Tool calls intermittently emitted as plain text (stray `court` + legacy `<invoke>` XML) instead of executing — hangs the session

Summary

Intermittently, instead of issuing a real tool call, Claude Code emits the tool call as plain text in the assistant message: a stray token court followed by the legacy XML-style <invoke name="..."> / <parameter name="..."> markup. When this happens the tool does not execute and the turn hangs (no tool result is ever returned). Re-emitting the same call cleanly almost always works.

Environment

• Claude Code: 2.1.183
• Model: Opus 4.8 (claude-opus-4-8)
• OS: Linux on WSL2 (Windows) — 6.6.87.2-microsoft-standard-WSL2, x86_64
• Node: v20.19.5
• MCP: Playwright MCP (the affected calls were MCP tools)

What happens

The assistant output contains literal text like:

court
<invoke name="mcp__playwright__browser_navigate">
<parameter name="url">https://example.com/...</parameter>
</invoke>

instead of an actual function call. No tool runs and the session appears frozen until the user points it out, at which point re-emitting the call works.

Affected tools (observed)

• mcp__playwright__browser_navigate
• mcp__playwright__browser_evaluate

Both are MCP tools. It happened 8+ times across a single long session, more often on browser_navigate.

Frequency / pattern

• Intermittent, non-deterministic. The same call re-emitted immediately usually executes fine.
• Seemed more likely on longer browser_evaluate blocks and on navigation calls.
• The leading stray token was consistently court.

Expected behavior

Tool calls should always be emitted in the proper function-call format and execute; they should never be rendered as literal <invoke>/<parameter> text.

Workarounds found

• Re-emitting the identical call immediately usually succeeds.
• For navigation, using browser_evaluate with window.location.href = '<url>' was more reliable than browser_navigate (though the leak still occasionally appeared on evaluate too).

Impact

Repeated hangs in long agentic / browser-automation sessions, requiring manual user intervention to recover.