open-standards/mesh/SPEC.md

# Mesh — Energy-Accounted Inference Serving & Routing

**Version:** 0.1.0-draft.1 · **Status:** Draft · **Profile:** `mesh/1`
**Specification text:** CC-BY-4.0 · **Reference code (`mesh-rs/`):** Apache-2.0

Mesh is the open standard for **serving and routing inference as a metered
transaction**. A request declares a joule ceiling and a fidelity floor; the mesh
routes it to the cheapest-sufficient model on the cheapest-sufficient backend,
serves it under an energy meter, and seals a receipt whose headline figure is
**microjoules per accepted output token** — measured at the meter, not estimated
from a price list.

Mesh is one of the [Transaction Science open standards](../README.md).
Transaction Science is the steward, not the proprietor: the wire format and the
right to fork are public.

---

## §1 Why Mesh exists

The serving shelf reports two numbers: dollars per token and tokens per second.
Neither tells an operator, an auditor, or a regulator what an inference **cost**
— in the one unit that is physical, comparable across hardware, and impossible to
inflate: the joule. Mesh makes that number first-class. Every served inference
produces a signed receipt carrying the route that was taken and *why*, the recipe
that served it, the honest provenance of the energy figure, and the joules per
accepted token.

Mesh does not replace the runtime that executes one inference, nor the substrate
that supplies the compute. It is the **front door** in front of many models and
many backends: the layer that decides where a request goes, meters what it spent,
and proves it (§9).

---

## §2 Roles and the serve lifecycle

A Mesh deployment has four roles:

- **Caller** — issues a `ServeRequest` and, optionally, the JCP grant that
  authorises it.
- **Router** — selects a backend (§4).
- **Engine** — a backend that serves the request (§5).
- **Steward** — the endpoint that meters the span (§5/§6) and seals the receipt
  (§6). The steward identity is the COSE `kid` and signs the receipt log.

One serve proceeds in four phases, in order:

1. **Route.** The router selects the cheapest admissible backend (§4). If none is
   admissible, the serve fails with the router's recorded reason. When the
   request rides on a JCP `SignedGrant` carrying a `ModelIn` caveat (JCP §4.9),
   a backend whose model the grant does not permit is inadmissible, and so is a
   backend that names no model.
2. **Authorise.** If the request rides on a grant, the steward is a JCP
   enforcement point and MUST decide the grant in JCP's two-phase metered path
   (JCP §7, §4.9) before any work is done. The frame it decides over names the
   action `infer` on the request's content id, the request's `prompt_hash` as
   payload, and, as `model`, the content address of the weights the chosen
   backend runs, when the backend names one. Every check of that decision
   applies: signature, expiry, revocation, and every cost-independent caveat.
   The steward MUST also refuse the serve when what the grant has left (its
   budget less what earlier serves on it were debited) is below the request's
   joule ceiling. A failure aborts the serve before any work is done.
3. **Meter.** The steward opens an energy window, calls the engine, and closes
   the window. Energy MUST be metered **around** the engine; an engine MUST NOT
   self-report energy. With a grant, the steward then debits the metered joules
   against it (JCP's second phase), where a cost-dependent caveat such as
   `MaxCostUj` binds. The work has run, so the joules are debited even when the
   debit breaches a caveat, and the breach is recorded on the receipt
   (`grant_breach`, §6.1). An engine that names its weights before serving MUST
   report the same weights after; the steward MUST NOT seal a serve whose
   engine reports others, since they are not the weights the grant was decided
   over.
4. **Seal.** The steward builds the receipt (§6), stamps it into its hash-chained
   log, and seals it as a JCR-1 envelope.

---

## §3 The request and the energy record

### §3.1 `ServeRequest`

A request is content-addressed. Its identity `request_id = ContentId.of(request)`
is the resource a JCP capability authorises and the `request_id` on the receipt.

| Field | Type | Meaning |
|---|---|---|
| `prompt_hash` | ContentId (BLAKE3) | content address of the prompt bytes — never the prompt text |
| `prompt_tokens` | u32 | declared input token count (for the estimate) |
| `max_tokens` | u32 | output token ceiling |
| `fidelity_floor` | Fidelity | minimum acceptable fidelity (§3.2) |
| `joule_ceiling_uj` | u64 | hard energy budget, microjoules |

A conforming request MUST carry both a `fidelity_floor` and a `joule_ceiling_uj`.
The pair is the contract: *give me an answer at least this good, for at most this
much energy.*

A request MAY additionally carry a `decision` (§3.6), which says it is asking for
a bounded typed decision rather than generated text. Its absence is a generation,
and is omitted from the canonical form — so the `request_id` of every request
written before this field existed is unchanged.

