Say when a vault has moved, so nobody waits out the minute

The delta pull was cheap enough to run on a timer and the client did, once a
minute. That is fine for a machine and wrong for two people: an edit a colleague
makes is up to a minute stale, which is long enough for both of them to make it
and produce a conflict neither needed to have. Shortening the interval is the
obvious answer and the wrong one — it costs a request per client per interval
whether or not anything happened, and it converges on a busier server that is
still late.

So the server now says so. A client holds a WebSocket open at GET /api/v1/events,
subprotocol dodossh.events.v1, and gets a line down it when something it can read
has changed. ADR 0012 has the reasoning; three parts of it are worth repeating
here, because they are what everything else rests on.

**What crosses the socket is a notice, never data.** A frame names a vault and
how far its change log has got. No item, no ciphertext, not even which item it
was. The client's answer is the delta pull it would have run anyway, so there is
still exactly one code path that applies a change to a keychain, and it is not
this one. Pushing the items themselves would save a round trip and fork that path
in two, with the cursor, the merge and the tombstone rules duplicated across both
— ADR 0003 put every mutation through one write path for that reason, and this
keeps every read on one for the same one. It also makes a dropped notice
harmless, which is what lets the fan-out below be as simple as it is.

**Polling stays, and is what guarantees a pass.** The minute timer is unchanged.
A network that eats WebSockets, a server with Events:Enabled off, an older
server, a proxy that will not upgrade, a notice dropped under backpressure —
every one of those leaves a client behaving exactly as it did before this commit.
Nothing is reachable only over the socket and nothing is meant to become so;
VaultViewModel's AutoSyncInterval remark now says that where somebody changing it
will read it.

**The bearer token authorises the upgrade, unlike the relay's ticket.** Not an
inconsistency with ADR 0004: the relay's socket is a byte pipe whose whole
authorization decision — which host, which IPs, which port — is made before it
opens and never revisited, and it is the extraction seam for a process that must
hold no ACL code. This one is a view of the caller's own vault list and has to
keep answering "what may this account read" for as long as it is held. A ticket
would carry that answer in a token and be wrong the moment the account's access
changed. The two bounds that arrangement needs are met rather than waved at: the
socket is closed at the token's exp with close code 4401 and the client comes
straight back with a fresh one, and the vault set is re-resolved every few
minutes as well as on the changes known to affect it. Both bound *metadata*,
because a notice contains nothing else and reading a vault still needs a key this
server has never held.

**The fan-out.** VaultEventHub is a singleton holding the sockets this node
accepted; publishing walks them and asks each whether it cares, rather than
keeping a vault-to-subscriber index that every re-subscription would have to move
entries between under a lock publishing also takes. At a few hundred sockets per
node and an event rate bounded by how often people edit keychains, the walk is
not measurable and its races are obvious. Per-connection queues are bounded and
drop the *oldest*: a notice means "pull vault X, which is at least at sequence
N", so the newest subsumes what it displaces and the client's answer is identical
either way — which is what lets the publish path be void, never block, and never
fail.

Announced from the endpoint rather than from SyncService, and that placement is
the point: by then the push has committed and released the per-vault advisory
lock. From inside it would name a sequence no reader can see yet and would hold
the lock that serialises writers across a socket write. Only the highest
*applied* sequence, so a batch of pure conflicts announces nothing, and a
duplicate — already announced when it first landed — announces nothing either.

Grants and membership publish too, and those take the *recipient* rather than the
actor. This is what AdmitNewVaultsAsync has been apologising for since sharing
shipped — "the recipient is handed nothing, there is no push channel" — and the
README with it. A vault shared with somebody now turns up as it is shared. The
comment and the README paragraph both say what is true now, and both keep saying
that the pass is what *discovers* the vault, because a client with no socket has
to arrive at the same place.

**On the client**, VaultEventStream is really a reconnection policy wrapped round
a ClientWebSocket: a dropped socket is the ordinary case here — laptops sleep,
proxies time out, tokens expire, servers are redeployed — so nothing in it treats
a failure as exceptional, and every path ends in "wait, then dial again". A
connection that lived long enough to say hello resets the backoff, so a laptop
that woke, worked, and lost its network an hour later does not inherit a
minute-long wait it has already proved it need not take. A 4401 close skips the
backoff entirely and asks the token provider again, which is the whole reason
that close code is distinct. A server that does not advertise the events feature
gets IdleVaultEventStream, which never delivers — so IVaultServer.Events is never
null and every caller stays on one shape, because the correct behaviour without a
socket is the behaviour with a silent one.

The shell's background loop now selects between the timer and a notice, and both
waits are held across iterations. That is load-bearing rather than tidy:
PeriodicTimer permits one outstanding WaitForNextTickAsync and throws on a
second, and an abandoned channel read stays registered and consumes the next
notice written. Either defect leaves the first notice working and every one after
it silently lost, which is why NoticesKeepWakingTheLoop_NotJustTheFirst pushes
three and not one. Notices are coalesced over a quarter of a second, so one
person's save — a host and its log entry are two items — and a colleague clearing
a folder each cost one pass rather than a dozen.

**The kind is a string, not an enum**, and that is a compatibility decision.
UseStringEnumConverter throws on a value it does not know, so a newer server
sending a kind an older client had never heard of would not add an unreadable
frame — it would break that client's socket outright. A string is ignored
instead. ProblemCodes is the same shape for the same reason.

**Tested on both sides, through the real pipeline.** The endpoint suite opens a
genuine socket against TestServer and proves a push produces a notice, that
another account's push does not reach it, that a ping is answered, and that a
frame this server cannot parse does not end the connection. Two of those assert
on *ordering* rather than on absence within a timeout — the stranger's write goes
first, so a socket that leaked would have announced it before the one the test
waits for — because "nothing arrived in two seconds" is a test that passes on a
slow machine for the wrong reason. And ANoticeCarriesNoCiphertext asserts on the
bytes that crossed the wire rather than on the record's fields, since the latter
would only prove that this type has no payload member, which is a tautology; the
former is what catches a field added later without anybody thinking about
disclosure.

The client suite drives VaultEventStream through an injected connector, because
the one thing a test cannot do to a real network is make it fail on cue — and
failure is the entire subject. The shell suite proves a notice produces a pull
inside ten seconds against a sixty-second timer, so the timer cannot be what
caused it.

