diff --git a/.informant/config.toml b/.informant/config.toml
index fc44506..bfa1add 100644
--- a/.informant/config.toml
+++ b/.informant/config.toml
@@ -14,7 +14,7 @@ prepare = """
 set -eu
 export DEBIAN_FRONTEND=noninteractive
 apt-get update
-apt-get install -y --no-install-recommends git
+apt-get install -y --no-install-recommends git lsof
 rm -rf /var/lib/apt/lists/*
 cd "$INFORMANT_PREPARE_ROOT"
 bun install --frozen-lockfile --ignore-scripts
diff --git a/.informant/jobs/build.toml b/.informant/jobs/build.toml
index bf0c70e..84a2d53 100644
--- a/.informant/jobs/build.toml
+++ b/.informant/jobs/build.toml
@@ -2,8 +2,11 @@ name = "build"
 needs = ["test", "typecheck"]
 command = """
 set -eu
+expected_dist="$(mktemp -d)"
+trap 'rm -rf "$expected_dist"' EXIT
+cp -R web/dist "$expected_dist/dist"
 bun run build
-git diff --exit-code -- web/dist
+diff -ru "$expected_dist/dist" web/dist
 """
 timeout_minutes = 15
 container = { cpu = 2, memory_mb = 4096 }
diff --git a/extensions/subagents.ts b/extensions/subagents.ts
index d949f8a..815ea96 100644
--- a/extensions/subagents.ts
+++ b/extensions/subagents.ts
@@ -1,1712 +1,45 @@
-import { resolve } from "node:path";
 import {
-	createAgentSession,
 	CustomEditor,
-	DefaultResourceLoader,
-	DynamicBorder,
-	getAgentDir,
-	ModelRuntime,
-	SessionManager,
-	SettingsManager,
-	type AgentSession,
-	type AgentSessionEvent,
 	type ExtensionAPI,
 	type ExtensionContext,
-	type KeybindingsManager,
-	type ModelRegistry,
-	type Theme,
 } from "@earendil-works/pi-coding-agent";
-import {
-	Container,
-	type EditorComponent,
-	type Focusable,
-	matchesKey,
-	SelectList,
-	type SelectItem,
-	Text,
-	truncateToWidth,
-	visibleWidth,
-	wrapTextWithAnsi,
-	type Component,
-	type TUI,
-} from "@earendil-works/pi-tui";
-import { Type } from "typebox";
-import {
-	FOOTER_CONTRIBUTION_EVENT,
-	type FooterContribution,
-	type FooterUsage,
-} from "./footer-events.js";
 import {
 	parseSubagentAbortRequest,
 	SUBAGENT_ABORT_EVENT,
-	SUBAGENT_STATUS_EVENT,
-	type SubagentStatusEvent,
-	type SubagentWebSnapshot,
-	type SubagentWebUpdate,
 } from "./subagent-events.js";
-
-const MAX_SUBAGENTS = 8;
-const MAX_ACTIVITY_ITEMS = 500;
-const MAX_TRANSCRIPT_ITEMS = 500;
-const MAX_TRANSCRIPT_ENTRY_CHARS = 100_000;
-const MAX_TRANSCRIPT_CHARS = 1_000_000;
-const MAX_WEB_TRANSCRIPT_CHARS = 100_000;
-export const MAX_WEB_STREAMING_CHARS = 20_000;
-const WEB_STATUS_PUBLISH_INTERVAL_MS = 1_000;
-const MAX_TOOL_OUTPUT_BYTES = 50 * 1024;
-const DEFAULT_READ_WAIT_SECONDS = 15;
-const DETAIL_VIEW_LINES = 22;
-const USAGE_STATE_ENTRY = "vessup-subagent-usage";
-const SUBAGENT_SYSTEM_PROMPT = [
-	"You are a subagent working for a main coding agent.",
-	"Work independently on the delegated task in the current working directory.",
-	"Use tools when useful, keep changes scoped to the task, and finish with a concise report of findings, changes, tests, and remaining risks.",
-	"Messages received after the initial task are instructions from the main agent; urgent steering messages supersede your current approach.",
-].join(" ");
-
-export const THINKING_LEVELS = ["off", "minimal", "low", "medium", "high", "xhigh", "max"] as const;
-export type SubagentEffort = (typeof THINKING_LEVELS)[number];
-export type SubagentStatus = "creating" | "working" | "completed" | "failed" | "terminating" | "terminated";
-export type MessageUrgency = "normal" | "urgent";
-
-type ActivityItem = {
-	timestamp: number;
-	text: string;
-};
-
-type TranscriptItem = {
-	timestamp: number;
-	role: string;
-	text: string;
-};
-
-type ManagedSubagent = {
-	id: string;
-	prompt: string;
-	cwd: string;
-	createdAt: number;
-	updatedAt: number;
-	completedAt?: number;
-	status: SubagentStatus;
-	model: string;
-	effort: SubagentEffort;
-	currentTool?: string;
-	error?: string;
-	lastStopReason?: string;
-	turns: number;
-	queuedSteering: number;
-	queuedFollowUp: number;
-	activity: ActivityItem[];
-	lastReadActivity: number;
-	transcript: TranscriptItem[];
-	streamingText: string;
-	lastStreamActivityAt: number;
-	usage: Usage;
-	session?: AgentSession;
-	unsubscribe?: () => void;
-	runPromise?: Promise<void>;
-	waiters: Set<() => void>;
-};
-
-type AgentSnapshot = {
-	id: string;
-	status: SubagentStatus;
-	model: string;
-	effort: SubagentEffort;
-	turns: number;
-	currentTool?: string;
-	queued: number;
-};
-
-type ToolDetails = {
-	agents: SubagentWebSnapshot[];
-};
-
-type Usage = FooterUsage;
-type AgentModel = NonNullable<ReturnType<ModelRuntime["getModel"]>>;
-type PersistedUsageState = { total: Usage; accounted: Usage };
-
-type ManagerDialogResult =
-	| { action: "close" }
-	| { action: "view"; id: string }
-	| { action: "back" }
-	| { action: "model"; id: string }
-	| { action: "effort"; id: string }
-	| { action: "urgent"; id: string }
-	| { action: "queue"; id: string }
-	| { action: "terminate"; id: string };
-
-function isRecord(value: unknown): value is Record<string, unknown> {
-	return typeof value === "object" && value !== null;
-}
-
-function zeroUsage(): Usage {
-	return {
-		input: 0,
-		output: 0,
-		cacheRead: 0,
-		cacheWrite: 0,
-		totalTokens: 0,
-		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
-	};
-}
-
-function parseUsage(value: unknown): Usage | undefined {
-	if (!isRecord(value) || !isRecord(value.cost)) return undefined;
-	const cost = value.cost;
-	const fields = ["input", "output", "cacheRead", "cacheWrite", "totalTokens"] as const;
-	if (fields.some((field) => typeof value[field] !== "number" || !Number.isFinite(value[field]))) return undefined;
-	const costFields = ["input", "output", "cacheRead", "cacheWrite", "total"] as const;
-	if (costFields.some((field) => typeof cost[field] !== "number" || !Number.isFinite(cost[field]))) return undefined;
-	return {
-		input: value.input as number,
-		output: value.output as number,
-		cacheRead: value.cacheRead as number,
-		cacheWrite: value.cacheWrite as number,
-		totalTokens: value.totalTokens as number,
-		cost: {
-			input: cost.input as number,
-			output: cost.output as number,
-			cacheRead: cost.cacheRead as number,
-			cacheWrite: cost.cacheWrite as number,
-			total: cost.total as number,
-		},
-	};
-}
-
-export function parsePersistedUsageState(value: unknown): PersistedUsageState | undefined {
-	if (!isRecord(value)) return undefined;
-	const total = parseUsage(value.total);
-	const accounted = parseUsage(value.accounted);
-	return total && accounted ? { total, accounted } : undefined;
-}
-
-export function appendBoundedStreamingText(current: string, delta: string): string {
-	const combined = current + delta;
-	return combined.length <= MAX_WEB_STREAMING_CHARS
-		? combined
-		: combined.slice(-MAX_WEB_STREAMING_CHARS);
-}
-
-function cloneUsage(usage: Usage): Usage {
-	return {
-		input: usage.input,
-		output: usage.output,
-		cacheRead: usage.cacheRead,
-		cacheWrite: usage.cacheWrite,
-		totalTokens: usage.totalTokens,
-		cost: { ...usage.cost },
-	};
-}
-
-function addUsage(target: Usage, usage: Usage | undefined): void {
-	if (!usage) return;
-	target.input += usage.input || 0;
-	target.output += usage.output || 0;
-	target.cacheRead += usage.cacheRead || 0;
-	target.cacheWrite += usage.cacheWrite || 0;
-	target.totalTokens += usage.totalTokens || 0;
-	target.cost.input += usage.cost?.input || 0;
-	target.cost.output += usage.cost?.output || 0;
-	target.cost.cacheRead += usage.cost?.cacheRead || 0;
-	target.cost.cacheWrite += usage.cost?.cacheWrite || 0;
-	target.cost.total += usage.cost?.total || 0;
-}
-
-function subtractUsage(total: Usage, accounted: Usage): Usage {
-	return {
-		input: Math.max(0, total.input - accounted.input),
-		output: Math.max(0, total.output - accounted.output),
-		cacheRead: Math.max(0, total.cacheRead - accounted.cacheRead),
-		cacheWrite: Math.max(0, total.cacheWrite - accounted.cacheWrite),
-		totalTokens: Math.max(0, total.totalTokens - accounted.totalTokens),
-		cost: {
-			input: Math.max(0, total.cost.input - accounted.cost.input),
-			output: Math.max(0, total.cost.output - accounted.cost.output),
-			cacheRead: Math.max(0, total.cost.cacheRead - accounted.cost.cacheRead),
-			cacheWrite: Math.max(0, total.cost.cacheWrite - accounted.cost.cacheWrite),
-			total: Math.max(0, total.cost.total - accounted.cost.total),
-		},
-	};
-}
-
-function hasUsage(usage: Usage): boolean {
-	return (
-		usage.input > 0 ||
-		usage.output > 0 ||
-		usage.cacheRead > 0 ||
-		usage.cacheWrite > 0 ||
-		usage.totalTokens > 0 ||
-		usage.cost.total > 0
-	);
-}
-
-function formatTokens(count: number): string {
-	if (count < 1_000) return `${count}`;
-	if (count < 10_000) return `${(count / 1_000).toFixed(1)}k`;
-	if (count < 1_000_000) return `${Math.round(count / 1_000)}k`;
-	return `${(count / 1_000_000).toFixed(1)}M`;
-}
-
-function formatDuration(milliseconds: number): string {
-	const seconds = Math.max(0, Math.floor(milliseconds / 1_000));
-	if (seconds < 60) return `${seconds}s`;
-	const minutes = Math.floor(seconds / 60);
-	if (minutes < 60) return `${minutes}m ${seconds % 60}s`;
-	return `${Math.floor(minutes / 60)}h ${minutes % 60}m`;
-}
-
-function formatClock(timestamp: number): string {
-	return new Date(timestamp).toLocaleTimeString([], { hour: "2-digit", minute: "2-digit", second: "2-digit" });
-}
-
-function sanitizeName(value: string): string {
-	return value
-		.trim()
-		.toLowerCase()
-		.replace(/[^a-z0-9._-]+/g, "-")
-		.replace(/^-+|-+$/g, "")
-		.slice(0, 40);
-}
-
-function stringifyCompact(value: unknown, max = 200): string {
-	let text: string;
-	try {
-		text = JSON.stringify(value);
-	} catch {
-		text = String(value);
-	}
-	return text.length > max ? `${text.slice(0, max)}…` : text;
-}
-
-function truncateChars(text: string, maximum: number): string {
-	return text.length <= maximum ? text : `${text.slice(0, maximum)}\n[… ${text.length - maximum} characters omitted]`;
-}
-
-function contentToText(content: unknown): string {
-	if (typeof content === "string") return content;
-	if (!Array.isArray(content)) return "";
-	const parts: string[] = [];
-	for (const block of content) {
-		if (!block || typeof block !== "object") continue;
-		const item = block as Record<string, unknown>;
-		if (item.type === "text" && typeof item.text === "string") parts.push(item.text);
-		else if (item.type === "thinking" && typeof item.thinking === "string") parts.push(`[thinking]\n${item.thinking}`);
-		else if (item.type === "toolCall" && typeof item.name === "string") {
-			parts.push(`→ ${item.name} ${stringifyCompact(item.arguments)}`);
-		} else if (item.type === "image") {
-			parts.push("[image]");
-		}
-	}
-	return parts.join("\n");
-}
-
-function messageToTranscript(message: unknown): TranscriptItem | undefined {
-	if (!message || typeof message !== "object") return undefined;
-	const item = message as Record<string, unknown>;
-	if (typeof item.role !== "string") return undefined;
-	const text = truncateChars(contentToText(item.content), MAX_TRANSCRIPT_ENTRY_CHARS).trim();
-	if (!text) return undefined;
-	return {
-		timestamp: typeof item.timestamp === "number" ? item.timestamp : Date.now(),
-		role: item.role,
-		text,
-	};
-}
-
-function messageUsage(message: unknown): Usage | undefined {
-	if (!message || typeof message !== "object") return undefined;
-	const usage = (message as Record<string, unknown>).usage;
-	if (!usage || typeof usage !== "object") return undefined;
-	return usage as Usage;
-}
-
-function messageRole(message: unknown): string | undefined {
-	return message && typeof message === "object" && typeof (message as Record<string, unknown>).role === "string"
-		? ((message as Record<string, unknown>).role as string)
-		: undefined;
-}
-
-function messageStopReason(message: unknown): string | undefined {
-	return message && typeof message === "object" && typeof (message as Record<string, unknown>).stopReason === "string"
-		? ((message as Record<string, unknown>).stopReason as string)
-		: undefined;
-}
-
-function messageError(message: unknown): string | undefined {
-	return message && typeof message === "object" && typeof (message as Record<string, unknown>).errorMessage === "string"
-		? ((message as Record<string, unknown>).errorMessage as string)
-		: undefined;
-}
-
-function finalAssistantText(agent: ManagedSubagent): string {
-	for (let index = agent.transcript.length - 1; index >= 0; index--) {
-		const item = agent.transcript[index];
-		if (item?.role === "assistant") return item.text;
-	}
-	return agent.streamingText.trim();
-}
-
-function boundedWebTranscript(items: readonly TranscriptItem[]): TranscriptItem[] {
-	const retained: TranscriptItem[] = [];
-	let characters = 0;
-	for (let index = items.length - 1; index >= 0; index--) {
-		const item = items[index];
-		if (!item) continue;
-		const remaining = MAX_WEB_TRANSCRIPT_CHARS - characters;
-		if (remaining <= 0 && retained.length > 0) break;
-		const text = truncateChars(item.text, Math.max(1, remaining));
-		retained.push({ ...item, text });
-		characters += text.length;
-	}
-	return retained.reverse();
-}
-
-function webTranscript(agent: ManagedSubagent): TranscriptItem[] {
-	return boundedWebTranscript(agent.transcript);
-}
-
-export function isFailedStopReason(stopReason: string | undefined): boolean {
-	return stopReason === "error" || stopReason === "aborted";
-}
-
-export function countsAgainstSubagentLimit(agent: { status: SubagentStatus; session?: unknown }): boolean {
-	return agent.status === "creating" || agent.session !== undefined;
-}
-
-export function isTerminalSubagentStatus(status: SubagentStatus): boolean {
-	return status === "completed" || status === "failed" || status === "terminated";
-}
-
-export function shouldArchiveTerminalSubagent(agent: {
-	status: SubagentStatus;
-	lastReadActivity: number;
-	activity: readonly unknown[];
-}): boolean {
-	return isTerminalSubagentStatus(agent.status) && agent.lastReadActivity < agent.activity.length;
-}
-
-export async function abortRunningSubagentSessions<T extends { status: SubagentStatus; session?: { abort(): Promise<unknown> } }>(
-	agents: readonly T[],
-): Promise<Array<{ agent: T; error?: Error }>> {
-	const running = agents.filter((agent) => agent.session && (agent.status === "creating" || agent.status === "working"));
-	return await Promise.all(running.map(async (agent) => {
-		try {
-			await agent.session!.abort();
-			return { agent };
-		} catch (error) {
-			return { agent, error: error instanceof Error ? error : new Error(String(error)) };
-		}
-	}));
-}
-
-export function filterModelsToScope<T extends { provider: string; id: string }>(
-	available: readonly T[],
-	scoped: ReadonlyArray<{ model: { provider: string; id: string } }>,
-): readonly T[] {
-	if (scoped.length === 0) return available;
-	const allowed = new Set(scoped.map(({ model }) => `${model.provider}/${model.id}`));
-	return available.filter((model) => allowed.has(`${model.provider}/${model.id}`));
-}
-
-export function inheritedSubagentModel<T extends { provider: string; id: string }>(
-	current: T | undefined,
-	runtimeModel: T | undefined,
-): T | undefined {
-	return runtimeModel ?? current;
-}
-
-export function subagentModelRuntime(modelRegistry: ModelRegistry): ModelRuntime {
-	// ModelRegistry is the extension-facing compatibility facade around the
-	// canonical runtime. Sharing that runtime preserves runtime-only keys and
-	// provider-resolved headers/env/base URLs, while leaving stored OAuth in the
-	// credential store so both host and child continue to refresh it normally.
