fix(translator): emit tool_result messages before user content in Claude-to-OpenAI conversion

internal/translator/openai/claude/openai_claude_request.go

@@ -181,6 +181,14 @@ func ConvertClaudeRequestToOpenAI(modelName string, inputRawJSON []byte, stream
 				hasContent := len(contentItems) > 0
 				hasReasoning := reasoningContent != ""
 				hasToolCalls := len(toolCalls) > 0
+				hasToolResults := len(toolResults) > 0
+
+				// OpenAI requires: tool messages MUST immediately follow the assistant message with tool_calls.
+				// Therefore, we emit tool_result messages FIRST (they respond to the previous assistant's tool_calls),
+				// then emit the current message's content.
+				for _, toolResultJSON := range toolResults {
+					messagesJSON, _ = sjson.Set(messagesJSON, "-1", gjson.Parse(toolResultJSON).Value())
+				}
 
 				// For assistant messages: emit a single unified message with content, tool_calls, and reasoning_content
 				// This avoids splitting into multiple assistant messages which breaks OpenAI tool-call adjacency
@@ -214,6 +222,7 @@ func ConvertClaudeRequestToOpenAI(modelName string, inputRawJSON []byte, stream
 					}
 				} else {
 					// For non-assistant roles: emit content message if we have content
+					// If the message only contains tool_results (no text/image), we still processed them above
 					if hasContent {
 						msgJSON := `{"role":""}`
 						msgJSON, _ = sjson.Set(msgJSON, "role", role)
@@ -225,14 +234,11 @@ func ConvertClaudeRequestToOpenAI(modelName string, inputRawJSON []byte, stream
 						msgJSON, _ = sjson.SetRaw(msgJSON, "content", contentArrayJSON)
 
 						messagesJSON, _ = sjson.Set(messagesJSON, "-1", gjson.Parse(msgJSON).Value())
+					} else if hasToolResults && !hasContent {
+						// tool_results already emitted above, no additional user message needed
 					}
 				}
 
-				// Emit tool_result messages after the main message (ensures proper OpenAI ordering)
-				for _, toolResultJSON := range toolResults {
-					messagesJSON, _ = sjson.Set(messagesJSON, "-1", gjson.Parse(toolResultJSON).Value())
-				}
-
 			} else if contentResult.Exists() && contentResult.Type == gjson.String {
 				// Simple string content
 				msgJSON := `{"role":"","content":""}`

internal/translator/openai/claude/openai_claude_request_test.go

@@ -317,8 +317,8 @@ func TestConvertClaudeRequestToOpenAI_ToolResultOrderAndContent(t *testing.T) {
 	resultJSON := gjson.ParseBytes(result)
 	messages := resultJSON.Get("messages").Array()
 
-	// New behavior: user text is combined, tool_result emitted after user message
+	// OpenAI requires: tool messages MUST immediately follow assistant(tool_calls).
-	// Expect: system + assistant(tool_calls) + user(before+after) + tool(result)
+	// Correct order: system + assistant(tool_calls) + tool(result) + user(before+after)
 	if len(messages) != 4 {
 		t.Fatalf("Expected 4 messages, got %d. Messages: %s", len(messages), resultJSON.Get("messages").Raw)
 	}
@@ -331,26 +331,28 @@ func TestConvertClaudeRequestToOpenAI_ToolResultOrderAndContent(t *testing.T) {
 		t.Fatalf("Expected messages[1] to be assistant tool_calls, got %s: %s", messages[1].Get("role").String(), messages[1].Raw)
 	}
 
-	if messages[2].Get("role").String() != "user" {
+	// tool message MUST immediately follow assistant(tool_calls) per OpenAI spec
-		t.Fatalf("Expected messages[2] to be user, got %s", messages[2].Get("role").String())
+	if messages[2].Get("role").String() != "tool" {
+		t.Fatalf("Expected messages[2] to be tool (must follow tool_calls), got %s", messages[2].Get("role").String())
 	}
-	// User message should contain both "before" and "after" text
+	if got := messages[2].Get("tool_call_id").String(); got != "call_1" {
-	if got := messages[2].Get("content.0.text").String(); got != "before" {
-		t.Fatalf("Expected user text[0] %q, got %q", "before", got)
-	}
-	if got := messages[2].Get("content.1.text").String(); got != "after" {
-		t.Fatalf("Expected user text[1] %q, got %q", "after", got)
-	}
-
-	if messages[3].Get("role").String() != "tool" {
-		t.Fatalf("Expected messages[3] to be tool, got %s", messages[3].Get("role").String())
-	}
-	if got := messages[3].Get("tool_call_id").String(); got != "call_1" {
 		t.Fatalf("Expected tool_call_id %q, got %q", "call_1", got)
 	}
-	if got := messages[3].Get("content").String(); got != "tool ok" {
+	if got := messages[2].Get("content").String(); got != "tool ok" {
 		t.Fatalf("Expected tool content %q, got %q", "tool ok", got)
 	}
+
+	// User message comes after tool message
+	if messages[3].Get("role").String() != "user" {
+		t.Fatalf("Expected messages[3] to be user, got %s", messages[3].Get("role").String())
+	}
+	// User message should contain both "before" and "after" text
+	if got := messages[3].Get("content.0.text").String(); got != "before" {
+		t.Fatalf("Expected user text[0] %q, got %q", "before", got)
+	}
+	if got := messages[3].Get("content.1.text").String(); got != "after" {
+		t.Fatalf("Expected user text[1] %q, got %q", "after", got)
+	}
 }
 
 func TestConvertClaudeRequestToOpenAI_ToolResultObjectContent(t *testing.T) {