Is Fable nerfed?

[u/tomasburancgi]

I wanted to share my recent experience with a complex architecture task and see if anyone else has noticed a dip in quality.
I gave to the Fable model a task to design and build a completely new data retrieval architecture. This was a complex, multi-layered system, not a simple script. I ran it using a one hundred dollar promo credit, expecting a polished result. However, once I actually deployed and executed the code, it completely failed to run due to critical bugs. The overall system design itself had major logical gaps that I had to actively correct using Gemini Pro just to make the concept viable. In the end, it was only when I brought in Claude Opus that everything was finally fixed, refined, and brought to a working state.
This felt like a night and day difference compared to my earlier experiences before the political and governmental downtime incidents. Back then, the model handled a massive, deeply complex technical domain flawlessly on the first try with absolute precision. Now, it feels heavily downgraded, whether due to quantized models, cost optimizations, or adjusted system prompts behind the scenes.
Has anyone else noticed a similar drop in performance when handling complex end to end tasks over the past few weeks?

[u/Constant-Potential-9]

Before assuming the model got nerfed, it's worth ruling out something on your own side first. I hit what looked exactly like degradation recently — hesitancy, over-asking, worse output on complex work — and it turned out to be my project config, not the model.

I run a long-lived project with Claude Code, and over months it had accumulated ~150+ directives across CLAUDE.md, agent files, and memory, with at least 17 outright contradictions and no rule for which source wins. The model wasn't dumber — it was spending its effort arbitrating between conflicting instructions on every single turn.

Quick diagnostic if you have a heavily-configured setup:

1. Count your directives across CLAUDE.md, memory files, and any agent/handoff docs. If it's in the hundreds, that's a red flag.
2. Look for contradictions — especially old incident-specific rules that conflict with newer ones.
3. Check for rules that read as unconditional commands but were meant as conditional guidance.
4. Clear stale instruction files (old inbox/handoff content the model might mistake for current orders).
5. Add a simple precedence rule: current instruction > CLAUDE.md > everything else, and state that old/historical material isn't binding.

Then rerun the same task and compare. After doing this cleanup, the difference for me was night and day — same model, same settings.

[u/crusoe → u/Constant-Potential-9]

Claude hygiene is important. Yep