From 0089040f2dfb10a64cc55db4737bf2a4790e779d Mon Sep 17 00:00:00 2001
From: Stardust <1441308506a@gmail.com>
Date: Mon, 16 Mar 2026 17:21:05 +0800
Subject: [PATCH] fix(llm): flatten content array for OpenAI-compatible
 providers (#1222)

* fix(llm): flatten content array for OpenAI-compatible providers

* fix(llm): improve type safety in sanitizeMessages

* fix(stage-ui): add notice comment for message content flattening compatibility

Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>

---------

Co-authored-by: Neko <neko@ayaka.moe>
Co-authored-by: gemini-code-assist[bot] <176961590+gemini-code-assist[bot]@users.noreply.github.com>
---
 packages/stage-ui/src/stores/llm.ts | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/packages/stage-ui/src/stores/llm.ts b/packages/stage-ui/src/stores/llm.ts
index 8adb6efb5..f47b181ab 100644
--- a/packages/stage-ui/src/stores/llm.ts
+++ b/packages/stage-ui/src/stores/llm.ts
@@ -34,6 +34,16 @@ function sanitizeMessages(messages: unknown[]): Message[] {
         content: `User encountered error: ${String(m.content ?? '')}`,
       } as Message
     }
+    // NOTICE: This block is critical for backward compatibility with LLM providers (e.g., DeepSeek)
+    // that expect message content to be a string, not an array of content parts.
+    // Failure to flatten array content (when no image_url is present) can lead to
+    // deserialization errors like "invalid type: sequence, expected a string".
+    if (m && Array.isArray(m.content)) {
+      const contentParts = m.content as { type?: string, text?: string }[]
+      if (!contentParts.some(p => p?.type === 'image_url')) {
+        return { ...m, content: contentParts.map(p => p?.text ?? '').join('') } as Message
+      }
+    }
     return m as Message
   })
 }