diff --git a/internal/platform/canvas_model_integration_test.go b/internal/platform/canvas_model_integration_test.go
index c376f8f..469b3cc 100644
--- a/internal/platform/canvas_model_integration_test.go
+++ b/internal/platform/canvas_model_integration_test.go
@@ -236,4 +236,25 @@ func TestCanonicalModelMigrationAndIncrementalLifecycle(t *testing.T) {
 	if writer.Code != 409 {
 		t.Fatal("expected-account barrier was ignored")
 	}
+	// A new partition's entry, owning canvas and versions publish atomically.
+	newCanvas, newFrame := modelTestID(5000), modelTestID(5001)
+	frame := modelTestNode(newFrame, root)
+	frame["componentId"] = "frame"
+	canvas := modelCanvas{ID: newCanvas, Parent: &modelParent{CanvasID: root, EntryElementID: newFrame}}
+	edit(1010, map[string]int64{root: 8, newCanvas: 0}, modelChange{Kind: "canvas", ID: newCanvas, Before: modelJSON(nil), After: modelJSON(canvas)}, modelChange{Kind: "element", ID: newFrame, Before: modelJSON(nil), After: modelJSON(frame)})
+	model = read()
+	if model.Versions[newCanvas] != 1 || model.Canvases[newCanvas].Parent.EntryElementID != newFrame {
+		t.Fatal("partition creation was not atomic")
+	}
+	edit(1011, map[string]int64{root: 9, newCanvas: 1}, modelChange{Kind: "canvas", ID: newCanvas, Before: modelJSON(canvas), After: modelJSON(nil)}, modelChange{Kind: "element", ID: newFrame, Before: modelJSON(frame), After: modelJSON(nil)})
+	model = read()
+	if _, exists := model.Canvases[newCanvas]; exists || model.Versions[newCanvas] != 2 {
+		t.Fatal("partition archive lost its version fence")
+	}
+	frame["incarnation"] = float64(2)
+	edit(1012, map[string]int64{root: 10, newCanvas: 2}, modelChange{Kind: "element", ID: newFrame, Before: modelJSON(nil), After: modelJSON(frame)}, modelChange{Kind: "canvas", ID: newCanvas, Before: modelJSON(nil), After: modelJSON(canvas)})
+	model = read()
+	if model.Versions[newCanvas] != 3 || modelInt(model.Elements[newFrame]["incarnation"]) != 2 {
+		t.Fatal("partition restore reused a stale lifecycle or version")
+	}
 }
diff --git a/internal/platform/canvas_model_test.go b/internal/platform/canvas_model_test.go
index aeedd12..4c905be 100644
--- a/internal/platform/canvas_model_test.go
+++ b/internal/platform/canvas_model_test.go
@@ -1,8 +1,10 @@
 package platform
 
 import (
+	"bytes"
 	"encoding/json"
 	"fmt"
+	"os"
 	"testing"
 )
 
@@ -149,3 +151,28 @@ func TestCanonicalValidationRejectsPartialChangesAndWrongEdgeOwner(t *testing.T)
 		t.Fatal("cross-child connection acquired a child owner")
 	}
 }
+
+func TestCanonicalFrontendProtocolFixture(t *testing.T) {
+	raw, err := os.ReadFile("testdata/foundry-model-operation-v2.json")
+	if err != nil {
+		t.Fatal(err)
+	}
+	var input modelBatch
+	decoder := json.NewDecoder(bytes.NewReader(raw))
+	decoder.DisallowUnknownFields()
+	if err = decoder.Decode(&input); err != nil {
+		t.Fatal(err)
+	}
+	if input.ProtocolVersion != canvasModelProtocol || !uuidSlugPattern.MatchString(input.RequestID) || input.Expected[modelRootID] != 3 {
+		t.Fatal("frontend fixture envelope is incompatible")
+	}
+	before := modelTestDocument()
+	before.Versions[modelRootID] = 3
+	after, touched, err := applyModelOperations(before, input.Operations)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if !touched[modelRootID] || after.Versions[modelRootID] != 4 || after.Elements["a"]["data"].(map[string]any)["title"] != "renamed" || after.Elements["a"]["data"].(map[string]any)["text"] != "preserved" {
+		t.Fatal("frontend fixture did not apply exactly its intended field change")
+	}
+}
diff --git a/internal/platform/testdata/foundry-model-operation-v2.json b/internal/platform/testdata/foundry-model-operation-v2.json
new file mode 100644
index 0000000..165b8ea
--- /dev/null
+++ b/internal/platform/testdata/foundry-model-operation-v2.json
@@ -0,0 +1,26 @@
+{
+  "protocol_version": 2,
+  "request_id": "90000000-0000-4000-8000-000000000002",
+  "expected_versions": {
+    "10000000-0000-4000-8000-000000000001": 3
+  },
+  "operations": [
+    {
+      "id": "90000000-0000-4000-8000-000000000001",
+      "changes": [
+        {
+          "kind": "field",
+          "target": {
+            "id": "a",
+            "incarnation": 1
+          },
+          "field": "data.title",
+          "before": "a",
+          "after": "renamed",
+          "beforePresent": true,
+          "afterPresent": true
+        }
+      ]
+    }
+  ]
+}