diff --git a/CHANGELOG.md b/CHANGELOG.md
index 7222d4e400..d8eb2bd8e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,14 @@
 
 ## Unreleased
 
+- Fixed: BrowserStack sessions honour `--provider-project`, `--provider-build`, and
+  `--provider-session-name`. The capability builder emitted the legacy JSON Wire keys `device`,
+  `os_version`, and `app` at the top level next to the W3C `bstack:options` block; the hub treats a
+  request carrying any legacy key as a legacy session, reads the labels from the legacy top-level
+  `project`/`build`/`name` (never set), and ignores `bstack:options`, so every session landed in
+  "Untitled Project" / "Untitled Build" with an empty name — even after #2495 carried the flags to
+  the provider (#2494). The builder now emits `appium:deviceName`, `appium:platformVersion`, and
+  `appium:app` and no legacy key, verified against live App Automate sessions.
 - Changed (sessions): the implicit session is now keyed by workspace **and platform**, so one checkout
   can drive iOS and Android without inventing a `--session` name for every command (#2580). An
   implicit session was addressed by `cwd:<workspace>:default`, one slot per checkout, and it stayed
diff --git a/packages/provider-webdriver/src/browserstack.ts b/packages/provider-webdriver/src/browserstack.ts
index 0a1dde4140..ca845ea93f 100644
--- a/packages/provider-webdriver/src/browserstack.ts
+++ b/packages/provider-webdriver/src/browserstack.ts
@@ -222,14 +222,23 @@ export function createBrowserStackUploadApp(
   };
 }
 
+/**
+ * Builds the W3C `alwaysMatch` capabilities for a BrowserStack App Automate session.
+ *
+ * Every key is either W3C-standard (`platformName`), `appium:`-prefixed, or inside
+ * `bstack:options`. The legacy JSON Wire keys (`device`, `os_version`, `app`, `project`, `build`,
+ * `name`) must not appear: when the hub sees any of them it treats the whole request as a legacy
+ * session and reads the labels from the legacy top-level keys instead of `bstack:options`, so the
+ * project/build/session names are silently dropped and the session lands in "Untitled Project".
+ */
 export function buildBrowserStackCapabilities(
   options: BrowserStackCapabilitiesOptions,
 ): Record<string, unknown> {
   const { 'bstack:options': configuredBstackOptions, ...configured } = options.configured ?? {};
   return {
-    device: options.deviceName,
-    os_version: options.osVersion,
-    ...(options.app ? { app: options.app } : {}),
+    'appium:deviceName': options.deviceName,
+    'appium:platformVersion': options.osVersion,
+    ...(options.app ? { 'appium:app': options.app } : {}),
     ...configured,
     // Merged per key, never assigned: `configured` carrying its own `bstack:options` used to
     // replace the whole object and silently drop the session/build labels below.
diff --git a/test/integration/provider-scenarios/cloud-webdriver-lease-http.test.ts b/test/integration/provider-scenarios/cloud-webdriver-lease-http.test.ts
index 7dc5168d00..3dd8139dda 100644
--- a/test/integration/provider-scenarios/cloud-webdriver-lease-http.test.ts
+++ b/test/integration/provider-scenarios/cloud-webdriver-lease-http.test.ts
@@ -107,9 +107,8 @@ test('lease_allocate over HTTP prepares the BrowserStack session end to end', as
       assert.deepEqual(alwaysMatch(create), {
         platformName: 'Android',
         'appium:deviceName': 'Google Pixel 8',
-        device: 'Google Pixel 8',
-        os_version: '14.0',
-        app: 'bs://preuploaded',
+        'appium:platformVersion': '14.0',
+        'appium:app': 'bs://preuploaded',
         'bstack:options': {
           projectName: 'MyProject',
           buildName: 'Build-2026-09-11',
diff --git a/test/integration/provider-scenarios/cloud-webdriver-provider-adapters.test.ts b/test/integration/provider-scenarios/cloud-webdriver-provider-adapters.test.ts
index 991b4707f6..fdf18eabc7 100644
--- a/test/integration/provider-scenarios/cloud-webdriver-provider-adapters.test.ts
+++ b/test/integration/provider-scenarios/cloud-webdriver-provider-adapters.test.ts
@@ -131,8 +131,12 @@ test('BrowserStack facade nests device-feature capabilities inside bstack:option
       locale: 'Fr',
       networkProfile: '4g-lte-advanced-good',
     });
-    // Vendor capabilities stay nested; only BrowserStack's legacy selectors sit at the top level.
+    // Vendor capabilities stay nested, and no legacy JSON Wire selector reaches the top level —
+    // the hub would otherwise treat the request as legacy and ignore bstack:options entirely.
     assert.equal(alwaysMatch?.deviceOrientation, undefined);
+    for (const legacyKey of ['device', 'os_version', 'app', 'project', 'build', 'name']) {
+      assert.equal(alwaysMatch?.[legacyKey], undefined, `legacy key ${legacyKey} leaked`);
+    }
   });
 }, 15_000);
 
@@ -390,9 +394,8 @@ function assertBrowserStackCalls(
       alwaysMatch: {
         platformName: 'Android',
         'appium:deviceName': 'Google Pixel 8',
-        device: 'Google Pixel 8',
-        os_version: '14.0',
-        app: 'bs://preuploaded',
+        'appium:platformVersion': '14.0',
+        'appium:app': 'bs://preuploaded',
         'bstack:options': {
           projectName: 'agent-device',
           buildName: `build-${lease.runId}`,
diff --git a/test/integration/provider-scenarios/cloud-webdriver-runtime.test.ts b/test/integration/provider-scenarios/cloud-webdriver-runtime.test.ts
index 3dd4633731..ca846cd0aa 100644
--- a/test/integration/provider-scenarios/cloud-webdriver-runtime.test.ts
+++ b/test/integration/provider-scenarios/cloud-webdriver-runtime.test.ts
@@ -480,9 +480,8 @@ function assertWebDriverCalls(calls: readonly CloudWebDriverHttpCall[], leaseId:
       alwaysMatch: {
         platformName: 'Android',
         'appium:deviceName': 'Google Pixel 8',
-        device: 'Google Pixel 8',
-        os_version: '14.0',
-        app: 'bs://app-id',
+        'appium:platformVersion': '14.0',
+        'appium:app': 'bs://app-id',
         'bstack:options': {
           projectName: 'agent-device',
           buildName: 'run-a',