diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1384b1d..e813ad9 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -81,6 +81,8 @@ set(FGC_SOURCES
   src/camera/ImagePipeline.cpp
   src/serial/SerialMotorController.cpp
   src/serial/MtiImuSource.cpp
+  src/sensors/I2cBus.cpp
+  src/sensors/Sht41EnvSensor.cpp
 )
 if(WITH_MQTT)
   list(APPEND FGC_SOURCES src/mqtt/MqttControlChannel.cpp)
diff --git a/config/config.example.ini b/config/config.example.ini
index b38dad8..4b115ed 100644
--- a/config/config.example.ini
+++ b/config/config.example.ini
@@ -72,6 +72,15 @@ baud = 115200
 device =
 baud = 115200
 
+[Env]
+; Ambient temperature/humidity sensor (Adafruit SHT41), wired to the
+; LattePanda's OWN native I2C bus - NOT the Arduino/motor serial link. Bus
+; number varies by board; confirm with `i2cdetect -y N` (SHT41 shows up at
+; 0x44). Enable with [Features] enable_env = true.
+i2c_device = /dev/i2c-1
+i2c_addr = 68
+period_ms = 2000
+
 [Motor]
 ; Degrees<->encoder-counts calibration for each axis. The firmware speaks only
 ; in absolute encoder counts; these map them to the heading/elevation degrees
@@ -137,6 +146,8 @@ enable_imu = false
 mock_camera = false
 mock_serial = false
 mock_imu = false
+enable_env = false
+mock_env = false
 
 [Test]
 ; Hardware self-test command (`test`). `profile` is the default profile used when
diff --git a/docs/configuration.md b/docs/configuration.md
index 08311d3..7b092ed 100644
--- a/docs/configuration.md
+++ b/docs/configuration.md
@@ -55,8 +55,13 @@ Parsed and validated by `ConfigLoader` ([src/core/Config.cpp](../src/core/Config
 | `Features` | `mock_camera` | bool | `false` | Use the simulated camera |
 | `Features` | `mock_serial` | bool | `false` | Use the simulated motor controller |
 | `Features` | `mock_imu` | bool | `false` | Use the simulated IMU instead of the MTi |
+| `Features` | `enable_env` | bool | `false` | Use the ambient temp/humidity sensor (SHT41) |
+| `Features` | `mock_env` | bool | `false` | Use the simulated env sensor instead of the SHT41 |
 | `IMU` | `device` | string | — | MTi serial device (see `[IMU]` note); required when `enable_imu` |
 | `IMU` | `baud` | int | `115200` | MTi serial baud rate |
+| `Env` | `i2c_device` | string | `/dev/i2c-1` | SHT41 I2C bus device (see `[Env]` note); required when `enable_env` |
+| `Env` | `i2c_addr` | int | `68` (`0x44`) | SHT41 I2C slave address |
+| `Env` | `period_ms` | int | `2000` | Sample interval |
 | `Logging` | `level` | enum | `info` | Linear log level (`--log-level` overrides) |
 | `Logging` | `trace` | csv | — | Wire-trace categories, off by default (`--trace` overrides) |
 | `UI` | `enable_tui` | bool | `false` | Full-screen terminal dashboard (`--tui`/`--no-tui` override; needs `WITH_TUI=ON`) |
@@ -140,6 +145,18 @@ The config is read **once at startup** and cached, so if you change the XKF prof
 stays stale until you **refresh** it: press `r` (or type `refresh`). That re-queries the device (briefly
 pausing the stream) and also requests a fresh firmware dump for the gimbal `g` view.
 
+### `[Env]` — SHT41 ambient temperature/humidity sensor
+
+Enable with `[Features] enable_env = true` and point `[Env] i2c_device` at the LattePanda's **own
+native I2C bus** — this is a separate physical link from the motor Leonardo's serial connection, not
+the Arduino's D2 pin (the original DHT11 plan). Bus number varies by board; confirm with
+`i2cdetect -y N` (the SHT41 answers at `0x44`/`68`). The backend (`Sht41EnvSensor`) polls at
+`period_ms`, discarding any sample that fails the SHT4x CRC-8 check. Set `[Features] mock_env = true`
+to use a synthetic reading on dev machines (no hardware) — this is also the checked-in
+`config.example.ini` default. The sensor sits behind the generic `IEnvSensor` interface
+([include/fgc/IEnvSensor.h](../include/fgc/IEnvSensor.h)), so swapping in a different ambient sensor
+later means adding a new backend, not touching `Application`, the UI, or MQTT.
+
 ### Secrets
 
 `mqtt_user` / `mqtt_pw` are read from the environment variables **`FGC_MQTT_USER` / `FGC_MQTT_PW`** first,
@@ -220,8 +237,9 @@ operation is unchanged and remains the default — the same binary runs under sy
 logs on stdout.
 
 Dashboard panels: **Gimbal** (per-axis state, heading, encoder counts, flag badges, target),
-**Sensors** (DHT11 still *pending*; the **Xsens MTi** shows live roll/pitch/yaw + temp once
-`enable_imu`), **Camera** (count, capture state, rate, last capture), **Connectivity** (MQTT state,
+**Sensors** (the **Xsens MTi** shows live roll/pitch/yaw + temp once `enable_imu`; the ambient
+**SHT41** shows live temp/humidity once `enable_env` — see [known-issues.md](known-issues.md) for
+its hardware-bring-up status), **Camera** (count, capture state, rate, last capture), **Connectivity** (MQTT state,
 broker, tower, control mode, target heading). Adding a panel later is a struct in `UiSnapshot.h` plus
 one node in [src/ui/TuiUi.cpp](../src/ui/TuiUi.cpp).
