Upstream TLS

Upstream TLS (self-signed certificates, private CAs, mTLS)

Internal MCP servers often use certificates from a private CA or self-signed ones. Give the upstream a tls block instead of weakening verification:

{
  "tls": {
    "caPem": "-----BEGIN CERTIFICATE-----\n...\n-----END CERTIFICATE-----\n",
    "serverName": "mcp.internal.example",
    "clientCertPem": "-----BEGIN CERTIFICATE-----...",
    "clientKeyPem": "-----BEGIN EC PRIVATE KEY-----..."
  }
}

Field	Behaviour
caPem	PEM bundle (up to 10 certificates, 64 KiB). It becomes the only trusted root for this upstream, not a global trust store. A self-signed server certificate can be used directly as the CA
serverName	Host name used for SNI and certificate verification. Needed when you connect by IP or an alias that is not in the certificate
clientCertPem + clientKeyPem	Client certificate for mutual TLS. Must be a valid pair

Applies everywhere vMCP connects: tool discovery, connection tests, health checks and agent sessions.

Rules

• There is no "skip verification" option, by design.
• clientKeyPem is encrypted at rest, write-only, and never returned or exported. If you omit it while keeping the same certificate, the stored key is kept; clearing clientCertPem also clears the key.
• PUT/POST replace the whole block (omit it to keep the stored one); PATCH merges per field and "" clears a field.
• Export/apply carry caPem, serverName and clientCertPem, never the key.
• The UI shows each CA certificate's subject and expiry (and flags expired ones). Renew certificates before they expire: connections fail once they do.

Troubleshooting

Symptom	Likely cause
x509: certificate signed by unknown authority	Missing or wrong caPem
x509: certificate is valid for X, not Y	Connecting by IP/alias: set serverName to a name in the certificate
remote error: tls: certificate required	Server needs mTLS: add the client certificate and key
Connection test fails for an mTLS upstream in the UI but the stored upstream works	The test can only use a key you pasted in this session; stored keys cannot be read back