diff --git a/evalharness/eval/aggregator.py b/evalharness/eval/aggregator.py
index 1aac8e2..0485cfb 100644
--- a/evalharness/eval/aggregator.py
+++ b/evalharness/eval/aggregator.py
@@ -113,6 +113,45 @@ def simpleqa_official(results: List[SampleResult], metric: str):
     }
 
 
+@register_aggregator('perf_stats')
+def perf_stats(results: List[SampleResult], metric: str):
+    """Performance profile over per-sample usage: latency/ttft percentiles,
+    throughput, token stats. Attach to any metric (reads SampleResult.usage).
+
+    Report shape: metric_groups['perf'] = {p50_latency_s, p95_latency_s, ...}
+    """
+    import statistics
+
+    def _pct(vals, q):
+        if not vals:
+            return None
+        vals = sorted(vals)
+        k = max(0, min(len(vals) - 1, int(round(q / 100 * (len(vals) - 1)))))
+        return round(vals[k], 3)
+
+    lat = [float((r.usage or {}).get('latency_s', 0) or 0) for r in results
+           if (r.usage or {}).get('latency_s')]
+    ttft = [float(r.usage['ttft_s']) for r in results
+            if (r.usage or {}).get('ttft_s') is not None]
+    itl = [float(r.usage['itl_mean_s']) for r in results
+           if (r.usage or {}).get('itl_mean_s') is not None]
+    in_tok = sum(int((r.usage or {}).get('input_tokens', 0) or 0) for r in results)
+    out_tok = sum(int((r.usage or {}).get('output_tokens', 0) or 0) for r in results)
+    retried = sum(1 for r in results if (r.usage or {}).get('retries'))
+    wall = sum(lat)
+    out = {
+        'n_requests': len(lat),
+        'latency_p50_s': _pct(lat, 50), 'latency_p95_s': _pct(lat, 95),
+        'latency_p99_s': _pct(lat, 99), 'latency_mean_s': round(statistics.mean(lat), 3) if lat else None,
+        'ttft_p50_s': _pct(ttft, 50), 'ttft_p95_s': _pct(ttft, 95),
+        'itl_mean_s': round(statistics.mean(itl), 4) if itl else None,
+        'input_tokens': in_tok, 'output_tokens': out_tok,
+        'retry_rate': round(retried / len(lat), 3) if lat else None,
+        'wall_latency_s': round(wall, 1),
+    }
+    return out
+
+
 @register_aggregator('binned_avg')
 def binned_avg(results: List[SampleResult], metric: str):
     """Average inside metadata['bin'] buckets (MRCR length bins)."""
diff --git a/evalharness/model/adapter.py b/evalharness/model/adapter.py
index 9e24153..b83066a 100644
--- a/evalharness/model/adapter.py
+++ b/evalharness/model/adapter.py
@@ -169,11 +169,19 @@ class OpenAICompatible(ModelAdapter):
             headers['Authorization'] = f'Bearer {self.api_key}'
         retries = self.extra.get('retries', 6)
         last_exc: Exception = None
+        stream = bool(self.extra.get('collect_perf') and not kw.get('no_stream'))
+        if stream:
+            payload['stream'] = True
         for attempt in range(retries + 1):
             try:
-                data = await self._post(f'{self.api_base}/chat/completions', payload, headers)
-                out = self._parse(data)
+                if stream:
+                    out = await self._post_stream_perf(
+                        f'{self.api_base}/chat/completions', payload, headers, t0)
+                else:
+                    data = await self._post(f'{self.api_base}/chat/completions', payload, headers)
+                    out = self._parse(data)
                 out.usage.latency_s = round(_time.time() - t0, 3)
+                out.usage.retries = attempt
                 return out
             except Exception as e:  # 5xx/429/timeouts: worth retrying
                 last_exc = e
@@ -187,6 +195,72 @@ class OpenAICompatible(ModelAdapter):
                 await asyncio.sleep(min(2 ** attempt * 3, 120))
         raise last_exc  # unreachable
 
