Entity trail

Claude Fable 5.1

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

Briefing refs

Findings

Edges

Sources

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

Corpus findings

2026-09-06 / reddit-researcherAstra debuts at #1 on Code Arena with a ~140 Elo lead, and the sub's own summary calls the chart misleadingThe 275-upvote r/ClaudeAI thread posts Astra and Fable 5.1 topping arena.ai's Code Arena, and the mod-bot summary after 50 comments is more useful than the chart: the y-axis starts at 1550, and the ~140-point lead over GPT-5.6 translates to roughly a 69% head-to-head win rate, not the visual gap. Commenters also note Elo is a zero-sum metric where a modest win-rate edge at the top says little about code quality, and that arenas test small one-shot projects. Practitioner reports split cleanly: 'almost one-shotted' a landing page on one side, burned an entire weekly limit without finishing on the other.
2026-09-06 / reddit-researcherRoboCurve put GPT-6 Astra on real robot arms: 19/20 on block-into-bowl versus Fable 5.1's 8/20, at 6x fewer output tokensRoboCurve ran 20 trials per model per task on bimanual I2RT YAM arms (6-DoF, parallel-jaw grippers) through Inspect Robots 0.58.0 and published results on 2026-09-04. Astra hit 19/20 on block-into-bowl against Claude Fable 5.1's 8/20 and Fable 5's 1/20, averaging 2.1k output tokens versus Fable 5.1's 12.9k, $0.94 versus $2.12 per run, and 2.5 minutes versus 6.8. The counterweight is the second task: on puzzle-piece-into-groove both Astra and Fable 5.1 managed 2/20, so precision manipulation is untouched and the headline number covers only the coarse task.
2026-09-06 / news-researcherFable 5.1 and Mythos 5.1 Quietly Broke `tool_choice` and Cut Cache Reads to a QuarterThe September 1, 2026 release notes for Claude Fable 5.1 and Mythos 5.1 confirm both keep the $10/$50 per million token price and add a 1M-token default context with 128k max output, while dropping cache read cost to $0.25 per million, a quarter of the rate on every other Claude model. The breaking change buried in the same notes: `tool_choice` types `any` and `tool` now return HTTP 400, so callers must move to strict tool use or structured outputs. Thinking blocks are also only preserved for equal or newer models, and replaying them to an earlier model gets the block rejected or dropped.
2026-09-06 / thought-leaders-researcherZvi Mowshowitz's Fable 5.1 capabilities review: Terminal-Bench-Science jumps 24.7% to 52.6%, but users report 3x token burnZvi published his capabilities review of Claude Mythos 5.1 and Fable 5.1 on September 5, separate from his earlier system-card post. He pulls out Terminal-Bench-Science rising from 24.7% to 52.6%, CursorBench 3.2 at 73.4% vs 70.5%, OSWorld 2.0 at 78% partial/42% strict, HLE at 60.9%, a cache-read price drop from $1 to $0.25 per million tokens, and a roughly 60% fall in safety-classifier false positives. The catch for builders on subscriptions: multiple users report Fable 5.1 consuming up to 3x the tokens of Fable 5, so cheaper per-token API pricing coexists with faster subscription-limit exhaustion.
2026-09-06 / projects-researcherArtificial Analysis pushed Intelligence Index v4.2 with private held-out test sets and dropped IFBench as saturatedAnnounced 2026-09-04 and at 156 points on HN, v4.2 is an interim release pulling forward parts of v5. It adds AA-Briefcase, an in-house agentic knowledge-work eval with a private held-out set, and Surge's GDP.pdf, a long-context eval over 4,592 PDF pages, while removing IFBench for no longer separating frontier models. The ten-eval composite now puts Claude Fable 5.1 at 57, GPT-6 Astra (max) at 55 and GPT-6 Astra (xhigh) at 54.
2026-09-05 / agents-researcherEEBench scores agents on real circuit boards with SPICE, and Claude Opus 5 leads at 61.6% while GPT-5.6 Sol trails at 39.4%EEBench, written up 2026-09-04, has models design circuit boards in atopile, a declarative electronics language, so agents work on components, connections and electrical constraints instead of navigating a CAD GUI. Grading is deterministic: it builds the design, constructs the circuit graph and bill of materials, runs SPICE and design-rule checks, and measures electrical performance across tolerance corners plus component availability, pricing and manufacturer specs pulled from datasheets. On the 2026-09-01 board Claude Opus 5 leads at 61.6%, followed by Grok 4.6 at 57.1%, Claude Fable 5.1 at 56.4%, Fable 5 at 54.3% and Opus 4.8 Max at 51.4%, with GPT-5.5 at 42.3% and GPT-5.6 Sol at 39.4%.
2026-09-05 / reddit-researcherFable 5.1 generated a 1km square game zone in Blender in one shot by chaining two MCP servers on its ownThe top r/ClaudeAI post of the day (1,136 upvotes, 276 comments) shows Fable 5.1 building a WoW-style region in Blender from a short prompt, and the detail worth noting is that it chose to call a second, local image-generation MCP server for textures without being told to. A parallel r/OpenAI thread at 922 upvotes puts the same class of Blender task side by side against GPT-6 Astra and calls the gap large. Both are eyeball comparisons with no controlled prompt, so treat them as evidence that multi-MCP tool chaining now works unprompted, not as a ranking.
2026-09-05 / reddit-researcherEpoch's FrontierMath Erdős benchmark: GPT-6 Astra solves 2 of 68 open problems, every other model scores zeroEpoch AI launched FrontierMath Erdős on September 1, built from 68 unsolved Erdős problems that Thomas Bloom picked out of roughly 652 in his catalog, with 50 already formalized in Lean via Google's Formal Conjectures and 18 newly formalized. Each attempt gets a fixed budget of $300 and 72 hours. GPT-6 Astra scored 3% by disproving one problem and proving another; GPT-5.6 Sol, GPT-5.5, Claude Fable 5.1 and Claude Fable 5 all ran out of budget with no verified proof, scoring 0%.
2026-09-05 / vibe-coding-researcherCopilot CLI now waits for managed settings before letting any MCP server startThe 1.0.83 stable notes state that enterprise-denied MCP servers can no longer start before the managed allow/deny policy resolves; server startup now waits for the managed-settings fetch instead of racing it. That race meant a denied server got a window to run at every launch, on exactly the slow-network conditions an attacker would find easiest to induce. The same release adds Client ID Metadata Document support for MCP OAuth sign-in and support for claude-fable-5.1.
2026-09-05 / sources-researcherfable-orchestrator: a 493-star MIT skill where Fable 5.1 plans and adjudicates but is barred from writing any codeCreated 2026-09-02 and at 493 stars by 09-05, this local-first routing skill for Codex splits roles hard: Claude Fable 5.1 plans and adjudicates and stays outside the implementation graph entirely, GPT-5.6 Luna does normal implementation, and DeepSeek V4 Flash handles loops and high-throughput iteration. It ships no proxy, dashboard, model catalog or credential store, consuming the callable opencode-go agents supplied by Codex Router instead. It is the same cost thesis as HydraFusion and Spotify's Portal reached from the opposite direction: this week's pattern is that the frontier model's job is deciding, not typing.
2026-09-05 / sources-researcherClaude produced the first end-to-end machine-checked proof of Fermat's Last Theorem: 13M lines of Lean, 30,300 theorems, 11 days, ~6B output tokensAnthropic published the result on 2026-09-04: an internal general-purpose research model roughly comparable to Claude Fable 5.1 formalized Fermat's Last Theorem in Lean over 11 days working largely autonomously, producing 13 million lines of Lean and 30,300 proved theorems (29,500 used in the final proof) at a cost of about 6 billion output tokens. The artifact is roughly 5x the size of Mathlib and Kevin Buzzard of Imperial College reviewed it, saying it proves the theorem with no assumptions beyond the axioms of mathematics. The buried practical detail for builders is the secondary result: three personal Claude Max plans driving the Prove2Me platform formalized Vinogradov's Three Primes Theorem in three days, so this is not purely a datacenter-scale stunt.
2026-09-05 / thought-leaders-researcherArtificial Analysis moves 40% of its Intelligence Index to private held-out sets, double v4.1The v4.2 update published September 4 adds AA-Briefcase, a private eval of agentic knowledge work on expert-built projects, and GDP.pdf, a document-reasoning test over 4,592 pages of tables, charts and footnotes. GPQA Diamond was dropped as saturated. Claude Fable 5.1 leads the overall index, GPT-6 Astra gained roughly 85 Elo over its predecessor and dominates GDP.pdf at 33.2%, and Meta ranks third among labs. The doubling of held-out weighting is the real signal: public benchmarks are being treated as compromised.

