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Public Portfolio Challenge · Episode 11

Moderna basically cured cancer, so I used Grok Bot to create a trading strategy on it. It’s DESTROYING the market.

Before deployment, the biotech book returned 62.97% on a sealed window that ended the day before Moderna’s readout; the semis book returned 44.43% on its own holdout. Those are historical tests, not measurements of the news thesis. Here is what Grok Bot decided, what I prescribed, and what happens next.

Austin Starks Austin Starks ✦ Founder, NexusTrade ✦ August 23, 2026 ✦ 13 min read

LinkedIn is drowning in AI trading apps.

A LinkedIn post from a student describing an AI app that analyzes trade history for panic-selling, overtrading and concentration, still in sandbox
One from my feed: an app that audits trade history for panic-selling, overtrading and concentration. Still in sandbox.

This one audits your habits. Others launch backtests or generate signals. Some are useful. None of those demos answer the question I care about.

Would you give the AI real money and publish every fill?

I did.

Public Portfolio Challenge · article snapshot, August 23 2026 · click through for the live account

Funded in February, first trade May 5, and up 26.58% in the 108 days since against SPY's 6.64%. A nineteen-name rotation of long-dated calls, built by describing it to an AI in plain English. I was writing about the same idea three years ago, using GPT-3. Every fill is public at that link.

$25,000 live account vs SPY · May 5 to August 21, 2026
+0% +10% +20% THE ACCOUNT +26.58% SPY +6.64% May 5 · first trade Aug 21
Both indexed to 100 at the first fill. Portfolio series from the public shared-portfolio feed, SPY from the same price API. 108 days.

People call it dumb luck. So I am going to do it again, this time around the first positive Phase 3 result for a personalized mRNA cancer therapy.

The same platform Covid-19 accelerated. A new target: recurrence after melanoma surgery.

This time I am not going to hold the AI's hand. xAI shipped Grok Bot, an autonomous agent that gets its own cloud computer, signs into your services, and works for days without you. This is the test to see how good Grok Bot really is at developing trading strategies.

Grok Bot spawning an agent, checking connected services, and signing into Salesforce on its own machine
Grok Bot working on its own cloud computer: it spins up an agent, checks what is connected, and signs itself into Salesforce. Now point that at a brokerage.

I pointed it at the Public Portfolio Challenge runbook, the same discipline that built the account above. Then I gave it the thesis.

The edge is simple. Moderna's innovation proves AI is not a fad. Which means two things: biotech is about to have its most explosive rally ever, and AI is not going to stop.

That was the whole brief. A few hours later it came back.

Before I show you what it built, you need to understand what Moderna actually did.

What actually happened, and why it is an AI result

On August 19, Moderna and Merck announced that their personalized cancer vaccine passed a Phase 3 trial. Every patient had melanoma a surgeon had already removed and was at high risk of it returning. Both arms got Keytruda; one arm also got a vaccine built from their own tumor. Did the cancer come back less often, and did it spread to distant organs less often? Yes to both. Nobody has released survival data, so we do not know yet whether people live longer. It is still the first Phase 3 win ever recorded for a personalized mRNA cancer therapy.

It is built one patient at a time. Sequence the tumor, compare it to healthy tissue, and you get hundreds of mutations unique to that person. Then the step that made me want to trade this: an AI model reads every one of them and keeps the 34 most likely to provoke an immune response. Everything on either side of that prediction is chemistry Moderna already knew how to do.

Moderna has said this on their own site since December 2023. Their program materials label the step plainly: "Up to 34 neoantigens. Automated algorithm integrated with workflow." And in the Phase 1 data, every immune response they measured came from a target the algorithm had predicted would work.

The hard part was never synthesizing the mRNA. It was choosing what to put in it, and an AI model did that. Biology just became a compute problem.

How a personalized cancer vaccine is built: tumor sequencing, AI ranking from hundreds of mutations down to 34 targets, one mRNA instruction, and the T cell that finds the tumor.

Which is exactly why I am still long AI

I know the prevailing wisdom on social media and in the mainstream media is that AI has run its course.

That is backwards, and Moderna is the proof.

An individualized neoantigen vaccine creates a fresh compute workload for every patient. Each dose requires tumor and healthy-tissue sequencing, variant calling, neoantigen ranking, and the scheduling of a bespoke manufacturing batch. Melanoma alone is roughly 100,000 new US cases a year, and intismeran trials are already running in lung, kidney and bladder.

