VS Code extension: conversation that entered a git worktree restores as an empty conversation after VS Code restart (restored tab loses its sessionID)

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?

Close VS Code while a conversation that has entered a git worktree is open/working. On relaunch, VS Code restores the conversation tab, but the tab comes back as a brand-new empty conversation — no history, generic "Claude Code" title, no error. The original transcript is intact on disk the whole time, in the worktree-keyed project directory. Conversations that stayed in the main checkout restore fine in the same relaunch.

The failure is in the extension's tab-restore path, not the CLI resume path: the persisted webview state for the affected tab has lost its sessionID, so on restore the webview sends launch_claude with no resume parameter and the extension spawns a fresh session. (The CLI itself resumes worktree sessions by ID without problems — a third worktree conversation in the same relaunch was resumed by ID and recovered fully, see "Counter-example" below.)

Because the workspace's "Past conversations" list is keyed to the workspace folder's project dir, the orphaned worktree conversation doesn't appear there either (see #34437), so from inside the UI the conversation looks permanently lost.

Evidence (from an occurrence on 2026-07-30 → 2026-07-31)

Three conversations were in git worktrees when VS Code was closed at ~00:07 local:

| Conversation (worktree) | Session ID | Outcome on relaunch |
|---|---|---|
| contracts-section-spec | 9719e32b-… | restored empty (no resume sent) |
| iot-commands-arm-signatures | 3acda470-… | restored empty (no resume sent) |
| plan200-wave5 | e8529909-… | resumed correctly by ID |

All main-checkout conversations (6+) resumed correctly.

1. Transcripts intact on disk — the "lost" conversations still exist, sizeable, last written at VS Code close time (00:07):

~/.claude/projects/…-Milbank-Platform--claude-worktrees-contracts-section-spec/
    9719e32b-….jsonl   432 KB   mtime Jul 31 00:07  (ends with a "last-prompt" record)
~/.claude/projects/…-Milbank-Platform--claude-worktrees-iot-commands-arm-signatures/
    3acda470-….jsonl   1.7 MB   mtime Jul 31 00:07

No duplicate/empty .jsonl with the same IDs was created anywhere — this is purely a lost-reference bug, not transcript corruption.

2. Healthy tabs persist their session ID in the workspace state.vscdb (webview serializer state):

"extensionId":"Anthropic.claude-code","state":"{\"isFullEditor\":false,\"sessionID\":\"fb8463b2-…\"}"

Grepping the workspace's state.vscdb finds the session IDs of every conversation that restored correctly — and zero occurrences of 9719e32b or 3acda470. The affected tabs' persisted webview state had lost the sessionID before/at shutdown.

3. Extension log on relaunch (…/logs/20260731T065003/window1/exthost/Anthropic.claude-code/Claude VSCode.log) — restored tabs that kept their state relaunch with resume:

06:50:11 Received message from webview: {"type":"launch_claude","channelId":"…","cwd":"c:\\…\\Milbank Platform","resume":"bbcdaab7-…", …}
06:52:10 … "resume":"d82f6bc4-…" …
06:55:14 … "resume":"e8529909-…" …   ← worktree session, resumed fine

…while exactly two launches (matching the two lost worktree conversations) arrive with no resume at all, preceded by rename_tab back to the generic default title:

06:51:46 {"type":"request", …"type":"rename_tab","title":"Claude Code", …}
06:51:46 {"type":"launch_claude","channelId":"1x24b2djycnj","cwd":"c:\\…\\Milbank Platform","permissionMode":"auto","thinkingLevel":"default_on"}   ← no resume
06:51:59 {"type":"launch_claude","channelId":"mkw1sj9lblj", …}                                                                                      ← no resume

Neither lost session ID appears anywhere in the relaunch log as a resume target.

Counter-example / narrowing observation

Being in a worktree does not break restore by itself: e8529909 (worktree plan200-wave5, a 20 MB transcript dating from Jul 15 that has survived many restarts) resumed correctly in the same relaunch. The observable difference: the two conversations that lost their tab state had been idle for ~30–60 minutes before VS Code was closed (last transcript activity 23:07 / 23:34 local; close at 00:07), while the surviving worktree conversation was active in the final minutes before close. This suggests the webview's persisted state (or the extension's session bookkeeping for the tab) is cleared or overwritten at some point after the session goes idle in a worktree, so whatever is on disk at shutdown no longer contains the sessionID.

What Should Happen?

Any of:

1. The restored tab keeps its sessionID and resumes the conversation (the CLI-side resume demonstrably works, even across worktree-keyed project dirs); or
2. If the tab state is unusable, the extension recovers the mapping some other way (e.g. its own tab→session store, or matching live/most-recent sessions for the workspace incl. worktree-keyed project dirs); or
3. At minimum, the tab restores to a "couldn't restore this conversation — find it in past conversations" state instead of silently opening a brand-new empty conversation, and worktree-session transcripts are findable from the workspace's Past Conversations list.

Actual

Tab silently restores as a fresh empty conversation. The original conversation is invisible in the workspace's Past Conversations (worktree-keyed project dir), so to the user it reads as total loss of a long-running task's history.

Error Messages/Logs

Steps to Reproduce

1. In the VS Code extension, open a conversation in a git repo workspace and have it EnterWorktree (transcript relocates to ~/.claude/projects/<munged-repo>--claude-worktrees-<name>/).
2. Let the conversation go idle for a while (the failures correlate with ≥ ~30 min idle; a busy-until-close worktree conversation survived).
3. Close the VS Code window; reopen the same workspace.
4. The restored tab shows an empty "Claude Code" conversation; extension log shows launch_claude without resume; workspace state.vscdb contains no webview state with that sessionID.

Claude Model

Opus

Is this a regression?

I don't know

Last Working Version

_No response_

Claude Code Version

v2.1.220

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

_No response_

total launch_claude : 10
with resume         : 2
without resume      : 8

13:17:45  "cwd":"<repo>",  "resume":"1e5ed476-…"
13:17:50  "cwd":"<repo>",  "resume":"208b4bfc-…"

sessionID\":\"01cabb89-…\"   (×5 occurrences)
sessionID\":\"b2b8a2ad-…\"   (×4)
sessionID\":\"790354b9-…\"   (×4)
sessionID\":\"4a7da477-…\"   (×3)
sessionID\":\"7bc8dde8-…\"   (×2)
sessionID\":\"52e4c21f-…\"   (×1)

case "/open": {
  let session = params.get("session"), prompt = params.get("prompt");
  vscode.commands.executeCommand("claude-vscode.primaryEditor.open", session, prompt);
  return;
}

code --open-url "vscode://anthropic.claude-code/open?session=<worktree-session-id>"

14:39:09  {"type":"launch_claude","channelId":"uf3w273jwkk","cwd":"<repo>","permissionMode":"plan","thinkingLevel":"default_on"}

code <repo>/.claude/worktrees/<name>
# wait for the window to register, then
code --open-url "vscode://anthropic.claude-code/open?session=<worktree-session-id>"

14:39:57  {"type":"launch_claude","channelId":"4x2c3iht5fk",
           "cwd":"<repo>/.claude/worktrees/ops-monitor-selfcheck-fix",
           "resume":"7bc8dde8-…","permissionMode":"plan"}
14:39:57  Spawning Claude with SDK query function - cwd: <repo>/.claude/worktrees/ops-monitor-selfcheck-fix