What you can rely on
An Apple-attested Mac ran the request. SIP is on, Secure Boot isfull, ARV is on, and the MDM SecurityInfo sidecar is at most 25 hours old (90000 seconds). The gateway checks the signed receipt before returning a non-stream byte; streaming still verifies on the final chunk.
The receipt is request-bound: the provider signs H(request) || H(response) plus model, trust, and nonce, so anyone can verify offline that those bytes were emitted in reply to that exact body.
On transparent and hardware, the build is logged. x-mifr-cdhash is the codesign CDHash from the receipt; x-mifr-log-index is the leaf of mifr/builds/v1 when that hash is in the log. This is not a TEE or Confidential AI builder.
The default floor is hardware, with no “best available” fallback. Setting MIFR_GATEWAY_MIN_TRUST=process is low-trust mode: self-reported posture, not Apple-backed. That is an operator choice, not a caller flag.
x-mifr-* headers are a convenience copy of facts the gateway already verified. An independent check uses mifr_receipt plus Apple’s chain from MDM GET /v1/attestation/{id}.
Completions send x-mifr-serial (the full serial) at hardware, and gateway GET /v1/providers returns the serial at that floor. The MDA chain GET also carries serial and UDID. The redacted fleet view omits them. Do not enroll a Mac whose serial must stay private, and do not treat hardware_eligible on that redacted list as a grant.
This path also does not give you confidentiality from the Mac’s owner.
The hosted gateway seals the request for you, so Mifr can read the prompt and the answer. Power users who need that not to happen can seal on their own Mac with
mifr ask.