**Two limits, stated rather than left to be discovered.** Fan-out is in-process,
so a deployment running more than one API replica only pushes for writes its own
replica handled and the rest arrive on the timer. IVaultEventPublisher is the
seam a PostgreSQL LISTEN/NOTIFY backplane implements and it is deliberately not
implemented: an untested backplane is worse than a documented gap, and multiple
replicas degrade to the behaviour before this commit rather than breaking. And a
client is notified of its own writes; it pushed, so it already pulled, and the
extra pass finds nothing. Suppressing that echo correctly needs a per-device
identity on the socket, and the same user's other machines must still be told.

Manual checks phase 15 covers what no test here can reach, which is the network
in between: a proxy that will not upgrade, one that drops an idle socket without
telling either end, a laptop lid, a token expiring. Every one of those is
invisible inside a test host, and every check there passes only if the change
arrives quickly *and* still arrives with the socket taken away.

ADR 0012 also fixes one thing about the shared terminal session this is the
transport for, so it need not be renegotiated later: session data will be binary
frames on this same socket, because base64 in a JSON envelope is the wrong shape
for the one payload here that is continuous rather than occasional. Two questions
it explicitly does not answer by implication — whether those bytes go through the
API at all, and what end-to-end encryption means when the second party watches a
stream rather than holding a key — are ADR 0001 questions and get their own
decision.

1512 tests pass. DodoSSH.SystemTests was not run — it needs the whole compose
stack — so the end-to-end path is unverified for this change beyond what the
manual checks describe.

tests/DodoSSH.Api.Tests/ApiFixture.cs

@@ -1,4 +1,6 @@
 using System.Net.Http.Headers;
+using System.Net.WebSockets;
+using DodoSSH.Contracts;
 using DodoSSH.Infrastructure;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.Mvc.Testing;
@@ -107,6 +109,34 @@ public sealed class ApiFixture : WebApplicationFactory<Program>, IAsyncLifetime
 
     /// <summary>Opens a database scope for arranging state and asserting on it.</summary>
     public AsyncServiceScope CreateScope() => Services.CreateAsyncScope();
+
+    /// <summary>
+    /// Opens the event socket as the given subject, through the real pipeline.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The bearer token goes on the upgrade request, which is the whole of the socket's authorization
+    /// — see ADR 0012 — so a test that stubbed it would be testing nothing. The subprotocol is offered
+    /// because the server refuses an upgrade that does not, and that refusal is itself under test.
+    /// </para>
+    /// <para>
+    /// <c>TestServer</c> speaks WebSockets in-memory with no port and no network, so these run
+    /// wherever the rest of the suite does.
+    /// </para>
+    /// </remarks>
+    public Task<WebSocket> ConnectEventsAsync(string subject, CancellationToken cancellationToken)
+    {
+        var token = IdentityProvider.MintToken(subject);
+        var client = Server.CreateWebSocketClient();
+
+        client.SubProtocols.Add(VaultEvents.SubProtocol);
+        // The server-side request, so the header is a raw string rather than a typed value.
+        client.ConfigureRequest = request => request.Headers.Authorization = $"Bearer {token}";
+
+        return client.ConnectAsync(
+            new Uri(Server.BaseAddress, VaultEvents.Path.TrimStart('/')),
+            cancellationToken);
+    }
 }
 
 /// <summary>Shares one host and container across every test class in the assembly.</summary>

tests/DodoSSH.Api.Tests/EndpointInventoryTests.cs

@@ -56,6 +56,12 @@ public sealed class EndpointInventoryTests(ApiFixture fixture)
         "POST /api/v1/vaults/{vaultId:guid}/sync/pull name=SyncPull tags=Sync policies=Enrolled anon=False",
         "POST /api/v1/vaults/{vaultId:guid}/sync/push name=SyncPush tags=Sync policies=Enrolled anon=False",
 
+        // The WebSocket, gated exactly as sync is and for the same reason — it announces changes to
+        // vaults, and a caller who could not read one has nothing to be told about. It appears here as
+        // an ordinary route because that is what it is until the upgrade: the bearer token authorises
+        // the handshake, unlike the relay's ticket. See ADR 0012.
+        "GET /api/v1/events name=VaultEvents tags=Events policies=Enrolled anon=False",
+
         // Enrolled, because the answer exists to be wrapped to and a caller with no key of their own has
         // nothing to wrap and no signature to attribute it with. There is no search here — see
         // DirectoryService for why an exact-match-only directory is a decision rather than a shortcut.

