tengu_silly_waterfall
A Claude Code feature flag, read out of the shipped bundle. It has been in the build since v2.1.271, including the newest one read.
A gated fix can now remove stale leftover transcript entries when resuming a headless session
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.271.
In the changelogs
4Releases whose published page names tengu_silly_waterfall.
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v2.1.317
An unsent prompt is no longer always removed when a remote session resumes
When a remote session resumes, an unsent prompt can now stay in the conversation marked as a placeholder instead of always being removed
gate cited by this entry
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v2.1.295
Transcript tail cleanup now passes over empty SessionStart hook entries
A switchable cleanup of trailing transcript messages no longer stops at empty SessionStart hook progress or success entries
gate cited by this entry
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v2.1.273
Duplicate 'waterfall' assistant/system messages pruned from transcript, gated by tengu_silly_waterfall
A gated cleanup step now removes stray duplicate 'waterfall' messages from the conversation transcript
gate cited by this entry, found in this entry's text
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v2.1.271
New gated cleanup for stale waterfall-style transcript entries: tengu_silly_waterfall
A gated fix can now remove stale leftover transcript entries when resuming a headless session
gate cited by this entry, found in this entry's text
Gate readings
4| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.317 read on another version | Off by default, switched on for this account | on | on | off |
| v2.1.295 read on another version | Off by default, switched on for this account | on | on | off |
| v2.1.273 read on another version | Off in both readings | off | off | off |
| v2.1.271 read on another version | Not enough to say | no value returned | no value returned | off |
Two arms, because they disagree: this account is the one account this site reads and anonymous is a baseline with no identity attached. A reading says nothing about your account, and off cannot rule out a rollout both readings sit outside of. What these readings can and cannot show.
Flag server, over time
8| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| anonymous | on | 2026-10-17T05:30:04Z | 2026-11-06T10:30:06Z | v2.1.302 to v2.1.318 |
| this account | on | 2026-09-18T15:25:04Z | 2026-11-06T10:30:06Z | v2.1.276 to v2.1.318 |
| anonymous | no longer carried | 2026-10-17T05:25:57Z | 2026-10-17T05:25:57Z | v2.1.302 |
| anonymous | on | 2026-09-18T14:30:05Z | 2026-10-17T05:10:04Z | v2.1.276 to v2.1.302 |
| this account | off | 2026-09-15T03:05:04Z | 2026-09-18T14:30:05Z | v2.1.272 to v2.1.276 |
| anonymous | off | 2026-09-15T18:05:05Z | 2026-09-18T14:00:05Z | v2.1.272 to v2.1.276 |
| anonymous | on | 2026-09-15T17:40:05Z | 2026-09-15T18:00:06Z | v2.1.272 |
| anonymous | off | 2026-09-15T02:50:04Z | 2026-09-15T16:25:04Z | v2.1.272 |
One row per unbroken stretch of one reading, newest first, from snapshots taken every twenty-five minutes or so. No longer carried is not off: it means the flag server stopped returning the gate at all, which is what a retired experiment looks like. The version column is what was installed when the reading was taken, not what caused it.
First cited
3The earliest release whose published evidence quoted tengu_silly_waterfall was v2.1.271, 14 Sep 2026. That is the oldest release this project wrote about it, so it is a floor on the name's age and not the release that introduced it. It is not a presence reading: which builds carried the name is the table below.
Presence across releases
1Build by build
45One row per release since the first build this name was read out of. Absent means the build was read and the name was not in it, never mined means no bundle for that release was ever archived, and a declared type or a default is only ever what that release's own bundle stated.
Read out of the published npm bundle release by release, and out of Anthropic's own documentation as this site captured it. Nothing on this page is a description anybody here wrote about what the feature flag does. All feature flags.