### §3.2 Fidelity

Fidelity is an ordered scale `F0 … F4` — `F0` the coarsest sufficient answer
(cache / lawful / tiny model), `F4` a frontier-grade response. Ordering is
normative: a backend is admissible only when its level ≥ the request's floor
(§4).

#### §3.2.1 Advertised and delivered

A Mesh request carries two bounds, and until this revision only one of them was
held to a standard of honesty. Energy has a provenance model whose coupling MUST
be enforced before sealing (§3.3) — the rule that keeps "measured" from meaning
"estimated". Fidelity had none: a backend's level is an **advertisement**, read
out of the route table *before* the engine runs, and `fidelity_met` was derived
from it and never reconciled with what came back. A backend admitted at `F3`
that degraded at serve time still sealed `fidelity_met: 1` against an `F3`
floor.

Fidelity therefore has two figures, and they are different claims:

| figure | who says it | when |
|---|---|---|
| **advertised** — `ServingEngine::fidelity` | the route table | before the work; the basis the router admits on (§4) |
| **delivered** — `ServeOutcome.delivered_fidelity` | the backend that served | after the work |

The coupling is normative:

- Where the backend reports a delivered level, `fidelity_met` **MUST** be
  derived from it, not from the advertisement.
- A backend **MUST NOT** report a delivered level **above** its advertised
  rating. The router admitted it on the rating; it cannot raise that basis after
  the fact. An implementation **MUST** refuse such a serve rather than clamp the
  figure — clamping hides a misconfigured or dishonest engine behind a receipt
  that looks ordinary.
- Where the backend reports nothing, `fidelity_met` rests on the advertisement.
  This is the older and weaker basis and is retained, because an engine that
  cannot report what it served is still conformant. A consumer that requires the
  stronger basis **MUST** check for `fidelity_delivered` rather than reading
  `fidelity_met` alone.
- The receipt **MUST** carry `fidelity_advertised` and `fidelity_delivered`
  together or carry neither. Their purpose is the comparison; the advertisement
  alone adds nothing a verifier does not already have from `backend`. Carrying
  neither is what a receipt sealed before these fields existed means, so such a
  receipt is unchanged and `mesh/1` stays byte-stable.

**What this does not claim.** A delivered figure is the account of the party that
did the work. It is better grounded than a table entry written before the work,
and it is not an independent assessment of the output — Mesh does not score
responses. What the pair buys is that a divergence between promise and delivery
is *visible in the receipt* and attributable to a named backend, where before it
was invisible.

### §3.3 Energy and provenance

Energy is a two-part integer-microjoule record with an honest provenance tag:

```
Energy { measured_uj: Option<u64>, estimated_uj: u64, provenance: Provenance }
Provenance ∈ { HwShunt, ModelBased, Estimator }
```

The coupling is normative and MUST be enforced before a receipt is sealed:

- `HwShunt` ⇒ `measured_uj` is present (a hardware reading exists).
- `Estimator` ⇒ `measured_uj` is absent (no measurement is implied).
- `ModelBased` ⇒ `measured_uj` MAY be absent.

A receipt that violates the coupling MUST NOT be sealable. This is the rule that
keeps "measured" honest: a deployment with no hardware meter reports `Estimator`
and says so, rather than dressing an estimate up as a measurement.

`HwShunt` covers a shunt and a vendor energy counter (RAPL, NVML, Apple
IOReport), but a counter counts only while it is live:

> A reading from a vendor energy counter (RAPL, NVML, Apple IOReport, …) MAY be
> graded as a hardware reading only while the counter is demonstrably live for
> the domain the figure claims: the implementation MUST have observed the
> counter covering that domain advance under load (for Apple IOReport: the CPU
> energy rail itself advancing in at least 5 sample intervals, in at least 4 of
> every 5, over at least 300 ms while the probing thread burns CPU). A counter
> that is present but not live — frozen, or republished in lumps — MUST NOT
> produce a hardware-graded figure; the implementation falls back to its
> estimator or reports the work unmetered, and SHOULD record why. A figure MUST
> NOT claim coverage of a domain its counter does not read; where the format
> has a coverage field, such a figure is Partial.

