Core concepts

CHP has a small vocabulary. Each term below is defined in plain English first, then precisely.

Capability

Plain: something a person, agent, product, process, or organization can do.

Precise: a named, invokable unit exposed by a host with a stable id, version, declared modes, inputs and outputs, policy metadata, and mandatory evidence emission. payments.transfer, schedule_technician, and classify_risk are capabilities.

Host

Plain: where a capability lives.

Precise: a runtime that registers capabilities and participates in CHP — a process, service, CLI, agent runtime, MCP wrapper, API adapter, device, or business system. It admits invocations and writes evidence.

Invocation

Plain: a single use of a capability.

Precise: an envelope that carries the capability id, mode, correlation context, subject identity, payload, and requested time across the boundary.

Evidence

Plain: the record of what actually happened.

Precise: an append-only, SHA256 hash-chained event for every attempt — one of execution_started, execution_completed, execution_failed, execution_denied, or execution_skipped — with a stable schema that callers and infrastructure can replay, verify, and export.

Correlation

Plain: the thread that ties a session together.

Precise: a correlation id supplied by the caller (or generated by the host) that flows through every invocation and evidence event, enabling causal replay across agents, tools, and hosts.

Denial

Plain: the boundary said no — on purpose.

Precise: a first-class outcome (not an exception) returned when a host rejects an invocation: capability not found, unsupported mode, disabled, invariant failed, or entitlement denied. It carries a stable code, a message, and a retryable flag — and it is recorded as evidence.

Conformance

Plain: proof that an implementation behaves like CHP.

Precise: a suite of minimum checks an independent host must pass — declaration, discovery, invocation through an envelope, correlation propagation, evidence on success / failure / denial, replay, and representation of skipped execution.