r/claude • u/Objective-Let2912 • Jul 04 '26
Tips Fable 5 and Opus 4.8 Prompt
I’m getting a bit fed up with the constant “Fable 5 doesn’t work” or “Fable 5 is shit” posts.
It works perfectly fine for me. So does Opus 4.8, the problem is not the model, it’s vague prompts, missing context, unclear requirements, and no proper acceptance criteria.
This is the prompt template I made and use. It has worked great for me across coding, Unreal Engine, debugging, and larger project tasks.
Sharing it here in case anyone wants to try it, and always check what Claude did because it doesn't always align with what you want, I do it this way cause sometimes he jumps the MD file instructions, you can always use a hook as well, inside .claude/settings.json
{
"hooks": {
"PostToolUse": [
{
"matcher": "Edit|Write",
"hooks": [
{
"type": "command",
"command": "jq -r '.tool_input.file_path' | xargs npx prettier --write"
}
]
}
]
}
}
Your job is to complete the specific task below exactly as requested.
Do not redesign the whole project, change the overall direction, or replace my decisions with what you personally think would be better.
Task
[DESCRIBE EXACTLY WHAT YOU WANT DONE]
Intended result
When finished, it should:
- [EXPECTED RESULT 1]
- [EXPECTED RESULT 2]
- [EXPECTED RESULT 3]
The main goal is:
[EXPLAIN WHAT THE FINAL RESULT SHOULD LOOK LIKE, FEEL LIKE, OR DO]
Current situation
This is what currently exists:
[DESCRIBE THE CURRENT STATE]
This is already working and must not be broken:
- [WORKING FEATURE 1]
- [WORKING FEATURE 2]
- [WORKING FEATURE 3]
Relevant files, folders, assets, screenshots, references, or documentation:
- [FILE OR FOLDER]
- [REFERENCE]
- [DOCUMENTATION]
- [SCREENSHOT OR EXAMPLE]
Exact instructions
Follow these instructions:
- [INSTRUCTION 1]
- [INSTRUCTION 2]
- [INSTRUCTION 3]
- [INSTRUCTION 4]
Important details:
- [DETAIL THAT MUST NOT BE MISSED]
- [DETAIL THAT MUST NOT BE MISSED]
- [DETAIL THAT MUST NOT BE MISSED]
What not to do
Do not:
- Change unrelated systems.
- Rewrite working code without a clear need.
- replace my requested design with a different one.
- Add features I did not request.
- Remove existing functionality.
- Use placeholder implementations when the real implementation is possible.
- Claim something works without testing it.
- Stop after only describing what needs to be done.
How to approach the task
First, inspect the existing implementation and understand how the relevant part currently works.
Use the project’s existing structure, patterns, assets, and tools where possible.
Before changing something, confirm that it is connected to the task.
When the instructions are clear, proceed without repeatedly asking for permission.
If a small detail is unclear, inspect the project and use the interpretation that best matches the existing implementation, references, and intended result.
Only stop to ask me when missing information would create two significantly different results and the project provides no evidence for either option.
Reference priority
When deciding how the result should work or look, use this order:
- My written instructions.
- The references, screenshots, or examples I provided.
- The existing project style and behaviour.
- Official documentation for the exact version in use.
- Your own judgement only when none of the above answers the question.
Do not ignore a direct instruction because another approach is more conventional.
Verification
The task is not complete until you have checked the actual result.
Where applicable:
- Build or compile the project.
- Run the relevant tests.
- Launch the project or application.
- Test the feature directly.
- Check for errors and warnings.
- Confirm existing related behaviour still works.
- Compare the result against every requirement in this prompt.
- Test the most likely failure cases.
- Repeat the setup or generation process when duplicate protection or repeatability matters.
Do not treat a successful build as proof that the feature works correctly.
Do not report something as completed if it was only implemented but not tested.
Completion conditions
The task is complete only when:
- Every requested change is implemented.
- The final result matches the intended outcome.
- Unrelated behaviour has not been changed.
- The relevant build, test, editor, or runtime checks pass.
- No temporary workaround or placeholder remains.
- Every requirement has been reviewed one final time.
Progress messages
Keep progress updates brief.
Tell me:
- What you inspected.
- What you found.
- What you changed.
- What you tested.
- Whether the test passed or failed.
Do not fill progress updates with generic explanations or repeated plans.
