diff --git a/src/aituner/cli.py b/src/aituner/cli.py
index 0ed09b1..2c1d4a0 100644
--- a/src/aituner/cli.py
+++ b/src/aituner/cli.py
@@ -376,6 +376,8 @@ def cmd_study_tune(args: argparse.Namespace) -> int:
                     "stop_authorized_by": (
                         "validator"
                         if (is_harness_stop or authorized)
+                        else "file_proposal"
+                        if proposal_source is not None
                         else "llm_after_veto_budget"
                     ),
                     "diagnosis": proposal.diagnosis,
diff --git a/src/aituner/lca.py b/src/aituner/lca.py
index 399fc89..5ca2f15 100644
--- a/src/aituner/lca.py
+++ b/src/aituner/lca.py
@@ -373,12 +373,13 @@ def _prefix_profile(
     length_mode: str,
 ) -> WorkloadProfile:
     prefix = requests[:index]
+    start = float(prefix[0].arrival_s) if prefix else float(window.window_start)
     end = float(prefix[-1].arrival_s) if prefix else float(window.window_start)
     prefix_window = WindowRecord(
         window_id=window.window_id,
         trace_path=window.trace_path,
         trace_type=window.trace_type,
-        window_start=window.window_start,
+        window_start=start,
         window_end=end,
         source_payload=window.source_payload,
     )
diff --git a/src/aituner/spec.py b/src/aituner/spec.py
index 85ce37e..dfe6e41 100644
--- a/src/aituner/spec.py
+++ b/src/aituner/spec.py
@@ -364,6 +364,11 @@ class AdaptiveStopSpec:
             raise SpecError(
                 "trace.adaptive_stop.stable_checks and max_checks must be > 0."
             )
+        if stable_checks > max_checks:
+            raise SpecError(
+                "trace.adaptive_stop.stable_checks must be <= max_checks, "
+                "otherwise convergence can never be detected."
+            )
         return cls(
             enabled=enabled,
             tau=tau,