Workflow tool: one invocation spawned 46 Opus subagents (~3M tokens) with no cost confirmation

Description

One Workflow tool invocation (run wf_abf6120f-5f6, a code-review orchestration) spawned 46 subagents consuming ~2,986,845 subagent tokens / 791 tool uses in ~18 minutes, for a task whose output was ultimately discarded.

All 46 subagents ran on Opus 4.8: subagents inherit the main-loop model by default, and the Workflow tool guidance instructs the model to omit per-agent overrides ("Default to omitting it"). Combined with ultracode mode ("token cost is not a constraint"), a single user prompt produced ~3M Opus tokens with:

• no cost warning,
• no projected-agent-count confirmation before launch,
• no automatic downgrade of sweep/verification subagents to cheaper models.

Expected behavior

A cost/scale confirmation before a 40+ agent fan-out, or cheaper default models (Haiku/Sonnet) for sweep and verification subagents, or at minimum a projected token estimate surfaced to the user before the run starts.

Environment

• Claude Code CLI on macOS (darwin 25.5.0)
• Session model: claude-opus-4-8 (all subagents inherited it)
• Effort set to ultracode via /effort
• Workflow run: 46 agents, 2,986,845 subagent tokens, 791 tool uses, 1,064,880 ms

Filed from the affected session on behalf of the account owner.