refactor(coding-agent): extracted shared auto-backgrounding and job wait helpers

- Extract foreground wait, notice formatting, and settlement racing logic into a shared module.
- Update async job type definitions to support eval jobs alongside bash and task jobs.
- Add configuration settings for eval auto-background thresholds.

packages/coding-agent/CHANGELOG.md

@@ -11,6 +11,7 @@
 - Added `extendedContext` setting (`/settings` → Context → General, default on). When off, models with a premium long-context price tier (OpenAI GPT-5.6 Sol/Terra/Luna bill 2x input / 1.5x output above 272K input tokens, on both the API and subscription Codex) are capped at the standard-pricing threshold — they appear as 272K again and compaction fires before a request crosses into premium billing. Toggling mid-session re-clamps or restores the active model's window immediately. Anthropic Claude 4.6+ serves its full 1M window at standard pricing, so no Anthropic model is affected.
 - Added click-to-toggle and drag-to-reorder controls for list-valued `/settings` editors.
 - Added `compaction.asyncEnabled` (Async Compaction, default on): when context enters the band just below the compaction threshold, maintenance speculatively summarizes in the background off a branch snapshot (first configured LLM-backed method — remote, handoff, or soft — isolated from the live turn by a side session id) and holds the armed result; crossing the threshold then splices it in instantly instead of blocking on a summarization round-trip. Armed results are invalidated by branch changes, reset boundaries, model switches that strand provider-native replay payloads, and context growth past `keepRecentTokens` (which re-speculates). The status line pulses the auto-compact icon while a speculation runs and holds it in accent once a result is armed.
+- Added auto-backgrounding for eval cells, mirroring the bash policy: with `eval.autoBackground.enabled` (default off), a cell still running after `eval.autoBackground.thresholdMs` (default 60s) — or when a queued user/peer message steers mid-wait — converts into a background job that keeps executing on the kernel and delivers its result automatically. Both settings inherit the RPC-host default treatment alongside their bash counterparts.
 
 ### Changed
 
@@ -20,6 +21,7 @@
 - `/settings` rows can now carry a risk note: a warning glyph on the row plus a warning-colored line above the description. `External Thinking` (`externalThinking`, `--external-thinking`) is the first user — providers have flagged the request shape it produces as abuse, up to account-level enforcement, so both the settings entry and `--help` now say so.
 - The todo HUD header now draws a summed progress bar counting closed/total tasks across every stage. Once all tasks close, the bar smoothly collapses before the row disappears.
 - The todo HUD now carries overall progress in the tree spine instead of a horizontal header bar: the top-level connector column runs unbroken from the `TODO` header down the left edge and closes with a short `└────` elbow tail under the block. The closed/total fraction (summed across every stage) fills that path in accent — down the spine, around the bend, out along the tail. Once all tasks close, the accent smoothly drains back up before the header row disappears.
+- The todo HUD now carries overall progress in the tree spine instead of a horizontal header bar: the top-level connector column runs unbroken from the `TODO` header to the last row, and the closed/total fraction (summed across every stage) colors it top-down in accent. Once all tasks close, the accent smoothly drains out of the spine before the header row disappears.
 - Token counting is now scoped to the model being billed rather than to a process-global tokenizer: session maintenance, stats, advisors, `/context`, snapcompact inline imaging, and `compress` each count through the owning agent's `Tokenizer` (`agent.tokenizer`). Message counting is `Tokenizer.countMessage`/`countMessages` (replacing the free `estimateTokens(message, tokenizer)` helper; the legacy shim keeps a compat `estimateTokens` export for legacy pi extensions). `estimateToolSchemaTokens`, `estimateSkillsTokens`, `computeNonMessageTokens`, and `computeNonMessageBreakdown` take an explicit tokenizer; standalone prompt inspection intentionally keeps the default estimate because it has no resolved catalog model.
 - The advisor runtime's `maintainContext` hook now receives the pending update as a message instead of a pre-computed token count — sizing it needs the advisor model's tokenizer, which the host owns.
 - Handoff no longer starts a new session: `/handoff` and the auto-maintenance `handoff` method now commit the generated document as a regular compaction entry on the current session (document becomes the summary, recent history is kept per `compaction.keepRecentTokens`, session id/transcript/cache key unchanged). The `session_before_switch`/`session_switch` extension events no longer fire with reason `"handoff"`, mid-turn maintenance no longer skips the handoff preference, and overflow recovery can now apply a pre-armed handoff result.

packages/coding-agent/src/async/auto-background.ts

@@ -0,0 +1,78 @@
+/**
+ * Shared foreground-wait helpers for tools that auto-background long-running
+ * work as {@link AsyncJobManager} jobs (bash commands, eval cells): the
+ * LLM-facing background notice, the threshold-vs-timeout wait budget, and the
+ * settlement race against abort/steering signals.
+ */
+
+/** Default foreground-wait threshold before a tool call auto-backgrounds. */
+export const DEFAULT_AUTO_BACKGROUND_THRESHOLD_MS = 60_000;
+/** LLM-facing footer appended when a tool call is converted into a background job. */
+export function formatBackgroundNotice(jobId: string): string {
+	return `Backgrounded as job ${jobId}; result will be delivered automatically.`;
+}
+
+/**
+ * How long a tool foreground-waits before backgrounding. Bounded by the call's
+ * own timeout minus a small buffer so a deadline expiry resolves inline instead
+ * of backgrounding moments before it fires. `0` means background immediately.
+ */
+export function resolveAutoBackgroundWaitMs(thresholdMs: number, timeoutMs: number | undefined): number {
+	if (thresholdMs <= 0) return 0;
+	if (timeoutMs === undefined) return thresholdMs;
+	const timeoutBufferMs = 1_000;
+	return Math.max(0, Math.min(thresholdMs, timeoutMs - timeoutBufferMs));
+}
+
+/** Non-settled outcomes of {@link raceJobSettlement}. */
+export type JobWaitInterrupt = { kind: "running" } | { kind: "steer" } | { kind: "aborted" };
+
+/**
+ * Race a managed job's settlement against the auto-background threshold, the
+ * caller's abort signal, and the turn's steering signal. Returns the job's own
+ * completion when it settles first; otherwise reports why the wait ended:
+ * "running" = threshold elapsed (background it), "steer" = a queued message
+ * arrived mid-wait, "aborted" = the caller cancelled.
+ */
+export async function raceJobSettlement<C>(
+	completion: Promise<C>,
+	thresholdMs: number,
+	signal?: AbortSignal,
+	steeringSignal?: AbortSignal,
+): Promise<C | JobWaitInterrupt> {
+	if (signal?.aborted) {
+		return { kind: "aborted" };
+	}
+	if (steeringSignal?.aborted) {
+		return { kind: "steer" };
+	}
+
+	// Cancellable threshold: a bare Bun.sleep(thresholdMs) leaves a live, ref'd
+	// timer for the full threshold after the job finishes (or abort/steer) wins
+	// the race first — delaying SDK/headless shutdown and accumulating timers
+	// under fast completion rates. Settle a withResolvers promise from
+	// setTimeout so the finally can clear it regardless of which waiter wins.
+	const { promise: thresholdPromise, resolve: resolveThreshold } = Promise.withResolvers<{ kind: "running" }>();
+	const thresholdTimer = setTimeout(() => resolveThreshold({ kind: "running" }), thresholdMs);
+	const waiters: Array<Promise<C | JobWaitInterrupt>> = [completion, thresholdPromise];
+
+	const { promise: abortedPromise, resolve: resolveAborted } = Promise.withResolvers<{ kind: "aborted" }>();
+	const onAbort = () => resolveAborted({ kind: "aborted" });
+	const { promise: steerPromise, resolve: resolveSteer } = Promise.withResolvers<{ kind: "steer" }>();
+	const onSteer = () => resolveSteer({ kind: "steer" });
+	if (signal) {
+		signal.addEventListener("abort", onAbort, { once: true });
+		waiters.push(abortedPromise);
+	}
+	if (steeringSignal) {
+		steeringSignal.addEventListener("abort", onSteer, { once: true });
+		waiters.push(steerPromise);
+	}
+	try {
+		return await Promise.race(waiters);
+	} finally {
+		clearTimeout(thresholdTimer);
+		signal?.removeEventListener("abort", onAbort);
+		steeringSignal?.removeEventListener("abort", onSteer);
+	}
+}

