diff --git a/src/agents/model-selection.plugin-runtime.test.ts b/src/agents/model-selection.plugin-runtime.test.ts
index ba62b712261..fcfb2c25a82 100644
--- a/src/agents/model-selection.plugin-runtime.test.ts
+++ b/src/agents/model-selection.plugin-runtime.test.ts
@@ -16,25 +16,25 @@ describe("model-selection plugin runtime normalization", () => {
   it("delegates provider-owned model id normalization to plugin runtime hooks", async () => {
     normalizeProviderModelIdWithPluginMock.mockImplementation(({ provider, context }) => {
       if (
-        provider === "xai" &&
-        (context as { modelId?: string }).modelId === "grok-4.20-experimental-beta-0304-reasoning"
+        provider === "custom-provider" &&
+        (context as { modelId?: string }).modelId === "custom-legacy-model"
       ) {
-        return "grok-4.20-beta-latest-reasoning";
+        return "custom-modern-model";
       }
       return undefined;
     });
 
     const { parseModelRef } = await import("./model-selection.js");
 
-    expect(parseModelRef("grok-4.20-experimental-beta-0304-reasoning", "xai")).toEqual({
-      provider: "xai",
-      model: "grok-4.20-beta-latest-reasoning",
+    expect(parseModelRef("custom-legacy-model", "custom-provider")).toEqual({
+      provider: "custom-provider",
+      model: "custom-modern-model",
     });
     expect(normalizeProviderModelIdWithPluginMock).toHaveBeenCalledWith({
-      provider: "xai",
+      provider: "custom-provider",
       context: {
-        provider: "xai",
-        modelId: "grok-4.20-experimental-beta-0304-reasoning",
+        provider: "custom-provider",
+        modelId: "custom-legacy-model",
       },
     });
   });
diff --git a/src/agents/model-selection.ts b/src/agents/model-selection.ts
index 066b1570be6..b3c3c12d273 100644
--- a/src/agents/model-selection.ts
+++ b/src/agents/model-selection.ts
@@ -6,6 +6,8 @@ import {
   toAgentModelListLike,
 } from "../config/model-input.js";
 import { createSubsystemLogger } from "../logging/subsystem.js";
+import { normalizeGoogleModelId } from "../plugin-sdk/google.js";
+import { normalizeXaiModelId } from "../plugin-sdk/xai.js";
 import { resolveRuntimeCliBackends } from "../plugins/cli-backends.runtime.js";
 import { normalizeProviderModelIdWithPlugin } from "../plugins/provider-runtime.js";
 import { sanitizeForLog } from "../terminal/ansi.js";
@@ -117,6 +119,18 @@ function normalizeProviderModelId(provider: string, model: string): string {
   if (provider === "anthropic") {
     return normalizeAnthropicModelId(model);
   }
+  if (provider === "google" || provider === "google-vertex") {
+    return normalizeGoogleModelId(model);
+  }
+  if (provider === "openai") {
+    return model;
+  }
+  if (provider === "openrouter") {
+    return model.includes("/") ? model : `openrouter/${model}`;
+  }
+  if (provider === "xai") {
+    return normalizeXaiModelId(model);
+  }
   if (provider === "vercel-ai-gateway" && !model.includes("/")) {
     // Allow Vercel-specific Claude refs without an upstream prefix.
     const normalizedAnthropicModel = normalizeAnthropicModelId(model);
@@ -124,13 +138,6 @@ function normalizeProviderModelId(provider: string, model: string): string {
       return `anthropic/${normalizedAnthropicModel}`;
     }
   }
-  // OpenRouter-native models (e.g. "openrouter/aurora-alpha") need the full
-  // "openrouter/<name>" as the model ID sent to the API. Models from external
-  // providers already contain a slash (e.g. "anthropic/claude-sonnet-4-5") and
-  // are passed through as-is (#12924).
-  if (provider === "openrouter" && !model.includes("/")) {
-    return `openrouter/${model}`;
-  }
   return (
     normalizeProviderModelIdWithPlugin({
       provider,
@@ -201,7 +208,9 @@ export function inferUniqueProviderFromConfiguredModels(params: {
     if (!ref || !ref.includes("/")) {
       continue;
     }
-    const parsed = parseModelRef(ref, DEFAULT_PROVIDER);
+    const parsed = parseModelRef(ref, DEFAULT_PROVIDER, {
+      allowPluginNormalization: false,
+    });
     if (!parsed) {
       continue;
     }