diff --git a/extensions/codex/provider-catalog.ts b/extensions/codex/provider-catalog.ts
index 33b6e0442b9..76a4ac4df2b 100644
--- a/extensions/codex/provider-catalog.ts
+++ b/extensions/codex/provider-catalog.ts
@@ -13,9 +13,9 @@ const DEFAULT_MAX_TOKENS = 128_000;
 
 export const FALLBACK_CODEX_MODELS = [
   {
-    id: "gpt-5.4",
-    model: "gpt-5.4",
-    displayName: "gpt-5.4",
+    id: "gpt-5.5",
+    model: "gpt-5.5",
+    displayName: "gpt-5.5",
     description: "Latest frontier agentic coding model.",
     isDefault: true,
     inputModalities: ["text", "image"],
diff --git a/extensions/codex/provider.test.ts b/extensions/codex/provider.test.ts
index 773cc569c7e..71571cab11b 100644
--- a/extensions/codex/provider.test.ts
+++ b/extensions/codex/provider.test.ts
@@ -17,7 +17,7 @@ function expectStaticFallbackCatalog(
   result: Awaited<ReturnType<typeof buildCodexProviderCatalog>>,
 ) {
   expect(result.provider.models.map((model) => model.id)).toEqual([
-    "gpt-5.4",
+    "gpt-5.5",
     "gpt-5.4-mini",
     "gpt-5.2",
   ]);
@@ -241,7 +241,7 @@ describe("codex provider", () => {
 
     expect(
       result && "provider" in result ? result.provider.models.map((model) => model.id) : [],
-    ).toEqual(["gpt-5.4", "gpt-5.4-mini", "gpt-5.2"]);
+    ).toEqual(["gpt-5.5", "gpt-5.4-mini", "gpt-5.2"]);
   });
 
   it("adds the GPT-5 prompt overlay to Codex provider runs", () => {
diff --git a/extensions/codex/provider.ts b/extensions/codex/provider.ts
index 6e8e1b40a1f..1c4cf0ee9a8 100644
--- a/extensions/codex/provider.ts
+++ b/extensions/codex/provider.ts
@@ -110,7 +110,7 @@ export async function buildCodexProviderCatalog(
   };
 }
 
-function resolveCodexDynamicModel(modelId: string): ProviderRuntimeModel | undefined {
+function resolveCodexDynamicModel(modelId: string) {
   const id = modelId.trim();
   if (!id) {
     return undefined;
@@ -191,5 +191,7 @@ function isKnownXHighCodexModel(modelId: string): boolean {
 
 function isModernCodexModel(modelId: string): boolean {
   const lower = modelId.trim().toLowerCase();
-  return lower === "gpt-5.4" || lower === "gpt-5.4-mini" || lower === "gpt-5.2";
+  return (
+    lower === "gpt-5.5" || lower === "gpt-5.4" || lower === "gpt-5.4-mini" || lower === "gpt-5.2"
+  );
 }
diff --git a/extensions/openai/openai-provider.ts b/extensions/openai/openai-provider.ts
index 67adb2f7c91..0eb75ee6dbc 100644
--- a/extensions/openai/openai-provider.ts
+++ b/extensions/openai/openai-provider.ts
@@ -114,9 +114,7 @@ function normalizeOpenAITransport(model: ProviderRuntimeModel): ProviderRuntimeM
   };
 }
 
-function resolveOpenAIGptForwardCompatModel(
-  ctx: ProviderResolveDynamicModelContext,
-): ProviderRuntimeModel | undefined {
+function resolveOpenAIGptForwardCompatModel(ctx: ProviderResolveDynamicModelContext) {
   const trimmedModelId = ctx.modelId.trim();
   const lower = normalizeLowercaseStringOrEmpty(trimmedModelId);
   let templateIds: readonly string[];
@@ -286,7 +284,7 @@ export function buildOpenAIProvider(): ProviderPlugin {
       }
       return {
         suppress: true,
-        errorMessage: `Unknown model: ${ctx.provider}/${OPENAI_DIRECT_SPARK_MODEL_ID}. ${OPENAI_DIRECT_SPARK_MODEL_ID} is only supported via openai-codex OAuth. Use openai-codex/${OPENAI_DIRECT_SPARK_MODEL_ID}.`,
+        errorMessage: `Unknown model: ${ctx.provider}/${OPENAI_DIRECT_SPARK_MODEL_ID}. ${OPENAI_DIRECT_SPARK_MODEL_ID} is only supported through Codex OAuth. Use openai/${OPENAI_DIRECT_SPARK_MODEL_ID} with the Codex OAuth profile.`,
       };
     },
     augmentModelCatalog: (ctx) => {
diff --git a/src/agents/pi-embedded-runner/model.forward-compat.errors-and-overrides.test.ts b/src/agents/pi-embedded-runner/model.forward-compat.errors-and-overrides.test.ts
index 63837087938..ed564cb7e85 100644
--- a/src/agents/pi-embedded-runner/model.forward-compat.errors-and-overrides.test.ts
+++ b/src/agents/pi-embedded-runner/model.forward-compat.errors-and-overrides.test.ts
@@ -31,7 +31,7 @@ vi.mock("../model-suppression.js", () => ({
     ) {
       return undefined;
     }
-    return `Unknown model: ${provider}/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported via openai-codex OAuth. Use openai-codex/gpt-5.3-codex-spark.`;
+    return `Unknown model: ${provider}/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported through Codex OAuth. Use openai/gpt-5.3-codex-spark with the Codex OAuth profile.`;
   },
 }));
 