 
diff --git a/docs/known-issues.md b/docs/known-issues.md
index 8b56bb5..602619a 100644
--- a/docs/known-issues.md
+++ b/docs/known-issues.md
@@ -94,4 +94,8 @@ persistence for LPM + usbfs, and verify a full sweep captures white-balanced fra
   yet (not homed / no `gimbal dump`), nudge requests one and does nothing that press — it never falls
   back to the configured degree clamps (which, if `*_min_deg`/`*_max_deg` were unset, produced absurd
   ±100000° steps).
-- DHT11 temperature/humidity is still a Sensors-panel placeholder (the IMU half is integrated).
+- Ambient temperature/humidity (SHT41, `IEnvSensor`/`Sht41EnvSensor`/`MockEnvSensor`) is
+  integrated in software — config-gated (`[Features] enable_env`/`mock_env`, `[Env]`), Sensors
+  panel + MQTT `Env` topic wired — but defaults to `mock_env = true` in the checked-in example
+  config. Bus/address bring-up and validation against the physical sensor on the LattePanda's I2C
+  bus is still pending; flip `mock_env = false` on the deployed `config.ini` once confirmed.
diff --git a/docs/mqtt-api.md b/docs/mqtt-api.md
index 0b89a2e..5818d87 100644
--- a/docs/mqtt-api.md
+++ b/docs/mqtt-api.md
@@ -52,6 +52,7 @@ 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
 
@@ -72,6 +73,22 @@ Built by `MqttControlChannel::publishCamEvent` from a `CamEvent`:
 > The `time` value is the same Unix-ms timestamp used as the image filename, so a consumer can locate the file
 > for a given event: `<RGB|ACR|NIR>/<time>.jxl`.
 
+### 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
 
 ```
@@ -80,6 +97,7 @@ 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/docs/roadmap.md b/docs/roadmap.md
index fb36c6c..0efb58c 100644
--- a/docs/roadmap.md
+++ b/docs/roadmap.md
@@ -27,9 +27,6 @@ Keep entries dated; move shipped items into the reference docs.
   a new `IControlChannel` implementation (richer routing/durable queues, but must
   re-engineer retained "last value" semantics). The abstraction seam already
   exists (`IControlChannel`). _(TODO: confirm approach, target release.)_
-- **DHT11 environmental sensor.** Temperature + humidity on the Arduino side; new
-  firmware `READ DHT` command, host `env` telemetry, condensation monitoring.
-  Enables the `env/dht11` self-test. _(TODO: wiring, sampling cadence.)_
 - **RGB camera.** Integrate the production RGB sensor end-to-end (acquire → JXL →
   CamEvent); enables the `camera/rgb` self-test. _(TODO: model/SDK, mounting.)_
 - **Thermal camera.** Add the thermal sensor with radiometric handling (NUC,
diff --git a/docs/test-roadmap.md b/docs/test-roadmap.md
index 7faed3c..9abd298 100644
--- a/docs/test-roadmap.md
+++ b/docs/test-roadmap.md
@@ -7,20 +7,22 @@ apply unchanged). **Status: planned — blocked on component.** When a component
 lands, promote its entry into [test-command.md](test-command.md) and the taxonomy
 table.
 
-## 1. `env / *` — environmental sensing — *blocked on: DHT11*
+## 1. `env / *` — environmental sensing — *blocked on: SHT41 hardware bring-up*
 
-The DHT11 (temperature + humidity) attaches to the Arduino/firmware side.
+The ambient sensor is now an SHT41 on the LattePanda's **own I2C bus** (not the Arduino) — see
+[configuration.md](configuration.md) `[Env]`. The software side has landed: `IEnvSensor` /
+`Sht41EnvSensor` / `MockEnvSensor`, config-gated, wired into the Sensors panel and the MQTT `Env`
+topic. What's still blocking this self-test leaf is validating the real backend against physical
+hardware (bus/address confirmation, a run with `mock_env = false`).
 
-- **`env / dht11`** — _Healthy:_ sensor responds every read; temperature and
-  humidity in plausible range; values update (not stuck). _Checks:_ issue the
-  firmware read N times over a window; verify each returns a valid frame (DHT11
-  checksum ok). _Metrics:_ temperature °C, relative humidity %, read-failure count,
-  **dewpoint margin** (flag condensation risk when humidity is high and temperature
-  is near the computed dewpoint — relevant for an outdoor tower enclosure).
-  _Firmware:_ add a `READ DHT` command → `EN T <decideg> RH <deci%> OK|ERR` line
-  (DHT11 is bit-banged; the firmware already owns timing-critical I/O). _Host:_ an
-  `EnvReport` parser mirroring `DiagParser`; add `IEnvSource` if the IMU-style
-  abstraction is wanted, else read over the motor serial link.
+- **`env / sht41`** — _Healthy:_ sensor responds every poll (`period_ms`); temperature and humidity
+  in plausible range; values update (not stuck); CRC-8 failures stay rare. _Checks:_ read the sensor
+  N times over a window via `Sht41EnvSensor`; verify each returns a CRC-valid frame; count CRC
+  failures / stale (`connected() == false`) periods. _Metrics:_ temperature °C, relative humidity %,
+  read-failure count, **dewpoint margin** (flag condensation risk when humidity is high and
+  temperature is near the computed dewpoint — relevant for an outdoor tower enclosure). _Host:_ a
+  `TestRunner` leaf reading `IEnvSensor::sample()` directly (no new wire protocol needed — the
+  abstraction the IMU-style tests already use).
