/resume reports 'No conversations found' in git submodule directories (sessions-index.json not created)

Description

/resume reports "No conversations found to resume" immediately after exiting a conversation. The explicit claude --resume <session-id> command works fine using the ID shown at session exit.

Environment

• Claude Code v2.1.89
• macOS (Darwin 25.4.0)
• Working directory is a git submodule inside a parent monorepo

Steps to Reproduce

1. cd into a git submodule directory (a repo nested inside a parent repo)
2. Start a Claude Code session and do some work
3. Exit the session — note the "Resume this session with: claude --resume <id>" message
4. Immediately launch claude again from the same directory
5. Type /resume

Expected: The previous conversation is listed and resumable.
Actual: "No conversations found to resume"

Root Cause

Session JSONL files are written correctly to the project directory under ~/.claude/projects/:

-rw------- 393637 Apr  3 06:44 711e22af-....jsonl   # previous session
-rw------- 195527 Apr  3 06:47 b13f7ea7-....jsonl   # current session

However, sessions-index.json does not exist in that project directory. /resume appears to rely on this index to discover sessions, while --resume <id> reads the JSONL directly by ID, bypassing the index.

Other project directories under ~/.claude/projects/ (non-submodule repos) do have a sessions-index.json, though at least one was observed to be empty ({"version":1,"entries":[]}).

Prior Reports

This is a regression of previously reported issues that were auto-closed:

• #29256 — exact same scenario (submodule + /resume fails), closed for inactivity
• #27676 — same root cause (git submodule + worktree path mismatch), incorrectly auto-closed as duplicate of unrelated Windows issue #24515

Also related to the broader sessions-index.json not being populated:

• #22205, #24729, #25032, #19995

Workaround

Use the explicit resume command shown at session exit:

claude --resume <session-id>