diff --git a/local_install.go b/local_install.go
index 1efc1866..478c7fbd 100644
--- a/local_install.go
+++ b/local_install.go
@@ -94,7 +94,7 @@ func installLocalPKGBUILD(
 
 	opService := sync.NewOperationService(ctx, dbExecutor, run)
 	multiErr := &multierror.MultiError{}
-	targets := graph.TopoSortedLayerMap(func(name string, ii *dep.InstallInfo) error {
+	targets := graph.TopoSortedLayers(func(name string, ii *dep.InstallInfo) error {
 		if ii.Source == dep.Missing {
 			multiErr.Add(fmt.Errorf("%w: %s %s", ErrPackagesNotFound, name, ii.Version))
 		}
diff --git a/pkg/cmd/graph/main.go b/pkg/cmd/graph/main.go
index 41540646..486fe410 100644
--- a/pkg/cmd/graph/main.go
+++ b/pkg/cmd/graph/main.go
@@ -76,7 +76,7 @@ func graphPackage(
 	}
 
 	fmt.Fprintln(os.Stdout, graph.String())
-	fmt.Fprintln(os.Stdout, "\nlayers map\n", graph.TopoSortedLayerMap(nil))
+	fmt.Fprintln(os.Stdout, "\nlayers map\n", graph.TopoSortedLayers(nil))
 
 	return nil
 }
diff --git a/pkg/dep/dep_graph.go b/pkg/dep/dep_graph.go
index 1009673e..5dbac475 100644
--- a/pkg/dep/dep_graph.go
+++ b/pkg/dep/dep_graph.go
@@ -227,7 +227,7 @@ func (g *Grapher) addAurPkgProvides(pkg *aurc.Pkg, graph *topo.Graph[string, *In
 	for i := range pkg.Provides {
 		depName, mod, version := splitDep(pkg.Provides[i])
 		g.logger.Debugln(pkg.String() + " provides: " + depName)
-		graph.Provides(depName, &alpm.Depend{
+		graph.AddProvides(depName, &alpm.Depend{
 			Name:    depName,
 			Version: version,
 			Mod:     aurDepModToAlpmDep(mod),
@@ -319,7 +319,7 @@ func (g *Grapher) GraphSyncPkg(ctx context.Context,
 	graph.AddNode(pkg.Name())
 	_ = pkg.Provides().ForEach(func(p *alpm.Depend) error {
 		g.logger.Debugln(pkg.Name() + " provides: " + p.String())
-		graph.Provides(p.Name, p, pkg.Name())
+		graph.AddProvides(p.Name, p, pkg.Name())
 		return nil
 	})
 
@@ -588,7 +588,7 @@ func (g *Grapher) addNodes(
 	// Check if in graph already
 	for _, depString := range targetsToFind.ToSlice() {
 		depName, _, _ := splitDep(depString)
-		if !graph.Exists(depName) && !graph.ProvidesExists(depName) {
+		if !graph.Exists(depName) && !graph.HasProvides(depName) {
 			continue
 		}
 
@@ -600,7 +600,7 @@ func (g *Grapher) addNodes(
 			targetsToFind.Remove(depString)
 		}
 