 
 ## 2. `comms / *` — message bus — *blocked on: RabbitMQ integration*
 
diff --git a/include/fgc/Config.h b/include/fgc/Config.h
index bbd63f5..8a95470 100644
--- a/include/fgc/Config.h
+++ b/include/fgc/Config.h
@@ -70,6 +70,8 @@ struct FeaturesConfig {
     bool mock_camera   = false;  // use a simulated camera instead of Vimba X
     bool mock_serial   = false;  // use a simulated motor controller
     bool mock_imu      = false;  // use a simulated IMU instead of the MTi
+    bool enable_env    = false;  // ambient temp/humidity sensor (off by default)
+    bool mock_env      = false;  // use a simulated env sensor instead of the SHT41
 };
 
 // [IMU]: Xsens MTi connected over the LattePanda's RS-232 UART (a hardware
@@ -79,6 +81,15 @@ struct ImuConfig {
     unsigned int baud   = 115200;
 };
 
+// [Env]: ambient temperature/humidity sensor (SHT41) on the LattePanda's own
+// native I2C bus — NOT the Arduino/motor serial link. Bus number varies by
+// board; confirm with `i2cdetect -y N` (expect the SHT41 at 0x44).
+struct EnvConfig {
+    std::string  i2c_device = "/dev/i2c-1";  // empty => required when enabled
+    unsigned int i2c_addr   = 0x44;
+    int          period_ms  = 2000;          // sample interval
+};
+
 struct LoggingConfig {
     std::string level;  // trace|debug|info|warn|error|off; empty => default (CLI overrides)
     std::string trace;  // verbatim wire-trace categories: serial,mqtt,camera,control,all,none
@@ -142,6 +153,7 @@ struct AppConfig {
     long           enc_error_warn_counts = 400;       // [Motor] live encoder-error WARN (0=off)
     ScanConfig     scan;      // [Scan] grid source
     ImuConfig      imu;       // [IMU] Xsens MTi serial device
+    EnvConfig      env;       // [Env] SHT41 ambient sensor, LattePanda I2C
     TestConfig     test;      // [Test] hardware self-test profiles
 
     // Capture rate in images/second (derived from general.image_interval).
diff --git a/include/fgc/IControlChannel.h b/include/fgc/IControlChannel.h
index 090a275..ef6f9ca 100644
--- a/include/fgc/IControlChannel.h
+++ b/include/fgc/IControlChannel.h
@@ -22,6 +22,14 @@ 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;
+};
+
 // Abstraction over the remote control/telemetry channel. Implemented by
 // MqttControlChannel (Eclipse Paho) and NullControlChannel (no broker; used
 // for development - publishes are dropped and poll() yields a default).
@@ -36,6 +44,7 @@ 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/IEnvSensor.h b/include/fgc/IEnvSensor.h
new file mode 100644
index 0000000..e1fa86a
--- /dev/null
+++ b/include/fgc/IEnvSensor.h
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <optional>
+#include <string>
+
+namespace fgc {
+
+struct EnvSample {
+    bool      valid        = false;
+    float     temp_c       = 0.0f;
+    float     humidity_pct = 0.0f;
+    long long timestamp_ms = 0;
+};
+
+// Abstraction over an ambient temperature/humidity sensor. Implemented by
+// Sht41EnvSensor (SHT41 on the LattePanda's native I2C bus) and MockEnvSensor
+// (synthetic). The interface intentionally exposes nothing chip-specific, so
+// swapping the sensor (a different I2C part, or a serial one) means writing a
+// new backend, not touching Application/UiSnapshot/MQTT.
+class IEnvSensor {
+public:
+    virtual ~IEnvSensor() = default;
+
+    virtual void start() = 0;
+    virtual void stop()  = 0;
+
+    // Whether a valid, recent reading is available.
+    virtual bool connected() const = 0;
+
+    // Latest reading, or nullopt if none/stale.
+    virtual std::optional<EnvSample> sample() = 0;
+
+    // Identity string for logs/UI, e.g. "SHT41".
+    virtual std::string name() const { return "env"; }
+};
+
+}  // namespace fgc
diff --git a/include/fgc/MqttControlChannel.h b/include/fgc/MqttControlChannel.h
index 973b0df..6168444 100644
--- a/include/fgc/MqttControlChannel.h
+++ b/include/fgc/MqttControlChannel.h
@@ -32,6 +32,7 @@ public:
 
     void publishStatus(int code) override;
     void publishCamEvent(const CamEvent& event) override;
+    void publishEnv(const EnvEvent& event) override;
     ControlCommand poll() override;
 
 private:
@@ -50,6 +51,7 @@ 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/MockEnvSensor.h b/include/fgc/mock/MockEnvSensor.h
new file mode 100644
index 0000000..b8bceb4
--- /dev/null
+++ b/include/fgc/mock/MockEnvSensor.h
@@ -0,0 +1,43 @@
+#pragma once
+
+#include "fgc/IEnvSensor.h"
+#include "fgc/Logger.h"
+
+#include <chrono>
+#include <cmath>
+
+namespace fgc {
+
+// Simulated ambient sensor for development without hardware: synthesizes a
+// slowly varying, plausible temp/humidity reading so the Sensors panel
+// animates without an SHT41 attached.