-	const runtime: unknown = Reflect.get(modelRegistry, "runtime");
-	if (!(runtime instanceof ModelRuntime)) {
-		throw new Error("The host model registry does not expose its canonical runtime");
-	}
-	return runtime;
-}
-
-function statusIcon(status: SubagentStatus): string {
-	switch (status) {
-		case "creating":
-		case "working":
-		case "terminating":
-			return "◐";
-		case "completed":
-			return "✓";
-		case "failed":
-			return "✗";
-		case "terminated":
-			return "■";
-	}
-}
-
-function statusColor(status: SubagentStatus): "warning" | "success" | "error" | "muted" {
-	switch (status) {
-		case "creating":
-		case "working":
-		case "terminating":
-			return "warning";
-		case "completed":
-			return "success";
-		case "failed":
-			return "error";
-		case "terminated":
-			return "muted";
-	}
-}
-
-function truncateToolOutput(text: string): string {
-	const bytes = Buffer.byteLength(text, "utf8");
-	if (bytes <= MAX_TOOL_OUTPUT_BYTES) return text;
-	let output = text.slice(0, MAX_TOOL_OUTPUT_BYTES);
-	while (Buffer.byteLength(output, "utf8") > MAX_TOOL_OUTPUT_BYTES) output = output.slice(0, -1);
-	return `${output}\n\n[Output truncated: ${bytes - Buffer.byteLength(output, "utf8")} bytes omitted. Re-read a specific subagent or use the transcript modal for details.]`;
-}
-
-function modelName(model: { provider: string; id: string } | undefined): string {
-	return model ? `${model.provider}/${model.id}` : "no-model";
-}
-
-export function subagentModelGuidance(
-	current: { provider: string; id: string } | undefined,
-	available: readonly { provider: string; id: string }[],
-): string {
-	const choices = [...new Set(available.map(modelName))];
-	const inherited = modelName(current);
-	return [
-		"Subagent model selection for this session:",
-		`- subagent_create inherits ${inherited} when model is omitted.`,
-		"- Only pass model when intentionally overriding the inherited model.",
-		`- Exact available provider/model IDs: ${choices.length > 0 ? choices.join(", ") : "none"}.`,
-		"- Never shorten, generalize, or invent a model ID.",
-	].join("\n");
-}
-
-function unavailableModelMessage(
-	requested: string,
-	available: readonly { provider: string; id: string }[],
-	current: { provider: string; id: string } | undefined,
-	withinScope: boolean,
-): string {
-	const choices = [...new Set(available.map(modelName))];
-	const scope = withinScope ? " within the session scope" : "";
-	const allowed = choices.length > 0 ? choices.join(", ") : "none";
-	const inherit = current ? ` Omit model to inherit ${modelName(current)}.` : "";
-	return `Model is unavailable${scope}: ${requested}. Exact available models: ${allowed}.${inherit}`;
-}
-
-function asFooterUsage(usage: Usage): FooterUsage {
-	return cloneUsage(usage);
-}
-
-class SubagentManager {
-	readonly agents = new Map<string, ManagedSubagent>();
-	private archivedAgents = new Map<string, ManagedSubagent>();
-	private nextId = 1;
-	private currentContext?: ExtensionContext;
-	private totalUsage = zeroUsage();
-	private accountedUsage = zeroUsage();
-	private usageDirty = false;
-	private footerSelected = false;
-	private lastWebStatusPublishedAt = 0;
-	private webStatusPublishTimer?: ReturnType<typeof setTimeout>;
-	private webTranscriptCursors = new Map<string, TranscriptItem | undefined>();
-	private webStreamingSnapshots = new Map<string, string>();
-	private abortAllInFlight?: Promise<number>;
-
-	constructor(private readonly pi: ExtensionAPI) {}
-
-	setContext(ctx: ExtensionContext): void {
-		this.currentContext = ctx;
-		this.footerSelected = false;
-		this.totalUsage = zeroUsage();
-		this.accountedUsage = zeroUsage();
-		this.usageDirty = false;
-		this.webTranscriptCursors.clear();
-		this.webStreamingSnapshots.clear();
-		for (const entry of [...ctx.sessionManager.getBranch()].reverse()) {
-			if (entry.type !== "custom" || entry.customType !== USAGE_STATE_ENTRY) continue;
-			const restored = parsePersistedUsageState(entry.data);
-			if (restored) {
-				this.totalUsage = cloneUsage(restored.total);
-				this.accountedUsage = cloneUsage(restored.accounted);
-			}
-			break;
-		}
-		this.publishFooter();
-	}
-
-	persistUsage(): void {
-		if (!this.usageDirty || !hasUsage(this.totalUsage)) return;
-		this.pi.appendEntry(USAGE_STATE_ENTRY, {
-			total: cloneUsage(this.totalUsage),
-			accounted: cloneUsage(this.accountedUsage),
-		} satisfies PersistedUsageState);
-		this.usageDirty = false;
-	}
-
-	clearContext(): void {
-		if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
-		this.webStatusPublishTimer = undefined;
-		this.lastWebStatusPublishedAt = 0;
-		this.webTranscriptCursors.clear();
-		this.webStreamingSnapshots.clear();
-		this.archivedAgents.clear();
-		const ctx = this.currentContext;
-		if (ctx) {
-			const sessionId = ctx.sessionManager.getSessionId();
-			this.pi.events.emit(FOOTER_CONTRIBUTION_EVENT, {
-				sessionId,
-				key: "subagents",
-				remove: true,
-			} satisfies FooterContribution);
-			this.pi.events.emit(SUBAGENT_STATUS_EVENT, {
-				sessionId,
-				agents: [],
-				usage: zeroUsage(),
-				remove: true,
-			} satisfies SubagentStatusEvent);
-		}
-		this.currentContext = undefined;
-		this.footerSelected = false;
-	}
-
-	hasAgents(): boolean {
-		return this.agents.size > 0;
-	}
-
-	isFooterSelected(): boolean {
-		return this.footerSelected;
-	}
-
-	setFooterSelected(selected: boolean): void {
-		if (this.footerSelected === selected) return;
-		this.footerSelected = selected && this.hasAgents();
-		this.publishFooter();
-	}
-
-	getAgent(id: string): ManagedSubagent {
-		const agent = this.agents.get(id) ?? this.archivedAgents.get(id);
-		if (!agent) throw new Error(`Unknown subagent: ${id}`);
-		return agent;
-	}
-
-	list(): ManagedSubagent[] {
-		return Array.from(this.agents.values()).sort((a, b) => a.createdAt - b.createdAt);
-	}
-
-	snapshots(): AgentSnapshot[] {
-		return this.list().map((agent) => ({
-			id: agent.id,
-			status: agent.status,
-			model: agent.model,
-			effort: agent.effort,
-			turns: agent.turns,
-			currentTool: agent.currentTool,
-			queued: agent.queuedSteering + agent.queuedFollowUp,
-		}));
-	}
-
-	webSnapshots(): SubagentWebSnapshot[] {
-		return this.list().map((agent) => ({
-			id: agent.id,
-			status: agent.status,
-			model: agent.model,
-			effort: agent.effort,
-			turns: agent.turns,
-			currentTool: agent.currentTool,
-			queued: agent.queuedSteering + agent.queuedFollowUp,
-			createdAt: agent.createdAt,
-			updatedAt: agent.updatedAt,
-			completedAt: agent.completedAt,
-			error: agent.error,
-			usage: cloneUsage(agent.usage),
-			transcript: webTranscript(agent),
-			streamingText: agent.streamingText || undefined,
-		}));
-	}
-
-	private webStatusUpdates(): SubagentWebUpdate[] {
-		return this.list().map((agent) => {
-			const update: SubagentWebUpdate = {
-				id: agent.id,
-				status: agent.status,
-				model: agent.model,
-				effort: agent.effort,
-				turns: agent.turns,
-				currentTool: agent.currentTool ?? null,
-				queued: agent.queuedSteering + agent.queuedFollowUp,
-				createdAt: agent.createdAt,
-				updatedAt: agent.updatedAt,
-				completedAt: agent.completedAt ?? null,
-				error: agent.error ?? null,
-				usage: cloneUsage(agent.usage),
-			};
-
-			const hadTranscriptCursor = this.webTranscriptCursors.has(agent.id);
-			const previousTranscriptItem = this.webTranscriptCursors.get(agent.id);
-			const previousIndex = previousTranscriptItem ? agent.transcript.indexOf(previousTranscriptItem) : -1;
-			if (!hadTranscriptCursor || (previousTranscriptItem && previousIndex < 0)) {
-				update.transcriptReset = true;
-				update.transcriptDelta = webTranscript(agent);
-			} else {
-				const firstNewIndex = previousTranscriptItem ? previousIndex + 1 : 0;
-				if (firstNewIndex < agent.transcript.length) {
-					update.transcriptDelta = boundedWebTranscript(agent.transcript.slice(firstNewIndex));
-				}
-			}
-			this.webTranscriptCursors.set(agent.id, agent.transcript.at(-1));
-
-			const hadStreamingSnapshot = this.webStreamingSnapshots.has(agent.id);
-			const previousStreamingText = this.webStreamingSnapshots.get(agent.id) ?? "";
-			if (!hadStreamingSnapshot || !agent.streamingText.startsWith(previousStreamingText)) {
-				update.streamingTextReset = true;
-				update.streamingTextDelta = agent.streamingText;
-			} else if (agent.streamingText.length > previousStreamingText.length) {
-				update.streamingTextDelta = agent.streamingText.slice(previousStreamingText.length);
-			}
-			this.webStreamingSnapshots.set(agent.id, agent.streamingText);
-			return update;
-		});
-	}
-
-	private makeId(requestedName?: string): string {
-		const base = requestedName ? sanitizeName(requestedName) : `agent-${this.nextId++}`;
-		if (!base) return this.makeId();
-		if (!this.agents.has(base) && !this.archivedAgents.has(base)) return base;
-		let suffix = 2;
-		while (this.agents.has(`${base}-${suffix}`) || this.archivedAgents.has(`${base}-${suffix}`)) suffix++;
-		return `${base}-${suffix}`;
-	}
-
-	private activeSessionCount(): number {
-		return this.list().filter(countsAgainstSubagentLimit).length;
-	}
-
-	private getModelRuntime(ctx: ExtensionContext): ModelRuntime {
-		return subagentModelRuntime(ctx.modelRegistry);
-	}
-
-	async availableModels(ctx: ExtensionContext): Promise<readonly AgentModel[]> {
-		const available = await this.getModelRuntime(ctx).getAvailable();
-		return filterModelsToScope(available, ctx.scopedModels);
-	}
-
-	private async resolveModel(ctx: ExtensionContext, requested?: string, runtime?: ModelRuntime): Promise<AgentModel | undefined> {
-		if (!requested) {
-			if (!ctx.model) return undefined;
-			const inheritedRuntime = runtime ?? this.getModelRuntime(ctx);
-			// Omitted model means exact host-session inheritance. Session model scope
-			// applies only to explicit overrides and may intentionally exclude the
-			// separately selected --model value.
-			return inheritedSubagentModel(
-				ctx.model as AgentModel,
-				inheritedRuntime.getModel(ctx.model.provider, ctx.model.id),
-			);
-		}
-
-		const available = await this.availableModels(ctx);
-		const slash = requested.indexOf("/");
-		if (slash > 0) {
-			const provider = requested.slice(0, slash);
-			const id = requested.slice(slash + 1);
-			const model = available.find((item) => item.provider === provider && item.id === id);
-			if (model) return model;
-			throw new Error(unavailableModelMessage(requested, available, ctx.model, ctx.scopedModels.length > 0));
-		}
-
-		const matches = available.filter((item) => item.id === requested || item.name === requested);
-		if (matches.length === 1) return matches[0];
-		if (matches.length > 1) {
-			throw new Error(`Model name is ambiguous; use provider/model: ${matches.map(modelName).join(", ")}`);
-		}
-		throw new Error(unavailableModelMessage(requested, available, ctx.model, ctx.scopedModels.length > 0));
-	}
-
-	private scopedEffort(ctx: ExtensionContext, model: AgentModel | undefined): SubagentEffort | undefined {
-		if (!model) return undefined;
-		return ctx.scopedModels.find(
-			(scoped) => scoped.model.provider === model.provider && scoped.model.id === model.id,
-		)?.thinkingLevel as SubagentEffort | undefined;
-	}
-
-	private activity(agent: ManagedSubagent, text: string): void {
-		agent.updatedAt = Date.now();
-		agent.activity.push({ timestamp: agent.updatedAt, text });
-		if (agent.activity.length > MAX_ACTIVITY_ITEMS) {
-			const removed = agent.activity.length - MAX_ACTIVITY_ITEMS;
-			agent.activity.splice(0, removed);
-			agent.lastReadActivity = Math.max(0, agent.lastReadActivity - removed);
-		}
-		for (const waiter of agent.waiters) waiter();
-		agent.waiters.clear();
-		this.publishFooter();
-	}
-
-	private addTranscript(agent: ManagedSubagent, message: unknown): void {
-		const transcript = messageToTranscript(message);
-		if (!transcript) return;
-		agent.transcript.push(transcript);
-		if (agent.transcript.length > MAX_TRANSCRIPT_ITEMS) agent.transcript.splice(0, agent.transcript.length - MAX_TRANSCRIPT_ITEMS);
-		let retainedCharacters = agent.transcript.reduce((total, item) => total + item.text.length, 0);
-		while (retainedCharacters > MAX_TRANSCRIPT_CHARS && agent.transcript.length > 1) {
-			retainedCharacters -= agent.transcript.shift()?.text.length ?? 0;
-		}
-	}
-
-	private accountUsage(agent: ManagedSubagent, usage: Usage | undefined): void {
-		if (!usage) return;
-		addUsage(agent.usage, usage);
-		addUsage(this.totalUsage, usage);
-		this.usageDirty = true;
-		this.publishFooter();
-	}
-
-	private subscribe(agent: ManagedSubagent, session: AgentSession): void {
-		agent.unsubscribe = session.subscribe((event: AgentSessionEvent) => {
-			switch (event.type) {
-				case "agent_start":
-					agent.status = "working";
-					agent.error = undefined;
-					agent.lastStopReason = undefined;
-					this.activity(agent, "started an agent turn");
-					break;
-				case "turn_start":
-					agent.turns++;
-					this.activity(agent, `started turn ${agent.turns}`);
-					break;
-				case "tool_execution_start":
-					agent.currentTool = event.toolName;
-					this.activity(agent, `running ${event.toolName} ${stringifyCompact(event.args)}`);
-					break;
-				case "tool_execution_end":
-					this.activity(agent, `${event.isError ? "failed" : "finished"} ${event.toolName}`);
-					agent.currentTool = undefined;
-					break;
-				case "message_update": {
-					const update = event.assistantMessageEvent;
-					if (update.type === "text_delta") {
-						agent.streamingText = appendBoundedStreamingText(agent.streamingText, update.delta);
-					}
-					const now = Date.now();
-					if (agent.streamingText && now - agent.lastStreamActivityAt >= 5_000) {
-						agent.lastStreamActivityAt = now;
-						this.activity(agent, "writing a response");
-					}
-					break;
-				}
-				case "message_end": {
-					this.addTranscript(agent, event.message);
-					const role = messageRole(event.message);
-					if (role === "assistant" || role === "toolResult") this.accountUsage(agent, messageUsage(event.message));
-					if (role === "assistant") {
-						agent.streamingText = "";
-						const stopReason = messageStopReason(event.message);
-						agent.lastStopReason = stopReason;
-						const error = messageError(event.message);
-						if (error) agent.error = error;
-						else if (stopReason !== "error" && stopReason !== "aborted") agent.error = undefined;
-						this.activity(agent, `assistant response finished${stopReason ? ` (${stopReason})` : ""}`);
-					}
-					break;
-				}
-				case "queue_update":
-					agent.queuedSteering = event.steering.length;
-					agent.queuedFollowUp = event.followUp.length;
-					this.activity(
-						agent,
-						`queue updated: ${agent.queuedSteering} steering, ${agent.queuedFollowUp} follow-up`,
-					);
-					break;
-				case "agent_end":
-					if (event.willRetry) this.activity(agent, "waiting to retry");
-					break;
-				case "agent_settled":
-					if (agent.status !== "terminated" && agent.status !== "terminating") {
-						const failed = isFailedStopReason(agent.lastStopReason);
-						agent.status = failed ? "failed" : "completed";
-						agent.completedAt = Date.now();
-						this.activity(
-							agent,
-							failed
-								? `failed${agent.error ? `: ${agent.error}` : ` (${agent.lastStopReason})`}`
-								: "completed and is waiting for more instructions",
-						);
-					}
-					break;
-				case "auto_retry_start":
-					this.activity(agent, `retrying after an error (attempt ${event.attempt}/${event.maxAttempts})`);
-					break;
-				case "compaction_start":
-					this.activity(agent, `compacting context (${event.reason})`);
-					break;
-				case "compaction_end":
-					this.accountUsage(agent, event.result?.usage);
-					this.activity(
-						agent,
-						event.errorMessage
-							? `context compaction failed: ${event.errorMessage}`
-							: event.aborted
-								? "context compaction aborted"
-								: `context compaction finished (${event.reason})`,
-					);
-					break;
-			}
-		});
-	}
-
-	private attachRun(agent: ManagedSubagent, promise: Promise<void>): void {
-		agent.runPromise = promise
-			.then(() => {
-				if (agent.status !== "terminated" && agent.status !== "terminating" && agent.status !== "failed") {
-					agent.status = "completed";
-					agent.completedAt = Date.now();
-					this.activity(agent, "task run settled");
-				}
-			})
-			.catch((error: unknown) => {
-				if (agent.status === "terminated" || agent.status === "terminating") return;
-				agent.status = "failed";
-				agent.error = error instanceof Error ? error.message : String(error);
-				agent.completedAt = Date.now();
-				this.activity(agent, `failed: ${agent.error}`);
-			});
-	}
-
-	async create(
-		ctx: ExtensionContext,
-		options: { prompt: string; name?: string; model?: string; effort?: SubagentEffort; cwd?: string },
-		signal?: AbortSignal,
-	): Promise<ManagedSubagent> {
-		if (this.activeSessionCount() >= MAX_SUBAGENTS) {
-			throw new Error(`At most ${MAX_SUBAGENTS} live subagent sessions may be retained at once. Terminate one before creating another.`);
-		}
-		if (signal?.aborted) throw new Error("Subagent creation was cancelled");
-
-		const cwd = resolve(ctx.cwd, options.cwd ?? ".");
-		const id = this.makeId(options.name);
-		const activeTools = this.pi.getActiveTools();
-		const effort = options.effort ?? (ctx.thinkingLevel as SubagentEffort);
-		const agent: ManagedSubagent = {
-			id,
-			prompt: options.prompt,
-			cwd,
-			createdAt: Date.now(),
-			updatedAt: Date.now(),
-			status: "creating",
-			model: options.model ?? modelName(ctx.model),
-			effort,
-			turns: 0,
-			queuedSteering: 0,
-			queuedFollowUp: 0,
-			activity: [],
-			lastReadActivity: 0,
-			transcript: [],
-			streamingText: "",
-			lastStreamActivityAt: 0,
-			usage: zeroUsage(),
-			waiters: new Set(),
-		};
-		this.agents.set(id, agent);
-		this.activity(agent, "creating isolated session");
-
-		try {
-			const runtime = await this.getModelRuntime(ctx);
-			const selectedModel = await this.resolveModel(ctx, options.model, runtime);
-			const selectedEffort = options.effort ?? this.scopedEffort(ctx, selectedModel) ?? effort;
-			agent.effort = selectedEffort;
-			const settingsManager = SettingsManager.create(ctx.cwd, getAgentDir());
-			const resourceLoader = new DefaultResourceLoader({
-				cwd,
-				agentDir: getAgentDir(),
-				settingsManager,
-				noExtensions: true,
-				appendSystemPrompt: [SUBAGENT_SYSTEM_PROMPT],
-			});
-			await resourceLoader.reload();
-			if (signal?.aborted) throw new Error("Subagent creation was cancelled");
-
-			const { session } = await createAgentSession({
-				cwd,
-				agentDir: getAgentDir(),
-				modelRuntime: runtime,
-				model: selectedModel,
-				thinkingLevel: selectedEffort,
-				tools: activeTools,
-				resourceLoader,
-				settingsManager,
-				sessionManager: SessionManager.inMemory(cwd),
-			});
-			if (!session.model) {
-				session.dispose();
-				throw new Error("No authenticated model is available for the subagent");
-			}
-			if (signal?.aborted) {
-				session.dispose();
-				throw new Error("Subagent creation was cancelled");
-			}
-
-			agent.session = session;
-			agent.model = modelName(session.model);
-			agent.effort = session.thinkingLevel as SubagentEffort;
-			agent.status = "working";
-			this.subscribe(agent, session);
-			this.activity(agent, `started with ${agent.model} at ${agent.effort} effort`);
-			this.attachRun(agent, session.prompt(options.prompt, { source: "extension" }));
-			// Creation already reports these startup events, so the first read waits for new activity.
