github/copilot-sdk · error

marshal elicitation schema wrapper for property

Error message

marshal elicitation schema wrapper for property %q: %w

What it means

After marshaling an individual property, the function wraps it as {properties:{name:...}, type:"object"} and marshals that wrapper struct. Failure here means the wrapper itself could not be encoded, which in practice indicates a deeply broken property value or an environment-level encoding problem, since the wrapper only holds json.RawMessage and a constant type. The error names the offending property.

Solutions

1. Inspect the wrapped error for the root marshal cause
2. Replace custom json.Marshaler implementations on property types with plain tagged structs
3. Rebuild the property definition from primitive map/struct data
4. Marshal the property to json.RawMessage yourself and validate before calling

Example fix

// before
type P struct{ V io.Reader } // custom marshaler errors
// after
type P struct{ V string `json:"v"` }

if _, err := json.Marshal(property); err != nil {
    return fmt.Errorf("property unencodable: %w", err)
}

res, err := ui.Elicitation(ctx, msg, schema)
if err != nil && strings.Contains(err.Error(), "marshal elicitation schema wrapper") {
    log.Printf("schema conversion failed: %v", err)
    return err
}

When it happens

Trigger: toRPCUIElicitationSchemaProperty reaching the wrapper json.Marshal step with a value whose earlier encoding produced something inconsistent, or an exotic marshaler failure (e.g. unsupported underlying writer state, cyclic data escaping earlier checks).

Common situations: Custom json.Marshaler implementations returning errors; corrupted property data after manual RawMessage manipulation; extremely unusual for plain maps/structs.

Understand the failure class

Background: json.Marshal / "failed to marshal" errors in Go: why "unsupported type" happens and how to fix it — this error's family across 22 libraries.

Related errors

• marshal elicitation schema property
• decode elicitation schema property
• failed to unmarshal response
• failed to unmarshal arguments into %T
• invalid hook input

AI-assisted analysis of github/copilot-sdk@cd8cf15dc3 (2026-09-09). Data as JSON: /api/errors/8a7b341bd27281c2. Report an issue: GitHub.

Appendix: source

Thrown at go/session.go:1229

		return nil, fmt.Errorf("elicitation schema property %q is nil", name)
	}
	if rpcProperty, ok := property.(rpc.UIElicitationSchemaProperty); ok {
		return rpcProperty, nil
	}

	data, err := json.Marshal(property)
	if err != nil {
		return nil, fmt.Errorf("marshal elicitation schema property %q: %w", name, err)
	}
	wrapperData, err := json.Marshal(struct {
		Properties map[string]json.RawMessage  `json:"properties"`
		Type       rpc.UIElicitationSchemaType `json:"type"`
	}{
		Properties: map[string]json.RawMessage{name: data},
		Type:       rpc.UIElicitationSchemaTypeObject,
	})
	if err != nil {
		return nil, fmt.Errorf("marshal elicitation schema wrapper for property %q: %w", name, err)
	}

	var rpcSchema rpc.UIElicitationSchema
	if err := json.Unmarshal(wrapperData, &rpcSchema); err != nil {
		return nil, fmt.Errorf("decode elicitation schema property %q: %w", name, err)
	}
	rpcProperty, ok := rpcSchema.Properties[name]
	if !ok {
		return nil, fmt.Errorf("decode elicitation schema property %q: property missing after conversion", name)
	}
	return rpcProperty, nil
}

// Confirm shows a confirmation dialog and returns the user's boolean answer.
// Returns false if the user declines or cancels.
func (ui *SessionUI) Confirm(ctx context.Context, message string) (bool, error) {
	if err := ui.session.assertElicitation(); err != nil {
		return false, err

View on GitHub (pinned to cd8cf15dc3)