That is the bridge to silicon: more personalized programs mean more recurring sequencing, model inference, storage and networking. It does not prove the revenue impact will be material to any chip company. That uncertainty is why semiconductors are a separate forward thesis and a separate book, rather than a result I smuggled into the Moderna readout.

Two theses, so I created two agents in Grok Bot.

Why two portfolios

I run one account per sector. If they were a single book I could not tell which thesis was working. Moderna Trading Bot trades the neoantigen chain, and SemiConductor Trading trades compute.

Grok Bot named SemiConductor Trading receiving a pasted campaign runbook
The second Grok Bot taking its runbook. I paste a spec, it works through it and only stops at deploy sign-off.

How I used Grok Bot to create my AI and biotech strategies

Grok Bot is only as good as the tools you hand it. Left alone with a browser it will read Reddit and guess. I gave mine three surfaces into one engine: MCP for the entire toolbox, the Python SDK for anything that has to run a hundred times, and a browser it barely touched.

Grok Bot named Moderna Trading Bot connected to the NexusTrade MCP server
The Moderna Trading Bot on its first task. It found the MCP server already connected and listed 157 portfolios before I finished typing.

MCP is where all of the work happens. NexusTrade exposes 122 tools over it, and they are not only execution. Backtesting, walk-forward certification, options chains and deploys on one side. News search, SEC filings and web research on the other. Grok Bot never had to leave the connection to build either book. Connecting is one config block and an API key.

NexusTrade MCP Server & API
Give your AI agent real trading tools. Connect Grok Bot, Claude, Cursor or your own harness over MCP, or use the Python SDK.
nexustrade.io/developers

Live orders only ever stage. Nothing Grok Bot decides reaches the market without me clicking approve.

That includes the filings. Ten-Ks, 10-Qs, 8-Ks and the news wire, queried the same way as a backtest. It is why Personalis, which runs the tumor sequencing behind the Moderna program, is one of the twenty names the book trades. Tempus AI agreed to buy it on August 21 at a 28% premium, two days after the readout and three days after my measured window closed.

The Python SDK handles volume (pip install nexustrade). Studies enqueue and poll, so the Bot fires off a hundred backtests and collects them later.

The browser is pure redundancy. It can open NexusTrade and read the UI. Mine never needed to.

What I decided vs. what Grok Bot decided

I set the experiment: the theses, funded accounts, calendars, four-fold structure, lockbox rules and pass/fail gates. For biotech, I also wrote the universe criteria and supplied a long-dated-call skeleton to test. For semis, I left the universe and every trading mechanic open.

Grok Bot did the strategy work: it researched and froze the names, designed and swept the candidate mechanisms, killed the ones that missed a gate, chose the cross-fold robust settings, assembled the final books and staged them for my approval. I remained the only person allowed to approve a live order.

The rules it came back with

Here are both books, rule for rule. Not summaries, the literal conditions each account trades on. Once deployed, the only human step is order approval.

Both books, rule for rule · every value read off the deployed portfolio
MODERNA TRADING BOTthe biotech thesisSEMICONDUCTOR TRADINGthe compute thesis · S13 AUNIVERSE20 names, 5 layers7 chip names, frozenTREND FILTERnoneSMA100 + ROC63 > 0RANK63d return ÷ 63d voltop 7 by ROC126GATESVIX < 35 · 7 daysVIX < 35 · 63 daysBUYΔ0.50 calls20/25 debit verticalsEXPIRY365-730 DTE365-730 + 90-180, 2 sleevesSIZE6% each · 75% cap12% and 15% per nameTAKE PROFIT+80%+300%TIME STOP< 90 DTEDTE 21, and 22-45Same skeleton, different clock. One long bet against two sleeves that run to +300%.

BUY and SIZE are the pair that matters in both. A few hundred dollars of premium carries the exposure of several thousand dollars of stock, so each book runs a median of 15.44% deployed for biotech and 14.70% for compute and still moves like it is fully invested. That cuts both ways, and it is where the drawdowns come from.

I made Grok Bot prove it on data it was never allowed to see

Anyone can produce a backtest that looks incredible. Turn enough knobs against enough history and you will always find a setting that would have made a fortune, and then it dies the month you fund it. That is the whole problem with the genre.

So I made the tuning and the grading happen on different years. Grok Bot was allowed to adjust the rules on one stretch of market history, then graded on the year immediately after it, which it had never been shown. Then everything slid forward and repeated. Four times. Those four graded years are the four bars below, and no rule was ever tuned on the year it was graded on.

