diff --git a/crates/core/shturman-power/src/fsm.rs b/crates/core/shturman-power/src/fsm.rs
new file mode 100644
index 0000000..afa6b16
--- /dev/null
+++ b/crates/core/shturman-power/src/fsm.rs
@@ -0,0 +1,199 @@
+//! Чистый FSM питания (B03, спека v0.3 §5). Без D-Bus/async/I/O — сервис исполняет `Action`.
+
+use shturman_ipc::types::{IgnitionState, PowerSource, PowerState, ShutdownReason};
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Phase {
+    Abortable,
+    Committed,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum State {
+    Off,
+    Accessory,
+    Running,
+    ShuttingDown { phase: Phase, reason: ShutdownReason },
+    Sleep,         // зарезервировано (полные sleep/wake — v1/v2)
+    BatteryCutoff, // зарезервировано (long-park — v1/v2)
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Event {
+    AccOn,
+    AccOff,
+    EngineOn,
+    EngineOff,
+    UnderVoltage,
+    ThermalTrip,
+    GraceExpired,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum Action {
+    ShutdownImminent(ShutdownReason),
+    ShutdownAborted,
+    AccChanged(bool),
+    StartGrace,
+    Commit,
+}
+
+pub struct PowerFsm {
+    state: State,
+}
+
+impl Default for PowerFsm {
+    fn default() -> Self {
+        Self { state: State::Running }
+    }
+}
+
+impl PowerFsm {
+    pub fn new() -> Self {
+        Self::default()
+    }
+    pub fn state(&self) -> State {
+        self.state
+    }
+
+    /// D-Bus-проекция состояния (`PowerState`).
+    pub fn power_state(&self) -> PowerState {
+        match self.state {
+            State::Off => PowerState::Off,
+            State::Accessory => PowerState::Accessory,
+            State::Running => PowerState::Running,
+            State::ShuttingDown { .. } => PowerState::ShuttingDown,
+            State::Sleep => PowerState::Sleep,
+            State::BatteryCutoff => PowerState::BatteryCutoff,
+        }
+    }
+    /// Ось зажигания (канон, B §1).
+    pub fn ignition(&self) -> IgnitionState {
+        match self.state {
+            State::Running => IgnitionState::Running,
+            State::Accessory => IgnitionState::Accessory,
+            _ => IgnitionState::Off,
+        }
+    }
+    /// Источник питания — сигнал потребителям «времени мало» при shutdown.
+    pub fn source(&self) -> PowerSource {
+        match self.state {
+            State::ShuttingDown { reason: ShutdownReason::UnderVoltage, .. } => PowerSource::LowBattery,
+            State::ShuttingDown { .. } => PowerSource::HoldupCap,
+            _ => PowerSource::Vehicle12v,
+        }
+    }
+
+    /// Шаг FSM. Возвращает действия для исполнения сервисом (спека §5).
+    pub fn step(&mut self, ev: Event) -> Vec<Action> {
+        use Event as E;
+        use Phase::*;
+        use State::*;
+        match (self.state, ev) {
+            (Off, E::AccOn) => {
+                self.state = Accessory;
+                vec![Action::AccChanged(true)]
+            }
+            (Accessory, E::EngineOn) => {
+                self.state = Running;
+                vec![]
+            }
+            (Running, E::EngineOff) => {
+                self.state = Accessory;
+                vec![]
+            }
+            (Accessory | Running, E::AccOff) => self.begin_shutdown(ShutdownReason::AccOff),
+            (Accessory | Running, E::UnderVoltage) => self.begin_shutdown(ShutdownReason::UnderVoltage),
+            (Accessory | Running, E::ThermalTrip) => self.begin_shutdown(ShutdownReason::Thermal),
+            (ShuttingDown { phase: Abortable, .. }, E::AccOn) => {
+                self.state = Running;
+                vec![Action::ShutdownAborted, Action::AccChanged(true)]
+            }
