Default 122B server to 128k context, add health-check script

- 11_start_server_122b.sh: raise MAX_MODEL_LEN default to 131072 (128k),
  make max-num-seqs overridable via MAX_NUM_SEQS (default 4 for low
  concurrency / large KV cache). Echo concurrency in startup banner.
- 13_check_server.sh: new health check that polls /v1/models until ready,
  then sends a properly-sized test prompt and reports OK/failure.

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

11_start_server_122b.sh

@@ -13,10 +13,13 @@
 # Environment variables (override defaults):
 #   MODEL_DIR       - Path to model weights (default: ~/models/Qwen3.5-122B-A10B-FP8)
 #   PORT            - Server port (default: 7080)
-#   MAX_MODEL_LEN   - Maximum context length (default: 32768)
+#   MAX_MODEL_LEN   - Maximum context length (default: 131072 = 128k)
 #   GPU_MEM_UTIL    - GPU memory utilization fraction (default: 0.92)
 #   API_KEY         - API key for authentication (default: none)
 #   TENSOR_PARALLEL - Number of GPUs for tensor parallelism (default: 4)
+#   MAX_NUM_SEQS    - Max concurrent sequences (default: 4). Raise this
+#                     when more users need it AND the KV cache fits;
+#                     lower it if 128k context runs out of memory.
 # ------------------------------------------------------------------
 set -euo pipefail
 
@@ -25,10 +28,11 @@ SIF_FILE="${SCRIPT_DIR}/vllm_qwen.sif"
 
 MODEL_DIR="${MODEL_DIR:-$HOME/models/Qwen3.5-122B-A10B-FP8}"
 PORT="${PORT:-7080}"
-MAX_MODEL_LEN="${MAX_MODEL_LEN:-32768}"
+MAX_MODEL_LEN="${MAX_MODEL_LEN:-131072}"
 GPU_MEM_UTIL="${GPU_MEM_UTIL:-0.92}"
 API_KEY="${API_KEY:-}"
 TENSOR_PARALLEL="${TENSOR_PARALLEL:-4}"
+MAX_NUM_SEQS="${MAX_NUM_SEQS:-4}"
 
 if [ ! -f "$SIF_FILE" ]; then
     echo "ERROR: Container image not found at ${SIF_FILE}"
@@ -56,7 +60,7 @@ VLLM_ARGS=(
     --trust-remote-code
     --reasoning-parser qwen3
     --served-model-name "qwen3.5-122b-a10b-fp8"
-    --max-num-seqs 16
+    --max-num-seqs "$MAX_NUM_SEQS"
     --enable-prefix-caching
 )
 
@@ -73,6 +77,7 @@ echo " Port:        ${PORT}"
 echo " Context len: ${MAX_MODEL_LEN}"
 echo " GPU util:    ${GPU_MEM_UTIL}"
 echo " TP size:     ${TENSOR_PARALLEL}"
+echo " Max seqs:    ${MAX_NUM_SEQS}"
 echo " dtype:       auto (FP8)"
 echo " API key:     ${API_KEY:-<none>}"
 echo "=============================================="