`mesh/1` has no coverage field. So a figure from a counter that does not cover
the whole request, such as a GPU counter on a host whose CPU has none, MUST NOT
be graded `HwShunt`.

### §3.6 Typed decisions — the other unit of work

A **decision model** takes state plus typed questions and returns a calibrated
probability per allowed answer, generating no text. The category converged
through 2026 on three primitives — a proposition (`noul`), a choice over 1–255
named options, and a score over an ordered rubric — and backends score the
schema **non-autoregressively** rather than emitting tokens.

Everything else in this spec measures work in tokens, and a decision's output
token count is zero. Measured on a 421M decision model: `output_tokens: 0`, with
132 input tokens of which **121 were the question schema and 11 the state under
judgement**. Three consequences follow, and a conforming implementation MUST
handle each.

A request asking for a decision carries:

| Field | Type | Meaning |
|---|---|---|
| `questions` | u32 | typed questions in the request |
| `options_scored` | u32 | options scored across all of them |
| `schema_tokens` | u32 | how many of `prompt_tokens` are schema, not state |

1. **It MUST NOT be priced for tokens it cannot emit.** The estimate for a
   decision MUST exclude `max_tokens`. Including it refuses work at a ceiling
   that would in fact have covered it.
2. **Cost MUST be allowed to follow the schema.** A profile MAY declare a cost
   per scored option; one question over 20 options is more work than one over 2
   at identical token counts, and no token count expresses the difference.
   Declaring nothing reproduces the token-only model exactly, so an unmeasured
   profile claims nothing.
3. **The efficiency figure MUST be defined.** `uj_per_accepted_token` (§6) is
   undefined when no tokens were accepted, which is every request in this
   category. A decision receipt MUST instead carry `uj_per_decision`, and
   SHOULD carry `uj_per_option_scored`. The unit of work is the answered
   question.

`schema_tokens` is reported because a fixed schema is a **cacheable input
prefix** — distinct from `cache_hit_tokens`, which counts output tokens served
from cache, of which a decision has none. In the measured request 92% of the
input was schema, so a reader that cannot see the split cannot tell a cold
decision from a warm one.

> **Why a decision receipt is worth more than a generation receipt.** A decision
> is a single forward pass with no sampling. Given the weight digest, revision
> and numeric precision, it is reproducible — so a receipt over one is verifiable
> **by re-execution**, which a receipt over sampled text can never be. A receipt
> for a decision SHOULD therefore bind the weight digest and the precision; the
> probabilities of a published decision model differ between `fp16` and `fp32`
> even where the selected answer agrees, so a receipt that omits precision does
> not reproduce.
>
> The fields are `weights_digest` and `precision` (§6.1), both OPTIONAL. A
> backend that can address its weights **SHOULD** report both; one that cannot
> omits them, and the receipt then binds the model by `recipe` alone — a name,
> which an operator can re-point at other weights while every receipt sealed
> under it goes on verifying. That is the weaker basis, and the absence of the
> fields is how a verifier can tell it apart from the stronger one, rather than
> having to assume.

---

## §4 Routing — cheapest-sufficient

For each registered backend the router computes an estimate
`est_total_uj = uj_per_token × (prompt_tokens + max_tokens)`, or for a typed
decision (§3.6) `uj_per_token × prompt_tokens + uj_per_option_scored ×
options_scored`, and marks it **admissible** iff:

```
backend.fidelity ≥ request.fidelity_floor   AND   est_total_uj ≤ request.joule_ceiling_uj
```

The router MUST choose the admissible backend with the **lowest** `est_total_uj`.
Ties are broken deterministically (registration order). When no backend is
admissible the serve fails, and the decision records why.

The router MUST record, for every backend it weighed, a `RouteCandidate` with its
fidelity, estimate, admissibility, and — when inadmissible — a human-readable
reason (below floor / over ceiling). The chosen route MUST carry a one-line
justification. This is what makes a route **auditable from the receipt alone**:
the cheapest sufficient answer is preferred and a frontier model is the expensive
last resort, and the comparison is denominated in joules.

