diff --git a/apps/x/packages/core/src/models/gateway.ts b/apps/x/packages/core/src/models/gateway.ts
index ee14a7fa..bdaa7ab5 100644
--- a/apps/x/packages/core/src/models/gateway.ts
+++ b/apps/x/packages/core/src/models/gateway.ts
@@ -3,6 +3,7 @@ import { createOpenRouter } from '@openrouter/ai-sdk-provider';
 import { getAccessToken } from '../auth/tokens.js';
 import { getCurrentUseCase } from '../analytics/use_case.js';
 import { API_URL } from '../config/env.js';
+import { annotateReasoningFlags } from './models-dev.js';
 
 const authedFetch: typeof fetch = async (input, init) => {
     const token = await getAccessToken();
@@ -30,6 +31,7 @@ type ProviderSummary = {
         id: string;
         name?: string;
         release_date?: string;
+        reasoning?: boolean;
     }>;
 };
 
@@ -42,7 +44,9 @@ export async function listGatewayModels(): Promise<{ providers: ProviderSummary[
         throw new Error(`Gateway /v1/models failed: ${response.status}`);
     }
     const body = await response.json() as { data: Array<{ id: string }> };
-    const models = body.data.map((m) => ({ id: m.id }));
+    // The gateway returns bare "vendor/model" ids; the models.dev cache
+    // supplies the reasoning capability the composer's effort control needs.
+    const models = await annotateReasoningFlags(body.data.map((m) => ({ id: m.id })));
     return {
         providers: [{
             id: 'rowboat',
diff --git a/apps/x/packages/core/src/models/models-dev.ts b/apps/x/packages/core/src/models/models-dev.ts
index 5be56c9f..14286a08 100644
--- a/apps/x/packages/core/src/models/models-dev.ts
+++ b/apps/x/packages/core/src/models/models-dev.ts
@@ -85,6 +85,8 @@ type ProviderSummary = {
     id: string;
     name?: string;
     release_date?: string;
+    // Supports reasoning/extended thinking per models.dev; absent = unknown.
+    reasoning?: boolean;
   }>;
 };
 
@@ -195,10 +197,11 @@ function normalizeModels(models: Record<string, z.infer<typeof ModelsDevModel>>)
       name: model.name,
       release_date: model.release_date,
       tool_call: model.tool_call,
+      reasoning: model.reasoning,
       status: model.status,
     }))
     .filter((model) => isStableModel(model) && supportsToolCall(model))
-    .map(({ id, name, release_date }) => ({ id, name, release_date }));
+    .map(({ id, name, release_date, reasoning }) => ({ id, name, release_date, reasoning }));
 
   list.sort((a, b) => {
     const aDate = a.release_date ? Date.parse(a.release_date) : 0;
@@ -268,6 +271,44 @@ export async function isReasoningModel(
   }
 }
 
+/**
+ * Annotate gateway-style "vendor/model" ids with the models.dev reasoning
+ * flag. Reads the cache once for the whole batch; ids whose vendor or model
+ * is unknown keep `reasoning` absent (= unknown). Cache-only, like
+ * isReasoningModel.
+ */
+export async function annotateReasoningFlags<T extends { id: string }>(
+  models: T[],
+): Promise<Array<T & { reasoning?: boolean }>> {
+  let catalog: z.infer<typeof ModelsDevResponse> | null = null;
+  try {
+    const cached = await readCache();
+    if (cached) {
+      const parsed = ModelsDevResponse.safeParse(cached.data);
+      if (parsed.success) catalog = parsed.data;
+    }
+  } catch {
+    catalog = null;
+  }
+  if (!catalog) return models;
+
+  const flags = new Map<string, boolean>();
+  for (const vendor of ["openai", "anthropic", "google"] as const) {
+    const provider = pickProvider(catalog, vendor);
+    if (!provider) continue;
+    for (const [key, model] of Object.entries(provider.models)) {
+      if (typeof model.reasoning === "boolean") {
+        flags.set(`${vendor}/${model.id ?? key}`, model.reasoning);
+      }
+    }
+  }
+
+  return models.map((model) => {
+    const reasoning = flags.get(model.id);
+    return reasoning === undefined ? model : { ...model, reasoning };
+  });
+}
+
 export async function getChatModelIds(
   flavor: "openai" | "anthropic" | "google",
 ): Promise<Set<string>> {
diff --git a/apps/x/packages/shared/src/ipc.ts b/apps/x/packages/shared/src/ipc.ts
index 77b573f9..17872e88 100644
--- a/apps/x/packages/shared/src/ipc.ts
+++ b/apps/x/packages/shared/src/ipc.ts
@@ -586,6 +586,9 @@ const ipcSchemas = {
           id: z.string(),
           name: z.string().optional(),
           release_date: z.string().optional(),
+          // models.dev "supports reasoning/extended thinking" flag; absent =
+          // unknown. Gates the composer's reasoning-effort control.
+          reasoning: z.boolean().optional(),
         })),
       })),
       lastUpdated: z.string().optional(),