[BUG] VS Code Session History panel ignores hook-set sessionTitle (custom-title present in transcript) — regression in 2.1.170

Summary

The VS Code extension's Session History panel (Local tab) ignores session titles set by a SessionStart hook via hookSpecificOutput.sessionTitle. The hook fires correctly and a custom-title record is written into the session transcript (.jsonl), but the panel displays the raw first user message (in my case, a file path) instead of the custom title.

This is a regression: the same hook-set titles were displayed in the Session History panel before the extension auto-updated to 2.1.170 (installed 2026-06-10 08:17 local time). After the update, the panel stopped reading them.

Environment

• Claude Code CLI: 2.1.170
• VS Code extension: anthropic.claude-code-2.1.170-linux-x64 (remote Linux, vscode-server)
• OS: Debian-based LXC (Proxmox), connected via VS Code Remote

Repro

1. Register a SessionStart hook (matcher: startup) that outputs:

``json
{
"hookSpecificOutput": {
"hookEventName": "SessionStart",
"sessionTitle": "10.06.2026 22-04 Session"
}
}
``

1. Start a new session from the VS Code extension; first message = a file path (e.g. /root/AI/projects/.../NEXT_SESSION.md).
2. Open Session History (Local tab).

Expected

The session is listed as 10.06.2026 22-04 Session (the hook-set title), as it was before 2.1.170.

Actual

The session is listed as the raw first message (the file path). The hook did run — the transcript contains the title record:

{"type":"custom-title","customTitle":"10.06.2026 22-04 Сессия","sessionId":"80baad5b-462b-492a-bd84-d1e7a5a87c4e"}

(Verified in ~/.claude/projects/<encoded-cwd>/<uuid>.jsonl for two sessions started today — both have correct custom-title records, both are displayed by their first message instead.)

Notes

• Docs state sessionTitle is supported for SessionStart (added in v2.1.152) and equivalent to /rename.
• The VS Code docs say "New sessions receive AI-generated titles based on your first message" — if the panel now always prefers the AI/first-message title, that silently breaks the documented hook feature for VS Code users.
• Possibly related: #55951 (Desktop sidebar ignores UserPromptSubmit sessionTitle), #32150 (titles revert to last-prompt text overriding custom-title), #65010 (extension overwrites manually-renamed titles).