Retry the first connect and bind on reconnect fromStart (#80)

* Regression tests for a client that retries its first connect and bind

* Retry the first connect and bind on reconnect: { fromStart: true }

* Pin that the signal bounding the first bind also closes the session

* Name a failed connect once, default the backoff where it lives, and fix the deadline advice

* Carry the failure that started the retries on the abort that ends them

* Pin one retry announcement per attempt when a link drops mid-bind

* Announce a retry when its wait is over, not when it is scheduled

* Say what the process-hold assertion expects, not what a failure would mean

AGENTS.md

@@ -382,6 +382,23 @@ Grouped by what each one constrains.
   on arrival a fresh `minDelay` every cycle — one TCP connect and bind per second, forever. A drop
   after a healthy link still retries at `minDelay`.
 
+- **`reconnect: { fromStart: true }` puts the first connect and bind through that same loop, and
+  `client()` then resolves only once it is bound.** Maintainer's call, 2026-09-05: an application
+  started before its SMSC is up otherwise writes that retry itself, around the one this library
+  already owns. A field on `reconnect` rather than an option of its own, so the combination that
+  would contradict `false` cannot be written at all — `false` carries no fields — and a top-level
+  `fromStart` is refused by name rather than ignored. Nothing but the caller's `signal` ends the
+  wait: a bound of its own would be a second spelling of a deadline the caller already writes with
+  that signal, and giving up after one is what the default does. A bind the SMSC refuses is
+  retried like any other failure — rejected: giving up on `ESME_RINVPASWD` and `ESME_RBINDFAIL`,
+  which would have the initial attempts and a rebind disagree about what a refused bind means, and
+  gives up on the operator whose provisioning lands a minute later; the backoff is what bounds the
+  rate goal 4 cares about. The attempts before the first link report nothing, because the session
+  running one has not reached the application: `disconnected` would have no listener and `close`
+  would be a lie. Its wait is the one retry timer that is not `unref()`'d, for the reason
+  `LinkGate`'s hold is not — it is awaited with no other handle, so a process whose only work is
+  `client()` would exit unbound.
+
 - **A stream this library cannot frame is a dead link; one PDU it cannot parse is not.**
   Maintainer's call, 2026-08-31, narrowed 2026-09-05 via the interop plan: a `command_length` below
   16 or above `maxPduLength` leaves nothing that can say where the next PDU starts, so it tears the

README.md

@@ -78,10 +78,17 @@ Every one is optional.
 | `shutdownTimeout` | `5000` | How long `close()` and `unbind()` wait for the requests this end already sent and the messages the application has not answered. `0` waits forever for the requests, which end when the peer answers or `responseTimeout` expires — so setting both to `0` never ends. The messages fall back to `responseTimeout`, or to its default where that is `0` too, since nothing but the application ends that wait. |
 | `maxOutstanding` | `10` | Requests allowed on the wire at once; further sends queue. |
 | `smsIdFormat` | — | The notation the SMSC writes message ids in, per place it writes them: `{ receipt: 'decimal', submitResp: 'hex' }`. Only needed where the two disagree. |
-| `reconnect` | on | Re-binds after a drop, an idle timeout, or a stream the library cannot frame, backing off from `minDelay` 1 s to `maxDelay` 30 s and starting over at `minDelay` once a link has lasted `maxDelay`. `{ minDelay, maxDelay }` retunes it; `false` turns it off, so a drop ends the session. |
+| `reconnect` | on | Re-binds after a drop, an idle timeout, or a stream the library cannot frame, backing off from `minDelay` 1 s to `maxDelay` 30 s and starting over at `minDelay` once a link has lasted `maxDelay`. `{ minDelay, maxDelay }` retunes it; `false` turns it off, so a drop ends the session; `{ fromStart: true }` retries the first connect and bind too — see below. |
 | `log` | silent | Any object with `debug`, `error`, `info`, `verbose` and `warn` methods — see [Logging](#logging). |
 | `signal` | — | An `AbortSignal` that cancels connecting and tears the session down. |
 
+`reconnect: { fromStart: true }` puts the very first connect and bind through that same loop, so a
+client started while its SMSC is down keeps retrying — a bind the SMSC refuses included — instead of
+failing on the first attempt. `client()` then resolves once it is bound, and nothing but an aborted
+`signal` ends the wait, however long the SMSC stays down. That signal also closes the session once it
+is bound, so write a deadline for the wait as an `AbortController` you stop arming when `client()`
+returns, rather than as `AbortSignal.timeout(ms)`, which would close the session it just bound.
