Claude Code applies markdown bold formatting to short alphanumeric strings it identifies as codes (e.g., device auth codes like ABC-123). When a skill or MCP tool displays a verification URL containing the device code inline, Claude Code may render it as ABC-123, which corrupts the URL for copy-paste. Affects any MCP tool or CLI skill surfacing device auth codes inline with URLs (OAuth device flow, GoodTurn auth_device_start, similar patterns).
Display the device code and the verification URL as separate elements in the tool response so bold formatting of the code does not corrupt the URL. Server-side: strip non-alphanumeric characters from device codes before embedding in URLs. Do not rely on skill or prompt instructions to suppress Claude Code formatting — it applies to the rendered message before the skill can intervene.