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PrBabysitter platform-build trigger aborts with OutOfMemoryException during message deserialization — event-triggered passes stop until recycle

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
35/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Active
Tech stack
csharp, json
Domain
backend, observability

Research direction

Start with MeshWeaver.Messaging.Hub/Serialization/ObjectPolymorphicConverter.cs, especially TryReadRegisteredTypeFromReader and ReadObject, then inspect the trigger wiring in Hosting/Deployment/Source/PrBabysitter.cs. Compare the pod memory limit with delivery sizes in Hosting/PlatformBuilds/_Inbox and Hosting/Babysitter/_Inbox to distinguish memory pressure from an oversized payload. Done means identifying the cause and addressing the deserialization failure without disabling the trigger.

Written by the indexing model from the issue text.

Description

bug sev:M

What is failing

The PR babysitter's platform-build trigger on the build instance (the Hosting/PlatformBuilds hub, namespace memex) aborted while deserializing an inbound message: MeshWeaver.Messaging's ObjectPolymorphicConverter hit a System.OutOfMemoryException mid-read (the failing allocation is System.Text.Json's string transcode/unescape). The handler caught it and disabled the trigger for that hub — so event- and build-triggered passes no longer fire, while the 30-minute fallback schedule continues to run full passes.

Probable cause — medium-low confidence; the evidence does not single one out:

  • An OOM raised inside JsonReaderHelper.TranscodeHelper means one ordinary string allocation failed — that almost always means the pod was already at its memory ceiling (container limit / LOH fragmentation) when the payload was read, rather than that this one message was pathologically large.
  • The competing explanation is an oversized message payload being deserialized on this hub (a forwarded GitHub event or platform-build delivery). Nothing in the incident distinguishes the two; the pod's memory metrics and the size of the undecoded delivery would.

Impact

Single occurrence on a single pod. The babysitter is degraded, not down: red pull requests are still classified by the scheduled 30-minute passes, heals are still proposed, and the page stays current at schedule cadence. What is lost until the hub/pod is recycled is event responsiveness — reds are no longer caught within a minute of the event, which the Hosting/PrBabysitter doc already names as the price of a schedule-only host. No portal outage and no data loss observed.

Where to look

  • MeshWeaver.Messaging.Hub/Serialization/ObjectPolymorphicConverter.cs — TryReadRegisteredTypeFromReader (line 248 in the burst's stack) and ReadObject (line 118 in a 2026-09-22 burst on the same site): how polymorphic payloads are read and what size guard, if any, exists.
  • The trigger wiring on the Hosting/PlatformBuilds hub: Hosting/Deployment/Source/PrBabysitter.cs (the pass and the schedule; documented in Hosting/PrBabysitter § Triggers and cadence).
  • The pod's memory limit and the size of the last deliveries in Hosting/PlatformBuilds/_Inbox and Hosting/Babysitter/_Inbox on the build instance, to separate memory pressure from an oversized payload.

Possibly related — same component, different defect: Systemorph/MeshWeaver#6120 (a PrBabysitter pass aborts row recording on ThreadNames.Prepared throwing MissingMethodException). Not a duplicate; listed because pass-abort defects at this site are accumulating.

Severity judgement: one occurrence, one pod, an operational automation degraded with a working fallback — sev:M. A human may re-rule if the trigger recurs and the build instance's event-driven healing becomes effectively dead.

Evidence
Fingerprint 076f1d7b309ac5bd
Category PrBabysitter
Severity Error
Exception System.OutOfMemoryException
Top frame MeshWeaver.Messaging.Serialization.ObjectPolymorphicConverter.TryReadRegisteredTypeFromReader(Utf8JsonReader& reader, JsonSerializerOptions options, Object& result)
Namespace memex
Pods memex-portal-deployment-6cfcf78898-gkkdv
Occurrences 1
First seen 2026-10-05 16:28:03Z
Last seen 2026-10-05 16:28:03Z
Routing not determined — no configured route matches the category PrBabysitter. This repository is the configured fallback, not a finding about who owns the fault; the category names the LOGGER, which may not be the subject.
Recent log lines 
2026-10-05 16:28:03Z memex-portal-deployment-6cfcf78898-gkkdv fail: PrBabysitter[0]
      [PrBabysitter] the platform-build trigger STOPPED — the schedule still runs
      System.OutOfMemoryException: Exception of type 'System.OutOfMemoryException' was thrown.
         at System.Text.Json.JsonReaderHelper.TranscodeHelper(ReadOnlySpan`1 utf8Unescaped)
         at System.Text.Json.JsonReaderHelper.GetUnescapedString(ReadOnlySpan`1 utf8Source)
         at System.Text.Json.Serialization.Metadata.JsonPropertyInfo`1.ReadJsonAndSetMember(Object obj, ReadStack& state, Utf8JsonReader& reader)
         at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
         at System.Text.Json.Serialization.JsonConverter`1.OnTryReadAsObject(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, Object& value)
         at System.Text.Json.Serialization.Converters.ObjectDefaultConverter`1.OnTryRead(Utf8JsonReader& reader, Type typeToConvert, JsonSerializerOptions options, ReadStack& state, T& value)
         at System.Text.Json.Serialization.JsonConverter`1.ReadCore(Utf8JsonReader& reader, T& value, JsonSerializerOptions options, ReadStack& state)
         at System.Text.Json.Serialization.Metadata.JsonTypeInfo`1.DeserializeAsObject(Utf8JsonReader& reader, ReadStack& state)
         at System.Text.Json.JsonSerializer.ReadAsObject(Utf8JsonReader& reader, JsonTypeInfo jsonTypeInfo)
         at MeshWeaver.Messaging.Serialization.ObjectPolymorphicConverter.TryReadRegisteredTypeFromReader(Utf8JsonReader& reader, JsonSerializerOptions options, Object& result) in /home/runner/work/MeshWeaver/MeshWeaver/src/MeshWeaver.Messaging.Hub/Serialization/ObjectPolymorphicConverter.cs:line 248
         at MeshWeaver.Messaging.Serialization.ObjectPolymorphicConverter.ReadObject(Utf8JsonReader& reader, JsonSerializerOptions options) in /home/runner/work/MeshWeaver/MeshWeaver/src/MeshWeaver.Messaging.Hub/…[truncated]

Opened automatically from Admin/_LogIncident/076f1d7b309ac5bd. Recurrences are folded into this issue rather than opening new ones.
It also stands for the whole log site 522dc7d73511e52b: other fingerprints of this site fold in here as comments rather than opening tickets of their own.

Dominant language
C#
Stars
12
Forks
5
Avg merge
3h 53m
Merged PRs (30d)
968

Getting set up

  • No Dockerfile or Docker Compose file
  • Has a pull request template
  • No contributing guide

First steps

  1. Read the whole issue, then the project's contributing guide.
  2. Comment on the issue to say you are picking it up — it saves two people doing the same work.
  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

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