+
 ### Sending
 
 ```javascript

src/client.ts

@@ -6,6 +6,7 @@ import type { SmsIdFormat } from './sms-id.ts';
 import type { Socket } from 'node:net';
 export type { BindType };
 
+import { ReconnectLoop } from './reconnect-loop.ts';
 import { Session } from './session.ts';
 import { checkSessionOptions, undeclaredInterfaceVersion } from './session-options.ts';
 import { connect as netConnect } from 'node:net';
@@ -13,6 +14,9 @@ import { connect as tlsConnect } from 'node:tls';
 import { defaultInterfaceVersion } from './defs/constants.ts';
 import { guardedLog } from './log.ts';
 
+/** `fromStart` puts the very first connect and bind through the same backoff loop as a drop. */
+type ReconnectTuning = { fromStart?: boolean; maxDelay?: number; minDelay?: number };
+
 export type ClientOptions = {
 	addressRange?: string;
 	addrNpi?: number;
@@ -26,7 +30,7 @@ export type ClientOptions = {
 	maxOutstanding?: number;
 	password?: string;
 	port?: number;
-	reconnect?: { maxDelay?: number; minDelay?: number } | false;
+	reconnect?: ReconnectTuning | false;
 	responseTimeout?: number;
 	shutdownTimeout?: number;
 	signal?: AbortSignal;
@@ -96,6 +100,21 @@ function openSocket(options: ClientOptions): Promise<Result<{ sock: Socket }>> {
 	});
 }
 
+/** Every connect this client makes goes through here, so a failed one is named the same way once. */
+async function connectSocket(options: ClientOptions, log: SmppLog): Promise<Result<{ sock: Socket }>> {
+	const opened = await openSocket(options);
+
+	if (opened.err) {
+		log.warn('client - could not connect', {
+			host: options.host ?? defaults.host,
+			message: opened.err.message,
+			port: options.port ?? defaults.port,
+		});
+	}
+
+	return opened;
+}
+
 function bindParams(options: ClientOptions, systemId: string) {
 	return {
 		address_range: options.addressRange ?? '',
@@ -139,13 +158,13 @@ async function bind(session: Session, options: ClientOptions): Promise<VoidResul
 	return {};
 }
 
-function reconnectFor(options: ClientOptions): ReconnectOptions | undefined {
+function reconnectFor(options: ClientOptions, log: SmppLog): ReconnectOptions | undefined {
 	if (options.reconnect === false) return undefined;
 
 	const tuning = options.reconnect ?? {};
 
 	return {
-		connect: () => openSocket(options),
+		connect: () => connectSocket(options, log),
 		maxDelay: tuning.maxDelay,
 		minDelay: tuning.minDelay,
 		onConnected: reconnected => bind(reconnected, options),
@@ -160,7 +179,7 @@ function createSession(options: ClientOptions, log: SmppLog, sock: Socket): Sess
 		idleTimeout: options.idleTimeout ?? enquireLinkInterval * defaults.idleTimeoutFactor,
 		log,
 		maxOutstanding: options.maxOutstanding,
-		reconnect: reconnectFor(options),
+		reconnect: reconnectFor(options, log),
 		responseTimeout: options.responseTimeout,
 		shutdownTimeout: options.shutdownTimeout,
 		smsIdFormat: options.smsIdFormat,
@@ -168,38 +187,22 @@ function createSession(options: ClientOptions, log: SmppLog, sock: Socket): Sess
 	});
 }
 
-async function connect(options: ClientOptions, log: SmppLog): Promise<Result<{ sock: Socket }>> {
-	const checked = checkSessionOptions(options);
-
-	if (checked.err) {
-		log.warn('client - unusable option', { message: checked.err.message });
-
-		return { err: checked.err };
-	}
-
-	const opened = await openSocket(options);
-
-	if (opened.err) {
-		log.warn('client - could not connect', {
-			host: options.host ?? defaults.host,
-			message: opened.err.message,
-			port: options.port ?? defaults.port,
