diff --git a/packages/opencode/src/provider/transform.ts b/packages/opencode/src/provider/transform.ts
index 2fa7649c75f9..947ccf342555 100644
--- a/packages/opencode/src/provider/transform.ts
+++ b/packages/opencode/src/provider/transform.ts
@@ -122,7 +122,7 @@ function normalizeMessages(
     })
   }
   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
+    // Anthropic rejects assistant turns where client 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...
     //
@@ -130,19 +130,26 @@ function normalizeMessages(
     // 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.
+    // Provider-executed tools are different: the AI SDK intentionally represents
+    // their tool-call and tool-result together in assistant content.
     msgs = msgs.flatMap((msg) => {
       if (msg.role !== "assistant" || !Array.isArray(msg.content)) return [msg]
 
       const parts = msg.content
-      const first = parts.findIndex((part) => part.type === "tool-call")
+      const providerExecuted = new Set(
+        parts.flatMap((part) => (part.type === "tool-call" && part.providerExecuted === true ? [part.toolCallId] : [])),
+      )
+      const isClientToolPart = (part: (typeof parts)[number]) => {
+        if (part.type === "tool-call") return part.providerExecuted !== true
+        if (part.type === "tool-result") return !providerExecuted.has(part.toolCallId)
+        return false
+      }
+      const first = parts.findIndex((part) => part.type === "tool-call" && part.providerExecuted !== true)
       if (first === -1) return [msg]
-      if (!parts.slice(first).some((part) => part.type !== "tool-call")) return [msg]
+      if (!parts.slice(first).some((part) => !isClientToolPart(part))) return [msg]
       return [
-        { ...msg, content: parts.filter((part) => part.type !== "tool-call") },
-        { ...msg, content: parts.filter((part) => part.type === "tool-call") },
+        { ...msg, content: parts.filter((part) => !isClientToolPart(part)) },
+        { ...msg, content: parts.filter(isClientToolPart) },
       ]
     })
   }
diff --git a/packages/opencode/test/provider/transform.test.ts b/packages/opencode/test/provider/transform.test.ts
index 9b66eaa77c5d..d701ca26fbe6 100644
--- a/packages/opencode/test/provider/transform.test.ts
+++ b/packages/opencode/test/provider/transform.test.ts
@@ -1498,6 +1498,117 @@ describe("ProviderTransform.message - anthropic empty content filtering", () =>
     ])
   })
 
+  test("keeps tool-call and tool-result paired when splitting anthropic messages", () => {
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+          { type: "tool-result", toolCallId: "toolu_1", toolName: "read", output: { type: "text", value: "ok" } },
+          { type: "text", text: "I checked your home directory." },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, anthropicModel, {}) as any[]
+
+    expect(result).toHaveLength(2)
+    expect(result[0]).toMatchObject({
+      role: "assistant",
+      content: [{ type: "text", text: "I checked your home directory." }],
+    })
+    expect(result[1]).toMatchObject({
+      role: "assistant",
+      content: [
+        { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+        { type: "tool-result", toolCallId: "toolu_1", toolName: "read", output: { type: "text", value: "ok" } },
+      ],
+    })
+  })
+
+  test("leaves provider-executed anthropic tool results with trailing text unchanged", () => {
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "tool-call",
+            toolCallId: "srvtoolu_1",
+            toolName: "code_execution",
+            input: { code: "print('ok')", type: "programmatic-tool-call" },
+            providerExecuted: true,
+          },
+          {
+            type: "tool-result",
+            toolCallId: "srvtoolu_1",
+            toolName: "code_execution",
+            output: {
+              type: "json",
+              value: { type: "code_execution_result", stdout: "ok", stderr: "", return_code: 0 },
+            },
+          },
+          { type: "text", text: "The code ran successfully." },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, anthropicModel, {}) as any[]
+
+    expect(result).toHaveLength(1)
+    expect(result[0].content).toMatchObject(msgs[0].content)
+  })
+
+  test("keeps provider-executed pairs together when splitting mixed anthropic tool parts", () => {
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+          {
+            type: "tool-call",
+            toolCallId: "srvtoolu_1",
+            toolName: "code_execution",
+            input: { code: "print('ok')", type: "programmatic-tool-call" },
+            providerExecuted: true,
+          },
+          {
+            type: "tool-result",
+            toolCallId: "srvtoolu_1",
+            toolName: "code_execution",
+            output: {
+              type: "json",
+              value: { type: "code_execution_result", stdout: "ok", stderr: "", return_code: 0 },
+            },
+          },
+          { type: "text", text: "The server-side tool ran successfully." },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, anthropicModel, {}) as any[]
+
+    expect(result).toHaveLength(2)
+    expect(result[0].content).toMatchObject([
+      {
+        type: "tool-call",
+        toolCallId: "srvtoolu_1",
+        toolName: "code_execution",
+        input: { code: "print('ok')", type: "programmatic-tool-call" },
+        providerExecuted: true,
+      },
+      {
+        type: "tool-result",
+        toolCallId: "srvtoolu_1",
+        toolName: "code_execution",
+        output: { type: "json", value: { type: "code_execution_result", stdout: "ok", stderr: "", return_code: 0 } },
+      },
+      { type: "text", text: "The server-side tool ran successfully." },
+    ])
+    expect(result[1].content).toMatchObject([
+      { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+    ])
+  })
+
   test("splits vertex anthropic assistant messages when text trails tool calls", () => {
     const model = {
       ...anthropicModel,