fix: reject unknown keys in nested quirk objects

src/responses.test.ts

@@ -101,6 +101,23 @@ describe("Responses adapter — block-index lifecycle", () => {
       }),
     ).toThrow();
   });
+
+  test.each([
+    ["headers", { headers: { statc: {} } }],
+    [
+      "headers.fromOption",
+      {
+        headers: { fromOption: [{ optionKey: "a", header: "x-a", hedr: "" }] },
+      },
+    ],
+    [
+      "systemPrompt",
+      { systemPrompt: { role: "system", shape: "string", rol: "system" } },
+    ],
+    ["reasoning", { reasoning: { sumary: "auto" } }],
+  ])("rejects an unrecognized %s field instead of ignoring it", (_, quirks) => {
+    expect(() => createOpenAIResponsesAdapter(source, quirks)).toThrow();
+  });
 });
 
 describe("Responses request builder — quirk matrix", () => {

src/responses.ts

@@ -31,13 +31,15 @@ import {
 const HeaderFromOption = type({
   optionKey: "string",
   header: "string",
+  "+": "reject",
 });
 type HeaderFromOption = typeof HeaderFromOption.infer;
 
 const ResponsesHeaders = type({
   "static?": { "[string]": "string" },
   "modelHeader?": "string",
   "fromOption?": HeaderFromOption.array(),
+  "+": "reject",
 });
 
 // `shape: "string"` sends plain string content (Grok/OpenAI); `"parts"`
@@ -46,6 +48,7 @@ const ResponsesHeaders = type({
 const SystemPromptPlacement = type({
   role: "'system' | 'developer'",
   shape: "'string' | 'parts'",
+  "+": "reject",
 });
 type SystemPromptPlacement = typeof SystemPromptPlacement.infer;
 
@@ -55,6 +58,7 @@ const ReasoningQuirks = type({
   // The wire value Interchange's neutral `max` effort becomes. The highest
   // level differs per model, so only the source can name it.
   "maxEffort?": "'xhigh' | 'max'",
+  "+": "reject",
 });
 type ReasoningQuirks = typeof ReasoningQuirks.infer;