diff --git a/source/capability.go b/source/capability.go
index 905bfbb..2558a9c 100644
--- a/source/capability.go
+++ b/source/capability.go
@@ -120,7 +120,8 @@ type OrderedDelivery interface {
 // substitute for per-message settlement.
 type Batched interface {
 	// NextBatch returns up to limit messages, blocking for at least one, or
-	// ctx.Err()/ErrDrained as [Subscription.Next] would.
+	// ctx.Err()/ErrDrained as [Subscription.Next] would. A limit below one is
+	// treated as one.
 	NextBatch(ctx context.Context, limit int) ([]Message, error)
 	// SettleBatch applies the single result r to every message in ms in one call.
 	// It is for a caller settling a uniform batch directly; the Hopper settles per
diff --git a/source/handler.go b/source/handler.go
index 0235e75..c88c7f2 100644
--- a/source/handler.go
+++ b/source/handler.go
@@ -172,6 +172,8 @@ func Skip() Result { return Result{Action: ActionAck, Class: Drop} }
 func InProgress() Result { return Result{Action: ActionInProgress} }
 
 // Manual returns a Result reporting the handler settled the message itself.
+// The message's in-flight slot is released like any other settle — drain
+// accounting treats Manual as settled — but the backend takes no action.
 func Manual() Result { return Result{Action: ActionManual} }
 
 // Failed reports whether the result carries a failure (anything that is not a
diff --git a/source/kafka/capability.go b/source/kafka/capability.go
index b9901c1..b359696 100644
--- a/source/kafka/capability.go
+++ b/source/kafka/capability.go
@@ -424,8 +424,11 @@ func toRecordHeaders(hs source.Headers) []kgo.RecordHeader {
 // m's offset is marked only after fn succeeds and only inside the transaction, so
 // a failed transform never advances the consumed position: the commit-after-
 // process invariant holds, now atomically with the produce side. Begin is the
-// full settle path for m; the caller must not also call [Subscription.Settle] for
-// m.
+// full settle path for m; the caller must not also call [Subscription.Settle]
+// for m. A direct Settle for m during an open Begin, or after Begin returned,
+// is a caller error with undefined results — it is not detected or coordinated
+// with the transaction: at best it duplicates an already-committed mark
+// (harmless at-least-once), at worst it races End's commit/abort.
 //
 // It is available only when the inlet was built with [WithTransactional];
 // otherwise it reports the capability is absent rather than silently running fn