diff --git a/ampg/manifest.py b/ampg/manifest.py
index bf39248..7f57447 100644
--- a/ampg/manifest.py
+++ b/ampg/manifest.py
@@ -84,6 +84,7 @@ def _fixture_entry(
         "checks": {
             "transport": transport,
             "profile": transport,
+            "isolation": "transport-profile",
         },
         "interaction": _interaction_policy(protocol, route_policy),
     }
diff --git a/docs/architecture.md b/docs/architecture.md
index 10d0f11..ee7ca73 100644
--- a/docs/architecture.md
+++ b/docs/architecture.md
@@ -94,6 +94,10 @@ Daemon adapters provide a common interface:
 Adapters must be conservative. They do not modify non-AMPG config without showing a
 plan first, and managed config lives under AMPG-owned state directories.
 
+Fixture manifests are the AMPG-to-AMPB boundary. They declare the published URL, expected
+transport, expected profile, and transport-profile isolation result. They do not prescribe
+browser process management or local daemon ownership; those decisions remain inside AMPB.
+
 ## Platform providers
 
 Platform providers decide what daemon management means on the current host. AMPG detects
diff --git a/docs/fixture-manifests.md b/docs/fixture-manifests.md
index 2d4fb82..852cf66 100644
--- a/docs/fixture-manifests.md
+++ b/docs/fixture-manifests.md
@@ -19,7 +19,7 @@ The manifest contains public route expectations only:
 - enabled protocol fixtures.
 - protocol renderer and relative output path.
 - route URL for AMPB checks.
-- expected AMPB transport and profile.
+- expected AMPB transport, profile, and transport-profile isolation.
 - declared interaction tier, identity adapter, payment adapter, realtime flag, and
   public exposure flag.
 - optional route-group metadata for configured public route policies.
@@ -27,6 +27,10 @@ The manifest contains public route expectations only:
 It must not contain private host inventory, hidden-service keys, tunnel keys, credentials,
 or deployment notes.
 
+The isolation check is a browser-facing result, not a daemon-management instruction.
+AMPG declares which transport profile must consume the route; AMPB independently decides
+whether to adopt or start the local transport needed to reach it.
+
 ## Commands
 
 ```sh
diff --git a/tests/test_fixture_manifest.py b/tests/test_fixture_manifest.py
index 0c3e70d..673e4d2 100644
--- a/tests/test_fixture_manifest.py
+++ b/tests/test_fixture_manifest.py
@@ -72,7 +72,14 @@ cid = "bafyexample"
             self.assertEqual("placeholder", by_protocol["tor"]["address_status"])
             self.assertEqual("gemini://example.test/", by_protocol["gemini"]["url"])
             self.assertEqual("ipfs://bafyexample", by_protocol["ipfs"]["url"])
-            self.assertEqual({"transport": "ipfs", "profile": "ipfs"}, by_protocol["ipfs"]["checks"])
+            self.assertEqual(
+                {
+                    "transport": "ipfs",
+                    "profile": "ipfs",
+                    "isolation": "transport-profile",
+                },
+                by_protocol["ipfs"]["checks"],
+            )
             self.assertEqual(
                 {
                     "identity": "none",
diff --git a/tests/test_preview.py b/tests/test_preview.py
index 5bac712..92f0022 100644
--- a/tests/test_preview.py
+++ b/tests/test_preview.py
@@ -38,7 +38,10 @@ class PreviewTest(unittest.TestCase):
             self.assertEqual("http://127.0.0.1:19101/", tor_root["url"])
             self.assertEqual({"transport": "clearnet", "profile": "clearnet"}, tor_root["checks"])
             self.assertEqual("http://preview.onion/", tor_root["published"]["url"])
-            self.assertEqual({"transport": "tor", "profile": "tor"}, tor_root["published"]["checks"])
+            self.assertEqual(
+                {"transport": "tor", "profile": "tor", "isolation": "transport-profile"},
+                tor_root["published"]["checks"],
+            )
             self.assertEqual("preview", tor_root["address_status"])
             self.assertEqual("ready", tor_root["preview"]["status"])