feat(OpenAI Node): Add reasoning effort for GPT-5 (#18644)

packages/@n8n/nodes-langchain/nodes/llms/LMChatOpenAi/LmChatOpenAi.node.ts

@@ -290,8 +290,8 @@ export class LmChatOpenAi implements INodeType {
 						],
 						displayOptions: {
 							show: {
-								// reasoning_effort is only available on o1, o1-versioned, or on o3-mini and beyond. Not on o1-mini or other GPT-models.
+								// reasoning_effort is only available on o1, o1-versioned, or on o3-mini and beyond, and gpt-5 models. Not on o1-mini or other GPT-models.
-								'/model': [{ _cnd: { regex: '(^o1([-\\d]+)?$)|(^o[3-9].*)' } }],
+								'/model': [{ _cnd: { regex: '(^o1([-\\d]+)?$)|(^o[3-9].*)|(^gpt-5.*)' } }],
 							},
 						},
 					},

packages/@n8n/nodes-langchain/nodes/vendors/OpenAi/actions/text/message.operation.ts

@@ -174,6 +174,38 @@ const properties: INodeProperties[] = [
 					'An alternative to sampling with temperature, controls diversity via nucleus sampling: 0.5 means half of all likelihood-weighted options are considered. We generally recommend altering this or temperature but not both.',
 				type: 'number',
 			},
+			{
+				displayName: 'Reasoning Effort',
+				name: 'reasoning_effort',
+				default: 'medium',
+				description:
+					'Controls the amount of reasoning tokens to use. A value of "low" will favor speed and economical token usage, "high" will favor more complete reasoning at the cost of more tokens generated and slower responses.',
+				type: 'options',
+				options: [
+					{
+						name: 'Low',
+						value: 'low',
+						description: 'Favors speed and economical token usage',
+					},
+					{
+						name: 'Medium',
+						value: 'medium',
+						description: 'Balance between speed and reasoning accuracy',
+					},
+					{
+						name: 'High',
+						value: 'high',
+						description:
+							'Favors more complete reasoning at the cost of more tokens generated and slower responses',
+					},
+				],
+				displayOptions: {
+					show: {
+						// reasoning_effort is only available on o1, o1-versioned, or on o3-mini and beyond, and gpt-5 models. Not on o1-mini or other GPT-models.
+						'/modelId': [{ _cnd: { regex: '(^o1([-\\d]+)?$)|(^o[3-9].*)|(^gpt-5.*)' } }],
+					},
+				},
+			},
 			{
 				displayName: 'Max Tool Calls Iterations',
 				name: 'maxToolsIterations',