diff --git a/components/blockTargetKind.js b/components/blockTargetKind.js
index a894a47d..f31445ba 100644
--- a/components/blockTargetKind.js
+++ b/components/blockTargetKind.js
@@ -15,6 +15,7 @@ export const switchKind = (targetKind, mappings) => {
     rsvpReading,
     movie,
     vernier,
+    readlab,
   } = mappings;
   switch (targetKind) {
     case "reading":
@@ -47,6 +48,9 @@ export const switchKind = (targetKind, mappings) => {
     case "vernier":
       safeExecuteFunc(vernier);
       break;
+    case "readlab":
+      safeExecuteFunc(readlab);
+      break;
     default:
       break;
   }
diff --git a/components/readlabBlock.js b/components/readlabBlock.js
new file mode 100644
index 00000000..02c3006f
--- /dev/null
+++ b/components/readlabBlock.js
@@ -0,0 +1,423 @@
+import { Scheduler } from "../psychojs/src/util";
+import { phrases } from "./i18n";
+import { thisExperimentInfo } from "./global";
+import { psychoJS } from "./globalPsychoJS";
+import {
+  loadRecruitmentServiceConfig,
+  recruitmentServiceData,
+} from "./recruitmentService";
+
+const READLAB_BASE_URL = "https://readlab.net/";
+const READLAB_CONFIG_DEFAULT = "config/sample-experiment.csv";
+const READLAB_BUTTON_ID = "readlab-continue-button";
+const READLAB_OVERLAY_ID = "readlab-overlay";
+
+const DEFAULT_TEXT_EN = {
+  heading: "Continue on ReadLab",
+  body:
+    "For this part of the experiment, you will be redirected to ReadLab " +
+    "(readlab.net) to complete a reading task. When you finish there, " +
+    "ReadLab will bring you back here automatically. Please do not close " +
+    "this tab. Click the button below to continue.",
+  button: "Continue to ReadLab",
+};
+
+const phraseOrFallback = (phraseName, language, fallback) => {
+  try {
+    if (
+      phrases &&
+      Object.prototype.hasOwnProperty.call(phrases, phraseName) &&
+      Object.prototype.hasOwnProperty.call(phrases[phraseName], language)
+    ) {
+      return phrases[phraseName][language];
+    }
+    if (
+      phrases &&
+      Object.prototype.hasOwnProperty.call(phrases, phraseName) &&
+      Object.prototype.hasOwnProperty.call(phrases[phraseName], "en")
+    ) {
+      return phrases[phraseName]["en"];
+    }
+  } catch (_) {}
+  return fallback;
+};
+
+const safeReadParam = (paramReader, name, blockOrCondition, fallback) => {
+  try {
+    if (!paramReader || typeof paramReader.read !== "function") return fallback;
+    const value = paramReader.read(name, blockOrCondition);
+    if (value === undefined || value === null || value === "") return fallback;
+    return value;
+  } catch (_) {
+    return fallback;
+  }
+};
+
+export const buildReadlabRedirectUrl = ({
+  config = READLAB_CONFIG_DEFAULT,
+  participantID = "",
+  returnUrl = window.location.href,
+} = {}) => {
+  const params = new URLSearchParams();
+  params.set("config", config);
+  params.set("participant", participantID || "");
+  const url = `${READLAB_BASE_URL}?${params.toString()}`;
+  return `${url}&redirectUrl=${encodeURIComponent(returnUrl)}`;
+};
+
+export const buildEasyEyesReturnUrl = ({
+  blockNumber,
+  experimentFilename,
+  participantID,
+  prolificParticipantID,
+  prolificStudyID,
+  prolificSessionID,
+  session,
+} = {}) => {
+  const u = new URL(window.location.href);
+  u.searchParams.set("EE_resume", "1");
+  if (typeof blockNumber === "number")
+    u.searchParams.set("EE_block", String(blockNumber));
+  if (experimentFilename) u.searchParams.set("EE_experiment", experimentFilename);
+  if (participantID) u.searchParams.set("EE_participant", participantID);
+  if (session) u.searchParams.set("EE_session", String(session));
+  if (prolificParticipantID)
+    u.searchParams.set("PROLIFIC_PID", prolificParticipantID);
+  if (prolificStudyID) u.searchParams.set("STUDY_ID", prolificStudyID);
+  if (prolificSessionID) u.searchParams.set("SESSION_ID", prolificSessionID);
+  u.searchParams.set("EE_t", String(Date.now()));
+  return u.toString();
+};
+
+const removeOverlay = () => {
+  const existing = document.getElementById(READLAB_OVERLAY_ID);
+  if (existing) existing.remove();
+};
+
