BoundaryML/baml · error

BAML_CACHE_VERIFY: cached bytecode for key

Error message

BAML_CACHE_VERIFY: cached bytecode for key {} differs from a fresh compile ({} vs {} bytes). This means emit is nondeterministic or a compile input is missing from the cache key — please report this.

What it means

Error "BAML_CACHE_VERIFY: cached bytecode for key {} differs from a fresh compile ({} vs {} bytes). This means emit is nondeterministic or a compile input is missing from the cache key — please report this." thrown in BoundaryML/baml.

Solutions

1. Do not disable BAML_CACHE_VERIFY while iterating; keep it on so the drift is caught early
2. If the error is reproducible, minimize the .baml project that triggers it and report it to the BAML maintainers — a deterministic emit or a complete cache key is required
3. For the missing-cache-key case, check whether any compile inputs (env vars, file mtimes, generated files) participate in compilation but are absent from the key computation

When it happens

Trigger: Thrown at baml_language/crates/baml_cli/src/bytecode_cache.rs:217 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of BoundaryML/baml@bd85ce9dee (2026-09-12). Data as JSON: /api/errors/cb17be3ea16b1cb9. Report an issue: GitHub.

Appendix: source

Thrown at baml_language/crates/baml_cli/src/bytecode_cache.rs:217

        }
    }

    pub(crate) fn load(&self) -> Option<Program> {
        self.cache.load_shared(&self.key)
    }

    /// The `BAML_CACHE_VERIFY` tripwire: byte-compare a fresh compile against
    /// any existing entry under the same key. A mismatch is a hard error —
    /// it means emit is nondeterministic or a compile input is missing from
    /// the cache key.
    pub(crate) fn verify_against(&self, program: &Program) -> anyhow::Result<()> {
        if !Self::verify_enabled() {
            return Ok(());
        }
        if let Some(cached) = self.cache.load_raw(&self.key) {
            let fresh = borsh::to_vec(program)?;
            if fresh != cached {
                anyhow::bail!(
                    "BAML_CACHE_VERIFY: cached bytecode for key {} differs from a fresh \
                     compile ({} vs {} bytes). This means emit is nondeterministic or a \
                     compile input is missing from the cache key — please report this.",
                    self.key.hex(),
                    cached.len(),
                    fresh.len(),
                );
            }
        }
        Ok(())
    }

    /// Write-through after a successful compile. Best-effort: a cache write
    /// problem must never fail the run.
    pub(crate) fn store(&self, program: &Program) -> std::io::Result<()> {
        self.cache.store_shared(&self.key, program)?;
        self.cache.maybe_trim();
        Ok(())

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