diff --git a/adapter/strings/omp-spt.mjs b/adapter/strings/omp-spt.mjs
index e6ef979..8c8fc7d 100644
--- a/adapter/strings/omp-spt.mjs
+++ b/adapter/strings/omp-spt.mjs
@@ -11,190 +11,1138 @@ export function decodeBody(body) {
 		.replaceAll("&", "&");
 }
 
-function attribute(tag, name) {
-	const marker = ` ${name}="`;
-	const start = tag.indexOf(marker);
-	if (start < 0) return undefined;
-	const valueStart = start + marker.length;
-	const end = tag.indexOf('"', valueStart);
-	return end < 0 ? undefined : tag.slice(valueStart, end);
+function protocolError(message) {
+	const error = new Error(`invalid spt EVENT stream: ${message}`);
+	error.code = "SPT_PROTOCOL_ERROR";
+	return error;
 }
 
-export function drainEvents(raw) {
+function parseEventTag(tag) {
+	if (!tag.startsWith("<EVENT")) return { error: protocolError("invalid opening tag") };
+	let cursor = "<EVENT".length;
+	const attributes = Object.create(null);
+	while (cursor < tag.length) {
+		if (!/\s/.test(tag[cursor])) {
+			return { error: protocolError("malformed EVENT attributes") };
+		}
+		while (cursor < tag.length && /\s/.test(tag[cursor])) cursor += 1;
+		if (cursor === tag.length) break;
+		const match = /^([A-Za-z_:][A-Za-z0-9_.:-]*)="([^"<>]*)"/.exec(tag.slice(cursor));
+		if (!match) return { error: protocolError("malformed EVENT attributes") };
+		const [, name, value] = match;
+		if (Object.hasOwn(attributes, name)) {
+			return { error: protocolError(`duplicate EVENT ${name} attribute`) };
+		}
+		attributes[name] = value;
+		cursor += match[0].length;
+	}
+	if (!attributes.type) return { error: protocolError("missing EVENT type attribute") };
+	if (attributes.type === "msg" && !attributes.from) {
+		return { error: protocolError("missing EVENT from attribute") };
+	}
+	return { attributes };
+}
+
+export function drainEvents(raw, options = {}) {
+	const maxEvents = options.maxEvents ?? Number.POSITIVE_INFINITY;
+	const maxFrameChars = options.maxFrameChars ?? DEFAULT_LISTENER_BUFFER_LIMIT;
 	const events = [];
 	let cursor = 0;
 	while (true) {
 		const start = raw.indexOf("<EVENT", cursor);
 		if (start < 0) return { events, rest: raw.slice(cursor) };
 		const openEnd = raw.indexOf(">", start);
-		if (openEnd < 0) return { events, rest: raw.slice(start) };
+		if (openEnd < 0) {
+			if (raw.length - start > maxFrameChars) {
+				return {
+					error: protocolError(`EVENT frame exceeded ${maxFrameChars} characters`),
+					events,
+					rest: raw.slice(start),
+				};
+			}
+			return { events, rest: raw.slice(start) };
+		}
+		if (openEnd + 1 - start > maxFrameChars) {
+			return {
+				error: protocolError(`EVENT frame exceeded ${maxFrameChars} characters`),
+				events,
+				rest: raw.slice(start),
+			};
+		}
 		const close = raw.indexOf("</EVENT>", openEnd + 1);
-		if (close < 0) return { events, rest: raw.slice(start) };
-		const tag = raw.slice(start, openEnd);
-		if (attribute(tag, "type") === "msg") {
+		const nested = raw.indexOf("<EVENT", openEnd + 1);
+		if (nested >= 0 && (close < 0 || nested < close)) {
+			return {
+				error: protocolError("nested EVENT before closing the current frame"),
+				events,
+				rest: raw.slice(start),
+			};
+		}
+		if (close < 0) {
+			if (raw.length - start > maxFrameChars) {
+				return {
+					error: protocolError(`EVENT frame exceeded ${maxFrameChars} characters`),
+					events,
+					rest: raw.slice(start),
+				};
+			}
+			return { events, rest: raw.slice(start) };
+		}
+		const end = close + "</EVENT>".length;
+		if (end - start > maxFrameChars) {
+			return {
+				error: protocolError(`EVENT frame exceeded ${maxFrameChars} characters`),
+				events,
+				rest: raw.slice(start),
+			};
+		}
+		const parsed = parseEventTag(raw.slice(start, openEnd));
+		if (parsed.error) return { error: parsed.error, events, rest: raw.slice(start) };
+		if (parsed.attributes.type === "msg") {
 			events.push({
-				from: attribute(tag, "from"),
+				from: parsed.attributes.from,
 				body: decodeBody(raw.slice(openEnd + 1, close)),
+				envelope: raw.slice(start, end),
 			});
 		}
-		cursor = close + "</EVENT>".length;
+		cursor = end;
+		if (events.length >= maxEvents) return { events, rest: raw.slice(cursor) };
 	}
 }
 
-export function extractReply(messages) {
-	const assistant = [...(messages ?? [])].reverse().find((message) => message?.role === "assistant");
-	if (!assistant) return "";
-	if (typeof assistant.content === "string") return assistant.content;
-	return (assistant.content ?? [])
+function messageText(message) {
+	if (typeof message?.content === "string") return message.content;
+	return (message?.content ?? [])
 		.filter((part) => part?.type === "text" && typeof part.text === "string")
 		.map((part) => part.text)
 		.join("");
 }
 
+export function extractReply(messages, afterUserMessage) {
+	const allMessages = messages ?? [];
+	let start = 0;
+	if (afterUserMessage !== undefined) {
+		const userIndex = allMessages.findLastIndex((message) => {
+			if (message?.role !== "user") return false;
+			const text = messageText(message);
+			return text === afterUserMessage || text.startsWith(`${afterUserMessage}\n\n<EVENT`);
+		});
+		if (userIndex < 0) return "";
+		start = userIndex + 1;
+	}
+	const assistant = allMessages
+		.slice(start)
+		.reverse()
+		.find((message) => message?.role === "assistant");
+	return assistant ? messageText(assistant) : "";
+}
+
 function firstLine(text) {
 	return text.split(/\r?\n/).find((line) => line.trim()) ?? "";
 }
 
-function runSpt(args, input) {
+function errorSummary(error) {
+	const detail = error instanceof Error ? error.message : String(error);
+	return firstLine(detail).trim() || "unknown error";
+}
+
+function failureMessage(reason, error) {
+	const detail = error === undefined ? "" : `: ${errorSummary(error)}`;
+	return `[omp-spt] ${reason}${detail}`;
+}
+
+function senderStub(sender) {
+	const escaped = sender
+		.replaceAll("&", "&amp;")
+		.replaceAll('"', "&quot;")
+		.replaceAll("<", "&lt;")
+		.replaceAll(">", "&gt;");
+	return `<msg from="${escaped}"/>`;
+}
+
+function injectEnvelope(messages, item) {
+	const index = messages.findLastIndex(
+		(message) => message?.role === "user" && messageText(message) === item.stub,
+	);
+	if (index < 0) return messages;
+	const original = messages[index];
+	const content =
+		typeof original.content === "string"
+			? `${original.content}\n\n${item.envelope}`
+			: [...(original.content ?? []), { type: "text", text: `\n\n${item.envelope}` }];
+	const injected = [...messages];
+	injected[index] = { ...original, content };
+	return injected;
+}
+
+const DEFAULT_COMMAND_TIMEOUT_MS = 15_000;
+const DEFAULT_KILL_GRACE_MS = 100;
+const DEFAULT_KILL_FORCE_MS = 100;
+const DEFAULT_LISTENER_BUFFER_LIMIT = 256 * 1024;
+const DEFAULT_ACCEPTED_QUEUE_LIMIT = 128;
+const DEFAULT_ACCEPTED_BYTES_LIMIT = 1024 * 1024;
+const DEFAULT_SHUTDOWN_BUDGET_MS = 1_800;
+const DEFAULT_SHUTDOWN_COMMAND_TIMEOUT_MS = 300;
+
+function childExited(child) {
+	return (
+		(child.exitCode !== undefined && child.exitCode !== null) ||
+		(child.signalCode !== undefined && child.signalCode !== null)
+	);
+}
+
+function waitForChildExit(child, timeoutMs, setTimer, clearTimer) {
+	if (childExited(child)) return Promise.resolve(true);
+	return new Promise((resolve) => {
+		let timer;
+		let finished = false;
+		const finish = (exited) => {
+			if (finished) return;
+			finished = true;
+			if (timer !== undefined) clearTimer(timer);
+			child.off("close", onClose);
+			resolve(exited);
+		};
+		const onClose = () => finish(true);
+		child.once("close", onClose);
+		timer = setTimer(() => finish(false), timeoutMs);
+		timer?.unref?.();
+		if (childExited(child)) finish(true);
+	});
+}
+
+async function terminateChild(child, label, options) {
+	const { clearTimer, forceMs, graceMs, setTimer } = options;
+	if (childExited(child)) return;
+
+	const gracefulExit = waitForChildExit(child, graceMs, setTimer, clearTimer);
+	let killError;
+	try {
+		child.kill();
+	} catch (error) {
+		killError = error;
+	}
+	if (await gracefulExit) return;
+
+	const forcedExit = waitForChildExit(child, forceMs, setTimer, clearTimer);
+	try {
+		child.kill("SIGKILL");
+	} catch (error) {
+		killError ??= error;
+	}
+	if (await forcedExit) return;
+
+	child.stdin?.destroy?.();
+	child.stdout?.destroy?.();
+	child.stderr?.destroy?.();
+	child.unref?.();
+	const detail = killError === undefined ? "" : `: ${errorSummary(killError)}`;
+	throw new Error(`${label} did not exit after forced termination${detail}`);
+}
+
+function commandLabel(args) {
+	const command = args[0] === "api" ? args[3] : args[0];
+	return `spt ${command ?? "command"}`;
+}
+
+export function runSpt(args, input, overrides = {}) {
+	const spawnProcess = overrides.spawnProcess ?? spawn;
+	const setTimer = overrides.setTimeout ?? globalThis.setTimeout;
+	const clearTimer = overrides.clearTimeout ?? globalThis.clearTimeout;
+	const timeoutMs = overrides.commandTimeoutMs ?? DEFAULT_COMMAND_TIMEOUT_MS;
+	const graceMs = overrides.killGraceMs ?? DEFAULT_KILL_GRACE_MS;
+	const forceMs = overrides.killForceMs ?? DEFAULT_KILL_FORCE_MS;
+	const env = overrides.env ?? process.env;
+	const label = commandLabel(args);
+	const signal = overrides.signal;
+	if (signal?.aborted) {
+		return Promise.reject(
+			signal.reason instanceof Error ? signal.reason : new Error(`${label} aborted`),
+		);
+	}
+
 	return new Promise((resolve, reject) => {
-		const child = spawn(process.env.OMP_SPT_SPT_BIN || "spt", args, {
-			stdio: [input === undefined ? "ignore" : "pipe", "pipe", "pipe"],
-			windowsHide: true,
-		});
+		let child;
+		try {
+			child = spawnProcess(env.OMP_SPT_SPT_BIN || "spt", args, {
+				stdio: [input === undefined ? "ignore" : "pipe", "pipe", "pipe"],
+				windowsHide: true,
+			});
+		} catch (error) {
+			reject(error);
+			return;
+		}
+
 		let output = "";
+		let settled = false;
+		let terminating = false;
+		let stdinFinished = input === undefined;
+		let timeoutTimer;
+		const onAbort = () => {
+			const error =
+				signal.reason instanceof Error ? signal.reason : new Error(`${label} aborted`);
+			void terminateAndReject(error);
+		};
+		const onStdout = (chunk) => (output += chunk);
+		const onStderr = (chunk) => (output += chunk);
+		const cleanup = () => {
+			if (timeoutTimer !== undefined) clearTimer(timeoutTimer);
+			child.stdout.off("data", onStdout);
+			child.stderr.off("data", onStderr);
+			child.stdin?.off("finish", onStdinFinish);
+			child.off("close", onClose);
+			signal?.removeEventListener("abort", onAbort);
+		};
+		const settle = (error) => {
+			if (settled) return;
+			settled = true;
+			cleanup();
+			if (error === undefined) resolve(output.trim());
+			else reject(error);
+		};
+		const terminateAndReject = async (error) => {
+			if (settled || terminating) return;
+			terminating = true;
+			if (timeoutTimer !== undefined) {
+				clearTimer(timeoutTimer);
+				timeoutTimer = undefined;
+			}
+			try {
+				await terminateChild(child, label, {
+					clearTimer,
+					forceMs,
+					graceMs,
+					setTimer,
+				});
+			} catch (terminationError) {
+				error = new Error(`${errorSummary(error)}; ${errorSummary(terminationError)}`, {
+					cause: error,
+				});
+			}
+			settle(error);
+		};
+		const onStdinError = (error) => {
+			void terminateAndReject(error);
+		};
+		const onStdinFinish = () => {
+			stdinFinished = true;
+		};
+		const onClose = (code, signal) => {
+			if (terminating || settled) return;
+			if (code === 0 && stdinFinished) {
+				settle();
+				return;
+			}
+			const status = signal ? `signal ${signal}` : `exit ${code}`;
+			const detail = firstLine(output);
+			const suffix = detail ? `: ${detail}` : "";
+			if (code === 0) {
+				void terminateAndReject(new Error(`${label} exited before stdin completed${suffix}`));
+			} else {
+				void terminateAndReject(new Error(`${label} ${status}${suffix}`));
+			}
+		};
+
 		child.stdout.setEncoding("utf8");
 		child.stderr.setEncoding("utf8");
-		child.stdout.on("data", (chunk) => (output += chunk));
-		child.stderr.on("data", (chunk) => (output += chunk));
-		child.on("error", reject);
-		child.on("close", (code) => {
-			if (code === 0) resolve(output.trim());
-			else reject(new Error(`spt exited ${code}: ${firstLine(output)}`));
-		});
-		if (input !== undefined) child.stdin.end(input);
+		child.stdout.on("data", onStdout);
+		child.stderr.on("data", onStderr);
+		child.on("error", onStdinError);
+		child.on("close", onClose);
+		if (input !== undefined) {
+			child.stdin.on("error", onStdinError);
+			child.stdin.once("finish", onStdinFinish);
+		}
+		signal?.addEventListener("abort", onAbort, { once: true });
+		if (signal?.aborted) {
+			onAbort();
+			return;
+		}
+		timeoutTimer = setTimer(() => {
+			timeoutTimer = undefined;
+			void terminateAndReject(new Error(`${label} timed out after ${timeoutMs}ms`));
+		}, timeoutMs);
+		timeoutTimer?.unref?.();
+		if (input !== undefined) {
+			try {
+				child.stdin.end(input);
+			} catch (error) {
+				void terminateAndReject(error);
+			}
+		}
 	});
 }
 
