diff --git a/ui/desktop/src/acp/__tests__/providers.test.ts b/ui/desktop/src/acp/__tests__/providers.test.ts
new file mode 100644
index 000000000..0d419e244
--- /dev/null
+++ b/ui/desktop/src/acp/__tests__/providers.test.ts
@@ -0,0 +1,80 @@
+import { beforeEach, describe, expect, it, vi } from 'vitest';
+import { getAcpClient } from '../acpConnection';
+import { acpSetSessionProviderModel } from '../providers';
+
+vi.mock('../acpConnection', () => ({
+  getAcpClient: vi.fn(),
+}));
+
+function selectConfigOption(id: string, currentValue: string) {
+  return {
+    id,
+    name: id,
+    type: 'select',
+    currentValue,
+    options: [],
+  };
+}
+
+describe('ACP providers', () => {
+  beforeEach(() => {
+    vi.clearAllMocks();
+  });
+
+  it('sets thinking effort after provider and model, then returns the final config response', async () => {
+    const client = {
+      setSessionConfigOption: vi
+        .fn()
+        .mockResolvedValueOnce({
+          configOptions: [
+            selectConfigOption('provider', 'anthropic'),
+            selectConfigOption('model', 'provider-default-model'),
+          ],
+        })
+        .mockResolvedValueOnce({
+          configOptions: [
+            selectConfigOption('provider', 'anthropic'),
+            selectConfigOption('model', 'claude-sonnet-4-5'),
+          ],
+        })
+        .mockResolvedValueOnce({
+          configOptions: [
+            selectConfigOption('provider', 'anthropic'),
+            selectConfigOption('model', 'claude-sonnet-4-5'),
+            selectConfigOption('thinking_effort', 'high'),
+          ],
+        }),
+    };
+    vi.mocked(getAcpClient).mockResolvedValue(
+      client as unknown as Awaited<ReturnType<typeof getAcpClient>>
+    );
+
+    const applied = await acpSetSessionProviderModel(
+      'session-1',
+      'anthropic',
+      'claude-sonnet-4-5',
+      'high'
+    );
+
+    expect(client.setSessionConfigOption).toHaveBeenCalledTimes(3);
+    expect(client.setSessionConfigOption).toHaveBeenNthCalledWith(1, {
+      sessionId: 'session-1',
+      configId: 'provider',
+      value: 'anthropic',
+    });
+    expect(client.setSessionConfigOption).toHaveBeenNthCalledWith(2, {
+      sessionId: 'session-1',
+      configId: 'model',
+      value: 'claude-sonnet-4-5',
+    });
+    expect(client.setSessionConfigOption).toHaveBeenNthCalledWith(3, {
+      sessionId: 'session-1',
+      configId: 'thinking_effort',
+      value: 'high',
+    });
+    expect(applied).toEqual({
+      providerId: 'anthropic',
+      modelId: 'claude-sonnet-4-5',
+    });
+  });
+});
diff --git a/ui/desktop/src/acp/providers.ts b/ui/desktop/src/acp/providers.ts
index 933559a17..e2e2100ce 100644
--- a/ui/desktop/src/acp/providers.ts
+++ b/ui/desktop/src/acp/providers.ts
@@ -198,6 +198,55 @@ export async function acpSaveThinkingEffort(effort: ThinkingEffort): Promise<voi
   });
 }
 
