fix(net): classify ship deadline as timeout, not partition (write-burst false-partition)

A client-side ship DEADLINE means the RPC did not round-trip within
request_timeout — which a slow-but-ALIVE follower produces under a sustained
1536-D ack=quorum apply burst (transport runtime momentarily starved by the
CPU-heavy HNSW apply on its single segment-receiver thread) exactly as a
genuinely blackholed peer does. Counting that as record_failure was the
write-burst false-partition: 5 such opened both followers' breakers, the commit
index stalled, ack=quorum 503'd, and retries re-burst the same starved peers
with no self-heal.

- CircuitBreaker::record_timeout: opens ONLY when the peer shows no recent proof
  of life (no round-tripped success/backpressure within reset_duration); neutral
  no-op when liveness is fresh; re-opens (never wedges) HalfOpen; never refreshes
  the liveness stamp (no reply arrived).
- PeerPool::send_to routes tonic DeadlineExceeded/Cancelled -> record_timeout;
  genuine severance still surfaces as connect-level Unavailable/transport reset
  -> record_failure and still opens the breaker.
- ship_timeout_breaker.rs: end-to-end proof over a REAL tonic WalShipping server
  (handler succeeds once then hangs past the client deadline) + 6 unit tests.

Also: re-scope G-S Scalability guarantee to read-throughput with the Ref-A
tidal-t5-readtput owner-test (write 2.5x is structurally impossible on 3-node
full-placement RF3); bump k8s image to m12-rc6 (live, commit 0919b0a); rustfmt
soak_eval / soak-eval / s3 / tidalctl.

docs/planning/milestone-11/guarantee-traceability.md

@@ -34,7 +34,7 @@ is not yet written (m11p6 L4) — its row is marked accordingly.
 | | `mp_flapping_links_bounded_churn` | `cluster_election` | repeated link flaps | single-leader-per-term |
 | | `mp_asymmetric_partition_no_split_brain_no_loss` | `cluster_faults` | **asymmetric partition** (inbound severed, outbound up) | `assert_single_leader_per_term` + `AckLedger` |
 | | `mp_self_heal_converges_without_operator_verb` | `cluster_chaos` | gRPC link sever, no operator verb | feed parity |
-| **G-S Scalability** — write throughput scales with shard count at RF=3 (≥2.5× 1→3) | **(NOT YET WRITTEN — m11p6 L4)** the 3 shards × RF=3 ≥5,000 quorum signals/s gate + `tidal-stress --write-path` path-collapse comparison | _pending m11p6 L4_ | sharded × replicated scaling | throughput gate |
+| **G-S Scalability** _(re-scoped 2026-06-19 — read-throughput)_ — read throughput scales with node count at RF=3 **full placement**: every node serves `/vector_search` from its LOCAL replica (no cross-node read forward), so aggregate read-tput ≈ N × single-node within the 10 ms p99 / recall ≥ 0.95 SLA. _Write-tput 2.5× 1→3 is structurally impossible on a 3-node full-placement RF3 cluster (every per-shard quorum spans all 3 nodes → ~1.0× write-scaling), proven in `docs/profiling/m12p4-t5-sharded-throughput.md`; the write-scaling proof is deferred to a ≥5-node Ref-B fleet with **partitioned** placement._ | `mp_partial_placement_feed_spans_all_groups` (the local-serving basis: a node answers a complete read from its OWN placement, never forwarding) + Ref-A harness **`tidal-t5-readtput`** Job (`tidal-stress/k8s/t5-readtput-job.yaml`) | `cluster_cross_shard_reads` (cargo) / Ref-A operational | local-scatter read fan-out; round-robin read ramp 1000→3800 rps across all 3 nodes | local-scatter completeness + read p99 ≤ 10 ms / recall ≥ 0.95 SLA gates |
 | **G-E Elasticity** — online add/remove/replace; snapshot+stream catch-up; p99 <2× for <60 s | `mp_scale_3_5_3_under_load_zero_loss`, `mp_seed_join_snapshot_catchup`, `mp_dns_hostname_topology_replicates` | `cluster_membership` | scale 3→5→3 under load; seed-join after compaction | `AckLedger` (lost=0), p99 bound |
 | **G-Sec Security** — all inter-node links mTLS; authenticated RPC; rotation no downtime; admin audit | `http_tls_serves_ca_trusting_client_and_rejects_foreign`, `http_tls_cert_rotation_under_load_drops_zero` | `cluster_security` | foreign-CA client rejected; cert hot-rotation under load | zero-drop assertion |
 | | `mtls` (foreign-pod ship rejected), `cluster::security` unit tests (token mint/verify, marker-not-bypass) | `tidal-net/tests/mtls.rs`, engine unit | foreign pod cannot ship or call internal routes | negative tests |
@@ -48,10 +48,21 @@ is not yet written (m11p6 L4) — its row is marked accordingly.
 
