PTV Fund II
L2 deep dive / The machinery

Who actually builds each part

The L1 page explained the journey of a prompt. This page names names: the specific products, open-source projects, and hardware that perform each step — the machinery behind the magic, from chat window to GPU.

Named products & projects Open source ↔ commercial Companion to L0 and L1
01 / How to read this page

Five tags, four zones

Products are grouped into four zones that mirror the prompt’s journey: the workbench, the control room, the engine room, and the power plant. Every product carries tags for how it is delivered.

Open source
Code you can inspect, self-host, and fork. Freedom at the price of operating it yourself.
Commercial
Proprietary product, typically sold as software or subscription.
Managed
Run for you as a cloud service — someone else’s operations team.
Standard / protocol
Not a product at all: a shared convention everyone builds against. Standards outlive vendors.
Hardware
Physical chips, networks, and machines — the capex layer.

Selections are representative, not exhaustive, and reflect broad adoption or technical influence as of August 2026. Inclusion is not endorsement; omission is not criticism. Many products span several zones — they are placed where they do the most work.

02 / The workbench

Where prompts are born and briefs are built

The user-facing surface and the software that assembles the full dossier — L1 steps 1 and 2: chat clients, agent harnesses, protocols, and memory.

Zone A · L1 step 1

Chat clients & front ends

The window the user types into. Enterprises either adopt the model vendors’ own products or self-host a client for control and branding.

Concepts served: prompt, chat UI
ChatGPTOpenAI · flagship assistant

The product that defined the category; enterprise tier adds admin, SSO, and data controls.

Commercial Managed
ClaudeAnthropic · assistant & Claude Code

Anthropic’s assistant family; Claude Code popularized the terminal-based agent harness.

Commercial Managed
Microsoft CopilotEmbedded in M365 & Windows

The distribution play: AI inside the tools enterprises already pay for and govern.

Commercial Managed
Open WebUISelf-hosted chat front end

The default self-hosted chat UI; pairs with local or remote model servers.

Open source
LibreChatSelf-hosted multi-model client

One UI over many providers — a common enterprise pattern for avoiding lock-in at the surface.

Open source
Vercel AI SDKToolkit for building custom chat UIs

What product teams use to build their own streaming chat experiences.

Open source
Zone A · L1 step 2

Agent harnesses & frameworks

The chief of staff: assembles system prompt, tools, memory, and history; runs the tool-call loop. The most contested software layer in the stack.

Concepts served: harness, skills & tools, system prompt
Claude Agent SDKAnthropic · harness toolkit

The machinery behind Claude Code, offered as a library for building agents.

Commercial
Agents SDKOpenAI · agent framework

OpenAI’s framework for tool-using, multi-step agents against its models.

Open source
LangGraphLangChain · graph orchestration

Models an agent as a state machine with retries and checkpoints — a common production default.

Open source Managed option
LlamaIndexData & RAG framework

Specialist in connecting models to enterprise documents and data sources.

Open source Managed option
TemporalDurable workflow execution

Pre-AI infrastructure now widely used to make long agent runs crash-proof and resumable.

Open source Managed option
MCPModel Context Protocol · Anthropic

The emerging USB-C of tools: one standard way for agents to discover and call external systems.

Standard / protocol Open source
Zone A · L1 step 2

Memory & retrieval

What the harness pulls into the dossier: conversation memory and document retrieval, usually backed by a vector database.

Concepts served: memory, context assembly
Mem0Memory layer for agents

Remembers user facts across sessions so the dossier starts pre-filled.

Open source Managed option
ZepLong-term agent memory

Builds a temporal knowledge graph from conversations and business data.

Open source Managed option
pgvectorPostgres extension

Adds vector search to the database enterprises already run — the quiet incumbent.

Open source
QdrantVector database

Dedicated vector search engine; Rust-based, popular for self-hosted retrieval.

Open source Managed option
PineconeManaged vector database

The pure-play managed vector DB; buy instead of operate.

