Support the Bedrock Mantle Anthropic Messages endpoint in `@ai-sdk/amazon-bedrock`

[gustaferiksson]

Description

Recent Claude models (Opus 4.7/4.8, Sonnet 5, Haiku 4.5) are only available on bedrock-runtime through cross-region inference profiles:

$ aws bedrock get-foundation-model --model-identifier anthropic.claude-opus-4-7 \
    --query 'modelDetails.inferenceTypesSupported'
["INFERENCE_PROFILE"]

For in-region use, AWS instead serves them on the Bedrock Mantle Anthropic Messages endpoint, https://bedrock-mantle.{region}.api.aws/anthropic/v1/messages (Opus 4.7 model card, Messages API docs).

No @ai-sdk/amazon-bedrock entry point can reach this endpoint. Tested against anthropic.claude-opus-4-7 in eu-west-1:

• bedrock(...) and bedrockAnthropic(...): Invocation of model ID anthropic.claude-opus-4-7 with on-demand throughput isn't supported
• bedrockMantle(...): 400, The model 'anthropic.claude-opus-4-7' does not support the '/v1/chat/completions' API. Claude on Mantle only supports the Messages API, and the mantle subpath only implements the OpenAI-compatible surfaces.

This can't be worked around with provider settings: baseURL on createBedrockAnthropic still gets /model/{id}/invoke appended (the Mantle host 404s that shape), and a custom fetch can't rewrite the URL because SigV4 signing happens inside the provider before the fetch is called, so any rewrite invalidates the signature.

Proposed solution

@ai-sdk/amazon-bedrock/anthropic already has all the pieces (SigV4 and API-key fetch functions, AnthropicMessagesLanguageModel via @ai-sdk/anthropic/internal). The differences between the two endpoints are small:

	bedrock-runtime (current)	Mantle
Base URL	https://bedrock-runtime.{region}.amazonaws.com	https://bedrock-mantle.{region}.api.aws/anthropic
Request URL	{base}/model/{id}/invoke[-with-response-stream]	{base}/v1/messages
Versioning	anthropic_version in body, model/stream stripped	anthropic-version header, first-party body
Streaming	Amazon eventstream framing	native SSE

So an endpoint option on the existing factory would cover it:

const bedrockAnthropic = createBedrockAnthropic({ endpoint: "mantle" }) // default: "runtime"
const model = bedrockAnthropic("anthropic.claude-opus-4-7")

keyed off in getBaseURL, buildRequestUrl, and transformRequestBody. Auth, tool remapping, and error normalization are shared as-is. bedrockMantle.anthropic(...) would also work as a shape, but the anthropic subpath already owns the Messages dialect.

Current workaround

Pointing stock @ai-sdk/anthropic at the Mantle base URL with a SigV4-signing fetch. This works (verified with tool calling through an agent loop) because the endpoint speaks the exact first-party Messages dialect, only the auth differs:

import { createAnthropic } from "@ai-sdk/anthropic"
import { Sha256 } from "@aws-crypto/sha256-js"
import { fromNodeProviderChain } from "@aws-sdk/credential-providers"
import { SignatureV4 } from "@smithy/signature-v4"

async function signedFetch(input: string | URL | Request, init?: RequestInit): Promise<Response> {
    const url = new URL(input instanceof Request ? input.url : input)
    const headers = Object.fromEntries(new Headers(init?.headers).entries())
    delete headers["x-api-key"]
    const signer = new SignatureV4({
        service: "bedrock",
        region: process.env.AWS_REGION ?? "eu-west-1",
        sha256: Sha256,
        credentials: fromNodeProviderChain(),
    })
    const signed = await signer.sign({
        method: init?.method ?? "POST",
        protocol: url.protocol,
        hostname: url.hostname,
        path: url.pathname,
        headers: { ...headers, host: url.hostname },
        body: init?.body,
    })
    return fetch(url, { ...init, headers: signed.headers })
}

const mantleAnthropic = createAnthropic({
    baseURL: `https://bedrock-mantle.${process.env.AWS_REGION}.api.aws/anthropic/v1`,
    apiKey: "unused-requests-are-sigv4-signed",
    fetch: signedFetch,
})

const model = mantleAnthropic("anthropic.claude-opus-4-7")

AI SDK Version

• ai: 6.0.222
• @ai-sdk/amazon-bedrock: 4.0.132 (also checked 4.0.133, 5.0.17 / ai v7, and 5.0.0-canary.84: none reach the Mantle Messages endpoint)

Code of Conduct

• I agree to follow this project's Code of Conduct

[lgrammel]

Identify issue type

Identified as Feature
Confidence: High

Rationale

This requests support for a new Bedrock endpoint and model-access path rather than reporting a failure of documented existing behavior.

Evidence

• The Amazon Bedrock provider has no entry point for the Mantle Anthropic Messages endpoint.
• Existing provider paths target either Bedrock Runtime invocation URLs or Mantle's OpenAI-compatible chat completions API.
• The reporter proposes adding an endpoint: "mantle" option to support this additional AWS API surface.

[heiwen]

To my understanding, ChatGPT models (5.5 & 5.6) on AWS are only offered via the mantle engine and would require some support here as well. Though this would be through the /responses or /chat/completions URL within mantle.