fix(webapp): eliminate SSE abort-signal memory leak

[ericallam]

Summary

Fixes a server-side memory leak in the webapp's SSE helper. Every aborted SSE connection (client tab close, navigation, timeout) was pinning its full request/response graph indefinitely on Node 20, so any long-running webapp process accumulated retained memory proportional to streaming-request churn.

Root cause

apps/webapp/app/utils/sse.ts combined four abort signals via AbortSignal.any([requestAbortSignal, timeoutSignal, internalController.signal]). The composite signal tracks its source signals in an internal Set<WeakRef> registered against a FinalizationRegistry; under sustained traffic those entries accumulate faster than they're cleaned up, pinning every source signal (and its listeners, and anything those listeners close over) until the parent signal itself is GC'd or aborts.

This is a long-standing Node issue with multiple open reports:

• nodejs/node#54614 — original report, still open. A follow-up from ChainSafe describes the exact same shape in a Lodestar production workload (req + timeout signals composed per request accumulating in long-running worker) and the same mitigation: drop AbortSignal.any, compose manually.
• nodejs/node#55351 — mechanism confirmed by Node member @jasnell: "the set of dependent signals known to the AbortSignal are kept in an internal Set using WeakRefs. The AbortSignals are being properly gc'd but the Set is never cleaned out of the WeakRefs making those leak." Partially fixed by PR #55354, shipped in Node 22.12.0 — but only covers the tight-loop case, not long-lived parent signals.
• nodejs/node#57584 — circular-dependency variant, still open.
• nodejs/node#62363 — regression in Node 24/25 from an unrelated V8 change ("Don't pretenure WeakCells"). Different root cause, same symptom.

A separate issue in apps/webapp/app/entry.server.tsx — setTimeout(abort, ABORT_DELAY) with no clearTimeout on success paths — kept the React render tree + remixContext alive for 30s per successful HTML request. Same pattern fixed upstream in React Router templates (react-router#14200), never backported to Remix v2.

What changed

• apps/webapp/app/utils/sse.ts — single-signal abort chain. AbortSignal.any removed; AbortSignal.timeout replaced by a plain setTimeout cleared when the controller aborts; named sentinel constants used as stackless abort reasons; request-abort handler explicitly removed on cleanup.
• apps/webapp/app/entry.server.tsx — clears the setTimeout(abort, ABORT_DELAY) timer in onShellReady / onAllReady / onShellError.
• apps/webapp/app/v3/tracer.server.ts + env.server.ts — gates OpenTelemetry HttpInstrumentation and ExpressInstrumentation behind DISABLE_HTTP_INSTRUMENTATION=true as an escape hatch for future OTel-listener retention patterns. Defaults to enabled.
• apps/webapp/app/presenters/v3/RunStreamPresenter.server.ts — uses the shared ABORT_REASON_SEND_ERROR sentinel.

Verification

Full-app reproduction (memlab)

Isolated local harness, 500 abrupt SSE disconnects against a dev-presence route, GC between passes, heap snapshot diff with memlab:

Run	Heap delta after 500 conns + GC	memlab retained leaks
Before	+16.0 MB (linear with request count)	158 clusters; 250 ServerResponse, 1000 AbortController, 250 SpanImpl retained
After	+3.3 MB (noise)	0 app-code leaks

Standalone mechanism isolation

To confirm which axis of the change is load-bearing, a separate standalone Node script (/tmp/abort-leak-test.mjs) ran 2000 requests × 200 KB payload per variant:

Variant	Heap delta after GC
baseline (no signal machinery)	0 MB
V1: AbortSignal.any + string abort reason	+9.1 MB
V2: AbortSignal.any only (no reason)	+10.8 MB
V3: string reason only (no AbortSignal.any)	0 MB
V4: neither (the fix)	0 MB
V5: AbortSignal.any with no listener on the composite	+10.2 MB

This proves AbortSignal.any is the sole mechanism. The reason type (.abort() vs .abort("string")) is irrelevant for retention — V3 is clean, V5 leaks even without a listener on the composite.

Risk

• sse.ts is used by the dev-presence routes. Behaviour is equivalent — timeouts and client disconnects still abort the stream. signal.reason is now a named string sentinel ("timeout", "request_aborted", etc.) instead of the previous string arg or default AbortError. No in-tree reader of signal.reason exists.
• entry.server.tsx change is a standard cleanup of an abort timer, matches upstream React Router guidance.
• tracer.server.ts change is env-gated and defaults to current behaviour.
• Three other webapp AbortSignal.timeout() callsites (alert delivery, remote-build status) are fire-and-forget passed directly to fetch — not composed with anything long-lived, no retention risk, untouched.