tests/DodoSSH.Api.Tests/EventsEndpointTests.cs

@@ -0,0 +1,461 @@
+using System.Net;
+using System.Net.WebSockets;
+using System.Text;
+using System.Text.Json;
+using DodoSSH.Contracts;
+using DodoSSH.Domain;
+using DodoSSH.Infrastructure;
+using Microsoft.Extensions.DependencyInjection;
+
+namespace DodoSSH.Api.Tests;
+
+/// <summary>
+/// The push channel, over a real socket through the real authentication pipeline.
+/// </summary>
+/// <remarks>
+/// <para>
+/// The tests that matter most here are the two negatives: an unauthenticated upgrade is refused, and a
+/// change to somebody else's vault does not reach this socket. A push channel that leaked <em>which
+/// vault ids exist and when they change</em> would be a disclosure the pull path takes deliberate
+/// trouble to avoid — <c>SyncPullEndpoint</c> answers 404 rather than 403 for exactly that reason —
+/// and it would be invisible in a test that only checked that notices arrive.
+/// </para>
+/// <para>
+/// Ordering is asserted rather than absence-within-a-timeout wherever possible. "Nothing arrived in
+/// two seconds" is a test that passes on a slow machine for the wrong reason; "the first notice this
+/// socket saw was about its own vault, although another vault was written to first" is not.
+/// </para>
+/// </remarks>
+[Collection(ApiCollection.Name)]
+public sealed class EventsEndpointTests(ApiFixture fixture)
+{
+    private static readonly DateTimeOffset Now = new(2026, 8, 4, 12, 0, 0, TimeSpan.Zero);
+
+    /// <summary>
+    /// How long a test will wait for a frame before calling it a failure.
+    /// </summary>
+    /// <remarks>
+    /// Generous, because it is not a measurement: every wait here is for something already committed,
+    /// so the only thing this bounds is how long a genuinely broken build hangs before it reports.
+    /// </remarks>
+    private static readonly TimeSpan FrameTimeout = TimeSpan.FromSeconds(30);
+
+    // ---- The handshake ----
+
+    [Fact]
+    public async Task WithoutAToken_TheUpgradeIsRefused()
+    {
+        var client = fixture.Server.CreateWebSocketClient();
+        client.SubProtocols.Add(VaultEvents.SubProtocol);
+
+        var connecting = client.ConnectAsync(
+            new Uri(fixture.Server.BaseAddress, VaultEvents.Path.TrimStart('/')),
+            TestContext.Current.CancellationToken);
+
+        await Should.ThrowAsync<InvalidOperationException>(connecting);
+    }
+
+    [Fact]
+    public async Task BeforeEnrolling_Is403WithAnActionableCode()
+    {
+        // The same bar as sync: a caller with no identity key holds no vault key either, so every
+        // notice this socket could carry is about ciphertext they cannot read.
+        var client = fixture.CreateClientFor(NewSubject());
+
+        var response = await client.GetAsync(
+            new Uri(VaultEvents.Path, UriKind.Relative),
+            TestContext.Current.CancellationToken);
+
+        response.StatusCode.ShouldBe(HttpStatusCode.Forbidden);
+
+        var problem = await response.Content.ReadProblemAsync();
+        problem.ShouldNotBeNull();
+        problem.Code.ShouldBe(ProblemCodes.EnrollmentRequired);
+    }
+
+    [Fact]
+    public async Task APlainGet_SaysItIsAWebSocket()
+    {
+        // A person, or a client with the wrong URL. Answering with a problem document rather than a
+        // socket that closes is the difference between a diagnosable mistake and a mysterious one.
+        var client = fixture.CreateClientFor(await SeedEnrolledUserAsync());
+
+        var response = await client.GetAsync(
+            new Uri(VaultEvents.Path, UriKind.Relative),
+            TestContext.Current.CancellationToken);
+
+        response.StatusCode.ShouldBe(HttpStatusCode.BadRequest);
+
+        var problem = await response.Content.ReadProblemAsync();
+        problem.ShouldNotBeNull();
+        problem.Code.ShouldBe(ProblemCodes.MalformedRequest);
+        problem.Detail.ShouldNotBeNull().ShouldContain(VaultEvents.SubProtocol);
+    }
+
+    [Fact]
+    public async Task AnUpgradeWithoutTheSubprotocol_IsRefused()
+    {
+        // The subprotocol is this socket's version negotiation, so accepting an upgrade that did not
+        // offer it would mean answering a client in a dialect it never agreed to read.
+        var (subject, _) = await SeedUserWithVaultAsync();
+
+        var client = fixture.Server.CreateWebSocketClient();
+        client.ConfigureRequest = request => request.Headers.Authorization =
+            $"Bearer {fixture.IdentityProvider.MintToken(subject)}";
+
+        var connecting = client.ConnectAsync(
+            new Uri(fixture.Server.BaseAddress, VaultEvents.Path.TrimStart('/')),
+            TestContext.Current.CancellationToken);
+
+        await Should.ThrowAsync<InvalidOperationException>(connecting);
+    }
+
+    [Fact]
+    public async Task TheFirstFrameIsHello()
+    {
+        var (subject, _) = await SeedUserWithVaultAsync();
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        var hello = await ReadAsync(socket, timeout.Token);
+
+        hello.Kind.ShouldBe(VaultEventKinds.Hello);
+
+        // Sent so a client knows when silence means the socket is dead rather than quiet, and so a
+        // socket following nothing — a real state, for an account with no vaults — is distinguishable
+        // from one that is broken.
+        hello.HeartbeatSeconds.ShouldNotBeNull().ShouldBeGreaterThan(0);
+        hello.VaultCount.ShouldBe(1);
+    }
+
+    [Fact]
+    public async Task MetaAdvertisesTheFeature()
+    {
+        // How a client decides whether to hold a socket open at all. Absence is not an error — it
+        // means synchronise on the timer, which is what every client did before this existed.
+        var client = fixture.CreateClient();
+
+        var meta = await (await client.GetAsync(
+                new Uri("/api/v1/meta", UriKind.Relative),
+                TestContext.Current.CancellationToken))
+            .Content.ReadContractAsync<MetaResponse>();
+
+        meta.ShouldNotBeNull();
+        meta.Features.ShouldContain(
+            feature => string.Equals(feature, VaultEvents.Feature, StringComparison.Ordinal));
+    }
+
+    // ---- Notices ----
+
+    [Fact]
+    public async Task APush_AnnouncesTheVaultToAFollowingSocket()
+    {
+        var (subject, vaultId) = await SeedUserWithVaultAsync();
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        await ReadAsync(socket, timeout.Token);
+
+        var client = fixture.CreateClientFor(subject);
+        var push = await client.PostContractAsync(PushUrl(vaultId), NewCreateBatch());
+        push.EnsureSuccessStatusCode();
+
+        var notice = await ReadUntilAsync(socket, VaultEventKinds.VaultChanged, timeout.Token);
+
+        notice.VaultId.ShouldBe(vaultId);
+
+        // A hint for logging and coalescing, never a cursor: cursors are opaque and integrity-tagged,
+        // and a client that tried to resume from this would be resuming from a number it invented.
+        notice.Sequence.ShouldNotBeNull().ShouldBeGreaterThan(0);
+    }
+
+    [Fact]
+    public async Task ANoticeCarriesNoCiphertext()
+    {
+        // The load-bearing property of the whole design. A notice says only that a vault moved; the
+        // client's answer is the delta pull it would have run on its timer anyway, which keeps exactly
+        // one code path applying changes. See ADR 0012.
+        var (subject, vaultId) = await SeedUserWithVaultAsync();
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        await ReadAsync(socket, timeout.Token);
+
+        var client = fixture.CreateClientFor(subject);
+        var batch = NewCreateBatch();
+        await client.PostContractAsync(PushUrl(vaultId), batch);
+
+        var raw = await ReadRawUntilAsync(socket, VaultEventKinds.VaultChanged, timeout.Token);
+
+        // The envelope this test pushed, as it would appear if a payload had been forwarded.
+        raw.ShouldNotContain(Convert.ToBase64String(batch.Operations[0].Payload!.Envelope));
+        raw.ShouldNotContain("payload", Case.Insensitive);
+        raw.ShouldNotContain(batch.Operations[0].EntityId.ToString());
+    }
+
+    [Fact]
+    public async Task APushToAnotherAccountsVault_IsNotAnnouncedHere()
+    {
+        // The disclosure that would matter: a socket learning that vault ids it cannot read exist,
+        // and when somebody works on them.
+        var (subject, vaultId) = await SeedUserWithVaultAsync();
+        var (stranger, strangersVaultId) = await SeedUserWithVaultAsync();
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        await ReadAsync(socket, timeout.Token);
+
+        // The stranger's write goes first, so a socket that leaked would have announced it before the
+        // one this test then waits for. Ordering, not a timeout: "nothing arrived in two seconds"
+        // passes on a slow machine for the wrong reason.
+        var strangersClient = fixture.CreateClientFor(stranger);
