Judex — Evidence-Based Investment Copilot
Everydecision traceable — id, rules-version, verdict, outcome, grade
Goal
Build a daily investment copilot that recommends with written reasons, asks for a human verdict, executes only on approval — and grades its own calls, and the user's, in public. Live on real portfolios, multi-tenant, pre-launch.
Backstory
Retail investors drown in noise and act on impulse; AI investment tools answer with demos that were never trusted with real money. The interesting problem was not the model — it was the operating loop: who decides, who executes, and who gets graded.
So Judex was built for the hardest first customer — myself — in production from the first week, with every design decision made next to the problem: a two-minute daily brief, a one-tap approval, a ledger that remembers every verdict. Once the loop held up under real use, it was made multi-tenant and opened to family and friends.
Details & Artifacts
Solution:
- Two decision engines on a Databricks medallion lakehouse: a Control Tower defending holdings via a graded risk ladder, and an Opportunity Finder that qualifies on strength and buys on weakness.
- Strict division of labour: rules decide, AI only explains — the LLM writes readable reasons, never picks the trade; missing data is excluded, never guessed.
- Human-in-command execution: email brief → one-tap approval → broker execution on a dedicated agent account; the main account is record-only.
- Full audit spine: every recommendation carries an id and a rules-version hash; a ledger grades system calls and user verdicts, including the what-if for declined advice.
- Multi-tenant with a 24-check tenant-isolation suite run against the live system after every relevant deployment.
- Operated, not just shipped: versioned rule revisions from live evidence, cost-tuned across three clouds.
Impact: In daily production since mid-2026 on real portfolios; every decision — machine and human — traceable end to end; rule changes shipped from field evidence without rewriting history.
Stack: Databricks (Delta, Unity Catalog) on Azure, Windmill, Next.js, PostgreSQL, OCI, Terraform, eToro API, LLM explanations.
Artifacts: Published method statements, a dated end-to-end case file, decision-trace portal, monthly scorecard. judex.simplificare.ch (pre-launch).