fix(tui): preserve usage telemetry fields

tests/providers/test_usage_contract.py

@@ -102,7 +102,10 @@ def test_usage_projects_compact_turn_observability_shape() -> None:
         output_tokens=3,
         total_tokens=20,
         cache_read_tokens=4,
-    ) + LLMUsage.estimated(input_tokens=18, output_tokens=2)
+    ).with_timing(generation_ms=250, ttft_ms=50) + LLMUsage.estimated(
+        input_tokens=18,
+        output_tokens=2,
+    ).with_timing(generation_ms=100, ttft_ms=None)
 
     assert usage.to_turn_dict() == {
         "prompt_tokens": 30,
@@ -111,6 +114,10 @@ def test_usage_projects_compact_turn_observability_shape() -> None:
         "context_tokens": 18,
         "request_count": 2,
         "estimated_tokens": 20,
+        "generation_ms": 350,
+        "measured_completion_tokens": 5,
+        "ttft_ms": 50,
+        "timed_requests": 1,
     }
 
 

tests/webui/test_session_context.py

@@ -59,7 +59,12 @@ def test_session_context_tolerates_untrusted_summary_metadata() -> None:
 
 
 def test_session_context_sanitizes_usage_metadata() -> None:
-    usage = LLMUsage.reported(input_tokens=120, output_tokens=8, total_tokens=175)
+    usage = LLMUsage.reported(
+        input_tokens=120,
+        output_tokens=8,
+        total_tokens=175,
+        cache_read_tokens=48,
+    ).with_timing(generation_ms=400, ttft_ms=75)
     session = Session(
         key="websocket:context",
         metadata={"_last_usage": usage.to_dict()},
@@ -67,4 +72,16 @@ def test_session_context_sanitizes_usage_metadata() -> None:
 
     payload = session_context_payload(session)
 
-    assert payload["last_usage"] == usage.to_dict()
+    assert payload["last_usage"] == {
+        "prompt_tokens": 120,
+        "completion_tokens": 8,
+        "total_tokens": 175,
+        "context_tokens": 120,
+        "cached_tokens": 48,
+        "request_count": 1,
+        "estimated_tokens": 0,
+        "generation_ms": 400,
+        "measured_completion_tokens": 8,
+        "ttft_ms": 75,
+        "timed_requests": 1,
+    }