diff --git a/changelog.d/fixes/6927-qwen-web-content-array.md b/changelog.d/fixes/6927-qwen-web-content-array.md
new file mode 100644
index 0000000000..5eff8b6ed9
--- /dev/null
+++ b/changelog.d/fixes/6927-qwen-web-content-array.md
@@ -0,0 +1 @@
+- fix(sse): Qwen Web executor no longer sends `[object Object]` when a message uses structured (array) content — the text parts are now flattened (#6927)
diff --git a/open-sse/executors/qwen-web.ts b/open-sse/executors/qwen-web.ts
index 485eb93758..bb812a10e7 100644
--- a/open-sse/executors/qwen-web.ts
+++ b/open-sse/executors/qwen-web.ts
@@ -255,11 +255,32 @@ export class QwenWebExecutor extends BaseExecutor {
     };
   }
 
+  /** Flatten OpenAI-style content (string | Array<{type,text}>) into plain text.
+   *  A bare String() on an array of content parts yields "[object Object]" — the
+   *  serialization bug reported on the support mesh. */
+  private contentToText(content: unknown): string {
+    if (typeof content === "string") return content;
+    if (Array.isArray(content)) {
+      return content
+        .map((part) => {
+          if (typeof part === "string") return part;
+          if (part && typeof part === "object") {
+            const p = part as { type?: unknown; text?: unknown };
+            if (typeof p.text === "string") return p.text;
+          }
+          return "";
+        })
+        .filter(Boolean)
+        .join("\n");
+    }
+    return content == null ? "" : String(content);
+  }
+
   private foldMessages(messages: Array<{ role: string; content: unknown }>): string {
     let systemContent = "";
     let userContent = "";
     for (const m of messages) {
-      const text = String(m.content ?? "");
+      const text = this.contentToText(m.content);
       if (m.role === "system") {
         systemContent += (systemContent ? "\n\n" : "") + text;
       } else if (m.role === "user") {
diff --git a/stryker.conf.json b/stryker.conf.json
index ffa4f9f17f..f944f3c27d 100644
--- a/stryker.conf.json
+++ b/stryker.conf.json
@@ -218,6 +218,7 @@
       "tests/unit/quota-policy-generalization.test.ts",
       "tests/unit/quota-pool-log-route.test.ts",
       "tests/unit/quota-streaming-consumption-usd.test.ts",
+      "tests/unit/qwen-web-content-array-serialization.test.ts",
       "tests/unit/rate-limit-enhanced.test.ts",
       "tests/unit/rate-limit-manager.test.ts",
       "tests/unit/rate-limit-queue-timeout-lockout.test.ts",
diff --git a/tests/unit/qwen-web-content-array-serialization.test.ts b/tests/unit/qwen-web-content-array-serialization.test.ts
new file mode 100644
index 0000000000..3949f6484b
--- /dev/null
+++ b/tests/unit/qwen-web-content-array-serialization.test.ts
@@ -0,0 +1,83 @@
+// Regression: Qwen Web executor folded structured (array) message content with a
+// bare String(m.content), producing the literal "[object Object]" prompt instead of
+// the real text (reported on the support mesh: "[[object][object]] serialisation error").
+// The executor must flatten OpenAI-style content parts into their text before sending.
+import { describe, it, afterEach } from "node:test";
+import assert from "node:assert/strict";
+
+const mod = await import("../../open-sse/executors/qwen-web.ts");
+
+type FetchCall = { url: string; init: { method?: string; body?: string } };
+const realFetch = globalThis.fetch;
+
+function sseResponse(events: Array<Record<string, unknown>>): Response {
+  const encoder = new TextEncoder();
+  const stream = new ReadableStream({
+    start(controller) {
+      for (const ev of events) {
+        controller.enqueue(encoder.encode(`data: ${JSON.stringify(ev)}\n\n`));
+      }
+      controller.enqueue(encoder.encode("data: [DONE]\n\n"));
+      controller.close();
+    },
+  });
+  return new Response(stream, {
+    status: 200,
+    headers: { "content-type": "text/event-stream" },
+  });
+}
+
+function chatCreatedResponse(id = "chat-arr"): Response {
+  return new Response(JSON.stringify({ success: true, data: { id } }), {
+    status: 200,
+    headers: { "content-type": "application/json" },
+  });
+}
+
+afterEach(() => {
+  globalThis.fetch = realFetch;
+});
+
+describe("QwenWebExecutor — structured (array) content serialization", () => {
+  it("flattens OpenAI-style content parts to text (no '[object Object]')", async () => {
+    const calls: FetchCall[] = [];
+    globalThis.fetch = (async (url: string | URL | Request, init: RequestInit = {}) => {
+      calls.push({ url: String(url), init: init as { method?: string; body?: string } });
+      if (String(url).includes("/api/v2/chats/new")) return chatCreatedResponse();
+      return sseResponse([
+        { choices: [{ delta: { phase: "answer", content: "ok", status: "finished" } }] },
+      ]);
+    }) as typeof fetch;
+
+    const executor = new mod.QwenWebExecutor();
+    await executor.execute({
+      model: "qwen3.7-max",
+      body: {
+        messages: [
+          { role: "system", content: [{ type: "text", text: "You are helpful." }] },
+          {
+            role: "user",
+            content: [
+              { type: "text", text: "First part." },
+              { type: "text", text: "Second part." },
+            ],
+          },
+        ],
+      },
+      stream: false,
+      credentials: { apiKey: "token=jwt-tok; cna=abc" },
+      signal: null,
+    } as unknown as Parameters<typeof executor.execute>[0]);
+
+    const compBody = JSON.parse(calls[1].init.body);
+    const sent = String(compBody.messages[0].content);
+
+    assert.ok(
+      !sent.includes("[object Object]"),
+      `prompt must not contain '[object Object]', got: ${sent}`
+    );
+    assert.ok(sent.includes("First part."), "text of first content part must survive");
+    assert.ok(sent.includes("Second part."), "text of second content part must survive");
+    assert.ok(sent.includes("You are helpful."), "system content part must survive");
+  });
+});