packages/coding-agent/src/async/index.ts

@@ -1 +1,2 @@
+export * from "./auto-background";
 export * from "./job-manager";

packages/coding-agent/src/async/job-manager.ts

@@ -29,9 +29,12 @@ interface PollEscalationState {
 	lastPollEndAt: number;
 }
 
+/** Kind of work a managed job runs; drives job-row badges and delivery labels. */
+export type AsyncJobType = "bash" | "task" | "eval";
+
 export interface AsyncJob {
 	id: string;
-	type: "bash" | "task";
+	type: AsyncJobType;
 	status: "running" | "completed" | "failed" | "cancelled";
 	startTime: number;
 	label: string;
@@ -183,7 +186,7 @@ export class AsyncJobManager {
 	}
 
 	register(
-		type: "bash" | "task",
+		type: AsyncJobType,
 		label: string,
 		run: (ctx: {
 			jobId: string;

packages/coding-agent/src/config/settings-schema.ts

@@ -3652,6 +3652,22 @@ export const SETTINGS_SCHEMA = {
 		},
 	},
 
+	"eval.autoBackground.enabled": {
+		type: "boolean",
+		default: false,
+		ui: {
+			tab: "shell",
+			group: "Eval & Runtimes",
+			label: "Eval Auto-Background",
+			description: "Automatically background long-running eval cells and deliver the result later",
+		},
+	},
+
+	"eval.autoBackground.thresholdMs": {
+		type: "number",
+		default: 60_000,
+	},
+
 	// Runtime knobs (consumed by eval backends and the /python slash command)
 	"python.kernelMode": {
 		type: "enum",

packages/coding-agent/src/eval/types.ts

@@ -45,4 +45,10 @@ export interface EvalToolDetails {
 	languages?: EvalLanguage[];
 	/** Optional human-readable notice (e.g. fallback explanation). */
 	notice?: string;
+	/** Present when the cell was auto-backgrounded as an async job. */
+	async?: {
+		state: "running" | "completed" | "failed";
+		jobId: string;
+		type: "eval";
+	};
 }

packages/coding-agent/src/main.ts

@@ -155,6 +155,8 @@ const RPC_BACKGROUND_DEFAULTED_SETTING_PATHS: SettingPath[] = [
 	"async.maxJobs",
 	"bash.autoBackground.enabled",
 	"bash.autoBackground.thresholdMs",
+	"eval.autoBackground.enabled",
+	"eval.autoBackground.thresholdMs",
 ];
 
 // Protocol-mode hosts opt into a small set of paths whose host-default we

packages/coding-agent/src/modes/utils/transcript-render-helpers.ts

@@ -7,6 +7,7 @@
 import type { AgentMessage } from "@oh-my-pi/pi-agent-core";
 import { type Component, Text } from "@oh-my-pi/pi-tui";
 import { formatBytes, formatDuration } from "@oh-my-pi/pi-utils";
+import type { AsyncJobType } from "../../async";
 import {
 	type CustomMessage,
 	type FileMentionMessage,
@@ -32,10 +33,10 @@ export function buildAsyncResultBlock(message: CustomOrHookMessage): ToolActivit
 	const details = (
 		message as CustomMessage<{
 			jobId?: string;
-			type?: "bash" | "task";
+			type?: AsyncJobType;
 			label?: string;
 			durationMs?: number;
-			jobs?: Array<{ jobId?: string; type?: "bash" | "task"; label?: string; durationMs?: number }>;
+			jobs?: Array<{ jobId?: string; type?: AsyncJobType; label?: string; durationMs?: number }>;
 		}>
 	).details;
 	const jobs =

packages/coding-agent/src/prompts/tools/eval.md

@@ -43,3 +43,5 @@ Acyclic waves via `agent(…, handle=true)` + `pipeline`/`parallel`:
 <critical>
 Prior top-level names survive into the next cell — reuse; NEVER re-import/re-declare. Re-read only if file changed since last read.
 </critical>
+
+{{#if autoBackgroundEnabled}}Long-running cells may auto-background and deliver later; the kernel stays busy until the cell finishes. Need inline? Raise `timeout`.{{/if}}

packages/coding-agent/src/session/async-job-delivery.ts

@@ -9,7 +9,7 @@
  * every completion — regardless of owner — into the first top-level session.
  */
 import { prompt } from "@oh-my-pi/pi-utils";
-import type { AsyncJob } from "../async";
+import type { AsyncJob, AsyncJobType } from "../async";
 import asyncResultTemplate from "../prompts/tools/async-result.md" with { type: "text" };
 import type { CustomMessage } from "./messages";
 
@@ -41,7 +41,7 @@ export interface AsyncResultEntry {
 
 type AsyncResultJobDetails = {
 	jobId: string;
-	type?: "bash" | "task";
+	type?: AsyncJobType;
 	label?: string;
 	durationMs?: number;
 };

packages/coding-agent/src/task/executor.ts

@@ -888,7 +888,7 @@ export function createSubagentSettings(
 	return Settings.isolated(
 		{
 			...snapshot,
-			// Async jobs and bash auto-backgrounding are inherited from the parent:
+			// Async jobs and bash/eval auto-backgrounding are inherited from the parent:
 			// background jobs are owner-routed to the subagent's own session, and
 			// the run driver's quiescence barrier + teardown reap guarantee no
 			// owner job outlives the run, so worktree capture/cleanup stays

packages/coding-agent/src/tools/bash.ts

@@ -10,6 +10,12 @@ import type {
 import type { Component } from "@oh-my-pi/pi-tui";
 import { ImageProtocol, TERMINAL } from "@oh-my-pi/pi-tui";
 import { getProjectDir, isEnoent, logger, prompt } from "@oh-my-pi/pi-utils";
+import {
+	DEFAULT_AUTO_BACKGROUND_THRESHOLD_MS,
+	formatBackgroundNotice,
+	raceJobSettlement,
+	resolveAutoBackgroundWaitMs,
+} from "../async";
 import type { Settings } from "../config/settings";
 import { applyDirenvPreflight, type BashResult, executeBash } from "../exec/bash-executor";
 import type { RenderResultOptions } from "../extensibility/custom-tools/types";
@@ -57,7 +63,6 @@ import { clampTimeout, TOOL_TIMEOUTS } from "./tool-timeouts";
 export const BASH_DEFAULT_PREVIEW_LINES = DEFAULT_TERMINAL_PREVIEW_LINES;
 
 const BASH_ENV_NAME_PATTERN = /^[A-Za-z_][A-Za-z0-9_]*$/;
-const DEFAULT_AUTO_BACKGROUND_THRESHOLD_MS = 60_000;
 const BASH_APPROVAL_SHELL_CONTROL_CHARS: Record<string, true> = {
 	"\n": true,
 	"\r": true,
@@ -505,10 +510,6 @@ function formatExitCodeNotice(exitCode: number): string {
 	return `Command exited with code ${exitCode}`;
 }
 
-function formatBackgroundNotice(jobId: string): string {
-	return `Backgrounded as job ${jobId}; result will be delivered automatically.`;
-}
-
 /**
  * Strip the trailing occurrence of `notice` (plus a single surrounding newline
  * on each side) so the TUI can echo the value via a styled footer label
@@ -894,60 +895,6 @@ export class BashTool implements AgentTool<typeof bashSchemaBase | typeof bashSc
 		};
 	}
 