-		});
-
-		return { err: opened.err };
-	}
-
-	return { sock: opened.sock };
-}
-
-/** Connects to an SMSC and binds. */
-export async function client(options: ClientOptions = {}): Promise<Result<{ session: Session }>> {
-	const log = guardedLog(options.log);
-	const opened = await connect(options, log);
+async function connectAndBind(
+	options: ClientOptions,
+	log: SmppLog,
+): Promise<Result<{ session: Session }>> {
+	const opened = await connectSocket(options, log);
 
 	if (opened.err) return { err: opened.err };
 
-	const session = createSession(options, log, opened.sock);
+	return bindOn(createSession(options, log, opened.sock), options);
+}
+
+/** Binds a session the caller has not seen yet, so a failure takes it down instead of surfacing. */
+async function bindOn(
+	session: Session,
+	options: ClientOptions,
+): Promise<Result<{ session: Session }>> {
 	const signal = options.signal;
 
 	if (signal?.aborted === true) {
@@ -208,12 +211,16 @@ export async function client(options: ClientOptions = {}): Promise<Result<{ sess
 		return { err: new Error('Aborted before binding') };
 	}
 
+	const onAbort = (): void => { void session.close({ signal }); };
+
 	// Registered before the bind: an abort landing while it is in flight has to close the session.
-	signal?.addEventListener('abort', () => { void session.close({ signal }); }, { once: true });
+	signal?.addEventListener('abort', onAbort, { once: true });
 
 	const bound = await bind(session, options);
 
 	if (bound.err) {
+		signal?.removeEventListener('abort', onAbort);
+		// close() must reach the loop's stop() before its first await, or this session retries too.
 		void session.close({ signal });
 
 		return { err: bound.err };
@@ -221,3 +228,96 @@ export async function client(options: ClientOptions = {}): Promise<Result<{ sess
 
 	return { session };
 }
+
+function retriesFromStart(reconnect: ClientOptions['reconnect']): reconnect is ReconnectTuning {
+	return reconnect !== undefined && reconnect !== false && reconnect.fromStart === true;
+}
+
+/** A fresh session per attempt, and the failure to answer an abort with when none of them binds. */
+function initialAttempts(options: ClientOptions, log: SmppLog, failed: Error) {
+	let lastErr = failed;
+
+	return {
+		bind: async (sock: Socket): Promise<Result<{ session: Session }>> => {
+			const bound = await bindOn(createSession(options, log, sock), options);
+
+			if (bound.err) lastErr = bound.err;
+
+			return bound;
+		},
+		connect: async (): Promise<Result<{ sock: Socket }>> => {
+			const opened = await connectSocket(options, log);
+
+			if (opened.err) lastErr = opened.err;
+
+			return opened;
+		},
+		lastErr: (): Error => lastErr,
+	};
+}
+
+/** Retries the first connect and bind, on the backoff a drop takes, until one of them binds. */
+function keepTrying(
+	options: ClientOptions,
+	log: SmppLog,
+	tuning: ReconnectTuning,
+	failed: Error,
+): Promise<Result<{ session: Session }>> {
+	return new Promise(resolve => {
+		const attempts = initialAttempts(options, log, failed);
+		const signal = options.signal;
+		let settled = false;
+		const loop = new ReconnectLoop({
+			connect: attempts.connect,
+			log,
+			maxDelay: tuning.maxDelay,
+			minDelay: tuning.minDelay,
+			onConnected: async sock => {
+				const bound = await attempts.bind(sock);
+
+				if (bound.err) return { err: bound.err };
+
+				settle({ session: bound.session });
+
+				return {};
+			},
+			// Awaited with no other handle, so an unref()'d wait would exit the process unbound.
