What's new on Arithmos

A new range option beside 1Y/3Y/5Y/10Y that re-anchors the chart to the day your index was generated. The index, the benchmark and every holding restart at 100 on that date, and CAGR, volatility, Sharpe, Sortino and max drawdown are all recomputed over that window — so the numbers above the chart describe exactly the span you're looking at.

• Labelled "since creation", not "backtest" — none of it is fitted with hindsight
• Available on every plan; no range clamp in this view

The home-page galleries can now be sorted by "Since creation" and "Since creation vs S&P", ahead of headline return. These are the only figures on a card that were earned in the open rather than backfitted, which is what makes them worth ranking on.

• Indices under a week old report no figure and sink to the bottom rather than topping the list on noise

Every chart now marks the day the index was created with a dotted line and shades everything after it, alongside a scorecard showing how the index, the benchmark and the alpha between them have done since that date. It's an honest split between the backtested stretch and the part that has actually played out.

Connect an IBKR account to turn any index into a reviewable order ticket that lands in your own account with a deep link to submit it yourself. Arithmos does the portfolio arithmetic and hands over a ready-to-review basket — it never places orders, exercises discretion, or holds your assets.

• Plus and Pro can set an allocation and a rebalance cadence per index
• A daily check restages drifted baskets and emails you when one is waiting
• Nothing is ever submitted without you reviewing and confirming it in IBKR

Backtest charts could freeze on the day an index was created and never move again. Cached series now expire as soon as the market prints a close they don't include, so every chart you open is current. If a refresh fails we show the last good series marked stale instead of an error.

We mapped and end-to-end tested every market we can genuinely build from — 23 of them — and taught the builder the correct ticker format for each. Prompts aimed exclusively at something we can't cover (crypto, bonds, FX, or an unsupported exchange) now stop immediately with a suggested alternative instead of burning a doomed run.

• Non-US briefs now screen, price, and build reliably
• Clear "try this instead" panel rather than a generic failure

The first-index offer now states its rules plainly on the card: one index build during the trial window, and building a second converts you to Plus on the spot rather than quietly running on.

When a trial lapsed, some accounts kept showing their old plan in dashboards and emails long after it expired. A daily reconciliation now recomputes plan status from the live source of truth in both directions. Access controls were never affected — only what was displayed.

Our model provider retired the model IDs we were calling, which caused index builds to fail. We migrated to the current generation and added a safeguard that rewrites retired IDs automatically, so a future retirement can't take builds offline the same way.

A low-commitment way in: pay 1.99, build a full index with holdings, backtest and export, then roll onto Plus monthly automatically after 24 hours unless you cancel. The card states the auto-roll and the cancel window up front.

Landing on someone else's shared index? There's now a one-click way to drop its prompt straight into the builder and make your own version of it.

Every public index page carries its own title, description and preview card, so a link pasted into Slack, X, WhatsApp or LinkedIn unfurls with the index name, its prompt, and its top holdings instead of a bare URL. Search engines see the same detail.

• Private and unfinished indices stay out of search results

Some builds used up their research budget without ever committing to a final basket, and failed outright despite having gathered enough to finish. The builder now makes a decisive final pass and returns the best defensible index from what it found.

Market data now fails over between providers automatically, and index generation falls back to a second model provider if the first is unavailable, so a single upstream outage no longer takes index building offline.

A handful of public pages the sitemap advertised were quietly bouncing logged-out visitors and search crawlers to the sign-up page. They're now genuinely public, and an automated check keeps it that way.

The five-step walkthrough was rewritten to describe what the product actually does, with a light-on-dark pinboard layout, corrected plan claims throughout, and richer structured data for search.

/how-it-works got a pinboard treatment — the path from prompt to index to backtest to export laid out as a single visual board rather than a wall of text.

New guides covering how to take an Arithmos index into Trading 212, Fidelity, Interactive Brokers, Alpaca and Tradier, plus side-by-side comparisons, each with broker-specific starter prompts.

A running award for the most interesting thesis of the week. Each entry shows the prompt that built it, the holdings, an illustrative backtest, and links through to every ticker involved. The award belongs to the idea, not to a person.

The home page can now suggest ready-to-build index briefs generated from recent financial news, so there's always a concrete starting point if you're staring at an empty prompt box.

Public pages referred to a 14-day trial that didn't exist. Removed — pricing copy is now checked against the actual plan limits.

A self-serve cancellation flow, so ending a subscription no longer means emailing us and waiting.

Hitting a plan limit now takes you to a page explaining exactly what you've reached and what lifts it, rather than a generic error. The header also keeps a sign-up or profile button visible wherever you are.

Index cards on the home page now show the logos of their largest holdings, so you can tell at a glance what's inside before opening one.

A proper email layer: a short onboarding sequence for new accounts and an optional monthly digest covering what's moved, what's been built, and prompt ideas worth trying. Every message carries one-click unsubscribe, and marketing email is off unless you opt in.

