improve background functionality

Author: ava-silver

pi/AGENTS.md

@@ -18,6 +18,7 @@
 
 ## Tools
 
+- Use the normal bash tool unless a command is expected to run indefinitely, such as a dev server.
 - Run commands needing AWS auth through `aws-sso-exec` (for example, `aws-sso-exec aws sts get-caller-identity`). It uses native AWS SSO and opens a browser for the user to auth only when required.
 - Use Colima instead of Docker.
 - Use the `ffgrep` tool or `rg` instead of `grep`

pi/extensions/background/subagents.ts

@@ -29,7 +29,7 @@ import { Markdown, Text } from "@earendil-works/pi-tui";
 import { Type } from "typebox";
 import { formatElapsed, latestText, REASONING_EFFORTS, type SubagentSnapshot } from "./src/domain.ts";
 import { formatContextUtilization } from "../shared/context-utilization.ts";
-import { registerTransientSegment } from "../shared/footer-segments.ts";
+import { registerBackgroundCost, registerTransientSegment } from "../shared/footer-segments.ts";
 import { resolveStandaloneChildProjectTrust } from "../shared/child-session.ts";
 import { SubagentManager, type SubagentManagerShape } from "./src/manager.ts";
 import {
@@ -86,6 +86,7 @@ export function setupSubagents(pi: ExtensionAPI, background: BackgroundHub) {
 	let sessionContext: ExtensionContext | undefined;
 	let ui: ExtensionUIContext | undefined;
 	let unsubStatus: (() => void) | undefined;
+	let costKey: string | undefined;
 	const resultDelivery = createDeferredResultDelivery<SubagentSnapshot>();
 
 	const getRuntime = () => (runtime ??= createSubagentRuntime());
@@ -106,17 +107,21 @@ export function setupSubagents(pi: ExtensionAPI, background: BackgroundHub) {
 	};
 
 	const updateStatus = (manager: SubagentManagerShape) => {
-		if (!ui) return;
 		const subs = manager.view.list();
+		if (costKey)
+			registerBackgroundCost(
+				costKey,
+				subs.reduce((total, snap) => total + snap.cost, 0),
+			);
+		if (!ui) return;
 		if (subs.length === 0) {
 			registerTransientSegment("subagents", null);
 			return;
 		}
 		const running = subs.filter((snap) => snap.status === "running").length;
 		const failed = subs.filter((snap) => snap.status === "error").length;
 		const done = subs.length - running - failed;
-		const cost = subs.reduce((total, snap) => total + snap.cost, 0);
-		const parts: string[] = [`$${cost.toFixed(2)} sub`];
+		const parts: string[] = [];
 		if (running > 0) parts.push(`${running} running`);
 		if (done > 0) parts.push(`${done} done`);
 		if (failed > 0) parts.push(`${failed} failed`);
@@ -163,6 +168,7 @@ export function setupSubagents(pi: ExtensionAPI, background: BackgroundHub) {
 
 	pi.on("session_start", (_event, ctx) => {
 		sessionContext = ctx;
+		costKey = `subagents:${ctx.sessionManager.getSessionId()}`;
 		if (ctx.hasUI) ui = ctx.ui;
 		unregisterProvider?.();
 		unregisterProvider = background.registerProvider("subagents", {
@@ -203,6 +209,8 @@ export function setupSubagents(pi: ExtensionAPI, background: BackgroundHub) {
 		unsubStatus?.();
 		unsubStatus = undefined;
 		registerTransientSegment("subagents", null);
+		if (costKey) registerBackgroundCost(costKey, null);
+		costKey = undefined;
 		const closing = runtime;
 		runtime = undefined;
 		managerPromise = undefined;
@@ -246,11 +254,14 @@ export function setupSubagents(pi: ExtensionAPI, background: BackgroundHub) {
 			),
 		}),
 		renderCall(args, theme) {
-			return new Text(
-				theme.fg("toolTitle", "subagent_spawn") + (args.name ? " " + theme.fg("dim", String(args.name)) : ""),
-				0,
-				0,
-			);
+			const lines = [
+				theme.fg("toolTitle", "subagent_spawn") + (args.name ? " " + theme.fg("dim", args.name) : ""),
+				...(args.prompt ? [theme.fg("text", args.prompt)] : []),
+				...(args.working_dir ? [theme.fg("muted", `cwd: ${args.working_dir}`)] : []),
+				...(args.model ? [theme.fg("muted", `model: ${args.model}`)] : []),
+				...(args.reasoning_effort ? [theme.fg("muted", `effort: ${args.reasoning_effort}`)] : []),
+			];
+			return new Text(lines.join("\n"), 0, 0);
 		},
 		async execute(_toolCallId, params, _signal, _onUpdate, ctx) {
 			const manager = await getManager();