Commercial Managed
WeaviateVector database

Open-source vector DB with hybrid search, strong in European enterprise deployments.

Open source Managed option
03 / The control room

Admit, route, watch

Everything that sits between the harness and the model — L1 steps 3, 6, and 7: gateways that check and route, streaming infrastructure, and the observability layer that records it all.

Zone B · L1 step 3

AI gateways & routers

The front desk: one endpoint for many models, with identity, budgets, fallbacks, and logging. The enterprise control point of the L0 landscape.

Concepts served: API gateway, router
LiteLLMOpen-source proxy & router

One OpenAI-compatible interface over 100+ providers; the default open-source gateway.

Open source Managed option
Kong AI GatewayAPI gateway veteran, AI plugins

The incumbent API gateway extending its policy machinery to tokens and models.

Open core Commercial
PortkeyAI gateway & controls

Gateway plus guardrails, caching, and analytics aimed at production AI teams.

Open core Managed option
Cloudflare AI GatewayGateway at the edge

Lives on Cloudflare’s network, close to users; caching and rate-limiting included.

Commercial Managed
OpenRouterModel marketplace & router

One API key for nearly every model on the market, priced per token with a markup.

Commercial Managed
Azure API ManagementEnterprise API estate, AI-aware

Where Microsoft shops extend existing API governance over AI endpoints.

Commercial Managed
Zone B · L1 step 7

Observability & evaluation

The paper trail: traces of every request, cost metering, quality scoring, and prompt regression testing.

Concepts served: observability, evidence
LangfuseLLM observability

The open-source default for tracing, scoring, and prompt management; self-hostable.

Open source Managed option
LangSmithLangChain · tracing & eval

Deep integration with the LangChain/LangGraph ecosystem; strong evaluation tooling.

Commercial Managed
Arize PhoenixTracing & evaluation

Open-source observability with strong RAG and drift analysis; built on OpenTelemetry.

Open source Managed option
BraintrustEvals-first platform

Treats evaluation as the core engineering loop; popular with product teams shipping fast.

Commercial Managed
Datadog LLM ObsIncumbent monitoring, extended

Brings AI traces into the dashboards enterprises already watch.

Commercial Managed
OpenTelemetry GenAITracing conventions

The shared standard for what a “span” means in AI systems — the reason tools interoperate.

Standard / protocol Open source
04 / The engine room

Models and the software that runs them

L1 steps 4 and 5: the brains themselves (rented frontier or owned open weights), the inference servers that make them fast, and the KV-cache machinery that keeps the economics sane.

Zone C · brain, rented

Frontier model APIs

The strongest models, consumed per token. Families, not versions — version numbers age in months; the vendors do not.

Concepts served: LLM (frontier)
OpenAIGPT family

Market default; its API shape became the industry’s de facto interface.

Commercial Managed API
AnthropicClaude family

Strong enterprise reputation for coding, long context, and safety posture.

Commercial Managed API
Google DeepMindGemini family

Multimodal from the ground up, bundled with Google’s cloud and TPU hardware.

Commercial Managed API
xAIGrok family

Challenger scaling aggressively on its own colossal GPU clusters.

Commercial Managed API
Mistral AIEuropean frontier lab

Frontier-quality models with an open-weights heritage; the sovereignty option for Europe.

Commercial Open weights
Zone C · brain, owned

Open-weight models

Downloadable weights you run yourself — the foundation of the self-hosted option from L1.

Concepts served: LLM (self-hosted)
LlamaMeta

The family that made open weights a serious enterprise option; enormous ecosystem.

Open weights
QwenAlibaba

Prolific family across sizes; often the benchmark leader among open weights.

Open weights
DeepSeekDeepSeek

Proved frontier-adjacent reasoning at a fraction of assumed cost; reset price expectations.

Open weights
GemmaGoogle

Google’s open line, distilled from Gemini research; strong at small sizes.

