hasura/graphql-engine · error · Error

Error parsing the request: {0}

Error message

Error parsing the request: {0}

What it means

The pre-route plugin failed to deserialize the JSON payload exchanged with the hook (serde_json::error::Error). It signals a request-schema mismatch between the engine and the pre-route hook.

Source

Thrown at v3/crates/plugins/pre-route-plugin/src/execute.rs:30

    LifecyclePreRoutePluginHook, LifecyclePreRoutePluginHookConfigRequestMethod,
    LifecyclePreRoutePluginHookIncomingHTTPMethod,
};
use serde_json::json;
use tracing_util::{
    ErrorVisibility, SpanVisibility, Traceable, TraceableError, set_attribute_on_active_span,
};

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Error while making the HTTP request to the pre-parse plugin {0} - {1}")]
    ErrorWhileMakingHTTPRequestToTheHook(String, reqwest::Error),
    #[error("Error while building the request for the pre-parse plugin {0} - {1}")]
    BuildRequestError(String, String),
    #[error("Reqwest error: {0}")]
    ReqwestError(reqwest::Error),
    #[error("Unexpected status code: {0}")]
    UnexpectedStatusCode(u16),
    #[error("Error parsing the request: {0}")]
    PluginRequestParseError(serde_json::error::Error),
    #[error("HTTP method {0} not supported")]
    UnsupportedHTTPMethod(String),
    #[error("Invalid header name {0}")]
    InvalidHeaderName(String),
    #[error("Invalid header value {0}")]
    InvalidHeaderValue(String),
    #[error("Not found")]
    NotFound,
    // Only used in the pre-route plugin handler function. Defined to ensure consistent
    // response formatting in IntoResponse impl.
    #[error("Cannot load pre-route plugins: {0}")]
    CannotLoadPlugins(String),
}

impl TraceableError for Error {
    fn visibility(&self) -> ErrorVisibility {
        ErrorVisibility::Internal

View on GitHub (pinned to 724551b9ae)

Solutions

1. Log the raw JSON exchanged with the hook and compare to the expected schema.
2. Align engine and pre-route plugin versions.
3. Ensure no ingress/proxy intercepts the hook route with non-JSON error pages.
4. Use tolerant serde options (#[serde(default)], Option) for forward compatibility.

// hook side self-test: response must parse as the contract type
serde_json::from_value::<HookResponse>(my_json).expect("contract violation");

match serde_json::from_str::<HookResponse>(&raw) {
    Ok(h) => apply(h),
    Err(_) => { tracing::warn!("hook schema mismatch; ignoring instructions"); route_default() }
}

When it happens

Trigger: The hook's JSON response (or the request body being prepared) does not match the expected structure — missing required fields, wrong types, or invalid JSON entirely.

Common situations: Version skew between engine and hook crate; hook returning an HTML error page from an ingress instead of JSON; renamed fields in a newer hook schema.

Related errors

• Serialization error: {0}
• Serialization error: {0}
• Error parsing the request: {0}
• Error parsing the request: {0}
• Error parsing the engine response: {0}

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/4ca0baea63b63d22. Report an issue: GitHub.