[BUG] Streaming "thought" events are mixed directly into visible message content

[vipul674]

Description of the Bug

In frontend/src/components/chat/ChatPanel.tsx, when the streaming endpoint sends a thought event type, the message content is appended directly to the visible chat bubble:

if (event.type === "thought") {
    setCurrentAnswer(prev => prev + `\n[thought] ${event.data}`);
}

When subsequent token events arrive (the actual answer), the thought text becomes permanently embedded within the visible response. The user sees something like:

[thought] The user is asking about the revenue figures from the Q3 report. I need to search the document for relevant data.
Based on the document, the Q3 revenue was $4.2 million...

This is confusing because:

• The thought process should be visually distinct from the final answer
• The [thought] prefix looks like a debug artifact
• Thoughts can be lengthy (paragraphs of reasoning) and clutter the response
• There is no way for the user to hide or expand thoughts

Steps to Reproduce

1. Start a chat session and ask a complex question
2. The streaming response includes intermediate thought steps
3. Observe that thoughts and the final answer are mixed together in the same text bubble
4. The [thought] prefix is displayed to the user as plain text

Expected Behavior

Thought events should be displayed separately from the answer, for example in:

• A collapsible "Show reasoning" section above the answer
• A separate UI element with a subtle style (smaller font, muted color)
• A separate pane or drawer

Affected File

frontend/src/components/chat/ChatPanel.tsx (lines ~329-336)

Suggested Fix

Store thoughts in a separate field/state and render them distinctly:

// Separate states
const [thoughts, setThoughts] = useState<string[]>([]);
const [currentAnswer, setCurrentAnswer] = useState("");

// Handler
if (event.type === "thought") {
    setThoughts(prev => [...prev, event.data]);
} else if (event.type === "token") {
    setCurrentAnswer(prev => prev + event.data);
}

Render thoughts in a collapsible section above the answer.

GSSoC '26

• Yes, I am participating in GirlScript Summer of Code and would like to fix this.

[vipul674]

@param20h I would like to work on this issue under GSSoC 2026. Please assign it to me.

[github-actions]

Hi @vipul674! 👋

Thanks for opening this issue! We are thrilled to have you contribute to PDF-Assistant-RAG for GSSoC 2026.

📌 Before you start:

• Make sure you have read our Contributing Guidelines.
• Wait for a project admin to assign this issue to you before working on it.
• Remember to branch off dev and not main.

Happy Coding! 🚀