GPT-5.1 Pro vs. Gemini 3 Pro Preview: How Does GPT-5.1 Pro Solve Complex Problems?

TL;DR

GPT-5.1 Pro tackles complex problems by reasoning for extended periods, connecting clues, and checking relationships across the available data. On the DEF CON Smuggler’s Manifest puzzle, it identified the ADFGX cipher and discovered a decisive 2.1-unit location imbalance after reasoning for almost 30 minutes. It still proposed an incorrect route and needed a hint about the required 24-character path, so read on to see both its strongest deductions and its limitations.

Transcript

It feels like just yesterday that we got the best LLM ever made with Gemini 3 Pro preview. Oh. Uh, it was yesterday, but that changed today because there's another great new model from OpenAI. There's actually two. The first is GPT 5.1 Codeex Max. Quite a name, but it's also seemingly quite a model. It's a completely new snapshot focused on being a... Read More

Key Insights

• GPT-5.1 Pro is presented as the more impressive of OpenAI's two newly released models for the reviewer's use cases. The reviewer had several days of early access and preferred its broad reasoning performance, while noting that it was only available through OpenAI's website and not through the API.
• GPT-5.1 Codex Max is a new model snapshot focused on agentic coding and long-running tasks. The transcript introduces it alongside GPT-5.1 Pro, but postpones the detailed Codex Max discussion until later so the reviewer can first examine GPT-5.1 Pro's performance on a complex non-coding challenge.
• The DEF CON Gold Bug challenge combines difficult reasoning, research, cryptographic techniques, and pirate-themed answers. The featured Smuggler's Manifest puzzle required finding a 12-character phrase without spaces by tracing how an emerald was smuggled from the jungle to the port and decoding relevant manifest identifiers.
• The ADFGX cipher is indicated by the reference to Germans intercepting messages and by the A, D, F, G, and X characters appearing in the IDs. GPT-5.1 Pro identified this connection correctly, while the other models tested by the reviewer had not managed to recognize it.
• The decisive mass discrepancy is a 2.1-unit imbalance between two locations. GPT-5.1 Pro calculated that the jungle had 6.7 units entering and 8.8 leaving, while the port showed the opposite net difference, indicating unexplained weight appearing in the jungle and disappearing at the port.
• The 2.6-unit package entry is suspicious because comparable small carved boxes with foam lining weigh 2.5 units. Both the reviewer and others focused heavily on this inconsistency, but the broader location-level weight balance provided a more useful clue for reconstructing how the emerald moved.
• The identifier-length constraint determines which routes can form the cipher input. The required path contains 24 characters, four relevant IDs have three characters, and the remaining IDs have four. If any three-character IDs are used, all four must be included for the total to remain mathematically compatible.
• GPT-5.1 Pro produced valuable discoveries without reaching a correct solution immediately. Its initial route relied only on four-character IDs and was wrong, so the reviewer supplied a small hint emphasizing the 24-character requirement. The model then spent another eight minutes searching for plausible paths of the correct length.

Questions & Answers

Q: How does GPT-5.1 Pro solve complex problems?

GPT-5.1 Pro examines multiple kinds of evidence, forms connections between clues, and continues reasoning for extended periods. In the Smuggler’s Manifest puzzle, it analyzed cipher indicators, weights, locations, route identifiers, and thematic references. Its analysis produced important discoveries, although its first proposed route was incorrect.

Q: How did GPT-5.1 Pro approach the DEF CON Smuggler’s Manifest puzzle?

The model received the puzzle PDF and was instructed to identify clues, create a solution plan, and execute it without further guidance. It reasoned for almost 30 minutes before producing a detailed analysis. That response identified the cipher and a location-level weight imbalance but did not produce the correct route.

Q: What clues led GPT-5.1 Pro to identify the ADFGX cipher?

The puzzle mentioned Germans intercepting messages, while its manifest identifiers used the characters A, D, F, G, and X. GPT-5.1 Pro connected those clues and correctly recognized the ADFGX cipher. The relevant route IDs then had to be combined into a 24-character cipher input.

Q: What weight imbalance did GPT-5.1 Pro discover?

GPT-5.1 Pro calculated that 6.7 weight units entered the jungle while 8.8 left it, producing an unexplained 2.1-unit increase. The port showed the opposite 2.1-unit difference. This suggested that the emerald’s unexplained weight appeared in the jungle and disappeared at the port.

Q: Why was the 2.6-unit package entry suspicious?

Several small carved boxes with foam lining weighed 2.5 units, while one comparable entry weighed 2.6. That mismatch appeared relevant to the hint that some numbers did not add up. However, the broader 2.1-unit imbalance between locations was more useful for tracing the emerald.

Q: Why did the cipher route need exactly 24 characters?

The ADFGX decoding process required 24 characters to produce the puzzle’s 12-character answer. Most route IDs had four characters, while four IDs had three. If a route used any three-character ID, all four short IDs had to be included for the total length to remain compatible.

Q: Did GPT-5.1 Pro solve the puzzle without help?

No. It independently identified the ADFGX cipher, connected the puzzle to Romancing the Stone, and found the 2.1-unit imbalance, but its first route used only four-character IDs and was incorrect. After the reviewer emphasized the 24-character requirement, the model reasoned for another eight minutes.

Q: What limitations of GPT-5.1 Pro did the reviewer describe?

GPT-5.1 Pro was available through OpenAI’s website but not through the API used for integration into T3 Chat. The reviewer also encountered broken chat titles, a frozen-looking thought timer, and an error that required refreshing the page. Most importantly, its strong reasoning did not guarantee a correct final answer.

Summary & Key Takeaways

• GPT-5.1 Pro impressed the reviewer most when handling a difficult DEF CON Gold Bug puzzle that had previously required three days of human effort. Given the puzzle PDF and instructions to identify clues, create a plan, and execute it, the model reasoned for almost 30 minutes before producing a detailed analysis.

• The model correctly linked the German interception clue and the characters used in the manifest IDs to an ADFGX cipher. It also connected the puzzle to Romancing the Stone, examined a suspicious 2.6 weight among similar 2.5 entries, and found a broader location imbalance that the reviewer had originally missed.

• GPT-5.1 Pro calculated that the jungle gained 2.1 unexplained weight units while the port lost the same amount, revealing the emerald's likely movement. Its first proposed route was still incorrect because it used only four-character IDs. After receiving a hint about the required 24-character path, it continued reasoning for eight minutes.