+            (ShuttingDown { phase: Abortable, reason }, E::GraceExpired) => {
+                self.state = ShuttingDown { phase: Committed, reason };
+                vec![Action::Commit]
+            }
+            // committed/off/sleep/battery_cutoff + всё прочее — no-op (committed не abort-ится)
+            _ => vec![],
+        }
+    }
+
+    fn begin_shutdown(&mut self, reason: ShutdownReason) -> Vec<Action> {
+        self.state = State::ShuttingDown { phase: Phase::Abortable, reason };
+        vec![Action::ShutdownImminent(reason), Action::StartGrace]
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn off_acc_on_to_accessory() {
+        let mut f = PowerFsm { state: State::Off };
+        assert_eq!(f.step(Event::AccOn), vec![Action::AccChanged(true)]);
+        assert_eq!(f.state(), State::Accessory);
+    }
+
+    #[test]
+    fn accessory_engine_on_to_running_and_back() {
+        let mut f = PowerFsm { state: State::Accessory };
+        assert_eq!(f.step(Event::EngineOn), vec![]);
+        assert_eq!(f.state(), State::Running);
+        assert_eq!(f.step(Event::EngineOff), vec![]);
+        assert_eq!(f.state(), State::Accessory);
+    }
+
+    #[test]
+    fn acc_off_begins_abortable_shutdown() {
+        let mut f = PowerFsm::new(); // Running
+        assert_eq!(
+            f.step(Event::AccOff),
+            vec![Action::ShutdownImminent(ShutdownReason::AccOff), Action::StartGrace]
+        );
+        assert_eq!(f.power_state(), PowerState::ShuttingDown);
+        assert_eq!(f.source(), PowerSource::HoldupCap);
+    }
+
+    #[test]
+    fn under_voltage_reason_and_source() {
+        let mut f = PowerFsm::new();
+        let a = f.step(Event::UnderVoltage);
+        assert_eq!(a[0], Action::ShutdownImminent(ShutdownReason::UnderVoltage));
+        assert_eq!(f.source(), PowerSource::LowBattery);
+    }
+
+    #[test]
+    fn abort_before_ponr() {
+        let mut f = PowerFsm::new();
+        f.step(Event::AccOff);
+        assert_eq!(
+            f.step(Event::AccOn),
+            vec![Action::ShutdownAborted, Action::AccChanged(true)]
+        );
+        assert_eq!(f.state(), State::Running);
+    }
+
+    #[test]
+    fn grace_expired_commits_and_is_irreversible() {
+        let mut f = PowerFsm::new();
+        f.step(Event::AccOff);
+        assert_eq!(f.step(Event::GraceExpired), vec![Action::Commit]);
+        assert_eq!(f.step(Event::AccOn), vec![]); // committed: abort игнорируется
+        assert!(matches!(f.state(), State::ShuttingDown { phase: Phase::Committed, .. }));
+    }
+
+    #[test]
+    fn reserved_states_noop() {
+        let mut f = PowerFsm { state: State::Sleep };
+        assert_eq!(f.step(Event::AccOn), vec![]);
+        assert_eq!(f.state(), State::Sleep);
+    }
+
+    #[test]
+    fn ignition_projection() {
+        assert_eq!(PowerFsm { state: State::Running }.ignition(), IgnitionState::Running);
+        assert_eq!(PowerFsm { state: State::Accessory }.ignition(), IgnitionState::Accessory);
+        assert_eq!(PowerFsm { state: State::Off }.ignition(), IgnitionState::Off);
+    }
+}
diff --git a/crates/core/shturman-power/src/lib.rs b/crates/core/shturman-power/src/lib.rs
index 7e41428..3fb0d82 100644
--- a/crates/core/shturman-power/src/lib.rs
+++ b/crates/core/shturman-power/src/lib.rs
@@ -1,6 +1,7 @@
-//! `ru.shturman.Power1` — стаб питания/жизненного цикла (домен B).
-//! v0: статичное состояние `running`, мутируется только dev-mock (fake-ACC). Полная FSM/секвенсинг — v0.3.
+//! `ru.shturman.Power1` — питание/жизненный цикл (домен B). v0.3: реальный lifecycle-FSM
+//! (`fsm`), сервис оборачивает его (D-Bus state/signals из FSM; dev-mock кормит входы).
 
+pub mod fsm;
 pub mod service;
 
 pub use service::PowerService;