-// [impl->REQ-OMP-NATIVE-TUI]
-export default function ompSpt(pi) {
-	const id = process.env.SPT_ENDPOINT_ID?.trim();
-	if (!id) return;
-
-	let sid;
-	let token;
-	let listener;
-	let listenerBuffer = "";
-	let agentActive = false;
-	let current;
-	let stopping = false;
-	let ui;
-	const queue = [];
-
-	const logError = (message, error) => {
-		pi.logger.error(message, { error: String(error) });
-		ui?.notify(`${message}: ${error}`, "error");
-	};
+export function createOmpSpt(overrides = {}) {
+	const spawnProcess = overrides.spawnProcess ?? spawn;
+	const setTimer = overrides.setTimeout ?? globalThis.setTimeout;
+	const clearTimer = overrides.clearTimeout ?? globalThis.clearTimeout;
+	const env = overrides.env ?? process.env;
+	const killGraceMs = overrides.killGraceMs ?? DEFAULT_KILL_GRACE_MS;
+	const killForceMs = overrides.killForceMs ?? DEFAULT_KILL_FORCE_MS;
+	const customRunSptCommand = overrides.runSptCommand;
+	const commandTimeoutMs = overrides.commandTimeoutMs ?? DEFAULT_COMMAND_TIMEOUT_MS;
+	const runSptCommand =
+		customRunSptCommand ??
+		((args, input, options = {}) =>
+			runSpt(args, input, {
+				clearTimeout: clearTimer,
+				commandTimeoutMs: options.timeoutMs ?? commandTimeoutMs,
+				env,
+				killForceMs,
+				killGraceMs,
+				setTimeout: setTimer,
+				signal: options.signal,
+				spawnProcess,
+			}));
+	const shutdownBudgetMs =
+		overrides.shutdownBudgetMs ?? DEFAULT_SHUTDOWN_BUDGET_MS;
+	const shutdownCommandTimeoutMs =
+		overrides.shutdownCommandTimeoutMs ?? DEFAULT_SHUTDOWN_COMMAND_TIMEOUT_MS;
+	const listenerBufferLimit =
+		overrides.listenerBufferLimit ?? DEFAULT_LISTENER_BUFFER_LIMIT;
+	const acceptedQueueLimit =
+		overrides.acceptedQueueLimit ?? DEFAULT_ACCEPTED_QUEUE_LIMIT;
+	const acceptedBytesLimit =
+		overrides.acceptedBytesLimit ?? DEFAULT_ACCEPTED_BYTES_LIMIT;
+	const restartDelaysMs = [...(overrides.restartDelaysMs ?? [250, 1000, 4000])];
+	const outcomeRetryDelaysMs = [
+		...(overrides.outcomeRetryDelaysMs ?? [250, 1000, 4000]),
+	];
+	const sessionEndRetryDelaysMs = [
+		...(overrides.sessionEndRetryDelaysMs ?? [250, 1000]),
+	];
+	const listenerStableMs =
+		overrides.listenerStableMs === false ? undefined : (overrides.listenerStableMs ?? 30_000);
 
-	async function setState(state) {
-		if (!sid) return;
-		const auth = token ? ["--token", token] : ["--session-id", sid];
-		await runSpt(["api", "--adapter", ADAPTER, "state", state, id, ...auth]);
-	}
+	return function ompSpt(pi) {
+		const id = env.SPT_ENDPOINT_ID?.trim();
+		if (!id) return;
 
