[BUG] [Critical Data Loss] VSCode extension does not persist main conversation transcripts to disk

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The Claude Code VSCode extension stores main conversation transcripts only in memory, not on disk. Extension upgrades wipe this memory, causing complete and permanent data loss of all conversation history. Only subagent (Task tool) conversations are persisted to disk.

What Should Happen?

• Main conversation transcripts should be persisted to disk in session folders
• Expected file: <session-uuid>/main.jsonl containing full conversation history
• Conversations should survive VSCode restarts and extension upgrades
• Similar to how the CLI version persists conversations

Error Messages/Logs

Steps to Reproduce

1. Install Claude Code VSCode extension (any version)
2. Have conversations with Claude
3. Note that session folders only contain tool-results/ and subagents/
4. Restart VSCode → conversations appear to persist (loaded from memory)
5. Upgrade extension to new version
6. All conversation history permanently lost

Claude Model

Opus

Is this a regression?

Yes, this worked in a previous version

Last Working Version

2.1.3

Claude Code Version

2.1.3

Platform

Anthropic API

Operating System

macOS

Terminal/Shell

VS Code integrated terminal

Additional Information

VSCode Extension Does Not Persist Main Conversation Transcripts to Disk

Summary

The Claude Code VSCode extension stores main conversation transcripts only in memory, not on disk. Extension upgrades wipe this memory, causing complete and permanent data loss of all conversation history. Only subagent (Task tool) conversations are persisted to disk.

Environment

• OS: Windows 10/11
• VSCode Version: Latest
• Claude Code Extension Versions Tested:
• v2.1.3 (current, rolled back from 2.1.30)
• v2.1.20 (previous working version)
• v2.1.30 (triggered the data loss)
• Project Path: e:\repo\ai-assistant-assem-struct
• Session Storage: C:\Users\yiv\.claude\projects\e--repo-ai-assistant-assem-struct\

Issue Description

What Happened

1. Extension auto-updated from v2.1.20 → v2.1.30
2. After update, all previous conversation history disappeared
3. Conversation titles changed from actual titles to generic "Claude Code"
4. Rolled back to v2.1.3 - conversations still missing
5. Investigation revealed conversations were never written to disk

Expected Behavior

• Main conversation transcripts should be persisted to disk in session folders
• Expected file: <session-uuid>/main.jsonl containing full conversation history
• Conversations should survive VSCode restarts and extension upgrades
• Similar to how the CLI version persists conversations

Actual Behavior

• No main.jsonl files exist in any session folders (30+ sessions checked)
• Only subagents/*.jsonl files exist (with "isSidechain":true)
• Only tool-results/ folders exist
• Main conversations stored in memory only
• Extension upgrade wiped memory → complete data loss

Evidence

1. Session Folder Structure (All 30 Sessions)

C:\Users\yiv\.claude\projects\e--repo-ai-assistant-assem-struct\
├── 199fa9b3-e735-4d03-9e07-c936f994e9c8\  (current session)
│   └── tool-results\
├── 8404b0a2-1a45-400c-abc7-1af52c7f7ca1\  (recent session)
│   └── tool-results\
├── 4cc878ec-c436-410e-8ac0-3f3a2807ca84\  (largest session - 8.4MB)
│   ├── subagents\  (23 files, all with "isSidechain":true)
│   └── tool-results\
└── [27 more sessions - same structure]

Missing in ALL sessions: main.jsonl, conversation.jsonl, or any main transcript file

2. What IS Persisted

A. Subagent Conversations (subagents/*.jsonl):

{
  "parentUuid": null,
  "isSidechain": true,
  "sessionId": "4cc878ec-c436-410e-8ac0-3f3a2807ca84",
  "version": "2.1.20",
  "agentId": "a0a7cc0",
  "type": "user",
  "message": {"role": "user", "content": "Search the codebase..."}
}

B. History Metadata (~/.claude/history.jsonl):

• Only user prompts (display text)
• Timestamps and project paths
• No assistant responses

C. Tool Results (tool-results/*.txt, *.json)

3. System-Wide Search Results

# Search for ANY main conversation files
find /c/Users/yiv/.claude/ -name "main.jsonl" -o -name "conversation.jsonl"
# Result: NO FILES FOUND

