generating-custom-lightning-type

SKILL.md

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

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.

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).

(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.

(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.

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/.

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

Error / Symptom
Likely Cause
Fix

Schema validation fails due to unknown keyword
unevaluatedProperties: false + disallowed keyword (commonly examples, items)
Remove the offending keyword; keep schema minimal

Nested object validation failure
Org/channel validation rejects nested object typing in LightningTypeBundle
Use CLT reference (c__<CLTName>) or Apex class types

Invalid CLT reference
Referenced CLT doesn't exist in org or incorrect syntax
Deploy the referenced CLT first; c__<CLTName> must match the referenced type’s lightning:type value / FQN / registered identifier, not title

Invalid or misspelled lightning:type (for example, lightning__richtextType instead of lightning__richTextType)
Incorrect generated type name
Cross-check all lightning:type values against supported type names and correct them before deployment

Array property rejected
Use of items (or lightning:type in nested arrays) rejected by validator
For nested arrays: keep only type: "array". For root arrays: use minimal structure; remove items if rejected

Apex-based CLT rejected
Extra fields added (e.g., type, properties)
Use only title, optional description, and lightning:type

Editor config rejected
Use of invalid patterns (es_property_editors/inputList, itemSchema) or unrecognized top-level keys
Use editor.componentOverrides and editor.layout; keep config minimal

additionalProperties error on layout attributes
Adding label or other attributes to lightning/propertyLayout
Only use property attribute in lightning/propertyLayout. Remove label, title, or any other attributes

Invalid target configuration for custom LWC
Custom LWC component's -meta.xml missing required target (lightning__AgentforceInput or lightning__AgentforceOutput)
Add correct target to LWC's -meta.xml: use lightning__AgentforceInput for editors, lightning__AgentforceOutput for renderers

Attribute mapping doesn't exist in type schema
Using {!$attrs.propertyName} where propertyName is not defined in schema
Ensure all attribute mappings reference actual properties in your type schema's properties section

additionalProperties error with deprecated keys
Using propertyRenderers or view in editor/renderer config
Replace deprecated propertyRenderers with componentOverrides and view with layout

Type mismatch in component attributes
Passing wrong type for component attribute (e.g., integer instead of string)
Ensure attribute values match the expected type defined by the component

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