feat: support per-mode FDv1 fallback configuration by kinyoklion · Pull Request #1246 · launchdarkly/js-core

kinyoklion · 2026-04-06T21:13:03Z

The FDv1 fallback polling interval and endpoints are now configurable per connection mode instead of using a single global pollInterval. Background mode defaults to 1 hour, foreground modes default to 5 minutes. When a user overrides a mode without specifying fdv1Fallback, the built-in default is preserved.

Note

Medium Risk
Moderate risk because it changes how the FDv1 fallback synchronizer is constructed (poll interval and service endpoints) based on per-mode configuration, which could affect data sync behavior across modes. Changes are scoped and covered by new validation and data manager tests.

Overview
Adds per-connection-mode configuration for the FDv1 polling fallback via a new ModeDefinition.fdv1Fallback (poll interval + endpoint overrides) and exports FDv1FallbackConfig.

Updates the built-in MODE_TABLE to include FDv1 fallback defaults (5 min for foreground modes, 1 hr for background) and extends validation (modeDefinitionValidators, recordOf defaults precedence, and top-level dataSystem defaults) so partial mode overrides preserve these built-in fallback defaults.

Changes FDv2DataManagerBase to build the FDv1 fallback synchronizer using the mode’s fdv1Fallback poll interval and optional per-mode ServiceEndpoints, and adds tests covering defaulting/merging and correct poll interval selection for background mode and endpoint-only overrides.

^{Reviewed by Cursor Bugbot for commit 749c59f. Bugbot is set up for automated code reviews on this repo. Configure here.}

The FDv1 fallback polling interval and endpoints are now configurable per connection mode instead of using a single global pollInterval. Background mode defaults to 1 hour, foreground modes default to 5 minutes. When a user overrides a mode without specifying fdv1Fallback, the built-in default is preserved.

github-actions · 2026-04-06T21:14:32Z

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25661 bytes
Compressed size limit: 29000
Uncompressed size: 126143 bytes

github-actions · 2026-04-06T21:14:54Z

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 179221 bytes
Compressed size limit: 200000
Uncompressed size: 830035 bytes

github-actions · 2026-04-06T21:14:54Z

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 31733 bytes
Compressed size limit: 34000
Uncompressed size: 112845 bytes

github-actions · 2026-04-06T21:14:57Z

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 37166 bytes
Compressed size limit: 38000
Uncompressed size: 204365 bytes

kinyoklion · 2026-04-06T21:24:28Z

bugbot review

A partial fdv1Fallback override (e.g. only endpoints) no longer discards the mode's default pollInterval. The merge now spreads the default fallback config under the user override at the field level.

kinyoklion · 2026-04-06T21:41:29Z

bugbot review

cursor

✅ Bugbot reviewed your changes and found no new issues!

Comment @cursor review or bugbot run to trigger another review on this PR

^{Reviewed by Cursor Bugbot for commit 118f816. Configure here.}

joker23 · 2026-04-06T22:11:47Z

  setFlushCallback(callback: () => void): void;
 }

+function mergeModeTables(


Wouldn't the validator already handle most of what this function is doing?

Not as it is, but I am looking into it.

There was already a mode merge for modes that weren't defined.
There are defaults for incorrect definitions.
But not validation time defaults exactly.

joker23 · 2026-04-06T22:59:53Z

going to approve since the potential validator redundancy comment should be a nit imo

Wire MODE_TABLE as the default for connectionModes in the dataSystem validator so per-mode fdv1Fallback defaults (pollInterval, endpoints) are filled in during validation. This removes the mergeModeTables function and restores the simple spread merge in FDv2DataManagerBase. Also adds a defaults option to recordOf (matching validatorOf pattern) for compound validators that need built-in defaults.

Add direct unit tests for the recordOf built-in defaults option in validateOptions.test.ts. Add integration tests in LDClientDataSystemOptions.test.ts verifying fdv1Fallback defaults flow through the full dataSystem validation pipeline.

