diff --git a/CHANGELOG.md b/CHANGELOG.md
index d5b422fc05..4707bf82ee 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -13,6 +13,8 @@
 ### 🐛 Bug Fixes
 
 - **fix(gemini-cli):** separate Cloud Code transport from Antigravity (#1869 — thanks @dhaern)
+- **fix(codex):** map prompt field to input array for Cursor compatibility (fixes #1872)
+- **fix(core):** align stream parameter default to false per strict OpenAI spec (fixes #1873)
 
 ### 🏆 Release Attribution & Retroactive Credits
 
diff --git a/open-sse/executors/codex.ts b/open-sse/executors/codex.ts
index e84be095b6..2e7b6f35fe 100644
--- a/open-sse/executors/codex.ts
+++ b/open-sse/executors/codex.ts
@@ -1198,6 +1198,21 @@ export class CodexExecutor extends BaseExecutor {
                 })
               : [],
       }));
+    } else if (!body.input && typeof body.prompt === "string" && body.prompt.trim()) {
+      // Issue #1872: Cursor occasionally passes the request as `prompt` instead of `messages`.
+      body.input = [
+        {
+          type: "message",
+          role: "user",
+          content: [{ type: "input_text", text: body.prompt }],
+        },
+      ];
+    } else if (!body.input && Array.isArray(body.prompt)) {
+      body.input = body.prompt.map((p: any) => ({
+        type: "message",
+        role: "user",
+        content: [{ type: "input_text", text: typeof p === "string" ? p : JSON.stringify(p) }],
+      }));
     }
 
     // ── Cache-aware system prompt handling (both paths) ──
diff --git a/open-sse/utils/aiSdkCompat.ts b/open-sse/utils/aiSdkCompat.ts
index 91d284bfc1..5f0100b08f 100644
--- a/open-sse/utils/aiSdkCompat.ts
+++ b/open-sse/utils/aiSdkCompat.ts
@@ -22,8 +22,10 @@ export function resolveStreamFlag(bodyStream: unknown, acceptHeader: unknown): b
   // Explicit body value always wins
   if (bodyStream === true) return true;
   if (bodyStream === false) return false;
-  // No explicit stream param — fall back to Accept header heuristic
-  return !clientWantsJsonResponse(acceptHeader);
+
+  // No explicit stream param — default to false per OpenAI spec
+  // (Fixes #1873 - previously relied on Accept header heuristic)
+  return false;
 }
 
 /**