A model is addressed as a **recipe** — a base plus optional merges/adapters — not
a fixed blob, so the receipt can record *which* composed model answered.

---

## §5 The serving engine

A backend implements one interface: advertise a fidelity level and a modeled
per-token energy cost, and serve a request producing tokens and a `ServeOutcome`:

```
ServeOutcome {
  tokens_in, tokens_out, tokens_accepted,
  cache_hit_tokens, spec_proposed, spec_accepted,
  delivered_fidelity: Option<Fidelity>          // §3.2.1
}
```

The advertised level is a promise made before the work; `delivered_fidelity` is
what the backend says it actually served. An engine that cannot degrade may
report its rating; an engine that can — a fallback, a truncation, a timeout that
drops to a cheaper path — reports what it served. Omitting it is conformant and
means `fidelity_met` rests on the advertisement (§3.2.1).

The input token payload travels **with** the serve call, alongside the request —
it is never part of the request's sealed identity and never enters the receipt,
which records only the content-addressed `prompt_hash` (§3.1). A receipt is
therefore safe to publish without disclosing the prompt.

`tokens_accepted` is the denominator of the wedge metric. For greedy decode it
equals `tokens_out`; under speculative decoding it is the number of proposed
tokens the target model accepted. `cache_hit_tokens` records output served from a
prefix/result cache (energy saved). An engine MUST do real work proportional to
the tokens it serves so the surrounding meter reads a real span; it MUST NOT
self-report energy.

The reference engine (`mesh-engine::ReferenceEngine`) is deterministic and
weights-free, for conformance. Production backends — a quantized device-resident
decoder, a high-throughput batching server — implement the same interface and
drop in unchanged; `mesh-engine-gguf::GgufEngine` (behind the `gguf` feature) is
one such backend over a pure-Rust GGUF/Metal decoder, so the mesh routes and
meters real model tokens.

---

## §6 The receipt — `mesh/1`

A `MeshReceipt` is sealed with **JCR-1**: canonical det-CBOR (RFC 8949 §4.2.1)
inside a COSE_Sign1 envelope (RFC 9052, EdDSA/Ed25519, `alg = -8`), byte-compatible
with the rest of the family's receipts. The signed core forbids floats, booleans,
and nulls; booleans are encoded as `0|1` uints and absent options dropped.

### §6.1 Wire fields (`mesh/1`)

| Key | Meaning |
|---|---|
| `mesh_receipt` | `"mesh/1"` |
| `request_id` | hex content id of the request |
| `grant_id` | hex JCP grant id this inference debited (omitted if ungranted) |
| `backend`, `recipe` | the backend and composed model that served it — `recipe` is a name, read it with the two fields below |
| `weights_digest` | hex content address of the weights that answered (OPTIONAL — §3.6; absent means the receipt binds the model by name alone) |
| `precision` | the numeric precision the forward pass ran at, as the backend names it — `fp32`, `fp16`, `bf16`, `int8` (OPTIONAL — §3.6; paired with `weights_digest`, since neither reproduces alone) |
| `route` | the router's one-line justification |
| `tokens_in/out/accepted`, `cache_hit_tokens`, `spec_proposed/accepted` | the outcome counters |
| `fidelity_floor` | the floor the request demanded (uint) |
| `fidelity_advertised` | the level the backend is rated for (uint, OPTIONAL — paired with the next) |
| `fidelity_delivered` | the level the backend says it served (uint, OPTIONAL — §3.2.1) |
| `fidelity_met` | `0|1` — was the floor met, on the delivered figure where there is one |
| `estimated_uj` | always present |
| `measured_uj` | present **iff** provenance is `HwShunt` |
| `uj_per_accepted_token` | **the wedge metric** for a generation — `energy.uj() / tokens_accepted`; omitted when no tokens were accepted |
| `questions_answered`, `options_scored`, `schema_tokens` | present **iff** the request was a typed decision (§3.6) |
| `uj_per_decision` | **the wedge metric** for a decision — `energy.uj() / questions_answered` |
| `uj_per_option_scored` | the finer decision figure — `energy.uj() / options_scored` |
| `energy_provenance` | `HwShunt | ModelBased | Estimator` |
| `grant_breach` | the JCP denial label when debiting the metered joules breached the grant, e.g. `caveat-unsatisfied` for a per-call cost caveat (OPTIONAL — §2; absent means the debit was within the grant, or the serve rode on none) |
| `sequence`, `prev` | hash-chain position and prior envelope's content id |
| `nonce`, `steward` | per-receipt nonce and the sealing identity (COSE `kid`) |

