diff --git a/client/src/routes/ChatRoute.tsx b/client/src/routes/ChatRoute.tsx
index 5f55df51dd..a514a60bfe 100644
--- a/client/src/routes/ChatRoute.tsx
+++ b/client/src/routes/ChatRoute.tsx
@@ -166,10 +166,6 @@ export default function ChatRoute() {
     }
 
     const getNewConvoPreset = () => {
-      const result = getDefaultModelSpec(startupConfig, endpointsQuery.data);
-      const spec = result?.default ?? result?.last ?? result?.softDefault;
-      const specPreset = spec ? getModelSpecPreset(spec) : undefined;
-
       const queryParams: Record<string, string> = {};
       searchParams.forEach((value, key) => {
         if (key !== 'prompt' && key !== 'q' && key !== 'submit' && key !== 'projectId') {
@@ -178,6 +174,18 @@ export default function ChatRoute() {
       });
       const querySettings = processValidSettings(queryParams);
 
+      /** A spec named in the URL is an explicit selection: it must resolve to its own
+       * full preset, or stale last-selection state (endpoint/agent) fills the gaps.
+       * Names absent from the client config (e.g. `showInMenu: false`) stay in the
+       * query settings untouched, since they remain resolvable server-side by name. */
+      const urlSpec = querySettings.spec
+        ? startupConfig?.modelSpecs?.list?.find((spec) => spec.name === querySettings.spec)
+        : undefined;
+
+      const result = urlSpec ? undefined : getDefaultModelSpec(startupConfig, endpointsQuery.data);
+      const spec = urlSpec ?? result?.default ?? result?.last ?? result?.softDefault;
+      const specPreset = spec ? getModelSpecPreset(spec) : undefined;
+
       if (Object.keys(querySettings).length > 0) {
         return mergeQuerySettingsWithSpec(specPreset, querySettings);
       }
diff --git a/e2e/specs/mock/soft-default.spec.ts b/e2e/specs/mock/soft-default.spec.ts
index 98cf01062f..640eed2bd1 100644
--- a/e2e/specs/mock/soft-default.spec.ts
+++ b/e2e/specs/mock/soft-default.spec.ts
@@ -1,6 +1,7 @@
 import { expect, test } from '@playwright/test';
 import type { TStartupConfig } from 'librechat-data-provider';
 import type { Page } from '@playwright/test';
+import { getPrimaryE2EUser } from '../../setup/users.mock';
 import {
   NEW_CHAT_PATH,
   getAccessToken,
@@ -13,6 +14,9 @@ import {
 /** Label of the `softDefault: true` spec in e2e/config/librechat.e2e.yaml. */
 const SOFT_DEFAULT_LABEL = 'E2E Soft Default';
 
+/** Name (URL identity) of the `softDefault: true` spec in e2e/config/librechat.e2e.yaml. */
+const SOFT_DEFAULT_NAME = 'e2e-soft-default';
+
 /** Ephemeral endpoint from e2e/config/librechat.e2e.yaml with no mirroring spec. */
 const EPHEMERAL_ENDPOINT = { label: 'Mock Provider C', model: 'mock-model-c' };
 
@@ -32,7 +36,7 @@ type AgentResponse = {
   name?: string | null;
 };
 
-async function createAgent(page: Page, name: string): Promise<AgentResponse> {
+async function createAgent(page: Page, name: string, description?: string): Promise<AgentResponse> {
   const token = await getAccessToken(page);
   return requestJson<AgentResponse>(page, {
     path: '/api/agents',
@@ -40,6 +44,7 @@ async function createAgent(page: Page, name: string): Promise<AgentResponse> {
     method: 'POST',
     body: {
       name,
+      ...(description ? { description } : {}),
       provider: 'Mock Provider A',
       model: 'mock-model-a',
       model_parameters: {},
@@ -226,4 +231,45 @@ test.describe('soft default model spec', () => {
     await expect(modelTrigger(page)).toContainText(SOFT_DEFAULT_LABEL, { timeout: 15000 });
     await expect(modelTrigger(page)).not.toHaveText('Select a model');
   });
+
+  // Regression: two tabs share localStorage — one on the soft default spec, one on a
+  // configured agent. Refreshing the agent tab stamps the agent as the last setup; a
+  // cold load of `/c/new?spec=<name>` then carried only the spec NAME while the
+  // endpoint and agent_id resurfaced from storage, rendering a chimera (spec chip over
+  // an agent landing/composer). A spec named in the URL must resolve to its full preset.
+  test('a spec named in the URL wins over a previously selected agent on a cold load', async ({
+    page,
+  }) => {
+    test.setTimeout(120000);
+    await startFresh(page);
+    await expect(modelTrigger(page)).toContainText(SOFT_DEFAULT_LABEL, { timeout: 15000 });
+
+    const agentName = uniqueName('E2E URL Spec Agent');
+    const agentDescription = 'Powered by E2E Mock';
+    await createAgent(page, agentName, agentDescription);
+    await page.goto(NEW_CHAT_PATH, { timeout: 10000 });
+    await selectAgent(page, agentName);
+
+    // Mirrors refreshing the agent tab: the restored selection is re-stamped as the
+    // last conversation setup.
+    await page.reload({ timeout: 10000 });
+    await expect(modelTrigger(page)).toContainText(agentName, { timeout: 15000 });
+
+    await page.goto(`${NEW_CHAT_PATH}?spec=${SOFT_DEFAULT_NAME}`, { timeout: 10000 });
+    await expect(modelTrigger(page)).toContainText(SOFT_DEFAULT_LABEL, { timeout: 15000 });
+
+    const main = page.getByRole('main');
+    const composer = page.getByRole('textbox', { name: 'Message input' });
+    const user = getPrimaryE2EUser();
+    await expect(composer).toHaveAttribute('placeholder', /Mock Provider A/, { timeout: 15000 });
+    await expect(main).toContainText(user.name, { timeout: 15000 });
+    await expect(main).not.toContainText(agentName);
+    await expect(main).not.toContainText(agentDescription);
+
+    // The mixed state used to be written back to localStorage; a follow-up cold load
+    // of a plain New Chat must stay on the spec, not resurrect the agent.
+    await page.goto(NEW_CHAT_PATH, { timeout: 10000 });
+    await expect(modelTrigger(page)).toContainText(SOFT_DEFAULT_LABEL, { timeout: 15000 });
+    await expect(main).not.toContainText(agentName);
+  });
 });