Remove the FDv2DataManagerBase test that hardcoded validated output instead of testing the actual validation path. Add comprehensive fdv1Fallback permutation tests to the dataSystem validation suite covering: interval only, endpoints only, both, empty object, non-number pollInterval, non-string endpoint URIs, and non-object fdv1Fallback. Each verifies that defaults are filled in and invalid values are dropped with warnings.

devin-ai-integration

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

View in Devin Review to see 4 additional findings.

🤖 I have created a release *beep* *boop* --- <details><summary>akamai-edgeworker-sdk-common: 2.0.18</summary> ## [2.0.18](akamai-edgeworker-sdk-common-v2.0.17...akamai-edgeworker-sdk-common-v2.0.18) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common bumped from ^2.18.3 to ^2.18.4 </details> <details><summary>akamai-server-base-sdk: 3.0.19</summary> ## [3.0.19](akamai-server-base-sdk-v3.0.18...akamai-server-base-sdk-v3.0.19) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/akamai-edgeworker-sdk-common bumped from ^2.0.17 to ^2.0.18 * @launchdarkly/js-server-sdk-common bumped from ^2.18.3 to ^2.18.4 </details> <details><summary>akamai-server-edgekv-sdk: 1.4.21</summary> ## [1.4.21](akamai-server-edgekv-sdk-v1.4.20...akamai-server-edgekv-sdk-v1.4.21) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/akamai-edgeworker-sdk-common bumped from ^2.0.17 to ^2.0.18 * @launchdarkly/js-server-sdk-common bumped from ^2.18.3 to ^2.18.4 </details> <details><summary>browser: 0.1.14</summary> ## [0.1.14](browser-v0.1.13...browser-v0.1.14) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk bumped from 4.4.1 to 4.5.0 </details> <details><summary>browser-telemetry: 1.0.30</summary> ## [1.0.30](browser-telemetry-v1.0.29...browser-telemetry-v1.0.30) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/js-client-sdk bumped from 4.4.1 to 4.5.0 </details> <details><summary>cloudflare-server-sdk: 2.7.18</summary> ## [2.7.18](cloudflare-server-sdk-v2.7.17...cloudflare-server-sdk-v2.7.18) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common-edge bumped from 2.6.16 to 2.6.17 </details> <details><summary>fastly-server-sdk: 0.2.10</summary> ## [0.2.10](fastly-server-sdk-v0.2.9...fastly-server-sdk-v0.2.10) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common bumped from 2.18.3 to 2.18.4 </details> <details><summary>jest: 1.0.9</summary> ## [1.0.9](jest-v1.0.8...jest-v1.0.9) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/react-native-client-sdk bumped from ~10.15.1 to ~10.15.2 </details> <details><summary>js-client-sdk: 4.5.0</summary> ## [4.5.0](js-client-sdk-v4.4.1...js-client-sdk-v4.5.0) (2026-04-14) ### Features * add retry logic to FDv2 polling initializer ([#1230](#1230)) ([fe8bd37](fe8bd37)) * expose setConnectionMode on browser SDK ([#1232](#1232)) ([9019808](9019808)) * FDv2 contract test wiring, suppressions, and example app, cleanup configuration exports. ([#1225](#1225)) ([c67c5f6](c67c5f6)) * wire FDv2 data manager into BrowserClient ([#1222](#1222)) ([0b855f0](0b855f0)) ### Bug Fixes * FDv2 - Support dynamic reconnect URL for streaming. Handle 'error' event types for SSE. ([#1252](#1252)) ([4ef6cdd](4ef6cdd)) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk-common bumped from 1.23.0 to 1.24.0 </details> <details><summary>js-client-sdk-common: 1.24.0</summary> ## [1.24.0](js-client-sdk-common-v1.23.0...js-client-sdk-common-v1.24.0) (2026-04-14) ### Features * add retry logic to FDv2 polling initializer ([#1230](#1230)) ([fe8bd37](fe8bd37)) * expose setConnectionMode on browser SDK ([#1232](#1232)) ([9019808](9019808)) * FDv2 contract test wiring, suppressions, and example app, cleanup configuration exports. ([#1225](#1225)) ([c67c5f6](c67c5f6)) * FDv2DataManagerBase for mode switching and data source lifecycle ([#1210](#1210)) ([8f8051c](8f8051c)) * support per-mode FDv1 fallback configuration ([#1246](#1246)) ([9956bce](9956bce)) * wire FDv2 data manager into BrowserClient ([#1222](#1222)) ([0b855f0](0b855f0)) ### Bug Fixes * FDv2 - Support dynamic reconnect URL for streaming. Handle 'error' event types for SSE. ([#1252](#1252)) ([4ef6cdd](4ef6cdd)) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-sdk-common bumped from 2.24.0 to 2.24.1 </details> <details><summary>js-sdk-common: 2.24.1</summary> ## [2.24.1](js-sdk-common-v2.24.0...js-sdk-common-v2.24.1) (2026-04-14) ### Bug Fixes * FDv2 - Support dynamic reconnect URL for streaming. Handle 'error' event types for SSE. ([#1252](#1252)) ([4ef6cdd](4ef6cdd)) </details> <details><summary>js-server-sdk-common: 2.18.4</summary> ## [2.18.4](js-server-sdk-common-v2.18.3...js-server-sdk-common-v2.18.4) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-sdk-common bumped from 2.24.0 to 2.24.1 </details> <details><summary>js-server-sdk-common-edge: 2.6.17</summary> ## [2.6.17](js-server-sdk-common-edge-v2.6.16...js-server-sdk-common-edge-v2.6.17) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common bumped from 2.18.3 to 2.18.4 </details> <details><summary>node-server-sdk: 9.10.11</summary> ## [9.10.11](node-server-sdk-v9.10.10...node-server-sdk-v9.10.11) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common bumped from 2.18.3 to 2.18.4 </details> <details><summary>node-server-sdk-dynamodb: 6.2.23</summary> ## [6.2.23](node-server-sdk-dynamodb-v6.2.22...node-server-sdk-dynamodb-v6.2.23) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/node-server-sdk bumped from 9.10.10 to 9.10.11 * peerDependencies * @launchdarkly/node-server-sdk bumped from >=9.4.3 to >=9.10.11 </details> <details><summary>node-server-sdk-otel: 1.3.11</summary> ## [1.3.11](node-server-sdk-otel-v1.3.10...node-server-sdk-otel-v1.3.11) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/node-server-sdk bumped from 9.10.10 to 9.10.11 * peerDependencies * @launchdarkly/node-server-sdk bumped from >=9.4.3 to >=9.10.11 </details> <details><summary>node-server-sdk-redis: 4.2.23</summary> ## [4.2.23](node-server-sdk-redis-v4.2.22...node-server-sdk-redis-v4.2.23) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/node-server-sdk bumped from 9.10.10 to 9.10.11 * peerDependencies * @launchdarkly/node-server-sdk bumped from >=9.4.3 to >=9.10.11 </details> <details><summary>react-native-client-sdk: 10.15.2</summary> ## [10.15.2](react-native-client-sdk-v10.15.1...react-native-client-sdk-v10.15.2) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk-common bumped from 1.23.0 to 1.24.0 </details> <details><summary>react-sdk: 0.2.0</summary> ## [0.2.0](react-sdk-v0.1.1...react-sdk-v0.2.0) (2026-04-14) ### Features * adding isomorphic provider to bridge client and server ([#1218](#1218)) ([d766f39](d766f39)) * support static client component rendering ([#1227](#1227)) ([6b3a100](6b3a100)) ### Bug Fixes * adding wrapper name for react client ([#1199](#1199)) ([f92a8f9](f92a8f9)) * **deps:** update