diff --git a/docs/known-issues.md b/docs/known-issues.md
index 649b710..d09026c 100644
--- a/docs/known-issues.md
+++ b/docs/known-issues.md
@@ -107,6 +107,13 @@ scripts for this are worth keeping; note that wrapping them in `timeout` SIGTERM
 
 ## Possible follow-ups (not done)
 
+- **A retained `Env` payload may still sit on the broker.** `GGS/FWT/<tower>/Env` was
+  published retained until it was removed, so a broker that saw the old build still holds
+  the last ambient reading and hands it to every new subscriber — a frozen temperature and
+  humidity with an old timestamp, indistinguishable from a sensor that stopped reporting.
+  Nothing in the code does this any more, so nothing here would otherwise explain it.
+  Clear it broker-side by publishing a zero-length retained message to that topic.
+
 - **NWU vs ENU is decided by a constant, not by the device.** `kMtiReference`
   ([MtiProtocol.h](../include/fgc/MtiProtocol.h)) says the MTi reports against NWU, and the
   host re-references it to NED. The two candidates give *identical* roll and pitch and
diff --git a/docs/modules-reference.md b/docs/modules-reference.md
index 934f2ac..d927060 100644
--- a/docs/modules-reference.md
+++ b/docs/modules-reference.md
@@ -24,7 +24,7 @@ Per-file reference for the refactored tree, plus the shared data structures.
 | [include/fgc/sensors/Sht41Protocol.h](../include/fgc/sensors/Sht41Protocol.h), [src/sensors/Sht41Protocol.cpp](../src/sensors/Sht41Protocol.cpp) | Sensirion SHT4x wire protocol, pure: command bytes, `sht41Crc8` (poly 0x31/init 0xFF), `decodeSht41Measurement` (6-byte response → `Sht41Reading`, CRC-checked, raw→°C/%RH with RH clamped 0..100) |
 | [include/fgc/CameraProfile.h](../include/fgc/CameraProfile.h), [src/core/CameraProfile.cpp](../src/core/CameraProfile.cpp) | `loadCameraProfile` / `loadCameraProfiles`: one VimbaX settings XML per profile. Hashes the XML, regenerates the `.txt` record when it changes, and reports which settings moved. A missing XML throws — the record is never a fallback |
 | [include/fgc/CameraSettingsXml.h](../include/fgc/CameraSettingsXml.h), [src/core/CameraSettingsXml.cpp](../src/core/CameraSettingsXml.cpp) | Parses the Viewer export's `<RemoteDevice>` features (ordered, selector-aware), renders the human-readable `.txt` record, reads one back, and diffs two settings lists. Used for display and change detection only — never to configure a camera |
-| [include/fgc/ChannelTopics.h](../include/fgc/ChannelTopics.h), [src/core/ChannelTopics.cpp](../src/core/ChannelTopics.cpp) | The MQTT wire format in one place: topic builders for the `GGS/FWT/<tower>/…` tree and the `CamEvent`/`EnvEvent`/status payload builders. Pure, so the documented format is unit-tested rather than assembled inline at each publish site |
+| [include/fgc/ChannelTopics.h](../include/fgc/ChannelTopics.h), [src/core/ChannelTopics.cpp](../src/core/ChannelTopics.cpp) | The MQTT wire format in one place: topic builders for the `GGS/FWT/<tower>/…` tree and the `CamEvent`/status payload builders. Pure, so the documented format is unit-tested rather than assembled inline at each publish site |
 | [include/fgc/ChannelHistory.h](../include/fgc/ChannelHistory.h), [src/core/ChannelHistory.cpp](../src/core/ChannelHistory.cpp) | Ring buffer of recently published messages (time, topic, payload, outcome) plus the delivery counters — sent, failed, connects, losses, last status. Feeds the expanded Connectivity view so a publish can be confirmed without a broker-side subscriber |
 | [include/fgc/Hash.h](../include/fgc/Hash.h), [src/core/Hash.cpp](../src/core/Hash.cpp) | FNV-1a 64 over a string or a file, with an algorithm-prefixed label. Change detection for the profile records, deliberately not a crypto hash |
 | [include/fgc/CaptureScheduler.h](../include/fgc/CaptureScheduler.h), [src/core/CaptureScheduler.cpp](../src/core/CaptureScheduler.cpp) | Capture state machine over the interfaces; injectable clock; `setGeometry` adopts a recalibration |
@@ -38,7 +38,7 @@ Per-file reference for the refactored tree, plus the shared data structures.
 | File | Interface | Shared structs |
 |------|-----------|----------------|
 | [include/fgc/IMotorController.h](../include/fgc/IMotorController.h) | `IMotorController` | `MotorTelemetry` |
-| [include/fgc/IControlChannel.h](../include/fgc/IControlChannel.h) | `IControlChannel` | `ControlCommand`, `CamEvent`, `EnvEvent` |
+| [include/fgc/IControlChannel.h](../include/fgc/IControlChannel.h) | `IControlChannel` | `ControlCommand`, `CamEvent` |
 | [include/fgc/ICameraSource.h](../include/fgc/ICameraSource.h) | `ICameraSource` | `Frame` |
 | [include/fgc/IImuSource.h](../include/fgc/IImuSource.h) | `IImuSource` (incl. `config()`, `configProblems()`, `refreshConfig()`, `noRotation()`, `headingReset()`, `setFilterProfile()`) | `ImuSample` (from `MtiProtocol.h`) |
 | [include/fgc/IEnvSensor.h](../include/fgc/IEnvSensor.h) | `IEnvSensor` (`connected()`, `sample()`, `name()`) | `EnvSample` |
@@ -98,10 +98,6 @@ homing or `gimbal reset`, so a lit badge means "position untrustworthy since the
 `tower`, `camera` (RGB/ACR/NIR), `heading_decideg` (yaw×10), `pitch_decideg` (pitch×10) and
 `timestamp_ms` (which matches the image filename). Serialized to the CamEvent JSON payload (see [mqtt-api.md](mqtt-api.md)).
 
