Environment Variables#

All environment variables share the LLM_ROUTER_ prefix. They are loaded from os.environ in llm_router_api/base/constants.py at import time and validated by _StartAppVerificator.

Core variables#

Variable	Default	Description
`LLM_ROUTER_PROMPTS_DIR`	`resources/prompts`	Directory containing predefined system prompts.
`LLM_ROUTER_MODELS_CONFIG`	`resources/configs/models-config.json`	Path to the models configuration JSON file.
`LLM_ROUTER_DEFAULT_EP_LANGUAGE`	`pl`	Default language for endpoint prompts (fallback).
`LLM_ROUTER_TIMEOUT`	`0`	Timeout (seconds) for llm-router API calls.
`LLM_ROUTER_EXTERNAL_TIMEOUT`	`300`	Timeout (seconds) for external model API calls.
`LLM_ROUTER_MAX_REQUEST_BODY_SIZE`	`10485760` (10 MB)	Maximum request body size in bytes; oversized payloads get HTTP 413.
`LLM_ROUTER_LOG_FILENAME`	`llm-router.log`	Name of the log file.
`LLM_ROUTER_LOG_LEVEL`	`INFO`	Logging level (e.g. INFO, DEBUG).
`LLM_ROUTER_LOG_TO_FILE`	`false`	Also write logs to the log file (in addition to console).
`LLM_ROUTER_LOG_MAX_BYTES`	`52428800` (50 MB)	Rotate the log file once it reaches this size in bytes (applied when `LLM_ROUTER_LOG_TO_FILE` is set).
`LLM_ROUTER_LOG_BACKUP_COUNT`	`5`	Maximum number of rotated log files to keep, `<name>.1` … `<name>.N`.
`LLM_ROUTER_EP_PREFIX`	`/api`	Prefix for all API endpoints.
`LLM_ROUTER_MINIMUM`	`False`	Run service in proxy-only mode.
`LLM_ROUTER_IN_DEBUG`	`False`	Run server in debug mode; also forces log level to DEBUG.
`LLM_ROUTER_BALANCE_STRATEGY`	`balanced`	Load-balancing strategy: `balanced`, `weighted`, `dynamic_weighted`, `first_available`, `first_available_optim`.
`LLM_ROUTER_SERVER_TYPE`	`flask`	Server implementation: flask, gunicorn, waitress.
`LLM_ROUTER_SERVER_PORT`	`8080`	Port on which the server listens.
`LLM_ROUTER_SERVER_HOST`	`localhost`	Host address for the server.
`LLM_ROUTER_SERVER_WORKERS_COUNT`	`2`	Number of workers (for servers that support them).
`LLM_ROUTER_SERVER_THREADS_COUNT`	`8`	Number of worker threads (for servers that support them).
`LLM_ROUTER_SERVER_WORKER_CLASS`	`None`	Worker class for servers that support it (e.g. gevent).
`LLM_ROUTER_USE_PROMETHEUS`	`False`	Enable Prometheus metrics collection (`/metrics` endpoint).

See also PROMETHEUS_MULTIPROC_DIR for the directory where Prometheus multiprocess worker data files are stored.

Redis variables#

Variable	Default	Description
`LLM_ROUTER_REDIS_HOST`	(empty)	Redis host for load-balancing state and provider availability.
`LLM_ROUTER_REDIS_PORT`	`6379`	Redis port.
`LLM_ROUTER_REDIS_DB`	`0`	Redis database number.
`LLM_ROUTER_REDIS_PASSWORD`	(empty)	Redis password.

When LLM_ROUTER_REDIS_HOST is set, the router uses Redis for load-balancing state and provider availability tracking.

Masking & Guardrail variables#

Payload masking#

Variable	Default	Description
`LLM_ROUTER_FORCE_MASKING`	`False`	Enable masking of every endpoint's payload before provider call.
`LLM_ROUTER_MASKING_STRATEGY_PIPELINE`	(empty)	Comma-separated list of masker plugins (e.g. `fast_masker,pii_masker`).
`LLM_ROUTER_MASKING_WITH_AUDIT`	`False`	Record each masking operation in the audit log.

