First-rate technical account by **Jarred Sumner**, creator of **Bun** (JS/TS runtime, >22M downloads/month), on the **complete rewrite of Bun from Zig to Rust in 11 days** (May 3→14, 2026) driven by **Claude** — an exceptional case study in AI-assisted software engineering **at industrial scale**. Motivation: a recurring class of bugs (use-after-free, double-free, leaks) arising from the mix of GC-managed memory (JavaScriptCore) and manual memory (Zig); in **safe Rust**, these bugs become **compile errors** with automatic cleanup (`Drop`/RAII) — "a better feedback loop than a style guide." Rejecting the dogma that "a rewrite is always a bad idea" (a year of bugfix freeze for 3 engineers), Sumner chooses a **mechanical port** (preserve the architecture, minimal behavior change) validated by the **existing test suite, written in TypeScript and therefore language-independent** (60,624 tests, 1.39M `expect()` assertions, 0 tests removed, 6 platforms). The harness: **~50 dynamic workflows** in **Claude Code**, *write → 2+ adversarial reviewers → apply* loops, up to **64 Claude instances in parallel** (4 worktrees × 16), with **PORTING.md** + **LIFETIMES.tsv** generated in preparation. Numbers: **6,502 commits** (peak 695/h, 58/min, ~1,300 lines/min), final diff **+1,009,272 lines**, ~16,000 compile errors treated as a queue, **5.9B uncached input tokens + 690M output ≈ $165,000**. Key methodological levers: **adversarial review** (a second Claude, separate context, sees only the diff, tasked with finding why it's wrong — catches subtle bugs that are *semantically* different but *syntactically* identical) and the principle **"fix the process that generates the code, not the code by hand."** Model used: a pre-release of **Claude Fable 5** (Mythos class). Since the merge: **11 rounds of Claude Code security review**, 24/7 coverage-guided fuzzing (100B executions → ~15 PRs), **4% `unsafe` code** (78% on a single line), **19** known regressions fixed. In production: Claude Code v2.1.181, the first release on Bun-in-Rust, **+10% faster startup on Linux**. Disclosed upfront: **Bun was acquired by Anthropic in December 2025**.
#Bun#Jarred Sumner#Zig-to-Rust rewrite
Jarred Sumner (créateur de Bun ; travaille chez Anthropic depuis le rachat de Bun en décembre 2025)
Testimony of **Arthur Mensch** (co-founder and CEO of **Mistral AI**) accompanied by **Audry Herblin-Stoupe** (director of public affairs) before the **commission d'enquête sur les vulnérabilités numériques** of the National Assembly (chaired by Philippe Latombe, absent — session chaired by the rapporteur). Testimony under oath, ~1h15, May 2026. Mensch's pivot thesis: ***"cloud is artificial intelligence"*** — no distinction between digital services and AI, AI is the atomic unit of the cloud value chain, from semiconductors (ASML) to enterprise deployment. **Mistral in 2026**: 1,000 employees, €12 billion valuation, target of **€1 billion in revenue by end of 2026**, €1 billion invested in R&D over the year, 30% of revenue in France / 70% outside France / ~75% in Europe, clients: DINUM, Caisse des dépôts, France Travail, MACGM, Stellantis, TotalEnergies, BNP Paribas, ministère des Armées, Luxembourg (central administration). **Mensch's conceptual framework**: AI is a **natural resource** — *"we transform electricity into intelligence, into token generation."* Economics: 1 GW of datacenter = **$50 billion in investment over 5 years**, generates **$20 billion in tokens/year** ≈ 50% gross margin. Along the electron→token chain, **~10% of the value is in the electron**, 90% elsewhere (chips, software, services). **Alarmist macro thesis**: if Europe imports 10% of its payroll in non-European AI, that amounts to **an additional €1 trillion trade deficit**; €20 trillion in infrastructure investment is needed to serve Europe (40 GW France / 400 GW Europe). **Sovereignty strategy**: ***"don't think of sovereignty as isolationism but as leverage."*** **Time pressure**: *"we don't have time"* — a **2-year** window before European energy resources are monopolized by American hyperscalers deploying **$1 trillion/year**. **Five operational diagnoses**: (1) Regulatory burden = 5 compliance staff at Mistral, 27 unsynchronized regulations, entrepreneurs leaving for the US; (2) Fragmented market = ~60 European telcos vs. 3 in the US; (3) Public procurement underused as strategic leverage (50% of EU GDP); (4) Energy: 9 GW of French surplus at risk of being monopolized by US players within 2 years; (5) Distillation = a cost-reduction technique, **not** technological catch-up. **Defense doctrine**: Mistral works with the ministère des Armées, explicitly refusing "oversight" of final use ("we don't have democratic legitimacy"), a positioning *anti-Anthropic-Mythos*. **Cybersecurity**: acknowledges the offensive capabilities of models ("it's rising in a linear, predictable way, for everyone at the same time"), opposes the *fear marketing* of an American competitor (implicitly Anthropic). **Campus IA**: very minority stake, potential supplier (Mistral + hyperscalers), €35 billion MGX/Abu Dhabi + Nvidia, 100 hectares at Saint-Arnoult, 1.4–1.6 GW (= Flamanville), French nuclear power = reduced carbon footprint. **Annotation**: teams of PhD candidates (no more microworkers), Madagascar for robotics with wage guarantees. **Business model**: no bubble on the demand side, **supply bottleneck** (chips, memory, helium, electrons). **Warning conclusion**: *"if we don't do it fast enough, we will become a vassal state."*
#Arthur Mensch#Mistral AI#Audry Herblin-Stoupe
**Arthur Mensch** (cofondateur et directeur général de **Mistral AI**) accompagné d'**Audry Herblin-Stoupe** (directrice des affaires publiques et de la communication, Mistral AI). Mensch a cofondé Mistral AI le 28 avril 2023 avec **Guillaume Lample** et **Timothée Lacroix** — tous les trois précédemment dans les *« gros acteurs américains »* (Google DeepMind / Meta FAIR). Audition tenue devant la **commission d'enquête de l'Assemblée nationale sur les vulnérabilités numériques** · présidée par **Philippe Latombe** (député MoDem, Vendée — absent ce jour). Séance présidée par la **rapporteur** (non nommée dans le transcript) · avec interventions du président lui-même (revenu en cours) · du député **Arnaud Saint-Martin** (LFI/Saint-Arnoult — sa circonscription accueille Campus IA) · et de la rapporteur sur les questions économiques.