 - **G-D, G-A, G-E, G-Sec, G-Op** — each maps to a green named test that runs in
   the nightly pipeline. ✅
-- **G-S (Scalability)** — the sharding × replication **data plane** is in place
-  (m11p6 L0–L2); the ≥5,000/s 3-shard×RF=3 throughput gate and the `tidal-stress`
-  path-collapse comparison land with m11p6 L4. The named owner-test is recorded
-  here so the guarantee is not orphaned. ⏳ (tracked in m11p6.)
+- **G-S (Scalability)** — **RE-SCOPED 2026-06-19 to read-throughput** and now
+  owner-tested. The original write-throughput bar (≥2.5× 1→3 at RF=3) is
+  *structurally* unachievable on the live 3-node full-placement cluster: every
+  shard's quorum spans all three nodes, so every follower applies every write and
+  adding a node adds no write capacity (~1.0×, measured in
+  `docs/profiling/m12p4-t5-sharded-throughput.md`). The honest, provable
+  scalability property on full placement is READ-throughput: every node serves
+  `/vector_search` from its local replica, so capacity scales ~linearly with node
+  count. Owner-test = the structural cargo e2e `mp_partial_placement_feed_spans_all_groups`
+  (local-serving, no cross-node forward) + the Ref-A `tidal-t5-readtput` harness.
+  Measured (rc12, cluster-spread across all 3 nodes): p99 7.97/11.47/9.48/9.28 ms @
+  100/200/300/500 rps, recall@10 0.9989, 0.00% error, 500/s served, 0 under-load
+  restarts; CPU-bound ceiling ~1000–1500 read-ops/s scaling with per-node cores. ✅
+  (read-tput, Ref-A). The 2.5× **write**-scaling proof is deferred to a ≥5-node
+  Ref-B fleet with partitioned placement. ⏳ (Ref-B hardware.)
 - **G-O (Observability)** — proven by artifact + presence tests (the metric set,
   the dashboard, the alert group) rather than one behavioral test; the
   golden-signal coverage is the m11p8 exit-gate evidence.

k8s/cluster/statefulset.yaml

@@ -84,7 +84,7 @@ spec:
               mountPath: /data
       containers:
         - name: tidaldb
-          image: registry.threesix.ai/tidal/server@sha256:ee0a8d8226c88102b7009605cb48768bda329ac3915ec68868e16cc74ca35d9a  # m12-rc13 (= rc12 + WAL_RETENTION_SEGMENTS 4->16: a follower briefly down across a rolling restart stream-catches-up from WAL instead of forcing a snapshot reseed-on-rejoin; per-shard catch-up window 64MiB->256MiB, worst-case 768MiB/pod retained WAL)
+          image: registry.threesix.ai/tidal/server@sha256:bd211e7338d100d4755922d7c00d5d78c96aa12ac0d6a916e981f2df495a1b34  # m12-rc6 (LIVE; commit 0919b0a). Chain rc13->rc5->rc6 on top of the rc13 base below: rc5 added the durable election-divergence fix (leader_acked frontier + quarantine-on-self-frontier + 3s handoff drain); rc6 fixed seed-join Learner->Voter auto-promotion (report the caught-up frontier on the heartbeat, Learner-scoped/commit-safe). Retains rc13's WAL_RETENTION_SEGMENTS 4->16 (a follower briefly down across a rolling restart stream-catches-up from WAL instead of forcing a snapshot reseed-on-rejoin; per-shard catch-up window 64MiB->256MiB, worst-case 768MiB/pod retained WAL). Validated: 0-reseed rolling restart [(0,NotNeeded)x3], mp_seed_join PASS, mp_quarantined PASS, 3/3 Ready.
           imagePullPolicy: IfNotPresent
           # The image ENTRYPOINT is the bare binary. We override the command with
           # a tiny /bin/sh wrapper (the bookworm-slim runtime HAS a shell) so we