-	function dispatchNext() {
-		if (stopping || agentActive || current || queue.length === 0) return;
-		current = queue.shift();
-		try {
-			pi.sendUserMessage(current.body);
-		} catch (error) {
-			logError("omp-spt could not submit an inbound message", error);
+		let sid;
+		let token;
+		let listener;
+		let listenerBuffer = "";
+		let listenerRestartCount = 0;
+		let listenerStableTimer;
+		let restartTimer;
+		let dispatchTimer;
+		let bindPromise;
+		let agentActive = false;
+		let desiredState = "idle";
+		let dispatching = false;
+		let turnCompletionPromise;
+		let listenerTerminationPromise;
+		let shutdownMode = false;
+		let shutdownDeadlineExpired = false;
+		const activeCommands = new Map();
+		const retryWaiters = new Set();
+		let current;
+		let stopping = false;
+		let ui;
+		let runtimeCtx;
+		let endpointState;
+		let stateOperation = Promise.resolve();
+		let endPromise;
+		let fatalPromise;
+		let teardownPromise;
+		let acceptedBytes = 0;
+		let overflowItem;
+		const queue = [];
+
+		const logError = (message, error) => {
+			pi.logger.error(message, { error: errorSummary(error) });
+			ui?.notify(`${message}: ${errorSummary(error)}`, "error");
+		};
+
+		function runCommand(args, input, options = {}) {
+			if (shutdownDeadlineExpired) {
+				return Promise.reject(new Error("omp-spt shutdown deadline expired"));
+			}
+			const timeoutMs =
+				options.timeoutMs ?? (shutdownMode ? shutdownCommandTimeoutMs : commandTimeoutMs);
+			const controller = new AbortController();
+			activeCommands.set(controller, { args, abortTimer: undefined });
+			let command;
+			try {
+				command = Promise.resolve(
+					runSptCommand(args, input, {
+						signal: controller.signal,
+						timeoutMs,
+					}),
+				);
+			} catch (error) {
+				activeCommands.delete(controller);
+				return Promise.reject(error);
+			}
+			if (customRunSptCommand) {
+				const rawCommand = command;
+				command = new Promise((resolve, reject) => {
+					let timer;
+					let finished = false;
+					const finish = (error, value) => {
+						if (finished) return;
+						finished = true;
+						if (timer !== undefined) clearTimer(timer);
+						controller.signal.removeEventListener("abort", onAbort);
+						if (error === undefined) resolve(value);
+						else reject(error);
+					};
+					const onAbort = () =>
+						finish(
+							controller.signal.reason instanceof Error
+								? controller.signal.reason
+								: new Error(`${commandLabel(args)} aborted`),
+						);
+					controller.signal.addEventListener("abort", onAbort, { once: true });
+					if (shutdownMode) {
+						timer = setTimer(
+							() =>
+								controller.abort(
+									new Error(`${commandLabel(args)} timed out after ${timeoutMs}ms`),
+								),
+							timeoutMs,
+						);
+						timer?.unref?.();
+					}
+					rawCommand.then(
+						(value) => finish(undefined, value),
+						(error) => finish(error),
+					);
+				});
+			}
+			return command.finally(() => {
+				const active = activeCommands.get(controller);
+				if (active?.abortTimer !== undefined) clearTimer(active.abortTimer);
+				activeCommands.delete(controller);
+			});
+		}
+
+		function abortActiveCommands(reason, allowBindGrace = false) {
+			for (const [controller, active] of activeCommands) {
+				const isBind = active.args[0] === "api" && active.args[3] === "bind";
+				if (allowBindGrace && isBind && active.abortTimer === undefined) {
+					active.abortTimer = setTimer(
+						() => controller.abort(reason),
+						shutdownCommandTimeoutMs,
+					);
+					active.abortTimer?.unref?.();
+					continue;
+				}
+				controller.abort(reason);
+			}
+		}
+
+		function waitForRetry(delay) {
+			if (shutdownMode) return Promise.resolve();
+			return new Promise((resolve) => {
+				let timer;
+				const finish = () => {
+					if (timer !== undefined) clearTimer(timer);
+					retryWaiters.delete(finish);
+					resolve();
+				};
+				retryWaiters.add(finish);
+				timer = setTimer(finish, delay);
+				timer?.unref?.();
+			});
+		}
+
+		function enterShutdownMode() {
+			if (shutdownMode) return;
+			shutdownMode = true;
+			const reason = new Error("omp-spt command interrupted for bounded shutdown");
+			abortActiveCommands(reason, true);
+			for (const finish of [...retryWaiters]) finish();
+		}
+
+		function authArgs() {
+			if (!token) throw new Error("bind did not return an authentication token");
+			return ["--token", token];
+		}
+
+		function setState(state) {
+			if (!sid || !token || stopping) return Promise.resolve();
+			const operation = stateOperation.catch(() => {}).then(async () => {
+				if (endpointState === state || stopping) return;
+				await runCommand(["api", "--adapter", ADAPTER, "state", state, id, ...authArgs()]);
+				endpointState = state;
+			});
+			stateOperation = operation;
+			return operation;
+		}
+
+		async function syncDesiredState() {
+			if (!bindPromise) return;
+			await bindPromise;
+			while (!stopping && endpointState !== desiredState) {
+				await setState(desiredState);
+			}
+		}
+
+		function endSession() {
+			if (!sid || !token) return Promise.resolve();
+			if (!endPromise) {
+				const operation = (async () => {
+					await stateOperation.catch(() => {});
+					await runCommand(["api", "--adapter", ADAPTER, "session-end", id, ...authArgs()]);
+					endpointState = undefined;
+				})();
+				endPromise = operation;
+				void operation.catch(() => {
+					if (endPromise === operation) endPromise = undefined;
+				});
+			}
+			return endPromise;
+		}
+
+		async function endSessionWithRetry() {
+			for (let attempt = 0; ; attempt += 1) {
+				try {
+					await endSession();
+					return;
+				} catch (error) {
+					if (shutdownMode || attempt >= sessionEndRetryDelaysMs.length) throw error;
+					const delay = sessionEndRetryDelaysMs[attempt];
+					pi.logger.error(
+						`omp-spt session teardown failed; retrying ${
+							attempt + 1
+						}/${sessionEndRetryDelaysMs.length} in ${delay}ms`,
+						{ error: errorSummary(error) },
+					);
+					await waitForRetry(delay);
+				}
+			}
+		}
+
+		// [impl->REQ-OMP-EXTENSION-CUSTODY]
+		function settleItem(item, payload) {
+			if (!item) return Promise.resolve();
+			if (item.outcomePromise) return item.outcomePromise;
+			item.settling = true;
+			item.outcomePromise = (async () => {
+				if (!item.from) throw new Error("missing EVENT from attribute");
+				for (let attempt = 0; ; attempt += 1) {
+					try {
+						await runCommand(["send", item.from, "--from", id], payload);
+						item.settled = true;
+						return;
+					} catch (error) {
+						if (shutdownMode || attempt >= outcomeRetryDelaysMs.length) throw error;
+						const delay = outcomeRetryDelaysMs[attempt];
+						pi.logger.error(
+							`omp-spt could not send the outcome to ${item.from}; retrying ${
+								attempt + 1
+							}/${outcomeRetryDelaysMs.length} in ${delay}ms`,
+							{ error: errorSummary(error) },
+						);
+						await waitForRetry(delay);
+					}
+				}
+			})();
+			return item.outcomePromise;
+		}
+
+		function releaseItem(item) {
+			if (!item?.accounted) return;
+			item.accounted = false;
+			acceptedBytes -= item.acceptedBytes;
+		}
+
+		function beginListenerTermination(child, label) {
+			if (listenerTerminationPromise) return listenerTerminationPromise;
+			const operation = (async () => {
+				try {
+					await terminateChild(child, label, {
+						clearTimer,
+						forceMs: killForceMs,
+						graceMs: killGraceMs,
+						setTimer,
+					});
+				} catch (error) {
+					pi.logger.error("omp-spt could not reap the listener", {
+						error: errorSummary(error),
+					});
+				}
+			})();
+			listenerTerminationPromise = operation;
+			void operation.then(() => {
+				if (listenerTerminationPromise === operation) listenerTerminationPromise = undefined;
+			});
+			return operation;
+		}
+
+		async function stopResources() {
+			if (dispatchTimer !== undefined) {
+				clearTimer(dispatchTimer);
+				dispatchTimer = undefined;
+			}
+			if (restartTimer !== undefined) {
+				clearTimer(restartTimer);
+				restartTimer = undefined;
+			}
+			if (listenerStableTimer !== undefined) {
+				clearTimer(listenerStableTimer);
+				listenerStableTimer = undefined;
+			}
+			const child = listener;
+			listener = undefined;
+			listenerBuffer = "";
+			if (child) {
+				await beginListenerTermination(child, "spt ready listener");
+			} else {
+				await listenerTerminationPromise;
+			}
+		}
+
+		async function settlePendingItem(item, reason) {
+			try {
+				if (item.outcomePromise && !item.settled) {
+					let existingError;
+					try {
+						await item.outcomePromise;
+					} catch (error) {
+						existingError = error;
+					}
+					if (item.settled) return;
+					if (existingError && !shutdownMode) {
+						logError(
+							`omp-spt could not return custody to ${item.from ?? "unknown"}`,
+							existingError,
+						);
+						return;
+					}
+					item.outcomePromise = undefined;
+					item.settling = false;
+				}
+				try {
+					await settleItem(item, failureMessage(reason));
+				} catch (error) {
+					logError(`omp-spt could not return custody to ${item.from ?? "unknown"}`, error);
+				}
+			} finally {
+				releaseItem(item);
+			}
+		}
+
+		async function failPending(reason) {
+			const pending = current ? [current, ...queue] : [...queue];
+			if (overflowItem) pending.push(overflowItem);
 			current = undefined;
-			setTimeout(dispatchNext, 0);
+			queue.length = 0;
+			overflowItem = undefined;
+			for (let index = 0; index < pending.length; index += 1) {
+				if (shutdownMode) {
+					await Promise.all(
+						pending.slice(index).map((item) => settlePendingItem(item, reason)),
+					);
+					return;
+				}
+				await settlePendingItem(pending[index], reason);
+			}
 		}
-	}
 
-	function startListener() {
-		const args = ["ready", id];
-		if (process.env.OMP_SPT_SUBNET) args.push("--subnet", process.env.OMP_SPT_SUBNET);
-		listener = spawn(process.env.OMP_SPT_SPT_BIN || "spt", args, {
-			stdio: ["ignore", "pipe", "pipe"],
-			windowsHide: true,
-		});
-		listener.stdout.setEncoding("utf8");
-		listener.stderr.setEncoding("utf8");
-		listener.stdout.on("data", (chunk) => {
-			listenerBuffer += chunk;
-			const drained = drainEvents(listenerBuffer);
-			listenerBuffer = drained.rest;
-			for (const event of drained.events) queue.push(event);
-			dispatchNext();
-		});
-		listener.stderr.on("data", (chunk) => pi.logger.debug("omp-spt listener", { output: chunk.trim() }));
-		listener.on("error", (error) => logError("omp-spt listener failed", error));
-		listener.on("close", (code) => {
+		function teardownSession(pendingReason) {
+			if (!teardownPromise) {
+				stopping = true;
+				const operation = (async () => {
+					await stopResources();
+					await failPending(pendingReason);
+					await bindPromise?.catch(() => {});
+					await endSessionWithRetry();
+				})();
+				teardownPromise = operation;
+				void operation.catch(() => {
+					if (teardownPromise === operation) teardownPromise = undefined;
+				});
+			}
+			return teardownPromise;
+		}
+
+		async function shutdownWithinBudget(pendingReason) {
+			enterShutdownMode();
+			const teardown = teardownSession(pendingReason);
+			let budgetTimer;
+			const expired = new Promise((resolve) => {
+				budgetTimer = setTimer(() => {
+					budgetTimer = undefined;
+					shutdownDeadlineExpired = true;
+					const error = new Error(
+						`omp-spt shutdown exceeded its ${shutdownBudgetMs}ms budget`,
+					);
+					abortActiveCommands(error);
+					for (const finish of [...retryWaiters]) finish();
+					resolve(false);
+				}, shutdownBudgetMs);
+				budgetTimer?.unref?.();
+			});
+			const completed = teardown.then(
+				() => true,
+				(error) => {
+					logError("omp-spt session teardown failed", error);
+					return true;
+				},
+			);
+			const finished = await Promise.race([completed, expired]);
+			if (budgetTimer !== undefined) clearTimer(budgetTimer);
+			if (!finished) {
+				pi.logger.error("omp-spt bounded shutdown expired", {
+					error: `${shutdownBudgetMs}ms budget exhausted`,
+				});
+			}
+		}
+
+		// [impl->REQ-OMP-LISTENER-FAIL-CLOSED]
+		async function failClosed(message, error) {
+			if (stopping && shutdownMode) return teardownPromise ?? Promise.resolve();
+			if (fatalPromise) return fatalPromise;
+			fatalPromise = (async () => {
+				ui?.setStatus("omp-spt", "spt failed");
+				logError(message, error);
+				try {
+					await teardownSession("endpoint stopped before your message could complete");
+				} catch (teardownError) {
+					logError("omp-spt session teardown failed", teardownError);
+				}
+				runtimeCtx?.shutdown();
+			})();
+			return fatalPromise;
+		}
+
+		function scheduleDispatch() {
+			if (
+				stopping ||
+				agentActive ||
+				dispatching ||
+				current ||
+				queue.length === 0 ||
+				dispatchTimer !== undefined
+			) {
+				return;
+			}
+			dispatchTimer = setTimer(() => {
+				dispatchTimer = undefined;
+				void dispatchNext().catch((error) => {
+					if (!stopping) return failClosed("omp-spt dispatch failed", error);
+				});
+			}, 0);
+			dispatchTimer?.unref?.();
+		}
+
+		async function rejectItem(item, reason, error) {
+			if (stopping) return;
+			logError(`omp-spt ${reason}`, error);
+			try {
+				await settleItem(item, failureMessage(reason, error));
+			} catch (outcomeError) {
+				if (stopping) return;
+				await failClosed(`omp-spt could not send the outcome to ${item.from ?? "unknown"}`, outcomeError);
+				return;
+			}
+			if (current === item) {
+				current = undefined;
+				releaseItem(item);
+			}
 			if (!stopping) {
-				ui?.setStatus("omp-spt", "spt offline");
-				ui?.notify(`omp-spt listener exited (${code})`, "error");
+				desiredState = "idle";
+				try {
+					await setState("idle");
+				} catch (stateError) {
+					await failClosed(
+						"omp-spt could not restore idle state after a failed submission",
+						stateError,
+					);
+				}
 			}
-		});
-	}
+		}
 
-	pi.on("session_start", async (_event, ctx) => {
-		ui = ctx.ui;
-		sid = ctx.sessionManager.getSessionId();
-		try {
-			const bindArgs = ["api", "--adapter", ADAPTER, "bind", id, "--set-session-id", sid];
-			if (process.env.OMP_SPT_SUBNET) bindArgs.push("--subnet", process.env.OMP_SPT_SUBNET);
-			const bound = await runSpt(bindArgs);
-			token = bound.match(/\btoken=([^\s]+)/)?.[1];
-			await setState("idle");
-			startListener();
-			ctx.ui.setStatus("omp-spt", `spt:${id}`);
-		} catch (error) {
-			ctx.ui.setStatus("omp-spt", "spt bind failed");
-			logError(`omp-spt could not bind ${id}`, error);
+		// [impl->REQ-OMP-EXTENSION-CUSTODY]
+		async function dispatchNext() {
+			if (stopping || agentActive || dispatching || current || queue.length === 0) return;
+			dispatching = true;
+			const item = queue.shift();
+			current = item;
+			try {
+				try {
+					desiredState = "busy";
+					await setState("busy");
+				} catch (error) {
+					await rejectItem(item, "could not accept your message", error);
+					return;
+				}
+				if (stopping) return;
+				if (agentActive) {
+					if (current === item) current = undefined;
+					queue.unshift(item);
+					return;
+				}
+				item.stub = senderStub(item.from ?? "unknown");
+				item.submitted = true;
+				try {
+					pi.sendUserMessage(item.stub);
+				} catch (error) {
+					item.submitted = false;
+					await rejectItem(item, "could not submit your message to OMP", error);
+				}
+			} finally {
+				dispatching = false;
+				scheduleDispatch();
+			}
 		}
-	});
 