+			unref: false,
+		});
+
+		function settle(result: Result<{ session: Session }>): void {
+			if (settled) return;
+
+			settled = true;
+			loop.stop();
+			signal?.removeEventListener('abort', onAbort);
+			resolve(result);
+		}
+
+		function onAbort(): void {
+			settle({ err: new Error('Aborted while connecting', { cause: attempts.lastErr() }) });
+		}
+
+		signal?.addEventListener('abort', onAbort, { once: true });
+		loop.schedule();
+	});
+}
+
+/** Connects to an SMSC and binds. */
+export async function client(options: ClientOptions = {}): Promise<Result<{ session: Session }>> {
+	const log = guardedLog(options.log);
+	const checked = checkSessionOptions(options);
+
+	if (checked.err) {
+		log.warn('client - unusable option', { message: checked.err.message });
+
+		return { err: checked.err };
+	}
+
+	const first = await connectAndBind(options, log);
+	const reconnect = options.reconnect;
+
+	if (!first.err || options.signal?.aborted === true || !retriesFromStart(reconnect)) return first;
+
+	return keepTrying(options, log, reconnect, first.err);
+}

src/reconnect-loop.ts

@@ -2,18 +2,27 @@ import type { Result, VoidResult } from './result.ts';
 import type { SmppLog } from './log.ts';
 import type { Socket } from 'node:net';
 
+export const backoffDefaults = {
+	maxDelay: 30_000,
+	minDelay: 1000,
+};
+
 export type ReconnectLoopOptions = {
 	connect: () => Promise<Result<{ sock: Socket }>>;
 	log: SmppLog;
-	maxDelay: number;
-	minDelay: number;
+	maxDelay?: number | undefined;
+	minDelay?: number | undefined;
 	now?: (() => number) | undefined;
 	/** Brings the owner back up on a freshly opened socket. An err means try again. */
 	onConnected: (sock: Socket) => Promise<VoidResult>;
+	/** Whether the wait between attempts lets the process exit. Default true. */
+	unref?: boolean | undefined;
 };
 
 /** Reopens a dropped connection, backing off between attempts until it is told to stop. */
 export class ReconnectLoop {
+	private readonly maxDelay: number;
+	private readonly minDelay: number;
 	private readonly now: () => number;
 	private readonly options: ReconnectLoopOptions;
 	private attempting = false;
@@ -23,9 +32,11 @@ export class ReconnectLoop {
 	private upAt: number | undefined;
 
 	constructor(options: ReconnectLoopOptions) {
+		this.maxDelay = options.maxDelay ?? backoffDefaults.maxDelay;
+		this.minDelay = options.minDelay ?? backoffDefaults.minDelay;
 		this.now = options.now ?? Date.now;
 		this.options = options;
-		this.delay = options.minDelay;
+		this.delay = this.minDelay;
 	}
 
 	/** Read through a method: stop() can land while an attempt is awaiting. */
@@ -37,23 +48,24 @@ export class ReconnectLoop {
 		if (this.timer || this.attempting || this.isStopped()) return;
 
 		// Coming up is not proof: a stream we cannot read is only found once the link is bound.