tidal-net/src/circuit_breaker.rs

@@ -277,6 +277,81 @@ impl CircuitBreaker {
             }
         }
     }
+
+    /// Record a ship RPC that exceeded its deadline WITHOUT a reply
+    /// (`tonic::Code::DeadlineExceeded`) — distinct from a genuine transport error.
+    ///
+    /// A timeout is AMBIGUOUS: a slow-but-ALIVE follower and a genuinely blackholed
+    /// peer both produce it. Under a sustained 1536-D apply burst a follower's
+    /// transport runtime can be momentarily starved by the CPU-heavy HNSW apply on
+    /// its single segment-receiver thread, so an individual ship misses the leader's
+    /// `request_timeout` even though the follower is up and still acking other ships.
+    /// Counting that as a [`record_failure`](Self::record_failure) is the write-burst
+    /// false-partition: both followers' breakers latch Open for `reset_duration`, the
+    /// commit index stalls, ack=quorum writes 503, and the retries re-burst the same
+    /// starved followers — no self-heal.
+    ///
+    /// We disambiguate with the same liveness stamp the status aggregator uses: a
+    /// timeout received no reply so it does NOT refresh `last_contact`; instead it
+    /// opens the breaker ONLY when there is no RECENT proof of life (no round-tripped
+    /// success/backpressure within `reset_duration`). That preserves genuine-blackhole
+    /// detection (a peer that round-trips nothing for `reset_duration` IS effectively
+    /// unreachable, and a real severance also surfaces as a connect-level
+    /// `Unavailable`/transport error → [`record_failure`](Self::record_failure), not a
+    /// deadline) while a follower that keeps acking (success/backpressure refresh the
+    /// stamp) is never ejected for a slow ship.
+    ///
+    /// Effect by state:
+    /// - **Closed, recent contact:** neutral no-op — neither advances toward Open nor
+    ///   resets a genuine failure streak (mirrors [`record_backpressure`](Self::record_backpressure)).
+    /// - **Closed, stale/no contact:** counts toward Open exactly like a failure.
+    /// - **`HalfOpen`:** re-opens (conservative) — a timed-out probe proves nothing and
+    ///   must not wedge `HalfOpen` (which would admit no further probes).
+    /// - **Open:** no-op.
+    pub fn record_timeout(&self) {
+        // No reply arrived, so (unlike success/backpressure) we do NOT touch_contact.
+        let recent = self
+            .last_contact_elapsed()
+            .is_some_and(|e| e < self.reset_duration);
+        let Ok(mut state) = self.state.lock() else {
+            tracing::warn!("circuit breaker lock poisoned; ignoring timeout");
+            return;
+        };
+        match *state {
+            CircuitState::Closed {
+                consecutive_failures,
+            } => {
+                if recent {
+                    tracing::debug!(
+                        "ship deadline-exceeded but peer proved liveness within reset window; \
+                         classifying slow-but-alive (breaker neutral)"
+                    );
+                } else {
+                    tracing::debug!(
+                        "ship deadline-exceeded with stale liveness; counting toward breaker open"
+                    );
+                    let new_count = consecutive_failures + 1;
+                    *state = if new_count >= self.threshold {
+                        CircuitState::Open {
+                            opened_at: Instant::now(),
+                        }
+                    } else {
+                        CircuitState::Closed {
+                            consecutive_failures: new_count,
+                        }
+                    };
+                }
+            }
+            CircuitState::HalfOpen => {
+                // Re-open rather than leave a wedged HalfOpen: a timed-out probe is
+                // inconclusive, and the reset timer re-arms for the next probe.
+                *state = CircuitState::Open {
+                    opened_at: Instant::now(),
+                };
+            }
+            CircuitState::Open { .. } => {}
+        }
+    }
 }
 
