diff --git a/client/src/hooks/Input/useQueryParams.ts b/client/src/hooks/Input/useQueryParams.ts
index b29f408a3a..85b5d8838b 100644
--- a/client/src/hooks/Input/useQueryParams.ts
+++ b/client/src/hooks/Input/useQueryParams.ts
@@ -12,6 +12,7 @@ import type {
 import {
   clearModelForNonEphemeralAgent,
   removeUnavailableTools,
+  specDisplayFieldReset,
   processValidSettings,
   getModelSpecIconURL,
   getConvoSwitchLogic,
@@ -128,13 +129,10 @@ export default function useQueryParams({
         endpointsConfig,
       });
 
-      let resetParams = {};
+      const resetFields = newPreset.spec == null ? specDisplayFieldReset : {};
       if (newPreset.spec == null) {
-        template.spec = null;
-        template.iconURL = null;
-        template.modelLabel = null;
-        resetParams = { spec: null, iconURL: null, modelLabel: null };
-        newPreset = { ...newPreset, ...resetParams };
+        Object.assign(template, specDisplayFieldReset);
+        newPreset = { ...newPreset, ...specDisplayFieldReset };
       }
 
       // Sync agent_id from newPreset to template, then clear model if non-ephemeral agent
@@ -152,7 +150,7 @@ export default function useQueryParams({
           conversation: {
             ...(conversation ?? {}),
             endpointType: template.endpointType,
-            ...resetParams,
+            ...resetFields,
           },
           preset: template,
           cleanOutput: newPreset.spec != null && newPreset.spec !== '',
diff --git a/client/src/routes/ChatRoute.tsx b/client/src/routes/ChatRoute.tsx
index dcb58c3f49..a17d349037 100644
--- a/client/src/routes/ChatRoute.tsx
+++ b/client/src/routes/ChatRoute.tsx
@@ -6,20 +6,21 @@ import { Constants, EModelEndpoint } from 'librechat-data-provider';
 import { useGetModelsQuery } from 'librechat-data-provider/react-query';
 import type { TPreset } from 'librechat-data-provider';
 import {
-  useNewConvo,
-  useAppStartup,
+  mergeQuerySettingsWithSpec,
+  processValidSettings,
+  getDefaultModelSpec,
+  getModelSpecPreset,
+  isNotFoundError,
+  logger,
+} from '~/utils';
+import {
   useAssistantListMap,
   useIdChangeEffect,
+  useAppStartup,
+  useNewConvo,
   useLocalize,
 } from '~/hooks';
 import { useGetConvoIdQuery, useGetStartupConfig, useGetEndpointsQuery } from '~/data-provider';
-import {
-  getDefaultModelSpec,
-  getModelSpecPreset,
-  processValidSettings,
-  logger,
-  isNotFoundError,
-} from '~/utils';
 import { ToolCallsMapProvider } from '~/Providers';
 import ChatView from '~/components/Chat/ChatView';
 import { NotificationSeverity } from '~/common';
@@ -102,9 +103,10 @@ export default function ChatRoute() {
       });
       const querySettings = processValidSettings(queryParams);
 
-      return Object.keys(querySettings).length > 0
-        ? { ...specPreset, ...querySettings }
-        : specPreset;
+      if (Object.keys(querySettings).length > 0) {
+        return mergeQuerySettingsWithSpec(specPreset, querySettings);
+      }
+      return specPreset;
     };
 
