tengu_mcp_tool_call_auth_error

A Claude Code feature flag, read out of the shipped bundle. No mined inventory carries it: everything below comes from what this site has written about it.

Releases whose published page names tengu_mcp_tool_call_auth_error.

1. v2.1.274 16 Sep 2026
   MCP auth-error classification reworked to add a 403 'step-up' (insufficient scope) case

   MCP auth errors now distinguish an expired token from a 403 requiring extra OAuth permission ('step-up')

   gate cited by this entry

2. v2.1.274 16 Sep 2026
   MCP OAuth "step-up" scope re-authorization is fully wired

   MCP tool calls that need extra permission scope now prompt for a specific re-authorization instead of a generic message

   gate cited by this entry

3. v2.1.273 15 Sep 2026
   MCP tool-call auth-error telemetry no longer thrown as an exception

   A bug that could crash MCP auth-error logging with a stray exception has been fixed

   gate cited by this entry

No release here has a gate table behind it for this flag. Most published releases have none at all: the readings exist only for versions the pipeline captured flag state on.

The earliest release whose published evidence quoted tengu_mcp_tool_call_auth_error was v2.1.273, 15 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.

The miner has never read a build containing this name. It is here because a changelog entry of ours names it, which is evidence that it existed and not evidence of which releases carried it. The inventory starts at v2.1.138 and everything older than that was never mined.

Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the feature flag does. All feature flags.