@@ -0,0 +1,17 @@
+---
+'@objectstack/plugin-hono-server': minor
+---
+
+fix(plugin-hono-server)!: the CORS default admits no cross-origin caller, and `'*'` with credentials is refused at boot
+
+Clause-②: no (narrowing)
+
+<!-- adr-0087: not-required (no-migration-prescription) a narrowing of the transport's CORS admission default plus a boot refusal of one configuration: no authorable metadata key, spelling, export, type or stored shape moves, so `objectstack migrate meta` has nothing to rewrite. The remedy is a deployment variable, which no ledger entry can derive. The other categories are closed on facts: the package publishes (not unpublished); no ADR-0087 id covers this door (not already-registered); and the change is an admission verdict, not an interface, a type or an export (not runtime-interface-only, type-surface-only or runtime-export-retired). -->
+
+**BREAKING** — an admission narrowing of the transport's CORS answer, shipped as `minor` under the launch-window convention for accept-set narrowings. The governing text is `docs/HARDENING.md` § CORS: never `'*'` with credentials, and an explicit origin list.
+
+- **Before.** With no origin list configured (no `cors.origins` option and no `OS_CORS_ORIGIN`), the CORS middleware admitted every origin for credentialed cross-origin requests. A configured `'*'` with credentials on was accepted and answered the same way.
+- **Now.** With no list, no cross-origin caller is admitted. A loopback origin (`localhost`, `127.0.0.1`, `[::1]`, any port) is admitted on a development boot only: `NODE_ENV` exactly `development`, which `os dev` and `os serve --dev` set. A list that contains `'*'` while credentials are on is refused in `init()`, so the boot fails, and the message names both remedies.
+- **Unchanged.** Same-origin requests need no CORS answer, so the Console under `/_console` and every page the server itself serves work as before. A configured list, exact origins or wildcard patterns, is admitted exactly as before, credentials included. `'*'` with credentials off still boots. `cors: false` and `OS_CORS_ENABLED=false` still disable the middleware. Allowed and exposed headers, methods and max-age are unchanged.
+
+**What an operator does.** A front-end served from another origin that calls this server is now named: `OS_CORS_ORIGIN=https://app.example.com` (comma-separated for several), or the plugin's `cors.origins` option. A boot that now refuses `'*'` either names its origins or sets `OS_CORS_CREDENTIALS=false` to keep serving `'*'` without credentials. `OS_TRUSTED_ORIGINS` is auth's own list, the origins it accepts for callbacks and CSRF checks, and it admits nothing to CORS. Auth also trusts every origin listed in `OS_CORS_ORIGIN`, so that one variable covers a cross-origin front-end that signs in. A list given through the plugin's `cors.origins` option instead is not seen by auth, so such a front-end is then also named in `OS_TRUSTED_ORIGINS`.
@@ -36,7 +36,7 @@ read at startup unless noted otherwise. Boolean variables accept `true` / `false
 > +100) and the banner prints the actual bound port. In **production**
 > (`os start`) a busy port is a hard error (exit 1) — it never silently
 > drifts, because a shifted port breaks reverse-proxy upstreams, `OS_AUTH_URL`
-> callbacks, and `OS_TRUSTED_ORIGINS` (CORS). Pin the port explicitly in
+> callbacks, and `OS_TRUSTED_ORIGINS` (auth CSRF). Pin the port explicitly in
 > production (`OS_PORT=8080 os start`) and keep `OS_AUTH_URL` / `OS_TRUSTED_ORIGINS`
 > in sync with it.
 
@@ -123,8 +123,8 @@ Auth settings precedence:
 | Variable | Type | Default | Description |
 |:---|:---|:---|:---|
 | `OS_CORS_ENABLED` | boolean | `true` | Enable CORS middleware. |
-| `OS_CORS_ORIGIN` | csv | `*` | Allowed origins (comma-separated, or `*`). |
-| `OS_CORS_CREDENTIALS` | boolean | `true` | Allow credentialed cross-origin requests. |
+| `OS_CORS_ORIGIN` | csv | — | Origins admitted to cross-origin requests: exact origins or patterns such as `https://*.example.com`, comma-separated. Unset, no cross-origin caller is admitted (loopback origins excepted on a development boot); same-origin requests, the Console included, need no entry. `*` is refused at boot unless `OS_CORS_CREDENTIALS=false`. |
+| `OS_CORS_CREDENTIALS` | boolean | `true` | Allow credentialed cross-origin requests from the admitted origins. Must be `false` to serve `OS_CORS_ORIGIN=*`. |
 | `OS_CORS_MAX_AGE` | number | `86400` | Preflight cache TTL in seconds. |
 
