diff --git a/canvas/src/components/canvas/__tests__/useOrgDeployState.test.ts b/canvas/src/components/canvas/__tests__/useOrgDeployState.test.ts
new file mode 100644
index 00000000..421fcd42
--- /dev/null
+++ b/canvas/src/components/canvas/__tests__/useOrgDeployState.test.ts
@@ -0,0 +1,311 @@
+/**
+ * Unit tests for buildDeployMap — the pure tree-traversal core of
+ * useOrgDeployState.
+ *
+ * What is tested here:
+ *   - Root / leaf identification via parent-chain walk
+ *   - isDeployingRoot: true when any descendant is "provisioning"
+ *   - isActivelyProvisioning: true only for the node itself in that state
+ *   - isLockedChild: true for non-root nodes in a deploying tree
+ *   - isLockedChild: also true for nodes in deletingIds (even if not deploying)
+ *   - descendantProvisioningCount: non-zero only on root nodes
+ *   - Performance contract: O(n) single-pass walk — tested by verifying
+ *     correctness across 50-node trees (n=50, all cases above)
+ *
+ * What is NOT tested here (hook integration — appropriate for E2E):
+ *   - The useMemo / Zustand subscription wiring
+ *   - React Flow integration (flowToScreenPosition, getInternalNode)
+ *
+ * Issue: #2071 (Canvas test gaps follow-up).
+ */
+import { describe, expect, it } from "vitest";
+import { buildDeployMap, type OrgDeployState } from "../useOrgDeployState";
+
+// ── Helpers ──────────────────────────────────────────────────────────────────
+
+type Projection = { id: string; parentId: string | null; status: string };
+
+function proj(
+  id: string,
+  parentId: string | null,
+  status: string,
+): Projection {
+  return { id, parentId, status };
+}
+
+/** Unchecked cast — test helpers aren't production code paths. */
+function m(
+  ps: Projection[],
+  deletingIds: string[] = [],
+): Map<string, OrgDeployState> {
+  return buildDeployMap(ps, new Set(deletingIds));
+}
+
+function s(
+  map: Map<string, OrgDeployState>,
+  id: string,
+): OrgDeployState {
+  const got = map.get(id);
+  if (!got) throw new Error(`no entry for id=${id}`);
+  return got;
+}
+
+// ── Empty / trivial ───────────────────────────────────────────────────────────
+
+describe("buildDeployMap — empty", () => {
+  it("returns empty map for empty projections", () => {
+    expect(m([]).size).toBe(0);
+  });
+});
+
+// ── Single node ─────────────────────────────────────────────────────────────
+
+describe("buildDeployMap — single node", () => {
+  it("isolated node is its own root and not deploying", () => {
+    const map = m([proj("a", null, "online")]);
+    expect(s(map, "a")).toEqual({
+      isActivelyProvisioning: false,
+      isDeployingRoot: false,
+      isLockedChild: false,
+      descendantProvisioningCount: 0,
+    });
+  });
+
+  it("isolated provisioning node is deploying root", () => {
+    const map = m([proj("a", null, "provisioning")]);
+    expect(s(map, "a")).toEqual({
+      isActivelyProvisioning: true,
+      isDeployingRoot: true,
+      isLockedChild: false,
+      descendantProvisioningCount: 1,
+    });
+  });
+});
+
+// ── Parent / child chains ─────────────────────────────────────────────────────
+
+describe("buildDeployMap — parent / child chains", () => {
+  it("root with online child: root is not deploying, child is not locked", () => {
+    // A ──► B
+    const map = m([
+      proj("A", null, "online"),
+      proj("B", "A", "online"),
+    ]);
+    expect(s(map, "A")).toMatchObject({ isDeployingRoot: false, isLockedChild: false });
+    expect(s(map, "B")).toMatchObject({ isDeployingRoot: false, isLockedChild: false });
+  });
+
+  it("root with provisioning child: root is deploying, child is locked", () => {
+    // A ──► B (B is provisioning)
+    const map = m([
+      proj("A", null, "online"),
+      proj("B", "A", "provisioning"),
+    ]);
+    expect(s(map, "A")).toMatchObject({ isDeployingRoot: true, descendantProvisioningCount: 1 });
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true, isActivelyProvisioning: true });
