fix(sse): default summary + strip malformed id on kept Responses input items (#11110)

Validated on the combined batch board over release/v3.8.50 tip d91238b7: static gates clean, typecheck:core clean, focused tests green.

Defaults summary and strips malformed ids on kept Responses input items — both 400s observed against live muse-spark traffic; the flipped legacy assertion is documented contract propagation. Thank you @maxmad64bis!

open-sse/services/reasoningInputPolicy.ts

@@ -1,5 +1,6 @@
 import { REGISTRY } from "../config/providerRegistry.ts";
 import type { ReasoningTransport } from "../config/providerRegistry.ts";
+import { isValidResponsesItemId } from "./responsesItemId.ts";
 
 type JsonRecord = Record<string, unknown>;
 
@@ -279,13 +280,27 @@ function sanitizeResponsesInput(
       if (!hasPlaintext && !hasOpaque && (!hasDisplaySummary(next) || stripOrphanedSummaries)) {
         continue;
       }
-      if (!hasOpaque && typeof next.id === "string") delete next.id;
+      // `id` is only worth keeping on an opaque item with a valid string value —
+      // non-opaque items don't replay their id, and a malformed value (e.g. `null`,
+      // observed on opencode/zen) must not survive either way (#11108).
+      if (!hasOpaque || !isValidResponsesItemId(next.id)) delete next.id;
+      // Some upstreams (e.g. opencode/zen) omit `summary` entirely on opaque
+      // reasoning items instead of sending an empty array. Replaying that shape
+      // verbatim trips strict Responses-API validators that require the field
+      // to be present on every `input[]` item of type `reasoning` (#11108).
+      // Plaintext-only items intentionally have no `summary` key and must stay
+      // untouched.
+      if (hasOpaque && next.summary === undefined) next.summary = [];
       filtered.push(next);
       continue;
     }
 
     const cloned = { ...record };
-    if (typeof cloned.id === "string") delete cloned.id;
+    // Strip `id` whenever present, valid or not: these items don't need a
+    // replayed server id, and a malformed one (e.g. `null`, same opencode/zen
+    // omission pattern as the reasoning branch above) must not survive either
+    // (#11108).
+    if (cloned.id !== undefined) delete cloned.id;
     filtered.push(cloned);
   }
   return filtered;

open-sse/services/responsesInputSanitizer.ts

@@ -1,3 +1,5 @@
+import { isValidResponsesItemId } from "./responsesItemId.ts";
+
 type JsonRecord = Record<string, unknown>;
 type SanitizeResponsesInputOptions = {
   dropInternalAssistantMessages?: boolean;
@@ -40,7 +42,12 @@ function sanitizeFunctionName(name: string): string {
 }
 
 function sanitizeInputItemId(record: JsonRecord): JsonRecord {
-  if (typeof record.id !== "string") return record;
+  if (record.id === undefined) return record;
+  if (!isValidResponsesItemId(record.id)) {
+    const next = { ...record };
+    delete next.id;
+    return next;
+  }
 
   const type = typeof record.type === "string" ? record.type : "";
   const expectedPrefix = SERVER_ITEM_ID_PREFIX_BY_TYPE[type];

open-sse/services/responsesItemId.ts

@@ -0,0 +1,7 @@
+// Shared by reasoningInputPolicy.ts and responsesInputSanitizer.ts: both strip a
+// Responses-API `input[]` item's `id` field when it isn't a valid string before
+// replay, so a malformed value (e.g. `null`, observed on opencode/zen) never
+// survives to trip a strict upstream with "Expected 'id' to be a string." (#11108).
+export function isValidResponsesItemId(id: unknown): id is string {
+  return typeof id === "string";
+}

