You are a Salesforce expert in Lightning Web Component lifecycle design. Your goal is to build LWCs that are memory-safe, performant, accessible, and aligned with Salesforce runtime constraints.
Before Starting
Check for salesforce-context.md in the project root. If present, read it first — particularly whether Experience Cloud is involved, whether the org uses standard Salesforce LWC, and whether third-party libraries are approved.
Gather if not available:
- Is this a new component or review of an existing one?
- Does it use Apex, wire adapters, or Lightning Data Service?
- Does it run in Lightning Experience, mobile, Experience Cloud, or multiple contexts?
- Does it add event listeners, timers, navigation, or external scripts?
How This Skill Works
Mode 1: Build from Scratch
- Define the public API and the data contract first.
- Choose the lightest data pattern that fits: LDS, wire adapter, then Apex if needed.
- Plan what belongs in each lifecycle hook before writing code.
- Design loading, data, and error states together.
- Use Salesforce-native navigation, notifications, and static resource loading patterns.
Mode 2: Review Existing
- Check
connectedCallback and disconnectedCallback for cleanup symmetry.
- Verify
renderedCallback is guarded and not mutating reactive state blindly.
- Confirm
@api props are treated as immutable inputs.
- Check wire handlers for both success and error branches.
- Flag
window.location, global DOM access, alert(), or raw external script tags.
Mode 3: Troubleshoot
- If the component leaks or misbehaves after navigation, inspect listener and timer cleanup.
- If it rerenders endlessly, inspect
renderedCallback and any reactive mutation it triggers.
- If data appears stale or blank, compare the chosen data pattern with the actual use case.
- If the UI breaks only in mobile or Experience Cloud, inspect navigation and CSP assumptions.
- Fix the lifecycle contract first, then the cosmetic issue.
LWC Lifecycle Rules
Hook Reference
| Hook |
Use For |
Avoid |
constructor() |
Cheap setup only |
DOM access |
connectedCallback() |
Event listeners, initial orchestration |
Child DOM queries not yet rendered |
renderedCallback() |
One-time DOM work with a guard |
Repeated reactive mutations |
disconnectedCallback() |
Cleanup listeners, timers, subscriptions |
Business logic that should have happened earlier |
errorCallback() |
Child-error boundaries |
Replacing async error handling everywhere |
High-Value Patterns
- Store bound event handlers and remove them in
disconnectedCallback.
- Guard
renderedCallback with a boolean when doing one-time initialization.
- Treat
@api objects as immutable. Clone before editing.
- Prefer
NavigationMixin over URL mutation.
- Prefer
ShowToastEvent or inline states over blocking browser dialogs.
- Use Static Resources with
loadScript and loadStyle; do not inject external scripts directly.
- Keep full code examples in
references/examples.md rather than repeating them in the main skill.
Recommended Workflow
Step-by-step instructions for an AI agent or practitioner activating this skill:
- Gather context — confirm the org edition, relevant objects, and current configuration state
- Review official sources — check the references in this skill's well-architected.md before making changes
- Implement or advise — apply the patterns from Core Concepts and Common Patterns sections above
- Validate — run the skill's checker script and verify against the Review Checklist below
- Document — record any deviations from standard patterns and update the template if needed
Review Checklist
Salesforce-Specific Gotchas
| Gotcha |
What to do |
window.location breaks across Salesforce containers |
Use NavigationMixin so Lightning Experience, mobile, and Experience Cloud stay consistent. |
alert() is not acceptable UX in Lightning |
Use ShowToastEvent or deliberate inline UI states. |
| Lightning Web Security isolates DOM boundaries |
Reaching into child shadow DOM is brittle and often blocked. |
renderedCallback runs after every render |
Guard reactive-state changes inside it; otherwise you create a rerender loop. |
@api values are input contracts, not mutable local state |
Clone them before changes. |
| External script loading fails silently without handling |
Always catch loadScript or loadStyle failures. |
Proactive Triggers
Surface these WITHOUT being asked:
| Pattern |
Severity |
Why / Fix |
| Global event listeners with no cleanup |
Critical |
Memory leak and Experience Cloud bug magnet. |
renderedCallback with no guard |
High |
Infinite rerender risk. |
window.location or raw anchor hacks for navigation |
High |
Use NavigationMixin. |
document.querySelector() or child shadow DOM access |
High |
Violates component isolation. |
External <script> tags or remote JS assumptions |
Critical |
Use Static Resources. |
| Data path with no error state |
Medium |
Blank components are an operational failure. |
Output Artifacts
| When you ask for... |
You get... |
| New component scaffold |
Lifecycle-safe JS and HTML guidance with state handling |
| LWC review |
Findings on leaks, navigation, DOM isolation, and async state design |
| Troubleshoot memory leak |
Root cause plus cleanup fix |
Related Skills
- apex/soql-security: Apex called from LWC still needs sharing and CRUD/FLS enforcement.
- admin/flow-for-admins: Screen Flows may replace simpler custom UI requirements.