+class MockEnvSensor : public IEnvSensor {
+public:
+    void start() override {
+        start_ = clock::now();
+        LOG_INFO << "[mock] env sensor started";
+    }
+    void stop() override { LOG_INFO << "[mock] env sensor stopped"; }
+
+    bool connected() const override { return true; }
+
+    std::optional<EnvSample> sample() override {
+        const double t = std::chrono::duration<double>(clock::now() - start_).count();
+        EnvSample s;
+        s.valid        = true;
+        s.temp_c       = static_cast<float>(22.0 + 3.0 * std::sin(t * 0.02));
+        s.humidity_pct = static_cast<float>(45.0 + 10.0 * std::sin(t * 0.013 + 1.0));
+        s.timestamp_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
+                             std::chrono::system_clock::now().time_since_epoch())
+                             .count();
+        return s;
+    }
+
+    std::string name() const override { return "SHT41 (mock)"; }
+
+private:
+    using clock = std::chrono::steady_clock;
+    clock::time_point start_ = clock::now();
+};
+
+}  // namespace fgc
diff --git a/include/fgc/mock/NullControlChannel.h b/include/fgc/mock/NullControlChannel.h
index 7f7de69..e502a56 100644
--- a/include/fgc/mock/NullControlChannel.h
+++ b/include/fgc/mock/NullControlChannel.h
@@ -22,6 +22,11 @@ public:
                                     << " hdg=" << e.heading_decideg << " t=" << e.timestamp_ms
                                     << " (null channel)";
     }
+    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)";
+    }
 
     ControlCommand poll() override { return {}; }
 };
diff --git a/include/fgc/sensors/I2cBus.h b/include/fgc/sensors/I2cBus.h
new file mode 100644
index 0000000..1427fd0
--- /dev/null
+++ b/include/fgc/sensors/I2cBus.h
@@ -0,0 +1,37 @@
+#pragma once
+
+#include <cstdint>
+#include <string>
+#include <vector>
+
+namespace fgc {
+
+// Thin RAII wrapper around a Linux I2C device node (/dev/i2c-N), talking to
+// one fixed slave address via the kernel i2c-dev ioctl interface. Generic
+// (not sensor-specific) so any future I2C device reuses it.
+class I2cBus {
+public:
+    I2cBus(std::string device, uint8_t addr);
+    ~I2cBus();
+
+    I2cBus(const I2cBus&) = delete;
+    I2cBus& operator=(const I2cBus&) = delete;
+
+    // Opens the device node and binds the slave address. Returns false on failure.
+    bool open();
+    void close();
+    bool isOpen() const { return fd_ >= 0; }
+
+    // Writes `tx`, then (if `rx` is non-empty) reads into it. Combined so a
+    // single call can do "write command, read reply". Returns false on any I/O
+    // error.
+    bool writeRead(const std::vector<uint8_t>& tx, std::vector<uint8_t>& rx);
+    bool write(const std::vector<uint8_t>& tx);
+
+private:
+    std::string device_;
+    uint8_t     addr_;
+    int         fd_ = -1;
+};
+
+}  // namespace fgc
diff --git a/include/fgc/sensors/Sht41EnvSensor.h b/include/fgc/sensors/Sht41EnvSensor.h
new file mode 100644
index 0000000..46a6575
--- /dev/null
+++ b/include/fgc/sensors/Sht41EnvSensor.h
@@ -0,0 +1,34 @@
+#pragma once
+
+#include "fgc/IEnvSensor.h"
+
+#include <chrono>
+#include <cstdint>
+#include <memory>
+#include <string>
+
+namespace fgc {
+
+// Real backend: Adafruit SHT41 temperature/humidity sensor on the
+// LattePanda's own native I2C bus (NOT the Arduino/motor serial link).
+// Triggers a high-precision measurement every `period`, sleeps out the ~10ms
+// conversion delay, and reads back on its own thread so the ~100Hz control
+// loop is never blocked. CRC-8-checked; a failed checksum discards the
+// sample rather than reporting a bad reading.
+class Sht41EnvSensor : public IEnvSensor {
+public:
+    Sht41EnvSensor(std::string i2c_device, uint8_t addr, std::chrono::milliseconds period);
+    ~Sht41EnvSensor() override;
+
+    void                      start() override;
+    void                      stop() override;
+    bool                      connected() const override;
+    std::optional<EnvSample>  sample() override;
+    std::string               name() const override { return "SHT41"; }
+
+private:
+    struct Impl;
+    std::unique_ptr<Impl> impl_;
+};
+
+}  // namespace fgc
diff --git a/include/fgc/ui/UiSnapshot.h b/include/fgc/ui/UiSnapshot.h
index 941a5ed..0f798ec 100644
--- a/include/fgc/ui/UiSnapshot.h
+++ b/include/fgc/ui/UiSnapshot.h
@@ -68,7 +68,7 @@ struct SensorField {
 // A labelled group of readings from one physical sensor, rendered as its own
 // subsection in the Sensors panel.
 struct SensorGroup {
-    std::string              title;            // "MTi (orientation)" / "DHT11 (ambient)"
+    std::string              title;            // "MTi (orientation)" / "SHT41 (ambient)"
     std::string              status = "pending";  // "live" / "pending" / "no fix"
     bool                     present = false;  // true once the driver feeds real data
     std::vector<SensorField> fields;
@@ -76,11 +76,13 @@ struct SensorGroup {
 
 // The Sensors panel, split by source so it is clear which parameters come from
 // which device. Each group is filled with pending placeholders until its driver
-// lands. NOTE: the MTi's Temp is the device's *internal* temperature; the DHT11
-// Temp (separate group) is *ambient* — deliberately kept apart.
