04. Taste - Safety Evaluation

Taste is the CMN safety evaluation mechanism. Before executing foreign code, a visitor analyzes it and records a verdict. There is no global authority — each visitor decides who to trust.

1. Overview

Code distribution requires trust decisions. A visitor downloading a spore must evaluate whether the code is safe before placing it in their working environment. CMN formalizes this through taste — a structured evaluation step that produces a signed verdict.

Taste is:

• Required — gated operations (spawn, grow, absorb, bond) check the taste verdict before proceeding
• Subjective — each visitor performs their own evaluation and chooses which tasters to trust
• Shareable — publishers can sign and distribute taste reports for others to reference

2. Verdict Scale

Verdicts use a 5-level scale:

The scale is ordered from most positive (sweet) to most negative (toxic). The middle value (safe) represents basic review — enough to proceed but not a strong signal.

3. Gate Rules

All operations that place code into a visitor’s working directory are taste-gated:

Processing rules:

Normative behavior:

• Implementations MUST run this gate before any operation writes foreign code into a working directory.
• Untasted targets MUST fail closed with a machine-readable error code.
• toxic verdicts MUST fail closed with a machine-readable error code.
• rotten verdicts MUST emit a warning and MAY proceed.
• safe, fresh, and sweet verdicts MAY proceed.

Tasting itself downloads code to the global cache for review — this cache step is not gated.

Implementations MAY provide an explicit override for sandboxed environments (e.g., containers) where code execution is isolated. If override is used, it SHOULD be explicit and auditable (for example, taste_override_sandbox in logs/output).

4. Taste Capsule

A taste report is a signed capsule submitted via POST /synapse/pulse using the taste.json schema.

4.1 Format

{
  "$schema": "https://cmn.dev/schemas/v1/taste.json",
  "capsule": {
    "uri": "cmn://bob.dev/taste/b3.7tRkW2xPqL9nH4mYeZcFjA5sD8vBwKgU6pXb3",
    "core": {
      "target_uri": "cmn://cmn.dev/b3.3yMR7vZQ9hL2xKJdFtN8wPcB6sY1mXgU4eH5pTa2",
      "domain": "bob.dev",
      "verdict": "safe",
      "notes": [],
      "tasted_at_epoch_ms": 1739280000000
    },
    "core_signature": "ed25519...."
  },
  "capsule_signature": "ed25519...."
}

4.2 Fields

core.target_uri supports exactly three target kinds:

• cmn://{domain} (Domain)
• cmn://{domain}/{hash} (Spore)
• cmn://{domain}/mycelium/{hash} (Mycelium)

4.3 Two-Layer Signature

Taste capsules use the same two-layer signature scheme as spores and mycelium:

• core_signature — signs capsule.core with the taster’s Ed25519 key (JCS canonical)
• capsule_signature — signs the entire capsule with the taster’s key

For self-published reports, both signatures use the same key. For replicates (a different domain re-hosting a taste report), the capsule_signature uses the host’s key while core_signature retains the original taster’s signature.

5. Hash & Signature

5.1 Hash Calculation

The hash in capsule.uri is computed from core + core_signature:

1. Construct hash input: {"core": <core>, "core_signature": "<signature>"}
2. Serialize using JCS (RFC 8785)
3. Hash with BLAKE3 → b3.<base58>

The resulting URI: cmn://{domain}/taste/b3.<base58>

5.2 Verification

To verify a taste report:

1. Fetch the taster domain’s cmn.json to obtain the public key
2. Verify core_signature against the taster’s public key (proves the taster authored this verdict)
3. Verify capsule_signature against the host’s public key (proves the host authorized this distribution)
4. Recompute the hash from {core, core_signature} and compare with the URI hash

6. Local vs Shared

6.1 Local Taste

Any visitor can taste a spore and cache the result locally — no domain or signing key required. Local taste results are stored on the visitor’s machine and checked by gated operations (§3).

6.2 Shared Taste

Sharing taste reports with the network requires:

1. A domain with an Ed25519 signing key
2. Sign the taste capsule (§4.3)
3. Submit via POST /synapse/pulse

Shared reports are indexed by Synapse and served to other visitors. Spore-target reports are available via GET /synapse/spore/:hash/tastes; domain/mycelium target reports are available via GET /synapse/mycelium/:domain/tastes. Reports are advisory — no global safety score is computed or enforced.

7. Trust Model

CMN taste operates on a subjective trust model:

• No global authority — there is no central entity that decides what is safe. Each visitor chooses which taster domains to trust and how to weigh their reports.
• Independent verification — any visitor can fetch a taste report from a Synapse, then independently verify the taster’s signature against the taster domain’s public key. Trust in the Synapse is not required.
• Advisory only — Synapse aggregates and serves taste reports but does not adjudicate. It does not compute global scores or enforce verdicts across visitors.
• Reputation is emergent — over time, visitors learn which taster domains produce reliable evaluations. This is a social property, not a protocol mechanism.