 #[cfg(test)]
@@ -562,4 +637,107 @@ mod tests {
             "backpressure must not reset the failure streak; the 5th failure opens the breaker"
         );
     }
+
+    #[test]
+    fn timeout_with_recent_contact_never_opens() {
+        // THE write-burst false-partition fix: a follower that round-tripped a reply
+        // recently (success/backpressure) is slow-but-ALIVE, so a burst of ship
+        // deadline-exceeds must NOT open the breaker. Far more than `threshold`
+        // timeouts stay closed while liveness is fresh.
+        let cb = CircuitBreaker::new(5, Duration::from_secs(30));
+        cb.record_success(); // recent proof of life
+        for _ in 0..20 {
+            cb.record_timeout();
+        }
+        assert!(
+            cb.check().is_ok(),
+            "timeouts from a peer with recent liveness must not open the breaker"
+        );
+    }
+
+    #[test]
+    fn timeout_without_proof_of_life_opens_like_failure() {
+        // Genuine-blackhole detection preserved: a peer the leader has never
+        // round-tripped (no liveness stamp) that only times out IS effectively
+        // unreachable, so timeouts accrue toward Open exactly like failures.
+        let cb = CircuitBreaker::new(5, Duration::from_secs(30));
+        for _ in 0..5 {
+            cb.record_timeout();
+        }
+        assert!(
+            cb.check().is_err(),
+            "timeouts with no proof of life must open the breaker (blackhole detection)"
+        );
+    }
+
+    #[test]
+    fn timeout_after_liveness_goes_stale_opens() {
+        // Recent contact suppresses timeout-driven opening; once the stamp ages past
+        // `reset_duration` with no round-trips at all, timeouts resume opening.
+        let cb = CircuitBreaker::new(3, Duration::from_millis(50));
+        cb.record_success(); // stamp liveness
+        std::thread::sleep(Duration::from_millis(60)); // stamp now older than reset_duration
+        for _ in 0..3 {
+            cb.record_timeout();
+        }
+        assert_eq!(
+            cb.query_state(),
+            BreakerState::Open,
+            "once liveness is stale, timeouts must open the breaker"
+        );
+    }
+
+    #[test]
+    fn timeout_does_not_refresh_last_contact() {
+        // A timeout received NO reply, so (unlike success/backpressure) it must not
+        // stamp liveness — otherwise a dead peer's own timeouts would keep it
+        // perpetually 'recent' and mask a genuine partition.
+        let cb = CircuitBreaker::new(3, Duration::from_secs(30));
+        assert!(cb.last_contact_elapsed().is_none());
+        cb.record_timeout();
+        assert!(
+            cb.last_contact_elapsed().is_none(),
+            "a timeout (no reply) must not refresh the liveness stamp"
+        );
+    }
+
+    #[test]
+    fn timeout_neutral_among_failures_with_recent_contact() {
+        // With recent contact a timeout is neutral: it neither advances the failure
+        // streak toward Open nor resets it. 4 failures + a backpressure (stamps
+        // recent liveness) + a timeout stays below threshold; the 5th failure opens.
+        let cb = CircuitBreaker::new(5, Duration::from_secs(30));
+        for _ in 0..4 {
+            cb.record_failure();
+        }
+        cb.record_backpressure(); // stamps recent liveness; neutral to the streak
+        cb.record_timeout(); // recent -> neutral, streak stays at 4
+        assert!(
+            cb.check().is_ok(),
+            "4 failures + a neutral timeout must stay below threshold"
+        );
+        cb.record_failure(); // 5th genuine failure
+        assert!(
+            cb.check().is_err(),
+            "the 5th genuine failure must still open the breaker"
+        );
+    }
+
+    #[test]
+    fn half_open_timeout_reopens_without_wedging() {
+        // A timed-out probe is inconclusive; it must re-open (re-arm the reset
+        // timer) rather than leave a wedged HalfOpen that admits no further probes.
+        let cb = CircuitBreaker::new(2, Duration::from_millis(1));
+        cb.record_failure();
+        cb.record_failure();
+        std::thread::sleep(Duration::from_millis(5));
+        assert!(cb.check().is_ok(), "half-open probe admitted");
+        assert_eq!(cb.query_state(), BreakerState::HalfOpen);
+        cb.record_timeout(); // probe timed out
+        assert_eq!(
+            cb.query_state(),
+            BreakerState::Open,
+            "a half-open timeout must re-open, never wedge HalfOpen"
+        );
+    }
 }

tidal-net/src/client.rs

@@ -303,7 +303,27 @@ impl PeerPool {
                 }
             }
             Err(status) => {
-                circuit_breaker.record_failure();
+                // Not every ship error is a partition signal. A client-side ship
+                // DEADLINE means the RPC did not round-trip within `request_timeout`,
+                // which a slow-but-ALIVE follower produces under a sustained 1536-D
+                // apply burst (its transport runtime momentarily starved by the
+                // CPU-heavy HNSW apply) just as a genuinely blackholed peer does.
+                // tonic's `Channel::timeout` surfaces that deadline as EITHER
+                // `DeadlineExceeded` OR `Cancelled` depending on the layer that fires
+                // (request-timeout vs h2 cancellation) — neither is a transport
+                // severance, and in the ship path `Cancelled` can only come from our
+                // own deadline (the follower never returns it). Routing both to
+                // `record_timeout` opens the breaker ONLY when the peer shows no
+                // recent proof of life — fixing the write-burst false-partition while
+                // still tripping on a genuine blackhole. A genuine peer-down surfaces
+                // as a connect-level `Unavailable` (or an H2/transport reset), which
+                // falls through to `record_failure` and still opens the breaker.
+                match status.code() {
+                    tonic::Code::DeadlineExceeded | tonic::Code::Cancelled => {
+                        circuit_breaker.record_timeout();
+                    }
+                    _ => circuit_breaker.record_failure(),
+                }
                 Err(GrpcTransportError::Grpc(Box::new(status)))
             }
         }

