diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2847a9c..6602599 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -74,6 +74,8 @@
   `alert_on_message_delivery` and `broadcast_area_identifier`, the names they read back under. The
   two alternate names are gone from `tlvs` too, which is now typed by `TlvName`: narrow a `string` with `isTlvName()` before indexing it.
 - `cmds.broadcast_sm_resp.tlvMap` is removed; nothing read it.
+- The `SmsInput` type is no longer exported; nothing exported took one. Read the `Sms` an `sms`
+  event carries.
 - `session.boundAs` and `session.peerInterfaceVersion` are read-only, and `session.loggedIn` is
   removed: read `session.boundAs !== undefined`. A session you wire yourself records the bind it
   accepted or had accepted with `session.bound(bindType, declaredVersion)`, which returns `err` for a
diff --git a/src/held-messages.ts b/src/held-messages.ts
index a952835..a970f6a 100644
--- a/src/held-messages.ts
+++ b/src/held-messages.ts
@@ -9,8 +9,6 @@ import { IdleWaiters } from './idle-waiters.ts';
 import { createSms } from './sms.ts';
 import { retainedOctets } from './retained-pdu.ts';
 
-type Send = (input: PduObjectInput) => Promise<Result<{ pduObj: PduObject }>>;
-
 export type HeldMessagesOptions = {
 	link: LinkLife;
 	log: SmppLog;
@@ -19,7 +17,7 @@ export type HeldMessagesOptions = {
 	/** Injected so expiry can be exercised without a wall clock. */
 	now?: (() => number) | undefined;
 	/** Past a drain's refusal, for a receipt the drain is itself waiting for. */
-	sendPastDrain: Send;
+	sendPastDrain: SmsHandlers['send'];
 	session: Session;
 	timeout: number;
 };
@@ -34,9 +32,9 @@ function keyOf(pduObjs: PduObject[]): string | undefined {
 type HoldRoute = Pick<HeldMessagesOptions, 'link' | 'sendPastDrain' | 'session'>;
 
 /**
- * One message offered to the application, and the handlers its `Sms` answers through. A drain waits on it until the first of: `answered()`,
- * every listener that took it rejecting, no listener taking it or one throwing, a later message on
- * its sequence number, its deadline, or the link going.
+ * One message offered to the application, and the handlers its `Sms` answers through. A drain
+ * waits on it until the first of: `answered()`, every listener that took it rejecting, no listener
+ * taking it or one throwing, a later message on its sequence number, its deadline, or the link going.
  */
 export class MessageHold implements SmsHandlers {
 	private readonly generation: number;
@@ -160,14 +158,12 @@ export class HeldMessages {
 		this.offered.get(message)?.listenerGaveUp();
 	}
 
-	/** Called by `MessageHold`; everything else asks the hold. */
 	holds(pduObjs: PduObject[]): boolean {
 		const key = keyOf(pduObjs);
 
 		return key !== undefined && this.held.get(key) === pduObjs;
 	}
 
-	/** Called by `MessageHold`; everything else releases through the hold. */
 	release(pduObjs: PduObject[]): void {
 		const key = keyOf(pduObjs);
 
diff --git a/src/incoming-requests.ts b/src/incoming-requests.ts
index cf61499..51aeec7 100644
--- a/src/incoming-requests.ts
+++ b/src/incoming-requests.ts
@@ -1,11 +1,12 @@
 import type { Concat } from './concat.ts';
 import type { DlrMerger } from './dlr-merger.ts';
 import type { ErrorName } from './defs/errors.ts';
+import type { HeldMessagesOptions } from './held-messages.ts';
 import type { LinkLife } from './link-life.ts';
 import type { LostGroup, Refusal } from './reassembly.ts';
 import type { OnRequest } from './session-options.ts';
-import type { PduObject, PduObjectInput } from './pdu.ts';
-import type { Result, VoidResult } from './result.ts';
+import type { PduObject } from './pdu.ts';
+import type { VoidResult } from './result.ts';
 import type { Session } from './session.ts';
 import type { SmppLog } from './log.ts';
 import type { SmsIdFormat } from './sms-id.ts';
@@ -50,8 +51,7 @@ export type IncomingRequestsOptions = {
 	maxReassembly?: number | undefined;
 	onRequest?: OnRequest | undefined;
 	reassemblyTimeout?: number | undefined;
-	/** Past a drain's refusal, for a receipt the drain is itself waiting for. */
-	sendPastDrain: (input: PduObjectInput) => Promise<Result<{ pduObj: PduObject }>>;
+	sendPastDrain: HeldMessagesOptions['sendPastDrain'];
 	session: Session;
 	smsIdFormat?: SmsIdFormat | undefined;
 	systemId?: string | undefined;
diff --git a/src/index.ts b/src/index.ts
index 509250a..71fa973 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -38,7 +38,7 @@ export { uuidv7 } from './uuid.ts';
 
 export type { BindType, ClientOptions } from './client.ts';
 export type { Dlr, Receipt } from './dlr.ts';
-export type { SendDlrResult, SendRespOptions, Sms, SmsInput } from './sms.ts';
+export type { SendDlrResult, SendRespOptions, Sms } from './sms.ts';
 export type { Concat } from './concat.ts';
 export type { ConcatInfo } from './udh.ts';
 export type { Result, VoidResult } from './result.ts';