feat: Add FDv2 DataManager and enable experimental FDv2 support.

.github/workflows/browser.yml

@@ -41,7 +41,7 @@ jobs:
           target_file: 'packages/sdk/browser/dist/index.js'
           package_name: '@launchdarkly/js-client-sdk'
           pr_number: ${{ github.event.number }}
-          size_limit: 25000
+          size_limit: 34000
 
       # Contract Tests
       - name: Install contract test dependencies

.github/workflows/combined-browser.yml

@@ -41,4 +41,4 @@ jobs:
           target_file: 'packages/sdk/combined-browser/dist/index.js'
           package_name: '@launchdarkly/browser'
           pr_number: ${{ github.event.number }}
-          size_limit: 200000
+          size_limit: 194000

.github/workflows/common.yml

@@ -35,4 +35,4 @@ jobs:
           target_file: 'packages/shared/common/dist/esm/index.mjs'
           package_name: '@launchdarkly/js-sdk-common'
           pr_number: ${{ github.event.number }}
-          size_limit: 26000
+          size_limit: 29000

.github/workflows/sdk-client.yml

@@ -32,4 +32,4 @@ jobs:
           target_file: 'packages/shared/sdk-client/dist/esm/index.mjs'
           package_name: '@launchdarkly/js-client-sdk-common'
           pr_number: ${{ github.event.number }}
-          size_limit: 24000
+          size_limit: 38000

packages/sdk/browser/__tests__/BrowserClient.test.ts

@@ -872,4 +872,72 @@ describe('given a mock platform for a BrowserClient', () => {
     // Verify that no fetch calls were made
     expect(platform.requests.fetch.mock.calls.length).toBe(0);
   });
+
+  it('uses FDv1 endpoints when dataSystem is not set', async () => {
+    const client = makeClient(
+      'client-side-id',
+      { key: 'user-key', kind: 'user' },
+      AutoEnvAttributes.Disabled,
+      { streaming: false, logger, diagnosticOptOut: true, sendEvents: false, fetchGoals: false },
+      platform,
+    );
+
+    await client.start();
+
+    const fetchUrl = platform.requests.fetch.mock.calls[0][0];
+    expect(fetchUrl).toContain('/sdk/evalx/');
+    expect(fetchUrl).not.toContain('/sdk/poll/eval');
+  });
+
+  it('uses FDv2 endpoints when dataSystem is set', async () => {
+    const client = makeClient(
+      'client-side-id',
+      { key: 'user-key', kind: 'user' },
+      AutoEnvAttributes.Disabled,
+      {
+        streaming: false,
+        logger,
+        diagnosticOptOut: true,
+        sendEvents: false,
+        fetchGoals: false,
+        // @ts-ignore dataSystem is @internal
+        dataSystem: {},
+      },
+      platform,
+    );
+
+    await client.start();
+
+    const fetchUrl = platform.requests.fetch.mock.calls[0][0];
+    expect(fetchUrl).toContain('/sdk/poll/eval/');
+  });
+
+  it('validates dataSystem options and applies browser defaults', async () => {
+    const client = makeClient(
+      'client-side-id',
+      { key: 'user-key', kind: 'user' },
+      AutoEnvAttributes.Disabled,
+      {
+        streaming: false,
+        logger,
+        diagnosticOptOut: true,
+        sendEvents: false,
+        fetchGoals: false,
+        // @ts-ignore dataSystem is @internal
+        dataSystem: { initialConnectionMode: 'invalid-mode' },
+      },
+      platform,
+    );
+
+    // Invalid mode should produce a warning
+    expect(logger.warn).toHaveBeenCalledWith(
+      expect.stringContaining('dataSystem.initialConnectionMode'),
+    );
+
+    await client.start();
+
+    // Should still use FDv2 — invalid sub-fields fall back to defaults, not disable FDv2
+    const fetchUrl = platform.requests.fetch.mock.calls[0][0];
+    expect(fetchUrl).toContain('/sdk/poll/eval/');
+  });
 });

packages/sdk/browser/contract-tests/entity/src/ClientEntity.ts

@@ -4,6 +4,9 @@ import {
   CommandType,
   CreateInstanceParams,
   makeLogger,
+  SDKConfigDataInitializer,
+  SDKConfigDataSynchronizer,
+  SDKConfigModeDefinition,
   SDKConfigParams,
   ClientSideTestHook as TestHook,
   ValueType,
@@ -12,6 +15,59 @@ import {
 export const badCommandError = new Error('unsupported command');
 export const malformedCommand = new Error('command was malformed');
 
