fix web search fallback explicitness

src/web-search/runtime.test.ts

@@ -503,6 +503,49 @@ describe("web search runtime", () => {
     ).rejects.toThrow('Unknown web_search provider "missing-id".');
   });
 
+  it("still falls back when config names an unknown provider id", async () => {
+    resolveRuntimeWebSearchProvidersMock.mockReturnValue([
+      createProvider({
+        pluginId: "google",
+        id: "google",
+        credentialPath: "tools.web.search.google.apiKey",
+        autoDetectOrder: 1,
+        getCredentialValue: () => "configured",
+        createTool: () => {
+          throw new Error("google aborted");
+        },
+      }),
+      createProvider({
+        pluginId: "duckduckgo",
+        id: "duckduckgo",
+        credentialPath: "",
+        autoDetectOrder: 100,
+        requiresCredential: false,
+      }),
+    ]);
+
+    await expect(
+      runWebSearch({
+        config: {
+          tools: {
+            web: {
+              search: {
+                provider: "missing-id",
+              },
+            },
+          },
+        },
+        args: { query: "config-typo" },
+      }),
+    ).resolves.toMatchObject({
+      provider: "duckduckgo",
+      result: expect.objectContaining({
+        provider: "duckduckgo",
+        query: "config-typo",
+      }),
+    });
+  });
+
   it("honors preferRuntimeProviders during execution", async () => {
     const configuredProvider = createProvider({
       pluginId: "google",

src/web-search/runtime.ts

@@ -265,19 +265,36 @@ function hasExplicitWebSearchSelection(params: {
   search?: WebSearchConfig;
   runtimeWebSearch?: RuntimeWebSearchMetadata;
   providerId?: string;
+  providers?: PluginWebSearchProviderEntry[];
 }): boolean {
   if (params.providerId?.trim()) {
     return true;
   }
-  if (
+  const availableProviderIds = new Set(
+    (params.providers ?? []).map((provider) => provider.id.trim().toLowerCase()),
+  );
+  const configuredProviderId =
     params.search &&
     "provider" in params.search &&
-    typeof params.search.provider === "string" &&
-    params.search.provider.trim()
+    typeof params.search.provider === "string"
+      ? params.search.provider.trim().toLowerCase()
+      : "";
+  if (configuredProviderId && availableProviderIds.has(configuredProviderId)) {
+    return true;
+  }
+  const runtimeConfiguredId = (
+    params.runtimeWebSearch?.selectedProvider ?? params.runtimeWebSearch?.providerConfigured
+  )
+    ?.trim()
+    .toLowerCase();
+  if (
+    params.runtimeWebSearch?.providerSource === "configured" &&
+    runtimeConfiguredId &&
+    availableProviderIds.has(runtimeConfiguredId)
   ) {
     return true;
   }
-  return params.runtimeWebSearch?.providerSource === "configured";
+  return false;
 }
 
 export async function runWebSearch(
@@ -297,6 +314,7 @@ export async function runWebSearch(
     search,
     runtimeWebSearch,
     providerId: params.providerId,
+    providers: candidates,
   });
   let lastError: unknown;
   let sawUnavailableProvider = false;