Summary

Follow-up to #13466 / #13744.

The same pattern that caused Bedrock ValidationException: messages: text content blocks must be non-empty in @ai-sdk/openai-compatible and @ai-sdk/openai also exists in four other provider packages. When an assistant message contains only tool-call parts (no text), the converter emits content: "", which Bedrock-backed endpoints reject.

Affected files

• packages/xai/src/convert-to-xai-chat-messages.ts:111
• packages/deepseek/src/chat/convert-to-deepseek-chat-messages.ts:126
• packages/groq/src/convert-to-groq-chat-messages.ts:105
• packages/mistral/src/convert-to-mistral-chat-messages.ts:122

Each has the same shape:

messages.push({
  role: 'assistant',
  content: text, // <-- empty string when only tool-calls are present
  tool_calls: toolCalls.length > 0 ? toolCalls : undefined,
});

Proposed fix

Apply the same change as #13744:

content: text || null,

This matches the OpenAI spec (content is nullable when tool_calls is present) and what official OpenAI SDKs send.

Scope

• Update each converter.
• Update corresponding unit tests to expect null for tool-only assistant messages.
• Add a patch changeset covering the four packages.

Note: Mistral uses its own API shape; verify Mistral's spec accepts null before applying there. The other three (xai, deepseek, groq) are OpenAI-compatible.