diff --git a/packages/api/src/__tests__/timeline-shift-router-support.test.ts b/packages/api/src/__tests__/timeline-shift-router-support.test.ts
new file mode 100644
index 0000000..3e04b3d
--- /dev/null
+++ b/packages/api/src/__tests__/timeline-shift-router-support.test.ts
@@ -0,0 +1,59 @@
+import { describe, expect, it, vi } from "vitest";
+
+vi.mock("../sse/event-bus.js", () => ({
+  emitProjectShifted: vi.fn(),
+}));
+
+vi.mock("../router/timeline-project-load-support.js", () => ({
+  loadProjectShiftContext: vi.fn(),
+}));
+
+vi.mock("../router/timeline-shift-procedure-support.js", () => ({
+  applyTimelineProjectShift: vi.fn(),
+}));
+
+import { emitProjectShifted } from "../sse/event-bus.js";
+import { loadProjectShiftContext } from "../router/timeline-project-load-support.js";
+import { applyTimelineProjectShiftMutation } from "../router/timeline-shift-router-support.js";
+import { applyTimelineProjectShift } from "../router/timeline-shift-procedure-support.js";
+
+const emitProjectShiftedMock = vi.mocked(emitProjectShifted);
+const loadProjectShiftContextMock = vi.mocked(loadProjectShiftContext);
+const applyTimelineProjectShiftMock = vi.mocked(applyTimelineProjectShift);
+
+describe("timeline shift router support", () => {
+  it("loads context, applies the shift, emits the event, and returns the response payload", async () => {
+    const db = {} as never;
+    const context = { project: { id: "project_1" } } as never;
+    const result = {
+      project: { id: "project_1" },
+      validation: { valid: true },
+      event: { projectId: "project_1" },
+    } as never;
+
+    loadProjectShiftContextMock.mockResolvedValueOnce(context);
+    applyTimelineProjectShiftMock.mockResolvedValueOnce(result);
+
+    await expect(
+      applyTimelineProjectShiftMutation({
+        db,
+        projectId: "project_1",
+        newStartDate: new Date("2026-04-03T00:00:00.000Z"),
+        newEndDate: new Date("2026-04-12T00:00:00.000Z"),
+      }),
+    ).resolves.toEqual({
+      project: { id: "project_1" },
+      validation: { valid: true },
+    });
+
+    expect(loadProjectShiftContextMock).toHaveBeenCalledWith(db, "project_1");
+    expect(applyTimelineProjectShiftMock).toHaveBeenCalledWith({
+      db,
+      projectId: "project_1",
+      newStartDate: new Date("2026-04-03T00:00:00.000Z"),
+      newEndDate: new Date("2026-04-12T00:00:00.000Z"),
+      context,
+    });
+    expect(emitProjectShiftedMock).toHaveBeenCalledWith({ projectId: "project_1" });
+  });
+});
diff --git a/packages/api/src/router/timeline-mutations.ts b/packages/api/src/router/timeline-mutations.ts
new file mode 100644
index 0000000..b8876a0
--- /dev/null
+++ b/packages/api/src/router/timeline-mutations.ts
@@ -0,0 +1,21 @@
+import { PermissionKey, ShiftProjectSchema } from "@capakraken/shared";
+import { managerProcedure, requirePermission } from "../trpc.js";
+import { timelineAllocationMutationProcedures } from "./timeline-allocation-mutations.js";
+import { applyTimelineProjectShiftMutation } from "./timeline-shift-router-support.js";
+
+export const timelineMutationProcedures = {
+  ...timelineAllocationMutationProcedures,
+
+  applyShift: managerProcedure
+    .input(ShiftProjectSchema)
+    .mutation(async ({ ctx, input }) => {
+      requirePermission(ctx, PermissionKey.MANAGE_ALLOCATIONS);
+
+      return applyTimelineProjectShiftMutation({
+        db: ctx.db,
+        projectId: input.projectId,
+        newStartDate: input.newStartDate,
+        newEndDate: input.newEndDate,
+      });
+    }),
+};
diff --git a/packages/api/src/router/timeline-shift-router-support.ts b/packages/api/src/router/timeline-shift-router-support.ts
new file mode 100644
index 0000000..f360fa5
--- /dev/null
+++ b/packages/api/src/router/timeline-shift-router-support.ts
@@ -0,0 +1,27 @@
+import type { PrismaClient } from "@capakraken/db";
+import { emitProjectShifted } from "../sse/event-bus.js";
+import { loadProjectShiftContext } from "./timeline-project-load-support.js";
+import { applyTimelineProjectShift } from "./timeline-shift-procedure-support.js";
+
+export async function applyTimelineProjectShiftMutation(input: {
+  db: PrismaClient;
+  projectId: string;
+  newStartDate: Date;
+  newEndDate: Date;
+}) {
+  const context = await loadProjectShiftContext(input.db, input.projectId);
+  const result = await applyTimelineProjectShift({
+    db: input.db,
+    projectId: input.projectId,
+    newStartDate: input.newStartDate,
+    newEndDate: input.newEndDate,
+    context,
+  });
+
+  emitProjectShifted(result.event);
+
+  return {
+    project: result.project,
+    validation: result.validation,
+  };
+}
diff --git a/packages/api/src/router/timeline.ts b/packages/api/src/router/timeline.ts
index e70cb6a..d0934bb 100644
--- a/packages/api/src/router/timeline.ts
+++ b/packages/api/src/router/timeline.ts
@@ -1,38 +1,8 @@
-import { PermissionKey, ShiftProjectSchema } from "@capakraken/shared";
-import { emitProjectShifted } from "../sse/event-bus.js";
-import { createTRPCRouter, managerProcedure, requirePermission } from "../trpc.js";
-import { timelineAllocationMutationProcedures } from "./timeline-allocation-mutations.js";
+import { createTRPCRouter } from "../trpc.js";
+import { timelineMutationProcedures } from "./timeline-mutations.js";
 import { timelineReadProcedures } from "./timeline-read.js";
-import { loadProjectShiftContext } from "./timeline-project-load-support.js";
-import { applyTimelineProjectShift } from "./timeline-shift-procedure-support.js";
 
 export const timelineRouter = createTRPCRouter({
   ...timelineReadProcedures,
-  ...timelineAllocationMutationProcedures,
-
-  /**
-   * Apply a project shift: validate, then commit all allocation date changes.
-   * Reads includeSaturday from each allocation's metadata.
-   */
-  applyShift: managerProcedure
-    .input(ShiftProjectSchema)
-    .mutation(async ({ ctx, input }) => {
-      requirePermission(ctx, PermissionKey.MANAGE_ALLOCATIONS);
-      const { projectId, newStartDate, newEndDate } = input;
-      const context = await loadProjectShiftContext(ctx.db, projectId);
-      const result = await applyTimelineProjectShift({
-        db: ctx.db,
-        projectId,
-        newStartDate,
-        newEndDate,
-        context,
-      });
-
-      emitProjectShifted(result.event);
-
-      return {
-        project: result.project,
-        validation: result.validation,
-      };
-    }),
+  ...timelineMutationProcedures,
 });