workspace provider returned project ID ; IDs must use the…

Error message

workspace provider {provider_id:?} returned project ID {:?}; IDs must use the {expected_prefix:?} namespace

What it means

Each provider must return project IDs already namespaced with its own ID as the prefix (`provider:local`). When a discovered project's ID does not start with `provider_id + ":"`, the collector bails because cross-provider ID lookups and lockfile attribution depend on this convention.

Solutions

Fix the provider to format project IDs as `format!("{provider_id}:{local_id}")`
Ensure the provider's `id()` matches the prefix used when constructing project IDs
Check for a rename: update both the provider ID and the prefix used in project ID generation together

Example fix

// before
project.id = local_id.to_string();
// after
project.id = format!("{}:{}", self.id(), local_id);

Defensive patterns

Strategy: try-catch

Validate before calling

for project in discovered {
    assert!(project.id.starts_with(&format!("{}:", provider_id)), "project {:?} lacks provider prefix", project.id);
}

Type guard

fn in_namespace(id: &str, provider_id: &str) -> bool { id.starts_with(&format!("{provider_id}:")) }

Try / catch

match collect_projects(provider) {
    Ok(ps) => ps,
    Err(e) if e.to_string().contains("namespace") => {
        eprintln!("provider returned unprefixed project IDs; fix provider id formatting");
        return Err(e);
    }
    Err(e) => return Err(e),
}

Prevention

Centralize project-ID construction in one helper that applies the prefix
Add provider tests asserting returned IDs match the namespace
When renaming a provider, update ID generation and prefix checks together

When it happens

Trigger: A provider implementation (in `collect_provider_projects`) returns projects whose `id` field was not formatted as `{provider_id}:{local_id}` — e.g. it set the raw local name or a differently-prefixed ID.

Common situations: Writing a custom provider that forgets to prefix IDs; a provider renamed (ID changed) while its project discovery code still builds the old prefix; concatenating the prefix with the wrong separator.

Understand the failure class

Background: "This is a bug, please report it": internal invariant violations, unreachable panics, and SNH errors explained — this error's family across 47 libraries.

Related errors

AI-assisted analysis of jdx/mise@533346cc37 (2026-09-17). Data as JSON: /api/errors/71e1e13b2cc3c5b6. Report an issue: GitHub.

Appendix: source

Thrown at src/task/workspace.rs:654

        for (provider_id, provider) in providers {
            let discovered = match provider.discover_with_context(workspace_root, context) {
                Ok(projects) => projects,
                Err(error) if skip_provider_errors => {
                    let error = format!("{error:#}");
                    warn!(
                        "failed to discover {provider_id} workspace projects at {}; inferred tasks \
                         and upstream task dependencies from this provider are unavailable: {error}",
                        workspace_root.display(),
                    );
                    provider_errors.insert(provider_id, error);
                    continue;
                }
                Err(error) => return Err(error),
            };
            for mut project in discovered {
                let expected_prefix = format!("{provider_id}:");
                let Some(local_id) = project.id.as_str().strip_prefix(&expected_prefix) else {
                    bail!(
                        "workspace provider {provider_id:?} returned project ID {:?}; IDs must use the {expected_prefix:?} namespace",
                        project.id
                    );
                };
                validate_id_part("project", local_id)?;
                project.root = normalize_project_root(&project.id, &project.root)?;
                attach_provider_provenance(&mut project, &provider_id);
                let id = project.id.clone();
                if projects.insert(id.clone(), project).is_some() {
                    bail!(
                        "workspace provider {provider_id:?} returned duplicate project ID {id:?}"
                    );
                }
            }
        }

        Ok(Self {
            projects,

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