Extreme Movers: Claude Sonnet 5.5's picks for 2026-09-29
Claude Sonnet 5.5 picked MDB, SMMT, NVTS, KOD, BA for a 1-day horizon. Average directional return: +1.77%. Directions called correctly: 80%.
| Experiment | Extreme Movers |
|---|---|
| Model | Claude Sonnet 5.5 |
| Prompt version | extreme-movers-v9 |
| Asked | |
| Horizon | 1-day |
| Measured from | 2026-09-29 |
| Measured to | 2026-09-30 |
| Benchmark | SPY |
| Status | Settled |
| Average directional return | +1.77% |
| Directions called correctly | 80% |
| Benchmark return | +0.51% |
The picks
| Rank | Symbol | Direction | Price change | Return in the called direction | Confidence | vs benchmark | Called right |
|---|---|---|---|---|---|---|---|
| 1 | MDB | up | +10.29% | +10.29% | 45% | +9.78% | Yes |
| 2 | SMMT | up | +2.71% | +2.71% | 50% | +2.20% | Yes |
| 3 | NVTS | up | +0.33% | +0.33% | 40% | -0.18% | Yes |
| 4 | KOD | down | +4.77% | -4.77% | 40% | -5.28% | No |
| 5 | BA | down | -0.30% | +0.30% | 40% | -0.21% | Yes |
The model's market view
I treated the Sept 28 regular session as the source session: the S&P 500 fell about 0.5% and the Nasdaq 100 about 1%, driven by high oil and Treasury yields. The extreme movers that day were event-driven: an oversized CEO-departure selloff, a 178% biotech spike, and a 7% drop on a Boeing software issue. Overnight news then changed the setup for a few names. I mostly bet on reversals of the source-session move where the overnight news or the size of the move looks like an overreaction. I did not confirm market caps for any pick, so market_cap_usd is omitted throughout. Where I could not reach a fresher quote, the last verified price and its real date are given.
Why each pick
MDB
MongoDB fell 18.46% on Sept 28 to close at $334.68, after CEO Chirantan Desai left for a senior role at Meta. Former CEO Dev Ittycheria returned as interim CEO. The catalyst is substantive but not a fundamental deterioration: Q2 revenue grew 30% and it reported a GAAP operating profit. An 18% one-day drop on a leadership change looks like an overreaction, and the return of the founder-era CEO gives a credible stabilizer. I expect a partial rebound, so direction is up, a reversal of the negative source-session change. Risks: a permanent CEO search can weigh on the stock, software remains under AI-disruption pressure, and the stock could keep falling toward Monday's $300 low. Reference price is the Sept 28 regular-session close. I did not find a Sept 29 intraday quote.
SMMT
Summit Therapeutics closed Sept 28 down 0.83% at $15.48, so any rise is a reversal of the source-session change. Overnight, AstraZeneca announced a $2 billion investment and a joint clinical collaboration to test ivonescimab and sonesitatug vedotin in combination. The stock gained about 18-27% in premarket trading on Sept 29, depending on the report. The catalyst is substantive: a large strategic investment and validation from a major pharma partner. Direction is up on the view that the gap holds or extends on analyst target raises. Risks: partnership-driven gaps often fade, and the gap is already large, so the next-session close could give back part of it. Reference price is the last verified regular-session close on Sept 28. I did not find a verified Sept 29 intraday quote, so this price is stale.
NVTS
Navitas Semiconductor fell 3.85% on Sept 28 to close at $11.73. After the close, it announced that the U.S. Army selected it for the ALATTIS program to develop 10 kV silicon carbide power semiconductors. The stock initially jumped about 20% after hours and was up about 9% at $12.82 at roughly 8:41 AM ET on Sept 29. The catalyst is substantive but early stage: it is a prototype and manufacturing-validation award rather than a large revenue contract. Direction is up, a reversal of the negative source-session move. Risks: the pre-market gain has already faded from its peak, it is a high-volatility small-cap AI-power name, and a further fade is plausible. Reference price is a pre-market quote from Sept 29.
KOD
Kodiak Sciences was the Nasdaq's top percentage gainer on Sept 28, rising 177.96% to close at $89.92, after its Phase 3 DAYBREAK trial in wet AMD met primary endpoints for Zenkuda and tabirafusp-ted. The catalyst is substantive, and analysts raised targets to $96-$145. But the stock went from about $32 to $90 in one session, the intraday high was $95.77, and short interest was about 18% of float before the move. It was down more than 4% in early premarket on Sept 29. I expect partial profit-taking, so direction is down, a reversal of the positive source-session change. Risks: analyst target raises above the current price, a possible BLA filing in Q4 2026, and momentum buying could extend the run. Reference price is the Sept 28 regular-session close. I did not find a Sept 29 intraday quote.
BA
Boeing fell 6.91% on Sept 28 to close at $184.39 after acknowledging a previously undisclosed software glitch affecting 737 MAX jets. The problem can cause an automated navigation feature to fail after a missed approach. The FAA has reportedly delayed 737 MAX 10 certification because of the issue. The catalyst is substantive, with potential delivery and certification timing implications. Direction is down, a continuation of the negative source-session move. The stock is 14.9% below its 200-day moving average, and support near $187.50 broke. Risks: a quick software fix or FAA clarification could trigger a sharp rebound, the drop is already large, and oil easing today would help airlines and aerospace sentiment. Reference price is the Sept 28 regular-session close. I did not find a Sept 29 intraday quote.
Other models on the same run
| Model | Picks | Average directional return | Directions called correctly |
|---|---|---|---|
| GPT-6 | KOD, MDB, RBLX, BE, LFCR | +3.22% | 60% |
| Muse Spark 1.1 | PANW, ARM, QCOM, CRWD, BE | -0.09% | 40% |
| Gemini 3 Pro | BE, DASH, PSKY, CRWD, QCOM | +1.33% | 80% |
| Perplexity | SMMT, SSTI, IOVA, QURE, FICO | +3.28% | 80% |
| Grok 4.5 | KOD, MDB, BA, QCOM, BE | -3.92% | 0% |
| DeepSeek | KOD, ARM, QCOM, DASH, INTC | -1.39% | 20% |
Written up on ForecastNest Insights: Extreme Movers: Claude Sonnet 5.5's picks for 2026-09-29.
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