1 files changed, 32 insertions, 0 deletions
diff --git a/internal/llm/openai_request_test.go b/internal/llm/openai_request_test.go
new file mode 100644
index 0000000..f9925f9
--- /dev/null
+++ b/internal/llm/openai_request_test.go
@@ -0,0 +1,32 @@
+package llm
+
+import (
+	"encoding/json"
+	"testing"
+)
+
+func TestBuildOAChatRequest_MaxTokensKeyByModel(t *testing.T) {
+	msgs := []Message{{Role: "user", Content: "hi"}}
+	mt := 123
+	// Legacy model: use max_tokens
+	r1 := buildOAChatRequest(Options{Model: "gpt-4.1", MaxTokens: mt}, msgs, nil, false)
+	b1, _ := json.Marshal(r1)
+	if !contains(string(b1), "max_tokens") || contains(string(b1), "max_completion_tokens") {
+		t.Fatalf("expected max_tokens only, got %s", string(b1))
+	}
+	// gpt-5 family: use max_completion_tokens
+	r2 := buildOAChatRequest(Options{Model: "gpt-5.0-preview", MaxTokens: mt}, msgs, nil, false)
+	b2, _ := json.Marshal(r2)
+	if !contains(string(b2), "max_completion_tokens") || contains(string(b2), "max_tokens\":") {
+		t.Fatalf("expected max_completion_tokens only, got %s", string(b2))
+	}
+}
+
+func contains(s, sub string) bool {
+	for i := 0; i+len(sub) <= len(s); i++ {
+		if s[i:i+len(sub)] == sub {
+			return true
+		}
+	}
+	return false
+}