claude-code - 💡(How to fix) Fix Opus 4.8 (1M): tool-call emission repeatedly malformed (stray 'court' token + dropped namespace), renders as text and does not execute, no self-correction across ~10 retries

Environment: Claude Code CLI, model Opus 4.8 (1M context, claude-opus-4-8).

Symptom: When opening a tool call, the model intermittently emits a malformed invocation — a stray literal token 'court' prepended and the tool-call namespace prefix dropped — so the block renders as plain text and the tool never executes (no tool_result returned). The model then continued as if the call had succeeded.

Severity: It recurred ~10 consecutive times within one session. Explicit user feedback ('that printed as text, nothing ran') did not trigger self-diagnosis; the model re-emitted the same malformed pattern, apparently conditioning on its own prior malformed output as the template. It persisted across a session restart.

Expected: malformed/again should be detected (missing tool_result == call did not run) and corrected by matching a known-good prior invocation.

Repro: not deterministic; occurred mid-session during repeated Bash/Edit calls. Happy to provide a session transcript privately.