-		if p := graph.GetProviderNode(depName); p != nil {
+		if p := graph.GetProviderInfo(depName); p != nil {
 			if provideSatisfies(p.String(), depString, p.Version) {
 				if err := graph.DependOn(p.Provider, parentPkgName); err != nil {
 					g.logger.Warnln(p.Provider, parentPkgName, err)
diff --git a/pkg/dep/dep_graph_test.go b/pkg/dep/dep_graph_test.go
index 1a3025ae..befbe6e2 100644
--- a/pkg/dep/dep_graph_test.go
+++ b/pkg/dep/dep_graph_test.go
@@ -205,7 +205,7 @@ func TestGrapher_GraphFromTargets_jellyfin(t *testing.T) {
 				text.NewLogger(io.Discard, io.Discard, &os.File{}, true, "test"))
 			got, err := g.GraphFromTargets(context.Background(), nil, tt.args.targets)
 			require.NoError(t, err)
-			layers := got.TopoSortedLayerMap(nil)
+			layers := got.TopoSortedLayers(nil)
 			require.EqualValues(t, tt.want, layers, layers)
 		})
 	}
@@ -319,7 +319,7 @@ func TestGrapher_GraphProvides_androidsdk(t *testing.T) {
 				text.NewLogger(io.Discard, io.Discard, &os.File{}, true, "test"))
 			got, err := g.GraphFromTargets(context.Background(), nil, tt.args.targets)
 			require.NoError(t, err)
-			layers := got.TopoSortedLayerMap(nil)
+			layers := got.TopoSortedLayers(nil)
 			require.EqualValues(t, tt.want, layers, layers)
 		})
 	}
@@ -521,7 +521,7 @@ func TestGrapher_GraphFromAUR_Deps_ceph_bin(t *testing.T) {
 				text.NewLogger(io.Discard, io.Discard, &os.File{}, true, "test"))
 			got, err := g.GraphFromTargets(context.Background(), nil, tt.targets)
 			require.NoError(t, err)
-			layers := got.TopoSortedLayerMap(nil)
+			layers := got.TopoSortedLayers(nil)
 			require.EqualValues(t, tt.wantLayers, layers, layers)
 		})
 	}
@@ -666,7 +666,7 @@ func TestGrapher_GraphFromAUR_Deps_gourou(t *testing.T) {
 				text.NewLogger(io.Discard, io.Discard, &os.File{}, true, "test"))
 			got, err := g.GraphFromTargets(context.Background(), nil, tt.targets)
 			require.NoError(t, err)
-			layers := got.TopoSortedLayerMap(nil)
+			layers := got.TopoSortedLayers(nil)
 			require.EqualValues(t, tt.wantLayers, layers, layers)
 		})
 	}
@@ -804,7 +804,7 @@ func TestGrapher_GraphFromTargets_ReinstalledDeps(t *testing.T) {
 				text.NewLogger(io.Discard, io.Discard, &os.File{}, true, "test"))
 			got, err := g.GraphFromTargets(context.Background(), nil, tt.targets)
 			require.NoError(t, err)
-			layers := got.TopoSortedLayerMap(nil)
+			layers := got.TopoSortedLayers(nil)
 			require.EqualValues(t, tt.wantLayers, layers, layers)
 		})
 	}
diff --git a/pkg/dep/topo/dep.go b/pkg/dep/topo/dep.go
index 30a8e392..65944980 100644
--- a/pkg/dep/topo/dep.go
+++ b/pkg/dep/topo/dep.go
@@ -9,11 +9,21 @@ import (
 )
 
 type (
-	NodeSet[T comparable]     map[T]bool
+	// NodeSet is a set of nodes represented as a map for O(1) membership checks.
+	// The boolean value is not meaningful; presence of the key indicates membership.
+	NodeSet[T comparable] map[T]bool
+
+	// ProvidesMap maps a "provides" key (an alias/satisfier name) to information about the
+	// node that provides it.
 	ProvidesMap[T comparable] map[T]*DependencyInfo[T]
-	DepMap[T comparable]      map[T]NodeSet[T]
+
+	// DepMap maps a node to a set of nodes. In Graph this is used for adjacency:
+	// - dependencies: node -> its direct dependencies
+	// - dependents:   node -> its direct dependents
+	DepMap[T comparable] map[T]NodeSet[T]
 )
 
+// Slice returns the set contents as a slice in unspecified order.
 func (n NodeSet[T]) Slice() []T {
 	var slice []T
 
@@ -24,19 +34,29 @@ func (n NodeSet[T]) Slice() []T {
 	return slice
 }
 
+// NodeInfo carries optional rendering metadata (Color/Background) plus the node's value.
 type NodeInfo[V any] struct {
 	Color      string
 	Background string
 	Value      V
 }
 
