diff --git a/.quixos-subtree-source.json b/.quixos-subtree-source.json
index e4239c0..14bf34c 100644
--- a/.quixos-subtree-source.json
+++ b/.quixos-subtree-source.json
@@ -1,7 +1,7 @@
 {
   "version": 1,
   "sourceRepo": "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/quixos",
-  "sourceCommit": "a45fd9a85b541ce6b449b28e8b47954bf04de96b",
+  "sourceCommit": "db6d7990a4ffec273258ac313b7d2aeac57b261a",
   "sourcePath": "quixos-protocol",
   "exportName": "quixos-protocol",
   "mirrorRemote": "https://gitea-external.egads.tutti.syntaxblitz.net/quixos/quixos-protocol.git"
diff --git a/src/bindings/index.ts b/src/bindings/index.ts
index 00d20a6..bce2140 100644
--- a/src/bindings/index.ts
+++ b/src/bindings/index.ts
@@ -285,19 +285,35 @@ export const generateTypeScriptBindings = (
       genericImplementationType(definition, [...schema.interfaces, ...(schema.interfaceTemplates ?? [])], type),
     ]);
   }
-  const contracts = schema.interfaces.map((iface) => {
-    const generated = port({
-      id: capabilityId.dependencyPort("contract"),
-      displayName: iface.displayName,
-      requirement: { kind: "interface", interfaceRevisionId: iface.revisionId },
+  // Unused imported interfaces must not introduce new message-codec obligations.
+  // A used port still fails above if its own required codec is missing.
+  const hasCodec = (value: ValueType): boolean => {
+    if (value.kind === "message") return !!options.messages?.[value.descriptorId];
+    if (value.kind === "record") return Object.values(value.fields).every(hasCodec);
+    if (value.kind === "list" || value.kind === "optional") return hasCodec(value.value);
+    return true;
+  };
+  const contracts = schema.interfaces
+    .filter((iface) =>
+      iface.members.every((member) =>
+        member.operations
+          .filter((operation) => operation.mode === "call" && operation.scope !== "class")
+          .every((operation) => hasCodec(operation.inputType) && hasCodec(operation.outputType)),
+      ),
+    )
+    .map((iface) => {
+      const generated = port({
+        id: capabilityId.dependencyPort("contract"),
+        displayName: iface.displayName,
+        requirement: { kind: "interface", interfaceRevisionId: iface.revisionId },
+      });
+      const spec = generated.spec as { operations: unknown };
+      return {
+        iface,
+        type: generated.type,
+        code: `defineQxInterfaceContract<${generated.type}>(${q(iface.revisionId)}, ${JSON.stringify(spec.operations)})`,
+      };
     });
-    const spec = generated.spec as { operations: unknown };
-    return {
-      iface,
-      type: generated.type,
-      code: `defineQxInterfaceContract<${generated.type}>(${q(iface.revisionId)}, ${JSON.stringify(spec.operations)})`,
-    };
-  });
   const imports = [...messages].map(([id, alias]) => {
     const binding = options.messages![id]!;
     if (!/^[A-Za-z_$][A-Za-z0-9_$]*$/.test(binding.export))
diff --git a/src/bindings/react.ts b/src/bindings/react.ts
index 020f71f..4622560 100644
--- a/src/bindings/react.ts
+++ b/src/bindings/react.ts
@@ -78,21 +78,44 @@ export function generateReactBindings(
       throw new Error("React component check must name a local module relative to generated bindings");
     return `type Component${i} = CheckedComponent<${q(component.propsExport)}, typeof import(${q(component.module)})["default"]>;`;
   });
-  const contracts = schema.interfaces.map((iface) => {
-    const reference = type({
-      kind: "object-ref",
-      expectation: { kind: "interface", interfaceRevisionId: iface.revisionId },
-    });
-    const calls = iface.members.flatMap((member) =>
+  // Emit optional discovery descriptors only when the browser has all codecs.
+  // Unrelated opaque-message imports must not break an otherwise checked UI.
