[hpouillot]

Problem

Cymbal needs a bounded, failure-safe evaluator for the severity-rule contract before issue linking can use configured rules.

Changes

• Loads enabled severity rules for the current team and evaluates them in configured order.
• Uses the same HogVM issue and processed-property globals as assignment rules.
• Returns the first matching typed severity and preserves no-match fallback for callers.
• Disables invalid programs while allowing later rules to run; step exhaustion skips only the current event.
• Adds dedicated bounded caching and static-label processing metrics.
• Does not yet call the evaluator from issue linking.

PR stack

Merge in this order:

1. feat(error-tracking): add severity rules API #86267
2. feat(cymbal): evaluate error tracking severity rules #86268 — this PR
3. feat(cymbal): apply severity rules on issue creation #86270
4. feat(error-tracking): add severity rules settings #86271

Depends on: #86267
Followed by: #86270

This PR is based on hp/error-tracking-severity-rules-01-api; review only changes relative to that branch. After PR 1 is squash-merged, replay only this PR's unique commit onto updated master, force-push with lease, then retarget. Do not retarget blindly.

How did you test this code?

• cargo fmt --check
• cargo test -p cymbal --test severity_rules
• cargo check -p cymbal

The tests cover team isolation, enabled-only loading, every supported severity, first-match ordering, fallback, invalid-program disabling, and step-budget skipping.

👉 Stay up-to-date with PostHog coding conventions for a smoother review.

Automatic notifications

• Publish to changelog?

Docs update

None for this internal evaluator layer.

🤖 Agent context

Autonomy: Human-driven (agent-assisted)

Implemented with pi coding agent. Repo guidance and the OpenSpec apply, Rust testing, and stacked PR skills shaped the implementation and split. A dedicated typed rule severity keeps the evaluator testable without widening Cymbal's internal inferred-severity type.

[github-actions]

🤖 CI report

✅ Trunk lane — non-backend lane

This PR is assigned to the non-backend lane. It does not run backend Python tests and may merge in parallel with PRs in other lanes.

[trunk-io]

   

View Full Report ↗︎ ⋅ Docs

[greptile-apps]

Prompt To Fix All With AI

### Issue 1
rust/cymbal/src/modes/processing/rules/severity.rs:220-228
**Disabled rules remain cached**

After an invalid rule is disabled in Postgres, `get_severity_rules` continues returning the cached vector containing it. Each event for that team re-executes the invalid program and issues another database update until the default five-minute TTL expires, adding repeated writes and processing overhead.

---

For each issue above, determine whether it is valid and should be fixed. If so, fix it directly.

_{Reviews (1): Last reviewed commit: "feat(cymbal): evaluate severity rules" | Re-trigger Greptile}

[ablaszkiewicz]

I approved to not block but I think greptiles comment should be addressed. Removed auto merge

[trunk-io]

😎 Merged successfully - details.

[deployment-status-posthog]

Deploy status

Environment	Status	Deployed At	Workflow
dev	✅ Deployed	2026-08-24 10:13 UTC	Run
prod-us	✅ Deployed	2026-08-24 10:36 UTC	Run
prod-eu	✅ Deployed	2026-08-24 10:33 UTC	Run