From a7d2dba1eb7722ceadb5100a174c6c7d42cf551f Mon Sep 17 00:00:00 2001
From: Diego Rodrigues de Sa e Souza <diegosouza.pw@gmail.com>
Date: Sun, 9 Aug 2026 09:52:54 -0300
Subject: [PATCH] fix(types): narrow DeepSeek tool calls (#9860)

Co-authored-by: backryun <bakryun0718@proton.me>
---
 open-sse/executors/deepseek-web.ts                      | 6 +++---
 tests/unit/deepseek-web-tool-result-prompt-4712.test.ts | 8 ++++++++
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/open-sse/executors/deepseek-web.ts b/open-sse/executors/deepseek-web.ts
index 99fda068af..4f3314ca8d 100644
--- a/open-sse/executors/deepseek-web.ts
+++ b/open-sse/executors/deepseek-web.ts
@@ -515,7 +515,6 @@ export function messagesToPrompt(
   historyWindow = 0
 ): string {
   if (messages.length === 0) return "";
-
   const systemParts: string[] = [];
   const conversation: Array<{ role: string; text: string }> = [];
   const callNameById = new Map<string, string>();
@@ -527,8 +526,9 @@ export function messagesToPrompt(
     } else if (m.role === "user" || m.role === "assistant") {
       if (text) conversation.push({ role: m.role, text });
       if (m.role === "user") lastUserContent = text;
-      const calls = Array.isArray((m as { tool_calls?: unknown }).tool_calls)
-        ? (m as { tool_calls: Array<{ id?: string; function?: { name?: string } }> }).tool_calls
+      const toolCalls = (m as { tool_calls?: unknown }).tool_calls;
+      const calls = Array.isArray(toolCalls)
+        ? (toolCalls as Array<{ id?: string; function?: { name?: string } }>)
         : [];
       for (const c of calls) {
         if (c?.id && typeof c.function?.name === "string") callNameById.set(c.id, c.function.name);
diff --git a/tests/unit/deepseek-web-tool-result-prompt-4712.test.ts b/tests/unit/deepseek-web-tool-result-prompt-4712.test.ts
index 38136f270d..eed0311b8c 100644
--- a/tests/unit/deepseek-web-tool-result-prompt-4712.test.ts
+++ b/tests/unit/deepseek-web-tool-result-prompt-4712.test.ts
@@ -64,3 +64,11 @@ test("messagesToPrompt still drops empty tool results without crashing (#4712)",
   assert.match(prompt, /hello/);
   assert.match(prompt, /world/);
 });
+
+test("messagesToPrompt ignores malformed assistant tool calls", () => {
+  const prompt = messagesToPrompt([
+    { role: "assistant", content: "thinking", tool_calls: { id: "not-an-array" } },
+    { role: "user", content: "continue" },
+  ]);
+  assert.match(prompt, /continue/);
+});