VS Code extension: a single prompt submission was dispatched into 3 separate sessions (duplicated token usage)

Environment

• Claude Code VS Code extension (entrypoint: "claude-vscode")
• Windows 11

What happened

A single message I sent from the VS Code extension was processed as three independent sessions running in parallel, each executing the full task from scratch. All three sessions consumed a full agentic run (hundreds of assistant turns each), roughly tripling token/quota usage for what was intended as one request.

Evidence (from local ~/.claude/projects/<project>/*.jsonl transcripts)

Three session files were created within the same second:

• Session A: 3cb5e67c-9a1d-4ccd-abca-81e1efb97fcf
• Session B: 99a4d3be-9f1c-471d-a042-ae7578c82994
• Session C: 454c035f-6482-4afa-a1ee-d6d120e4f092

Key correlating identifiers that are identical across sessions A and C (indicating they originated from the same user submission, not two separate messages I typed):

• promptId: 127520aa-e797-4ee8-b68b-7502f86c1e3d — identical in both session A and session C's first user message
• User-message timestamp: 2026-09-15T09:02:22.868Z — identical to the millisecond in both
• User-message content length: identical (48702 chars) in both
• cwd identical in both
• SessionStart hook toolUseID: 0ec5dd30-2a2b-4e60-8f23-3593939dc83d — identical across all three sessions' first log line

Session B additionally logged an explicit queue race right at the same moment:

{"type":"queue-operation","operation":"enqueue","timestamp":"2026-09-15T09:02:22.817Z","sessionId":"99a4d3be-..."}
{"type":"queue-operation","operation":"dequeue","timestamp":"2026-09-15T09:02:22.819Z","sessionId":"99a4d3be-..."}

(2ms apart), suggesting the same queued operation got picked up/processed into a distinct session rather than being deduplicated or routed to the single active session.

Despite the identical origin, the three sessions have zero overlapping message UUIDs afterward — each proceeded completely independently, each producing several hundred unique messages (927 / 678 / 577 unique message UUIDs respectively) over the next ~1-4 hours, i.e. three full independent agentic runs of what should have been one conversation.

Impact

This tripled token/session-quota consumption for a single user request — in my case this one duplication alone accounted for roughly a third of my 5-hour rate limit window.

Ask

Could you look into the session dispatch/queue logic in the VS Code extension for a race condition where one submitted prompt (same promptId) gets delivered to multiple newly-created sessions instead of exactly one? Happy to share the raw JSONL lines (sanitized) if useful — I've kept the actual task content out of this report since it involved private repository work, but the structural/metadata evidence above (uuids, timestamps, queue trace) should be reproducible-looking without needing that content.