-			agent.lastReadActivity = agent.activity.length;
-			return agent;
-		} catch (error) {
-			agent.status = signal?.aborted ? "terminated" : "failed";
-			agent.error = error instanceof Error ? error.message : String(error);
-			agent.completedAt = Date.now();
-			this.activity(agent, `${agent.status}: ${agent.error}`);
-			throw error;
-		}
-	}
-
-	async send(id: string, message: string, urgency: MessageUrgency): Promise<void> {
-		const agent = this.getAgent(id);
-		const session = agent.session;
-		if (!session) throw new Error(`Subagent ${id} no longer has a live session`);
-		if (agent.status === "terminating" || agent.status === "terminated") {
-			throw new Error(`Subagent ${id} is ${agent.status}`);
-		}
-
-		if (session.isStreaming) {
-			if (urgency === "urgent") await session.steer(message);
-			else await session.followUp(message);
-			this.activity(agent, `${urgency === "urgent" ? "steered with" : "queued"} instruction: ${truncateChars(message, 160)}`);
-			return;
-		}
-
-		agent.status = "working";
-		this.activity(agent, `started follow-on instruction: ${truncateChars(message, 160)}`);
-		this.attachRun(agent, session.prompt(message, { source: "extension" }));
-	}
-
-	async configure(
-		ctx: ExtensionContext,
-		id: string,
-		options: { model?: string; effort?: SubagentEffort },
-	): Promise<ManagedSubagent> {
-		const agent = this.getAgent(id);
-		const session = agent.session;
-		if (!session) throw new Error(`Subagent ${id} no longer has a live session`);
-		if (!options.model && !options.effort) throw new Error("Specify a model, effort, or both");
-
-		if (options.model) {
-			const model = await this.resolveModel(ctx, options.model);
-			if (!model) throw new Error("No model was selected");
-			await session.setModel(model);
-			agent.model = modelName(session.model);
-			const pinnedEffort = this.scopedEffort(ctx, model);
-			if (!options.effort && pinnedEffort) session.setThinkingLevel(pinnedEffort);
-			agent.effort = session.thinkingLevel as SubagentEffort;
-			this.activity(agent, `model changed to ${agent.model} at ${agent.effort} effort`);
-		}
-		if (options.effort) {
-			session.setThinkingLevel(options.effort);
-			agent.effort = session.thinkingLevel as SubagentEffort;
-			this.activity(agent, `effort changed to ${agent.effort}`);
-		}
-		return agent;
-	}
-
-	async abortAll(): Promise<number> {
-		if (this.abortAllInFlight) return await this.abortAllInFlight;
-		const operation = (async () => {
-			const results = await abortRunningSubagentSessions(this.list());
-			for (const { agent, error } of results) {
-				if (error) {
-					agent.error = error.message;
-					this.activity(agent, `abort failed: ${agent.error}`);
-				} else {
-					this.activity(agent, "aborted with the main agent");
-				}
-			}
-			return results.length;
-		})();
-		this.abortAllInFlight = operation;
-		try {
-			return await operation;
-		} finally {
-			if (this.abortAllInFlight === operation) this.abortAllInFlight = undefined;
-		}
-	}
-
-	async terminate(id: string, remove = false): Promise<ManagedSubagent> {
-		const agent = this.getAgent(id);
-		if (agent.status !== "terminated") {
-			agent.status = "terminating";
-			this.activity(agent, "termination requested");
-			const session = agent.session;
-			if (session) {
-				try {
-					await session.abort();
-				} catch (error) {
-					agent.error = error instanceof Error ? error.message : String(error);
-				} finally {
-					agent.unsubscribe?.();
-					agent.unsubscribe = undefined;
-					try {
-						session.dispose();
-					} catch (error) {
-						agent.error = error instanceof Error ? error.message : String(error);
-					}
-					agent.session = undefined;
-				}
-			}
-			agent.status = "terminated";
-			agent.completedAt = Date.now();
-			this.activity(agent, "terminated and released session resources");
-		}
-		this.agents.delete(id);
-		this.webTranscriptCursors.delete(id);
-		this.webStreamingSnapshots.delete(id);
-		if (remove) this.archivedAgents.delete(id);
-		else if (shouldArchiveTerminalSubagent(agent)) this.archivedAgents.set(id, agent);
-		this.footerSelected = false;
-		this.publishFooter();
-		if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
-		this.publishWebStatus();
-		return agent;
-	}
-
-	async terminateAll(remove = false): Promise<void> {
-		await Promise.all(this.list().map(async (agent) => this.terminate(agent.id, remove)));
-		if (remove) this.archivedAgents.clear();
-	}
-
-	async clearTerminalAgents(): Promise<number> {
-		const terminalAgents = this.list().filter((agent) => isTerminalSubagentStatus(agent.status));
-		if (terminalAgents.length === 0) return 0;
-
-		await Promise.all(terminalAgents.map(async (agent) => {
-			const preserveUnreadOutput = shouldArchiveTerminalSubagent(agent);
-			await this.terminate(agent.id, true);
-			if (preserveUnreadOutput) this.archivedAgents.set(agent.id, agent);
-		}));
-		if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
-		this.publishWebStatus();
-		return terminalAgents.length;
-	}
-
-	private hasUnread(agent: ManagedSubagent): boolean {
-		return agent.lastReadActivity < agent.activity.length;
-	}
-
-	async waitForUpdates(agents: ManagedSubagent[], seconds: number, signal?: AbortSignal): Promise<void> {
-		if (seconds <= 0 || agents.some((agent) => this.hasUnread(agent))) return;
-		const running = agents.filter((agent) => agent.status === "creating" || agent.status === "working");
-		if (running.length === 0) return;
-
-		await new Promise<void>((done) => {
-			let finished = false;
-			const finish = () => {
-				if (finished) return;
-				finished = true;
-				clearTimeout(timer);
-				for (const agent of running) agent.waiters.delete(finish);
-				signal?.removeEventListener("abort", finish);
-				done();
-			};
-			const timer = setTimeout(finish, Math.min(30, seconds) * 1_000);
-			for (const agent of running) agent.waiters.add(finish);
-			signal?.addEventListener("abort", finish, { once: true });
-		});
-	}
-
-	read(agents: ManagedSubagent[], includeTranscript: boolean): string {
-		if (agents.length === 0) return "No subagents are involved in this session.";
-		const now = Date.now();
-		const sections: string[] = [];
-		for (const agent of agents) {
-			const heading = `## ${statusIcon(agent.status)} ${agent.id} — ${agent.status}`;
-			const metadata = [
-				`Model: ${agent.model}`,
-				`Effort: ${agent.effort}`,
-				`Elapsed: ${formatDuration((agent.completedAt ?? now) - agent.createdAt)}`,
-				`Turns: ${agent.turns}`,
-				`Usage: ↑${formatTokens(agent.usage.input)} ↓${formatTokens(agent.usage.output)}${agent.usage.cost.total ? ` $${agent.usage.cost.total.toFixed(4)}` : ""}`,
-			];
-			if (agent.currentTool) metadata.push(`Current tool: ${agent.currentTool}`);
-			if (agent.queuedSteering || agent.queuedFollowUp) {
-				metadata.push(`Queued: ${agent.queuedSteering} steering, ${agent.queuedFollowUp} follow-up`);
-			}
-			if (agent.error) metadata.push(`Error: ${agent.error}`);
-
-			const unread = agent.activity.slice(agent.lastReadActivity);
-			const activity = unread.length
-				? unread.map((item) => `- ${formatClock(item.timestamp)} ${item.text}`).join("\n")
-				: "- No new activity.";
-			agent.lastReadActivity = agent.activity.length;
-
-			let output = `${heading}\n${metadata.join("\n")}\n\nActivity since last read:\n${activity}`;
-			if (includeTranscript) {
-				const transcript = agent.transcript
-					.map((item) => `### ${formatClock(item.timestamp)} ${item.role}\n${item.text}`)
-					.join("\n\n");
-				output += `\n\nTranscript:\n${transcript || agent.streamingText || "(empty)"}`;
-			} else {
-				const latest = finalAssistantText(agent);
-				if (latest) output += `\n\nLatest assistant output:\n${latest}`;
-			}
-			sections.push(output);
-			if (this.archivedAgents.get(agent.id) === agent) this.archivedAgents.delete(agent.id);
-		}
-		return truncateToolOutput(sections.join("\n\n---\n\n"));
-	}
-
-	claimUnaccountedUsage(): Usage | undefined {
-		const usage = subtractUsage(this.totalUsage, this.accountedUsage);
-		if (!hasUsage(usage)) return undefined;
-		this.accountedUsage = cloneUsage(this.totalUsage);
-		this.usageDirty = true;
-		this.publishFooter();
-		return usage;
-	}
-
-	private footerText(): string | undefined {
-		if (this.agents.size === 0) return undefined;
-		let working = 0;
-		let completed = 0;
-		let failed = 0;
-		let terminated = 0;
-		for (const agent of this.agents.values()) {
-			if (agent.status === "creating" || agent.status === "working" || agent.status === "terminating") working++;
-			else if (agent.status === "completed") completed++;
-			else if (agent.status === "failed") failed++;
-			else terminated++;
-		}
-		const parts = [`◆ ${this.agents.size} subagent${this.agents.size === 1 ? "" : "s"}`];
-		if (working) parts.push(`${working} working`);
-		if (completed) parts.push(`${completed} done`);
-		if (failed) parts.push(`${failed} failed`);
-		if (terminated) parts.push(`${terminated} stopped`);
-		return parts.join(" • ");
-	}
-
-	private publishWebStatus(): void {
-		this.webStatusPublishTimer = undefined;
-		const ctx = this.currentContext;
-		if (!ctx) return;
-		const sessionId = ctx.sessionManager.getSessionId();
-		const usage = asFooterUsage(subtractUsage(this.totalUsage, this.accountedUsage));
-		this.lastWebStatusPublishedAt = Date.now();
-		this.pi.events.emit(SUBAGENT_STATUS_EVENT, {
-			sessionId,
-			agents: this.webStatusUpdates(),
-			usage,
-		} satisfies SubagentStatusEvent);
-	}
-
-	private publishFooter(): void {
-		const ctx = this.currentContext;
-		if (!ctx) return;
-		const sessionId = ctx.sessionManager.getSessionId();
-		const usage = asFooterUsage(subtractUsage(this.totalUsage, this.accountedUsage));
-		const statusText = this.footerText();
-		const contribution: FooterContribution = {
-			sessionId,
-			key: "subagents",
-			status: statusText ? { text: statusText, selected: this.footerSelected } : undefined,
-			usage,
-		};
-		this.pi.events.emit(FOOTER_CONTRIBUTION_EVENT, contribution);
-
-		// Footer metadata stays immediate, while coalesced web events carry only
-		// transcript/streaming deltas. The server retains a bounded full snapshot
-		// for newly subscribed clients without retransmitting it on every burst.
-		const delay = WEB_STATUS_PUBLISH_INTERVAL_MS - (Date.now() - this.lastWebStatusPublishedAt);
-		if (delay <= 0) {
-			if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
-			this.publishWebStatus();
-		} else if (!this.webStatusPublishTimer) {
-			this.webStatusPublishTimer = setTimeout(() => this.publishWebStatus(), delay);
-			this.webStatusPublishTimer.unref?.();
-		}
-	}
-}
-
-interface AppEditorComponent extends EditorComponent, Partial<Focusable> {
-	getCursor?: () => { line: number; col: number };
-	getLines?: () => string[];
-	isShowingAutocomplete?: () => boolean;
-	dispose?: () => void;
-	actionHandlers?: Map<unknown, () => void>;
-	onEscape?: () => void;
-	onCtrlD?: () => void;
-	onPasteImage?: () => void;
-	onExtensionShortcut?: (data: string) => boolean;
-}
-
-class FooterNavigationEditor implements EditorComponent, Focusable {
-	readonly actionHandlers?: Map<unknown, () => void>;
-
-	constructor(
-		private readonly base: AppEditorComponent,
-		private readonly keybindings: KeybindingsManager,
-		private readonly manager: SubagentManager,
-		private readonly openManager: () => void,
-	) {
-		this.actionHandlers = base.actionHandlers;
-	}
-
-	get focused(): boolean {
-		return this.base.focused ?? false;
-	}
-	set focused(value: boolean) {
-		if ("focused" in this.base) this.base.focused = value;
-	}
-	get onSubmit(): ((text: string) => void) | undefined {
-		return this.base.onSubmit;
-	}
-	set onSubmit(value: ((text: string) => void) | undefined) {
-		this.base.onSubmit = value;
-	}
-	get onChange(): ((text: string) => void) | undefined {
-		return this.base.onChange;
-	}
-	set onChange(value: ((text: string) => void) | undefined) {
-		this.base.onChange = value;
-	}
-	get borderColor(): ((text: string) => string) | undefined {
-		return this.base.borderColor;
-	}
-	set borderColor(value: ((text: string) => string) | undefined) {
-		this.base.borderColor = value;
-	}
-	get onEscape(): (() => void) | undefined {
-		return this.base.onEscape;
-	}
-	set onEscape(value: (() => void) | undefined) {
-		this.base.onEscape = value;
-	}
-	get onCtrlD(): (() => void) | undefined {
-		return this.base.onCtrlD;
-	}
-	set onCtrlD(value: (() => void) | undefined) {
-		this.base.onCtrlD = value;
-	}
-	get onPasteImage(): (() => void) | undefined {
-		return this.base.onPasteImage;
-	}
-	set onPasteImage(value: (() => void) | undefined) {
-		this.base.onPasteImage = value;
-	}
-	get onExtensionShortcut(): ((data: string) => boolean) | undefined {
-		return this.base.onExtensionShortcut;
-	}
-	set onExtensionShortcut(value: ((data: string) => boolean) | undefined) {
-		this.base.onExtensionShortcut = value;
-	}
-
-	render(width: number): string[] {
-		return this.base.render(width);
-	}
-	invalidate(): void {
-		this.base.invalidate();
-	}
-	dispose(): void {
-		this.base.dispose?.();
-	}
-	getText(): string {
-		return this.base.getText();
-	}
-	setText(text: string): void {
-		this.base.setText(text);
-	}
-	addToHistory(text: string): void {
-		this.base.addToHistory?.(text);
-	}
-	insertTextAtCursor(text: string): void {
-		this.base.insertTextAtCursor?.(text);
-	}
-	getExpandedText(): string {
-		return this.base.getExpandedText?.() ?? this.base.getText();
-	}
-	setAutocompleteProvider(provider: Parameters<NonNullable<EditorComponent["setAutocompleteProvider"]>>[0]): void {
-		this.base.setAutocompleteProvider?.(provider);
-	}
-	setPaddingX(padding: number): void {
-		this.base.setPaddingX?.(padding);
-	}
-	setAutocompleteMaxVisible(maximum: number): void {
-		this.base.setAutocompleteMaxVisible?.(maximum);
-	}
-
-	handleInput(data: string): void {
-		if (this.manager.isFooterSelected()) {
-			if (this.keybindings.matches(data, "tui.select.confirm")) {
-				this.manager.setFooterSelected(false);
-				this.openManager();
-				return;
-			}
-			if (
-				this.keybindings.matches(data, "tui.select.up") ||
-				this.keybindings.matches(data, "tui.select.cancel")
-			) {
-				this.manager.setFooterSelected(false);
-				return;
-			}
-			this.manager.setFooterSelected(false);
-		}
-
-		if (
-			this.manager.hasAgents() &&
-			this.base.getText().length === 0 &&
-			!this.base.isShowingAutocomplete?.() &&
-			matchesKey(data, "alt+down")
-		) {
-			const cursor = this.base.getCursor?.();
-			const lines = this.base.getLines?.();
-			if (!cursor || !lines || cursor.line === lines.length - 1) {
-				this.manager.setFooterSelected(true);
-				return;
-			}
-		}
-		this.base.handleInput(data);
-	}
-}
-
-function padAnsi(text: string, width: number): string {
-	const fitted = truncateToWidth(text, Math.max(0, width), "…");
-	return fitted + " ".repeat(Math.max(0, width - visibleWidth(fitted)));
-}
-
-function frameLines(theme: Theme, title: string, body: string[], width: number): string[] {
-	if (width < 4) return body.map((line) => truncateToWidth(line, width, ""));
-	const inner = width - 2;
-	const titleText = truncateToWidth(` ${title} `, Math.max(0, inner - 2), "…");
-	const topFill = Math.max(0, inner - visibleWidth(titleText));
-	const top = theme.fg("borderAccent", `┌${titleText}${"─".repeat(topFill)}┐`);
-	const bottom = theme.fg("borderAccent", `└${"─".repeat(inner)}┘`);
-	return [
-		top,
-		...body.map(
-			(line) => theme.fg("borderAccent", "│") + padAnsi(line, inner) + theme.fg("borderAccent", "│"),
-		),
-		bottom,
-	];
-}
-
-class AgentListDialog implements Component {
-	private selected = 0;
-	private timer: ReturnType<typeof setInterval>;
-
-	constructor(
-		private readonly manager: SubagentManager,
-		private readonly tui: TUI,
-		private readonly theme: Theme,
-		private readonly keybindings: KeybindingsManager,
-		private readonly done: (result: ManagerDialogResult) => void,
-	) {
-		this.timer = setInterval(() => tui.requestRender(), 500);
-	}
-
-	dispose(): void {
-		clearInterval(this.timer);
-	}
-	invalidate(): void {}
-
-	handleInput(data: string): void {
-		const agents = this.manager.list();
-		if (this.keybindings.matches(data, "tui.select.cancel")) return this.done({ action: "close" });
-		if (this.keybindings.matches(data, "tui.select.up")) {
-			this.selected = Math.max(0, this.selected - 1);
-			this.tui.requestRender();
-			return;
-		}
-		if (this.keybindings.matches(data, "tui.select.down")) {
-			this.selected = Math.min(Math.max(0, agents.length - 1), this.selected + 1);
-			this.tui.requestRender();
-			return;
-		}
-		const agent = agents[this.selected];
-		if (!agent) return;
-		if (this.keybindings.matches(data, "tui.select.confirm")) return this.done({ action: "view", id: agent.id });
-		if (data === "m") return this.done({ action: "model", id: agent.id });
-		if (data === "e") return this.done({ action: "effort", id: agent.id });
-		if (data === "x") return this.done({ action: "terminate", id: agent.id });
-	}
-
-	render(width: number): string[] {
-		const agents = this.manager.list();
-		this.selected = Math.min(this.selected, Math.max(0, agents.length - 1));
-		const body: string[] = [];
-		if (agents.length === 0) body.push(this.theme.fg("muted", " No subagents in this session"));
-		for (let index = 0; index < agents.length; index++) {
-			const agent = agents[index];
-			const icon = this.theme.fg(statusColor(agent.status), statusIcon(agent.status));
-			const queue = agent.queuedSteering + agent.queuedFollowUp;
-			let line = `${index === this.selected ? "›" : " "} ${icon} ${agent.id}  ${agent.status}`;
-			if (agent.currentTool) line += ` · ${agent.currentTool}`;
-			if (queue) line += ` · ${queue} queued`;
-			line += ` · ${agent.model} · ${agent.effort}`;
-			if (index === this.selected) line = this.theme.bg("selectedBg", this.theme.fg("accent", line));
-			body.push(line);
-		}
-		body.push("");
-		body.push(this.theme.fg("dim", " ↑↓ select · enter transcript · m model · e effort · x terminate · esc close"));
-		return frameLines(this.theme, "Subagents", body, width);
-	}
-}
-
-class AgentDetailDialog implements Component {
-	private scrollOffset = 0;
-	private timer: ReturnType<typeof setInterval>;
-
-	constructor(
-		private readonly agent: ManagedSubagent,
-		private readonly tui: TUI,
-		private readonly theme: Theme,
-		private readonly keybindings: KeybindingsManager,
-		private readonly done: (result: ManagerDialogResult) => void,
-	) {
-		this.timer = setInterval(() => tui.requestRender(), 300);
-	}
-
-	dispose(): void {
-		clearInterval(this.timer);
-	}
-	invalidate(): void {}
-
-	handleInput(data: string): void {
-		if (this.keybindings.matches(data, "tui.select.cancel") || data === "b") return this.done({ action: "back" });
-		if (this.keybindings.matches(data, "tui.select.up") || this.keybindings.matches(data, "tui.select.pageUp")) {
-			this.scrollOffset += this.keybindings.matches(data, "tui.select.pageUp") ? DETAIL_VIEW_LINES : 1;
-			this.tui.requestRender();
-			return;
-		}
-		if (this.keybindings.matches(data, "tui.select.down") || this.keybindings.matches(data, "tui.select.pageDown")) {
-			this.scrollOffset = Math.max(
-				0,
-				this.scrollOffset - (this.keybindings.matches(data, "tui.select.pageDown") ? DETAIL_VIEW_LINES : 1),
-			);
-			this.tui.requestRender();
-			return;
-		}
-		if (data === "m") return this.done({ action: "model", id: this.agent.id });
-		if (data === "e") return this.done({ action: "effort", id: this.agent.id });
-		if (data === "u") return this.done({ action: "urgent", id: this.agent.id });
-		if (data === "q") return this.done({ action: "queue", id: this.agent.id });
-		if (data === "x") return this.done({ action: "terminate", id: this.agent.id });