+        (await strangersClient.PostContractAsync(PushUrl(strangersVaultId), NewCreateBatch()))
+            .EnsureSuccessStatusCode();
+
+        var ownClient = fixture.CreateClientFor(subject);
+        (await ownClient.PostContractAsync(PushUrl(vaultId), NewCreateBatch()))
+            .EnsureSuccessStatusCode();
+
+        var notice = await ReadUntilAsync(socket, VaultEventKinds.VaultChanged, timeout.Token);
+
+        notice.VaultId.ShouldBe(vaultId);
+        notice.VaultId.ShouldNotBe(strangersVaultId);
+    }
+
+    [Fact]
+    public async Task APushThatAppliedNothing_AnnouncesNothing()
+    {
+        // A batch of pure conflicts moved no vault. Announcing one anyway would have every client on
+        // it pull for a change that is not there.
+        var (subject, vaultId) = await SeedUserWithVaultAsync();
+        var client = fixture.CreateClientFor(subject);
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        await ReadAsync(socket, timeout.Token);
+
+        // An update to an item that does not exist: rejected as a conflict, nothing written.
+        var stale = new SyncPushRequest(
+        [
+            NewOperation(Guid.CreateVersion7(), expectedVersion: 7, envelope: [9, 9]),
+        ]);
+
+        var conflicted = await client.PostContractAsync(PushUrl(vaultId), stale);
+        conflicted.EnsureSuccessStatusCode();
+
+        var results = await conflicted.Content.ReadContractAsync<SyncPushResponse>();
+        results.ShouldNotBeNull();
+        results.Results[0].Status.ShouldBe(SyncOperationStatus.Conflict);
+
+        // Then a write that did land. The first notice must be that one.
+        (await client.PostContractAsync(PushUrl(vaultId), NewCreateBatch())).EnsureSuccessStatusCode();
+
+        var notice = await ReadUntilAsync(socket, VaultEventKinds.VaultChanged, timeout.Token);
+
+        notice.Sequence.ShouldNotBeNull().ShouldBeGreaterThan(0);
+    }
+
+    [Fact]
+    public async Task APing_IsAnswered()
+    {
+        var (subject, _) = await SeedUserWithVaultAsync();
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        await ReadAsync(socket, timeout.Token);
+
+        await SendAsync(socket, new VaultEvent(VaultEventKinds.Ping), timeout.Token);
+
+        var pong = await ReadUntilAsync(socket, VaultEventKinds.Pong, timeout.Token);
+
+        pong.Kind.ShouldBe(VaultEventKinds.Pong);
+    }
+
+    [Fact]
+    public async Task AFrameThisServerCannotRead_DoesNotEndTheSocket()
+    {
+        // A control channel whose failure mode is "the client polls instead" should tolerate a frame
+        // from a newer client rather than cost that client its push for the whole session.
+        var (subject, vaultId) = await SeedUserWithVaultAsync();
+
+        using var timeout = Timeout();
+        using var socket = await fixture.ConnectEventsAsync(subject, timeout.Token);
+
+        await ReadAsync(socket, timeout.Token);
+
+        await socket.SendAsync(
+            Encoding.UTF8.GetBytes("{ not json at all"),
+            WebSocketMessageType.Text,
+            endOfMessage: true,
+            timeout.Token);
+
+        var client = fixture.CreateClientFor(subject);
+        (await client.PostContractAsync(PushUrl(vaultId), NewCreateBatch())).EnsureSuccessStatusCode();
+
+        var notice = await ReadUntilAsync(socket, VaultEventKinds.VaultChanged, timeout.Token);
+
+        notice.VaultId.ShouldBe(vaultId);
+        socket.State.ShouldBe(WebSocketState.Open);
+    }
+
+    // ---- Helpers ----
+
+    /// <summary>A token that gives up rather than letting a broken build hang the suite.</summary>
+    private static CancellationTokenSource Timeout()
+    {
+        var source = CancellationTokenSource.CreateLinkedTokenSource(
+            TestContext.Current.CancellationToken);
+
+        source.CancelAfter(FrameTimeout);
+
+        return source;
+    }
+
+    private static async Task<VaultEvent> ReadAsync(WebSocket socket, CancellationToken cancellationToken)
+    {
+        var json = await ReadRawAsync(socket, cancellationToken);
+
+        return JsonSerializer.Deserialize(json, DodoSshJsonContext.Default.VaultEvent)
+            ?? throw new InvalidOperationException($"The server sent a null frame: {json}");
+    }
+
+    private static async Task<string> ReadRawAsync(WebSocket socket, CancellationToken cancellationToken)
+    {
+        var buffer = new byte[8 * 1024];
+
+        var received = await socket.ReceiveAsync(buffer, cancellationToken);
+
+        if (received.MessageType == WebSocketMessageType.Close)
+        {
+            throw new InvalidOperationException(
+                $"The server closed the socket: {received.CloseStatus} {received.CloseStatusDescription}");
+        }
+
+        return Encoding.UTF8.GetString(buffer, 0, received.Count);
+    }
+
+    /// <summary>Reads past the frames a test does not care about — hello, and heartbeats.</summary>
+    private static async Task<VaultEvent> ReadUntilAsync(
+        WebSocket socket,
+        string kind,
+        CancellationToken cancellationToken)
+    {
+        while (true)
+        {
+            var frame = await ReadAsync(socket, cancellationToken);
+
+            if (string.Equals(frame.Kind, kind, StringComparison.Ordinal))
+            {
+                return frame;
+            }
+        }
+    }
+
+    /// <summary>
+    /// The same, but keeping the bytes.
+    /// </summary>
+    /// <remarks>
+    /// Deserialising and asserting on the fields would prove only that this <em>record</em> has no
+    /// payload member, which is a tautology. Asserting on what actually crossed the socket is what
+    /// would catch a field added to the frame later without anybody thinking about disclosure.
+    /// </remarks>
+    private static async Task<string> ReadRawUntilAsync(
+        WebSocket socket,
+        string kind,
+        CancellationToken cancellationToken)
+    {
+        while (true)
+        {
+            var json = await ReadRawAsync(socket, cancellationToken);
+            var frame = JsonSerializer.Deserialize(json, DodoSshJsonContext.Default.VaultEvent);
+
+            if (string.Equals(frame?.Kind, kind, StringComparison.Ordinal))
+            {
+                return json;
+            }
+        }
+    }
+
+    private static Task SendAsync(WebSocket socket, VaultEvent frame, CancellationToken cancellationToken) =>
+        socket.SendAsync(
+            JsonSerializer.SerializeToUtf8Bytes(frame, DodoSshJsonContext.Default.VaultEvent),
+            WebSocketMessageType.Text,
+            endOfMessage: true,
+            cancellationToken);
+
+    private static string PushUrl(Guid vaultId) => $"/api/v1/vaults/{vaultId}/sync/push";
+
+    private static string NewSubject() => $"events-{Guid.CreateVersion7():N}";
+
+    private static SyncPushOperation NewOperation(Guid entityId, int? expectedVersion, byte[] envelope) =>
+        new(
+            Guid.CreateVersion7(),
+            SyncEntityType.Host,
+            entityId,
+            SyncOperation.Upsert,
+            expectedVersion,
+            new EncryptedPayload(envelope, [0xD, 0xE], Guid.CreateVersion7(), 1, 1),
+            new SyncPlaintextFields());
+
+    private static SyncPushRequest NewCreateBatch() =>
+        new([NewOperation(Guid.CreateVersion7(), expectedVersion: null, envelope: [1, 2, 3, 4])]);
+
+    private async Task<string> SeedEnrolledUserAsync()
+    {
+        var subject = NewSubject();
+
+        await using var scope = fixture.CreateScope();
+        var database = scope.ServiceProvider.GetRequiredService<DodoDbContext>();
+
+        var user = NewUser(subject);
+        database.Users.Add(user);
+        database.UserKeys.Add(Seed.CurrentKey(user.Id, Now));
+        await database.SaveChangesAsync();
+
+        return subject;
+    }
+
+    private async Task<(string Subject, Guid VaultId)> SeedUserWithVaultAsync()
+    {
+        var subject = NewSubject();
+
+        await using var scope = fixture.CreateScope();
+        var database = scope.ServiceProvider.GetRequiredService<DodoDbContext>();
+
+        var user = NewUser(subject);
+
+        var vault = new Vault
+        {
+            Id = Guid.CreateVersion7(),
+            Name = "Personal",
+            OwnerKind = VaultOwnerKind.Personal,
+            OwnerUserId = user.Id,
+            KeyGeneration = 1,
+            CreatedAtUtc = Now,
+            UpdatedAtUtc = Now,
+        };
+
+        database.Users.Add(user);
+        database.UserKeys.Add(Seed.CurrentKey(user.Id, Now));
+        database.Vaults.Add(vault);
+        await database.SaveChangesAsync();
+
+        return (subject, vault.Id);
+    }
+
+    private UserAccount NewUser(string subject) => new()
+    {
+        Id = Guid.CreateVersion7(),
+        Issuer = fixture.IdentityProvider.Authority,
+        Subject = subject,
+        Status = UserStatus.Active,
+        CreatedAtUtc = Now,
+        UpdatedAtUtc = Now,
+    };
+}

