Have drop() name the event a lost link warrants, and name requestOnCurrentLink() for what it does

src/link-life.ts

@@ -107,14 +107,14 @@ export class LinkLife {
 		this.release({});
 	}
 
-	/** The attached link is gone. False means there was none to lose. */
-	drop(): boolean {
-		if (!this.isAttached()) return false;
+	/** The attached link is gone: the event that says so, or undefined when there was none to lose. */
+	drop(): 'close' | 'disconnected' | undefined {
+		if (!this.isAttached()) return undefined;
 
 		this.phase = 'down';
 		this.drops++;
 
-		return true;
+		return this.retrying() ? 'disconnected' : 'close';
 	}
 
 	stop(): void {

src/outgoing-requests.ts

@@ -97,7 +97,7 @@ export class OutgoingRequests {
 		if (bindCommands.includes(input.cmdName)) {
 			const shut = this.link.refusal();
 
-			return shut ? { err: shut } : this.requestPastDrainGateAndWindow(input, options);
+			return shut ? { err: shut } : this.requestOnCurrentLink(input, options);
 		}
 
 		const waitForLink = this.link.hold(options.signal);
@@ -118,7 +118,7 @@ export class OutgoingRequests {
 	}
 
 	/** Straight onto the current link, for what has to go out either way. */
-	async requestPastDrainGateAndWindow(
+	async requestOnCurrentLink(
 		input: PduObjectInput,
 		options: SendOptions = {},
 	): Promise<Result<{ pduObj: PduObject }>> {

src/session.ts

@@ -237,7 +237,7 @@ export class Session extends EventEmitter<SessionEvents> {
 		const drained = await this.drain(undefined);
 		const wasOpen = this.link.isAttached();
 		const sent = wasOpen
-			? await this.outgoing.requestPastDrainGateAndWindow({ cmdName: 'unbind' })
+			? await this.outgoing.requestOnCurrentLink({ cmdName: 'unbind' })
 			: { err: new Error('Session is closed') };
 		const closedOnUnbind = wasOpen && !this.link.isAttached();
 
@@ -376,17 +376,17 @@ export class Session extends EventEmitter<SessionEvents> {
 	}
 
 	private teardown(): void {
-		// Read once: clear() reports lost segments, and a listener could stop the session between reads.
-		const retrying = this.link.retrying();
+		const lost = this.link.drop();
 
-		if (!this.link.drop()) return;
+		if (!lost) return;
 
 		this.outgoing.linkLost();
 		this.timers.clear();
 		this.incoming.clear();
 		this.sock.destroy();
 
-		if (retrying) this.emit('disconnected');
+		// Not re-read: clear() reports lost segments, and a listener can stop the session in between.
+		if (lost === 'disconnected') this.emit('disconnected');
 		else this.emitClose();
 	}
 

test/session-extras.test.ts

@@ -1460,19 +1460,20 @@ describe('LinkLife', () => {
 		assert.match(link.refusal()?.message ?? '', /closed/, 'stopped while down');
 		link.end();
 		assert.equal(link.awaitsNextLink(), false, 'ended');
-		assert.equal(new LinkLife({ log: silentLog, reconnects: false, timeout: 100 }).drop(), true);
 	});
 
-	test('drops an attached link once, and counts each drop', () => {
+	test('drops an attached link once, counts each drop, and names the event it warrants', () => {
 		const link = new LinkLife({ log: silentLog, reconnects: true, timeout: 100 });
 		const generation = link.generation();
 
-		assert.equal(link.drop(), true);
-		assert.equal(link.drop(), false, 'already down');
+		assert.equal(link.drop(), 'disconnected');
+		assert.equal(link.drop(), undefined, 'already down');
 		assert.equal(link.generation(), generation + 1);
 		link.attach();
-		assert.equal(link.drop(), true, 'a new link drops again');
+		link.stop();
+		assert.equal(link.drop(), 'close', 'a new link drops again, with none to follow it');
 		assert.equal(link.generation(), generation + 2);
+		assert.equal(new LinkLife({ log: silentLog, reconnects: false, timeout: 100 }).drop(), 'close');
 	});
 
 	test('releases a held request with the reason once the link ends', async () => {

todo.md

@@ -201,13 +201,22 @@ next work ([decision](docs/decisions.md#internals-and-tests)).
 
 A second four-seat run on 2026-09-28, after #35–#40, read 6, 6, 7 and 6 again, Locality 5, 5, 6
 and 5. Every seat ranked the session's lifecycle hardest and least wanted to modify it. A third,
-after #46, read 6, 6, 7 and 7, Locality 5, 5, 6 and 6; the link's liveness now has one owner.
+after #46, read 6, 6, 7 and 7, Locality 5, 5, 6 and 6. A fourth, after the link's liveness got one
+owner in #48, read 6, 6, 6 and 6, Locality 5 from every seat: all four still ranked `Session.teardown()`
+hardest, and the held-message flow across `incoming-requests.ts`, `held-messages.ts`, `sms.ts` and
+`Session`'s rejection handler second.
 
 - [ ] **Lift Locality to 7, and confirm it with a scoring run.** A run reading 7.0 or above also
       retires the #30 and #46 decision.
 
 ### Correctness
 
+- [ ] **Register a multipart send's receipt merge before its segments go out.** `Session.sendSms()`
+      calls `dlrMerger.expect()` only once `submitSms()` resolves, after the last segment's response,
+      so a receipt for an early segment that arrives first is logged at `debug` as naming no merge,
+      and the group then waits out `dlrMergeTimeout` with no `messageDlr`. Likeliest with a fast SMSC
+      or more segments than `maxOutstanding`. Goal 2. From the 2026-09-28 scoring run on #48.
+
 - [ ] **Settle what a repeated tag not marked `multiple` reads as, and pin it in a test.** A vendor
       tag or a known single-value tag a peer sends twice keeps the last occurrence and drops the
       rest silently, which goal 3 argues against; listing it would change every such tag's shape.