# canvas.writeHtml
mutation write
Use when the requested change exactly matches canvas.writeHtml; read the current state first when a version or identifier may have changed.
## Before calling
- Authenticate as the accountable Enhance person.
- Use only resource identifiers returned by an earlier capability result or supplied by the person.
- Reuse clientToken only when retrying this exact mutation input.
## Input
Show complete JSON Schema
```json
{
"$schema": "https://json-schema.org/draft/2020-12/schema",
"type": "object",
"properties": {
"canvasId": {
"type": "string",
"format": "uuid",
"pattern": "^([0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-8][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}|00000000-0000-0000-0000-000000000000|ffffffff-ffff-ffff-ffff-ffffffffffff)$"
},
"targetNodeId": {
"type": "string",
"minLength": 1,
"maxLength": 200,
"description": "Stable container id for insert-children, or subtree root id for replace."
},
"mode": {
"type": "string",
"enum": [
"insert-children",
"replace"
],
"description": "Insert the compiled group inside the target, or replace the target subtree."
},
"html": {
"type": "string",
"minLength": 1,
"maxLength": 1000000,
"description": "Exactly one safe top-level HTML/CSS visual group to compile into editable nodes."
},
"idPrefix": {
"description": "Optional stable namespace for the node ids generated by this import.",
"type": "string",
"minLength": 1,
"maxLength": 100
},
"baseVersion": {
"type": "integer",
"exclusiveMinimum": 0,
"maximum": 9007199254740991
},
"renderOutputPath": {
"anyOf": [
{
"type": "string",
"minLength": 1
},
{
"type": "null"
}
],
"description": "Local review PNG path, or null for a protected temporary artifact."
},
"overwriteRender": {
"type": "boolean",
"description": "Whether an existing renderOutputPath may be replaced."
},
"renderScale": {
"type": "number",
"minimum": 0.1,
"maximum": 4,
"description": "Review PNG pixels per canvas unit, from 0.1 through 4."
},
"renderTimeoutMs": {
"type": "integer",
"exclusiveMinimum": 0,
"maximum": 9007199254740991,
"description": "Local import and review-render polling deadline in milliseconds."
}
},
"required": [
"canvasId",
"targetNodeId",
"mode",
"html",
"baseVersion",
"renderOutputPath",
"overwriteRender",
"renderScale",
"renderTimeoutMs"
],
"additionalProperties": false
}
```
### Example
Show example input
```json
{
"canvasId": "00000000-0000-4000-8000-000000000010",
"targetNodeId": "root",
"mode": "insert-children",
"html": "",
"idPrefix": "example",
"baseVersion": 1,
"renderOutputPath": null,
"overwriteRender": false,
"renderScale": 1,
"renderTimeoutMs": 120000
}
```
## Result
Returns a typed canvas.writeHtml result from the Enhance API without transport-specific prose.
## Recovery
- BAD_REQUEST: correct the named fields and call again.
- UNAUTHORIZED: restore Enhance authentication, then retry once.
- FORBIDDEN or NOT_FOUND: list accessible resources and choose an allowed identifier.
- CONFLICT: read the current resource, merge the intended change, and retry with its version.
- INTERNAL: run Enhance diagnostics, report the failure, and stop repeating the call.
## Continue with
- Read the affected canvas resource to confirm the result.
Compatibility: `db9ff722fffa97aea8b06521b08acad08a91e5acc9ae467a378e86b75c387a5d`.