diff --git a/tines-core/tests/public_api.rs b/tines-core/tests/public_api.rs
index 51f7fd3e..f203b92d 100644
--- a/tines-core/tests/public_api.rs
+++ b/tines-core/tests/public_api.rs
@@ -1,21 +1,26 @@
-//! Compile probe for the tines-core 1.0 public surface (Task 5).
+//! Compile probe for the tines-core 1.0 public surface (spec §3, decisions H
+//! and K).
 //!
-//! Every `use` path here must keep resolving against `tines_core`. A future
-//! change that removes any of these items from the public API — or drops a
-//! crate-root re-export that Task 5 established — fails to build here, which
-//! is exactly what the probe guards against. CI compiles it on the workspace
-//! both with and without the default (alloc) features.
-#![allow(unused_imports)]
+//! Every path and signature here must keep resolving against `tines_core`. A
+//! change that removes or reshapes any of these items fails to build here.
+//! CI compiles it with and without the default (`alloc`) feature.
+//!
+//! The probe deliberately names nothing that §3 makes private: `Frame`,
+//! `WireError` and the local constants (`MAX_PEERS`, `PEER_IDLE_MS`, ...).
+//! Their absence is pinned by `compile_fail` doctests on `wire::Frame` and
+//! `consts::MAX_PEERS` inside the crate.
+#![allow(unused_imports, dead_code)]
 
-// Re-exported at the crate root by Task 5's `tines_core::lib`.
-use tines_core::consts::WIRE_VERSION;
+use tines_core::consts::{
+    ACK_IDS_CAP, BLOOM_K, MAX_FRAME, MAX_PAYLOAD, MAX_SIG, MAX_TOPIC, SUMMARY_BYTES, WIRE_VERSION,
+};
 use tines_core::{
     belief::{BeliefPolicy, LatestWins, SelfFirst},
     node::{Node, ObserveError},
     observation::{
         Dest, NodeId, Observation, ObservationId, Payload, SigAlgo, Signature, Tick, Topic,
     },
-    store::{Store, StoreError, TrimPolicy},
+    store::{Store, StoreError, TrimPolicy, WallClockStore},
     transport::{Event, FrameBuf, SendError, Transport},
     DropReason, NodeEvent,
 };
@@ -24,3 +29,72 @@ use tines_core::{consts, frame_sender};
 // `MemStore` lives behind the `alloc` feature.
 #[cfg(feature = "alloc")]
 use tines_core::MemStore;
+
+// The crate-root re-exports name the same items as their modules.
+use tines_core::{
+    BeliefPolicy as _, Dest as _, Event as _, LatestWins as _, Node as _, Observation as _,
+    SelfFirst as _, SendError as _, Signature as _, Store as _, StoreError as _, Transport as _,
+    TrimPolicy as _, WallClockStore as _,
+};
+
+/// `frame_sender` keeps its signature.
+const _FRAME_SENDER: fn(&[u8]) -> Option<NodeId> = frame_sender;
+
+/// The `Node` methods §3 lists, with their signatures, for any store and
+/// transport.
+fn node_methods<S: Store, T: Transport>(mut node: Node<S, T>, now: Tick) {
+    let _: NodeId = node.id();
+    let _: u64 = node.next_seq();
+    let _: Result<ObservationId, ObserveError> = node.observe(b"t", b"p", None, now);
+    let _: Result<ObservationId, ObserveError> =
+        node.observe_to([0; 16], 1_000, b"t", b"p", None, now);
+    let _: usize = node.poll(now);
+    for _ev in node.drain_events() {}
+    let _: Option<Observation> = node.belief(b"t", &LatestWins, now);
+    let _: usize = node.trim(&TrimPolicy::default(), now);
+    let _: &S = node.store();
+    let _: &mut T = node.transport_mut();
+    let _: Result<(), StoreError> = node.flush(now);
+    let _ = Node::<S, T>::new;
+}
+
+/// `set_wall_clock` and `peer_time_estimate` exist when the store is a
+/// `WallClockStore` (decision H).
+fn node_wall_clock<S: WallClockStore, T: Transport>(mut node: Node<S, T>, now: Tick) {
+    let _: S::FoldReport = node.set_wall_clock(1_700_000_000_000, now);
+    let _: Option<u64> = node.peer_time_estimate(now);
+}
+
+/// `WallClockStore`'s shape.
+fn wall_clock_store<S: WallClockStore>(mut s: S, now: Tick) {
+    let _: S::FoldReport = s.set_wall_clock(1_700_000_000_000, now);
+    let _: Option<u64> = s.peer_time_estimate(now);
+}
+
+/// `NodeEvent` carries the transport address and is matched with a wildcard
+/// (it is `#[non_exhaustive]`).
+fn node_event<A: Clone>(ev: NodeEvent<A>) {
+    match ev {
+        NodeEvent::Delivered { peer, id } => {
+            let _: (NodeId, ObservationId) = (peer, id);
+        }
+        NodeEvent::Dropped {
+            addr,
+            reason,
+            count,
+        } => {
+            let _: (Option<A>, DropReason, u32) = (addr, reason, count);
+        }
+        _ => {}
+    }
+}
+
+#[test]
+fn wire_constants_are_public() {
+    assert_eq!(WIRE_VERSION, 4);
+    assert_eq!(
+        (MAX_TOPIC, MAX_PAYLOAD, MAX_FRAME, SUMMARY_BYTES),
+        (64, 1024, 1500, 512)
+    );
+    assert_eq!((ACK_IDS_CAP, MAX_SIG, BLOOM_K), (90, 64, 3));
+}