2.1.217 regression: every Agent-tool subagent registers an empty desktop-<hostname>-* session on claude.ai, flooding Recents

Summary

Since CLI 2.1.217 (auto-updated from 2.1.215 on 2026-07-22 ~20:52 JST), every background subagent spawned via the Agent tool from the Claude Code Desktop app registers an empty session entry on claude.ai, named desktop-<hostname>-<random-words> (e.g. desktop-p3o8bvn-goofy-summit). Heavy multi-agent workflows create dozens of these per day, flooding the "Recents" list on claude.ai and in the desktop app sidebar.

Environment

• Windows 10 Pro 10.0.19045
• Claude Desktop app 1.24012.1 (MSIX)
• Claude Code CLI 2.1.217 (bundled, %APPDATA%\Claude\claude-code\2.1.217\)
• Max (20x) plan

Repro

1. In a Claude Code Desktop session, have the model spawn background subagents via the Agent tool (general-purpose, model override etc.).
2. Each spawn creates one desktop-<hostname>-<adjective-noun> session on claude.ai with user_message_count: 0.
3. Confirmed via /v1/code/sessions listing: dozens of entries, all empty, timestamps matching each subagent launch.

Expected

Subagent runs should not surface as standalone claude.ai session entries (or should be grouped/hidden under the parent session).

Regression evidence

• On 2.1.215 (same machine, same workflows, 10+ subagents/day for weeks): no such entries.
• App log: [CCD] Resolved CLI identity changed (fallback_version:2.1.215 → required_version:2.1.217) at 2026-07-22 20:54 JST; the flood started immediately after.
• Not related to bridge/remote-tools reconnects (verified: bridge quiet for 3h while entries kept appearing with each subagent launch).

Workaround

Manual bulk-delete of user_message_count === 0 sessions via /v1/code/sessions DELETE from the browser console.