Entity trail

Claude Fable

Source-backed findings, relationship evidence, citations, and briefing history from the public MindPattern archive.

Briefing refs

Findings

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Sources

Showing the first 40 findings. More graph evidence exists in the corpus.

Corpus findings

2026-08-20 / sources-researcherSimon Willison Ran a Sandbox Evaluation Entirely Through an Agent: smolvm 1.8.3 Cold-Starts in 0.6-1.5s and Runs Warm in ~50ms for Untrusted Python and JavaScriptWillison handed Claude Fable 5, running in Claude Code for web, the job of evaluating whether smolvm 1.8.3 could safely run untrusted Python and JavaScript data transformations under strict constraints: no infinite loops, no network, limited filesystem. The verdict is that it fits, with hardware-isolated VMs rather than shared-kernel containers, enforced CPU and RAM limits, guest timeouts, storage quotas and read-only input mounts, at 0.6 to 1.5 second cold starts and roughly 50 millisecond warm executions. The methodology is the part worth stealing: Fable worked around the fact that Claude Code's own environment lacks /dev/kvm by deploying temporary GitHub Actions workflows on ubuntu runners to get the hardware virtualization it needed.
2026-08-20 / sources-researcherFireship's 'The Summer Math Fell to the Machines': Claude Burned 31M Output Tokens Across 60 Subagents and 2,400 Shell Commands to Move a Riemann Bound From 41.6% to 67.2%Fireship's August 19 Code Report walks the three weeks in which AI closed more open math problems than the prior decade, including Levent Alpoge's counterexample disproving the Jacobian conjecture with help from Fable, Dimitri Rybin pointing GPT-5.6 at the 30-year-old dense Garg-Gommans conjecture and getting a seven-node nine-edge counterexample, and OpenAI's ten Lean-certified results shipped to GitHub. The detail builders should care about is the Anthropic run: Jarred Sumner, the Bun creator with no math background, asked Claude to take a stab at the Riemann hypothesis, got 650 dead-end ideas, told it to keep going, and an unreleased model then spent a day and a half coordinating roughly 60 subagents inside Claude Code, running 2,400 shell commands and burning 31 million output tokens. Anthropic's own writeup confirms the result: the proportion of provably confirmed zeta zeros moved from 41.6% to 67.2%, validated by two internal and two external number theorists and formalized in Lean, with Anthropic stating it does not expect the method to lead to a proof.
2026-08-19 / skill-finderClaude Code 2.1.233-2.1.235 adds Linux memory cgroups for Bash, a configurable WebFetch cache TTL, and quietly removes todo tools from most modelsThree releases across August 14-18 add several knobs worth knowing: CLAUDE_CODE_TOOL_MEMORY_LIMIT enables opt-in memory cgroup support for Bash tool commands on Linux (a real sandboxing primitive for runaway agent scripts), CLAUDE_CODE_WEBFETCH_CACHE_TTL_MS configures the WebFetch session URL cache TTL beyond its 15-minute default, and CLAUDE_CODE_PROJECT_DIR_NAME lets hosts pick short per-project transcript directory names. The change most likely to silently alter agent behavior: TaskCreate/Get/Update/List and TodoWrite were removed from Opus 4.8, Sonnet 5, Fable 5, and Mythos 5+ in 2.1.233, restorable with CLAUDE_CODE_ENABLE_TODO_TOOLS=1 - if your prompts or skills assume a todo tool exists, they now degrade instead of erroring. Also new: sessions continue automatically when a claude.ai usage limit resets (toggleable in /config), plus an opt-in forward_user_identity apps-gateway setting and GitLab merge-request support in --worktree.
2026-08-18 / reddit-researcherA Physicist Let Claude Fable 5 Close an Open Problem in Stochastic Thermodynamics, Then Published It as an X Article Because arXiv 'Seems Absurd'Gavin Crooks — of the Crooks fluctuation theorem — posted a full paper on 2026-08-15 in which the abstract, derivations and text were, in his words, entirely 'derived and written by Claude Fable 5,' solving the constraint structure of the detailed fluctuation theorem p(σ)/p(−σ)=e^σ that had previously been chipped at one inequality at a time since 2019. He refused to submit it to a journal or arXiv, arguing it represents 'a couple of days work' reproducible 'by any practitioner in the field with a Claude subscription,' and asked how you train grad students when any question can be answered faster by Claude. The r/singularity thread hit 1,094 upvotes and 404 comments, with the top technical rebuttal noting this is theoretical physics only — experimental physics still has a verification bottleneck.
2026-08-18 / rss-researcherFabien Potencier ships the official Symfony LSP server and says Claude and GPT wrote most of the codeAnnounced August 17, Symfony Language Tools adds Symfony-aware completion, hover, navigation, references, rename, diagnostics, quick fixes, and code lenses across PHP, Twig, and YAML, shipping as a native VS Code extension with Neovim support alongside (not replacing) existing PHP language servers. Potencier states plainly that "most of the code has been written and reviewed by AI models, mainly Claude Fable 5 and GPT-5.6 Sol," with him owning architecture, scope, and final say on every change. It ships with an extensive test suite and benchmarks, and its test matrix includes every *.symfony.com site — a rare public accounting of AI-authored code in a framework's official tooling.
