/**
 * Task tool - Delegate tasks to specialized agents.
 *
 * Discovers agent definitions from:
 *   - Bundled agents (shipped with xcsh-coding-agent)
 *   - ~/.xcsh/agent/agents/*.md (user-level)
 *   - .xcsh/agents/*.md (project-level)
 *
 * Supports:
 *   - Single agent execution
 *   - Parallel execution with concurrency limits
 *   - Progress tracking via JSON events
 *   - Session artifacts for debugging
 */
import * as fs from "node:fs/promises";
import * as os from "node:os";
import path from "node:path";
import type { AgentTool, AgentToolResult, AgentToolUpdateCallback } from "@f5-sales-demo/pi-agent-core";
import type { Usage } from "@f5-sales-demo/pi-ai";
import { $env, prompt, Snowflake } from "@f5-sales-demo/pi-utils";
import type { ToolSession } from "..";
import { resolveAgentModelPatterns } from "../config/model-resolver";
import type { Theme } from "../modes/theme/theme";
import planModeSubagentPrompt from "../prompts/system/plan-mode-subagent.md" with { type: "text" };
import taskDescriptionTemplate from "../prompts/tools/task.md" with { type: "text" };
import taskSummaryTemplate from "../prompts/tools/task-summary.md" with { type: "text" };
import { formatDuration } from "../tools/render-utils";
// Import review tools for side effects (registers subagent tool handlers)
import "../tools/review";
import { generateCommitMessage } from "../utils/commit-message-generator";
import * as git from "../utils/git";
import { discoverAgents, getAgent } from "./discovery";
import { runSubprocess } from "./executor";
import { resolveIsolationBackendForTaskExecution } from "./isolation-backend";
import { AgentOutputManager } from "./output-manager";
import { mapWithConcurrencyLimit, Semaphore } from "./parallel";
import { renderCall, renderResult } from "./render";
import { buildTaskOutputSummaries } from "./summary";
import { renderTemplate } from "./template";
import {
	type AgentDefinition,
	type AgentProgress,
	type SingleResult,
	type TaskParams,
	type TaskSchema,
	type TaskToolDetails,
	taskSchema,
	taskSchemaNoIsolation,
} from "./types";
import {
	applyBaseline,
	applyNestedPatches,
	captureBaseline,
	captureDeltaPatch,
	cleanupFuseOverlay,
	cleanupProjfsOverlay,
	cleanupTaskBranches,
	cleanupWorktree,
	commitToBranch,
	ensureFuseOverlay,
	ensureProjfsOverlay,
	ensureWorktree,
	getRepoRoot,
	mergeTaskBranches,
	type WorktreeBaseline,
} from "./worktree";

function createUsageTotals(): Usage {
	return {
		input: 0,
		output: 0,
		cacheRead: 0,
		cacheWrite: 0,
		totalTokens: 0,
		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
	};
}

function addUsageTotals(target: Usage, usage: Partial<Usage>): void {
	const input = usage.input ?? 0;
	const output = usage.output ?? 0;
	const cacheRead = usage.cacheRead ?? 0;
	const cacheWrite = usage.cacheWrite ?? 0;
	const totalTokens = usage.totalTokens ?? input + output + cacheRead + cacheWrite;
	const cost =
		usage.cost ??
		({
			input: 0,
			output: 0,
			cacheRead: 0,
			cacheWrite: 0,
			total: 0,
		} satisfies Usage["cost"]);

	target.input += input;
	target.output += output;
	target.cacheRead += cacheRead;
	target.cacheWrite += cacheWrite;
	target.totalTokens += totalTokens;
	target.cost.input += cost.input;
	target.cost.output += cost.output;
	target.cost.cacheRead += cost.cacheRead;
	target.cost.cacheWrite += cost.cacheWrite;
	target.cost.total += cost.total;
}

// Re-export types and utilities
export { loadBundledAgents as BUNDLED_AGENTS } from "./agents";
export { discoverCommands, expandCommand, getCommand } from "./commands";
export { discoverAgents, getAgent } from "./discovery";
export { AgentOutputManager } from "./output-manager";
export { buildTaskOutputSummaries, type TaskOutputSummary } from "./summary";
export type {
	AgentDefinition,
	AgentProgress,
	SingleResult,
	SubagentLifecyclePayload,
	SubagentProgressPayload,
	TaskParams,
	TaskToolDetails,
} from "./types";
export {
	TASK_SUBAGENT_EVENT_CHANNEL,
	TASK_SUBAGENT_LIFECYCLE_CHANNEL,
	TASK_SUBAGENT_PROGRESS_CHANNEL,
	taskSchema,
} from "./types";

/**
 * Render the tool description from a cached agent list and current settings.
 */
function renderDescription(
	agents: AgentDefinition[],
	maxConcurrency: number,
	isolationEnabled: boolean,
	asyncEnabled: boolean,
	disabledAgents: string[],
): string {
	const filteredAgents = disabledAgents.length > 0 ? agents.filter(a => !disabledAgents.includes(a.name)) : agents;
	return prompt.render(taskDescriptionTemplate, {
		agents: filteredAgents,
		MAX_CONCURRENCY: maxConcurrency,
		isolationEnabled,
		asyncEnabled,
	});
}