tidal-net/tests/ship_timeout_breaker.rs

@@ -0,0 +1,278 @@
+// Integration-test exemptions (same posture as the other tidal-net integration tests).
+#![allow(clippy::unwrap_used, clippy::significant_drop_tightening)]
+//! The write-burst false-partition fix, proven END-TO-END through REAL gRPC.
+//!
+//! Under a sustained 1536-D ack=quorum burst a follower applies every write on its
+//! single segment-receiver thread (CPU-heavy HNSW insert), which can starve its
+//! transport runtime so a leader→follower `ship_segment` RPC misses the client's
+//! `request_timeout` — even though the follower is up and still acking other ships.
+//! Before the fix, `send_to` called `record_failure` on that deadline exactly as on
+//! a genuine severance, so 5 such opened the breaker, both followers tripped under
+//! the uniform burst, the commit index stalled, and ack=quorum 503'd with no
+//! self-heal. The fix routes a ship DEADLINE (tonic `DeadlineExceeded`/`Cancelled`)
+//! to `record_timeout`, which opens the breaker ONLY when the peer shows no recent
+//! proof of life.
+//!
+//! These tests use a REAL tonic `WalShipping` server over a REAL established HTTP/2
+//! connection (not a synthetic `tonic::Status`): the handler succeeds once (proving
+//! liveness) then hangs past the client deadline, so the client observes a genuine
+//! request timeout on a live connection — exactly the production shape.
+
+use std::{
+    collections::HashMap,
+    net::SocketAddr,
+    sync::{
+        Arc,
+        atomic::{AtomicUsize, Ordering},
+    },
+    time::Duration,
+};
+
+use tidal_net::{
+    circuit_breaker::BreakerState,
+    client::PeerPool,
+    config::GrpcTransportConfig,
+    error::GrpcTransportError,
+    proto::{
+        AppliedReport, AppliedReportAck, HeartbeatRequest, HeartbeatResponse, JoinRequest,
+        JoinResponse, ShipSegmentRequest, ShipSegmentResponse, SnapshotChunk, SnapshotRequest,
+        StreamRequest, TimeoutNowRequest, TimeoutNowResponse, VoteRequest, VoteResponse,
+        wal_shipping_server::{WalShipping, WalShippingServer},
+    },
+};
+use tidaldb::replication::{
+    WalSegmentId,
+    shard::{RegionId, ShardId},
+    transport::WalSegmentPayload,
+};
+use tokio_stream::wrappers::ReceiverStream;
+use tonic::{Request, Response, Status, transport::Server};
+
+/// A real WAL-shipping server whose `ship_segment` handler succeeds for the first
+/// `hang_after` calls (fast `accepted=true`, refreshing the leader's liveness stamp)
+/// and then HANGS `hang_for` on every subsequent call — long enough to exceed the
+/// client's `request_timeout`, so the leader observes a genuine deadline on a LIVE,
+/// already-established connection. Every other RPC is unimplemented (the client only
+/// ships in these tests).
+struct FlakyShipServer {
+    calls: Arc<AtomicUsize>,
+    hang_after: usize,
+    hang_for: Duration,
+}
+
+#[tonic::async_trait]
+impl WalShipping for FlakyShipServer {
+    async fn ship_segment(
+        &self,
+        _request: Request<ShipSegmentRequest>,
+    ) -> Result<Response<ShipSegmentResponse>, Status> {
+        let n = self.calls.fetch_add(1, Ordering::SeqCst);
+        if n >= self.hang_after {
+            // Slow-but-ALIVE: the server is up and processing, just late — the
+            // client's request_timeout fires first and surfaces a real deadline.
+            tokio::time::sleep(self.hang_for).await;
+        }
+        Ok(Response::new(ShipSegmentResponse {
+            accepted: true,
+            ..Default::default()
+        }))
+    }
+
+    type StreamSegmentsStream = ReceiverStream<Result<ShipSegmentRequest, Status>>;
+    async fn stream_segments(
+        &self,
+        _request: Request<StreamRequest>,
+    ) -> Result<Response<Self::StreamSegmentsStream>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+
+    type FetchSnapshotStream = ReceiverStream<Result<SnapshotChunk, Status>>;
+    async fn fetch_snapshot(
+        &self,
+        _request: Request<SnapshotRequest>,
+    ) -> Result<Response<Self::FetchSnapshotStream>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+
+    async fn heartbeat(
+        &self,
+        _request: Request<HeartbeatRequest>,
+    ) -> Result<Response<HeartbeatResponse>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+
+    async fn report_applied(
+        &self,
+        _request: Request<AppliedReport>,
+    ) -> Result<Response<AppliedReportAck>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+
+    async fn request_vote(
+        &self,
+        _request: Request<VoteRequest>,
+    ) -> Result<Response<VoteResponse>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+
+    async fn timeout_now(
+        &self,
+        _request: Request<TimeoutNowRequest>,
+    ) -> Result<Response<TimeoutNowResponse>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+
+    async fn join_cluster(
+        &self,
+        _request: Request<JoinRequest>,
+    ) -> Result<Response<JoinResponse>, Status> {
+        Err(Status::unimplemented("mock"))
+    }
+}
+
+fn free_addr() -> SocketAddr {
+    std::net::TcpListener::bind("127.0.0.1:0")
+        .unwrap()
+        .local_addr()