-		if (this.upAt !== undefined && this.now() - this.upAt >= this.options.maxDelay) {
-			this.delay = this.options.minDelay;
+		if (this.upAt !== undefined && this.now() - this.upAt >= this.maxDelay) {
+			this.delay = this.minDelay;
 		}
 
 		this.upAt = undefined;
 
 		const delay = this.delay;
 
-		this.options.log.info('reconnect - retrying after a drop', { delay });
-
+		// Announced when the wait is over rather than when it starts: a cancelled one never happened.
 		this.timer = setTimeout(() => {
 			this.timer = undefined;
+			this.options.log.info('reconnect - retrying', { delay });
 			void this.run();
 		}, delay);
-		this.timer.unref();
 
-		this.delay = Math.min(delay * 2, this.options.maxDelay);
+		if (this.options.unref ?? true) this.timer.unref();
+
+		this.delay = Math.min(delay * 2, this.maxDelay);
 	}
 
 	stop(): void {

src/session-options.ts

@@ -7,6 +7,7 @@ import type { SmppLog } from './log.ts';
 import type { SmsIdFormat } from './sms-id.ts';
 import type { Sms } from './sms.ts';
 import type { Socket } from 'node:net';
+import { backoffDefaults } from './reconnect-loop.ts';
 import { isSmsIdNotation, smsIdNotations, smsIdPlaces } from './sms-id.ts';
 
 export type SessionEvents = {
@@ -103,12 +104,10 @@ export const defaults = {
 	dlrMergeTimeout: 86_400_000,
 	/** The peer gave up on an unanswered message long before this; the bound is against growth. */
 	heldMessageTimeout: 300_000,
-	maxDelay: 30_000,
 	maxDlrMerges: 1000,
 	maxHeldMessages: 1000,
 	maxOutstanding: 10,
 	maxReassembly: 1000,
-	minDelay: 1000,
 	reassemblyTimeout: 300_000,
 	responseTimeout: 30_000,
 	shutdownTimeout: 5000,
@@ -120,6 +119,10 @@ export const defaults = {
  * queued behind a slot that is never freed, so the call never settles at all.
  */
 export function checkSessionOptions(options: CheckableOptions): VoidResult {
+	if (options.fromStart !== undefined) {
+		return { err: new Error('fromStart is part of the reconnect policy, spell it reconnect: { fromStart: true }') };
+	}
+
 	const checked = checkLimits([
 		['idleTimeout', options.idleTimeout ?? 0, 0],
 		['maxOutstanding', options.maxOutstanding ?? defaults.maxOutstanding, 1],
@@ -146,23 +149,27 @@ function checkLimits(limits: [string, number, number][]): VoidResult {
 	return {};
 }
 
-const backoffDelays: readonly string[] = ['maxDelay', 'minDelay'];
+const reconnectKeys: readonly string[] = ['fromStart', 'maxDelay', 'minDelay'];
 
 function checkReconnect(reconnect: unknown): VoidResult {
 	if (reconnect === undefined || reconnect === false) return {};
 
 	if (!isRecord(reconnect)) {
-		return { err: new Error('reconnect takes { maxDelay, minDelay }, or false to turn it off') };
+		return { err: new Error('reconnect takes { fromStart, maxDelay, minDelay }, or false to turn it off') };
 	}
 
 	for (const key of Object.keys(reconnect)) {
-		if (!backoffDelays.includes(key)) {
-			return { err: new Error(`reconnect has no ${key}, name ${backoffDelays.join(' or ')}`) };
+		if (!reconnectKeys.includes(key)) {
+			return { err: new Error(`reconnect has no ${key}, name ${reconnectKeys.join(', ')}`) };
 		}
 	}
 
-	const maxDelay = delayOr(reconnect.maxDelay, defaults.maxDelay);
-	const minDelay = delayOr(reconnect.minDelay, defaults.minDelay);
+	if (reconnect.fromStart !== undefined && typeof reconnect.fromStart !== 'boolean') {
+		return { err: new Error(`reconnect.fromStart must be true or false, got ${typeof reconnect.fromStart}`) };
+	}
+
+	const maxDelay = delayOr(reconnect.maxDelay, backoffDefaults.maxDelay);
+	const minDelay = delayOr(reconnect.minDelay, backoffDefaults.minDelay);
 	// A delay of 0 never doubles, so the backoff never starts and every retry lands at once.