### §6.2 The wedge metric

`uj_per_accepted_token = energy.uj() / tokens_accepted`, where `energy.uj()` is
the measured figure if present, else the estimate. It is `null`/absent when no
tokens were accepted. This is the number Mesh exists to make legible, and it is
sealed into every receipt.

### §6.3 Hash chain

A steward keeps a receipt log. Appending a receipt stamps its `sequence` (from 0)
and `prev` (the content id of the previous sealed envelope; absent at genesis),
seals it, and advances the head. The log is tamper-evident end to end: altering
any envelope breaks verification of that receipt and the chain link from the next.

---

## §7 Conformance

A conforming implementation MUST:

1. Decide a serve's grant as a JCP enforcement point before any work (§2): reject
   one that fails verification, has expired or been revoked, does not permit
   `infer` on the request, carries a cost-independent caveat that does not hold,
   or has less left than the request's joule ceiling; debit the metered joules
   against it after the work, recording a breach on the receipt.
2. Choose the cheapest admissible backend and record every candidate weighed
   (§4).
3. Meter energy around the engine and tag provenance honestly, enforcing the
   `Energy` coupling before sealing (§3.3).
4. Seal the receipt as a JCR-1 `mesh/1` envelope and compute
   `uj_per_accepted_token` (§6).
5. Maintain a tamper-evident hash chain (§6.3).

The published vectors in [`../conformance/v1/`](../conformance/v1/) pin a
deterministic reference serve. `reference/signed_core.hex` MUST canonical-CBOR
encode identically across implementations, and `reference/envelope.hex` MUST be
reproducible from it with the steward key in `meta.json`. Regenerate with:

```text
cargo run -p mesh-conformance --bin gen-vectors -- ../conformance/v1
```

---

## §8 Security considerations

Mesh composes proven primitives: Ed25519 signatures, BLAKE3 content addressing,
RFC 9052 COSE_Sign1, and the JCP capability model. It introduces no new
cryptography. Two properties are correctness, not style:

- **Authorisation happens outside the model.** The grant check (§2) is enforced
  by the steward before any inference runs; a prompt cannot grant itself budget
  or capability.
- **The caller is not authenticated.** Mesh honours a grant as a bearer token
  of its subject: whoever presents it is decided as the subject. A grant that
  must not be usable by anyone who obtains it needs a binding Mesh can check
  without an identity, such as `PayloadIs` or a short `NotAfter`.
- **A grant's spend is per steward.** The debit ledger is the steward's own, in
  memory. A grant presented to several stewards, or to one that restarts, is
  spent separately at each (JCP §4.5, §4.11).
- **Honesty is enforced at seal time.** A receipt cannot claim a measurement it
  does not have (§3.3). An operator without a hardware meter produces honest
  `Estimator` receipts.

Energy figures are only as honest as the worst meter in the span. A receipt's
provenance tag states which meter produced its figure; consumers SHOULD treat
`Estimator` figures as bounds, not measurements.

---

## §9 Relationship to the family

Mesh is the serving + routing fabric. It is expressed in primitives the family
already publishes, and it composes with the neighbouring standards rather than
duplicating them:

- It **rides on [JCP](../jcp/)**: a serve request is authorised by a JCP `Grant`
  (capability ⊗ joule-budget), and the receipt seals in JCR-1 — the same envelope
  every family receipt uses.
- It **dispatches to runtimes** such as [JouleClaw](../jouleclaw/): a backend that
  executes one inference cheaply is one engine behind the mesh.
- It **routes across compute** described by [EOC](../eoc/) and isolated by
  [Sandbox](../sandbox/): a backend may be a metered, attested execution target.

The boundary is deliberate: a runtime executes *one* inference; Mesh routes
across *many* models and *many* backends and proves what each one cost.