CircleCI config.yml validation error

April 30, 2026 · View on GitHub

Playbook ID: circleci-config-validation Category: ci Severity: high Tags: circleci, config, yaml, validation, ci

What this failure means

CircleCI rejected the .circleci/config.yml file because it contains a syntax error, references an undefined parameter or executor, or violates the CircleCI config schema. No jobs ran.

Common log signals

config compilation failed
Invalid config detected
config.yml is invalid
was not accepted by the CircleCI API
Error parsing config
Configuration error
value of type .* is not assignable to type
Unknown executor

Diagnosis

CircleCI validates the config file before scheduling any jobs. When validation fails the pipeline is blocked immediately with an error such as:

  • Error: config compilation failed: ...
  • Invalid config detected: ...
  • was not accepted by the CircleCI API
  • An undefined anchor reference or YAML alias error.
  • A required field (e.g., working_directory, executor, docker) is missing or mistyped.
  • A version mismatch: version: 2.1 features used in a version: 2 file.

Fix steps

  1. Validate the config locally before pushing:

    circleci config validate .circleci/config.yml

  2. Fix any YAML syntax errors (indentation, missing colons, invalid anchors).

  3. Ensure all referenced executors, commands, and orbs are declared in the same file or imported via the orbs: stanza.

  4. Check that the version: key is 2.1 if you are using orbs, parameters, or reusable commands.

  5. Remove or qualify any deprecated keys flagged in the validation output.

  6. For orb-related errors, confirm the orb namespace and version exist at circleci.com/developer/orbs.

Validation

  • circleci config validate .circleci/config.yml exits 0 with no errors.
  • The pipeline triggers and at least one job is scheduled.

Likely files to inspect

  • .circleci/config.yml

Run Faultline

faultline analyze build.log
faultline explain circleci-config-validation
faultline workflow build.log --json --mode agent

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Generated from playbooks/bundled/log/ci/circleci-config-validation.yaml. Do not edit directly — run make docs-generate.