Under the hood
Useful2 Signal3
MCP clients now recognise a new denied-issuer-echo error code.
What's wrong with this entry?
Anonymous. No account, no email.
What
ISSUER_ECHO_DENIED was added to the recognised error codes of both MCP client generations, alongside the existing rejected-auth-header and rejected-bearer codes.
Evidence
ISSUER_ECHO_DENIED
Strings lifted out of the shipped bundle, so the claim above can be checked against them.