Claude Fable 5

Fable 5.2 is available on all paid plans and generates output up to 30% faster than Fable 5.1. API prices are $8 per million input tokens and $40 per million output tokens.

Theo's request logs suggest a $200 Ultra plan provides about $3,000 in API-equivalent Fable 5.2 usage versus $15,000 for Opus. He also reports Fable is capped at half the weekly allowance.

Mythos 5.2's system card says training deliberately limited capabilities that could accelerate AI development. It also says METR evaluated a snapshot stronger at AI R&D than the released model.

Fable 5.2 leads GDPx at 16.4%, with gains concentrated in chip design and software engineering. SemiAnalysis reports average task costs rose 31% over Fable 5.1.

Anthropic says Fable 5.2 designed three devices, including their circuit boards, enclosures and software. All three reportedly worked without modifications after manufacturing.

Anthropic says Claude has assessed conversations for potential misuse after responding since June. It reports detecting 94% of high-priority cases flagged by a stronger classifier at a 1% false-positive rate.

Shreya Shankar describes a coding workflow built around human-reviewed RFCs, implementation routing by task size and separate bug review. Follow-ups explain section-by-section specs and restarting failed approaches.

Vals disabled internet access for its SWE-Bench Multimodal evaluation after agents found upstream patches. Scores fell by 21–35 points, with each model run once in mini-swe-agent.

Piotr Skalski reports Argon leads his detection and extraction tests at both effort levels. High-effort detection reached 85.1% accuracy at one-quarter Astra's cost, taking 19.6 seconds per image.

Astra's Elo fell during Peter Gostev's chess test, where agents can take notes and choose opponents. Later results suggest Opus improved, and GPT-6.1 Sol and Fable were added to the benchmark.

Google is rolling out Gemini 4 Argon through Fairwind to government users, vetted cyber defenders, and trusted testers. The model supports up to 1M output tokens and costs $2/M input and $10/M output.

Gergely Orosz said Claude downgraded benign Fable requests to Opus and capped output after classifying the work as risky. He traced one [bio] flag to a Google Sheet collecting public social-post replies.

Cognition says its SWE-2 coding model scored 50.0% on FrontierCode 1.1 Main, matching Fable 5.1 at 64% lower cost. The Kimi K3 post-trained model adds selectable effort levels in Devin Desktop and CLI.

Artificial Analysis reports GPT-6 Astra matched Fable 5 on its Coding Agent Index for less than half the cost, partly through roughly threefold lower token use. Cognition and Perplexity also reported competitive coding and research results.

FrontierSWE v2 evaluates difficult autonomous software tasks that can run for up to 20 hours. Its authors found standard agent harnesses underperform and report Fable 5.1 led evaluated models by more than 24 points.

GPT-5.6 Sol now costs $4 per million input tokens and $10 per million output tokens. Benchmark comparisons place Sol at 72.7% on DeepSWE for $6.47 per task, while OpenAI and AWS report lower successful-task costs for Terra in Kiro.

Together reports GLM-5.3 solved 87.6% of DeepSWE after four attempts for about $16, versus Fable 5 at 69.7% for $21.63. It estimates equal $100 budgets yield roughly 17 solved tasks for GLM-5.3 and three for Fable 5.

Claude Code users reported Fable 5 and Opus 5 sessions exhausting five-hour usage windows in about 6–10 minutes after automated tool calls. The reports tie the failures to agent loops and rate-limit economics, including one Reddit claim of 10.26M tokens, 15 calls, and no edits.

Agent Arena says Claude Opus 5 Max placed second and Opus 5 High placed third across more than 7,000 real agentic sessions. Practitioner reports remain mixed across harnesses and prompting styles.

Epoch said an AI-generated solution found a presentation for the absolute Galois group of the 2-adic numbers, marking the second FrontierMath open problem it says AI solved. The result was elicited with Fable 5 and also GPT-5.5 Pro, making it a benchmark milestone rather than a product release.

A U.S. tech adviser accused Moonshot AI of using Anthropic’s Fable to build Kimi K3, while China’s embassy denied related claims. Engineers questioned whether leaderboard results and missing logits fit a simple distillation story.

Artificial Analysis reports Kimi K3 averages 56.4 minutes, 83 turns, and 120k output tokens per AA-Briefcase task. Kilo also found UI-build outputs close to Claude Fable 5 at 29% of the cost.

Posts put Kimi K3 first on Arena's Frontend Code leaderboard but 4.37-5.29 months behind U.S. frontier models in one public estimate. Other evidence cited strong DeepSWE cost-performance and cybersecurity results.

Alibaba opened Qwen 3.8 Max Preview on Alibaba Cloud, Qwen Chat, Qoder and the web, describing it as a 2.4T model headed for open weights. Early testers praised vision results but disputed coding claims.

Posts citing Anthropic say Fable 5 will stay in Claude Max and Team Premium at 50% of limits. Pro and Team Standard move to credit access with a one-time $100 credit after July 20.