tests/DodoSSH.Client.Api.Tests/VaultEventStreamTests.cs

@@ -0,0 +1,388 @@
+using System.Net.WebSockets;
+using System.Text;
+using System.Text.Json;
+using System.Threading.Channels;
+using DodoSSH.Client.Api;
+using DodoSSH.Contracts;
+
+namespace DodoSSH.Client.Api.Tests;
+
+/// <summary>
+/// The reconnection policy, which is what this class actually is.
+/// </summary>
+/// <remarks>
+/// <para>
+/// A dropped socket is the ordinary case here rather than the exception — laptops sleep, proxies time
+/// out, tokens expire, servers are redeployed — so the behaviour worth covering is what happens
+/// <em>after</em> a failure, not the happy path. Driven through the injected connector, because the one
+/// thing a test cannot do to a real network is make it fail on cue.
+/// </para>
+/// <para>
+/// The backoff is configured down to milliseconds throughout. What is under test is the shape of the
+/// policy — does it try again, does it wait, does it stop waiting when told the token was the problem —
+/// and none of that depends on the intervals a shipped client uses.
+/// </para>
+/// </remarks>
+public sealed class VaultEventStreamTests
+{
+    private static readonly Uri Server = new("https://dodossh.example");
+
+    private static readonly VaultEventStreamOptions Impatient = new()
+    {
+        InitialBackoff = TimeSpan.FromMilliseconds(1),
+        MaxBackoff = TimeSpan.FromMilliseconds(5),
+        InitialSilenceTimeout = TimeSpan.FromSeconds(30),
+    };
+
+    [Fact]
+    public async Task ItDialsTheWebSocketFormOfTheServersUrl()
+    {
+        // https becomes wss, and the path is the one in the contract. Getting either wrong is a client
+        // that reconnects against a 404 for the whole session, which from outside is indistinguishable
+        // from a network that eats WebSockets.
+        var dialled = new List<Uri>();
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream(
+            (url, _, _) =>
+            {
+                dialled.Add(url);
+                return Task.FromResult<WebSocket>(socket);
+            });
+
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 1));
+
+        await stream.ReadAsync(Token);
+
+        dialled[0].ShouldBe(new Uri("wss://dodossh.example/api/v1/events"));
+    }
+
+    [Fact]
+    public async Task ItSendsTheBearerTokenOnTheUpgrade()
+    {
+        // The whole of this socket's authorization, unlike the relay's ticket. See ADR 0012.
+        var presented = new List<string>();
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream(
+            (_, token, _) =>
+            {
+                presented.Add(token);
+                return Task.FromResult<WebSocket>(socket);
+            });
+
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 1));
+
+        await stream.ReadAsync(Token);
+
+        presented[0].ShouldBe(StubTokens.Token);
+    }
+
+    [Fact]
+    public async Task ANoticeReachesTheReader()
+    {
+        var vaultId = Guid.CreateVersion7();
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream((_, _, _) => Task.FromResult<WebSocket>(socket));
+
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, vaultId, 42));
+
+        var notice = await stream.ReadAsync(Token);
+
+        notice.Kind.ShouldBe(VaultEventKinds.VaultChanged);
+        notice.VaultId.ShouldBe(vaultId);
+        notice.Sequence.ShouldBe(42);
+    }
+
+    [Fact]
+    public async Task AHeartbeatIsAnsweredAndNotHandedToTheReader()
+    {
+        // A ping is housekeeping between the two ends. Passing it up would wake a synchronisation loop
+        // every thirty seconds for a frame that says nothing happened.
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream((_, _, _) => Task.FromResult<WebSocket>(socket));
+
+        socket.Deliver(new VaultEvent(VaultEventKinds.Ping, HeartbeatSeconds: 30));
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 1));
+
+        var first = await stream.ReadAsync(Token);
+
+        first.Kind.ShouldBe(VaultEventKinds.VaultChanged, "the ping should not have been forwarded");
+
+        var answered = await socket.SentAsync(Token);
+        answered.Kind.ShouldBe(VaultEventKinds.Pong);
+    }
+
+    [Fact]
+    public async Task AKindThisBuildDoesNotKnow_IsStillHandedOver()
+    {
+        // What makes the frame table extensible: this class must not decide what a newer server may
+        // say. Deciding to ignore it is the caller's, and costs that caller one redundant pass.
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream((_, _, _) => Task.FromResult<WebSocket>(socket));
+
+        socket.Deliver(new VaultEvent("session.offered"));
+
+        var notice = await stream.ReadAsync(Token);
+
+        notice.Kind.ShouldBe("session.offered");
+    }
+
+    [Fact]
+    public async Task AFailedDial_IsRetried()
+    {
+        // No server yet, or no network. Neither is an error to report: the caller's synchronisation
+        // timer is running regardless, which is what lets this stay silent and keep trying.
+        var attempts = 0;
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream((_, _, _) =>
+        {
+            if (++attempts < 3)
+            {
+                throw new WebSocketException("no route to host");
+            }
+
+            return Task.FromResult<WebSocket>(socket);
+        });
+
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 1));
+
+        var notice = await stream.ReadAsync(Token);
+
+        notice.Kind.ShouldBe(VaultEventKinds.VaultChanged);
+        attempts.ShouldBe(3);
+    }
+
+    [Fact]
+    public async Task ADroppedSocket_IsReplaced()
+    {
+        // The case that decides whether this feature survives a laptop lid. A stream that gave up on
+        // the first close would work all morning and be silently dead after lunch.
+        var sockets = new List<FakeWebSocket>();
+
+        await using var stream = Stream((_, _, _) =>
+        {
+            var socket = new FakeWebSocket();
+            sockets.Add(socket);
+
+            if (sockets.Count == 1)
+            {
+                socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 1));
+                socket.Close(WebSocketCloseStatus.EndpointUnavailable);
+            }
+            else
+            {
+                socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 2));
+            }
+
+            return Task.FromResult<WebSocket>(socket);
+        });
+
+        (await stream.ReadAsync(Token)).Sequence.ShouldBe(1);
+        (await stream.ReadAsync(Token)).Sequence.ShouldBe(2);
+
+        sockets.Count.ShouldBeGreaterThanOrEqualTo(2);
+    }
+
+    [Fact]
+    public async Task AnExpiredTokenClose_ReconnectsAndAsksForAFreshToken()
+    {
+        // The bound that lets a long-lived socket be authorised by a short-lived credential: the server
+        // closes at the token's expiry and the client comes straight back with a new one. The token
+        // provider being asked again is the half that matters — reconnecting with the spent token would
+        // be an unbroken loop of closes.
+        var tokens = new StubTokens();
+        var sockets = 0;
+
+        await using var stream = new VaultEventStream(
+            Server,
