diff --git a/src/server/responses-reasoning-summary-rewrite.ts b/src/server/responses-reasoning-summary-rewrite.ts
index 21a8b6a5bf..55c6d8ae7b 100644
--- a/src/server/responses-reasoning-summary-rewrite.ts
+++ b/src/server/responses-reasoning-summary-rewrite.ts
@@ -34,6 +34,13 @@ function reasoningTextOf(item: Record<string, unknown>): string {
 /** Move a reasoning item's content channel into the summary channel. */
 function reasoningItemToSummaryShape(item: Record<string, unknown>): Record<string, unknown> {
   if (item.type !== "reasoning") return item;
+  // `encrypted_content` is opaque, state-bearing provider data, so the entire item must retain its
+  // upstream shape unless that backend has an explicit replay contract permitting a rewrite. This
+  // defensively protects content-channel backends that do issue blobs when the client replays the
+  // stored item. The delta rewrite can still provide the expandable trace for the live turn.
+  // DeepSeek — the provider this rewrite was verified against — is `statelessResponses` and issues
+  // no blob, so it is unaffected.
+  if (typeof item.encrypted_content === "string" && item.encrypted_content.length > 0) return item;
   const text = reasoningTextOf(item);
   // Items that already use the summary channel (or carry no content text at
   // all) are left untouched: rewriting them could clear a valid summary.
diff --git a/structure/04_transports-and-sidecars.md b/structure/04_transports-and-sidecars.md
index efd1c87dbb..2074d78978 100644
--- a/structure/04_transports-and-sidecars.md
+++ b/structure/04_transports-and-sidecars.md
@@ -797,6 +797,16 @@ Codex app, so tool cells group like native models — while the text still round
 `content[reasoning_text]` shape. Diagnosis and codex-rs grouping evidence:
 `devlog/_fin/260709_native_response_pattern/`.
 
+The content-to-summary channel rewrite skips any reasoning item that carries a native
+`encrypted_content` blob. The blob is opaque, state-bearing provider data, so the item must
+round-trip unchanged unless that backend has an explicit replay contract permitting a rewrite.
+This defensively protects providers that issue blobs and later join the route through
+`preserveReasoningContentModels`. The rewrite's round trip was verified against DeepSeek, which is
+`statelessResponses` and issues no blob. Grok is unaffected in practice because it natively emits
+summary-channel reasoning and no `reasoning_text` events, so this content-to-summary item rewrite
+does not engage on its route. Only the stored item is exempt — `reasoning_text` delta events carry
+no blob and still route to the summary channel, so the live expandable trace is unchanged.
+
 The process-local raw-reasoning fallback is fail-closed unless a request has an explicit client
 thread plus an exact provider destination, wire adapter, final model, and physical credential
 identity. API-key material is represented only by a process-keyed HMAC; OAuth replay is bound to the
diff --git a/tests/responses-reasoning-summary-rewrite.test.ts b/tests/responses-reasoning-summary-rewrite.test.ts
index 09b8e1bad7..4ba42acf91 100644
--- a/tests/responses-reasoning-summary-rewrite.test.ts
+++ b/tests/responses-reasoning-summary-rewrite.test.ts
@@ -209,6 +209,52 @@ describe("responses reasoning summary channel rewrite", () => {
     expect(rewrite("not json")).toBe("not json");
     expect(rewrite("[1,2]")).toBe("[1,2]");
   });
+
+  // `encrypted_content` is opaque, state-bearing provider data, so preserve the complete item
+  // shape defensively when the client replays it. This rewrite's round-trip was verified against
+  // DeepSeek, which is stateless and issues no blob; providers that do issue one joined later
+  // through `preserveReasoningContentModels`.
+  describe("items carrying encrypted_content", () => {
+    const blobItem = {
+      type: "reasoning",
+      id: "rs_1",
+      status: "completed",
+      encrypted_content: "gAAAAAB-upstream-issued-blob",
+      content: [{ type: "reasoning_text", text: "thinking" }],
+      summary: [],
+    };
+
+    test("are returned byte-for-byte on output_item.done", () => {
+      const payload = { type: "response.output_item.done", output_index: 0, item: blobItem };
+      expect(apply(payload)).toEqual(payload);
+    });
+
+    test("are returned byte-for-byte inside response.completed output", () => {
+      const payload = {
+        type: "response.completed",
+        response: { id: "resp_1", output: [blobItem] },
+      };
+      expect(apply(payload)).toEqual(payload);
+    });
+
+    test("are returned byte-for-byte through the non-streaming document rewrite", () => {
+      const doc = { id: "resp_1", object: "response", output: [blobItem] };
+      expect(rewriteReasoningSummaryInJson(doc)).toBe(doc);
+      const json = JSON.stringify(doc);
+      expect(rewriteReasoningSummaryInJsonString(json)).toBe(json);
+    });
+
+    // Only the stored item is protected: the live trace Codex renders comes from the delta events,
+    // which carry no blob and are still routed to the summary channel.
+    test("do not disable the delta rewrite that renders the live trace", () => {
+      expect(apply({
+        type: "response.reasoning_text.delta",
+        delta: "think",
+        item_id: "rs_1",
+        output_index: 0,
+      })).toMatchObject({ type: "response.reasoning_summary_text.delta", delta: "think" });
+    });
+  });
 });
 
 describe("routeUsesContentChannelReasoning", () => {