// ═══════════════════════════════════════════════════════════════════════════
// Tool Class
// ═══════════════════════════════════════════════════════════════════════════

/**
 * Task tool - Delegate tasks to specialized agents.
 *
 * Requires async initialization to discover available agents.
 * Use `TaskTool.create(session)` to instantiate.
 */
export class TaskTool implements AgentTool<TaskSchema, TaskToolDetails, Theme> {
	readonly name = "task";
	readonly label = "Task";
	readonly strict = true;
	readonly parameters: TaskSchema;
	readonly renderCall = renderCall;
	readonly renderResult = renderResult;
	readonly #discoveredAgents: AgentDefinition[];
	readonly #blockedAgent: string | undefined;

	/** Dynamic description that reflects current disabled-agent settings */
	get description(): string {
		const disabledAgents = this.session.settings.get("task.disabledAgents") as string[];
		const maxConcurrency = this.session.settings.get("task.maxConcurrency");
		const isolationMode = this.session.settings.get("task.isolation.mode");
		return renderDescription(
			this.#discoveredAgents,
			maxConcurrency,
			isolationMode !== "none",
			this.session.settings.get("async.enabled"),
			disabledAgents,
		);
	}
	private constructor(
		private readonly session: ToolSession,
		discoveredAgents: AgentDefinition[],
		isolationEnabled: boolean,
	) {
		this.parameters = isolationEnabled ? taskSchema : taskSchemaNoIsolation;
		this.#blockedAgent = $env.PI_BLOCKED_AGENT;
		this.#discoveredAgents = discoveredAgents;
	}

	/**
	 * Create a TaskTool instance with async agent discovery.
	 */
	static async create(session: ToolSession): Promise<TaskTool> {
		const isolationMode = session.settings.get("task.isolation.mode");
		const { agents } = await discoverAgents(session.cwd);
		return new TaskTool(session, agents, isolationMode !== "none");
	}

	async execute(
		_toolCallId: string,
		params: TaskParams,
		signal?: AbortSignal,
		onUpdate?: AgentToolUpdateCallback<TaskToolDetails>,
	): Promise<AgentToolResult<TaskToolDetails>> {
		const asyncEnabled = this.session.settings.get("async.enabled");
		const selectedAgent = this.#discoveredAgents.find(agent => agent.name === params.agent);
		if (!asyncEnabled || selectedAgent?.blocking === true) {
			return this.#executeSync(_toolCallId, params, signal, onUpdate);
		}

		const manager = this.session.asyncJobManager;
		if (!manager) {
			return {
				content: [{ type: "text", text: "Async execution is enabled but no async job manager is available." }],
				details: { projectAgentsDir: null, results: [], totalDurationMs: 0 },
			};
		}

		const taskItems = params.tasks ?? [];
		if (taskItems.length === 0) {
			return this.#executeSync(_toolCallId, params, signal, onUpdate);
		}

		const outputManager =
			this.session.agentOutputManager ?? new AgentOutputManager(this.session.getArtifactsDir ?? (() => null));
		const uniqueIds = await outputManager.allocateBatch(taskItems.map(t => t.id));
		const fallbackAgentSource =
			this.#discoveredAgents.find(agent => agent.name === params.agent)?.source ?? "bundled";
		const renderedTasks = taskItems.map(taskItem => renderTemplate(params.context, taskItem));
		const progressByTaskId = new Map<string, AgentProgress>();
		for (let index = 0; index < renderedTasks.length; index++) {
			const renderedTask = renderedTasks[index];
			progressByTaskId.set(renderedTask.id, {
				index,
				id: renderedTask.id,
				agent: params.agent,
				agentSource: fallbackAgentSource,
				status: "pending",
				task: renderedTask.task,
				assignment: renderedTask.assignment,
				description: renderedTask.description,
				recentTools: [],
				recentOutput: [],
				toolCount: 0,
				tokens: 0,
				durationMs: 0,
			});
		}

		const startedJobs: Array<{ jobId: string; taskId: string }> = [];
		const failedSchedules: string[] = [];
		let completedJobs = 0;
		let failedJobs = 0;

		const getProgressSnapshot = (): AgentProgress[] => {
			return Array.from(progressByTaskId.values())
				.sort((a, b) => a.index - b.index)
				.map(progress => structuredClone(progress));
		};

		const buildAsyncDetails = (state: "running" | "completed" | "failed", jobId: string): TaskToolDetails => ({
			projectAgentsDir: null,
			results: [],
			totalDurationMs: 0,
			progress: getProgressSnapshot(),
			async: { state, jobId, type: "task" },
		});

