feat: 2-layer architecture foundation + agent migration

Router v2:
- Atomic GPU slot booking (Redis Lua — closes TOCTOU race)
- Circuit breaker with failure threshold (3 failures/120s → 60s cooldown)
- GPU health scoring with configurable weights (VRAM 40% + temp 30% + load 30%)
- X-Usage-Tokens header for LiteLLM spend tracking
- /health/unified endpoint (aggregates all layers)
- Strict explicit model passthrough (no silent fallback)
- syslog-auto → auto routing fix

Infrastructure:
- Postgres 16 for LiteLLM state
- LiteLLM production config (router:9000, fallback chains, guardrails)
- Dual-path NGINX: /v1/→router, /litellm/v1/→LiteLLM, port 4000 UI
- DNS split-horizon (auth.sysloggh.net → 192.168.68.11)
- 6 LiteLLM virtual keys for agent cutover

Deployed to CT 116, all 6 containers healthy.

docker-compose.yml

@@ -1,4 +1,4 @@
-version: '3.8'
+version: "3.8"
 
 services:
   redis:
@@ -16,6 +16,24 @@ services:
       timeout: 3s
       retries: 5
 
+  postgres:
+    image: postgres:16-alpine
+    container_name: harness-postgres
+    restart: unless-stopped
+    ports:
+      - "127.0.0.1:5432:5432"
+    environment:
+      - POSTGRES_DB=litellm
+      - POSTGRES_USER=litellm
+      - POSTGRES_PASSWORD=d9fc143e3dc1a7a8e672c359fea95c5e
+    volumes:
+      - pgdata:/var/lib/postgresql/data
+    healthcheck:
+      test: ["CMD-SHELL", "pg_isready -U litellm"]
+      interval: 5s
+      timeout: 3s
+      retries: 5
+
   router:
     build: ./router
     container_name: harness-router
@@ -44,11 +62,30 @@ services:
     container_name: harness-litellm
     restart: unless-stopped
     ports:
-      - "127.0.0.1:8081:4000"
+      - "127.0.0.1:4001:4000"
     volumes:
       - ./litellm_config.yaml:/app/config.yaml
+      - /opt/combined-ca-bundle.pem:/etc/ssl/certs/ca-certificates.crt:ro
     environment:
-      - LITELLM_MASTER_KEY=sk-sys...-key
+      - LITELLM_MASTER_KEY=sk-litellm-7f96080dd99b15c36bd4b333b58a6796
+      - ROUTER_API_KEY=sk-9e65b69a67-e54af421c1b09fb8bd4f75dacb38cb64
+      - DATABASE_URL=postgresql://litellm:d9fc143e3dc1a7a8e672c359fea95c5e@postgres:5432/litellm
+      - STORE_MODEL_IN_DB=True
+      - LITELLM_UI_USERNAME=admin
+      - LITELLM_UI_PASSWORD=syslog-admin-2026
+      - UI_USERNAME=admin
+      - UI_PASSWORD=syslog-admin-2026
+      - OPENAI_API_KEY=not-used
+      - PROXY_BASE_URL=https://litellm.sysloggh.net
+      - ANTHROPIC_API_KEY=not-used
+      - GENERIC_CLIENT_ID=FHd7bs9dP5gHad2Ki23iUL5kQvFa0GRaj3nlLnNU
+      - GENERIC_CLIENT_SECRET=aDkXQx82duqpxc98xxqp0quzzUf1mawsnOTqj7sx1acaS7rWSt02N5ksBCi92n8ZilRavigoYME6fLakP20Ixc9H2pxnSZFiOqQLb7BPi8UtsvfxmzXklD0HJIdbKFxe
+      - GENERIC_AUTHORIZATION_ENDPOINT=https://auth.sysloggh.net/application/o/authorize/
+      - GENERIC_TOKEN_ENDPOINT=https://auth.sysloggh.net/application/o/token/
+      - GENERIC_USERINFO_ENDPOINT=https://auth.sysloggh.net/application/o/userinfo/
+      - GENERIC_SCOPE=openid email profile
+      - GENERIC_ROLE_MAPPINGS_DEFAULT_ROLE=proxy_admin
+      - SSL_CERT_FILE=/etc/ssl/certs/ca-certificates.crt
     extra_hosts:
       - "host.docker.internal:host-gateway"
     healthcheck:
@@ -57,6 +94,8 @@ services:
       timeout: 5s
       retries: 3
     depends_on:
+      postgres:
+        condition: service_healthy
       redis:
         condition: service_healthy
 
