diff --git a/packages/nodes-base/credentials/SlackOAuth2Api.credentials.ts b/packages/nodes-base/credentials/SlackOAuth2Api.credentials.ts
index 9c923fcb4d6ae..6315269e23274 100644
--- a/packages/nodes-base/credentials/SlackOAuth2Api.credentials.ts
+++ b/packages/nodes-base/credentials/SlackOAuth2Api.credentials.ts
@@ -1,7 +1,7 @@
 import type { ICredentialType, INodeProperties } from 'n8n-workflow';
 
 //https://api.slack.com/authentication/oauth-v2
-const userScopes = [
+export const userScopes = [
 	'channels:read',
 	'channels:write',
 	'channels:history',
@@ -54,18 +54,49 @@ export class SlackOAuth2Api implements ICredentialType {
 			type: 'hidden',
 			default: 'https://slack.com/api/oauth.v2.access',
 		},
-		//https://api.slack.com/scopes
 		{
 			displayName: 'Scope',
 			name: 'scope',
 			type: 'hidden',
-			default: 'chat:write',
+			default: '',
+		},
+		{
+			displayName: 'Custom Scopes',
+			name: 'customScopes',
+			type: 'boolean',
+			default: false,
+			description: 'Define custom scopes',
+		},
+		{
+			displayName:
+				'The default scopes needed for the node to work are already set. If you change these the node may not function correctly.',
+			name: 'customScopesNotice',
+			type: 'notice',
+			default: '',
+			displayOptions: {
+				show: {
+					customScopes: [true],
+				},
+			},
 		},
+		{
+			displayName: 'User Scope',
+			name: 'userScope',
+			type: 'string',
+			displayOptions: {
+				show: {
+					customScopes: [true],
+				},
+			},
+			default: userScopes.join(' '),
+			description: 'Space-separated user-level scopes for your Slack app',
+		},
+		//https://api.slack.com/scopes
 		{
 			displayName: 'Auth URI Query Parameters',
 			name: 'authQueryParameters',
 			type: 'hidden',
-			default: `user_scope=${userScopes.join(' ')}`,
+			default: `={{$self["customScopes"] ? "user_scope=" + $self["userScope"] : "user_scope=${userScopes.join(' ')}"}}`,
 		},
 		{
 			displayName: 'Authentication',
diff --git a/packages/nodes-base/credentials/test/SlackOAuth2Api.credentials.test.ts b/packages/nodes-base/credentials/test/SlackOAuth2Api.credentials.test.ts
new file mode 100644
index 0000000000000..0f9c8055de8dc
--- /dev/null
+++ b/packages/nodes-base/credentials/test/SlackOAuth2Api.credentials.test.ts
@@ -0,0 +1,42 @@
+import { SlackOAuth2Api, userScopes } from '../SlackOAuth2Api.credentials';
+
+describe('SlackOAuth2Api Credential', () => {
+	const credential = new SlackOAuth2Api();
+
+	it('should have correct credential metadata', () => {
+		expect(credential.name).toBe('slackOAuth2Api');
+		expect(credential.extends).toEqual(['oAuth2Api']);
+
+		const authUrlProperty = credential.properties.find((p) => p.name === 'authUrl');
+		expect(authUrlProperty?.default).toBe('https://slack.com/oauth/v2/authorize');
+
+		const accessTokenUrlProperty = credential.properties.find((p) => p.name === 'accessTokenUrl');
+		expect(accessTokenUrlProperty?.default).toBe('https://slack.com/api/oauth.v2.access');
+	});
+
+	it('should not have a hardcoded bot scope field', () => {
+		const scopeProperty = credential.properties.find(
+			(p) => p.name === 'scope' && p.default === 'chat:write',
+		);
+		expect(scopeProperty).toBeUndefined();
+	});
+
+	it('should have custom scopes toggle defaulting to false', () => {
+		const customScopesProperty = credential.properties.find((p) => p.name === 'customScopes');
+		expect(customScopesProperty?.default).toBe(false);
+	});
+
+	it('should have userScope defaulting to the full default scope list', () => {
+		const userScopeProperty = credential.properties.find((p) => p.name === 'userScope');
+		expect(userScopeProperty?.default).toBe(userScopes.join(' '));
+	});
+
+	it('should use userScope in authQueryParameters when customScopes is true, otherwise use defaults', () => {
+		const authQueryParamsProperty = credential.properties.find(
+			(p) => p.name === 'authQueryParameters',
+		);
+		expect(authQueryParamsProperty?.default).toBe(
+			`={{$self["customScopes"] ? "user_scope=" + $self["userScope"] : "user_scope=${userScopes.join(' ')}"}}`,
+		);
+	});
+});
diff --git a/packages/testing/playwright/tests/e2e/ai/assistant-credential-help.spec.ts b/packages/testing/playwright/tests/e2e/ai/assistant-credential-help.spec.ts
index f064d3b57f548..f1d28c0b5a7e8 100644
--- a/packages/testing/playwright/tests/e2e/ai/assistant-credential-help.spec.ts
+++ b/packages/testing/playwright/tests/e2e/ai/assistant-credential-help.spec.ts
@@ -107,12 +107,12 @@ test.describe(
 
 				// Default is managed OAuth (click to connect) — no assistant button
 				await expect(n8n.canvas.credentialModal.oauthConnectButton).toHaveCount(1);
-				await expect(n8n.canvas.credentialModal.getCredentialInputs()).toHaveCount(2);
+				await expect(n8n.canvas.credentialModal.getCredentialInputs()).toHaveCount(3);
 				await expect(n8n.aiAssistant.getCredentialEditAssistantButton()).toHaveCount(0);
 
 				// Switch to custom OAuth via dropdown — assistant button should appear
 				await n8n.canvas.credentialModal.selectAuthTypeFromDropdown('Custom OAuth2');
-				await expect(n8n.canvas.credentialModal.getCredentialInputs()).toHaveCount(4);
+				await expect(n8n.canvas.credentialModal.getCredentialInputs()).toHaveCount(5);
 				await expect(n8n.aiAssistant.getCredentialEditAssistantButton()).toHaveCount(1);
 			});