		const emitAsyncUpdate = (state: "running" | "completed" | "failed", text: string): void => {
			const primaryJobId = startedJobs[0]?.jobId ?? "task";
			onUpdate?.({
				content: [{ type: "text", text }],
				details: buildAsyncDetails(state, primaryJobId),
			});
		};

		const maxConcurrency = this.session.settings.get("task.maxConcurrency");
		const semaphore = new Semaphore(maxConcurrency);

		for (let i = 0; i < taskItems.length; i++) {
			const taskItem = taskItems[i];
			if (signal?.aborted) {
				failedSchedules.push(`${taskItem.id}: cancelled before scheduling`);
				const progress = progressByTaskId.get(taskItem.id);
				if (progress) {
					progress.status = "aborted";
				}
				continue;
			}

			const uniqueId = uniqueIds[i];
			const singleParams: TaskParams = { ...params, tasks: [taskItem] };
			const label = uniqueId;
			try {
				const jobId = manager.register(
					"task",
					label,
					async ({ signal: runSignal, reportProgress }) => {
						const startedAt = Date.now();
						const progress = progressByTaskId.get(taskItem.id);
						await semaphore.acquire();
						if (runSignal.aborted) {
							semaphore.release();
							if (progress) {
								progress.status = "aborted";
							}
							throw new Error("Aborted before execution");
						}
						if (progress) {
							progress.status = "running";
						}
						await reportProgress(
							`Running background task ${taskItem.id}...`,
							buildAsyncDetails("running", startedJobs[0]?.jobId ?? label) as unknown as Record<string, unknown>,
						);
						try {
							const result = await this.#executeSync(_toolCallId, singleParams, runSignal, undefined, [
								uniqueId,
							]);
							const finalText = result.content.find(part => part.type === "text")?.text ?? "(no output)";
							const singleResult = result.details?.results[0];
							if (progress) {
								progress.status = singleResult?.aborted
									? "aborted"
									: (singleResult?.exitCode ?? 0) === 0
										? "completed"
										: "failed";
								progress.durationMs = singleResult?.durationMs ?? Math.max(0, Date.now() - startedAt);
								progress.tokens = singleResult?.tokens ?? 0;
								progress.extractedToolData = singleResult?.extractedToolData;
							}
							completedJobs += 1;
							if (singleResult && ((singleResult.aborted ?? false) || singleResult.exitCode !== 0)) {
								failedJobs += 1;
							}
							const remaining = taskItems.length - completedJobs;
							const isDone = remaining === 0;
							await reportProgress(
								isDone
									? `Background task batch complete: ${completedJobs}/${taskItems.length} finished.`
									: `Background task batch progress: ${completedJobs}/${taskItems.length} finished (${remaining} running).`,
								buildAsyncDetails(
									isDone ? (failedJobs > 0 || failedSchedules.length > 0 ? "failed" : "completed") : "running",
									startedJobs[0]?.jobId ?? label,
								) as unknown as Record<string, unknown>,
							);
							if (isDone) {
								emitAsyncUpdate(
									failedJobs > 0 || failedSchedules.length > 0 ? "failed" : "completed",
									`Background task batch complete: ${completedJobs}/${taskItems.length} finished.`,
								);
							}
							return finalText;
						} catch (error) {
							if (progress) {
								progress.status = "failed";
								progress.durationMs = Math.max(0, Date.now() - startedAt);
							}
							completedJobs += 1;
							failedJobs += 1;
							const remaining = taskItems.length - completedJobs;
							const isDone = remaining === 0;
							await reportProgress(
								isDone
									? `Background task batch complete with failures: ${failedJobs} failed.`
									: `Background task batch progress: ${completedJobs}/${taskItems.length} finished (${remaining} running).`,
								buildAsyncDetails(
									isDone ? "failed" : "running",
									startedJobs[0]?.jobId ?? label,
								) as unknown as Record<string, unknown>,
							);
							if (isDone) {
								emitAsyncUpdate(
									"failed",
									`Background task batch complete with failures: ${failedJobs} failed.`,
								);
							}
							throw error;
						} finally {
							semaphore.release();
						}
					},
					{
						id: label,
						onProgress: (text, details) => {
							const progressDetails =
								(details as TaskToolDetails | undefined) ??
								buildAsyncDetails("running", startedJobs[0]?.jobId ?? label);
							onUpdate?.({ content: [{ type: "text", text }], details: progressDetails });
						},
					},
				);
				startedJobs.push({ jobId, taskId: taskItem.id });
			} catch (error) {
				const message = error instanceof Error ? error.message : String(error);
				failedSchedules.push(`${taskItem.id}: ${message}`);
				const progress = progressByTaskId.get(taskItem.id);
				if (progress) {
					progress.status = "failed";
				}
			}
		}

		if (startedJobs.length === 0) {
			const failureText = `Failed to start background task jobs: ${failedSchedules.join("; ")}`;
			return {
				content: [{ type: "text", text: failureText }],
				details: { projectAgentsDir: null, results: [], totalDurationMs: 0 },
			};
		}

