fix: include cached tokens in opencode prompt_tokens calculation

src/otlp.py

@@ -362,13 +362,13 @@ def _extract_opencode_fields(
         str(provider_from_attr) if provider_from_attr is not None else None,
     )
 
-    prompt_tokens = int(input_tokens) if input_tokens is not None else None
+    prompt_tokens = (int(input_tokens or 0)) + (int(cached or 0))
     completion_tokens = int(output_tokens) if output_tokens is not None else None
     cached_tokens = int(cached) if cached is not None else None
 
     if total is not None:
         total_tokens = int(total)
-    elif prompt_tokens is not None and completion_tokens is not None:
+    elif completion_tokens is not None:
         total_tokens = prompt_tokens + completion_tokens + int(reasoning or 0)
     else:
         total_tokens = None

tests/test_otlp.py

@@ -220,7 +220,7 @@ def test_extract_opencode_fields_basic(otlp_module):
 
     assert fields["model"] == "claude-sonnet-4-5"
     assert fields["provider"] == "anthropic"
-    assert fields["prompt_tokens"] == 150
+    assert fields["prompt_tokens"] == 180
     assert fields["completion_tokens"] == 80
     assert fields["reasoning_tokens"] == 20
     assert fields["cached_tokens"] == 30
@@ -267,7 +267,7 @@ def test_parse_opencode_record_routes_to_record_usage(otlp_module, monkeypatch):
     assert captured["usage"].client_source == "opencode"
     assert captured["usage"].model == "claude-sonnet-4-5"
     assert captured["usage"].provider == "anthropic"
-    assert captured["usage"].prompt_tokens == 100
+    assert captured["usage"].prompt_tokens == 120
     assert captured["usage"].completion_tokens == 50
     assert captured["usage"].reasoning_tokens == 10
     assert captured["usage"].cached_tokens == 20