fix(host): pin model discovery to loopback and drop its unread wire field

llm.discoverModels was reachable from any declared trusted host. The
method takes a caller-supplied baseURL and makes the host issue a GET to
it, then reports the status or the parsed body — so on a LAN deployment
an anonymous caller had a probe for whatever the host can reach and the
browser cannot, plus a path that carries a draft credential. The
PRIVILEGED_METHODS doc already states the rule this broke: trustedHosts
is a DNS-rebinding fence, not authentication, so the configuration plane
stays loopback-same-origin. It is in that set now, asserted both against
the hand-built fence and over real HTTP beside the catalog reads that
deliberately stay reachable.

supportsDiscovery and listModelDiscoveryNamespaces are gone. The field
was required on the wire and read by nobody: its own contract said a
surface should offer the action "instead of naming an adapter family it
would have to hardcode", while the surface hardcodes llm-pi-ai in two
places and gates the button on whether there is anything to probe. Its
shape did not fit the second caller either — the create card has no row
to read a per-row field from. Keeping a required field alive for a
consumer that may never arrive costs every producer and fixture a value
nobody consults, which is exactly how the fixtures drifted. The registry
that fed it had no other production consumer, so registration and
disposal are now observed through the offer itself.

The Agent Note claimed the key is never logged, which the wire schema
beside it already contradicts, and predated both the provider field and
the catalog-answer path. The two new public types pointed at core.md
without a type-equiv block or manifest entry, so the generated service
catalog named documentation that did not exist.

packages/client/connection/src/client/fixture.ts

@@ -2438,9 +2438,9 @@ export function createFixtureApi(options: FixtureOptions = {}): ApiProxy {
     llm: {
       providers: request => ok(request, {
         providers: [
-          { provider: 'deepseek-official', displayName: 'DeepSeek', settingsNs: 'llm-deepseek', settingsPath: [], active: true, supportsDiscovery: false },
-          { provider: 'openai', displayName: 'openai', settingsNs: 'llm-pi-ai', settingsPath: ['providers', 'openai'], active: true, supportsDiscovery: true },
-          { provider: 'anthropic', displayName: 'anthropic', settingsNs: 'llm-pi-ai', settingsPath: ['providers', 'anthropic'], active: false, supportsDiscovery: true },
+          { provider: 'deepseek-official', displayName: 'DeepSeek', settingsNs: 'llm-deepseek', settingsPath: [], active: true },
+          { provider: 'openai', displayName: 'openai', settingsNs: 'llm-pi-ai', settingsPath: ['providers', 'openai'], active: true },
+          { provider: 'anthropic', displayName: 'anthropic', settingsNs: 'llm-pi-ai', settingsPath: ['providers', 'anthropic'], active: false },
         ],
       }),
       models: request => ok(request, { groups: fixtureModelGroups(), failures: [] }),

packages/client/connection/src/index.ts

@@ -44,10 +44,15 @@ export const Config: z<ConnectionConfig> = z.object({
  * reconnaissance no anonymous caller should have. `trustedHosts` is a
  * DNS-rebinding fence, explicitly not authentication, so the whole
  * configuration plane stays loopback-same-origin until a real authentication
- * layer exists. The model catalog (`llm.providers`, `llm.models`) is
- * deliberately NOT here: it carries provider ids, display names, and model
- * lists — no endpoints, keys, or key state — and a LAN client's model picker
- * legitimately needs it.
+ * layer exists. `llm.discoverModels` belongs to that plane on both counts: it
+ * carries a draft credential, and it makes the HOST issue a GET to a URL the
+ * caller chose and reports back the status or the parsed body — an anonymous
+ * LAN caller would have a probe for whatever the host can reach and the
+ * browser cannot.
+ *
+ * The model catalog (`llm.providers`, `llm.models`) is deliberately NOT here:
+ * it carries provider ids, display names, and model lists — no endpoints,
+ * keys, or key state — and a LAN client's model picker legitimately needs it.
  */
 const PRIVILEGED_METHODS = new Set([
   'host.pickDirectory',
@@ -60,6 +65,7 @@ const PRIVILEGED_METHODS = new Set([
   'credentials.describe',
   'credentials.set',
   'credentials.unset',
+  'llm.discoverModels',
 ])
 
 /**

packages/client/connection/tests/node-half.spec.ts

@@ -129,13 +129,15 @@ describe('connection node half', () => {
   it('pins privileged methods to loopback even for a declared trusted authority', async () => {
     const { routes, dispose } = await mounted({ trustedHosts: ['harness.example'] })
     // The privileged set: native dialogs plus the whole settings/credential
-    // configuration plane, reads included. The same declared authority reaches
+    // configuration plane, reads included, plus the one method that makes the
+    // host fetch a caller-chosen URL. The same declared authority reaches
     // ordinary reads (carrier-level 404 from the empty proxy proves the fence
     // passed), but each privileged method stays loopback-only and 403s.
     for (const method of [
       'host.pickDirectory', 'host.openPath',
       'settings.describe', 'settings.openDocument', 'settings.update', 'settings.replace', 'settings.mutate',
       'credentials.describe', 'credentials.set', 'credentials.unset',
+      'llm.discoverModels',
     ]) {
       const denied = fakeResponse()
       await routes[0]!.handler(
@@ -221,6 +223,9 @@ describe('connection node half over a real HTTP server', () => {
         'settings.describe', 'settings.openDocument', 'settings.update', 'settings.replace', 'settings.mutate',
         'credentials.describe', 'credentials.set', 'credentials.unset',
         'host.pickDirectory', 'host.openPath',
+        // Carries a draft credential and turns the host into a fetcher for a
+        // URL the caller picked: an anonymous LAN caller must not reach it.
+        'llm.discoverModels',
       ]) {
         expect([method, await call(port, method, 'harness.example')]).toEqual([method, 403])
       }