-	pi.on("agent_start", async () => {
-		agentActive = true;
-		try {
-			await setState("busy");
-		} catch (error) {
-			logError("omp-spt could not mark the endpoint busy", error);
+		// [impl->REQ-OMP-LISTENER-FAIL-CLOSED]
+		function handleListenerDeath(reason) {
+			listenerBuffer = "";
+			if (listenerStableTimer !== undefined) {
+				clearTimer(listenerStableTimer);
+				listenerStableTimer = undefined;
+			}
+			if (stopping || restartTimer !== undefined) return;
+			if (listenerRestartCount >= restartDelaysMs.length) {
+				void failClosed("omp-spt listener restart budget exhausted", reason);
+				return;
+			}
+			const attempt = listenerRestartCount + 1;
+			const delay = restartDelaysMs[listenerRestartCount];
+			listenerRestartCount = attempt;
+			const message = `omp-spt listener stopped; restarting ${attempt}/${restartDelaysMs.length} in ${delay}ms`;
+			pi.logger.error(message, { error: errorSummary(reason) });
+			ui?.setStatus("omp-spt", `spt reconnecting (${attempt}/${restartDelaysMs.length})`);
+			ui?.notify(message, "warning");
+			restartTimer = setTimer(() => {
+				restartTimer = undefined;
+				startListener();
+			}, delay);
+			restartTimer?.unref?.();
 		}
-	});
 
-	pi.on("agent_end", async (event) => {
-		agentActive = false;
-		const completed = current;
-		current = undefined;
-		if (completed?.from) {
-			const reply = extractReply(event.messages) || "[omp-spt] turn ended without an assistant response.";
+		function startListener() {
+			if (stopping) return;
+			const args = ["ready", id];
+			if (env.OMP_SPT_SUBNET) args.push("--subnet", env.OMP_SPT_SUBNET);
+			let child;
 			try {
-				await runSpt(["send", completed.from, "--from", id], reply);
+				child = spawnProcess(env.OMP_SPT_SPT_BIN || "spt", args, {
+					stdio: ["ignore", "pipe", "pipe"],
+					windowsHide: true,
+				});
 			} catch (error) {
-				logError(`omp-spt could not reply to ${completed.from}`, error);
+				handleListenerDeath(error);
+				return;
 			}
+			listener = child;
+			listenerBuffer = "";
+			let dead = false;
+			const died = (reason, alreadyExited) => {
+				if (dead) return;
+				dead = true;
+				if (listener === child) listener = undefined;
+				if (stopping || alreadyExited) {
+					handleListenerDeath(reason);
+					return;
+				}
+				const termination = beginListenerTermination(child, "dead spt ready listener");
+				void termination.then(() => handleListenerDeath(reason));
+			};
+			if (listenerStableMs !== undefined) {
+				listenerStableTimer = setTimer(() => {
+					listenerStableTimer = undefined;
+					if (listener === child && !stopping) listenerRestartCount = 0;
+				}, listenerStableMs);
+				listenerStableTimer?.unref?.();
+			}
+			child.stdout.setEncoding("utf8");
+			child.stderr.setEncoding("utf8");
+			child.stdout.on("data", (chunk) => {
+				if (listener !== child || stopping) return;
+				listenerBuffer += String(chunk);
+				if (listenerBuffer.length > listenerBufferLimit) {
+					void failClosed(
+						"omp-spt listener protocol corruption",
+						protocolError(
+							`EVENT buffer exceeded ${listenerBufferLimit} characters without a complete drain`,
+						),
+					);
+					return;
+				}
+				while (!stopping) {
+					const drained = drainEvents(listenerBuffer, {
+						maxEvents: 1,
+						maxFrameChars: listenerBufferLimit,
+					});
+					listenerBuffer = drained.rest;
+					if (drained.error) {
+						void failClosed("omp-spt listener protocol corruption", drained.error);
+						return;
+					}
+					if (drained.events.length === 0) break;
+					const event = drained.events[0];
+					const acceptedCount = queue.length + (current ? 1 : 0);
+					const eventBytes = Buffer.byteLength(event.envelope, "utf8");
+					if (
+						acceptedCount >= acceptedQueueLimit ||
+						acceptedBytes + eventBytes > acceptedBytesLimit
+					) {
+						overflowItem = event;
+						void failClosed(
+							"omp-spt inbound custody capacity exceeded",
+							new Error(
+								`accepted queue limit is ${acceptedQueueLimit} messages and ${acceptedBytesLimit} bytes`,
+							),
+						);
+						return;
+					}
+					event.acceptedBytes = eventBytes;
+					event.accounted = true;
+					acceptedBytes += eventBytes;
+					queue.push(event);
+				}
+				if (!agentActive && !current && !dispatching) void dispatchNext();
+			});
+			child.stderr.on("data", (chunk) =>
+				pi.logger.debug("omp-spt listener", { output: String(chunk).trim() }),
+			);
+			child.on("error", (error) => died(error, false));
+			child.on("close", (code, signal) => {
+				const status = signal ? `signal ${signal}` : code;
+				died(new Error(`spt ready exited ${status}`), true);
+			});
+			ui?.setStatus("omp-spt", `spt:${id}`);
 		}
-		try {
-			await setState("idle");
-		} catch (error) {
-			logError("omp-spt could not mark the endpoint idle", error);
-		}
-		setTimeout(dispatchNext, 0);
-	});
 
-	pi.on("session_shutdown", async () => {
-		stopping = true;
-		listener?.kill();
-		ui?.setStatus("omp-spt", undefined);
-		if (!sid) return;
-		const auth = token ? ["--token", token] : ["--session-id", sid];
-		try {
-			await runSpt(["api", "--adapter", ADAPTER, "session-end", id, ...auth]);
-		} catch (error) {
-			pi.logger.error("omp-spt session teardown failed", { error: String(error) });
+		// [impl->REQ-OMP-NATIVE-TUI]
+		pi.on("session_start", async (_event, ctx) => {
+			runtimeCtx = ctx;
+			ui = ctx.ui;
+			sid = ctx.sessionManager.getSessionId();
+			const bindArgs = ["api", "--adapter", ADAPTER, "bind", id, "--set-session-id", sid];
+			if (env.OMP_SPT_SUBNET) bindArgs.push("--subnet", env.OMP_SPT_SUBNET);
+			bindPromise = (async () => {
+				const bound = await runCommand(bindArgs);
+				token = bound.match(/\btoken=([^\s]+)/)?.[1];
+				if (!token) throw new Error("spt bind response did not include token=<value>");
+			})();
+			try {
+				await bindPromise;
+			} catch (error) {
+				if (stopping) return;
+				ui.setStatus("omp-spt", "spt bind failed");
+				await failClosed(`omp-spt could not bind ${id}`, error);
+				return;
+			}
+			if (stopping) {
+				try {
+					await teardownSession("OMP session shut down before initialization completed");
+				} catch (error) {
+					logError("omp-spt session teardown failed", error);
+				}
+				return;
+			}
+			try {
+				await syncDesiredState();
+				if (stopping) {
+					await teardownSession("OMP session shut down before initialization completed");
+					return;
+				}
+				ui.setStatus("omp-spt", `spt:${id}`);
+				startListener();
+			} catch (error) {
+				if (stopping) {
+					logError("omp-spt session teardown failed", error);
+					return;
+				}
+				ui.setStatus("omp-spt", "spt bind failed");
+				await failClosed(`omp-spt could not bind ${id}`, error);
+			}
+		});
+
+		// [impl->REQ-OMP-SESSION-IMMUTABLE]
+		const blockSessionChange = (description, ctx) => {
+			ctx.ui.notify(
+				`omp-spt blocked the in-TUI ${description}; end this SPT session first`,
+				"warning",
+			);
+			return { cancel: true };
+		};
+
+		pi.on("session_before_switch", (event, ctx) =>
+			blockSessionChange(`${event.reason} session switch`, ctx),
+		);
+		pi.on("session_before_branch", (_event, ctx) =>
+			blockSessionChange("session branch", ctx),
+		);
+
+		// [impl->REQ-OMP-MESSAGE-CONTEXT]
+		pi.on("context", (event) => {
+			if (!current?.submitted || current.settling) return;
+			const messages = injectEnvelope(event.messages, current);
+			if (messages !== event.messages) return { messages };
+		});
+
+		async function completeTurn(event) {
+			agentActive = false;
+			desiredState = "idle";
+			if (stopping) return;
+			const completed = current;
+			if (completed?.submitted && !completed.settled) {
+				const reply = extractReply(event.messages, completed.stub);
+				try {
+					await settleItem(
+						completed,
+						reply || failureMessage("turn ended without an assistant response"),
+					);
+				} catch (error) {
+					if (stopping) return;
+					await failClosed(
+						`omp-spt could not send the outcome to ${completed.from ?? "unknown"}`,
+						error,
+					);
+					return;
+				}
+			}
+			if (current === completed) {
+				current = undefined;
+				releaseItem(completed);
+			}
+			try {
+				await setState("idle");
+			} catch (error) {
+				if (stopping) return;
+				await failClosed("omp-spt could not mark the endpoint idle", error);
+				return;
+			}
+			scheduleDispatch();
 		}
-	});
+
+		pi.on("agent_start", async () => {
+			if (stopping) return;
+			turnCompletionPromise = undefined;
+			agentActive = true;
+			desiredState = "busy";
+			try {
+				await syncDesiredState();
+			} catch (error) {
+				if (!stopping) await failClosed("omp-spt could not mark the endpoint busy", error);
+			}
+		});
+
+		// [impl->REQ-OMP-EXTENSION-CUSTODY]
+		pi.on("agent_end", (event) => {
+			turnCompletionPromise ??= completeTurn(event);
+			return turnCompletionPromise;
+		});
+
+		pi.on("session_stop", async (event) => {
+			turnCompletionPromise ??= completeTurn(event);
+			await turnCompletionPromise;
+		});
+
+		pi.on("session_shutdown", async (_event, ctx) => {
+			runtimeCtx ??= ctx;
+			ui?.setStatus("omp-spt", undefined);
+			await shutdownWithinBudget("OMP session shut down before your message could complete");
+		});
+	};
 }
+
+export default createOmpSpt();
diff --git a/tests/omp-extension.mjs b/tests/omp-extension.mjs
index 2ccf034..6bde45a 100644
--- a/tests/omp-extension.mjs
+++ b/tests/omp-extension.mjs
@@ -1,25 +1,1266 @@
 import assert from "node:assert/strict";
-import { decodeBody, drainEvents, extractReply } from "../adapter/strings/omp-spt.mjs";
+import { EventEmitter } from "node:events";
+import {
+	createOmpSpt,
+	decodeBody,
+	drainEvents,
+	extractReply,
+	runSpt,
+} from "../adapter/strings/omp-spt.mjs";
 
