Keys instead of accounts. Receipts instead of surveillance. Math instead of middlemen.
PolyCap is an authority substrate for people, devices, and agents: capabilities that attenuate, expire, and are receipted, on a wire that runs on ordinary MQTT 5.
What it provides
Messaging fabric, mesh, and routing
MQTT 5 native: every frame rides a standard PUBLISH on any unmodified broker, an embedded micro-broker, or a peer bridge. Closed traffic lanes map to four priority bands, so an emergency frame is never the victim of eviction. Above the brokers, a scored, churn-tolerant mesh routes by locality and cost, islands when the wider network is unreachable, and heals with revocations processed first.
Authority, discovery, and matching
Capabilities are delegable, attenuable, expiring, and revocable; no delegate can hold more than its grantor, and every refusal names the authority that was missing. Discovery advertises competences into affinity spaces visible only as k-anonymous centroids: an unauthorized query learns nothing, not even that a neighborhood exists.
State and sync
Content-addressed objects and range-based reconciliation converge replicas by exchanging fingerprints, not full state. Retained values make the fabric behave as shared memory implemented over message passing. Offline-first by nature: a node that was away catches up by reconciling, not by replaying a log it might have missed.
Venues
Governed groups with membership-as-capability, roles, treasury and escrow, and policy overlays that can only tighten what the substrate allows. Nine closed templates cover the common shapes, from Family and Incident to Marketplace, Compliance, and Emergency. What a venue may do is determined by the authority it was granted, never by a special-case protocol.
Executable artifacts and plugins
Hosted code receives authority only by sealed capability injection: no ambient access, no dynamic code loading, host-mediated spending. The same discipline applies to native plugins, device drivers, and agent-authored scripts, so third-party or AI-generated automation runs against real equipment with a bounded blast radius and a provenance trail.
Boundary adapters
External systems attach through adapters that preserve the attenuation invariant at the seam: telecom and 6G boundaries, spatial-web scene graphs, and a steward pattern for plain-MQTT or vendor devices that cannot speak PolyCap themselves. At the actuation surface of agent-operated hardware, PolyCap is a reference monitor with receipts.
Specification complete. Reference implementation under way, graded against the oracle from its first commit. polyZero, the runtime for N0-class nodes (structurally minimal, microcontroller-class), implements the first three modules, each independently reproduced hash-for-hash. Test net running: polyZero nodes talk to one another through a standard MQTT 5 broker, emitting real-time OpenTelemetry traces as they do. Partners receive the conformance program today; public verification suites are on the roadmap.
The problem it solves
What may this program do?
Every system that lets software act on the world answers one question: what may this program do? Most answer it with ambient authority — an API key, a session, an account’s standing permissions — and most breaches are that surplus being used. PolyCap answers it with capabilities: unforgeable, explicit, delegable only narrower, expiring, revocable, and receipted.
Three rules that explain the design
Keys instead of accounts.
Every participant is a keypair. No account store, no login, no identity provider to stand up or to breach.
Authority lives in the message, never in the connection.
Transport authentication proves you can reach a node; it grants nothing. Every frame carries its own proof — so any broker, any bearer, and a hostile network can delay or drop but never forge or escalate.
Receipts instead of surveillance.
Every authorized action can emit a signed, attributable, tamper-evident record — audit as a property of the wire, not a log someone kept.
Where it fits
On any standard MQTT 5 broker, or with none.
From microcontroller-class leaves to consensus-holding servers. As a gateway that owns the actuation surface of a lab, plant, or fleet. As the backplane of an application that has to work when the network doesn’t.
What it is not
Not a blockchain. Not a currency. Not an identity provider. Not a replacement for your broker.