From 46d27a014480df81ccaf6b04eb317dc4af8907f2 Mon Sep 17 00:00:00 2001
From: liquidraver <504870+liquidraver@users.noreply.github.com>
Date: Fri, 3 Jul 2026 19:30:53 +0200
Subject: [PATCH] meshtimesync p2

---
 zephcore/MESHTIMESYNC.md => MESHTIMESYNC.md |   7 +-
 zephcore/ARCHITECTURE.md                    |   4 +-
 zephcore/Repeater_CLI_commands.md           |   4 +-
 zephcore/app/CompanionMesh.cpp              |  40 +-----
 zephcore/app/CompanionMesh.h                |  11 +-
 zephcore/app/ObserverMesh.cpp               |  42 ++----
 zephcore/app/ObserverMesh.h                 |   2 -
 zephcore/app/RepeaterDataStore.cpp          |   2 +-
 zephcore/app/RepeaterMesh.cpp               |  66 +++------
 zephcore/app/RepeaterMesh.h                 |   1 -
 zephcore/app/RoomServerMesh.cpp             |  54 ++-----
 zephcore/app/RoomServerMesh.h               |   8 +-
 zephcore/helpers/BaseChatMesh.cpp           |   7 +-
 zephcore/helpers/CommonCLI.cpp              |   9 +-
 zephcore/helpers/CommonCLI.h                |   6 +
 zephcore/helpers/MeshTimeSync.cpp           | 148 +++++++++++++++-----
 zephcore/helpers/MeshTimeSync.h             | 119 ++++++++--------
 17 files changed, 262 insertions(+), 268 deletions(-)
 rename zephcore/MESHTIMESYNC.md => MESHTIMESYNC.md (91%)

diff --git a/zephcore/MESHTIMESYNC.md b/MESHTIMESYNC.md
similarity index 91%
rename from zephcore/MESHTIMESYNC.md
rename to MESHTIMESYNC.md
index 8b34b9d..e71b615 100644
--- a/zephcore/MESHTIMESYNC.md
+++ b/MESHTIMESYNC.md
@@ -35,7 +35,10 @@ worth watching that dry-run output for a day before (and after) enabling.
 
 ## What it will NOT do
 
-- It never overrides GPS time. Nodes with GPS enabled only observe.
+- It never fights GPS: a node whose GPS has delivered a real fix in the
+  last 72 hours only observes. If GPS is on but cannot get a fix (indoors,
+  dead antenna), mesh correction takes over after 72 hours — until the
+  next real fix.
 - It never overrides a recent manual `time <epoch>` or `clock sync` — any
   manual set protects the clock from automatic changes for 7 days.
 - It never steps more than 1 hour at a time, and at most one step per 6 hours.
@@ -81,4 +84,4 @@ adverts take tens of minutes to accumulate after a reboot, so an operator
 syncing right after login always wins.
 
 For the design details (consensus algorithm, security model, why the limits
-are what they are), see [ARCHITECTURE.md](ARCHITECTURE.md) section 4.9.
+are what they are), see [ARCHITECTURE.md](zephcore/ARCHITECTURE.md) section 4.9.
diff --git a/zephcore/ARCHITECTURE.md b/zephcore/ARCHITECTURE.md
index 5cc329d..0614f0a 100644
--- a/zephcore/ARCHITECTURE.md
+++ b/zephcore/ARCHITECTURE.md
@@ -303,7 +303,7 @@ ZephCore-only divergence from Arduino MeshCore (like the Adaptive Contention Win
 **Consensus**: Marzullo interval intersection over eligible votes, each `[skew − r, skew + r]` with `r = 150 s + 15 s × hop` (the 150 s base covers the real fleet's good-clock scatter, not just RF delay). No absolute outlier thresholds against the local clock — clustering does the rejection, so an epoch-reset clock still finds the true cluster. Stepping requires `CONFIG_ZEPHCORE_TIMESYNC_QUORUM` (default 6, floor 3, build-time security knob) eligible senders AND a strict majority inside the intersection; otherwise abstain.
 
 **Correction policy** (priority: GPS > manual set > mesh consensus):
-- GPS gate: boards with GPS available + enabled never step (sensing continues).
+- GPS gate: nodes whose GPS delivered a validated fix within **72 h** never step (covers the repeater's 48 h GPS duty cycle with margin). Only a real fix makes the mesh yield — a GPS that is enabled but cannot fix (indoors, dead antenna) stops gating after the window, so those units stay mesh-correctable. Sensing always continues; the dry-run marks refused steps `(gps-gated)`.
 - Manual set (`time`, `clock sync`, app time set) arms a **7-day suppression** of all stepping, bootstrap included, plus drift-envelope pedigree.
 - Step trigger 10 min, dead band 5 min, step capped **±1 h**, one step per **6 h**, logged loudly. Production contains coherent wrong-time islands (+28 h × 63 repeaters at analysis time); the cap bounds capture drag to 4 h/day.
 - **Drift-envelope gate**: with a trusted sync + continuous uptime since (pedigree, RAM-only), corrections beyond `elapsed × 300 ppm + 10 min` are physically impossible for a crystal — refused regardless of quorum.
@@ -317,7 +317,7 @@ ZephCore-only divergence from Arduino MeshCore (like the Adaptive Contention Win
 | Room server | forward-only | post timestamps feed client `sync_since` ordering |
 | Companion | forward-only | own clock stamps outgoing DMs; peers hold per-sender replay high-water marks |
 
-**Step application** (repeater reference, `applyTimeSyncStep`): set clock, one `zephcore_rtc_save` per step (never per evaluation), shift neighbor `heard_timestamp`s and ACL `last_activity` by the delta (unsigned "seconds ago" math), reset the login/anon/discover rate limiters.
+**Step application**: the shared policy (GPS gate, forward-only skip, uint32-overflow guard, set clock, one `zephcore_rtc_save` per step — never per evaluation) lives in `MeshTimeSync::runTick()`; when it returns true, the role shifts its wall-clock-anchored bookkeeping by `lastStepDelta()` — repeater: neighbor `heard_timestamp`s, ACL `last_activity`, login/anon/discover rate-limiter resets; room server: ACL + login limiter.
 
 All policy timers (6 h rate limit, 7-day suppression, tenure, sample age) anchor on **uptime, never wall clock** — otherwise the very steps they govern would distort them.
 
