@ultimat3/policy

@ultimat3/policy 🔐

One authz system. Two authz systems — one for HTTP, one for "the API", one for jobs — is how every Meteor-shaped framework died: the surfaces drift, one of them is wrong, and nobody finds out until it is a CVE. This package exists so a second one is never necessary. Every MCP tool, live query, job and route resolves the same policy object through the same evaluate().

export const publishPost = action({
  policy: can('post:publish', ({ input, actor }) => ownsPost(actor, input.postId)),
});

No exception, as of 1.3.0. @ultimat3/auth's requireRole() / requireScope() used to gate routes on the ambient actor without evaluating a policy; they are deleted. They were documented here as "one honest exception" and had zero callers in the framework or in either tracked app — a sanctioned second door nobody walked through, whose own documentation admitted that a route gated that way is invisible to x policy list, to framework.manifest.json and to openapi.json. Gate a route with a Policy: can('admin:access'), which every introspection surface can read. requireActor() and currentActor() remain — those assert authentication, which is what @ultimat3/auth produces.

Shape

A policy is a pure (input, actor, row, ctx) => PolicyDecision.

type PolicyDecision =
  | { allowed: true }
  | { allowed: false; reason: string; code: string };

reason is always safe to log (it names permissions, never row data) and useful to an agent: actor lacks post:publish and post:publish predicate returned false are different problems with different fixes.

One predicate signature, every surface

interface PolicyArgs<I = unknown, R = unknown> {
  input: I;
  actor: Actor | null;
  row: R | null; // required — `null` means "this rule decides on input alone"
  ctx?: Ctx;
}

A predicate is written once and is correct in an HTTP route, a job, an MCP tool and a live query's per-row gate:

// decides on input alone — `row` is null
can<{ orgId: string }>('post:create', ({ actor, input }) => actor?.orgId === input.orgId);

// decides about a row the surface already loaded
can<{ postId: string }, Post>('post:publish', ({ actor, row }) => row?.authorId === actor?.id);

row is required and nullable, not optional. An optional field is how the two shapes drifted apart the first time: the realtime row gate nested the row inside input, so a row rule and an input rule received different objects and nothing caught it.

Callers have it easier — EvaluateArgs.row is optional, and evaluate() normalises a missing row to null. A surface that has no row passes { input, actor, ctx } unchanged.

Combinators

Builder	Behaviour
can(p, predicate?)	permission first, then the row-level predicate
allow() / deny(reason)	terminal; allow() is how "public" is said out loud
and(...)	first denial wins, its reason is the reason
or(...)	first allowance wins; otherwise the last denial is reported
not(p)	inverts — except X_UNAUTHENTICATED, which propagates unchanged

not() never turns "there is no actor" into an allow. can() denies a null actor with X_UNAUTHENTICATED, and inverting that would make not(can('order:internal')) — the natural simplification of and(can('order:read'), not(can('order:internal'))) — a public door into the internal one.

policy.permissions (or policyPermissions(policy)) is the flattened, deduped, sorted list of every permission a tree references, not() clauses included. It is what a compliance report has to read: label renders a composite as and(post:publish, org:administer), which is a sentence, never a permission.

admitsAnonymous(policy) is the other derived question As of 2026-08, and it is a walk, not a root read: whether an anonymous caller can be allowed at all. policy.kind === 'allow' is the read it replaces, and it answered "needs a session" for or(allow(), can('x:y')) — so an HTTP route 401'd a caller the policy itself allows, while the same policy over MCP or a job let that caller in.

import { admitsAnonymous, allow, and, can, not, or } from '@ultimat3/policy';

admitsAnonymous(or(allow('public'), can('post:publish'))); // true
admitsAnonymous(and(allow('public'), can('post:publish'))); // false
admitsAnonymous(not(can('order:internal'))); // false — X_UNAUTHENTICATED propagates

It is exact for an anonymous caller, not a heuristic: with actor === null, can() short-circuits on the actor check before its predicate runs and allow()/deny() ignore their arguments, so no predicate is ever consulted and the tree alone decides. true never means "unguarded" — it says only that a 401 before the handler is wrong; the surface still calls enforce(). @ultimat3/action and @ultimat3/query derive RouteMeta.auth from it.

Four surfaces, four adapters, one rule

surfaces.ts is the proof. Each adapter evaluates and maps a denial to that surface's error shape; allowed returns undefined.

Adapter	Denial shape
enforceHttp	403 + RFC-9457 fields
enforceLive	close frame 4403
enforceJob	failed, retryable: false — the answer will not change on retry
enforceMcp	isError: true with readable text

Adding a fifth surface means adding an adapter here and nothing else.

enforce(surface, policy, args) dispatches over that table with Object.hasOwn, and a surface with no adapter is X_POLICY_SURFACE_UNKNOWN. Not a formality: the table is an object literal, so it inherits Object.prototype — enforce('valueOf' as Surface, …) used to call Object.prototype.valueOf with the table as its receiver and return a truthy value, so an authz dispatch failed closed with a SurfaceDenial no caller could read.

Permissions and roles

definePermissions(['post:publish', ...]) gives a typed set; augmenting PermissionRegistry (which x g policy generates) makes a typo a compile error, and can() throws X_PERMISSION_UNKNOWN at declaration time either way. Roles are sugar: defineRoles({ owner: { grants: ['post:delete'], inherits: ['editor'] } }) expands depth-first to a flat set, cycles included. post:* and * are supported.

defineRoles() merges into the app's one role map. A second call in a new feature folder adds roles; it never deletes the first module's. A role two modules define differently is X_ROLE_REDEFINED, naming both declaration sites — and an identical re-declaration is a no-op, so defineRoles({ ...roleDefinitions(), … }) stays legal.

The flattened grant set is memoised per actor and invalidated the moment the role map changes. It is keyed on the actor object, so it lives exactly as long as the request does: @ultimat3/auth re-reads the user row every request, and a revoked role takes effect on the next one.

Traces

evaluate() returns a depth-first trace naming the clause that decided. /_x renders it, explain() logs one line, and policyMatrix() turns actors × policy into an assert-ready table:

owner   allow
editor  deny   post:read predicate returned false
viewer  deny   actor lacks post:publish

Building it is opt-in: on outside production, and in production only once a decision sink is installed. A live query evaluates policy per subscriber on every change event, so an unread TraceEntry[] per evaluation is real allocation on the busiest path there is. Force it with evaluate(policy, args, { trace: true }).

The decision log

setDecisionSink({
  record(event) {
    // { label, allowed, code, reason, actorId, actorKind, orgId, surface, deciding }
  },
});

No-op until installed, emitted from one place — inside evaluate(), so a fifth surface inherits it — and it records the allow as well as the denial, which is the half an access review actually asks for. It never carries row or input: reason is safe to log by construction, and the sink inherits that guarantee. A sink that throws is logged and swallowed; it never turns an allowed request into a 500.

Errors

X_FORBIDDEN · X_POLICY_MISSING · X_PERMISSION_UNKNOWN · X_POLICY_SURFACE_UNKNOWN · X_ROLE_REDEFINED

A missing policy is a type error, not a throw: ActionDef.policy is required, so an action without one does not compile. policyMissing() stays for a declaration site that cannot say it in a type — a config-driven route table, a policy resolved by name.

Boundaries

Tier 2. Imports @ultimat3/core only. Surface error shapes are declared structurally so this package never imports @ultimat3/http (sibling tier) or the tier-3/4 surfaces that import it.