diff --git a/bin/commands/runs.js b/bin/commands/runs.js
index daea68b7..b2181303 100644
--- a/bin/commands/runs.js
+++ b/bin/commands/runs.js
@@ -72,7 +72,7 @@ module.exports = function run(args, rawArgs) {
     utils.setCypressConfigFilename(bsConfig, args);
 
     /* Set testObservability & browserstackAutomation flags */
-    const [isTestObservabilitySession, isBrowserstackInfra] = setTestObservabilityFlags(bsConfig);
+    let [isTestObservabilitySession, isBrowserstackInfra] = setTestObservabilityFlags(bsConfig);
     const checkAccessibility = checkAccessibilityPlatform(bsConfig);
     let isAccessibilitySession = bsConfig.run_settings.accessibility || checkAccessibility;
     const turboScaleSession = isTurboScaleSession(bsConfig);
@@ -91,6 +91,19 @@ module.exports = function run(args, rawArgs) {
 
     let buildReportData = (turboScaleSession || !isBrowserstackInfra) ? null : await getInitialDetails(bsConfig, args, rawArgs);
 
+    // APS-22894: the TestHub and Accessibility hooks injected into the support file call
+    // Cypress.env(), which Cypress 16 removed from the browser, so neither can run there yet.
+    // Decided here, before the support file is patched and the suite is zipped.
+    const cypressMajorVersion = utils.getCypressMajorVersion(bsConfig, buildReportData);
+    if (isBrowserstackInfra && (isTestObservabilitySession || isAccessibilitySession)
+        && cypressMajorVersion >= Constants.TESTHUB_A11Y_UNSUPPORTED_FROM_CYPRESS_MAJOR) {
+      logger.warn(Constants.userMessages.TESTHUB_A11Y_NOT_SUPPORTED_ON_CYPRESS_MAJOR.replace('<cypressMajor>', cypressMajorVersion));
+      isTestObservabilitySession = false;
+      isAccessibilitySession = false;
+      bsConfig["testObservability"] = false;
+      process.env.BROWSERSTACK_TEST_OBSERVABILITY = 'false';
+    }
+
     // accept the build name from command line if provided
     utils.setBuildName(bsConfig, args);
 
diff --git a/bin/helpers/constants.js b/bin/helpers/constants.js
index c0bdd495..2642cfe6 100644
--- a/bin/helpers/constants.js
+++ b/bin/helpers/constants.js
@@ -19,6 +19,8 @@ const syncCLI = {
 };
 
 const userMessages = {
+  TESTHUB_A11Y_NOT_SUPPORTED_ON_CYPRESS_MAJOR:
+    "TestHub (Test Observability) and Accessibility are not yet supported on Cypress <cypressMajor>. Disabling both for this build; your tests will still run. Read more about supported versions here: http://browserstack.com/docs/automate/cypress/supported-versions",
   ACCESSIBILITY_PLUGIN_NOT_LOADED:
     "BrowserStack Accessibility Automation plugin is not loaded in your cypress config file. Disabling accessibility for this build. Please follow https://www.browserstack.com/docs/accessibility/automated-tests/get-started/cypress to enable accessibility testing.",
   BUILD_FAILED: "Build creation failed.",
@@ -469,6 +471,11 @@ const CYPRESS_CONFIG_FILE_MAPPING = {
 
 const CYPRESS_CONFIG_FILE_NAMES = Object.keys(CYPRESS_CONFIG_FILE_MAPPING);
 
+// APS-22894: the TestHub and Accessibility support-file hooks read Cypress.env(), which
+// Cypress 16 removed from the browser. Both are disabled from this major until the hooks
+// move to Cypress.expose().
+const TESTHUB_A11Y_UNSUPPORTED_FROM_CYPRESS_MAJOR = 16;
+
 const CYPRESS_V10_AND_ABOVE_CONFIG_FILE_EXTENSIONS = ['js', 'ts', 'cjs', 'mjs']
 
 // Maximum size of VCS info which is allowed
@@ -514,6 +521,7 @@ module.exports = Object.freeze({
   CYPRESS_CONFIG_FILE_MAPPING,
   CYPRESS_CONFIG_FILE_NAMES,
   CYPRESS_V10_AND_ABOVE_CONFIG_FILE_EXTENSIONS,
+  TESTHUB_A11Y_UNSUPPORTED_FROM_CYPRESS_MAJOR,
   MAX_GIT_META_DATA_SIZE_IN_BYTES,
   GIT_META_DATA_TRUNCATED
 });
diff --git a/bin/helpers/utils.js b/bin/helpers/utils.js
index 2cc7f133..5632c7d6 100644
--- a/bin/helpers/utils.js
+++ b/bin/helpers/utils.js
@@ -1452,6 +1452,20 @@ exports.setConfig = (bsConfig, args) => {
   }
 }
 
+// Major of the Cypress version this run will get: the requested cypress_version when
+// browserstack.json sets one ("16", "16.latest", "16.2.0"), else the default the server
+// applies (default_cypress_version from get_initial_details). undefined when neither parses.
+exports.getCypressMajorVersion = (bsConfig, buildReportData) => {
+  const requested = (bsConfig && bsConfig.run_settings && bsConfig.run_settings.cypress_version)
+    ? bsConfig.run_settings.cypress_version.toString() : undefined;
+  const fallback = (buildReportData && buildReportData.default_cypress_version)
+    ? buildReportData.default_cypress_version.toString() : undefined;
+  const version = requested || fallback;
+  if (this.isUndefined(version)) return undefined;
+  const match = version.match(/^(\d+)/);
+  return match ? parseInt(match[1], 10) : undefined;
+}
+
 exports.setVideoCliConfig = (bsConfig, videoConfig) => {
   // set cli config for video for cypress 13 and above to attain default value of true.
   if(this.isUndefined(videoConfig) || this.isUndefined(videoConfig.video) || this.isUndefined(videoConfig.videoUploadOnPasses) || this.isUndefined(bsConfig)) return;
diff --git a/test/unit/bin/helpers/utils.js b/test/unit/bin/helpers/utils.js
index 480cb5f4..4d6ee1df 100644
--- a/test/unit/bin/helpers/utils.js
+++ b/test/unit/bin/helpers/utils.js
@@ -5748,4 +5748,29 @@ describe('utils', () => {
     });
   });
 
+  describe('getCypressMajorVersion', () => {
+    it('reads the major from an exact requested version', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: { cypress_version: '16.2.0' } }, {})).to.eql(16);
+    });
+    it('reads the major from the <major>.latest syntax', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: { cypress_version: '16.latest' } }, {})).to.eql(16);
+    });
+    it('reads the major from a bare major, including numeric values', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: { cypress_version: 15 } }, {})).to.eql(15);
+    });
+    it('falls back to the server default when no version is requested', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: {} }, { default_cypress_version: '16.2.0' })).to.eql(16);
+    });
+    it('prefers the requested version over the server default', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: { cypress_version: '13.15.0' } }, { default_cypress_version: '16.2.0' })).to.eql(13);
+    });
+    it('is undefined when neither a requested nor a default version is known', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: {} }, {})).to.be.undefined;
+      expect(utils.getCypressMajorVersion({ run_settings: {} }, null)).to.be.undefined;
+    });
+    it('is undefined when the version does not start with a number', () => {
+      expect(utils.getCypressMajorVersion({ run_settings: { cypress_version: 'latest' } }, {})).to.be.undefined;
+    });
+  });
+
 });