# 05 · Exact Durable Capabilities

> The fundamental authority primitive.

## Overview

A capability is the only way authority enters the system. There is no ambient
trust: an agent can do exactly what some granted capability permits, for as
long as that grant survives, and nothing more.

## The seven properties

| Property | Meaning | Failure mode it eliminates |
|---|---|---|
| durable | Survives process restarts, stored in signed state | "Reboot wiped the ACL" loopholes |
| exact | Bounded to specific actions × resources | Wildcard grants like "fs:*" |
| scoped | Bound to principal · session · workspace · contract | Credentials leaking across contexts |
| expiring | Hard expiry timestamp | Zombie authority living forever |
| use-limited | Consumes one use per execution; N uses total | Unbounded reuse of a single grant |
| revocable | Revocation cascades to descendants | Dead authority surviving revocation |
| ancestry-tracked | Full delegation chain recorded | Unattributable permission chains |

## Execution precondition

A capability alone is never enough. Effect(q) requires the conjunction:

```text
Effect(q) ⇒ Capability ∧ Intent ∧ ProvenancePolicy ∧ Workspace ∧ conditionalApproval
```

All five, evaluated fresh at the PEP. Missing any one ⇒ deny.

## Lifecycle

1. **Grant** — created through policy or explicit user action; signed into
   durable state; scoped and bounded at creation.
2. **Use** — each execution claims one use atomically at the PEP; the claim
   and the execution receipt are recorded together.
3. **Exhaustion** — when uses hit N, the grant is dead even if unexpired.
4. **Expiry** — past expiry, claims fail regardless of remaining uses.
5. **Revocation** — immediate; cascades to every descendant grant derived
   from it (see [Delegation](/governance/delegation.md)).

## Enforcement location

Capabilities are evaluated at the **logical PEP boundary**. Physical
containment (sandbox, OS, broker) is tracked separately per effect path —
see [Assurance & Boundaries](/governance/assurance.md).

## Related

- Previous: [Intent–Action Binding](/governance/intent.md)
- Next: [Delegation & Attenuation](/governance/delegation.md)