+const flush = () => new Promise((resolve) => setImmediate(resolve));
+function deferred() {
+	let resolve;
+	let reject;
+	const promise = new Promise((resolvePromise, rejectPromise) => {
+		resolve = resolvePromise;
+		reject = rejectPromise;
+	});
+	return { promise, reject, resolve };
+}
+
+class FakeStream extends EventEmitter {
+	setEncoding(encoding) {
+		this.encoding = encoding;
+	}
+
+	end(input) {
+		this.input = input;
+		if (this.onEnd?.(input) === false) return;
+		this.emit("finish");
+	}
+}
+
+class FakeChild extends EventEmitter {
+	constructor(options = {}) {
+		super();
+		this.stdin = new FakeStream();
+		this.stdout = new FakeStream();
+		this.stderr = new FakeStream();
+		this.exitCode = null;
+		this.signalCode = null;
+		this.kills = 0;
+		this.killSignals = [];
+		this.onKill = options.onKill;
+	}
+
+	close(code = 0, signal = null) {
+		this.exitCode = code;
+		this.signalCode = signal;
+		this.emit("close", code, signal);
+	}
+
+	kill(signal = "SIGTERM") {
+		this.kills += 1;
+		this.killSignals.push(signal);
+		const handled = this.onKill?.(signal, this);
+		if (handled !== undefined) return handled;
+		this.close(null, signal);
+		return true;
+	}
+}
+
+class FakeClock {
+	constructor() {
+		this.nextId = 1;
+		this.timers = new Map();
+	}
+
+	setTimeout(fn, delay) {
+		const handle = { id: this.nextId++, unref() {} };
+		this.timers.set(handle, { fn, delay });
+		return handle;
+	}
+
+	clearTimeout(handle) {
+		this.timers.delete(handle);
+	}
+
+	delays() {
+		return [...this.timers.values()].map(({ delay }) => delay);
+	}
+
+	async runNext(expectedDelay) {
+		const entry = [...this.timers.entries()].sort((left, right) => left[1].delay - right[1].delay)[0];
+		assert.ok(entry, `expected a ${expectedDelay}ms timer`);
+		const [handle, timer] = entry;
+		assert.equal(timer.delay, expectedDelay);
+		this.timers.delete(handle);
+		timer.fn();
+		await flush();
+	}
+}
+
+function createHarness(options = {}) {
+	const handlers = new Map();
+	const calls = [];
+	const children = [];
+	const submitted = [];
+	const statuses = [];
+	const notifications = [];
+	const errors = [];
+	const debug = [];
+	const clock = new FakeClock();
+	let shutdowns = 0;
+
+	const ui = {
+		notify(message, type) {
+			notifications.push({ message, type });
+		},
+		setStatus(key, text) {
+			statuses.push({ key, text });
+		},
+	};
+	const ctx = {
+		ui,
+		sessionManager: { getSessionId: () => options.sessionId ?? "session-1" },
+		shutdown() {
+			shutdowns += 1;
+		},
+	};
+	const pi = {
+		logger: {
+			error(message, details) {
+				errors.push({ message, details });
+			},
+			debug(message, details) {
+				debug.push({ message, details });
+			},
+		},
+		on(name, handler) {
+			const registered = handlers.get(name) ?? [];
+			registered.push(handler);
+			handlers.set(name, registered);
+		},
+		sendUserMessage(content) {
+			submitted.push(content);
+			options.onSubmit?.(content);
+		},
+	};
+	const runSptCommand = async (args, input) => {
+		const call = { args: [...args], input };
+		calls.push(call);
+		const overridden = await options.onRun?.(call);
+		if (overridden !== undefined) return overridden;
+		if (args[0] === "api" && args[3] === "bind") {
+			return options.bindOutput ?? "BOUND endpoint token=token-123";
+		}
+		return "";
+	};
+	const spawnProcess = (binary, args, spawnOptions) => {
+		const child = new FakeChild();
+		child.binary = binary;
+		child.args = [...args];
+		child.spawnOptions = spawnOptions;
+		options.onSpawn?.(child);
+		children.push(child);
+		return child;
+	};
+	const extension = createOmpSpt({
+		env: {
+			SPT_ENDPOINT_ID: options.id ?? "omp-agent",
+			OMP_SPT_SUBNET: options.subnet,
+			OMP_SPT_SPT_BIN: "spt-test",
+		},
+		acceptedBytesLimit: options.acceptedBytesLimit,
+		acceptedQueueLimit: options.acceptedQueueLimit,
+		restartDelaysMs: options.restartDelaysMs ?? [5, 10],
+		outcomeRetryDelaysMs: options.outcomeRetryDelaysMs ?? [],
+		sessionEndRetryDelaysMs: options.sessionEndRetryDelaysMs ?? [],
+		shutdownBudgetMs: options.shutdownBudgetMs,
+		shutdownCommandTimeoutMs: options.shutdownCommandTimeoutMs,
+		listenerStableMs: options.listenerStableMs ?? false,
+		killForceMs: options.killForceMs ?? 4,
+		killGraceMs: options.killGraceMs ?? 3,
+		listenerBufferLimit: options.listenerBufferLimit,
+		runSptCommand,
+		spawnProcess,
+		setTimeout: clock.setTimeout.bind(clock),
+		clearTimeout: clock.clearTimeout.bind(clock),
+	});
+	extension(pi);
+
+	async function emit(name, event = {}) {
+		let result;
+		for (const handler of handlers.get(name) ?? []) {
+			const returned = await handler({ type: name, ...event }, ctx);
+			if (returned !== undefined) result = returned;
+		}
+		return result;
+	}
+
+	return {
+		calls,
+		children,
+		clock,
+		ctx,
+		debug,
+		emit,
+		errors,
+		handlers,
+		notifications,
+		statuses,
+		submitted,
+		get shutdowns() {
+			return shutdowns;
+		},
+	};
+}
+
+function commandCalls(harness, command) {
+	return harness.calls.filter((call) => call.args[0] === command);
+}
+
+function stateCalls(harness) {
+	return harness.calls.filter((call) => call.args[0] === "api" && call.args[3] === "state");
+}
+
+async function testParsingAndReplies() {
+	assert.equal(decodeBody('a&lt;b&gt;<br>&quot;c&quot; &amp; &amp;lt;'), 'a<b>\n"c" & &lt;');
+
+	const partialEnvelope = '<EVENT type="msg" from="doyle">hello<br>wo';
+	const partial = drainEvents(`noise${partialEnvelope}`);
+	assert.deepEqual(partial.events, []);
+	assert.equal(partial.rest, partialEnvelope);
+
+	const envelope = `${partial.rest}rld</EVENT>`;
+	const complete = drainEvents(`${envelope}<EVENT type="notify">skip</EVENT>`);
+	assert.deepEqual(complete.events, [
+		{ from: "doyle", body: "hello\nworld", envelope },
+	]);
+	assert.equal(complete.rest, "");
+
+	const truncatedA =
+		'<EVENT type="msg" from="a">truncated<EVENT type="msg" from="b">valid</EVENT>';
+	const nested = drainEvents(truncatedA);
+	assert.deepEqual(nested.events, []);
+	assert.equal(nested.rest, truncatedA);
+	assert.match(nested.error.message, /nested EVENT/);
+	assert.match(
+		drainEvents('<EVENT type="msg">missing sender</EVENT>').error.message,
+		/missing EVENT from/,
+	);
+	assert.match(
+		drainEvents('<EVENT type=msg from="a">bad attrs</EVENT>').error.message,
+		/malformed EVENT attributes/,
+	);
+	assert.match(
+		drainEvents('<EVENT type="msg" from="a">0123456789</EVENT>', {
+			maxFrameChars: 32,
+		}).error.message,
+		/EVENT frame exceeded/,
+	);
+
+	assert.equal(
+		extractReply([
+			{ role: "assistant", content: [{ type: "text", text: "first" }] },
+			{ role: "toolResult", content: [] },
+			{
+				role: "assistant",
+				content: [
+					{ type: "text", text: "final " },
+					{ type: "text", text: "answer" },
+				],
+			},
+		]),
+		"final answer",
+	);
+	assert.equal(
+		extractReply(
+			[
+				{ role: "assistant", content: "stale answer" },
+				{ role: "user", content: '<msg from="doyle"/>' },
+			],
+			'<msg from="doyle"/>',
+		),
+		"",
+	);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-SESSION-IMMUTABLE]
+// [unit->REQ-OMP-MESSAGE-CONTEXT]
 // [unit->REQ-OMP-NATIVE-TUI]
-assert.equal(decodeBody('a&lt;b&gt;<br>&quot;c&quot; &amp; &amp;lt;'), 'a<b>\n"c" & &lt;');
-
-const partial = drainEvents('noise<EVENT type="msg" from="doyle">hello<br>wo');
-assert.deepEqual(partial.events, []);
-assert.equal(partial.rest, '<EVENT type="msg" from="doyle">hello<br>wo');
-
-const complete = drainEvents(`${partial.rest}rld</EVENT><EVENT type="notify">skip</EVENT>`);
-assert.deepEqual(complete.events, [{ from: "doyle", body: "hello\nworld" }]);
-assert.equal(complete.rest, "");
-
-assert.equal(
-	extractReply([
-		{ role: "assistant", content: [{ type: "text", text: "first" }] },
-		{ role: "toolResult", content: [] },
-		{ role: "assistant", content: [{ type: "text", text: "final " }, { type: "text", text: "answer" }] },
-	]),
-	"final answer",
-);
-assert.equal(extractReply([{ role: "user", content: "hello" }]), "");
+async function testLifecycleCustodyAndContext() {
+	const harness = createHarness({ subnet: "mesh-a" });
+	assert.deepEqual([...harness.handlers.keys()], [
+		"session_start",
+		"session_before_switch",
+		"session_before_branch",
+		"context",
+		"agent_start",
+		"agent_end",
+		"session_stop",
+		"session_shutdown",
+	]);
+
+	await harness.emit("session_start");
+	assert.deepEqual(harness.calls[0], {
+		args: [
+			"api",
+			"--adapter",
+			"omp-spt",
+			"bind",
+			"omp-agent",
+			"--set-session-id",
+			"session-1",
+			"--subnet",
+			"mesh-a",
+		],
+		input: undefined,
+	});
+	assert.deepEqual(harness.calls[1].args, [
+		"api",
+		"--adapter",
+		"omp-spt",
+		"state",
+		"idle",
+		"omp-agent",
+		"--token",
+		"token-123",
+	]);
+	assert.equal(harness.children.length, 1);
+	assert.equal(harness.children[0].binary, "spt-test");
+	assert.deepEqual(harness.children[0].args, ["ready", "omp-agent", "--subnet", "mesh-a"]);
+
+	for (const reason of ["new", "resume", "fork", "handoff"]) {
+		assert.deepEqual(await harness.emit("session_before_switch", { reason }), { cancel: true });
+		assert.ok(
+			harness.notifications.some(({ message }) =>
+				message.includes(`${reason} session switch`),
+			),
+		);
+	}
+	assert.deepEqual(await harness.emit("session_before_branch"), { cancel: true });
+	assert.ok(
+		harness.notifications.some(({ message }) => message.includes("session branch")),
+	);
+
+	const aliceEnvelope =
+		'<EVENT type="msg" from="alice" event_id="evt-1">hello&lt;world<br>line</EVENT>';
+	const bobEnvelope = '<EVENT type="msg" from="bob" event_id="evt-2">second</EVENT>';
+	harness.children[0].stdout.emit("data", `${aliceEnvelope}${bobEnvelope}`);
+	await flush();
+	assert.deepEqual(harness.submitted, ['<msg from="alice"/>']);
+	assert.deepEqual(
+		stateCalls(harness).map((call) => call.args[4]),
+		["idle", "busy"],
+	);
+
+	const originalMessages = [{ role: "user", content: '<msg from="alice"/>' }];
+	const context = await harness.emit("context", { messages: originalMessages });
+	assert.equal(originalMessages[0].content, '<msg from="alice"/>');
+	assert.equal(context.messages[0].content, `<msg from="alice"/>\n\n${aliceEnvelope}`);
+