-### `EnvEvent` ([IControlChannel.h](../include/fgc/IControlChannel.h))
-`tower`, `temp_c`, `humidity_pct`, `timestamp_ms`. Published once per **fresh** sample (deduplicated
-on `timestamp_ms`, not per control-loop tick) to the `Env` topic — see [mqtt-api.md](mqtt-api.md).
-
 ### `EnvSample` ([IEnvSensor.h](../include/fgc/IEnvSensor.h))
 One ambient reading: `valid`, `temp_c` (°C), `humidity_pct` (0..100), `timestamp_ms` (epoch ms).
 `IEnvSensor::sample()` returns `nullopt` rather than a stale sample once nothing valid has arrived
diff --git a/docs/mqtt-api.md b/docs/mqtt-api.md
index f68b584..53755c3 100644
--- a/docs/mqtt-api.md
+++ b/docs/mqtt-api.md
@@ -56,7 +56,6 @@ When a ControlCode message arrives, the program echoes the current code back on
 |-------|------|---------|--------------|
 | `GGS/FWT/<tower>/StatusCode` | At startup (`"0"`); whenever a ControlCode message is received (echoes the code) | integer as string | 1 / retained |
 | `GGS/FWT/<tower>/CamEvent` | After each image is saved | JSON object (below) | 1 / retained |
-| `GGS/FWT/<tower>/Env` | Once per fresh ambient sensor sample (see `[Env] period_ms`) | JSON object (below) | 1 / retained |
 
 ### CamEvent payload
 
@@ -101,22 +100,6 @@ Both `hdg` and `pit` are sampled **when the frame arrives**, not when its JPEG X
 finishes, so a slow encode or a backed-up queue cannot attribute a later pose to earlier
 pixels.
 
-### Env payload
-
-Built by `MqttControlChannel::publishEnv` from an `EnvEvent`, sourced from whichever `IEnvSensor` backend is
-active (SHT41 on the LattePanda's own I2C bus by default; see [configuration.md](configuration.md)):
-
-```json
-{ "fwt":"ExampleTower", "temp_c":22.4, "humid_pct":46.1, "time":1719312345678 }
-```
-
-| Field | Type | Meaning |
-|-------|------|---------|
-| `fwt` | string | Tower name (`config.ini` `tower_name`) |
-| `temp_c` | float | Ambient temperature, °C |
-| `humid_pct` | float | Ambient relative humidity, % |
-| `time` | int | Sample timestamp, Unix epoch **milliseconds** |
-
 ## Topic summary
 
 ```
@@ -125,7 +108,6 @@ subscribe:  GGS/FWT/<tower>/target_HDG      (int heading)
 
 publish:    GGS/FWT/<tower>/StatusCode      (echoed control code)
             GGS/FWT/<tower>/CamEvent        (JSON: fwt, cam, hdg×10, pit×10, time-ms)
-            GGS/FWT/<tower>/Env             (JSON: fwt, temp_c, humid_pct, time-ms)
 ```
 