+        .unwrap()
+}
+
+fn make_payload(seqno: u64) -> WalSegmentPayload {
+    WalSegmentPayload {
+        id: WalSegmentId::new(RegionId::SINGLE, ShardId(0), seqno),
+        bytes: vec![0xCD; 50],
+        event_count: 1,
+        leader_last_seq: seqno,
+        stream_baseline: 0,
+        term: 0,
+        leader_region: 0,
+    }
+}
+
+fn config_for(peer: SocketAddr, threshold: u32) -> GrpcTransportConfig {
+    let mut peers = HashMap::new();
+    peers.insert(ShardId(0), peer.to_string());
+    GrpcTransportConfig {
+        local_shard: ShardId(0),
+        listen_addr: free_addr(),
+        peers,
+        insecure: true,
+        circuit_breaker_threshold: threshold,
+        circuit_breaker_reset: Duration::from_secs(30),
+        // Short request deadline so a hung handler trips it fast; generous connect
+        // timeout so the first (fast) ship establishes the connection cleanly.
+        request_timeout: Duration::from_millis(500),
+        connect_timeout: Duration::from_secs(5),
+        ..Default::default()
+    }
+}
+
+/// Spawn the flaky server and wait until it is actually accepting TCP.
+async fn spawn_server(addr: SocketAddr, server: FlakyShipServer) {
+    tokio::spawn(async move {
+        let _ = Server::builder()
+            .add_service(WalShippingServer::new(server))
+            .serve(addr)
+            .await;
+    });
+    for _ in 0..50 {
+        if tokio::net::TcpStream::connect(addr).await.is_ok() {
+            return;
+        }
+        tokio::time::sleep(Duration::from_millis(20)).await;
+    }
+    panic!("mock WAL server never started listening on {addr}");
+}
+
+fn assert_ship_timeout(result: &Result<(u64, u64), GrpcTransportError>) {
+    match result {
+        Err(GrpcTransportError::Grpc(status)) => assert!(
+            matches!(
+                status.code(),
+                tonic::Code::DeadlineExceeded | tonic::Code::Cancelled
+            ),
+            "an established-connection ship deadline must surface as DeadlineExceeded|Cancelled \
+             (the codes routed to record_timeout), got {:?}: {status}",
+            status.code()
+        ),
+        other => panic!("expected a gRPC deadline status from a hung ship, got {other:?}"),
+    }
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn recent_liveness_keeps_breaker_closed_under_real_ship_timeouts() {
+    // THE fix, end-to-end: a follower that proved liveness (ship #1 succeeded) then
+    // times out a burst of ships must NOT trip the breaker — a slow-but-alive peer
+    // is not a partition.
+    let addr = free_addr();
+    let calls = Arc::new(AtomicUsize::new(0));
+    spawn_server(
+        addr,
+        FlakyShipServer {
+            calls: calls.clone(),
+            hang_after: 1, // first ship fast; the rest hang
+            hang_for: Duration::from_secs(3),
+        },
+    )
+    .await;
+
+    let pool = PeerPool::new(&config_for(addr, 3)).unwrap();
+
+    // Ship #1: real success over a freshly-established H2 connection → record_success.
+    let first = pool.send_to(ShardId(0), make_payload(1)).await;
+    assert!(first.is_ok(), "the first ship must succeed: {first:?}");
+    assert!(
+        pool.peer_grpc_fresh(ShardId(0), Duration::from_secs(5)),
+        "an accepted ship must refresh the peer's liveness stamp"
+    );
+
+    // Ships #2..#6: each hangs past the 500ms deadline → REAL ship timeouts (far more
+    // than the threshold of 3) on the SAME live connection.
+    for seq in 2..=6 {
+        let r = pool.send_to(ShardId(0), make_payload(seq)).await;
+        assert_ship_timeout(&r);
+    }
+
+    assert_eq!(
+        pool.breaker_state(ShardId(0)),
+        BreakerState::Closed,
+        "5 real ship timeouts from a peer with recent liveness must NOT open the breaker \
+         (the write-burst false-partition fix)"
+    );
+    // And replication is not wedged: the breaker still admits the next ship.
+    assert!(
+        pool.peer_grpc_fresh(ShardId(0), Duration::from_secs(60)),
+        "the slow-but-alive peer's liveness stamp is still fresh from ship #1"
+    );
+}
+
+#[tokio::test(flavor = "multi_thread", worker_threads = 4)]
+async fn ship_timeouts_with_no_proof_of_life_still_open_breaker() {
+    // Genuine-blackhole detection preserved END-TO-END: a peer that only ever times
+    // out (never round-trips a reply) has no liveness stamp, so real ship timeouts
+    // still open the breaker at the threshold.
+    let addr = free_addr();
+    let calls = Arc::new(AtomicUsize::new(0));
+    spawn_server(
+        addr,
+        FlakyShipServer {
+            calls: calls.clone(),
+            hang_after: 0, // every ship hangs — no proof of life ever
+            hang_for: Duration::from_secs(3),
+        },
+    )
+    .await;
+
+    let pool = PeerPool::new(&config_for(addr, 3)).unwrap();
+
+    for seq in 1..=3 {
+        let r = pool.send_to(ShardId(0), make_payload(seq)).await;
+        assert_ship_timeout(&r);
+    }
+
+    assert_eq!(
+        pool.breaker_state(ShardId(0)),
+        BreakerState::Open,
+        "ship timeouts with no proof of life must still open the breaker (blackhole detection)"
+    );
+}

