Claude Fable 5

What hackers pick instead

• Claude OpusRecommended as a top coding model that fixes bugs and ships features with fewer mistakes than earlier LLMs, though critics cite weak architecture choices, usage limits and confident errors.3331recommend
• OpenAI GPTRecommended for strong coding, debugging and research help with good reasoning and token efficiency, though critics cite hallucinations, overcomplication, verbose output and high cost.1205recommend
• Claude SonnetA capable coding model that has improved noticeably with each version and is faster and cheaper than Opus, though it needs careful supervision and usage limits bite.854recommend
• DeepSeek V4 FlashA very cheap, fast model that people find close to frontier quality for coding and everyday tasks; critics say it errs more, loops, and needs steering.828recommend
• FableRecommended as a top coding model for hard, long-running tasks and large refactors, though critics cite over-engineered code, costly usage limits and safety guards that switch models mid-task.823recommend

Every quote

The 40 most detailed of 2381 comments. Each links to the original.

1. Useful interactively in coding agent but boy if you have a kind of task that Fable can do in an agentic loop that Opus can't then you're in a good place.

   Recommends · Jul 2026 · in “Redeploying Fable 5”

2. Fable was in a different league. Especially when tasked with long horizon goals that involved reasoning at a high and low level to solve the task.

   Recommends · Jun 2026 · in “US Government directive to suspend access to Fable 5 and Mythos 5”

3. I think the results wouldn't be so different if you manually challenged 4.6 with enough iterations of logs, screenshots, and follow up questions.

   Mixed · Jun 2026 · in “Claude Fable is relentlessly proactive”

4. Fable 5.1 found the cause of a rare crash on their internal systems that none of their engineers (or any other model) had been able to explain

   Recommends · Sep 2026 · in “Claude Fable 5.1 and Claude Mythos 5.1”

5. I had good experiences doing multi-hour refactoring/housekeeping tasks that basically consisted of applying the same steps and rules n times.

   Recommends · Jun 2026 · in “Claude Fable 5: mid-tier results on coding tasks”

6. this feels like the difference between having a post-doctoral colleague and educating a student that I have to constantly guide and correct

   Recommends · Jun 2026 · in “US Government directive to suspend access to Fable 5 and Mythos 5”

7. Limiting it to half the weekly limit stings, but if you have a quota reset in the middle of it you still get effectively one weekly limit.

   Mixed · Jul 2026 · in “Claude Fable 5 Promotional Access”

8. you should probably be doing this discussion work along with Fable 5. It will give good feedback if you're working on the correct things.

   Recommends · Aug 2026 · in “Databricks drove down AI coding spend 70%”

9. these guardrails are counter productive for well intentioned cyber security, because I can't use it to test and harden my own software

   Mixed · Jun 2026 · in “Anthropic apologizes for invisible Claude Fable guardrails”

10. it was pretty impressive that it could consume four pages of KiCad schematic and reconstruct the full topology and theory of operation

    Mixed · Jun 2026 · in “Claude Fable 5: mid-tier results on coding tasks”

11. The writing style has significantly improved, however the token burn rate for tasks I have been working on seems to have skyrocketed.

    Mixed · Sep 2026 · in “Claude Fable 5.1 and Claude Mythos 5.1”

12. This has been a much better rollout. The tool calling is not broken out of the gate like 4.8 was, and the tokens generation is fast.

    Recommends · Jun 2026 · in “Claude Fable 5”

13. Claude Fable produces Masters-degree level output, and then I spend lots of round trips asking it to explain different parts to me.

    Mixed · Aug 2026 · in “Maximizing the value of your Claude Code sessions”

14. I have been using fable to try to collect cutting edge math in one area and work on a hopefully new result with lean verification.

    Recommends · Jun 2026 · in “US Government directive to suspend access to Fable 5 and Mythos 5”

15. It seems mathematics has at least gotten a powerful new tool to automate the work to cascade results after breakthroughs are made.

    Recommends · Jul 2026 · in “Claude Fable produced a counterexample to the Jacobian Conjecture”

16. Fable actually returned a result that fails and confidently stated it ran X, Y, Z tests to ensure it works and got these results.

    Mixed · Jun 2026 · in “Claude Fable 5: mid-tier results on coding tasks”

17. Still does not crack my hardest nuts. Gave it one of them and it blew through my entire allowance on thinking about one question

    Mixed · Jun 2026 · in “Claude Fable 5”

18. Claude Fable will act a whole lot more aggressively in pursuit of the goals that you set it than other models I've worked with.

