fix: Prevent partial tool call JSON leaks in stream processing by removing size-based buffer limits and holding incomplete blocks longer.

internal/adapter/openai/handler_toolcall_test.go

@@ -416,3 +416,50 @@ func TestHandleStreamToolCallMixedWithPlainTextSegments(t *testing.T) {
 		t.Fatalf("expected finish_reason=tool_calls, body=%s", rec.Body.String())
 	}
 }
+
+func TestHandleStreamToolCallKeyAppearsLateStillNoPrefixLeak(t *testing.T) {
+	h := &Handler{}
+	spaces := strings.Repeat(" ", 200)
+	resp := makeSSEHTTPResponse(
+		`data: {"p":"response/content","v":"{`+spaces+`"}`,
+		`data: {"p":"response/content","v":"\"tool_calls\":[{\"name\":\"search\",\"input\":{\"q\":\"go\"}}]}"}`,
+		`data: {"p":"response/content","v":"后置正文C。"}`,
+		`data: [DONE]`,
+	)
+	rec := httptest.NewRecorder()
+	req := httptest.NewRequest(http.MethodPost, "/v1/chat/completions", nil)
+
+	h.handleStream(rec, req, resp, "cid8", "deepseek-chat", "prompt", false, false, []string{"search"})
+
+	frames, done := parseSSEDataFrames(t, rec.Body.String())
+	if !done {
+		t.Fatalf("expected [DONE], body=%s", rec.Body.String())
+	}
+	if !streamHasToolCallsDelta(frames) {
+		t.Fatalf("expected tool_calls delta, body=%s", rec.Body.String())
+	}
+	if streamHasRawToolJSONContent(frames) {
+		t.Fatalf("raw tool_calls JSON leaked in content delta: %s", rec.Body.String())
+	}
+	content := strings.Builder{}
+	for _, frame := range frames {
+		choices, _ := frame["choices"].([]any)
+		for _, item := range choices {
+			choice, _ := item.(map[string]any)
+			delta, _ := choice["delta"].(map[string]any)
+			if c, ok := delta["content"].(string); ok {
+				content.WriteString(c)
+			}
+		}
+	}
+	got := content.String()
+	if strings.Contains(got, "{") {
+		t.Fatalf("unexpected suspicious prefix leak in content: %q", got)
+	}
+	if !strings.Contains(got, "后置正文C。") {
+		t.Fatalf("expected stream to continue after tool json convergence, got=%q", got)
+	}
+	if streamFinishReason(frames) != "tool_calls" {
+		t.Fatalf("expected finish_reason=tool_calls, body=%s", rec.Body.String())
+	}
+}