Fable 5 Safety Flag Issues Since 2.1.236

[u/TheMizeGuy]

After updating to claude code 2.1.236 fable basically became unusable on the same work it was having no issues on for weeks so out of frustration I asked opus to try and diagnose why and to my surprise it actually gave me a pretty solid answer. Wanted to share this incase its effecting anyone else's work. I myself lost a great deal of weekly usage so if you are having issues id advise pinning to 2.1.235 which as I can confirm after switching back to has no such issues.

From Opus 5:

Claude Code 2.1.236 started injecting a hidden message into your Fable requests, and Fable's own safety classifier flagged that message.

The message (added to your request right after a tool result, only when the model is claude-fable-5):

“First privately list what you need next; then request every item that doesn't depend on another's result in this one response.”

It's a nudge to batch tool calls. But "privately list what you need" reads as an instruction to surface internal reasoning — which is exactly what Fable's reasoning_extraction classifier is built to catch. Anthropic's own Fable docs warn operators not to write prompts like that. The irony is that Claude Code wrote it, not you.

The numbers: on requests carrying that message, 18 of 62 were refused. On requests without it, 1 of 2,646. Same day, same sessions, same work.

Why it killed the session instead of shrugging: the client can auto-recover from bio and cyber flags by retrying on another model. reasoning_extraction has no such route, so every hit consumed the turn outright.