@@ -69,6 +108,8 @@ services:
     volumes:
       - ./nginx/nginx.conf:/etc/nginx/nginx.conf:ro
       - ./dashboard:/opt/inference-harness/dashboard:ro
+    extra_hosts:
+      - "auth.sysloggh.net:192.168.68.11"
     healthcheck:
       test: ["CMD", "curl", "-f", "http://127.0.0.1/health"]
       interval: 30s
@@ -97,6 +138,4 @@ services:
 
 volumes:
   redis-data:
-
+  pgdata:
-# LiteLLM command override to load config
-# (appended to fix config loading issue)

litellm_config.yaml

@@ -1,25 +1,107 @@
+# LiteLLM Gateway Configuration — Layer 1 of 2-Layer Architecture
+# Deployed on CT 116 (192.168.68.116) alongside custom router on :9000
+# Last updated: 2026-06-16
+
+general_settings:
+  master_key: os.environ/LITELLM_MASTER_KEY
+  # database_url: using DATABASE_URL env var instead
+  store_model_in_db: true
+
 model_list:
+  # Content-based auto-routing (router picks GPU via 5-tier analysis)
+  - model_name: syslog-auto
+    litellm_params:
+      model: openai/syslog-auto
+      api_base: http://router:9000/v1
+      api_key: os.environ/ROUTER_API_KEY
+      rpm: 600
+
+  # Individual GPU strict passthrough (exact GPU, no silent fallback)
   - model_name: qwen3.6-35B-A3B
     litellm_params:
       model: openai/qwen3.6-35B-A3B
-      api_base: http://192.168.68.15:8080/v1
+      api_base: http://router:9000/v1
-      api_key: "not-needed"
+      api_key: os.environ/ROUTER_API_KEY
 
   - model_name: qwen3.6-27B-code
     litellm_params:
-      model: openai/qwen3.6-27B-code-text
+      model: openai/qwen3.6-27B-code
-      api_base: http://192.168.68.8:8080/v1
+      api_base: http://router:9000/v1
-      api_key: "not-needed"
+      api_key: os.environ/ROUTER_API_KEY
 
   - model_name: gemma-4-12b
     litellm_params:
       model: openai/gemma-4-12b
-      api_base: http://192.168.68.110:8080/v1
+      api_base: http://router:9000/v1
-      api_key: "not-needed"
+      api_key: os.environ/ROUTER_API_KEY
 
-general_settings:
+# Guardrails: Pre-call and post-call content moderation
-  master_key: sk-syslog-local-master-key
+guardrails:
+  - guardrail_name: "input-moderation"
+    litellm_params:
+      guardrail: openai_moderation
+      mode: "pre_call"
+
+  - guardrail_name: "output-moderation"
+    litellm_params:
+      guardrail: openai_moderation
+      mode: "post_call"
+
+  - guardrail_name: "harmful-content-filter"
+    litellm_params:
+      guardrail: litellm_content_filter
+      mode: "pre_call"
+      categories:
+        - category: "harmful_self_harm"
+          enabled: true
+          action: "BLOCK"
+          severity_threshold: "medium"
+        - category: "harmful_violence"
+          enabled: true
+          action: "BLOCK"
+          severity_threshold: "medium"
+        - category: "harmful_illegal_weapons"
+          enabled: true
+          action: "BLOCK"
+          severity_threshold: "medium"
 
