Plugins: fail fast on channel and binding collisions (#45628)

* Plugins: reject duplicate channel ids

* Bindings: reject duplicate adapter registration

* Plugins: fail on export id mismatch

src/infra/outbound/session-binding-service.test.ts

@@ -198,4 +198,24 @@ describe("session binding service", () => {
       placements: [],
     });
   });
+
+  it("rejects duplicate adapter registration for the same channel account", () => {
+    registerSessionBindingAdapter({
+      channel: "discord",
+      accountId: "default",
+      bind: async (input) => createRecord(input),
+      listBySession: () => [],
+      resolveByConversation: () => null,
+    });
+
+    expect(() =>
+      registerSessionBindingAdapter({
+        channel: "Discord",
+        accountId: "DEFAULT",
+        bind: async (input) => createRecord(input),
+        listBySession: () => [],
+        resolveByConversation: () => null,
+      }),
+    ).toThrow("Session binding adapter already registered for discord:default");
+  });
 });

src/infra/outbound/session-binding-service.ts

@@ -148,15 +148,22 @@ function resolveAdapterCapabilities(
 const ADAPTERS_BY_CHANNEL_ACCOUNT = new Map<string, SessionBindingAdapter>();
 
 export function registerSessionBindingAdapter(adapter: SessionBindingAdapter): void {
-  const key = toAdapterKey({
-    channel: adapter.channel,
-    accountId: adapter.accountId,
-  });
-  ADAPTERS_BY_CHANNEL_ACCOUNT.set(key, {
+  const normalizedAdapter = {
     ...adapter,
     channel: adapter.channel.trim().toLowerCase(),
     accountId: normalizeAccountId(adapter.accountId),
+  };
+  const key = toAdapterKey({
+    channel: normalizedAdapter.channel,
+    accountId: normalizedAdapter.accountId,
   });
+  const existing = ADAPTERS_BY_CHANNEL_ACCOUNT.get(key);
+  if (existing && existing !== adapter) {
+    throw new Error(
+      `Session binding adapter already registered for ${normalizedAdapter.channel}:${normalizedAdapter.accountId}`,
+    );
+  }
+  ADAPTERS_BY_CHANNEL_ACCOUNT.set(key, normalizedAdapter);
 }
 
 export function unregisterSessionBindingAdapter(params: {