Content
# observed_effect v0
This export contains three worked observed-effect experiments:
- `below-harness-observer-carrier-2026-06/` shows observer/coverage normalization and a Tetragon adapter.
- `observed-effect-drift-consumer-2026-06/` shows the v0 producer/consumer contract, sample records, and an independent consumer.
- `observed-effect-neutral-carriers-2026-06/` shows the same frozen v0 record embedded in four neutral carriers (standalone JCS, in-toto DSSE Statement, an MCP reference slot, and a SCITT-shaped COSE statement), recomputing to one identical content address in each.
The examples are bounded evidence-contract artifacts. They do not claim runtime truth, intent inference,
maliciousness detection, safety, compliance, or runtime enforcement. The external verdict vocabulary is
`match | mismatch | incomplete | invalid`.
## Source class and claim ceiling
An observed-effect record is independently issued: the observer that emits it is not the component whose
behaviour it describes. That places it in a different source class than a self-report, or a record signed
by the party that made the decision it records. The class is part of the contract, because it bounds what
a verifier may conclude.
Recomputing a digest confirms the bytes are intact under the declared canonicalization. It does not raise
the record's vantage. Recomputing a self-issued record confirms what the issuer recorded, not what
occurred; the same recompute over an independently observed record supports a stronger conclusion because
the vantage is stronger, not because the hash is. Signing, hash-chaining, and time-anchoring raise
tamper-evidence, never vantage.
These records are correspondingly not an envelope for other formats to profile under, and they do not
conform to any vendor's envelope. The same frozen record travels in four carriers below and recomputes to
one content address in each; any carrier that declares its canonicalization beside its digest can hold
it. What the record contributes is the observation and its explicit limits (the `non_claims` ride inside
the digest), nothing more.
## Composing with MCP
The neutral-carriers example carries the record in an MCP reference slot. Since late June 2026 that shape
is specified in the Tool Annotations extension draft
([experimental-ext-tool-annotations](https://github.com/modelcontextprotocol/experimental-ext-tool-annotations),
`specification/draft/trust-annotations.mdx`, merged 2026-06-26): an `evidenceRef` whose
`type`/`digest`/`canonicalization` triple is the minimum a client needs to re-derive the referenced
record locally, with `cbor/rfc8949` and `jcs/rfc8785` both valid and neither the default.
A worked pointer to the frozen record in this export, using the merged field set:
```jsonc
{
"_meta": {
"io.modelcontextprotocol/trust-annotations": {
"evidenceRef": {
"type": "observed-effect",
"digest": "sha256:c2a9723ea19504aad6f8336ccbac9d9e434d6246064d404ed8e741e1930c789c",
"canonicalization": "jcs/rfc8785",
"schema": "https://assay.dev/schemas/observed-effect.v0.json",
"ref": "audit://observed-effect/match_agreement"
}
}
}
}
```
A client that resolves the record behind this pointer can recompute the address from the bytes alone with
the stdlib consumer in `observed-effect-drift-consumer-2026-06/`, and should read the record's own
`non_claims` before concluding anything. The carrier example in
`observed-effect-neutral-carriers-2026-06/` predates the merged draft and uses an equivalent earlier
canonicalization label; the recompute is label-independent, which that example's alias record
demonstrates. The record is not part of, nor endorsed by, the extension. It composes with the reference
shape, the same way it resolves under in-toto and SCITT.
To verify deterministic goldens:
```sh
cd below-harness-observer-carrier-2026-06 && ./verify-golden.sh
cd ../observed-effect-drift-consumer-2026-06 && ./verify-golden.sh
cd ../observed-effect-neutral-carriers-2026-06 && ./verify-golden.sh
```
To run tests:
```sh
python -m pytest below-harness-observer-carrier-2026-06 observed-effect-drift-consumer-2026-06 observed-effect-neutral-carriers-2026-06
```
## Related
- [Assay](https://github.com/Rul1an/assay) produces and verifies evidence bundles at the MCP tool-call boundary; these records compose with that layer.
- [gateway-evidence-replay](https://github.com/Rul1an/gateway-evidence-replay) replays gateway-path evidence offline to a bounded verdict.
- [RGE-Bench](https://github.com/rge-bench/rge-bench) is a neutral conformance kit whose axes can be read against this record format (among others).