Test plan

• Existing SSE integration tests pass
• Dev-presence SSE behaves normally across tab open/close cycles
• No heap growth under sustained aborted-connection traffic (heap snapshot diff)

Follow-up

The same AbortSignal.any([userSignal, internalSignal]) pattern exists in several SDK/core callsites that ship to customers (packages/core/src/v3/realtimeStreams/manager.ts, packages/trigger-sdk/src/v3/{ai,chat,chat-client,sessions}.ts, packages/core/src/v3/workers/warmStartClient.ts). Whether those leak in practice depends on the user passing a long-lived signal. Tracked separately.

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Walkthrough

Adds a server changelog entry and fixes an SSE memory leak by reworking abort/cancellation wiring: removes AbortSignal.any() and string abort reasons, introduces an internalController used directly by event streams, makes the timeout-driven abort clearable and synchronously invokable on request abort, and ensures internal aborts occur without string reasons. entry.server.tsx now stores and clears the abort timer on terminal paths. RunStreamPresenter aborts without a reason when send throws. Telemetry initialization now conditionally prepends HTTP/Express instrumentation based on a new DISABLE_HTTP_INSTRUMENTATION env flag added to the environment schema.

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~45 minutes

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title 'fix(webapp): eliminate SSE abort-signal memory leak' directly describes the primary change—eliminating a memory leak in SSE abort signal handling—and uses clear, specific language.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Description check	✅ Passed	The PR description is comprehensive and well-structured, covering root cause analysis, changes made, verification results, risk assessment, and test plan—exceeding template requirements.

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♻️ Duplicate comments (1)

apps/webapp/app/v3/tracer.server.ts (1)

310-312: ⚠️ Potential issue | 🟡 Minor

Route DISABLE_HTTP_INSTRUMENTATION through env.server.ts.

Line 310 still bypasses the webapp env schema. Add DISABLE_HTTP_INSTRUMENTATION to the env export, then use env.DISABLE_HTTP_INSTRUMENTATION here.

Suggested local change

-  if (process.env.DISABLE_HTTP_INSTRUMENTATION !== "true") {
+  if (env.DISABLE_HTTP_INSTRUMENTATION !== "true") {
     instrumentations.unshift(new HttpInstrumentation(), new ExpressInstrumentation());
   }

As per coding guidelines, “Access environment variables via env export from app/env.server.ts. Never use process.env directly”.

🤖 Prompt for AI Agents

Verify each finding against the current code and only fix it if needed.

In `@apps/webapp/app/v3/tracer.server.ts` around lines 310 - 312, Add
DISABLE_HTTP_INSTRUMENTATION to the env export in app/env.server.ts (the same
env object used throughout the app) and then replace the direct process.env
access in tracer.server.ts with env.DISABLE_HTTP_INSTRUMENTATION; update any
associated types or schema in env.server.ts (e.g., the exported Env interface or
zod/schema validator) so the new key is typed/validated, and change the
conditional in instrumentations.unshift(...) to check
env.DISABLE_HTTP_INSTRUMENTATION === "true".

🤖 Prompt for all review comments with AI agents

Verify each finding against the current code and only fix it if needed.

Duplicate comments:
In `@apps/webapp/app/v3/tracer.server.ts`:
- Around line 310-312: Add DISABLE_HTTP_INSTRUMENTATION to the env export in
app/env.server.ts (the same env object used throughout the app) and then replace
the direct process.env access in tracer.server.ts with
env.DISABLE_HTTP_INSTRUMENTATION; update any associated types or schema in
env.server.ts (e.g., the exported Env interface or zod/schema validator) so the
new key is typed/validated, and change the conditional in
instrumentations.unshift(...) to check env.DISABLE_HTTP_INSTRUMENTATION ===
"true".