-	}
-
-	private transcriptLines(width: number): string[] {
-		const lines: string[] = [];
-		for (const item of this.agent.transcript) {
-			lines.push(this.theme.fg("muted", `[${formatClock(item.timestamp)}] ${item.role}`));
-			const roleColor = item.role === "assistant" ? "text" : item.role === "toolResult" ? "dim" : "accent";
-			for (const line of wrapTextWithAnsi(this.theme.fg(roleColor, item.text), Math.max(1, width))) lines.push(line);
-			lines.push("");
-		}
-		if (this.agent.streamingText) {
-			lines.push(this.theme.fg("warning", "[streaming] assistant"));
-			for (const line of wrapTextWithAnsi(this.agent.streamingText, Math.max(1, width))) lines.push(line);
-		}
-		if (lines.length === 0) lines.push(this.theme.fg("muted", "(transcript is empty)"));
-		return lines;
-	}
-
-	render(width: number): string[] {
-		const inner = Math.max(1, width - 4);
-		const allLines = this.transcriptLines(inner);
-		const maxOffset = Math.max(0, allLines.length - 1);
-		this.scrollOffset = Math.min(this.scrollOffset, maxOffset);
-		const end = Math.max(0, allLines.length - this.scrollOffset);
-		const start = Math.max(0, end - DETAIL_VIEW_LINES);
-		const visible = allLines.slice(start, end);
-		const status = this.theme.fg(statusColor(this.agent.status), `${statusIcon(this.agent.status)} ${this.agent.status}`);
-		const body = [
-			` ${status} · ${this.agent.model} · effort ${this.agent.effort} · ${formatDuration(Date.now() - this.agent.createdAt)}`,
-			this.theme.fg("dim", ` Task: ${truncateChars(this.agent.prompt.replace(/\s+/g, " "), 180)}`),
-			this.theme.fg(
-				"dim",
-				` Usage: ↑${formatTokens(this.agent.usage.input)} ↓${formatTokens(this.agent.usage.output)}${this.agent.usage.cost.total ? ` $${this.agent.usage.cost.total.toFixed(4)}` : ""}`,
-			),
-			this.theme.fg("borderMuted", " " + "─".repeat(Math.max(0, inner - 1))),
-			...visible.map((line) => ` ${line}`),
-			this.theme.fg("borderMuted", " " + "─".repeat(Math.max(0, inner - 1))),
-			this.theme.fg(
-				"dim",
-				` ↑↓/pg scroll${this.scrollOffset ? ` · ${this.scrollOffset} lines below` : ""} · m model · e effort · u steer · q queue · x terminate · b back`,
-			),
-		];
-		return frameLines(this.theme, this.agent.id, body, width);
-	}
-}
-
-async function selectOverlay(
-	ctx: ExtensionContext,
-	title: string,
-	items: SelectItem[],
-): Promise<string | undefined> {
-	if (ctx.mode !== "tui") return undefined;
-	return ctx.ui.custom<string | undefined>(
-		(tui, theme, _keybindings, done) => {
-			const container = new Container();
-			container.addChild(new DynamicBorder((text: string) => theme.fg("accent", text)));
-			container.addChild(new Text(theme.fg("accent", theme.bold(title)), 1, 0));
-			const list = new SelectList(items, Math.min(12, Math.max(1, items.length)), {
-				selectedPrefix: (text) => theme.fg("accent", text),
-				selectedText: (text) => theme.fg("accent", text),
-				description: (text) => theme.fg("muted", text),
-				scrollInfo: (text) => theme.fg("dim", text),
-				noMatch: (text) => theme.fg("warning", text),
-			});
-			list.onSelect = (item) => done(item.value);
-			list.onCancel = () => done(undefined);
-			container.addChild(list);
-			container.addChild(new Text(theme.fg("dim", "↑↓ navigate · enter select · esc cancel"), 1, 0));
-			container.addChild(new DynamicBorder((text: string) => theme.fg("accent", text)));
-			return {
-				render: (width) => container.render(width),
-				invalidate: () => container.invalidate(),
-				handleInput: (data) => {
-					list.handleInput(data);
-					tui.requestRender();
-				},
-			};
-		},
-		{ overlay: true, overlayOptions: { anchor: "center", width: "70%", maxHeight: "80%", minWidth: 48 } },
-	);
-}
-
-async function showManager(manager: SubagentManager, ctx: ExtensionContext): Promise<void> {
-	if (ctx.mode !== "tui") {
-		ctx.ui.notify("The subagent manager is only available in TUI mode", "warning");
-		return;
-	}
-
-	let detailId: string | undefined;
-	while (true) {
-		let result: ManagerDialogResult;
-		if (detailId && manager.agents.has(detailId)) {
-			const agent = manager.getAgent(detailId);
-			result = await ctx.ui.custom<ManagerDialogResult>(
-				(tui, theme, keybindings, done) => new AgentDetailDialog(agent, tui, theme, keybindings, done),
-				{ overlay: true, overlayOptions: { anchor: "center", width: "85%", maxHeight: "90%", minWidth: 56 } },
-			);
-		} else {
-			detailId = undefined;
-			result = await ctx.ui.custom<ManagerDialogResult>(
-				(tui, theme, keybindings, done) => new AgentListDialog(manager, tui, theme, keybindings, done),
-				{ overlay: true, overlayOptions: { anchor: "center", width: "85%", maxHeight: "85%", minWidth: 56 } },
-			);
-		}
-
-		if (!result || result.action === "close") return;
-		if (result.action === "back") {
-			detailId = undefined;
-			continue;
-		}
-		if (result.action === "view") {
-			detailId = result.id;
-			continue;
-		}
-
-		detailId = result.id;
-		try {
-			if (result.action === "model") {
-				const models = await manager.availableModels(ctx);
-				const selected = await selectOverlay(
-					ctx,
-					`Model for ${result.id}`,
-					models.map((model) => ({ value: modelName(model), label: model.id, description: `${model.provider} · ${model.name}` })),
-				);
-				if (selected) await manager.configure(ctx, result.id, { model: selected });
-			} else if (result.action === "effort") {
-				const selected = await selectOverlay(
-					ctx,
-					`Effort for ${result.id}`,
-					THINKING_LEVELS.map((level) => ({ value: level, label: level })),
-				);
-				if (selected) await manager.configure(ctx, result.id, { effort: selected as SubagentEffort });
-			} else if (result.action === "urgent" || result.action === "queue") {
-				const message = await ctx.ui.input(
-					result.action === "urgent" ? `Steer ${result.id}` : `Queue for ${result.id}`,
-					"Instruction for the subagent",
-				);
-				if (message) await manager.send(result.id, message, result.action === "urgent" ? "urgent" : "normal");
-			} else if (result.action === "terminate") {
-				const confirmed = await ctx.ui.confirm("Terminate subagent?", `Stop ${result.id} and release its resources?`);
-				if (confirmed) await manager.terminate(result.id);
-			}
-		} catch (error) {
-			ctx.ui.notify(error instanceof Error ? error.message : String(error), "error");
-		}
-	}
-}
-
-function toolResult(manager: SubagentManager, text: string): { content: [{ type: "text"; text: string }]; details: ToolDetails; usage?: Usage } {
-	const usage = manager.claimUnaccountedUsage();
-	return {
-		content: [{ type: "text", text }],
-		details: { agents: manager.webSnapshots() },
-		...(usage ? { usage } : {}),
-	};
-}
-
-function stringEnum<T extends readonly string[]>(
-	values: T,
-	options?: { description?: string; default?: T[number] },
-) {
-	return Type.Unsafe<T[number]>({
-		type: "string",
-		enum: values,
-		...(options?.description ? { description: options.description } : {}),
-		...(options?.default ? { default: options.default } : {}),
-	});
-}
-
-const EffortSchema = stringEnum(THINKING_LEVELS, {
-	description: "Reasoning effort. The selected model may clamp unsupported levels.",
-});
-
-const CreateParams = Type.Object({
-	prompt: Type.String({ description: "Complete task prompt for the new isolated subagent" }),
-	name: Type.Optional(Type.String({ description: "Short stable name used to address the subagent" })),
-	model: Type.Optional(Type.String({ description: "Exact provider/model-id or exact unambiguous model id. Omit to inherit the current model; never use a shortened family alias." })),
-	effort: Type.Optional(EffortSchema),
-	cwd: Type.Optional(Type.String({ description: "Working directory, relative to the main session unless absolute" })),
-});
-
-const ReadParams = Type.Object({
-	id: Type.Optional(Type.String({ description: "Subagent id. Omit to read all subagents." })),
-	wait_seconds: Type.Optional(
-		Type.Integer({
-			description: `Wait for meaningful new activity before returning. Default ${DEFAULT_READ_WAIT_SECONDS}, maximum 30.`,
-			minimum: 0,
-			maximum: 30,
-		}),
-	),
-	include_transcript: Type.Optional(Type.Boolean({ description: "Include the full retained transcript instead of only latest output" })),
-});
-
-const SendParams = Type.Object({
-	id: Type.String({ description: "Subagent id" }),
-	message: Type.String({ description: "Instruction to send" }),
-	urgency: stringEnum(["normal", "urgent"] as const, {
-		description: "urgent steers after the current tool batch; normal queues until the current run finishes",
-	}),
-});
-
-const ConfigureParams = Type.Object({
-	id: Type.String({ description: "Subagent id" }),
-	model: Type.Optional(Type.String({ description: "Exact new provider/model-id or exact unambiguous model id. Omit to retain the current model; never use a shortened family alias." })),
-	effort: Type.Optional(EffortSchema),
-});
-
-const TerminateParams = Type.Object({
-	id: Type.Optional(Type.String({ description: "Subagent id. Omit with all=true to terminate every subagent." })),
-	all: Type.Optional(Type.Boolean({ description: "Terminate every subagent" })),
-	remove: Type.Optional(Type.Boolean({ description: "Also remove terminated records from the footer and manager" })),
-});
+import { SubagentManager } from "./subagents/manager.js";
+import {
+	filterModelsToScope,
+	subagentModelGuidance,
+} from "./subagents/models.js";
+import { registerSubagentTools } from "./subagents/tools.js";
+import {
+	FooterNavigationEditor,
+	showManager,
+	type AppEditorComponent,
+} from "./subagents/ui.js";
+
+export {
+	abortRunningSubagentSessions,
+	countsAgainstSubagentLimit,
+	isFailedStopReason,
+	isTerminalSubagentStatus,
+	shouldArchiveTerminalSubagent,
+} from "./subagents/lifecycle.js";
+export {
+	filterModelsToScope,
+	inheritedSubagentModel,
+	subagentModelGuidance,
+	subagentModelRuntime,
+} from "./subagents/models.js";
+export { appendBoundedStreamingText } from "./subagents/transcript.js";
+export { MAX_WEB_STREAMING_CHARS, THINKING_LEVELS } from "./subagents/types.js";
+export type {
+	MessageUrgency,
+	SubagentEffort,
+	SubagentStatus,
+} from "./subagents/types.js";
+export { parsePersistedUsageState } from "./subagents/usage.js";
 
 export default function subagentsExtension(pi: ExtensionAPI): void {
 	const manager = new SubagentManager(pi);
@@ -1742,131 +75,7 @@ export default function subagentsExtension(pi: ExtensionAPI): void {
 		return { systemPrompt: `${event.systemPrompt}\n\n${subagentModelGuidance(ctx.model, available)}` };
 	});
 
-	pi.registerTool({
-		name: "subagent_create",
-		label: "Create subagent",
-		description: `Create a background subagent with an isolated context, model, and reasoning effort. Returns immediately after startup. Up to ${MAX_SUBAGENTS} live subagent sessions are allowed.`,
-		promptSnippet: "Create a background subagent with a chosen prompt, model, and effort",
-		promptGuidelines: [
-			"When calling subagent_create, omit model to inherit the current model unless deliberately choosing one of the exact session-available provider/model IDs listed in the system prompt; never shorten or invent a model ID.",
-			"After subagent_create returns, use subagent_read with its default wait roughly every 15–30 seconds while work continues; briefly tell the user about meaningful progress between polls without narrating every event.",
-			"Wait for subagent_create to return before calling another subagent management tool for that id.",
-			"Use subagent_send with urgent only when the current approach must change immediately; use normal for work that can wait until the current run finishes.",
-			"Use subagent_terminate when delegated work is no longer needed, and clean up retained subagents before finishing when appropriate.",
-		],
-		parameters: CreateParams,
-		async execute(_toolCallId, params, signal, _onUpdate, ctx) {
-			const agent = await manager.create(ctx, params, signal);
-			return toolResult(
-				manager,
-				`Created ${agent.id} with ${agent.model} at ${agent.effort} effort. It is running in ${agent.cwd}. Use subagent_read to wait for and inspect progress.`,
-			);
-		},
-		renderCall(args, theme) {
-			const name = args.name ? ` ${theme.fg("accent", args.name)}` : "";
-			const model = args.model ? ` · ${args.model}` : "";
-			const effort = args.effort ? ` · ${args.effort}` : "";
-			return new Text(`${theme.fg("toolTitle", theme.bold("subagent_create"))}${name}${theme.fg("muted", model + effort)}\n${theme.fg("dim", truncateChars(args.prompt, 180))}`, 0, 0);
-		},
-		renderResult(result, _options, theme) {
-			const text = result.content[0];
-			return new Text(theme.fg("toolOutput", text?.type === "text" ? text.text : "Created subagent"), 0, 0);
-		},
-	});
-
-	pi.registerTool({
-		name: "subagent_read",
-		label: "Read subagents",
-		description: "Wait for and read meaningful subagent activity, status, output, usage, or full transcripts. Omit id to monitor all subagents.",
-		promptSnippet: "Read and monitor background subagent activity and output",
-		parameters: ReadParams,
-		async execute(_toolCallId, params, signal) {
-			const agents = params.id ? [manager.getAgent(params.id)] : manager.list();
-			await manager.waitForUpdates(agents, params.wait_seconds ?? DEFAULT_READ_WAIT_SECONDS, signal);
-			if (signal?.aborted) throw new Error("Subagent read was cancelled");
-			return toolResult(manager, manager.read(agents, params.include_transcript ?? false));
-		},
-		renderCall(args, theme) {
-			return new Text(
-				theme.fg("toolTitle", theme.bold("subagent_read")) +
-					theme.fg("muted", ` ${args.id ?? "all"} · wait ${args.wait_seconds ?? DEFAULT_READ_WAIT_SECONDS}s`),
-				0,
-				0,
-			);
-		},
-		renderResult(result, { expanded }, theme) {
-			const raw = result.content[0];
-			const text = raw?.type === "text" ? raw.text : "(no output)";
-			return new Text(theme.fg("toolOutput", expanded ? text : text.split("\n").slice(0, 14).join("\n")), 0, 0);
-		},
-	});
-
-	pi.registerTool({
-		name: "subagent_send",
-		label: "Message subagent",
-		description: "Send an urgent steering message to a running subagent or queue a normal follow-up message for it.",
-		promptSnippet: "Steer a subagent urgently or queue a normal follow-up instruction",
-		parameters: SendParams,
-		async execute(_toolCallId, params) {
-			await manager.send(params.id, params.message, params.urgency);
-			return toolResult(
-				manager,
-				params.urgency === "urgent"
-					? `Steering message sent to ${params.id}.`
-					: `Follow-up message queued for ${params.id}.`,
-			);
-		},
-		renderCall(args, theme) {
-			return new Text(
-				`${theme.fg("toolTitle", theme.bold("subagent_send"))} ${theme.fg("accent", args.id)} ${theme.fg(args.urgency === "urgent" ? "warning" : "muted", args.urgency)}\n${theme.fg("dim", truncateChars(args.message, 180))}`,
-				0,
-				0,
-			);
-		},
-	});
-
-	pi.registerTool({
-		name: "subagent_configure",
-		label: "Configure subagent",
-		description: "Change a retained subagent's model and/or reasoning effort. Changes apply to its next model request.",
-		promptSnippet: "Change a subagent model or reasoning effort",
-		parameters: ConfigureParams,
-		async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
-			const agent = await manager.configure(ctx, params.id, params);
-			return toolResult(manager, `${agent.id} now uses ${agent.model} at ${agent.effort} effort.`);
-		},
-		renderCall(args, theme) {
-			return new Text(
-				`${theme.fg("toolTitle", theme.bold("subagent_configure"))} ${theme.fg("accent", args.id)}${theme.fg("muted", `${args.model ? ` · ${args.model}` : ""}${args.effort ? ` · ${args.effort}` : ""}`)}`,
-				0,
-				0,
-			);
-		},
-	});
-
-	pi.registerTool({
-		name: "subagent_terminate",
-		label: "Terminate subagent",
-		description: "Abort one or all subagents, dispose their sessions, and optionally remove their retained transcript records.",
-		promptSnippet: "Terminate subagents and release their resources",
-		parameters: TerminateParams,
-		async execute(_toolCallId, params) {
-			if (params.all) {
-				await manager.terminateAll(params.remove ?? false);
-				return toolResult(manager, "Terminated all subagents and released their session resources.");
-			}
-			if (!params.id) throw new Error("Specify id or all=true");
-			await manager.terminate(params.id, params.remove ?? false);
-			return toolResult(manager, `Terminated ${params.id} and released its session resources.`);
-		},
-		renderCall(args, theme) {
-			return new Text(
-				`${theme.fg("toolTitle", theme.bold("subagent_terminate"))} ${theme.fg("warning", args.all ? "all" : (args.id ?? "?"))}`,
-				0,
-				0,
-			);
-		},
-	});
+	registerSubagentTools(pi, manager);
 
 	pi.registerCommand("subagents", {
 		description: "Open the subagent manager",
diff --git a/extensions/subagents/format.ts b/extensions/subagents/format.ts
new file mode 100644
index 0000000..1e8687e
--- /dev/null
+++ b/extensions/subagents/format.ts
@@ -0,0 +1,99 @@
+import { MAX_TOOL_OUTPUT_BYTES, type SubagentStatus } from "./types.js";
+
+export function formatTokens(count: number): string {
+	if (count < 1_000) return `${count}`;
+	if (count < 10_000) return `${(count / 1_000).toFixed(1)}k`;
+	if (count < 1_000_000) return `${Math.round(count / 1_000)}k`;
+	return `${(count / 1_000_000).toFixed(1)}M`;
+}
+
+export function formatDuration(milliseconds: number): string {
+	const seconds = Math.max(0, Math.floor(milliseconds / 1_000));
+	if (seconds < 60) return `${seconds}s`;
+	const minutes = Math.floor(seconds / 60);
+	if (minutes < 60) return `${minutes}m ${seconds % 60}s`;
+	return `${Math.floor(minutes / 60)}h ${minutes % 60}m`;
+}
+
+export function formatClock(timestamp: number): string {
+	return new Date(timestamp).toLocaleTimeString([], { hour: "2-digit", minute: "2-digit", second: "2-digit" });
+}
+
+export function sanitizeName(value: string): string {
+	return value
+		.trim()
+		.toLowerCase()
+		.replace(/[^a-z0-9._-]+/g, "-")
+		.replace(/^-+|-+$/g, "")
+		.slice(0, 40);
+}
+
+export function stringifyCompact(value: unknown, max = 200): string {
+	let text: string;
+	try {
+		text = JSON.stringify(value) ?? String(value);
+	} catch {
+		text = String(value);
+	}
+	const characters = Array.from(text);
+	return characters.length > max ? `${characters.slice(0, max).join("")}…` : text;
+}
+
+export function truncateChars(text: string, maximum: number): string {
+	const characters = Array.from(text);
+	return characters.length <= maximum
+		? text
+		: `${characters.slice(0, maximum).join("")}\n[… ${characters.length - maximum} characters omitted]`;
+}
+
+export function statusIcon(status: SubagentStatus): string {
+	switch (status) {
+		case "creating":
+		case "working":
+		case "terminating":
+			return "◐";
+		case "completed":
+			return "✓";
+		case "failed":
+			return "✗";
+		case "terminated":
+			return "■";
+	}
+}
+
+export function statusColor(status: SubagentStatus): "warning" | "success" | "error" | "muted" {
+	switch (status) {
+		case "creating":
+		case "working":
+		case "terminating":
+			return "warning";
+		case "completed":
+			return "success";
+		case "failed":
+			return "error";
+		case "terminated":
+			return "muted";
+	}
+}
+
+export function truncateToolOutput(text: string): string {
+	const buffer = Buffer.from(text, "utf8");
+	if (buffer.length <= MAX_TOOL_OUTPUT_BYTES) return text;
+	let end = MAX_TOOL_OUTPUT_BYTES;
+	let output = "";
+	while (end > 0) {
+		try {
+			output = new TextDecoder("utf-8", { fatal: true }).decode(buffer.subarray(0, end));
+			break;
+		} catch {
+			// A valid JavaScript string can only leave a partial UTF-8 code point at
+			// the byte boundary, so at most three trailing bytes are discarded.
