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During client initialization, user has the option to specify connection policy.

If no connection policy is supplied, then defaultConnectionPolicy is picked up (Value of enableBackgroundEndpointRefreshing flag is true here)

If a connection policy is supplied and enableBackgroundEndpointRefreshing is not set in the custom connection policy, then by default it picks up value as false.

If a connection policy is supplied and enableBackgroundEndpointRefreshing is not set in the custom connection policy, then by default it picks up value as false.

I believe this is not correct. My understanding is that it is only treated as false if enableBackgroundEndpointRefreshing: false (or any falsy value) is explicitly set during client initialization.

As seen here, Object.assign() merges defaultConnectionPolicy with the connectionPolicy provided by the user. Unless the user explicitly sets the enableBackgroundEndpointRefreshing property, the default value of true from defaultConnectionPolicy is applied.

For example, when configured as shown below, enableBackgroundEndpointRefreshing is treated as true, and I confirmed that this.backgroundRefreshEndpointList() is executed within CosmosClient.ts.

const client = new CosmosClient({
  endpoint: "something",
  key: "something",
  connectionPolicy: {
    requestTimeout: 1_000_000,
    // enableBackgroundEndpointRefreshing property is not specified
  },
});

If no connection policy is supplied, then defaultConnectionPolicy is picked up (Value of enableBackgroundEndpointRefreshing flag is true here)

Furthermore, this behavior (that the default is true when no connection policy is supplied or when the property is not explicitly set in a supplied policy) is not mentioned anywhere in the documentation. This lack of documentation, requiring users to read the source code to understand the actual default behavior, can be confusing.