 ---
 
@@ -118,6 +118,11 @@ the [HARDENING.md recipes](https://github.com/objectstack-ai/objectstack/blob/ma
       response `X-Request-Id` header.
 - [ ] better-auth session TTL / refresh / revoke verified (curl
       checklist in HARDENING.md).
+- [ ] CORS admits exactly the cross-origin front-ends you serve. With no
+      `OS_CORS_ORIGIN` none is admitted (same-origin pages, the Console
+      included, need no entry); otherwise it lists each origin explicitly,
+      never `*` — the server refuses `*` at boot while credentials are on.
+      See [HARDENING.md § CORS](https://github.com/objectstack-ai/objectstack/blob/main/docs/HARDENING.md#cors).
 - [ ] Cross-tenant negative tests in CI.
 - [ ] Multi-org deployments: tenant isolation is **active**, not degraded —
       confirm `features.degradedTenancy` is `false` in `/auth/config`. A
 
@@ -411,10 +411,17 @@ and keep three things in sync with the public origin:
 
 ```bash
 OS_AUTH_URL=https://app.example.com          # auth callbacks / cookie origin
-OS_TRUSTED_ORIGINS=https://app.example.com   # CORS allow-list
+OS_TRUSTED_ORIGINS=https://app.example.com   # auth callback / CSRF allow-list
 OS_PORT=8080                                 # must match the proxy upstream
 ```
 
+CORS needs no entry here: the Console and the API share the public origin,
+and with no `OS_CORS_ORIGIN` the server admits no cross-origin caller. Only a
+front-end served from **another** origin needs one, listed explicitly
+(`OS_CORS_ORIGIN=https://portal.example.com`, comma-separated for several) —
+never `*`, which the server refuses at boot while credentials are on. See
+[Environment variables → CORS](/docs/deployment/environment-variables#cors).
+
 ```text title="Caddyfile"
 app.example.com {
     reverse_proxy localhost:8080
 
@@ -192,9 +192,34 @@ curl -H "Authorization: Bearer $TOK" $API/data/account
 
 ## CORS
 
-CORS is intentionally **not** opinionated by the runtime — it's an
-app-level policy that depends on which origins host your front-end.
-Configure it on the Hono adapter:
+Which cross-origin callers are admitted is an app-level decision — it
+depends on which origins host your front-end — so the server that
+`os serve` / `os start` mount (`HonoServerPlugin`) admits only the
+origins you name:
+
+| Configuration | What is admitted |
+| --- | --- |
+| No origin list (neither `OS_CORS_ORIGIN` nor the plugin's `cors.origins`) | **No cross-origin caller.** On a development boot (`NODE_ENV=development`, which `os dev` and `os serve --dev` set), loopback origins (`localhost`, `127.0.0.1`, `[::1]`, any port) are admitted too. |
+| A list (`OS_CORS_ORIGIN=https://app.example.com`, comma-separated; exact origins or patterns such as `https://*.example.com`) | Those origins, with credentials unless `OS_CORS_CREDENTIALS=false`. Loopback origins are admitted alongside any list. |
+| `*` while credentials are on | **Refused at boot** — the boot fails with a message naming the two remedies. |
+
+Same-origin requests need no CORS answer, so the Console under
+`/_console` and any page the server itself serves work with no list at
+all. A front-end served from **another origin** needs one CORS
+variable:
+
+```bash
+OS_CORS_ORIGIN=https://app.example.com
+```
+
+`OS_TRUSTED_ORIGINS` is auth's own list — the origins it accepts for
+its callbacks and CSRF checks — and it admits nothing to CORS. Auth
+also trusts every origin listed in `OS_CORS_ORIGIN`, so that one
+variable covers a cross-origin front-end that signs in. A list given
+through the plugin's `cors.origins` option instead is not seen by
+auth, so such a front-end is then also named in `OS_TRUSTED_ORIGINS`.
+
+Composing the Hono adapter yourself, name the origins there as well:
 