+			end--;
+		}
+	}
+	return `${output}\n\n[Output truncated: ${buffer.length - end} bytes omitted. Re-read a specific subagent or use the transcript modal for details.]`;
+}
+
+export function modelName(model: { provider: string; id: string } | undefined): string {
+	return model ? `${model.provider}/${model.id}` : "no-model";
+}
diff --git a/extensions/subagents/lifecycle.ts b/extensions/subagents/lifecycle.ts
new file mode 100644
index 0000000..a308d66
--- /dev/null
+++ b/extensions/subagents/lifecycle.ts
@@ -0,0 +1,35 @@
+import type { SubagentStatus } from "./types.js";
+
+export function isFailedStopReason(stopReason: string | undefined): boolean {
+	return stopReason === "error" || stopReason === "aborted";
+}
+
+export function countsAgainstSubagentLimit(agent: { status: SubagentStatus; session?: unknown }): boolean {
+	return agent.status === "creating" || agent.session !== undefined;
+}
+
+export function isTerminalSubagentStatus(status: SubagentStatus): boolean {
+	return status === "completed" || status === "failed" || status === "terminated";
+}
+
+export function shouldArchiveTerminalSubagent(agent: {
+	status: SubagentStatus;
+	lastReadActivity: number;
+	activity: readonly unknown[];
+}): boolean {
+	return isTerminalSubagentStatus(agent.status) && agent.lastReadActivity < agent.activity.length;
+}
+
+export async function abortRunningSubagentSessions<T extends { status: SubagentStatus; session?: { abort(): Promise<unknown> } }>(
+	agents: readonly T[],
+): Promise<Array<{ agent: T; error?: Error }>> {
+	const running = agents.filter((agent) => agent.session && (agent.status === "creating" || agent.status === "working"));
+	return await Promise.all(running.map(async (agent) => {
+		try {
+			await agent.session!.abort();
+			return { agent };
+		} catch (error) {
+			return { agent, error: error instanceof Error ? error : new Error(String(error)) };
+		}
+	}));
+}
diff --git a/extensions/subagents/manager.ts b/extensions/subagents/manager.ts
new file mode 100644
index 0000000..f83320f
--- /dev/null
+++ b/extensions/subagents/manager.ts
@@ -0,0 +1,811 @@
+import { resolve } from "node:path";
+import {
+	createAgentSession,
+	DefaultResourceLoader,
+	getAgentDir,
+	SessionManager,
+	SettingsManager,
+	type AgentSession,
+	type AgentSessionEvent,
+	type ExtensionAPI,
+	type ExtensionContext,
+	type ModelRuntime,
+} from "@earendil-works/pi-coding-agent";
+import { FOOTER_CONTRIBUTION_EVENT, type FooterContribution } from "../footer-events.js";
+import {
+	SUBAGENT_STATUS_EVENT,
+	type SubagentStatusEvent,
+	type SubagentWebSnapshot,
+	type SubagentWebUpdate,
+} from "../subagent-events.js";
+import {
+	formatClock,
+	formatDuration,
+	formatTokens,
+	modelName,
+	sanitizeName,
+	statusIcon,
+	stringifyCompact,
+	truncateChars,
+	truncateToolOutput,
+} from "./format.js";
+import {
+	abortRunningSubagentSessions,
+	countsAgainstSubagentLimit,
+	isFailedStopReason,
+	isTerminalSubagentStatus,
+	shouldArchiveTerminalSubagent,
+} from "./lifecycle.js";
+import {
+	filterModelsToScope,
+	inheritedSubagentModel,
+	subagentModelRuntime,
+	unavailableModelMessage,
+} from "./models.js";
+import {
+	appendBoundedStreamingText,
+	boundedWebTranscript,
+	finalAssistantText,
+	messageError,
+	messageRole,
+	messageStopReason,
+	messageToTranscript,
+	messageUsage,
+	webTranscript,
+} from "./transcript.js";
+import {
+	MAX_ACTIVITY_ITEMS,
+	MAX_SUBAGENTS,
+	MAX_TRANSCRIPT_CHARS,
+	MAX_TRANSCRIPT_ITEMS,
+	SUBAGENT_SYSTEM_PROMPT,
+	USAGE_STATE_ENTRY,
+	WEB_STATUS_PUBLISH_INTERVAL_MS,
+	type AgentModel,
+	type AgentSnapshot,
+	type ManagedSubagent,
+	type MessageUrgency,
+	type PersistedUsageState,
+	type SubagentEffort,
+	type TranscriptItem,
+	type Usage,
+} from "./types.js";
+import {
+	addUsage,
+	asFooterUsage,
+	cloneUsage,
+	hasUsage,
+	parsePersistedUsageState,
+	subtractUsage,
+	zeroUsage,
+} from "./usage.js";
+
+export class SubagentManager {
+	readonly agents = new Map<string, ManagedSubagent>();
+	private archivedAgents = new Map<string, ManagedSubagent>();
+	private nextId = 1;
+	private currentContext?: ExtensionContext;
+	private totalUsage = zeroUsage();
+	private accountedUsage = zeroUsage();
+	private usageDirty = false;
+	private footerSelected = false;
+	private lastWebStatusPublishedAt = 0;
+	private webStatusPublishTimer?: ReturnType<typeof setTimeout>;
+	private webTranscriptCursors = new Map<string, TranscriptItem | undefined>();
+	private webStreamingSnapshots = new Map<string, string>();
+	private abortAllInFlight?: Promise<number>;
+
+	constructor(private readonly pi: ExtensionAPI) {}
+
+	setContext(ctx: ExtensionContext): void {
+		this.currentContext = ctx;
+		this.footerSelected = false;
+		this.totalUsage = zeroUsage();
+		this.accountedUsage = zeroUsage();
+		this.usageDirty = false;
+		this.webTranscriptCursors.clear();
+		this.webStreamingSnapshots.clear();
+		for (const entry of [...ctx.sessionManager.getBranch()].reverse()) {
+			if (entry.type !== "custom" || entry.customType !== USAGE_STATE_ENTRY) continue;
+			const restored = parsePersistedUsageState(entry.data);
+			if (restored) {
+				this.totalUsage = cloneUsage(restored.total);
+				this.accountedUsage = cloneUsage(restored.accounted);
+			}
+			break;
+		}
+		this.publishFooter();
+	}
+
+	persistUsage(): void {
+		if (!this.usageDirty || !hasUsage(this.totalUsage)) return;
+		this.pi.appendEntry(USAGE_STATE_ENTRY, {
+			total: cloneUsage(this.totalUsage),
+			accounted: cloneUsage(this.accountedUsage),
+		} satisfies PersistedUsageState);
+		this.usageDirty = false;
+	}
+
+	clearContext(): void {
+		if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
+		this.webStatusPublishTimer = undefined;
+		this.lastWebStatusPublishedAt = 0;
+		this.webTranscriptCursors.clear();
+		this.webStreamingSnapshots.clear();
+		this.archivedAgents.clear();
+		const ctx = this.currentContext;
+		if (ctx) {
+			const sessionId = ctx.sessionManager.getSessionId();
+			this.pi.events.emit(FOOTER_CONTRIBUTION_EVENT, {
+				sessionId,
+				key: "subagents",
+				remove: true,
+			} satisfies FooterContribution);
+			this.pi.events.emit(SUBAGENT_STATUS_EVENT, {
+				sessionId,
+				agents: [],
+				usage: zeroUsage(),
+				remove: true,
+			} satisfies SubagentStatusEvent);
+		}
+		this.currentContext = undefined;
+		this.footerSelected = false;
+	}
+
+	hasAgents(): boolean {
+		return this.agents.size > 0;
+	}
+
+	isFooterSelected(): boolean {
+		return this.footerSelected;
+	}
+
+	setFooterSelected(selected: boolean): void {
+		if (this.footerSelected === selected) return;
+		this.footerSelected = selected && this.hasAgents();
+		this.publishFooter();
+	}
+
+	getAgent(id: string): ManagedSubagent {
+		const agent = this.agents.get(id) ?? this.archivedAgents.get(id);
+		if (!agent) throw new Error(`Unknown subagent: ${id}`);
+		return agent;
+	}
+
+	list(): ManagedSubagent[] {
+		return Array.from(this.agents.values()).sort((a, b) => a.createdAt - b.createdAt);
+	}
+
+	snapshots(): AgentSnapshot[] {
+		return this.list().map((agent) => ({
+			id: agent.id,
+			status: agent.status,
+			model: agent.model,
+			effort: agent.effort,
+			turns: agent.turns,
+			currentTool: agent.currentTool,
+			queued: agent.queuedSteering + agent.queuedFollowUp,
+		}));
+	}
+
+	webSnapshots(): SubagentWebSnapshot[] {
+		return this.list().map((agent) => ({
+			id: agent.id,
+			status: agent.status,
+			model: agent.model,
+			effort: agent.effort,
+			turns: agent.turns,
+			currentTool: agent.currentTool,
+			queued: agent.queuedSteering + agent.queuedFollowUp,
+			createdAt: agent.createdAt,
+			updatedAt: agent.updatedAt,
+			completedAt: agent.completedAt,
+			error: agent.error,
+			usage: cloneUsage(agent.usage),
+			transcript: webTranscript(agent),
+			streamingText: agent.streamingText || undefined,
+		}));
+	}
+
+	private webStatusUpdates(): SubagentWebUpdate[] {
+		return this.list().map((agent) => {
+			const update: SubagentWebUpdate = {
+				id: agent.id,
+				status: agent.status,
+				model: agent.model,
+				effort: agent.effort,
+				turns: agent.turns,
+				currentTool: agent.currentTool ?? null,
+				queued: agent.queuedSteering + agent.queuedFollowUp,
+				createdAt: agent.createdAt,
+				updatedAt: agent.updatedAt,
+				completedAt: agent.completedAt ?? null,
+				error: agent.error ?? null,
+				usage: cloneUsage(agent.usage),
+			};
+
+			const hadTranscriptCursor = this.webTranscriptCursors.has(agent.id);
+			const previousTranscriptItem = this.webTranscriptCursors.get(agent.id);
+			const previousIndex = previousTranscriptItem ? agent.transcript.indexOf(previousTranscriptItem) : -1;
+			if (!hadTranscriptCursor || (previousTranscriptItem && previousIndex < 0)) {
+				update.transcriptReset = true;
+				update.transcriptDelta = webTranscript(agent);
+			} else {
+				const firstNewIndex = previousTranscriptItem ? previousIndex + 1 : 0;
+				if (firstNewIndex < agent.transcript.length) {
+					update.transcriptDelta = boundedWebTranscript(agent.transcript.slice(firstNewIndex));
+				}
+			}
+			this.webTranscriptCursors.set(agent.id, agent.transcript.at(-1));
+
+			const hadStreamingSnapshot = this.webStreamingSnapshots.has(agent.id);
+			const previousStreamingText = this.webStreamingSnapshots.get(agent.id) ?? "";
+			if (!hadStreamingSnapshot || !agent.streamingText.startsWith(previousStreamingText)) {
+				update.streamingTextReset = true;
+				update.streamingTextDelta = agent.streamingText;
+			} else if (agent.streamingText.length > previousStreamingText.length) {
+				update.streamingTextDelta = agent.streamingText.slice(previousStreamingText.length);
+			}
+			this.webStreamingSnapshots.set(agent.id, agent.streamingText);
+			return update;
+		});
+	}
+
+	private makeId(requestedName?: string): string {
+		const base = requestedName ? sanitizeName(requestedName) : `agent-${this.nextId++}`;
+		if (!base) return this.makeId();
+		if (!this.agents.has(base) && !this.archivedAgents.has(base)) return base;
+		let suffix = 2;
+		while (this.agents.has(`${base}-${suffix}`) || this.archivedAgents.has(`${base}-${suffix}`)) suffix++;
+		return `${base}-${suffix}`;
+	}
+
+	private activeSessionCount(): number {
+		return this.list().filter(countsAgainstSubagentLimit).length;
+	}
+
+	private getModelRuntime(ctx: ExtensionContext): ModelRuntime {
+		return subagentModelRuntime(ctx.modelRegistry);
+	}
+
+	async availableModels(ctx: ExtensionContext): Promise<readonly AgentModel[]> {
+		const available = await this.getModelRuntime(ctx).getAvailable();
+		return filterModelsToScope(available, ctx.scopedModels);
+	}
+
+	private async resolveModel(ctx: ExtensionContext, requested?: string, runtime?: ModelRuntime): Promise<AgentModel | undefined> {
+		if (!requested) {
+			if (!ctx.model) return undefined;
+			const inheritedRuntime = runtime ?? this.getModelRuntime(ctx);
+			// Omitted model means exact host-session inheritance. Session model scope
+			// applies only to explicit overrides and may intentionally exclude the
+			// separately selected --model value.
+			return inheritedSubagentModel(
+				ctx.model as AgentModel,
+				inheritedRuntime.getModel(ctx.model.provider, ctx.model.id),
+			);
+		}
+
+		const available = await this.availableModels(ctx);
+		const slash = requested.indexOf("/");
+		if (slash > 0) {
+			const provider = requested.slice(0, slash);
+			const id = requested.slice(slash + 1);
+			const model = available.find((item) => item.provider === provider && item.id === id);
+			if (model) return model;
+			throw new Error(unavailableModelMessage(requested, available, ctx.model, ctx.scopedModels.length > 0));
+		}
+
+		const matches = available.filter((item) => item.id === requested || item.name === requested);
+		if (matches.length === 1) return matches[0];
+		if (matches.length > 1) {
+			throw new Error(`Model name is ambiguous; use provider/model: ${matches.map(modelName).join(", ")}`);
+		}
+		throw new Error(unavailableModelMessage(requested, available, ctx.model, ctx.scopedModels.length > 0));
+	}
+
+	private scopedEffort(ctx: ExtensionContext, model: AgentModel | undefined): SubagentEffort | undefined {
+		if (!model) return undefined;
+		return ctx.scopedModels.find(
+			(scoped) => scoped.model.provider === model.provider && scoped.model.id === model.id,
+		)?.thinkingLevel as SubagentEffort | undefined;
+	}
+
+	private activity(agent: ManagedSubagent, text: string): void {
+		agent.updatedAt = Date.now();
+		agent.activity.push({ timestamp: agent.updatedAt, text });
+		if (agent.activity.length > MAX_ACTIVITY_ITEMS) {
+			const removed = agent.activity.length - MAX_ACTIVITY_ITEMS;
+			agent.activity.splice(0, removed);
+			agent.lastReadActivity = Math.max(0, agent.lastReadActivity - removed);
+		}
+		for (const waiter of agent.waiters) waiter();
+		agent.waiters.clear();
+		this.publishFooter();
+	}
+
+	private addTranscript(agent: ManagedSubagent, message: unknown): void {
+		const transcript = messageToTranscript(message);
+		if (!transcript) return;
+		agent.transcript.push(transcript);
+		if (agent.transcript.length > MAX_TRANSCRIPT_ITEMS) agent.transcript.splice(0, agent.transcript.length - MAX_TRANSCRIPT_ITEMS);
+		let retainedCharacters = agent.transcript.reduce((total, item) => total + item.text.length, 0);
+		while (retainedCharacters > MAX_TRANSCRIPT_CHARS && agent.transcript.length > 1) {
+			retainedCharacters -= agent.transcript.shift()?.text.length ?? 0;
+		}
+	}
+
+	private accountUsage(agent: ManagedSubagent, usage: Usage | undefined): void {
+		if (!usage) return;
+		addUsage(agent.usage, usage);
+		addUsage(this.totalUsage, usage);
+		this.usageDirty = true;
+		this.publishFooter();
+	}
+
+	private subscribe(agent: ManagedSubagent, session: AgentSession): void {
+		agent.unsubscribe = session.subscribe((event: AgentSessionEvent) => {
+			switch (event.type) {
+				case "agent_start":
+					agent.status = "working";
+					agent.error = undefined;
+					agent.lastStopReason = undefined;
+					this.activity(agent, "started an agent turn");
+					break;
+				case "turn_start":
+					agent.turns++;
+					this.activity(agent, `started turn ${agent.turns}`);
+					break;
+				case "tool_execution_start":
+					agent.currentTool = event.toolName;
+					this.activity(agent, `running ${event.toolName} ${stringifyCompact(event.args)}`);
+					break;
+				case "tool_execution_end":
+					this.activity(agent, `${event.isError ? "failed" : "finished"} ${event.toolName}`);
+					agent.currentTool = undefined;
+					break;
+				case "message_update": {
+					const update = event.assistantMessageEvent;
+					if (update.type === "text_delta") {
+						agent.streamingText = appendBoundedStreamingText(agent.streamingText, update.delta);
+					}
+					const now = Date.now();
+					if (agent.streamingText && now - agent.lastStreamActivityAt >= 5_000) {
+						agent.lastStreamActivityAt = now;
+						this.activity(agent, "writing a response");
+					}
+					break;
+				}
+				case "message_end": {
+					this.addTranscript(agent, event.message);
+					const role = messageRole(event.message);
+					if (role === "assistant" || role === "toolResult") this.accountUsage(agent, messageUsage(event.message));
+					if (role === "assistant") {
+						agent.streamingText = "";
+						const stopReason = messageStopReason(event.message);
+						agent.lastStopReason = stopReason;
+						const error = messageError(event.message);
+						if (error) agent.error = error;
+						else if (stopReason !== "error" && stopReason !== "aborted") agent.error = undefined;
+						this.activity(agent, `assistant response finished${stopReason ? ` (${stopReason})` : ""}`);
+					}
+					break;
+				}
+				case "queue_update":
+					agent.queuedSteering = event.steering.length;
+					agent.queuedFollowUp = event.followUp.length;
+					this.activity(
+						agent,
+						`queue updated: ${agent.queuedSteering} steering, ${agent.queuedFollowUp} follow-up`,
+					);
+					break;
+				case "agent_end":
+					if (event.willRetry) this.activity(agent, "waiting to retry");
+					break;
+				case "agent_settled":
+					if (agent.status !== "terminated" && agent.status !== "terminating") {
+						const failed = isFailedStopReason(agent.lastStopReason);
+						agent.status = failed ? "failed" : "completed";
+						agent.completedAt = Date.now();
+						this.activity(
+							agent,
+							failed
+								? `failed${agent.error ? `: ${agent.error}` : ` (${agent.lastStopReason})`}`
+								: "completed and is waiting for more instructions",
+						);
+					}
+					break;
+				case "auto_retry_start":
+					this.activity(agent, `retrying after an error (attempt ${event.attempt}/${event.maxAttempts})`);
+					break;
+				case "compaction_start":
+					this.activity(agent, `compacting context (${event.reason})`);
+					break;
+				case "compaction_end":
+					this.accountUsage(agent, event.result?.usage);
+					this.activity(
+						agent,
+						event.errorMessage
+							? `context compaction failed: ${event.errorMessage}`
+							: event.aborted
+								? "context compaction aborted"
+								: `context compaction finished (${event.reason})`,
+					);
+					break;
+			}
+		});
+	}
+
+	private attachRun(agent: ManagedSubagent, promise: Promise<void>): void {
+		agent.runPromise = promise
+			.then(() => {
+				if (agent.status !== "terminated" && agent.status !== "terminating" && agent.status !== "failed") {
+					agent.status = "completed";
+					agent.completedAt = Date.now();
+					this.activity(agent, "task run settled");
+				}
+			})
+			.catch((error: unknown) => {
+				if (agent.status === "terminated" || agent.status === "terminating") return;
+				agent.status = "failed";
+				agent.error = error instanceof Error ? error.message : String(error);
+				agent.completedAt = Date.now();
+				this.activity(agent, `failed: ${agent.error}`);
+			});
+	}
+
+	async create(
+		ctx: ExtensionContext,
+		options: { prompt: string; name?: string; model?: string; effort?: SubagentEffort; cwd?: string },
+		signal?: AbortSignal,
+	): Promise<ManagedSubagent> {
+		if (this.activeSessionCount() >= MAX_SUBAGENTS) {
+			throw new Error(`At most ${MAX_SUBAGENTS} live subagent sessions may be retained at once. Terminate one before creating another.`);
+		}
+		if (signal?.aborted) throw new Error("Subagent creation was cancelled");
+
+		const cwd = resolve(ctx.cwd, options.cwd ?? ".");
+		const id = this.makeId(options.name);
+		const activeTools = this.pi.getActiveTools();
+		const effort = options.effort ?? (ctx.thinkingLevel as SubagentEffort);
+		const agent: ManagedSubagent = {
+			id,
+			prompt: options.prompt,
+			cwd,
+			createdAt: Date.now(),
+			updatedAt: Date.now(),
+			status: "creating",
+			model: options.model ?? modelName(ctx.model),
+			effort,
+			turns: 0,
+			queuedSteering: 0,
+			queuedFollowUp: 0,
+			activity: [],
+			lastReadActivity: 0,
+			transcript: [],
+			streamingText: "",
+			lastStreamActivityAt: 0,
+			usage: zeroUsage(),
+			waiters: new Set(),
+		};
+		this.agents.set(id, agent);
+		this.activity(agent, "creating isolated session");
+
+		try {
+			const runtime = await this.getModelRuntime(ctx);
+			const selectedModel = await this.resolveModel(ctx, options.model, runtime);
+			const selectedEffort = options.effort ?? this.scopedEffort(ctx, selectedModel) ?? effort;
+			agent.effort = selectedEffort;
+			const settingsManager = SettingsManager.create(ctx.cwd, getAgentDir());
+			const resourceLoader = new DefaultResourceLoader({
+				cwd,
+				agentDir: getAgentDir(),
+				settingsManager,
+				noExtensions: true,
+				appendSystemPrompt: [SUBAGENT_SYSTEM_PROMPT],
+			});
+			await resourceLoader.reload();
+			if (signal?.aborted) throw new Error("Subagent creation was cancelled");
+
+			const { session } = await createAgentSession({
+				cwd,
+				agentDir: getAgentDir(),
+				modelRuntime: runtime,
+				model: selectedModel,
+				thinkingLevel: selectedEffort,
+				tools: activeTools,
+				resourceLoader,
+				settingsManager,
+				sessionManager: SessionManager.inMemory(cwd),
+			});
+			if (!session.model) {
+				session.dispose();
+				throw new Error("No authenticated model is available for the subagent");
+			}
+			if (signal?.aborted) {
+				session.dispose();
+				throw new Error("Subagent creation was cancelled");
+			}
+
+			agent.session = session;
+			agent.model = modelName(session.model);
+			agent.effort = session.thinkingLevel as SubagentEffort;
+			agent.status = "working";
+			this.subscribe(agent, session);
+			this.activity(agent, `started with ${agent.model} at ${agent.effort} effort`);
+			this.attachRun(agent, session.prompt(options.prompt, { source: "extension" }));
+			// Creation already reports these startup events, so the first read waits for new activity.
