Claude Code connects to external tools through MCP (Model Context Protocol, a standard way for Claude Code to call out to other tools and services). When an MCP tool call fails and its arguments had already been redacted (hidden for privacy), Claude Code can now also withhold the error message itself before it is sent to telemetry, the internal system that records what happened during a session for diagnostics.
This only applies to a specific kind of internal error tied to an MCP tool call whose arguments were flagged for redaction. In that case, the recorded error text is replaced with a redacted placeholder instead of the real message.
This closes a gap where sensitive information could still leak out through an error message even after the tool call's arguments had been redacted. Error text sent for diagnostics should not reveal what the redaction was meant to hide.
The finding does not say what the redacted placeholder text looks like or exactly which conditions mark an MCP tool call's args as redacted.