# The Sandbox proof matrix

The standard's claim to be a universal substrate is only worth what the proof behind it is worth. This directory holds that proof: a ledger of **signed proof cells**, each one a real run of the conformance pack plus a sealed workload on a real target, recording the substrate, OS, architecture, cloud, hardware classes, and tier it actually demonstrated.

A green cell is never a claim. It is an Ed25519 signature (over the cell's JCS-canonical form — the family attestation primitive) that references an **attestation and receipt which themselves verify**. What a host cannot prove — no `/dev/kvm` → no microVM tier, no `configfs-tsm` → no confidential tier — is recorded as *unavailable*, never faked. Run the harness on more targets and the matrix fills with real proofs.

## The matrix axes

```
substrate : Wasm · Container · MicroVm · Tee · BareMetal · Browser
OS        : linux · macos · windows
arch      : x86_64 · aarch64 · riscv64
cloud     : local · aws · azure · gcp · alibaba · cloudflare · fly · …
hardware  : Cpu · Simd · Gpu · Npu · Tpu · Lpu · Photonic · Quantum
tier      : S0 … S7
```

A cell is one point in `{substrate × OS × arch × cloud × hardware × tier}`. `matrix.jsonl` accumulates the cells that have been proved.

## Producing and checking proofs

The harness is [`sandbox-proof`](../sandbox-rs/crates/sandbox-proof/):

```bash
cd ../sandbox-rs
# Prove THIS host — runs the conformance pack + a sealed S2 (WASM) run,
# probes which higher substrates are available, and appends a signed cell.
SANDBOX_CLOUD=local cargo run -p sandbox-proof -- prove ../proof/matrix.jsonl

# Re-verify every cell's signature (CI-friendly exit code).
cargo run -p sandbox-proof -- verify ../proof/matrix.jsonl

# Render the proved cells.
cargo run -p sandbox-proof -- show ../proof/matrix.jsonl
```

Set `SANDBOX_CLOUD` to the cloud/region the host runs in (e.g. `aws`, `gcp`), and `SANDBOX_PROOF_KEY` (64 hex) to the operator's own signing key; a fixed dev key is used otherwise.

## What a cell records

Each line of `matrix.jsonl` is a `SignedProofCell`: the substrate/OS/arch/cloud/hardware/tier proved, the per-class conformance outcome, the content addresses of the run's **attestation** and energy **receipt**, the substrates the host reported available, a timestamp, and the Ed25519 signature + public key. Anyone can re-verify a cell without trusting the operator who produced it.

## Honesty

The harness proves what the host can actually demonstrate. Today the universal cell is `Wasm / S2`, which runs anywhere the reference runtime does (Linux, macOS, Windows, any arch — and in a browser via WASM). Higher tiers (microVM, confidential) light up only on hosts that genuinely provide them. The matrix grows by running on more substrates, clouds, and accelerators — never by asserting a cell that wasn't run.