Subagent (Agent tool, isolation: worktree) completed with 443,914 tokens consumed and zero tool calls

Summary: A subagent launched via the Agent tool (fork/general-purpose type, isolation: "worktree") terminated after 11.8 seconds having made zero tool calls, while consuming 443,914 tokens. No work was produced: no worktree was created, no files were read or written, no commands were run.

Context: Claude Code session, three subagents launched in parallel via the Agent tool with isolation: "worktree" for independent development tasks on the same repo. Two of the three failed via a progress-stall timeout after ~600s (understandable — resource contention from concurrent pnpm install runs in separate worktrees). The third subagent — the one in question — never began its task at all: no git worktree was created, no file was read, no command was executed. It terminated immediately, reporting only "No response requested," after apparently processing the full inherited parent-conversation context without acting on it.

Impact: Token consumption with no corresponding work product, on a task that then had to be relaunched twice before it completed successfully.

Expected behavior: A subagent that performs zero tool calls should not consume a large fraction of a million tokens — token cost should be roughly proportional to actual work performed (context processing + tool use), not incurred for doing nothing.

Request: Investigation into why this subagent spawn consumed input/context tokens without taking any action, and a billing adjustment for this specific consumption, since 0 tool calls clearly indicates no useful work was performed.

I'm happy to provide additional session details if needed, though I don't have a session/request ID captured for this specific spawn.