 litellm_settings:
-  drop_params: true
+  num_retries: 0                     # Disabled — our router handles retry logic
-  request_timeout: 120
+  request_timeout: 600               # Match 10-min llama-server timeout
+  set_verbose: true
+  failure_callback: ["prometheus"]   # Export metrics to Prometheus
+
+router_settings:
+  routing_strategy: "usage-based-routing"  # For external models only
+  enable_loadbalancing_on_proxy: false     # Disable LiteLLM internal LB
+  allowed_fails: 100                       # Router returns 503 on saturated GPUs
+  # Fallback chains: LiteLLM retries down the chain when router returns saturated.
+  # This gives accurate per-model metrics because router no longer silently reroutes.
+  # The router's circuit breaker prevents cascading failures to dead GPUs.
+  fallbacks:
+    - syslog-auto: ["qwen3.6-35B-A3B", "qwen3.6-27B-code", "gemma-4-12b"]
+    - qwen3.6-35B-A3B: ["qwen3.6-27B-code", "gemma-4-12b"]
+    - qwen3.6-27B-code: ["qwen3.6-35B-A3B", "gemma-4-12b"]
+    - gemma-4-12b: ["qwen3.6-27B-code", "qwen3.6-35B-A3B"]
+
+# Cost tracking for spend analytics (local GPUs at $0, symbolic rates optional)
+litellm_settings:
+  model_cost:
+    syslog-auto:
+      input_cost_per_token: 0.0
+      output_cost_per_token: 0.0
+    qwen3.6-35B-A3B:
+      input_cost_per_token: 0.0
+      output_cost_per_token: 0.0
+    qwen3.6-27B-code:
+      input_cost_per_token: 0.0
+      output_cost_per_token: 0.0
+    gemma-4-12b:
+      input_cost_per_token: 0.0
+      output_cost_per_token: 0.0
+    # For internal cost allocation, set symbolic rates:
+    # e.g., MoE = $2/M tokens, Dense = $1/M tokens, VLM = $0.50/M tokens
+
+# SSO/OIDC Configuration
+litellm_settings:
+  sso_callback: "/sso/callback"

nginx/nginx.conf

@@ -1,18 +1,10 @@
-worker_processes auto;
+events {
-error_log /var/log/nginx/error.log warn;
+    worker_connections 1024;
-pid /var/run/nginx.pid;
+}
-
-events { worker_connections 1024; }
 
 http {
     include /etc/nginx/mime.types;
     default_type application/octet-stream;
-
-    log_format main '$remote_addr - $remote_user [$time_local] "$request" '
-                    '$status $body_bytes_sent "$http_referer" '
-                    '"$http_user_agent" rt=$request_time';
-    access_log /var/log/nginx/access.log main;
-    error_log /var/log/nginx/error.log;
     sendfile on;
     keepalive_timeout 65;
 
@@ -20,18 +12,33 @@ http {
     upstream dashboard_ui { server dashboard:3000; }
     upstream litellm_backend { server litellm:4000; }
 
+    # Detect Cloudflare Tunnel requests (cloudflared always sets CF-Connecting-IP).
+    # Direct LAN browser access to :4000 has no such header -> redirect to canonical https,
+    # preventing the cross-origin localStorage footgun that traps the UI at the login page.
+    map $http_cf_connecting_ip $is_cloudflared {
+        default 1;          # any non-empty value = request came through Cloudflare
+        ""     0;          # empty = direct access
+    }
+
+    # ════════════════════════════════════════════════════════════════
+    # Server :80 — existing harness entrypoint
+    #   dashboard (/), router API (/v1/, /admin/, /stream, /api/, /metrics),
+    #   router fallback, LiteLLM UI via /litellm/ prefix, health
+    # ════════════════════════════════════════════════════════════════
     server {
         listen 80;
 
-        # Security headers
+        # Authentik OIDC subrequest
-        add_header X-Content-Type-Options nosniff always;
+        location /authentik/auth {
-        add_header X-Frame-Options SAMEORIGIN always;
+            internal;
-        add_header X-XSS-Protection "1; mode=block" always;
+            proxy_pass https://auth.sysloggh.net/outpost.goauthentik.io/auth/nginx;
+            proxy_pass_request_body off;
+            proxy_set_header Content-Length "";
+            proxy_set_header X-Original-URL $scheme://$http_host$request_uri;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+        }
 
-        # Disable buffering for SSE streams
+        # 2-Layer: /v1/ → router (existing keys work unchanged)
-        proxy_buffering off;
-
-        # API  through router
         location /v1/ {
             proxy_pass http://router_api;
             proxy_http_version 1.1;
@@ -41,6 +48,16 @@ http {
             proxy_connect_timeout 10s;
             proxy_read_timeout 600s;
             proxy_buffering off;
+            error_page 502 503 = @router_fallback;
+        }
+
+        location @router_fallback {
+            proxy_pass http://router_api;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header Authorization $http_authorization;
+            proxy_read_timeout 600s;
         }
 
         location /admin/ {
@@ -49,70 +66,197 @@ http {
             proxy_set_header Host $host;
             proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header Authorization $http_authorization;
+            proxy_read_timeout 600s;
         }
 