+// DependencyInfo describes which node provides a given dependency/satisfier, along with the
+// original dependency metadata (alpm.Depend).
 type DependencyInfo[T comparable] struct {
 	Provider T
 	alpm.Depend
 }
 
+// CheckFn is a callback used by traversal helpers. It receives the node id plus the node's value.
 type CheckFn[T comparable, V any] func(T, V) error
 
+// Graph is a directed dependency graph.
+//
+// Edge direction:
+// - An edge is added with DependOn(child, parent), meaning "child depends on parent".
+// - Internally, dependencies maps child -> parents (direct dependencies).
+// - Internally, dependents maps parent -> children (direct dependents).
 type Graph[T comparable, V any] struct {
 	nodes NodeSet[T]
 
@@ -52,6 +72,7 @@ type Graph[T comparable, V any] struct {
 	dependents DepMap[T]
 }
 
+// New returns an empty Graph.
 func New[T comparable, V any]() *Graph[T, V] {
 	return &Graph[T, V]{
 		nodes:        make(NodeSet[T]),
@@ -62,40 +83,57 @@ func New[T comparable, V any]() *Graph[T, V] {
 	}
 }
 
+// Len returns the number of nodes currently present in the graph.
 func (g *Graph[T, V]) Len() int {
 	return len(g.nodes)
 }
 
+// Exists reports whether node exists in the graph's node set.
 func (g *Graph[T, V]) Exists(node T) bool {
 	_, ok := g.nodes[node]
 
 	return ok
 }
 
+// AddNode adds node to the graph. It is safe to call multiple times.
 func (g *Graph[T, V]) AddNode(node T) {
 	g.nodes[node] = true
 }
 
-func (g *Graph[T, V]) ProvidesExists(provides T) bool {
+// HasProvides reports whether the given provides key is registered.
+func (g *Graph[T, V]) HasProvides(provides T) bool {
 	_, ok := g.provides[provides]
 
 	return ok
 }
 
-func (g *Graph[T, V]) GetProviderNode(provides T) *DependencyInfo[T] {
+// GetProviderInfo returns the dependency info for a provider.
+func (g *Graph[T, V]) GetProviderInfo(provides T) *DependencyInfo[T] {
 	return g.provides[provides]
 }
 
-func (g *Graph[T, V]) Provides(provides T, depInfo *alpm.Depend, node T) {
+// AddProvides registers that node provides the given provides key.
+//
+// Note: despite the "Add" name, this is a single mapping; calling it again with the same
+// provides key overwrites the previous entry.
+func (g *Graph[T, V]) AddProvides(provides T, depInfo *alpm.Depend, node T) {
 	g.provides[provides] = &DependencyInfo[T]{
 		Provider: node,
 		Depend:   *depInfo,
 	}
 }
 
+// ForEach calls f for every node in the graph.
+//
+// The value passed to f is the node's NodeInfo.Value if set via SetNodeInfo; otherwise it is
+// the zero value of V.
 func (g *Graph[T, V]) ForEach(f CheckFn[T, V]) error {
 	for node := range g.nodes {
-		if err := f(node, g.nodeInfo[node].Value); err != nil {
+		var v V
+		if info := g.nodeInfo[node]; info != nil {
+			v = info.Value
+		}
+		if err := f(node, v); err != nil {
 			return err
 		}
 	}
@@ -103,14 +141,21 @@ func (g *Graph[T, V]) ForEach(f CheckFn[T, V]) error {
 	return nil
 }
 
+// SetNodeInfo sets metadata and value for node. Node does not need to already exist in the graph.
 func (g *Graph[T, V]) SetNodeInfo(node T, nodeInfo *NodeInfo[V]) {
 	g.nodeInfo[node] = nodeInfo
 }
 
+// GetNodeInfo returns metadata/value for node, or nil if none was set.
 func (g *Graph[T, V]) GetNodeInfo(node T) *NodeInfo[V] {
 	return g.nodeInfo[node]
 }
 
