Address review of two-stop branch

- lca._prefix_profile: anchor the prefix window to the prefix's own first arrival
  so the A-rate is measured over the prefix span (matches the design intent;
  no-op for the 0-based canonical pipeline).
- cli study tune: label file-originated stops as file_proposal rather than
  llm_after_veto_budget (the veto never applies to file proposals).
- spec.AdaptiveStopSpec: reject stable_checks > max_checks (would make
  convergence undetectable and silently disable Stop-A).

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

configs/examples/dash0_qwen30b_a3b_stopA_fulldata.json

@@ -0,0 +1,141 @@
+{
+  "study_id": "dash0-qwen30b-a3b-stopA-fulldata-chat-0-8k",
+  "hardware": {
+    "gpu_count": 8,
+    "gpu_model": "H20",
+    "host_candidates": [
+      "dash0"
+    ]
+  },
+  "model": {
+    "model_id": "Qwen/Qwen3-30B-A3B",
+    "served_model_name": "qwen3-30b-a3b-community"
+  },
+  "engine": {
+    "engine_name": "vllm",
+    "engine_version": "0.20.0",
+    "exec_path": "/tmp/wjh/venvs/vllm-0.20.0-cu129/bin/vllm",
+    "cwd": "/home/admin/cpfs/wjh/aituner/aituner",
+    "host": "127.0.0.1",
+    "port": 18230,
+    "healthcheck_path": "/v1/models",
+    "ready_timeout_s": 900,
+    "request_timeout_s": 900,
+    "launch_args": [
+      "serve",
+      "/home/admin/cpfs/wjh/models/Qwen/Qwen3-30B-A3B"
+    ],
+    "base_envs": {
+      "CUDA_VISIBLE_DEVICES": "0,1,2,3,4,5,6,7",
+      "HOME": "/tmp/wjh",
+      "XDG_CACHE_HOME": "/tmp/wjh/.cache"
+    },
+    "base_flags": {
+      "host": "127.0.0.1",
+      "port": 18230,
+      "served-model-name": "qwen3-30b-a3b-community"
+    },
+    "tunable_envs": [],
+    "tunable_flags": [
+      "tensor-parallel-size",
+      "data-parallel-size",
+      "enable-expert-parallel",
+      "expert-parallel-size",
+      "gpu-memory-utilization",
+      "max-num-batched-tokens",
+      "max-num-seqs",
+      "block-size",
+      "enable-prefix-caching",
+      "enable-chunked-prefill"
+    ],
+    "topology_constraints": {
+      "require_tp_dp_product_equals_gpu_count": false,
+      "require_ep_size_leq_tp_dp_product": true,
+      "require_ep_size_divides_tp_dp_product": true,
+      "require_enable_expert_parallel_when_ep_gt_one": true,
+      "validate_cuda_graph_sizes_divisible_by_tp_when_tp_ep_reduce_scatter": true,
+      "allowed_tp_dp_products": [
+        1,
+        2,
+        4,
+        8
+      ],
+      "allowed_tensor_parallel_sizes": [
+        1,
+        2,
+        4,
+        8
+      ],
+      "allowed_data_parallel_sizes": [
+        1,
+        2,
+        4,
+        8
+      ],
+      "allowed_expert_parallel_sizes": [
+        1,
+        2,
+        4,
+        8
+      ]
+    },
+    "python_executable": "/tmp/wjh/venvs/vllm-0.20.0-cu129/bin/python"
+  },
+  "trace": {
+    "windows_path": "/home/admin/cpfs/wjh/aituner/aituner/trace_windows/windows.json",
+    "window_id": "chat_w20260311_1000",
+    "completion_tokens_override": 128,
+    "u_field": "sampling_u",
+    "timestamp_field": "timestamp",
+    "max_concurrency": 64,
+    "input_length_filter": {
+      "min_input_tokens": 0,
+      "max_input_tokens": 8192
+    },
+    "replay_time_scale": 1.0,
+    "early_stop_max_lag_s": 120.0,
+    "early_stop_max_elapsed_s": 900.0
+  },
+  "slo": {
+    "target_pass_rate": 0.95,
+    "ttft_rule": {
+      "kind": "step_ms",
+      "buckets": [
+        {
+          "max_input_tokens": 4096,
+          "threshold_ms": 2000
+        },
+        {
+          "max_input_tokens": 32768,
+          "threshold_ms": 4000
+        },
+        {
+          "threshold_ms": 6000
+        }
+      ]
+    },
+    "tpot_rule": {
+      "kind": "fixed_ms",
+      "threshold_ms": 50
+    }
+  },
+  "search": {
+    "low": 0.0,
+    "high": 0.125,
+    "tolerance": 0.001,
+    "max_probes": 5,
+    "sample_seed": 20260325
+  },
+  "llm": {
+    "system_prompt": "Tune community vLLM 0.20.0 serving for Qwen3-30B-A3B. Start from the default vLLM engine configuration, use only launch-safe patches, and optimize request_rate_per_gpu under the configured SLO.",
+    "max_history_trials": 8,
+    "use_harness": true,
+    "endpoint": {
+      "provider": "codex",
+      "model": "gpt-5.4",
+      "stream": true,
+      "api_key_env": "OPENAI_API_KEY",
+      "timeout_s": 240
+    }
+  }
+}

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,

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,
     )

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,