+			agent.lastReadActivity = agent.activity.length;
+			return agent;
+		} catch (error) {
+			agent.status = signal?.aborted ? "terminated" : "failed";
+			agent.error = error instanceof Error ? error.message : String(error);
+			agent.completedAt = Date.now();
+			this.activity(agent, `${agent.status}: ${agent.error}`);
+			throw error;
+		}
+	}
+
+	async send(id: string, message: string, urgency: MessageUrgency): Promise<void> {
+		const agent = this.getAgent(id);
+		const session = agent.session;
+		if (!session) throw new Error(`Subagent ${id} no longer has a live session`);
+		if (agent.status === "terminating" || agent.status === "terminated") {
+			throw new Error(`Subagent ${id} is ${agent.status}`);
+		}
+
+		if (session.isStreaming) {
+			if (urgency === "urgent") await session.steer(message);
+			else await session.followUp(message);
+			this.activity(agent, `${urgency === "urgent" ? "steered with" : "queued"} instruction: ${truncateChars(message, 160)}`);
+			return;
+		}
+
+		agent.status = "working";
+		this.activity(agent, `started follow-on instruction: ${truncateChars(message, 160)}`);
+		this.attachRun(agent, session.prompt(message, { source: "extension" }));
+	}
+
+	async configure(
+		ctx: ExtensionContext,
+		id: string,
+		options: { model?: string; effort?: SubagentEffort },
+	): Promise<ManagedSubagent> {
+		const agent = this.getAgent(id);
+		const session = agent.session;
+		if (!session) throw new Error(`Subagent ${id} no longer has a live session`);
+		if (!options.model && !options.effort) throw new Error("Specify a model, effort, or both");
+
+		if (options.model) {
+			const model = await this.resolveModel(ctx, options.model);
+			if (!model) throw new Error("No model was selected");
+			await session.setModel(model);
+			agent.model = modelName(session.model);
+			const pinnedEffort = this.scopedEffort(ctx, model);
+			if (!options.effort && pinnedEffort) session.setThinkingLevel(pinnedEffort);
+			agent.effort = session.thinkingLevel as SubagentEffort;
+			this.activity(agent, `model changed to ${agent.model} at ${agent.effort} effort`);
+		}
+		if (options.effort) {
+			session.setThinkingLevel(options.effort);
+			agent.effort = session.thinkingLevel as SubagentEffort;
+			this.activity(agent, `effort changed to ${agent.effort}`);
+		}
+		return agent;
+	}
+
+	async abortAll(): Promise<number> {
+		if (this.abortAllInFlight) return await this.abortAllInFlight;
+		const operation = (async () => {
+			const results = await abortRunningSubagentSessions(this.list());
+			for (const { agent, error } of results) {
+				if (error) {
+					agent.error = error.message;
+					this.activity(agent, `abort failed: ${agent.error}`);
+				} else {
+					this.activity(agent, "aborted with the main agent");
+				}
+			}
+			return results.length;
+		})();
+		this.abortAllInFlight = operation;
+		try {
+			return await operation;
+		} finally {
+			if (this.abortAllInFlight === operation) this.abortAllInFlight = undefined;
+		}
+	}
+
+	async terminate(id: string, remove = false): Promise<ManagedSubagent> {
+		const agent = this.getAgent(id);
+		if (agent.status !== "terminated") {
+			agent.status = "terminating";
+			this.activity(agent, "termination requested");
+			const session = agent.session;
+			if (session) {
+				try {
+					await session.abort();
+				} catch (error) {
+					agent.error = error instanceof Error ? error.message : String(error);
+				} finally {
+					agent.unsubscribe?.();
+					agent.unsubscribe = undefined;
+					try {
+						session.dispose();
+					} catch (error) {
+						agent.error = error instanceof Error ? error.message : String(error);
+					}
+					agent.session = undefined;
+				}
+			}
+			agent.status = "terminated";
+			agent.completedAt = Date.now();
+			this.activity(agent, "terminated and released session resources");
+		}
+		this.agents.delete(id);
+		this.webTranscriptCursors.delete(id);
+		this.webStreamingSnapshots.delete(id);
+		if (remove) this.archivedAgents.delete(id);
+		else if (shouldArchiveTerminalSubagent(agent)) this.archivedAgents.set(id, agent);
+		this.footerSelected = false;
+		this.publishFooter();
+		if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
+		this.publishWebStatus();
+		return agent;
+	}
+
+	async terminateAll(remove = false): Promise<void> {
+		await Promise.all(this.list().map(async (agent) => this.terminate(agent.id, remove)));
+		if (remove) this.archivedAgents.clear();
+	}
+
+	async clearTerminalAgents(): Promise<number> {
+		const terminalAgents = this.list().filter((agent) => isTerminalSubagentStatus(agent.status));
+		if (terminalAgents.length === 0) return 0;
+
+		await Promise.all(terminalAgents.map(async (agent) => {
+			const preserveUnreadOutput = shouldArchiveTerminalSubagent(agent);
+			await this.terminate(agent.id, true);
+			if (preserveUnreadOutput) this.archivedAgents.set(agent.id, agent);
+		}));
+		if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
+		this.publishWebStatus();
+		return terminalAgents.length;
+	}
+
+	private hasUnread(agent: ManagedSubagent): boolean {
+		return agent.lastReadActivity < agent.activity.length;
+	}
+
+	async waitForUpdates(agents: ManagedSubagent[], seconds: number, signal?: AbortSignal): Promise<void> {
+		if (seconds <= 0 || agents.some((agent) => this.hasUnread(agent))) return;
+		const running = agents.filter((agent) => agent.status === "creating" || agent.status === "working");
+		if (running.length === 0) return;
+
+		await new Promise<void>((done) => {
+			let finished = false;
+			const finish = () => {
+				if (finished) return;
+				finished = true;
+				clearTimeout(timer);
+				for (const agent of running) agent.waiters.delete(finish);
+				signal?.removeEventListener("abort", finish);
+				done();
+			};
+			const timer = setTimeout(finish, Math.min(30, seconds) * 1_000);
+			for (const agent of running) agent.waiters.add(finish);
+			signal?.addEventListener("abort", finish, { once: true });
+		});
+	}
+
+	read(agents: ManagedSubagent[], includeTranscript: boolean): string {
+		if (agents.length === 0) return "No subagents are involved in this session.";
+		const now = Date.now();
+		const sections: string[] = [];
+		for (const agent of agents) {
+			const heading = `## ${statusIcon(agent.status)} ${agent.id} — ${agent.status}`;
+			const metadata = [
+				`Model: ${agent.model}`,
+				`Effort: ${agent.effort}`,
+				`Elapsed: ${formatDuration((agent.completedAt ?? now) - agent.createdAt)}`,
+				`Turns: ${agent.turns}`,
+				`Usage: ↑${formatTokens(agent.usage.input)} ↓${formatTokens(agent.usage.output)}${agent.usage.cost.total ? ` $${agent.usage.cost.total.toFixed(4)}` : ""}`,
+			];
+			if (agent.currentTool) metadata.push(`Current tool: ${agent.currentTool}`);
+			if (agent.queuedSteering || agent.queuedFollowUp) {
+				metadata.push(`Queued: ${agent.queuedSteering} steering, ${agent.queuedFollowUp} follow-up`);
+			}
+			if (agent.error) metadata.push(`Error: ${agent.error}`);
+
+			const unread = agent.activity.slice(agent.lastReadActivity);
+			const activity = unread.length
+				? unread.map((item) => `- ${formatClock(item.timestamp)} ${item.text}`).join("\n")
+				: "- No new activity.";
+			agent.lastReadActivity = agent.activity.length;
+
+			let output = `${heading}\n${metadata.join("\n")}\n\nActivity since last read:\n${activity}`;
+			if (includeTranscript) {
+				const transcript = agent.transcript
+					.map((item) => `### ${formatClock(item.timestamp)} ${item.role}\n${item.text}`)
+					.join("\n\n");
+				output += `\n\nTranscript:\n${transcript || agent.streamingText || "(empty)"}`;
+			} else {
+				const latest = finalAssistantText(agent);
+				if (latest) output += `\n\nLatest assistant output:\n${latest}`;
+			}
+			sections.push(output);
+			if (this.archivedAgents.get(agent.id) === agent) this.archivedAgents.delete(agent.id);
+		}
+		return truncateToolOutput(sections.join("\n\n---\n\n"));
+	}
+
+	claimUnaccountedUsage(): Usage | undefined {
+		const usage = subtractUsage(this.totalUsage, this.accountedUsage);
+		if (!hasUsage(usage)) return undefined;
+		this.accountedUsage = cloneUsage(this.totalUsage);
+		this.usageDirty = true;
+		this.publishFooter();
+		return usage;
+	}
+
+	private footerText(): string | undefined {
+		if (this.agents.size === 0) return undefined;
+		let working = 0;
+		let completed = 0;
+		let failed = 0;
+		let terminated = 0;
+		for (const agent of this.agents.values()) {
+			if (agent.status === "creating" || agent.status === "working" || agent.status === "terminating") working++;
+			else if (agent.status === "completed") completed++;
+			else if (agent.status === "failed") failed++;
+			else terminated++;
+		}
+		const parts = [`◆ ${this.agents.size} subagent${this.agents.size === 1 ? "" : "s"}`];
+		if (working) parts.push(`${working} working`);
+		if (completed) parts.push(`${completed} done`);
+		if (failed) parts.push(`${failed} failed`);
+		if (terminated) parts.push(`${terminated} stopped`);
+		return parts.join(" • ");
+	}
+
+	private publishWebStatus(): void {
+		this.webStatusPublishTimer = undefined;
+		const ctx = this.currentContext;
+		if (!ctx) return;
+		const sessionId = ctx.sessionManager.getSessionId();
+		const usage = asFooterUsage(subtractUsage(this.totalUsage, this.accountedUsage));
+		this.lastWebStatusPublishedAt = Date.now();
+		this.pi.events.emit(SUBAGENT_STATUS_EVENT, {
+			sessionId,
+			agents: this.webStatusUpdates(),
+			usage,
+		} satisfies SubagentStatusEvent);
+	}
+
+	private publishFooter(): void {
+		const ctx = this.currentContext;
+		if (!ctx) return;
+		const sessionId = ctx.sessionManager.getSessionId();
+		const usage = asFooterUsage(subtractUsage(this.totalUsage, this.accountedUsage));
+		const statusText = this.footerText();
+		const contribution: FooterContribution = {
+			sessionId,
+			key: "subagents",
+			status: statusText ? { text: statusText, selected: this.footerSelected } : undefined,
+			usage,
+		};
+		this.pi.events.emit(FOOTER_CONTRIBUTION_EVENT, contribution);
+
+		// Footer metadata stays immediate, while coalesced web events carry only
+		// transcript/streaming deltas. The server retains a bounded full snapshot
+		// for newly subscribed clients without retransmitting it on every burst.
+		const delay = WEB_STATUS_PUBLISH_INTERVAL_MS - (Date.now() - this.lastWebStatusPublishedAt);
+		if (delay <= 0) {
+			if (this.webStatusPublishTimer) clearTimeout(this.webStatusPublishTimer);
+			this.publishWebStatus();
+		} else if (!this.webStatusPublishTimer) {
+			this.webStatusPublishTimer = setTimeout(() => this.publishWebStatus(), delay);
+			this.webStatusPublishTimer.unref?.();
+		}
+	}
+}
diff --git a/extensions/subagents/models.ts b/extensions/subagents/models.ts
new file mode 100644
index 0000000..4800b2d
--- /dev/null
+++ b/extensions/subagents/models.ts
@@ -0,0 +1,58 @@
+import { ModelRuntime, type ModelRegistry } from "@earendil-works/pi-coding-agent";
+import { modelName } from "./format.js";
+
+export function filterModelsToScope<T extends { provider: string; id: string }>(
+	available: readonly T[],
+	scoped: ReadonlyArray<{ model: { provider: string; id: string } }>,
+): readonly T[] {
+	if (scoped.length === 0) return available;
+	const allowed = new Set(scoped.map(({ model }) => `${model.provider}/${model.id}`));
+	return available.filter((model) => allowed.has(`${model.provider}/${model.id}`));
+}
+
+export function inheritedSubagentModel<T extends { provider: string; id: string }>(
+	current: T | undefined,
+	runtimeModel: T | undefined,
+): T | undefined {
+	return runtimeModel ?? current;
+}
+
+export function subagentModelRuntime(modelRegistry: ModelRegistry): ModelRuntime {
+	// ModelRegistry is the extension-facing compatibility facade around the
+	// canonical runtime. Sharing that runtime preserves runtime-only keys and
+	// provider-resolved headers/env/base URLs, while leaving stored OAuth in the
+	// credential store so both host and child continue to refresh it normally.
+	const runtime: unknown = Reflect.get(modelRegistry, "runtime");
+	if (!(runtime instanceof ModelRuntime)) {
+		throw new Error("The host model registry does not expose its canonical runtime");
+	}
+	return runtime;
+}
+
+export function subagentModelGuidance(
+	current: { provider: string; id: string } | undefined,
+	available: readonly { provider: string; id: string }[],
+): string {
+	const choices = [...new Set(available.map(modelName))];
+	const inherited = modelName(current);
+	return [
+		"Subagent model selection for this session:",
+		`- subagent_create inherits ${inherited} when model is omitted.`,
+		"- Only pass model when intentionally overriding the inherited model.",
+		`- Exact available provider/model IDs: ${choices.length > 0 ? choices.join(", ") : "none"}.`,
+		"- Never shorten, generalize, or invent a model ID.",
+	].join("\n");
+}
+
+export function unavailableModelMessage(
+	requested: string,
+	available: readonly { provider: string; id: string }[],
+	current: { provider: string; id: string } | undefined,
+	withinScope: boolean,
+): string {
+	const choices = [...new Set(available.map(modelName))];
+	const scope = withinScope ? " within the session scope" : "";
+	const allowed = choices.length > 0 ? choices.join(", ") : "none";
+	const inherit = current ? ` Omit model to inherit ${modelName(current)}.` : "";
+	return `Model is unavailable${scope}: ${requested}. Exact available models: ${allowed}.${inherit}`;
+}
diff --git a/extensions/subagents/tools.ts b/extensions/subagents/tools.ts
new file mode 100644
index 0000000..8af545e
--- /dev/null
+++ b/extensions/subagents/tools.ts
@@ -0,0 +1,206 @@
+import type { ExtensionAPI } from "@earendil-works/pi-coding-agent";
+import { Text } from "@earendil-works/pi-tui";
+import { Type } from "typebox";
+import { truncateChars } from "./format.js";
+import type { SubagentManager } from "./manager.js";
+import {
+	DEFAULT_READ_WAIT_SECONDS,
+	MAX_SUBAGENTS,
+	THINKING_LEVELS,
+	type ToolDetails,
+	type Usage,
+} from "./types.js";
+
+function toolResult(manager: SubagentManager, text: string): { content: [{ type: "text"; text: string }]; details: ToolDetails; usage?: Usage } {
+	const usage = manager.claimUnaccountedUsage();
+	return {
+		content: [{ type: "text", text }],
+		details: { agents: manager.webSnapshots() },
+		...(usage ? { usage } : {}),
+	};
+}
+
+function stringEnum<T extends readonly string[]>(
+	values: T,
+	options?: { description?: string; default?: T[number] },
+) {
+	return Type.Unsafe<T[number]>({
+		type: "string",
+		enum: values,
+		...(options?.description ? { description: options.description } : {}),
+		...(options?.default ? { default: options.default } : {}),
+	});
+}
+
+const EffortSchema = stringEnum(THINKING_LEVELS, {
+	description: "Reasoning effort. The selected model may clamp unsupported levels.",
+});
+
+const CreateParams = Type.Object({
+	prompt: Type.String({ description: "Complete task prompt for the new isolated subagent" }),
+	name: Type.Optional(Type.String({ description: "Short stable name used to address the subagent" })),
+	model: Type.Optional(Type.String({ description: "Exact provider/model-id or exact unambiguous model id. Omit to inherit the current model; never use a shortened family alias." })),
+	effort: Type.Optional(EffortSchema),
+	cwd: Type.Optional(Type.String({ description: "Working directory, relative to the main session unless absolute" })),
+});
+
+const ReadParams = Type.Object({
+	id: Type.Optional(Type.String({ description: "Subagent id. Omit to read all subagents." })),
+	wait_seconds: Type.Optional(
+		Type.Integer({
+			description: `Wait for meaningful new activity before returning. Default ${DEFAULT_READ_WAIT_SECONDS}, maximum 30.`,
+			minimum: 0,
+			maximum: 30,
+		}),
+	),
+	include_transcript: Type.Optional(Type.Boolean({ description: "Include the full retained transcript instead of only latest output" })),
+});
+
+const SendParams = Type.Object({
+	id: Type.String({ description: "Subagent id" }),
+	message: Type.String({ description: "Instruction to send" }),
+	urgency: stringEnum(["normal", "urgent"] as const, {
+		description: "urgent steers after the current tool batch; normal queues until the current run finishes",
+	}),
+});
+
+const ConfigureParams = Type.Object({
+	id: Type.String({ description: "Subagent id" }),
+	model: Type.Optional(Type.String({ description: "Exact new provider/model-id or exact unambiguous model id. Omit to retain the current model; never use a shortened family alias." })),
+	effort: Type.Optional(EffortSchema),
+});
+
+const TerminateParams = Type.Object({
+	id: Type.Optional(Type.String({ description: "Subagent id. Omit with all=true to terminate every subagent." })),
+	all: Type.Optional(Type.Boolean({ description: "Terminate every subagent" })),
+	remove: Type.Optional(Type.Boolean({ description: "Also remove terminated records from the footer and manager" })),
+});
+
+
+export function registerSubagentTools(pi: ExtensionAPI, manager: SubagentManager): void {
+	pi.registerTool({
+		name: "subagent_create",
+		label: "Create subagent",
+		description: `Create a background subagent with an isolated context, model, and reasoning effort. Returns immediately after startup. Up to ${MAX_SUBAGENTS} live subagent sessions are allowed.`,
+		promptSnippet: "Create a background subagent with a chosen prompt, model, and effort",
+		promptGuidelines: [
+			"When calling subagent_create, omit model to inherit the current model unless deliberately choosing one of the exact session-available provider/model IDs listed in the system prompt; never shorten or invent a model ID.",
+			"After subagent_create returns, use subagent_read with its default wait roughly every 15–30 seconds while work continues; briefly tell the user about meaningful progress between polls without narrating every event.",
+			"Wait for subagent_create to return before calling another subagent management tool for that id.",
+			"Use subagent_send with urgent only when the current approach must change immediately; use normal for work that can wait until the current run finishes.",
+			"Use subagent_terminate when delegated work is no longer needed, and clean up retained subagents before finishing when appropriate.",
+		],
+		parameters: CreateParams,
+		async execute(_toolCallId, params, signal, _onUpdate, ctx) {
+			const agent = await manager.create(ctx, params, signal);
+			return toolResult(
+				manager,
+				`Created ${agent.id} with ${agent.model} at ${agent.effort} effort. It is running in ${agent.cwd}. Use subagent_read to wait for and inspect progress.`,
+			);
+		},
+		renderCall(args, theme) {
+			const name = args.name ? ` ${theme.fg("accent", args.name)}` : "";
+			const model = args.model ? ` · ${args.model}` : "";
+			const effort = args.effort ? ` · ${args.effort}` : "";
+			return new Text(`${theme.fg("toolTitle", theme.bold("subagent_create"))}${name}${theme.fg("muted", model + effort)}\n${theme.fg("dim", truncateChars(args.prompt, 180))}`, 0, 0);
+		},
+		renderResult(result, _options, theme) {
+			const text = result.content[0];
+			return new Text(theme.fg("toolOutput", text?.type === "text" ? text.text : "Created subagent"), 0, 0);
+		},
+	});
+
+	pi.registerTool({
+		name: "subagent_read",
+		label: "Read subagents",
+		description: "Wait for and read meaningful subagent activity, status, output, usage, or full transcripts. Omit id to monitor all subagents.",
+		promptSnippet: "Read and monitor background subagent activity and output",
+		parameters: ReadParams,
+		async execute(_toolCallId, params, signal) {
+			const agents = params.id ? [manager.getAgent(params.id)] : manager.list();
+			await manager.waitForUpdates(agents, params.wait_seconds ?? DEFAULT_READ_WAIT_SECONDS, signal);
+			if (signal?.aborted) throw new Error("Subagent read was cancelled");
+			return toolResult(manager, manager.read(agents, params.include_transcript ?? false));
+		},
+		renderCall(args, theme) {
+			return new Text(
+				theme.fg("toolTitle", theme.bold("subagent_read")) +
+					theme.fg("muted", ` ${args.id ?? "all"} · wait ${args.wait_seconds ?? DEFAULT_READ_WAIT_SECONDS}s`),
+				0,
+				0,
+			);
+		},
+		renderResult(result, { expanded }, theme) {
+			const raw = result.content[0];
+			const text = raw?.type === "text" ? raw.text : "(no output)";
+			return new Text(theme.fg("toolOutput", expanded ? text : text.split("\n").slice(0, 14).join("\n")), 0, 0);
+		},
+	});
+
+	pi.registerTool({
+		name: "subagent_send",
+		label: "Message subagent",