diff --git a/zephcore/Repeater_CLI_commands.md b/zephcore/Repeater_CLI_commands.md
index 0671b88..f555969 100644
--- a/zephcore/Repeater_CLI_commands.md
+++ b/zephcore/Repeater_CLI_commands.md
@@ -206,7 +206,7 @@ All `set uplink.*` changes are saved immediately and only applied after reboot.
 | `get radio.rxgain` | RX gain boost: `0` or `1` |
 | `get rxduty` | RX duty cycle mode: `0` or `1` |
 | `get gps duty` | Now-effective GPS duty interval in seconds (`always on (0)` when continuous) |
-| `get meshtimesync` | Mesh time-sync state + live dry-run: on/off, eligible voter count, votes for/against, consensus skew and radius, would-be verdict (`ok`/`in-band`/`step±N`/`abstain (reason)`/`hold (reason)`), step counters, suppression countdown, and a per-sender evidence table (`prefix hops count skew E`, `E` = tenure-eligible). Sensing runs even while off, so this works as a dry-run before enabling. Over remote admin the reply is truncated to the packet size (summary always fits); the full table needs the USB CLI. |
+| `get meshtimesync` | Mesh time-sync state + live dry-run: on/off, eligible voter count, votes for/against, consensus skew and radius, would-be verdict (`ok`/`in-band`/`step±N`/`abstain (reason)`/`hold (reason)`; steps the policy would refuse are annotated `(gps-gated)` or `(skipped: forward-only)`), step counters, suppression countdown, and a per-sender evidence table (`prefix hops count skew E`, `E` = tenure-eligible). Sensing runs even while off, so this works as a dry-run before enabling. Over remote admin the reply is truncated to the packet size (summary always fits); the full table needs the USB CLI. |
 | `get dc.restarts` | Duty-cycle preamble false-positive re-arm counter (RxTimeout re-arms + parked-RX watchdog recoveries). High values mean the preamble detector is tripping on noise/interference without real packets arriving — inflates RX-on time and drains battery; packets are never lost to it. Reset by `clear stats`. |
 | `get adc.multiplier` | Battery voltage ADC calibration multiplier |
 | `get bootloader.ver` | Bootloader version string |
@@ -251,7 +251,7 @@ Changes are persisted immediately unless noted. Some require a reboot.
 | `set radio.rxgain <0\|1\|on\|off>` | | RX gain boost, applied live. Replies `Error: unsupported` on radios without RX boost (SX127x); the pref is still saved. |
 | `set rxduty <0\|1\|on\|off>` | | RX duty cycle mode *(reboot required)*. Window timing auto-sized per SF/BW/preamble from the SX126x datasheet constraints (boot log line `rxduty:` shows the result). Zero-loss guarantee assumes senders on preamble-32 firmware (current MeshCore at SF≤8); legacy preamble-16 senders are only caught ~50% worst-phase — keep off until the local mesh has converted. Presets with 16-symbol preambles (SF≥9) fall back to continuous RX automatically. |
 | `set adc.multiplier <mult>` | (0 = use board default) | Battery voltage ADC calibration multiplier |
-| `set meshtimesync <on\|off>` | default **off** | Mesh time sync: automatically correct this node's clock from the consensus of Ed25519-signed advert timestamps heard on the mesh. Steps at most ±1 h per step, one step per 6 h; abstains without a quorum (default 6) of tenured agreeing senders; never overrides GPS or a manual set less than 7 days old. See `MESHTIMESYNC.md`. |
+| `set meshtimesync <on\|off>` | default **off** | Mesh time sync: automatically correct this node's clock from the consensus of Ed25519-signed advert timestamps heard on the mesh. Steps at most ±1 h per step, one step per 6 h; abstains without a quorum (default 6) of tenured agreeing senders; never overrides a GPS clock with a validated fix in the last 72 h, or a manual set less than 7 days old. See `MESHTIMESYNC.md`. |
 | `set prv.key <hex>` | 64-char hex (32-byte key) | Replace private key; derive new identity *(reboot to apply)* |
 
 ---
diff --git a/zephcore/app/CompanionMesh.cpp b/zephcore/app/CompanionMesh.cpp
index eef252b..a4074c5 100644
--- a/zephcore/app/CompanionMesh.cpp
+++ b/zephcore/app/CompanionMesh.cpp
@@ -353,43 +353,9 @@ void CompanionMesh::onAdvertTimeSample(const mesh::Identity &id, uint32_t timest
 void CompanionMesh::timeSyncTick()
 {
 	if (!prefs.meshtimesync) return;
-
-	uint32_t up = (uint32_t)(k_uptime_get() / 1000);
-	uint32_t now = getRTCClock()->getCurrentTime();
-	MeshTimeSync::Verdict v = _timesync.tick(now, up);
-	if (v.type != MeshTimeSync::VERDICT_STEP) return;
-
-	/* GPS gate: sense only while GPS owns the clock. */
-	if (gps_is_available() && gps_is_enabled()) {
-		LOG_INF("meshtimesync: step %+d s wanted, GPS gate active - not applied",
-			(int)v.delta);
-		return;
-	}
-	/* Forward-only role: our clock stamps outgoing DMs and peers hold
-	 * per-sender replay high-water marks — a backward step gets our
-	 * messages dropped as replays. Report, never apply. */
-	if (v.delta < 0) {
-		_timesync.noteBackwardSkipped();
-		LOG_WRN("meshtimesync: backward step %+d s wanted - skipped (companion is forward-only)",
-			(int)v.delta);
-		return;
-	}
-	applyTimeSyncStep(v, now, up);
-}
-
-void CompanionMesh::applyTimeSyncStep(const MeshTimeSync::Verdict &v, uint32_t now,
-				      uint32_t uptime_secs)
-{
-	uint32_t new_time = (uint32_t)((int64_t)now + v.delta);
-	getRTCClock()->setCurrentTime(new_time);
-	zephcore_rtc_save(new_time);
-	time_sync_report(TIME_SYNC_MESH);
-
-	_timesync.noteStepApplied(v.delta, new_time, uptime_secs, v.bootstrap);
-	LOG_WRN("meshtimesync: stepped clock %+d s (%s, votes %u/%u) -> %u",
-		(int)v.delta, v.bootstrap ? "bootstrap" : "consensus",
-		(unsigned)v.consensus.votes_for, (unsigned)v.consensus.votes_against,
-		(unsigned)new_time);
+	/* Shared policy (GPS fix-freshness gate, forward-only) lives in
+	 * runTick; no companion-side bookkeeping needs shifting on a step. */
+	_timesync.runTick(*getRTCClock());
 }
 
 void CompanionMesh::onLoginSent(const ContactInfo &contact)
diff --git a/zephcore/app/CompanionMesh.h b/zephcore/app/CompanionMesh.h
index ae58c54..e292a3a 100644
--- a/zephcore/app/CompanionMesh.h
+++ b/zephcore/app/CompanionMesh.h
@@ -233,9 +233,7 @@ public:
 	bool onChannelLoaded(uint8_t idx, const ChannelDetails &ch) override;
 	bool getChannelForSave(uint8_t idx, ChannelDetails &ch) override;
 
-	/* Mesh time sync (forward-only: our clock stamps outgoing DMs and peers
-	 * hold per-sender replay high-water marks, so a backward step gets our
-	 * messages dropped as replays until wall-clock catches up) */
+	/* Mesh time sync */
 	MeshTimeSync *getMeshTimeSync() { return &_timesync; }
 	void noteGPSTimeSync() { _timesync.noteGPSSync((uint32_t)(k_uptime_get() / 1000)); }
 	/* Paced evaluation — called from the housekeeping event (loop() only runs
@@ -380,12 +378,11 @@ private:
 	void flushDirtyContacts();
 	void flushDirtyChannels();
 
-	/* Mesh time sync */
-	MeshTimeSync _timesync{FIRMWARE_BUILD_EPOCH};
+	/* Mesh time sync (forward-only: our clock stamps outgoing DMs and peers
+	 * hold per-sender replay high-water marks) */
+	MeshTimeSync _timesync{FIRMWARE_BUILD_EPOCH, true};
 	void onAdvertTimeSample(const mesh::Identity &id, uint32_t timestamp,
 		uint8_t hops) override;
-	void applyTimeSyncStep(const MeshTimeSync::Verdict &v, uint32_t now,
-		uint32_t uptime_secs);
 
 	/* Protocol version negotiation */
 	uint8_t _app_target_ver;
diff --git a/zephcore/app/ObserverMesh.cpp b/zephcore/app/ObserverMesh.cpp
index d809a0b..1ccd973 100644
--- a/zephcore/app/ObserverMesh.cpp
+++ b/zephcore/app/ObserverMesh.cpp
@@ -9,8 +9,6 @@
 #include <mesh/Utils.h>
 #include <mesh/LoRaConfig.h>
 #include <adapters/radio/LoRaRadioBase.h>
-#include <adapters/clock/ZephyrRTCDiscover.h>
-#include <adapters/gps/ZephyrGPSManager.h>
 #include <helpers/MeshcoreJson.h>
 
