feat: send error tracking stack frames in canonical bottom-up order

[cat-ph]

💡 Motivation and Context

Part of cross-SDK error tracking standardization: PostHog/sdk-specs#11.

The canonical wire order for $exception_list[].stacktrace.frames is bottom-up: frames[0] is the outermost/entry point and the last frame is the crash site. Today the shared exception coercer emits Java's native innermost-first order (crash site first), which is the opposite of the canonical convention.

This PR flips the frame order to match the spec.

🔧 The change

ThrowableCoercer.fromThrowableToPostHogProperties now walks throwable.stackTrace in reverse when building the frames list, so the emitted order is entry-point-first / crash-site-last.

The $exception_list ordering itself is unchanged (already canonical: [0] = outermost exception, built by walking .cause). Only the per-exception frame order flips.

Because this coercer is shared, the change covers both shipped $libs:

• posthog-android (Android SDK)
• posthog-server (Java server SDK)

💚 How did you test it?

• Updated the existing frame-order assertions in posthog/src/test/java/com/posthog/PostHogTest.kt.
• Added explicit regression assertions: the emitted frames are the reverse of the native stackTrace — first frame = entry point, last frame = crash site, and the crash-site (last) frame is the in-app method that threw.
• ./gradlew spotlessCheck :posthog:test passes (748 tests).

🤝 Coordination

This is a BREAKING wire-order change. Merge and release only after the ingestion pipeline's frame-order normalization gate (cymbal) is live, so older-order and newer-order events are both normalized correctly server-side.

The release must be a MINOR version bump for both posthog-android and posthog-server so the pipeline can gate normalization on $lib_version. The changeset in this PR declares minor bumps for posthog, posthog-android, and posthog-server.

📝 Checklist

• I reviewed the submitted code.
• I added tests to verify the changes.
• I updated the docs if needed.
• Ran the changeset (.changeset/canonical-frame-order.md, minor bumps).
• Added the "release" label to the PR (hold until the normalization gate is live).

[greptile-apps]

_{Reviews (1): Last reviewed commit: "feat: send error tracking stack frames i..." | Re-trigger Greptile}

[github-actions]

posthog-android Compliance Report

Date: 2026-07-03 00:13:26 UTC
Duration: 118262ms

✅ All Tests Passed!

46/46 tests passed

---

Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	335ms
Format Validation.Event Has Uuid	✅	27ms
Format Validation.Event Has Lib Properties	✅	31ms
Format Validation.Distinct Id Is String	✅	27ms
Format Validation.Token Is Present	✅	24ms
Format Validation.Custom Properties Preserved	✅	23ms
Format Validation.Event Has Timestamp	✅	25ms
Retry Behavior.Retries On 503	✅	7026ms
Retry Behavior.Does Not Retry On 400	✅	4022ms
Retry Behavior.Does Not Retry On 401	✅	4022ms
Retry Behavior.Respects Retry After Header	✅	7026ms
Retry Behavior.Implements Backoff	✅	17019ms
Retry Behavior.Retries On 500	✅	7018ms
Retry Behavior.Retries On 502	✅	7019ms
Retry Behavior.Retries On 504	✅	7018ms
Retry Behavior.Max Retries Respected	✅	17029ms
Deduplication.Generates Unique Uuids	✅	37ms
Deduplication.Preserves Uuid On Retry	✅	7016ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	12028ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7020ms
Deduplication.No Duplicate Events In Batch	✅	32ms
Deduplication.Different Events Have Different Uuids	✅	24ms
Compression.Sends Gzip When Enabled	✅	18ms
Batch Format.Uses Proper Batch Structure	✅	16ms
Batch Format.Flush With No Events Sends Nothing	✅	11ms
Batch Format.Multiple Events Batched Together	✅	36ms
Error Handling.Does Not Retry On 403	✅	4018ms
Error Handling.Does Not Retry On 413	✅	4021ms
Error Handling.Retries On 408	✅	5025ms

Feature_Flags Tests

✅ 17/17 tests passed

View Details

Test	Status	Duration
Request Payload.Request With Person Properties Device Id	✅	41ms
Request Payload.Flags Request Uses V2 Query Param	✅	20ms
Request Payload.Flags Request Hits Flags Path Not Decide	✅	21ms
Request Payload.Flags Request Omits Authorization Header	✅	21ms
Request Payload.Token In Flags Body Matches Init	✅	18ms
Request Payload.Groups Round Trip	✅	22ms
Request Payload.Groups Default To Empty Object	✅	19ms
Request Payload.Disable Geoip False Propagates As Geoip Disable False	✅	22ms
Request Payload.Disable Geoip Omitted Defaults To False	✅	20ms
Request Payload.Flag Keys To Evaluate Contains Only Requested Key	✅	19ms
Request Lifecycle.No Flags Request On Init Alone	✅	8ms
Request Lifecycle.No Flags Request On Normal Capture	✅	19ms
Request Lifecycle.Two Flag Calls Produce Two Remote Requests	✅	34ms
Request Lifecycle.Mock Response Value Is Returned To Caller	✅	17ms
Retry Behavior.Retries Flags On 502	✅	320ms
Retry Behavior.Retries Flags On 504	✅	320ms
Side Effect Events.Get Feature Flag Captures Feature Flag Called Event	✅	22ms