+function translateInitializer(init: SDKConfigDataInitializer): any | undefined {
+  if (init.polling) {
+    return {
+      type: 'polling',
+      ...(init.polling.pollIntervalMs !== undefined && {
+        pollInterval: init.polling.pollIntervalMs / 1000,
+      }),
+      ...(init.polling.baseUri && {
+        endpoints: { pollingBaseUri: init.polling.baseUri },
+      }),
+    };
+  }
+  return undefined;
+}
+
+function translateSynchronizer(sync: SDKConfigDataSynchronizer): any | undefined {
+  if (sync.streaming) {
+    return {
+      type: 'streaming',
+      ...(sync.streaming.initialRetryDelayMs !== undefined && {
+        initialReconnectDelay: sync.streaming.initialRetryDelayMs / 1000,
+      }),
+      ...(sync.streaming.baseUri && {
+        endpoints: { streamingBaseUri: sync.streaming.baseUri },
+      }),
+    };
+  }
+  if (sync.polling) {
+    return {
+      type: 'polling',
+      ...(sync.polling.pollIntervalMs !== undefined && {
+        pollInterval: sync.polling.pollIntervalMs / 1000,
+      }),
+      ...(sync.polling.baseUri && {
+        endpoints: { pollingBaseUri: sync.polling.baseUri },
+      }),
+    };
+  }
+  return undefined;
+}
+
+function translateModeDefinition(modeDef: SDKConfigModeDefinition): any {
+  const initializers = (modeDef.initializers ?? [])
+    .map(translateInitializer)
+    .filter((x: any) => x !== undefined);
+
+  const synchronizers = (modeDef.synchronizers ?? [])
+    .map(translateSynchronizer)
+    .filter((x: any) => x !== undefined);
+
+  return { initializers, synchronizers };
+}
+
 function makeSdkConfig(options: SDKConfigParams, tag: string) {
   if (!options.clientSide) {
     throw new Error('configuration did not include clientSide options');
@@ -23,30 +79,65 @@ function makeSdkConfig(options: SDKConfigParams, tag: string) {
   const cf: LDOptions = {
     withReasons: options.clientSide.evaluationReasons,
     logger: makeLogger(`${tag}.sdk`),
-    useReport: options.clientSide.useReport,
+    useReport: options.clientSide.useReport ?? undefined,
   };
 
-  if (options.serviceEndpoints) {
-    cf.streamUri = options.serviceEndpoints.streaming;
-    cf.baseUri = options.serviceEndpoints.polling;
-    cf.eventsUri = options.serviceEndpoints.events;
-  }
+  if (options.dataSystem?.connectionModeConfig) {
+    const connMode = options.dataSystem.connectionModeConfig;
+    const dataSystem: any = {
+      initialConnectionMode: connMode.initialConnectionMode,
+      automaticModeSwitching: false,
+    };
+
+    if (connMode.customConnectionModes) {
+      const connectionModes: Record<string, any> = {};
+      Object.entries(connMode.customConnectionModes).forEach(([modeName, modeDef]) => {
+        connectionModes[modeName] = translateModeDefinition(modeDef);
 
-  if (options.polling) {
-    if (options.polling.baseUri) {
-      cf.baseUri = options.polling.baseUri;
+        // Also set global endpoint URIs for compatibility with ServiceEndpoints.
+        (modeDef.synchronizers ?? []).forEach((sync) => {
+          if (sync.streaming?.baseUri) {
+            cf.streamUri = sync.streaming.baseUri;
+            cf.streamInitialReconnectDelay = maybeTime(sync.streaming.initialRetryDelayMs);
+          }
+          if (sync.polling?.baseUri) {
+            cf.baseUri = sync.polling.baseUri;
+          }
+        });
+        (modeDef.initializers ?? []).forEach((init) => {
+          if (init.polling?.baseUri) {
+            cf.baseUri = init.polling.baseUri;
+          }
+        });
+      });
+      dataSystem.connectionModes = connectionModes;
     }
-  }
 
-  // Can contain streaming and polling, if streaming is set override the initial connection
-  // mode. This can be removed when we add JS specific initialization that uses polling
-  // and then streaming.
-  if (options.streaming) {
-    if (options.streaming.baseUri) {
-      cf.streamUri = options.streaming.baseUri;
+    (cf as any).dataSystem = dataSystem;
+
+    if (options.dataSystem.payloadFilter) {
+      cf.payloadFilterKey = options.dataSystem.payloadFilter;
+    }
+  } else {
+    if (options.serviceEndpoints) {
+      cf.streamUri = options.serviceEndpoints.streaming;
+      cf.baseUri = options.serviceEndpoints.polling;
+      cf.eventsUri = options.serviceEndpoints.events;
+    }
+
+    if (options.polling) {
+      if (options.polling.baseUri) {
+        cf.baseUri = options.polling.baseUri;
+      }
+    }
+
+    if (options.streaming) {
+      if (options.streaming.baseUri) {
+        cf.streamUri = options.streaming.baseUri;
+      }
+      cf.streaming = true;
+      cf.streamInitialReconnectDelay = maybeTime(options.streaming.initialRetryDelayMs);
     }
-    cf.streaming = true;
-    cf.streamInitialReconnectDelay = maybeTime(options.streaming.initialRetryDelayMs);
   }
 