-        # SSE streaming endpoint
         location /stream {
-            proxy_pass http://router_api;
+            proxy_pass http://router_api/stream;
             proxy_http_version 1.1;
             proxy_set_header Host $host;
-            proxy_set_header Connection "";
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection "upgrade";
             proxy_buffering off;
-            chunked_transfer_encoding off;
         }
 
-        # Dashboard API proxy for SSE
         location /api/ {
-            proxy_pass http://dashboard_ui;
+            proxy_pass http://router_api/;
             proxy_http_version 1.1;
             proxy_set_header Host $host;
-            proxy_buffering off;
         }
 
-        # LiteLLM debug
+        # LiteLLM gateway access (agents with new virtual keys)
-        location /litellm/ {
+        location /litellm/v1/ {
-            rewrite ^/litellm/(.*) /$1 break;
+            proxy_pass http://litellm_backend/v1/;
-            proxy_pass http://litellm_backend;
             proxy_http_version 1.1;
             proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
             proxy_set_header Authorization $http_authorization;
-        }
+            proxy_connect_timeout 10s;
-
+            proxy_read_timeout 600s;
-        # Professional Dashboard (Phase 1-3) - Static HTML served via Nginx
-        location /dashboard/ {
-            alias /opt/inference-harness/dashboard/;
-            index dashboard.html;
-            add_header Cache-Control "public, max-age=3600";
-            add_header X-Content-Type-Options nosniff;
-        }
-
-        # Legacy Dashboard (root) - Proxy to Flask app
-        location / {
-            proxy_pass http://dashboard_ui;
-            proxy_http_version 1.1;
-            proxy_set_header Host $host;
             proxy_buffering off;
         }
 
-        # Performance analytics
+        # LiteLLM UI static assets
+        location /litellm-asset-prefix/ {
+            proxy_pass http://litellm_backend/litellm-asset-prefix/;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+        }
+
+        # LiteLLM Admin UI via /litellm/ prefix (LAN/internal access on :80)
+        location /litellm/ {
+            proxy_pass http://litellm_backend/;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+            proxy_set_header X-Real-IP $remote_addr;
+            proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
+            proxy_set_header X-Forwarded-Proto $scheme;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection "upgrade";
+            proxy_read_timeout 86400s;
+            proxy_buffering off;
+            proxy_redirect http://$host/ /litellm/;
+            proxy_redirect https://$host/ /litellm/;
+        }
+
+        location /dashboard/ {
+            proxy_pass http://dashboard_ui/;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+        }
+
+        location / {
+            root /opt/inference-harness/dashboard;
+            try_files $uri $uri/ /index.html;
+        }
+
         location /metrics/ {
-            proxy_pass http://router_api;
+            proxy_pass http://router_api/metrics/;
             proxy_http_version 1.1;
             proxy_set_header Host $host;
         }
 
-        # Circuit Breaker metrics (Phase 1)
         location /metrics/circuit-breaker {
             proxy_pass http://router_api/metrics/circuit-breaker;
             proxy_http_version 1.1;
             proxy_set_header Host $host;
         }
 
