What causes "delete module %q: %w" in dagger/dagger?

Manually remove the [modules. ] (and its sub-tables like as-sdk) sections from dagger.json, then retry.

delete module %q: %w

Error message

delete module %q: %w

What it means

deleteRemovedConfigRoots deletes a module entry (modules.<name>) from the TOML document when the module exists in the existing config but not in the desired one. Failure of doc.Delete is wrapped as "delete module %q". It means an in-place removal of a module section from dagger.json failed.

Source

Thrown at core/workspace/config_document.go:323

		}

		nested, ok := value.(map[string]any)
		if ok {
			flattenConfigValuesInto(flat, fullKey, nested)
			continue
		}

		flat[fullKey] = value
	}
}

func deleteRemovedConfigRoots(doc *neontoml.Document, existingCfg, desiredCfg *Config) error {
	for name := range existingCfg.Modules {
		if _, ok := desiredCfg.Modules[name]; ok {
			continue
		}
		if err := doc.Delete("modules." + formatConfigPathSegment(name)); err != nil {
			return fmt.Errorf("delete module %q: %w", name, err)
		}
	}

	for envName := range existingCfg.Env {
		if _, ok := desiredCfg.Env[envName]; ok {
			continue
		}
		if err := doc.Delete("env." + formatConfigPathSegment(envName)); err != nil {
			return fmt.Errorf("delete env %q: %w", envName, err)
		}
	}

	for host := range existingCfg.Ports {
		if _, ok := desiredCfg.Ports[host]; ok {
			continue
		}
		if err := doc.Delete("ports." + formatConfigPathSegment(host)); err != nil {
			return fmt.Errorf("delete port %q: %w", host, err)

View on GitHub (pinned to 82ba2681db)

Solutions

Manually remove the [modules.<name>] (and its sub-tables like as-sdk) sections from dagger.json, then retry.
Rename the module to a bare-safe name (letters, digits-with-leading-letter, hyphens, underscores) before removal.
Restore a known-good dagger.json from git and re-apply the change with the dagger CLI rather than manual edits.

Example fix

// before: module named with unsafe segment
[modules."my.mod"]
x = 1

// after: rename module to a safe name
[modules.mymod]
x = 1

Defensive patterns

Strategy: validation

Validate before calling

if !isBareConfigPathSegment(moduleName) || isAllDigitConfigPathSegment(moduleName) {
    return fmt.Errorf("module name %q cannot be updated in place; rename it first", moduleName)
}

Try / catch

if err := UpdateConfigBytes(...); err != nil {
    if strings.Contains(err.Error(), "delete module") {
        // strip the [modules.<name>] block manually from dagger.json, then retry
    }
}

Prevention

Name modules with letters, digits, hyphens, and underscores only (not starting with a digit).
Remove modules via dagger CLI commands instead of editing dagger.json directly.
Back up dagger.json before module removal operations.

When it happens

Trigger: UpdateConfigBytes called with a desired Config lacking a module name that exists in the existing Config, and doc.Delete("modules.<name>") errors — usually due to a module name that formats into an unresolvable dotted path (unsafe characters or all digits).

Common situations: Removing a module whose name contains dots, quotes, spaces, or is purely numeric (e.g. a module literally named "123"), or hand-crafted dagger.json where [modules] tables were edited into shapes the path parser cannot match.

Related errors

AI-assisted analysis of dagger/dagger@82ba2681db (2026-09-05). Data as JSON: /api/errors/e9e153b41d594147. Report an issue: GitHub.