		emitAsyncUpdate(
			"running",
			`Launching ${startedJobs.length} background ${startedJobs.length === 1 ? "task" : "tasks"}...`,
		);

		const scheduleFailureSummary =
			failedSchedules.length > 0
				? ` Failed to schedule ${failedSchedules.length} task${failedSchedules.length === 1 ? "" : "s"}.`
				: "";

		return {
			content: [
				{
					type: "text",
					text: `Started ${startedJobs.length} background task job${startedJobs.length === 1 ? "" : "s"} using ${params.agent}.${scheduleFailureSummary} Results will be delivered when complete.`,
				},
			],
			details: {
				projectAgentsDir: null,
				results: [],
				totalDurationMs: 0,
				progress: getProgressSnapshot(),
				async: { state: "running", jobId: startedJobs[0].jobId, type: "task" },
			},
		};
	}

	async #executeSync(
		_toolCallId: string,
		params: TaskParams,
		signal?: AbortSignal,
		onUpdate?: AgentToolUpdateCallback<TaskToolDetails>,
		preAllocatedIds?: string[],
	): Promise<AgentToolResult<TaskToolDetails>> {
		const startTime = Date.now();
		const { agents, projectAgentsDir } = await discoverAgents(this.session.cwd);
		const { agent: agentName, context, schema: outputSchema } = params;
		const isolationMode = this.session.settings.get("task.isolation.mode");
		const isolationRequested = "isolated" in params ? params.isolated === true : false;
		const isIsolated = isolationMode !== "none" && isolationRequested;
		const mergeMode = this.session.settings.get("task.isolation.merge");
		const commitStyle = this.session.settings.get("task.isolation.commits");
		const maxConcurrency = this.session.settings.get("task.maxConcurrency");
		const taskDepth = this.session.taskDepth ?? 0;

		if (isolationMode === "none" && "isolated" in params) {
			return {
				content: [
					{
						type: "text",
						text: "Task isolation is disabled. Remove the isolated argument or set task.isolation.mode to 'worktree', 'fuse-overlay', or 'fuse-projfs'.",
					},
				],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: 0,
				},
			};
		}

		// Validate agent exists
		const agent = getAgent(agents, agentName);
		if (!agent) {
			const available = agents.map(a => a.name).join(", ") || "none";
			return {
				content: [
					{
						type: "text",
						text: `Unknown agent "${agentName}". Available: ${available}`,
					},
				],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: 0,
				},
			};
		}

		// Check if agent is disabled in settings
		const disabledAgents = this.session.settings.get("task.disabledAgents") as string[];
		if (disabledAgents.length > 0 && disabledAgents.includes(agentName)) {
			const enabled = agents.filter(a => !disabledAgents.includes(a.name)).map(a => a.name);
			return {
				content: [
					{
						type: "text",
						text: `Agent "${agentName}" is disabled in settings. Enable it via /agents, or use a different agent type.${enabled.length > 0 ? ` Available: ${enabled.join(", ")}` : ""}`,
					},
				],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: 0,
				},
			};
		}

		const planModeState = this.session.getPlanModeState?.();
		const planModeTools = ["read", "grep", "find", "ls", "lsp", "web_search"];
		const effectiveAgent: typeof agent = planModeState?.enabled
			? {
					...agent,
					systemPrompt: `${planModeSubagentPrompt}\n\n${agent.systemPrompt}`,
					tools: planModeTools,
					spawns: undefined,
				}
			: agent;

		// Apply per-agent model override from settings (highest priority)
		const agentModelOverrides = this.session.settings.get("task.agentModelOverrides");
		const settingsModelOverride = agentModelOverrides[agentName];
		const modelOverride = resolveAgentModelPatterns({
			settingsOverride: settingsModelOverride,
			agentModel: effectiveAgent.model,
			settings: this.session.settings,
			activeModelPattern: this.session.getActiveModelString?.(),
			fallbackModelPattern: this.session.getModelString?.(),
		});
		const thinkingLevelOverride = effectiveAgent.thinkingLevel;

		// Output schema priority: caller params > agent frontmatter > inherited from parent session
		const effectiveOutputSchema = outputSchema ?? effectiveAgent.output ?? this.session.outputSchema;