 ## Local testing
diff --git a/include/fgc/ChannelTopics.h b/include/fgc/ChannelTopics.h
index e430635..71fa987 100644
--- a/include/fgc/ChannelTopics.h
+++ b/include/fgc/ChannelTopics.h
@@ -18,12 +18,10 @@ inline constexpr const char* kTopicTargetHdg   = "target_HDG";
 inline constexpr const char* kTopicControlCode = "ControlCode";
 inline constexpr const char* kTopicStatusCode  = "StatusCode";
 inline constexpr const char* kTopicCamEvent    = "CamEvent";
-inline constexpr const char* kTopicEnv         = "Env";
 
 std::string towerTopic(const std::string& tower, const std::string& leaf);
 
 // Payload builders. One definition each, used by both channels.
 std::string camEventJson(const CamEvent& e);
-std::string envJson(const EnvEvent& e);
 
 }  // namespace fgc
diff --git a/include/fgc/IControlChannel.h b/include/fgc/IControlChannel.h
index 4144f2a..3c22ecd 100644
--- a/include/fgc/IControlChannel.h
+++ b/include/fgc/IControlChannel.h
@@ -23,14 +23,6 @@ struct CamEvent {
     long long   timestamp_ms = 0;     // Unix epoch ms; matches the image filename
 };
 
-// Ambient temperature/humidity reading published once per fresh sensor sample.
-struct EnvEvent {
-    std::string tower;
-    float       temp_c = 0.0f;
-    float       humidity_pct = 0.0f;
-    long long   timestamp_ms = 0;
-};
-
 // What became of an outbound message. Dropped and Failed are separated because
 // they mean different things operationally: Dropped is "the link was down and we
 // discarded it silently", Failed is "the broker or library rejected it".
@@ -71,7 +63,6 @@ public:
 
     virtual void publishStatus(int code)               = 0;
     virtual void publishCamEvent(const CamEvent& event) = 0;
-    virtual void publishEnv(const EnvEvent& event)      = 0;
 
     // Latest control input; clears the *_available flags so each update is
     // acted on once.
diff --git a/include/fgc/MqttControlChannel.h b/include/fgc/MqttControlChannel.h
index bec08d3..1984942 100644
--- a/include/fgc/MqttControlChannel.h
+++ b/include/fgc/MqttControlChannel.h
@@ -35,7 +35,6 @@ public:
 
     void publishStatus(int code) override;
     void publishCamEvent(const CamEvent& event) override;
-    void publishEnv(const EnvEvent& event) override;
     ControlCommand poll() override;
 
     std::vector<ChannelMessage> recentMessages() const override { return history_.recent(); }
@@ -59,7 +58,6 @@ private:
     std::string           topic_control_code_;
     std::string           topic_status_;
     std::string           topic_cam_event_;
-    std::string           topic_env_;
 
     mqtt::async_client     client_;
     mqtt::connect_options  conn_opts_;
diff --git a/include/fgc/mock/NullControlChannel.h b/include/fgc/mock/NullControlChannel.h
index a830202..f2fc764 100644
--- a/include/fgc/mock/NullControlChannel.h
+++ b/include/fgc/mock/NullControlChannel.h
@@ -38,13 +38,6 @@ public:
                                     << " (null channel)";
         drop(kTopicCamEvent, camEventJson(e));
     }
-    void publishEnv(const EnvEvent& e) override {
-        LOG_TRACE_CAT(LogCat::Mqtt) << "PUB Env temp_c=" << e.temp_c
-                                    << " humid_pct=" << e.humidity_pct << " t=" << e.timestamp_ms
-                                    << " (null channel)";
-        drop(kTopicEnv, envJson(e));
-    }
-
     ControlCommand poll() override { return {}; }
 
     std::vector<ChannelMessage> recentMessages() const override { return history_.recent(); }
diff --git a/src/core/Application.cpp b/src/core/Application.cpp
index 96d5b71..b0b1053 100644
--- a/src/core/Application.cpp
+++ b/src/core/Application.cpp
@@ -230,7 +230,6 @@ struct Application::Impl {
     bool                     test_drift_gate_ = false;
     mutable ImuConfigView    imu_config_view_;     // formatted MTi config (read once)
     mutable bool             imu_config_done_ = false;
-    mutable long long        last_env_published_ts_ = 0;  // gate MQTT publish to one per fresh sample
     // Latches the "no IMU sample, publishing encoder pitch" warning so an outage
     // costs one line, not one per frame. Written from the camera delivery
     // thread(s) via the orientation supplier, hence atomic.
@@ -746,16 +745,6 @@ struct Application::Impl {
                     setField(g.fields[0], fmt1(m->temp_c));
                     setField(g.fields[1], fmt1(m->humidity_pct));
                 }
-                // Publish once per fresh sample, not every ~10ms control-loop tick.
-                if (channel && m->timestamp_ms != last_env_published_ts_) {
-                    last_env_published_ts_ = m->timestamp_ms;
-                    EnvEvent ev;
-                    ev.tower        = cfg.general.tower_name;
-                    ev.temp_c       = m->temp_c;
-                    ev.humidity_pct = m->humidity_pct;
-                    ev.timestamp_ms = m->timestamp_ms;
-                    channel->publishEnv(ev);
-                }
             } else {
                 s.sensors.env.status = "no fix";
             }
diff --git a/src/core/ChannelTopics.cpp b/src/core/ChannelTopics.cpp
index fc5e178..280aa91 100644
--- a/src/core/ChannelTopics.cpp
+++ b/src/core/ChannelTopics.cpp
@@ -13,10 +13,4 @@ std::string camEventJson(const CamEvent& e) {
            ", \"time\":" + std::to_string(e.timestamp_ms) + " }";
 }
 
