tools: add correctness + performance test scripts for Qwen3-8B

- test_correctness.py: compare prefill logits top-20 vs HF transformers
- bench_server.py: HTTP API benchmark (throughput, streaming, concurrent, EOS leak check)

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tools/bench_server.py

@@ -0,0 +1,140 @@
+#!/usr/bin/env python3
+"""Benchmark xserv server performance and check correctness vs HF."""
+
+import json
+import time
+import sys
+import urllib.request
+
+PORT = int(sys.argv[1]) if len(sys.argv) > 1 else 8090
+
+def chat(prompt, max_tokens=80, temperature=0):
+    data = json.dumps({
+        "model": "qwen3-8b",
+        "messages": [{"role": "user", "content": prompt}],
+        "max_tokens": max_tokens,
+        "temperature": temperature,
+        "stream": False
+    }).encode()
+    req = urllib.request.Request(
+        f"http://localhost:{PORT}/v1/chat/completions",
+        data=data, headers={"Content-Type": "application/json"}
+    )
+    t0 = time.perf_counter()
+    with urllib.request.urlopen(req, timeout=180) as resp:
+        result = json.loads(resp.read())
+    elapsed = time.perf_counter() - t0
+    usage = result.get("usage", {})
+    content = result["choices"][0]["message"]["content"]
+    finish = result["choices"][0]["finish_reason"]
+    ct = usage.get("completion_tokens", 0)
+    pt = usage.get("prompt_tokens", 0)
+    return ct / elapsed if elapsed > 0 else 0, elapsed, ct, pt, content, finish
+
+
+def chat_stream(prompt, max_tokens=80, temperature=0):
+    data = json.dumps({
+        "model": "qwen3-8b",
+        "messages": [{"role": "user", "content": prompt}],
+        "max_tokens": max_tokens,
+        "temperature": temperature,
+        "stream": True
+    }).encode()
+    req = urllib.request.Request(
+        f"http://localhost:{PORT}/v1/chat/completions",
+        data=data, headers={"Content-Type": "application/json"}
+    )
+    t0 = time.perf_counter()
+    tokens = 0
+    content = ""
+    with urllib.request.urlopen(req, timeout=180) as resp:
+        for line in resp:
+            line = line.decode().strip()
+            if line.startswith("data: "):
+                payload = line[6:]
+                if payload == "[DONE]":
+                    break
+                chunk = json.loads(payload)
+                delta = chunk["choices"][0].get("delta", {})
+                c = delta.get("content", "")
+                if c:
+                    tokens += 1
+                    content += c
+    elapsed = time.perf_counter() - t0
+    return tokens / elapsed if elapsed > 0 else 0, elapsed, tokens, content
+
+
+print("=" * 60)
+print(f"xserv Server Benchmark (port {PORT})")
+print("=" * 60)
+
+# Health check
+try:
+    urllib.request.urlopen(f"http://localhost:{PORT}/health", timeout=3)
+except:
+    print(f"Server not responding on port {PORT}")
+    sys.exit(1)
+
+# 1. EOS leak check
+print("\n--- EOS Leak Check ---")
+tps, t, ct, pt, content, finish = chat("Say hello", 30)
+has_eos = "<|im_end|>" in content or "<|endoftext|>" in content or "<|im_start|>" in content
+print(f"  finish_reason: {finish}")
+print(f"  EOS in content: {'YES (BUG!)' if has_eos else 'NO (good)'}")
+print(f"  Content: {content[:100]}")
+
+# 2. Warmup
+print("\n--- Warmup ---")
+chat("Hi", 10)
+time.sleep(0.5)
+
+# 3. Non-streaming benchmark
+print("\n--- Non-streaming Performance (greedy, batch=1) ---")
+prompts = [
+    ("short", "What is 2+2?", 50),
+    ("medium", "Explain quantum computing in simple terms.", 80),
+    ("long", "Write a detailed comparison of Python and Rust programming languages, covering syntax, performance, memory management, and ecosystem.", 150),
+]
+
+for name, prompt, max_tok in prompts:
+    tps, t, ct, pt, content, finish = chat(prompt, max_tok)
+    print(f"  [{name}] {tps:.1f} tok/s | {ct} tokens in {t:.2f}s | prompt={pt} | finish={finish}")
+
+# 4. Streaming benchmark
+print("\n--- Streaming Performance ---")
+tps, t, ct, content = chat_stream("Explain the theory of relativity.", 80)
+print(f"  stream: {tps:.1f} tok/s | {ct} tokens in {t:.2f}s")
+
+# 5. max_tokens validation
+print("\n--- max_tokens Validation ---")
+try:
+    tps, t, ct, pt, content, finish = chat("Hi", 999999)
+    print(f"  max_tokens=999999: OK (server clamped to {ct} tokens, no crash)")
+except Exception as e:
+    print(f"  max_tokens=999999: {e}")
+
+# 6. Concurrent requests (if server supports batching)
+print("\n--- Concurrent Requests (2 parallel) ---")
+import threading
+results = [None, None]
+
+def do_request(idx, prompt, max_tok):
+    results[idx] = chat(prompt, max_tok)
+
+t1 = threading.Thread(target=do_request, args=(0, "What is gravity?", 50))
+t2 = threading.Thread(target=do_request, args=(1, "What is light?", 50))
+t0 = time.perf_counter()
+t1.start(); t2.start()
+t1.join(); t2.join()
+wall_time = time.perf_counter() - t0
+
+total_tokens = sum(r[2] for r in results if r)
+combined_tps = total_tokens / wall_time
+print(f"  2 concurrent: {combined_tps:.1f} tok/s total | wall={wall_time:.2f}s")
+for i, r in enumerate(results):
+    if r:
+        print(f"    req{i}: {r[0]:.1f} tok/s, {r[2]} tokens in {r[1]:.2f}s")
+
+print(f"\n{'=' * 60}")
+print("DONE")
+print("=" * 60)