+            tokens,
+            TimeProvider.System,
+            (_, _, _) =>
+            {
+                var socket = new FakeWebSocket();
+
+                if (++sockets == 1)
+                {
+                    socket.Close((WebSocketCloseStatus)VaultEvents.TokenExpiredCloseCode);
+                }
+                else
+                {
+                    socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 7));
+                }
+
+                return Task.FromResult<WebSocket>(socket);
+            },
+            Impatient);
+
+        (await stream.ReadAsync(Token)).Sequence.ShouldBe(7);
+
+        tokens.Requests.ShouldBeGreaterThanOrEqualTo(2);
+    }
+
+    [Fact]
+    public async Task TryRead_TakesWhatIsWaitingAndSaysWhenNothingIs()
+    {
+        // How a caller coalesces a burst: read one, wait a moment, swallow the rest. Without this a
+        // colleague tidying a folder would produce a synchronisation pass per item.
+        var socket = new FakeWebSocket();
+
+        await using var stream = Stream((_, _, _) => Task.FromResult<WebSocket>(socket));
+
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 1));
+        socket.Deliver(new VaultEvent(VaultEventKinds.VaultChanged, Guid.CreateVersion7(), 2));
+
+        (await stream.ReadAsync(Token)).Sequence.ShouldBe(1);
+
+        // Delivery is asynchronous, so the second may not have landed yet; this is the same
+        // wait-then-drain the caller performs.
+        await Task.Delay(TimeSpan.FromMilliseconds(200), Token);
+
+        stream.TryRead(out var queued).ShouldBeTrue();
+        queued.Sequence.ShouldBe(2);
+
+        stream.TryRead(out _).ShouldBeFalse();
+    }
+
+    [Fact]
+    public async Task AnIdleStream_NeverDelivers()
+    {
+        // What a server without the feature supplies. Waiting for ever rather than completing is the
+        // point: a caller selecting between this and a timer has to fall through to the timer, and a
+        // read that returned at once would spin that loop as fast as the machine allows.
+        using var stream = IdleVaultEventStream.Instance;
+        using var giveUp = CancellationTokenSource.CreateLinkedTokenSource(Token);
+
+        giveUp.CancelAfter(TimeSpan.FromMilliseconds(100));
+
+        await Should.ThrowAsync<OperationCanceledException>(
+            async () => await stream.ReadAsync(giveUp.Token));
+
+        stream.TryRead(out _).ShouldBeFalse();
+        stream.IsConnected.ShouldBeFalse();
+    }
+
+    private static CancellationToken Token => TestContext.Current.CancellationToken;
+
+    private static VaultEventStream Stream(
+        Func<Uri, string, CancellationToken, Task<WebSocket>> connect) =>
+        new(Server, new StubTokens(), TimeProvider.System, connect, Impatient);
+
+    /// <summary>A token provider that hands out one value and counts who asked.</summary>
+    private sealed class StubTokens : IAccessTokenProvider
+    {
+        internal const string Token = "access-token";
+
+        internal int Requests { get; private set; }
+
+        public ValueTask<string> GetAccessTokenAsync(CancellationToken cancellationToken)
+        {
+            Requests++;
+
+            return ValueTask.FromResult(Token);
+        }
+    }
+
+    /// <summary>
+    /// A socket a test writes the server's half of.
+    /// </summary>
+    /// <remarks>
+    /// Frames queued with <see cref="Deliver"/> are handed out by <see cref="ReceiveAsync"/> in order;
+    /// once the queue is empty the receive waits, which is what an idle connection does. <see
+    /// cref="Close"/> queues the close instead, so a test can script "two notices and then the server
+    /// went away" as a value rather than as a race.
+    /// </remarks>
+    private sealed class FakeWebSocket : WebSocket
+    {
+        private readonly Channel<byte[]> inbound = Channel.CreateUnbounded<byte[]>();
+        private readonly Channel<VaultEvent> outbound = Channel.CreateUnbounded<VaultEvent>();
+
+        private WebSocketCloseStatus? closing;
+        private WebSocketState state = WebSocketState.Open;
+
+        public override WebSocketCloseStatus? CloseStatus => closing;
+
+        public override string? CloseStatusDescription => null;
+
+        public override WebSocketState State => state;
+
+        public override string? SubProtocol => VaultEvents.SubProtocol;
+
+        /// <summary>Queues a frame for the client to read.</summary>
+        internal void Deliver(VaultEvent frame) =>
+            inbound.Writer.TryWrite(
+                JsonSerializer.SerializeToUtf8Bytes(frame, DodoSshJsonContext.Default.VaultEvent));
+
+        /// <summary>Ends the socket, after everything already queued has been read.</summary>
+        internal void Close(WebSocketCloseStatus status)
+        {
+            closing = status;
+            inbound.Writer.TryWrite([]);
+        }
+
+        /// <summary>The next frame the client sent.</summary>
+        internal ValueTask<VaultEvent> SentAsync(CancellationToken cancellationToken) =>
+            outbound.Reader.ReadAsync(cancellationToken);
+
+        public override async Task<WebSocketReceiveResult> ReceiveAsync(
+            ArraySegment<byte> buffer,
+            CancellationToken cancellationToken)
+        {
+            var frame = await inbound.Reader.ReadAsync(cancellationToken);
+
+            // The empty frame Close queues. Reported as a close, exactly as a real socket does once the
+            // peer's close frame arrives.
+            if (frame.Length == 0)
+            {
+                state = WebSocketState.Closed;
+
+                return new WebSocketReceiveResult(
+                    0, WebSocketMessageType.Close, endOfMessage: true, closing, null);
+            }
+
+            frame.CopyTo(buffer.Array!, buffer.Offset);
+
+            return new WebSocketReceiveResult(frame.Length, WebSocketMessageType.Text, endOfMessage: true);
+        }
+
+        public override Task SendAsync(
+            ArraySegment<byte> buffer,
+            WebSocketMessageType messageType,
+            bool endOfMessage,
+            CancellationToken cancellationToken)
+        {
+            var json = Encoding.UTF8.GetString(buffer.Array!, buffer.Offset, buffer.Count);
+
+            if (JsonSerializer.Deserialize(json, DodoSshJsonContext.Default.VaultEvent) is { } frame)
+            {
+                outbound.Writer.TryWrite(frame);
+            }
+
+            return Task.CompletedTask;
+        }
+
+        public override void Abort() => state = WebSocketState.Aborted;
+
+        public override Task CloseAsync(
+            WebSocketCloseStatus closeStatus,
+            string? statusDescription,
+            CancellationToken cancellationToken) => CloseOutputAsync(
+            closeStatus, statusDescription, cancellationToken);
+
+        public override Task CloseOutputAsync(
+            WebSocketCloseStatus closeStatus,
+            string? statusDescription,
+            CancellationToken cancellationToken)
+        {
+            state = WebSocketState.Closed;
+
+            return Task.CompletedTask;
+        }
+
+        public override void Dispose() => state = WebSocketState.Closed;
+    }
+}