+  });
+
+  it("provisioning root with online child: root is deploying, child is locked", () => {
+    // A (provisioning) ──► B (online)
+    const map = m([
+      proj("A", null, "provisioning"),
+      proj("B", "A", "online"),
+    ]);
+    expect(s(map, "A")).toMatchObject({ isDeployingRoot: true, isActivelyProvisioning: true });
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true, isActivelyProvisioning: false });
+  });
+
+  it("grandchild inherits deploy lock through intermediate online node", () => {
+    // A ──► B ──► C  (A is provisioning)
+    const map = m([
+      proj("A", null, "provisioning"),
+      proj("B", "A", "online"),
+      proj("C", "B", "online"),
+    ]);
+    // B and C are both non-root descendants of the deploying root
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true });
+    expect(s(map, "C")).toMatchObject({ isLockedChild: true });
+    expect(s(map, "A")).toMatchObject({ isDeployingRoot: true, descendantProvisioningCount: 1 });
+  });
+
+  it("deep chain: only the topmost node with a null parent counts as root", () => {
+    // A ──► B ──► C ──► D  (A is provisioning)
+    const map = m([
+      proj("A", null, "provisioning"),
+      proj("B", "A", "online"),
+      proj("C", "B", "online"),
+      proj("D", "C", "online"),
+    ]);
+    const roots = ["A", "B", "C", "D"].filter((id) => s(map, id).isDeployingRoot);
+    expect(roots).toEqual(["A"]);
+  });
+});
+
+// ── Sibling branching ─────────────────────────────────────────────────────────
+
+describe("buildDeployMap — sibling branching", () => {
+  it("parent with multiple children: deploying root propagates to all children", () => {
+    //         A (provisioning)
+    //        / \
+    //       B   C
+    const map = m([
+      proj("A", null, "provisioning"),
+      proj("B", "A", "online"),
+      proj("C", "A", "online"),
+    ]);
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true });
+    expect(s(map, "C")).toMatchObject({ isLockedChild: true });
+    expect(s(map, "A")).toMatchObject({ descendantProvisioningCount: 1 });
+  });
+
+  it("only one provisioning descendant marks the root as deploying", () => {
+    //           A
+    //         / | \
+    //        B  C  D   (only C is provisioning)
+    const map = m([
+      proj("A", null, "online"),
+      proj("B", "A", "online"),
+      proj("C", "A", "provisioning"),
+      proj("D", "A", "online"),
+    ]);
+    expect(s(map, "A")).toMatchObject({ isDeployingRoot: true, descendantProvisioningCount: 1 });
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true });
+    expect(s(map, "C")).toMatchObject({ isLockedChild: true, isActivelyProvisioning: true });
+    expect(s(map, "D")).toMatchObject({ isLockedChild: true });
+  });
+
+  it("two provisioning siblings: count reflects both", () => {
+    const map = m([
+      proj("A", null, "online"),
+      proj("B", "A", "provisioning"),
+      proj("C", "A", "provisioning"),
+    ]);
+    expect(s(map, "A")).toMatchObject({ descendantProvisioningCount: 2 });
+    expect(s(map, "B")).toMatchObject({ isActivelyProvisioning: true });
+    expect(s(map, "C")).toMatchObject({ isActivelyProvisioning: true });
+  });
+});
+
+// ── Multiple disjoint trees ───────────────────────────────────────────────────
+
+describe("buildDeployMap — multiple disjoint trees", () => {
+  it("each tree has its own root; deploying nodes are independent", () => {
+    // Tree 1: X (provisioning) ──► Y
+    // Tree 2: P ──► Q  (no provisioning)
+    const map = m([
+      proj("X", null, "provisioning"),
+      proj("Y", "X", "online"),
+      proj("P", null, "online"),
+      proj("Q", "P", "online"),
+    ]);
+    expect(s(map, "X")).toMatchObject({ isDeployingRoot: true });
+    expect(s(map, "Y")).toMatchObject({ isLockedChild: true });
+    expect(s(map, "P")).toMatchObject({ isDeployingRoot: false, isLockedChild: false });
+    expect(s(map, "Q")).toMatchObject({ isDeployingRoot: false, isLockedChild: false });
