diff --git a/integration/agentcompat/internal/fixture/agent_path.go b/integration/agentcompat/internal/fixture/agent_path.go
index 3a4c3bfb..ebf4485e 100644
--- a/integration/agentcompat/internal/fixture/agent_path.go
+++ b/integration/agentcompat/internal/fixture/agent_path.go
@@ -90,6 +90,9 @@ func validateRelativeAgentPath(candidate string, destructive bool) (string, erro
 	if strings.TrimSpace(candidate) == "" {
 		return "", rejectPath(PathRejectionEmpty)
 	}
+	if hasWindowsAbsolutePath(candidate) {
+		return "", rejectPath(PathRejectionAbsolute)
+	}
 	if hasWindowsVolume(candidate) {
 		return "", rejectPath(PathRejectionVolume)
 	}
@@ -118,6 +121,10 @@ func validateRelativeAgentPath(candidate string, destructive bool) (string, erro
 	return nativeRelative, nil
 }
 
+func hasWindowsAbsolutePath(candidate string) bool {
+	return len(candidate) >= 3 && ((candidate[0] >= 'A' && candidate[0] <= 'Z') || (candidate[0] >= 'a' && candidate[0] <= 'z')) && candidate[1] == ':' && (candidate[2] == '\\' || candidate[2] == '/')
+}
+
 func hasWindowsVolume(candidate string) bool {
 	if strings.HasPrefix(candidate, `\\`) || strings.HasPrefix(candidate, `//`) {
 		return true
diff --git a/integration/agentcompat/internal/fixture/agent_path_test.go b/integration/agentcompat/internal/fixture/agent_path_test.go
index d7c77051..c35c54dc 100644
--- a/integration/agentcompat/internal/fixture/agent_path_test.go
+++ b/integration/agentcompat/internal/fixture/agent_path_test.go
@@ -52,16 +52,17 @@ func TestFixture_AgentPathRejectsParentEscape(t *testing.T) {
 	}
 }
 
-func TestFixture_AgentPathRejectsVolumeOrSeparatorEscape(t *testing.T) {
+func TestFixture_AgentPathRejectsWindowsVolumeOrSeparatorEscape(t *testing.T) {
 	root := newTestAgentRoot(t, "agent-volume")
 	tests := []struct {
 		name      string
 		candidate string
 		reason    PathRejectionReason
 	}{
-		{name: "drive absolute", candidate: `C:\outside.txt`, reason: PathRejectionVolume},
+		{name: "drive absolute", candidate: `C:\outside.txt`, reason: PathRejectionAbsolute},
 		{name: "drive relative", candidate: `C:outside.txt`, reason: PathRejectionVolume},
 		{name: "UNC", candidate: `\\server\share\outside.txt`, reason: PathRejectionVolume},
+		{name: "extended UNC", candidate: `\\?\UNC\server\share\outside.txt`, reason: PathRejectionVolume},
 		{name: "alternate separator", candidate: `inside\outside.txt`, reason: PathRejectionSeparator},
 		{name: "empty component", candidate: "inside//outside.txt", reason: PathRejectionSeparator},
 	}
diff --git a/integration/agentcompat/internal/scenario/legacy_fm_protocol_test.go b/integration/agentcompat/internal/scenario/legacy_fm_protocol_test.go
index 42931e62..82ffcf80 100644
--- a/integration/agentcompat/internal/scenario/legacy_fm_protocol_test.go
+++ b/integration/agentcompat/internal/scenario/legacy_fm_protocol_test.go
@@ -91,7 +91,7 @@ func TestLegacyFM_RejectedPathDispatchesNoFrame(t *testing.T) {
 		{name: "absolute", candidate: filepath.Join(t.TempDir(), "outside"), wantReason: fixture.PathRejectionAbsolute},
 		{name: "parent", candidate: "../outside", wantReason: fixture.PathRejectionParent},
 		{name: "destructive root", candidate: ".", wantReason: fixture.PathRejectionDestructiveRoot},
-		{name: "volume", candidate: `C:\outside`, wantReason: fixture.PathRejectionVolume},
+		{name: "absolute", candidate: `C:\outside`, wantReason: fixture.PathRejectionAbsolute},
 		{name: "separator", candidate: `inside\outside`, wantReason: fixture.PathRejectionSeparator},
 		{name: "symlink parent", candidate: "linked/file", wantReason: fixture.PathRejectionSymlinkParent},
 	}