diff --git a/src/sequencer/project-sequences.ts b/src/sequencer/project-sequences.ts
new file mode 100644
index 00000000..9ebdcdb9
--- /dev/null
+++ b/src/sequencer/project-sequences.ts
@@ -0,0 +1,125 @@
+import { createOpaqueId } from "../core/ids";
+
+import {
+  cloneSequenceStep,
+  type SequenceStep
+} from "./project-sequence-steps";
+
+export interface ProjectSequence {
+  id: string;
+  title: string;
+  steps: SequenceStep[];
+}
+
+export interface ProjectSequenceLibrary {
+  sequences: Record<string, ProjectSequence>;
+}
+
+function normalizeProjectSequenceTitle(title: string | undefined): string {
+  const normalizedTitle = title?.trim() ?? "";
+
+  if (normalizedTitle.length === 0) {
+    throw new Error("Project sequence title must be non-empty.");
+  }
+
+  return normalizedTitle;
+}
+
+export function createEmptyProjectSequenceLibrary(): ProjectSequenceLibrary {
+  return {
+    sequences: {}
+  };
+}
+
+export function createProjectSequence(
+  overrides: Partial<Pick<ProjectSequence, "id" | "title">> & {
+    steps?: SequenceStep[];
+  } = {}
+): ProjectSequence {
+  return {
+    id: overrides.id ?? createOpaqueId("sequence"),
+    title: normalizeProjectSequenceTitle(overrides.title ?? "Sequence"),
+    steps: overrides.steps?.map(cloneSequenceStep) ?? []
+  };
+}
+
+export function cloneProjectSequence(
+  sequence: ProjectSequence
+): ProjectSequence {
+  return {
+    id: sequence.id,
+    title: sequence.title,
+    steps: sequence.steps.map(cloneSequenceStep)
+  };
+}
+
+export function cloneProjectSequenceLibrary(
+  library: ProjectSequenceLibrary
+): ProjectSequenceLibrary {
+  return {
+    sequences: Object.fromEntries(
+      Object.entries(library.sequences).map(([sequenceId, sequence]) => [
+        sequenceId,
+        cloneProjectSequence(sequence)
+      ])
+    )
+  };
+}
+
+export function areProjectSequencesEqual(
+  left: ProjectSequence,
+  right: ProjectSequence
+): boolean {
+  if (
+    left.id !== right.id ||
+    left.title !== right.title ||
+    left.steps.length !== right.steps.length
+  ) {
+    return false;
+  }
+
+  return left.steps.every((step, index) => {
+    const rightStep = right.steps[index];
+
+    if (rightStep === undefined) {
+      return false;
+    }
+
+    return JSON.stringify(step) === JSON.stringify(rightStep);
+  });
+}
+
+export function areProjectSequenceLibrariesEqual(
+  left: ProjectSequenceLibrary,
+  right: ProjectSequenceLibrary
+): boolean {
+  const leftIds = Object.keys(left.sequences);
+  const rightIds = Object.keys(right.sequences);
+
+  if (leftIds.length !== rightIds.length) {
+    return false;
+  }
+
+  return leftIds.every((sequenceId) => {
+    const rightSequence = right.sequences[sequenceId];
+
+    return (
+      rightSequence !== undefined &&
+      areProjectSequencesEqual(left.sequences[sequenceId]!, rightSequence)
+    );
+  });
+}
+
+export function getProjectSequences(
+  library: ProjectSequenceLibrary
+): ProjectSequence[] {
+  return Object.values(library.sequences).sort((left, right) => {
+    const titleCompare = left.title.localeCompare(right.title);
+
+    if (titleCompare !== 0) {
+      return titleCompare;
+    }
+
+    return left.id.localeCompare(right.id);
+  });
+}