 	const checked = checkLimits([['maxDelay', maxDelay, 1], ['minDelay', minDelay, 1]]);
 
@@ -211,6 +218,8 @@ function checkSmsIdFormat(smsIdFormat: unknown): VoidResult {
 
 /** What the checker reads, as it arrives: a caller without types can put anything in it. */
 export type CheckableOptions = {
+	/** Not an option: the one spelling is inside reconnect, and this is where the other is refused. */
+	fromStart?: unknown;
 	idleTimeout?: number | undefined;
 	maxOutstanding?: number | undefined;
 	maxReassembly?: number | undefined;

src/session.ts

@@ -265,8 +265,8 @@ export class Session extends EventEmitter<SessionEvents> {
 		return new ReconnectLoop({
 			connect: reconnect.connect,
 			log: this.log,
-			maxDelay: reconnect.maxDelay ?? defaults.maxDelay,
-			minDelay: reconnect.minDelay ?? defaults.minDelay,
+			maxDelay: reconnect.maxDelay,
+			minDelay: reconnect.minDelay,
 			onConnected: sock => this.comeBackUp(sock, reconnect.onConnected),
 		});
 	}

test/session-extras.test.ts

@@ -74,6 +74,11 @@ function delay(ms: number): Promise<void> {
 	return new Promise(resolve => { setTimeout(resolve, ms); });
 }
 
+/** Undefined where the promise never settled, which is an assertion rather than a hung run. */
+function within<T>(ms: number, promise: Promise<T>): Promise<T | undefined> {
+	return Promise.race([promise, delay(ms).then((): undefined => undefined)]);
+}
+
 function submitPdu(seqNr: number, cmdStatus: ErrorName = 'ESME_ROK'): PduObject {
 	return {
 		cmdId: 0x00000004,
@@ -547,7 +552,7 @@ describe('reconnect', () => {
 		await closed;
 
 		assert.equal(disconnects, 0);
-		assert.ok(!infos.includes('reconnect - retrying after a drop'));
+		assert.ok(!infos.includes('reconnect - retrying'));
 	});
 
 	test('re-binds after the connection drops, keeping the same session object', async t => {
@@ -732,6 +737,267 @@ describe('reconnect', () => {
 	});
 });
 
+describe('reconnect from the first bind', () => {
+	type LogSpy = { delays: number[]; log: SmppLog; messages: string[] };
+
+	/** The backoff is only visible in the log, which is where the loop announces each wait. */
+	function logSpy(): LogSpy {
+		const delays: number[] = [];
+		const messages: string[] = [];
+		const noop = (): void => undefined;
+		const record = (msg: string): void => { messages.push(msg); };
+
+		return {
+			delays,
+			log: {
+				debug: noop,
+				error: record,
+				info: (msg, metadata) => {
+					messages.push(msg);
+
+					if (msg === 'reconnect - retrying') delays.push(Number(metadata?.delay));
+				},
+				verbose: noop,
+				warn: record,
+			},
+			messages,
+		};
+	}
+
+	/** A port nothing answers on: taken and given straight back. */
+	async function closedPort(): Promise<number> {
+		const listener = net.createServer();
+
+		await new Promise<void>(resolve => { listener.listen(0, resolve); });
+
+		const address = listener.address();
+		const port = typeof address === 'object' && address !== null ? address.port : 0;
+
+		await new Promise<void>(resolve => { listener.close(() => { resolve(); }); });
+
+		return port;
+	}
+
+	/** A client still retrying holds a socket and a timer nothing else releases. */
+	function abortAfter(
+		t: TestContext,
+		controller: AbortController,
+		connecting: ReturnType<typeof client>,
+	): void {
+		t.after(async () => {
+			controller.abort();
+
+			const { session } = await connecting;
+
+			await session?.close({ signal: AbortSignal.abort() });
+		});
+	}
+
+	test('gives up on the first attempt where reconnect alone is asked for', async () => {
+		const port = await closedPort();
+		const spy = logSpy();
+		const started = Date.now();
+		const { err, session } = await client({ log: spy.log, port, reconnect: { maxDelay: 40, minDelay: 10 } });
+
+		assert.ok(err instanceof Error);
+		assert.equal(session, undefined);
+		assert.ok(Date.now() - started < 1000, 'the default answers the caller rather than retrying');
+		assert.ok(!spy.messages.includes('reconnect - retrying'), 'nothing may retry what the default gave up on');
+	});
+