+// lands. NOTE: the MTi's Temp is the device's *internal* temperature; the env
+// sensor's Temp (separate group) is *ambient* — deliberately kept apart. The
+// env group's title/backing sensor is swappable (currently SHT41 over I2C; see
+// IEnvSensor) without touching this struct.
 struct SensorsView {
     SensorGroup imu;   // Xsens MTi: Roll/Pitch/Yaw + internal temperature
-    SensorGroup dht;   // DHT11: ambient temperature + humidity
+    SensorGroup env;   // ambient temperature + humidity (SHT41)
 };
 
 // One auto-sweep scan-grid waypoint, for the expanded camera view.
diff --git a/src/core/Application.cpp b/src/core/Application.cpp
index e591757..894e64a 100644
--- a/src/core/Application.cpp
+++ b/src/core/Application.cpp
@@ -9,6 +9,7 @@
 #include "fgc/Paths.h"
 #include "fgc/ICameraSource.h"
 #include "fgc/IControlChannel.h"
+#include "fgc/IEnvSensor.h"
 #include "fgc/IImuSource.h"
 #include "fgc/IMotorController.h"
 #include "fgc/ImagePipeline.h"
@@ -19,9 +20,11 @@
 #include "fgc/TestReport.h"
 #include "fgc/TestRunner.h"
 #include "fgc/mock/MockCameraSource.h"
+#include "fgc/mock/MockEnvSensor.h"
 #include "fgc/mock/MockImuSource.h"
 #include "fgc/mock/MockMotorController.h"
 #include "fgc/mock/NullControlChannel.h"
+#include "fgc/sensors/Sht41EnvSensor.h"
 #include "fgc/ui/HeadlessUi.h"
 #include "fgc/ui/IUserInterface.h"
 #include "fgc/ui/UiSnapshot.h"
@@ -179,6 +182,7 @@ struct Application::Impl {
     std::unique_ptr<IMotorController> motor;
     std::unique_ptr<ICameraSource>    camera;
     std::unique_ptr<IImuSource>       imu;
+    std::unique_ptr<IEnvSensor>       env;
     std::unique_ptr<ImagePipeline>    pipeline;
     std::unique_ptr<CaptureScheduler> scheduler;
     std::unique_ptr<IUserInterface>   ui;
@@ -219,6 +223,7 @@ 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
 
     std::atomic<bool>       running{true};
     std::mutex              cmd_mutex;
@@ -261,6 +266,18 @@ struct Application::Impl {
         return std::make_unique<MtiImuSource>(cfg.imu.device, cfg.imu.baud);
     }
 
+    std::unique_ptr<IEnvSensor> makeEnv() {
+        if (!cfg.features.enable_env) return nullptr;  // sensors panel stays "pending"
+        if (cfg.features.mock_env) return std::make_unique<MockEnvSensor>();
+        if (cfg.env.i2c_device.empty()) {
+            LOG_WARN << "Env sensor enabled but [Env] i2c_device is empty; disabling";
+            return nullptr;
+        }
+        return std::make_unique<Sht41EnvSensor>(cfg.env.i2c_device,
+                                                static_cast<uint8_t>(cfg.env.i2c_addr),
+                                                std::chrono::milliseconds(cfg.env.period_ms));
+    }
+
     std::unique_ptr<ICameraSource> makeCamera() {
         bool mock = opts.mock_camera.value_or(cfg.features.mock_camera);
 #if !FGC_WITH_VIMBA
@@ -353,7 +370,7 @@ struct Application::Impl {
             }
         }
 
-        // --- Sensors: MTi (orientation) live if present; DHT11 (ambient) pending ---
+        // --- Sensors: MTi (orientation) + SHT41 (ambient), each live if present ---
         s.sensors = pendingSensorsView();
         if (imu) {
             auto fmt1 = [](float v) {
@@ -401,6 +418,39 @@ struct Application::Impl {
             }
         }
 
+        if (env) {
+            auto fmt1 = [](float v) {
+                char b[24];
+                std::snprintf(b, sizeof(b), "%.1f", v);
+                return std::string(b);
+            };
+            auto setField = [&](SensorField& f, const std::string& v) {
+                f.value   = v;
+                f.present = true;
+            };
+            if (auto m = env->sample()) {
+                auto& g = s.sensors.env;
+                g.present = true;
+                g.status  = "live";
+                if (g.fields.size() >= 2) {
+                    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";
+            }
+        }
+
         // --- Camera / capture ---
         s.capture.present      = true;
         s.capture.active       = scheduler && scheduler->captureActive();
@@ -1331,6 +1381,7 @@ struct Application::Impl {
         motor   = makeMotor();
         camera  = makeCamera();
         imu     = makeImu();
+        env     = makeEnv();
 
         if (!channel->connect())
             LOG_WARN << "Control channel not connected; continuing in degraded mode";
@@ -1382,6 +1433,7 @@ struct Application::Impl {
 
         motor->start();
         if (imu) imu->start();
+        if (env) env->start();
         camera->open();
         pipeline->start();
         channel->publishStatus(0);
@@ -1438,6 +1490,7 @@ struct Application::Impl {
         camera->stop();