Request guardrails#

Variable	Default	Description
`LLM_ROUTER_FORCE_GUARDRAIL_REQUEST`	`False`	Force guardrail evaluation on every request.
`LLM_ROUTER_GUARDRAIL_WITH_AUDIT_REQUEST`	`False`	Audit all guardrail decisions for requests.
`LLM_ROUTER_GUARDRAIL_STRATEGY_PIPELINE_REQUEST`	(empty)	Comma-separated list of guardrail strategies (request).

Response guardrails#

Variable	Default	Description
`LLM_ROUTER_FORCE_GUARDRAIL_RESPONSE`	`False`	Force guardrail evaluation on every response.
`LLM_ROUTER_GUARDRAIL_WITH_AUDIT_RESPONSE`	`False`	Audit all guardrail decisions for responses.
`LLM_ROUTER_GUARDRAIL_STRATEGY_PIPELINE_RESPONSE`	(empty)	Comma-separated list of guardrail strategies (response).

Semantic BiEncoder Routing variables#

Requires the llm-router-plugins package. When LLM_ROUTER_UTILS_PLUGINS_PIPELINE includes semantic_biencoder_routing, these variables configure the plugin:

Variable	Default	Description
`LLM_ROUTER_ROUTING_SEMANTIC_BIENCODER_CONFIG`	(empty)	Config source of truth — raw JSON string or file path. Falls back to bundled `semantic_biencoder.json`. Individual env vars below override loaded config values only when explicitly set.
`LLM_ROUTER_ROUTING_SEMANTIC_BIENCODER_MODEL`	(empty)	Override the embedding model name or local path.
`LLM_ROUTER_ROUTING_SEMANTIC_BIENCODER_TARGETS`	(empty)	Pipe-separated list of target names (overrides all targets).
`LLM_ROUTER_ROUTING_SEMANTIC_BIENCODER_CHUNK_SIZE`	(empty)	Token chunk size for embedding.
`LLM_ROUTER_ROUTING_SEMANTIC_BIENCODER_CHUNK_OVERLAP`	(empty)	Token overlap between consecutive chunks.
`LLM_ROUTER_ROUTING_SEMANTIC_BIENCODER_PERSIST_DIR`	(empty)	Directory for FAISS index + docstore persistence (`index.faiss`, `docstore.pkl`).

LangChainRAG variables#

Requires the llm-router-plugins package. When LLM_ROUTER_UTILS_PLUGINS_PIPELINE includes langchain_rag, these variables configure the RAG plugin:

Variable	Default	Description
`LLM_ROUTER_LANGCHAIN_RAG_COLLECTION`	(empty)	Vector store collection name (required when langchain_rag is used).
`LLM_ROUTER_LANGCHAIN_RAG_EMBEDDER`	(empty)	Path to the embedding model (e.g. `/mnt/data2/llms/models/community/google/embeddinggemma-300m`).
`LLM_ROUTER_LANGCHAIN_RAG_DEVICE`	`cpu`	Compute device for the embedding model (`cpu`, `cuda:0`, …).
`LLM_ROUTER_LANGCHAIN_RAG_CHUNK_SIZE`	(empty)	Chunk size for document splitting (required when langchain_rag is used).
`LLM_ROUTER_LANGCHAIN_RAG_CHUNK_OVERLAP`	(empty)	Overlap between consecutive chunks (required when langchain_rag is used).
`LLM_ROUTER_LANGCHAIN_RAG_PERSIST_DIR`	(empty)	Directory for LangChainRAG index persistence.

Utils plugins variables#

Variable	Default	Description
`LLM_ROUTER_UTILS_PLUGINS_PIPELINE`	(empty)	Comma-separated list of utility plugins to apply (e.g. `simple_semantic_routing,langchain_rag`).

Available plugins: simple_semantic_routing, semantic_biencoder_routing, langchain_rag. Each plugin has additional configuration documented above.