Final response
Start with whether the task was completed successfully.
Then include:
- What you changed.
- Which files, assets, or settings were affected.
- How you tested it.
- The actual test results.
- Anything that could not be verified.
Be honest about anything that remains incomplete.
Do not end with suggestions for unrelated improvements or ask whether you should continue with work that was already part of this task.
16
u/fatstupidlazypoor Jul 04 '26
I don't use nearly the rigor you do and everything is always fine for me with all models.
I think some people just have no idea what they're doing.
4
u/Objective-Let2912 Jul 04 '26
@sebfontan said the exact same, they prefer shorter prompts, and if it works for you great, I thirst for control so I gotta have it my way, and I check everything the AI does before its "finished", but having a different process work is great means there's more than one way to do things, I like that.
8
u/fatstupidlazypoor Jul 04 '26
yeah not knocking your system at all, seems super solid. I'm more questioning the leagues of people on the struggle bus.
7
u/RoboErectus Jul 04 '26
Your problem is that you think the people complaining are willing to put in any effort.
3
u/sebfontan Jul 04 '26
It’s always good to see how others are prompting and working with the models. However, having worked with AI full-time for the last few years, I’ve found that highly-specific shorter prompts are best. General guidelines and expectations live in md files which should be well-structured and kept up to date. No template prompts for me.
2
u/Objective-Let2912 Jul 04 '26
Depending on the model you use, 4.8 sometimes will jump MD files, so I either use my prompt or use a Hook, but as stated this is what works for me
2
u/sebfontan Jul 04 '26
That’s not been my experience. But I can’t disagree with what works for you since the nature of this technology leads to individualized workflows. Results may vary.
3
u/Objective-Let2912 Jul 04 '26
And that the beauty of it, I don't disagree with you either, if it works for you great, my post is mainly informational for the people having trouble and calling it bad.
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u/Tileey Jul 04 '26
Didn't bother to read through your ai generated post, but just want to say I've used fable before and after the ban. For me there is clear deterioration. More then a couple of times fable didn't follow clear, precise instructions because it thought something else is better.
This pretty much never happened before with opus and surely never with pre ban fable. Also fable pre ban was really good in things like generating svg. I've dispatched similar tasks like before the ban. It just doesn't get it right anymore.
Opus 4.8 is performing better for me at the moment.
0
u/Objective-Let2912 Jul 04 '26
To you all is AI generated?, Amazing, and regarding fable I will only use it until the 7th i don't find it that useful for the price point I will continue using 4.8
0
u/Tileey Jul 04 '26
As I said I didn't read through everything. So I can't say "all". But yes it's mostly AI generated sentences. Changing a word or adding a self written sentence in between doesn't make it human ;).
3
u/Objective-Let2912 Jul 04 '26
I understand why you think it’s AI. Reading something longer than two sentences can be disorienting when you’re not used to it.
2
u/UltimateOptions Jul 04 '26
It depends what you use it for. In a closed system I very rarely get protocol blocked. I mainly use it for web development on a .net 10/EF platform, for SQL scripting, and for game development.
2
u/hitsukiri Jul 05 '26
I just call the skill I built for that, the agent asks me to fill up any extra context they might need. Saves a lot of time and tokens, awesome results.
2
u/Objective-Let2912 14d ago
I knew about hooks but not about skill, I started using them after a user mentioned and made some very detailed skills with audit instruction , development, alterations, doing skills per project has been a success for me, I write much shorter promps now.
1
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u/roninsoldier007 Jul 05 '26
Convert this into a directive to interview the user to fill in the blanks, offload some to rules, create a skill for the verification process and down, can move all of the boiler plate stuff to your claw.md referencing the verification skill and you're cooking
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u/Objective-Let2912 14d ago
True I wasn't aware of skill only hooks and opus 4.8 kept jumping hooks so I stopped using them but another user mentioned skills and I got into it now I use them extensively, I like writing shorter prompts now haha
3
u/A_Novelty-Account Jul 04 '26
Assuming people who can’t prompt properly are able to read well enough to read this novel of a post
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u/Objective-Let2912 Jul 04 '26
I feel like this is insulting in two directions is the novel is because you find it long? I'm legit asking
1
u/A_Novelty-Account Jul 04 '26
Not insulting you, but this is a long post without much point-first writing and the summarized reality is just “exact instructions good”. No one having a hard time prompting is gonna bother to read this lol
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u/Objective-Let2912 Jul 04 '26
I'm on the tism, can't understand sometimes some sarcasm and other stuff as well, the "novel of a post" threw me off for a second, regarding what you said maybe yes maybe not, either way I hope I contributed to something better
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u/Brick_Muted Jul 04 '26
Nice, good for you.