-	async #waitForManagedBashJob(
-		job: ManagedBashJobHandle,
-		thresholdMs: number,
-		signal?: AbortSignal,
-		steeringSignal?: AbortSignal,
-	): Promise<ManagedBashJobCompletion | { kind: "running" } | { kind: "steer" } | { kind: "aborted" }> {
-		if (signal?.aborted) {
-			return { kind: "aborted" };
-		}
-		if (steeringSignal?.aborted) {
-			return { kind: "steer" };
-		}
-
-		// Cancellable threshold: a bare Bun.sleep(thresholdMs) leaves a live, ref'd
-		// timer for the full threshold after the command finishes (or abort/steer)
-		// wins the race first — delaying SDK/headless shutdown and accumulating
-		// timers under fast command rates. Settle a withResolvers promise from
-		// setTimeout so the finally can clear it regardless of which waiter wins.
-		const { promise: thresholdPromise, resolve: resolveThreshold } = Promise.withResolvers<{
-			kind: "running";
-		}>();
-		const thresholdTimer = setTimeout(() => resolveThreshold({ kind: "running" }), thresholdMs);
-		const waiters: Array<
-			Promise<ManagedBashJobCompletion | { kind: "running" } | { kind: "steer" } | { kind: "aborted" }>
-		> = [job.completion, thresholdPromise];
-
-		const { promise: abortedPromise, resolve: resolveAborted } = Promise.withResolvers<{ kind: "aborted" }>();
-		const onAbort = () => resolveAborted({ kind: "aborted" });
-		const { promise: steerPromise, resolve: resolveSteer } = Promise.withResolvers<{ kind: "steer" }>();
-		const onSteer = () => resolveSteer({ kind: "steer" });
-		if (signal) {
-			signal.addEventListener("abort", onAbort, { once: true });
-			waiters.push(abortedPromise);
-		}
-		if (steeringSignal) {
-			steeringSignal.addEventListener("abort", onSteer, { once: true });
-			waiters.push(steerPromise);
-		}
-		try {
-			return await Promise.race(waiters);
-		} finally {
-			clearTimeout(thresholdTimer);
-			signal?.removeEventListener("abort", onAbort);
-			steeringSignal?.removeEventListener("abort", onSteer);
-		}
-	}
-
-	#resolveAutoBackgroundWaitMs(timeoutMs: number | undefined): number {
-		if (this.#autoBackgroundThresholdMs <= 0) return 0;
-		if (timeoutMs === undefined) return this.#autoBackgroundThresholdMs;
-		const timeoutBufferMs = 1_000;
-		return Math.max(0, Math.min(this.#autoBackgroundThresholdMs, timeoutMs - timeoutBufferMs));
-	}
-
 	async execute(
 		_toolCallId: string,
 		{
@@ -1099,7 +1046,7 @@ export class BashTool implements AgentTool<typeof bashSchemaBase | typeof bashSc
 			autoBgManager &&
 			!autoBgManager.atCapacity
 		) {
-			const autoBackgroundWaitMs = this.#resolveAutoBackgroundWaitMs(timeoutMs);
+			const autoBackgroundWaitMs = resolveAutoBackgroundWaitMs(this.#autoBackgroundThresholdMs, timeoutMs);
 			const startBackgrounded = autoBackgroundWaitMs === 0;
 			const job = this.#startManagedBashJob({
 				command,
@@ -1123,8 +1070,8 @@ export class BashTool implements AgentTool<typeof bashSchemaBase | typeof bashSc
 			// foreground-wait cannot also be injected by the delivery loop. Lifted
 			// via resumeDeliveries() if we end up backgrounding after all.
 			autoBgManager.acknowledgeDeliveries([job.jobId]);
-			const waitResult = await this.#waitForManagedBashJob(
-				job,
+			const waitResult = await raceJobSettlement(
+				job.completion,
 				autoBackgroundWaitMs,
 				signal,
 				ctx?.toolCall?.steeringSignal,

packages/coding-agent/src/tools/eval-render.ts

@@ -586,6 +586,10 @@ export const evalToolRenderer = {
 			warningLine = formatStyledTruncationWarning(details.meta, uiTheme) ?? undefined;
 		}
 		const noticeLine = details?.notice ? uiTheme.fg("dim", wrapBrackets(details.notice, uiTheme)) : undefined;
+		const asyncLine =
+			details?.async?.state === "running"
+				? uiTheme.fg("dim", wrapBrackets(`Backgrounded: ${details.async.jobId}`, uiTheme))
+				: undefined;
 
 		const cellResults = details?.cells;
 		if (cellResults && cellResults.length > 0) {
@@ -670,6 +674,9 @@ export const evalToolRenderer = {
 					if (noticeLine) {
 						lines.push(noticeLine);
 					}
+					if (asyncLine) {
+						lines.push(asyncLine);
+					}
 					if (warningLine) {
 						lines.push(warningLine);
 					}
@@ -693,14 +700,19 @@ export const evalToolRenderer = {
 		);
 
 		if (!combinedOutput && statusLines.length === 0) {
-			const lines = [timeoutLine, noticeLine, warningLine].filter(Boolean) as string[];
+			const lines = [timeoutLine, noticeLine, asyncLine, warningLine].filter(Boolean) as string[];
 			return new Text(lines.join("\n"), 0, 0);
 		}
 
 		if (!combinedOutput && statusLines.length > 0) {
-			const lines = [uiTheme.fg("dim", "Status"), ...statusLines, timeoutLine, noticeLine, warningLine].filter(
-				Boolean,
-			) as string[];
+			const lines = [
+				uiTheme.fg("dim", "Status"),
+				...statusLines,
+				timeoutLine,
+				noticeLine,
+				asyncLine,
+				warningLine,
+			].filter(Boolean) as string[];
 			return new Text(lines.join("\n"), 0, 0);
 		}
 
@@ -714,6 +726,7 @@ export const evalToolRenderer = {
 				...(statusLines.length > 0 ? [uiTheme.fg("dim", "Status"), ...statusLines] : []),
 				timeoutLine,
 				noticeLine,
+				asyncLine,
 				warningLine,
 			].filter(Boolean) as string[];
 			return new Text(lines.join("\n"), 0, 0);
@@ -765,6 +778,9 @@ export const evalToolRenderer = {
 				if (noticeLine) {
 					outputLines.push(truncateToWidth(noticeLine, width));
 				}
+				if (asyncLine) {
+					outputLines.push(truncateToWidth(asyncLine, width));
+				}
 				if (warningLine) {
 					outputLines.push(truncateToWidth(warningLine, width));
 				}

packages/coding-agent/src/tools/eval.ts

@@ -2,6 +2,12 @@ import { type } from "@oh-my-pi/omptype";
 import type { AgentTool, AgentToolContext, AgentToolResult, AgentToolUpdateCallback } from "@oh-my-pi/pi-agent-core";
 import type { ImageContent, ToolExample } from "@oh-my-pi/pi-ai";
 import { prompt } from "@oh-my-pi/pi-utils";
+import {
+	DEFAULT_AUTO_BACKGROUND_THRESHOLD_MS,
+	formatBackgroundNotice,
+	raceJobSettlement,
+	resolveAutoBackgroundWaitMs,
+} from "../async";
 import { jsBackend, juliaBackend, pythonBackend, rubyBackend } from "../eval";
 import type { ExecutorBackend, ExecutorBackendResult } from "../eval/backend";
 import { EVAL_TIMEOUT_PAUSE_OP, EVAL_TIMEOUT_RESUME_OP } from "../eval/bridge-timeout";
@@ -169,6 +175,8 @@ export interface EvalToolDescriptionOptions {
 	 * `false`/`""` hides `agent()`, and a comma list drives the advertised default.
 	 */
 	spawns?: boolean | string | null;
+	/** Advertise auto-backgrounding of long-running cells in the tool prompt. */
+	autoBackgroundEnabled?: boolean;
 }
 
 export function getEvalToolDescription(options: EvalToolDescriptionOptions = {}): string {
@@ -182,6 +190,7 @@ export function getEvalToolDescription(options: EvalToolDescriptionOptions = {})
 		js,
 		rb,
 		jl,
+		autoBackgroundEnabled: options.autoBackgroundEnabled ?? false,
 		spawns: spawnPolicy.enabled,
 		spawnDefaultAgent: spawnPolicy.defaultAgent,
 		spawnAllowedAgentsText: spawnPolicy.allowedPromptText,
@@ -206,6 +215,11 @@ interface ResolvedEvalCell {
 	resolved: ResolvedBackend;
 }
 