dependency next to v16.2.3 [security] ([#1263](#1263)) ([10f582a](10f582a)) * **react-sdk:** double evaluation on client side init ([#1229](#1229)) ([6a4c42f](6a4c42f)) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-client-sdk bumped from ^4.4.1 to ^4.5.0 * @launchdarkly/js-server-sdk-common bumped from ^2.18.3 to ^2.18.4 </details> <details><summary>server-sdk-ai: 0.16.8</summary> ## [0.16.8](server-sdk-ai-v0.16.7...server-sdk-ai-v0.16.8) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/js-server-sdk-common bumped from 2.18.3 to 2.18.4 * peerDependencies * @launchdarkly/js-server-sdk-common bumped from 2.x to 2.18.4 </details> <details><summary>server-sdk-ai-langchain: 0.5.4</summary> ## [0.5.4](server-sdk-ai-langchain-v0.5.3...server-sdk-ai-langchain-v0.5.4) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/server-sdk-ai bumped from ^0.16.7 to ^0.16.8 * peerDependencies * @launchdarkly/server-sdk-ai bumped from ^0.15.0 || ^0.16.0 to ^0.16.8 </details> <details><summary>server-sdk-ai-openai: 0.5.4</summary> ## [0.5.4](server-sdk-ai-openai-v0.5.3...server-sdk-ai-openai-v0.5.4) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/js-server-sdk-common bumped from 2.18.3 to 2.18.4 * @launchdarkly/server-sdk-ai bumped from ^0.16.7 to ^0.16.8 * peerDependencies * @launchdarkly/server-sdk-ai bumped from ^0.15.0 || ^0.16.0 to ^0.16.8 </details> <details><summary>server-sdk-ai-vercel: 0.5.4</summary> ## [0.5.4](server-sdk-ai-vercel-v0.5.3...server-sdk-ai-vercel-v0.5.4) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * devDependencies * @launchdarkly/server-sdk-ai bumped from ^0.16.7 to ^0.16.8 * peerDependencies * @launchdarkly/server-sdk-ai bumped from ^0.15.0 || ^0.16.0 to ^0.16.8 </details> <details><summary>shopify-oxygen-sdk: 0.1.8</summary> ## [0.1.8](shopify-oxygen-sdk-v0.1.7...shopify-oxygen-sdk-v0.1.8) (2026-04-14) ### Bug Fixes * **shopify:** standardizing the pre-release banner ([#1268](#1268)) ([82adddb](82adddb)) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common bumped from 2.18.3 to 2.18.4 </details> <details><summary>vercel-server-sdk: 1.3.43</summary> ## [1.3.43](vercel-server-sdk-v1.3.42...vercel-server-sdk-v1.3.43) (2026-04-14) ### Dependencies * The following workspace dependencies were updated * dependencies * @launchdarkly/js-server-sdk-common-edge bumped from 2.6.16 to 2.6.17 </details> --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please).  --- > [!NOTE] > **Low Risk** > Primarily automated version/changelog updates across many packages; the only functional change in-code is updating embedded SDK/version identifiers, which is low risk but could affect user-agent/wrapper reporting. > > **Overview** > Bumps versions and publishes release metadata across the monorepo (manifest, `package.json`s, and changelogs), including `js-client-sdk` `4.5.0`, `react-sdk` `0.2.0`, and multiple server/edge/provider packages. > > Updates embedded `x-release-please-version` constants used for SDK identification (e.g., `BrowserInfo`, `NodeInfo`, edge platform info) and updates the React client default `wrapperVersion` to `0.2.0` for telemetry/user-agent reporting. > > <sup>Reviewed by [Cursor Bugbot](https://cursor.com/bugbot) for commit a09a298. Bugbot is set up for automated code reviews on this repo. Configure [here](https://www.cursor.com/dashboard/bugbot).</sup>  Co-authored-by: github-actions[bot] <41898282+github-actions[bot]@users.noreply.github.com>