+// DependOn adds an edge meaning "child depends on parent".
+//
+// This ensures both nodes exist in the graph and rejects:
+// - self edges (ErrSelfReferential)
+// - edges that would introduce a cycle (ErrCircular)
 func (g *Graph[T, V]) DependOn(child, parent T) error {
 	if child == parent {
 		return ErrSelfReferential
@@ -124,12 +169,16 @@ func (g *Graph[T, V]) DependOn(child, parent T) error {
 	g.AddNode(child)
 
 	// Add edges.
-	g.dependents.addNodeToNodeset(parent, child)
-	g.dependencies.addNodeToNodeset(child, parent)
+	g.dependents.add(parent, child)
+	g.dependencies.add(child, parent)
 
 	return nil
 }
 
+// String renders the graph in GraphViz DOT format.
+//
+// Nodes are emitted as `"node"` entries with optional color metadata from NodeInfo.
+// Edges are emitted in the direction: dependent -> dependency (child -> parent).
 func (g *Graph[T, V]) String() string {
 	var sb strings.Builder
 
@@ -161,6 +210,7 @@ func (g *Graph[T, V]) String() string {
 	return sb.String()
 }
 
+// DependsOn reports whether child depends (transitively) on parent.
 func (g *Graph[T, V]) DependsOn(child, parent T) bool {
 	deps := g.Dependencies(child)
 	_, ok := deps[parent]
@@ -168,9 +218,10 @@ func (g *Graph[T, V]) DependsOn(child, parent T) bool {
 	return ok
 }
 
-func (g *Graph[T, V]) HasDependent(parent, child T) bool {
+// HasDependent reports whether parent has dependent as a (transitive) dependent.
+func (g *Graph[T, V]) HasDependent(parent, dependent T) bool {
 	deps := g.Dependents(parent)
-	_, ok := deps[child]
+	_, ok := deps[dependent]
 
 	return ok
 }
@@ -193,8 +244,18 @@ func (g *Graph[T, V]) leavesMap() map[T]V {
 	return leaves
 }
 
-// TopoSortedLayerMap returns a slice of all of the graph nodes in topological sort order with their node info.
-func (g *Graph[T, V]) TopoSortedLayerMap(checkFn CheckFn[T, V]) []map[T]V {
+// TopoSortedLayers returns a slice of all of the graph nodes in topological sort order with their node info.
+//
+// The returned slice is layered: each element is a "layer" of nodes that have no remaining
+// dependencies at that stage of the process.
+//
+// Practical meaning with this graph's edge direction (DependOn(child, parent)):
+// - Earlier layers contain nodes with fewer/zero dependencies (i.e. dependencies-first order).
+// - A node appears only after all of its dependencies have appeared in earlier layers.
+//
+// If checkFn is non-nil, it is called once per node when it is emitted in a layer. Returning an
+// error causes TopoSortedLayers to return nil.
+func (g *Graph[T, V]) TopoSortedLayers(checkFn CheckFn[T, V]) []map[T]V {
 	layers := []map[T]V{}
 
 	// Copy the graph
@@ -222,7 +283,7 @@ func (g *Graph[T, V]) TopoSortedLayerMap(checkFn CheckFn[T, V]) []map[T]V {
 }
 
 // returns if it was the last
-func (dm DepMap[T]) removeFromDepmap(key, node T) bool {
+func (dm DepMap[T]) remove(key, node T) bool {
 	if nodes := dm[key]; len(nodes) == 1 {
 		// The only element in the nodeset must be `node`, so we
 		// can delete the entry entirely.
@@ -238,11 +299,14 @@ func (dm DepMap[T]) removeFromDepmap(key, node T) bool {
 // Prune removes the node,
 // its dependencies if there are no other dependents
 // and its dependents
+//
+// It returns the list of nodes that were removed (including node). The returned order is based
+// on recursive traversal and is not guaranteed to be stable.
 func (g *Graph[T, V]) Prune(node T) []T {
 	pruned := []T{node}
 	// Remove edges from things that depend on `node`.
 	for dependent := range g.dependents[node] {
-		last := g.dependencies.removeFromDepmap(dependent, node)
+		last := g.dependencies.remove(dependent, node)
 		if last {
 			pruned = append(pruned, g.Prune(dependent)...)
 		}
@@ -252,7 +316,7 @@ func (g *Graph[T, V]) Prune(node T) []T {
 