+	test('retries the first connect with backoff and binds once the SMSC listens', async t => {
+		const port = await closedPort();
+		const spy = logSpy();
+		const controller = new AbortController();
+		const connecting = client({
+			log: spy.log,
+			port,
+			reconnect: { fromStart: true, maxDelay: 40, minDelay: 10 },
+			signal: controller.signal,
+		});
+
+		abortAfter(t, controller, connecting);
+		await delay(200);
+
+		const listening = await server({ port });
+
+		assert.equal(listening.err, undefined);
+		assert.ok(listening.server);
+		closeAfter(t, listening.server);
+
+		const { err, session } = await connecting;
+
+		assert.equal(err, undefined);
+		assert.ok(session);
+		assert.equal(session.loggedIn, true);
+		assert.ok(spy.delays.length >= 3, 'the SMSC was down for several attempts');
+		assert.deepEqual(spy.delays.slice(0, 3), [10, 20, 40], 'each wait doubles, up to maxDelay');
+		assert.ok(
+			!spy.messages.includes('session - reconnected'),
+			'a first link is not a link coming back',
+		);
+	});
+
+	// Bind flooding is what the backoff bounds; credentials an SMSC refuses now it may take later.
+	test('retries a bind the SMSC refuses rather than giving up on it', async t => {
+		let binds = 0;
+		const spy = logSpy();
+		const smpp = await startServer(t, { authenticate: () => ++binds > 2 });
+		const controller = new AbortController();
+		const connecting = client({
+			log: spy.log,
+			port: smpp.port,
+			reconnect: { fromStart: true, maxDelay: 40, minDelay: 10 },
+			signal: controller.signal,
+		});
+
+		abortAfter(t, controller, connecting);
+
+		const { err, session } = await connecting;
+
+		assert.equal(err, undefined);
+		assert.ok(session);
+		assert.equal(binds, 3, 'the two refusals were retried, not reported');
+		assert.deepEqual(spy.delays, [10, 20], 'a link the SMSC refused a bind on does not reset the backoff');
+	});
+
+	// A drop while the bind is in flight is where the attempt's own session could retry as well.
+	test('retries once per attempt when the peer drops the link mid-bind', async t => {
+		let binds = 0;
+		const spy = logSpy();
+		const smpp = await startServer(t, {
+			authenticate: input => {
+				binds++;
+
+				if (binds > 2) return true;
+
+				input.session.sock.destroy();
+
+				return false;
+			},
+		});
+		const controller = new AbortController();
+		const connecting = client({
+			log: spy.log,
+			port: smpp.port,
+			reconnect: { fromStart: true, maxDelay: 40, minDelay: 10 },
+			signal: controller.signal,
+		});
+
+		abortAfter(t, controller, connecting);
+
+		const { err, session } = await connecting;
+
+		assert.equal(err, undefined);
+		assert.ok(session);
+		assert.deepEqual(spy.delays, [10, 20], 'only the loop that owns the retry announces one');
+	});
+
+	test('hands back a session that reported nothing and reconnects like any other', async t => {
+		const port = await closedPort();
+		const controller = new AbortController();
+		const connecting = client({
+			port,
+			reconnect: { fromStart: true, maxDelay: 40, minDelay: 10 },
+			signal: controller.signal,
+		});
+
+		abortAfter(t, controller, connecting);
+		await delay(100);
+
+		const listening = await server({ port });
+
+		assert.equal(listening.err, undefined);
+		assert.ok(listening.server);
+		closeAfter(t, listening.server);
+
+		const { session } = await connecting;
+
+		assert.ok(session);
+
+		const events: string[] = [];
+
+		session.on('close', () => { events.push('close'); });
+		session.on('disconnected', () => { events.push('disconnected'); });
+
+		const reconnected = once<true>(resolve => { session.on('reconnected', () => { resolve(true); }); });
+
+		await peerOf(listening.server).close();
+		await reconnected;
+
+		assert.deepEqual(events, ['disconnected'], 'the attempts before the first link reported nothing');
+
+		const closed = once<true>(resolve => { session.on('close', () => { resolve(true); }); });
+
+		controller.abort();
+		await closed;
+
+		// Which is why a deadline for the wait may not be a signal that goes on arming afterwards.
