Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
git clone --depth 1 https://github.com/hatch3r/hatch3rWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/rules/hatch3r/hatch3r/hatch3r-event-schema-evolution)<a href="https://agentmods.dev/rules/hatch3r/hatch3r/hatch3r-event-schema-evolution"><img src="https://agentmods.dev/badge/rules/hatch3r/hatch3r/hatch3r-event-schema-evolution/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/rules/hatch3r/hatch3r/hatch3r-event-schema-evolution"><img src="https://agentmods.dev/badge/rules/hatch3r/hatch3r/hatch3r-event-schema-evolution.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00000 | $0.01955 |
| Opus 5 | $0.00000 | $0.00978 |
| Sonnet 5 | $0.00000 | $0.00391 |
| Haiku 4.5 | $0.00000 | $0.00196 |
Grade A, and why
hatch3r-event-schema-evolution scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 6d ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
How it starts
The opening of the file, as written. The whole thing — 88 lines — stays where its author put it; the contents beside it link to each section on GitHub.
Event Schema Evolution
Schemas for events, messages, and stream records evolve independently of producer and consumer deploy order. Every change must declare an explicit compatibility mode and pass a registry compatibility check before merge.
Compatibility Modes
A registry compatibility mode constrains the diff between adjacent schema versions. Pick the mode that matches the deploy-order guarantee available in the target system.
BACKWARD— a consumer using the new schema reads data written with the old schema. Allowed diffs: delete a field, add a field that has a default value. Deploy consumers first. Default for evolving consumer code.FORWARD— a consumer using the old schema reads data written with the new schema. Allowed diffs: add a field, delete a field that had a default value. Deploy producers first. Default for evolving producer code.FULL— both directions. Required when producer and consumer deploy order cannot be controlled (e.g., split across teams or platforms).*_TRANSITIVEvariants (BACKWARD_TRANSITIVE, FORWARD_TRANSITIVE, FULL_TRANSITIVE) — the constraint holds against every prior schema version, not just the immediately preceding one. Required when consumers may replay from offset zero or read a historical archive.NONE— disables compatibility checking; breaking changes accepted. Permitted only on a dedicated*-v2subject during a planned migration window with a dated deprecation plan in the migration ticket.
Default recommendation when in doubt: BACKWARD_TRANSITIVE — consumers can deploy first and replay from offset zero.
Schema Registry Mandate
- Every event topic / stream / subscription has a registered schema in Confluent Schema Registry, Apicurio Registry, AWS Glue Schema Registry, or Karapace. No in-tree schema-only repos without a registry binding.
- Subject naming strategy is declared per topic:
TopicNameStrategy(one schema per topic — default),RecordNameStrategy(one schema per record type across topics), orTopicRecordNameStrategy(multiple record types per topic). Mixing strategies inside the same topic is forbidden. - Compatibility mode is set per subject in the registry and asserted in CI. Changing the mode requires a registry-admin role and a logged justification.
- Schemas are versioned by the registry; the producer pins the schema ID it serialized with, and the consumer fetches by ID — never by name + "latest".
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 6d ago First seen · 88 lines · 0 tokens per session scan A 69d8f5cb035a
hatch3r-event-schema-evolution is a cursor rule published in the GitHub repository hatch3r/hatch3r (26 stars, last pushed 5d ago), licensed MIT. It costs nothing until one of its globs matches a file; then it loads 1,955 tokens. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-09-03.
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