+  });
+});
+
+// ── Deleting nodes ────────────────────────────────────────────────────────────
+
+describe("buildDeployMap — deletingIds", () => {
+  it("node in deletingIds is locked even if tree is not deploying", () => {
+    const map = m(
+      [
+        proj("A", null, "online"),
+        proj("B", "A", "online"),
+      ],
+      ["B"], // B is being deleted
+    );
+    expect(s(map, "A")).toMatchObject({ isLockedChild: false });
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true, isActivelyProvisioning: false });
+  });
+
+  it("node in deletingIds: isLockedChild is true regardless of provisioning", () => {
+    const map = m(
+      [
+        proj("A", null, "provisioning"),
+        proj("B", "A", "online"),
+      ],
+      ["B"],
+    );
+    // B is both a deploying-child AND a deleting node — either alone locks it
+    expect(s(map, "B")).toMatchObject({ isLockedChild: true });
+  });
+
+  it("empty deletingIds set has no effect", () => {
+    const map = m(
+      [
+        proj("A", null, "online"),
+        proj("B", "A", "online"),
+      ],
+      [],
+    );
+    expect(s(map, "B")).toMatchObject({ isLockedChild: false });
+  });
+});
+
+// ── descendantProvisioningCount ───────────────────────────────────────────────
+
+describe("buildDeployMap — descendantProvisioningCount", () => {
+  it("is 0 for non-root nodes", () => {
+    const map = m([
+      proj("A", null, "provisioning"),
+      proj("B", "A", "provisioning"),
+    ]);
+    expect(s(map, "B").descendantProvisioningCount).toBe(0);
+  });
+
+  it("includes the root's own status when provisioning", () => {
+    const map = m([
+      proj("A", null, "provisioning"),
+      proj("B", "A", "online"),
+    ]);
+    // A is both root and provisioning → count includes itself
+    expect(s(map, "A").descendantProvisioningCount).toBe(1);
+  });
+
+  it("accumulates all provisioning descendants (not just immediate children)", () => {
+    const map = m([
+      proj("A", null, "online"),
+      proj("B", "A", "online"),
+      proj("C", "B", "provisioning"),
+    ]);
+    expect(s(map, "A").descendantProvisioningCount).toBe(1);
+  });
+});
+
+// ── O(n) performance ─────────────────────────────────────────────────────────
+
+describe("buildDeployMap — O(n) performance contract", () => {
+  it("handles a 50-node three-level tree without incorrect node assignments", () => {
+    // Level 0: 1 root
+    // Level 1: 7 children
+    // Level 2: 42 leaves
+    // Total: 50 nodes
+    const projections: Projection[] = [];
+    projections.push(proj("root", null, "provisioning"));
+    for (let i = 0; i < 7; i++) {
+      projections.push(proj(`l1-${i}`, "root", "online"));
+    }
+    for (let i = 0; i < 42; i++) {
+      const parent = `l1-${Math.floor(i / 6)}`;
+      projections.push(proj(`l2-${i}`, parent, "online"));
+    }
+    const map = m(projections);
+
+    // Root is the only deploying node
+    expect(s(map, "root")).toMatchObject({
+      isDeployingRoot: true,
+      isLockedChild: false,
+      descendantProvisioningCount: 1,
+    });
+
+    // Every other node is a locked child
+    for (let i = 0; i < 7; i++) {
+      expect(s(map, `l1-${i}`)).toMatchObject({ isLockedChild: true, isDeployingRoot: false });
+    }
+    for (let i = 0; i < 42; i++) {
+      expect(s(map, `l2-${i}`)).toMatchObject({ isLockedChild: true, isDeployingRoot: false });
+    }
+  });
+});
diff --git a/canvas/src/components/canvas/useOrgDeployState.ts b/canvas/src/components/canvas/useOrgDeployState.ts
index 587643df..b69682c7 100644
--- a/canvas/src/components/canvas/useOrgDeployState.ts
+++ b/canvas/src/components/canvas/useOrgDeployState.ts
@@ -40,7 +40,8 @@ interface NodeProjection {
   status: string;
 }
 
-function buildDeployMap(
+// Exported for unit testing — the function is pure and deterministic.
+export function buildDeployMap(
   projections: NodeProjection[],
   deletingIds: ReadonlySet<string>,
 ): Map<string, OrgDeployState> {