attempted to encode a malformed backend state file…

Error message

attempted to encode a malformed backend state file; provider data is missing

What it means

StateStoreConfigState.Validate() found Provider == nil. A state_store requires a backing provider to manage it, so a missing Provider pointer means the record is incomplete and unsafe to encode/use.

Solutions

Delete .terraform/terraform.tfstate and re-run `terraform init` so Provider is populated.
If building the struct in code, always set Provider (Source, Version, ConfigRaw) alongside Type.
Restore the file from backup.

Example fix

rm .terraform/terraform.tfstate
terraform init

Defensive patterns

Strategy: validation

Validate before calling

// pre-flight: require Provider for state_store
if s.Provider == nil {
    return errors.New("state_store requires a nested provider; populate Provider before encoding")
}

Type guard

func (s *StateStoreConfigState) hasProvider() bool { return s != nil && s.Provider != nil }

Prevention

Always run `terraform init` to populate Provider.
In code, construct Provider via a factory that sets Source, Version, and ConfigRaw.

When it happens

Trigger: Programmatic construction of StateStoreConfigState that sets Type but never assigns Provider; or a corrupted on-disk file whose `state_store.provider` section was stripped.

Common situations: Custom tooling, partial deserialisation, hand-editing the backend state file, or an interrupted `terraform init` that left Provider unwritten.

Understand the failure class

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of hashicorp/terraform@d32a084675 (2026-08-11). Data as JSON: /api/errors/43b74c85795f641b. Report an issue: GitHub.

Appendix: source

Thrown at internal/command/workdir/statestore_config_state.go:52

// Empty returns true if there is no active state store.
func (s *StateStoreConfigState) Empty() bool {
	return s == nil || s.Type == ""
}

// Validate returns true if there are no missing expected values, and
// important values have been validated, e.g. FQNs. When the config is
// invalid an error will be returned.
func (s *StateStoreConfigState) Validate() error {
	// Are any bits of data totally missing?
	if s.Empty() {
		return fmt.Errorf("attempted to encode a malformed backend state file; data is empty")
	}
	if s.Type == "" {
		return fmt.Errorf("attempted to encode a malformed backend state file; state store type is missing")
	}
	if s.Provider == nil {
		return fmt.Errorf("attempted to encode a malformed backend state file; provider data is missing")
	}
	if s.ConfigRaw == nil {
		return fmt.Errorf("attempted to encode a malformed backend state file; state_store configuration data is missing")
	}

	// Validity of data that is there
	err := s.Provider.Source.Validate()
	if err != nil {
		return fmt.Errorf("state store is not valid: %w", err)
	}

	// Version information is required if the provider isn't builtin or unmanaged by Terraform
	switch s.ProviderSupplyMode {
	case getproviders.BuiltIn, getproviders.Reattached, getproviders.DevOverride:
		// These modes do not require version information
	case getproviders.ManagedByTerraform:
		if s.Provider.Version == nil {
			return fmt.Errorf("state store is not valid: provider version data is missing despite provider %s being managed by Terraform.", s.Provider.Source.ForDisplay())

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