diff --git a/src/backends/isolation_session/common/src/availability.rs b/src/backends/isolation_session/common/src/availability.rs
index d8226c45f..0bd3d65e9 100644
--- a/src/backends/isolation_session/common/src/availability.rs
+++ b/src/backends/isolation_session/common/src/availability.rs
@@ -3,13 +3,13 @@
 
 //! IsolationSession host-availability probe.
 //!
-//! Availability is whether the in-proc `Windows.AI.IsolationSession`
-//! `IsoSessionOps` WinRT class is registered on the OS (its activation factory
-//! resolves), matching PR #761 rather than gating on a Windows build number.
+//! Available when `IsoSessionOps` activates and reports a feature level above
+//! zero for `LocalAgentUser`, which the lifecycle requires. No build number is
+//! consulted.
 
 use std::sync::OnceLock;
 
-use isolation_session_bindings::bindings::IsoSessionOps;
+use isolation_session_bindings::bindings::{IsoSessionFeature, IsoSessionOps};
 use windows::Win32::System::Com::{CoInitializeEx, CoUninitialize, COINIT_MULTITHREADED};
 use windows_core::HRESULT;
 
@@ -17,25 +17,23 @@ static AVAILABLE: OnceLock<bool> = OnceLock::new();
 
 /// Cached for the process; never requires elevation.
 pub fn is_isolation_session_available() -> bool {
-    *AVAILABLE.get_or_init(|| available_from(probe_activation()))
+    *AVAILABLE.get_or_init(|| available_from(probe_feature_level()))
 }
 
-/// Split from [`probe_activation`] so the decision is testable without COM/WinRT.
-/// Any activation failure (class not registered, or the OS feature gate off)
-/// means not available here.
-fn available_from(activation: Result<(), HRESULT>) -> bool {
-    activation.is_ok()
+/// Split from [`probe_feature_level`] so the decision is testable without
+/// COM/WinRT. A failed probe or a zero level means not available.
+fn available_from(probe: Result<i32, HRESULT>) -> bool {
+    matches!(probe, Ok(level) if level > 0)
 }
 
-fn probe_activation() -> Result<(), HRESULT> {
+fn probe_feature_level() -> Result<i32, HRESULT> {
     // Guard uninitializes on drop, so a panic in `IsoSessionOps::new()` still
-    // balances `CoInitializeEx`. The `_ops` handle drops before `_apartment`
+    // balances `CoInitializeEx`. The `ops` handle drops before `_apartment`
     // (reverse declaration order), preserving COM's create-before-uninit rule.
     let _apartment = ComApartment::enter();
-    match IsoSessionOps::new() {
-        Ok(_ops) => Ok(()),
-        Err(e) => Err(e.code()),
-    }
+    let ops = IsoSessionOps::new().map_err(|e| e.code())?;
+    ops.GetFeatureLevel(IsoSessionFeature::LocalAgentUser)
+        .map_err(|e| e.code())
 }
 
 /// Owns the COM apartment for the duration of a probe and uninitializes it on
@@ -71,8 +69,11 @@ mod tests {
     use windows::Win32::Foundation::{CLASS_E_CLASSNOTAVAILABLE, REGDB_E_CLASSNOTREG};
 
     #[test]
-    fn only_successful_activation_means_available() {
-        assert!(available_from(Ok(())));
+    fn availability_needs_a_positive_feature_level() {
+        assert!(available_from(Ok(1)));
+        assert!(!available_from(Ok(0)));
+        // Pins the predicate as `> 0` rather than `!= 0`.
+        assert!(!available_from(Ok(-1)));
         assert!(!available_from(Err(CLASS_E_CLASSNOTAVAILABLE)));
         assert!(!available_from(Err(REGDB_E_CLASSNOTREG)));
         assert!(!available_from(Err(HRESULT(0x8000_4005u32 as i32))));
diff --git a/tests/scripts/README.md b/tests/scripts/README.md
index f3e3d534a..62887713b 100644
--- a/tests/scripts/README.md
+++ b/tests/scripts/README.md
@@ -97,9 +97,7 @@ node scripts/ci/resolve-validation-test-matrix.mjs --plan nightly
 
 **Skip semantics.** Several suites degrade gracefully on an unsupported host:
 the IsolationSession suites decide availability from a single `wxc-exec --probe`
-read of `probes.isolationSessionAvailable` (covering both a host that cannot
-activate the API and a binary built without `--features isolation_session`),
-print `SKIPPED`, and exit 0.
+read of `probes.isolationSessionAvailable`, print `SKIPPED`, and exit 0.
 
