platform-custom-lightning-type-generate

When to Use This Skill

Use this skill when you need to:

• Create Custom Lightning Types (CLTs) for structured inputs/outputs
• Generate JSON Schema-based type definitions for Lightning Platform
• Configure CLTs for Einstein Agent actions
• Set up editor and renderer configurations for custom UI
• Create CLTs with widget/mosaic/fragment rendition
• Troubleshoot deployment errors related to Custom Lightning Types

Specification

CustomLightningType Metadata Specification

Overview & Purpose

Custom Lightning Types (CLTs) are JSON Schema-based type definitions used by the Lightning Platform (including Einstein Agent actions) to describe structured inputs/outputs and drive editor/renderer experiences.

Configuration

• Choose referenced CLT pattern for nested objects - When you need a reusable or separately deployed nested type, create a CLT for that shape and reference it with "lightning:type": "c__<CLTName>". That string is the referenced type’s lightning:type value / FQN / registered identifier — not the JSON Schema title.
• Choose standard Lightning types when the structure is simple and can be expressed with properties and supported primitive lightning:type identifiers.
• Choose Apex class types (@apexClassType/...) when the structure already exists server-side and you want the Apex class to define the shape.
• Include editor/renderer config only when you need custom UI behavior (custom LWC input/output components). Otherwise, omit.

Critical Rules (Read First)

• CRITICAL: NEVER include the "$schema" field in schema.json
• Salesforce CLT validator WILL REJECT schemas with this field, even if it's a valid JSON Schema $schema declaration.
• Root object schemas MUST include:
• "type": "object"
• "title"
• "lightning:type": "lightning__objectType"
• "unevaluatedProperties": false
• "unevaluatedProperties" is enforced as false by the CLT metaschema. Do not set it to true.
• Root object schemas MUST NOT include "examples" when "unevaluatedProperties": false is set.
• Nested objects (inside properties) MUST NOT set "lightning:type": "lightning__objectType".
• Nested objects can be: references to other CLTs using c__<CLTName> syntax.
• List/array properties are highly restricted by the CLT metaschema:
• CRITICAL LIMITATION: the CLT metaschema may reject the items keyword entirely. Treat items as disallowed by default.
• Root-level arrays (direct children of the root properties):
• MUST include "lightning:type": "lightning__listType"
• MUST NOT include "items"
• OPTIONAL "type": "array"
• Nested arrays (arrays inside nested objects) are the most common failure:
• MUST include "type": "array"
• MUST NOT include "lightning:type": "lightning__listType"
• MUST NOT include "items"
• When "unevaluatedProperties": false is set, any unknown keyword will fail validation. Prefer removing keywords over relaxing strictness.
• Apex class CLTs are minimal:
• Include only title, description (optional), and lightning:type set to @apexClassType/....
• Do not add type, properties, required, or unevaluatedProperties.

Additional CLT Metaschema Validations

• Org namespace validation: titles/descriptions and other string fields may be validated to ensure you are not using an org namespace in places that are disallowed.
• Lightning type validation: CLTs are validated to prevent referencing internal namespaces (for example, disallowing types from internal namespaces like sfdc_cms where not permitted).
• Object type validation: the CLT root is validated to ensure lightning:type is exactly lightning__objectType.

Primitive Types & Constraints

When you need the full list of supported primitive lightning:type identifiers, their constraints, and the allowed property-level keywords, read assets/primitive-types-and-constraints.md in this skill's directory.

Generation Workflow

1. Confirm the CLT approach

• If referencing Apex: capture the exact class reference (@apexClassType/namespace__ClassName$InnerClass).
• If using standard primitives: list the fields, their Lightning primitive types, and which fields are required.

1. Draft schema.json

• DO NOT include "$schema" at the top
• Start with the root object structure (required root fields).
• Add properties using valid primitive lightning:type identifiers.
• For nested-object properties, use CLT Reference pattern:
• "lightning:type": "c__<CLTName>" to reference another CLT
• The referenced CLT must be deployed to the org before the parent CLT.
• For Apex-based nested objects: Use @apexClassType/... when structure exists server-side.
• If the prompt explicitly requires true nested object output, prefer an Apex-based CLT (@apexClassType/...) for deploy-safe nested structures.
• For arrays: follow the strict list rules (avoid items; avoid lightning:type on nested arrays).
• Before deployment, verify exact lightning:type spellings (for example, use lightning__richTextType, not misspelled variants).