+const renderReadlabOverlay = ({ heading, body, buttonLabel, onClick }) => {
+  removeOverlay();
+
+  const overlay = document.createElement("div");
+  overlay.id = READLAB_OVERLAY_ID;
+  Object.assign(overlay.style, {
+    position: "fixed",
+    inset: "0",
+    background: "#ffffff",
+    color: "#222",
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "center",
+    zIndex: "10000",
+    padding: "2rem",
+    fontFamily: "system-ui, -apple-system, Segoe UI, Roboto, sans-serif",
+  });
+
+  const card = document.createElement("div");
+  Object.assign(card.style, {
+    maxWidth: "640px",
+    width: "100%",
+    textAlign: "left",
+    lineHeight: "1.5",
+  });
+
+  const h1 = document.createElement("h1");
+  h1.textContent = heading;
+  Object.assign(h1.style, {
+    fontSize: "1.75rem",
+    margin: "0 0 1rem 0",
+  });
+
+  const p = document.createElement("p");
+  p.textContent = body;
+  Object.assign(p.style, {
+    fontSize: "1.1rem",
+    margin: "0 0 1.5rem 0",
+  });
+
+  const button = document.createElement("button");
+  button.id = READLAB_BUTTON_ID;
+  button.type = "button";
+  Object.assign(button.style, {
+    display: "inline-flex",
+    alignItems: "center",
+    gap: "0.5rem",
+    padding: "0.75rem 1.25rem",
+    fontSize: "1.05rem",
+    fontWeight: "600",
+    color: "#fff",
+    background: "#1a73e8",
+    border: "none",
+    borderRadius: "6px",
+    cursor: "pointer",
+  });
+  button.addEventListener("mouseenter", () => {
+    button.style.background = "#1557b0";
+  });
+  button.addEventListener("mouseleave", () => {
+    button.style.background = "#1a73e8";
+  });
+
+  const label = document.createElement("span");
+  label.textContent = buttonLabel;
+
+  // External-link SVG icon
+  const icon = document.createElementNS("http://www.w3.org/2000/svg", "svg");
+  icon.setAttribute("width", "18");
+  icon.setAttribute("height", "18");
+  icon.setAttribute("viewBox", "0 0 24 24");
+  icon.setAttribute("fill", "none");
+  icon.setAttribute("stroke", "currentColor");
+  icon.setAttribute("stroke-width", "2");
+  icon.setAttribute("stroke-linecap", "round");
+  icon.setAttribute("stroke-linejoin", "round");
+  icon.setAttribute("aria-hidden", "true");
+  icon.innerHTML =
+    '<path d="M18 13v6a2 2 0 0 1-2 2H5a2 2 0 0 1-2-2V8a2 2 0 0 1 2-2h6"/>' +
+    '<polyline points="15 3 21 3 21 9"/>' +
+    '<line x1="10" y1="14" x2="21" y2="3"/>';
+
+  button.appendChild(label);
+  button.appendChild(icon);
+  button.addEventListener("click", onClick);
+
+  card.appendChild(h1);
+  card.appendChild(p);
+  card.appendChild(button);
+  overlay.appendChild(card);
+  document.body.appendChild(overlay);
+};
+
+export const isReadlabResume = () => {
+  try {
+    const params = new URLSearchParams(window.location.search);
+    return params.get("EE_resume") === "1";
+  } catch (_) {
+    return false;
+  }
+};
+
+const restoreExperimentInfoFromResumeUrl = () => {
+  try {
+    const p = new URLSearchParams(window.location.search);
+    const eeParticipant = p.get("EE_participant");
+    if (eeParticipant) {
+      thisExperimentInfo.participant = eeParticipant;
+      thisExperimentInfo.EasyEyesID = eeParticipant;
+      thisExperimentInfo.PavloviaSessionID = eeParticipant;
+    }
+    const prolificPID = p.get("PROLIFIC_PID");
+    const studyID = p.get("STUDY_ID");
+    const sessionID = p.get("SESSION_ID");
+    if (prolificPID) thisExperimentInfo.ProlificParticipantID = prolificPID;
+    if (studyID) thisExperimentInfo.ProlificStudyID = studyID;
+    if (sessionID) thisExperimentInfo.ProlificSessionID = sessionID;
+  } catch (_) {}
+};
+
+const renderReadlabReturnEnding = ({
+  heading,
+  body,
+  buttonLabel,
+  buttonUrl,
+}) => {
+  removeOverlay();
+  const overlay = document.createElement("div");
+  overlay.id = READLAB_OVERLAY_ID;
+  Object.assign(overlay.style, {
+    position: "fixed",
+    inset: "0",
+    background: "#ffffff",
+    color: "#222",
+    display: "flex",
+    alignItems: "center",
+    justifyContent: "center",
+    zIndex: "10000",
+    padding: "2rem",
+    fontFamily: "system-ui, -apple-system, Segoe UI, Roboto, sans-serif",
+  });
+