+/** Settlement handed from a managed eval job to its foreground waiter. */
+type ManagedEvalJobCompletion =
+	| { kind: "completed"; result: AgentToolResult<EvalToolDetails | undefined> }
+	| { kind: "failed"; error: unknown };
+
 function uniqueEvalLanguages(cells: ResolvedEvalCell[]): EvalLanguage[] {
 	return [...new Set(cells.map(cell => cell.resolved.backend.id))];
 }
@@ -302,6 +316,7 @@ export class EvalTool implements AgentTool<typeof evalSchema> {
 			rb: backends.ruby,
 			jl: backends.julia,
 			spawns: sessionSpawns,
+			autoBackgroundEnabled: this.session.settings.get("eval.autoBackground.enabled"),
 		});
 	}
 	/** All reuse-chain examples; the `examples` getter filters by enabled languages. */
@@ -394,7 +409,7 @@ export class EvalTool implements AgentTool<typeof evalSchema> {
 		params: typeof evalSchema.infer,
 		signal?: AbortSignal,
 		onUpdate?: AgentToolUpdateCallback,
-		_ctx?: AgentToolContext,
+		ctx?: AgentToolContext,
 	): Promise<AgentToolResult<EvalToolDetails | undefined>> {
 		if (this.#proxyExecutor) {
 			return this.#proxyExecutor(params, signal);
@@ -428,6 +443,185 @@ export class EvalTool implements AgentTool<typeof evalSchema> {
 		const languages = uniqueEvalLanguages(cells);
 		const notice = detailsNotice(cells);
 		const sessionAbortController = new AbortController();
+		const emitToolUpdate = onUpdate
+			? (text: string, details: EvalToolDetails): void => {
+					onUpdate({ content: [{ type: "text", text }], details });
+				}
+			: undefined;
+		const run = (
+			runSignal: AbortSignal | undefined,
+			emitUpdate: ((text: string, details: EvalToolDetails) => void) | undefined,
+		): Promise<AgentToolResult<EvalToolDetails | undefined>> => {
+			const execution = this.#runCells({
+				session,
+				cells,
+				languages,
+				notice,
+				excludeWebP,
+				signal: runSignal,
+				sessionAbortController,
+				emitUpdate,
+			});
+			return session.trackEvalExecution?.(execution, sessionAbortController) ?? execution;
+		};
+
+		const autoBgManager = session.asyncJobManager;
+		// At the running-job cap, fall through to direct foreground execution
+		// instead of failing every eval call until a slot frees up.
+		if (!session.settings.get("eval.autoBackground.enabled") || !autoBgManager || autoBgManager.atCapacity) {
+			return await run(signal, emitToolUpdate);
+		}
+
+		const thresholdMs = Math.max(
+			0,
+			Math.floor(session.settings.get("eval.autoBackground.thresholdMs") ?? DEFAULT_AUTO_BACKGROUND_THRESHOLD_MS),
+		);
+		// The wait budget mirrors #runCells' clamped cell timeout. The cell budget
+		// is runtime work (it pauses across agent()/tool bridge calls), so a cell
+		// can legitimately outlive it in wall time — exactly the case
+		// backgrounding exists for.
+		const cellTimeoutMs =
+			cells[0].timeoutMs === 0
+				? undefined
+				: clampTimeout("eval", cells[0].timeoutMs / 1000, session.settings.get("tools.maxTimeout")) * 1000;
+		const autoBackgroundWaitMs = resolveAutoBackgroundWaitMs(thresholdMs, cellTimeoutMs);
+		const startBackgrounded = autoBackgroundWaitMs === 0;
+
+		const rawLabel = params.title?.trim() || params.code.trim().split("\n", 1)[0] || "eval cell";
+		const label = rawLabel.length > 120 ? `${rawLabel.slice(0, 117)}...` : rawLabel;
+
+		let latestText = "";
+		let latestDetails: EvalToolDetails | undefined;
+		let forwardUpdates = !startBackgrounded;
+		const completion = Promise.withResolvers<ManagedEvalJobCompletion>();
+
+		const jobId = autoBgManager.register(
+			"eval",
+			label,
+			async ({ jobId, signal: runSignal, reportProgress }) => {
+				try {
+					const result = await run(runSignal, (text, details) => {
+						latestText = text;
+						latestDetails = details;
+						void reportProgress(text, { async: { state: "running", jobId, type: "eval" } });
+						if (forwardUpdates) emitToolUpdate?.(text, details);
+					});
+					const finalText = result.content.find(block => block.type === "text")?.text ?? "";
+					latestText = finalText;
+					// Hand the full result (images included) to the foreground waiter
+					// before deciding the job's terminal state.
+					completion.resolve({ kind: "completed", result });
+					if (result.isError === true) {
+						// A failed, cancelled, or timed-out cell is a completed execution
+						// that errored. Re-enter the failure path so the job manager
+						// records it as failed and delivers the error text.
+						throw new ToolError(finalText || "Eval cell failed");
+					}
+					await reportProgress(finalText, { async: { state: "completed", jobId, type: "eval" } });
+					return finalText;
+				} catch (error) {
+					const message = error instanceof Error ? error.message : String(error);
+					latestText = message;
+					completion.resolve({ kind: "failed", error });
+					await reportProgress(message, { async: { state: "failed", jobId, type: "eval" } });
+					throw error;
+				}
+			},
+			{ ownerId: session.getAgentId?.() ?? undefined },
+		);
+
+		if (startBackgrounded) {
+			return this.#buildBackgroundStartResult(jobId, cells, languages, notice, latestText, latestDetails);
+		}
+		// Suppress the completion delivery up front so a job finishing while we
+		// foreground-wait cannot also be injected by the delivery loop. Lifted
+		// via resumeDeliveries() if we end up backgrounding after all.
+		autoBgManager.acknowledgeDeliveries([jobId]);
+		const waitResult = await raceJobSettlement(
+			completion.promise,
+			autoBackgroundWaitMs,
+			signal,
+			ctx?.toolCall?.steeringSignal,
+		);
+		if (waitResult.kind === "completed") {
+			return waitResult.result;
+		}
+		if (waitResult.kind === "failed") {
+			throw waitResult.error;
+		}
+		if (waitResult.kind === "aborted") {
+			autoBgManager.cancel(jobId);
+			throw new ToolAbortError(latestText || "Eval cell aborted");
+		}
+		forwardUpdates = false;
+		autoBgManager.resumeDeliveries([jobId]);
+		// "steer": a queued user/peer message arrived mid-wait — background the
+		// cell (it keeps running) so the message injects promptly.
+		const steerNotice =
+			waitResult.kind === "steer"
+				? "Backgrounded early to handle an incoming message; the cell keeps running."
+				: undefined;
+		return this.#buildBackgroundStartResult(jobId, cells, languages, notice, latestText, latestDetails, steerNotice);
+	}
+
+	/**
+	 * Tool result returned when a cell converts into a background job: the live
+	 * output tail plus the background notice, with details carrying the running
+	 * cell snapshot and the async job marker the transcript renderer keys on.
+	 */
+	#buildBackgroundStartResult(
+		jobId: string,
+		cells: ResolvedEvalCell[],
+		languages: EvalLanguage[],
+		notice: string | undefined,
+		previewText: string,
+		latestDetails: EvalToolDetails | undefined,
+		extraNotice?: string,
+	): AgentToolResult<EvalToolDetails> {
+		// latestDetails snapshots are per-update copies (buildUpdateDetails), so
+		// tagging the async marker on cannot leak into later job progress.
+		const details: EvalToolDetails = latestDetails ?? {
+			language: languages[0],
+			languages,
+			cells: cells.map(cell => ({
+				index: cell.index,
+				title: cell.title,
+				code: cell.code,
+				language: cell.resolved.backend.id,
+				output: previewText,
+				status: "running" as const,
+			})),
+		};
+		if (notice) details.notice ??= notice;
+		details.async = { state: "running", jobId, type: "eval" };
+		const lines: string[] = [];
+		const trimmedPreview = previewText.trimEnd();
+		if (trimmedPreview.length > 0) {
+			lines.push(trimmedPreview, "");
+		}
+		if (extraNotice) {
+			lines.push(extraNotice, "");
+		}
+		lines.push(formatBackgroundNotice(jobId));
+		return { content: [{ type: "text", text: lines.join("\n") }], details };
+	}
+
+	/**
+	 * Execute the resolved cells against their backends, streaming tail/detail
+	 * updates through `emitUpdate`. Runs identically in the foreground path and
+	 * inside a managed background job (which passes the job's own signal).
+	 */
+	async #runCells(options: {
+		session: ToolSession;
+		cells: ResolvedEvalCell[];
+		languages: EvalLanguage[];
+		notice: string | undefined;
+		excludeWebP: boolean | undefined;
+		signal: AbortSignal | undefined;
+		sessionAbortController: AbortController;
+		emitUpdate?: (text: string, details: EvalToolDetails) => void;
+	}): Promise<AgentToolResult<EvalToolDetails | undefined>> {
+		const { session, cells, languages, notice, excludeWebP, signal, sessionAbortController, emitUpdate } = options;
 		let outputSink: OutputSink | undefined;
 		let outputSummary: OutputSummary | undefined;
 		let outputDumped = false;
@@ -437,309 +631,299 @@ export class EvalTool implements AgentTool<typeof evalSchema> {
 			outputDumped = true;
 			return outputSummary;
 		};
+		try {
+			if (signal?.aborted) {
+				throw new ToolAbortError();
+			}
+			session.assertEvalExecutionAllowed?.();
 
