diff --git a/tests/cypress/cypress/e2e/specs/api/tempus/tempus.collisions.cy.js b/tests/cypress/cypress/e2e/specs/api/tempus/tempus.collisions.cy.js
new file mode 100644
index 000000000..364647ef5
--- /dev/null
+++ b/tests/cypress/cypress/e2e/specs/api/tempus/tempus.collisions.cy.js
@@ -0,0 +1,298 @@
+const KALENDER_API = "/index.ci.php/api/frontend/v1/tempus";
+
+const getPlannerEvents = (startDate, endDate) =>
+  cy
+    .request({
+      method: "GET",
+      url: `${KALENDER_API}/Kalender/getPlan`,
+      qs: {
+        start_date: startDate,
+        end_date: endDate,
+      },
+    })
+    .then((response) => {
+      expect(response.status).to.eq(200);
+      expect(response.body).to.have.nested.property("meta.status", "success");
+      expect(response.body.data).to.be.an("array");
+
+      return response.body.data;
+    });
+
+const findEditableLessonEvent = (events) =>
+  events.find(
+    (event) =>
+      event.type === "lehreinheit" &&
+      ["live", "preview"].includes(event.status_kurzbz) &&
+      Number(event.kalender_id) > 0 &&
+      event.datum &&
+      Array.isArray(event.lehreinheit_id) &&
+      event.lehreinheit_id.length > 0,
+  );
+
+const getReturnedKalenderId = (body) => {
+  const payload = body?.data;
+  const rawKalenderId =
+    payload?.retval?.kalender_id ??
+    payload?.retval ??
+    payload?.kalender_id ??
+    payload;
+  const kalenderId = Number(rawKalenderId);
+
+  expect(kalenderId, "returned kalender_id").to.be.greaterThan(0);
+
+  return kalenderId;
+};
+
+const updateKalenderEvent = (kalenderId, startDateTime, endDateTime) =>
+  cy.request({
+    method: "POST",
+    url: `${KALENDER_API}/Kalender/updateKalenderEvent`,
+    form: true,
+    body: {
+      kalender_id: kalenderId,
+      "updatedInfos[start_time]": startDateTime,
+      "updatedInfos[end_time]": endDateTime,
+    },
+    failOnStatusCode: false,
+  });
+
+const deleteKalenderEvent = (kalenderId) =>
+  cy.request({
+    method: "POST",
+    url: `${KALENDER_API}/Kalender/deleteEntry`,
+    form: true,
+    body: {
+      kalender_id: kalenderId,
+    },
+    failOnStatusCode: false,
+  });
+
+const findEventByKalenderId = (events, kalenderId) =>
+  events.find((event) => Number(event.kalender_id) === Number(kalenderId));
+
+const getSettingsData = () => ({
+  ignore_kollision: false,
+  kollision_student: false,
+  ignore_reservierung: false,
+  ignore_zeitsperre: false,
+});
+
+const updateSettingsData = (options) =>
+  cy.request({
+    method: "POST",
+    url: `${KALENDER_API}/config/set`,
+    failOnStatusCode: false,
+    headers: { "Cache-Control": "no-cache", Pragma: "no-cache" },
+    body: { ...options },
+  });
+
+describe("Tempus Kalender API", () => {
+  beforeEach(() => {
+    cy.login();
+  });
+
+  it("event update works for non collision case", () => {
+    updateSettingsData(getSettingsData()).then((response) => {
+      getPlannerEvents("2026-06-02", "2026-06-02").then((events) => {
+        const sourceEvent = events.find(
+          (event) =>
+            event.type === "lehreinheit" &&
+            event.beginn === "19:30:00" &&
+            event.ende === "20:15:00" &&
+            event.organisationseinheit === "kfSprachen",
+        );
+        expect(
+          sourceEvent,
+          "source event without collision for update test",
+        ).to.exist;
+
+        const startDateTime = `${sourceEvent.datum} 20:15`;
+        const endDateTime = `${sourceEvent.datum} 21:00`;
+
+        updateKalenderEvent(
+          sourceEvent.kalender_id,
+          startDateTime,
+          endDateTime,
+        ).then((response) => {
+          expect(response.status).to.eq(200);
+          expect(response.body).to.have.nested.property("meta.status", "success");
+        });
+      });
+    });
+  });
+
+  it("prohibited event update due to room collision", () => {
+    updateSettingsData(getSettingsData()).then((response) => {
+      getPlannerEvents("2026-06-01", "2026-06-01").then((events) => {
+        const sourceEvent = events.find(
+          (event) =>
+            event.type === "lehreinheit" &&
+            event.beginn === "19:30:00" &&
+            event.ende === "20:15:00" &&
+            event.organisationseinheit === "kfSocialSkills",
+        );
+        expect(
+          sourceEvent,
+          "source event with fixed time and room for collision test",
+        ).to.exist;
+
+        const startDateTime = `${sourceEvent.datum} 20:15`;
+        const endDateTime = `${sourceEvent.datum} 21:00`;
+
+        updateKalenderEvent(
+          sourceEvent.kalender_id,
+          startDateTime,
+          endDateTime,
+        ).then((response) => {
+          expect(response.status).to.eq(500);
+          expect(response.body).to.have.nested.property("meta.status", "error");
+          expect(response.body.errors).to.be.an("array");
+
+          let hasRoomCollisionError = response.body.errors.some(
+            (error) =>
+              error.message.toLowerCase().includes("raum kollision") ||
+              error.message.toLowerCase().includes("room collision"),
+          );
+          expect(