+	const arrayContext = await harness.emit("context", {
+		messages: [{ role: "user", content: [{ type: "text", text: '<msg from="alice"/>' }] }],
+	});
+	assert.deepEqual(arrayContext.messages[0].content, [
+		{ type: "text", text: '<msg from="alice"/>' },
+		{ type: "text", text: `\n\n${aliceEnvelope}` },
+	]);
+
+	await harness.emit("agent_start");
+	assert.deepEqual(
+		stateCalls(harness).map((call) => call.args[4]),
+		["idle", "busy"],
+		"agent_start must not duplicate the already-honest busy transition",
+	);
+	await harness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="alice"/>' },
+			{ role: "assistant", content: [{ type: "text", text: "alice reply" }] },
+		],
+	});
+	assert.deepEqual(harness.submitted, ['<msg from="alice"/>']);
+	assert.deepEqual(harness.clock.delays(), [0]);
+
+	await harness.clock.runNext(0);
+	assert.deepEqual(harness.submitted, ['<msg from="alice"/>', '<msg from="bob"/>']);
+	await harness.emit("agent_start");
+	await harness.emit("agent_end", {
+		messages: [
+			{ role: "assistant", content: "previous reply" },
+			{ role: "user", content: '<msg from="bob"/>' },
+		],
+	});
+
+	const outcomes = commandCalls(harness, "send");
+	assert.equal(outcomes.length, 2);
+	assert.deepEqual(
+		outcomes.map((call) => call.args),
+		[
+			["send", "alice", "--from", "omp-agent"],
+			["send", "bob", "--from", "omp-agent"],
+		],
+	);
+	assert.equal(outcomes[0].input, "alice reply");
+	assert.match(outcomes[1].input, /turn ended without an assistant response/);
+	assert.deepEqual(
+		stateCalls(harness).map((call) => call.args[4]),
+		["idle", "busy", "idle", "busy", "idle"],
+	);
+	for (const call of [...stateCalls(harness), ...harness.calls.filter((candidate) => candidate.args[3] === "session-end")]) {
+		assert.deepEqual(call.args.slice(-2), ["--token", "token-123"]);
+	}
+
+	await harness.emit("session_shutdown");
+	const ended = harness.calls.filter((call) => call.args[3] === "session-end");
+	assert.equal(ended.length, 1);
+	assert.deepEqual(ended[0].args.slice(-2), ["--token", "token-123"]);
+	assert.equal(harness.children[0].kills, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+async function testDeferredBindLifecycleSerialization() {
+	const busyBind = deferred();
+	const busyHarness = createHarness({
+		onRun(call) {
+			if (call.args[0] === "api" && call.args[3] === "bind") return busyBind.promise;
+		},
+	});
+	const startingBusy = busyHarness.emit("session_start");
+	await flush();
+	const becomingBusy = busyHarness.emit("agent_start");
+	await flush();
+	assert.deepEqual(stateCalls(busyHarness), []);
+	assert.equal(busyHarness.children.length, 0);
+
+	busyBind.resolve("BOUND endpoint token=token-busy");
+	await Promise.all([startingBusy, becomingBusy]);
+	assert.deepEqual(
+		stateCalls(busyHarness).map((call) => call.args[4]),
+		["busy"],
+		"agent_start before bind completion must suppress the stale idle publication",
+	);
+	assert.equal(busyHarness.children.length, 1);
+	await busyHarness.emit("session_shutdown");
+	assert.deepEqual(busyHarness.clock.delays(), []);
+
+	const shutdownBind = deferred();
+	const shutdownHarness = createHarness({
+		onRun(call) {
+			if (call.args[0] === "api" && call.args[3] === "bind") return shutdownBind.promise;
+		},
+	});
+	const startingShutdown = shutdownHarness.emit("session_start");
+	await flush();
+	const shuttingDown = shutdownHarness.emit("session_shutdown");
+	await flush();
+	assert.equal(shutdownHarness.children.length, 0);
+	assert.equal(
+		shutdownHarness.calls.filter((call) => call.args[3] === "session-end").length,
+		0,
+	);
+
+	shutdownBind.resolve("BOUND endpoint token=token-shutdown");
+	await Promise.all([startingShutdown, shuttingDown]);
+	assert.deepEqual(stateCalls(shutdownHarness), []);
+	assert.equal(shutdownHarness.children.length, 0);
+	assert.equal(
+		shutdownHarness.calls.filter((call) => call.args[3] === "session-end").length,
+		1,
+	);
+	assert.ok(
+		!shutdownHarness.statuses.some(({ text }) => text === "spt:omp-agent"),
+		"bind completion after shutdown must not restore live status",
+	);
+	assert.deepEqual(shutdownHarness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testOutcomeSendRetriesAndExhaustion() {
+	let retryAttempts = 0;
+	const retryHarness = createHarness({
+		outcomeRetryDelaysMs: [5, 10],
+		onRun(call) {
+			if (call.args[0] === "send" && call.args[1] === "retry") {
+				retryAttempts += 1;
+				if (retryAttempts < 3) throw new Error(`outcome failure ${retryAttempts}`);
+			}
+		},
+	});
+	await retryHarness.emit("session_start");
+	retryHarness.children[0].stdout.emit(
+		"data",
+		'<EVENT type="msg" from="retry">work</EVENT>',
+	);
+	await flush();
+	await retryHarness.emit("agent_start");
+	const retryEnding = retryHarness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="retry"/>' },
+			{ role: "assistant", content: "eventual outcome" },
+		],
+	});
+	await flush();
+	assert.equal(commandCalls(retryHarness, "send").length, 1);
+	assert.deepEqual(retryHarness.clock.delays(), [5]);
+	await retryHarness.clock.runNext(5);
+	assert.equal(commandCalls(retryHarness, "send").length, 2);
+	assert.deepEqual(retryHarness.clock.delays(), [10]);
+	await retryHarness.clock.runNext(10);
+	await retryEnding;
+	assert.equal(commandCalls(retryHarness, "send").length, 3);
+	assert.equal(commandCalls(retryHarness, "send").at(-1).input, "eventual outcome");
+	assert.equal(retryHarness.shutdowns, 0);
+	await retryHarness.emit("session_shutdown");
+	assert.deepEqual(retryHarness.clock.delays(), []);
+
+	const exhaustedHarness = createHarness({
+		outcomeRetryDelaysMs: [7],
+		onRun(call) {
+			if (call.args[0] === "send") throw new Error("outcome channel unavailable");
+		},
+	});
+	await exhaustedHarness.emit("session_start");
+	const exhaustedListener = exhaustedHarness.children[0];
+	exhaustedListener.stdout.emit(
+		"data",
+		'<EVENT type="msg" from="exhausted">work</EVENT>',
+	);
+	await flush();
+	await exhaustedHarness.emit("agent_start");
+	const exhaustedEnding = exhaustedHarness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="exhausted"/>' },
+			{ role: "assistant", content: "undeliverable outcome" },
+		],
+	});
+	await flush();
+	assert.equal(commandCalls(exhaustedHarness, "send").length, 1);
+	assert.deepEqual(exhaustedHarness.clock.delays(), [7]);
+	await exhaustedHarness.clock.runNext(7);
+	await exhaustedEnding;
+
+	assert.equal(commandCalls(exhaustedHarness, "send").length, 2);
+	assert.deepEqual(
+		stateCalls(exhaustedHarness).map((call) => call.args[4]),
+		["idle", "busy"],
+		"exhausted custody must never be advertised idle",
+	);
+	assert.equal(exhaustedHarness.shutdowns, 1);
+	assert.equal(exhaustedListener.kills, 1);
+	assert.equal(
+		exhaustedHarness.calls.filter((call) => call.args[3] === "session-end").length,
+		1,
+	);
+	assert.ok(
+		exhaustedHarness.errors.some(({ message }) =>
+			message.includes("could not send the outcome to exhausted"),
+		),
+	);
+	await exhaustedHarness.emit("session_shutdown");
+	assert.deepEqual(exhaustedHarness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+async function testSubmissionFailureAdvancesQueue() {
+	const harness = createHarness({
+		onSubmit(content) {
+			if (content === '<msg from="broken"/>') throw new Error("OMP prompt flow rejected input");
+		},
+	});
+	await harness.emit("session_start");
+	harness.children[0].stdout.emit(
+		"data",
+		'<EVENT type="msg" from="broken">one</EVENT><EVENT type="msg" from="next">two</EVENT>',
+	);
+	await flush();
+
+	const firstOutcome = commandCalls(harness, "send");
+	assert.equal(firstOutcome.length, 1);
+	assert.deepEqual(firstOutcome[0].args, ["send", "broken", "--from", "omp-agent"]);
+	assert.match(firstOutcome[0].input, /could not submit your message to OMP/);
+	assert.deepEqual(harness.clock.delays(), [0]);
+
+	await harness.clock.runNext(0);
+	assert.deepEqual(harness.submitted, ['<msg from="broken"/>', '<msg from="next"/>']);
+	await harness.emit("agent_start");
+	await harness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="next"/>' },
+			{ role: "assistant", content: "next reply" },
+		],
+	});
+	const outcomes = commandCalls(harness, "send");
+	assert.equal(outcomes.length, 2);
+	assert.deepEqual(
+		outcomes.map((call) => call.args[1]),
+		["broken", "next"],
+	);
+	assert.equal(outcomes[1].input, "next reply");
+	await harness.emit("session_shutdown");
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+async function testFailedIdleRecoveryFailsClosed() {
+	let idleCalls = 0;
+	const harness = createHarness({
+		onSubmit() {
+			throw new Error("OMP prompt flow rejected input");
+		},
+		onRun(call) {
+			if (call.args[0] === "api" && call.args[3] === "state" && call.args[4] === "idle") {
+				idleCalls += 1;
+				if (idleCalls === 2) throw new Error("state channel unavailable");
+			}
+		},
+	});
+	await harness.emit("session_start");
+	harness.children[0].stdout.emit("data", '<EVENT type="msg" from="broken">one</EVENT>');
+	await flush();
+
+	assert.equal(commandCalls(harness, "send").length, 1);
+	assert.match(commandCalls(harness, "send")[0].input, /could not submit your message to OMP/);
+	assert.equal(harness.shutdowns, 1);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.ok(
+		harness.errors.some(({ message }) =>
+			message.includes("could not restore idle state after a failed submission"),
+		),
+	);
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testListenerRestartExhaustion() {
+	const harness = createHarness({ restartDelaysMs: [5, 10] });
+	await harness.emit("session_start");
+	const first = harness.children[0];
+	first.emit("close", 7);
+	assert.deepEqual(harness.clock.delays(), [5]);
+
+	await harness.clock.runNext(5);
+	const second = harness.children[1];
+	second.stdout.emit("data", '<EVENT type="msg" from="partial">half');
+	second.emit("error", new Error("listener crashed"));
+	second.emit("close", 8);
+	await flush();
+	assert.deepEqual(harness.clock.delays(), [10], "error plus close schedules one restart");
+
+	await harness.clock.runNext(10);
+	const third = harness.children[2];
+	third.emit("close", 9);
+	await flush();
+
+	assert.equal(harness.children.length, 3);
+	assert.equal(harness.shutdowns, 1);
+	assert.ok(
