[P1] Add Chatbot Conversation History / Save Past Threads

[flexykrn]

Bug Description

When users refresh the page or navigate to a different documentation section, their chatbot conversation is lost. There is no way to reference previous answers, continue a conversation, or review past interactions. This forces users to re-ask questions and re-explain context, creating significant friction.

Competitor Benchmark

• ChatGPT: Full conversation history sidebar, searchable
• Claude: Project-based threads with persistence
• Perplexity: Thread library with shareable links
• Intercom: Conversation history tied to user profile
• Crisp: Chat history across sessions

Affected Users

• Users researching across multiple pages
• Developers working through multi-step tutorials
• Users who need to reference previous answers
• Anyone who accidentally refreshes the page

Blast Radius

• Primary: All chatbot users in multi-session workflows
• Secondary: Complex queries requiring follow-up questions
• Impact: Reduced repetition, better UX, higher retention

Root Cause Analysis

Chatbot state is stored in memory (JavaScript variable) only. No localStorage, no backend persistence, no session restoration. Page refresh = total loss.

Proposed Solution

Option A: localStorage Persistence (Recommended for immediate fix)

Store conversations in browser localStorage:

// Save on each message
localStorage.setItem('xdc_chat_history', JSON.stringify(messages));

// Restore on page load
const history = JSON.parse(localStorage.getItem('xdc_chat_history'));

Option B: Session-Based Threads

Group conversations by session with timestamps:

• 'Today, 2:30 PM' - 5 messages
• 'Yesterday, 10:15 AM' - 12 messages
• Show list of recent threads

Additional Fixes Required

• localStorage serialization/deserialization
• Thread list UI (collapsible sidebar or dropdown)
• 'New conversation' button
• Clear history option
• Storage limit (e.g., last 10 conversations, max 100KB)
• Privacy notice about local storage

Acceptance Criteria

• Conversations persist after page refresh
• User can view list of past conversations
• User can click a past conversation to resume
• 'New conversation' starts fresh thread
• 'Clear history' removes all stored data
• Works across different doc pages (same domain)
• Mobile: thread list in modal or bottom sheet
• Graceful fallback if localStorage disabled

Raw Context

A developer asking 'How do I deploy a subnet?' gets a 10-step answer. They navigate to a code example page, come back, and the answer is gone. They must re-ask and wait for the same response. This is frustrating and wastes time.