dagger/dagger · error

no runtime implemented

Error message

no runtime implemented

What it means

Module.LoadRuntime requires the module's SDK to implement the ModuleRuntime interface. AsRuntime() returns false when the SDK config (e.g. a config-only or static SDK) does not provide a runtime implementation, so Dagger cannot instantiate code execution for this module and throws 'no runtime implemented'.

Source

Thrown at core/module.go:2173

			ifaceID, err := ResultIDInput(updatedIface)
			if err != nil {
				return fmt.Errorf("patched interface typedef id: %w", err)
			}
			if err := dag.Select(ctx, iface, &mod.InterfaceDefs[i], dagql.Selector{
				Field: "__withInterfaceTypeDef",
				Args:  []dagql.NamedInput{{Name: "interfaceTypeDef", Value: ifaceID}},
			}); err != nil {
				return fmt.Errorf("patch interface typedef enum defaults: %w", err)
			}
		}
	}
	return nil
}

func (mod *Module) LoadRuntime(ctx context.Context) (ModuleRuntime, error) {
	runtimeImpl, ok := mod.Source.Value.Self().SDKImpl.AsRuntime()
	if !ok {
		return nil, fmt.Errorf("no runtime implemented")
	}

	if !mod.Source.Valid {
		return nil, fmt.Errorf("no source")
	}

	runtime, err := runtimeImpl.Runtime(ctx, mod.Deps, mod.Source.Value)
	if err != nil {
		return nil, fmt.Errorf("failed to load runtime: %w", err)
	}

	return runtime, nil
}

/*
Mod is a module in loaded into the server's DAG of modules; it's the vertex type of the DAG.
It's an interface so we can abstract over user modules and core and treat them the same.
*/

View on GitHub (pinned to 82ba2681db)

Solutions

1. Verify the module's dagger.json sdk field names a supported SDK (go, python, typescript, etc.) that implements ModuleRuntime
2. If writing a custom SDK, implement the Runtime(ctx, deps, source) method so AsRuntime() succeeds
3. Re-generate or update the module so SDKImpl is populated with a runtime-capable implementation

Example fix

// before: custom SDK missing runtime
func (s *mySDK) AsRuntime() (ModuleRuntime, bool) { return nil, false }
// after
func (s *mySDK) AsRuntime() (ModuleRuntime, bool) { return s, true }
func (s *mySDK) Runtime(ctx context.Context, deps ... , src *ModuleSource) (ModuleRuntime, error) { ... }

if src, err := mod.GetSource(); err == nil && src.SDKConfig != nil { /* SDK present */ }
// only proceed to LoadRuntime when the module's dagger.json sdk field is set and supported

rt, ok := mod.Source.Value.Self().SDKImpl.AsRuntime()
if !ok { return fmt.Errorf("SDK does not implement a runtime") }

rt, err := mod.LoadRuntime(ctx)
if err != nil {
    if strings.Contains(err.Error(), "no runtime implemented") {
        // fall back to static/config-only handling
    }
    return err
}

When it happens

Trigger: Calling Module.LoadRuntime (directly or via module loading internals) on a module whose ModuleSource resolves to an SDKImpl that does not implement Runtime — e.g. an SDK registered without a runtime, or a placeholder/sdk-config-only SDKImpl.

Common situations: Developing a custom Dagger SDK that only implements part of the ModuleRuntime interface; using an SDK kind the engine does not recognize as runnable; loading a module whose SDK field points to an unsupported or stub SDK.

Related errors

• no runtime implemented
• failed to load runtime: %w
• unknown type %q
• enum types must be named
• failed to find decl for object %s: %w

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/6f007e1ed6060504. Report an issue: GitHub.