-std::string envJson(const EnvEvent& e) {
-    return "{ \"fwt\":\"" + e.tower + "\", \"temp_c\":" + std::to_string(e.temp_c) +
-           ", \"humid_pct\":" + std::to_string(e.humidity_pct) +
-           ", \"time\":" + std::to_string(e.timestamp_ms) + " }";
-}
-
 }  // namespace fgc
diff --git a/src/mqtt/MqttControlChannel.cpp b/src/mqtt/MqttControlChannel.cpp
index d76833d..a34c5d7 100644
--- a/src/mqtt/MqttControlChannel.cpp
+++ b/src/mqtt/MqttControlChannel.cpp
@@ -22,7 +22,6 @@ MqttControlChannel::MqttControlChannel(const std::string& broker_uri, const std:
       topic_control_code_(towerTopic(tower, kTopicControlCode)),
       topic_status_(towerTopic(tower, kTopicStatusCode)),
       topic_cam_event_(towerTopic(tower, kTopicCamEvent)),
-      topic_env_(towerTopic(tower, kTopicEnv)),
       client_(broker_uri, tower) {
     conn_opts_.set_keep_alive_interval(20);
     conn_opts_.set_clean_session(true);
@@ -136,8 +135,4 @@ void MqttControlChannel::publishCamEvent(const CamEvent& e) {
     publish(topic_cam_event_, camEventJson(e));
 }
 
-void MqttControlChannel::publishEnv(const EnvEvent& e) {
-    publish(topic_env_, envJson(e));
-}
-
 }  // namespace fgc
diff --git a/src/ui/TuiUi.cpp b/src/ui/TuiUi.cpp
index 85733d7..cad52f6 100644
--- a/src/ui/TuiUi.cpp
+++ b/src/ui/TuiUi.cpp
@@ -544,7 +544,7 @@ Element connDetailPanel(const ConnView& v, ScrollState& st) {
     struct TopicRow { const char* dir; const char* leaf; };
     static const TopicRow kTopics[] = {
         {"sub", kTopicTargetHdg},   {"sub", kTopicControlCode}, {"pub", kTopicStatusCode},
-        {"pub", kTopicCamEvent},    {"pub", kTopicEnv},
+        {"pub", kTopicCamEvent},
     };
     for (const auto& t : kTopics) {
         const ChannelMessage* last = nullptr;
diff --git a/tests/test_channelhistory.cpp b/tests/test_channelhistory.cpp
index a29759f..1d4e40d 100644
--- a/tests/test_channelhistory.cpp
+++ b/tests/test_channelhistory.cpp
@@ -82,11 +82,4 @@ TEST_CASE("topic and payload builders match the documented wire format") {
     CHECK(j.find("\"time\":1719312345678") != std::string::npos);
     // The quality gate is gone; nothing should still be publishing a verdict.
     CHECK(j.find("degraded") == std::string::npos);
-
-    EnvEvent e;
-    e.tower = "Tower"; e.temp_c = 21.5f; e.humidity_pct = 48.0f; e.timestamp_ms = 42;
-    const std::string ej = envJson(e);
-    CHECK(ej.find("\"fwt\":\"Tower\"") != std::string::npos);
-    CHECK(ej.find("\"temp_c\":21.5") != std::string::npos);
-    CHECK(ej.find("\"time\":42") != std::string::npos);
 }
diff --git a/tests/test_scheduler.cpp b/tests/test_scheduler.cpp
index 8c29f16..74ee66c 100644
--- a/tests/test_scheduler.cpp
+++ b/tests/test_scheduler.cpp
@@ -44,7 +44,6 @@ struct FakeChannel : IControlChannel {
     bool connected() const override { return true; }
     void publishStatus(int c) override { last_status = c; }
     void publishCamEvent(const CamEvent&) override {}
-    void publishEnv(const EnvEvent&) override {}
     ControlCommand poll() override {
         ControlCommand c = next;
         next = {};