diff --git a/scripts/e2e/proxy-swap.sh b/scripts/e2e/proxy-swap.sh
index a40e5009a..a8e19f382 100755
--- a/scripts/e2e/proxy-swap.sh
+++ b/scripts/e2e/proxy-swap.sh
@@ -300,6 +300,11 @@ matrix() {
 import pathlib, sys
 # Accepted differences (P7-DEPL-03 lead ruling 2026-10-12): transport framing and Vary are proxy-owned, and Traefik
 # adds no response headers to a 101 upgrade, so a websocket row keeps only its handshake headers.
+# Browsers do not apply CSP or X-Frame-Options from a websocket handshake response (they govern the document). However,
+# Chromium learns HSTS from secure WebSocket handshakes and enforces it on subsequent requests
+# (https://github.com/chromium/chromium/blob/main/net/websockets/websocket_end_to_end_test.cc#L670); the missing HSTS
+# header on 101 responses is therefore an unresolved difference. Vary (D-0769) stays open until the traefik renderer decides
+# whether to add Accept-Encoding; the matrix is tightened in the same change as the renderer.
 skip={'date','server','connection','content-length','transfer-encoding','keep-alive','vary'}
 handshake={'upgrade','sec-websocket-accept'}
 headers=[]
diff --git a/test/e2e/sdk_compat_parity_test.go b/test/e2e/sdk_compat_parity_test.go
new file mode 100644
index 000000000..bbbee1672
--- /dev/null
+++ b/test/e2e/sdk_compat_parity_test.go
@@ -0,0 +1,39 @@
+package e2e
+
+import (
+	"os"
+	"testing"
+
+	internalcompat "github.com/nself-org/cli/internal/compat"
+	sdkcompat "github.com/nself-org/cli/sdk/go/v2/compat"
+)
+
+// TestSDKCopyAgreesInCLIProcess pins D-0705. The CLI links sdk/go/compat (the
+// pin store ancestor gate in sdk/go/remote reads it), and that copy reads only
+// NSELF_V15. Today both copies apply the same rule, so they agree for every
+// value. If P7-SHIP flips this package's default without the sdk copy following
+// (or the CLI exporting its resolved mode), the CLI would print the v1.4
+// ancestor warning where it must refuse. This test fails the moment they
+// diverge, so the flip has to handle the sdk copy in the same change.
+//
+// Lives in test/e2e (L3) rather than internal/compat (L0) because L0 may not
+// import the SDK module; see internal/repoqa/testdata/layers.yaml D1.
+func TestSDKCopyAgreesInCLIProcess(t *testing.T) {
+	for _, v := range []string{"<unset>", "", "0", "1", "true", "TRUE", "True", "yes", "on", " 1"} {
+		t.Run(v, func(t *testing.T) {
+			if v == "<unset>" {
+				t.Setenv(internalcompat.EnvVar, "x")
+				if err := os.Unsetenv(internalcompat.EnvVar); err != nil {
+					t.Fatalf("unset %s: %v", internalcompat.EnvVar, err)
+				}
+			} else {
+				t.Setenv(internalcompat.EnvVar, v)
+			}
+			if cli, sdk := internalcompat.V15(), sdkcompat.V15(); cli != sdk {
+				t.Fatalf("NSELF_V15=%q: internal/compat.V15() = %v but sdk/go/compat.V15() = %v; "+
+					"the CLI process links both (sdk/go/remote/knownhosts_compat.go, D-0484): "+
+					"export the resolved mode to the sdk copy or delete the v1.4 branch in the same change (D-0705)", v, cli, sdk)
+			}
+		})
+	}
+}