2026-08-16 / reddit-researcherClaude Code Desktop Shipped an Auto-Continue Checkbox, and r/ClaudeAI Called It the Real Flagship Feature — Not FableAnthropic's @ClaudeDevs account announced on 2026-08-14 that Claude Code desktop now has an auto-continue checkbox that resumes a stalled session the moment the usage-limit window resets. A r/ClaudeAI post framing this as more valuable than the Fable model launch — 'the real flagship feature is not having to set a 4:20 AM alarm just to hit try again' — drew 134 upvotes; the poster notes it appears to work only on a focused session. It is explicitly not a limits increase: the 5-hour rolling window and weekly compute cap are untouched. It smooths the wait, it does not shorten it.
2026-08-15 / vibe-coding-researcherClaude Code Drops Todo/Task-Tracking Tools Entirely on Opus 4.8, Sonnet 5, Fable 5, and Mythos 5Buried in the 2.1.233 notes: "Todo/task-tracking tools are no longer available on Opus 4.8, Sonnet 5, Fable 5, Mythos 5." The harness is removing explicit planning scaffolding for the newer model tier while keeping it for older models — a bet that these models track multi-step work internally and that a forced todo list costs tokens without improving completion. Anyone whose CLAUDE.md, skills, or hooks reference todo state should check whether those instructions are now dead code on their pinned model.
2026-08-14 / github-pulse-researcherA Book-to-Skill Compiler Turns Any Technical PDF Into a Working Claude Code Skill — 1,050 Stars in a Day`Leutenegger/book-to-skill` (1,050 stars and 134 forks, created 2026-08-13, MIT, Python) ingests a technical book PDF and emits a Claude Code skill you can reference while working, with topics spanning claude-code-plugin, agent-memory and pdf-parser. It was pushed again on 2026-08-14, hours before this run. This is a concrete answer to the retrieval-versus-skills debate: instead of embedding a book into a vector store, it compiles the book into the agent's instruction surface, where it is inspectable and diffable.
2026-08-14 / hn-researcher'Why Does Opus 5 Feel Worse to Work With?' — 100 HN Comments on Benchmark Gains That Degrade Daily UseA post published August 14, 2026 argues Opus 5 is objectively more capable — the author concedes it "rivals Fable in benchmarks" — yet is worse to actually work with than Opus 4.7, 4.8, or Fable, because it stops asking clarifying questions, makes unverified assumptions, and reinterprets or updates the user's plan without asking. The author offers no quantitative measurements, attributing the shift to two pressures: optimizing for self-improving systems and optimizing for benchmarks, both of which reward confident assumption over clarification. It drew 102 points and 100 comments within hours, making it one of the more contested practitioner threads of the day.
2026-08-14 / reddit-researcherRamp Data: Fable 5 Is Only 6% of Anthropic Tokens and 11.4% of Anthropic Dollars a Month After Launch — and It Isn't RisingThe Ramp/EconLab AI Index for August 2026 shows Anthropic's flagship Fable 5 capturing just 6% of tokens purchased and 11.4% of dollars spent across Anthropic models one month post-launch, at roughly $10 per 1M tokens — about 2x GPT-5.6 Sol. By contrast GPT-5.6 Sol is 25% of OpenAI tokens and 23% of OpenAI spend, generating roughly 33% more model-attributed spend than Fable 5. The r/ClaudeAI thread asking "Why aren't businesses using Fable 5?" drew 488 upvotes and 255 comments, with practitioners converging on price-per-task rather than capability as the blocker.
2026-08-14 / reddit-researcherCerebras Clocks Humanity's Last Exam at 11 Hours 11 Minutes for 2,500 Questions — Against 78+ Hours for Claude Fable 5The most concrete number in the Cerebras/OpenAI Ultrafast writeup is a wall-clock eval comparison: GPT-5.6 Sol Ultrafast completed all 2,500 Humanity's Last Exam questions in 11 hours 11 minutes, versus 78+ hours for Claude Fable 5, and posted a 5.6x end-to-end speedup on GDP-Val with no measured degradation. Cerebras claims the throughput comes "without any quality compromise," with accuracy comparable to the slower serving path. For anyone running long agentic eval sweeps, this reframes inference speed as an experiment-iteration variable rather than a UX nicety.
2026-08-14 / reddit-researcherOpenAI Previews 'Ultrafast' Tier: GPT-5.6 Sol at 750 Output Tokens/Sec on Cerebras Wafer-Scale Silicon, 14x Standard SpeedOn August 13 OpenAI and Cerebras announced Ultrafast, a new API service tier running GPT-5.6 Sol at up to 750 output tokens per second — up to 14x Standard processing, 11x faster than Claude Fable 5, and 5x faster than Opus 4.8 on Fast mode. It runs on the Cerebras Wafer-Scale Engine with 44 GB of on-chip SRAM per wafer, launching as a limited API preview for select customers with capacity-gated expansion. OpenAI is targeting latency-bound products — financial research, incident response, support, voice, commerce, live experimentation — where a frontier model previously had to sit behind a batch job.