# All JSONL files are subagents
find /c/Users/yiv/.claude/projects/e--repo-ai-assistant-assem-struct/ -name "*.jsonl" -type f
# Result: 100% are in subagents/ folders with "isSidechain":true

4. Version Timeline

• Jan 10-29: v2.1.20 - Conversations appeared to persist (memory only)
• Feb 2-3: v2.1.30 - Auto-update caused all conversations to disappear
• Feb 3: Rolled back to v2.1.3 - Data still missing (memory already wiped)

5. Comparison with CLI Version

The CLI version creates proper session structure:

session-uuid/
├── main.jsonl          ← MAIN CONVERSATION (missing in VSCode extension)
├── subagents/
│   └── agent-*.jsonl
└── tool-results/

Impact

Data Loss Scope

• 30 sessions with this project alone
• 8.4MB of subagent data preserved (proves tools were used extensively)
• 146 conversation entries in history.jsonl (only prompts, no responses)
• Months of work documented only in unretrievable memory

Example Lost Conversations

From history.jsonl, I asked about (responses lost):

• MCP tool loading and integration patterns
• Fixing authentication and password handling
• Refactoring agent code to be stateless
• Multi-phase implementation plans
• CRUD agent debugging and error analysis
• Test assertion fixes
• Code review and architectural decisions

Root Cause Analysis

1. Design Flaw: Extension stores main conversations in memory (possibly in VSCode's state.vscdb or similar)
2. No Disk Persistence: Only subagent conversations written to *.jsonl files
3. No Migration Path: Extension upgrades don't migrate/backup in-memory data
4. Inconsistent Architecture: Subagents persisted to disk, main conversations not

Why Rollback Didn't Work

1. v2.1.30 wiped the in-memory conversation store during upgrade
2. Rolling back to v2.1.3 reinstalled old code
3. But the in-memory data was already gone
4. v2.1.3 has nowhere to restore conversations from

Reproduction Steps

1. Install Claude Code VSCode extension (any version)
2. Have conversations with Claude
3. Note that session folders only contain tool-results/ and subagents/
4. Restart VSCode → conversations appear to persist (loaded from memory)
5. Upgrade extension to new version
6. All conversation history permanently lost

Expected Fix

Short-term

1. Persist main conversations to <session-uuid>/main.jsonl (same format as CLI)
2. Write incrementally after each message exchange
3. Load from disk on extension restart

Long-term

1. Implement data migration for extension upgrades
2. Add backup/export functionality
3. Warn users before upgrades that may affect data
4. Document data persistence behavior clearly

Workaround

Use Claude CLI instead of VSCode extension:

npm install -g @anthropic-ai/claude-code
claude

The CLI properly persists all conversations to disk.

Additional Context

Related Observations

1. Developer Mode enabled: Conversation title initially displays correctly, then changes to "Claude Code" after extension loads (indicating failed session restore)

1. No EPERM symlink errors found: These were red herrings - no symlinks exist in session folders

1. All versions affected: v2.1.3, v2.1.20, v2.1.30 all have the same fundamental issue (no main conversation persistence)

Files to Inspect

For Anthropic developers investigating this:

• Extension's session manager code
• Where conversations are stored (likely in-memory or VSCode state DB)
• Subagent persistence logic (this WORKS correctly)
• Why main conversations aren't persisted like subagents

System Info

Working directory: e:\repo\ai-assistant-assem-struct
Platform: win32
Extension path: C:\Users\yiv\.vscode\extensions\anthropic.claude-code-2.1.3-win32-x64
Session storage: C:\Users\yiv\.claude\projects\e--repo-ai-assistant-assem-struct\
History file: C:\Users\yiv\.claude\history.jsonl (70KB, 146 entries)

Request

Please prioritize this as a critical data loss bug. Users are losing valuable conversation history with no warning and no way to recover it. The extension should persist conversations to disk like the CLI version does.

---

Diagnostic Session: 2026-02-03
Affected User: yiv
Data Loss: Months of conversations across 30+ sessions