fix(stream-chat): fixed chat streaming

[aadamgough]

Summary

The chat streaming had a few bugs:

1. The function result would append at the top of the entire streaming output despite it being the first block in execution order
2. Even when I removed some of the chat outputs (e.g. I have two agent outputs and I remove one of them), the old output would still get streamed
3. The router system prompt would get appended to the streaming

Added logic to fix the order of streaming to be 1 to 1 with workflow block execution, got rid of router system prompt getting added to chat, and got rid of stale block outputs that were still getting streamed.

Type of Change

• Bug fix

Testing

Tested with workflow child blocks, function blocks with different outputs, multiple agent block outputs with multiple function block outputs, and adding and removing outputs to update the chat.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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[greptile-apps]

Greptile Summary

This PR fixes three critical chat streaming bugs by implementing a comprehensive overhaul of the streaming architecture. The changes address: 1) function results appearing at the top of streaming output despite being first in execution order, 2) old outputs persisting when chat outputs are removed from selection, and 3) router system prompts leaking into user-facing chat streams.

The solution involves multiple coordinated changes across the streaming pipeline. The frontend (use-chat-streaming.ts) switches from single-message accumulation to per-block message tracking, creating individual streaming messages for each block with suppressCopy flags, followed by a consolidated message with hideContent for copy functionality. The executor (index.ts) adds stream order hints by emitting zero-length start events for selected blocks, establishing proper execution order and implementing output filtering based on selectedOutputIds. The agent handler (agent-handler.ts) enriches StreamingExecution objects with block metadata (blockId, blockType, blockName) to enable proper stream routing. The chat utils (utils.ts) adds router block filtering, log reordering based on streaming sequence, and enhanced function block result handling. The router handler (router-handler.ts) returns empty content instead of exposing internal prompts. Finally, the message component (message.tsx) adds UI controls for the new streaming flags.

This architecture separates streaming display concerns from copy functionality while maintaining execution order consistency between the streaming experience and final aggregated results. The changes ensure that only user-relevant content streams while hiding implementation details like routing decisions.

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