 #include <zephyr/logging/log.h>
@@ -230,6 +228,12 @@ void ObserverMesh::harvestTimeSample(Packet *pkt)
 	if (pkt->getPayloadType() != PAYLOAD_TYPE_ADVERT) return;
 	if (pkt->getPathHashCount() > MeshTimeSync::HOP_CAP) return;
 	if (pkt->payload_len < PUB_KEY_SIZE + 4 + SIGNATURE_SIZE) return;
+	/* Skip share rebroadcasts (transport codes {0,0}) — they replay stale
+	 * stored adverts and would churn the original sender's tenure. */
+	if (pkt->hasTransportCodes() &&
+	    pkt->transport_codes[0] == 0 && pkt->transport_codes[1] == 0) {
+		return;
+	}
 
 	int i = 0;
 	Identity id;
@@ -241,6 +245,10 @@ void ObserverMesh::harvestTimeSample(Packet *pkt)
 	const uint8_t *signature = &pkt->payload[i];
 	i += SIGNATURE_SIZE;
 
+	/* Observers have no dedup and hear every flood copy — skip the
+	 * expensive Ed25519 verify when the sample cannot update the table. */
+	if (!_timesync.wouldAccept(id.pub_key, timestamp)) return;
+
 	size_t app_data_len = pkt->payload_len - (size_t)i;
 	if (app_data_len > MAX_ADVERT_DATA_SIZE) app_data_len = MAX_ADVERT_DATA_SIZE;
 
@@ -259,19 +267,9 @@ void ObserverMesh::harvestTimeSample(Packet *pkt)
 void ObserverMesh::timeSyncTick()
 {
 	if (!_prefs.meshtimesync || !_rtc) return;
-
-	uint32_t up = (uint32_t)(k_uptime_get() / 1000);
-	uint32_t now = _rtc->getCurrentTime();
-	MeshTimeSync::Verdict v = _timesync.tick(now, up);
-	if (v.type != MeshTimeSync::VERDICT_STEP) return;
-
-	/* GPS gate: sense only while GPS owns the clock. */
-	if (gps_is_available() && gps_is_enabled()) {
-		LOG_INF("meshtimesync: step %+d s wanted, GPS gate active - not applied",
-			(int)v.delta);
-		return;
-	}
-	applyTimeSyncStep(v, now, up);
+	/* Shared policy (GPS fix-freshness gate) lives in runTick; no
+	 * observer-side bookkeeping needs shifting on a step. */
+	_timesync.runTick(*_rtc);
 }
 
 void ObserverMesh::noteTrustedTimeSync()
@@ -279,20 +277,6 @@ void ObserverMesh::noteTrustedTimeSync()
 	_timesync.noteManualSync((uint32_t)(k_uptime_get() / 1000));
 }
 
-void ObserverMesh::applyTimeSyncStep(const MeshTimeSync::Verdict &v, uint32_t now,
-				     uint32_t uptime_secs)
-{
-	uint32_t new_time = (uint32_t)((int64_t)now + v.delta);
-	_rtc->setCurrentTime(new_time);
-	zephcore_rtc_save(new_time);
-
-	_timesync.noteStepApplied(v.delta, new_time, uptime_secs, v.bootstrap);
-	LOG_WRN("meshtimesync: stepped clock %+d s (%s, votes %u/%u) -> %u",
-		(int)v.delta, v.bootstrap ? "bootstrap" : "consensus",
-		(unsigned)v.consensus.votes_for, (unsigned)v.consensus.votes_against,
-		(unsigned)new_time);
-}
-
 /* ========== Serial CLI ========== */
 
 #define CLI_REPLY_SIZE 256
diff --git a/zephcore/app/ObserverMesh.h b/zephcore/app/ObserverMesh.h
index c311bee..10eed5b 100644
--- a/zephcore/app/ObserverMesh.h
+++ b/zephcore/app/ObserverMesh.h
@@ -63,8 +63,6 @@ class ObserverMesh : public Dispatcher {
 	 * advert signatures itself before harvesting. */
 	MeshTimeSync _timesync{FIRMWARE_BUILD_EPOCH};
 	void harvestTimeSample(Packet *pkt);
-	void applyTimeSyncStep(const MeshTimeSync::Verdict &v, uint32_t now,
-			       uint32_t uptime_secs);
 
 protected:
 	/* Capture RSSI + raw bytes before packet is parsed */
diff --git a/zephcore/app/RepeaterDataStore.cpp b/zephcore/app/RepeaterDataStore.cpp
index 3293df5..308643e 100644
--- a/zephcore/app/RepeaterDataStore.cpp
+++ b/zephcore/app/RepeaterDataStore.cpp
@@ -243,7 +243,7 @@ bool RepeaterDataStore::loadPrefs(NodePrefs& prefs) {
         prefs.path_hash_mode = 1;
         prefs.loop_detect = LOOP_DETECT_MODERATE;
         savePrefs(prefs);
-        LOG_INF("loadPrefs: upgraded prefs format (%d -> 296 bytes)", (int)entry.size);
+        LOG_INF("loadPrefs: upgraded prefs format (%d -> 297 bytes)", (int)entry.size);
     }
 
     /* Repeater GPS-interval unification migration: before this firmware the
diff --git a/zephcore/app/RepeaterMesh.cpp b/zephcore/app/RepeaterMesh.cpp
index db5da08..792dcee 100644
--- a/zephcore/app/RepeaterMesh.cpp
+++ b/zephcore/app/RepeaterMesh.cpp
@@ -12,8 +12,6 @@
 #include <adapters/sensors/SimpleLPP.h>
 #include <adapters/sensors/ZephyrEnvSensors.h>
 #include <adapters/gps/ZephyrGPSManager.h>
-#include <adapters/clock/ZephyrRTCDiscover.h>
-#include <helpers/time_sync.h>
 #include <zephyr/kernel.h>
 #include <zephyr/device.h>
 #include <zephyr/devicetree.h>
@@ -52,10 +50,14 @@ LOG_MODULE_REGISTER(zephcore_repeater, CONFIG_ZEPHCORE_MAIN_LOG_LEVEL);
 
 #if IS_ENABLED(CONFIG_ZEPHCORE_REPEATER_UPLINK) && IS_ENABLED(CONFIG_MQTT_LIB)
 static RepeaterMesh *s_uplink_mesh;
+/* Runs on the WiFi thread; the mesh time-sync module is main-thread-only, so
+ * flag the trusted sync and let loop() arm suppression + drift envelope. */
+static atomic_t s_uplink_sntp_pending;
 static void uplink_time_sync_cb(uint32_t unix_ts)
 {
 	if (s_uplink_mesh) {
 		s_uplink_mesh->getRTCClock()->setCurrentTime(unix_ts);
+		atomic_set(&s_uplink_sntp_pending, 1);
 	}
 }
 #endif
@@ -713,9 +715,13 @@ void RepeaterMesh::onAdvertRecv(mesh::Packet* packet, const mesh::Identity& id,
                                 const uint8_t* app_data, size_t app_data_len) {
     mesh::Mesh::onAdvertRecv(packet, id, timestamp, app_data, app_data_len);
 
