[BUG] Sessions started with TeamCreate (e.g. custom skills) permanently hidden from --resume

Bug Description

Sessions that use TeamCreate (e.g., a custom skill that spawns a team of review agents) have two resume visibility bugs:

1. The main session becomes permanently invisible to --resume and /resume, even after the team is deleted with TeamDelete
2. Subagent sessions leak into the resume picker as visible entries that users should never see

Environment

• Claude Code version: 2.1.81
• OS: Fedora Linux 42 (kernel 6.19.6)
• Shell: zsh

Root Cause (from reverse-engineering v2.1.81 binary)

Bug 1: teamName persists on every message, blocking resume

teamName is written to every JSONL record during the team phase, not just the init record:

line 1:   (init — no teamName)
line 12:  teamName=audit  type=user
line 13:  teamName=audit  type=assistant
...
line 152: teamName=audit  type=assistant

The resume picker filters on this:

// Decompiled from v2.1.81 binary
if (L.teamName) {
    return v(`Session ${H.sessionId} filtered from /resume: teamName=${L.teamName}`), null;
}

TeamDelete removes the team directory but does NOT clear teamName from the session JSONL, making the session permanently invisible.

Bug 2: Subprocess teammates lack isSidechain flag

When teammateMode is subprocess, team agents are spawned as independent sessions with their own JSONL files at the project root. These have agentName set (e.g., "bug-reviewer", "validator-legal") but isSidechain: false.

The resume picker only filters on isSidechain and teamName — not agentName. So once bug 1 is fixed (teamName cleared), all subagent sessions become visible in the resume list, cluttering it with internal agent sessions.

Reproduction

# 1. Start claude and invoke a skill that calls TeamCreate
claude
> /my-skill   # e.g. a custom skill that creates a team of parallel review agents

# 2. Skill completes, team is deleted, exit claude

# 3. Try to resume
claude --resume        # main session not listed
claude --resume <id>   # also fails

# 4. Verify: teamName on every message in the session
python3 -c "
import json
with open('<session>.jsonl') as f:
    for i, line in enumerate(f):
        d = json.loads(line)
        if d.get('teamName'):
            print(f'line {i}: teamName={d[\"teamName\"]}')
            if i > 5: break
"

Impact

• Main sessions using TeamCreate become permanently unresumable
• TeamDelete cleans up the team directory but does NOT clear teamName from the session
• Subprocess teammate sessions pollute the resume picker (no isSidechain flag)
• Affects anyone building custom skills/workflows that use agent teams

Suggested Fix

1. For bug 1: Change the resume filter to only exclude sessions where the team is still active (check if ~/.claude/teams/{teamName}/ exists), rather than unconditionally filtering on teamName presence. Alternatively, have TeamDelete strip teamName from all records in the session JSONL.

1. For bug 2: Set isSidechain: true automatically when creating subprocess teammate sessions, or add agentName to the resume picker's filter list.

Related Issues

• #26123 — /resume broken since v2.1.31 (identified similar picker filtering bugs)