---

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📒 Files selected for processing (4)

• .server-changes/fix-sse-memory-leak.md
• apps/webapp/app/entry.server.tsx
• apps/webapp/app/utils/sse.ts
• apps/webapp/app/v3/tracer.server.ts

✅ Files skipped from review due to trivial changes (1)

• apps/webapp/app/entry.server.tsx

🚧 Files skipped from review as they are similar to previous changes (2)

• .server-changes/fix-sse-memory-leak.md
• apps/webapp/app/utils/sse.ts

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• apps/webapp/app/v3/tracer.server.ts

{packages/core,apps/webapp}/**/*.{ts,tsx}

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**/*.ts

📄 CodeRabbit inference engine (.cursor/rules/otel-metrics.mdc)

**/*.ts: When creating or editing OTEL metrics (counters, histograms, gauges), ensure metric attributes have low cardinality by using only enums, booleans, bounded error codes, or bounded shard IDs
Do not use high-cardinality attributes in OTEL metrics such as UUIDs/IDs (envId, userId, runId, projectId, organizationId), unbounded integers (itemCount, batchSize, retryCount), timestamps (createdAt, startTime), or free-form strings (errorMessage, taskName, queueName)
When exporting OTEL metrics via OTLP to Prometheus, be aware that the exporter automatically adds unit suffixes to metric names (e.g., 'my_duration_ms' becomes 'my_duration_ms_milliseconds', 'my_counter' becomes 'my_counter_total'). Account for these transformations when writing Grafana dashboards or Prometheus queries

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• apps/webapp/app/v3/tracer.server.ts

apps/webapp/**/*.{ts,tsx}

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apps/webapp/**/*.{ts,tsx}: Access environment variables through the env export of env.server.ts instead of directly accessing process.env
Use subpath exports from @trigger.dev/core package instead of importing from the root @trigger.dev/core path

Use named constants for sentinel/placeholder values (e.g. const UNSET_VALUE = '__unset__') instead of raw string literals scattered across comparisons

Files:

• apps/webapp/app/v3/tracer.server.ts

apps/webapp/**/*.server.ts

📄 CodeRabbit inference engine (apps/webapp/CLAUDE.md)

apps/webapp/**/*.server.ts: Never use request.signal for detecting client disconnects. Use getRequestAbortSignal() from app/services/httpAsyncStorage.server.ts instead, which is wired directly to Express res.on('close') and fires reliably
Access environment variables via env export from app/env.server.ts. Never use process.env directly
Always use findFirst instead of findUnique in Prisma queries. findUnique has an implicit DataLoader that batches concurrent calls and has active bugs even in Prisma 6.x (uppercase UUIDs returning null, composite key SQL correctness issues, 5-10x worse performance). findFirst is never batched and avoids this entire class of issues

Files:

• apps/webapp/app/v3/tracer.server.ts

🧠 Learnings (19)

📓 Common learnings

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3399
File: apps/webapp/app/services/realtime/redisRealtimeStreams.server.ts:282-291
Timestamp: 2026-04-16T14:07:46.808Z
Learning: In `apps/webapp/app/services/realtime/redisRealtimeStreams.server.ts` (`streamResponse`), the pattern `signal.addEventListener("abort", cleanup, { once: true })` does NOT need an explicit `removeEventListener` call in the non-abort cleanup paths (inactivity, cancel). The `AbortController` is per-request, scoped to `httpAsyncStorage` (created in `apps/webapp/server.ts` per-request middleware), so it gets GC'd when the request ends — taking the listener and closure with it. The `isCleanedUp` guard prevents double-execution, and `redis.disconnect()` is called before the request ends. Do not flag this as a listener/closure leak.

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: apps/webapp/CLAUDE.md:0-0
Timestamp: 2026-04-16T14:19:16.330Z
Learning: Applies to apps/webapp/**/*.server.ts : Never use `request.signal` for detecting client disconnects. Use `getRequestAbortSignal()` from `app/services/httpAsyncStorage.server.ts` instead, which is wired directly to Express `res.on('close')` and fires reliably

📚 Learning: 2026-03-25T15:29:25.889Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: .cursor/rules/writing-tasks.mdc:0-0
Timestamp: 2026-03-25T15:29:25.889Z
Learning: Applies to trigger.config.ts : Configure telemetry instrumentations and exporters in the `telemetry` option

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-03-02T12:43:25.254Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: internal-packages/run-engine/CLAUDE.md:0-0
Timestamp: 2026-03-02T12:43:25.254Z
Learning: Applies to internal-packages/run-engine/src/engine/systems/**/*.ts : Integrate OpenTelemetry tracer and meter instrumentation in RunEngine systems for observability

