failed to validate the instance YAML after filling defaults

Error message

failed to validate the instance YAML after filling defaults: %w

What it means

After successfully building the driver, createConfiguredDriver re-validates the instance's fully-defaulted YAML with limayaml.Validate(inst.Config, true). If the configuration is invalid even after defaults are filled in (contradictory or out-of-range fields), the snapshot operation aborts with this message. It guards against running snapshot operations on configs that the driver layer would silently mishandle.

Solutions

Read the wrapped validation detail; it names the exact offending field — fix that field in ~/.lima/<instance>/lima.yaml
Run limactl validate (or limayaml.Load+Validate locally) on the instance YAML to see all validation errors at once
Restore the YAML to a known-good state: re-edit, or recreate the instance and re-apply your customizations
If it broke after a Lima upgrade, consult release notes for removed/renamed fields and migrate the config accordingly

Example fix

// before (instance lima.yaml)
cpus: -2
// after
// lima.yaml
cpus: 4

Defensive patterns

Strategy: validation

Validate before calling

if err := limayaml.Validate(inst.Config, true); err != nil {
	return fmt.Errorf("instance YAML invalid, fix before snapshot ops: %w", err)
}

Type guard

func validInstanceConfig(inst *limatype.Instance) bool {
	return inst != nil && inst.Config != nil && limayaml.Validate(inst.Config, true) == nil
}

Prevention

Run limayaml.Validate (or limactl validate) on instance YAML after any manual edit or tooling that rewrites it
Read the wrapped validation message — it names the exact invalid field and expected values
Migrate configs flagged deprecated when upgrading Lima instead of leaving old fields in place
Avoid merging template fragments blindly; re-validate the merged result before snapshot operations

When it happens

Trigger: Any snapshot operation (Del/Save/Load/List, i.e. limactl snapshot save/apply/delete/list) on an instance whose stored lima.yaml fails schema/range validation after defaults: e.g. invalid vmType value, conflicting cpu/memory settings, deprecated fields that no longer validate, or a hand-edited YAML with a bad enum value that the driver lookup tolerated but validation rejects.

Common situations: Manual edits to ~/.lima/<instance>/lima.yaml (typo'd enum, negative CPU count, invalid architecture); configs written by an older Lima version that no longer pass the stricter validator after upgrade; cloner/external tooling that mutated the instance YAML; merging templates with incompatible fields.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of lima-vm/lima@dd909d0973 (2026-09-01). Data as JSON: /api/errors/f6a776460b0a9835. Report an issue: GitHub.

Appendix: source

Thrown at pkg/snapshot/snapshot.go:55

	}
	return limaDriver.ApplySnapshot(ctx, tag)
}

func List(ctx context.Context, inst *limatype.Instance) (string, error) {
	limaDriver, err := createConfiguredDriver(ctx, inst)
	if err != nil {
		return "", fmt.Errorf("failed to create driver instance: %w", err)
	}
	return limaDriver.ListSnapshots(ctx)
}

func createConfiguredDriver(ctx context.Context, inst *limatype.Instance) (*driver.ConfiguredDriver, error) {
	limaDriver, err := driverutil.CreateConfiguredDriver(ctx, inst, 0)
	if err != nil {
		return nil, fmt.Errorf("failed to create driver instance: %w", err)
	}
	if err := limayaml.Validate(inst.Config, true); err != nil {
		return nil, fmt.Errorf("failed to validate the instance YAML after filling defaults: %w", err)
	}
	return limaDriver, nil
}

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