chore!: adopt posthog-ios 4.0

[turnipdabeets]

💡 Motivation and Context

Stacked on #637. This is the only part of v6 that needs posthog-ios 4.0, split out so #637 can pass CI against posthog-ios 3.x. Merge this once posthog-ios 4.0 is released.

• Raise the posthog-ios range to 4.x (the iOS 15 / macOS 11 minimums are already in chore!: Flutter Major Release v6 #637)
• Adapt to the reloadFeatureFlags(_:) callback, which now passes a PostHogFeatureFlagsLoaded (chore!: pass the reload result to reloadFeatureFlags' callback posthog-ios#913, previously chore: adapt to posthog-ios 4.0 reloadFeatureFlags callback #643)
• One changeset: the 4.x adoption plus the payload decoding changes from chore!: note posthog-ios 4.0 feature flag payload decoding changes #644 (chore!: return nil for malformed feature flag payloads posthog-ios#903)
• The changeset also notes that iOS and macOS stop sending the legacy version/build properties on lifecycle events (chore!: drop legacy version and build from lifecycle events posthog-ios#905). Android keeps sending them for now

💚 How did you test it?

• CI. This will not go green until posthog-ios 4.0 is published.
• Locally, with Xcode 26.4.1: built the example app for the iOS simulator and for macOS against posthog-ios 4.0, with the open 4.0 PRs chore!: remove wireframe session replay capture posthog-ios#907 and #909 merged in, pointing Package.swift temporarily at the local checkout with .package(path:). The plugin produced no warnings, including for the @Sendable callback from chore!: mark off-main public callbacks @Sendable for v4 posthog-ios#914. Not tested locally: the CocoaPods build.

📝 Checklist

• 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

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

🤖 Generated with Claude Code

[github-actions]

posthog-flutter Compliance Report

Date: 2026-10-08 15:49:40 UTC
Duration: 96844ms

✅ All Tests Passed!

45/45 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	144ms
Format Validation.Event Has Uuid	✅	121ms
Format Validation.Event Has Lib Properties	✅	116ms
Format Validation.Distinct Id Is String	✅	116ms
Format Validation.Token Is Present	✅	115ms
Format Validation.Custom Properties Preserved	✅	118ms
Format Validation.Event Has Timestamp	✅	119ms
Retry Behavior.Retries On 503	✅	5334ms
Retry Behavior.Does Not Retry On 400	✅	2119ms
Retry Behavior.Does Not Retry On 401	✅	2118ms
Retry Behavior.Respects Retry After Header	✅	8126ms
Retry Behavior.Implements Backoff	✅	15435ms
Retry Behavior.Retries On 500	✅	5225ms
Retry Behavior.Retries On 502	✅	5228ms
Retry Behavior.Retries On 504	✅	5226ms
Retry Behavior.Max Retries Respected	✅	15445ms
Deduplication.Generates Unique Uuids	✅	124ms
Deduplication.Preserves Uuid On Retry	✅	5226ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	10335ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	5232ms
Deduplication.No Duplicate Events In Batch	✅	124ms
Deduplication.Different Events Have Different Uuids	✅	116ms
Compression.Sends Gzip When Enabled	✅	117ms
Batch Format.Uses Proper Batch Structure	✅	114ms
Batch Format.Flush With No Events Sends Nothing	✅	109ms
Batch Format.Multiple Events Batched Together	✅	123ms
Error Handling.Does Not Retry On 403	✅	2117ms
Error Handling.Does Not Retry On 413	✅	2118ms
Error Handling.Retries On 408	✅	5225ms

Feature_Flags Tests

✅ 16/16 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	12ms
Request Payload.Flags Request Uses V2 Query Param	✅	10ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	9ms
Request Payload.Flags Request Omits Authorization Header	✅	10ms
Request Payload.Token In Flags Body Matches Init	✅	9ms
Request Payload.Groups Round Trip	✅	10ms
Request Payload.Groups Default To Empty Object	✅	10ms
Request Payload.Person Properties Distinct Id Auto Populated When Caller Omits It	✅	9ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	10ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	9ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	9ms
Request Lifecycle.No Flags Request On Init Alone	✅	5ms
Request Lifecycle.No Flags Request On Normal Capture	✅	113ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	17ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	10ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	117ms