+  const browserValue = (value: ValueType, seen: Set<string>): boolean => {
+    if (value.kind === "message") return false;
+    if (value.kind === "builtin") return value.name === "unit";
+    if (value.kind === "record") return Object.values(value.fields).every((field) => browserValue(field, seen));
+    if (value.kind === "list" || value.kind === "optional") return browserValue(value.value, seen);
+    if (value.kind === "object-ref" && value.expectation.kind === "interface") {
+      const id = value.expectation.interfaceRevisionId;
+      if (seen.has(id)) return true;
+      const contract = schema.interfaces.find((entry) => entry.revisionId === id);
+      return !!contract && browserInterface(contract, new Set([...seen, id]));
+    }
+    return true;
+  };
+  const browserInterface = (iface: (typeof schema.interfaces)[number], seen: Set<string>): boolean =>
+    iface.members.every((member) =>
       member.operations
-        .filter((operation) => operation.mode === "call" && operation.scope !== "class")
-        .map(
-          (operation) =>
-            `${q(`${member.displayName}.${operation.displayName}`)}: (${operation.inputType.kind === "builtin" && operation.inputType.name === "unit" ? "" : `input: ${type(operation.inputType)}`}) => Promise<${type(operation.outputType)}>`,
-        ),
+        .filter((op) => op.mode === "call" && op.scope !== "class")
+        .every((op) => browserValue(op.inputType, seen) && browserValue(op.outputType, seen)),
     );
-    return { iface, view: `${reference} & {call: {${calls.join(";")}}}` };
-  });
+  const contracts = schema.interfaces
+    .filter((iface) => browserInterface(iface, new Set([iface.revisionId])))
+    .map((iface) => {
+      const reference = type({
+        kind: "object-ref",
+        expectation: { kind: "interface", interfaceRevisionId: iface.revisionId },
+      });
+      const calls = iface.members.flatMap((member) =>
+        member.operations
+          .filter((operation) => operation.mode === "call" && operation.scope !== "class")
+          .map(
+            (operation) =>
+              `${q(`${member.displayName}.${operation.displayName}`)}: (${operation.inputType.kind === "builtin" && operation.inputType.name === "unit" ? "" : `input: ${type(operation.inputType)}`}) => Promise<${type(operation.outputType)}>`,
+          ),
+      );
+      return { iface, view: `${reference} & {call: {${calls.join(";")}}}` };
+    });
   return (
     `// Generated from checked QX contracts. Do not edit.\nimport {defineReactInterfaceContract} from "@quixos/web-studio-react-runtime";\nimport type {ObjectRef, InterfaceReference, ReadableField, WritableField} from "@quixos/web-studio-react-runtime";\n${declarations.join("\n")}\nexport type ReactResults = {${results.join(";\n")}};\n` +
     `const contractsData = ${JSON.stringify(schema.interfaces)};\n` +
diff --git a/test/react-fields.test.ts b/test/react-fields.test.ts
index c0bfc4b..f83a704 100644
--- a/test/react-fields.test.ts
+++ b/test/react-fields.test.ts
@@ -33,6 +33,18 @@ test("React bindings preserve read-only, writable and nested reference contracts
     interfaces: [iface.resource.revision],
     packages: [pkg.resource.revision],
   } as const;
+  const opaque = structuredClone(iface.resource.revision);
+  opaque.revisionId = "opaque@1" as typeof opaque.revisionId;
+  opaque.displayName = "Opaque";
+  for (const member of opaque.members)
+    for (const operation of member.operations)
+      operation.outputType = { kind: "message", descriptorId: "UnsupportedBrowserMessage" };
+  const withUnusedOpaque = generateReactBindings(
+    { ...schema, interfaces: [...schema.interfaces, opaque], packages: [...schema.packages] },
+    "p@1",
+    ["props"],
+  );
+  assert.doesNotMatch(withUnusedOpaque, /"opaque@1": defineReactInterfaceContract/);
   const generated = generateReactBindings(
     { ...schema, interfaces: [...schema.interfaces], packages: [...schema.packages] },
     "p@1",