diff --git a/scripts/ci/check-scopes.json b/scripts/ci/check-scopes.json
index a368e08a4..50f15a3b0 100644
--- a/scripts/ci/check-scopes.json
+++ b/scripts/ci/check-scopes.json
@@ -28,6 +28,19 @@
     "NOTICE"
   ],
   "rules": [
+    {
+      "paths": [
+        "docs/internals/architecture/appserver/app-protocol-*.schema.json"
+      ],
+      "checks": [
+        "gui",
+        "architecture",
+        "coding",
+        "apphost",
+        "appservice"
+      ],
+      "reason": "App Protocol shared contract and direct consumers"
+    },
     {
       "paths": ["gui/**", "scripts/gui/**"],
       "checks": ["gui"],
diff --git a/tests/appserver/test_connection.py b/tests/appserver/test_connection.py
index ce34b3d18..b2f51c357 100644
--- a/tests/appserver/test_connection.py
+++ b/tests/appserver/test_connection.py
@@ -38,6 +38,8 @@
     SessionEventKindV1,
     SessionEventV1,
     SessionIdentityV1,
+    SessionModelSelectV1,
+    SessionModelsV1,
     SessionOpenSpecV1,
     SessionScopeV1,
     SessionSnapshotRequestV1,
@@ -150,6 +152,7 @@ async def scenario() -> None:
         mux = MuxSpaceV1("mux", "dev", 1, ())
         snapshot = SessionSnapshotV1(identity, "Coding", 0, 0, False)
         attachment = MuxAttachmentV1("a", mux, 1, ())
+        models = SessionModelsV1(None, ())
         event = AttachmentEventV1(
             "a", "m", SessionEventV1("s", 1, SessionEventKindV1.TURN_COMPLETED)
         )
@@ -172,6 +175,16 @@ async def scenario() -> None:
             ),
             ("close_member", MuxMemberCloseV1(selector, "m"), mux),
             ("snapshot_session", SessionSnapshotRequestV1("a", 1, "m"), snapshot),
+            (
+                "list_session_models",
+                SessionSnapshotRequestV1("a", 1, "m"),
+                models,
+            ),
+            (
+                "select_session_model",
+                SessionModelSelectV1("a", 1, "m", "provider:model"),
+                models,
+            ),
             ("start_turn", TurnTextV1("a", 1, "m", "start"), AckV1()),
             ("steer_turn", TurnTextV1("a", 1, "m", "steer"), AckV1()),
             ("follow_up_turn", TurnTextV1("a", 1, "m", "follow up"), AckV1()),
diff --git a/tests/architecture/test_hosted_application_g11.py b/tests/architecture/test_hosted_application_g11.py
index 215cccfe5..c5b42e8f0 100644
--- a/tests/architecture/test_hosted_application_g11.py
+++ b/tests/architecture/test_hosted_application_g11.py
@@ -245,11 +245,13 @@ def test_g11_package_budgets_keep_new_owners_reviewable() -> None:
         # 271 lines to this exact group; all protocol modules still count.
         # See hosted-session-workflow-g17.md, Reviewability Budget Supplement.
         "appserver": 2_100,
-        "appservice-core": 1_500,
+        # Attachment-scoped model discovery and selection extend the existing
+        # AppService authority boundary without exposing provider credentials.
+        "appservice-core": 1_550,
         "appservice-continuity": 1_250,
-        # Optional execution adds omission metadata and a synchronous projection
-        # seam; its two owners have a separate budget in the Wave A contract.
-        "coding-adapter": 420,
+        # Optional execution plus the redacted, session-local model control
+        # bridge remain isolated in the Coding AppService adapter.
+        "coding-adapter": 470,
         "harnesstui-mux": 600,
     }
     for name, paths in groups.items():
diff --git a/tests/ci/test_change_gates.py b/tests/ci/test_change_gates.py
index 1d2a6376a..764b7d09e 100644
--- a/tests/ci/test_change_gates.py
+++ b/tests/ci/test_change_gates.py
@@ -30,6 +30,42 @@ def load_script(name: str):
 
 
 class ScopeTests(unittest.TestCase):
+    def test_app_protocol_schema_selects_only_direct_consumers(self):
+        path = "docs/internals/architecture/appserver/app-protocol-v1.schema.json"
+        actual = self.selected(path)
+
+        self.assertEqual(
+            actual,
+            {
+                "docs",
+                "gui",
+                "architecture",
+                "coding",
+                "apphost",
+                "appservice",
+                "host_runtime",
+            },
+        )
+        self.assertFalse(
+            {
+                "ai",
+                "agent",
+                "harness",
+                "harness_native",
+                "harnesstui",
+                "coding_ui",
+                "tui_unit",
+                "tui_playback",
+                "tui_native",
+                "hosting",
+                "windows_shell",
+                "install",
+                "lsp",
+                "foundation",
+            }
+            & actual
+        )
+
     def test_gui_code_and_tooling_select_only_gui_and_docs(self):
         for path in ("gui/src/App.tsx", "gui/src-tauri/Cargo.lock", "gui/pnpm-lock.yaml", "scripts/gui/run.mjs"):
             with self.subTest(path=path):