[BUG] Conversation .jsonl not written to disk on Windows 11 — v2.1.70 regression

Describe the bug

After updating to v2.1.70 (released 2026-03-06), conversation data is no longer persisted to disk. Session directories are created under ~/.claude/projects/<project>/<session-id>/ but contain no main conversation .jsonl file — only tool-results/ and subagents/ subdirectories.

Both --resume <session-id> and --continue fail:

$ claude --continue
No conversation found to continue

$ claude --resume 8c47cb6e-2586-485c-b4c3-449ade62e27a
No conversation found with session ID: 8c47cb6e-2586-485c-b4c3-449ade62e27a

This is a regression. I am a heavy Claude Code user and --resume / --continue have been working fine until today's update. This is not the long-standing issue from v2.1.31 (#26123) — that bug never affected me.

Evidence

Session directory exists but has no conversation transcript:

$ ls -la ~/.claude/projects/D--python-optiflightpoc/8c47cb6e-2586-485c-b4c3-449ade62e27a/
total 12
drwxr-xr-x 1 mike 197121 0 Mar  6 21:07 .
drwxr-xr-x 1 mike 197121 0 Mar  6 21:07 ..
drwxr-xr-x 1 mike 197121 0 Mar  6 21:07 tool-results

No .session_index file exists either. Only subagent .jsonl files are present across all session directories — zero main conversation .jsonl files.

Platform

• OS: Windows 11 (native, not WSL)
• Shell: MSYS2 / Git Bash
• Claude Code: v2.1.70
• Previous version: was working correctly

Steps to reproduce

1. Update to v2.1.70 on Windows 11
2. Start a new claude session, have a conversation with tool use
3. Exit the session
4. Run claude --continue → "No conversation found to continue"
5. Run claude --resume <session-id> → "No conversation found with session ID: ..."
6. Inspect ~/.claude/projects/<project>/<session-id>/ — directory exists but has no .jsonl

Expected behavior

Main conversation .jsonl should be written to the session directory, and --resume / --continue should work as they did prior to v2.1.70.