Root & Reason

Spencer Clark

Software architect · Three-time founder

I've spent nearly thirty years building software for UK financial services, mostly wealth management platforms. I was the first employee at Third Financial, then co-founded Wealth Dynamix and Portemis, which Wealth Dynamix later acquired. Since July 2026 I've been building Cairn full time.

Alongside Cairn, I work extensively with LLMs: building tool-calling agents, multi-agent harnesses, MCP tooling and model evaluation infrastructure in C# and Python. I run and benchmark models locally, build the tooling I need to understand their behaviour, and write about the results.

// Skills

Architecture
System and platform architecture, distributed SaaS, multi-tenancy, security, APIs and long-lived systems in regulated domains
Azure
AKS, Service Bus, Key Vault, Entra ID, Cosmos DB, Azure Database for PostgreSQL
Infrastructure
Kubernetes, Docker, Terraform, Helm, Cloudflare
Delivery
GitHub Actions, GitLab CI/CD, Containerization, DevOps process and tooling
Observability
Grafana, Prometheus, Sentry, OTel
Engineering
C# and .NET, Python, PostgreSQL, JavaScript and TypeScript
AI
Local LLMs with Ollama, tool-calling agents, multi-agent harnesses, MCP, LLM observability, evaluation and benchmarking
Domain
Wealth management, client lifecycle management, portfolio management

// Experience

  1. Jul 2026 - now

    Founder · Cairn River

    Building Cairn, an evidence-keeping SaaS platform for regulated work. Designed and built the product end-to-end using .NET, React and PostgreSQL, including tenant isolation and row-level security, encrypted file storage, procedure versioning, audit history and cloud infrastructure.

  2. 2020 - 2025

    Senior System Architect · Wealth Dynamix

    Returned when Wealth Dynamix acquired Portemis, whose product was rebranded as CLMi. Owned the cross-cutting platform architecture: Azure infrastructure and hosting, DevOps, reliability, scalability, observability and the architectural concerns spanning individual product teams. Worked closely with engineering and product teams to ensure the platform met both functional and non-functional requirements. Wealth Dynamix was acquired by CA Indosuez Wealth in November 2025.

  3. 2019 - 2020

    Co-founder & CTO · Portemis

    Co-founded an early-stage SaaS product for wealth management and led its technical direction: system architecture and hands-on development, infrastructure and deployment, and the first engineering hires. Acquired by Wealth Dynamix the following year and subsequently developed as CLMi.

  4. 2012 - 2019

    Co-founder, CTO and Architect · Wealth Dynamix

    Co-founded Wealth Dynamix with two partners and led the architecture and core platform design as the company grew from inception to around 90 staff, tier-1 financial-services clients and £9m annual revenue. Built and mentored the early engineering team. Set technical direction and oversaw the transition from a startup to a scale-up. In 2017 it ranked 18th in the Sunday Times Tech Track 100 and 19th in the Deloitte UK Technology Fast 50, 7th among fintechs. From 2018, moved to solution design and architecture across client implementations and internal product development, working between product, engineering and client-facing teams.

    Sunday Times clippingpress release

  5. 2012

    Software Consultant · Equipos Group

    Short consultancy engagement providing development and architecture support on an existing document management platform.

  6. 2007 - 2012

    Chief Technical Architect · Third Financial Software

    First employee, brought in to design and deliver a new wealth management platform, from inception to production. Owned the overall system architecture, wrote code, and recruited and mentored a growing engineering team.

  7. 2007

    Business Analyst · Financial Objects

    Front-office system implementations at client sites: configuration, data migration, requirements and user training.

  8. 2005 - 2007

    Developer · GAM

    Support and development of internal investment systems, including fund research and asset allocation tools, in the Fund of Hedge Funds group.

  9. 2001 - 2005

    Senior Developer · Wealth Management Software

    Led small teams delivering front- and back-office systems for wealth management clients, covering technical design and delivery.

  10. 1997 - 2001

    Developer · DC Systems

    Business systems for financial services and manufacturing clients.

// Projects

  • 2026

    Vessel

    An observability proxy for LLM traffic. Point an agent's base URL at it and every request to Ollama, OpenAI or Anthropic is recorded byte-for-byte to a local SQLite database, with search, replay against other models and scoring on top. C#, MIT licensed, installable through Homebrew and Scoop.

    vesselproxy.appsource

  • 2026

    Models & Monsters

    A multi-agent harness in which LLM characters act in a fantasy world through an LLM Dungeon Master, while a deterministic rules engine decides what actually happens. Runs on a local model in 8 GB of VRAM.

    write-upsource

  • newman-reporter-json-summary

    Open-source Newman reporter for reducing large test runs to compact JSON summaries. Published on npm and currently downloaded ~5,000 times per week.

    npm

// Writing

Articles on Root & Reason about running language models locally, each built around a working harness and its measurements.