dbt-labs/dbt-core · error

Failed to serialize object

Error message

Failed to serialize object

What it means

This panic comes from `serde_yaml::to_value` (dbt_yaml) while serializing the node's deprecated raw config into a YAML value during run-phase node context building. Serialization can only fail here if the config contains non-string map keys or other YAML-incompatible structures, which indicates an invariant violation in how the config was constructed upstream rather than bad user YAML. The library treats this as unrecoverable and panics via `.expect`.

Source

Thrown at crates/dbt-jinja-utils/src/phases/run/run_node_context.rs:128

    let model = node.serialize();
    let common_attr = node.common();
    let base_attr = node.base();
    let resource_type = node.resource_type();
    // Create a relation for 'this' using config values
    let this_relation = dbt_adapter::relation::RelationObject::new(Arc::from(
        dbt_adapter::relation::do_create_relation(
            adapter_type,
            base_attr.database.clone(),
            base_attr.schema.clone(),
            Some(base_attr.alias.clone()),
            None,
            base_attr.quoting,
        )
        .unwrap(),
    ))
    .into_value();

    let config_yml = dbt_yaml::to_value(deprecated_config).expect("Failed to serialize object");

    // `ModelConfig`/`SeedConfig`/`SnapshotConfig` serialize hooks under the underscored
    // name; `FunctionConfig` doubles as its own manifest type and so uses dbt-core's
    // hyphenated key. Accept either.
    let hooks_of = |underscored: &str, hyphenated: &str| {
        config_yml
            .get(underscored)
            .or_else(|| config_yml.get(hyphenated))
    };

    let pre_hooks = hooks_of("pre_hook", "pre-hook").map(|pre_hook| {
        let values: Vec<HookConfig> = match pre_hook {
            YmlValue::String(_, _) | YmlValue::Mapping(_, _) => {
                parse_hook_item(pre_hook).into_iter().collect()
            }
            YmlValue::Sequence(arr, _) => arr.iter().filter_map(parse_hook_item).collect(),
            YmlValue::Null(_) => vec![],
            _ => {

View on GitHub (pinned to 0267ce9170)

Solutions

1. Reproduce with the failing model/seed/snapshot and inspect the rendered `config` dict for non-string or exotic map keys
2. Update to the latest dbt-fusion/dbt-jinja-utils version — config coercion fixes often land here
3. Check the custom adapter/materialization for code that inserts into node config with non-String keys
4. Capture RUST_BACKTRACE=1 output and file a bug with the model SQL and config block

Example fix

// before (internal, illustrative)
let config_yml = dbt_yaml::to_value(deprecated_config).expect("Failed to serialize object");
// after
let config_yml = dbt_yaml::to_value(&deprecated_config)
    .map_err(|e| ErrFatal.load_error(format!("failed to serialize node config: {e}")))?;

// sanity-check config keys before serializing
fn serializable_config(cfg: &serde_json::Value) -> bool {
    cfg.as_object().map(|m| m.keys().all(|k| !k.is_empty())).unwrap_or(false)
}
if !serializable_config(&deprecated_config) { return Err(...); }

// replace .expect with error propagation
let config_yml = dbt_yaml::to_value(&deprecated_config)
    .map_err(|e| format!("config serialization failed: {e}"))?;

When it happens

Trigger: `build_model_context_fields` calls `dbt_yaml::to_value(deprecated_config)` and the `DeprecatedConfig`/config value contains keys or values that cannot round-trip into a YAML mapping (e.g. non-string map keys produced by templating, or a poisoned config built by an adapter hook).

Common situations: Custom materializations or adapters injecting config entries with unexpected key types; internal dbt version mismatches where `ModelConfig`/`SeedConfig`/`SnapshotConfig`/`FunctionConfig` hooks were stored under a key type the serializer rejects; exotic user configs surviving Jinja rendering as non-scalar keys.

Understand the failure class

Background: "JSON serialization failed", "not JSON serializable", "Failed to serialize": why JSON marshaling errors happen and how to fix them — this error's family across 46 libraries.

Related errors

• Failed to serialize merged node config to dbt_yaml::Value fo
• Version '{:?}' does not meet the required format
• Failed to convert value to YAML: {err}
• invalid serialized time precision
• invalid serialized timestamp precision

AI-assisted analysis of dbt-labs/dbt-core@0267ce9170 (2026-09-07). Data as JSON: /api/errors/d8a60f16826cf5ad. Report an issue: GitHub.