kinyoklion marked this pull request as ready for review April 6, 2026 21:30

kinyoklion requested a review from a team as a code owner April 6, 2026 21:30

This comment was marked as resolved.

Sign in to view

kinyoklion marked this pull request as draft April 6, 2026 21:31

fix: deep-merge fdv1Fallback so partial overrides preserve mode defaults

118f816

A partial fdv1Fallback override (e.g. only endpoints) no longer discards the mode's default pollInterval. The merge now spreads the default fallback config under the user override at the field level.

cursor Bot reviewed Apr 6, 2026

View reviewed changes

kinyoklion marked this pull request as ready for review April 6, 2026 22:05

joker23 reviewed Apr 6, 2026

View reviewed changes

joker23 approved these changes Apr 6, 2026

View reviewed changes

kinyoklion marked this pull request as draft April 6, 2026 23:07

kinyoklion added 2 commits April 6, 2026 16:07

kinyoklion marked this pull request as ready for review April 7, 2026 16:12

joker23 self-requested a review April 7, 2026 16:16

devin-ai-integration Bot reviewed Apr 7, 2026

View reviewed changes

joker23 approved these changes Apr 7, 2026

View reviewed changes

kinyoklion merged commit 9956bce into main Apr 7, 2026
45 checks passed

kinyoklion deleted the rlamb/sdk-2127/fdv1-fallback-configuration branch April 7, 2026 16:24

github-actions Bot mentioned this pull request Apr 6, 2026

chore: release main #1221

Merged

Provide feedback

Saved searches

Use saved searches to filter your results more quickly

feat: support per-mode FDv1 fallback configuration#1246

feat: support per-mode FDv1 fallback configuration#1246
kinyoklion merged 5 commits into
mainfrom
rlamb/sdk-2127/fdv1-fallback-configuration

kinyoklion commented Apr 6, 2026 •

edited by devin-ai-integration Bot

Loading

Uh oh!

github-actions Bot commented Apr 6, 2026

Uh oh!

github-actions Bot commented Apr 6, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Apr 6, 2026 •

edited

Loading

Uh oh!

github-actions Bot commented Apr 6, 2026 •

edited

Loading

Uh oh!

kinyoklion commented Apr 6, 2026

Uh oh!

This comment was marked as resolved.

Uh oh!

kinyoklion commented Apr 6, 2026

Uh oh!

cursor Bot left a comment

Uh oh!

joker23 Apr 6, 2026

Uh oh!

kinyoklion Apr 6, 2026

Uh oh!

joker23 commented Apr 6, 2026

Uh oh!

devin-ai-integration Bot left a comment

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

Conversation

kinyoklion commented Apr 6, 2026 • edited by devin-ai-integration Bot Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot commented Apr 6, 2026

Uh oh!

github-actions Bot commented Apr 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot commented Apr 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

github-actions Bot commented Apr 6, 2026 • edited Loading Uh oh! There was an error while loading. Please reload this page.

Uh oh!

Uh oh!

kinyoklion commented Apr 6, 2026

Uh oh!

This comment was marked as resolved.

Uh oh!

kinyoklion commented Apr 6, 2026

Uh oh!

cursor Bot left a comment

Choose a reason for hiding this comment

Uh oh!

joker23 Apr 6, 2026

Choose a reason for hiding this comment

Uh oh!

kinyoklion Apr 6, 2026

Choose a reason for hiding this comment

Uh oh!

joker23 commented Apr 6, 2026

Uh oh!

devin-ai-integration Bot left a comment

Choose a reason for hiding this comment

✅ Devin Review: No Issues Found

Uh oh!

Uh oh!

Reviewers

Assignees

Labels

Projects

Milestone

Development

Uh oh!

2 participants

kinyoklion commented Apr 6, 2026 •

edited by devin-ai-integration Bot

Loading

github-actions Bot commented Apr 6, 2026 •

edited

Loading

github-actions Bot commented Apr 6, 2026 •

edited

Loading

github-actions Bot commented Apr 6, 2026 •

edited

Loading