If you are quant-minded, you recognize this as walk-forward optimization.

Two rules on top of that. It had to deploy the settings that held up across all four graded years, not the settings that won the best one, because shipping your single best year is how you overfit while feeling rigorous. And the data stopped at April 14. No rule was tuned on a single day after that date, and I did not look at what happened next until the design was frozen.

The other place options backtests die is fills. Every fill is priced against real OPRA bid and ask, roughly 400 million quote rows per trading day. The engine does not fill at the midpoint. It fills at the midpoint plus half the spread against you, going in and coming out, and rejects contracts wider than the strategy's spread limit before the order is built. Minutes with no quote fall back to a measured spread table bucketed by moneyness and expiry, so a far out-of-the-money LEAP is charged about twice what an at-the-money one is.

Four graded years neither agent had seen · each book against its own benchmark
MODERNA TRADING BOTmean +32.22% vs ARKG −3.73%-25%0%25%50%75%26.4-21.8YR 125.4-11.5YR 256.3-5.2YR 320.823.6YR 4SEMICONDUCTOR TRADING · S13 Amean +63.02% vs SMH +32.54%-25%0%25%50%75%57.344.8YR 158.97.4YR 266.920.8YR 369.157.2YR 4THE BOOKITS BENCHMARKSeven of eight graded years beat the benchmark.

Eight graded years across the two books, every one positive, and seven of the eight beat their own benchmark. ARKG actually lost money in three of the four biotech years while the book made 26%, 25%, 56% and 21%. The semis book beat SMH in all four. No single lucky stretch dragging up an average, which is the failure mode that kills most strategies the day they go live.

Then I opened the lockbox

April 14 through August 18, 2026. Four months of real market history that neither agent had ever been allowed to see, replayed against the frozen rules with nothing left to tune.

The Moderna book returned 62.97%. Over those same four months the S&P returned 11.29%, and ARKG, the biotech ETF, returned 50.10%.

It did that with a median of 15.44% of the account actually spent, against benchmarks that are 96% invested every day by construction.

What that window does not contain is the news. The readout landed August 19, the day after the lockbox closed. So 62.97% does not measure the Moderna trade, it measures whether the rules survive four months they were never shown. I also froze the twenty names in August knowing how that stretch had gone, and that hindsight is in the name list. The rules got tested. The thesis is the forward bet, and it starts now.

The lockbox · April 14 to August 18, 2026 · daily equity, and how much cash was actually at work
GROK BOTTHE SAME 20, AS STOCKARKGSPY0%20%40%60%80%APRMAYJUNJULAUG+62.97%+50.10%+39.43%+11.29%CAPITAL ACTUALLY DEPLOYED0%50%100%ARKG & SPY AT 96% EVERY DAY15.44%Daily closes. Deployment is position mark ÷ account value; median 15.44% across all ticks.

The names were right, and that is most of the story. Those same twenty tickers held as ordinary stock, equal weight, no options and no ranking, returned 39.43% over the lockbox against the S&P's 11.29%. The sector carried it. That is the gold dashed line above.

ARKG caught the same wave, which is the honest part: a dedicated biotech ETF did 50.10% on those four months, so the sector was the tide, not my stock picking. The distance from there to 62.97% is step 5. It owned the move in long-dated calls instead of shares, and it did that on a sixth of the capital.

The semis book did the same thing on the silicon side, over its own window. Each campaign froze its holdout before it started, so the semis lockbox runs April 17 to August 23 rather than April 14 to August 18. +44.43% against SMH's +21.09%, and the same seven names held as ordinary stock returned 20.35%. So the book more than doubled both of them, and it did that at 14.70% deployed against their 96%. Twice the return on a seventh of the capital at risk.

The semis lockbox · April 17 to August 23, 2026 · S13 A against SMH
SEMIS BOTTHE SAME 7, AS STOCKSMHSPY-30%-15%0%15%30%45%APRMAYJUNJULAUG+44.43%+21.09%+20.35%+8.18%CAPITAL ACTUALLY DEPLOYED0%50%100%14.70%BENCHMARKS AT 96% EVERY DAYTwice the sector's return, on a seventh of the capital at risk.
What it got right
  • Beat ARKG by 12.9 points and SPY by 51.7
  • Did it with 15.44% of the account spent, against 96% for both
  • All four graded years positive, worst +20.75%
  • Better return per unit of downside risk than SPY (Sortino 4.25 against 3.50)
  • 17 of 20 names traded, so no single-name lottery
What it got wrong
  • ARKG earned its return more smoothly (Sortino 5.16 against 4.25)
  • Worst peak-to-trough fall was 24.88%, against ARKG's 13.48%
  • Universe was picked in August 2026, so hindsight is in it
  • Replayed on historical chains, not live fills

Both books are live.