@@ -140,7 +140,7 @@ describe("resolveModel forward-compat errors and overrides", () => {
 
     expect(result.model).toBeUndefined();
     expect(result.error).toBe(
-      "Unknown model: openai/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported via openai-codex OAuth. Use openai-codex/gpt-5.3-codex-spark.",
+      "Unknown model: openai/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported through Codex OAuth. Use openai/gpt-5.3-codex-spark with the Codex OAuth profile.",
     );
   });
 
@@ -161,7 +161,7 @@ describe("resolveModel forward-compat errors and overrides", () => {
 
     expect(result.model).toBeUndefined();
     expect(result.error).toBe(
-      "Unknown model: openai/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported via openai-codex OAuth. Use openai-codex/gpt-5.3-codex-spark.",
+      "Unknown model: openai/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported through Codex OAuth. Use openai/gpt-5.3-codex-spark with the Codex OAuth profile.",
     );
   });
 
@@ -174,7 +174,7 @@ describe("resolveModel forward-compat errors and overrides", () => {
 
     expect(result.model).toBeUndefined();
     expect(result.error).toBe(
-      "Unknown model: azure-openai-responses/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported via openai-codex OAuth. Use openai-codex/gpt-5.3-codex-spark.",
+      "Unknown model: azure-openai-responses/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported through Codex OAuth. Use openai/gpt-5.3-codex-spark with the Codex OAuth profile.",
     );
   });
 
diff --git a/src/agents/pi-embedded-runner/model.test.ts b/src/agents/pi-embedded-runner/model.test.ts
index 6c3472177bb..2a3f18a4f30 100644
--- a/src/agents/pi-embedded-runner/model.test.ts
+++ b/src/agents/pi-embedded-runner/model.test.ts
@@ -13,7 +13,7 @@ vi.mock("../model-suppression.js", () => ({
     ) {
       return undefined;
     }
-    return `Unknown model: ${provider}/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported via openai-codex OAuth. Use openai-codex/gpt-5.3-codex-spark.`;
+    return `Unknown model: ${provider}/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported through Codex OAuth. Use openai/gpt-5.3-codex-spark with the Codex OAuth profile.`;
   },
 }));
 
@@ -1260,7 +1260,7 @@ describe("resolveModel", () => {
 
     expect(result.model).toBeUndefined();
     expect(result.error).toBe(
-      "Unknown model: openai/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported via openai-codex OAuth. Use openai-codex/gpt-5.3-codex-spark.",
+      "Unknown model: openai/gpt-5.3-codex-spark. gpt-5.3-codex-spark is only supported through Codex OAuth. Use openai/gpt-5.3-codex-spark with the Codex OAuth profile.",
     );
   });
 
diff --git a/src/plugins/provider-runtime.test-support.ts b/src/plugins/provider-runtime.test-support.ts
index b2c9a26e645..3fd7485557f 100644
--- a/src/plugins/provider-runtime.test-support.ts
+++ b/src/plugins/provider-runtime.test-support.ts
@@ -77,7 +77,9 @@ export function expectCodexBuiltInSuppression(
     }),
   ).toMatchObject({
     suppress: true,
-    errorMessage: expect.stringContaining("openai-codex/gpt-5.3-codex-spark"),
+    errorMessage: expect.stringContaining(
+      "openai/gpt-5.3-codex-spark with the Codex OAuth profile",
+    ),
   });
 }
 
diff --git a/src/plugins/provider-runtime.test.ts b/src/plugins/provider-runtime.test.ts
index d9e65f5f9a9..da9ffcc75ae 100644
--- a/src/plugins/provider-runtime.test.ts
+++ b/src/plugins/provider-runtime.test.ts
@@ -134,7 +134,10 @@ function createOpenAiCatalogProviderPlugin(
     suppressBuiltInModel: ({ provider, modelId }) =>
       (provider === "openai" || provider === "azure-openai-responses") &&
       modelId === "gpt-5.3-codex-spark"
-        ? { suppress: true, errorMessage: "openai-codex/gpt-5.3-codex-spark" }
+        ? {
+            suppress: true,
+            errorMessage: "openai/gpt-5.3-codex-spark with the Codex OAuth profile",
+          }
         : undefined,
     augmentModelCatalog: () => [
       { provider: "openai", id: "gpt-5.4", name: "gpt-5.4" },