hasura/graphql-engine · error · Error

Error parsing the engine response: {0}

Error message

Error parsing the engine response: {0}

What it means

The pre-response plugin received the engine's response body but could not deserialize it into the expected engine-response structure before passing it to the hook. This is a schema mismatch on the engine→plugin response contract.

Source

Thrown at v3/crates/plugins/pre-response-plugin/src/execute/common.rs:25

use hasura_authn_core::Session;
use lang_graphql::{ast::common as ast, http::RawRequest};
use open_dds::plugins::{LifecyclePluginUrl, LifecyclePreResponsePluginHookConfigRequest};
use reqwest::header::HeaderValue;
use serde::Serialize;
use tracing_util::{ErrorVisibility, TraceableError};

#[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("Error parsing the request: {0}")]
    PluginRequestParseError(serde_json::Error),
    #[error("Error parsing the engine response: {0}")]
    EngineResponseParseError(serde_json::Error),
    #[error("Unexpected status code: {0}")]
    UnexpectedStatusCode(u16),
    #[error("Error serializing the modified response: {0}")]
    ResponseSerializationError(serde_json::Error),
    #[error("Error while preparing the response: {0}")]
    ResponsePreparationError(axum::http::Error),
}

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

impl Error {
    pub fn to_graphql_response(self) -> lang_graphql::http::Response {
        let is_internal = match &self {

View on GitHub (pinned to 724551b9ae)

Solutions

1. Upgrade the pre-response plugin crate to the version matching the engine release.
2. Log the raw engine response body to identify the schema divergence.
3. If you own the schema, make plugin parsing tolerant (Option fields, aliases).

Example fix

// before
#[derive(Deserialize)]
struct EngineResponse { data: Data }

// after (tolerate new engine shapes)
#[derive(Deserialize)]
struct EngineResponse { data: Data, #[serde(default)] meta: Option<serde_json::Value> }

match parse_engine_response(&bytes) {
    Ok(r) => r,
    Err(e) => { tracing::warn!("engine response schema mismatch: {e}"); return original_response; } // pass through unmodified
}

When it happens

Trigger: A change in the engine's serialized response shape (new/renamed fields) while the pre-response plugin crate is older, causing serde to fail while parsing the engine response.

Common situations: Upgrading the engine but not the plugins; response format changes between minor versions; non-UTF8 or truncated body upstream.

Related errors

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

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/02a2e02c43f341fd. Report an issue: GitHub.