-		const execution = (async (): Promise<AgentToolResult<EvalToolDetails | undefined>> => {
-			try {
-				if (signal?.aborted) {
-					throw new ToolAbortError();
-				}
-				session.assertEvalExecutionAllowed?.();
+			const tailBuffer = new TailBuffer(DEFAULT_MAX_BYTES * 2);
+			const jsonOutputs: unknown[] = [];
+			const images: ImageContent[] = [];
+			const statusEvents: EvalStatusEvent[] = [];
 
-				const tailBuffer = new TailBuffer(DEFAULT_MAX_BYTES * 2);
-				const jsonOutputs: unknown[] = [];
-				const images: ImageContent[] = [];
-				const statusEvents: EvalStatusEvent[] = [];
+			const cellResults: EvalCellResult[] = cells.map(cell => ({
+				index: cell.index,
+				title: cell.title,
+				code: cell.code,
+				language: cell.resolved.backend.id,
+				output: "",
+				status: "pending",
+			}));
+			const cellOutputs: string[] = [];
+			// The cell currently inside backend.execute(). Streamed stdout is
+			// appended to its rendered `output` live so a long-running cell (e.g. a
+			// sleep loop) shows progress instead of nothing until it returns. A
+			// dedicated per-cell tail buffer keeps attribution correct and avoids
+			// double-counting against the aggregate `tailBuffer`; on completion the
+			// authoritative `cellResult.output` (below) overwrites this live tail.
+			let activeLiveCell: { result: EvalCellResult; buf: TailBuffer } | undefined;
 
-				const cellResults: EvalCellResult[] = cells.map(cell => ({
-					index: cell.index,
-					title: cell.title,
-					code: cell.code,
-					language: cell.resolved.backend.id,
-					output: "",
-					status: "pending",
-				}));
-				const cellOutputs: string[] = [];
-				// The cell currently inside backend.execute(). Streamed stdout is
-				// appended to its rendered `output` live so a long-running cell (e.g. a
-				// sleep loop) shows progress instead of nothing until it returns. A
-				// dedicated per-cell tail buffer keeps attribution correct and avoids
-				// double-counting against the aggregate `tailBuffer`; on completion the
-				// authoritative `cellResult.output` (below) overwrites this live tail.
-				let activeLiveCell: { result: EvalCellResult; buf: TailBuffer } | undefined;
-
-				const appendTail = (text: string) => {
-					tailBuffer.append(text);
-				};
-
-				const buildUpdateDetails = (): EvalToolDetails => {
-					const details: EvalToolDetails = {
-						language: languages[0],
-						languages,
-						cells: cellResults.map(cell => ({
-							...cell,
-							statusEvents: cell.statusEvents ? [...cell.statusEvents] : undefined,
-						})),
-					};
-					if (jsonOutputs.length > 0) {
-						details.jsonOutputs = jsonOutputs;
-					}
-					if (images.length > 0) {
-						details.images = images;
-					}
-					if (statusEvents.length > 0) {
-						details.statusEvents = statusEvents;
-					}
-					if (notice) {
-						details.notice = notice;
-					}
-					return details;
-				};
-
-				const pushUpdate = () => {
-					if (!onUpdate) return;
-					const tailText = tailBuffer.text();
-					onUpdate({
-						content: [{ type: "text", text: tailText }],
-						details: buildUpdateDetails(),
-					});
-				};
-
-				const sessionFile = session.getSessionFile?.() ?? undefined;
-				const kernelOwnerId = session.getEvalKernelOwnerId?.() ?? undefined;
-				const { path: artifactPath, id: artifactId } = (await session.allocateOutputArtifact?.("eval")) ?? {};
-				session.assertEvalExecutionAllowed?.();
-				outputSink = new OutputSink({
-					artifactPath,
-					artifactId,
-					headBytes: resolveOutputSinkHeadBytes(session.settings),
-					maxColumns: resolveOutputMaxColumns(session.settings),
-					onChunk: chunk => {
-						appendTail(chunk);
-						if (activeLiveCell) {
-							activeLiveCell.buf.append(chunk);
-							activeLiveCell.result.output = activeLiveCell.buf.text();
-						}
-						pushUpdate();
-					},
-				});
-				const sessionId = session.getEvalSessionId?.() ?? defaultEvalSessionId(session);
-
-				for (let i = 0; i < cells.length; i++) {
-					const cell = cells[i];
-					const backend = cell.resolved.backend;
-					// The per-cell `timeout` is a budget on the cell runtime's *own*
-					// work. Host-side `agent()`/`parallel()`/`completion()` bridge calls suspend
-					// that budget entirely and restart a fresh timeout window when control
-					// returns to the active backend runtime. Compute, stdout, `log()`/`phase()`, and
-					// ordinary tool calls all count against the budget. The watchdog drives
-					// `combinedSignal`; we pass no wall-clock deadline downstream so the
-					// backends never arm a competing fixed timer.
-					const idleTimeoutMs =
-						cell.timeoutMs === 0
-							? undefined
-							: clampTimeout("eval", cell.timeoutMs / 1000, session.settings.get("tools.maxTimeout")) * 1000;
-					const idle = idleTimeoutMs === undefined ? undefined : new IdleTimeout(idleTimeoutMs);
-					const combinedSignal =
-						signal && idle
-							? AbortSignal.any([signal, idle.signal, sessionAbortController.signal])
-							: signal
-								? AbortSignal.any([signal, sessionAbortController.signal])
-								: idle
-									? AbortSignal.any([idle.signal, sessionAbortController.signal])
-									: sessionAbortController.signal;
-
-					const cellResult = cellResults[i];
-					cellResult.status = "running";
-					cellResult.output = "";
-					cellResult.statusEvents = undefined;
-					cellResult.exitCode = undefined;
-					cellResult.durationMs = undefined;
-					activeLiveCell = { result: cellResult, buf: new TailBuffer(DEFAULT_MAX_BYTES * 2) };
-					pushUpdate();
-
-					const startTime = Date.now();
-					let result: ExecutorBackendResult;
-					try {
-						result = await backend.execute(cell.code, {
-							cwd: session.cwd,
-							sessionId,
-							sessionFile: sessionFile ?? undefined,
-							kernelOwnerId,
-							signal: combinedSignal,
-							session,
-							idleTimeoutMs,
-							reset: cell.reset,
-							onChunk: chunk => {
-								outputSink!.push(chunk);
-							},
-							onStatus: event => {
-								if (event.op === EVAL_TIMEOUT_PAUSE_OP) {
-									idle?.pause();
-									return;
-								}
-								if (event.op === EVAL_TIMEOUT_RESUME_OP) {
-									idle?.resume();
-									return;
-								}
-								cellResult.statusEvents ??= [];
-								upsertStatusEvent(cellResult.statusEvents, event);
-								pushUpdate();
-							},
-						});
-					} finally {
-						idle?.dispose();
-						activeLiveCell = undefined;
-					}
-					const durationMs = Date.now() - startTime;
-
-					const cellStatusEvents: EvalStatusEvent[] = [];
-					const cellDisplayOutputs: EvalDisplayOutput[] = [];
-					const cellImageNotes: string[] = [];
-					let cellHasMarkdown = false;
-					for (const output of result.displayOutputs) {
-						if (output.type === "json") {
-							jsonOutputs.push(output.data);
-							cellDisplayOutputs.push(output);
-						}
-						if (output.type === "image") {
-							const resized = await resizeImage(
-								{
-									type: "image",
-									data: output.data,
-									mimeType: output.mimeType,
-								},
-								{ excludeWebP },
-							);
-							const image: ImageContent = {
-								type: "image",
-								data: resized.data,
-								mimeType: resized.mimeType,
-							};
-							images.push(image);
-							cellDisplayOutputs.push({
-								type: "image",
-								data: image.data,
-								mimeType: image.mimeType,
-							});
-							const dimensionNote = formatDimensionNote(resized);
-							if (dimensionNote) {
-								cellImageNotes.push(`display image ${cellImageNotes.length + 1}: ${dimensionNote}`);
-							}
-						}
-						if (output.type === "status") {
-							upsertStatusEvent(statusEvents, output.event);
-							upsertStatusEvent(cellStatusEvents, output.event);
-						}
-						if (output.type === "markdown") {
-							cellHasMarkdown = true;
-						}
-					}
-
-					const stdoutTrimmed = result.output.trim();
-					const imageText = cellImageNotes.join("\n");
-					const displayText = formatDisplayOutputsForText(cellDisplayOutputs);
-					const visibleDisplayText =
-						displayText && imageText ? `${displayText}\n\n${imageText}` : displayText || imageText;
-					const cellOutput =
-						stdoutTrimmed && visibleDisplayText
-							? `${stdoutTrimmed}\n\n${visibleDisplayText}`
-							: stdoutTrimmed || visibleDisplayText;
-					cellResult.output = cellOutput;
-					cellResult.exitCode = result.exitCode;
-					cellResult.durationMs = durationMs;
-					cellResult.statusEvents = cellStatusEvents.length > 0 ? cellStatusEvents : undefined;
-					cellResult.hasMarkdown = cellHasMarkdown || undefined;
-
-					if (cellOutput) {
-						cellOutputs.push(cellOutput);
-						appendTail(cellOutput);
-					}
-
-					if (result.cancelled) {
-						cellResult.status = "error";
-						pushUpdate();
-						const errorMsg = result.output || "Command aborted";
-						const combinedOutput = cellOutputs.join("\n\n");
-						const outputText = combinedOutput || errorMsg;
-
-						const summaryForMeta = await summarizeFinal(combinedOutput, finalizeOutput);
-						const details: EvalToolDetails = {
-							language: languages[0],
-							languages,
-							cells: cellResults,
-							jsonOutputs: jsonOutputs.length > 0 ? jsonOutputs : undefined,
-							statusEvents: statusEvents.length > 0 ? statusEvents : undefined,
-							isError: true,
-						};
-						if (notice) details.notice = notice;
-
-						return toolResult(details)
-							.content([{ type: "text", text: outputText }, ...images])
-							.truncationFromSummary(summaryForMeta, { direction: "tail" })
-							.done();
-					}
-
-					if (result.exitCode !== 0 && result.exitCode !== undefined) {
-						cellResult.status = "error";
-						pushUpdate();
-						const combinedOutput = cellOutputs.join("\n\n");
-						const outputText = combinedOutput
-							? `${combinedOutput}\n\nCommand exited with code ${result.exitCode}`
-							: `Command exited with code ${result.exitCode}`;
-
-						const summaryForMeta = await summarizeFinal(combinedOutput, finalizeOutput);
-						const details: EvalToolDetails = {
-							language: languages[0],
-							languages,
-							cells: cellResults,
-							jsonOutputs: jsonOutputs.length > 0 ? jsonOutputs : undefined,
-							statusEvents: statusEvents.length > 0 ? statusEvents : undefined,
-							isError: true,
-						};
-						if (notice) details.notice = notice;
-
-						return toolResult(details)
-							.content([{ type: "text", text: outputText }, ...images])
-							.truncationFromSummary(summaryForMeta, { direction: "tail" })
-							.done();
-					}
-
-					cellResult.status = "complete";
-					pushUpdate();
-				}
-
-				const combinedOutput = cellOutputs.join("\n\n");
-				const hasImages = images.length > 0;
-				const outputText =
-					combinedOutput ||
-					(hasImages
-						? `(displayed ${images.length} image${images.length === 1 ? "" : "s"}; no text output)`
-						: "(no output)");
-				const summaryForMeta = await summarizeFinal(combinedOutput, finalizeOutput);
+			const appendTail = (text: string) => {
+				tailBuffer.append(text);
+			};
 