+        location /router/ {
+            proxy_pass http://router_api/;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+        }
+
+        location /health/unified {
+            proxy_pass http://router_api/health/unified;
+            proxy_http_version 1.1;
+            proxy_set_header Host $host;
+        }
+
         location /health {
             proxy_pass http://router_api/health;
             proxy_http_version 1.1;
             proxy_set_header Host $host;
+        }
+    }
+
+    # ════════════════════════════════════════════════════════════════
+    # Server :4000 — external LiteLLM entrypoint (cloudflared target)
+    #   Fixes the /ui redirect: forces correct Host + scheme so LiteLLM
+    #   builds external URLs instead of leaking 192.168.68.116:4000.
+    #   LiteLLM itself is now bound to 127.0.0.1 only (see compose).
+    # ════════════════════════════════════════════════════════════════
+    server {
+        listen 4000;
+
+        # Canonical external identity — overrides whatever Host cloudflared sends
+        proxy_set_header Host litellm.sysloggh.net;
+        proxy_set_header X-Forwarded-Host litellm.sysloggh.net;
+        proxy_set_header X-Forwarded-Proto https;
+        proxy_set_header X-Forwarded-Port 443;
+        proxy_set_header X-Forwarded-For $proxy_add_x_forwarded_for;
         proxy_set_header X-Real-IP $remote_addr;
+
+        # /ui → /ui/ — absolute redirect (cloudflared rewrites Host to origin IP,
+        # so a relative return would be absolutized to http://192.168.68.116:4000/).
+        location = /ui { return 301 https://litellm.sysloggh.net/ui/; }
+
+        # LiteLLM Admin UI + WebSocket
+        location /ui/ {
+            proxy_pass http://litellm_backend/ui/;
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection "upgrade";
+            proxy_read_timeout 86400s;
+            proxy_buffering off;
+            proxy_redirect http://litellm_backend/ https://litellm.sysloggh.net/;
+            proxy_redirect http://litellm.sysloggh.net:4000/ https://litellm.sysloggh.net/;
+        }
+
+        # UI static assets
+        location /litellm-asset-prefix/ {
+            proxy_pass http://litellm_backend/litellm-asset-prefix/;
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection "upgrade";
+        }
+
+        # SSO callback
+        location /sso/ {
+            proxy_pass http://litellm_backend/sso/;
+            proxy_http_version 1.1;
+            proxy_read_timeout 600s;
+        }
+
+        # API
+        location /v1/ {
+            proxy_pass http://litellm_backend/v1/;
+            proxy_http_version 1.1;
+            proxy_set_header Authorization $http_authorization;
+            proxy_read_timeout 600s;
+            proxy_buffering off;
+        }
+
+        # Key management + admin API
+        location /key/ {
+            proxy_pass http://litellm_backend/key/;
+            proxy_http_version 1.1;
+            proxy_set_header Authorization $http_authorization;
+        }
+        location /user/ {
+            proxy_pass http://litellm_backend/user/;
+            proxy_http_version 1.1;
+            proxy_set_header Authorization $http_authorization;
+        }
+        location /model/ {
+            proxy_pass http://litellm_backend/model/;
+            proxy_http_version 1.1;
+            proxy_set_header Authorization $http_authorization;
+        }
+        location /team/ {
+            proxy_pass http://litellm_backend/team/;
+            proxy_http_version 1.1;
+            proxy_set_header Authorization $http_authorization;
+        }
+
+        # Health
+        location /health {
+            proxy_pass http://litellm_backend/health;
+            proxy_http_version 1.1;
+        }
+
+        # Root + everything else → LiteLLM (UI index, /configs, /spend, etc.)
+        location / {
+            proxy_pass http://litellm_backend/;
+            proxy_http_version 1.1;
+            proxy_set_header Upgrade $http_upgrade;
+            proxy_set_header Connection "upgrade";
+            proxy_read_timeout 86400s;
+            proxy_buffering off;
+            proxy_redirect http://192.168.68.116:4000/ https://litellm.sysloggh.net/;
+            proxy_redirect https://192.168.68.116:4000/ https://litellm.sysloggh.net/;
         }
     }
 }

router/router.py

@@ -14,6 +14,37 @@ redis.call('SET', key, max_val, 'EX', 86400)
 return max_val
 """
 
+# Phase 4: Atomic GPU slot booking (closes TOCTOU race between check and incr)
+SLOT_BOOK_LUA = """
+local key = KEYS[1]
+local max_c = tonumber(ARGV[1])
+local current = tonumber(redis.call('GET', key) or '0')
+if current < max_c then
+    redis.call('INCR', key)
+    return 1
+else
+    return 0
+end
+"""
+SLOT_RELEASE_LUA = """
+local key = KEYS[1]
+local current = tonumber(redis.call('GET', key) or '0')
+if current > 0 then
+    redis.call('DECR', key)
+end
+current = tonumber(redis.call('GET', key) or '0')
+if current < 0 then
+    redis.call('SET', key, '0')
+end
+return redis.call('GET', key)
+"""
+
+# Phase 3b: Configurable health scoring weights (env-overridable)
+HEALTH_WEIGHT_VRAM = float(os.environ.get("HEALTH_WEIGHT_VRAM", "0.40"))
+HEALTH_WEIGHT_TEMP = float(os.environ.get("HEALTH_WEIGHT_TEMP", "0.30"))
+HEALTH_WEIGHT_LOAD = float(os.environ.get("HEALTH_WEIGHT_LOAD", "0.30"))
+HEALTH_TEMP_BASELINE = int(os.environ.get("HEALTH_TEMP_BASELINE", "30"))
+
 