-    /* Signature already verified by mesh::Mesh before this hook fires. */
-    _timesync.onAdvertHeard(id.pub_key, timestamp, packet->getPathHashCount(),
-                            (uint32_t)(k_uptime_get() / 1000));
+    /* Signature already verified by mesh::Mesh before this hook fires.
+     * Skip share rebroadcasts — they replay stale stored adverts and would
+     * churn the original sender's tenure. */
+    if (!isShare(packet)) {
+        _timesync.onAdvertHeard(id.pub_key, timestamp, packet->getPathHashCount(),
+                                (uint32_t)(k_uptime_get() / 1000));
+    }
 
     if (packet->getPathHashCount() == 0 && !isShare(packet)) {
         AdvertDataParser parser(app_data, app_data_len);
@@ -790,7 +796,7 @@ void RepeaterMesh::onPeerDataRecv(mesh::Packet* packet, uint8_t type, int sender
                 }
             }
 
-            uint8_t temp[166];
+            uint8_t temp[5 + CLI_REMOTE_REPLY_SIZE];
             char* command = (char*)&data[5];
             char* reply = (char*)&temp[5];
             if (is_retry) {
@@ -1378,6 +1384,10 @@ void RepeaterMesh::loop() {
         publishUplinkStatus("online");
         _uplink_next_status_at = futureMillis(300000);
     }
+    if (atomic_cas(&s_uplink_sntp_pending, 1, 0)) {
+        /* SNTP set the clock (trusted) — arm suppression + drift envelope. */
+        _timesync.noteManualSync((uint32_t)(k_uptime_get() / 1000));
+    }
 #endif
 
     timeSyncTick();
@@ -1389,47 +1399,23 @@ void RepeaterMesh::loop() {
 
 void RepeaterMesh::timeSyncTick() {
     if (!_prefs.meshtimesync) return;
+    if (!_timesync.runTick(*getRTCClock())) return;
 
-    uint32_t up = (uint32_t)(k_uptime_get() / 1000);
-    uint32_t now = getRTCClock()->getCurrentTime();
-    MeshTimeSync::Verdict v = _timesync.tick(now, up);
-    if (v.type != MeshTimeSync::VERDICT_STEP) {
-        if (v.type == MeshTimeSync::VERDICT_ABSTAIN) {
-            LOG_DBG("meshtimesync: abstain (%s)", MeshTimeSync::reasonStr(v.reason));
-        }
-        return;
-    }
-    /* GPS gate: GPS sets the clock unconditionally — a wrong mesh step
-     * followed by a GPS step-back would poison our own advert high-water
-     * marks at peers. Sense only. */
-    if (gps_is_available() && gps_is_enabled()) {
-        LOG_INF("meshtimesync: step %+d s wanted, GPS gate active - not applied",
-                (int)v.delta);
-        return;
-    }
-    applyTimeSyncStep(v, now, up);
-}
-
-void RepeaterMesh::applyTimeSyncStep(const MeshTimeSync::Verdict& v, uint32_t now,
-                                     uint32_t uptime_secs) {
-    uint32_t new_time = (uint32_t)((int64_t)now + v.delta);
-    getRTCClock()->setCurrentTime(new_time);
-    zephcore_rtc_save(new_time);
-    time_sync_report(TIME_SYNC_MESH);
-
-    /* Wall-clock-anchored bookkeeping must move with the step, or a backward
-     * step underflows the unsigned "seconds ago" math. 0 = unset sentinel. */
+    /* Step applied — wall-clock-anchored bookkeeping must move with it, or a
+     * backward step underflows the unsigned "seconds ago" math. 0 = unset
+     * sentinel. */
+    int64_t delta = _timesync.lastStepDelta();
 #if MAX_NEIGHBOURS > 0
     for (int i = 0; i < MAX_NEIGHBOURS; i++) {
         if (neighbours[i].heard_timestamp == 0) continue;
-        int64_t shifted = (int64_t)neighbours[i].heard_timestamp + v.delta;
+        int64_t shifted = (int64_t)neighbours[i].heard_timestamp + delta;
         neighbours[i].heard_timestamp = (shifted > 0) ? (uint32_t)shifted : 1;
     }
 #endif
     for (int i = 0; i < acl.getNumClients(); i++) {
         ClientInfo* c = acl.getClientByIdx(i);
         if (c->last_activity == 0) continue;
-        int64_t shifted = (int64_t)c->last_activity + v.delta;
+        int64_t shifted = (int64_t)c->last_activity + delta;
         c->last_activity = (shifted > 0) ? (uint32_t)shifted : 1;
     }
     /* A backward step would otherwise wedge these shut until wall-clock
@@ -1437,12 +1423,6 @@ void RepeaterMesh::applyTimeSyncStep(const MeshTimeSync::Verdict& v, uint32_t no
     discover_limiter.reset();
     anon_limiter.reset();
     login_fail_limiter.reset();
-
-    _timesync.noteStepApplied(v.delta, new_time, uptime_secs, v.bootstrap);
-    LOG_WRN("meshtimesync: stepped clock %+d s (%s, votes %u/%u) -> %u",
-            (int)v.delta, v.bootstrap ? "bootstrap" : "consensus",
-            (unsigned)v.consensus.votes_for, (unsigned)v.consensus.votes_against,
-            (unsigned)new_time);
 }
 
 bool RepeaterMesh::hasPendingWork() const {
diff --git a/zephcore/app/RepeaterMesh.h b/zephcore/app/RepeaterMesh.h
index 4f54106..448d6c7 100644
--- a/zephcore/app/RepeaterMesh.h
+++ b/zephcore/app/RepeaterMesh.h
@@ -134,7 +134,6 @@ class RepeaterMesh : public mesh::Mesh, public CommonCLICallbacks {
 
     void putNeighbour(const mesh::Identity& id, uint32_t timestamp, float snr);
     void timeSyncTick();
-    void applyTimeSyncStep(const MeshTimeSync::Verdict& v, uint32_t now, uint32_t uptime_secs);
     uint8_t handleLoginReq(const mesh::Identity& sender, const uint8_t* secret, uint32_t sender_timestamp, const uint8_t* data, bool is_flood);
     uint8_t handleAnonRegionsReq(const mesh::Identity& sender, uint32_t sender_timestamp, const uint8_t* data, size_t data_len);
     uint8_t handleAnonOwnerReq(const mesh::Identity& sender, uint32_t sender_timestamp, const uint8_t* data, size_t data_len);
diff --git a/zephcore/app/RoomServerMesh.cpp b/zephcore/app/RoomServerMesh.cpp
index 75f63a8..b567776 100644
--- a/zephcore/app/RoomServerMesh.cpp
+++ b/zephcore/app/RoomServerMesh.cpp
@@ -19,8 +19,6 @@
 #include <adapters/sensors/SimpleLPP.h>
 #include <adapters/sensors/ZephyrEnvSensors.h>
 #include <adapters/gps/ZephyrGPSManager.h>
-#include <adapters/clock/ZephyrRTCDiscover.h>
-#include <helpers/time_sync.h>
 #include <zephyr/kernel.h>
 #include <zephyr/device.h>
 #include <zephyr/devicetree.h>
@@ -579,7 +577,7 @@ void RoomServerMesh::onPeerDataRecv(mesh::Packet* packet, uint8_t type, int send
             mesh::Utils::sha256((uint8_t*)&ack_hash, 4, data, 5 + strlen((char*)&data[5]),
                                client->id.pub_key, PUB_KEY_SIZE);
 