		// Handle empty or missing tasks
		if (!params.tasks || params.tasks.length === 0) {
			return {
				content: [
					{
						type: "text",
						text: `No tasks provided. Use: { agent, context, tasks: [{id, description, args}, ...] }`,
					},
				],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: 0,
				},
			};
		}

		const tasks = params.tasks;
		const missingTaskIndexes: number[] = [];
		const idIndexes = new Map<string, number[]>();

		for (let i = 0; i < tasks.length; i++) {
			const id = tasks[i]?.id;
			if (typeof id !== "string" || id.trim() === "") {
				missingTaskIndexes.push(i);
				continue;
			}
			const normalizedId = id.toLowerCase();
			const indexes = idIndexes.get(normalizedId);
			if (indexes) {
				indexes.push(i);
			} else {
				idIndexes.set(normalizedId, [i]);
			}
		}

		const duplicateIds: Array<{ id: string; indexes: number[] }> = [];
		for (const [normalizedId, indexes] of idIndexes.entries()) {
			if (indexes.length > 1) {
				duplicateIds.push({
					id: tasks[indexes[0]]?.id ?? normalizedId,
					indexes,
				});
			}
		}

		if (missingTaskIndexes.length > 0 || duplicateIds.length > 0) {
			const problems: string[] = [];
			if (missingTaskIndexes.length > 0) {
				problems.push(`Missing task ids at indexes: ${missingTaskIndexes.join(", ")}`);
			}
			if (duplicateIds.length > 0) {
				const details = duplicateIds.map(entry => `${entry.id} (indexes ${entry.indexes.join(", ")})`).join("; ");
				problems.push(`Duplicate task ids detected (case-insensitive): ${details}`);
			}
			return {
				content: [{ type: "text", text: `Invalid tasks: ${problems.join(". ")}` }],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: 0,
				},
			};
		}

		let repoRoot: string | null = null;
		let baseline: WorktreeBaseline | null = null;
		if (isIsolated) {
			try {
				repoRoot = await getRepoRoot(this.session.cwd);
				baseline = await captureBaseline(repoRoot);
			} catch (err) {
				const message = err instanceof Error ? err.message : String(err);
				return {
					content: [
						{
							type: "text",
							text: `Isolated task execution requires a git repository. ${message}`,
						},
					],
					details: {
						projectAgentsDir,
						results: [],
						totalDurationMs: Date.now() - startTime,
					},
				};
			}
		}

		let effectiveIsolationMode = isolationMode;
		let isolationBackendWarning = "";
		try {
			const resolvedIsolation = await resolveIsolationBackendForTaskExecution(isolationMode, isIsolated, repoRoot);
			effectiveIsolationMode = resolvedIsolation.effectiveIsolationMode;
			isolationBackendWarning = resolvedIsolation.warning;
		} catch (err) {
			const message = err instanceof Error ? err.message : String(err);
			return {
				content: [
					{
						type: "text",
						text: message,
					},
				],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: Date.now() - startTime,
				},
			};
		}

		// Derive artifacts directory
		const sessionFile = this.session.getSessionFile();
		const artifactsDir = sessionFile ? sessionFile.slice(0, -6) : null;
		// Under a fixed `xcsh-tasks/` parent rather than a flat `xcsh-task-<id>` sibling, so the
		// containment fence can deny every session's task artifacts with ONE rule (#2624). Flat names
		// forced it to enumerate the OS temp dir, which cost 15ms on a 17k-entry directory — per fence
		// build, growing without bound as the temp dir fills — and still could not cover a dir created
		// after the fence was built. A fixed parent covers both.
		const tempArtifactsDir = artifactsDir ? null : path.join(os.tmpdir(), "xcsh-tasks", Snowflake.next());
		const effectiveArtifactsDir = artifactsDir || tempArtifactsDir!;

		// Initialize progress tracking
		const progressMap = new Map<number, AgentProgress>();

		// Update callback
		const emitProgress = () => {
			const progress = Array.from(progressMap.values()).sort((a, b) => a.index - b.index);
			onUpdate?.({
				content: [{ type: "text", text: `Running ${params.tasks.length} agents...` }],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: Date.now() - startTime,
					progress,
				},
			});
		};

		try {
			// Check self-recursion prevention
			if (this.#blockedAgent && agentName === this.#blockedAgent) {
				return {
					content: [
						{
							type: "text",
							text: `Cannot spawn ${this.#blockedAgent} agent from within itself (recursion prevention). Use a different agent type.`,
						},
					],
					details: {
						projectAgentsDir,
						results: [],
						totalDurationMs: Date.now() - startTime,
					},
				};
			}

			// Check spawn restrictions from parent
			const parentSpawns = this.session.getSessionSpawns() ?? "*";
			const allowedSpawns = parentSpawns.split(",").map(s => s.trim());
			const isSpawnAllowed = (): boolean => {
				if (parentSpawns === "") return false; // Empty = deny all
				if (parentSpawns === "*") return true; // Wildcard = allow all
				return allowedSpawns.includes(agentName);
			};

			if (!isSpawnAllowed()) {
				const allowed = parentSpawns === "" ? "none (spawns disabled for this agent)" : parentSpawns;
				return {
					content: [{ type: "text", text: `Cannot spawn '${agentName}'. Allowed: ${allowed}` }],
					details: {
						projectAgentsDir,
						results: [],
						totalDurationMs: Date.now() - startTime,
					},
				};
			}

			// Write parent conversation context for subagents
			await fs.mkdir(effectiveArtifactsDir, { recursive: true });
			const compactContext = this.session.getCompactContext?.();
			let contextFilePath: string | undefined;
			if (compactContext) {
				contextFilePath = path.join(effectiveArtifactsDir, "context.md");
				await Bun.write(contextFilePath, compactContext);
			}