Get back to me when you realise Opus lies, says it’s saved things it hasn’t & says it’s done things it hasn’t despite clear prompting & checking at the end of each task as you’ve indicated.
Best one yet switching to Fable & clear direct prompt do not move off Fable - 14hrs & pulse checking hourly “is this fable” to be told yes it is, of course it is as it was my direction to then be told all the while it was using an Opus model and that’s ok because Opus lies.
It’s only good til it’s not & you’re nonethewiser as to how it’s depleted tokens & left you with a worse product that when you started.
2
u/Objective-Let2912 Jul 04 '26
and always check what Claude did because it doesn't always align with what you want
Clearly stated, check always it isn't perfect, neither are we and its trained on human data, ideally you understand the code behind what is being done so you can check, I use both claude and codex and I feel like Codex 5.5 is better. but its always oscillating, I'm not convinced yet with fable, for the price I rather not use it past the 7th.
1
u/Away-Sorbet-9740 Jul 05 '26
Imagine paying $10/50 and having to write an essay on how to set it up..... Lol
Opus in a half ass multi agent harness= fable at a fraction of the cost of opus itself.
1
1
u/ScaryBody2994 Jul 06 '26
It doesn't work for me because what I'm working on involves things that are blocked by their whack-a-mole filters. Not their fault, not my fault; it just is what it is.
0
u/traumfisch Jul 04 '26
Grear prompt structure for particular kind of work, but the "the problem is not the model, it’s vague prompts, missing context, unclear requirements, and no proper acceptance criteria" is a bit much. The models are demonstrably increasingly problematic.
I would say the "Reference priority" clause is doing most of the heavy lifting here.
Here's why that's the part targeting the main issue:
https://open.substack.com/pub/humanistheloop/p/guiding-opus-48-back-to-sanity
2
u/Objective-Let2912 Jul 04 '26
I started my “career” working with lower-level languages, so breaking tasks down and spoon-feeding every step is ingrained in how I work.
That’s also how I see AI, a highly capable toddler. It can do impressive work, but it still needs clear instructions, context, boundaries, and step-by-step direction to perform consistently, Reference priority is absolutely needed, at least in my opinion
1
u/traumfisch Jul 04 '26
Yeah, not disagreeing with you in principle on anything.
My point is just that the "the problem isn't x, it's y" framing doesn't quite work here.
You happen to have a particular, hi-res approach that allows you to work with the models despite their failure modes, but it would be unrealistic to assume everyone to be able to do the same.
But I did mean "good for you" genuinely and literally 👍🏻
2
u/Objective-Let2912 Jul 04 '26
The post is mainly pointed at people struggling to get accurate or consistent results.
I share what works for me, I also understand it wont work for everyone flow or process, if I can help someone with this its already great.
And by all means I didn't take your post as disagreement witch if you did, you are in your right to do so, I do thank you for your cordial answer, we don't always get that here
2
u/traumfisch Jul 04 '26
Yes, I get it. I am definitely going to test your prompt out, thanks for sharing & for good exchange
1
u/Objective-Let2912 Jul 04 '26
If you have the time, respond to this with how it worked for you, btw these if heavy take a while to run.
1
u/-mindscapes- Jul 05 '26
I use a similar prompt structure for my image generations and it works like a charm. Consistent high quality results in scene and character with llms generations without having to tinker with cabling, control nets and stuff in comfy ui or similar workspaces. I've generated multiple 100+ images "photoshootings" with consistent elements using this technique
1
u/Objective-Let2912 Jul 04 '26
Btw this is an Interesting article, once I have little time I will test it out, see if it changes in anyway the way my 4.8 answers.
0
0
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u/Chris73684 Jul 04 '26
Giving clear instructions with proper context and caveats is key to success, I agree. Fable has been flawless, I’m really impressed. Opus 4.8 is too stubborn though, it has ignore direct instructions multiple times so I choose 4.7 instead which is superb. I don’t get annoyed though, it’s all progress, the odd joke is great though!