dagger/dagger · error

encode workspace config: %w

Error message

encode workspace config: %w

What it means

When the module carries a WorkspaceConfig, buildScaleOutModuleQuery marshals it to JSON to pass as legacyWorkspaceConfigJson to the asModule selection. This error wraps a json.Marshal failure on the workspace config, meaning the config structure contains values that cannot be serialized to JSON.

Source

Thrown at core/modtree.go:567

	if mod.LegacyDefaultPath {
		query = query.Arg("legacyDefaultPath", true)
	}
	if mod.ContextSource.Valid {
		contextSrc := mod.ContextSource.Value.Self()
		if contextSrc != nil {
			contextRef := contextSrc.AsString()
			if contextRef != "" && (contextRef != modSrc.AsString() || contextSrc.Pin() != modSrc.Pin()) {
				query = query.Arg("defaultPathContextSourceRef", contextRef)
				if contextPin := contextSrc.Pin(); contextPin != "" {
					query = query.Arg("defaultPathContextSourcePin", contextPin)
				}
			}
		}
	}
	if len(mod.WorkspaceConfig) > 0 {
		workspaceConfigJSON, err := json.Marshal(mod.WorkspaceConfig)
		if err != nil {
			return nil, fmt.Errorf("encode workspace config: %w", err)
		}
		query = query.Arg("legacyWorkspaceConfigJson", string(workspaceConfigJSON))
		if mod.DefaultsFromDotEnv {
			query = query.Arg("legacyDefaultsFromDotEnv", true)
		}
	}
	if len(mod.LegacyArgCustomizations) > 0 {
		customizationsJSON, err := json.Marshal(mod.LegacyArgCustomizations)
		if err != nil {
			return nil, fmt.Errorf("encode arg customizations: %w", err)
		}
		query = query.Arg("legacyArgCustomizationsJson", string(customizationsJSON))
	}
	return query, nil
}

// Initialize a standalone dagql server for querying the given module
func dagqlServerForModule(ctx context.Context, mod dagql.ObjectResult[*Module]) (*dagql.Server, error) {

View on GitHub (pinned to 82ba2681db)

Solutions

1. Inspect the wrapped marshal error to find the offending field in the workspace config.
2. Ensure the Module object was built from decoded JSON config (dagger.json) rather than hand-populated structures.
3. Validate dagger.json workspace section parses cleanly before running scale-out commands.
4. Report/upgrade if triggered by valid config — indicates a marshaling regression.

// sanity-check the workspace config parses as JSON before module load
const cfg = JSON.parse(fs.readFileSync('dagger.json', 'utf8'));
if (cfg.workspace) JSON.stringify(cfg.workspace); // throws early on bad shapes

When it happens

Trigger: Scale-out module load where mod.WorkspaceConfig is non-empty and json.Marshal(mod.WorkspaceConfig) fails — e.g. unsupported types (channels, funcs, cycles) somehow present in the config map, or NaN/invalid values.

Common situations: Rare in practice since WorkspaceConfig comes from decoded JSON; can occur with programmatically constructed Module objects containing non-JSON-serializable fields, or custom marshaler errors on the config type.

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

• encode arg customizations: %w
• marshal: %w
• marshal persisted generated code payload: %w
• decode persisted generated code payload: %w
• decode persisted container withEntrypoint lazy payload: %w

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/2c0269b86ce965ad. Report an issue: GitHub.