[karthink]

Thanks for the PR @leezu. Is this a duplicate of #983?

[leezu]

@karthink they are similar. This PR adds support for the AWS_BEARER_TOKEN_BEDROCK environment variable which is the standard environment variable name for Bedrock https://docs.aws.amazon.com/bedrock/latest/userguide/api-keys-use.html #983 adds support for passing the key as an argument in elisp. Ideally we should support both ways to specify the key.

The other difference between the PRs is that #983 uses :header argument to pass the token AND modifies the gptel-bedrock--curl-args to remove the other arguments if bearer token is present, whereas this PR handles both inside gptel-bedrock--curl-args. I think handling both in gptel-bedrock--curl-args is cleaner.

[leezu]

Also FYI, Bedrock now supports an OpenAI compatible endpoint (at least for the gpt-oss models): https://aws.amazon.com/blogs/aws/openai-open-weight-models-now-available-on-aws/

(gptel-make-openai "Bedrock-OpenAI"
    :host "bedrock-runtime.us-west-2.amazonaws.com"
    :protocol "https"
    :key "REDACTED"
    :endpoint "/openai/v1/chat/completions"
    :stream nil
    :models '((openai.gpt-oss-20b-1:0 :capabilities (reasoning))
              (openai.gpt-oss-120b-1:0 :capabilities (reasoning))))

Additional patches are required for the reasoning support with GPT-OSS as it uses <reasoning> </reasoning> tags instead of the currently supported <think> </think>.

[karthink]

leezu left a comment (karthink/gptel#1007) @karthink they are similar. This PR adds support for the AWS_BEARER_TOKEN_BEDROCK environment variable which is the standard environment variable name for Bedrock https://docs.aws.amazon.com/bedrock/latest/userguide/api-keys-use.html #983 adds support for passing the key as an argument in elisp. Ideally we should support both ways to specify the key. The other difference between the PRs is that #983 uses :header argument to pass the token AND modifies the gptel-bedrock--curl-args to remove the other arguments if bearer token is present, whereas this PR handles both inside gptel-bedrock--curl-args. I think handling both in gptel-bedrock--curl-args is cleaner.

Thanks for the clarification. Any design changes to gptel-bedrock are the purview of @felipeochoa and @akssri, so I'll defer to them on this proposal.

[leezu]

Thanks, @karthink. It's not really a design change but simply adjustment to support the new API key functionality. It became available only last month: https://aws.amazon.com/blogs/machine-learning/accelerate-ai-development-with-amazon-bedrock-api-keys/

[akssri]

(Moved to #1053)

[karthink]

Closing in favor of #1053.