fix(codex): await image URL fetches before sending to upstream (closes #575)

Remote HTTP(S) image URLs are fetched and inlined as base64 data URIs
in a new prefetchImages() step run before super.execute(), so the body
sent to Codex contains resolved image bytes instead of URLs the backend
cannot access.

Scope is limited to the Codex executor — base executor and other
providers are untouched.

Co-authored-by: anuragg-saxenaa <anuragg.saxenaa@gmail.com>
Made-with: Cursor

open-sse/executors/codex.js

@@ -3,6 +3,7 @@ import { BaseExecutor } from "./base.js";
 import { CODEX_DEFAULT_INSTRUCTIONS } from "../config/codexInstructions.js";
 import { PROVIDERS } from "../config/providers.js";
 import { normalizeResponsesInput } from "../translator/helpers/responsesApiHelper.js";
+import { fetchImageAsBase64 } from "../translator/helpers/imageHelper.js";
 import { getConsistentMachineId } from "../../src/shared/utils/machineId.js";
 
 // In-memory map: hash(machineId + first assistant content) → { sessionId, lastUsed }
@@ -93,7 +94,36 @@ export class CodexExecutor extends BaseExecutor {
   }
 
   /**
-   * Transform request before sending - inject default instructions if missing
+   * Prefetch remote image URLs and inline them as base64 data URIs.
+   * Runs before execute() because Codex backend cannot fetch remote images.
+   * Mutates body.input in place.
+   */
+  async prefetchImages(body) {
+    if (!Array.isArray(body?.input)) return;
+    for (const item of body.input) {
+      if (!Array.isArray(item.content)) continue;
+      const pending = item.content.map(async (c) => {
+        if (c.type !== "image_url") return c;
+        const url = typeof c.image_url === "string" ? c.image_url : c.image_url?.url;
+        const detail = c.image_url?.detail || "auto";
+        if (!url) return c;
+        if (url.startsWith("data:")) return { type: "input_image", image_url: url, detail };
+        const fetched = await fetchImageAsBase64(url, { timeoutMs: 15000 });
+        return { type: "input_image", image_url: fetched?.url || url, detail };
+      });
+      item.content = await Promise.all(pending);
+    }
+  }
+
+  async execute(args) {
+    // Fetch remote images before the synchronous transform/execute pipeline
+    await this.prefetchImages(args.body);
+    return super.execute(args);
+  }
+
+  /**
+   * Transform request before sending - inject default instructions if missing.
+   * Image fetching is handled separately in prefetchImages() so this stays sync.
    */
   transformRequest(model, body, stream, credentials) {
     this._isCompact = !!body._compact;
@@ -109,21 +139,6 @@ export class CodexExecutor extends BaseExecutor {
       body.input = [{ type: "message", role: "user", content: [{ type: "input_text", text: "..." }] }];
     }
 
-    // Normalize image content: image_url → input_image (Responses API format)
-    if (Array.isArray(body.input)) {
-      for (const item of body.input) {
-        if (Array.isArray(item.content)) {
-          item.content = item.content.map(c => {
-            if (c.type === "image_url") {
-              const url = typeof c.image_url === "string" ? c.image_url : c.image_url?.url;
-              return { type: "input_image", image_url: url, detail: c.image_url?.detail || "auto" };
-            }
-            return c;
-          });
-        }
-      }
-    }
-
     // Ensure streaming is enabled (Codex API requires it)
     body.stream = true;
 

open-sse/translator/helpers/imageHelper.js

@@ -0,0 +1,34 @@
+/**
+ * Fetch a remote image URL and return it as a base64 data URI.
+ * Used when upstream providers (Codex, etc.) require inline base64 images
+ * instead of remote URLs they cannot fetch.
+ * Returns null if fetch fails.
+ *
+ * @param {string} imageUrl - HTTP(S) URL of the image
+ * @param {object} options - { signal, timeoutMs }
+ * @returns {Promise<{url: string, mimeType: string}|null>}
+ */
+export async function fetchImageAsBase64(imageUrl, options = {}) {
+  const { signal, timeoutMs = 10000 } = options;
+  if (!imageUrl || (!imageUrl.startsWith("http://") && !imageUrl.startsWith("https://"))) {
+    return null;
+  }
+
+  const controller = new AbortController();
+  const timeout = signal ? null : setTimeout(() => controller.abort(), timeoutMs);
+  const fetchSignal = signal || controller.signal;
+
+  try {
+    const response = await fetch(imageUrl, { signal: fetchSignal });
+    if (!response.ok) return null;
+
+    const mimeType = response.headers.get("Content-Type") || "image/jpeg";
+    const arrayBuffer = await response.arrayBuffer();
+    const base64 = Buffer.from(arrayBuffer).toString("base64");
+    return { url: `data:${mimeType};base64,${base64}`, mimeType };
+  } catch {
+    return null;
+  } finally {
+    if (timeout) clearTimeout(timeout);
+  }
+}