+            hasRoomCollisionError,
+            "response contains room collision error",
+          ).to.be.true;
+        });
+      });
+    });
+  });
+
+  it("prohibited event update due to student collision", () => {
+    let settingsData = getSettingsData();
+    settingsData.kollision_student = true;
+    
+    updateSettingsData(settingsData).then((response) => {
+      getPlannerEvents("2026-06-01", "2026-06-01").then((events) => {
+        const sourceEvent = events.find(
+          (event) =>
+            event.type === "lehreinheit" &&
+            event.beginn === "19:30:00" &&
+            event.ende === "20:15:00" &&
+            event.organisationseinheit === "kfMathematik",
+        );
+        expect(
+          sourceEvent,
+          "source event with fixed time and room for collision test",
+        ).to.exist;
+
+        const startDateTime = `${sourceEvent.datum} 20:15`;
+        const endDateTime = `${sourceEvent.datum} 21:00`;
+
+        updateKalenderEvent(
+          sourceEvent.kalender_id,
+          startDateTime,
+          endDateTime,
+        ).then((response) => {
+          expect(response.status).to.eq(500);
+          expect(response.body).to.have.nested.property("meta.status", "error");
+          expect(response.body.errors).to.be.an("array");
+          console.log(response.body.errors)
+          let hasStudentCollisionError = response.body.errors.some(
+            (error) =>
+              error.message.toLowerCase().includes("studierende kollision") ||
+              error.message.toLowerCase().includes("student collision"),
+          );
+          expect(
+            hasStudentCollisionError,
+            "response contains student collision error",
+          ).to.be.true;
+        });
+      });
+    });
+  });
+
+  it("prohibited event update due to lector collision", () => {
+    let settingsData = getSettingsData();
+    settingsData.kollision_student = false;
+    
+    updateSettingsData(settingsData).then((response) => {
+      getPlannerEvents("2026-06-02", "2026-06-02").then((events) => {
+        console.log(events)
+        const sourceEvent = events.find(
+          (event) =>
+            event.type === "lehreinheit" &&
+            event.beginn === "19:30:00" &&
+            event.ende === "20:15:00" &&
+            event.organisationseinheit === "kfWirtschaftRecht",
+        );
+        expect(
+          sourceEvent,
+          "source event with fixed time and room for collision test",
+        ).to.exist;
+
+        const startDateTime = `${sourceEvent.datum} 20:15`;
+        const endDateTime = `${sourceEvent.datum} 21:00`;
+
+        updateKalenderEvent(
+          sourceEvent.kalender_id,
+          startDateTime,
+          endDateTime,
+        ).then((response) => {
+          expect(response.status).to.eq(500);
+          expect(response.body).to.have.nested.property("meta.status", "error");
+          expect(response.body.errors).to.be.an("array");
+          console.log(response.body.errors)
+          let hasLectorCollisionError = response.body.errors.some(
+            (error) =>
+              error.message.toLowerCase().includes("lektorin kollision") ||
+              error.message.toLowerCase().includes("lector collision"),
+          );
+          expect(
+            hasLectorCollisionError,
+            "response contains lector collision error",
+          ).to.be.true;
+        });
+      });
+    });
+  });
+
+   it("prohibited event update due to lector - zeitsperre collision", () => {
+    let settingsData = getSettingsData();
+    settingsData.kollision_student = false;
+    
+    updateSettingsData(settingsData).then((response) => {
+      getPlannerEvents("2026-06-01", "2026-06-01").then((events) => {
+        console.log(events)
+        const sourceEvent = events.find(
+          (event) =>
+            event.type === "lehreinheit" &&
+            event.beginn === "19:30:00" &&
+            event.ende === "20:15:00" &&
+            event.organisationseinheit === "bic",
+        );
+        expect(
+          sourceEvent,
+          "source event with fixed time and room for collision test",
+        ).to.exist;
+
+        const startDateTime = `2026-06-02 20:15`;
+        const endDateTime = `2026-06-02 21:00`;
+
+        updateKalenderEvent(
+          sourceEvent.kalender_id,
+          startDateTime,
+          endDateTime,
+        ).then((response) => {
+          expect(response.status).to.eq(500);
+          expect(response.body).to.have.nested.property("meta.status", "error");
+          expect(response.body.errors).to.be.an("array");
+          console.log(response.body.errors)
+          let hasTimeLockCollisionError = response.body.errors.some(
+            (error) =>
+              error.message.toLowerCase().includes("zeitsperre kollision") ||
+              error.message.toLowerCase().includes("time lock collision"),
+          );
+          expect(
+            hasTimeLockCollisionError,
+            "response contains time lock collision error",
+          ).to.be.true;
+        });
+      });
+    });
+  });
+});