 	// Remove all edges from node to the things it depends on.
 	for dependency := range g.dependencies[node] {
-		last := g.dependents.removeFromDepmap(dependency, node)
+		last := g.dependents.remove(dependency, node)
 		if last {
 			pruned = append(pruned, g.Prune(dependency)...)
 		}
@@ -268,14 +332,14 @@ func (g *Graph[T, V]) Prune(node T) []T {
 func (g *Graph[T, V]) remove(node T) {
 	// Remove edges from things that depend on `node`.
 	for dependent := range g.dependents[node] {
-		g.dependencies.removeFromDepmap(dependent, node)
+		g.dependencies.remove(dependent, node)
 	}
 
 	delete(g.dependents, node)
 
 	// Remove all edges from node to the things it depends on.
 	for dependency := range g.dependencies[node] {
-		g.dependents.removeFromDepmap(dependency, node)
+		g.dependents.remove(dependency, node)
 	}
 
 	delete(g.dependencies, node)
@@ -284,19 +348,27 @@ func (g *Graph[T, V]) remove(node T) {
 	delete(g.nodes, node)
 }
 
+// Dependencies returns all transitive dependencies of child (excluding child itself).
+// The returned set is nil if child is not present in the graph.
 func (g *Graph[T, V]) Dependencies(child T) NodeSet[T] {
 	return g.buildTransitive(child, g.ImmediateDependencies)
 }
 
+// ImmediateDependencies returns the direct dependencies of node.
+// The returned set is nil if node has no direct dependencies (or is not present).
 func (g *Graph[T, V]) ImmediateDependencies(node T) NodeSet[T] {
 	return g.dependencies[node]
 }
 
+// Dependents returns all transitive dependents of parent (excluding parent itself).
+// The returned set is nil if parent is not present in the graph.
 func (g *Graph[T, V]) Dependents(parent T) NodeSet[T] {
-	return g.buildTransitive(parent, g.immediateDependents)
+	return g.buildTransitive(parent, g.ImmediateDependents)
 }
 
-func (g *Graph[T, V]) immediateDependents(node T) NodeSet[T] {
+// ImmediateDependents returns the direct dependents of node.
+// The returned set is nil if node has no direct dependents (or is not present).
+func (g *Graph[T, V]) ImmediateDependents(node T) NodeSet[T] {
 	return g.dependents[node]
 }
 
