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Fournex

What is an RL Runtime?

Understanding what "runtime" actually means. Not just model serving

A runtime is responsible for the hard stuff around execution. It's the infrastructure layer that takes your trained RL policy and makes it work reliably in production environments.

Core Capabilities

Policy Execution

Load policy artifacts from various formats and run inference efficiently:

  • Support for multiple formats: Stable-Baselines3, TorchScript, ONNX
  • Optimized inference pipelines
  • Hardware acceleration (GPU/CPU optimization)

Stateful Sessions

Maintain per-agent state across interactions:

  • RNN hidden states for recurrent policies
  • Observation and action normalization statistics
  • Last observation/action history
  • Episode context and metadata

Environment Loop Support

Optionally run step loops server-side with consistent timing:

  • Agent ↔ environment interaction cycles
  • Controlled frame rates and timing
  • Reduced network latency for tight loops

Determinism & Replay

Capture what happened and reproduce it exactly:

  • Random seed tracking and control
  • Version and configuration snapshots
  • Complete observation/action/reward traces
  • Full episode replay capabilities

Performance

Low overhead per step with production-grade optimizations:

  • Request batching for throughput
  • Efficient memory layout and allocation
  • CPU core pinning for consistency
  • Zero-copy data transfer where possible

Isolation

Crashes or bad policies shouldn't take down the system:

  • Process-level isolation per session
  • Resource caps (memory, CPU time)
  • Timeout enforcement
  • Graceful degradation

Observability

Minimal but essential signals for production monitoring:

  • Prometheus-compatible metrics
  • Distributed tracing support
  • Structured logging
  • Health checks and liveness probes

Integration Surface

Stable API/SDK that robotics, simulators, and games can embed against:

  • RESTful HTTP API for standard integrations
  • WebSocket support for real-time streaming
  • Language-agnostic protocol (gRPC, JSON-RPC)
  • Client SDKs for Python, JavaScript, C++

Why This Matters

Most RL deployment discussions focus solely on "serving a model," but that's only a small part of the picture. A production RL runtime needs to handle the complexity of stateful interactions, provide reproducibility guarantees, maintain performance under load, and integrate seamlessly with diverse systems.

Fournex provides all of these capabilities out of the box, letting you focus on training better policies instead of building infrastructure.

Get Started with Fournex