diff --git a/src/sls/state/generic_implementations.rs b/src/sls/state/generic_implementations.rs
new file mode 100644
index 0000000..869b238
--- /dev/null
+++ b/src/sls/state/generic_implementations.rs
@@ -0,0 +1,494 @@
+//! Generic, state-agnostic helpers that operate on [`State`] values.
+//!
+//! These are deliberately independent of any particular state function
+//! (file, service, package, ...) so they apply to every state the same way.
+//! They provide:
+//! * topological ordering of states for application, and
+//! * conditional links deciding whether a state should run based on the
+//!   outcome of the states it depends on.
+
+use super::{State, StateDirective};
+use std::collections::{HashMap, HashSet, VecDeque};
+
+/// The outcome of applying a single state. Used to evaluate conditional gates:
+/// whether the state succeeded and whether it reported changes.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct StateOutcome {
+    pub success: bool,
+    pub changed: bool,
+}
+
+impl StateOutcome {
+    pub const fn success_unchanged() -> Self {
+        Self {
+            success: true,
+            changed: false,
+        }
+    }
+
+    pub const fn success_changed() -> Self {
+        Self {
+            success: true,
+            changed: true,
+        }
+    }
+
+    pub const fn failure_unchanged() -> Self {
+        Self {
+            success: false,
+            changed: false,
+        }
+    }
+
+    pub const fn failure_changed() -> Self {
+        Self {
+            success: false,
+            changed: true,
+        }
+    }
+}
+
+/// How a set of target states gates the state that declares the link.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum GateRule {
+    /// Run only if *every* target succeeded (`require`, `require_in`).
+    AllSucceeded,
+    /// Run only if *at least one* target succeeded (`require_any`).
+    AnySucceeded,
+    /// Run only if *at least one* target failed (`onfail`, `onfail_in`).
+    AnyFailed,
+    /// Run only if *at least one* target failed **and** reported changes
+    /// (`onfailchanges`, `onfailchanges_in`).
+    AnyFailedChanged,
+    /// Run only if *at least one* target reported changes (`watch`, `onchanges`
+    /// and their `_in` / `_any` forms).
+    AnyChanged,
+}
+
+/// A conditional link: this state should only be applied when the rule holds
+/// against the recorded outcomes of its target states.
+#[derive(Debug, Clone, PartialEq)]
+pub struct Gate {
+    pub rule: GateRule,
+    pub targets: Vec<String>,
+}
+
+impl Gate {
+    /// Returns `true` when the rule is satisfied by the given outcomes.
+    ///
+    /// A target with no recorded outcome never satisfies the rule.
+    pub fn is_satisfied(&self, outcomes: &HashMap<String, StateOutcome>) -> bool {
+        match self.rule {
+            GateRule::AllSucceeded => self
+                .targets
+                .iter()
+                .all(|t| outcomes.get(t).is_some_and(|o| o.success)),
+            GateRule::AnySucceeded => self
+                .targets
+                .iter()
+                .any(|t| outcomes.get(t).is_some_and(|o| o.success)),
+            GateRule::AnyFailed => self
+                .targets
+                .iter()
+                .any(|t| outcomes.get(t).is_some_and(|o| !o.success)),
+            GateRule::AnyFailedChanged => self
+                .targets
+                .iter()
+                .any(|t| outcomes.get(t).is_some_and(|o| !o.success && o.changed)),
+            GateRule::AnyChanged => self
+                .targets
+                .iter()
+                .any(|t| outcomes.get(t).is_some_and(|o| o.changed)),
+        }
+    }
+}
+
+/// A state in its scheduled position, together with the conditional links that
+/// decide whether it should actually run once its predecessors have applied.
+#[derive(Debug, Clone, PartialEq)]
+pub struct PlannedState {
+    pub id: String,
+    /// Ids of states that must be applied before this one (ordering only).
+    pub predecessors: Vec<String>,
+    /// Conditional links; all must be satisfied for the state to run.
+    pub gates: Vec<Gate>,
+}
+
+impl PlannedState {
+    /// Returns `true` when every gate is satisfied by the given outcomes.
+    pub fn should_apply(&self, outcomes: &HashMap<String, StateOutcome>) -> bool {
+        self.gates.iter().all(|g| g.is_satisfied(outcomes))
+    }
+}
+
+/// Errors that can occur while planning state application.
+#[derive(Debug, Clone, PartialEq)]
+pub enum StatePlanError {
+    /// A set of states that form a dependency cycle and cannot be ordered.