         camera->close();
         if (imu) imu->stop();
+        if (env) env->stop();
         motor->stop();
         channel->disconnect();
         return 0;
diff --git a/src/core/Config.cpp b/src/core/Config.cpp
index d4c4d4d..b0da7e8 100644
--- a/src/core/Config.cpp
+++ b/src/core/Config.cpp
@@ -181,10 +181,16 @@ AppConfig ConfigLoader::fromMap(const std::map<std::string, std::string>& kv) {
     cfg.features.mock_camera   = getBool(kv, "Features.mock_camera", cfg.features.mock_camera);
     cfg.features.mock_serial   = getBool(kv, "Features.mock_serial", cfg.features.mock_serial);
     cfg.features.mock_imu      = getBool(kv, "Features.mock_imu", cfg.features.mock_imu);
+    cfg.features.enable_env    = getBool(kv, "Features.enable_env", cfg.features.enable_env);
+    cfg.features.mock_env      = getBool(kv, "Features.mock_env", cfg.features.mock_env);
 
     cfg.imu.device = get(kv, "IMU.device", cfg.imu.device);
     cfg.imu.baud   = static_cast<unsigned>(getInt(kv, "IMU.baud", cfg.imu.baud));
 
+    cfg.env.i2c_device = get(kv, "Env.i2c_device", cfg.env.i2c_device);
+    cfg.env.i2c_addr   = static_cast<unsigned>(getInt(kv, "Env.i2c_addr", cfg.env.i2c_addr));
+    cfg.env.period_ms  = getInt(kv, "Env.period_ms", cfg.env.period_ms);
+
     // [Test] + [TestProfile.<name>]: discover profiles by scanning the flattened
     // keys. inih gives us "TestProfile.<name>.<key>" => value; every numeric value
     // lands in that profile's open param map for the test modules to read.
diff --git a/src/mqtt/MqttControlChannel.cpp b/src/mqtt/MqttControlChannel.cpp
index 94d1aaf..fd2f6a0 100644
--- a/src/mqtt/MqttControlChannel.cpp
+++ b/src/mqtt/MqttControlChannel.cpp
@@ -19,6 +19,7 @@ MqttControlChannel::MqttControlChannel(const std::string& broker_ip, const std::
       topic_control_code_("GGS/FWT/" + tower + "/ControlCode"),
       topic_status_("GGS/FWT/" + tower + "/StatusCode"),
       topic_cam_event_("GGS/FWT/" + tower + "/CamEvent"),
+      topic_env_("GGS/FWT/" + tower + "/Env"),
       client_(broker_ip, tower) {
     conn_opts_.set_keep_alive_interval(20);
     conn_opts_.set_clean_session(true);
@@ -123,4 +124,12 @@ void MqttControlChannel::publishCamEvent(const CamEvent& e) {
     publish(topic_cam_event_, payload);
 }
 
+void MqttControlChannel::publishEnv(const EnvEvent& e) {
+    std::string payload = "{ \"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) + " }";
+    publish(topic_env_, payload);
+}
+
 }  // namespace fgc
diff --git a/src/sensors/I2cBus.cpp b/src/sensors/I2cBus.cpp
new file mode 100644
index 0000000..375feaa
--- /dev/null
+++ b/src/sensors/I2cBus.cpp
@@ -0,0 +1,51 @@
+#include "fgc/sensors/I2cBus.h"
+
+#include "fgc/Logger.h"
+
+#include <fcntl.h>
+#include <linux/i2c-dev.h>
+#include <sys/ioctl.h>
+#include <unistd.h>
+
+namespace fgc {
+
+I2cBus::I2cBus(std::string device, uint8_t addr) : device_(std::move(device)), addr_(addr) {}
+
+I2cBus::~I2cBus() { close(); }
+
+bool I2cBus::open() {
+    close();
+    fd_ = ::open(device_.c_str(), O_RDWR);
+    if (fd_ < 0) {
+        LOG_ERROR << "I2C: failed to open " << device_;
+        return false;
+    }
+    if (::ioctl(fd_, I2C_SLAVE, addr_) < 0) {
+        LOG_ERROR << "I2C: failed to select slave 0x" << std::hex << int(addr_) << std::dec
+                  << " on " << device_;
+        close();
+        return false;
+    }
+    return true;
+}
+
+void I2cBus::close() {
+    if (fd_ >= 0) {
+        ::close(fd_);
+        fd_ = -1;
+    }
+}
+
+bool I2cBus::write(const std::vector<uint8_t>& tx) {
+    if (fd_ < 0) return false;
+    return ::write(fd_, tx.data(), tx.size()) == static_cast<ssize_t>(tx.size());
+}
+
+bool I2cBus::writeRead(const std::vector<uint8_t>& tx, std::vector<uint8_t>& rx) {
+    if (fd_ < 0) return false;
+    if (!tx.empty() && !write(tx)) return false;
+    if (rx.empty()) return true;
+    return ::read(fd_, rx.data(), rx.size()) == static_cast<ssize_t>(rx.size());
+}
+
+}  // namespace fgc
diff --git a/src/sensors/Sht41EnvSensor.cpp b/src/sensors/Sht41EnvSensor.cpp
new file mode 100644
index 0000000..bacacaa
--- /dev/null
+++ b/src/sensors/Sht41EnvSensor.cpp
@@ -0,0 +1,123 @@
+#include "fgc/sensors/Sht41EnvSensor.h"
+
+#include "fgc/Logger.h"
+#include "fgc/sensors/I2cBus.h"
+
+#include <atomic>
+#include <chrono>
+#include <mutex>
+#include <thread>
+
+namespace fgc {
+
+namespace {
+
+constexpr uint8_t kCmdSoftReset          = 0x94;
+constexpr uint8_t kCmdMeasureHighPrec    = 0xFD;
+constexpr auto     kConversionDelay      = std::chrono::milliseconds(10);
+constexpr auto     kSoftResetSettle      = std::chrono::milliseconds(1);
+
+// SHT4x CRC-8: poly 0x31, init 0xFF. Datasheet test vector: 0xBE 0xEF -> 0x92.