A full privacy pass. There's now a cookie consent banner that genuinely gates analytics until you accept, and a privacy dashboard at /settings/privacy where you can export everything we hold on you, delete your account, and control marketing email.

• Download your data (GDPR Articles 15 and 20) or delete it (Article 17), self-serve
• Analytics and chat tracking stay off until you consent
• Privacy, Terms and Risk pages rewritten with transfer mechanisms, AI-decision disclosure, CCPA rights, and a 14-day cooling-off clause

We ship a Model Context Protocol server with OAuth 2.1 sign-in, so you can give your favourite AI agent live access to build, backtest, and query your indices. Tool annotations, scopes, and a public submission console are included.

• OAuth 2.1 with scoped consent
• Streaming tool calls for long-running index builds
• Public submission console at /admin/mcp for app-store readiness

Compare any two of your indices on a Sharpe ratio chart, switch between rolling windows, and let the optimiser propose the weights that would have produced the best risk-adjusted return over your chosen window.

Our portfolio-construction agent now runs on an upgraded compute backend. Most prompts finish in under 25 seconds, with no change to the rules or schema.

Every /locations page now renders a proper geographic atlas of the relevant exchange and major issuers, so you can see the geography behind an index at a glance. APAC tickers (Tokyo, Singapore, Hong Kong, Seoul) now resolve correctly across the platform.

Not sure where to start? The new wizard walks you through theme, geography, and weighting in three steps and hands you back to the prompt box pre-filled with a working brief.

/pricing now offers a third tier with bring-your-own-data feeds, dedicated support, and SLA-backed uptime. Self-serve through Stripe; talk to us through /contact for custom terms.

Founding Frontend Engineer, Data/Quant Engineer, and Head of Custom Index Solutions are live on /vacancies, with a filter UI and richer JobPosting schema so the listings show up properly on Google for Jobs.

The animated headline on the home page no longer glitches when the tab loses focus.

Two new SEO-friendly hubs: /locations indexes everything by geography, /compare lets you pit any two indices against each other on returns, drawdown, sector tilt, and overlap.

A new shortcut on the home page that picks a randomised but plausible prompt and runs it. Good for inspiration, good for stress-testing the agent.

A plain-English walkthrough of how the prompt → portfolio → backtest pipeline works, with structured data so it shows up properly in search.

Cards on the home gallery render faster, the trust bar makes the data sources explicit, and the Arithmos mark now sits above the wordmark for a sharper visual identity.

Chart ranges now respect the period you picked, and the underlying data refresh is much more reliable.

Our portfolio-construction agent now runs on a redundant compute backend with automatic failover, so a transient hiccup on one provider doesn't interrupt index generation.

Sign in with a magic link — no password to remember, no password to leak. New onboarding step asks for a display name so your indices show up under something more meaningful than your email prefix.

Every index card on the home page now shows a small price sparkline, so you can scan performance at a glance.

A clean link-in-bio page at /links with an animated wordmark and a curated set of CTAs. Great for posting from social profiles. Click-through tracking included so we can see what's working.

Visit /brand for an on-brand backdrop and downloadable social assets — square avatars, OG cards, and the wordmark in a few colour treatments.

Terms acceptance now lives on a friendlier post-verify welcome step. The whole onboarding sequence has been retightened, and the brand presentation has been cleaned up across the funnel.

Copy across the site now consistently positions Arithmos as an investment research and data tool — not investment advice and not a regulated broker. A clear terms gate sits at the top of the funnel.

We've published 84 curated, official Arithmos indices spanning sectors, themes, geographies, and factor styles. Browse them on the home gallery; clone any one of them as a starting point for your own.

Subscribe to /feed.xml to get every new index — yours, official, and public — straight into your reader. The major AI-assistant crawlers are now explicitly allowed on our public surface.

Published explainers on building your own index, prompt-to-portfolio, custom index vs ETF, and the best alternatives to the S&P 500. All linked from /blog.

Your in-progress prompt now survives a refresh, an accidental tab close, or a sign-in detour. No more retyping.

Yearly Plus and Pro plans can now be paid with crypto via Stripe. Same checkout, same entitlement, optionally settled on-chain.

These pages no longer require sign-in, so anyone can preview pricing, browse markets, and grab brand assets without an account.

Index runs now use a durable workflow runner under the hood. If a step takes a long time or the platform restarts mid-run, your index resumes cleanly instead of failing silently.

Crypto invoices now render the manual payment instructions correctly, the data-fabric cards no longer ship with broken links, and sortable tables are correctly locked for guest viewers.

Pricing now offers the cashflow of monthly billing with the savings of an annual commitment. Stripe and the dashboard show both numbers clearly.

The build button is now visually neutral so it doesn't feel like the only thing on the page, and signed-out visitors get a sign-up shortcut top-right.

A pass on denormalisation, caching, and static rendering cut payload weight dramatically across the home gallery, profile pages, and shared index pages. Everything just feels snappier.

Indices that are still building, or that failed mid-run, now render an informative state instead of a blank page. Stuck pendings auto-fail after a sensible timeout.