[Bug]: REST API queries fail when the response headers exceed 8 KB

[amelia-c0n]

Is there an existing issue for this?

• I have searched the existing issues

Description

REST API queries fail with:
WebClientRequestException: HTTP header is larger than 8192 bytes.
This happens even when the response body is tiny. Appsmith’s REST client uses Netty’s default 8 KB limit for the full response header block, and that limit is not configurable.

Google Sheets CSV endpoints (/gviz/tq and /export) now send ~8.5–9 KB of headers, so public-sheet REST queries that used to work now fail. The same error will affect any API that returns large headers.

Expected: The query succeeds and returns the body. Header size should be in line with the server’s 16 KB inbound limit, or at least high enough for common providers.

Discord thread - https://discord.com/channels/725602949748752515/1519709170570366976

Steps To Reproduce

1. Create a REST API GET query to
   https://docs.google.com/spreadsheets/d/1gwEWMgnEQcR_XgMhX6htmVK5ga6asXsI48WAkqsV_Ho/gviz/tq?tqx=out:csv&sheet=fruits
2. Run the query.
3. See HTTP header is larger than 8192 bytes.
   The /export?format=csv&gid=0 URL on the same sheet fails the same way.

Public Sample App

No response

Environment

Production

Severity

Medium (Frustrating UX)

Issue video log

No response

Version

v2.5

[linear-code]

APP-15963