Add start session hook #3497

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Merged

pwang347 merged 34 commits into main from pawang/startSessionHooks

Feb 6, 2026

+735 −1

src/extension/intents/node/toolCallingLoop.ts

-Original file line number
+Diff line change
@@ Expand Up / @@ -7,7 +7,7 @@ import * as l10n from '@vscode/l10n'; @@
     import { Raw } from '@vscode/prompt-tsx';
     import type { CancellationToken, ChatRequest, ChatResponseProgressPart, ChatResponseReferencePart, ChatResponseStream, ChatResult, LanguageModelToolInformation, Progress } from 'vscode';
     import { IAuthenticationChatUpgradeService } from '../../../platform/authentication/common/authenticationUpgrade';
-    import { IChatHookService, StopHookInput, StopHookOutput, SubagentStartHookInput, SubagentStartHookOutput, SubagentStopHookInput, SubagentStopHookOutput } from '../../../platform/chat/common/chatHookService';
+    import { IChatHookService, SessionStartHookInput, SessionStartHookOutput, StopHookInput, StopHookOutput, SubagentStartHookInput, SubagentStartHookOutput, SubagentStopHookInput, SubagentStopHookOutput } from '../../../platform/chat/common/chatHookService';
     import { FetchStreamSource, IResponsePart } from '../../../platform/chat/common/chatMLFetcher';
     import { CanceledResult, ChatFetchResponseType, ChatResponse } from '../../../platform/chat/common/commonTypes';
     import { IConfigurationService } from '../../../platform/configuration/common/configurationService';
@@ Expand Down Expand Up @@
     		this._logService.trace(`[ToolCallingLoop] Stop hook blocked stopping: ${reasons.join('; ')}`);
     	}
+    	/**
+    	 * Called when a session starts to allow hooks to provide additional context.
+    	 * @param input The session start hook input containing source
+    	 * @param token Cancellation token
+    	 * @returns Result containing additional context from hooks
+    	 */
+    	protected async executeSessionStartHook(input: SessionStartHookInput, token: CancellationToken): Promise<SubagentStartHookResult> {
+    		try {
+    			const results = await this._chatHookService.executeHook('SessionStart', {
+    				toolInvocationToken: this.options.request.toolInvocationToken,
+    				input: input
+    			}, token);
+    			// Collect additionalContext from all successful hook results
+    			const additionalContexts: string[] = [];
+    			for (const result of results) {
+    				if (result.success === true) {
+    					const output = result.output;
+    					if (typeof output === 'object' && output !== null) {
+    						const hookOutput = output as SessionStartHookOutput;
+    						if (hookOutput.additionalContext) {
+    							additionalContexts.push(hookOutput.additionalContext);
+    							this._logService.trace(`[ToolCallingLoop] SessionStart hook provided context: ${hookOutput.additionalContext.substring(0, 100)}...`);
+    						}
+    					}
+    				} else if (result.success === false) {
+    					const errorMessage = typeof result.output === 'string' ? result.output : 'Unknown error';
+    					this._logService.error(`[ToolCallingLoop] SessionStart hook error: ${errorMessage}`);
+    				}
+    			}
+    			return {
+    				additionalContext: additionalContexts.length > 0 ? additionalContexts.join('\n') : undefined
+    			};
+    		} catch (error) {
+    			this._logService.error('[ToolCallingLoop] Error executing SessionStart hook', error);
+    			return {};
+    		}
+    	}
     	/**
     	 * Called when a subagent starts to allow hooks to provide additional context.
     	 * @param input The subagent start hook input containing agent_id and agent_type
@@ Expand Down Expand Up @@
     		}
     	}
+    	/**
+    	 * Executes start hooks (SessionStart for regular sessions, SubagentStart for subagents).
+    	 * Should be called before run() to allow hooks to provide context before the first prompt.
+    	 *
+    	 * - For subagents: Always executes SubagentStart hook
+    	 * - For regular sessions: Only executes SessionStart hook on the first turn
+    	 */
+    	public async runStartHooks(token: CancellationToken): Promise<void> {
+    		// Execute SubagentStart hook for subagent requests, or SessionStart hook for first turn of regular sessions
+    		if (this.options.request.subAgentInvocationId) {
+    			const startHookResult = await this.executeSubagentStartHook({
+    				agent_id: this.options.request.subAgentInvocationId,
+    				agent_type: this.options.request.subAgentName ?? 'default'
+    			}, token);
+    			if (startHookResult.additionalContext) {
+    				this.additionalHookContext = startHookResult.additionalContext;
+    				this._logService.info(`[ToolCallingLoop] SubagentStart hook provided context for subagent ${this.options.request.subAgentInvocationId}`);
+    			}
+    		} else {
+    			const isFirstTurn = this.options.conversation.turns.length === 1;
+    			if (isFirstTurn) {
+    				const startHookResult = await this.executeSessionStartHook({
+    					source: 'new'
+    				}, token);
+    				if (startHookResult.additionalContext) {
+    					this.additionalHookContext = startHookResult.additionalContext;
+    					this._logService.info('[ToolCallingLoop] SessionStart hook provided context for session');
+    				}
+    			}
+    		}
+    	}
     	public async run(outputStream: ChatResponseStream | undefined, token: CancellationToken): Promise<IToolCallLoopResult> {
     		let i = 0;
     		let lastResult: IToolCallSingleResult | undefined;
@@ Expand Down @@

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Add start session hook #3497

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