hasura/graphql-engine · error · Error

Error while building the request for the pre-response plugin

Error message

Error while building the request for the pre-response plugin {0} - {1}

What it means

The engine failed while constructing the HTTP request it sends to the pre-NDC-response plugin — before any network activity. The wrapped BuildRequestError details the exact cause: invalid header name, invalid header value, session conversion problems, or serialization failure. The plugin name is included for context.

Source

Thrown at v3/crates/plugins/pre-ndc-response-plugin/src/execute.rs:18

use axum::http::HeaderName;
use engine_types::HttpContext;
use hasura_authn_core::{Role, Session, SessionVariableName};
use metadata_resolve::{DataConnectorLink, Qualified, ResolvedLifecyclePreNdcResponsePluginHook};
use open_dds::data_connector::DataConnectorName;
use reqwest::{
    Client,
    header::{InvalidHeaderName, InvalidHeaderValue},
};
use serde::{Deserialize, Serialize};
use std::{collections::BTreeMap, str::FromStr, sync::Arc};
use tracing_util::{ErrorVisibility, SpanVisibility, TraceableError, set_attribute_on_active_span};

#[derive(Debug, thiserror::Error)]
pub enum Error {
    #[error("Error while making the HTTP request to the pre-response plugin {0} - {1}")]
    ErrorWhileMakingHTTPRequestToTheHook(String, reqwest::Error),
    #[error("Error while building the request for the pre-response plugin {0} - {1}")]
    BuildRequestError(String, #[source] BuildRequestError),
    #[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("Internal error from plugin {plugin_name}")]
    PluginInternalError {
        plugin_name: String,
        error: serde_json::Value,
    },
    #[error("User error from plugin {plugin_name}")]
    PluginUserError {
        plugin_name: String,
        error: serde_json::Value,
    },
}

View on GitHub (pinned to 724551b9ae)

Solutions

1. Look at the wrapped BuildRequestError source to identify the real cause (header/session/serialization)
2. Fix the offending config value or session variable as indicated by the inner error
3. Re-deploy plugin and engine at matching versions
4. Validate plugin config in CI with a schema check before rollout

// validate all forwarded header names/values and session vars before enabling the hook
config.forward_headers.iter().for_each(|(k, v)| { assert!(valid_header_name(k)); assert!(ascii_header_value(v)); });

if let Err(Error::BuildRequestError(name, inner)) = res {
    tracing::error!(plugin = name, inner = ?inner, "hook request build failed");
}

When it happens

Trigger: Config of the response plugin references headers or session variables that fail conversion, or the response payload cannot be serialized, while building the outgoing webhook request.

Common situations: Malformed forwarded-header config; session variables with unexpected shapes after an auth change; engine/plugin version skew altering the wire format.

Related errors

• Error parsing the request: {0}
• Internal error from plugin {plugin_name}
• User error from plugin {plugin_name}
• Invalid header name {header_name}: {error}
• Invalid header value for header {header_name}: {error}

AI-assisted analysis of hasura/graphql-engine@724551b9ae (2026-08-28). Data as JSON: /api/errors/80f6059e8be76914. Report an issue: GitHub.