+uint8_t crc8Sht41(const uint8_t* data, size_t len) {
+    uint8_t crc = 0xFF;
+    for (size_t i = 0; i < len; ++i) {
+        crc ^= data[i];
+        for (int b = 0; b < 8; ++b)
+            crc = (crc & 0x80) ? static_cast<uint8_t>((crc << 1) ^ 0x31)
+                                : static_cast<uint8_t>(crc << 1);
+    }
+    return crc;
+}
+
+}  // namespace
+
+struct Sht41EnvSensor::Impl {
+    Impl(std::string dev, uint8_t a, std::chrono::milliseconds p)
+        : bus(std::move(dev), a), period(p) {}
+
+    using clock = std::chrono::steady_clock;
+
+    I2cBus                  bus;
+    std::chrono::milliseconds period;
+    std::thread              worker;
+    std::atomic<bool>        running{false};
+
+    std::mutex         mutex;
+    EnvSample          latest;
+    clock::time_point   last_ok{};
+
+    void readOnce() {
+        if (!bus.write({kCmdMeasureHighPrec})) return;
+        std::this_thread::sleep_for(kConversionDelay);
+        std::vector<uint8_t> rx(6);
+        if (!bus.writeRead({}, rx)) return;
+
+        if (crc8Sht41(rx.data(), 2) != rx[2] || crc8Sht41(rx.data() + 3, 2) != rx[5]) {
+            LOG_WARN << "SHT41: CRC mismatch, discarding sample";
+            return;
+        }
+
+        const uint16_t traw  = static_cast<uint16_t>((rx[0] << 8) | rx[1]);
+        const uint16_t rhraw = static_cast<uint16_t>((rx[3] << 8) | rx[4]);
+        float temp_c = -45.0f + 175.0f * (static_cast<float>(traw) / 65535.0f);
+        float rh_pct = -6.0f + 125.0f * (static_cast<float>(rhraw) / 65535.0f);
+        if (rh_pct < 0.0f) rh_pct = 0.0f;
+        if (rh_pct > 100.0f) rh_pct = 100.0f;
+
+        std::lock_guard<std::mutex> lock(mutex);
+        latest.valid        = true;
+        latest.temp_c       = temp_c;
+        latest.humidity_pct = rh_pct;
+        latest.timestamp_ms = std::chrono::duration_cast<std::chrono::milliseconds>(
+                                  std::chrono::system_clock::now().time_since_epoch())
+                                  .count();
+        last_ok = clock::now();
+    }
+
+    void run() {
+        while (running.load()) {
+            readOnce();
+            std::this_thread::sleep_for(period);
+        }
+    }
+};
+
+Sht41EnvSensor::Sht41EnvSensor(std::string i2c_device, uint8_t addr,
+                               std::chrono::milliseconds period)
+    : impl_(std::make_unique<Impl>(std::move(i2c_device), addr, period)) {}
+
+Sht41EnvSensor::~Sht41EnvSensor() { stop(); }
+
+void Sht41EnvSensor::start() {
+    if (!impl_->bus.open()) {
+        LOG_ERROR << "SHT41: failed to open I2C bus; sensor disabled";
+        return;
+    }
+    impl_->bus.write({kCmdSoftReset});
+    std::this_thread::sleep_for(kSoftResetSettle);
+    impl_->running = true;
+    impl_->worker  = std::thread([this] { impl_->run(); });
+    LOG_INFO << "SHT41 env sensor started";
+}
+
+void Sht41EnvSensor::stop() {
+    if (!impl_) return;
+    impl_->running = false;
+    if (impl_->worker.joinable()) impl_->worker.join();
+    impl_->bus.close();
+}
+
+bool Sht41EnvSensor::connected() const {
+    std::lock_guard<std::mutex> lock(impl_->mutex);
+    return impl_->latest.valid &&
+           (Impl::clock::now() - impl_->last_ok) < 2 * impl_->period;
+}
+
+std::optional<EnvSample> Sht41EnvSensor::sample() {
+    std::lock_guard<std::mutex> lock(impl_->mutex);
+    if (!impl_->latest.valid || (Impl::clock::now() - impl_->last_ok) >= 2 * impl_->period)
+        return std::nullopt;
+    return impl_->latest;
+}
+
+}  // namespace fgc
diff --git a/src/ui/TuiUi.cpp b/src/ui/TuiUi.cpp
index cfe74f7..4b65a27 100644
--- a/src/ui/TuiUi.cpp
+++ b/src/ui/TuiUi.cpp
@@ -82,8 +82,8 @@ Element gimbalPanel(const GimbalView& g) {
 
 Element sensorsPanel(const SensorsView& s) {
     // One labelled subsection per physical sensor: a title + status header, then
-    // its readings. Keeps MTi (orientation/device temp) and DHT11 (ambient)
-    // clearly separated.
