Fable's judgement

Simon Willison · 2026-07-03 · 3 min read

TLDR: When using Claude's top-tier "Fable" model, don't micromanage its decisions — let it exercise its own judgment, including which lower-powered subagent model to use for routine coding tasks. A simple prompt instructing Fable to delegate implementation work to Sonnet/Haiku subagents while retaining judgment-heavy tasks itself meaningfully cuts token costs without sacrificing quality.

Could an AI Win the Millennium Prize and not be AGI? – Grant Sanderson (@3blue1brown )

Dwarkesh Patel · 2026-07-03

This discussion explores the capabilities of AI in advanced mathematics, specifically contrasting its performance on problems requiring pattern recognition versus those demanding creative insight. While current AI excels at geometry and similar pattern-based mathematical challenges, achieving results in seconds, it struggles with combinatorial problems that require more playful and puzzle-like approaches. The conversation raises questions about whether solving a Millennium Prize Problem would automate white-collar work and suggests that such a breakthrough might involve AI's ability to bridge seemingly disparate mathematical fields, similar to historical breakthroughs in number theory and physics.

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The conversation delves into the fascinating intersection of Artificial Intelligence (AI) and advanced mathematics, specifically referencing the International Mathematical Olympiad (IMO) and the Millennium Prize Problems, such as the Riemann Hypothesis. The core question explored is whether AI's ability to solve such complex mathematical problems would signify a broader automation of white-collar work.

The speaker highlights a distinction in AI's current mathematical prowess: it is highly effective at problems that can be approached with a brute-force solver or involve recognizing complex patterns. For instance, in the context of the IMO, AI could potentially solve geometry problems in as little as 19 seconds. This success is attributed to the AI's deep knowledge within specific domains and its capacity for rapid computation, essentially 'cold-solving' these problems. The speaker even notes that for human students, there's a 'dirty secret' that many IMO problems can be trained for and tackled with a brute-force-like approach, suggesting that some challenges perceived as requiring creativity might actually be more amenable to systematic methods than commonly believed.

However, the discussion also points out a significant challenge for AI: combinatorics problems. These problems are described as requiring a more 'playful' and 'puzzle-like' approach, suggesting a higher demand for creative problem-solving rather than mere pattern recognition or brute-force application of known techniques. The speaker mentions that in a hypothetical 2024 IMO test, AI would struggle with combinatorics, which was a category with two questions that year, despite excelling in other areas like geometry. This suggests a spiky frontier to AI, where capabilities are not uniformly distributed across all types of mathematical challenges.

The conversation then pivots to the broader implications of AI solving a Millennium Prize Problem, such as the Riemann Hypothesis, on white-collar work. The speaker introduces two potential scenarios for how such a solution might emerge and what that would imply for AI's general intelligence and its impact on the economy.

One possibility is that the solution to the Riemann Hypothesis would emerge from AI's ability to find connections between previously disparate domains of knowledge. An anecdote about mathematicians Hugh Montgomery and Freeman Dyson is used to illustrate this. Montgomery, a number theorist, discovered a statistical correlation between pairs of zeros of the Riemann zeta function. Dyson, a physicist, recognized that this formula was identical to one used in quantum physics for studying the eigenvalues of random Hermitian matrices, which in turn relate to the energy levels of atomic nuclei. This unexpected connection between number theory and quantum physics was a significant insight. If AI were to make such interdisciplinary connections, effectively bridging vast fields it has 'known' (i.e., been trained on), this would be a powerful form of intelligence. This scenario suggests that the rate-limiter for solving complex problems and automating white-collar work might be this ability to synthesize knowledge across domains, moving beyond mere expertise within isolated fields.

The second, more challenging possibility for solving the Riemann Hypothesis, and one that resonates with the solution to Fermat's Last Theorem, is that it would require building entirely new 'mountains' of mathematical theory and ideas. Fermat's Last Theorem, despite its simple statement, was ultimately proven using highly advanced and complex machinery involving elliptic curves and modular forms, concepts that took centuries of mathematical development to establish. If an AI could generate such foundational new theories and frameworks, rather than merely connecting existing ones, that would represent an even higher level of intelligence and creativity. This kind of intelligence, capable of conceptual innovation at such a profound level, would likely have transformative effects far beyond specific mathematical fields, making it difficult to imagine that it wouldn't pervade and automate many aspects of the economy. The speaker implies that this level of intelligence is fundamentally different from what is needed for typical white-collar work, but if achieved, its widespread impact would be inevitable.

