From 84b2622c9e378bd266e01ef58fb7039cc090ad13 Mon Sep 17 00:00:00 2001
From: Paul Gear <paul.gear@mantelgroup.com.au>
Date: Wed, 25 Feb 2026 15:41:26 +1000
Subject: [PATCH] For non-anthropic providers, combine system prompts

This is a fix for issue #5034 which works for me using Qwen3.5-35B-A3B.
---
 packages/opencode/src/session/llm.ts | 14 ++++++++------
 1 file changed, 8 insertions(+), 6 deletions(-)

diff --git a/packages/opencode/src/session/llm.ts b/packages/opencode/src/session/llm.ts
index 4e42fb0d2ec7..3e2171af37b2 100644
--- a/packages/opencode/src/session/llm.ts
+++ b/packages/opencode/src/session/llm.ts
@@ -223,12 +223,14 @@ export namespace LLM {
       },
       maxRetries: input.retries ?? 0,
       messages: [
-        ...system.map(
-          (x): ModelMessage => ({
-            role: "system",
-            content: x,
-          }),
-        ),
+        ...(input.model.api.npm === "@ai-sdk/anthropic"
+          ? system.map(
+              (x): ModelMessage => ({
+                role: "system",
+                content: x,
+              }),
+            )
+          : ([{ role: "system", content: system.join("\n") }] as ModelMessage[])),
         ...input.messages,
       ],
       model: wrapLanguageModel({