+		harness.errors.some(({ message }) => message.includes("listener restart budget exhausted")),
+	);
+	assert.ok(
+		harness.notifications.some(({ message, type }) =>
+			type === "error" && message.includes("listener restart budget exhausted"),
+		),
+	);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+
+	await harness.emit("session_shutdown");
+	assert.equal(
+		harness.calls.filter((call) => call.args[3] === "session-end").length,
+		1,
+		"fatal shutdown and lifecycle shutdown share one teardown",
+	);
+}
+
+async function testListenerStableIntervalResetsRetries() {
+	const harness = createHarness({
+		listenerStableMs: 20,
+		restartDelaysMs: [5, 10],
+	});
+	await harness.emit("session_start");
+	await harness.emit("agent_start");
+	assert.deepEqual(harness.clock.delays(), [20]);
+
+	harness.children[0].emit("close", 1);
+	assert.deepEqual(harness.clock.delays(), [5]);
+	await harness.clock.runNext(5);
+
+	const shortLived = harness.children[1];
+	shortLived.stdout.emit(
+		"data",
+		'<EVENT type="msg" from="proof">a parsed event is not stability</EVENT>',
+	);
+	shortLived.emit("close", 2);
+	assert.deepEqual(
+		harness.clock.delays(),
+		[10],
+		"a parsed event followed by an immediate crash remains in the consecutive crash loop",
+	);
+	await harness.clock.runNext(10);
+
+	const stable = harness.children[2];
+	assert.deepEqual(harness.clock.delays(), [20]);
+	await harness.clock.runNext(20);
+	stable.emit("close", 3);
+	assert.deepEqual(
+		harness.clock.delays(),
+		[5],
+		"a listener surviving the stable interval resets the next retry to attempt one",
+	);
+	assert.match(
+		harness.notifications.filter(({ type }) => type === "warning").at(-1).message,
+		/restarting 1\/2 in 5ms/,
+	);
+
+	await harness.clock.runNext(5);
+	assert.equal(harness.children.length, 4);
+	await harness.emit("session_shutdown");
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testFatalTeardownAwaitsInFlightOutcome() {
+	let releaseOutcome;
+	const outcomeGate = new Promise((resolve) => {
+		releaseOutcome = resolve;
+	});
+	const harness = createHarness({
+		restartDelaysMs: [],
+		onRun(call) {
+			if (call.args[0] === "send" && call.args[1] === "slow") return outcomeGate;
+		},
+	});
+	await harness.emit("session_start");
+	harness.children[0].stdout.emit("data", '<EVENT type="msg" from="slow">work</EVENT>');
+	await flush();
+	await harness.emit("agent_start");
+	const ending = harness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="slow"/>' },
+			{ role: "assistant", content: "finished" },
+		],
+	});
+	await flush();
+	assert.equal(commandCalls(harness, "send").length, 1);
+
+	harness.children[0].emit("close", 11);
+	await flush();
+	assert.equal(harness.shutdowns, 0, "fatal teardown must join the sender outcome");
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 0);
+
+	const shutdown = harness.emit("session_shutdown");
+	await flush();
+	assert.equal(
+		harness.calls.filter((call) => call.args[3] === "session-end").length,
+		0,
+		"concurrent lifecycle shutdown must join fatal custody teardown",
+	);
+	for (const reason of ["new", "resume", "fork", "handoff"]) {
+		assert.deepEqual(
+			await harness.emit("session_before_switch", { reason }),
+			{ cancel: true },
+			`teardown must keep blocking the ${reason} switch while custody is pending`,
+		);
+	}
+	assert.deepEqual(
+		await harness.emit("session_before_branch"),
+		{ cancel: true },
+		"teardown must keep blocking branches while custody is pending",
+	);
+
+	releaseOutcome();
+	await Promise.all([ending, shutdown]);
+	await flush();
+	assert.equal(harness.shutdowns, 1);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+async function testSessionEndRetriesAfterTransientFailure() {
+	const firstEnd = deferred();
+	let endAttempts = 0;
+	const harness = createHarness({
+		restartDelaysMs: [],
+		sessionEndRetryDelaysMs: [5],
+		onRun(call) {
+			if (call.args[0] === "api" && call.args[3] === "session-end") {
+				endAttempts += 1;
+				if (endAttempts === 1) return firstEnd.promise;
+			}
+		},
+	});
+	await harness.emit("session_start");
+	harness.children[0].emit("close", 12);
+	await flush();
+	assert.equal(
+		harness.calls.filter((call) => call.args[3] === "session-end").length,
+		1,
+	);
+
+	firstEnd.reject(new Error("transient teardown failure"));
+	await flush();
+	assert.equal(harness.shutdowns, 0, "fatal close must wait for the bounded teardown retry");
+	assert.deepEqual(harness.clock.delays(), [5]);
+	assert.ok(
+		harness.errors.some(
+			({ message, details }) =>
+				message.includes("session teardown failed; retrying") &&
+				details.error.includes("transient teardown failure"),
+		),
+	);
+
+	await harness.clock.runNext(5);
+	await flush();
+	const shutdown = harness.emit("session_shutdown");
+	await shutdown;
+	await flush();
+	assert.equal(
+		harness.calls.filter((call) => call.args[3] === "session-end").length,
+		2,
+		"normal fatal teardown may retry before bounded lifecycle shutdown begins",
+	);
+	assert.equal(harness.shutdowns, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+async function testHumanBusyFailureFailsClosed() {
+	const harness = createHarness({
+		onRun(call) {
+			if (call.args[0] === "api" && call.args[3] === "state" && call.args[4] === "busy") {
+				throw new Error("state channel unavailable");
+			}
+		},
+	});
+	await harness.emit("session_start");
+	await harness.emit("agent_start");
+
+	assert.equal(harness.shutdowns, 1);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.ok(
+		harness.errors.some(({ message }) => message.includes("could not mark the endpoint busy")),
+	);
+	assert.equal(harness.children[0].kills, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testShutdownReapsAndFailsQueuedCustody() {
+	const harness = createHarness();
+	await harness.emit("session_start");
+	const listener = harness.children[0];
+	listener.stdout.emit(
+		"data",
+		'<EVENT type="msg" from="first">one</EVENT><EVENT type="msg" from="queued">two</EVENT>',
+	);
+	await flush();
+	await harness.emit("agent_start");
+	await harness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="first"/>' },
+			{ role: "assistant", content: "done" },
+		],
+	});
+	assert.deepEqual(harness.clock.delays(), [0]);
+
+	await harness.emit("session_shutdown");
+	assert.equal(listener.kills, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+	assert.deepEqual(
+		commandCalls(harness, "send").map((call) => call.args[1]),
+		["first", "queued"],
+	);
+	assert.match(commandCalls(harness, "send")[1].input, /OMP session shut down/);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.statuses.at(-1), { key: "omp-spt", text: undefined });
+	assert.equal(harness.shutdowns, 0, "normal lifecycle shutdown must not recursively shut down OMP");
+}
+async function testRunSptRejectsStdinErrorsAndHungCommands() {
+	const epipeClock = new FakeClock();
+	const epipeChild = new FakeChild();
+	const epipe = Object.assign(new Error("write EPIPE"), { code: "EPIPE" });
+	epipeChild.stdin.onEnd = () => {
+		epipeChild.stdin.emit("error", epipe);
+		return false;
+	};
+	await assert.rejects(
+		runSpt(["send", "peer", "--from", "omp-agent"], "reply", {
+			clearTimeout: epipeClock.clearTimeout.bind(epipeClock),
+			commandTimeoutMs: 20,
+			killForceMs: 4,
+			killGraceMs: 3,
+			setTimeout: epipeClock.setTimeout.bind(epipeClock),
+			spawnProcess: () => epipeChild,
+		}),
+		(error) => error === epipe && error.code === "EPIPE",
+	);
+	assert.deepEqual(epipeChild.killSignals, ["SIGTERM"]);
+	assert.deepEqual(epipeClock.delays(), []);
+
+	const fastExitClock = new FakeClock();
+	const fastExitChild = new FakeChild();
+	fastExitChild.stdin.onEnd = () => {
+		fastExitChild.close(0);
+		return false;
+	};
+	await assert.rejects(
+		runSpt(["send", "peer", "--from", "omp-agent"], "reply", {
+			clearTimeout: fastExitClock.clearTimeout.bind(fastExitClock),
+			commandTimeoutMs: 20,
+			killForceMs: 4,
+			killGraceMs: 3,
+			setTimeout: fastExitClock.setTimeout.bind(fastExitClock),
+			spawnProcess: () => fastExitChild,
+		}),
+		/exited before stdin completed/,
+	);
+	assert.deepEqual(fastExitChild.killSignals, []);
+	assert.deepEqual(fastExitClock.delays(), []);
+
+	const commandCases = [
+		["api", "--adapter", "omp-spt", "bind", "omp-agent"],
+		["send", "peer", "--from", "omp-agent"],
+		["api", "--adapter", "omp-spt", "state", "idle", "omp-agent"],
+		["api", "--adapter", "omp-spt", "session-end", "omp-agent"],
+	];
+	for (const args of commandCases) {
+		const clock = new FakeClock();
+		const child = new FakeChild();
+		const pending = runSpt(args, args[0] === "send" ? "outcome" : undefined, {
+			clearTimeout: clock.clearTimeout.bind(clock),
+			commandTimeoutMs: 7,
+			killForceMs: 4,
+			killGraceMs: 3,
+			setTimeout: clock.setTimeout.bind(clock),
+			spawnProcess: () => child,
+		});
+		const rejected = assert.rejects(pending, /timed out after 7ms/);
+		assert.deepEqual(clock.delays(), [7]);
+		await clock.runNext(7);
+		await rejected;
+		assert.deepEqual(child.killSignals, ["SIGTERM"]);
+		assert.deepEqual(clock.delays(), []);
+	}
+}
+
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testListenerTerminationEscalatesAndReaps() {
+	const harness = createHarness({
+		killForceMs: 4,
+		killGraceMs: 3,
+		onSpawn(child) {
+			child.onKill = (signal) => {
+				if (signal === "SIGKILL") child.close(null, signal);
+				return true;
+			};
+		},
+	});
+	await harness.emit("session_start");
+	const listener = harness.children[0];
+	const shutdown = harness.emit("session_shutdown");
+	await flush();
+	assert.deepEqual(listener.killSignals, ["SIGTERM"]);
+	assert.deepEqual(harness.clock.delays().sort((a, b) => a - b), [3, 1_800]);
+
+	await harness.clock.runNext(3);
+	await shutdown;
+	assert.deepEqual(listener.killSignals, ["SIGTERM", "SIGKILL"]);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+
+	const errorHarness = createHarness({
+		killForceMs: 4,
+		killGraceMs: 3,
+		onSpawn(child) {
+			child.onKill = (signal) => {
+				if (signal === "SIGKILL") child.close(null, signal);
+				return true;
+			};
+		},
+	});
+	await errorHarness.emit("session_start");
+	const erroredListener = errorHarness.children[0];
+	erroredListener.emit("error", new Error("listener pipe failed"));
