diff --git a/internal/platform/canvas_model_test.go b/internal/platform/canvas_model_test.go
index 4c905be..83e22c2 100644
--- a/internal/platform/canvas_model_test.go
+++ b/internal/platform/canvas_model_test.go
@@ -2,9 +2,9 @@ package platform
 
 import (
 	"bytes"
+	_ "embed"
 	"encoding/json"
 	"fmt"
-	"os"
 	"testing"
 )
 
@@ -12,6 +12,11 @@ const modelRootID = "10000000-0000-4000-8000-000000000001"
 const modelChildID = "10000000-0000-4000-8000-000000000002"
 const modelLegacyFrame = `{"id":"f","type":"frame","position":{"x":100,"y":200},"width":640,"height":400,"data":{"kind":"frame","title":"Partition","text":"","labelMode":"fixed"}}`
 
+// The schema runner mounts only the test binary, not the source tree.
+//
+//go:embed testdata/foundry-model-operation-v2.json
+var canonicalFrontendFixture []byte
+
 func modelJSON(value any) json.RawMessage { raw, _ := json.Marshal(value); return raw }
 func modelTestID(n int) string            { return fmt.Sprintf("90000000-0000-4000-8000-%012d", n) }
 func modelTestAllocator() func() string {
@@ -153,14 +158,10 @@ func TestCanonicalValidationRejectsPartialChangesAndWrongEdgeOwner(t *testing.T)
 }
 
 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 := json.NewDecoder(bytes.NewReader(canonicalFrontendFixture))
 	decoder.DisallowUnknownFields()
-	if err = decoder.Decode(&input); err != nil {
+	if err := decoder.Decode(&input); err != nil {
 		t.Fatal(err)
 	}
 	if input.ProtocolVersion != canvasModelProtocol || !uuidSlugPattern.MatchString(input.RequestID) || input.Expected[modelRootID] != 3 {