Mappers & observations

Observations enter Tarski as raw evidence — a chat message, a webhook payload, a provider receipt, a schedule fire. Mappers are the deterministic structural boundary that turns each observation into typed atom batches: the ontology’s inbox.

Mappers

Mappers are written in Rhai (mappings/*.rhai) and are deliberately constrained:

• Deterministic and structural. A mapper sees one observation and emits typed atoms. Same observation, same atoms — the mapper output digest is part of replay identity.
• No I/O. Mappers cannot fetch, call models, or read ambient state.
• Atoms are not truth. A mapper may emit atom-origin candidate.* or proposal.* evidence when the app declares those relations, but it can never write trusted facts, decisions, or executable intents — those are derived-only namespaces.

If a behavior is wrong and the observation is right, but the atom is wrong, the mapper is the thing to fix. That locality is the point.

Helpers

Helpers (helpers/*.rhai) are pure, capability-free functions callable from ontology rules — normalization, parsing, identity minting. The platform’s own helper.std.* standard library is version-pinned, and app helper digests join the evaluator identity, so helper behavior is part of the semantic contract, not an implementation detail.

Hiding I/O in a helper is one of the classic mistakes the loader and verifier are built to catch — helpers that do I/O would silently break replay.

Deterministic effect providers

Fixtures need to exercise external-effect shapes without the network. A deterministic effect provider is a Rhai script that stands in for a live provider (an HTTP API, an LLM) during fixture replay, with a documented contract: a named entrypoint, the capture envelope shape, and run-pinned values.

Pre-dispatch provider errors — a compile error, a missing entrypoint, an invalid envelope — are classified as typed provider_config_failure. They are explicitly not ambiguous effects: they never enter manual reconciliation, and fixing the script changes its configuration digest and re-admits the intent.

Live and deterministic modes never blur: a live example missing its credential surfaces a visible warning or a typed http.credential.unresolved block — never a silent fallback to deterministic output.

Provider record/replay

For live providers, Tarski captures external-call envelopes with redaction and replay identity. Recorded envelopes let tarski verify replay LLM-assisted behavior deterministically — and because every model-context section digest joins the request digest, a capture envelope proves byte-for-byte what a model saw. See Model context & the agent relay.