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BamlValidationError

fern/03-reference/baml_client/errors/baml-validation-error.mdx

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The BamlValidationError class represents an error that occurs when BAML fails to parse or validate LLM output.

Type Definition

<CodeBlocks> ```typescript Type Definition class BamlValidationError extends Error { type: 'BamlValidationError' message: string prompt: string raw_output: string detailed_message: string } ``` </CodeBlocks>

Properties

<ParamField path="type" type="'BamlValidationError'"

Literal type identifier for the error class. </ParamField>

<ParamField path="message" type="string"

Error message describing the specific validation failure. </ParamField>

<ParamField path="prompt" type="string"

The original prompt sent to the LLM. </ParamField>

<ParamField path="raw_output" type="string"

The raw output from the LLM that failed validation. </ParamField>

<ParamField path="detailed_message" type="string"

Comprehensive error information that includes the complete history of all failed attempts when using fallback clients or retry policies. When multiple attempts are made (via fallback or retry), this field contains formatted details about each failed attempt, making it invaluable for debugging complex client configurations. </ParamField>

Type Guards

The error can be identified using TypeScript's instanceof operator:

<CodeBlocks> ```typescript Type Check if (error instanceof BamlValidationError) { // Handle validation error } ``` </CodeBlocks>