-            uint8_t temp[166];
+            uint8_t temp[5 + CLI_REMOTE_REPLY_SIZE];
             bool send_ack;
             if (flags == TXT_TYPE_CLI_DATA) {  // admin CLI over the air
                 if (client->isAdmin()) {
@@ -1117,57 +1115,31 @@ void RoomServerMesh::onAdvertRecv(mesh::Packet* packet, const mesh::Identity& id
                                   uint32_t timestamp, const uint8_t* app_data,
                                   size_t app_data_len) {
     (void)app_data; (void)app_data_len;
-    /* Signature already verified by mesh::Mesh before this hook fires. */
+    /* Signature already verified by mesh::Mesh before this hook fires.
+     * Skip share rebroadcasts (transport codes {0,0}) — they replay stale
+     * stored adverts and would churn the original sender's tenure. */
+    if (packet->hasTransportCodes() &&
+        packet->transport_codes[0] == 0 && packet->transport_codes[1] == 0) {
+        return;
+    }
     _timesync.onAdvertHeard(id.pub_key, timestamp, packet->getPathHashCount(),
                             (uint32_t)(k_uptime_get() / 1000));
 }
 
 void RoomServerMesh::timeSyncTick() {
     if (!_prefs.meshtimesync) return;
+    if (!_timesync.runTick(*getRTCClock())) return;
 
-    uint32_t up = (uint32_t)(k_uptime_get() / 1000);
-    uint32_t now = getRTCClock()->getCurrentTime();
-    MeshTimeSync::Verdict v = _timesync.tick(now, up);
-    if (v.type != MeshTimeSync::VERDICT_STEP) return;
-
-    /* GPS gate: sense only while GPS owns the clock. */
-    if (gps_is_available() && gps_is_enabled()) {
-        LOG_INF("meshtimesync: step %+d s wanted, GPS gate active - not applied",
-                (int)v.delta);
-        return;
-    }
-    /* Forward-only role: post timestamps feed client sync_since ordering,
-     * so a backward step corrupts message sync. Report, never apply. */
-    if (v.delta < 0) {
-        _timesync.noteBackwardSkipped();
-        LOG_WRN("meshtimesync: backward step %+d s wanted - skipped (room server is forward-only)",
-                (int)v.delta);
-        return;
-    }
-    applyTimeSyncStep(v, now, up);
-}
-
-void RoomServerMesh::applyTimeSyncStep(const MeshTimeSync::Verdict& v, uint32_t now,
-                                       uint32_t uptime_secs) {
-    uint32_t new_time = (uint32_t)((int64_t)now + v.delta);
-    getRTCClock()->setCurrentTime(new_time);
-    zephcore_rtc_save(new_time);
-    time_sync_report(TIME_SYNC_MESH);
-
-    /* Wall-clock-anchored bookkeeping moves with the step (see RepeaterMesh). */
+    /* Step applied (forward-only enforced in runTick) — shift wall-clock-
+     * anchored bookkeeping with it. */
+    int64_t delta = _timesync.lastStepDelta();
     for (int i = 0; i < acl.getNumClients(); i++) {
         ClientInfo* c = acl.getClientByIdx(i);
         if (c->last_activity == 0) continue;
-        int64_t shifted = (int64_t)c->last_activity + v.delta;
+        int64_t shifted = (int64_t)c->last_activity + delta;
         c->last_activity = (shifted > 0) ? (uint32_t)shifted : 1;
     }
     login_fail_limiter.reset();
-
-    _timesync.noteStepApplied(v.delta, new_time, uptime_secs, v.bootstrap);
-    LOG_WRN("meshtimesync: stepped clock %+d s (%s, votes %u/%u) -> %u",
-            (int)v.delta, v.bootstrap ? "bootstrap" : "consensus",
-            (unsigned)v.consensus.votes_for, (unsigned)v.consensus.votes_against,
-            (unsigned)new_time);
 }
 
 bool RoomServerMesh::hasPendingWork() const {
diff --git a/zephcore/app/RoomServerMesh.h b/zephcore/app/RoomServerMesh.h
index d7354a0..bd33813 100644
--- a/zephcore/app/RoomServerMesh.h
+++ b/zephcore/app/RoomServerMesh.h
@@ -95,12 +95,13 @@ class RoomServerMesh : public mesh::Mesh, public CommonCLICallbacks {
     uint8_t pending_sf;
     uint8_t pending_cr;
     int matching_peer_indexes[MAX_CLIENTS];
-    MeshTimeSync _timesync{FIRMWARE_BUILD_EPOCH};
+    /* Forward-only: post timestamps feed client sync_since ordering, so a
+     * backward step would corrupt message sync. */
+    MeshTimeSync _timesync{FIRMWARE_BUILD_EPOCH, true};
 
     int handleRequest(ClientInfo* sender, uint32_t sender_timestamp, uint8_t* payload, size_t payload_len);
     mesh::Packet* createSelfAdvert();
     void timeSyncTick();
-    void applyTimeSyncStep(const MeshTimeSync::Verdict& v, uint32_t now, uint32_t uptime_secs);
 
     /* Room server: shared-post buffer + push-to-client sync */
     void addPost(ClientInfo* client, const char* postData);
@@ -197,8 +198,7 @@ public:
     void saveIdentity(const mesh::LocalIdentity& new_id) override;
     void clearStats() override;
 
-    /* Mesh time sync (forward-only: post timestamps feed client sync_since
-     * ordering, so a backward step would corrupt message sync) */
+    /* Mesh time sync */
     MeshTimeSync* getMeshTimeSync() override { return &_timesync; }
     void noteGPSTimeSync() { _timesync.noteGPSSync((uint32_t)(k_uptime_get() / 1000)); }
 
diff --git a/zephcore/helpers/BaseChatMesh.cpp b/zephcore/helpers/BaseChatMesh.cpp
index f0e4042..8b4fb26 100644
--- a/zephcore/helpers/BaseChatMesh.cpp
+++ b/zephcore/helpers/BaseChatMesh.cpp
@@ -139,7 +139,12 @@ void BaseChatMesh::onAdvertRecv(mesh::Packet *packet, const mesh::Identity &id,
 {
 	LOG_DBG("onAdvertRecv: timestamp=%u app_data_len=%u", timestamp, (unsigned)app_data_len);
 
-	onAdvertTimeSample(id, timestamp, packet->getPathHashCount());
+	/* Time-sample hook skips share rebroadcasts (transport codes {0,0}) —
+	 * they replay stale stored adverts and would churn the sender's tenure. */
+	if (!(packet->hasTransportCodes() &&
+	      packet->transport_codes[0] == 0 && packet->transport_codes[1] == 0)) {
+		onAdvertTimeSample(id, timestamp, packet->getPathHashCount());
+	}
 
 	AdvertDataParser parser(app_data, app_data_len);
 	if (!(parser.isValid() && parser.hasName())) {
diff --git a/zephcore/helpers/CommonCLI.cpp b/zephcore/helpers/CommonCLI.cpp
index 41f757b..d80b372 100644
--- a/zephcore/helpers/CommonCLI.cpp
+++ b/zephcore/helpers/CommonCLI.cpp
@@ -551,10 +551,11 @@ void CommonCLI::handleCommand(uint32_t sender_timestamp, const char* command, ch
             if (ts == nullptr) {
                 strcpy(reply, "not available");
             } else {
-                /* Remote replies ride in a ~160-byte packet buffer; only the
-                 * local USB CLI (sender_timestamp == 0) gets the full evidence
-                 * table. */
-                size_t cap = (sender_timestamp == 0) ? CLI_REPLY_SIZE : 158;
+                /* Only the local USB CLI (sender_timestamp == 0) gets the
+                 * full evidence table; remote replies are truncated to the
+                 * packet buffer. */
+                size_t cap = (sender_timestamp == 0) ? CLI_REPLY_SIZE
+                                                     : CLI_REMOTE_REPLY_SIZE;
                 ts->formatStatus(reply, cap, getRTCClock()->getCurrentTime(),
                                  (uint32_t)(k_uptime_get() / 1000),
                                  _prefs->meshtimesync != 0);
diff --git a/zephcore/helpers/CommonCLI.h b/zephcore/helpers/CommonCLI.h
index 99ad211..8667288 100644
--- a/zephcore/helpers/CommonCLI.h
+++ b/zephcore/helpers/CommonCLI.h
@@ -17,6 +17,12 @@ class MeshTimeSync;
 /* CLI reply buffer size — callers must provide at least this many bytes */
 #define CLI_REPLY_SIZE 256
 
