@@ -0,0 +1,13 @@
+---
+"@objectstack/core": minor
+---
+
+feat(core): export `resolveRequestExecutionContext`, the one composition that turns an inbound request into the caller's `ExecutionContext`
+
+Clause-②: yes (widening)
+
+- **New export from `@objectstack/core`'s `.` entry.** `resolveRequestExecutionContext(input)` reads the session through the auth service (the in-process rule: a request carrying a session cookie reads without renewal), classifies the tenancy posture with `classifyAdmissionTenancyPosture`, resolves the principal and its grants with `resolveAuthzContext`, resolves the reference localization, decides the ADR-0069 authentication-policy gate and assembles the envelope with `assembleExecutionContext` or `assembleExecutionContextOrGuest`. Its input type `RequestExecutionContextInput` and the types `RequestAuthService`, `EstablishedRequestSession` and `RequestAdmission` are exported with it.
+- **Two choices, made once.** `anonymous: 'fail-closed'` yields no context for a request that resolves no principal (the door answers 401); `anonymous: 'guest'` serves it as the guest principal with the guest anchor's grants. `authGate: 'withhold' | 'resolved' | 'reread-when-active'` says whether the gate's posture rides the envelope, and how it is read.
+- **Every other difference between doors is a named, required parameter:** `credentials`, `sessionApi`, `session`, `tenancy`, `localization`, `requestLocale`, `accessToken`, `oauth` and `onAdmission`. A door with no value passes `undefined` or the withholding literal, so no door can drop an input by omitting it.
+- **First caller.** The runtime dispatcher's identity door (`@objectstack/runtime`'s `resolveExecutionContext`) now calls it. What that door answers is unchanged: the same guest envelope, the same 503 for a tenancy service that failed to build, the same OAuth agent principal on `/mcp`.
+- **Faults propagate.** It catches nothing around the resolver: an unreadable permission store or tenancy service (`AuthzStoreUnavailableError`, 503) and an API key its own lifecycle refuses (`ApiKeyLifecycleRefusalError`, 403) reach the caller, which answers them at its own net.
@@ -180,7 +180,11 @@ const REPO_ROOT = fileURLToPath(new URL('../../../..', import.meta.url));
  */
 const TRANSPORT_LEDGER: Record<string, 'guarded' | 'propagates'> = {
   'packages/rest/src/rest-server.ts': 'guarded',
-  'packages/runtime/src/security/resolve-execution-context.ts': 'propagates',
+  // The one request-to-ExecutionContext composition (ruling record 6227928430,
+  // letter A). It catches nothing around the resolver: every door that calls
+  // it — the runtime dispatcher's `resolve-execution-context.ts` first —
+  // receives the outage and answers it at its own net.
+  'packages/core/src/security/request-execution-context.ts': 'propagates',
   'packages/mcp/src/plugin.ts': 'propagates',
   'packages/services/service-datasource/src/admin-routes.ts': 'guarded',
   'packages/services/service-settings/src/settings-service-plugin.ts': 'guarded',
 
@@ -160,6 +160,19 @@ export {
   type TenancyServiceResolver,
 } from './admission-tenancy-posture.js';
 
+// [ruling record 6227928430, letter A] The ONE request-to-ExecutionContext
+// composition the platform's doors call: the session read, the posture
+// classification above, `resolveAuthzContext`, the localization, the ADR-0069
+// gate and the assembly below, with the anonymous entry and the gate decided
+// once and every door's intentional difference a named parameter.
+export {
+  resolveRequestExecutionContext,
+  type RequestExecutionContextInput,
+  type RequestAuthService,
+  type EstablishedRequestSession,
+  type RequestAdmission,
+} from './request-execution-context.js';
+
 // [commit 6a180e42d] The LOUD failure an unreachable permission store raises, and the
 // brand predicate a fail-closed `catch` uses to re-raise it instead of
 // degrading an outage into a capability denial. Ruled 2026-08-30.
 
@@ -0,0 +1,288 @@
+// Copyright (c) 2026 ObjectStack. Licensed under the Apache-2.0 license.
+
+/**
+ * resolveRequestExecutionContext — the ONE composition that turns an inbound
+ * request into the caller's {@link ExecutionContext}.
+ *
+ * ## Why it exists (ruling record 6227928430, letter A)
+ *
+ * Five platform doors each hand-rolled the same steps around the shared
+ * pieces: read the session through the auth service, classify the tenancy
+ * posture, call `resolveAuthzContext`, pick the anonymous entry, resolve the
+ * localization, decide the ADR-0069 gate, and assemble the envelope. Each copy
+ * was repaired separately when it omitted one input another copy had (the
+ * tenancy posture, the in-process session read, six envelope fields). This
+ * function is those steps, once. A door supplies the pieces it holds and
+ * states its intentional differences as the named parameters below; ⛔ a door
+ * never re-composes the steps beside it.