1. (Optional) Draft editor.json (only if custom UI is required)

• Supported shape: Top-level editor object with editor.componentOverrides and editor.layout.
• Top-level editor object.
• Use editor.componentOverrides for component overrides.
• Use editor.layout for layout.
• DEPRECATED: Do NOT use propertyRenderers or view — these are legacy keys. Always use componentOverrides and layout instead.
• Root override pattern (most common for fully custom editing UI):
• editor.componentOverrides["$"] = { "definition": "c/<yourEditorComponent>", "attributes": { ... } }
• When passing schema data into a custom LWC, use attribute mapping with the {!$attrs.<name>} syntax: e.g. "attributes": { "myField": "{!$attrs.value}" } so the runtime binds schema values to your component's attributes.
• CRITICAL: The <name> in {!$attrs.<name>} must be a property defined in your type schema. For example, if your schema has a property called temperature, use {!$attrs.temperature}, not {!$attrs.value} unless value is an actual property.
• Property-level override pattern (for individual fields):
• editor.componentOverrides["<propertyName>"] = { "definition": "es_property_editors/<...>" }
• Valid editor components (examples): es_property_editors/inputText, es_property_editors/inputNumber, es_property_editors/inputRichText, es_property_editors/inputImage, es_property_editors/inputTextarea. Do not use es_property_editors/inputList.
• Collection editor (for root-level lightning__listType properties): Use a collection-level override so the list is edited by a custom component: collection.editor.componentOverrides["$"] = { "definition": "c/<yourCollectionEditorComponent>" }. Alternatively, use editor.layout with lightning/propertyLayout and attributes.property = "<listPropertyName>" for default list editing.
• Layout pattern:
• editor.layout.definition = "lightning/verticalLayout"
• editor.layout.children[*].definition = "lightning/propertyLayout" with attributes.property = "<propertyName>"
• CRITICAL: lightning/propertyLayout only accepts the property attribute. Do NOT add label, title, or any other attributes — these will fail validation with additionalProperties: false errors.
• Avoid known-invalid patterns:
• Do not use es_property_editors/inputList.
• Do not use itemSchema attributes.

1. (Optional) Draft renderer.json (only if custom UI or mosaic rendition is required)

• Supported shape: Top-level renderer object with renderer.componentOverrides and renderer.layout.
• Top-level renderer object.
• Use renderer.componentOverrides for component overrides.
• Use renderer.layout for layout.
• DEPRECATED: Do NOT use propertyRenderers or view — these are legacy keys. Always use componentOverrides and layout instead.
• Root override pattern (most common for fully custom rendering UI):
• renderer.componentOverrides["$"] = { "definition": "c/<yourRendererComponent>", "attributes": { ... } }
• Use {!$attrs.<name>} in attribute mappings when binding schema data to custom renderer component attributes.
• CRITICAL: Attribute mappings like {!$attrs.propertyName} must reference properties that actually exist in your type schema. Referencing non-existent properties will fail validation.
• Type matching: Attribute values must match the expected type for the component. For example, if a component expects a string attribute, passing an integer will fail validation.
• Widget renderer pattern (for widget rendition):
• When to use: Use this when users request "mosaic", "widget", "fragment", or "cross-platform rendering" for their CLT.
• Structure: renderer.componentOverrides["$"] = { "type": "mosaic", "definition": "tile/mosaic", "children": [ / UEM tree of blocks and regions / ] }
• REQUIRED workflow:
• STOP: Do NOT attempt to create the widget renderer yourself.
• MANDATORY FIRST STEP: You MUST fetch the reference file references/widget-rendition.md located in this skill's directory before proceeding.
• Follow the complete workflow documented in widget-rendition.md using the generated CLT schema as the grounding schema.
• The widget-rendition.md reference contains the full widget generation workflow: discovering UEM blocks via discoverUiComponents, calling getUiComponentSchemas, building the UEM tree, and writing renderer.json.
• Do not attempt to generate widget rendition without first fetching the widget-rendition.md reference file.
• Property-level override pattern:
• renderer.componentOverrides["<propertyName>"] = { "definition": "es_property_editors/outputText" | "es_property_editors/outputNumber" | "es_property_editors/outputImage" | ... }. Valid renderer components (examples): es_property_editors/outputText, es_property_editors/outputNumber, es_property_editors/outputImage. Avoid input-style components in the renderer.
• Layout pattern for renderer:
• renderer.layout.definition = "lightning/verticalLayout"
• renderer.layout.children[*].definition = "lightning/propertyLayout" with attributes.property = "<propertyName>"
• CRITICAL: Same as editor layouts, lightning/propertyLayout only accepts the property attribute. Do NOT add label, title, or any other attributes.
• Collection renderer (for root-level lightning__listType properties): Use collection.renderer.componentOverrides["$"] = { "definition": "c/<yourListRendererComponent>" } or es_property_editors/genericListTypeRenderer to render the list.