Graph relationships

BENCHMARKED AGAINST
Intelligence Index v4.2
Claude Fable 5.1 scored 57 points on Intelligence Index v4.2.
Source finding
DEPRECATES
tool_choice
Claude Fable 5.1 no longer supports tool_choice types 'any' and 'tool', returning HTTP 400.
Source finding
BENCHMARKED AGAINST
Claude Fable 5
Claude Fable 5.1 achieves 8/20 vs Claude Fable 5's 1/20 on block-into-bowl
Source finding
BENCHMARKED AGAINST
Astra
Astra achieves 19/20 on block-into-bowl vs Claude Fable 5.1's 8/20 at 6x fewer output tokens
Source finding
BENCHMARKED AGAINST
Intelligence Index
Claude Fable 5.1 leads Artificial Analysis's Intelligence Index overall.
Source finding
SUPPORTS
Copilot CLI
Copilot CLI added support for Claude Fable 5.1
Source finding
BENCHMARKED AGAINST
GPT-6 Astra
GPT-6 Astra scored 3% on FrontierMath while Claude Fable 5.1 and other models scored 0%.
Source finding
USES
MCP
Claude Fable 5.1 autonomously invoked a second MCP server for textures without explicit instruction.
Source finding
USES
Blender
Claude Fable 5.1 generated a WoW-style game region in Blender from a short prompt.
Source finding
USES
Simon Willison
Simon Willison used Claude Fable 5.1 with Max thinking at $3.30 cost for an SVG pelican generation.
Source finding
RELEASED
Anthropic
Anthropic released Claude Fable 5.1 with Max thinking capability.
Source finding
USES
Cline
Cline changed its default model from Claude Opus 5 to Claude Fable 5.1.
Source finding

Source trail

r/ClaudeAI (275 upvotes), r/OpenAI (327 upvotes), r/singularity (312 upvotes)RoboCurve (via r/singularity, 547 upvotes)Anthropic Release Notes Don't Worry About the Vase (Zvi Mowshowitz)Artificial Analysis EEBench r/ClaudeAI Epoch AI GitHub GitHub Anthropic Babylonian Twins Blog (via Hacker News)

Graph sources

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