# 06 · Delegation & Attenuation

> Authority can only get narrower.

## Overview

Subagents and child sessions need authority to work. Delegation is how a
parent lends its own grants downward — and attenuation is the rule that makes
this safe: **a child can never hold more authority than the parent that
delegated it**.

## The attenuation laws

```text
Authority(child) ⪯ Authority(parent)
Actions(child)  ⊆ Actions(parent)
Resources(child) ⊆ Resources(parent)
Expiry(child)   ≤ Expiry(parent)
Uses(child)     ≤ Uses(parent)
DelegationDepth(child) = DelegationDepth(parent) + 1 ≤ MaxDepth(parent)
```

Every dimension can only shrink or stay equal. There is no operation anywhere
in the system that widens a grant downward.

## Zero ambient authority

- A child starts with **nothing**. Not "fewer permissions" — none.
- Parent grant identifiers are not directly usable by the child; the child
  receives newly minted, attenuated grants.
- Revoked, expired, exhausted, missing, or cyclic ancestors invalidate the
  descendant **at execution time** — checked fresh at the PEP, not cached.

## Lifecycle (nine steps)

1. Parent requests bounded child work.
2. Select explicit parent grants to attenuate.
3. Validate parent & ancestor state (alive, unexpired, unexhausted).
4. Validate attenuation holds on every dimension.
5. Transactionally insert PENDING child grants.
6. Create child session / principal.
7. Activate grants only after identity confirmation.
8. Child executes through the normal PDP/PEP — same gate as everyone else.
9. Parent or ancestor revocation invalidates the child's grants.

## Worked example

Parent holds: run-tests (bash, tests/**, 1h, 50 uses).

- Child delegated "run the test suite": receives run-tests attenuated to
  exactly that command pattern, expiry ≤ parent's, uses ≤ parent's remaining.
- Child asks for `npm install`: denied — no grant covers install, and the
  parent's other capabilities were never selected for delegation.
- Parent's grant is revoked mid-run: child's very next tool call fails closed.

## Related

- Previous: [Exact Durable Capabilities](/governance/capabilities.md)
- Next: [Provenance & Sensitivity](/governance/provenance.md)