[turnipdabeets]

💡 Motivation and Context

Follow-up to #903, agreed with the capture v1 spec author on sdk-specs#146:

• Empty and personal API key (phx_...) setup errors print without debug. They now use logWarning in PostHog and PostHogStateless, so an app whose SDK is disabled at setup sees why.
• A batch PostHog rejects outright is logged. A terminal status (for example 400, 401, 402, or a 413 on a single event) deleted the batch without any log line. It now logs Flushing failed with <status>, dropping <n> records. (debug-only, like the other per-flush lines, since it can repeat during an outage).
• The 4.0 changeset mentions both.

💚 How did you test it?

• The setup tests now assert the warnings, and delete files if errored asserts the new line.
• ./gradlew :posthog:test --tests 'com.posthog.internal.PostHogQueueTest' --tests 'com.posthog.PostHogTest' --tests 'com.posthog.PostHogStatelessTest' spotlessCheck pass.

📝 Checklist

• All commits are signed (see Commit signing)
• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• No breaking change or entry added to the changelog.

If releasing new changes

• Ran pnpm changeset to generate a changeset file (updated the existing 4.0 major changeset)

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

• Claude Code checked the setup and flush logging on the iOS, Android and Flutter v1 branches to answer the spec thread, then made this change.

🤖 Generated with Claude Code

[dustinbyrne]

Looks good. Startup configuration errors use the existing warning channel, while terminal-batch diagnostics remain debug-only and preserve retry/split behavior.

AI-assisted review.