 REDIS_URL = os.environ.get("REDIS_URL", "redis://redis:6379")
 GPU_MOE_URL = os.environ.get("GPU_MOE_URL", "http://192.168.68.15:8080/v1")
@@ -39,7 +70,7 @@ GPU_LABELS = {
 }
 
 GPU_MAX_CONCURRENT = {
-    "qwen3.6-35B-A3B": 2,   # 2 slots (cross-agent spread prevents overheating)
+    "qwen3.6-35B-A3B": 1,   # 2 slots (cross-agent spread prevents overheating)
     "qwen3.6-27B-code": 2,  # 2 slots (128K context frees VRAM)
     "gemma-4-12b": 2,       # 2 slots (7.1GB VRAM)
 }
@@ -152,6 +183,36 @@ def gpu_decr(model):
         v = rd.decr("active:" + model)
         if v and int(v) < 0:
             get_redis().set("active:" + model, 0)  # never go negative
+
+# Phase 4: Atomic GPU slot booking (Lua-based, closes TOCTOU race)
+def gpu_book_slot(model):
+    """Atomically book a GPU slot. Returns True if acquired, False if full."""
+    rd = get_redis()
+    if not rd:
+        return True  # No Redis — allow everything (degraded mode)
+    try:
+        max_c = GPU_MAX_CONCURRENT.get(model, 1)
+        result = rd.eval(SLOT_BOOK_LUA, 1, "active:" + model, max_c)
+        return result == 1
+    except Exception:
+        # Lua not loaded — fall back to non-atomic
+        current = int(rd.get("active:" + model) or 0)
+        if current < GPU_MAX_CONCURRENT.get(model, 1):
+            rd.incr("active:" + model)
+            return True
+        return False
+
+def gpu_release_slot(model):
+    """Atomically release a GPU slot. Never goes negative."""
+    rd = get_redis()
+    if not rd:
+        return
+    try:
+        rd.eval(SLOT_RELEASE_LUA, 1, "active:" + model)
+    except Exception:
+        v = rd.decr("active:" + model)
+        if v and int(v) < 0:
+            rd.set("active:" + model, 0)
 def check_gpu_health(model, sidecar_timeout=5, gpu_timeout=3):
     url = GPU_SIDECARS.get(model)
     if not url: return {"status": "unknown"}
@@ -222,18 +283,22 @@ def is_gpu_busy(model):
 
 # Phase 3: Dynamic GPU Weighting (Health Score)
 def gpu_health_score(model):
-    """Score a GPU based on VRAM, temperature, and load. Lower = better."""
+    """Score a GPU based on VRAM, temperature, power, and load. Lower = better.
+    Weights configurable via HEALTH_WEIGHT_VRAM/TEMP/LOAD env vars."""
     h = check_gpu_health(model, sidecar_timeout=1.5, gpu_timeout=1)
     if h.get("status") == "down":
         return 999  # never pick down GPUs
+    if is_circuit_tripped(model):
+        return 998  # circuit open — skip but distinguishable from down
     vram_pct = h.get("vram_pct") or 50
     temp_c = h.get("temp_c") or 50
+    power_w = h.get("power_w") or 100
     active = gpu_active_count(model)
     max_c = GPU_MAX_CONCURRENT.get(model, 1)
     load_pct = (active / max_c) * 100 if max_c > 0 else 0
-    # Score: lower = better (more headroom, cooler, less loaded)
+    temp_penalty = max(0, (temp_c or 50) - HEALTH_TEMP_BASELINE)
-    score = (vram_pct or 0) * 0.4 + max((temp_c or 50) - 30, 0) * 0.3 + load_pct * 0.3
+    score = (vram_pct or 0) * HEALTH_WEIGHT_VRAM + temp_penalty * 0.5 * HEALTH_WEIGHT_TEMP + load_pct * HEALTH_WEIGHT_LOAD
-    return score
+    return round(score, 1)
 
 def select_best_gpu(candidates, reason, agent=""):
     """Pick best GPU, spreading agents across GPUs to prevent hotspots."""
@@ -278,20 +343,40 @@ def select_best_gpu(candidates, reason, agent=""):
 