BookCapitalStructureLockbox
Moderna Trading Bot$5,494.51Δ0.50 LEAP calls, 365-730 DTE+62.97%
SemiConductor Trading$8,00020/25 debit verticals, two sleeves+44.43%

Moderna Trading Bot launched on the twenty-name book above. On August 24 I cut three satellites after a fresh stock-quality and broker-eligibility audit. MRNA stayed. The live universe is now:

MRNA MRK BNTX · RXRX SDGR ADPT · GH NTRA VCYT ILMN TWST QGEN TXG · TMO DHR A · BMY
Moderna Trading Bot · Public Portfolio Challenge: Biotech · article snapshot, August 23 2026 · click through for the live account

SemiConductor Trading holds the silicon side on a frozen seven: NVDA, TSM, AVGO, AMAT, LRCX, ANET and MRVL. It runs two isolated sleeves of percent-debit call verticals, one dated a year or more out and one at 90 to 180 days, entering only when a name is above its 100-day average with positive three-month momentum, and letting winners run to +300%. The ranking step only bites once that filter has cut the list, since taking the top seven of seven names is otherwise a no-op. Defined risk, because an $8,000 book cannot buy naked convexity on a $180 NVDA call and still hold seven names.

SemiConductor Trading · Public Portfolio Challenge: Semis · article snapshot, August 23 2026 · click through for the live account

August 24 addendum: I cut three names. The book got better.

PSNL, TECH and PACB are gone. I reran the original twenty-name book and the cleaned seventeen-name book across the same five rolling out-of-sample folds from January 2022 through August 21, 2026. No parameter search. Same dates, same rules, same test.

Fixed bookMean OOSSortinoWorst drawdownPositive folds
Original 20+31.07%1.2425.52%4 of 5
Cleaned 17+41.18%1.5719.45%4 of 5
Semis, unchanged+67.69%1.7933.73%5 of 5

The cleanup added 10.11 percentage points of mean OOS return, raised Sortino by 0.34 and cut the worst fold drawdown by 6.07 points. The semis book did not need surgery. Its seven names stayed positive in all five held-out folds.

I also tested the obvious ways to force the live account closer to the headline thesis. A dedicated 30% MRNA sleeve cut mean OOS return to 21.04% and doubled the worst drawdown to 39.06%. Putting broker-friendly vertical spreads ahead of calls cut mean OOS return to 7.00%. Both were rejected. MRNA remains in the live book, but I am not going to make the tested strategy worse just to make one contract easier to buy.

Both portfolios now evaluate on NexusTrade's Constant deployment frequency. That is 24/7 signal evaluation, not permission to trade unattended. Automated approval is still off, so every broker order waits for me. The six-dollar Bitcoin dust sale filled, leaving the Biotech account with no positions and $5,500.09 in cash and buying power. The full fold tables, study IDs, rejected variants and deployment state are in the August 24 public audit.

Concluding thoughts

I expected to write the post where the agent produces a beautiful backtest that falls apart the second you hold out a window. That is what the LinkedIn posts never show you, because they never hold one out.

Instead, an agent twelve days old produced two strategies that survived four graded years they had never seen and a sealed four-month lockbox.

The measurement has limits. It is one holdout, replayed on historical chains, and I picked the universe in August 2026. What is not a limit is the capital. Both books are funded and live on Public, every order stages against my own account, and you can watch them at the links above.

Every campaign log, fold table and failed parameterization is in the Public Portfolio Challenge repo, including what Grok Bot tried and killed. The latest deployment audit includes two changes I rejected because their out-of-sample numbers got worse. A track record containing only winners is a marketing document.

Episode 12 is whether this survives real fills. I will post those numbers whether they are good or not.

Moderna's algorithm ranks 34 neoantigens out of hundreds and puts them in a syringe. My Grok Bot ranks 20 tickers and puts them in a portfolio.

Same math. Considerably lower stakes.

The Public Portfolio Challenge
Eleven episodes of a real $25,000 account traded by AI in public. Bakeoffs, deploy day, production bugs, and the panic sell.
nexustrade.io
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