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-13T21:44:00.032Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3368
File: apps/webapp/app/services/taskIdentifierRegistry.server.ts:24-67
Timestamp: 2026-04-13T21:44:00.032Z
Learning: In `apps/webapp/app/services/taskIdentifierRegistry.server.ts`, the sequential upsert/updateMany/findMany writes in `syncTaskIdentifiers` are intentionally NOT wrapped in a Prisma transaction. This function runs only during deployment-change events (low-concurrency path), and any partial `isInLatestDeployment` state is acceptable because it self-corrects on the next deployment. Do not flag this as a missing-transaction/atomicity issue in future reviews.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-15T15:39:31.575Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: .cursor/rules/webapp.mdc:0-0
Timestamp: 2026-04-15T15:39:31.575Z
Learning: Applies to apps/webapp/**/*.{ts,tsx} : Access environment variables through the `env` export of `env.server.ts` instead of directly accessing `process.env`

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-16T14:19:16.330Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: apps/webapp/CLAUDE.md:0-0
Timestamp: 2026-04-16T14:19:16.330Z
Learning: Applies to apps/webapp/**/*.server.ts : Access environment variables via `env` export from `app/env.server.ts`. Never use `process.env` directly

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-15T15:39:31.575Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: .cursor/rules/webapp.mdc:0-0
Timestamp: 2026-04-15T15:39:31.575Z
Learning: Applies to apps/webapp/**/*.test.{ts,tsx} : Do not import `env.server.ts` directly or indirectly into test files; instead pass environment-dependent values through options/parameters to make code testable

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2025-08-14T18:35:44.370Z

Learnt from: nicktrn
Repo: triggerdotdev/trigger.dev PR: 2390
File: apps/webapp/app/env.server.ts:764-765
Timestamp: 2025-08-14T18:35:44.370Z
Learning: The BoolEnv helper in apps/webapp/app/utils/boolEnv.ts uses z.preprocess with inconsistent default value types across the codebase - some usages pass boolean defaults (correct) while others pass string defaults (incorrect), leading to type confusion. The helper should enforce boolean-only defaults or have clearer documentation.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-03-27T18:11:57.032Z

Learnt from: nicktrn
Repo: triggerdotdev/trigger.dev PR: 3114
File: apps/supervisor/src/index.ts:83-98
Timestamp: 2026-03-27T18:11:57.032Z
Learning: In `apps/supervisor/src/index.ts`, `RESOURCE_MONITOR_ENABLED` (env var in `apps/supervisor/src/env.ts`) defaults to `false`. As a result, the local `ResourceMonitor`-based `maxResources`/`skipDequeue` gating in `preDequeue` is inactive in compute mode deployments. Do not flag local resource monitor usage in compute mode as a live bug; it has no practical impact unless `RESOURCE_MONITOR_ENABLED` is explicitly set to `true`.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2025-08-19T09:49:07.011Z

Learnt from: julienvanbeveren
Repo: triggerdotdev/trigger.dev PR: 2417
File: apps/webapp/app/routes/api.v1.projects.$projectRef.envvars.$slug.import.ts:56-61
Timestamp: 2025-08-19T09:49:07.011Z
Learning: In the Trigger.dev codebase, environment variables should default to `isSecret: false` when not explicitly marked as secrets in the syncEnvVars functionality. This is the intended behavior for both regular variables and parent variables.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-16T14:19:16.330Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: apps/webapp/CLAUDE.md:0-0
Timestamp: 2026-04-16T14:19:16.330Z
Learning: Applies to apps/webapp/**/*.test.{ts,tsx} : For testable code, never import `env.server.ts` in test files. Pass configuration as options instead (e.g., `realtimeClient.server.ts` takes config as constructor arg, `realtimeClientGlobal.server.ts` creates singleton with env config)

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-16T13:45:22.317Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3368
File: apps/webapp/test/engine/taskIdentifierRegistry.test.ts:3-19
Timestamp: 2026-04-16T13:45:22.317Z
Learning: In `apps/webapp/test/engine/taskIdentifierRegistry.test.ts`, the `vi.mock` calls for `~/services/taskIdentifierCache.server` (stubbing `getTaskIdentifiersFromCache` and `populateTaskIdentifierCache`), `~/models/task.server` (stubbing `getAllTaskIdentifiers`), and `~/db.server` (stubbing `prisma` and `$replica`) are intentional. The suite uses real Postgres via testcontainers for all `TaskIdentifier` DB operations, but isolates the Redis cache layer and legacy query fallback as separate concerns not exercised in this test file. Do not flag these mocks as violations of the no-mocks policy in future reviews.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-03-02T12:42:47.652Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: apps/supervisor/CLAUDE.md:0-0
Timestamp: 2026-03-02T12:42:47.652Z
Learning: Applies to apps/supervisor/src/env.ts : Environment configuration should be defined in `src/env.ts`

