Careers

Work on London5.

We are a small team in Cascais, Portugal, building a market research desk and simulator that runs on a person's own Mac. Below are the profiles we are looking for. If none of them is you and you still want to work on this, write anyway.

How we work

Where

Cascais, Portugal, or remote within European hours. We meet in person some weeks.

What we ship

A native Mac app, an engine in C++, a web client, a TV desk, this site. All of it on your own computer first.

How we decide

A design document before code, and the honesty rules: a simulation never sells a result, and the AI never tells anyone what to buy.

Languages

English at work; Portuguese too. The app speaks both.

Profiles

Who we are looking for.

Engine engineer

Engine · Cascais or remote · Full-time

The engine is a C++ process that holds the markets, the simulator, the research and the local model's server, and it must stop in two seconds. You would own parts of it.

Write to us about this →

You will

  • Build and test engine services: market data, the simulator, research.
  • Keep every worker honest about stopping, locking and memory.
  • Measure before you claim: the engine's own eval runs are yours too.

We look for

  • Modern C++ you can defend line by line.
  • Something you built that runs for days without a restart.
  • Comfort with a design document before code.

macOS engineer

macOS app · Cascais or remote · Full-time

The native app is the primary client: the conversation, the board, the markets and the settings, in SwiftUI, talking to the engine over a WebSocket on the same Mac.

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You will

  • Build screens the design documents specify, and match them on screen.
  • Keep the app honest about where the person is, what is live and what waited.
  • Ship updates through Sparkle, signed and notarised, on a schedule.

We look for

  • SwiftUI you have shipped to people, not only to a simulator.
  • An eye for a screen that is a few pixels off the design.
  • Patience with a product that says what it will not do.

Web engineer

Web app · Cascais or remote · Full-time

The Svelte client the Tauri desktop wraps, and london5.com itself, built with Astro. Parity with the Mac app is the job: a feature is done when both clients have it.

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You will

  • Mirror each macOS surface in Svelte, from the same engine protocol.
  • Keep the site fast, findable and true: every page measured, every claim sourced.
  • Write the tests that hold a page to its design.

We look for

  • Svelte or a framework you can argue against it with.
  • A site you made that loads in under two seconds on a phone.
  • Care for words: labels, errors and empty states are yours too.

Model researcher

Research · Cascais or remote · Full-time

Two lines of work: world models of market state, and small language models with knowledge of markets, trained further from open bases and graded in the simulator before they reach the desk.

Write to us about this →

You will

  • Design the data pipeline from the Londron network and synthetic desks.
  • Run the comparisons: open bases beside frontier models, the same three subjects.
  • Say where they diverge, in a report someone else can check.

We look for

  • Training and evaluating open-weight models, with the numbers to show.
  • Markets as a subject you have read about, not only as data.
  • Writing that states a result without selling it.
Writing to us

What to put in the message.

Four things. We read every message, and answer the ones that say them.

Which profile
One of the profiles above, or none: say what you would work on instead.
Where you are
Cascais, elsewhere in Portugal, or remote, and the hours you keep.
When
When you could start, and whether full-time is what you want.
Something you made
A link: a repository, a paper, an app, a video. A CV is welcome; the link says more.
Write to contact@london5.com →