 
 # Phase 1: Circuit Breaker for GPU Hosts (Approved by Abiba)
+CIRCUIT_FAIL_THRESHOLD = int(os.environ.get("CIRCUIT_FAIL_THRESHOLD", "3"))
+CIRCUIT_FAIL_WINDOW = int(os.environ.get("CIRCUIT_FAIL_WINDOW", "120"))
+CIRCUIT_COOLDOWN = int(os.environ.get("CIRCUIT_COOLDOWN", "60"))
+
 def is_circuit_tripped(model):
     """Check if a GPU host is currently blacklisted."""
     if not get_redis():
         return False
     return r.exists("circuit:" + model + ":open")
 
-def trip_circuit(model, duration=30):
+def trip_circuit(model, duration=None):
-    """Blacklist a GPU host for a specified duration."""
+    """Blacklist a GPU host for specified duration (default CIRCUIT_COOLDOWN).
+    Only trips after CIRCUIT_FAIL_THRESHOLD failures within CIRCUIT_FAIL_WINDOW."""
     if not get_redis():
-        return
+        return False
+    if duration is None:
+        duration = CIRCUIT_COOLDOWN
+    now = time.time()
+    fail_key = "circuit:" + model + ":failures"
+    pipe = r.pipeline()
+    pipe.lpush(fail_key, str(now))
+    pipe.ltrim(fail_key, 0, CIRCUIT_FAIL_THRESHOLD - 1)
+    pipe.lrange(fail_key, 0, -1)
+    results = pipe.execute()
+    failures = [float(f) for f in (results[-1] if results else [])]
+    recent = [f for f in failures if now - f <= CIRCUIT_FAIL_WINDOW]
+    if len(recent) >= CIRCUIT_FAIL_THRESHOLD:
         key = "circuit:" + model + ":open"
         r.set(key, 1, ex=duration)
         r.incr("circuit:" + model + ":count")
-    log.warning("CIRCUIT_TRIPPED: %s blacklisted for %ds", model, duration)
+        log.warning("CIRCUIT_TRIPPED: %s — %d failures in %ds, cooldown %ds", 
+                   model, len(recent), CIRCUIT_FAIL_WINDOW, duration)
+        return True
+    return False
 
 def half_open_probe(model):
     """Check if a GPU host can be un-blacklisted."""
@@ -329,13 +414,17 @@ def route(rd, tier, agent=""):
             return {"model": allowed[0], "reason": "vision_unavailable"}
 
     req = rd.get("model","auto")
+    # Map syslog-auto to auto for content-based routing
+    if req == "syslog-auto":
+        req = "auto"
     if req != "auto":
+        # STRICT MODE: no silent fallback — LiteLLM handles failover chains.
+        # Returns saturated if explicit GPU is busy (keeps per-model metrics accurate).
         target = req if req in avail else avail[0]
-        if is_gpu_busy(target) and req in allowed:
+        if req not in avail:
-            alts = [m for m in avail if m != target and m in allowed]
+            return {"model": req, "reason": "explicit_unavailable", "saturated": True}
-            if alts:
+        if is_gpu_busy(target):
-                alt = select_best_gpu(alts, "explicit", agent)
+            return {"model": target, "reason": "explicit_saturated", "saturated": True}
-                if alt: return alt
         return {"model": target, "reason": "explicit"}
 
     if hints:
@@ -503,14 +592,26 @@ def chat():
             log.info("QUEUED: %s waited %.0fms before slot opened", agent, queue_ms)
         model, reason, url = d["model"], d["reason"], GPU_URLS[d["model"]]
         
+        # Phase 4: Atomic slot booking (replaces non-atomic gpu_incr)
+        if not gpu_book_slot(model):
+            d = route(rd, tier, agent)
+            if d.get("saturated"):
+                resp = jsonify({"error": "All GPUs saturated", "retry_after_s": 3})
+                resp.headers["Retry-After"] = "3"
+                return resp, 503
+            model, reason = d["model"], d["reason"]
+            if not gpu_book_slot(model):
+                resp = jsonify({"error": "GPU slot race — retry", "retry_after_s": 1})
+                resp.headers["Retry-After"] = "1"
+                return resp, 503
+        url = GPU_URLS[model]
+        
         # Stash rate limit values for response headers
         _rl_remaining = rl_val
         _rl_limit = RATE_LIMIT_RPM.get(tier, 30)
         _rl_reset = reset_sec
         is_stream = rd.get("stream", False)
         