+			const buildUpdateDetails = (): EvalToolDetails => {
 				const details: EvalToolDetails = {
 					language: languages[0],
 					languages,
-					cells: cellResults,
-					jsonOutputs: jsonOutputs.length > 0 ? jsonOutputs : undefined,
-					statusEvents: statusEvents.length > 0 ? statusEvents : undefined,
+					cells: cellResults.map(cell => ({
+						...cell,
+						statusEvents: cell.statusEvents ? [...cell.statusEvents] : undefined,
+					})),
 				};
-				if (notice) details.notice = notice;
-
-				return toolResult(details)
-					.content([{ type: "text", text: outputText }, ...images])
-					.truncationFromSummary(summaryForMeta, { direction: "tail" })
-					.done();
-			} finally {
-				if (!outputDumped) {
-					try {
-						await finalizeOutput();
-					} catch {}
+				if (jsonOutputs.length > 0) {
+					details.jsonOutputs = jsonOutputs;
 				}
-			}
-		})();
+				if (images.length > 0) {
+					details.images = images;
+				}
+				if (statusEvents.length > 0) {
+					details.statusEvents = statusEvents;
+				}
+				if (notice) {
+					details.notice = notice;
+				}
+				return details;
+			};
 
-		return await (session.trackEvalExecution?.(execution, sessionAbortController) ?? execution);
+			const pushUpdate = () => {
+				emitUpdate?.(tailBuffer.text(), buildUpdateDetails());
+			};
+
+			const sessionFile = session.getSessionFile?.() ?? undefined;
+			const kernelOwnerId = session.getEvalKernelOwnerId?.() ?? undefined;
+			const { path: artifactPath, id: artifactId } = (await session.allocateOutputArtifact?.("eval")) ?? {};
+			session.assertEvalExecutionAllowed?.();
+			outputSink = new OutputSink({
+				artifactPath,
+				artifactId,
+				headBytes: resolveOutputSinkHeadBytes(session.settings),
+				maxColumns: resolveOutputMaxColumns(session.settings),
+				onChunk: chunk => {
+					appendTail(chunk);
+					if (activeLiveCell) {
+						activeLiveCell.buf.append(chunk);
+						activeLiveCell.result.output = activeLiveCell.buf.text();
+					}
+					pushUpdate();
+				},
+			});
+			const sessionId = session.getEvalSessionId?.() ?? defaultEvalSessionId(session);
+
+			for (let i = 0; i < cells.length; i++) {
+				const cell = cells[i];
+				const backend = cell.resolved.backend;
+				// The per-cell `timeout` is a budget on the cell runtime's *own*
+				// work. Host-side `agent()`/`parallel()`/`completion()` bridge calls suspend
+				// that budget entirely and restart a fresh timeout window when control
+				// returns to the active backend runtime. Compute, stdout, `log()`/`phase()`, and
+				// ordinary tool calls all count against the budget. The watchdog drives
+				// `combinedSignal`; we pass no wall-clock deadline downstream so the
+				// backends never arm a competing fixed timer.
+				const idleTimeoutMs =
+					cell.timeoutMs === 0
+						? undefined
+						: clampTimeout("eval", cell.timeoutMs / 1000, session.settings.get("tools.maxTimeout")) * 1000;
+				const idle = idleTimeoutMs === undefined ? undefined : new IdleTimeout(idleTimeoutMs);
+				const combinedSignal =
+					signal && idle
+						? AbortSignal.any([signal, idle.signal, sessionAbortController.signal])
+						: signal
+							? AbortSignal.any([signal, sessionAbortController.signal])
+							: idle
+								? AbortSignal.any([idle.signal, sessionAbortController.signal])
+								: sessionAbortController.signal;
+
+				const cellResult = cellResults[i];
+				cellResult.status = "running";
+				cellResult.output = "";
+				cellResult.statusEvents = undefined;
+				cellResult.exitCode = undefined;
+				cellResult.durationMs = undefined;
+				activeLiveCell = { result: cellResult, buf: new TailBuffer(DEFAULT_MAX_BYTES * 2) };
+				pushUpdate();
+
+				const startTime = Date.now();
+				let result: ExecutorBackendResult;
+				try {
+					result = await backend.execute(cell.code, {
+						cwd: session.cwd,
+						sessionId,
+						sessionFile: sessionFile ?? undefined,
+						kernelOwnerId,
+						signal: combinedSignal,
+						session,
+						idleTimeoutMs,
+						reset: cell.reset,
+						onChunk: chunk => {
+							outputSink!.push(chunk);
+						},
+						onStatus: event => {
+							if (event.op === EVAL_TIMEOUT_PAUSE_OP) {
+								idle?.pause();
+								return;
+							}
+							if (event.op === EVAL_TIMEOUT_RESUME_OP) {
+								idle?.resume();
+								return;
+							}
+							cellResult.statusEvents ??= [];
+							upsertStatusEvent(cellResult.statusEvents, event);
+							pushUpdate();
+						},
+					});
+				} finally {
+					idle?.dispose();
+					activeLiveCell = undefined;
+				}
+				const durationMs = Date.now() - startTime;
+
+				const cellStatusEvents: EvalStatusEvent[] = [];
+				const cellDisplayOutputs: EvalDisplayOutput[] = [];
+				const cellImageNotes: string[] = [];
+				let cellHasMarkdown = false;
+				for (const output of result.displayOutputs) {
+					if (output.type === "json") {
+						jsonOutputs.push(output.data);
+						cellDisplayOutputs.push(output);
+					}
+					if (output.type === "image") {
+						const resized = await resizeImage(
+							{
+								type: "image",
+								data: output.data,
+								mimeType: output.mimeType,
+							},
+							{ excludeWebP },
+						);
+						const image: ImageContent = {
+							type: "image",
+							data: resized.data,
+							mimeType: resized.mimeType,
+						};
+						images.push(image);
+						cellDisplayOutputs.push({
+							type: "image",
+							data: image.data,
+							mimeType: image.mimeType,
+						});
+						const dimensionNote = formatDimensionNote(resized);
+						if (dimensionNote) {
+							cellImageNotes.push(`display image ${cellImageNotes.length + 1}: ${dimensionNote}`);
+						}
+					}
+					if (output.type === "status") {
+						upsertStatusEvent(statusEvents, output.event);
+						upsertStatusEvent(cellStatusEvents, output.event);
+					}
+					if (output.type === "markdown") {
+						cellHasMarkdown = true;