   if (options.events) {

packages/sdk/browser/contract-tests/suppressions_datamode_changes.txt

@@ -0,0 +1,45 @@
+streaming/requests/method and headers/REPORT/http
+streaming/requests/URL path is computed correctly/no environment filter/base URI has no trailing slash/REPORT
+streaming/requests/URL path is computed correctly/no environment filter/base URI has a trailing slash/REPORT
+streaming/requests/query parameters/evaluationReasons set to [none]/REPORT
+streaming/requests/query parameters/evaluationReasons set to false/REPORT
+streaming/requests/query parameters/evaluationReasons set to true/REPORT
+streaming/requests/context properties/single kind minimal/REPORT
+streaming/requests/context properties/single kind with all attributes/REPORT
+streaming/requests/context properties/multi-kind/REPORT
+polling/requests/method and headers/REPORT/http
+polling/requests/URL path is computed correctly/no environment filter/base URI has no trailing slash/REPORT
+polling/requests/URL path is computed correctly/no environment filter/base URI has a trailing slash/REPORT
+polling/requests/query parameters/evaluationReasons set to [none]/REPORT
+polling/requests/query parameters/evaluationReasons set to false/REPORT
+polling/requests/query parameters/evaluationReasons set to true/REPORT
+polling/requests/context properties/single kind minimal/REPORT
+polling/requests/context properties/single kind with all attributes/REPORT
+polling/requests/context properties/multi-kind/REPORT
+tags/stream requests/{"applicationId":null,"applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/stream requests/{"applicationId":null,"applicationVersion":"________________________________________________________________"}
+tags/stream requests/{"applicationId":"","applicationVersion":null}
+tags/stream requests/{"applicationId":"","applicationVersion":""}
+tags/stream requests/{"applicationId":"","applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/stream requests/{"applicationId":"","applicationVersion":"________________________________________________________________"}
+tags/stream requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":null}
+tags/stream requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":""}
+tags/stream requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/stream requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":"________________________________________________________________"}
+tags/stream requests/{"applicationId":"________________________________________________________________","applicationVersion":null}
+tags/stream requests/{"applicationId":"________________________________________________________________","applicationVersion":""}
+tags/stream requests/{"applicationId":"________________________________________________________________","applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/stream requests/{"applicationId":"________________________________________________________________","applicationVersion":"________________________________________________________________"}
+tags/poll requests/{"applicationId":null,"applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/poll requests/{"applicationId":null,"applicationVersion":"________________________________________________________________"}
+tags/poll requests/{"applicationId":"","applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/poll requests/{"applicationId":"","applicationVersion":"________________________________________________________________"}
+tags/poll requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":null}
+tags/poll requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":""}
+tags/poll requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/poll requests/{"applicationId":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678","applicationVersion":"________________________________________________________________"}
+tags/poll requests/{"applicationId":"________________________________________________________________","applicationVersion":null}
+tags/poll requests/{"applicationId":"________________________________________________________________","applicationVersion":""}
+tags/poll requests/{"applicationId":"________________________________________________________________","applicationVersion":"._-abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ012345678"}
+tags/poll requests/{"applicationId":"________________________________________________________________","applicationVersion":"________________________________________________________________"}
+tags/disallowed characters

packages/sdk/browser/example/index.css

@@ -1,11 +1,69 @@
 body {
   margin: 0;
+  padding: 20px;
   background: #373841;
   color: white;
   font-family:
     -apple-system, BlinkMacSystemFont, 'Segoe UI', 'Roboto', 'Oxygen', 'Ubuntu', 'Cantarell',
     'Fira Sans', 'Droid Sans', 'Helvetica Neue', sans-serif;
   -webkit-font-smoothing: antialiased;
   -moz-osx-font-smoothing: grayscale;
-  text-align: center;
+}
+
+#status {
+  padding: 10px;
+  margin-bottom: 10px;
+  background: rgba(255,255,255,0.1);
+  border-radius: 4px;
+}
+
+#flag {
+  font-size: 1.4em;
+  padding: 15px;
+  margin-bottom: 20px;
+  background: rgba(255,255,255,0.05);
+  border-radius: 4px;
+}
+
+#controls {
+  display: grid;
+  grid-template-columns: 1fr 1fr;
+  gap: 15px;
+}
+
+#controls > div {
+  padding: 10px;
+  background: rgba(255,255,255,0.05);
+  border-radius: 4px;
+}
+
+#controls h3 {
+  margin: 0 0 8px 0;
+  font-size: 0.9em;
+  text-transform: uppercase;
+  opacity: 0.7;
+}
+
+button {
+  padding: 6px 14px;
+  margin: 3px 2px;
+  border: 1px solid rgba(255,255,255,0.3);
+  border-radius: 4px;
+  background: rgba(255,255,255,0.1);
+  color: white;
+  cursor: pointer;
+  font-size: 0.9em;
+}
+
+button:hover {
+  background: rgba(255,255,255,0.2);
+}
+
+#log {
+  max-height: 200px;
+  overflow-y: auto;
+  font-family: monospace;
+  font-size: 0.8em;
+  line-height: 1.5;
+  opacity: 0.8;
 }