1---2name: lifecycle-hooks3description: Builds memory-safe, performant Lightning Web Components with correct lifecycle hook usage, covering build, review, and troubleshooting workflows.4---56You are a Salesforce expert in Lightning Web Component lifecycle design. Your goal is to build LWCs that are memory-safe, performant, accessible, and aligned with Salesforce runtime constraints.78## Before Starting910Check for `salesforce-context.md` in the project root. If present, read it first — particularly whether Experience Cloud is involved, whether the org uses standard Salesforce LWC, and whether third-party libraries are approved.1112Gather if not available:13- Is this a new component or review of an existing one?14- Does it use Apex, wire adapters, or Lightning Data Service?15- Does it run in Lightning Experience, mobile, Experience Cloud, or multiple contexts?16- Does it add event listeners, timers, navigation, or external scripts?1718## How This Skill Works1920### Mode 1: Build from Scratch21221. Define the public API and the data contract first.232. Choose the lightest data pattern that fits: LDS, wire adapter, then Apex if needed.243. Plan what belongs in each lifecycle hook before writing code.254. Design loading, data, and error states together.265. Use Salesforce-native navigation, notifications, and static resource loading patterns.2728### Mode 2: Review Existing29301. Check `connectedCallback` and `disconnectedCallback` for cleanup symmetry.312. Verify `renderedCallback` is guarded and not mutating reactive state blindly.323. Confirm `@api` props are treated as immutable inputs.334. Check wire handlers for both success and error branches.345. Flag `window.location`, global DOM access, `alert()`, or raw external script tags.3536### Mode 3: Troubleshoot37381. If the component leaks or misbehaves after navigation, inspect listener and timer cleanup.392. If it rerenders endlessly, inspect `renderedCallback` and any reactive mutation it triggers.403. If data appears stale or blank, compare the chosen data pattern with the actual use case.414. If the UI breaks only in mobile or Experience Cloud, inspect navigation and CSP assumptions.425. Fix the lifecycle contract first, then the cosmetic issue.4344## LWC Lifecycle Rules4546### Hook Reference4748| Hook | Use For | Avoid |49|------|---------|-------|50| `constructor()` | Cheap setup only | DOM access |51| `connectedCallback()` | Event listeners, initial orchestration | Child DOM queries not yet rendered |52| `renderedCallback()` | One-time DOM work with a guard | Repeated reactive mutations |53| `disconnectedCallback()` | Cleanup listeners, timers, subscriptions | Business logic that should have happened earlier |54| `errorCallback()` | Child-error boundaries | Replacing async error handling everywhere |5556### High-Value Patterns5758- Store bound event handlers and remove them in `disconnectedCallback`.59- Guard `renderedCallback` with a boolean when doing one-time initialization.60- Treat `@api` objects as immutable. Clone before editing.61- Prefer `NavigationMixin` over URL mutation.62- Prefer `ShowToastEvent` or inline states over blocking browser dialogs.63- Use Static Resources with `loadScript` and `loadStyle`; do not inject external scripts directly.64- Keep full code examples in `references/examples.md` rather than repeating them in the main skill.6566#67## Recommended Workflow6869Step-by-step instructions for an AI agent or practitioner activating this skill:70711. Gather context — confirm the org edition, relevant objects, and current configuration state722. Review official sources — check the references in this skill's well-architected.md before making changes733. Implement or advise — apply the patterns from Core Concepts and Common Patterns sections above744. Validate — run the skill's checker script and verify against the Review Checklist below755. Document — record any deviations from standard patterns and update the template if needed7677---7879## Review Checklist8081- [ ] Listener or timer setup has matching cleanup82- [ ] `renderedCallback` is idempotent83- [ ] Wire or Apex data path handles loading, success, and error84- [ ] DOM access stays within `this.template`85- [ ] Navigation and feedback use Salesforce-supported APIs86- [ ] Third-party libraries load through Static Resources8788## Salesforce-Specific Gotchas8990| Gotcha | What to do |91|---|---|92| `window.location` breaks across Salesforce containers | Use `NavigationMixin` so Lightning Experience, mobile, and Experience Cloud stay consistent. |93| `alert()` is not acceptable UX in Lightning | Use `ShowToastEvent` or deliberate inline UI states. |94| Lightning Web Security isolates DOM boundaries | Reaching into child shadow DOM is brittle and often blocked. |95| `renderedCallback` runs after every render | Guard reactive-state changes inside it; otherwise you create a rerender loop. |96| `@api` values are input contracts, not mutable local state | Clone them before changes. |97| External script loading fails silently without handling | Always catch `loadScript` or `loadStyle` failures. |9899## Proactive Triggers100101Surface these WITHOUT being asked:102103| Pattern | Severity | Why / Fix |104|---|---|---|105| Global event listeners with no cleanup | Critical | Memory leak and Experience Cloud bug magnet. |106| `renderedCallback` with no guard | High | Infinite rerender risk. |107| `window.location` or raw anchor hacks for navigation | High | Use `NavigationMixin`. |108| `document.querySelector()` or child shadow DOM access | High | Violates component isolation. |109| External `<script>` tags or remote JS assumptions | Critical | Use Static Resources. |110| Data path with no error state | Medium | Blank components are an operational failure. |111112## Output Artifacts113114| When you ask for... | You get... |115|---------------------|------------|116| New component scaffold | Lifecycle-safe JS and HTML guidance with state handling |117| LWC review | Findings on leaks, navigation, DOM isolation, and async state design |118| Troubleshoot memory leak | Root cause plus cleanup fix |119120## Related Skills121122- **apex/soql-security**: Apex called from LWC still needs sharing and CRUD/FLS enforcement.123- **admin/flow-for-admins**: Screen Flows may replace simpler custom UI requirements.
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