Add Bedrock Converse client with --provider flag and worker subproces…

[Pidem]

Adds native AWS Bedrock support via the Converse API. No proxy or external server required — just AWS credentials.

Changes

• medarc_verifiers/bedrock/client.py — BedrockConverseClient implementing the verifiers Client interface using boto3's Converse API. Supports text, multi-turn, and tool-use messages. Runs the
  synchronous boto3 call via run_in_executor to avoid blocking the async event loop.
• medarc_verifiers/bedrock/init.py — Monkeypatch that registers bedrock_converse as a valid ClientType in verifiers. Rebuilds RunRolloutRequest/RunGroupRequest Pydantic models so worker
  subprocesses also accept the new client type.
• medarc_verifiers/init.py — Calls register() at import time so spawned env worker processes inherit the patched types.
• medarc_verifiers/cli/_single_run.py — Adds --provider flag to single-run mode (was previously only available in bench mode).
• medarc_verifiers/cli/verifiers_adapter.py — Adds "bedrock" to PROVIDER_CONFIGS with client_type: "bedrock_converse".
• configs/medmarks-endpoints-bedrock.toml — Endpoint aliases for Nova Pro/Lite/Micro and Claude models on Bedrock.
• docs/bedrock.md — Usage documentation.
• pyproject.toml — bedrock dependency group (boto3>=1.35.0).

Usage

uv sync --group bedrock

AWS_PROFILE=my-profile uv run medarc-eval medqa
-m nova-pro
--endpoints-path configs/medmarks-endpoints-bedrock.toml
--provider bedrock
-n 25

Authentication uses the standard boto3 credential chain (AWS_PROFILE, AWS_REGION, ~/.aws/config, SSO, instance roles).

Tested

• MedQA with us.amazon.nova-pro-v1:0 — 5 examples, 3 rollouts each, reward=0.8.

Note

This is a monkeypatch bridge until verifiers#1522 (PrimeIntellect-ai/verifiers#1522) is merged upstream, at which point medarc_verifiers/bedrock/ can be removed.

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