tests/DodoSSH.Client.App.Layout.Tests/StubTeamServer.cs

@@ -57,6 +57,17 @@ internal sealed class StubTeamServer : IVaultServer, ITeamApi, IVaultGrantApi
     /// <inheritdoc />
     public IKeyBindingAuthorizer KeyBinding => throw new NotSupportedException();
 
+    /// <summary>
+    /// A push channel that never pushes.
+    /// </summary>
+    /// <remarks>
+    /// Not <c>NotSupportedException</c> like its neighbours: the background synchronisation loop reads
+    /// this on every wait, so a layout test that opened a screen would throw from a timer thread rather
+    /// than draw anything. Waiting for ever is the honest stand-in — an offline layout test has no
+    /// server to be pushed from.
+    /// </remarks>
+    public IVaultEventStream Events => IdleVaultEventStream.Instance;
+
     /// <inheritdoc />
     public SyncOptions SyncOptions => new();
 

tests/DodoSSH.Client.App.Tests/FakeVaultEventStream.cs

@@ -0,0 +1,49 @@
+using System.Threading.Channels;
+using DodoSSH.Client.Api;
+using DodoSSH.Contracts;
+
+namespace DodoSSH.Client.App.Tests;
+
+/// <summary>
+/// A server's push channel, driven by a test rather than by a socket.
+/// </summary>
+/// <remarks>
+/// The real <c>VaultEventStream</c> is a reconnection policy wrapped round a WebSocket, and none of
+/// that is what the shell's behaviour depends on: what the shell does with a notice is the same
+/// whether it arrived over a healthy socket, after four reconnections, or from this. Driving it by
+/// hand is what makes "the loop synchronised because it was told to, not because a minute passed" a
+/// test that finishes in milliseconds and cannot flake.
+/// </remarks>
+internal sealed class FakeVaultEventStream : IVaultEventStream
+{
+    private readonly Channel<VaultEvent> notices = Channel.CreateUnbounded<VaultEvent>();
+
+    /// <inheritdoc />
+    public bool IsConnected => true;
+
+    /// <summary>How many times the shell has waited on this. Proves the loop is watching at all.</summary>
+    internal int Reads { get; private set; }
+
+    /// <summary>Delivers a notice, as a server would.</summary>
+    internal void Push(Guid vaultId, long sequence = 1) =>
+        notices.Writer.TryWrite(
+            new VaultEvent(VaultEventKinds.VaultChanged, vaultId, sequence));
+
+    /// <summary>Delivers the notice that says the caller's vault list has changed.</summary>
+    internal void PushAccessChanged() =>
+        notices.Writer.TryWrite(new VaultEvent(VaultEventKinds.VaultsChanged));
+
+    /// <inheritdoc />
+    public ValueTask<VaultEvent> ReadAsync(CancellationToken cancellationToken)
+    {
+        Reads++;
+
+        return notices.Reader.ReadAsync(cancellationToken);
+    }
+
+    /// <inheritdoc />
+    public bool TryRead(out VaultEvent notice) => notices.Reader.TryRead(out notice!);
+
+    /// <inheritdoc />
+    public void Dispose() => notices.Writer.TryComplete();
+}

