launchdarkly Client-Side Streaming API

Server-Sent Events streaming endpoints for client-side and mobile SDKs to receive real-time flag updates.

Documentation GitHub OpenAPI

Business capability

Operations 1

Each operation below carries the questions people ask an LLM about it and the instructions they give an agent to run it. Generated by API Evangelist overlay

GET /eval/{envId}/{contextBase64} Stream evaluated flags to a client · Stream evaluated flags (client-side) #

Ask an LLM

“How do I open a live stream of flag values for a browser client?”

“Can a client-side app get flag updates pushed over Server-Sent Events?”

Tell an agent

Open a client-side flag stream for environment {envId} and context {contextBase64}.

Stream evaluated flag values for encoded context {contextBase64} in env {envId}.

Documentation

📖

Documentation

https://launchdarkly.com/docs/api

📖

Documentation

https://launchdarkly.com/docs/sdk/relay-proxy

Specifications

⚙

OpenAPI

https://raw.githubusercontent.com/api-evangelist/launchdarkly/refs/heads/main/openapi/launchdarkly-client-side-streaming-api-openapi.yml

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OpenAPI Specification

openapi: 3.2.0
info:
  title: LaunchDarkly Relay Proxy Client-Side Streaming API
  description: The LaunchDarkly Relay Proxy is a small Go application that connects to the LaunchDarkly streaming API and proxies that connection to SDK clients within an organization's network. It exposes endpoints for status monitoring, flag evaluation, and SDK streaming that mirror the LaunchDarkly service endpoints. Instead of each server making outbound connections to LaunchDarkly's streaming service, multiple servers connect to the local Relay Proxy which maintains a single upstream connection.
  version: '8.0'
  contact:
    name: LaunchDarkly Support
    url: https://support.launchdarkly.com
  license:
    name: Apache 2.0
    url: https://www.apache.org/licenses/LICENSE-2.0
servers:
- url: http://localhost:8030
  description: Default Relay Proxy instance
tags:
- name: Client-Side Streaming
  description: Server-Sent Events streaming endpoints for client-side and mobile SDKs to receive real-time flag updates.
paths:
  /eval/{envId}/{contextBase64}:
    get:
      operationId: streamClientSideEval
      summary: Stream evaluated flags (client-side)
      description: Establishes a Server-Sent Events (SSE) stream that delivers evaluated flag values for the given context to client-side SDKs.
      tags:
      - Client-Side Streaming
      parameters:
      - $ref: '#/components/parameters/EnvironmentId'
      - $ref: '#/components/parameters/ContextBase64'
      responses:
        '200':
          description: SSE stream delivering evaluated flag values.
          content:
            text/event-stream:
              schema:
                type: string
                description: Server-Sent Events stream with evaluated flag data.
        '401':
          description: Unauthorized. Invalid environment ID.
        '503':
          description: Service unavailable. Flag data not yet available.
components:
  parameters:
    EnvironmentId:
      name: envId
      in: path
      required: true
      description: The client-side environment ID.
      schema:
        type: string
    ContextBase64:
      name: contextBase64
      in: path
      required: true
      description: A base64-encoded JSON representation of the evaluation context.
      schema:
        type: string
  securitySchemes:
    sdkKeyAuth:
      type: apiKey
      in: header
      name: Authorization
      description: Server-side SDK key for authenticating with the Relay Proxy.
    mobileKeyAuth:
      type: apiKey
      in: header
      name: Authorization
      description: Mobile SDK key for authenticating with the Relay Proxy.
externalDocs:
  description: Relay Proxy Documentation
  url: https://launchdarkly.com/docs/sdk/relay-proxy