Open weights
Mistral open lineMistral AI

Compact, efficient weights with permissive licensing — a self-hosting favorite.

Open weights
Zone C · L1 steps 4–5

Inference servers

The factory floor managers: batching, scheduling, and GPU-memory juggling that turn a model file into a fast, cheap API.

Concepts served: inference server, decode
vLLMThe open-source default

PagedAttention made GPU memory manageable; the engine under most self-hosted serving.

Open source
SGLangPerformance-focused server

Co-designed with its RadixAttention cache sharing; a favorite for structured agent workloads.

Open source
TensorRT-LLMNVIDIA

Squeezes maximum throughput from NVIDIA hardware; the vendor’s own path.

Open source Hardware-tied
NVIDIA DynamoDisaggregated serving

Splits reading (prefill) and writing (decode) onto different GPUs at datacenter scale.

Open source Hardware-tied
OllamaLocal & dev serving

Runs models on a laptop in one command; where most developers first touch local AI.

Open source
TGIHugging Face

The earlier generation of open serving; still deployed, now largely legacy beside vLLM.

Open source
Zone C · L1 step 4 · the magic

KV-cache & memory tier

The bookmark, productized: software that stores, shares, and moves cached context so nothing is read twice.

Concepts served: KV-cache, prefix caching
LMCacheKV-cache offloading layer

Spills cache from GPU memory to CPU, disk, and network so prefixes survive across requests.

Open source
MooncakeMoonshot AI · cache store

A distributed KV-cache pool proven at Kimi’s production scale; now open source.

Open source
NIXL / Dynamo KVNVIDIA

NVIDIA’s plumbing for moving cache between GPUs and storage at wire speed.

Open source Hardware-tied
HBMHigh-bandwidth memory

The physical substrate: scarce on-GPU memory where the cache lives. Its supply is an industry bottleneck.

Hardware
Zone C · shortcut

Managed serving platforms

“Self-hosting without the servers”: open weights run for you, billed per token or per GPU-hour.

Concepts served: LLM (self-hosted, minus the pain)
AWS BedrockMulti-model managed service

Frontier and open models behind AWS identity, billing, and compliance.

Commercial Managed
Azure AI FoundryMicrosoft’s model platform

Model catalog plus agent tooling inside the Azure enterprise estate.

Commercial Managed
Vertex AIGoogle Cloud

Gemini plus third-party models on Google’s TPU/GPU infrastructure.

Commercial Managed
Together AIOpen-model cloud

Fast serving of open weights; also rents dedicated GPU clusters.

Commercial Managed
Fireworks AIFast open-model serving

Performance-obsessed inference platform; compound-AI positioning.

Commercial Managed
BasetenDedicated model infra

Production serving with your own autoscaling GPU capacity, minus the platform team.

Commercial Managed
05 / The power plant

Chips, clouds, and the wires between

The physical layer everything else rents from: accelerators, the clouds and neoclouds that host them, the networks that bind them, and the orchestration that keeps them busy.

Zone D · silicon

Accelerators

The chips that read and write tokens. One vendor dominates; the rest exist because supply and price demand alternatives.

Concepts served: GPU cluster
NVIDIAHopper / Blackwell GPUs

The incumbent: hardware plus the CUDA software moat. Scarcity of its top chips shapes the market.

Hardware Commercial
AMD InstinctMI-series GPUs

The credible second source; wins on memory capacity per dollar.

Hardware Commercial
Google TPUCustom AI silicon

Google’s in-house chips; available only through Google Cloud.

Hardware Cloud-only
AWS Trainium / InferentiaAmazon custom silicon

Amazon’s cost lever: its own chips for training and inference inside AWS.

Hardware Cloud-only
GroqLPU inference chips

Purpose-built for decode speed; the extreme end of “tokens per second.”

Hardware Managed
CerebrasWafer-scale chips

Dinner-plate-sized chips that keep entire models on one piece of silicon.

