[turnipdabeets]

Problem

In a React Native app that installs neither expo-device nor react-native-device-info, every event the JS SDK sends lacks $os_name and $os_version. getAppProperties only reads them from those optional libraries and has no fallback.

Found while testing bare RN 0.79 and 0.76 apps (Release, Android and iOS) for #5271 / #5293. Every JS-sent event from those apps (custom events, $screen, non-fatal $exception) had no OS properties. Fatal $exception events from the same apps did have them, because they go through the native SDK, which adds its own device properties. The Expo example (with expo-device) has them on every event.

Impact:

• Events from bare apps can't be broken down or filtered by OS.
• $os_name feeds the default person properties used for flag targeting, so OS-targeted flags never match these users.

The posthog.com install command for bare RN includes react-native-device-info, but nothing says what is lost without it. The SDK's own logs already read the OS from Platform.

Changes

• When no device library has set $os_name, getAppProperties fills $os_name and $os_version from React Native's Platform:
  • Android: 'Android' and Platform.constants.Release (the user-facing version, not the API level).
  • iOS: Platform.constants.systemName (falls back to 'iOS') and Platform.Version.
  • This matches what posthog-android and posthog-ios report natively.
• Values from expo-device or react-native-device-info still win when either is installed.
• Other platforms (web, macOS, Windows) are unchanged.
• App and device-model properties ($app_version, $app_namespace, $device_manufacturer, …) still need a device-info library. A docs note saying so is worth adding separately.
• No sdk-spec requires $os_name (sdk-specs lists $os as collected from the host environment). No earlier issues or PRs found.

Test plan

• New test/native-deps-os.spec.ts (4 cases): 3 fail before the change and all pass after.
• posthog-react-native vitest suite (1248 tests), build, lint and format pass.
• Not run on a device yet. The missing properties were observed on device in the bare RN 0.79 / 0.76 apps.

Release info Sub-libraries affected

Libraries affected

• All of them
• posthog-js (web)
• posthog-js-lite (web lite)
• posthog-node
• posthog-react-native
• @posthog/react-native-plugin
• @posthog/react
• @posthog/ai
• @posthog/convex
• @posthog/next
• @posthog/nextjs-config
• @posthog/nuxt
• @posthog/openfeature-node-provider
• @posthog/openfeature-web-provider
• @posthog/rollup-plugin
• @posthog/webpack-plugin
• @posthog/types
• @posthog/browser-common

Checklist

• Tests for new code
• Accounted for the impact of any changes across different platforms
• Accounted for backwards compatibility of any changes (no breaking changes!)
• Took care not to unnecessarily increase the bundle size

If releasing new changes

• Ran pnpm changeset to generate a changeset file

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

• Claude Code (Claude Opus 5.5) subagent: read the SDK source and test-project events through the PostHog MCP, then wrote the fallback and its test.
• I confirmed the issue isn't specific to error boundaries: every JS-sent event from the bare apps lacked the properties, so the fix belongs in getAppProperties, not in the boundary.

🤖 Generated with Claude Code

[github-actions]

Coherence

2 spec problems · 0 failing chokepoints · 2 spec gaps · 0 guard failures

44 components, 5 bullets (5 invariants, 0 requirements), 2 problems

Spec problems (spec --check)

• Posthog-js.practice.md:20 practice add an invariant cites 187a5c5, which is no commit in this repository
• Posthog-js.practice.md:20 practice add an invariant cites 8922ab2, which is no commit in this repository

Chokepoints: none declared.

Spec gaps: 2 entrances with outside or unknown trust and no traced control, and 10 more held by the adoption baseline

• packages/web/Web.spec.md entrance public api (trust host-app): packages/web
• packages/webpack-plugin/Webpack-plugin.spec.md entrance webpack plugin (trust build): packages/webpack-plugin

Close one with guard: <chokepoint>, an invariant that names it on its entrances: line, or control: none — <reason>; scaffold control proposes it.

[github-actions]

This PR hasn't seen activity in a week! Should it be merged, closed, or further worked on? If you want to keep it open, post a comment or remove the stale label – otherwise this will be closed in another week.

[marandaneto]

The code looks good; no qualifying findings. Verdict: correct.