Authentication variables#

Core switch#

Variable	Default	Description
`LLM_ROUTER_AUTH_ENABLED`	`false`	Master switch — "true" enables all authentication.
`LLM_ROUTER_AUTH_KEY_STORE`	`memory`	Key store backend: vault, redis, or memory.

Memory store#

Seed file path (hardcoded): ${HOME}/.llm-router/configs/auth/memory-keys.json

Vault settings#

Variable	Default	Description
`LLM_ROUTER_AUTH_VAULT_ADDR`	(empty)	HashiCorp Vault server URL (e.g. `https://vault.example.com`).
`LLM_ROUTER_AUTH_VAULT_PATH`	`secret/data/llm-router/api-keys`	KV v2 mount path for key storage.
`LLM_ROUTER_AUTH_VAULT_AUTH_METHOD`	`kubernetes`	Auth method: kubernetes, approle, or token.
`LLM_ROUTER_AUTH_VAULT_ROLE_ID`	(empty)	AppRole role ID (or K8s SA token).
`LLM_ROUTER_AUTH_VAULT_SECRET_ID`	(empty)	AppRole secret ID.

Redis cache for keys#

Variable	Default	Description
`LLM_ROUTER_AUTH_KEY_CACHE_TTL`	`300`	Key cache TTL in seconds.
`LLM_ROUTER_AUTH_KEY_CACHE_JITTER`	`60`	Random jitter to prevent cache stampede.

Auth Redis (separate from general REDIS)#

Auth-specific Redis connection used by the key store and rate limiter:

Variable	Default	Description
`LLM_ROUTER_AUTH_REDIS_HOST`	(empty)	Auth Redis host.
`LLM_ROUTER_AUTH_REDIS_PORT`	`6379`	Auth Redis port.
`LLM_ROUTER_AUTH_REDIS_DB`	`0`	Auth Redis database number.
`LLM_ROUTER_AUTH_REDIS_PASSWORD`	(empty)	Auth Redis password.

Rate limiting#

Rate limiting is always applied when authentication is enabled:

Variable	Default	Description
`LLM_ROUTER_AUTH_DEFAULT_RATE_LIMIT`	`60`	Default rate limit (requests per minute).
`LLM_ROUTER_AUTH_RATE_LIMIT_ENABLED`	(empty)	Explicit toggle for rate limiting (usually unnecessary when AUTH_ENABLED=true).

Public endpoints#

Variable	Default	Description
`LLM_ROUTER_AUTH_PUBLIC_ENDPOINTS`	`/ping,/version,/models,/,/metrics`	Comma-separated paths that bypass authentication.

Key generation#

Variable	Default	Description
`LLM_ROUTER_AUTH_KEY_PREFIX`	`sk-litm`	Key prefix (like LiteLLM/OpenAI format).
`LLM_ROUTER_AUTH_KEY_LENGTH`	`48`	Entropy bytes for key generation (produces 64-char key).

Key rotation#

Variable	Default	Description
`LLM_ROUTER_AUTH_ROTATION_GRACE_PERIOD`	`3600`	Old keys remain valid this many seconds after rotation.

Audit#

Variable	Default	Description
`LLM_ROUTER_AUTH_AUDIT`	(empty)	Record auth events in the audit log.

Monitoring intervals#

Variable	Default	Description
`LLM_ROUTER_SERVICES_MONITOR_INTERVAL_SECONDS`	`5`	Seconds between llm-router-services checks.
`LLM_ROUTER_KEEPALIVE_MODEL_MONITOR_INTERVAL_SECONDS`	`1`	Interval (seconds) for model keepalive check.
`LLM_ROUTER_PROVIDER_MONITOR_INTERVAL_SECONDS`	`5`	Seconds between next checks of models providers.

Programmatic source#

The definitive list of all runtime environment variables is in the source code: llm_router_api/base/constants.py. Each constant is loaded from os.environ with a documented default and validated at import time.