Rum Tracking

RUM Tracking

Guides product-analytics and RUM event tracking for web (React/Next.js) and mobile (React Native/Expo) apps. Decides what to capture, what to drop, what's PII, and how to add, audit, update, and remove tracking code without breaking downstream dashboards.

External dependency. The OTel guidance in rules/otel-conventions.md builds on the otel-instrumentation and otel-semantic-conventions skills, which live in the dash0 agent-skills repo, not this one. That rule invokes them at runtime via Skill() when they're installed (and skips silently otherwise) — install them alongside this skill to get their authoritative span/metric/attribute guidance.

This SKILL.md is a thin index. Detailed rules live in rules/*.md and load on demand. Worked examples live in references/*.md. Literal scaffolding lives in templates/*.md.

Mode Detection

Parse $1 as the mode. State the detected mode in one line before continuing.

If $1 is a target file or directory, treat it as the scope for audit, implement, or remove.

Workflow by Mode

Guide mode (default)

The user is deciding whether and what to track at a specific point.

1. Load rules/what-to-track.md and rules/what-not-to-track.md.
2. Cross-check the proposal against rules/pii-and-compliance.md.
3. Recommend an event name + property set using rules/event-design.md.
4. If the project uses OpenTelemetry RUM (Dash0 SDK Web, OTel browser / mobile, Embrace), also apply rules/otel-conventions.md.
5. Surface canonical events from references/event-catalog.md instead of inventing new ones when one fits.

Implement mode

The user wants tracking code written.

1. Confirm the event is in the tracking plan (rules/tracking-plan.md). If not, propose adding it to the plan first and gate the user before writing instrumentation.
2. Pick the platform:
   • Web (React/Next.js) → rules/implementation-web.md.
   • Mobile (React Native/Expo) → rules/implementation-mobile.md.
3. If using OpenTelemetry, also load rules/otel-conventions.md.
4. All tracking calls must go through the centralized wrapper (templates/analytics-wrapper.template.ts). Never call the vendor SDK directly from a component.
5. Run the PII gate from rules/pii-and-compliance.md on every property before the diff is final.

Audit mode

The user wants existing tracking reviewed.

1. Walk the checklist in rules/audit-checklist.md.
2. For every finding, cite a file path and line number.
3. Group findings into: blocking (PII / consent / compliance), important (drift / ghost events / cardinality), nice-to-have (naming consistency).
4. Output a ranked fix list — do not auto-edit unless the user approved a pre-defined audit scope.

Remove mode

The user wants tracking deprecated or deleted.

1. Apply the lifecycle in rules/update-and-remove.md.
2. Find every callsite via the centralized wrapper's typed event names.
3. Identify downstream consumers (dashboards, funnels, dbt models, cohorts) before deletion.
4. Mark deprecated first, set a sunset date, then remove.
5. Update the tracking plan and the inventory in the same PR.

Plan mode

The user wants to design, update, or codegen a tracking plan.

1. Apply the structure in rules/tracking-plan.md.
2. Start from templates/tracking-plan.template.yaml.
3. Choose a naming school (rules/event-design.md) and freeze it for the project.
4. Wire codegen (Avo, RudderTyper, Typewriter, or hand-rolled json-schema-to-typescript) so the wrapper is type-checked.

Required Reading by Mode

Load on demand — do not preload.

references/platforms.md is optional — load when the user asks "which platform should we use" or names a specific vendor.

Core Principles

1. The tracking plan is the source of truth. Every event must exist in the plan before it exists in code.
2. Centralized wrapper, never raw SDK calls. One module owns every track() callsite; swapping vendors must be a single-file change.
3. Type-safe events. Use codegen (Avo, RudderTyper, Typewriter) or a hand-rolled discriminated union so renames break the build.
4. PII never appears in event properties. Use opaque user.id, hash for correlation, strip URLs and free-text.
5. Low-cardinality event names; rich, bounded properties. ≤ 30 event names in a typical app; high-value context in properties.
6. Defer sampling to the pipeline. SDKs export everything; the Collector or platform decides what to keep.
7. OpenTelemetry semantic conventions when present. user.id, session.id, browser.*, app.*, error.type come from the registry — do not invent custom names that overlap.
8. Remove tracking the same way you add it. Plan first, deprecate, find consumers, then delete.

Anti-patterns (one-liners)

• Scattering posthog.capture() / mixpanel.track() calls across components instead of one wrapper.
• Tracking every hover, scroll, or render — drowns signal, explodes cost.
• Putting email, full URLs with tokens, raw req.body, or stack traces with user input into event properties.
• Using email or username as distinct_id / user.id — always opaque.
• Naming events inconsistently (signup and user_registered for the same concept).
• Deleting an event before checking which dashboards consume it.
• Configuring SDK-side sampling — sample in the Collector instead.
• Treating hashed email as anonymous — it remains personal data under GDPR.

Definition of Done

• Mode detected and stated.
• Required reading for the mode loaded.
• If implement or remove: tracking plan updated in the same diff.
• PII gate run on every new or modified event.
• Centralized wrapper used; no raw SDK calls in feature code.
• Downstream consumers identified before removal.
• Recommendation cites file paths and line numbers, or proposes a concrete diff.