+  const card = document.createElement("div");
+  Object.assign(card.style, {
+    maxWidth: "640px",
+    width: "100%",
+    textAlign: "left",
+    lineHeight: "1.5",
+  });
+
+  const h1 = document.createElement("h1");
+  h1.textContent = heading;
+  Object.assign(h1.style, { fontSize: "1.75rem", margin: "0 0 1rem 0" });
+
+  const p = document.createElement("p");
+  p.textContent = body;
+  Object.assign(p.style, { fontSize: "1.1rem", margin: "0 0 1.5rem 0" });
+
+  card.appendChild(h1);
+  card.appendChild(p);
+
+  if (buttonUrl) {
+    const button = document.createElement("button");
+    button.id = READLAB_BUTTON_ID;
+    button.type = "button";
+    button.textContent = buttonLabel;
+    Object.assign(button.style, {
+      display: "inline-flex",
+      alignItems: "center",
+      gap: "0.5rem",
+      padding: "0.75rem 1.25rem",
+      fontSize: "1.05rem",
+      fontWeight: "600",
+      color: "#fff",
+      background: "#1a73e8",
+      border: "none",
+      borderRadius: "6px",
+      cursor: "pointer",
+    });
+    button.addEventListener("click", () => {
+      button.disabled = true;
+      window.location.href = buttonUrl;
+    });
+    card.appendChild(button);
+  }
+
+  overlay.appendChild(card);
+  document.body.appendChild(overlay);
+};
+
+export const showReadlabReturnEnding = async (language = "en") => {
+  restoreExperimentInfoFromResumeUrl();
+
+  // Make sure recruitment service config is loaded so we know whether to
+  // build a Prolific completion link.
+  try {
+    await loadRecruitmentServiceConfig();
+  } catch (_) {}
+
+  const heading = phraseOrFallback(
+    "EE_readlabReturnHeading",
+    language,
+    "Thank you!",
+  );
+  const body = phraseOrFallback(
+    "EE_readlabReturnBody",
+    language,
+    "Your responses have been recorded. The experiment is complete.",
+  );
+
+  let buttonLabel = "";
+  let buttonUrl = "";
+  if (
+    recruitmentServiceData &&
+    recruitmentServiceData.name === "Prolific" &&
+    recruitmentServiceData.url
+  ) {
+    buttonLabel = phraseOrFallback(
+      "EE_OKToTakeCompletionCodeToProlific",
+      language,
+      "Take me to Prolific to submit my completion code",
+    );
+    buttonUrl = recruitmentServiceData.url;
+  }
+
+  renderReadlabReturnEnding({ heading, body, buttonLabel, buttonUrl });
+};
+
+export const readlabBlockBegin = (snapshot, paramReader) => {
+  return async function () {
+    const blockN =
+      snapshot && typeof snapshot.block === "number" ? snapshot.block + 1 : 1;
+    const language = "en";
+
+    const config = safeReadParam(
+      paramReader,
+      "readlabConfig",
+      blockN,
+      READLAB_CONFIG_DEFAULT,
+    );
+    const customBody = safeReadParam(
+      paramReader,
+      "readlabInstructions",
+      blockN,
+      "",
+    );
+
+    const heading = phraseOrFallback(
+      "EE_readlabHeading",
+      language,
+      DEFAULT_TEXT_EN.heading,
+    );
+    const body =
+      customBody ||
+      phraseOrFallback("EE_readlabBody", language, DEFAULT_TEXT_EN.body);
+    const buttonLabel = phraseOrFallback(
+      "EE_readlabContinueButton",
+      language,
+      DEFAULT_TEXT_EN.button,
+    );
+
+    const returnUrl = buildEasyEyesReturnUrl({
+      blockNumber: blockN,
+      experimentFilename: thisExperimentInfo.experimentFilename,
+      participantID: thisExperimentInfo.participant,
+      prolificParticipantID: thisExperimentInfo.ProlificParticipantID,
+      prolificStudyID: thisExperimentInfo.ProlificStudyID,
+      prolificSessionID: thisExperimentInfo.ProlificSessionID,
+      session: thisExperimentInfo.session,
+    });
+
+    const readlabUrl = buildReadlabRedirectUrl({
+      config,
+      participantID: thisExperimentInfo.participant || "",
+      returnUrl,
+    });
+
+    renderReadlabOverlay({
+      heading,
+      body,
+      buttonLabel,
+      onClick: async () => {
+        const btn = document.getElementById(READLAB_BUTTON_ID);
+        if (btn) btn.disabled = true;
+
+        // Mark this navigation as intentional so the saveDataOnWindowClose
+        // beforeunload handler skips its preventDefault() (no "Leave site?"