Hardware Managed
Zone D · landlords

Clouds & neoclouds

Who you rent the chips from: the hyperscalers, plus a new class of GPU-only “neoclouds” born from the shortage.

Concepts served: GPU cluster, hosting
AWSHyperscaler

Largest cloud estate; GPU capacity plus its own silicon and Bedrock platform.

Commercial Managed
Microsoft AzureHyperscaler

OpenAI’s home cloud; enterprise agreements make it the default for many corporates.

Commercial Managed
Google CloudHyperscaler

TPUs plus GPUs; the most vertically integrated AI cloud.

Commercial Managed
CoreWeaveNeocloud

The breakout GPU-specialist cloud; prices in speed of access to the newest chips.

Commercial Managed
LambdaNeocloud

GPU clouds and clusters aimed at AI-native teams and labs.

Commercial Managed
NebiusNeocloud

European-rooted AI cloud building large NVIDIA capacity.

Commercial Managed
Oracle OCIHyperscaler challenger

Aggressive GPU capacity deals made it a surprise force in AI infrastructure.

Commercial Managed
Zone D · connective tissue

Networking & orchestration

Invisible until it breaks: the fabrics that let thousands of GPUs act as one machine, and the schedulers that place the work.

Concepts served: cluster fabric, scheduling
NVLink / NVSwitchNVIDIA

The high-speed fabric inside a rack of NVIDIA GPUs — why a pod behaves like one giant chip.

Hardware
InfiniBand / Spectrum-XNVIDIA networking

The datacenter-scale fabric between racks; Ethernet-based Spectrum-X is the challenger to classic InfiniBand.

Hardware
KubernetesCNCF · container orchestration

The default scheduler of the cloud era, extended to GPUs; where inference fleets live.

Open source Standard
Ray / KubeRayDistributed compute

The framework behind large-scale training and increasingly behind multi-node inference.

Open source
SlurmHPC workload manager

The supercomputing scheduler; still standard on big training clusters.

Open source
06 / The reference build

One request, real products, end to end

Two concrete stacks a company might actually run — one renting the frontier, one owning open weights. Every L1 step, with a name on it.

1 · Type and send Chat surface
ChatGPT Enterprise / Claude Vendor’s own client
Open WebUI or LibreChat in front, so the UI survives model swaps.
2 · Assemble Harness, memory, retrieval
Claude Agent SDK or OpenAI Agents SDK Vendor-native harness
LangGraph on Kubernetes + Mem0/Zep memory + pgvector or Qdrant retrieval, wired to tools over MCP.
3 · Admit Gateway, routing, budgets
Cloudflare AI Gateway / Portkey Or Kong if the enterprise already runs it
LiteLLM proxy as the internal control point; same policy model, fully self-hosted.
4–5 · Read & write Model + inference + KV-cache
OpenAI / Anthropic / Gemini API Their GPUs, their cache, their problem
Llama or Qwen weights on vLLM or SGLang, prefix caching on, LMCache for cross-request reuse.
6 · Deliver Streaming transport
Provider’s streaming API Token stream over SSE
Same SSE pattern from your own gateway — the UI cannot tell the difference.
7 · Act & record Tool loop + observability
LangSmith / Braintrust / Datadog Traces, evals, cost metering
Langfuse (self-hosted) + OpenTelemetry GenAI conventions, so traces outlive any vendor.
Underneath it all Power plant
Invisible to you The provider’s cloud bill, embedded in token prices
NVIDIA GPUs on AWS/Azure or a neocloud (CoreWeave, Lambda), scheduled by Kubernetes or Ray.
PTV Fund II / L2 takeaway

Names change fast. Positions change slowly.

Individual products will merge, rebrand, and die between editions of this page. What persists is the shape of the machine: a workbench, a control room, an engine room, and a power plant — with an open-source option at every position. Evaluate vendors by the position they occupy, not the logo they wear.