Auto-include askQuestions tool in Plan agent when enabled (#3100)

* Initial plan

* Include searchSubagent and askQuestions tools in Plan agent when enabled

- Modified PlanAgentProvider.buildCustomizedConfig to check if searchSubagent and askQuestions tools are enabled via configuration
- Added ToolName import to access tool name constants
- Added checks for ConfigKey.Advanced.SearchSubagentToolEnabled and ConfigKey.AskQuestionsEnabled
- Tools are automatically included in the Plan agent's tool list when their corresponding settings are enabled
- Updated onDidChangeConfiguration listener to monitor changes to these settings and refresh the agent
- Added comprehensive unit tests to verify the new functionality including:
  - Tools are included when enabled
  - Tools are not included when disabled
  - Both tools work together when both are enabled
  - Deduplication works when tools are also in additionalTools
  - Change events fire correctly when settings change
- All tests passing (31/31)

Co-authored-by: digitarald <8599+digitarald@users.noreply.github.com>

* Improve test robustness for tool deduplication check

- Updated regex pattern to match both single and double quotes for better robustness
- Addresses code review feedback about brittle test implementation

Co-authored-by: digitarald <8599+digitarald@users.noreply.github.com>

* Fix regex pattern for consistent quote matching in test

- Updated regex to match either single or double quotes consistently (not mixed)
- Pattern now uses alternation to prevent matching invalid mixed quotes like 'tool"
- Addresses code review feedback for more precise pattern matching

Co-authored-by: digitarald <8599+digitarald@users.noreply.github.com>

* Apply suggestion from @Copilot

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

* Add missing IExperimentationService import in PlanAgentProvider

* Fix askQuestions tool reference name and remove searchSubagent from Plan agent

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: digitarald <8599+digitarald@users.noreply.github.com>
Co-authored-by: Harald Kirschner <hkirschner@microsoft.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: 3 people

src/extension/agents/vscode-node/planAgentProvider.ts

@@ -214,7 +214,8 @@ export class PlanAgentProvider extends Disposable implements vscode.ChatCustomAg
 		// Listen for settings changes to refresh agents
 		this._register(this.configurationService.onDidChangeConfiguration(e => {
 			if (e.affectsConfiguration(ConfigKey.PlanAgentAdditionalTools.fullyQualifiedId) ||
-				e.affectsConfiguration(ConfigKey.PlanAgentModel.fullyQualifiedId)) {
+				e.affectsConfiguration(ConfigKey.PlanAgentModel.fullyQualifiedId) ||
+				e.affectsConfiguration(ConfigKey.AskQuestionsEnabled.fullyQualifiedId)) {
 				this.logService.trace('[PlanAgentProvider] Settings changed, refreshing agent');
 				this._onDidChangeCustomAgents.fire();
 			}
@@ -266,10 +267,20 @@ export class PlanAgentProvider extends Disposable implements vscode.ChatCustomAg
 			handoffs: [...BASE_PLAN_AGENT_CONFIG.handoffs],
 		};
 
+		// Collect tools to add
+		const toolsToAdd: string[] = [...additionalTools];
+
+		// Add askQuestions tool if enabled
+		const askQuestionsEnabled = this.configurationService.getConfig(ConfigKey.AskQuestionsEnabled);
+		if (askQuestionsEnabled) {
+			toolsToAdd.push('askQuestions');
+			this.logService.trace(`[PlanAgentProvider] Adding askQuestions tool (enabled)`);
+		}
+
 		// Merge additional tools (deduplicated)
-		if (additionalTools.length > 0) {
-			config.tools = [...new Set([...config.tools, ...additionalTools])];
-			this.logService.trace(`[PlanAgentProvider] Merged additional tools: ${additionalTools.join(', ')}`);
+		if (toolsToAdd.length > 0) {
+			config.tools = [...new Set([...config.tools, ...toolsToAdd])];
+			this.logService.trace(`[PlanAgentProvider] Merged additional tools: ${toolsToAdd.join(', ')}`);
 		}
 
 		// Apply model override

src/extension/agents/vscode-node/test/planAgentProvider.spec.ts

@@ -196,6 +196,45 @@ suite('PlanAgentProvider', () => {
 		assert.equal(eventFired, false);
 	});
 
+	test('includes askQuestions tool when AskQuestionsEnabled is true', async () => {
+		await mockConfigurationService.setConfig(ConfigKey.AskQuestionsEnabled, true);
+
+		const provider = createProvider();
+		const agents = await provider.provideCustomAgents({}, {} as any);
+
+		assert.equal(agents.length, 1);
+		const content = await getAgentContent(agents[0]);
+
+		// Should contain askQuestions tool
+		assert.ok(content.includes('askQuestions'));
+	});
+
+	test('does not include askQuestions tool when AskQuestionsEnabled is false', async () => {
+		await mockConfigurationService.setConfig(ConfigKey.AskQuestionsEnabled, false);
+
+		const provider = createProvider();
+		const agents = await provider.provideCustomAgents({}, {} as any);
+
+		assert.equal(agents.length, 1);
+		const content = await getAgentContent(agents[0]);
+
+		// Should not contain askQuestions tool
+		assert.ok(!content.includes('askQuestions'));
+	});
+
+	test('fires onDidChangeCustomAgents when AskQuestionsEnabled changes', async () => {
+		const provider = createProvider();
+
+		let eventFired = false;
+		provider.onDidChangeCustomAgents(() => {
+			eventFired = true;
+		});
+
+		await mockConfigurationService.setConfig(ConfigKey.AskQuestionsEnabled, false);
+
+		assert.equal(eventFired, true);
+	});
+
 	test('has correct label property', () => {
 		const provider = createProvider();
 		assert.ok(provider.label.includes('Plan'));