+					}
+				}
+
+				const stdoutTrimmed = result.output.trim();
+				const imageText = cellImageNotes.join("\n");
+				const displayText = formatDisplayOutputsForText(cellDisplayOutputs);
+				const visibleDisplayText =
+					displayText && imageText ? `${displayText}\n\n${imageText}` : displayText || imageText;
+				const cellOutput =
+					stdoutTrimmed && visibleDisplayText
+						? `${stdoutTrimmed}\n\n${visibleDisplayText}`
+						: stdoutTrimmed || visibleDisplayText;
+				cellResult.output = cellOutput;
+				cellResult.exitCode = result.exitCode;
+				cellResult.durationMs = durationMs;
+				cellResult.statusEvents = cellStatusEvents.length > 0 ? cellStatusEvents : undefined;
+				cellResult.hasMarkdown = cellHasMarkdown || undefined;
+
+				if (cellOutput) {
+					cellOutputs.push(cellOutput);
+					appendTail(cellOutput);
+				}
+
+				if (result.cancelled) {
+					cellResult.status = "error";
+					pushUpdate();
+					const errorMsg = result.output || "Command aborted";
+					const combinedOutput = cellOutputs.join("\n\n");
+					const outputText = combinedOutput || errorMsg;
+
+					const summaryForMeta = await summarizeFinal(combinedOutput, finalizeOutput);
+					const details: EvalToolDetails = {
+						language: languages[0],
+						languages,
+						cells: cellResults,
+						jsonOutputs: jsonOutputs.length > 0 ? jsonOutputs : undefined,
+						statusEvents: statusEvents.length > 0 ? statusEvents : undefined,
+						isError: true,
+					};
+					if (notice) details.notice = notice;
+
+					return toolResult(details)
+						.content([{ type: "text", text: outputText }, ...images])
+						.truncationFromSummary(summaryForMeta, { direction: "tail" })
+						.done();
+				}
+
+				if (result.exitCode !== 0 && result.exitCode !== undefined) {
+					cellResult.status = "error";
+					pushUpdate();
+					const combinedOutput = cellOutputs.join("\n\n");
+					const outputText = combinedOutput
+						? `${combinedOutput}\n\nCommand exited with code ${result.exitCode}`
+						: `Command exited with code ${result.exitCode}`;
+
+					const summaryForMeta = await summarizeFinal(combinedOutput, finalizeOutput);
+					const details: EvalToolDetails = {
+						language: languages[0],
+						languages,
+						cells: cellResults,
+						jsonOutputs: jsonOutputs.length > 0 ? jsonOutputs : undefined,
+						statusEvents: statusEvents.length > 0 ? statusEvents : undefined,
+						isError: true,
+					};
+					if (notice) details.notice = notice;
+
+					return toolResult(details)
+						.content([{ type: "text", text: outputText }, ...images])
+						.truncationFromSummary(summaryForMeta, { direction: "tail" })
+						.done();
+				}
+
+				cellResult.status = "complete";
+				pushUpdate();
+			}
+
+			const combinedOutput = cellOutputs.join("\n\n");
+			const hasImages = images.length > 0;
+			const outputText =
+				combinedOutput ||
+				(hasImages
+					? `(displayed ${images.length} image${images.length === 1 ? "" : "s"}; no text output)`
+					: "(no output)");
+			const summaryForMeta = await summarizeFinal(combinedOutput, finalizeOutput);
+
+			const details: EvalToolDetails = {
+				language: languages[0],
+				languages,
+				cells: cellResults,
+				jsonOutputs: jsonOutputs.length > 0 ? jsonOutputs : undefined,
+				statusEvents: statusEvents.length > 0 ? statusEvents : undefined,
+			};
+			if (notice) details.notice = notice;
+
+			return toolResult(details)
+				.content([{ type: "text", text: outputText }, ...images])
+				.truncationFromSummary(summaryForMeta, { direction: "tail" })
+				.done();
+		} finally {
+			if (!outputDumped) {
+				try {
+					await finalizeOutput();
+				} catch {}
+			}
+		}
 	}
 }
 

packages/coding-agent/src/tools/hub/jobs.ts

@@ -7,7 +7,7 @@
 import type { AgentToolResult } from "@oh-my-pi/pi-agent-core";
 import type { Component } from "@oh-my-pi/pi-tui";
 import { Text } from "@oh-my-pi/pi-tui";
-import type { AsyncJob, AsyncJobManager } from "../../async";
+import type { AsyncJob, AsyncJobManager, AsyncJobType } from "../../async";
 import { settings } from "../../config/settings";
 import type { RenderResultOptions } from "../../extensibility/custom-tools/types";
 import { shimmerEnabled, shimmerText } from "../../modes/theme/shimmer";
@@ -145,7 +145,7 @@ function describeAgents(agents: AgentActivitySnapshot[]): string[] {
 
 interface TrackedJobLike {
 	id: string;
-	type: "bash" | "task";
+	type: AsyncJobType;
 	status: string;
 	label: string;
 	startTime: number;

packages/coding-agent/src/tools/hub/types.ts

@@ -5,6 +5,7 @@
  */
 
 import type { AgentToolResult } from "@oh-my-pi/pi-agent-core";
+import type { AsyncJobType } from "../../async";
 import type { IrcDeliveryReceipt, IrcMessage } from "../../irc/bus";
 import type { LaunchParams, LaunchToolDetails } from "./launch";
 
@@ -42,7 +43,7 @@ export interface HubPeerInfo {
 /** Background-job row surfaced by `wait`/`cancel`/`jobs` results. */
 export interface JobSnapshot {
 	id: string;
-	type: "bash" | "task";
+	type: AsyncJobType;
 	status: "running" | "completed" | "failed" | "cancelled";
 	label: string;
 	durationMs: number;

packages/coding-agent/test/async-yield-queue.test.ts

@@ -5,7 +5,7 @@ import {
 	ASIDE_MESSAGE_DISCARD,
 	type CommittableAsideMessage,
 } from "@oh-my-pi/pi-agent-core";
-import { type AsyncJob, AsyncJobManager } from "@oh-my-pi/pi-coding-agent/async";
+import { type AsyncJob, AsyncJobManager, type AsyncJobType } from "@oh-my-pi/pi-coding-agent/async";
 import type { CustomMessage } from "@oh-my-pi/pi-coding-agent/session/messages";
 import { YieldQueue } from "@oh-my-pi/pi-coding-agent/session/yield-queue";
 import type { ToolSession } from "@oh-my-pi/pi-coding-agent/tools";
@@ -21,7 +21,7 @@ type AsyncEntry = {
 type AsyncDetails = {
 	jobs: Array<{
 		jobId: string;
-		type?: "bash" | "task";
+		type?: AsyncJobType;
 		label?: string;
 		durationMs?: number;
 	}>;