+export type AppliedSessionProviderModel = {
+  providerId?: string;
+  modelId?: string;
+};
+
+function extractAppliedSessionProviderModel(configOptions: unknown): AppliedSessionProviderModel {
+  if (!Array.isArray(configOptions)) {
+    return {};
+  }
+
+  const applied: AppliedSessionProviderModel = {};
+
+  for (const option of configOptions) {
+    if (!option || typeof option !== 'object') {
+      continue;
+    }
+
+    const id = 'id' in option ? option.id : undefined;
+    if (id !== 'provider' && id !== 'model') {
+      continue;
+    }
+
+    const currentValue = selectCurrentValue(option);
+    if (typeof currentValue !== 'string') {
+      continue;
+    }
+
+    if (id === 'provider') {
+      applied.providerId = currentValue;
+    } else {
+      applied.modelId = currentValue;
+    }
+  }
+
+  return applied;
+}
+
+function selectCurrentValue(kind: unknown): unknown {
+  if (!kind || typeof kind !== 'object') {
+    return undefined;
+  }
+
+  if ('type' in kind && kind.type === 'select' && 'currentValue' in kind) {
+    return kind.currentValue;
+  }
+
+  return undefined;
+}
+
 /**
  * Switch the provider (and model) for an active session via ACP config options.
  *
@@ -207,11 +256,29 @@ export async function acpSaveThinkingEffort(effort: ThinkingEffort): Promise<voi
 export async function acpSetSessionProviderModel(
   sessionId: string,
   providerId: string,
-  modelId?: string | null
-): Promise<void> {
+  modelId?: string | null,
+  thinkingEffort?: ThinkingEffort | null
+): Promise<AppliedSessionProviderModel> {
   const client = await getAcpClient();
-  await client.setSessionConfigOption({ sessionId, configId: 'provider', value: providerId });
+  let response = await client.setSessionConfigOption({
+    sessionId,
+    configId: 'provider',
+    value: providerId,
+  });
   if (modelId) {
-    await client.setSessionConfigOption({ sessionId, configId: 'model', value: modelId });
+    response = await client.setSessionConfigOption({
+      sessionId,
+      configId: 'model',
+      value: modelId,
+    });
   }
+  if (thinkingEffort != null) {
+    response = await client.setSessionConfigOption({
+      sessionId,
+      configId: 'thinking_effort',
+      value: thinkingEffort,
+    });
+  }
+
+  return extractAppliedSessionProviderModel(response.configOptions);
 }
diff --git a/ui/desktop/src/components/ModelAndProviderContext.tsx b/ui/desktop/src/components/ModelAndProviderContext.tsx
index 077c3b349..81b41baa4 100644
--- a/ui/desktop/src/components/ModelAndProviderContext.tsx
+++ b/ui/desktop/src/components/ModelAndProviderContext.tsx
@@ -2,7 +2,13 @@ import React, { createContext, useContext, useState, useEffect, useMemo, useCall
 import { toastError, toastSuccess } from '../toasts';
 import Model, { getProviderMetadata } from './settings/models/modelInterface';
 import { ProviderMetadata } from '../api';
-import { acpReadDefaults, acpSaveDefaults, acpSetSessionProviderModel } from '../acp/providers';
+import { acpChatSessionActions, acpChatSessionStore } from '../acp/chatSessionStore';
+import {
+  acpReadDefaults,
+  acpSaveDefaults,
+  acpSetSessionProviderModel,
+  type AppliedSessionProviderModel,
+} from '../acp/providers';
 import { errorMessage } from '../utils/conversionUtils';
 import {
   getModelDisplayName,
@@ -57,6 +63,27 @@ const ModelAndProviderContext = createContext<ModelAndProviderContextType | unde
 
 export { i18n as modelAndProviderMessages };
 
+function patchAcpSessionProviderModel(
+  sessionId: string,
+  { providerId, modelId }: AppliedSessionProviderModel
+) {
+  if (!providerId && !modelId) return;
+
+  const currentSession = acpChatSessionStore.getSnapshot(sessionId)?.session;
+  if (!currentSession) return;
+
+  acpChatSessionActions.setSessionMetadata(sessionId, {
+    ...currentSession,
+    provider_name: providerId ?? currentSession.provider_name,
+    model_config: modelId
+      ? {
+          ...(currentSession.model_config ?? { toolshim: false }),
+          model_name: modelId,
+        }
+      : currentSession.model_config,
+  });
+}
+
 export const ModelAndProviderProvider: React.FC<ModelAndProviderProviderProps> = ({ children }) => {
   const [currentModel, setCurrentModel] = useState<string | null>(null);
   const [currentProvider, setCurrentProvider] = useState<string | null>(null);
@@ -70,7 +97,13 @@ export const ModelAndProviderProvider: React.FC<ModelAndProviderProviderProps> =
 
       try {
         if (sessionId) {
-          await acpSetSessionProviderModel(sessionId, providerName, modelName);
+          const applied = await acpSetSessionProviderModel(
+            sessionId,
+            providerName,
+            modelName,
+            model.request_params?.thinking_effort ?? null
+          );
+          patchAcpSessionProviderModel(sessionId, applied);
         }
 
         // Only update the global config default when there's no session