+		description: "Send an urgent steering message to a running subagent or queue a normal follow-up message for it.",
+		promptSnippet: "Steer a subagent urgently or queue a normal follow-up instruction",
+		parameters: SendParams,
+		async execute(_toolCallId, params) {
+			await manager.send(params.id, params.message, params.urgency);
+			return toolResult(
+				manager,
+				params.urgency === "urgent"
+					? `Steering message sent to ${params.id}.`
+					: `Follow-up message queued for ${params.id}.`,
+			);
+		},
+		renderCall(args, theme) {
+			return new Text(
+				`${theme.fg("toolTitle", theme.bold("subagent_send"))} ${theme.fg("accent", args.id)} ${theme.fg(args.urgency === "urgent" ? "warning" : "muted", args.urgency)}\n${theme.fg("dim", truncateChars(args.message, 180))}`,
+				0,
+				0,
+			);
+		},
+	});
+
+	pi.registerTool({
+		name: "subagent_configure",
+		label: "Configure subagent",
+		description: "Change a retained subagent's model and/or reasoning effort. Changes apply to its next model request.",
+		promptSnippet: "Change a subagent model or reasoning effort",
+		parameters: ConfigureParams,
+		async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
+			const agent = await manager.configure(ctx, params.id, params);
+			return toolResult(manager, `${agent.id} now uses ${agent.model} at ${agent.effort} effort.`);
+		},
+		renderCall(args, theme) {
+			return new Text(
+				`${theme.fg("toolTitle", theme.bold("subagent_configure"))} ${theme.fg("accent", args.id)}${theme.fg("muted", `${args.model ? ` · ${args.model}` : ""}${args.effort ? ` · ${args.effort}` : ""}`)}`,
+				0,
+				0,
+			);
+		},
+	});
+
+	pi.registerTool({
+		name: "subagent_terminate",
+		label: "Terminate subagent",
+		description: "Abort one or all subagents, dispose their sessions, and optionally remove their retained transcript records.",
+		promptSnippet: "Terminate subagents and release their resources",
+		parameters: TerminateParams,
+		async execute(_toolCallId, params) {
+			if (params.all) {
+				await manager.terminateAll(params.remove ?? false);
+				return toolResult(manager, "Terminated all subagents and released their session resources.");
+			}
+			if (!params.id) throw new Error("Specify id or all=true");
+			await manager.terminate(params.id, params.remove ?? false);
+			return toolResult(manager, `Terminated ${params.id} and released its session resources.`);
+		},
+		renderCall(args, theme) {
+			return new Text(
+				`${theme.fg("toolTitle", theme.bold("subagent_terminate"))} ${theme.fg("warning", args.all ? "all" : (args.id ?? "?"))}`,
+				0,
+				0,
+			);
+		},
+	});
+}
diff --git a/extensions/subagents/transcript.ts b/extensions/subagents/transcript.ts
new file mode 100644
index 0000000..43eb4c0
--- /dev/null
+++ b/extensions/subagents/transcript.ts
@@ -0,0 +1,99 @@
+import { stringifyCompact, truncateChars } from "./format.js";
+import {
+	MAX_TRANSCRIPT_ENTRY_CHARS,
+	MAX_WEB_STREAMING_CHARS,
+	MAX_WEB_TRANSCRIPT_CHARS,
+	type ManagedSubagent,
+	type TranscriptItem,
+	type Usage,
+} from "./types.js";
+
+export function appendBoundedStreamingText(current: string, delta: string): string {
+	const combined = current + delta;
+	return combined.length <= MAX_WEB_STREAMING_CHARS
+		? combined
+		: combined.slice(-MAX_WEB_STREAMING_CHARS);
+}
+
+export function contentToText(content: unknown): string {
+	if (typeof content === "string") return content;
+	if (!Array.isArray(content)) return "";
+	const parts: string[] = [];
+	for (const block of content) {
+		if (!block || typeof block !== "object") continue;
+		const item = block as Record<string, unknown>;
+		if (item.type === "text" && typeof item.text === "string") parts.push(item.text);
+		else if (item.type === "thinking" && typeof item.thinking === "string") parts.push(`[thinking]\n${item.thinking}`);
+		else if (item.type === "toolCall" && typeof item.name === "string") {
+			parts.push(`→ ${item.name} ${stringifyCompact(item.arguments)}`);
+		} else if (item.type === "image") {
+			parts.push("[image]");
+		}
+	}
+	return parts.join("\n");
+}
+
+export function messageToTranscript(message: unknown): TranscriptItem | undefined {
+	if (!message || typeof message !== "object") return undefined;
+	const item = message as Record<string, unknown>;
+	if (typeof item.role !== "string") return undefined;
+	const text = truncateChars(contentToText(item.content), MAX_TRANSCRIPT_ENTRY_CHARS).trim();
+	if (!text) return undefined;
+	return {
+		timestamp: typeof item.timestamp === "number" ? item.timestamp : Date.now(),
+		role: item.role,
+		text,
+	};
+}
+
+export function messageUsage(message: unknown): Usage | undefined {
+	if (!message || typeof message !== "object") return undefined;
+	const usage = (message as Record<string, unknown>).usage;
+	if (!usage || typeof usage !== "object") return undefined;
+	return usage as Usage;
+}
+
+export function messageRole(message: unknown): string | undefined {
+	return message && typeof message === "object" && typeof (message as Record<string, unknown>).role === "string"
+		? ((message as Record<string, unknown>).role as string)
+		: undefined;
+}
+
+export function messageStopReason(message: unknown): string | undefined {
+	return message && typeof message === "object" && typeof (message as Record<string, unknown>).stopReason === "string"
+		? ((message as Record<string, unknown>).stopReason as string)
+		: undefined;
+}
+
+export function messageError(message: unknown): string | undefined {
+	return message && typeof message === "object" && typeof (message as Record<string, unknown>).errorMessage === "string"
+		? ((message as Record<string, unknown>).errorMessage as string)
+		: undefined;
+}
+
+export function finalAssistantText(agent: ManagedSubagent): string {
+	for (let index = agent.transcript.length - 1; index >= 0; index--) {
+		const item = agent.transcript[index];
+		if (item?.role === "assistant") return item.text;
+	}
+	return agent.streamingText.trim();
+}
+
+export function boundedWebTranscript(items: readonly TranscriptItem[]): TranscriptItem[] {
+	const retained: TranscriptItem[] = [];
+	let characters = 0;
+	for (let index = items.length - 1; index >= 0; index--) {
+		const item = items[index];
+		if (!item) continue;
+		const remaining = MAX_WEB_TRANSCRIPT_CHARS - characters;
+		if (remaining <= 0 && retained.length > 0) break;
+		const text = truncateChars(item.text, Math.max(1, remaining));
+		retained.push({ ...item, text });
+		characters += text.length;
+	}
+	return retained.reverse();
+}
+
+export function webTranscript(agent: ManagedSubagent): TranscriptItem[] {
+	return boundedWebTranscript(agent.transcript);
+}
diff --git a/extensions/subagents/types.ts b/extensions/subagents/types.ts
new file mode 100644
index 0000000..ec5be5a
--- /dev/null
+++ b/extensions/subagents/types.ts
@@ -0,0 +1,94 @@
+import type { AgentSession, ModelRuntime } from "@earendil-works/pi-coding-agent";
+import type { FooterUsage } from "../footer-events.js";
+import type { SubagentWebSnapshot } from "../subagent-events.js";
+
+export const MAX_SUBAGENTS = 8;
+export const MAX_ACTIVITY_ITEMS = 500;
+export const MAX_TRANSCRIPT_ITEMS = 500;
+export const MAX_TRANSCRIPT_ENTRY_CHARS = 100_000;
+export const MAX_TRANSCRIPT_CHARS = 1_000_000;
+export const MAX_WEB_TRANSCRIPT_CHARS = 100_000;
+export const MAX_WEB_STREAMING_CHARS = 20_000;
+export const WEB_STATUS_PUBLISH_INTERVAL_MS = 1_000;
+export const MAX_TOOL_OUTPUT_BYTES = 50 * 1024;
+export const DEFAULT_READ_WAIT_SECONDS = 15;
+export const DETAIL_VIEW_LINES = 22;
+export const USAGE_STATE_ENTRY = "vessup-subagent-usage";
+export const SUBAGENT_SYSTEM_PROMPT = [
+	"You are a subagent working for a main coding agent.",
+	"Work independently on the delegated task in the current working directory.",
+	"Use tools when useful, keep changes scoped to the task, and finish with a concise report of findings, changes, tests, and remaining risks.",
+	"Messages received after the initial task are instructions from the main agent; urgent steering messages supersede your current approach.",
+].join(" ");
+
+export const THINKING_LEVELS = ["off", "minimal", "low", "medium", "high", "xhigh", "max"] as const;
+export type SubagentEffort = (typeof THINKING_LEVELS)[number];
+export type SubagentStatus = "creating" | "working" | "completed" | "failed" | "terminating" | "terminated";
+export type MessageUrgency = "normal" | "urgent";
+
+export type ActivityItem = {
+	timestamp: number;
+	text: string;
+};
+
+export type TranscriptItem = {
+	timestamp: number;
+	role: string;
+	text: string;
+};
+
+export type ManagedSubagent = {
+	id: string;
+	prompt: string;
+	cwd: string;
+	createdAt: number;
+	updatedAt: number;
+	completedAt?: number;
+	status: SubagentStatus;
+	model: string;
+	effort: SubagentEffort;
+	currentTool?: string;
+	error?: string;
+	lastStopReason?: string;
+	turns: number;
+	queuedSteering: number;
+	queuedFollowUp: number;
+	activity: ActivityItem[];
+	lastReadActivity: number;
+	transcript: TranscriptItem[];
+	streamingText: string;
+	lastStreamActivityAt: number;
+	usage: Usage;
+	session?: AgentSession;
+	unsubscribe?: () => void;
+	runPromise?: Promise<void>;
+	waiters: Set<() => void>;
+};
+
+export type AgentSnapshot = {
+	id: string;
+	status: SubagentStatus;
+	model: string;
+	effort: SubagentEffort;
+	turns: number;
+	currentTool?: string;
+	queued: number;
+};
+
+export type ToolDetails = {
+	agents: SubagentWebSnapshot[];
+};
+
+export type Usage = FooterUsage;
+export type AgentModel = NonNullable<ReturnType<ModelRuntime["getModel"]>>;
+export type PersistedUsageState = { total: Usage; accounted: Usage };
+
+export type ManagerDialogResult =
+	| { action: "close" }
+	| { action: "view"; id: string }
+	| { action: "back" }
+	| { action: "model"; id: string }
+	| { action: "effort"; id: string }
+	| { action: "urgent"; id: string }
+	| { action: "queue"; id: string }
+	| { action: "terminate"; id: string };
diff --git a/extensions/subagents/ui.ts b/extensions/subagents/ui.ts
new file mode 100644
index 0000000..8510db8
--- /dev/null
+++ b/extensions/subagents/ui.ts
@@ -0,0 +1,480 @@
+import {
+	DynamicBorder,
+	type ExtensionContext,
+	type KeybindingsManager,
+	type Theme,
+} from "@earendil-works/pi-coding-agent";
+import {
+	Container,
+	type EditorComponent,
+	type Focusable,
+	matchesKey,
+	SelectList,
+	type SelectItem,
+	Text,
+	truncateToWidth,
+	visibleWidth,
+	wrapTextWithAnsi,
+	type Component,
+	type TUI,
+} from "@earendil-works/pi-tui";
+import {
+	formatClock,
+	formatDuration,
+	formatTokens,
+	modelName,
+	statusColor,
+	statusIcon,
+	truncateChars,
+} from "./format.js";
+import type { SubagentManager } from "./manager.js";
+import {
+	DETAIL_VIEW_LINES,
+	THINKING_LEVELS,
+	type ManagedSubagent,
+	type ManagerDialogResult,
+	type SubagentEffort,
+} from "./types.js";
+
+export interface AppEditorComponent extends EditorComponent, Partial<Focusable> {
+	getCursor?: () => { line: number; col: number };
+	getLines?: () => string[];
+	isShowingAutocomplete?: () => boolean;
+	dispose?: () => void;
+	actionHandlers?: Map<unknown, () => void>;
+	onEscape?: () => void;
+	onCtrlD?: () => void;
+	onPasteImage?: () => void;
+	onExtensionShortcut?: (data: string) => boolean;
+}
+
+export class FooterNavigationEditor implements EditorComponent, Focusable {
+	readonly actionHandlers?: Map<unknown, () => void>;
+
+	constructor(
+		private readonly base: AppEditorComponent,
+		private readonly keybindings: KeybindingsManager,
+		private readonly manager: SubagentManager,
+		private readonly openManager: () => void,
+	) {
+		this.actionHandlers = base.actionHandlers;
+	}
+
+	get focused(): boolean {
+		return this.base.focused ?? false;
+	}
+	set focused(value: boolean) {
+		if ("focused" in this.base) this.base.focused = value;
+	}
+	get wantsKeyRelease(): boolean | undefined {
+		return this.base.wantsKeyRelease;
+	}
+	set wantsKeyRelease(value: boolean | undefined) {
+		this.base.wantsKeyRelease = value;
+	}
+	get onSubmit(): ((text: string) => void) | undefined {
+		return this.base.onSubmit;
+	}
+	set onSubmit(value: ((text: string) => void) | undefined) {
+		this.base.onSubmit = value;
+	}
+	get onChange(): ((text: string) => void) | undefined {
+		return this.base.onChange;
+	}
+	set onChange(value: ((text: string) => void) | undefined) {
+		this.base.onChange = value;
+	}
+	get borderColor(): ((text: string) => string) | undefined {
+		return this.base.borderColor;
+	}
+	set borderColor(value: ((text: string) => string) | undefined) {
+		this.base.borderColor = value;
+	}
+	get onEscape(): (() => void) | undefined {
+		return this.base.onEscape;
+	}
+	set onEscape(value: (() => void) | undefined) {
+		this.base.onEscape = value;
+	}
+	get onCtrlD(): (() => void) | undefined {
+		return this.base.onCtrlD;
+	}
+	set onCtrlD(value: (() => void) | undefined) {
+		this.base.onCtrlD = value;
+	}
+	get onPasteImage(): (() => void) | undefined {
+		return this.base.onPasteImage;
+	}
+	set onPasteImage(value: (() => void) | undefined) {
+		this.base.onPasteImage = value;
+	}
+	get onExtensionShortcut(): ((data: string) => boolean) | undefined {
+		return this.base.onExtensionShortcut;
+	}
+	set onExtensionShortcut(value: ((data: string) => boolean) | undefined) {
+		this.base.onExtensionShortcut = value;
+	}
+
+	render(width: number): string[] {
+		return this.base.render(width);
+	}
+	invalidate(): void {
+		this.base.invalidate();
+	}
+	dispose(): void {
+		this.base.dispose?.();
+	}
+	getText(): string {
+		return this.base.getText();
+	}
+	setText(text: string): void {
+		this.base.setText(text);
+	}
+	addToHistory(text: string): void {
+		this.base.addToHistory?.(text);
+	}
+	insertTextAtCursor(text: string): void {
+		this.base.insertTextAtCursor?.(text);
+	}
+	getExpandedText(): string {
+		return this.base.getExpandedText?.() ?? this.base.getText();
+	}
+	setAutocompleteProvider(provider: Parameters<NonNullable<EditorComponent["setAutocompleteProvider"]>>[0]): void {
+		this.base.setAutocompleteProvider?.(provider);
+	}
+	setPaddingX(padding: number): void {
+		this.base.setPaddingX?.(padding);
+	}
+	setAutocompleteMaxVisible(maximum: number): void {
+		this.base.setAutocompleteMaxVisible?.(maximum);
+	}
+
+	handleInput(data: string): void {
+		if (this.manager.isFooterSelected()) {
+			if (this.keybindings.matches(data, "tui.select.confirm")) {
+				this.manager.setFooterSelected(false);
+				this.openManager();
+				return;
+			}
+			if (
+				this.keybindings.matches(data, "tui.select.up") ||
+				this.keybindings.matches(data, "tui.select.cancel")
+			) {
+				this.manager.setFooterSelected(false);
+				return;
+			}
+			this.manager.setFooterSelected(false);
+		}
+
+		if (
+			this.manager.hasAgents() &&
+			this.base.getText().length === 0 &&
+			!this.base.isShowingAutocomplete?.() &&
+			matchesKey(data, "alt+down")
+		) {
+			const cursor = this.base.getCursor?.();
+			const lines = this.base.getLines?.();
+			if (!cursor || !lines || cursor.line === lines.length - 1) {
+				this.manager.setFooterSelected(true);
+				return;
+			}
+		}
+		this.base.handleInput(data);
+	}
+}
+
+function padAnsi(text: string, width: number): string {
+	const fitted = truncateToWidth(text, Math.max(0, width), "…");
+	return fitted + " ".repeat(Math.max(0, width - visibleWidth(fitted)));
+}
+
+function frameLines(theme: Theme, title: string, body: string[], width: number): string[] {
+	if (width < 4) return body.map((line) => truncateToWidth(line, width, ""));
+	const inner = width - 2;
+	const titleText = truncateToWidth(` ${title} `, Math.max(0, inner - 2), "…");
+	const topFill = Math.max(0, inner - visibleWidth(titleText));
+	const top = theme.fg("borderAccent", `┌${titleText}${"─".repeat(topFill)}┐`);
+	const bottom = theme.fg("borderAccent", `└${"─".repeat(inner)}┘`);
+	return [
+		top,
+		...body.map(
+			(line) => theme.fg("borderAccent", "│") + padAnsi(line, inner) + theme.fg("borderAccent", "│"),
+		),
+		bottom,
+	];
+}
+
+class AgentListDialog implements Component {
+	private selected = 0;
+	private timer: ReturnType<typeof setInterval>;
+
+	constructor(
+		private readonly manager: SubagentManager,
+		private readonly tui: TUI,
+		private readonly theme: Theme,
+		private readonly keybindings: KeybindingsManager,
+		private readonly done: (result: ManagerDialogResult) => void,
+	) {
+		this.timer = setInterval(() => tui.requestRender(), 500);
+	}
+
+	dispose(): void {
+		clearInterval(this.timer);
+	}
+	invalidate(): void {}
+
+	handleInput(data: string): void {
+		const agents = this.manager.list();
+		if (this.keybindings.matches(data, "tui.select.cancel")) return this.done({ action: "close" });
+		if (this.keybindings.matches(data, "tui.select.up")) {
+			this.selected = Math.max(0, this.selected - 1);
+			this.tui.requestRender();
+			return;
+		}
+		if (this.keybindings.matches(data, "tui.select.down")) {
+			this.selected = Math.min(Math.max(0, agents.length - 1), this.selected + 1);
+			this.tui.requestRender();
+			return;
+		}
+		const agent = agents[this.selected];
+		if (!agent) return;
+		if (this.keybindings.matches(data, "tui.select.confirm")) return this.done({ action: "view", id: agent.id });
+		if (data === "m") return this.done({ action: "model", id: agent.id });
+		if (data === "e") return this.done({ action: "effort", id: agent.id });
+		if (data === "x") return this.done({ action: "terminate", id: agent.id });
+	}
+
+	render(width: number): string[] {
+		const agents = this.manager.list();
+		this.selected = Math.min(this.selected, Math.max(0, agents.length - 1));
+		const body: string[] = [];
+		if (agents.length === 0) body.push(this.theme.fg("muted", " No subagents in this session"));
+		for (let index = 0; index < agents.length; index++) {
+			const agent = agents[index];
+			const icon = this.theme.fg(statusColor(agent.status), statusIcon(agent.status));
+			const queue = agent.queuedSteering + agent.queuedFollowUp;
+			let line = `${index === this.selected ? "›" : " "} ${icon} ${agent.id}  ${agent.status}`;
+			if (agent.currentTool) line += ` · ${agent.currentTool}`;
+			if (queue) line += ` · ${queue} queued`;
+			line += ` · ${agent.model} · ${agent.effort}`;
+			if (index === this.selected) line = this.theme.bg("selectedBg", this.theme.fg("accent", line));
+			body.push(line);
+		}
+		body.push("");
+		body.push(this.theme.fg("dim", " ↑↓ select · enter transcript · m model · e effort · x terminate · esc close"));
+		return frameLines(this.theme, "Subagents", body, width);
+	}
+}
+
+export class AgentDetailDialog implements Component {
+	private scrollOffset = 0;
+	private timer: ReturnType<typeof setInterval>;
+	private transcriptCache: {
+		width: number;
+		length: number;
+		first: ManagedSubagent["transcript"][number] | undefined;
+		last: ManagedSubagent["transcript"][number] | undefined;
+		streamingText: string;
+		lines: string[];
+	} | undefined;
+
+	constructor(
+		private readonly agent: ManagedSubagent,
+		private readonly tui: TUI,
+		private readonly theme: Theme,
+		private readonly keybindings: KeybindingsManager,
+		private readonly done: (result: ManagerDialogResult) => void,
+	) {
+		this.timer = setInterval(() => tui.requestRender(), 300);
+	}
+
+	dispose(): void {
+		clearInterval(this.timer);
+	}
+	invalidate(): void {
+		this.transcriptCache = undefined;
+	}
+
+	handleInput(data: string): void {
+		if (this.keybindings.matches(data, "tui.select.cancel") || data === "b") return this.done({ action: "back" });
+		if (this.keybindings.matches(data, "tui.select.up") || this.keybindings.matches(data, "tui.select.pageUp")) {
+			this.scrollOffset += this.keybindings.matches(data, "tui.select.pageUp") ? DETAIL_VIEW_LINES : 1;
+			this.tui.requestRender();
+			return;
+		}
+		if (this.keybindings.matches(data, "tui.select.down") || this.keybindings.matches(data, "tui.select.pageDown")) {
+			this.scrollOffset = Math.max(
+				0,
+				this.scrollOffset - (this.keybindings.matches(data, "tui.select.pageDown") ? DETAIL_VIEW_LINES : 1),
+			);
+			this.tui.requestRender();
+			return;
+		}
+		if (data === "m") return this.done({ action: "model", id: this.agent.id });
+		if (data === "e") return this.done({ action: "effort", id: this.agent.id });
+		if (data === "u") return this.done({ action: "urgent", id: this.agent.id });
+		if (data === "q") return this.done({ action: "queue", id: this.agent.id });
+		if (data === "x") return this.done({ action: "terminate", id: this.agent.id });
+	}
+
+	private transcriptLines(width: number): string[] {
+		const length = this.agent.transcript.length;
+		const first = this.agent.transcript[0];
