Take the reading.
Measure the fleet without ingesting the cargo.

A hosted AI tool is a black box. Every prompt opens a connection to a model provider; every response carries the provider’s posture; every audit log lives on the vendor’s servers under the vendor’s schema. A firm that wants to measure the tool runs into the same wall every time: how do we evaluate behavior without ingesting the cargo.

The Port is the answer. It is the named, typed, code-enforced boundary between Planisphere’s measurement substrate and the customer’s data plane. Only sha-pinned evidence metadata crosses the Port outward; raw probe responses, callable references, secrets, and customer PII never do. The boundary is not a paragraph in a contract — it is a frozen dataclass in planisphere.backstaff.port and a continuous-integration test that fails the build if anything else tries to cross.

The Port’s crosses tuple lists the derived artifact classes that may cross the boundary outward. The schema names the seven kernel fields every board inherits; the Port is the packaging rule that turns those fields and their verdict material into concrete files a evidence check can hash. In the current record shape, eight artifacts cross: the seven-field kernel plus rank_collapse_attestation, a derived temporal verdict. Every crossing object is checked against a hash, the Merkle root that aggregates the hashes, and the Ed25519 signature that commits the root.

from planisphere.backstaff.port import PORT

PORT.crosses
# ("AttestationManifest",
#  "attestation_root",
#  "fleet_sha256",
#  "spectral_geometry_sha",
#  "per_adapter_signature",
#  "fleet_grades_csv",
#  "nist_controls",
#  "rank_collapse_attestation")

The never_crosses tuple is the structural commitment. These seven classes of object never traverse the Port — not because someone promised, but because the CI test fails the build if they appear in any payload that crosses. "We don’t exfiltrate your data" is a marketing claim; this list is the form-factor that lets the firm verify the claim against the running system.

PORT.never_crosses
# ("raw_probe_responses",
#  "callable_references",
#  "api_keys",
#  "bearer_tokens",
#  "customer_pii",
#  "raw_behavioral_signature_vector",
#  "raw_rank_trajectory")

Enforcement: editing PortContract.crosses or PortContract.never_crosses without updating planisphere.tests.test_port_contract fails the build. The two lists are the contract; the test is the proof. The customer’s security team verifies the contract by running the test on a published commit.

The Port’s value is that it is content-agnostic. A legal-research AI, a K-5 grader fleet, a defense-procurement classifier, a clinical-decision support tool — all of them are universal containers: hosted, opaque, vendor-controlled. The Port does not care what kind of cargo the container holds. It cares about the boundary itself, and the form-factor of the attestation that emerges from inside it.

The customer’s tool is the merchant ship. Our fleet is what we send out from the Port to inspect it. Six classes — each named in web/icons.html, each tuned to a different measurement posture.

The Port is one half of a paired schema. Its sibling is the Starboard — the outbound surface from which the *-board verticals emit. Together they name the entire Planisphere boundary: the universal container docks at the Port; the per-vertical attestation report emits from the Starboard.

The market’s instinct is to demand disclosure — show me the model, show me the prompts, show me the data. That request is unanswerable for a frontier vendor and undesirable for a regulated customer. The Port resolves the standoff by shaping the boundary itself so neither side has to disclose anything sensitive: the vendor’s weights stay with the vendor, the customer’s matter stays with the customer, and the attestation root is verifiable by any third party from the manifest and the public key alone.

That is the form of proof a court can rely on and a firm can produce without waiving anything. The seven entries in PORT.never_crosses are the runtime witness that the boundary holds.

The first engagement is a scoping conversation. Tool inventory, hosting topology, the matter-band profile of the engagement, the target evidence-record date. We return a Phase 0 scope and a record delivery date. The vendor never sees us; we never see the customer’s matter.