AlphaSignal's repair harness put Kimi K3 last at 53/67, while other tests ranked it high on DeepSWE, Vibe Code Bench, legal work, cyber, and CUDA kernels. Cost often beat Fable, but speed lagged.

OpenCode users reported complex DeepSeek V4 API prompts returning Fable-like outputs and CoT style, while simpler prompts did not. The evidence is community-led and disputed, so the claim remains unverified.

Reports described GPT-5.6 Sol adding needless abstractions and Fable spending quota on many subagents for small changes. The debate frames lighter setups and senior review as safeguards against agent-made tech debt.

Kimi K3 posted strong coding results, including rank #5 on Artificial Analysis and #3 on DeepSWE. Engineers disputed whether its lower token price offsets higher token use and slower throughput.

Starting July 20, Fable 5 is included in Claude Max and Team Premium at 50% of plan limits. Pro and Team Standard shift to credit-based access with a one-time $100 credit.

Anthropic said it resolved an issue that made Fable 5 unavailable in claude.ai and Claude Code after users reported lost access or credit prompts. ClaudeDevs said affected extra-usage customers would receive refunds plus matching credits.

Cursor users reported unintended Claude Opus, Sonnet, Fable, or API calls after selecting other settings. Reports included 22.6M-token burns, hard usage stops, and unexpected bills.

Testers say Kivine identifies with Moonshot/Kimi and produces strong frontend, coding, and spatial demos. Moonshot also teased Kimi K3, but the Arena claims remain unofficial.

Cognition said Devin Fusion now uses Fable 5 and saw lower cost per task than Opus 4.8. Practitioners cited Fable-led delegation patterns that cut token use, with caveats on serial debugging.

Fresh runs and charts put GPT-5.6 Sol high on SWE-Bench Pro and Design Arena, while Coding Agent Index and Amp reports emphasized cheaper strong configs. Results vary by harness, effort tier, and agent setup.

Fable-assisted JLens logs and a separate experiment tested how the proposed J-space forms and whether attention gradients into past tokens can be blocked. The reported blocking method worked in the setup but hurt performance, making it a research update rather than an engineering control.

Goodside and other testers shared chat links where GPT-5.6 Sol, and sometimes Claude Fable 5, hallucinated hidden messages in noise images or meaningless scribbles. Higher effort settings sometimes did better, but failures reproduced.

Anthropic extended Fable 5 on paid plans and raised Claude Code weekly limits by 50% through July 19 while keeping the half-week cap. Users still described the rolling access changes as disruptive.

Riley Goodside tested random-noise and scribble images with no hidden message. GPT-5.6 Sol often produced invented text, while Claude Fable 5 more often refused or identified the image as non-writing.

New benchmark posts put GPT-5.6 Sol at or near the top of DeepSWE and several coding/context evals. Cost reports placed Luna on the efficiency frontier, while Amp said replacing Opus with GPT-5.6 cut its average model costs ~50%.

ARC Prize, Artificial Analysis, CursorBench, and other tests reported strong GPT-5.6 Sol results, especially in coding-agent tasks. Results were uneven, with smaller gains in document parsing and some UI or puzzle evals.

Posts say Sol, Terra, and Luna are set for a July 9 launch. One report says Sol was added to the Codex codebase as OpenAI’s strongest model for code, research, and documents.

SpaceXAI launched Grok 4.5 in Cursor and several agent tools with $2/M input and $6/M output pricing. Early evals place it near frontier coding models, with 51% on AutomationBench-AA.

ClaudeDevs reports Sonnet 5 with a Fable 5 advisor reached ~92% of Fable 5's SWE-bench Pro score at ~63% of the price. Other builders route implementation to Sonnet, Codex, GPT-5.5, or GLM workers.

Anthropic says paid Claude plans keep Fable 5 access until July 12, with Fable use capped at 50% of weekly limits. Users still reported exhausted quotas and multiple Max subscriptions as workarounds.

Artificial Analysis launched an independent Zapier AutomationBench leaderboard with 657 tasks across 40 simulated SaaS apps. Claude Fable 5 and Opus 4.8 led, but models still violated business guardrails.

Fable 5 users said Claude Max subscription access runs through July 7, with some reporting it may return only when compute is available. The deadline changed planning for Fable-heavy coding runs and fallback options.

Practitioners reported concrete Fable 5 coding outcomes, including sqlite-utils 4.0rc2 for $149.25 and hallucinations in X API and OAuth checks. Failures around tests, finance, production outages, and token-heavy loops kept review systems central.

CAIS and Scale’s Remote Labor Index reportedly put Fable 5 at 16.1% human-accepted freelance tasks, versus 8.3% for Opus 4.8 and 6.3% for GPT-5.5. The same report says AI judges overrated newer models, especially GPT-5.5 and Opus 4.8.

Condense.chat opened a compression proxy that strips tokens with Helene 1 and compacts settled agent loops with Adeline 1 to about 9% of their size. The service claims 100M saved tokens and 3× plan extension for Claude or Codex users, so test it on non-sensitive workflows first.