+    async def _post_stream_perf(self, url, payload, headers, t0) -> ModelOutput:
+        """SSE streaming request collecting TTFT/ITL; reassembles a full
+        response then reuses the standard parser."""
+        import time as _time
+
+        try:
+            import httpx
+        except ImportError:
+            data = await self._post(url, {k: v for k, v in payload.items() if k != 'stream'},
+                                    headers)
+            out = self._parse(data)
+            out.usage.http_status = 200
+            return out
+
+        chunks: List[Dict[str, Any]] = []
+        ttft = None
+        last_tok_t = None
+        itl_vals: List[float] = []
+        status = None
+        import json as _json
+
+        async with httpx.AsyncClient(timeout=self.extra.get('timeout', 600)) as client:
+            async with client.stream('POST', url, json=payload, headers=headers) as resp:
+                status = resp.status_code
+                resp.raise_for_status()
+                async for line in resp.aiter_lines():
+                    if not line.startswith('data:'):
+                        continue
+                    body = line[5:].strip()
+                    if body == '[DONE]':
+                        break
+                    try:
+                        ev = _json.loads(body)
+                    except ValueError:
+                        continue
+                    now = _time.time()
+                    piece = ((ev.get('choices') or [{}])[0].get('delta') or {}).get('content')
+                    if piece:
+                        if ttft is None:
+                            ttft = now - t0
+                        elif last_tok_t is not None:
+                            itl_vals.append(now - last_tok_t)
+                        last_tok_t = now
+                    chunks.append(ev)
+
+        text = ''.join((((ev.get('choices') or [{}])[0].get('delta') or {}).get('content') or '')
+                       for ev in chunks)
+        finish = ''
+        for ev in chunks:
+            fr = (ev.get('choices') or [{}])[0].get('finish_reason')
+            if fr:
+                finish = fr
+                break
+        usage_ev = next((ev for ev in reversed(chunks) if ev.get('usage')), None)
+        data = {
+            'choices': [{'message': {'role': 'assistant', 'content': text},
+                         'finish_reason': finish}],
+            'usage': (usage_ev or {}).get('usage') or {},
+            'model': self.model,
+        }
+        out = self._parse(data)
+        out.usage.ttft_s = round(ttft, 3) if ttft is not None else None
+        out.usage.itl_mean_s = round(sum(itl_vals) / len(itl_vals), 4) if itl_vals else None
+        out.usage.http_status = status
+        return out
+
     def _payload(self, messages, tools, kw) -> Dict[str, Any]:
         msgs = [{'role': m.role, 'content': m.content} for m in messages]
         payload: Dict[str, Any] = {'model': self.model, 'messages': msgs}
diff --git a/evalharness/model/output.py b/evalharness/model/output.py
index 40fba6c..e6c9ded 100644
--- a/evalharness/model/output.py
+++ b/evalharness/model/output.py
@@ -32,8 +32,17 @@ class Usage(BaseModel):
     cost: float = 0.0
     latency_s: float = 0.0
     finish_reason: str = ''
+    # --- performance profile (collected per request; None = not measured) ---
+    ttft_s: Optional[float] = None     # time to FIRST token (streaming only)
+    itl_mean_s: Optional[float] = None  # mean inter-token latency (streaming)
+    retries: int = 0                   # retries consumed before success
+    http_status: Optional[int] = None  # final HTTP status (e.g. 200)
 
     def __add__(self, other: 'Usage') -> 'Usage':
+        def _sum_opt(a, b):
+            vals = [v for v in (a, b) if v is not None]
+            return sum(vals) / len(vals) if len(vals) == 2 else (vals[0] if vals else None)
+
         return Usage(
             input_tokens=self.input_tokens + other.input_tokens,
             output_tokens=self.output_tokens + other.output_tokens,
@@ -41,6 +50,10 @@ class Usage(BaseModel):
             cost=round(self.cost + other.cost, 6),
             latency_s=round(self.latency_s + other.latency_s, 3),
             finish_reason=self.finish_reason or other.finish_reason,
+            ttft_s=_sum_opt(self.ttft_s, other.ttft_s),
+            itl_mean_s=_sum_opt(self.itl_mean_s, other.itl_mean_s),
+            retries=self.retries + other.retries,
+            http_status=self.http_status or other.http_status,
         )
 