+	const concurrentShutdown = errorHarness.emit("session_shutdown");
+	await flush();
+	assert.deepEqual(erroredListener.killSignals, ["SIGTERM"]);
+	assert.deepEqual(errorHarness.clock.delays().sort((a, b) => a - b), [3, 1_800]);
+	await errorHarness.clock.runNext(3);
+	await concurrentShutdown;
+	assert.deepEqual(erroredListener.killSignals, ["SIGTERM", "SIGKILL"]);
+	assert.equal(
+		errorHarness.calls.filter((call) => call.args[3] === "session-end").length,
+		1,
+	);
+	assert.deepEqual(errorHarness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testProtocolCorruptionFailsClosed() {
+	async function failProtocol(payload, expected, options = {}) {
+		const harness = createHarness({ restartDelaysMs: [], ...options });
+		await harness.emit("session_start");
+		harness.children[0].stdout.emit("data", payload);
+		await flush();
+		assert.equal(harness.shutdowns, 1);
+		assert.deepEqual(harness.submitted, []);
+		assert.deepEqual(commandCalls(harness, "send"), []);
+		assert.ok(
+			harness.errors.some(
+				({ message, details }) =>
+					message.includes("listener protocol corruption") && expected.test(details.error),
+			),
+		);
+		assert.equal(harness.children[0].kills, 1);
+		assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+		assert.deepEqual(harness.clock.delays(), []);
+		await harness.emit("session_shutdown");
+		return harness;
+	}
+
+	const truncatedA =
+		'<EVENT type="msg" from="a">truncated<EVENT type="msg" from="b">valid</EVENT>';
+	const nested = await failProtocol(truncatedA, /nested EVENT/);
+	assert.deepEqual(
+		commandCalls(nested, "send").map((call) => call.args[1]),
+		[],
+		"the later valid b frame must not be merged into or consumed as a",
+	);
+	await failProtocol('<EVENT type="msg">missing sender</EVENT>', /missing EVENT from/);
+	await failProtocol('<EVENT type=msg from="a">bad attrs</EVENT>', /malformed EVENT attributes/);
+	await failProtocol('<EVENT type="msg" from="a">never closes'.padEnd(80, "x"), /buffer exceeded/, {
+		listenerBufferLimit: 64,
+	});
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testInboundQueueOverflowReturnsAcceptedCustody() {
+	const frames = ["a", "b", "overflow"].map(
+		(from) => `<EVENT type="msg" from="${from}">work</EVENT>`,
+	);
+	const harness = createHarness({
+		acceptedQueueLimit: 2,
+		restartDelaysMs: [],
+	});
+	await harness.emit("session_start");
+	harness.children[0].stdout.emit("data", frames.join(""));
+	await flush();
+
+	assert.equal(harness.shutdowns, 1);
+	assert.deepEqual(harness.submitted, []);
+	assert.deepEqual(
+		commandCalls(harness, "send").map((call) => call.args[1]),
+		["a", "b", "overflow"],
+		"every accepted item and the capacity-refused item receive an explicit terminal failure",
+	);
+	for (const call of commandCalls(harness, "send")) {
+		assert.match(call.input, /endpoint stopped before your message could complete/);
+	}
+	assert.ok(
+		harness.errors.some(({ message }) =>
+			message.includes("inbound custody capacity exceeded"),
+		),
+	);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+	await harness.emit("session_shutdown");
+
+	const byteFirst = '<EVENT type="msg" from="a">x</EVENT>';
+	const byteOverflow = '<EVENT type="msg" from="b">😀</EVENT>';
+	const byteHarness = createHarness({
+		acceptedBytesLimit: Buffer.byteLength(byteFirst, "utf8") + byteOverflow.length,
+		acceptedQueueLimit: 10,
+		restartDelaysMs: [],
+	});
+	await byteHarness.emit("session_start");
+	byteHarness.children[0].stdout.emit("data", `${byteFirst}${byteOverflow}`);
+	await flush();
+	assert.deepEqual(
+		commandCalls(byteHarness, "send").map((call) => call.args[1]),
+		["a", "b"],
+	);
+	assert.equal(byteHarness.shutdowns, 1);
+	assert.deepEqual(byteHarness.clock.delays(), []);
+	await byteHarness.emit("session_shutdown");
+}
+
+async function testSessionStopAwaitsOutcomeWithoutEndingEndpoint() {
+	const firstOutcome = deferred();
+	let attempts = 0;
+	const harness = createHarness({
+		outcomeRetryDelaysMs: [5],
+		onRun(call) {
+			if (call.args[0] === "send" && call.args[1] === "awaited") {
+				attempts += 1;
+				if (attempts === 1) return firstOutcome.promise;
+			}
+		},
+	});
+	await harness.emit("session_start");
+	harness.children[0].stdout.emit(
+		"data",
+		'<EVENT type="msg" from="awaited">work</EVENT>',
+	);
+	await flush();
+	await harness.emit("agent_start");
+	const messages = [
+		{ role: "user", content: '<msg from="awaited"/>' },
+		{ role: "assistant", content: "completed outcome" },
+	];
+	const agentEnd = harness.emit("agent_end", { messages });
+	await flush();
+	const sessionStop = harness.emit("session_stop", { messages });
+	await flush();
+	assert.equal(commandCalls(harness, "send").length, 1);
+	assert.equal(harness.children[0].kills, 0);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 0);
+
+	firstOutcome.reject(new Error("transient delayed outcome failure"));
+	await flush();
+	assert.deepEqual(harness.clock.delays(), [5]);
+	await harness.clock.runNext(5);
+	await Promise.all([agentEnd, sessionStop]);
+	assert.equal(commandCalls(harness, "send").length, 2);
+	assert.equal(commandCalls(harness, "send").at(-1).input, "completed outcome");
+	assert.equal(harness.children[0].kills, 0, "ordinary session_stop must leave the endpoint live");
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 0);
+
+	await harness.emit("session_shutdown");
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.equal(harness.children[0].kills, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+}
+
+// [unit->REQ-OMP-EXTENSION-CUSTODY]
+// [unit->REQ-OMP-LISTENER-FAIL-CLOSED]
+async function testShutdownFallbackStaysBelowHostCap() {
+	const never = new Promise(() => {});
+	const harness = createHarness({
+		shutdownBudgetMs: 1_800,
+		shutdownCommandTimeoutMs: 300,
+		onRun(call) {
+			if (call.args[0] === "send" || call.args[3] === "session-end") return never;
+		},
+	});
+	await harness.emit("session_start");
+	await harness.emit("agent_start");
+	harness.children[0].stdout.emit(
+		"data",
+		'<EVENT type="msg" from="queued">work</EVENT>',
+	);
+	await flush();
+
+	const shutdown = harness.emit("session_shutdown");
+	await flush();
+	assert.deepEqual(
+		harness.clock.delays().sort((a, b) => a - b),
+		[300, 1_800],
+		"queued custody has a short command timeout inside the 2s host cap",
+	);
+	await harness.clock.runNext(300);
+	assert.equal(commandCalls(harness, "send").length, 1);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.clock.delays().sort((a, b) => a - b), [300, 1_800]);
+	await harness.clock.runNext(300);
+	await shutdown;
+
+	assert.equal(harness.children[0].kills, 1);
+	assert.ok(
+		harness.errors.some(({ message }) =>
+			message.includes("could not return custody to queued"),
+		),
+	);
+	assert.equal(harness.calls.filter((call) => call.args[3] === "session-end").length, 1);
+	assert.deepEqual(harness.clock.delays(), []);
+	assert.ok(1_800 < 2_000);
+
+	const inFlightOutcome = deferred();
+	let inFlightAttempts = 0;
+	const inFlightHarness = createHarness({
+		onRun(call) {
+			if (call.args[0] === "send" && call.args[1] === "in-flight") {
+				inFlightAttempts += 1;
+				if (inFlightAttempts === 1) return inFlightOutcome.promise;
+			}
+		},
+	});
+	await inFlightHarness.emit("session_start");
+	inFlightHarness.children[0].stdout.emit(
+		"data",
+		'<EVENT type="msg" from="in-flight">work</EVENT>',
+	);
+	await flush();
+	await inFlightHarness.emit("agent_start");
+	const ending = inFlightHarness.emit("agent_end", {
+		messages: [
+			{ role: "user", content: '<msg from="in-flight"/>' },
+			{ role: "assistant", content: "answer racing shutdown" },
+		],
+	});
+	await flush();
+	assert.equal(commandCalls(inFlightHarness, "send").length, 1);
+	const inFlightShutdown = inFlightHarness.emit("session_shutdown");
+	await Promise.all([ending, inFlightShutdown]);
+	assert.deepEqual(
+		commandCalls(inFlightHarness, "send").map((call) => call.args[1]),
+		["in-flight", "in-flight"],
+	);
+	assert.match(commandCalls(inFlightHarness, "send")[1].input, /OMP session shut down/);
+	assert.equal(
+		inFlightHarness.calls.filter((call) => call.args[3] === "session-end").length,
+		1,
+	);
+	assert.equal(inFlightHarness.shutdowns, 0);
+	assert.deepEqual(inFlightHarness.clock.delays(), []);
+	inFlightOutcome.resolve();
+	await flush();
+	assert.equal(commandCalls(inFlightHarness, "send").length, 2);
+
+	const hardCapHarness = createHarness({
+		shutdownBudgetMs: 1_800,
+		shutdownCommandTimeoutMs: 5_000,
+		onRun(call) {
+			if (call.args[0] === "send") return never;
+		},
+	});
+	await hardCapHarness.emit("session_start");
+	await hardCapHarness.emit("agent_start");
+	hardCapHarness.children[0].stdout.emit(
+		"data",
+		'<EVENT type="msg" from="hard-cap">work</EVENT>',
+	);
+	await flush();
+	const hardCappedShutdown = hardCapHarness.emit("session_shutdown");
+	await flush();
+	assert.deepEqual(
+		hardCapHarness.clock.delays().sort((a, b) => a - b),
+		[1_800, 5_000],
+	);
+	await hardCapHarness.clock.runNext(1_800);
+	await hardCappedShutdown;
+	assert.ok(
+		hardCapHarness.errors.some(({ message }) =>
+			message.includes("bounded shutdown expired"),
+		),
+	);
+	assert.equal(hardCapHarness.children[0].kills, 1);
+	assert.deepEqual(hardCapHarness.clock.delays(), []);
+}
+
+await testParsingAndReplies();
+await testRunSptRejectsStdinErrorsAndHungCommands();
+await testLifecycleCustodyAndContext();
+await testDeferredBindLifecycleSerialization();
+await testOutcomeSendRetriesAndExhaustion();
+await testSubmissionFailureAdvancesQueue();
+await testFailedIdleRecoveryFailsClosed();
+await testListenerRestartExhaustion();
+await testListenerStableIntervalResetsRetries();
+await testFatalTeardownAwaitsInFlightOutcome();
+await testSessionEndRetriesAfterTransientFailure();
+await testHumanBusyFailureFailsClosed();
+await testShutdownReapsAndFailsQueuedCustody();
+await testListenerTerminationEscalatesAndReaps();
+await testProtocolCorruptionFailsClosed();
+await testInboundQueueOverflowReturnsAcceptedCustody();
+await testSessionStopAwaitsOutcomeWithoutEndingEndpoint();
+await testShutdownFallbackStaysBelowHostCap();
 
 console.log("OMP-EXTENSION OK");
[raw output: artifact://671]