From f4577c78bf98c3d443846239c92a75cfecb965fa Mon Sep 17 00:00:00 2001
From: Aiden Cline <aidenpcline@gmail.com>
Date: Wed, 15 Apr 2026 14:45:36 -0500
Subject: [PATCH] wip

---
 packages/opencode/src/provider/transform.ts   | 13 ++++++-
 .../opencode/test/provider/transform.test.ts  | 38 +++++++++++++++++++
 2 files changed, 50 insertions(+), 1 deletion(-)

diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index 3e2b61e039..61561ec969 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -101,7 +101,18 @@ export namespace ProviderTransform {
         return msg
       })
     }
-    if (model.api.npm === "@ai-sdk/anthropic") {
+    if (["@ai-sdk/anthropic", "@ai-sdk/google-vertex/anthropic"].includes(model.api.npm)) {
+      // Anthropic rejects assistant turns where tool_use blocks are followed by non-tool
+      // content, e.g. [tool_use, tool_use, text], with:
+      // `tool_use` ids were found without `tool_result` blocks immediately after...
+      //
+      // Reorder that invalid shape into [text] + [tool_use, tool_use]. Consecutive
+      // assistant messages are later merged by the provider/SDK, so preserving the
+      // original [tool_use...] then [text] order still produces the invalid payload.
+      //
+      // The root cause appears to be somewhere upstream where the stream is originally
+      // processed. We were unable to locate an exact narrower reproduction elsewhere,
+      // so we keep this transform in place for the time being.
       msgs = msgs.flatMap((msg) => {
         if (msg.role !== "assistant" || !Array.isArray(msg.content)) return [msg]
 
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index 1d99b06af3..4952a126b3 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -1337,6 +1337,44 @@ describe("ProviderTransform.message - anthropic empty content filtering", () =>
       { type: "tool-call", toolCallId: "toolu_2", toolName: "glob", input: { pattern: "**/*.pdf" } },
     ])
   })
+
+  test("splits vertex anthropic assistant messages when text trails tool calls", () => {
+    const model = {
+      ...anthropicModel,
+      providerID: "google-vertex-anthropic",
+      api: {
+        id: "claude-sonnet-4@20250514",
+        url: "https://us-central1-aiplatform.googleapis.com",
+        npm: "@ai-sdk/google-vertex/anthropic",
+      },
+    }
+
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+          { type: "tool-call", toolCallId: "toolu_2", toolName: "glob", input: { pattern: "**/*.pdf" } },
+          { type: "text", text: "I checked your home directory and looked for PDF files." },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, model, {}) as any[]
+
+    expect(result).toHaveLength(2)
+    expect(result[0]).toMatchObject({
+      role: "assistant",
+      content: [{ type: "text", text: "I checked your home directory and looked for PDF files." }],
+    })
+    expect(result[1]).toMatchObject({
+      role: "assistant",
+      content: [
+        { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+        { type: "tool-call", toolCallId: "toolu_2", toolName: "glob", input: { pattern: "**/*.pdf" } },
+      ],
+    })
+  })
 })
 
 describe("ProviderTransform.message - strip openai metadata when store=false", () => {