[sam2tom]

Summary

Add model_provider.headers to the frozen provider configuration so activity metadata reaches model requests across messages, tool continuations, retries, and session recovery. Support Codex, Claude SDK, and MiniMax through their native clients, including saved Agent and deployment-default configuration inputs.

Headers are for non-sensitive metadata only: Claude tools can read them. Existing API-key authentication is unchanged; authentication, protocol, and transport headers cannot be overridden. Values remain encrypted in stored configuration and omitted from public configuration views. This does not implement activity billing.

Validation

• Shared validation, public API/schema, model-configuration, execution and adapter tests; generated OpenAPI/TypeScript checks.
• Pinned native clients against local synthetic model endpoints: multi-turn, retry, tool continuation and restart/resume captures; Claude tool visibility explicitly tested.
• Independent review of both Core and Agents integration.

No deployment or live external-model acceptance is claimed. Existing unrelated MiniMax subagent and macOS Claude filename failures were reproduced on the unmodified baseline. Runtime and Core must both be upgraded before enabling this in Agents.