diff --git a/src/providers/registry/entries-extended.ts b/src/providers/registry/entries-extended.ts
index 2a92a9b832..5cea61a84f 100644
--- a/src/providers/registry/entries-extended.ts
+++ b/src/providers/registry/entries-extended.ts
@@ -110,6 +110,13 @@ export const PROVIDER_REGISTRY_EXTENDED: readonly ProviderRegistryEntry[] = [
     // Baseten says models outside its reasoning table do not support reasoning. Keep
     // unknown/new live slugs conservative until an official-docs registry refresh proves it.
     reasoningEfforts: [],
+    // `text.verbosity` is an OpenAI Responses parameter. Baseten documents its Model
+    // APIs as Chat Completions compatible, so there is nothing on that wire for it to
+    // become, and a routed row must not inherit the Codex template's verbosity picker
+    // (#4630: Codex sent `text: { verbosity: "low" }` and the turn 400'd before any
+    // model output). Provider-wide rather than per-model because this catalog is live-
+    // discovered: a slug that arrives tomorrow supports it no more than the seeded ones.
+    supportsVerbosity: false,
     modelReasoningEfforts: BASETEN_MODEL_REASONING_EFFORTS,
     modelReasoningEffortMap: BASETEN_MODEL_REASONING_EFFORT_MAP,
     modelDefaultReasoningEfforts: BASETEN_MODEL_DEFAULT_REASONING_EFFORTS,
diff --git a/tests/codex-integration/catalog-verbosity-default.test.ts b/tests/codex-integration/catalog-verbosity-default.test.ts
index 1ed5c8f164..a3224b5b3c 100644
--- a/tests/codex-integration/catalog-verbosity-default.test.ts
+++ b/tests/codex-integration/catalog-verbosity-default.test.ts
@@ -61,6 +61,60 @@ describe("catalog — default_verbosity is dropped when verbosity is unsupported
     expect(kiro?.default_verbosity).toBeUndefined();
   });
 
+  test("GREEN: a Baseten routed row opts out, defaults included", async () => {
+    // #4630: Baseten Model APIs are Chat Completions only, so `text.verbosity`
+    // — a Responses-only parameter — has nowhere to land. Advertising it made
+    // Codex send `text: { verbosity: "low" }` and the turn 400 before any model
+    // output. The opt-out is provider-wide because Baseten's catalog is live-
+    // discovered: a slug that arrives tomorrow supports it no more than this one.
+    const models = await gatherRoutedModels({
+      providers: {
+        baseten: {
+          adapter: "openai-chat",
+          baseUrl: "https://inference.baseten.co/v1",
+          authMode: "key",
+          liveModels: false,
+          models: ["deepseek-ai/DeepSeek-V4.1-Flash"],
+        },
+      },
+    });
+    const entries = buildCatalogEntries(null, [], models);
+    const baseten = entries.find(e => e.slug?.startsWith("baseten/"));
+
+    expect(baseten?.support_verbosity).toBe(false);
+    expect(baseten?.default_verbosity).toBeUndefined();
+  });
+
+  test("GREEN: a slug that only live discovery knows about opts out too", async () => {
+    // The opt-out is provider-wide precisely because baseten is `liveModels: true`:
+    // a pinned per-model map would leave tomorrow's discovered id advertising the
+    // control again. Seeding NO static models and letting discovery supply the slug
+    // is what makes that claim testable rather than a comment (raised in review of
+    // #4660 by @coderabbitai and @lidge-jun).
+    globalThis.fetch = (async (input: RequestInfo | URL) => {
+      if (!String(input).includes("/models")) return new Response(null, { status: 404 });
+      return Response.json({ data: [{ id: "deepseek-ai/DeepSeek-V4.1-Flash" }] });
+    }) as typeof fetch;
+
+    const models = await gatherRoutedModels({
+      providers: {
+        baseten: {
+          adapter: "openai-chat",
+          baseUrl: "https://inference.baseten.co/v1",
+          authMode: "key",
+          apiKey: "test-key",
+          liveModels: true,
+        },
+      },
+    });
+    const entries = buildCatalogEntries(null, [], models);
+    const baseten = entries.find(e => e.slug?.startsWith("baseten/"));
+
+    expect(baseten, "live discovery must have produced a routed baseten row").toBeDefined();
+    expect(baseten?.support_verbosity).toBe(false);
+    expect(baseten?.default_verbosity).toBeUndefined();
+  });
+
   test("CONTROL: rows that never declare a capability keep the permissive default", async () => {
     const models = await gatherRoutedModels({
       providers: {