+        // browser dialog).
+        window.__easyeyesIntentionalNavigation = true;
+
+        // Remove PsychoJS's own beforeunload guard if present.
+        try {
+          if (psychoJS && psychoJS.beforeunloadCallback) {
+            window.removeEventListener(
+              "beforeunload",
+              psychoJS.beforeunloadCallback,
+            );
+          }
+        } catch (_) {}
+
+        // Save any pending experiment data before unloading the page.
+        try {
+          if (psychoJS && psychoJS.experiment) {
+            await psychoJS.experiment.save({ sync: true });
+          }
+        } catch (_) {}
+
+        window.location.href = readlabUrl;
+      },
+    });
+
+    return Scheduler.Event.NEXT;
+  };
+};
+
+export const readlabBlockEachFrame = () => {
+  return async function () {
+    return Scheduler.Event.FLIP_REPEAT;
+  };
+};
+
+export const readlabBlockEnd = () => {
+  return async function () {
+    removeOverlay();
+    return Scheduler.Event.NEXT;
+  };
+};
diff --git a/components/utils.js b/components/utils.js
index c1a074a9..a9227c80 100644
--- a/components/utils.js
+++ b/components/utils.js
@@ -1522,6 +1522,10 @@ export const saveDataOnWindowClose = (experiment) => {
     experiment.save({ sync: true });
     if (eyeTrackingStimulusRecords.length)
       experiment.saveCSV(eyeTrackingStimulusRecords);
+    // When EasyEyes itself is navigating the participant away on purpose
+    // (e.g. handing off to ReadLab), don't show the browser "Leave site?"
+    // dialog — but still save data above.
+    if (window.__easyeyesIntentionalNavigation) return;
     e.preventDefault();
     return null;
   });
diff --git a/parameters/glossary.ts b/parameters/glossary.ts
index 4a745c3d..0ced34dd 100644
--- a/parameters/glossary.ts
+++ b/parameters/glossary.ts
@@ -5054,6 +5054,7 @@ export const GLOSSARY: Glossary = {
       "reading",
       "rsvpReading",
       "repeatedLetters",
+      "readlab",
     ],
   },
   targetLengthDeg: {
diff --git a/threshold.js b/threshold.js
index 1dc86250..74f18f05 100644
--- a/threshold.js
+++ b/threshold.js
@@ -393,6 +393,13 @@ import {
 /* ---------------------------------- */
 
 import { switchKind, switchTask } from "./components/blockTargetKind.js";
+import {
+  readlabBlockBegin,
+  readlabBlockEachFrame,
+  readlabBlockEnd,
+  isReadlabResume,
+  showReadlabReturnEnding,
+} from "./components/readlabBlock.js";
 import {
   addSkipTrialButton,
   handleEscapeKey,
@@ -652,6 +659,19 @@ const paramReaderInitialized = async (reader) => {
   // Fails gracefully if not actually prolific experiment, so run always
   saveProlificInfo(thisExperimentInfo);
 
+  // ReadLab return: participant has finished the readlab block and the
+  // browser has navigated back to this experiment URL with EE_resume=1.
+  // Skip the normal experiment flow (no calibration, no blocks) and show a
+  // thank-you with a Prolific completion link. PsychoJS is intentionally
+  // not started in this branch.
+  if (isReadlabResume()) {
+    const rootElement = document.getElementById("root");
+    if (rootElement) rootElement.classList.add("initialized");
+    if (window.removeLoadingScreen) window.removeLoadingScreen();
+    await showReadlabReturnEnding(rc.language.value);
+    return;
+  }
+
   setCurrentFn("paramReaderInitialized");
   // ! avoid opening windows twice
   if (typeof psychoJS._window !== "undefined") return;
@@ -2928,6 +2948,20 @@ const experiment = (howManyBlocksAreThereInTotal) => {
         blocksLoopScheduler.add(filterRoutineEachFrame());
         blocksLoopScheduler.add(filterRoutineEnd());
 
+        // ReadLab handoff block: render explanatory page + button, then
+        // navigate same-tab to readlab.net. No trials are scheduled.
+        // Intended to be the LAST block; the redirectUrl returns the
+        // participant to this experiment's URL with EE_resume params.
+        if (_thisBlock.targetKind === "readlab") {
+          blocksLoopScheduler.add(readlabBlockBegin(snapshot, paramReader));
+          blocksLoopScheduler.add(readlabBlockEachFrame());
+          blocksLoopScheduler.add(readlabBlockEnd());
+          blocksLoopScheduler.add(
+            endLoopIteration(blocksLoopScheduler, snapshot),
+          );
+          continue;
+        }
+
         // DELETE
         // if (
         //   conditions.every(