hashicorp/terraform · error

could not interpret output %s type: %w

Error message

could not interpret output %s type: %w

What it means

After marshaling DetailedType to JSON, Terraform unmarshals it into a cty.Type via ctype.UnmarshalJSON. This fails when the detailed type does not conform to cty's type JSON schema.

Source

Thrown at internal/cloud/state.go:673

	// We will only enable snapshots for intervals greater than zero
	log.Printf("[TRACE] Intermediate state interval is set by header to %v", s.stateSnapshotInterval)
	s.enableIntermediateSnapshots = s.stateSnapshotInterval > 0
}

// tfeOutputToCtyValue decodes a combination of TFE output value and detailed-type to create a
// cty value that is suitable for use in terraform.
func tfeOutputToCtyValue(output tfe.StateVersionOutput) (cty.Value, error) {
	var result cty.Value
	bufType, err := json.Marshal(output.DetailedType)
	if err != nil {
		return result, fmt.Errorf("could not marshal output %s type: %w", output.ID, err)
	}

	var ctype cty.Type
	err = ctype.UnmarshalJSON(bufType)
	if err != nil {
		return result, fmt.Errorf("could not interpret output %s type: %w", output.ID, err)
	}

	result, err = gocty.ToCtyValue(output.Value, ctype)
	if err != nil {
		return result, fmt.Errorf("could not interpret value %v as type %s for output %s: %w", result, ctype.FriendlyName(), output.ID, err)
	}

	return result, nil
}

View on GitHub (pinned to c9def3e214)

Solutions

1. Upgrade Terraform to a version that supports the output's type.
2. Re-define the output with a simpler, broadly-supported type and re-apply.
3. If produced by a newer TF, export the state and re-import with a compatible version.

Example fix

# before: TF X wrote an output type this TF cannot parse -> could not interpret output type
# after: upgrade to a TF version that understands the type (or simplify the type)
terraform version   # bump to a compatible release
terraform refresh

outs, err := state.GetRootOutputValues(ctx)
if err != nil && strings.Contains(err.Error(), "could not interpret output") && strings.Contains(err.Error(), "type") {
    // likely version skew; upgrade TF or simplify the output type and re-apply
}

When it happens

Trigger: An output whose detailed-type JSON is malformed or uses a type kind cty does not recognize, e.g. state written by a newer Terraform emitting a type this version cannot parse.

Common situations: Version skew: reading state produced by a newer Terraform that introduced an unrecognized type kind.

Related errors

• could not decode output %s (ID %s)
• could not marshal output %s type: %w
• resource %s has an unsupported mode %s
• failed to decode backend config: %w
• Unknown type: %#v

AI-assisted analysis of hashicorp/terraform@c9def3e214 (2026-08-07). Data as JSON: /api/errors/c1996e4e94454f80. Report an issue: GitHub.