ci(react-sdk): add contract tests

[joker23]

This PR will add the initial contract tests for react sdk

Current limitation of the contract tests is that they are basically just testing the underlying browser sdk. We will iterate these tests to be more idiomatic to the react SDK.

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Note

Medium Risk
Primarily adds CI/test-only infrastructure, but it also introduces a new Next.js/Playwright workspace and updates React type dependencies, which could affect installs/CI stability and TypeScript checks.

Overview
Adds an initial contract-test implementation for @launchdarkly/react-sdk by introducing a new packages/sdk/react/contract-tests workspace that spins up the existing browser adapter, a Next.js “entity” app, and a headless Playwright browser to execute SDK Test Harness commands over WebSocket.

Updates sdk/react CI (react.yaml) to install/build the new workspaces, install Playwright browsers, start the local test services, and run the shared contract-tests GitHub Action with a suppressions list. Also adds React package lint config overrides for the contract-test TS project and bumps @types/react/adds @types/react-dom in the React SDK dev deps.

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[github-actions]

@launchdarkly/js-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 25566 bytes
Compressed size limit: 26000
Uncompressed size: 125383 bytes

[github-actions]

@launchdarkly/browser size report
This is the brotli compressed size of the ESM build.
Compressed size: 172130 bytes
Compressed size limit: 200000
Uncompressed size: 800872 bytes

[github-actions]

@launchdarkly/js-client-sdk size report
This is the brotli compressed size of the ESM build.
Compressed size: 24212 bytes
Compressed size limit: 25000
Uncompressed size: 83755 bytes

[github-actions]

@launchdarkly/js-client-sdk-common size report
This is the brotli compressed size of the ESM build.
Compressed size: 21281 bytes
Compressed size limit: 24000
Uncompressed size: 110213 bytes

[cursor]

Unstable onReady callback causes effect re-runs and handler gaps

Medium Severity

The onReady prop is an inline arrow function (readyId) => handlerReadyMap.current.get(readyId)?.() that creates a new reference on every render. Since ClientInner's useEffect lists onReady as a dependency, the effect re-runs on every parent re-render. Each re-run first executes cleanup (deleting the command handler from the map), then re-registers it. This creates a brief window where no handler exists for that client. When a new client is added via setClients, all existing ClientInner components re-render, causing all their handlers to be momentarily removed — any runCommand arriving during that gap gets a 404 response. The onReady callback needs to be stabilized (e.g., via useCallback).

Additional Locations (1)

• packages/sdk/react/contract-tests/app/ClientEntity.ts#L190-L197

 

[cursor]

Side effect in React state updater may execute multiple times

Low Severity

The _onDeleteClient callback calls record.client.close() inside a setClients state updater function. React state updaters are expected to be pure — React may invoke them more than once (e.g., in StrictMode or concurrent rendering), which would call close() on the same client multiple times. The close() call is a side effect that belongs outside the updater.

 

[cursor]

WebSocket reconnects after intentional disconnect in StrictMode

Medium Severity

The onclose handler unconditionally schedules a reconnect via setTimeout. When layout.tsx's useEffect cleanup calls ws.disconnect(), this triggers onclose, which schedules a reconnect after 1 second. Under React StrictMode (active in Next.js dev mode), the effect mounts, unmounts, and remounts — creating a second TestHarnessWebSocket instance. The first instance also reconnects 1 second later, resulting in two active WebSocket connections processing commands in parallel and sending duplicate responses.

Additional Locations (1)

• packages/sdk/react/contract-tests/app/layout.tsx#L94-L96

 

[cursor]

Cursor Bugbot has reviewed your changes and found 1 potential issue.

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