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Fabrion

ML/AI Research Engineer — Agentic AI Lab (Founding Team)

San Francisco Bay Area
Level
Mid
Work type
On-site · San Francisco Bay Area

Not stated in the posting: salary, visa.

Open. First seen 2 October 2026.

About the role

ML/AI Research Engineer — Agentic AI Lab (Founding Team)

Location: San Francisco Bay Area
Type: Full-Time
Compensation: Competitive salary + meaningful equity (founding tier)

Fabrion's standard text

Backed by 8VC, we're building a world-class team to tackle one of the industry’s most critical infrastructure problems.

About the Role

We’re designing the future of enterprise AI infrastructure — grounded in agents, retrieval-augmented generation (RAG), knowledge graphs, and multi-tenant governance.

We’re looking for an ML/AI Research Engineer to join our AI Lab and lead the design, training, evaluation, and optimization of agent-native AI models. You'll work at the intersection of LLMs, vector search, graph reasoning, and reinforcement learning — building the intelligence layer that sits on top of our enterprise data fabric.

This isn’t a prompt engineer role. It’s full-cycle ML: from data curation and fine-tuning to evaluation, interpretability, and deployment — with cost-awareness, alignment, and agent coordination all in scope.

Core Responsibilities

  • Fine-tune and evaluate open-source LLMs (e.g. LLaMA 3, Mistral, Falcon, Mixtral) for enterprise use cases with both structured and unstructured data
  • Build and optimize RAG pipelines using LangChain, LangGraph, LlamaIndex, or Dust — integrated with our vector DBs and internal knowledge graph
  • Train agent architectures (ReAct, AutoGPT, BabyAGI, OpenAgents) using enterprise task data
  • Develop embedding-based memory and retrieval chains with token-efficient chunking strategies
  • Create reinforcement learning pipelines to optimize agent behaviors (e.g. RLHF, DPO, PPO)
  • Establish scalable evaluation harnesses for LLM and agent performance, including synthetic evals, trace capture, and explainability tools
  • Contribute to model observability, drift detection, error classification, and alignment
  • Optimize inference latency and GPU resource utilization across cloud and on-prem environments

Desired Experience

Model Training:

  • Deep experience fine-tuning open-source LLMs using HuggingFace Transformers, DeepSpeed, vLLM, FSDP, LoRA/QLoRA
  • Worked with both base and instruction-tuned models; familiar with SFT, RLHF, DPO pipelines
  • Comfortable building and maintaining custom training datasets, filters, and eval splits
  • Understand tradeoffs in batch size, token window, optimizer, precision (FP16, bfloat16), and quantization

RAG + Knowledge Graphs:

  • Experience building enterprise-grade RAG pipelines integrated with real-time or contextual data
  • Familiar with LangChain, LangGraph, LlamaIndex, and open-source vector DBs (Weaviate, Qdrant, FAISS)
  • Experience grounding models with structured data (SQL, graph, metadata) + unstructured sources
  • Bonus: Worked with Neo4j, Puppygraph, RDF, OWL, or other semantic modeling systems

Agent Intelligence:

  • Experience training or customizing agent frameworks with multi-step reasoning and memory
  • Understand common agent loop patterns (e.g. Plan→Act→Reflect), memory recall, and tools
  • Familiar with self-correction, multi-agent communication, and agent ops logging

Optimization:

  • Strong background in token cost optimization, chunking strategies, reranking (e.g. Cohere, Jina), compression, and retrieval latency tuning
  • Experience running models under quantized (int4/int8) or multi-GPU settings with inference tuning (vLLM, TGI)

Preferred Tech Stack

  • LLM Training & Inference: HuggingFace Transformers, DeepSpeed, vLLM, FlashAttention, FSDP, LoRA
  • Agent Orchestration: LangChain, LangGraph, ReAct, OpenAgents, LlamaIndex
  • Vector DBs: Weaviate, Qdrant, FAISS, Pinecone, Chroma
  • Graph Knowledge Systems: Neo4j, Puppygraph, RDF, Gremlin, JSON-LD
  • Storage & Access: Iceberg, DuckDB, Postgres, Parquet, Delta Lake
  • Evaluation: OpenLLM Evals, Trulens, Ragas, LangSmith, Weight & Biases
  • Compute: Ray, Kubernetes, TGI, Sagemaker, LambdaLabs, Modal
  • Languages: Python (core), optionally Rust (for inference layers) or JS (for UX experimentation)

Soft Skills & Mindset

  • Startup DNA: resourceful, fast-moving, and capable of working in ambiguity
  • Deep curiosity about agent-based architectures and real-world enterprise complexity
  • Comfortable owning model performance end-to-end: from dataset to deployment
  • Strong instincts around explainability, safety, and continuous improvement
  • Enjoy pair-designing with product and UX to shape capabilities, not just APIs

Why This Role Matters

This role is foundational to our thesis: that agents + enterprise data + knowledge modeling can create intelligent infrastructure for real-world, multi-billion-dollar workflows. Your work won’t be buried in research reports — it will be productionized and activated by hundreds of users and hundreds of thousands of decisions. If this is your dream role - we would love to hear from you.

What this role asks for

Particular to this role

Delta Lake · DuckDB · Neo4j · PostgreSQL · Rust · SageMaker

Rare in Fabrion's other 8 open postings.

Standard for data science / ML roles

LLM · Python · SQL

Common in data science / ML postings at any company.

In most of Fabrion's ads

Vector Databases

Named in most of its open postings, whatever the role.

97% of this description is written for the role. The rest is Fabrion's standard text, folded away below.

Read against Fabrion's other open postings on this site.

The team: Engineering

This role is one of 7 open in Engineering.

WHAT THE TEAM WORKS WITH, ACROSS ITS POSTINGS

Vector Databases (6 of 7), LangChain (5 of 7), LLM (5 of 7), React (5 of 7), JavaScript (4 of 7), Kubernetes (4 of 7), RAG (4 of 7)

OTHER ROLES ON THIS TEAM

From the team and dates on Fabrion's own job board.

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