tengu_synthetic_fog
A Claude Code feature flag, read out of the shipped bundle. It was in the build from v2.1.284 and was gone by v2.1.323.
When a remote tool answer is too big, Claude Code now shrinks embedded images to fit before refusing, and the size limit can be set remotely
Not Anthropic's. This is the line from the earliest changelog entry here that named it, v2.1.284.
In the changelogs
4Releases whose published page names tengu_synthetic_fog.
-
v2.1.321
Built-in fallback for a remote setting changes from a file name to a number
The value Claude Code uses for one remote setting when the server sends nothing changed from "history.jsonl" to 8
gate cited by this entry, found in this entry's text
-
v2.1.319
Loading a saved session handles rewinds differently and can skip two reports
The saved-session loader has a new mode that skips two diagnostic reports, and rewind records now note where the cut was made
gate cited by this entry, found in this entry's text
-
v2.1.317
A remote setting's built-in fallback changed from 0 to "/cwd"
The value Claude Code uses for one remote setting when the server sends nothing changed from 0 to "/cwd"
gate cited by this entry, found in this entry's text
-
v2.1.284
Large images from remote machines are shrunk to fit instead of refused
When a remote tool answer is too big, Claude Code now shrinks embedded images to fit before refusing, and the size limit can be set remotely
gate cited by this entry, found in this entry's text
Gate readings
4| Release | Resolved | This account | Anonymous | Compiled default |
|---|---|---|---|---|
| v2.1.321 read on another version | Not enough to say | no value returned | no value returned | not a boolean we can read |
| v2.1.319 read on another version | Not enough to say | no value returned | no value returned | not a boolean we can read |
| v2.1.317 read on another version | Not enough to say | no value returned | no value returned | not a boolean we can read |
| v2.1.284 read on another version | Not enough to say | no value returned | no value returned | not a boolean we can read |
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
5| Read as | Reading | From | Until | Version installed |
|---|---|---|---|---|
| anonymous | 4259840 | 2026-10-17T05:30:04Z | 2026-11-12T21:35:04Z | v2.1.302 to v2.1.322 |
| this account | 4259840 | 2026-09-25T17:25:04Z | 2026-11-12T21:35:04Z | v2.1.282 to v2.1.322 |
| anonymous | no longer carried | 2026-10-17T05:25:57Z | 2026-10-17T05:25:57Z | v2.1.302 |
| anonymous | 4259840 | 2026-09-25T17:10:04Z | 2026-10-17T05:10:04Z | v2.1.282 to v2.1.302 |
| anonymous | 5242880 | 2026-09-25T17:00:05Z | 2026-09-25T17:00:05Z | v2.1.282 |
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
1The earliest release whose published evidence quoted tengu_synthetic_fog was v2.1.284, 28 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
2Build by build
36One 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.