Bedrock Converse

codec/bedrockconverse speaks the model-neutral Converse request and response shape. The model ID is deliberately absent from the body because Bedrock puts it in the URL path.

Request

converseContentBlock is a tagged union with exactly one of Text, Image, Document, Audio, ReasoningContent, ToolUse, or ToolResult set. Audio requires inline bytes and a media type naming an AudioFormat member; an S3 source is decode-direction only. System content supports text only. Images require inline bytes and one of jpeg, png, gif, or webp. Documents can be bytes or text, require a valid name, and require a text block in the same message. Tool schemas are validated as JSON objects and required tool choice becomes toolChoice.any.

body, err := bedrockconverse.EncodeRequest(req)
if err != nil {
	var unsupported *bedrockconverse.UnsupportedBlockError
	if errors.As(err, &unsupported) {
		fmt.Println(unsupported.Reason)
	}
	return err
}
_ = body

Validation

The decoder rejects missing output.message, wrong assistant role, union blocks with zero or multiple variants, invalid tool objects, invalid document names, and unsupported media formats. EncodeCountTokensInput keeps only the conversation, system, tools, and additional model fields accepted by the CountTokens operation. Response usage maps Bedrock’s read/write cache fields to normalized usage; no request-side cache marker is emitted by this codec.

Source and proof

• bedrockconverse/types.go
• bedrockconverse/encode.go
• bedrockconverse/decode.go
• bedrockconverse/stream_test.go

Run go test ./codec/bedrockconverse.