@tanstack/ai-claude-code: stream tool-call arguments (forward input_json_delta → TOOL_CALL_ARGS)

[ozolcar]

Summary

@tanstack/ai-claude-code doesn't stream tool-call arguments. Its stream translator handles only text_delta and thinking_delta, so a tool call surfaces only once it's complete. This is the sole blocker for streaming structured output while using the Claude Code harness.

Request

Forward the Agent SDK's partial tool-input events as AG-UI TOOL_CALL_ARGS deltas — the same way @tanstack/ai-anthropic / @tanstack/ai-openai already stream tool args.

Details

@tanstack/ai-claude-code (0.2.0) is built on @anthropic-ai/claude-agent-sdk. With includePartialMessages: true, the SDK already emits partial tool input:

content_block_delta → delta.type: "input_json_delta"   (partial_json fragments)

But the adapter's stream/translate.js has cases only for text_delta and thinking_delta — there is no input_json_delta case, so those fragments are dropped and tool calls arrive whole. (structuredOutput() also throws "not yet supported — use a model adapter".)

Why it matters

Routing structured data through a tool call is the only streaming path on the Claude Code harness (subscription auth + native file tools). Today that metadata paints atomically at run end; forwarding input_json_delta would let it stream token-by-token. It would also be the foundation for a real supportsCombinedToolsAndSchema / structuredOutputStream on this adapter (wire outputSchema through a forced tool call and stream its args) — bringing the harness adapter to parity with the model adapters for streaming structured output.

Environment

• @tanstack/ai-claude-code 0.2.0 (latest; only 0.1.0 / 0.2.0 published)
• @tanstack/ai 0.39.x