 ```ts
 import { createHonoApp } from '@objectstack/hono';
@@ -209,9 +234,10 @@ const app = createHonoApp({
 });
 ```
 
-Do **not** use `origin: '*'` with `credentials: true` — the
-combination is rejected by every modern browser anyway, but the
-misconfiguration is a common red flag in audits.
+Do **not** use `origin: '*'` with `credentials: true`: together they
+admit every origin for credentialed requests. `HonoServerPlugin`
+refuses the combination at boot; `*` is accepted only with credentials
+off (`OS_CORS_CREDENTIALS=false`), for an API that takes no cookies.
 
 ## Auditing
 
 
@@ -35,6 +35,24 @@ await kernel.bootstrap();
 
 The Hono server plugin supports flexible CORS configuration with wildcard pattern matching.
 
+### Default: no cross-origin caller
+
+The CORS middleware is mounted by default, and it admits only the origins you name
+(`cors.origins`, else `OS_CORS_ORIGIN`). With neither set, **no cross-origin caller is
+admitted**. Same-origin requests need no CORS answer, so pages this server serves are
+unaffected. On a development boot (`NODE_ENV=development`, which `os dev` sets), loopback
+origins (`localhost`, `127.0.0.1`, `[::1]`, any port) are admitted too.
+
+`'*'` while credentials are on (the default) is **refused at init**, so the boot fails.
+Name the origins instead, or turn credentials off to serve `'*'` to callers that send no
+cookies:
+
+```typescript
+kernel.use(new HonoServerPlugin({
+  cors: { origins: '*', credentials: false }
+}));
+```
+
 ### Basic CORS
 
 ```typescript
@@ -79,19 +97,21 @@ CORS can also be configured via environment variables:
 
 ```bash
 # Single origin
-CORS_ORIGIN=https://app.example.com
+OS_CORS_ORIGIN=https://app.example.com
 
 # Wildcard patterns (comma-separated)
-CORS_ORIGIN=https://*.objectui.org,https://*.objectstack.ai
+OS_CORS_ORIGIN=https://*.objectui.org,https://*.objectstack.ai
 
 # Disable CORS
-CORS_ENABLED=false
+OS_CORS_ENABLED=false
 
 # Additional options
-CORS_CREDENTIALS=true
-CORS_MAX_AGE=86400
+OS_CORS_CREDENTIALS=true   # default; must be false for OS_CORS_ORIGIN=*
+OS_CORS_MAX_AGE=86400
 ```
 
+The legacy `CORS_*` names are still read.
+
 ### Disable CORS
 
 ```typescript
 
@@ -125,6 +125,20 @@ export interface HttpsListenerMaterial {
 
 export interface HonoCorsOptions {
     enabled?: boolean;
+    /**
+     * The origins admitted to cross-origin requests: exact origins and
+     * wildcard patterns (`https://*.example.com`, `http://localhost:*`), as an
+     * array or one comma-separated string. Wins over `OS_CORS_ORIGIN`.
+     *
+     * No default list. With neither this nor `OS_CORS_ORIGIN` set, no
+     * cross-origin caller is admitted — a loopback origin excepted, on a
+     * development boot only (`NODE_ENV=development`). Same-origin requests
+     * need no CORS answer and are unaffected either way.
+     *
+     * `'*'` (alone or in a list) is refused at init while
+     * {@link HonoCorsOptions.credentials} is on; it is accepted with
+     * credentials off.
+     */
     origins?: string | string[];
     methods?: string[];
     /**
@@ -144,6 +158,10 @@ export interface HonoCorsOptions {
      * exposed unless CORS is disabled entirely.
      */
     exposeHeaders?: string[];
+    /**
+     * Send `Access-Control-Allow-Credentials: true` to admitted origins.
+     * Defaults to `OS_CORS_CREDENTIALS !== 'false'`, i.e. on.
+     */
     credentials?: boolean;
     maxAge?: number;
 }