What causes "source output misconfigured" in vectordotdev/vector?

Run vector validate on the config and fix the sink inputs to reference existing source outputs/ports

source output misconfigured

Error message

source output misconfigured

What it means

expanded_definitions matches a sink's required input against candidate source definitions; on no match it raises unreachable! because topology validation elsewhere should have rejected a misconfigured graph first. Reaching it means an invalid sink→source connection slipped past earlier validation, so the schema layer hits dead code. The comment in the source confirms the topology builder owns this error state; this panic is a safety net.

Solutions

Run vector validate on the config and fix the sink inputs to reference existing source outputs/ports
Ensure topology construction goes through the standard builder/validation path
Upgrade Vector; if reproducible with a stock config, file a bug with the config

Defensive patterns

Strategy: validation

Validate before calling

// Check sink inputs resolve to real source outputs before building
vector validate config.yaml

Prevention

Fix sink inputs to reference existing source outputs and ports
Always build topologies through the validated builder path
Run vector validate in CI for every config change

When it happens

Trigger: A sink's inputs referencing a source/port that does not exist or emits incompatible types, while the earlier validation pass did not reject the config; programmatic topology construction bypassing validate().

Common situations: Hand-built topologies in embedded usage; Vector bugs where validation and schema expansion disagree; typos in port names combined with a validation skip (e.g. --skip-healthchecks style paths or tests).

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of vectordotdev/vector@bdb87aeaa4 (2026-09-16). Data as JSON: /api/errors/c57790d653574fa2. Report an issue: GitHub.

Appendix: source

Thrown at src/topology/schema.rs:151

            // After getting the source matching to the given input, we need to further narrow the
            // actual output of the source feeding into this input, and then get the definition
            // belonging to that output.
            let mut source_definitions =
                outputs
                    .into_iter()
                    .find_map(|output| {
                        if output.port == input.port {
                            Some(input.with_definitions(
                                output.schema_definition(config.schema_enabled()),
                            ))
                        } else {
                            None
                        }
                    })
                    .unwrap_or_else(|| {
                        // If we find no match, it means the topology is misconfigured. This is a fatal
                        // error, but other parts of the topology builder deal with this state.
                        unreachable!("source output misconfigured")
                    });

            if contains_never(&source_definitions) {
                return Err(Error::ContainsNever);
            }

            definitions.append(&mut source_definitions);

        // A transform can receive from multiple inputs, and each input needs to be expanded to
        // a new pipeline.
        } else if let Some(inputs) = config.transform_inputs(key) {
            let input_definitions =
                possible_definitions(inputs, config, enrichment_tables.clone(), &mut merged_cache)?;

            let mut transform_definition = config
                .transform_outputs(key, enrichment_tables.clone(), &input_definitions)
                .expect("already found inputs")
                .iter()

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