    Mixed · Jun 2026 · in “Claude Fable is relentlessly proactive”

19. it might be much better on all dimensions (speed, cost, quality) to just use Fable 5 on low/medium effort than switch to Opus

    Recommends · Jun 2026 · in “Claude Fable 5”

20. Fable on "high" is producing substantially better results than Open 4.8 on xhigh for me and my actual real-world evals today.

    Recommends · Jun 2026 · in “Claude Fable 5”

21. Claude's response has been degraded for innocuous research projects concerning population-level analyses of astronaut health.

    Mixed · Sep 2026 · in “Claude Fable 5.1 and Claude Mythos 5.1”

22. it was the first time when the model was able to catch up with my abandoned compiler project, and it did it extremely well

    Recommends · Jun 2026 · in “US Government directive to suspend access to Fable 5 and Mythos 5”

23. Fable seems to be a larger model. It costs more to run and does not seem superior for _typical_ software engineering work.

    Mixed · Jul 2026 · in “Fable 5 vs. GPT-5.6 Sol on an NP-Hard Problem: Does /goal help?”

24. I don't get any sycophancy from it. The conversations are actually quite good, and it'll push back if it thinks I'm wrong.

    Recommends · Jul 2026 · in “Claude Fable produced a counterexample to the Jacobian Conjecture”

25. They all work, they all are "good", they all are both "smart" and commit incredible basic mistakes a fair amount of times.

    Mixed · Sep 2026 · in “Claude Fable 5.1 and Claude Mythos 5.1”

26. Now it definitely seems to have figured out stuff that would have taken me more time than I have to spare on this problem

    Recommends · Jun 2026 · in “Claude Fable 5”

27. Fable isn't a good coding workhorse. That doesn't mean it's not good for actually complex problems and long horizon tasks

    Mixed · Jun 2026 · in “Claude Fable 5: mid-tier results on coding tasks”

28. I use these models as research assistants when writing lots of random blog posts ... and Fable 5 is a serious improvement

    Recommends · Jul 2026 · in “Kimi K3, and what we can still learn from the pelican benchmark”

29. fable and friends are useful for long-term agentic stuff like orchestrating glm-5.3 flash implementers and verifying them

    Recommends · Sep 2026 · in “Claude Fable 5.1 and Claude Mythos 5.1”

30. Fable 5's safeguards flagged this message. Our intentionally broad safeguards deliver more capabilities but can also flag safe coding, cybersecurity, and biology tasks.

    Criticizes · Jul 2026 · in “OpenAI and Hugging Face partner to address security incident”

31. It cannot be used to develop applications. Every application needs to be secure in some way, and any such mention in a review triggers Fable's upsell feature.

    Criticizes · Sep 2026 · in “Claude Fable 5.1 and Claude Mythos 5.1”

32. Fable post-ban was never the same. At the least, whatever system prompt munging or pre/post filtering they did to strengthen the guardrails nerfed it.

    Criticizes · Sep 2026 · in “Fable 5 – Median thinking declined in August”

33. I get to prompt it like 5 times on my subscription before it gets cut off, and even then I'm constantly fighting the insufferable safety classifier.

    Criticizes · Jul 2026 · in “Qwen3.8 is launching and going open-weight soon”

34. literally any mention of creating a program that does genome alignment (something I have a legitimate need for) is resulting in a switch to opus.

    Criticizes · Jun 2026 · in “Claude Fable 5”

35. this is backfiring in many ways including safety of your code because it may fail successfully if your context contains something they don't like

    Criticizes · Jun 2026 · in “Anthropic apologizes for invisible Claude Fable guardrails”

36. Silent sandbagging is not acceptable, especially given they've shown with this release their safety filters have HUGE amounts of false positives

    Criticizes · Jun 2026 · in “If Claude Fable stops helping you, you'll never know”

37. Unlike our interventions for cybersecurity, biology and chemistry, and distillation attempts, these safeguards will not be visible to the user.

    Criticizes · Jun 2026 · in “Claude Fable 5”

38. A simple code review of the most critical areas of my project got flagged as a cybersecurity risk. It really made me not want to try it again.

    Criticizes · Jun 2026 · in “Claude Fable 5”

39. It's not sabotaging it by using a worse model but by changing your prompt in your background, which means it silently destroys your code.

    Criticizes · Jun 2026 · in “Cybersecurity researchers aren't happy about the guardrails on Anthropic's Fable”

40. keeping the limits and duration the same as before the ban (or slightly being more generous with them) would have been a really cheap way

    Criticizes · Jul 2026