fix: ensure tool_use is always followed by tool_result (#22646)

Co-authored-by: opencode-agent[bot] <opencode-agent[bot]@users.noreply.github.com>

Author: rekram1-node

packages/opencode/src/provider/transform.ts

@@ -75,7 +75,7 @@ export namespace ProviderTransform {
 
     if (model.api.id.includes("claude")) {
       const scrub = (id: string) => id.replace(/[^a-zA-Z0-9_-]/g, "_")
-      return msgs.map((msg) => {
+      msgs = msgs.map((msg) => {
         if (msg.role === "assistant" && Array.isArray(msg.content)) {
           return {
             ...msg,
@@ -101,6 +101,31 @@ export namespace ProviderTransform {
         return msg
       })
     }
+    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]
+
+        const parts = msg.content
+        const first = parts.findIndex((part) => part.type === "tool-call")
+        if (first === -1) return [msg]
+        if (!parts.slice(first).some((part) => part.type !== "tool-call")) return [msg]
+        return [
+          { ...msg, content: parts.filter((part) => part.type !== "tool-call") },
+          { ...msg, content: parts.filter((part) => part.type === "tool-call") },
+        ]
+      })
+    }
     if (
       model.providerID === "mistral" ||
       model.api.id.toLowerCase().includes("mistral") ||

packages/opencode/test/provider/transform.test.ts

@@ -1271,6 +1271,110 @@ describe("ProviderTransform.message - anthropic empty content filtering", () =>
     expect(result[0].content).toBe("")
     expect(result[1].content).toHaveLength(1)
   })
+
+  test("splits anthropic assistant messages when text trails tool calls", () => {
+    const msgs = [
+      {
+        role: "user",
+        content: [{ type: "text", text: "Check my home directory for PDFs" }],
+      },
+      {
+        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." },
+        ],
+      },
+      {
+        role: "tool",
+        content: [
+          { type: "tool-result", toolCallId: "toolu_1", toolName: "read", output: { type: "text", value: "ok" } },
+          {
+            type: "tool-result",
+            toolCallId: "toolu_2",
+            toolName: "glob",
+            output: { type: "text", value: "No files found" },
+          },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, anthropicModel, {}) as any[]
+
+    expect(result).toHaveLength(4)
+    expect(result[1]).toMatchObject({
+      role: "assistant",
+      content: [{ type: "text", text: "I checked your home directory and looked for PDF files." }],
+    })
+    expect(result[2]).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" } },
+      ],
+    })
+  })
+
+  test("leaves valid anthropic assistant tool ordering unchanged", () => {
+    const msgs = [
+      {
+        role: "assistant",
+        content: [
+          { type: "text", text: "I checked your home directory and looked for PDF files." },
+          { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+          { type: "tool-call", toolCallId: "toolu_2", toolName: "glob", input: { pattern: "**/*.pdf" } },
+        ],
+      },
+    ] as any[]
+
+    const result = ProviderTransform.message(msgs, anthropicModel, {}) as any[]
+
+    expect(result).toHaveLength(1)
+    expect(result[0].content).toMatchObject([
+      { type: "text", text: "I checked your home directory and looked for PDF files." },
+      { type: "tool-call", toolCallId: "toolu_1", toolName: "read", input: { filePath: "/root" } },
+      { 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", () => {