@@ -359,7 +431,7 @@ func (dm DepMap[T]) copy() DepMap[T] {
 	return out
 }
 
-func (dm DepMap[T]) addNodeToNodeset(key, node T) {
+func (dm DepMap[T]) add(key, node T) {
 	nodes, ok := dm[key]
 	if !ok {
 		nodes = make(NodeSet[T])
diff --git a/pkg/dep/topo/dep_test.go b/pkg/dep/topo/dep_test.go
new file mode 100644
index 00000000..7b46d13f
--- /dev/null
+++ b/pkg/dep/topo/dep_test.go
@@ -0,0 +1,79 @@
+package topo
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestGraph_DependenciesAndDependents_Direct(t *testing.T) {
+	g := New[string, struct{}]()
+
+	// yay depends on go
+	require.NoError(t, g.DependOn("yay", "go"))
+
+	// Dependencies("yay") => {"go"}
+	depsYay := g.Dependencies("yay")
+	require.NotNil(t, depsYay)
+	require.Len(t, depsYay, 1)
+	require.True(t, depsYay["go"])
+
+	// Dependencies("go") => {} (empty set, because "go" is in the graph but has no deps)
+	depsGo := g.Dependencies("go")
+	require.NotNil(t, depsGo)
+	require.Len(t, depsGo, 0)
+
+	// Dependents("go") => {"yay"}
+	dependentsGo := g.Dependents("go")
+	require.NotNil(t, dependentsGo)
+	require.Len(t, dependentsGo, 1)
+	require.True(t, dependentsGo["yay"])
+
+	// Dependents("yay") => {} (empty set, because nothing depends on yay)
+	dependentsYay := g.Dependents("yay")
+	require.NotNil(t, dependentsYay)
+	require.Len(t, dependentsYay, 0)
+}
+
+func TestGraph_DependenciesAndDependents_Transitive(t *testing.T) {
+	g := New[string, struct{}]()
+
+	// yay depends on go; foo depends on yay
+	require.NoError(t, g.DependOn("yay", "go"))
+	require.NoError(t, g.DependOn("foo", "yay"))
+
+	// Dependencies("foo") => {"yay", "go"}
+	depsFoo := g.Dependencies("foo")
+	require.NotNil(t, depsFoo)
+	require.Len(t, depsFoo, 2)
+	require.True(t, depsFoo["yay"])
+	require.True(t, depsFoo["go"])
+
+	// Dependents("go") => {"yay", "foo"} (transitive)
+	dependentsGo := g.Dependents("go")
+	require.NotNil(t, dependentsGo)
+	require.Len(t, dependentsGo, 2)
+	require.True(t, dependentsGo["yay"])
+	require.True(t, dependentsGo["foo"])
+
+	// Dependents("yay") => {"foo"}
+	dependentsYay := g.Dependents("yay")
+	require.NotNil(t, dependentsYay)
+	require.Len(t, dependentsYay, 1)
+	require.True(t, dependentsYay["foo"])
+}
+
+func TestGraph_DependenciesAndDependents_MissingNodeReturnsNil(t *testing.T) {
+	g := New[string, struct{}]()
+
+	// For nodes not present in the graph, transitive queries return nil.
+	require.Nil(t, g.Dependencies("missing"))
+	require.Nil(t, g.Dependents("missing"))
+
+	// Adding edges adds nodes; existing nodes with no deps/dependents return an empty set (non-nil).
+	require.NoError(t, g.DependOn("yay", "go"))
+	require.NotNil(t, g.Dependencies("go"))
+	require.Len(t, g.Dependencies("go"), 0)
+	require.NotNil(t, g.Dependents("yay"))
+	require.Len(t, g.Dependents("yay"), 0)
+}
diff --git a/pkg/dep/topo/errors.go b/pkg/dep/topo/errors.go
index 3a2e4a05..a50155b7 100644
--- a/pkg/dep/topo/errors.go
+++ b/pkg/dep/topo/errors.go
@@ -3,7 +3,13 @@ package topo
 import "errors"
 
 var (
-	ErrSelfReferential  = errors.New(" self-referential dependencies not allowed")
+	// ErrSelfReferential is returned when attempting to create an edge where a node depends on itself.
+	ErrSelfReferential = errors.New(" self-referential dependencies not allowed")
+
+	// ErrConflictingAlias is reserved for when a "provides" alias is defined more than once.
+	// Note: current Graph APIs overwrite provides entries; this error is not currently returned.
 	ErrConflictingAlias = errors.New(" alias already defined")
-	ErrCircular         = errors.New(" circular dependencies not allowed")
+
+	// ErrCircular is returned when attempting to create an edge that would introduce a cycle.
+	ErrCircular = errors.New(" circular dependencies not allowed")
 )
diff --git a/sync.go b/sync.go
index 53a50137..b9d95845 100644
--- a/sync.go
+++ b/sync.go
@@ -76,7 +76,7 @@ func syncInstall(ctx context.Context,
 
 	opService := sync.NewOperationService(ctx, dbExecutor, run)
 	multiErr := &multierror.MultiError{}
-	targets := graph.TopoSortedLayerMap(func(s string, ii *dep.InstallInfo) error {
+	targets := graph.TopoSortedLayers(func(s string, ii *dep.InstallInfo) error {
 		if ii.Source == dep.Missing {
 			multiErr.Add(fmt.Errorf("%w: %s %s", ErrPackagesNotFound, s, ii.Version))
 		}