Stonebridge Legacy Partners
We build systems
that have to be
right.
Software for markets, tax and energy, where a silent error costs real money. Every product ships with its own controls, its own audit trail and its own measurement.
A control plane for systematic strategies that fails closed, reconciles to the broker's record and measures itself before it claims anything. No live performance is shown here, by design.
Desktop tools for tax professionals that recompute the whole return, keep client data on the device and put a human in control of every figure.
When an acquisition, a reserves close or a migration has a date on it, the data behind it rarely ties. A fixed-scope sprint finds the material differences first, from someone who has worked reserves for thirty years.
Four live systems, hundreds of thousands of lines, tens of thousands of tests, one operator. We are looking for people who want to build with that kind of rigour.
Choose a door and the site re-sequences for you. Or scroll.
Thesis
The expensive failures in markets, tax and energy are quiet ones.
A ledger that drifts from the account. A return that is silently incomplete. A tender that fails on a document nobody checked. Stonebridge exists to build the systems that refuse to be quietly wrong, and to run them long enough to prove it.
Products with their own controls, audit trail and measurement built in from the first commit.
We run what we build, in paper first, on real broker and document feeds, before anyone else relies on it.
Facts we can show on a public page; records we can open to a qualified counterparty; nothing in between.
How we build
Four rules, applied to every system we ship.
- 01
Fail closed
Missing data, a stale quote, an unreadable document or an unreachable counterparty means no new risk. The default state of every system is to stop and say why.
SUTP's pre-trade gate · TaxReturnStudio's completeness contract
- 02
Reconcile to the source of truth
The broker's record, the document's figure, the statute's number. Our ledgers are reconciled to them, never the other way round, and every correction is audited and reversible.
Broker-truth reconciliation · field provenance down to the cell
- 03
Measure before you claim
A strategy earns size with evidence that survives overfitting tests. A tax figure carries its assumption. A number nobody can defend does not ship.
Deflated Sharpe and walk-forward · full-return recomputation
- 04
Keep a human in control
Breakers latch until a person clears them. Nothing reaches a tax return unseen. Live capital waits on an authorisation chain the operator holds.
HALT.ALL · approval manifests · operator-owned activation
See the difference
The same bad quote, two kinds of system.
Orders flow left to right. Some arrive with a stale quote, a missing data point or an unreachable broker. Switch the mode and watch what reaches the book.
Synthetic events at a fixed rate. Not market data, not performance. The gate rule is real: missing data, stale quote or unreachable broker means no new risk.
Operating board
Facts we can show. Numbers we will not.
Under the SEC Marketing Rule, paper and model results are hypothetical performance and do not belong on a public page. What belongs here is what the systems do every day. Regenerated from the repositories at each release.
Ventures
Each stone cut to bear its own load.
Four systems and a practice, each with a status we would defend in diligence. Pick a door above and the ones for you move to the front.
SUTP
An institutional control plane for systematic strategies: execution, fail-closed risk, broker-truth reconciliation and a release gate, running three uncorrelated books across three brokers.
TaxStrategy Studio
A desktop planning engine for tax professionals that turns a client's facts into an optimised strategy plan with defensible numbers and presentation-ready deliverables, entirely on-device.
TaxReturnStudio
Turns a client's pile of documents into a complete, reviewable, approved set of return inputs, with provenance on every figure and a human in control of every one.
Clearance Hunter
A retail-arbitrage signal tool that verifies clearance prices at the user's local stores, prices them against resale value, and ranks the trip by expected dollars per hour.
Advisory
A fixed-scope technical data QA sprint around a live acquisition, close or migration decision, backed by thirty years of reserves work; plus operations work for accounting firms and small businesses.
Why no numbers
Restraint is a credential.
Our trading record so far is paper. Under the SEC Marketing Rule that makes it hypothetical performance, which does not belong on a page anyone can reach. Allocators who have seen a hundred backtests already know this; they ask about live implementation and risk controls instead. So that is what we show in public, and the record waits in a controlled room with its criteria, assumptions and risks attached.
Read the disclosure policy →Capital partners
Partner with Stonebridge.
A qualified-counterparty process, not a pitch. You tell us who you are; we show you the control plane, the release gate and, inside a controlled room, the paper record with its criteria, assumptions and risks.
Request the diligence pack →Collaborators
Build with Stonebridge.
Engineers, quants, tax technologists and domain experts who want to work on systems where being right is the whole job. Start with our open problems.
See the open problems →Insights
Notes from the build.
2026-11-08 · Engineering
Fail closed: why our trading platform refuses risk when it is unsure
A stale quote or an unreachable broker should never be a reason to trade. The pre-trade gate in SUTP makes that a property of the system, not a habit of the operator.
2026-11-08 · Method
What thirty years of working reserves taught us about building a trading system
A reserves number that reaches a 10-K has to survive an auditor, a reconciliation and the five-year rule. The habits that keep it honest turned out to be exactly what an automated trading platform needed.
2026-11-08 · Disclosure
Why there are no performance numbers on this site
Our trading record is paper. The SEC Marketing Rule calls that hypothetical performance, and the firms that attracted serious capital before they had a record led with method, not returns.