### Check for existing issues

- [x] I have searched the existing issues and checked that my issue is not a duplicate.

### What happened?

## Check for existing issues

Related, but I do not think these are the same bug:

- #26167: bridged Anthropic `/v1/responses` multi-turn tool calls fail with `previous_response_id` session reconstruction. This looks adjacent, but the failure here is live in-memory history being replayed into native OpenAI Responses. - #16215: OpenAI Responses API support for the Anthropic experimental adapter. - #14991: OpenAI rejects invalid Responses item ID namespaces for reasoning items. - #26927 and #26012: provider-specific thinking/reasoning cleanup, not message ID normalization.

## What happened?

We hit this in an agent workflow that switches providers inside one runner execution:

```text Claude via LiteLLM -> OpenAI Responses model ```

The previous assistant message from the Claude/LiteLLM side is kept in memory and then sent to the OpenAI Responses-backed agent. That assistant item still has a Chat Completions-style ID:

```text chatcmpl-dfa2da3a-1586-4ff7-b64e-f59c692a5d11 ```

OpenAI Responses rejects the request:

```text Invalid 'input[1].id…