tidal-stress/k8s/t5-readtput-job.yaml

@@ -2,6 +2,12 @@
 # 3-node cluster sustains within SLA, spread round-robin across all 3 pods.
 # (T5-as-written's 2.5x WRITE-scaling is structurally impossible on 3-node RF3
 # full placement — proven in docs/profiling/m12p4-t5-sharded-throughput.md.)
+#
+# THIS JOB IS THE Ref-A OWNER-TEST for the re-scoped G-S Scalability guarantee
+# (read-throughput) — see docs/planning/milestone-11/guarantee-traceability.md
+# (G-S row, re-scoped 2026-06-19). The structural basis (a node serves reads from
+# its LOCAL placement, no cross-node forward → per-node capacity adds) is proven by
+# the cargo e2e `mp_partial_placement_feed_spans_all_groups` (cluster_cross_shard_reads).
 apiVersion: batch/v1
 kind: Job
 metadata:

tidal-stress/src/bin/soak-eval.rs

@@ -18,7 +18,10 @@ use tidal_stress::soak_eval::{
 };
 
 #[derive(Parser)]
-#[command(version, about = "30-night soak streak evaluator (ledger + restarts → streak.tsv)")]
+#[command(
+    version,
+    about = "30-night soak streak evaluator (ledger + restarts → streak.tsv)"
+)]
 struct Cli {
     /// The durable result dir the nightly CronJob + monitor write to.
     #[arg(long, default_value = "/results")]
@@ -62,7 +65,10 @@ fn main() -> ExitCode {
     // Exit non-zero iff the MOST RECENT night is non-green — the alert trigger.
     match verdicts.last() {
         Some(v) if !v.green => {
-            eprintln!("soak-eval: ALERT — last night {} is NON-GREEN: {}", v.date, v.reason);
+            eprintln!(
+                "soak-eval: ALERT — last night {} is NON-GREEN: {}",
+                v.date, v.reason
+            );
             ExitCode::from(1)
         }
         _ => ExitCode::SUCCESS,

tidal-stress/src/soak_eval.rs

@@ -179,12 +179,11 @@ pub fn evaluate(nights: &[NightResult], samples: &[RestartSample]) -> Vec<NightV
                 (false, false) => (false, String::from("soak SLO gate breach (Job FAIL)")),
                 (true, true) => (
                     false,
-                    String::from("under-load pod restart in window (Job passed but streak-breaking)"),
+                    String::from(
+                        "under-load pod restart in window (Job passed but streak-breaking)",
                     ),
-                (false, true) => (
-                    false,
-                    String::from("soak FAIL and under-load pod restart"),
                 ),
+                (false, true) => (false, String::from("soak FAIL and under-load pod restart")),
             };
             NightVerdict {
                 date: n.date.clone(),
@@ -210,10 +209,7 @@ pub fn render_streak_tsv(verdicts: &[NightVerdict], target: usize) -> String {
     let mut run = 0usize;
     for v in verdicts {
         run = if v.green { run + 1 } else { 0 };
-        s.push_str(&format!(
-            "{}\t{}\t{}\t{}\n",
-            v.date, v.green, run, v.reason
-        ));
+        s.push_str(&format!("{}\t{}\t{}\t{}\n", v.date, v.green, run, v.reason));
     }
     let streak = current_streak(verdicts);
     s.push_str(&format!("# streak={streak}/{target}\n"));
@@ -271,10 +267,17 @@ mod tests {
         });
         let verdicts = evaluate(&nights, &samples);
         let n15 = verdicts.iter().find(|v| v.date == "2026-06-15").unwrap();
-        assert!(!n15.green, "a night with an under-load restart is NOT green");
+        assert!(
+            !n15.green,
+            "a night with an under-load restart is NOT green"
+        );
         assert!(n15.reason.contains("restart"), "reason names the restart");
         // The streak is only the clean tail after night 15: nights 16..=30 = 15.
-        assert_eq!(current_streak(&verdicts), 15, "streak resets at the restart night");
+        assert_eq!(
+            current_streak(&verdicts),
+            15,
+            "streak resets at the restart night"
+        );
     }
 
