Runtime plane / Tier 1 / Phase 1

Model & Inference

Which intelligence executes?

Serve, version and scale the models — proprietary and open-weight — with predictable latency and cost, and keep them swappable so no single provider becomes load-bearing.

01 / WHAT THIS BOUNDARY OWNS
  • Inference serving: batching, KV cache, tensor and pipeline parallelism
  • Model registry and version pinning, including deprecation calendars
  • Routing between model tiers, plus fallbacks when a provider degrades
  • Embedding and reranking endpoints used by retrieval
  • Capacity and quota per tenant on shared accelerators
02 / INTEGRATION POINTS
03 / ENTERPRISE ACCOUNTABILITY

ML Platform / AI Engineering

  • Head of ML Platform — accountable owner
  • Inference engineer — serving performance and memory
  • GPU performance engineer — batching, quantisation, cache
  • Model operations engineer — versions, rollouts, deprecations

Architectural recommendation, not a research finding.

04 / WHAT DONE LOOKS LIKE
Pilot needs one hosted model and one self-hosted fallback behind the same interface, both version-pinned, with a documented switch procedure.

Signals to watch

  • Time to first token and tokens per second
  • P99 end-to-end latency by model tier
  • Prefix cache hit rate
  • Cost per thousand tokens by tenant
  • Share of traffic that could fail over to the open-weight path
05 / FAILURE MODES
  1. Vendor lock-in through provider-specific features in prompts and tools
  2. Silent provider upgrades shifting behaviour mid-quarter
  3. KV cache reuse leaking context across tenants if isolation is careless
  4. P99 latency collapsing under burst without admission control
06 / REFERENCE LANDSCAPE

Tool and standards snapshot · last reviewed approximately mid-2026

Open source

  • vLLM
  • llm-d
  • SGLang
  • TensorRT-LLM
  • KServe or Ray Serve
  • Hugging Face TGI
  • Text Embeddings Inference

Managed

  • Anthropic API
  • Bedrock, Vertex AI, Azure AI Foundry
  • Managed embedding and rerank endpoints

Standards

  • OpenAI-compatible API surface
  • JSON Schema structured outputs
  • Model cards for each served version
ARCHITECTURE NOTE

Keeping this harness distinct from Infrastructure is what makes model choice reversible. If serving is buried in the platform, changing models becomes a platform migration.