Trust Only What You Built

"The engine serves what it minted. What is missing, it calls missing."

The Offer of Free State

Every long-lived engine eventually gets the same offer: a cache directory some other tool filled, an audio file placed by hand, artifacts restored from a different system's backup. It looks free — the sound already exists, so serving it would save a paid request, wouldn't it? The arithmetic leaves one thing out. This engine has no idea what rules made that file. And it never will.

No Honest Key

The content-addressed cache in Bellows keys on everything that affects synthesis: the normalized text, the resolved binding, the model, the voice settings, the dictionary version — Track 4 dissects the key field by field. A key is a promise: same key, same sound. An entry minted by any other tool was born outside that promise. Nothing records which settings shaped it, whether normalization ran, which dictionary version applied. So it has no honest key here. Importing it doesn't save a paid request, it plants a landmine that returns the wrong audio the day a setting means something new.

No Quiet Substitution

The rule has a twin on the serving side. If the cache doesn't have it, the engine doesn't have it. An empty slot goes exactly one of two ways: the normal paid path synthesizes it fresh, or an explicit error says why not. There is no third path where something found lying around fills the silence. An engine that quietly reaches for artifacts it did not build is two half-systems wearing one name.

Code

No receipt, no sound·python

# The cache answers for what THIS engine built -- and for nothing else.

def serve_cached(identity_key: str) -> CacheHit | None:
    entry = cache.get(identity_key)
    if entry is None:
        return None          # absent means absent: pay once, or fail loud

    receipt = receipts.for_entry(entry)    # the synth job that minted it
    if receipt is None:
        # No receipt means this engine never built it. A hand-planted file,
        # another tool's cache, a restored artifact -- no honest key, no
        # lineage, no service. Refusing is the feature.
        raise ForeignArtifactError(identity_key)

    return entry

# There is no branch that scans other directories for "close enough" audio.
# The empty slot is an answer the engine is allowed to give.

Exercise

Find one system you know that accepts artifacts it did not build: a cache directory that serves whatever file lands in it, a build that trusts prebuilt binaries, a database row inserted by hand. Write down one question that system cannot answer — 'exactly what settings produced this?' — and price that silence. A landmine doesn't go off the day you plant it. It goes off the day the rules change.

Hint

Ask of every artifact: does this system know the rules that made it? If not, it isn't an answer, it's a guess. The moment you call a guess a cache, the bug becomes a contract.