+/* Remote-admin replies ride in the caller's LoRa packet buffer:
+ * RepeaterMesh/RoomServerMesh onPeerDataRecv declare temp[5 + this] with the
+ * reply text at offset 5. Handlers that can exceed this must self-limit
+ * whenever sender_timestamp != 0 (0 marks the local USB CLI). */
+#define CLI_REMOTE_REPLY_SIZE 161
+
 /* Deferred reboot types */
 #define REBOOT_NONE       0
 #define REBOOT_NORMAL     1
diff --git a/zephcore/helpers/MeshTimeSync.cpp b/zephcore/helpers/MeshTimeSync.cpp
index e2c741e..15dced8 100644
--- a/zephcore/helpers/MeshTimeSync.cpp
+++ b/zephcore/helpers/MeshTimeSync.cpp
@@ -6,13 +6,42 @@
 
 #include "MeshTimeSync.h"
 
+#include <adapters/gps/ZephyrGPSManager.h>
+#include <adapters/clock/ZephyrRTCDiscover.h>
+#include <helpers/time_sync.h>
+#include <zephyr/kernel.h>
+#include <zephyr/logging/log.h>
 #include <stdio.h>
 #include <string.h>
 
-void MeshTimeSync::reset(uint32_t build_epoch)
+LOG_MODULE_REGISTER(zephcore_timesync, CONFIG_ZEPHCORE_MAIN_LOG_LEVEL);
+
+/* Clamp an int64 skew to a printable long (display only). */
+static long clampl(int64_t v)
+{
+	if (v > 2000000000LL) return 2000000000L;
+	if (v < -2000000000LL) return -2000000000L;
+	return (long)v;
+}
+
+/* GPS gate: only a validated fix younger than GPS_FIX_FRESH_SECS makes the
+ * mesh yield — a GPS that is enabled but cannot fix (indoors, dead antenna)
+ * stops gating after the window, so those units stay mesh-correctable. */
+static bool gps_gate_active(void)
+{
+	if (!gps_is_available() || !gps_is_enabled()) {
+		return false;
+	}
+	struct gps_state_info info;
+	gps_get_state_info(&info);
+	return info.last_fix_age_s < MeshTimeSync::GPS_FIX_FRESH_SECS;
+}
+
+void MeshTimeSync::reset(uint32_t build_epoch, bool forward_only)
 {
 	memset(_slots, 0, sizeof(_slots));
 	_build_epoch = build_epoch;
+	_forward_only = forward_only;
 	_next_eval_uptime = 0;
 	_suppress_uptime = 0;
 	_suppressed = false;
@@ -22,7 +51,6 @@ void MeshTimeSync::reset(uint32_t build_epoch)
 	_stepped_once = false;
 	_evals = _abstains = _steps = _bootstrap_steps = _backward_skips = 0;
 	_last_step_delta = 0;
-	_last_step_wall = 0;
 }
 
 MeshTimeSync::Slot *MeshTimeSync::findSlot(const uint8_t *prefix)
@@ -55,6 +83,17 @@ int64_t MeshTimeSync::slotSkew(const Slot &s, uint32_t local_time, uint32_t upti
 	       (int64_t)local_time;
 }
 
+bool MeshTimeSync::wouldAccept(const uint8_t *pubkey, uint32_t advert_ts) const
+{
+	for (int i = 0; i < MESHTIMESYNC_TABLE_SIZE; i++) {
+		const Slot &s = _slots[i];
+		if (s.used && memcmp(s.prefix, pubkey, sizeof(s.prefix)) == 0) {
+			return advert_ts > s.advert_ts;
+		}
+	}
+	return true;
+}
+
 void MeshTimeSync::onAdvertHeard(const uint8_t *pubkey, uint32_t advert_ts,
                                  uint8_t hops, uint32_t uptime_secs)
 {
@@ -125,19 +164,22 @@ MeshTimeSync::Consensus MeshTimeSync::computeConsensus(uint32_t local_time,
 	Consensus c;
 	memset(&c, 0, sizeof(c));
 
-	/* Collect eligible votes. Bootstrap relaxes tenure: any sender with a
-	 * fresh sample may vote (the table is RAM-only, so after the reboot that
-	 * dead-ended the clock everything in it is freshly heard anyway). */
-	int64_t skews[MESHTIMESYNC_TABLE_SIZE];
-	int32_t radii[MESHTIMESYNC_TABLE_SIZE];
-	int n = 0;
+	/* Collect eligible votes directly as Marzullo interval endpoints.
+	 * Bootstrap relaxes tenure: any sender with a fresh sample may vote
+	 * (the table is RAM-only, so after the reboot that dead-ended the
+	 * clock everything in it is freshly heard anyway). */
+	int64_t val[2 * MESHTIMESYNC_TABLE_SIZE];
+	int8_t typ[2 * MESHTIMESYNC_TABLE_SIZE];  /* +1 = start, -1 = end */
+	int n = 0, m = 0;
 	for (int i = 0; i < MESHTIMESYNC_TABLE_SIZE; i++) {
 		const Slot &s = _slots[i];
 		if (!s.used) continue;
 		if ((uptime_secs - s.arrival_uptime) > MAX_SAMPLE_AGE_SECS) continue;
 		if (!bootstrap && !slotTenured(s, uptime_secs)) continue;
-		skews[n] = slotSkew(s, local_time, uptime_secs);
-		radii[n] = RADIUS_BASE_SECS + RADIUS_PER_HOP_SECS * s.hops;
+		int64_t skew = slotSkew(s, local_time, uptime_secs);
+		int32_t r = RADIUS_BASE_SECS + RADIUS_PER_HOP_SECS * s.hops;
+		val[m] = skew - r; typ[m] = 1;  m++;
+		val[m] = skew + r; typ[m] = -1; m++;
 		n++;
 	}
 	c.eligible = (uint8_t)n;
@@ -145,15 +187,8 @@ MeshTimeSync::Consensus MeshTimeSync::computeConsensus(uint32_t local_time,
 
 	/* Marzullo endpoint sweep — interval intersection with the most votes.
 	 * No absolute outlier thresholds against our own clock: clustering does
-	 * the rejection, so an epoch-0 local clock still finds the true cluster. */
-	int64_t val[2 * MESHTIMESYNC_TABLE_SIZE];
-	int8_t typ[2 * MESHTIMESYNC_TABLE_SIZE];  /* +1 = start, -1 = end */
-	int m = 0;
-	for (int i = 0; i < n; i++) {
-		val[m] = skews[i] - radii[i]; typ[m] = 1;  m++;
-		val[m] = skews[i] + radii[i]; typ[m] = -1; m++;
-	}
-	/* Insertion sort by value; starts before ends at equal values so
+	 * the rejection, so an epoch-0 local clock still finds the true cluster.
+	 * Insertion sort by value; starts before ends at equal values so
 	 * touching intervals count as overlapping. */
 	for (int i = 1; i < m; i++) {
 		int64_t v = val[i];
@@ -301,6 +336,50 @@ MeshTimeSync::Verdict MeshTimeSync::tick(uint32_t local_time, uint32_t uptime_se
 	return v;
 }
 