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2025-11-10T09:09:07.399Z

Learnt from: myftija
Repo: triggerdotdev/trigger.dev PR: 2663
File: apps/webapp/app/env.server.ts:1205-1206
Timestamp: 2025-11-10T09:09:07.399Z
Learning: In the trigger.dev webapp, S2_ACCESS_TOKEN and S2_DEPLOYMENT_LOGS_BASIN_NAME environment variables must remain optional until an OSS version of S2 is available, to avoid breaking environments that don't have S2 provisioned.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-07T14:12:18.946Z

Learnt from: matt-aitken
Repo: triggerdotdev/trigger.dev PR: 3331
File: apps/webapp/test/engine/batchPayloads.test.ts:5-24
Timestamp: 2026-04-07T14:12:18.946Z
Learning: In `apps/webapp/test/engine/batchPayloads.test.ts`, using `vi.mock` for `~/v3/objectStore.server` (stubbing `hasObjectStoreClient` and `uploadPacketToObjectStore`), `~/env.server` (overriding offload thresholds), and `~/v3/tracer.server` (stubbing `startActiveSpan`) is intentional and acceptable. Simulating controlled transient upload failures (e.g., fail N times then succeed) to verify `p-retry` behavior cannot be reproduced with real services or testcontainers. This file is an explicit exception to the repo's general no-mocks policy.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-04-16T14:19:16.330Z

Learnt from: CR
Repo: triggerdotdev/trigger.dev PR: 0
File: apps/webapp/CLAUDE.md:0-0
Timestamp: 2026-04-16T14:19:16.330Z
Learning: Applies to apps/webapp/**/*.{ts,tsx} : Use named constants for sentinel/placeholder values (e.g. `const UNSET_VALUE = '__unset__'`) instead of raw string literals scattered across comparisons

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-03-22T13:26:12.060Z

Learnt from: ericallam
Repo: triggerdotdev/trigger.dev PR: 3244
File: apps/webapp/app/components/code/TextEditor.tsx:81-86
Timestamp: 2026-03-22T13:26:12.060Z
Learning: In the triggerdotdev/trigger.dev codebase, do not flag `navigator.clipboard.writeText(...)` calls for `missing-await`/`unhandled-promise` issues. These clipboard writes are intentionally invoked without `await` and without `catch` handlers across the project; keep that behavior consistent when reviewing TypeScript/TSX files (e.g., usages like in `apps/webapp/app/components/code/TextEditor.tsx`).

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-03-22T19:24:14.403Z

Learnt from: matt-aitken
Repo: triggerdotdev/trigger.dev PR: 3187
File: apps/webapp/app/v3/services/alerts/deliverErrorGroupAlert.server.ts:200-204
Timestamp: 2026-03-22T19:24:14.403Z
Learning: In the triggerdotdev/trigger.dev codebase, webhook URLs are not expected to contain embedded credentials/secrets (e.g., fields like `ProjectAlertWebhookProperties` should only hold credential-free webhook endpoints). During code review, if you see logging or inclusion of raw webhook URLs in error messages, do not automatically treat it as a credential-leak/secrets-in-logs issue by default—first verify the URL does not contain embedded credentials (for example, no username/password in the URL, no obvious secret/token query params or fragments). If the URL is credential-free per this project’s conventions, allow the logging.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts

📚 Learning: 2026-03-29T19:16:28.864Z

Learnt from: nicktrn
Repo: triggerdotdev/trigger.dev PR: 3291
File: apps/webapp/app/v3/featureFlags.ts:53-65
Timestamp: 2026-03-29T19:16:28.864Z
Learning: When reviewing TypeScript code that uses Zod v3, treat `z.coerce.*()` schemas as their direct Zod type (e.g., `z.coerce.boolean()` returns a `ZodBoolean` with `_def.typeName === "ZodBoolean"`) rather than a `ZodEffects`. Only `.preprocess()`, `.refine()`/`.superRefine()`, and `.transform()` are expected to wrap schemas in `ZodEffects`. Therefore, in reviewers’ logic like `getFlagControlType`, do not flag/unblock failures that require unwrapping `ZodEffects` when the input schema is a `z.coerce.*` schema.

Applied to files:

• apps/webapp/app/v3/tracer.server.ts