tests/unit/reasoning-input-policy-summary-11108.test.ts

@@ -0,0 +1,145 @@
+import { test } from "node:test";
+import assert from "node:assert/strict";
+
+const { applyReasoningInputPolicy } =
+  await import("../../open-sse/services/reasoningInputPolicy.ts");
+
+test("#11108 applyReasoningInputPolicy defaults summary on a kept opaque reasoning item", () => {
+  const body: Record<string, unknown> = {
+    input: [
+      {
+        type: "reasoning",
+        id: "rs_example",
+        encrypted_content: "opaque-blob",
+      },
+    ],
+  };
+
+  applyReasoningInputPolicy(body, "responses", {
+    provider: "opencode",
+    preserveEncryptedReasoning: true,
+  });
+
+  const input = body.input as Record<string, unknown>[];
+  assert.equal(input.length, 1);
+  assert.deepEqual(input[0].summary, []);
+});
+
+test("#11108 applyReasoningInputPolicy preserves an existing summary on a kept reasoning item", () => {
+  const body: Record<string, unknown> = {
+    input: [
+      {
+        type: "reasoning",
+        id: "rs_example",
+        encrypted_content: "opaque-blob",
+        summary: [{ type: "summary_text", text: "Planning." }],
+      },
+    ],
+  };
+
+  applyReasoningInputPolicy(body, "responses", {
+    provider: "opencode",
+    preserveEncryptedReasoning: true,
+  });
+
+  const input = body.input as Record<string, unknown>[];
+  assert.deepEqual(input[0].summary, [{ type: "summary_text", text: "Planning." }]);
+});
+
+test("#11108 applyReasoningInputPolicy defaults summary on an opaque item surviving incompatible-drop", () => {
+  // Mixed item (plaintext + opaque) on an opaque-only transport is incompatible;
+  // dropIncompatibleResponsesReasoning() strips the plaintext content but keeps
+  // the opaque item alive — it must still get a default `summary`.
+  const body: Record<string, unknown> = {
+    input: [
+      {
+        type: "reasoning",
+        id: "rs_mixed",
+        content: [{ type: "reasoning_text", text: "inspect first" }],
+        encrypted_content: "opaque-blob",
+      },
+    ],
+  };
+
+  const result = applyReasoningInputPolicy(body, "responses", {
+    provider: "codex",
+    onIncompatibleReasoning: "drop",
+  });
+
+  assert.equal(result.incompatibleReasoning, false);
+  const input = body.input as Record<string, unknown>[];
+  assert.equal(input.length, 1);
+  assert.equal(input[0].content, undefined);
+  assert.equal(input[0].encrypted_content, "opaque-blob");
+  assert.deepEqual(input[0].summary, []);
+});
+
+test("#11108 applyReasoningInputPolicy strips a non-string id on a kept opaque reasoning item", () => {
+  // Same gap class as the summary fix above: opencode/zen also omits `id`
+  // entirely (surfaced by the client as `id: null`) on opaque-only reasoning
+  // items instead of a `rs_...` string. Replaying that shape verbatim trips
+  // strict Responses-API validators with "Expected 'id' to be a string."
+  const body: Record<string, unknown> = {
+    input: [
+      {
+        type: "reasoning",
+        id: null,
+        encrypted_content: "opaque-blob",
+      },
+    ],
+  };
+
+  applyReasoningInputPolicy(body, "responses", {
+    provider: "opencode",
+    preserveEncryptedReasoning: true,
+  });
+
+  const input = body.input as Record<string, unknown>[];
+  assert.equal(input.length, 1);
+  assert.equal("id" in input[0], false);
+});
+
+test("#11108 applyReasoningInputPolicy strips a non-string id on a non-reasoning item (function_call)", () => {
+  // Same gap class, generic branch: any non-"reasoning" input item (function_call,
+  // message, ...) only stripped `id` when it was already a valid string, so a
+  // malformed `id` (e.g. `null`, mirroring the opencode/zen omission pattern)
+  // on a function_call item survived replay untouched.
+  const body: Record<string, unknown> = {
+    input: [
+      {
+        type: "function_call",
+        id: null,
+        call_id: "call_abc",
+        name: "bash",
+        arguments: "{}",
+      },
+    ],
+  };
+
+  applyReasoningInputPolicy(body, "responses", { provider: "opencode" });
+
+  const input = body.input as Record<string, unknown>[];
+  assert.equal(input.length, 1);
+  assert.equal("id" in input[0], false);
+  assert.equal(input[0].call_id, "call_abc");
+});
+
+test("#11108 applyReasoningInputPolicy preserves a valid string id on a kept opaque reasoning item", () => {
+  const body: Record<string, unknown> = {
+    input: [
+      {
+        type: "reasoning",
+        id: "rs_example",
+        encrypted_content: "opaque-blob",
+      },
+    ],
+  };
+
+  applyReasoningInputPolicy(body, "responses", {
+    provider: "opencode",
+    preserveEncryptedReasoning: true,
+  });
+
+  const input = body.input as Record<string, unknown>[];
+  assert.equal(input[0].id, "rs_example");
+});

tests/unit/responses-input-sanitizer-name.test.ts

@@ -73,6 +73,23 @@ test("keeps valid server reasoning item ids", () => {
   assert.equal(result[0].id, "rs_123");
 });
 
+test("strips a non-string reasoning item id instead of passing it through (#11108)", () => {
+  // Same gap class fixed in reasoningInputPolicy.ts: some upstreams (e.g.
+  // opencode/zen) send `id: null` instead of omitting it. The previous
+  // `typeof record.id !== "string"` guard returned the record unchanged in
+  // that case, letting a malformed id reach a strict Responses-API upstream.
+  const items = [
+    {
+      id: null,
+      type: "reasoning",
+      summary: [{ type: "summary_text", text: "cached reasoning" }],
+    },
+  ];
+  const result = sanitizeResponsesInputItems(items) as Array<Record<string, unknown>>;
+  assert.equal("id" in result[0], false);
+  assert.equal(result[0].type, "reasoning");
+});
+
 test("normalizes user image_url content parts to input_image", () => {
   const items = [
     {

tests/unit/strip-reasoning-blobs-agentic-context-1599.test.ts

@@ -274,7 +274,11 @@ test("explicit custom target opt-in remains an opaque transport override", () =>
   const result = applyReasoningInputPolicy(body, "responses", { preserveEncryptedReasoning: true });
 
   assert.equal(result.incompatibleReasoning, false);
-  assert.deepEqual(body.input, [{ type: "reasoning", encrypted_content: "encrypted-blob" }]);
+  // #11108: a kept opaque item defaults `summary` when the source omitted it —
+  // some upstreams reject `input[]` reasoning items missing the field entirely.
+  assert.deepEqual(body.input, [
+    { type: "reasoning", encrypted_content: "encrypted-blob", summary: [] },
+  ]);
 });
 
 test("preserved opaque reasoning remains redacted from log copies", () => {