In defense of AI mandates (xpost)

Charity Majors · 2026-07-02 · 5 min read

TLDR: A technology mandate is fundamentally a funding mechanism — it signals that leadership accepts the slowdown, deadline slippage, and cost of building new skills collectively. Without that explicit commitment, you're just silently telling engineers AI is not a real priority while adding pressure. If AI is genuinely existential to your business, be honest enough to mandate it and resource it properly; treating it as mandatory on the job ladder while refusing to allocate time for it is cowardice, not strategy.

The AI Compass

Simon Willison · 2026-06-30 · 1 min read

A political compass-style quiz maps you onto one of 30 AI ethics archetypes based on 29 questions, and the technically interesting part is that it's a single-page React app that skips the build toolchain entirely by using the `<script type="text/babel">` browser-side transpilation trick. For a senior engineer, that implementation detail is worth noting as a pattern for shipping simple interactive tools quickly without webpack or Vite overhead.

Find the North Star

Kent Beck · 2026-04-22 · 1 min read

Kent Beck and Amelia Wattenberger argue that optimizing every development task for measurable productivity is actively harmful, and that unstructured play and exploration are what generate genuine creative breakthroughs in software. This matters because as AI handles more routine coding, the competitive edge for engineers shifts toward the less quantifiable skill of knowing when to abandon the KPI and just experiment.

Context Engineering for Coding Agents

Martin Fowler · 2026-02-05 · 10 min read

TLDR: The core challenge in coding agents isn't getting the model to act — it's carefully controlling what information it sees and when. Rather than dumping everything into the context window, effective "context engineering" means layering inputs strategically: always-loaded project conventions, path-scoped rules that trigger only for relevant file types, and on-demand "skills" the LLM loads itself when needed. Getting this balance wrong — too much context, loaded indiscriminately — actively degrades agent performance and inflates costs.

Assessing internal quality while coding with an agent

Martin Fowler · 2026-01-27 · 11 min read

TLDR: AI coding agents consistently generate code that compiles and appears correct but introduces subtle internal quality issues — in this case, incorrectly typing optional authentication tokens as non-optional across all GitLab API wrapper functions. The bug only surfaced later when new code tried to pass an actual optional value, revealing that the agent cargo-culted patterns without understanding the semantic intent behind Swift's type system. Internal code quality requires active human review; agents won't flag these issues themselves.

Questionable Advice: “My boss says we don’t need any engineering managers. Is he right?”

Charity Majors · 2024-01-05 · 28 min read

TLDR: Engineering managers aren't overhead — they're a necessary abstraction that reduces coordination complexity as an org scales. Without them, every engineer must stay aligned with every other engineer (n(n-1)/2 connections), creating information overload that silently kills velocity. The real problem isn't the manager debate itself; it's a CEO who hired a VP of Engineering and then blocks her from structuring the org — which signals a deeper dysfunction worth taking seriously before accepting any headcount constraints.

Beyond “Taking Responsibility”: Why Leading for Agency is the Future of Modern Management

Henrik Kniberg · 2026-05-31 · 4 min read

TLDR: Agency is distinct from both responsibility and empowerment — it's the proactive, self-directed capacity to shape outcomes, not just execute assigned tasks or act within granted permissions. Leaders can't hand it out directly; instead, they must build the conditions (clarity, trust, real decision-making room) under which people naturally exercise it. Teams with genuine agency don't wait to be told or permitted — they identify root causes, influence processes, and drive results autonomously.

Passing Tests Bore Me

Kent Beck · 2026-04-22 · 1 min read

Kent Beck argues that passing tests provide no useful information — the interesting signal comes from failing tests, unexpected failures, and the patterns that emerge when things break. For a senior engineer, this reframes test suites from a green-light checkbox into a diagnostic tool where the real engineering judgment lives in interpreting failures, not celebrating passes.