Problem

A Claude coder could connect to its Band room, receive its dispatch, and then silently do nothing — no crash, no chat message, nothing the Watchdog could catch — so an assigned subtask sat pending forever.

Root cause (confirmed by live repro)

Reproduced with cb run --agent coder-claude_sdk-0 --debug + a human @mention; the debug log showed:

band.adapters.claude_sdk: Sending query to Claude SDK (first_msg=True, parts=3)
band.adapters.claude_sdk: Text: API Error: 400 {"type":"error","error":{"type":"invalid_request_error","message":"\"thinking.type.en...
band.adapters.claude_sdk: Complete - 348ms, 0ドル.0000
band.adapters.claude_sdk: Message ... processed successfully

• The coder ran an Opus model through the stale Claude Code CLI bundled inside an old claude-agent-sdk (bundled 2.1.81 vs system 2.1.179).
• That CLI emits the legacy thinking.type.enabled request shape, which current models reject with a 400 (thinking.type.enabled is not supported for this model. Use thinking.type.adaptive).
• band's claude_sdk adapter swallows the error (logs at DEBUG, 0ドル.0000, marks the message processed) and emits nothing → a healthy-looking zombie.
• It was invisible because preflight only probed a default Sonnet model, never the coder's Opus; Sonnet still accepts the legacy shape, so the auth probe passed.

Changes

• preflight (preflight.py): probe each distinct configured Claude model (not a hardcoded default), threading model through check_claude_auth. New classified patterns for the invalid_request_error / is not supported for this model 400 with remediation pointing at pip install -U claude-agent-sdk. A model that rejects the request shape now fails cb run fast instead of spawning a silent do-nothing agent.
• doctor (doctor.py): new "Bundled Claude CLI" check — warns when the CLI bundled in claude_agent_sdk is older than the system claude (agents use the bundled one), with the same remediation.
• version: bump to 0.1.2.

Deliberately out of scope

Per-turn "zombie" detection at runtime is not included: the 400 is swallowed inside band's adapter, which codeband can't intercept without band SDK hooks (player_claude.py only exposes .adapter to Agent.create()). The per-model preflight prevents this specific failure before agents spawn, which is the higher-leverage fix.

Tests

• preflight: detects the thinking/invalid_request 400; verifies the probe uses the configured model; verifies run_preflight probes each distinct model (Opus and Sonnet).
• doctor: bundled-vs-system version comparison (WARN when older, OK when current, INFO when absent) + version parsing.
• Full suite: 580 passed, ruff clean.

🤖 Generated with Claude Code