+ *
+ * ## The two choices, made here
+ *
+ * 1. **The anonymous entry** ({@link RequestExecutionContextInput.anonymous}).
+ *    `'fail-closed'` is the default entry: a request that resolves no
+ *    principal yields NO context, and the door answers 401
+ *    (`assembleExecutionContext`). `'guest'` serves the request as the
+ *    first-class guest principal and resolves the guest anchor's grants
+ *    (`assembleExecutionContextOrGuest`, `resolveAuthzContext`'s
+ *    `guestEntry`). A door takes `'guest'` only when serving anonymous
+ *    principals is its product semantics (ADR-0138 D2 lists those doors).
+ * 2. **The ADR-0069 authentication-policy gate**
+ *    ({@link RequestExecutionContextInput.authGate}). The posture is decided
+ *    for whichever credential admitted the caller, by the shared key-admission
+ *    seam for an API key and from the session read for a session. A door either
+ *    carries it on the envelope for a consumer that reads it there, or
+ *    withholds it because it enforces the gate at its own seam.
+ *
+ * ## The named parameters, and the door each one exists for
+ *
+ * Every key is REQUIRED, the way `ExecutionContextAssemblyInput`'s are: a door
+ * that has no value passes `undefined` or the withholding literal on the
+ * record, so a door cannot drop an input by omission.
+ *
+ * | parameter | values, and the door that takes each |
+ * |:--|:--|
+ * | `anonymous` | `'guest'`: the runtime / MCP dispatcher. `'fail-closed'`: REST, settings, storage, the `/auth/me` endpoints |
+ * | `authGate` | `'withhold'`: the dispatcher (its `enforceAuthGate` re-reads the session; a key's answer leaves through `onAdmission`) and the `/auth/me` endpoints (allow-listed for a gated user). `'resolved'`: settings. `'reread-when-active'`: REST and the storage family door |
+ * | `credentials` | `'session-only'`: the `/auth/me` endpoints, which never opened an API-key door. `'api-key-and-session'`: every other door |
+ * | `sessionApi` | `'required'`: REST and the `/auth/me` endpoints, which authenticate nobody without a session API. `'optional'`: the dispatcher, settings and storage, which still admit an API key |
+ * | `session` | `'request'`: every door. `{ established }` / `'none'`: the dispatcher's `/mcp` face, for a verified / an unverifiable OAuth access token |
+ * | `tenancy` | the door's own way to reach the `tenancy` service (#16013: the resolution stays at the door), or `undefined` where the door reads no posture (the `/auth/me` endpoints) |
+ * | `localization` | the door's settings-service lookup (the dispatcher, REST), or `'withhold'` (the `/auth/me` endpoints read the cascade per endpoint) |
+ * | `requestLocale` | the door's own parse: `Accept-Language` (the dispatcher), the header or `?locale` (REST), none (the `/auth/me` endpoints) |
+ * | `accessToken` | `'carry'`: the dispatcher. `'withhold'`: REST and the `/auth/me` endpoints |
+ * | `oauth` | the dispatcher's `/mcp` face, which alone speaks the OAuth scope vocabulary; `undefined` elsewhere |
+ * | `onAdmission` | the dispatcher, whose gate needs the credential the envelope does not carry; `undefined` elsewhere |
+ *
+ * ## What stays at the door
+ *
+ * How the door reaches its services (a kernel per environment, a plugin
+ * context, a registry slice), how it turns its transport's headers into a Web
+ * `Headers`, how it answers a fault (this function PROPAGATES every
+ * rejection: an unreadable permission store, an unreadable posture or gate, an
+ * API key its own lifecycle refuses), and what it does with the context
+ * afterwards. Those are transport facts, not the composition.
+ */
+
+import type { ExecutionContext } from '@objectstack/spec/kernel';
+import type { AuthSessionApi, IAuthService } from '@objectstack/spec/contracts';
+import { inProcessSessionReadInput } from '@objectstack/types';
+
+import { classifyAdmissionTenancyPosture, type TenancyServiceResolver } from './admission-tenancy-posture.js';
+import { apiKeyLifecyclePolicySourceOf } from './api-key.js';
+import {
+  assembleExecutionContext,
+  assembleExecutionContextOrGuest,
+  type EntryLocalization,
+  type ExecutionContextAssemblyInput,
+  type OAuthTokenProvenance,
+} from './assemble-execution-context.js';
+import { normalizeAuthGate, userAuthGateSourceOf, type AuthGate } from './auth-gate.js';
+import { AuthzStoreUnavailableError } from './authz-store-unavailable.js';
+import { resolveAuthzContext, resolveLocalizationContext, type ResolvedAuthzContext } from './resolve-authz-context.js';
+
+/** The slice of the kernel's `auth` service this composition reads. */
+export type RequestAuthService = Pick<
+  IAuthService,
+  'api' | 'getApi' | 'isAuthGateActive' | 'resolveUserAuthGates' | 'resolveApiKeyLifecyclePolicy'
+>;
+
+/**
+ * A session a door has already established from a credential other than the
+ * request's own session: the dispatcher's verified OAuth access token. The
+ * organization is the one the token's consent bound, and the session arm vets
+ * it as it vets a browser session's active organization (ADR-0090 D10).