+bool MeshTimeSync::runTick(mesh::RTCClock &rtc)
+{
+	uint32_t up = (uint32_t)(k_uptime_get() / 1000);
+	uint32_t now = rtc.getCurrentTime();
+	Verdict v = tick(now, up);
+	if (v.type != VERDICT_STEP) {
+		if (v.type == VERDICT_ABSTAIN) {
+			LOG_DBG("abstain (%s)", reasonStr(v.reason));
+		}
+		return false;
+	}
+	if (gps_gate_active()) {
+		LOG_INF("step %+ld s wanted, GPS fix is fresh - not applied",
+		        clampl(v.delta));
+		return false;
+	}
+	if (_forward_only && v.delta < 0) {
+		/* Forward-only roles: post timestamps feed client sync_since
+		 * ordering (room server) / peers hold per-sender replay high-water
+		 * marks for our DMs (companion). Report, never apply. */
+		_backward_skips++;
+		LOG_WRN("backward step %+ld s wanted - skipped (forward-only role)",
+		        clampl(v.delta));
+		return false;
+	}
+	int64_t nt = (int64_t)now + v.delta;
+	if (nt <= 0 || nt > (int64_t)UINT32_MAX) {
+		/* Would wrap the uint32 clock — only reachable with a garbage
+		 * bootstrap cluster near the timestamp ceiling. */
+		LOG_WRN("implausible step %+ld s refused", clampl(v.delta));
+		return false;
+	}
+	uint32_t new_time = (uint32_t)nt;
+	rtc.setCurrentTime(new_time);
+	zephcore_rtc_save(new_time);
+	time_sync_report(TIME_SYNC_MESH);
+	noteStepApplied(v.delta, up, v.bootstrap);
+	LOG_WRN("stepped clock %+ld s (%s, votes %u/%u) -> %u",
+	        clampl(v.delta), v.bootstrap ? "bootstrap" : "consensus",
+	        (unsigned)v.consensus.votes_for, (unsigned)v.consensus.votes_against,
+	        (unsigned)new_time);
+	return true;
+}
+
 void MeshTimeSync::noteManualSync(uint32_t uptime_secs)
 {
 	_suppress_uptime = uptime_secs;
@@ -315,15 +394,13 @@ void MeshTimeSync::noteGPSSync(uint32_t uptime_secs)
 	_pedigree = true;
 }
 
-void MeshTimeSync::noteStepApplied(int64_t delta, uint32_t local_time,
-                                   uint32_t uptime_secs, bool bootstrap)
+void MeshTimeSync::noteStepApplied(int64_t delta, uint32_t uptime_secs, bool bootstrap)
 {
 	_last_step_uptime = uptime_secs;
 	_stepped_once = true;
 	_steps++;
 	if (bootstrap) _bootstrap_steps++;
 	_last_step_delta = delta;
-	_last_step_wall = local_time;
 }
 
 bool MeshTimeSync::isSuppressed(uint32_t uptime_secs) const
@@ -351,24 +428,24 @@ const char *MeshTimeSync::reasonStr(Reason r)
 	}
 }
 
-/* Clamp an int64 skew to a printable long (display only). */
-static long clampl(int64_t v)
-{
-	if (v > 2000000000LL) return 2000000000L;
-	if (v < -2000000000LL) return -2000000000L;
-	return (long)v;
-}
-
 int MeshTimeSync::formatStatus(char *out, size_t cap, uint32_t local_time,
                                uint32_t uptime_secs, bool enabled) const
 {
 	Verdict v = evaluateNow(local_time, uptime_secs);
 	const Consensus &c = v.consensus;
 
-	char verdict[40];
+	char verdict[56];
 	if (v.type == VERDICT_STEP) {
-		snprintf(verdict, sizeof(verdict), "step%+ld%s", clampl(v.delta),
-		         v.bootstrap ? " (bootstrap)" : "");
+		/* Annotate steps the shared step policy would refuse, so the
+		 * dry-run never claims a step that will not happen. */
+		const char *note = "";
+		if (gps_gate_active()) {
+			note = " (gps-gated)";
+		} else if (_forward_only && v.delta < 0) {
+			note = " (skipped: forward-only)";
+		}
+		snprintf(verdict, sizeof(verdict), "step%+ld%s%s", clampl(v.delta),
+		         v.bootstrap ? " (bootstrap)" : "", note);
 	} else if (v.type == VERDICT_NONE && v.reason == REASON_IN_BAND) {
 		int64_t mag = c.mid < 0 ? -c.mid : c.mid;
 		snprintf(verdict, sizeof(verdict), "%s",
@@ -391,8 +468,9 @@ int MeshTimeSync::formatStatus(char *out, size_t cap, uint32_t local_time,
 	if (pos < 0 || (size_t)pos >= cap) goto full;
 
 	if (_steps > 0) {
-		pos += snprintf(out + pos, cap - pos, "; steps=%lu last=%+lds",
-		                (unsigned long)_steps, clampl(_last_step_delta));
+		pos += snprintf(out + pos, cap - pos, "; steps=%lu boot=%lu last=%+lds",
+		                (unsigned long)_steps, (unsigned long)_bootstrap_steps,
+		                clampl(_last_step_delta));
 		if (pos < 0 || (size_t)pos >= cap) goto full;
 	}
 	if (_backward_skips > 0) {
diff --git a/zephcore/helpers/MeshTimeSync.h b/zephcore/helpers/MeshTimeSync.h
index 51e88cc..6779e78 100644
--- a/zephcore/helpers/MeshTimeSync.h
+++ b/zephcore/helpers/MeshTimeSync.h
@@ -2,21 +2,25 @@
  * SPDX-License-Identifier: MIT
  * MeshTimeSync - mesh clock consensus from Ed25519-signed advert timestamps.
  *
- * Role-agnostic estimator: owns no clock. Each role feeds it signature-
- * verified adverts (onAdvertHeard), calls tick() from its loop, and applies
- * STEP verdicts under its own step policy (repeater/observer: bidirectional;
- * room server/companion: forward-only; GPS-synced boards: sense only).
- * ZephCore-only divergence from Arduino MeshCore — design rationale in
- * ARCHITECTURE.md, user-facing doc in MESHTIMESYNC.md.
+ * Role-agnostic estimator plus shared step policy. Each role feeds it
+ * signature-verified adverts (onAdvertHeard) and calls runTick() from its
+ * loop; runTick applies the shared policy (GPS fix-freshness gate,
+ * forward-only roles skip backward steps, ±1 h cap, 6 h rate limit) and
+ * steps the given clock. Role-specific bookkeeping (neighbor/ACL timestamp
+ * shifts, rate-limiter resets) happens in the role after runTick returns
+ * true. ZephCore-only divergence from Arduino MeshCore — design rationale
+ * in ARCHITECTURE.md, user-facing doc in MESHTIMESYNC.md.
  *
  * All policy timers anchor on uptime, never wall clock, so the very steps
- * they govern cannot distort them.
+ * they govern cannot distort them. Main-thread-only, like the mesh classes
+ * that own it.
  */
 
 #pragma once
 
 #include <stdint.h>
 #include <stddef.h>
+#include <mesh/RTC.h>
 
 #ifdef CONFIG_ZEPHCORE_TIMESYNC_TABLE_SIZE
   #define MESHTIMESYNC_TABLE_SIZE  CONFIG_ZEPHCORE_TIMESYNC_TABLE_SIZE
@@ -56,6 +60,12 @@ public:
 	static constexpr int64_t  PEDIGREE_PPM             = 300;
 	static constexpr int64_t  PEDIGREE_BASE_SECS       = 10 * 60;
 	static constexpr uint8_t  BOOTSTRAP_QUORUM         = 3;
+	/* GPS gate: a validated fix younger than this means GPS owns the clock
+	 * (it re-syncs and would step-back a wrong mesh step, poisoning our
+	 * advert high-water marks at peers). Covers the repeater's 48 h GPS
+	 * duty cycle with margin; a unit whose GPS cannot get a fix (indoors,
+	 * dead antenna) becomes mesh-correctable after this window. */
+	static constexpr uint32_t GPS_FIX_FRESH_SECS       = 72 * 3600;
 