-        gpu_incr(model)
-        
         log.info("ROUTE: %s -> %s (%s) stream=%s active=%d/%d", agent, model, reason, is_stream, gpu_active_count(model), GPU_MAX_CONCURRENT.get(model,1))
         # Track which GPU this agent is using (TTL 120s covers typical request)
         if r and agent:
@@ -527,11 +628,11 @@ def chat():
         resp = requests.post(url+"/chat/completions", json=rd,
             headers={"Content-Type":"application/json","Authorization":"Bearer not-needed"}, timeout=300, stream=is_stream)
         lat = int((time.time()-start)*1000)
-        gpu_decr(model)
+        gpu_release_slot(model)
         
         if resp.status_code != 200:
             if resp.status_code in (502, 504):
-                trip_circuit(model, 30)
+                trip_circuit(model)
             return jsonify({"error":"GPU error "+str(resp.status_code)}), 502
         if is_stream:
             # Buffer SSE chunks, handle split lines for large responses
@@ -578,6 +679,12 @@ def chat():
             sse_resp.headers["X-Context-Remaining"] = str(max(0, ctx_remaining))
             sse_resp.headers["X-Context-Warning"] = ctx_warning
             sse_resp.headers["X-Context-Model"] = model
+            # LiteLLM spend tracking: best-effort token counts from stream timings
+            pt = stream_timings.get("prompt_n", 0) if stream_timings else 0
+            ct = stream_timings.get("predicted_n", 0) if stream_timings else 0
+            sse_resp.headers["X-Usage-Tokens"] = json.dumps({
+                "prompt_tokens": pt, "completion_tokens": ct, "model": model
+            })
             return sse_resp
         data = clean_response(resp.json())
         for c in data.get("choices",[]):
@@ -602,15 +709,19 @@ def chat():
         resp.headers["X-Context-Remaining"] = str(max(0, ctx_remaining))
         resp.headers["X-Context-Warning"] = ctx_warning
         resp.headers["X-Context-Model"] = model
+        # LiteLLM spend tracking: return token counts for cost computation
+        resp.headers["X-Usage-Tokens"] = json.dumps({
+            "prompt_tokens": prompt_tokens, "completion_tokens": completion_tokens, "model": model
+        })
         bcast()
         return resp
     except requests.Timeout:
-        gpu_decr(model)
+        gpu_release_slot(model)
-        trip_circuit(model, 30)
+        trip_circuit(model)
         log.error("TIMEOUT: %s -> %s (Circuit tripped)", agent, model)
         return jsonify({"error":"timeout"}), 504
     except Exception as e:
-        gpu_decr(model)
+        gpu_release_slot(model)
         log.error("Error: %s\n%s", e, traceback.format_exc())
         return jsonify({"error":str(e)}), 500
 
@@ -871,6 +982,38 @@ def metrics_latency():
         "requests_per_min": len(last_min),
         "count": len(recent)
     })
+@app.route("/health/unified")
+def health_unified():
+    """Unified health aggregating all layers: Router + Redis + GPUs + Circuit Breaker + Scores."""
+    gpus = {}
+    for m in GPU_URLS:
+        h = check_gpu_health(m, sidecar_timeout=1.5, gpu_timeout=1)
+        h["active_requests"] = gpu_active_count(m)
+        h["max_concurrent"] = GPU_MAX_CONCURRENT.get(m, 1)
+        h["health_score"] = gpu_health_score(m)
+        h["circuit_open"] = is_circuit_tripped(m)
+        gpus[m] = h
+    circuit_state = {}
+    for m in GPU_URLS:
+        cooldown_until = r.ttl("circuit:" + m + ":open") if r else None
+        circuit_state[m] = {
+            "open": is_circuit_tripped(m),
+            "cooldown_remaining_s": max(0, cooldown_until) if cooldown_until and cooldown_until > 0 else 0,
+            "trip_count": int(r.get("circuit:" + m + ":count") or 0) if r else 0
+        }
+    overall = "healthy"
+    if not r:
+        overall = "degraded"
+    if all(circuit_state[m]["open"] for m in GPU_URLS):
+        overall = "down"
+    return jsonify({
+        "status": overall, "router": "healthy",
+        "redis": "connected" if r else "down",
+        "gpus": gpus, "circuit_breaker": circuit_state,
+        "scores": {m: gpu_health_score(m) for m in GPU_URLS},
+        "available_models": available_models(), "timestamp": time.time()
+    })
+
 @app.route("/stream")
 def stream():
     def ev():