pi/extensions/background/terminals.ts

@@ -28,7 +28,7 @@ import {
 	type Theme,
 } from "@earendil-works/pi-coding-agent";
 import type { Component, Focusable, TUI } from "@earendil-works/pi-tui";
-import { truncateToWidth } from "@earendil-works/pi-tui";
+import { Text, truncateToWidth } from "@earendil-works/pi-tui";
 import { Type } from "typebox";
 import { registerTransientSegment } from "../shared/footer-segments.ts";
 import { killProcessTree } from "../shared/process-tree.ts";
@@ -461,6 +461,14 @@ export function setupTerminals(pi: ExtensionAPI, background: BackgroundHub) {
 			title: Type.String({ description: "Short human-readable label for this terminal, shown in listings" }),
 			working_dir: Type.Optional(Type.String({ description: "Working directory (default: current directory)" })),
 		}),
+		renderCall(args, theme) {
+			const lines = [
+				theme.fg("toolTitle", "terminal_run") + (args.title ? " " + theme.fg("dim", args.title) : ""),
+				...(args.command ? [theme.fg("text", `$ ${args.command}`)] : []),
+				...(args.working_dir ? [theme.fg("muted", `cwd: ${args.working_dir}`)] : []),
+			];
+			return new Text(lines.join("\n"), 0, 0);
+		},
 		async execute(_id, params, signal, _onUpdate, ctx) {
 			const cwd = path.resolve(ctx.cwd, params.working_dir ?? ".");
 			if (!fs.existsSync(cwd) || !fs.statSync(cwd).isDirectory()) {

pi/extensions/powerline.ts

@@ -20,7 +20,7 @@ import type { ExtensionAPI, ExtensionContext } from "@earendil-works/pi-coding-a
 
 type ThinkingLevel = "off" | "minimal" | "low" | "medium" | "high" | "xhigh" | "max";
 import { visibleWidth, truncateToWidth } from "@earendil-works/pi-tui";
-import { getTransientSegments, setTransientOnChange } from "./shared/footer-segments.ts";
+import { getBackgroundCost, getTransientSegments, setTransientOnChange } from "./shared/footer-segments.ts";
 
 // ── Powerline characters ────────────────────────────────────────────────────
 const ARROW_RIGHT = "\uE0B4"; //  right half-circle
@@ -332,9 +332,9 @@ export default function powerlineExtension(pi: ExtensionAPI): void {
 						right.push({ text: `󰥔 ${elapsed} ago`, bg: C.panel, fg: C.dim });
 					}
 
-					// Session cost (always shown)
+					// Session cost, including background subagents (always shown)
 					right.push({
-						text: formatCost(sessionCost),
+						text: formatCost(sessionCost + getBackgroundCost()),
 						bg: C.panelAlt,
 						fg: C.dim,
 					});

pi/extensions/shared/footer-segments.ts

@@ -27,6 +27,7 @@ export type TransientSegment = {
 
 // Module-level singleton: one shared instance per process.
 const registry = new Map<string, TransientSegment>();
+const backgroundCosts = new Map<string, number>();
 let onChangeCallback: (() => void) | undefined;
 
 /**
@@ -48,6 +49,22 @@ export function getTransientSegments(): ReadonlyMap<string, TransientSegment> {
 	return registry;
 }
 
+/** Register or clear a background task cost for inclusion in the main session cost. */
+export function registerBackgroundCost(key: string, cost: number | null): void {
+	if (cost === null) {
+		if (!backgroundCosts.delete(key)) return;
+	} else {
+		backgroundCosts.set(key, cost);
+	}
+	onChangeCallback?.();
+}
+
+export function getBackgroundCost(): number {
+	let total = 0;
+	for (const cost of backgroundCosts.values()) total += cost;
+	return total;
+}
+
 /**
  * Called once by the footer extension. Returns a cleanup function.
  * Only one callback is active at a time (the footer owns this).