			// Build full prompts with context prepended
			// Allocate unique IDs across the session to prevent artifact collisions
			let uniqueIds: string[];
			if (preAllocatedIds && preAllocatedIds.length === tasks.length) {
				uniqueIds = preAllocatedIds;
			} else {
				const outputManager =
					this.session.agentOutputManager ?? new AgentOutputManager(this.session.getArtifactsDir ?? (() => null));
				uniqueIds = await outputManager.allocateBatch(tasks.map(t => t.id));
			}
			const tasksWithUniqueIds = tasks.map((t, i) => ({ ...t, id: uniqueIds[i] }));

			// Build full prompts with context prepended
			const tasksWithContext = tasksWithUniqueIds.map(t => renderTemplate(context, t));
			const availableSkills = [...(this.session.skills ?? [])];
			const contextFiles = this.session.contextFiles?.filter(
				file => path.basename(file.path).toLowerCase() !== "agents.md",
			);
			const promptTemplates = this.session.promptTemplates;

			// Initialize progress for all tasks
			for (let i = 0; i < tasksWithContext.length; i++) {
				const t = tasksWithContext[i];
				progressMap.set(i, {
					index: i,
					id: t.id,
					agent: agentName,
					agentSource: agent.source,
					status: "pending",
					task: t.task,
					assignment: t.assignment,
					recentTools: [],
					recentOutput: [],
					toolCount: 0,
					tokens: 0,
					durationMs: 0,
					modelOverride,
					description: t.description,
				});
			}
			emitProgress();

			const runTask = async (task: (typeof tasksWithContext)[number], index: number) => {
				if (!isIsolated) {
					return runSubprocess({
						cwd: this.session.cwd,
						agent,
						task: task.task,
						assignment: task.assignment,
						description: task.description,
						index,
						id: task.id,
						taskDepth,
						modelOverride,
						thinkingLevel: thinkingLevelOverride,
						outputSchema: effectiveOutputSchema,
						sessionFile,
						persistArtifacts: !!artifactsDir,
						artifactsDir: effectiveArtifactsDir,
						contextFile: contextFilePath,
						enableLsp: false,
						signal,
						eventBus: this.session.eventBus,
						onProgress: progress => {
							progressMap.set(index, {
								...structuredClone(progress),
							});
							emitProgress();
						},
						authStorage: this.session.authStorage,
						modelRegistry: this.session.modelRegistry,
						settings: this.session.settings,
						mcpManager: this.session.mcpManager,
						contextFiles,
						skills: availableSkills,
						promptTemplates,
					});
				}

				const taskStart = Date.now();
				let isolationDir: string | undefined;
				try {
					if (!repoRoot || !baseline) {
						throw new Error("Isolated task execution not initialized.");
					}
					const taskBaseline = structuredClone(baseline);

					if (effectiveIsolationMode === "fuse-overlay") {
						isolationDir = await ensureFuseOverlay(repoRoot, task.id);
					} else if (effectiveIsolationMode === "fuse-projfs") {
						isolationDir = await ensureProjfsOverlay(repoRoot, task.id);
					} else {
						isolationDir = await ensureWorktree(repoRoot, task.id);
						await applyBaseline(isolationDir, taskBaseline);
					}

