What causes "unsupported manifest schema {schema}" in BoundaryML/baml?

Re-fetch the manifest from the current release so its schema matches MANIFEST_SCHEMA.

unsupported manifest schema {schema}

Error message

unsupported manifest schema {schema}

What it means

validate_schema also rejects schema values that differ from MANIFEST_SCHEMA in the other direction: any schema less than the current one (after ruling out newer schemas) bails with "unsupported manifest schema {schema}". The wrapper only understands exactly one schema version; older manifest formats are intentionally not supported.

Source

Thrown at baml_language/crates/baml_release/src/manifest.rs:134

        validate_schema(self.schema)?;
        validate_artifacts(&self.version, &self.artifacts)
    }

    pub fn artifact_for_target(&self, target: &str) -> anyhow::Result<&Artifact> {
        self.artifacts.get(target).ok_or_else(|| {
            anyhow::anyhow!("target {target} not built for wrapper {}", self.version)
        })
    }
}

fn validate_schema(schema: u32) -> anyhow::Result<()> {
    if schema > MANIFEST_SCHEMA {
        anyhow::bail!(
            "manifest schema {schema} is newer than this wrapper; run `baml self-update`"
        );
    }
    if schema != MANIFEST_SCHEMA {
        anyhow::bail!("unsupported manifest schema {schema}");
    }
    Ok(())
}

fn validate_artifacts(version: &str, artifacts: &BTreeMap<String, Artifact>) -> anyhow::Result<()> {
    let expected: std::collections::BTreeSet<_> =
        SUPPORTED_RELEASE_TARGETS.iter().copied().collect();
    let actual: std::collections::BTreeSet<_> = artifacts.keys().map(String::as_str).collect();
    if actual != expected {
        anyhow::bail!("manifest for {version} has target set {actual:?}; expected {expected:?}");
    }
    for (target, artifact) in artifacts {
        validate_artifact(target, artifact)?;
    }
    Ok(())
}

fn validate_artifact(name: &str, artifact: &Artifact) -> anyhow::Result<()> {

View on GitHub (pinned to bd85ce9dee)

Solutions

Re-fetch the manifest from the current release so its schema matches MANIFEST_SCHEMA.
Delete stale cached manifests and re-run the install/update command.
Stop hand-editing the `schema` field; let the tool regenerate manifests.
If you must support old formats, upgrade the wrapper rather than downgrading schema expectations.

Example fix

// before
let m = parse(cached_manifest_from_v0_90)?; // schema 1
// after
let fresh = download_manifest(current_version)?;
let m = parse(fresh)?;

Defensive patterns

Strategy: try-catch

Validate before calling

if manifest.schema < KNOWN_MAX_SCHEMA && manifest.schema != CURRENT_SCHEMA {
    eprintln!("stale manifest schema {}; re-fetch current manifest", manifest.schema);
}

Try / catch

match parse_manifest(json) {
    Err(e) if e.to_string().contains("unsupported manifest schema") => { re_fetch_current_manifest()?; parse_manifest(&fresh_json) }
    r => r,
}

Prevention

Always parse freshly fetched manifests, not cached/archived copies.
Never hand-edit the schema field of manifests.
Purge stale manifest caches when upgrading tooling.

When it happens

Trigger: Parsing a manifest whose `schema` field is a valid u32 but lower than MANIFEST_SCHEMA, passed through validate() -> validate_schema(); e.g. a cached or archived manifest from an old release.

Common situations: Air-gapped environments replaying cached manifests from old releases; restoring an old wrapper data directory; manifests copied from an old project's vendored files; tampered or hand-edited schema fields.

Understand the failure class

Background: Schema validation failed / invalid input schema: payload rejected because its shape doesn't match the expected schema — this error's family across 28 libraries.

Related errors

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/5834de0747b4bbf2. Report an issue: GitHub.