- POST /v1/echo: returns the received request head + body (base64) and the observed TLS parameters (version, cipher, SNI, ALPN, resumed). The client diffs against what it sent to detect header injection/stripping, transparent proxying, or TLS interception (sec.http_echo). http-echo added to the capability set. - GET /v1/tls-reference: the served leaf-first DER chain + pin, so the app can compare an out-of-band copy against its own handshake (sec.tls_reference). Always available, no auth — public handshake info. - Optional CLEARTEXT http-echo listener (ECHOLOT_HTTP_ECHO_LISTEN, default off) exposing only /v1/echo for the plaintext-path tampering test. Live-smoke-tested (HTTPS echo reflected an injected header + observed TLS1.3; cleartext variant reports tls:none); httptest unit tests added. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>