					const result = await runSubprocess({
						cwd: this.session.cwd,
						worktree: isolationDir,
						agent,
						task: task.task,
						assignment: task.assignment,
						description: task.description,
						index,
						id: task.id,
						taskDepth,
						modelOverride,
						thinkingLevel: thinkingLevelOverride,
						outputSchema: effectiveOutputSchema,
						sessionFile,
						persistArtifacts: !!artifactsDir,
						artifactsDir: effectiveArtifactsDir,
						contextFile: contextFilePath,
						enableLsp: false,
						signal,
						eventBus: this.session.eventBus,
						onProgress: progress => {
							progressMap.set(index, {
								...structuredClone(progress),
							});
							emitProgress();
						},
						authStorage: this.session.authStorage,
						modelRegistry: this.session.modelRegistry,
						settings: this.session.settings,
						mcpManager: this.session.mcpManager,
						contextFiles,
						skills: availableSkills,
						promptTemplates,
					});
					if (mergeMode === "branch" && result.exitCode === 0) {
						try {
							const commitMsg =
								commitStyle === "ai" && this.session.modelRegistry
									? async (diff: string) => {
											return generateCommitMessage(
												diff,
												this.session.modelRegistry!,
												this.session.settings,
												this.session.getSessionId?.() ?? undefined,
											);
										}
									: undefined;
							const commitResult = await commitToBranch(
								isolationDir,
								taskBaseline,
								task.id,
								task.description,
								commitMsg,
							);
							return {
								...result,
								branchName: commitResult?.branchName,
								nestedPatches: commitResult?.nestedPatches,
							};
						} catch (mergeErr) {
							// Agent succeeded but branch commit failed — clean up stale branch
							const branchName = `xcsh/task/${task.id}`;
							await git.branch.tryDelete(repoRoot, branchName);
							const msg = mergeErr instanceof Error ? mergeErr.message : String(mergeErr);
							return { ...result, error: `Merge failed: ${msg}` };
						}
					}
					if (result.exitCode === 0) {
						try {
							const delta = await captureDeltaPatch(isolationDir, taskBaseline);
							const patchPath = path.join(effectiveArtifactsDir, `${task.id}.patch`);
							await Bun.write(patchPath, delta.rootPatch);
							return {
								...result,
								patchPath,
								nestedPatches: delta.nestedPatches,
							};
						} catch (patchErr) {
							const msg = patchErr instanceof Error ? patchErr.message : String(patchErr);
							return { ...result, error: `Patch capture failed: ${msg}` };
						}
					}
					return result;
				} catch (err) {
					const message = err instanceof Error ? err.message : String(err);
					return {
						index,
						id: task.id,
						agent: agent.name,
						agentSource: agent.source,
						task: task.task,
						assignment: task.assignment,
						description: task.description,
						exitCode: 1,
						output: "",
						stderr: message,
						truncated: false,
						durationMs: Date.now() - taskStart,
						tokens: 0,
						modelOverride,
						error: message,
					};
				} finally {
					if (isolationDir) {
						if (effectiveIsolationMode === "fuse-overlay") {
							await cleanupFuseOverlay(isolationDir);
						} else if (effectiveIsolationMode === "fuse-projfs") {
							await cleanupProjfsOverlay(isolationDir);
						} else {
							await cleanupWorktree(isolationDir);
						}
					}
				}
			};

			// Execute in parallel with concurrency limit
			const { results: partialResults, aborted } = await mapWithConcurrencyLimit(
				tasksWithContext,
				maxConcurrency,
				runTask,
				signal,
			);

			// Fill in skipped tasks (undefined entries from abort) with placeholder results
			const results: SingleResult[] = partialResults.map((result, index) => {
				if (result !== undefined) {
					return result;
				}
				const task = tasksWithContext[index];
				return {
					index,
					id: task.id,
					agent: agentName,
					agentSource: agent.source,
					task: task.task,
					assignment: task.assignment,
					description: task.description,
					exitCode: 1,
					output: "",
					stderr: "Skipped (cancelled before start)",
					truncated: false,
					durationMs: 0,
					tokens: 0,
					modelOverride,
					error: "Cancelled before start",
					aborted: true,
					abortReason: "Cancelled before start",
				};
			});

			// Aggregate usage from executor results (already accumulated incrementally)
			const aggregatedUsage = createUsageTotals();
			let hasAggregatedUsage = false;
			for (const result of results) {
				if (result.usage) {
					addUsageTotals(aggregatedUsage, result.usage);
					hasAggregatedUsage = true;
				}
			}

			// Collect output paths (artifacts already written by executor in real-time)
			const outputPaths: string[] = [];
			const patchPaths: string[] = [];
			for (const result of results) {
				if (result.outputPath) {
					outputPaths.push(result.outputPath);
				}
				if (result.patchPath) {
					patchPaths.push(result.patchPath);
				}
			}

			let mergeSummary = "";
			let changesApplied: boolean | null = null;
			let mergedBranchesForNestedPatches: Set<string> | null = null;
			if (isIsolated && repoRoot) {
				try {
					if (mergeMode === "branch") {
						// Branch mode: merge task branches sequentially
						const branchEntries = results
							.filter(r => r.branchName && r.exitCode === 0 && !r.aborted)
							.map(r => ({ branchName: r.branchName!, taskId: r.id, description: r.description }));

						if (branchEntries.length === 0) {
							changesApplied = true;
						} else {
							const mergeResult = await mergeTaskBranches(repoRoot, branchEntries);
							mergedBranchesForNestedPatches = new Set(mergeResult.merged);
							changesApplied = mergeResult.failed.length === 0;

							if (changesApplied) {
								mergeSummary = `\n\nMerged ${mergeResult.merged.length} branch${mergeResult.merged.length === 1 ? "" : "es"}: ${mergeResult.merged.join(", ")}`;
							} else {
								const mergedPart =
									mergeResult.merged.length > 0 ? `Merged: ${mergeResult.merged.join(", ")}.\n` : "";
								const failedPart = `Failed: ${mergeResult.failed.join(", ")}.`;
								const conflictPart = mergeResult.conflict ? `\nConflict: ${mergeResult.conflict}` : "";
								mergeSummary = `\n\n<system-notification>Branch merge failed. ${mergedPart}${failedPart}${conflictPart}\nUnmerged branches remain for manual resolution.</system-notification>`;
							}
						}