packages/coding-agent/test/tools/eval-auto-background.test.ts

@@ -0,0 +1,215 @@
+import { afterEach, describe, expect, it, vi } from "bun:test";
+import type { AgentToolContext } from "@oh-my-pi/pi-agent-core";
+import { AsyncJobManager } from "@oh-my-pi/pi-coding-agent/async";
+import { Settings } from "@oh-my-pi/pi-coding-agent/config/settings";
+import * as evalIndex from "@oh-my-pi/pi-coding-agent/eval";
+import { SessionManager } from "@oh-my-pi/pi-coding-agent/session/session-manager";
+import type { ToolSession } from "@oh-my-pi/pi-coding-agent/tools";
+import { EvalTool } from "@oh-my-pi/pi-coding-agent/tools/eval";
+
+function makeSession(settings: Settings, asyncJobManager: AsyncJobManager): ToolSession {
+	return {
+		cwd: "/tmp/eval-test",
+		hasUI: false,
+		getSessionFile: () => null,
+		getSessionSpawns: () => null,
+		settings,
+		asyncJobManager,
+	};
+}
+
+function baseResult(overrides: Record<string, unknown> = {}) {
+	return {
+		output: "",
+		exitCode: 0,
+		cancelled: false,
+		truncated: false,
+		artifactId: undefined,
+		totalLines: 0,
+		totalBytes: 0,
+		outputLines: 0,
+		outputBytes: 0,
+		displayOutputs: [] as unknown[],
+		...overrides,
+	};
+}
+
+/**
+ * Mock the JS backend with a cell that streams one chunk immediately and then
+ * blocks until the returned `release()` gate opens — so backgrounding is decided
+ * by the tool's own threshold/steer race, never by a guessed sleep.
+ */
+function mockGatedCell(finalOutput: string): { release: () => void } {
+	const gate = Promise.withResolvers<void>();
+	vi.spyOn(evalIndex.jsBackend, "execute").mockImplementation((async (
+		_code: string,
+		options: { onChunk?: (chunk: string) => void },
+	) => {
+		options.onChunk?.("start\n");
+		await gate.promise;
+		return baseResult({ output: finalOutput });
+	}) as never);
+	return { release: gate.resolve };
+}
+
+function steeringContext(steeringSignal: AbortSignal): AgentToolContext {
+	return {
+		sessionManager: SessionManager.inMemory(),
+		modelRegistry: {
+			find: () => undefined,
+			getAll: () => [],
+			getApiKey: async () => undefined,
+		} as unknown as AgentToolContext["modelRegistry"],
+		model: undefined,
+		isIdle: () => true,
+		hasQueuedMessages: () => false,
+		abort: () => {},
+		toolNames: [],
+		toolCall: {
+			batchId: "batch-1",
+			index: 0,
+			total: 1,
+			toolCalls: [{ id: "call-steer", name: "eval" }],
+			steeringSignal,
+		},
+	} as AgentToolContext;
+}
+
+/**
+ * Defends the eval auto-background contract (mirror of bash's): a cell that
+ * finishes before the threshold resolves inline with no job leftovers, a cell
+ * that outlives the threshold converts into a running async job whose result is
+ * delivered later, and a steering interrupt backgrounds the cell immediately so
+ * the queued message can inject while the kernel keeps working.
+ */
+describe("EvalTool auto-background", () => {
+	afterEach(() => {
+		vi.restoreAllMocks();
+	});
+
+	it("keeps fast cells inline and suppresses their job delivery", async () => {
+		const deliveries: string[] = [];
+		const asyncJobManager = new AsyncJobManager({
+			onJobComplete: async (_jobId, text) => {
+				deliveries.push(text);
+			},
+		});
+		vi.spyOn(evalIndex.jsBackend, "execute").mockImplementation((async () =>
+			baseResult({ output: "quick\n" })) as never);
+
+		const tool = new EvalTool(
+			makeSession(
+				Settings.isolated({
+					"eval.autoBackground.enabled": true,
+					"eval.autoBackground.thresholdMs": 2_000,
+				}),
+				asyncJobManager,
+			),
+		);
+		const result = await tool.execute("call-inline", { language: "js", code: "print('quick')" });
+
+		const text = result.content.map(c => (c.type === "text" ? c.text : "")).join("\n");
+		expect(text).toContain("quick");
+		expect(result.details?.async).toBeUndefined();
+		expect(result.details?.cells?.[0]?.status).toBe("complete");
+		await asyncJobManager.drainDeliveries({ timeoutMs: 1 });
+		expect(deliveries).toEqual([]);
+		await asyncJobManager.dispose();
+	});
+
+	it("backgrounds a cell that outlives the threshold and delivers its result", async () => {
+		const deliveries: Array<{ jobId: string; text: string }> = [];
+		const updates: string[] = [];
+		const asyncJobManager = new AsyncJobManager({
+			onJobComplete: async (jobId, text) => {
+				deliveries.push({ jobId, text });
+			},
+		});
+		const cell = mockGatedCell("start\ndone\n");
+
+		const tool = new EvalTool(
+			makeSession(
+				Settings.isolated({
+					"eval.autoBackground.enabled": true,
+					"eval.autoBackground.thresholdMs": 10,
+				}),
+				asyncJobManager,
+			),
+		);
+		// The gated cell cannot finish on its own, so execute() returning proves
+		// the threshold path backgrounded it.
+		const result = await tool.execute(
+			"call-background",
+			{ language: "js", code: "print('start'); await work(); print('done')" },
+			undefined,
+			update => {
+				updates.push(update.content?.find(block => block.type === "text")?.text ?? "");
+			},
+		);
+
+		expect(result.details?.async?.state).toBe("running");
+		expect(result.details?.async?.type).toBe("eval");
+		const text = result.content.map(c => (c.type === "text" ? c.text : "")).join("\n");
+		expect(text).toContain("Backgrounded as job");
+		// The snapshot keeps the running cell (with its streamed tail) for the transcript.
+		expect(result.details?.cells?.[0]?.status).toBe("running");
+
+		const jobId = result.details?.async?.jobId;
+		if (!jobId) {
+			throw new Error("expected an auto-backgrounded job id");
+		}
+		const runningJob = asyncJobManager.getJob(jobId);
+		expect(runningJob?.status).toBe("running");
+		const updatesAtBackground = updates.slice();
+		cell.release();
+		await runningJob?.promise;
+		await asyncJobManager.drainDeliveries({ timeoutMs: 1 });
+		expect(deliveries).toHaveLength(1);
+		expect(deliveries[0]?.jobId).toBe(jobId);
+		expect(deliveries[0]?.text).toContain("done");
+		// Tool-call updates stop once the cell is backgrounded.
+		expect(updates).toEqual(updatesAtBackground);
+		await asyncJobManager.dispose();
+	});
+
+	it("backgrounds a running cell when the steering signal fires mid-wait", async () => {
+		const asyncJobManager = new AsyncJobManager({});
+		const cell = mockGatedCell("steered\n");
+
+		const tool = new EvalTool(
+			makeSession(
+				Settings.isolated({
+					"eval.autoBackground.enabled": true,
+					// High threshold: only the steering signal can background this.
+					"eval.autoBackground.thresholdMs": 60_000,
+				}),
+				asyncJobManager,
+			),
+		);
+		const steering = new AbortController();
+		steering.abort();
+		const result = await tool.execute(
+			"call-steer",
+			{ language: "js", code: "await work()" },
+			undefined,
+			undefined,
+			steeringContext(steering.signal),
+		);
+
+		// The steer backgrounds the cell instead of killing it: the call returns a
+		// running job and the cell finishes on its own.
+		expect(result.details?.async?.state).toBe("running");
+		const text = result.content.map(c => (c.type === "text" ? c.text : "")).join("\n");
+		expect(text).toContain("Backgrounded early to handle an incoming message");
+		const jobId = result.details?.async?.jobId;
+		if (!jobId) {
+			throw new Error("expected a steer-backgrounded job id");
+		}
+		const job = asyncJobManager.getJob(jobId);
+		expect(job?.status).toBe("running");
+		cell.release();
+		await job?.promise;
+		expect(asyncJobManager.getJob(jobId)?.status).toBe("completed");
+		await asyncJobManager.dispose();
+	});
+});