1. Place files in the correct bundle structure

• lightningTypes/<TypeName>/schema.json
• (Optional) lightningTypes/<TypeName>/lightningDesktopGenAi/editor.json
• (Optional) lightningTypes/<TypeName>/lightningDesktopGenAi/renderer.json
• For Gen AI / Copilot the standard path is lightningDesktopGenAi/. Other targets (e.g. Experience Builder, Mobile Copilot, Enhanced Web Chat) use different subfolders when supported: experienceBuilder/, lightningMobileGenAi/, enhancedWebChat/.

1. Configure custom LWC components (if using custom components)

• CRITICAL: Custom LWC components referenced in editor/renderer configs MUST have the correct target configuration in their -meta.xml files:
• For editor components (c/<componentName> used in editor.json): The LWC's -meta.xml file must include <target>lightning__AgentforceInput</target>
• For renderer components (c/<componentName> used in renderer.json): The LWC's -meta.xml file must include <target>lightning__AgentforceOutput</target>
• Without the correct target, deployment will fail with: Invalid target configuration. To use 'c/componentName' as a renderer/editor, your js-meta.xml file must include valid target 'lightning__AgentforceOutput/Input'.
• Example -meta.xml for a renderer component:

     <?xml version="1.0" encoding="UTF-8"?>
     <LightningComponentBundle xmlns="http://soap.sforce.com/2006/04/metadata">
         <apiVersion>60.0</apiVersion>
         <isExposed>true</isExposed>
         <targets>
             <target>lightning__AgentforceOutput</target>
         </targets>
     </LightningComponentBundle>

Common Deployment Errors

Verification Checklist

• [ ] Root schema has type: "object", title, lightning:type: "lightning__objectType", and unevaluatedProperties: false
• [ ] Root schema does not include examples when strict validation is enabled
• [ ] No nested object includes lightning:type: "lightning__objectType"
• [ ] Arrays are defined minimally (especially nested arrays)
• [ ] Only supported primitive lightning:type identifiers are used for leaf properties
• [ ] Apex class CLTs contain only title/description and lightning:type: "@apexClassType/..."
• [ ] Bundle structure and filenames match Lightning Types requirements
• [ ] Editor config uses only allowed patterns (no es_property_editors/inputList, no itemSchema); use valid components (e.g. es_property_editors/inputText, es_property_editors/inputNumber) or custom c/ components
• [ ] Renderer config uses output-style components (e.g. es_property_editors/outputText, es_property_editors/outputNumber) where applicable, not input editors
• [ ] Layout configurations use lightning/propertyLayout with ONLY the property attribute (no label, title, or other attributes)
• [ ] All attribute mappings ({!$attrs.propertyName}) reference properties that exist in the type schema
• [ ] Custom LWC components have correct targets in -meta.xml: lightning__AgentforceInput for editors, lightning__AgentforceOutput for renderers
• [ ] Root schema does NOT include "$schema" field