+    Cycle(Vec<String>),
+    /// A dependency references a state id that is not part of the input.
+    UnknownState(String),
+}
+
+impl std::fmt::Display for StatePlanError {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        match self {
+            StatePlanError::Cycle(states) => {
+                write!(f, "dependency cycle among states: {}", states.join(", "))
+            }
+            StatePlanError::UnknownState(id) => write!(f, "dependency on unknown state id: {id}"),
+        }
+    }
+}
+
+impl std::error::Error for StatePlanError {}
+
+/// Topologically sorts the states, returning their ids in the order they
+/// should be applied.
+///
+/// Fails if the dependencies form a cycle or reference a state id that is not
+/// present in the input.
+pub fn topological_sort(states: &[State]) -> Result<Vec<String>, StatePlanError> {
+    build_graph(states).map(|(order, _)| order)
+}
+
+/// Topologically sorts the states and attaches the conditional links to each
+/// one, returning the full application plan in scheduling order.
+pub fn plan(states: &[State]) -> Result<Vec<PlannedState>, StatePlanError> {
+    let (order, predecessors) = build_graph(states)?;
+    let gates = gates_by_state(states);
+
+    Ok(order
+        .into_iter()
+        .map(|id| PlannedState {
+            id: id.clone(),
+            predecessors: predecessors.get(&id).cloned().unwrap_or_default(),
+            gates: gates.get(&id).cloned().unwrap_or_default(),
+        })
+        .collect())
+}
+
+/// Collects the conditional gate for each state.
+///
+/// A forward directive on a state gates that state itself on its targets; a
+/// reverse (`*_in`) directive on a state gates each of its targets on that
+/// state instead. `use`-style directives produce no gate.
+fn gates_by_state(states: &[State]) -> HashMap<String, Vec<Gate>> {
+    let mut gates: HashMap<String, Vec<Gate>> =
+        states.iter().map(|s| (s.id.clone(), Vec::new())).collect();
+
+    for state in states {
+        for dep in &state.dependency {
+            let rule = match rule_for(&dep.directive) {
+                Some(rule) => rule,
+                None => continue,
+            };
+            if is_reverse(&dep.directive) {
+                for target in &dep.target {
+                    if let Some(target_gates) = gates.get_mut(target) {
+                        target_gates.push(Gate {
+                            rule,
+                            targets: vec![state.id.clone()],
+                        });
+                    }
+                }
+            } else if let Some(self_gates) = gates.get_mut(&state.id) {
+                self_gates.push(Gate {
+                    rule,
+                    targets: dep.target.clone(),
+                });
+            }
+        }
+    }
+
+    gates
+}
+
+impl State {
+    /// Every state id referenced by this state's dependencies, regardless of
+    /// the directive used.
+    pub fn referenced_states(&self) -> Vec<String> {
+        self.dependency
+            .iter()
+            .flat_map(|d| d.target.iter().cloned())
+            .collect()
+    }
+}
+
+/// A topological ordering of state ids paired with the immediate predecessors
+/// of each state.
+type OrderAndPredecessors = (Vec<String>, HashMap<String, Vec<String>>);
+
+/// Builds the dependency graph and returns a topological ordering together
+/// with the immediate predecessors of each state.
+fn build_graph(states: &[State]) -> Result<OrderAndPredecessors, StatePlanError> {
+    let ids: HashSet<String> = states.iter().map(|s| s.id.clone()).collect();
+
+    let mut in_degree: HashMap<String, usize> =
+        states.iter().map(|s| (s.id.clone(), 0usize)).collect();
+    let mut adjacency: HashMap<String, Vec<String>> =
+        states.iter().map(|s| (s.id.clone(), Vec::new())).collect();
+    let mut predecessors: HashMap<String, Vec<String>> =
+        states.iter().map(|s| (s.id.clone(), Vec::new())).collect();
+
+    for state in states {
+        for dep in &state.dependency {
+            if !orders(&dep.directive) {
+                continue; // `use`-style directives do not impose an ordering
+            }
+            let reverse = is_reverse(&dep.directive);
+            for target in &dep.target {
+                if !ids.contains(target) {
+                    return Err(StatePlanError::UnknownState(target.clone()));
+                }
+                let (from, to) = if reverse {
+                    (state.id.clone(), target.clone())
+                } else {
+                    (target.clone(), state.id.clone())
+                };
+                adjacency
+                    .get_mut(&from)
+                    .expect("id must be part of the input")
+                    .push(to.clone());
+                *in_degree.get_mut(&to).expect("id must be part of the input") += 1;
+                predecessors
+                    .get_mut(&to)
+                    .expect("id must be part of the input")
+                    .push(from.clone());
+            }
+        }
+    }
+
+    // Deterministic start: sort the initially ready states.