13_check_server.sh

@@ -0,0 +1,128 @@
+#!/usr/bin/env bash
+# ------------------------------------------------------------------
+# 13_check_server.sh
+# Health-checks the vLLM server: polls /v1/models until the model is
+# ready, then sends a properly-sized test prompt and prints the reply.
+#
+# Works whether you run it ON the server (localhost) or from another
+# machine (use HOST=silicon.fhgr.ch).
+#
+# Usage:
+#   bash 13_check_server.sh
+#   HOST=silicon.fhgr.ch bash 13_check_server.sh
+#
+# Environment variables (override defaults):
+#   HOST       - Server hostname            (default: localhost)
+#   PORT       - Server port                (default: 7080)
+#   API_KEY    - API key, if the server needs one (default: none)
+#   TIMEOUT    - Seconds to wait for model  (default: 600)
+#   MAX_TOKENS - Tokens for the test prompt (default: 512)
+#
+# NOTE: The model is a reasoning model — it spends tokens "thinking"
+#       before the final answer. MAX_TOKENS must be generous (>=256),
+#       or the reply ends up empty with finish_reason "length".
+# ------------------------------------------------------------------
+set -euo pipefail
+
+HOST="${HOST:-localhost}"
+PORT="${PORT:-7080}"
+API_KEY="${API_KEY:-}"
+TIMEOUT="${TIMEOUT:-600}"
+MAX_TOKENS="${MAX_TOKENS:-512}"
+
+BASE_URL="http://${HOST}:${PORT}/v1"
+
+AUTH_ARGS=()
+if [ -n "$API_KEY" ]; then
+    AUTH_ARGS=(-H "Authorization: Bearer ${API_KEY}")
+fi
+
+echo "=============================================="
+echo " vLLM Server Health Check"
+echo "=============================================="
+echo " Endpoint:   ${BASE_URL}"
+echo " Timeout:    ${TIMEOUT}s"
+echo " Max tokens: ${MAX_TOKENS}"
+echo "=============================================="
+echo ""
+
+# --- Step 1: poll /v1/models until ready -------------------------
+echo "Waiting for server to respond at ${BASE_URL}/models ..."
+DEADLINE=$(( $(date +%s) + TIMEOUT ))
+MODELS_JSON=""
+while true; do
+    if MODELS_JSON=$(curl -s -m 5 ${AUTH_ARGS[@]+"${AUTH_ARGS[@]}"} "${BASE_URL}/models" 2>/dev/null) \
+        && echo "$MODELS_JSON" | grep -q '"data"'; then
+        break
+    fi
+    if [ "$(date +%s)" -ge "$DEADLINE" ]; then
+        echo "ERROR: Server did not become ready within ${TIMEOUT}s."
+        echo "       Check the log:  tail -f logs/vllm_server_122b_*.log"
+        exit 1
+    fi
+    printf '.'
+    sleep 5
+done
+echo ""
+
+# Extract the served model id (first entry under data[]).
+MODEL_ID=$(echo "$MODELS_JSON" | python3 -c \
+    "import sys, json; print(json.load(sys.stdin)['data'][0]['id'])" 2>/dev/null || true)
+
+if [ -z "$MODEL_ID" ]; then
+    echo "ERROR: Could not parse model id from /v1/models response:"
+    echo "$MODELS_JSON"
+    exit 1
+fi
+
+echo "Server is up. Serving model: ${MODEL_ID}"
+echo ""
+
+# --- Step 2: send a real generation request ----------------------
+echo "Sending test prompt..."
+REQUEST=$(python3 -c "
+import json, sys
+print(json.dumps({
+    'model': sys.argv[1],
+    'messages': [{'role': 'user', 'content': 'Reply with exactly one word: hello'}],
+    'max_tokens': int(sys.argv[2]),
+}))
+" "$MODEL_ID" "$MAX_TOKENS")
+
+RESPONSE=$(curl -s -m 120 ${AUTH_ARGS[@]+"${AUTH_ARGS[@]}"} \
+    -H "Content-Type: application/json" \
+    -d "$REQUEST" \
+    "${BASE_URL}/chat/completions")
+
+echo ""
+echo "$RESPONSE" | python3 -c "
+import sys, json
+try:
+    d = json.load(sys.stdin)
+except Exception:
+    print('ERROR: Non-JSON response from server:')
+    print(sys.stdin.read() if not sys.stdin.closed else '<empty>')
+    sys.exit(1)
+
+choice = d['choices'][0]
+msg = choice.get('message', {})
+content = msg.get('content')
+finish = choice.get('finish_reason')
+usage = d.get('usage', {})
+
+print('Finish reason: %s' % finish)
+print('Usage:         %s' % usage)
+print('Content:       %r' % content)
+print()
+
+if content and content.strip():
+    print('RESULT: OK — model generated a reply. Server is working.')
+elif finish == 'length':
+    print('RESULT: Model hit the token limit while reasoning and never')
+    print('        produced an answer. Re-run with a larger budget, e.g.:')
+    print('          MAX_TOKENS=1024 bash 13_check_server.sh')
+    sys.exit(2)
+else:
+    print('RESULT: Empty content with finish_reason=%r. Investigate.' % finish)
+    sys.exit(2)
+"