+    // its readings. Keeps MTi (orientation/device temp) and the ambient env
+    // sensor (SHT41) clearly separated.
     auto group = [](const SensorGroup& g, const std::string& hint) {
         std::vector<Element> rows;
         Element status = g.present ? (text(g.status) | color(Color::Green))
@@ -100,7 +100,7 @@ Element sensorsPanel(const SensorsView& s) {
     return panel("[i] SENSORS", Color::Magenta,
                  vbox({group(s.imu, "i to expand"),
                        separator(),
-                       group(s.dht, "")}));
+                       group(s.env, "")}));
 }
 
 Element cameraPanel(const CaptureView& c) {
diff --git a/src/ui/UiSnapshot.cpp b/src/ui/UiSnapshot.cpp
index 8038cfd..e422576 100644
--- a/src/ui/UiSnapshot.cpp
+++ b/src/ui/UiSnapshot.cpp
@@ -56,11 +56,12 @@ SensorsView pendingSensorsView() {
     v.imu.fields.push_back({"Pitch", "--.-", "\xC2\xB0", false});
     v.imu.fields.push_back({"Yaw",   "--.-", "\xC2\xB0", false});
     v.imu.fields.push_back({"Temp",  "--.-", "\xC2\xB0""C", false});  // MTi internal
-    // DHT11 temperature & humidity (Aosong): 0-50 °C ±2 °C, 20-90 %RH ±5 % (ambient).
-    v.dht.title  = "DHT11 (ambient)";
-    v.dht.status = "pending";
-    v.dht.fields.push_back({"Temp",  "--.-", "\xC2\xB0""C", false});
-    v.dht.fields.push_back({"Humid", "--",   "%RH",         false});
+    // SHT41 temperature & humidity (Adafruit, I2C on the LattePanda's own bus):
+    // ±0.2 °C, ±1.8 %RH (ambient).
+    v.env.title  = "SHT41 (ambient)";
+    v.env.status = "pending";
+    v.env.fields.push_back({"Temp",  "--.-", "\xC2\xB0""C", false});
+    v.env.fields.push_back({"Humid", "--",   "%RH",         false});
     return v;
 }
 
diff --git a/tests/test_config.cpp b/tests/test_config.cpp
index f22114f..060bc55 100644
--- a/tests/test_config.cpp
+++ b/tests/test_config.cpp
@@ -37,6 +37,29 @@ TEST_CASE("ConfigLoader maps and defaults typed values") {
     CHECK(std::abs(c.image_rate() - 1.0 / 3.0) < 1e-9);
 }
 
+TEST_CASE("ConfigLoader maps [Env]/env feature flags") {
+    AppConfig d = ConfigLoader::fromMap({});
+    CHECK(d.features.enable_env == false);
+    CHECK(d.features.mock_env == false);
+    CHECK(d.env.i2c_device == "/dev/i2c-1");
+    CHECK(d.env.i2c_addr == 0x44);
+    CHECK(d.env.period_ms == 2000);
+
+    std::map<std::string, std::string> kv = {
+        {"Features.enable_env", "true"},
+        {"Features.mock_env", "true"},
+        {"Env.i2c_device", "/dev/i2c-3"},
+        {"Env.i2c_addr", "68"},
+        {"Env.period_ms", "5000"},
+    };
+    AppConfig c = ConfigLoader::fromMap(kv);
+    CHECK(c.features.enable_env == true);
+    CHECK(c.features.mock_env == true);
+    CHECK(c.env.i2c_device == "/dev/i2c-3");
+    CHECK(c.env.i2c_addr == 68);
+    CHECK(c.env.period_ms == 5000);
+}
+
 TEST_CASE("environment overrides file credentials") {
     setenv("FGC_MQTT_USER", "envuser", 1);
     AppConfig c = ConfigLoader::fromMap({{"Network.mqtt_user", "fileuser"}});
diff --git a/tests/test_scheduler.cpp b/tests/test_scheduler.cpp
index 87b0b46..9036f3b 100644
--- a/tests/test_scheduler.cpp
+++ b/tests/test_scheduler.cpp
@@ -44,6 +44,7 @@ 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 = {};
diff --git a/tests/test_uisnapshot.cpp b/tests/test_uisnapshot.cpp
index aa73143..07de774 100644
--- a/tests/test_uisnapshot.cpp
+++ b/tests/test_uisnapshot.cpp
@@ -61,12 +61,12 @@ TEST_CASE("MockCameraSource::deviceInfo reports identity, dims, streaming, frame
 TEST_CASE("pendingSensorsView: grouped by sensor, all absent until drivers land") {
     SensorsView v = pendingSensorsView();
     CHECK_FALSE(v.imu.present);
-    CHECK_FALSE(v.dht.present);
+    CHECK_FALSE(v.env.present);
     CHECK_FALSE(v.imu.title.empty());
-    CHECK_FALSE(v.dht.title.empty());
+    CHECK_FALSE(v.env.title.empty());
     CHECK(v.imu.fields.size() >= 3);  // roll/pitch/yaw (+ device temp)
-    CHECK(v.dht.fields.size() >= 2);  // ambient temp + humidity
-    for (const auto* g : {&v.imu, &v.dht}) {
+    CHECK(v.env.fields.size() >= 2);  // ambient temp + humidity
+    for (const auto* g : {&v.imu, &v.env}) {
         for (const auto& f : g->fields) {
             CHECK_FALSE(f.present);
             CHECK_FALSE(f.label.empty());