+    let mut ready: Vec<String> = in_degree
+        .iter()
+        .filter(|(_, deg)| **deg == 0)
+        .map(|(id, _)| id.clone())
+        .collect();
+    ready.sort();
+    let mut queue: VecDeque<String> = ready.into_iter().collect();
+
+    let mut order: Vec<String> = Vec::with_capacity(states.len());
+    while let Some(id) = queue.pop_front() {
+        order.push(id.clone());
+        for next in adjacency.get(&id).into_iter().flatten().cloned() {
+            let deg = in_degree.get_mut(&next).expect("id must be part of the input");
+            *deg -= 1;
+            if *deg == 0 {
+                queue.push_back(next);
+            }
+        }
+    }
+
+    if order.len() != states.len() {
+        let remaining: Vec<String> = in_degree
+            .iter()
+            .filter(|(_, deg)| **deg > 0)
+            .map(|(id, _)| id.clone())
+            .collect();
+        return Err(StatePlanError::Cycle(remaining));
+    }
+
+    Ok((order, predecessors))
+}
+
+/// Returns `true` for the reverse (`*_in`) ordering directives, which declare
+/// that the current state is a prerequisite of the target rather than the
+/// other way around.
+fn is_reverse(d: &StateDirective) -> bool {
+    matches!(
+        d,
+        StateDirective::RequireIn
+            | StateDirective::WatchIn
+            | StateDirective::OnChangesIn
+            | StateDirective::OnFailIn
+            | StateDirective::OnFailChangesIn
+    )
+}
+
+/// Returns `true` when the directive imposes an ordering on the states.
+fn orders(d: &StateDirective) -> bool {
+    rule_for(d).is_some()
+}
+
+/// Maps a directive to the conditional gate it produces.
+///
+/// Returns `None` for `use`-style directives, which only share data and
+/// neither order the states nor condition their execution.
+fn rule_for(d: &StateDirective) -> Option<GateRule> {
+    match d {
+        StateDirective::Require | StateDirective::RequireIn => Some(GateRule::AllSucceeded),
+        StateDirective::RequireAny => Some(GateRule::AnySucceeded),
+        StateDirective::Watch
+        | StateDirective::WatchIn
+        | StateDirective::OnChanges
+        | StateDirective::OnChangesIn
+        | StateDirective::WatchAny
+        | StateDirective::OnChangesAny => Some(GateRule::AnyChanged),
+        StateDirective::OnFail | StateDirective::OnFailIn | StateDirective::OnFailAny => {
+            Some(GateRule::AnyFailed)
+        }
+        StateDirective::OnFailChanges | StateDirective::OnFailChangesIn => {
+            Some(GateRule::AnyFailedChanged)
+        }
+        StateDirective::Use | StateDirective::UseIn | StateDirective::UseAny => None,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{plan, topological_sort, GateRule, StateOutcome, StatePlanError};
+    use crate::sls::state::package::PackageState;
+    use crate::sls::state::{State, StateDependency, StateDirective, StateFunction};
+    use std::collections::HashMap;
+
+    fn dep(directive: StateDirective, targets: &[&str]) -> StateDependency {
+        StateDependency {
+            directive,
+            target: targets.iter().map(|t| t.to_string()).collect(),
+        }
+    }
+
+    fn state(id: &str, dependency: Vec<StateDependency>) -> State {
+        State {
+            id: String::from(id),
+            function: StateFunction::Package(PackageState::Installed {
+                name: String::from(id),
+            }),
+            dependency,
+        }
+    }
+
+    #[test]
+    fn require_orders_target_before_dependent() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::Require, &["b"])]),
+            state("b", vec![]),
+        ];
+        assert_eq!(
+            topological_sort(&states).unwrap(),
+            vec!["b".to_string(), "a".to_string()]
+        );
+    }
+
+    #[test]
+    fn require_in_orders_reverse() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::RequireIn, &["b"])]),
+            state("b", vec![]),
+        ];
+        assert_eq!(
+            topological_sort(&states).unwrap(),
+            vec!["a".to_string(), "b".to_string()]
+        );
+
+        let planned = plan(&states).unwrap();
+        let b = planned.iter().find(|p| p.id == "b").unwrap();