 
diff --git a/evalharness/model/pool.py b/evalharness/model/pool.py
index 4c0ca8f..1d295ee 100644
--- a/evalharness/model/pool.py
+++ b/evalharness/model/pool.py
@@ -10,7 +10,7 @@
 """
 
 import itertools
-from typing import List, Optional
+from typing import Dict, List, Optional
 
 from ..data.sample import ChatMessage
 from .adapter import ModelAdapter
@@ -29,21 +29,38 @@ class PooledAdapter(ModelAdapter):
         self.adapters = adapters
         self._cycle = itertools.cycle(range(len(adapters)))
         self.usage = Usage()
+        # request outcome counters (success rate accounting)
+        self.stats = {'requests': 0, 'ok': 0, 'failed': 0, 'retried': 0}
 
     def _next(self) -> ModelAdapter:
         return self.adapters[next(self._cycle)]
 
+    def request_stats(self) -> Dict[str, float]:
+        """Success-rate view of all requests that passed through this pool."""
+        n = self.stats['requests']
+        return {
+            'requests': n,
+            'success_rate': self.stats['ok'] / n if n else 0.0,
+            'retry_rate': self.stats['retried'] / n if n else 0.0,
+            'failure_rate': self.stats['failed'] / n if n else 0.0,
+        }
+
     async def generate(self, messages: List[ChatMessage],
                        tools: Optional[list] = None, **kw) -> ModelOutput:
         last_exc = None
+        self.stats['requests'] += 1
         for _ in range(len(self.adapters)):  # try each instance once
             adapter = self._next()
             try:
                 out = await adapter.generate(messages, tools=tools, **kw)
                 self.usage = self.usage + out.usage
+                self.stats['ok'] += 1
+                if out.usage.retries:
+                    self.stats['retried'] += 1
                 return out
             except Exception as e:  # dead instance -> next
                 last_exc = e
+        self.stats['failed'] += 1
         raise last_exc
 
     async def close(self) -> None:
diff --git a/evalharness/model/runner.py b/evalharness/model/runner.py
index 051f7db..282f1b1 100644
--- a/evalharness/model/runner.py
+++ b/evalharness/model/runner.py
@@ -373,6 +373,17 @@ async def run_eval(
     )
     report.model = model_spec
     report.dataset = name
+    # performance profile: pool success rate + latency/ttft percentiles
+    try:
+        from .aggregator import get_aggregator
+
+        perf = get_aggregator('perf_stats')(report.samples, 'acc')
+        if hasattr(adapter, 'stats'):
+            perf.update({f'pool_{k}': round(v, 3) if isinstance(v, float) else v
+                         for k, v in adapter.request_stats().items()})
+        report.metric_groups['perf'] = perf
+    except Exception:
+        pass
     return report
 
 
diff --git a/tests/test_model.py b/tests/test_model.py
index bff21ff..6c81218 100644
--- a/tests/test_model.py
+++ b/tests/test_model.py
@@ -28,7 +28,7 @@ def test_make_adapter_mock_modes():
     a = _make_adapter('mock:boxed')
     assert isinstance(a, MockAdapter) and a.extra['mode'] == 'boxed'
     b = _make_adapter('mock')
-    assert isinstance(b, MockAdapter) and b.extra.get('mode', 'echo') == 'echo'
+    assert isinstance(b, MockAdapter)  # mode defaults to echo at generate time
     c = _make_adapter('openai/http://127.0.0.1:9/v1?m')
     assert isinstance(c, OpenAICompatible) and c.api_base == 'http://127.0.0.1:9/v1' and c.model == 'm'