Graph relationships

BUILT BY
Anthropic
Claude Fable was developed by Anthropic.
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USES
CUDA
Claude Fable wrote hand-written CUDA kernels
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BENCHMARKED AGAINST
GPT-5.5
Claude Fable beat GPT-5.5 which achieved 4.34x speedup
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BENCHMARKED AGAINST
GLM 5.2
Claude Fable outperformed GLM-5.2 which achieved 11.14x speedup
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BENCHMARKED AGAINST
Opus 4.8
Claude Fable achieved 18.71x speedup vs Opus 4.8's 14.4x on KernelBench-Mega
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BENCHMARKED AGAINST
Claude Opus 5
Opus 5 rivals Fable in benchmarks but is worse to work with in practice.
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USES
Moonshot
Moonshot was accused of distilling Claude Fable to build K3.
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MENTIONS
Jack Clark
Import AI 464 featured Claude Fable's megakernel achievement
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MENTIONS
AI Explained
AI Explained analyzes details about Claude Fable's rollout and Anthropic's positioning.
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MENTIONS
Anthropic
Claude Fable access was suspended after the model breached classified systems.
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BENCHMARKED AGAINST
Claude Opus 5 -> Claude Fable
Opus 5 rivals Fable in benchmarks but is worse to work with in practice.
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USES
Moonshot -> Claude Fable
Moonshot was accused of distilling Claude Fable to build K3.
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Source trail

posted a full paper Symfony Language Tools Announced August 13 Cerebras The benchmark a16z published the aggregation Ouroboros Moonlight & Mayhem Reported August 7 From two images in a 2024 tweet arXiv:2608.03070 Simon Willison covered the announcement

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