						// Clean up merged branches (keep failed ones for manual resolution)
						const allBranches = branchEntries.map(b => b.branchName);
						if (changesApplied) {
							await cleanupTaskBranches(repoRoot, allBranches);
						}
					} else {
						// Patch mode: combine and apply patches
						const patchesInOrder = results.map(result => result.patchPath).filter(Boolean) as string[];
						const missingPatch = results.some(result => !result.patchPath);
						if (missingPatch) {
							changesApplied = false;
						} else {
							const patchStats = await Promise.all(
								patchesInOrder.map(async patchPath => ({
									patchPath,
									size: (await fs.stat(patchPath)).size,
								})),
							);
							const nonEmptyPatches = patchStats.filter(patch => patch.size > 0).map(patch => patch.patchPath);
							if (nonEmptyPatches.length === 0) {
								changesApplied = true;
							} else {
								const patchTexts = await Promise.all(
									nonEmptyPatches.map(async patchPath => Bun.file(patchPath).text()),
								);
								const combinedPatch = patchTexts
									.map(text => (text.endsWith("\n") ? text : `${text}\n`))
									.join("");
								if (!combinedPatch.trim()) {
									changesApplied = true;
								} else {
									changesApplied = await git.patch.canApplyText(repoRoot, combinedPatch);
									if (changesApplied) {
										try {
											await git.patch.applyText(repoRoot, combinedPatch);
										} catch {
											changesApplied = false;
										}
									}
								}
							}
						}

						if (changesApplied) {
							mergeSummary = "\n\nApplied patches: yes";
						} else {
							const notification =
								"<system-notification>Patches were not applied and must be handled manually.</system-notification>";
							const patchList =
								patchPaths.length > 0
									? `\n\nPatch artifacts:\n${patchPaths.map(patch => `- ${patch}`).join("\n")}`
									: "";
							mergeSummary = `\n\n${notification}${patchList}`;
						}
					}
				} catch (mergeErr) {
					const msg = mergeErr instanceof Error ? mergeErr.message : String(mergeErr);
					changesApplied = false;
					mergeSummary = `\n\n<system-notification>Merge phase failed: ${msg}\nTask outputs are preserved but changes were not applied.</system-notification>`;
				}
			}

			// Apply nested repo patches (separate from parent git)
			if (isIsolated && repoRoot && (mergeMode === "branch" || changesApplied !== false)) {
				const allNestedPatches = results
					.filter(r => {
						if (!r.nestedPatches || r.nestedPatches.length === 0 || r.exitCode !== 0 || r.aborted) {
							return false;
						}
						if (mergeMode !== "branch") {
							return true;
						}
						if (!r.branchName || !mergedBranchesForNestedPatches) {
							return false;
						}
						return mergedBranchesForNestedPatches.has(r.branchName);
					})
					.flatMap(r => r.nestedPatches!);
				if (allNestedPatches.length > 0) {
					try {
						const commitMsg =
							commitStyle === "ai" && this.session.modelRegistry
								? async (diff: string) => {
										return generateCommitMessage(
											diff,
											this.session.modelRegistry!,
											this.session.settings,
											this.session.getSessionId?.() ?? undefined,
										);
									}
								: undefined;
						await applyNestedPatches(repoRoot, allNestedPatches, commitMsg);
					} catch {
						// Nested patch failures are non-fatal to the parent merge
						mergeSummary +=
							"\n\n<system-notification>Some nested repository patches failed to apply.</system-notification>";
					}
				}
			}

			// Build final output - match plugin format
			const cancelledCount = results.filter(r => r.aborted).length;
			const successCount = results.filter(r => r.exitCode === 0 && !r.error && !r.aborted).length;
			const totalDuration = Date.now() - startTime;

			const summaries = buildTaskOutputSummaries(results, artifactsDir !== null);

			const backendSummaryPrefix = isolationBackendWarning ? `\n\n${isolationBackendWarning}` : "";
			const summary = prompt.render(taskSummaryTemplate, {
				successCount,
				totalCount: results.length,
				cancelledCount,
				hasCancelledNote: aborted && cancelledCount > 0,
				duration: formatDuration(totalDuration),
				summaries,
				agentName,
				mergeSummary: `${backendSummaryPrefix}${mergeSummary}`,
			});

			// Cleanup temp directory if used
			const shouldCleanupTempArtifacts =
				tempArtifactsDir && (!isIsolated || changesApplied === true || changesApplied === null);
			if (shouldCleanupTempArtifacts) {
				await fs.rm(tempArtifactsDir, { recursive: true, force: true });
			}

			return {
				content: [{ type: "text", text: summary }],
				details: {
					projectAgentsDir,
					results: results,
					totalDurationMs: totalDuration,
					usage: hasAggregatedUsage ? aggregatedUsage : undefined,
					outputPaths,
				},
			};
		} catch (err) {
			return {
				content: [{ type: "text", text: `Task execution failed: ${err}` }],
				details: {
					projectAgentsDir,
					results: [],
					totalDurationMs: Date.now() - startTime,
				},
			};
		}
	}
}