tests/DodoSSH.Client.App.Tests/FakeVaultServer.cs

@@ -39,6 +39,16 @@ internal sealed partial class FakeVaultServer : IVaultServer, IAccountApi, ISync
 
     internal int PushCount { get; private set; }
 
+    /// <summary>
+    /// How many delta reads this server has served.
+    /// </summary>
+    /// <remarks>
+    /// The one observable a synchronisation pass always produces. <see cref="PushCount"/> only moves when
+    /// there is something queued, so a test asking "did a pass run" — which is what the push channel's
+    /// whole purpose comes down to — has to count pulls.
+    /// </remarks>
+    internal int PullCount { get; private set; }
+
     internal bool IsEnrolled => statement is not null;
 
     /// <summary>
@@ -99,6 +109,19 @@ internal sealed partial class FakeVaultServer : IVaultServer, IAccountApi, ISync
     /// <inheritdoc />
     public IKeyBindingAuthorizer KeyBinding => this;
 
+    /// <summary>
+    /// The push channel, which a test drives by hand.
+    /// </summary>
+    /// <remarks>
+    /// A real queue rather than an idle stand-in, because the behaviour worth covering here is the one
+    /// the socket exists for: a notice arriving makes the background loop synchronise without waiting
+    /// out its minute. See <see cref="FakeVaultEventStream.Push"/>.
+    /// </remarks>
+    internal FakeVaultEventStream Notices { get; } = new();
+
+    /// <inheritdoc />
+    public IVaultEventStream Events => Notices;
+
     /// <inheritdoc />
     public SyncOptions SyncOptions => SyncOptions.Default;
 
@@ -238,6 +261,8 @@ internal sealed partial class FakeVaultServer : IVaultServer, IAccountApi, ISync
         SyncPullRequest request,
         CancellationToken cancellationToken)
     {
+        PullCount++;
+
         if (SyncFailure is { } failure)
         {
             return Task.FromException<SyncPullResponse>(failure);

tests/DodoSSH.Client.App.Tests/ShellFlowTests.cs

@@ -523,6 +523,90 @@ public sealed class ShellFlowTests : IAsyncLifetime
         vault.Status.ShouldContain("bad day");
     }
 
+    /// <summary>
+    /// The whole point of the push channel: a pass that did not wait for the minute.
+    /// </summary>
+    /// <remarks>
+    /// <para>
+    /// The timing is what makes this an assertion rather than a hope. The background timer is a full
+    /// minute and the wait below gives up in ten seconds, so a pull that arrives can only have been
+    /// caused by the notice — there is no interval at which the timer could have produced it.
+    /// </para>
+    /// <para>
+    /// The vault id in the notice is arbitrary, and deliberately so: a pass synchronises every vault
+    /// this session can reach, so the loop reads the notice as "there is something to fetch" and never
+    /// as "fetch this one". A test that seeded a real id would imply a targeting this does not do.
+    /// </para>
+    /// </remarks>
+    [Fact]
+    public async Task APushedNotice_SynchronisesWithoutWaitingForTheTimer()
+    {
+        await UnlockedAsync();
+
+        // The unlock starts the loop, whose first act is a pass; waited out so the count below is a
+        // baseline rather than a race with it.
+        await EventuallyAsync(
+            () => server.PullCount > 0,
+            "the pass on open should have run");
+
+        var before = server.PullCount;
+
+        server.Notices.Push(Guid.CreateVersion7());
+
+        await EventuallyAsync(
+            () => server.PullCount > before,
+            "a notice should have woken the loop long before the one-minute timer");
+    }
+
+    /// <remarks>
+    /// The half that is easy to get wrong. The loop selects between two waits, and both have to survive
+    /// losing: <c>PeriodicTimer</c> throws if a second wait is started while one is outstanding, and an
+    /// abandoned channel read stays registered and swallows the next notice written. Either defect
+    /// leaves the first notice working and every one after it silently lost, which is why one notice is
+    /// not enough to prove this.
+    /// </remarks>
+    [Fact]
+    public async Task NoticesKeepWakingTheLoop_NotJustTheFirst()
+    {
+        await UnlockedAsync();
+
+        await EventuallyAsync(() => server.PullCount > 0, "the pass on open should have run");
+
+        for (var round = 1; round <= 3; round++)
+        {
+            var before = server.PullCount;
+
+            server.Notices.Push(Guid.CreateVersion7());
+
+            await EventuallyAsync(
+                () => server.PullCount > before,
+                $"notice {round} should have woken the loop as the first one did");
+        }
+    }
+
+    /// <summary>Waits for something a background loop is expected to do, or fails saying what.</summary>
+    /// <remarks>
+    /// Polled rather than signalled because the thing under test is a loop nobody hands a completion
+    /// source to. The bound is generous — this is not measuring latency, only proving that the timer
+    /// cannot be what caused the result.
+    /// </remarks>
+    private static async Task EventuallyAsync(Func<bool> condition, string because)
+    {
+        var deadline = TimeProvider.System.GetUtcNow().AddSeconds(10);
+
+        while (TimeProvider.System.GetUtcNow() < deadline)
+        {
+            if (condition())
+            {
+                return;
+            }
+
+            await Task.Delay(TimeSpan.FromMilliseconds(20), Token);
+        }
+
+        throw new ShouldAssertException(because);
+    }
+
     /// <remarks>
     /// <para>
     /// The page's own <c>term.focus()</c> focuses the textarea inside the document, which does nothing