+		const last = this.agent.transcript.at(-1);
+		const streamingText = this.agent.streamingText;
+		const cached = this.transcriptCache;
+		if (
+			cached
+			&& cached.width === width
+			&& cached.length === length
+			&& cached.first === first
+			&& cached.last === last
+			&& cached.streamingText === streamingText
+		) return cached.lines;
+
+		const lines: string[] = [];
+		for (const item of this.agent.transcript) {
+			lines.push(this.theme.fg("muted", `[${formatClock(item.timestamp)}] ${item.role}`));
+			const roleColor = item.role === "assistant" ? "text" : item.role === "toolResult" ? "dim" : "accent";
+			for (const line of wrapTextWithAnsi(this.theme.fg(roleColor, item.text), Math.max(1, width))) lines.push(line);
+			lines.push("");
+		}
+		if (streamingText) {
+			lines.push(this.theme.fg("warning", "[streaming] assistant"));
+			for (const line of wrapTextWithAnsi(streamingText, Math.max(1, width))) lines.push(line);
+		}
+		if (lines.length === 0) lines.push(this.theme.fg("muted", "(transcript is empty)"));
+		this.transcriptCache = { width, length, first, last, streamingText, lines };
+		return lines;
+	}
+
+	render(width: number): string[] {
+		const inner = Math.max(1, width - 4);
+		const allLines = this.transcriptLines(inner);
+		const maxOffset = Math.max(0, allLines.length - DETAIL_VIEW_LINES);
+		this.scrollOffset = Math.min(this.scrollOffset, maxOffset);
+		const end = Math.max(0, allLines.length - this.scrollOffset);
+		const start = Math.max(0, end - DETAIL_VIEW_LINES);
+		const visible = allLines.slice(start, end);
+		const status = this.theme.fg(statusColor(this.agent.status), `${statusIcon(this.agent.status)} ${this.agent.status}`);
+		const body = [
+			` ${status} · ${this.agent.model} · effort ${this.agent.effort} · ${formatDuration(Date.now() - this.agent.createdAt)}`,
+			this.theme.fg("dim", ` Task: ${truncateChars(this.agent.prompt.replace(/\s+/g, " "), 180)}`),
+			this.theme.fg(
+				"dim",
+				` Usage: ↑${formatTokens(this.agent.usage.input)} ↓${formatTokens(this.agent.usage.output)}${this.agent.usage.cost.total ? ` $${this.agent.usage.cost.total.toFixed(4)}` : ""}`,
+			),
+			this.theme.fg("borderMuted", " " + "─".repeat(Math.max(0, inner - 1))),
+			...visible.map((line) => ` ${line}`),
+			this.theme.fg("borderMuted", " " + "─".repeat(Math.max(0, inner - 1))),
+			this.theme.fg(
+				"dim",
+				` ↑↓/pg scroll${this.scrollOffset ? ` · ${this.scrollOffset} lines below` : ""} · m model · e effort · u steer · q queue · x terminate · b back`,
+			),
+		];
+		return frameLines(this.theme, this.agent.id, body, width);
+	}
+}
+
+async function selectOverlay(
+	ctx: ExtensionContext,
+	title: string,
+	items: SelectItem[],
+): Promise<string | undefined> {
+	if (ctx.mode !== "tui") return undefined;
+	return ctx.ui.custom<string | undefined>(
+		(tui, theme, _keybindings, done) => {
+			const container = new Container();
+			container.addChild(new DynamicBorder((text: string) => theme.fg("accent", text)));
+			container.addChild(new Text(theme.fg("accent", theme.bold(title)), 1, 0));
+			const list = new SelectList(items, Math.min(12, Math.max(1, items.length)), {
+				selectedPrefix: (text) => theme.fg("accent", text),
+				selectedText: (text) => theme.fg("accent", text),
+				description: (text) => theme.fg("muted", text),
+				scrollInfo: (text) => theme.fg("dim", text),
+				noMatch: (text) => theme.fg("warning", text),
+			});
+			list.onSelect = (item) => done(item.value);
+			list.onCancel = () => done(undefined);
+			container.addChild(list);
+			container.addChild(new Text(theme.fg("dim", "↑↓ navigate · enter select · esc cancel"), 1, 0));
+			container.addChild(new DynamicBorder((text: string) => theme.fg("accent", text)));
+			return {
+				render: (width) => container.render(width),
+				invalidate: () => container.invalidate(),
+				handleInput: (data) => {
+					list.handleInput(data);
+					tui.requestRender();
+				},
+			};
+		},
+		{ overlay: true, overlayOptions: { anchor: "center", width: "70%", maxHeight: "80%", minWidth: 48 } },
+	);
+}
+
+export async function showManager(manager: SubagentManager, ctx: ExtensionContext): Promise<void> {
+	if (ctx.mode !== "tui") {
+		ctx.ui.notify("The subagent manager is only available in TUI mode", "warning");
+		return;
+	}
+
+	let detailId: string | undefined;
+	while (true) {
+		let result: ManagerDialogResult;
+		const fromDetail = Boolean(detailId && manager.agents.has(detailId));
+		if (fromDetail && detailId) {
+			const agent = manager.getAgent(detailId);
+			result = await ctx.ui.custom<ManagerDialogResult>(
+				(tui, theme, keybindings, done) => new AgentDetailDialog(agent, tui, theme, keybindings, done),
+				{ overlay: true, overlayOptions: { anchor: "center", width: "85%", maxHeight: "90%", minWidth: 56 } },
+			);
+		} else {
+			detailId = undefined;
+			result = await ctx.ui.custom<ManagerDialogResult>(
+				(tui, theme, keybindings, done) => new AgentListDialog(manager, tui, theme, keybindings, done),
+				{ overlay: true, overlayOptions: { anchor: "center", width: "85%", maxHeight: "85%", minWidth: 56 } },
+			);
+		}
+
+		if (!result || result.action === "close") return;
+		if (result.action === "back") {
+			detailId = undefined;
+			continue;
+		}
+		if (result.action === "view") {
+			detailId = result.id;
+			continue;
+		}
+
+		detailId = fromDetail ? result.id : undefined;
+		try {
+			if (result.action === "model") {
+				const models = await manager.availableModels(ctx);
+				const selected = await selectOverlay(
+					ctx,
+					`Model for ${result.id}`,
+					models.map((model) => ({ value: modelName(model), label: model.id, description: `${model.provider} · ${model.name}` })),
+				);
+				if (selected) await manager.configure(ctx, result.id, { model: selected });
+			} else if (result.action === "effort") {
+				const selected = await selectOverlay(
+					ctx,
+					`Effort for ${result.id}`,
+					THINKING_LEVELS.map((level) => ({ value: level, label: level })),
+				);
+				if (selected) await manager.configure(ctx, result.id, { effort: selected as SubagentEffort });
+			} else if (result.action === "urgent" || result.action === "queue") {
+				const message = await ctx.ui.input(
+					result.action === "urgent" ? `Steer ${result.id}` : `Queue for ${result.id}`,
+					"Instruction for the subagent",
+				);
+				if (message) await manager.send(result.id, message, result.action === "urgent" ? "urgent" : "normal");
+			} else if (result.action === "terminate") {
+				const confirmed = await ctx.ui.confirm("Terminate subagent?", `Stop ${result.id} and release its resources?`);
+				if (confirmed) await manager.terminate(result.id);
+			}
+		} catch (error) {
+			ctx.ui.notify(error instanceof Error ? error.message : String(error), "error");
+		}
+	}
+}
diff --git a/extensions/subagents/usage.ts b/extensions/subagents/usage.ts
new file mode 100644
index 0000000..00f0e6b
--- /dev/null
+++ b/extensions/subagents/usage.ts
@@ -0,0 +1,104 @@
+import type { FooterUsage } from "../footer-events.js";
+import type { PersistedUsageState, Usage } from "./types.js";
+
+export function isRecord(value: unknown): value is Record<string, unknown> {
+	return typeof value === "object" && value !== null;
+}
+
+export function zeroUsage(): Usage {
+	return {
+		input: 0,
+		output: 0,
+		cacheRead: 0,
+		cacheWrite: 0,
+		totalTokens: 0,
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+	};
+}
+
+export function parseUsage(value: unknown): Usage | undefined {
+	if (!isRecord(value) || !isRecord(value.cost)) return undefined;
+	const cost = value.cost;
+	const fields = ["input", "output", "cacheRead", "cacheWrite", "totalTokens"] as const;
+	if (fields.some((field) => typeof value[field] !== "number" || !Number.isFinite(value[field]))) return undefined;
+	const costFields = ["input", "output", "cacheRead", "cacheWrite", "total"] as const;
+	if (costFields.some((field) => typeof cost[field] !== "number" || !Number.isFinite(cost[field]))) return undefined;
+	return {
+		input: value.input as number,
+		output: value.output as number,
+		cacheRead: value.cacheRead as number,
+		cacheWrite: value.cacheWrite as number,
+		totalTokens: value.totalTokens as number,
+		cost: {
+			input: cost.input as number,
+			output: cost.output as number,
+			cacheRead: cost.cacheRead as number,
+			cacheWrite: cost.cacheWrite as number,
+			total: cost.total as number,
+		},
+	};
+}
+
+export function parsePersistedUsageState(value: unknown): PersistedUsageState | undefined {
+	if (!isRecord(value)) return undefined;
+	const total = parseUsage(value.total);
+	const accounted = parseUsage(value.accounted);
+	return total && accounted ? { total, accounted } : undefined;
+}
+
+export function cloneUsage(usage: Usage): Usage {
+	return {
+		input: usage.input,
+		output: usage.output,
+		cacheRead: usage.cacheRead,
+		cacheWrite: usage.cacheWrite,
+		totalTokens: usage.totalTokens,
+		cost: { ...usage.cost },
+	};
+}
+
+export function addUsage(target: Usage, usage: Usage | undefined): void {
+	if (!usage) return;
+	target.input += usage.input || 0;
+	target.output += usage.output || 0;
+	target.cacheRead += usage.cacheRead || 0;
+	target.cacheWrite += usage.cacheWrite || 0;
+	target.totalTokens += usage.totalTokens || 0;
+	target.cost.input += usage.cost?.input || 0;
+	target.cost.output += usage.cost?.output || 0;
+	target.cost.cacheRead += usage.cost?.cacheRead || 0;
+	target.cost.cacheWrite += usage.cost?.cacheWrite || 0;
+	target.cost.total += usage.cost?.total || 0;
+}
+
+export function subtractUsage(total: Usage, accounted: Usage): Usage {
+	return {
+		input: Math.max(0, total.input - accounted.input),
+		output: Math.max(0, total.output - accounted.output),
+		cacheRead: Math.max(0, total.cacheRead - accounted.cacheRead),
+		cacheWrite: Math.max(0, total.cacheWrite - accounted.cacheWrite),
+		totalTokens: Math.max(0, total.totalTokens - accounted.totalTokens),
+		cost: {
+			input: Math.max(0, total.cost.input - accounted.cost.input),
+			output: Math.max(0, total.cost.output - accounted.cost.output),
+			cacheRead: Math.max(0, total.cost.cacheRead - accounted.cost.cacheRead),
+			cacheWrite: Math.max(0, total.cost.cacheWrite - accounted.cost.cacheWrite),
+			total: Math.max(0, total.cost.total - accounted.cost.total),
+		},
+	};
+}
+
+export function hasUsage(usage: Usage): boolean {
+	return (
+		usage.input > 0 ||
+		usage.output > 0 ||
+		usage.cacheRead > 0 ||
+		usage.cacheWrite > 0 ||
+		usage.totalTokens > 0 ||
+		usage.cost.total > 0
+	);
+}
+
+export function asFooterUsage(usage: Usage): FooterUsage {
+	return cloneUsage(usage);
+}
diff --git a/tests/subagents.test.ts b/tests/subagents.test.ts
index b35d5b7..9074fca 100644
--- a/tests/subagents.test.ts
+++ b/tests/subagents.test.ts
@@ -4,7 +4,7 @@ import { tmpdir } from "node:os";
 import { join } from "node:path";
 import test from "node:test";
 import { ModelRegistry, ModelRuntime } from "@earendil-works/pi-coding-agent";
-import {
+import subagentsExtension, {
 	abortRunningSubagentSessions,
 	appendBoundedStreamingText,
 	countsAgainstSubagentLimit,
@@ -18,6 +18,30 @@ import {
 	subagentModelGuidance,
 	subagentModelRuntime,
 } from "../extensions/subagents.ts";
+import { stringifyCompact, truncateChars, truncateToolOutput } from "../extensions/subagents/format.ts";
+import { MAX_TOOL_OUTPUT_BYTES } from "../extensions/subagents/types.ts";
+import { AgentDetailDialog, FooterNavigationEditor } from "../extensions/subagents/ui.ts";
+
+test("subagent entrypoint preserves its tool, command, and lifecycle registrations", () => {
+	const tools: string[] = [];
+	const commands: string[] = [];
+	const hooks: string[] = [];
+	const events: string[] = [];
+	const pi = {
+		events: { on(name: string) { events.push(name); }, emit() {} },
+		on(name: string) { hooks.push(name); },
+		registerTool(tool: { name: string }) { tools.push(tool.name); },
+		registerCommand(name: string) { commands.push(name); },
+		getActiveTools() { return []; },
+	};
+
+	subagentsExtension(pi as never);
+
+	assert.deepEqual(tools, ["subagent_create", "subagent_read", "subagent_send", "subagent_configure", "subagent_terminate"]);
+	assert.deepEqual(commands, ["subagents", "subagents-cleanup"]);
+	assert.deepEqual(hooks, ["before_agent_start", "session_start", "input", "agent_start", "agent_settled", "session_shutdown"]);
+	assert.deepEqual(events, ["vessup:subagents:abort"]);
+});
 
 const usage = {
 	input: 10,
@@ -28,6 +52,67 @@ const usage = {
 	cost: { input: 0.1, output: 0.2, cacheRead: 0.01, cacheWrite: 0.02, total: 0.33 },
 };
 
+test("compact formatting handles non-JSON values and preserves Unicode code points", () => {
+	assert.equal(stringifyCompact(undefined), "undefined");
+	assert.equal(stringifyCompact(Symbol("value")), "Symbol(value)");
+	assert.equal(stringifyCompact("🙂", 2), '"🙂…');
+	assert.equal(truncateChars("a🙂b", 2), "a🙂\n[… 1 characters omitted]");
+});
+
+test("subagent tool output truncates at a valid UTF-8 byte boundary", () => {
+	const source = `a${"🙂".repeat(Math.ceil(MAX_TOOL_OUTPUT_BYTES / 4) + 10)}`;
+	const result = truncateToolOutput(source);
+	const output = result.split("\n\n[Output truncated:", 1)[0]!;
+	assert.ok(Buffer.byteLength(output, "utf8") <= MAX_TOOL_OUTPUT_BYTES);
+	assert.equal(output.endsWith("�"), false);
+	assert.match(result, new RegExp(`Output truncated: ${Buffer.byteLength(source, "utf8") - Buffer.byteLength(output, "utf8")} bytes omitted`));
+});
+
+test("subagent footer editor preserves key-release preferences", () => {
+	const base = { focused: false, wantsKeyRelease: true };
+	const editor = new FooterNavigationEditor(base as never, {} as never, {} as never, () => {});
+	assert.equal(editor.wantsKeyRelease, true);
+	editor.wantsKeyRelease = false;
+	assert.equal(base.wantsKeyRelease, false);
+});
+
+test("subagent detail rendering caches wrapped transcript lines", () => {
+	let contentFormats = 0;
+	const agent = {
+		id: "worker",
+		status: "completed",
+		model: "provider/model",
+		effort: "medium",
+		createdAt: Date.now(),
+		prompt: "task",
+		usage,
+		transcript: [{ timestamp: Date.now(), role: "assistant", text: "hello" }],
+		streamingText: "",
+	};
+	const theme = {
+		fg(_color: string, text: string) {
+			if (text === "hello") contentFormats++;
+			return text;
+		},
+	};
+	const dialog = new AgentDetailDialog(agent as never, { requestRender() {} } as never, theme as never, {} as never, () => {});
+	try {
+		dialog.render(80);
+		dialog.render(80);
+		assert.equal(contentFormats, 1);
+		agent.streamingText = "streaming";
+		dialog.render(80);
+		assert.equal(contentFormats, 2);
+		dialog.render(79);
+		assert.equal(contentFormats, 3);
+		agent.transcript.push({ timestamp: Date.now(), role: "assistant", text: "next" });
+		dialog.render(79);
+		assert.equal(contentFormats, 4);
+	} finally {
+		dialog.dispose();
+	}
+});
+
 test("creating agents reserve capacity before their session exists", () => {
 	assert.equal(countsAgainstSubagentLimit({ status: "creating" }), true);
 	assert.equal(countsAgainstSubagentLimit({ status: "completed", session: {} }), true);
diff --git a/tests/web-server.test.ts b/tests/web-server.test.ts
index f1ec7e4..7bf761b 100644
--- a/tests/web-server.test.ts
+++ b/tests/web-server.test.ts
@@ -830,6 +830,7 @@ test("TUI metadata changes update every connected web catalog", async () => {
 	let resolveRenamed!: () => void;
 	let resolveBranch!: () => void;
 	let resolvePullRequest!: () => void;
+	let resolveCompletedPullRequest!: () => void;
 	let resolveWorking!: () => void;
 	let resolveIdle!: () => void;
 	let resolvePreview!: () => void;
@@ -841,6 +842,7 @@ test("TUI metadata changes update every connected web catalog", async () => {
 	const renamed = new Promise<void>((resolve) => { resolveRenamed = resolve; });
 	const branchUpdated = new Promise<void>((resolve) => { resolveBranch = resolve; });
 	const pullRequestUpdated = new Promise<void>((resolve) => { resolvePullRequest = resolve; });
+	const completedPullRequestUpdated = new Promise<void>((resolve) => { resolveCompletedPullRequest = resolve; });
 	const working = new Promise<void>((resolve) => { resolveWorking = resolve; });
 	const idle = new Promise<void>((resolve) => { resolveIdle = resolve; });
 	const previewUpdated = new Promise<void>((resolve) => { resolvePreview = resolve; });
@@ -870,6 +872,7 @@ test("TUI metadata changes update every connected web catalog", async () => {
 		if (message.session.name === "Renamed in TUI") resolveRenamed();
 		if (message.session.branch === "feature/live-metadata") resolveBranch();
 		if (message.session.pullRequest?.number === 3) resolvePullRequest();
+		if (message.session.pullRequest?.number === 4) resolveCompletedPullRequest();
 		if (message.session.status === "working" && !message.session.compaction) {
 			observedWorking = true;
 			resolveWorking();
@@ -899,8 +902,10 @@ test("TUI metadata changes update every connected web catalog", async () => {
 		await Promise.race([pullRequestUpdated, timedOut]);
 		agent.send(JSON.stringify({ type: "agent.event", sessionId: tuiId, event: { type: "agent_start" } }));
 		await Promise.race([working, timedOut]);
+		await writeFile(prMetadataFile, JSON.stringify({ number: 4, url: "https://github.com/Vessup/pi-kit/pull/4" }));
 		agent.send(JSON.stringify({ type: "agent.event", sessionId: tuiId, event: { type: "agent_end" } }));
 		await Promise.race([idle, timedOut]);
+		await Promise.race([completedPullRequestUpdated, timedOut]);
 		agent.send(JSON.stringify({ type: "agent.event", sessionId: tuiId, event: { type: "message_end", message: { role: "assistant", content: "Latest assistant preview" } } }));
 		agent.send(JSON.stringify({ type: "agent.update", session: { ...tuiSession, name: "Renamed in TUI", branch: "feature/live-metadata", preview: "Stale first preview", updatedAt: Date.now() } }));
 		agent.send(JSON.stringify({ type: "agent.event", sessionId: tuiId, event: { type: "session_info_changed", name: "Preview barrier" } }));
diff --git a/tests/web-worktrees.test.ts b/tests/web-worktrees.test.ts
index e935070..a481f6e 100644
--- a/tests/web-worktrees.test.ts
+++ b/tests/web-worktrees.test.ts
@@ -320,16 +320,22 @@ test("async managed cleanup yields before spawning Git verification", async () =
 			import { removeManagedWorktreeAsync } from ${JSON.stringify(moduleUrl)};
 			const started = Date.now();
 			const cleanup = removeManagedWorktreeAsync({ path: "/missing/topic", repoRoot: "/missing", name: "topic", branch: "topic", branchCreated: true });
-			console.log(Date.now() - started);
+			const elapsed = Date.now() - started;
+			if (elapsed >= 500) {
+				console.error(\`removeManagedWorktreeAsync blocked for \${elapsed}ms before returning\`);
+				process.exitCode = 2;
+			}
 			await cleanup.catch(() => undefined);
 		`],
 		env: { ...process.env, PATH: `${fakeBin}:${process.env.PATH ?? ""}` },
-		stdout: "pipe",
+		stdout: "ignore",
 		stderr: "pipe",
 	});
-	const elapsed = Number((await new Response(probe.stdout).text()).trim());
-	expect(await probe.exited).toBe(0);
-	expect(elapsed).toBeLessThan(500);
+	const [stderr, exitCode] = await Promise.all([
+		new Response(probe.stderr).text(),
+		probe.exited,
+	]);
+	if (exitCode !== 0) throw new Error(`Async cleanup probe failed: ${stderr.trim() || `exit ${exitCode}`}`);
 }, 5_000);
 
 test("managed worktree metadata is parsed and cleanup removes its checkout and branch", async () => {
diff --git a/web/server/index.ts b/web/server/index.ts
index 79334c1..7f2a53a 100644
--- a/web/server/index.ts
+++ b/web/server/index.ts
@@ -1136,6 +1136,7 @@ async function createManagedSessionUnlocked(cwd: string, name?: string, sessionF
 				|| event.type === "message_end";
 			if (catalogChanged) broadcastSessionToAll(record);
 			else broadcast(record.id, { type: "server.session", session: sessionToClientPayload(record) } satisfies ServerSessionMessage);
+			if (event.type === "agent_end") void hydrateGitMetadata(record);
 		},
 		onExit: () => {
 			record.status = "offline";
@@ -1784,6 +1785,9 @@ async function handleAgentMessage(socket: Bun.ServerWebSocket<AgentSocketData>,
 			} else if (subagentsChanged) {
 				broadcast(record.id, { type: "server.session", session: sessionToClientPayload(record) } satisfies ServerSessionMessage);
 			}
+			// PRs are commonly opened during an agent run without changing branches.
+			// Refresh after completion so the catalog does not retain the pre-PR lookup.
+			if (event.event.type === "agent_end") void hydrateGitMetadata(record);
 		}
 		return;
 	}