Source Intelligence

DisclaimerUnofficial, and not affiliated with Anthropic. Nearly all of this is read straight out of what ships: npm bundles, captured prompts, published docs. Anthropic's own notes go in verbatim, marked as theirs. The rest is my reading, and every entry carries the strings behind it. If one looks wrong, vote it down and say why.

All of v2.1.170 Home All releases olderv2.1.169 v2.1.172newer

Fable 5 Launch Announcement Banner

Feature flag
tengu_saffron_lattice Not enough to say

Nothing here resolved what this flag was doing on this version, so nothing here should be read as on or off.

This account: no value returned · anonymous baseline: no value returned · compiled default in v2.1.170: not a boolean we can read

These values were read against a different version of Claude Code, so treat them as the nearest reading available instead of one taken on this release.

Read once, for one account on one subscription tier, against v2.1.170. It isn't a statement about your account. What a flag value here can and cannot tell you

What

First-party users who have Fable 5 available see a one-time "Fable 5 is here!" announcement at session start, replacing the old Opus 4.8 announcement.

Details
  • For users on Fable 5: "Fable 5 is here! Our newest model for complex, long-running work"
  • For users not yet on Fable 5 but with access to the picker: "Meet Fable 5, our newest model for complex, long-running work. Try anytime with /model."
  • If the account uses plan limits and the plan-limits end date is in the future: "Included in your plan limits until [date], then switch to usage credits to continue."
  • Controlled by the tengu_saffron_lattice feature flag (fields: enabled, planLimitsEndDate, hideRateLimitsDescription)
  • Shown once; suppressed after first view via tengu_fable5_launch_shown telemetry event
Evidence

Announcement component and feature flag (search for "Fable 5 is here!" and "tengu_saffron_lattice")

Strings lifted out of the shipped bundle, so the claim above can be checked against them.

Related

Other releases about the same thing. Found by shared names or similar wording; neither means one caused the other.

See this entry in the whole of v2.1.170 →