 	/* 8-byte prefix is a security floor, not a tuning knob: it is the
 	 * sender's identity for tenure/votes while signatures verify the full
@@ -104,78 +114,74 @@ public:
 		Consensus consensus;
 	};
 
-	explicit MeshTimeSync(uint32_t build_epoch = 0) { reset(build_epoch); }
+	explicit MeshTimeSync(uint32_t build_epoch = 0, bool forward_only = false)
+	{
+		reset(build_epoch, forward_only);
+	}
 
-	void reset(uint32_t build_epoch);
+	void reset(uint32_t build_epoch, bool forward_only);
 
 	/* Feed one signature-verified advert. hops = flood path length (0 = heard
-	 * direct). Samples beyond HOP_CAP are dropped. */
+	 * direct). Samples beyond HOP_CAP are dropped. Callers must not feed
+	 * share rebroadcasts (transport codes {0,0}) — those replay stale stored
+	 * adverts and would churn the sender's tenure. */
 	void onAdvertHeard(const uint8_t *pubkey, uint32_t advert_ts, uint8_t hops,
 	                   uint32_t uptime_secs);
 
-	/* Paced evaluation — returns VERDICT_NONE/REASON_NONE unless
-	 * EVAL_INTERVAL_SECS elapsed since the last real evaluation. The caller
-	 * applies STEP verdicts under its role policy and reports the outcome
-	 * via noteStepApplied() (the step rate limit counts applied steps only). */
-	Verdict tick(uint32_t local_time, uint32_t uptime_secs);
+	/* Cheap pre-check: would onAdvertHeard even consider this sample?
+	 * Lets callers skip the Ed25519 verify for per-sender duplicates
+	 * (observers hear every flood copy with no dedup of their own). */
+	bool wouldAccept(const uint8_t *pubkey, uint32_t advert_ts) const;
 
-	/* Unpaced consensus computation (CLI dry-run view). */
-	Consensus computeConsensus(uint32_t local_time, uint32_t uptime_secs,
-	                           bool bootstrap) const;
+	/* Paced policy run — call from the role's loop with its RTC clock.
+	 * Evaluates at most every EVAL_INTERVAL_SECS; applies the shared step
+	 * policy and steps the clock (incl. hardware-RTC save + UI time-source
+	 * report). Returns true when a step was applied — the role then shifts
+	 * its wall-clock-anchored bookkeeping by lastStepDelta(). The caller
+	 * gates on its own enable pref. */
+	bool runTick(mesh::RTCClock &rtc);
 
-	/* Unpaced full policy evaluation (no counter/pacing side effects) —
-	 * what tick() would decide right now. Used by the CLI dry-run. */
-	Verdict evaluateNow(uint32_t local_time, uint32_t uptime_secs) const;
-
-	bool isBootstrap(uint32_t local_time) const { return local_time < _build_epoch; }
-
-	/* Manual clock set (CLI time/clock sync, app time set): arms the 7-day
-	 * suppression window AND drift-envelope pedigree. Suppression gates
-	 * bootstrap too. */
+	/* Manual clock set (CLI time/clock sync, app time set, SNTP): arms the
+	 * 7-day suppression window AND drift-envelope pedigree. Suppression
+	 * gates bootstrap too. */
 	void noteManualSync(uint32_t uptime_secs);
-	/* GPS time sync: arms pedigree only (stepping is gated off by the role
-	 * whenever GPS is available and enabled, so no suppression needed). */
+	/* GPS time sync: arms pedigree only (stepping is gated by GPS fix
+	 * freshness, so no suppression needed). */
 	void noteGPSSync(uint32_t uptime_secs);
-	/* Report an applied step (rate-limit anchor + counters). local_time is
-	 * the wall clock AFTER the step (display only). */
-	void noteStepApplied(int64_t delta, uint32_t local_time, uint32_t uptime_secs,
-	                     bool bootstrap);
-	/* Forward-only roles report a refused backward verdict. */
-	void noteBackwardSkipped() { _backward_skips++; }
 
-	bool isSuppressed(uint32_t uptime_secs) const;
-	uint32_t suppressRemaining(uint32_t uptime_secs) const;
-
-	/* Table access for the CLI evidence dump. */
-	static int tableSize() { return MESHTIMESYNC_TABLE_SIZE; }
-	const Slot &slotAt(int i) const { return _slots[i]; }
-	bool slotEligible(const Slot &s, uint32_t uptime_secs) const;
-	int64_t slotSkew(const Slot &s, uint32_t local_time, uint32_t uptime_secs) const;
-
-	/* Counters for CLI/stats. */
-	uint32_t evalCount() const { return _evals; }
-	uint32_t abstainCount() const { return _abstains; }
-	uint32_t stepCount() const { return _steps; }
-	uint32_t bootstrapStepCount() const { return _bootstrap_steps; }
-	uint32_t backwardSkipCount() const { return _backward_skips; }
+	/* Delta of the most recent applied step (for role bookkeeping shifts). */
 	int64_t lastStepDelta() const { return _last_step_delta; }
-	uint32_t lastStepWall() const { return _last_step_wall; }
-	bool hasStepped() const { return _stepped_once; }
 
 	/* Compact status + evidence-table formatter shared by all role CLIs.
 	 * Writes at most `cap` bytes (NUL-terminated), summary first, then as
-	 * many per-sender entries as fit. */
+	 * many per-sender entries as fit. Annotates verdicts the step policy
+	 * would refuse ("gps-gated", "skipped: forward-only"). */
 	int formatStatus(char *out, size_t cap, uint32_t local_time,
 	                 uint32_t uptime_secs, bool enabled) const;
 
-	static const char *reasonStr(Reason r);
-
 private:
+	bool isBootstrap(uint32_t local_time) const { return local_time < _build_epoch; }
+
 	Slot *findSlot(const uint8_t *prefix);
 	bool slotTenured(const Slot &s, uint32_t uptime_secs) const;
+	bool slotEligible(const Slot &s, uint32_t uptime_secs) const;
+	int64_t slotSkew(const Slot &s, uint32_t local_time, uint32_t uptime_secs) const;
+
+	Consensus computeConsensus(uint32_t local_time, uint32_t uptime_secs,
+	                           bool bootstrap) const;
+	/* Unpaced full policy evaluation (no counter/pacing side effects). */
+	Verdict evaluateNow(uint32_t local_time, uint32_t uptime_secs) const;
+	/* Paced evaluation — VERDICT_NONE/REASON_NONE between evaluations. */
+	Verdict tick(uint32_t local_time, uint32_t uptime_secs);
+
+	void noteStepApplied(int64_t delta, uint32_t uptime_secs, bool bootstrap);
+	bool isSuppressed(uint32_t uptime_secs) const;
+	uint32_t suppressRemaining(uint32_t uptime_secs) const;
+	static const char *reasonStr(Reason r);
 
 	Slot _slots[MESHTIMESYNC_TABLE_SIZE];
 	uint32_t _build_epoch;
+	bool _forward_only;
 
 	/* Policy state — uptime-anchored (see header comment). */
 	uint32_t _next_eval_uptime;
@@ -186,8 +192,7 @@ private:
 	uint32_t _last_step_uptime;
 	bool _stepped_once;
 
-	/* Counters. */
+	/* Counters (shown by formatStatus). */
 	uint32_t _evals, _abstains, _steps, _bootstrap_steps, _backward_skips;
 	int64_t _last_step_delta;
-	uint32_t _last_step_wall;
 };