Release Incident Playbook

Analytics event schema broken: symptoms, cause, and the test that catches it

Tracking events change shape and downstream dashboards or experiments break.

Analytics event schema broken is documented by 2 accepted public reports from 2 organisations, 2 of them published in the last 5 years.

  • Likelihood: low (2 public reports in 5 years)
  • Impact: high (2 of 2 reports: data)

2 public reports · verified 2026-10-21

Symptoms

User-visible

  • Custom events recorded during the window contained only the event name, without its properties.[2]
  • Segments, metrics, funnels and conversions built on custom event properties were affected.[2]
  • Data export files were missing custom event properties.[2]
  • Event types arrived with an added prefix, so an event named Played Song appeared under a new prefixed name.[1]
  • Charts and workflows that relied on the existing event names may have been disrupted.[1]

Monitoring-visible

  • The analytics platform identified the unexpected prefix on some event types after it had started earlier that morning.[1]
  • Prefixed names showed up as event types in the schema and dropdowns.[1]

Root causes

  1. stage: code A change to the web capture script was incompatible with the capture snippet version that web clients had installed.[2]
  2. stage: release-process The automated integration suite had been switched to the upcoming snippet and lost coverage of the previous snippet version. The incompatible change passed CI and 14 days in staging.[2]
  3. stage: third-party An issue in the newer actions destination of an event pipeline added a prefix to event names between 11:00 and 16:36 UTC on 5 June 2025. Customers on the legacy classic destination were not affected.[1]

Public examples

  1. [1]Amplitude, 2025-06-05. For about five and a half hours, events sent from Segment through the Amplitude Actions destination arrived with a [Segment] prefix on the event name, so incorrect event names appeared in Amplitude and charts and workflows relying on existing names were disrupted until Segment deployed a fix and Amplitude merged the data. primary Unexpected "[Segment]" Prefix in Event Types
  2. [2]Fullstory, 2022-08-02. A release of the fs.js web capture script dropped all properties from logged Custom Events for about three days, so segments, metrics, funnels, conversions and data exports relying on those properties were affected. primary FS.event properties dropped

Test classes that catch it

Test classStageLimitationBasis
Integration testspre-deployAn integration suite catches dropped properties only when it runs against every snippet version clients still use, and this suite ran only against the upcoming snippet.cited in [2]
Contract testspre-mergeA contract test runs on the sender's own release, so it does not run when a vendor changes the destination integration that added the event name prefix.by design analysis
Synthetic monitoringpost-deployA test event sent only through the legacy classic destination arrives intact, because the prefix came from the newer actions destination alone.by design analysis

Risk

  • Likelihood: low (2 public reports in 5 years)
  • Impact: high (2 of 2 reports: data)
Counts behind the grades
Accepted public reports2
Published in the last 5 years2
Impact stated: data2

How the grades are computed

Pre-release checklist

  • PR-01
  • PR-02
  • PR-03
  • PR-04
  • PR-05
  • PR-06
  • PR-07

First 30 minutes

  • FM-01
  • FM-02
  • FM-03
  • FM-04
  • FM-05
  • FM-06
  • FM-07

Download the checklist

What catches this: catalogue entries

Listed because their own documentation or site names integration tests, contract tests, synthetic monitoring on the verification date. Alphabetical. Not a recommendation.

Tools whose documentation names these test classes

Providers whose site names these test classes

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Analytics event schema broken passed the integration suite that existed to catch it. In report [2], the suite had been moved to the upcoming capture snippet as part of a parallel upgrade, which removed coverage of the snippet version clients actually ran. The change then passed CI and 14 days in staging, and properties were dropped for about three days. Report [1] and report [2] both classify the impact as data.

In report [1], the fault sat in a destination integration of the event pipeline, not in the capture script. The prefix came from the newer actions destination of an event pipeline, and customers on the legacy classic destination were not affected. Recovery took a data merge rather than a rollback: the analytics platform merged the prefixed events into the original events and scrubbed the prefix by 11 June 2025.

Questions

What causes analytics event schema broken?

In report [2], a capture script change was incompatible with the snippet version clients used. In report [1], a destination integration added a prefix to event names between 11:00 and 16:36 UTC.

What are the symptoms of analytics event schema broken?

Custom events kept their names but lost all properties, which affected segments, funnels and data exports [2]. Event types appeared under new prefixed names in charts, the schema and dropdowns [1].

Why did tests not catch analytics event schema broken?

The integration suite had been switched to the upcoming snippet and no longer covered the version clients ran [2]. In report [1], the change sat in a vendor's destination integration, outside the sender's release.

Which test class catches analytics event schema broken, and what does it miss?

Integration tests carry the cited label from report [2]. They miss the fault when they run against the wrong snippet version. Contract tests and synthetic monitoring carry the by-design label.

Which public reports document analytics event schema broken?

Two primary reports from two organisations document it, published on 2022-08-02 [2] and 2025-06-05 [1]. Both classify the impact as data.

Should a team roll back or fix forward when analytics event schema broken happens?

Report [2] shipped a script fix and rolled the script and snippet back to the prior working version. Report [1] waited for the vendor's fix and then merged the prefixed events into the original events.

Release Incident Playbook (2026). Analytics event schema broken: symptoms, cause, and the test that catches it, content version 1.0.0. https://releasefailures.com/incidents/analytics-event-schema-broken/. Accessed 2026-10-21.