 Because a skip exits 0 and the dispatchers propagate only the exit code, **a
 green CI job does not by itself prove the suite ran.** Anything treating these
diff --git a/tests/scripts/run_isolation_session_resize_smoke.ps1 b/tests/scripts/run_isolation_session_resize_smoke.ps1
index ac1650c5e..5d40eae89 100644
--- a/tests/scripts/run_isolation_session_resize_smoke.ps1
+++ b/tests/scripts/run_isolation_session_resize_smoke.ps1
@@ -148,7 +148,7 @@ function Get-IsolationSessionProbe {
 
 $probeResult = Get-IsolationSessionProbe -Exe $WxcExec
 if ($probeResult.Status -eq 'unavailable') {
-    Write-Host "SKIPPED: wxc-exec --probe reports isolationSessionAvailable=false (host cannot activate the isolation session API, or this binary was built without --features isolation_session)" -ForegroundColor Yellow
+    Write-Host "SKIPPED: wxc-exec --probe reports isolationSessionAvailable=false" -ForegroundColor Yellow
     exit 0
 }
 if ($probeResult.Status -ne 'available') {
diff --git a/tests/scripts/run_isolation_session_state_aware_tests.ps1 b/tests/scripts/run_isolation_session_state_aware_tests.ps1
index 10ad8438d..2a7af4dd2 100644
--- a/tests/scripts/run_isolation_session_state_aware_tests.ps1
+++ b/tests/scripts/run_isolation_session_state_aware_tests.ps1
@@ -21,9 +21,7 @@
     PowerShell on that host.
 
     Prerequisite probe (skip if unavailable -- not a failure):
-      - `wxc-exec --probe` reports `probes.isolationSessionAvailable`. This
-        single signal covers an OS that cannot activate the isolation session
-        API as well as a binary built without `--features isolation_session`.
+      - `wxc-exec --probe` reports `probes.isolationSessionAvailable`.
 
 .PARAMETER WxcExePath
     Path to wxc-exec.exe. Default probes the host-arch target dir, then
@@ -148,7 +146,7 @@ function Get-IsolationSessionProbe {
 
 $probeResult = Get-IsolationSessionProbe -Exe $WxcExec
 if ($probeResult.Status -eq 'unavailable') {
-    Write-Host "SKIPPED: wxc-exec --probe reports isolationSessionAvailable=false (host cannot activate the isolation session API, or this binary was built without --features isolation_session)" -ForegroundColor Yellow
+    Write-Host "SKIPPED: wxc-exec --probe reports isolationSessionAvailable=false" -ForegroundColor Yellow
     exit 0
 }
 if ($probeResult.Status -ne 'available') {
diff --git a/tests/scripts/run_isolation_session_tests.ps1 b/tests/scripts/run_isolation_session_tests.ps1
index f63c239fe..c41f258fe 100644
--- a/tests/scripts/run_isolation_session_tests.ps1
+++ b/tests/scripts/run_isolation_session_tests.ps1
@@ -114,12 +114,7 @@ Write-Host "Configs: $ConfigDir`n" -ForegroundColor Gray
 # ---------------- Backend-availability probe ----------------
 #
 # Availability is decided by a single call to `wxc-exec --probe`, which reports
-# `probes.isolationSessionAvailable`. That one signal covers both reasons this
-# suite can be unrunnable:
-#
-#   - the host cannot activate the isolation session API, or
-#   - wxc-exec was built without `--features isolation_session`, in which case
-#     the field stays false because the backend is not compiled in.
+# `probes.isolationSessionAvailable`.
 #
 # This deliberately replaces the earlier checks for a specific DLL and a
 # hard-coded WinRT activatable-class registry key. Those named a runtime class
@@ -199,7 +194,7 @@ function Get-IsolationSessionProbe {
 
 $probeResult = Get-IsolationSessionProbe -Exe $WxcExec
 if ($probeResult.Status -eq 'unavailable') {
-    Write-Host "SKIPPED: wxc-exec --probe reports isolationSessionAvailable=false (host cannot activate the isolation session API, or this binary was built without --features isolation_session)" -ForegroundColor Yellow
+    Write-Host "SKIPPED: wxc-exec --probe reports isolationSessionAvailable=false" -ForegroundColor Yellow
     exit 0
 }
 if ($probeResult.Status -ne 'available') {