DatabricksAdapter yields text content during tool-calling rounds, causing response duplication

[cuchaga]

DatabricksAdapter yields text content during tool-calling rounds, causing response duplication

Problem

When using DatabricksAdapter with Claude models via Databricks Model Serving (OpenAI-compatible endpoint), the model produces substantial text content alongside tool calls in the same response turn. The adapter's streamCompletion() method yields all delta.content text as message_delta events regardless of whether the same response also contains tool calls.

In a multi-step ReAct loop, this causes the model's intermediate text (which often includes the full answer) to be emitted and displayed to the user on every tool-calling turn — resulting in the same answer appearing 3-4× in the final output.

Root Cause Analysis

Claude's native API uses a trained-in tool-use system prompt that shapes the model to produce brief commentary before tool_use blocks. The Databricks OpenAI-compatible translation layer does not include this trained-in prompt, so Claude produces more verbose text during tool-calling rounds.

The adapter loop (run() method, line ~196) correctly breaks when no tool calls are present, but during tool-calling rounds, streamCompletion() yields ALL delta.content as message_delta events — there's no mechanism to suppress or buffer text that arrives in a turn that also contains tool calls.

Expected Behavior

Text content from tool-calling rounds should either:

1. Be suppressed (not yielded as message_delta) when the same response also contains tool_calls
2. Be buffered until streamCompletion returns, and only yielded if no tool calls were detected
3. Be marked with metadata so consumers can distinguish intermediate text from final-answer text

Current Workaround

We added:

• A system prompt instruction telling the model to only write brief status notes during tool-calling turns
• Client-side text buffering in the SSE transport layer that discards accumulated text when a function_call event arrives in the same round

Environment

• AppKit version: 0.38.1
• Model: databricks-claude-opus-4-6 via Model Serving
• Adapter: DatabricksAdapter.fromServingEndpoint()

Reproduction

1. Create an agent with maxSteps: 10 and multiple tools (e.g., describeTable, executeSql)
2. Ask a question that triggers 3+ tool calls
3. Observe that the assistant's text response contains the full answer repeated once per tool-calling round