+        assert_eq!(b.predecessors, vec!["a".to_string()]);
+        assert_eq!(b.gates[0].rule, GateRule::AllSucceeded);
+        assert_eq!(b.gates[0].targets, vec!["a".to_string()]);
+
+        let a = planned.iter().find(|p| p.id == "a").unwrap();
+        assert!(a.gates.is_empty());
+    }
+
+    #[test]
+    fn use_is_neither_ordering_nor_gate() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::Use, &["b"])]),
+            state("b", vec![]),
+        ];
+        let a = plan(&states)
+            .unwrap()
+            .into_iter()
+            .find(|p| p.id == "a")
+            .unwrap();
+        assert!(a.predecessors.is_empty());
+        assert!(a.gates.is_empty());
+    }
+
+    #[test]
+    fn onfail_gate_depends_on_outcome() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::OnFail, &["b"])]),
+            state("b", vec![]),
+        ];
+        let a = plan(&states)
+            .unwrap()
+            .into_iter()
+            .find(|p| p.id == "a")
+            .unwrap();
+
+        assert!(!a.should_apply(&HashMap::new()));
+
+        let mut o = HashMap::new();
+        o.insert("b".to_string(), StateOutcome::failure_unchanged());
+        assert!(a.should_apply(&o));
+
+        o.insert("b".to_string(), StateOutcome::success_changed());
+        assert!(!a.should_apply(&o));
+    }
+
+    #[test]
+    fn onfailchanges_requires_changed_failure() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::OnFailChanges, &["b"])]),
+            state("b", vec![]),
+        ];
+        let a = plan(&states)
+            .unwrap()
+            .into_iter()
+            .find(|p| p.id == "a")
+            .unwrap();
+
+        let mut o = HashMap::new();
+        o.insert("b".to_string(), StateOutcome::failure_changed());
+        assert!(a.should_apply(&o));
+
+        o.insert("b".to_string(), StateOutcome::failure_unchanged());
+        assert!(!a.should_apply(&o));
+    }
+
+    #[test]
+    fn require_any_runs_when_one_target_succeeds() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::RequireAny, &["b", "c"])]),
+            state("b", vec![]),
+            state("c", vec![]),
+        ];
+        let a = plan(&states)
+            .unwrap()
+            .into_iter()
+            .find(|p| p.id == "a")
+            .unwrap();
+
+        let mut o = HashMap::new();
+        o.insert("b".to_string(), StateOutcome::failure_unchanged());
+        o.insert("c".to_string(), StateOutcome::success_unchanged());
+        assert!(a.should_apply(&o));
+
+        o.insert("c".to_string(), StateOutcome::failure_unchanged());
+        assert!(!a.should_apply(&o));
+    }
+
+    #[test]
+    fn detects_cycle() {
+        let states = vec![
+            state("a", vec![dep(StateDirective::Require, &["b"])]),
+            state("b", vec![dep(StateDirective::Require, &["a"])]),
+        ];
+        assert!(matches!(
+            topological_sort(&states),
+            Err(StatePlanError::Cycle(_))
+        ));
+    }
+
+    #[test]
+    fn detects_unknown_target() {
+        let states = vec![state("a", vec![dep(StateDirective::Require, &["missing"])])];
+        assert!(matches!(
+            topological_sort(&states),
+            Err(StatePlanError::UnknownState(id)) if id == "missing"
+        ));
+    }
+}
diff --git a/src/sls/state/mod.rs b/src/sls/state/mod.rs
index 6cd785a..7cc8f60 100644
--- a/src/sls/state/mod.rs
+++ b/src/sls/state/mod.rs
@@ -11,8 +11,10 @@ pub mod package;
 pub mod command;
 pub mod user;
 pub mod group;
+pub mod generic_implementations;
 
 pub struct State {
+    pub id: String,
     pub function: StateFunction,
     pub dependency: Vec<StateDependency>,
 }
@@ -26,6 +28,27 @@ pub enum StateFunction {
     Group (GroupState),
 }
 
-pub enum StateDependency {
+pub struct StateDependency {
+    pub directive: StateDirective,
+    pub target: Vec<String>,
+}
 
+pub enum StateDirective {
+    Require,
+    Watch,
+    OnChanges,
+    OnFail,
+    OnFailChanges,
+    Use,
+    RequireIn,
+    WatchIn,
+    OnChangesIn,
+    OnFailIn,
+    OnFailChangesIn,
+    UseIn,
+    RequireAny,
+    WatchAny,
+    OnChangesAny,
+    OnFailAny,
+    UseAny,
 }
\ No newline at end of file