From 5b1166a5bf6211df3b8a76585dfc34f709666d47 Mon Sep 17 00:00:00 2001
From: PratikDhanave <i.pratikdhanave@gmail.com>
Date: Fri, 18 Sep 2026 17:55:08 +0530
Subject: [PATCH] Normalize legacy function_call finish reason on the Chat path

Some OpenAI-compatible endpoints still emit the deprecated "function_call"
finish reason. The Chat path forwarded the raw string verbatim, so callers
saw "function_call" where the Python and .NET clients report "tool_calls".

Normalize "function_call" to "tool_calls" on both the streaming and
non-streaming paths, matching the Python client; other reasons pass through
unchanged.
---
 provider/openaiprovider/chat.go      | 15 +++++++++++++--
 provider/openaiprovider/chat_test.go | 19 +++++++++++++++++++
 2 files changed, 32 insertions(+), 2 deletions(-)

diff --git a/provider/openaiprovider/chat.go b/provider/openaiprovider/chat.go
index 1479a0bb..30386aba 100644
--- a/provider/openaiprovider/chat.go
+++ b/provider/openaiprovider/chat.go
@@ -149,7 +149,7 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 			if choice.Message.Refusal != "" {
 				contents = append(contents, &message.ErrorContent{Message: choice.Message.Refusal, ErrorCode: "Refusal"})
 			}
-			finishReason = choice.FinishReason
+			finishReason = normalizeChatFinishReason(choice.FinishReason)
 		}
 		if resp.JSON.Usage.Valid() {
 			contents = addUsage(contents, resp.Usage)
@@ -209,7 +209,7 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 			}
 			var finishReason string
 			if len(chunk.Choices) > 0 {
-				finishReason = chunk.Choices[0].FinishReason
+				finishReason = normalizeChatFinishReason(chunk.Choices[0].FinishReason)
 			}
 			resp := &agent.ResponseUpdate{
 				Contents:          contents,
@@ -230,6 +230,17 @@ func (a *chatClient) run(ctx context.Context, messages []*message.Message, optio
 	}
 }
 
+// normalizeChatFinishReason maps the deprecated "function_call" finish reason,
+// still emitted by some OpenAI-compatible endpoints, onto the canonical
+// "tool_calls", matching the Python client. Other reasons pass through
+// unchanged.
+func normalizeChatFinishReason(reason string) string {
+	if reason == "function_call" {
+		return "tool_calls"
+	}
+	return reason
+}
+
 func mapRole(r string) message.Role {
 	switch r {
 	case "user":
diff --git a/provider/openaiprovider/chat_test.go b/provider/openaiprovider/chat_test.go
index 20447b8c..f5504894 100644
--- a/provider/openaiprovider/chat_test.go
+++ b/provider/openaiprovider/chat_test.go
@@ -428,6 +428,25 @@ func TestChatBasicRequestResponse_NonStreaming(t *testing.T) {
 	}
 }
 
+// Some OpenAI-compatible endpoints still emit the deprecated "function_call"
+// finish reason; it must be normalized to the canonical "tool_calls", matching
+// the Python client.
+func TestChatLegacyFunctionCallFinishReasonNormalized(t *testing.T) {
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, _ *http.Request) {
+		w.Header().Set("Content-Type", "application/json")
+		_, _ = io.WriteString(w, `{"id":"chatcmpl-fc","object":"chat.completion","created":1727888631,"model":"gpt-4o-mini","choices":[{"index":0,"message":{"role":"assistant","content":"ok"},"finish_reason":"function_call"}]}`)
+	}))
+	defer server.Close()
+
+	resp, err := newTestClient(server).RunText(t.Context(), "hi").Collect()
+	if err != nil {
+		t.Fatalf("error = %v", err)
+	}
+	if resp.FinishReason != "tool_calls" {
+		t.Errorf("FinishReason = %q, want %q", resp.FinishReason, "tool_calls")
+	}
+}
+
 func TestChatURLCitationAnnotations_NonStreaming(t *testing.T) {
 	const input = `
             {