Skip to content

[vercel-flags-core] add vercel client mode #498

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Open
luismeyer wants to merge 11 commits into
base: main
Choose a base branch
from
Open

[vercel-flags-core] add vercel client mode #498

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
11 commits
Select commit Hold shift + click to select a range
7332270
[vercel-flags-core] add vercel client mode
luismeyer Sep 14, 2026
923ea09
stuff
luismeyer Sep 15, 2026
da0b044
fix(flags-core): handle cancelled header refreshes and add changeset
luismeyer Sep 15, 2026
004baf8
fix
luismeyer Sep 15, 2026
0fd2f41
debug
luismeyer Sep 15, 2026
48afe11
feat(flags-core): add bundled source debug diagnostics
luismeyer Sep 15, 2026
25154ed
fix(flags-core): use singular flags config version headers
luismeyer Sep 16, 2026
3c12c2c
revert(flags-core): remove source debug logging
luismeyer Sep 16, 2026
b167598
fix(flags-core): use plural flags config version headers
luismeyer Sep 16, 2026
2e03f56
op
luismeyer Sep 16, 2026
4a190b1
Merge branch 'main' into flags-version-header
luismeyer Sep 17, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
5 changes: 5 additions & 0 deletions .changeset/header-driven-vercel-mode.md
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"@vercel/flags-core": minor
---

Add a header-driven `vercel` client mode that uses timestamps from the `x-vercel-flags-config-versions` or `flags-config-versions` request header instead of streaming or polling. Reuse fresh definitions, refresh in the background when the request version is up to 10 seconds newer than the cached configuration, and block for a refresh when the gap is larger. Deduplicate concurrent refreshes, allow retries after fetch failures, and discard late responses after shutdown.
5 changes: 5 additions & 0 deletions packages/vercel-flags-core/README.md
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -47,6 +47,11 @@ const client = createClient(process.env.FLAGS!, {
This option is sent only to the metrics ingestion endpoint. It does not select
the environment used for flag evaluation.

## Configuration version headers

@dferber90 dferber90 Sep 17, 2026

Copy link
Copy Markdown
Collaborator

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

i'd leave it out of the README, this is way too deep in the weeds


The header source reads `x-vercel-flags-config-versions` or `flags-config-versions`,
with the `x-vercel-` header taking precedence when both are present.

## OpenFeature

An OpenFeature-compatible provider is available at `@vercel/flags-core/openfeature`:
Expand Down
Loading
Loading