+		assert.deepEqual(events, ['disconnected', 'close'], 'the signal that bounded the wait ends the session');
+	});
+
+	test('lets an abort out of the initial retries', async () => {
+		const port = await closedPort();
+		const controller = new AbortController();
+		const connecting = client({
+			port,
+			reconnect: { fromStart: true, maxDelay: 40, minDelay: 10 },
+			signal: controller.signal,
+		});
+
+		await delay(60);
+		controller.abort();
+
+		const settled = await within(2000, connecting);
+
+		assert.ok(settled, 'an aborted signal is the way out of a wait nothing else ends');
+		assert.ok(settled.err instanceof Error);
+		assert.ok(settled.err.cause instanceof Error, 'an abort carries what the attempts kept failing with');
+		assert.equal(settled.session, undefined);
+	});
+
+	test('holds the process open between the initial attempts', async t => {
+		const port = await closedPort();
+		const controller = new AbortController();
+		const timeouts = (): number => process.getActiveResourcesInfo().filter(name => name === 'Timeout').length;
+		const before = timeouts();
+		const connecting = client({
+			port,
+			reconnect: { fromStart: true, maxDelay: 5000, minDelay: 5000 },
+			signal: controller.signal,
+		});
+
+		abortAfter(t, controller, connecting);
+		await delay(200);
+
+		assert.ok(timeouts() > before, 'the wait should hold a process whose only work is this client');
+
+		controller.abort();
+
+		const settled = await within(2000, connecting);
+
+		assert.ok(settled);
+		assert.ok(settled.err instanceof Error);
+	});
+
+	test('refuses fromStart spelled anywhere but inside reconnect', async () => {
+		const misspelled = { fromStart: true, port: 1, reconnect: false } as const;
+
+		assert.match(
+			checkSessionOptions(misspelled).err?.message ?? '',
+			/reconnect: \{ fromStart: true \}/,
+			'off and from-start contradict each other, so the one spelling has to be named',
+		);
+
+		const refused = await client(misspelled);
+
+		assert.ok(refused.err instanceof Error);
+		assert.equal(refused.session, undefined);
+		assert.match(checkSessionOptions({ reconnect: { fromStart: 'yes' } }).err?.message ?? '', /fromStart/);
+		assert.equal(checkSessionOptions({ reconnect: { fromStart: true, minDelay: 10 } }).err, undefined);
+	});
+});
+
 describe('sends across a reconnect', () => {
 	/** Answers every message after the first, which is left to hold the send window open. */
 	function answerAfterTheFirst(smpp: SmppServer, arrived: string[]): Latch {

test/session.test.ts

@@ -1638,7 +1638,7 @@ describe('application hooks that throw or reject', () => {
 			debug: noop,
 			error: noop,
 			info: (msg, metadata) => {
-				if (msg === 'reconnect - retrying after a drop') delays.push(Number(metadata?.delay));
+				if (msg === 'reconnect - retrying') delays.push(Number(metadata?.delay));
 			},
 			verbose: noop,
 			warn: noop,