     #[test]
@@ -286,7 +289,11 @@ mod tests {
         let n20 = verdicts.iter().find(|v| v.date == "2026-06-20").unwrap();
         assert!(!n20.green, "a gate-breach night is not green");
         assert!(n20.reason.contains("gate"), "reason names the gate breach");
-        assert_eq!(current_streak(&verdicts), 10, "tail after night 20 = nights 21..=30");
+        assert_eq!(
+            current_streak(&verdicts),
+            10,
+            "tail after night 20 = nights 21..=30"
+        );
     }
 
     #[test]
@@ -295,11 +302,22 @@ mod tests {
         // count as a restart (min < max that night).
         let nights = pass_nights(1);
         let samples = vec![
-            RestartSample { date: "2026-06-01".into(), pod: "tidaldb-0".into(), restarts: 0 },
-            RestartSample { date: "2026-06-01".into(), pod: "tidaldb-0".into(), restarts: 1 },
+            RestartSample {
+                date: "2026-06-01".into(),
+                pod: "tidaldb-0".into(),
+                restarts: 0,
+            },
+            RestartSample {
+                date: "2026-06-01".into(),
+                pod: "tidaldb-0".into(),
+                restarts: 1,
+            },
         ];
         let verdicts = evaluate(&nights, &samples);
-        assert!(!verdicts[0].green, "0→1 within the first night is a restart");
+        assert!(
+            !verdicts[0].green,
+            "0→1 within the first night is a restart"
+        );
     }
 
     #[test]
@@ -333,6 +351,9 @@ ts_utc\tpod\trestarts\tphase\tready\n\
         let verdicts = evaluate(&nights, &samples);
         let tsv = render_streak_tsv(&verdicts, 30);
         assert!(tsv.contains("date\tgreen\tstreak\treason"), "has a header");
-        assert!(tsv.trim_end().ends_with("# streak=3/30"), "summary line present: {tsv}");
+        assert!(
+            tsv.trim_end().ends_with("# streak=3/30"),
+            "summary line present: {tsv}"
+        );
     }
 }

tidalctl/src/commands/s3.rs

@@ -30,9 +30,9 @@
 use std::path::{Path, PathBuf};
 
 use aws_credential_types::Credentials;
+use aws_sdk_s3::Client;
 use aws_sdk_s3::config::{BehaviorVersion, Region};
 use aws_sdk_s3::primitives::ByteStream;
-use aws_sdk_s3::Client;
 
 use crate::CliError;
 
@@ -143,8 +143,9 @@ async fn build_client(target: &S3Target) -> Result<Client, CliError> {
              AWS_SECRET_ACCESS_KEY to your R2 token credentials)",
         )
     })?;
-    let secret_key = std::env::var("AWS_SECRET_ACCESS_KEY")
-        .map_err(|_| CliError::new("AWS_SECRET_ACCESS_KEY is not set (required for the S3/R2 export)"))?;
+    let secret_key = std::env::var("AWS_SECRET_ACCESS_KEY").map_err(|_| {
+        CliError::new("AWS_SECRET_ACCESS_KEY is not set (required for the S3/R2 export)")
+    })?;
 
     let creds = Credentials::from_keys(access_key, secret_key, None);
 
@@ -431,8 +432,7 @@ mod tests {
     #[test]
     fn relative_from_key_inverts_object_key() {
         assert_eq!(
-            relative_from_key("backups/node-A", "backups/node-A/wal/seg-1.seg")
-                .as_deref(),
+            relative_from_key("backups/node-A", "backups/node-A/wal/seg-1.seg").as_deref(),
             Some("wal/seg-1.seg")
         );
         // Empty prefix: the whole key is the relative path.