From 521ac53ff8372a1a9349ee9cb58a93595c84bc71 Mon Sep 17 00:00:00 2001
From: Spencer Hong <11135652+spencer-hong@users.noreply.github.com>
Date: Tue, 31 Mar 2026 13:17:54 -0400
Subject: [PATCH] Revert "fix: filter empty assistant messages for all
 providers"

---
 packages/opencode/src/provider/transform.ts | 38 ++++++++++-----------
 1 file changed, 19 insertions(+), 19 deletions(-)

diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index c784c4f8e3ca..f651a5b91aaf 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -51,27 +51,27 @@ export namespace ProviderTransform {
     model: Provider.Model,
     options: Record<string, unknown>,
   ): ModelMessage[] {
-    // Filter out messages with empty content - many providers (Anthropic, Bedrock,
-    // Moonshot/Kimi, OpenAI-compatible) reject empty assistant messages.
-    // Apply unconditionally since no provider accepts truly empty messages.
-    // See: https://github.com/anomalyco/opencode/issues/6056
-    msgs = msgs
-      .map((msg) => {
-        if (typeof msg.content === "string") {
-          if (msg.content === "") return undefined
-          return msg
-        }
-        if (!Array.isArray(msg.content)) return msg
-        const filtered = msg.content.filter((part) => {
-          if (part.type === "text" || part.type === "reasoning") {
-            return part.text !== ""
+    // Anthropic rejects messages with empty content - filter out empty string messages
+    // and remove empty text/reasoning parts from array content
+    if (model.api.npm === "@ai-sdk/anthropic" || model.api.npm === "@ai-sdk/amazon-bedrock") {
+      msgs = msgs
+        .map((msg) => {
+          if (typeof msg.content === "string") {
+            if (msg.content === "") return undefined
+            return msg
           }
-          return true
+          if (!Array.isArray(msg.content)) return msg
+          const filtered = msg.content.filter((part) => {
+            if (part.type === "text" || part.type === "reasoning") {
+              return part.text !== ""
+            }
+            return true
+          })
+          if (filtered.length === 0) return undefined
+          return { ...msg, content: filtered }
         })
-        if (filtered.length === 0) return undefined
-        return { ...msg, content: filtered }
-      })
-      .filter((msg): msg is ModelMessage => msg !== undefined && msg.content !== "")
+        .filter((msg): msg is ModelMessage => msg !== undefined && msg.content !== "")
+    }
 
     if (model.api.id.includes("claude")) {
       const scrub = (id: string) => id.replace(/[^a-zA-Z0-9_-]/g, "_")