+ */
+export interface EstablishedRequestSession {
+  user: { id: string };
+  session: { userId: string; activeOrganizationId?: string };
+}
+
+/** Which credential admitted the principal, and the ADR-0069 posture decided for it. */
+export interface RequestAdmission {
+  credential: 'api_key' | 'session';
+  authGate: AuthGate | undefined;
+}
+
+/** Everything the composition reads. Every key is required; see the module docblock. */
+export interface RequestExecutionContextInput {
+  /** The request's headers, as a Web `Headers`. */
+  headers: Headers;
+  /** The data engine (ObjectQL), or `undefined` when the door has none. */
+  ql: unknown;
+  /** The kernel's `auth` service, or `undefined` when none is reachable. */
+  authService: RequestAuthService | undefined;
+  /**
+   * How this door reaches the `tenancy` service, handed to
+   * `classifyAdmissionTenancyPosture` (never registered: no posture; failed:
+   * the 503 outage). `undefined`: this door reads no posture.
+   */
+  tenancy: TenancyServiceResolver | undefined;
+  /** Choice 1: the anonymous entry. */
+  anonymous: 'fail-closed' | 'guest';
+  /**
+   * Choice 2: the ADR-0069 gate on the envelope.
+   *
+   * - `'withhold'`: never on the envelope; the door enforces the gate itself.
+   * - `'resolved'`: the posture `resolveAuthzContext` decided for whichever
+   *   credential admitted the caller, from the read that admitted it.
+   * - `'reread-when-active'`: an API key's posture as `'resolved'`; for the
+   *   request's own session, read again only while the auth service says a
+   *   gate is active (`isAuthGateActive()`, a probe that throws reads as
+   *   inactive). A re-read that fails is `AuthzStoreUnavailableError('auth_gate')`:
+   *   a gate the deployment declared active is never dropped silently.
+   */
+  authGate: 'withhold' | 'resolved' | 'reread-when-active';
+  /** Which credential doors this door opens. `'session-only'` reads no API key. */
+  credentials: 'api-key-and-session' | 'session-only';
+  /**
+   * `'required'`: with no auth service, or one exposing no session read, this
+   * door authenticates nobody, the API-key door included. `'optional'`: the
+   * API-key door still admits.
+   */
+  sessionApi: 'optional' | 'required';
+  /**
+   * Where the session arm reads its session. `'request'`: the auth service's
+   * read of this request, under the in-process rule (a request carrying a
+   * session cookie reads without renewal). `{ established }`: a session the
+   * door established from another credential. `'none'`: the door's own
+   * credential failed, and no session answers for it, ⛔ the cookie beside it
+   * included.
+   */
+  session: 'request' | 'none' | { readonly established: EstablishedRequestSession };
+  /**
+   * For an authenticated principal, the door's settings-service lookup for the
+   * reference localization (a lookup that rejects reads as no service), or
+   * `'withhold'` to resolve none.
+   */
+  localization: 'withhold' | { readonly settings: () => unknown };
+  /** The request's own locale preference, parsed by the door; wins over the workspace default. */
+  requestLocale: string | undefined;
+  /** Whether the session bearer rides the envelope to hooks (`session.accessToken`). */
+  accessToken: 'carry' | 'withhold';
+  /** OAuth access-token provenance, derived by the one door that accepts one. */
+  oauth: OAuthTokenProvenance | undefined;
+  /** Told which credential admitted the principal; not called for an anonymous request. */
+  onAdmission: ((admission: RequestAdmission) => void) | undefined;
+}
+
+/** `.api` (the legacy direct mount) or `getApi()` (the lazy plugin). */
+async function sessionApiOf(authService: RequestAuthService | undefined): Promise<AuthSessionApi | undefined> {
+  let api = authService?.api;
+  if (!api && typeof authService?.getApi === 'function') api = await authService.getApi();
+  return api;
+}
+
+/** Choice 2, for a resolved principal. */
+async function decideAuthGate(
+  input: RequestExecutionContextInput,
+  authz: ResolvedAuthzContext,
+  sessionApi: () => Promise<AuthSessionApi | undefined>,
+): Promise<AuthGate | undefined> {
+  if (input.authGate === 'withhold') return undefined;
+  if (input.authGate === 'resolved') return authz.authGate;
+  // 'reread-when-active'. A key, or a session the door established from another
+  // credential, is judged by the answer the admission already decided.
