file-upload-patterns
Upload files in LWC: lightning-file-upload, manual multipart, large-file chunked upload, and ContentDocument associations. NOT for ContentDocument query patterns.
Best use case
file-upload-patterns is best used when you need a repeatable AI agent workflow instead of a one-off prompt.
Upload files in LWC: lightning-file-upload, manual multipart, large-file chunked upload, and ContentDocument associations. NOT for ContentDocument query patterns.
Teams using file-upload-patterns should expect a more consistent output, faster repeated execution, less prompt rewriting.
When to use this skill
- You want a reusable workflow that can be run more than once with consistent structure.
When not to use this skill
- You only need a quick one-off answer and do not need a reusable workflow.
- You cannot install or maintain the underlying files, dependencies, or repository context.
Installation
Claude Code / Cursor / Codex
Manual Installation
- Download SKILL.md from GitHub
- Place it in
.claude/skills/file-upload-patterns/SKILL.mdinside your project - Restart your AI agent — it will auto-discover the skill
How file-upload-patterns Compares
| Feature / Agent | file-upload-patterns | Standard Approach |
|---|---|---|
| Platform Support | Not specified | Limited / Varies |
| Context Awareness | High | Baseline |
| Installation Complexity | Unknown | N/A |
Frequently Asked Questions
What does this skill do?
Upload files in LWC: lightning-file-upload, manual multipart, large-file chunked upload, and ContentDocument associations. NOT for ContentDocument query patterns.
Where can I find the source code?
You can find the source code on GitHub using the link provided at the top of the page.
SKILL.md Source
# LWC File Upload Patterns LWC file upload has three tiers: (1) `<lightning-file-upload>` for ≤2GB files associated with a record; (2) custom input + fetch for more control; (3) chunked upload for very large files using ContentVersion.VersionData. This skill picks the right tier and shows the minimal implementation. ## Adoption Signals Any file intake UI. Choose tier by max size, auth model, and UX requirements. - `lightning-file-upload` when files are <2 GB and the user already has CRUD on the parent record. - Chunked upload via Apex when files exceed the platform single-call limit and progress feedback matters. ## Recommended Workflow 1. Start with `<lightning-file-upload record-id="…">` if files are ≤2GB and tied to one record. 2. For custom flows: `<input type="file" @change=...>` → FileReader → POST to @AuraEnabled Apex with base64. 3. For files >12MB via Apex: chunk at 4.5MB and assemble ContentVersion with multiple ContentBody chunks via server-side concat. 4. Always validate MIME type client-side AND server-side. 5. Enforce size caps in Apex; don't trust client. ## Key Considerations - Apex heap is 6MB / 12MB (transaction). Base64 adds 33%. For larger files chunk or use the direct REST upload. - `lightning-file-upload` creates ContentDocumentLink automatically; custom flows must do this. - Virus scanning is not automatic; many orgs run a Lambda on ContentDocument insert. - Content types: validate with magic-bytes, not extension. ## Worked Examples (see `references/examples.md`) - *Simple record attachment* — Attach PDF to Case - *Chunked 50MB upload* — Legal contract ## Common Gotchas (see `references/gotchas.md`) - **Heap exceeded** — Error at 12MB file. - **No MIME validation** — User uploads .exe renamed .pdf. - **Missing ContentDocumentLink** — File uploaded but not visible on record. ## Top LLM Anti-Patterns (full list in `references/llm-anti-patterns.md`) - Base64-in-Apex for 100MB - Trusting client MIME - Skipping ContentDocumentLink ## Official Sources Used - Lightning Web Components Developer Guide — https://developer.salesforce.com/docs/platform/lwc/guide/ - Lightning Data Service — https://developer.salesforce.com/docs/platform/lwc/guide/data-wire-service-about.html - LWC Recipes — https://github.com/trailheadapps/lwc-recipes - SLDS 2 — https://www.lightningdesignsystem.com/2e/
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