     if (isNewConvo && endpointsQuery.data && modelsQuery.data) {
diff --git a/client/src/utils/__tests__/mergeQuerySettingsWithSpec.test.ts b/client/src/utils/__tests__/mergeQuerySettingsWithSpec.test.ts
new file mode 100644
index 0000000000..76e104f62f
--- /dev/null
+++ b/client/src/utils/__tests__/mergeQuerySettingsWithSpec.test.ts
@@ -0,0 +1,152 @@
+import { EModelEndpoint } from 'librechat-data-provider';
+import type { TPreset } from 'librechat-data-provider';
+import { mergeQuerySettingsWithSpec, specDisplayFieldReset } from '../endpoints';
+
+describe('mergeQuerySettingsWithSpec', () => {
+  const specPreset: TPreset = {
+    endpoint: EModelEndpoint.openAI,
+    model: 'gpt-4',
+    spec: 'my-spec',
+    iconURL: 'https://example.com/icon.png',
+    modelLabel: 'My Custom GPT',
+    greeting: 'Hello from the spec!',
+    temperature: 0.7,
+  };
+
+  describe('when specPreset is active and query has no spec', () => {
+    it('clears all spec display fields for agent share links', () => {
+      const querySettings: TPreset = {
+        agent_id: 'agent_123',
+        endpoint: EModelEndpoint.agents,
+      };
+
+      const result = mergeQuerySettingsWithSpec(specPreset, querySettings);
+
+      expect(result.agent_id).toBe('agent_123');
+      expect(result.endpoint).toBe(EModelEndpoint.agents);
+      expect(result.spec).toBeNull();
+      expect(result.iconURL).toBeNull();
+      expect(result.modelLabel).toBeNull();
+      expect(result.greeting).toBeUndefined();
+    });
+
+    it('preserves non-display settings from the spec base', () => {
+      const querySettings: TPreset = {
+        agent_id: 'agent_123',
+        endpoint: EModelEndpoint.agents,
+      };
+
+      const result = mergeQuerySettingsWithSpec(specPreset, querySettings);
+
+      expect(result.temperature).toBe(0.7);
+    });
+
+    it('clears spec display fields for assistant share links', () => {
+      const querySettings: TPreset = {
+        assistant_id: 'asst_abc',
+        endpoint: EModelEndpoint.assistants,
+      };
+
+      const result = mergeQuerySettingsWithSpec(specPreset, querySettings);
+
+      expect(result.assistant_id).toBe('asst_abc');
+      expect(result.endpoint).toBe(EModelEndpoint.assistants);
+      expect(result.spec).toBeNull();
+      expect(result.iconURL).toBeNull();
+      expect(result.modelLabel).toBeNull();
+      expect(result.greeting).toBeUndefined();
+    });
+
+    it('clears spec display fields for model override links', () => {
+      const querySettings: TPreset = {
+        model: 'claude-sonnet-4-20250514',
+        endpoint: EModelEndpoint.anthropic,
+      };
+
+      const result = mergeQuerySettingsWithSpec(specPreset, querySettings);
+
+      expect(result.model).toBe('claude-sonnet-4-20250514');
+      expect(result.endpoint).toBe(EModelEndpoint.anthropic);
+      expect(result.spec).toBeNull();
+      expect(result.iconURL).toBeNull();
+      expect(result.modelLabel).toBeNull();
+      expect(result.greeting).toBeUndefined();
+    });
+  });
+
+  describe('when query explicitly sets a spec', () => {
+    it('preserves spec display fields from the base', () => {
+      const querySettings = { spec: 'other-spec' } as TPreset;
+
+      const result = mergeQuerySettingsWithSpec(specPreset, querySettings);
+
+      expect(result.spec).toBe('other-spec');
+      expect(result.iconURL).toBe('https://example.com/icon.png');
+      expect(result.modelLabel).toBe('My Custom GPT');
+      expect(result.greeting).toBe('Hello from the spec!');
+    });
+  });
+
+  describe('when specPreset is undefined (no spec configured)', () => {
+    it('returns querySettings without injecting null display fields', () => {
+      const querySettings: TPreset = {
+        agent_id: 'agent_123',
+        endpoint: EModelEndpoint.agents,
+      };
+
+      const result = mergeQuerySettingsWithSpec(undefined, querySettings);
+
+      expect(result.agent_id).toBe('agent_123');
+      expect(result.endpoint).toBe(EModelEndpoint.agents);
+      expect(result).not.toHaveProperty('spec');
+      expect(result).not.toHaveProperty('iconURL');
+      expect(result).not.toHaveProperty('modelLabel');
+      expect(result).not.toHaveProperty('greeting');
+    });
+  });
+
+  describe('when querySettings is empty', () => {
+    it('still clears spec display fields (no query params is not an explicit spec)', () => {
+      const result = mergeQuerySettingsWithSpec(specPreset, {} as TPreset);
+
+      expect(result.spec).toBeNull();
+      expect(result.iconURL).toBeNull();
+      expect(result.modelLabel).toBeNull();
+      expect(result.greeting).toBeUndefined();
+      expect(result.endpoint).toBe(EModelEndpoint.openAI);
+      expect(result.model).toBe('gpt-4');
+      expect(result.temperature).toBe(0.7);
+    });
+  });
+
+  describe('query settings override spec values', () => {
+    it('overrides endpoint and model from spec', () => {
+      const querySettings: TPreset = {
+        endpoint: EModelEndpoint.anthropic,
+        model: 'claude-sonnet-4-20250514',
+      };
+
+      const result = mergeQuerySettingsWithSpec(specPreset, querySettings);
+
+      expect(result.endpoint).toBe(EModelEndpoint.anthropic);
+      expect(result.model).toBe('claude-sonnet-4-20250514');
+      expect(result.temperature).toBe(0.7);
+      expect(result.spec).toBeNull();
+    });
+  });
+});
+
+describe('specDisplayFieldReset', () => {
+  it('contains all spec display fields that need clearing', () => {
+    expect(specDisplayFieldReset).toEqual({
+      spec: null,
+      iconURL: null,
+      modelLabel: null,
+      greeting: undefined,
+    });
+  });
+
+  it('has exactly 4 fields', () => {
+    expect(Object.keys(specDisplayFieldReset)).toHaveLength(4);
+  });
+});
diff --git a/client/src/utils/endpoints.ts b/client/src/utils/endpoints.ts
index 33aa7a8525..a27f71b8e9 100644
--- a/client/src/utils/endpoints.ts
+++ b/client/src/utils/endpoints.ts
@@ -311,6 +311,30 @@ export function getModelSpecPreset(modelSpec?: t.TModelSpec) {
   };
 }
 
+/** Fields set by a model spec that should be cleared when switching to a non-spec conversation. */
+export const specDisplayFieldReset = {
+  spec: null as string | null,
+  iconURL: null as string | null,
+  modelLabel: null as string | null,
+  greeting: undefined as string | undefined,
+};
+
+/**
+ * Merges a spec preset base with URL query settings, clearing spec display fields
+ * when the query doesn't explicitly set a spec. Prevents spec contamination on
+ * agent/assistant share links.
+ */
+export function mergeQuerySettingsWithSpec(
+  specPreset: t.TPreset | undefined,
+  querySettings: t.TPreset,
+): t.TPreset {
+  return {
+    ...specPreset,
+    ...querySettings,
+    ...(specPreset != null && querySettings.spec == null ? specDisplayFieldReset : {}),
+  };
+}
+
 /** Gets the default spec iconURL by order or definition.
  *
  * First, the admin defined default, then last selected spec, followed by first spec