+  if (authz.credential !== 'session' || input.session !== 'request') return authz.authGate;
+  let active = false;
+  try {
+    active = input.authService?.isAuthGateActive?.() === true;
+  } catch {
+    // A probe that faults never declared a gate.
+    active = false;
+  }
+  if (!active) return undefined;
+  let gatedSession: Awaited<ReturnType<NonNullable<AuthSessionApi['getSession']>>>;
+  try {
+    const api = await sessionApi();
+    gatedSession = await api!.getSession!(inProcessSessionReadInput(input.headers));
+  } catch (err) {
+    throw new AuthzStoreUnavailableError('auth_gate', err);
+  }
+  return normalizeAuthGate(gatedSession?.user) ?? undefined;
+}
+
+/**
+ * Resolve the request's {@link ExecutionContext}: the guest entry always
+ * yields one; the fail-closed entry yields `undefined` for a request that
+ * resolves no principal.
+ *
+ * @throws {AuthzStoreUnavailableError} an authorization input that exists and
+ *   could not be read (the permission store, the `tenancy` service, an active
+ *   gate's re-read).
+ * @throws {ApiKeyLifecycleRefusalError} an API key its own lifecycle refuses.
+ */
+export function resolveRequestExecutionContext(
+  input: RequestExecutionContextInput & { anonymous: 'guest' },
+): Promise<ExecutionContext>;
+export function resolveRequestExecutionContext(
+  input: RequestExecutionContextInput,
+): Promise<ExecutionContext | undefined>;
+export async function resolveRequestExecutionContext(
+  input: RequestExecutionContextInput,
+): Promise<ExecutionContext | undefined> {
+  const { headers, ql, authService } = input;
+
+  // A door that requires a session API asks for it before any read, and
+  // without one authenticates nobody. A door that does not asks lazily, from
+  // the session read itself, so an API-key request never builds the auth
+  // instance.
+  let requiredApi: AuthSessionApi | undefined;
+  let credentialsOpen = true;
+  if (input.sessionApi === 'required') {
+    requiredApi = await sessionApiOf(authService);
+    if (typeof requiredApi?.getSession !== 'function') {
+      if (input.anonymous === 'fail-closed') return undefined;
+      credentialsOpen = false;
+    }
+  }
+  const sessionApi = () => (input.sessionApi === 'required' ? Promise.resolve(requiredApi) : sessionApiOf(authService));
+
+  const tenancyPosture = input.tenancy ? await classifyAdmissionTenancyPosture(input.tenancy) : undefined;
+
+  const session = input.session;
+  const readSession = async () => {
+    if (session === 'none') return undefined;
+    if (typeof session === 'object') return session.established;
+    try {
+      const api = await sessionApi();
+      return await api?.getSession?.(inProcessSessionReadInput(headers));
+    } catch {
+      return undefined;
+    }
+  };
+
+  const authz = await resolveAuthzContext({
+    ql,
+    headers: credentialsOpen && input.credentials === 'api-key-and-session' ? headers : undefined,
+    getSession: credentialsOpen ? readSession : undefined,
+    tenancyPosture,
+    guestEntry: input.anonymous === 'guest' ? true : undefined,
+    userAuthGates: userAuthGateSourceOf(authService),
+    apiKeyLifecycle: apiKeyLifecyclePolicySourceOf(authService),
+  });
+  if (authz.userId && authz.credential) {
+    input.onAdmission?.({ credential: authz.credential, authGate: authz.authGate });
+  }
+
+  // An anonymous request has no scope to localize against and no session for a
+  // gate to attach to: both are read only for a resolved principal.
+  let localization: EntryLocalization | undefined;
+  let authGate: AuthGate | undefined;
+  if (authz.userId) {
+    if (input.localization !== 'withhold') {
+      const settings = await Promise.resolve(input.localization.settings()).catch(() => undefined);
+      localization = await resolveLocalizationContext({ ql, settings, tenantId: authz.tenantId, userId: authz.userId });
+    }
+    authGate = await decideAuthGate(input, authz, sessionApi);
+  }
+
+  const assembly: ExecutionContextAssemblyInput = {
+    authz,
+    oauth: input.oauth,
+    localization,
+    requestLocale: input.requestLocale,
+    accessToken: input.accessToken === 'carry' ? authz.accessToken : undefined,
+    authGate,
+  };
+  return input.anonymous === 'guest' ? assembleExecutionContextOrGuest(assembly) : assembleExecutionContext(assembly);
+}