Support reasoning effort for Copilot CLI

Author: DonJayamanne

src/extension/chatSessions/copilotcli/node/copilotCli.ts

@@ -4,6 +4,7 @@
  *--------------------------------------------------------------------------------------------*/
 
 import type { SessionOptions, SweCustomAgent } from '@github/copilot/sdk';
+import * as l10n from '@vscode/l10n';
 import { promises as fs } from 'fs';
 import * as path from 'path';
 import type * as vscode from 'vscode';
@@ -44,6 +45,9 @@ export interface CopilotCLIModelInfo {
 	readonly maxOutputTokens?: number;
 	readonly maxContextWindowTokens: number;
 	readonly supportsVision?: boolean;
+	readonly supportsReasoningEffort?: boolean;
+	readonly defaultReasoningEffort?: string;
+	readonly supportedReasoningEfforts?: string[];
 }
 
 export interface ICopilotCLIModels {
@@ -124,6 +128,9 @@ export class CopilotCLIModels extends Disposable implements ICopilotCLIModels {
 				maxOutputTokens: model.capabilities.limits.max_output_tokens,
 				maxContextWindowTokens: model.capabilities.limits.max_context_window_tokens,
 				supportsVision: model.capabilities.supports.vision,
+				supportsReasoningEffort: model.capabilities.supports.reasoningEffort,
+				defaultReasoningEffort: model.defaultReasoningEffort,
+				supportedReasoningEfforts: model.supportedReasoningEfforts
 			} satisfies CopilotCLIModelInfo));
 		} catch (ex) {
 			this.logService.error(`[CopilotCLISession] Failed to fetch models`, ex);
@@ -164,9 +171,10 @@ export class CopilotCLIModels extends Disposable implements ICopilotCLIModels {
 				multiplier,
 				multiplierNumeric: model.multiplier,
 				isUserSelectable: true,
+				configurationSchema: buildConfigurationSchema(model),
 				capabilities: {
 					imageInput: model.supportsVision,
-					toolCalling: true
+					toolCalling: true,
 				},
 				targetChatSessionType: 'copilotcli',
 				isDefault: index === 0 // SDK guarantees the first item is the default model
@@ -175,6 +183,38 @@ export class CopilotCLIModels extends Disposable implements ICopilotCLIModels {
 	}
 }
 
+function buildConfigurationSchema(modelInfo: CopilotCLIModelInfo): vscode.LanguageModelConfigurationSchema | undefined {
+	const effortLevels = modelInfo.supportedReasoningEfforts ?? [];
+	if (!effortLevels || effortLevels.length === 0) {
+		return;
+	}
+
+	const defaultEffort = modelInfo.defaultReasoningEffort;
+
+	return {
+		properties: {
+			reasoningEffort: {
+				type: 'string',
+				title: l10n.t('Thinking Effort'),
+				enum: effortLevels,
+				enumItemLabels: effortLevels.map(level => level.charAt(0).toUpperCase() + level.slice(1)),
+				enumDescriptions: effortLevels.map(level => {
+					switch (level) {
+						case 'none': return l10n.t('No reasoning applied');
+						case 'low': return l10n.t('Faster responses with less reasoning');
+						case 'medium': return l10n.t('Balanced reasoning and speed');
+						case 'high': return l10n.t('Greater reasoning depth but slower');
+						case 'xhigh': return l10n.t('Maximum reasoning depth but slower');
+						default: return level;
+					}
+				}),
+				default: defaultEffort,
+				group: 'navigation',
+			}
+		}
+	};
+}
+
 export interface ICopilotCLIAgents {
 	readonly _serviceBrand: undefined;
 	readonly onDidChangeAgents: Event<void>;