fix: Retry on 408 and respect Retry-After header

[andehen]

Problem

The SDK failed 2 of 29 compliance tests:

• Retries On 408: 408 (Request Timeout) was treated as a non-retryable client error, so the SDK never retried.
• Respects Retry-After Header: The backoff library's exponential backoff ignored the Retry-After response header, so the SDK didn't wait the server-requested delay before retrying.

Changes

• posthog/request.py: Added retry_after field to APIError. Extract the Retry-After header from error responses and pass it through.
• posthog/consumer.py: Replaced backoff.on_exception with a manual retry loop that uses the Retry-After value when present and falls back to exponential backoff (2^attempt seconds, capped at 30s) otherwise. Added 408 to the set of retryable status codes alongside 429.

Testing

• All 621 existing unit tests pass.
• All 29 SDK compliance tests pass (previously 27/29).

[greptile-apps]

_{2 files reviewed, 3 comments}

_{Edit Code Review Agent Settings | Greptile}

[github-actions]

posthog-python Compliance Report

Date: 2026-02-09 12:15:42 UTC
Duration: 159333ms

✅ All Tests Passed!

29/29 tests passed

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Capture Tests

✅ 29/29 tests passed

View Details

Test	Status	Duration
Format Validation.Event Has Required Fields	✅	515ms
Format Validation.Event Has Uuid	✅	1507ms
Format Validation.Event Has Lib Properties	✅	1506ms
Format Validation.Distinct Id Is String	✅	1505ms
Format Validation.Token Is Present	✅	1506ms
Format Validation.Custom Properties Preserved	✅	1506ms
Format Validation.Event Has Timestamp	✅	1506ms
Retry Behavior.Retries On 503	✅	9517ms
Retry Behavior.Does Not Retry On 400	✅	3505ms
Retry Behavior.Does Not Retry On 401	✅	3506ms
Retry Behavior.Respects Retry After Header	✅	9508ms
Retry Behavior.Implements Backoff	✅	23520ms
Retry Behavior.Retries On 500	✅	7513ms
Retry Behavior.Retries On 502	✅	7513ms
Retry Behavior.Retries On 504	✅	7509ms
Retry Behavior.Max Retries Respected	✅	23527ms
Deduplication.Generates Unique Uuids	✅	1495ms
Deduplication.Preserves Uuid On Retry	✅	7514ms
Deduplication.Preserves Uuid And Timestamp On Retry	✅	14510ms
Deduplication.Preserves Uuid And Timestamp On Batch Retry	✅	7510ms
Deduplication.No Duplicate Events In Batch	✅	1507ms
Deduplication.Different Events Have Different Uuids	✅	1506ms
Compression.Sends Gzip When Enabled	✅	1506ms
Batch Format.Uses Proper Batch Structure	✅	1506ms
Batch Format.Flush With No Events Sends Nothing	✅	1004ms
Batch Format.Multiple Events Batched Together	✅	1504ms
Error Handling.Does Not Retry On 403	✅	3508ms
Error Handling.Does Not Retry On 413	✅	3507ms
Error Handling.Retries On 408	✅	7512ms