moxzi-onchain-builds

Trustless Motoko builds on the compiler canister: driving a paid build with moxzi build --remote, the escrow payment model (quote, ICRC-2 approve, settle, refund), CLI identity and funding, operator deployment and configuration (syncOperators, setLedger/setCmc, memory limits), abuse posture, and source-privacy tradeoffs. Use when producing an artifact whose build anyone can verify on-chain, paying for a remote build, or deploying/operating the compiler canister. Do NOT use for local compilation (use moxzi-cli) or for hosting the produced actors (use moxzid-server / moxzi-web).

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The compiler canister runs the same wasm moxzi build runs locally, so an on-chain build is byte-identical to a local one. That identity is the product: an artifact whose bytes were produced on-chain, by a compiler anyone can audit, from sources anyone can hash.

Critical rules#

ALWAYS:

• Compare provenance hashes: the deployed compiler/linker sha256s (from moxzi info and the release notes) are what a verifier checks.
• Fund the principal the CLI prints on connect — the CLI's identity is a 32-byte key at the platform config dir (MOXZI_IDENTITY overrides the path).
• Expect the escrow flow to REFUND most of the escrow: settlement charges 3× actual use and refunds the rest. A customer who walks away loses nothing (the operator can abandonSettlement(id), which measures real burn and refunds the rest).
• Warn closed-source users: uploaded source sits in the canister's VFS, readable by operators until removed or evicted. Builds from mops tags upload nothing (the canister already holds content-addressed blobs) — prefer tag builds for private code.

NEVER:

• Promise parallel builds on one canister: one canister = one job queue; builds serialize. Horizontal scale = deploy another canister.
• Skip the payment confirmation silently in interactive use — the CLI shows the escrow quote and asks; --yes is for scripts.
• Assume a fresh deployment charges: payment is inert until configured. It compiles for free and says so; it never silently charges.

Customer flow (one command)#

moxzi build src/main.mo --remote https://icp-api.io --canister <compiler-id>

The CLI: quotes the escrow → shows the caller's ICP balance → asks (skip with --yes) → icrc2_approves the canister → starts the escrowed job → drives it to completion → downloads and links the artifact → reports settlement:

remote: this build escrows 0.3501 ICP (rate 35000 XDR-permyriad/ICP); settlement charges 3x actual use and refunds the rest
remote: your balance is 2.0000 ICP
remote: escrow pulled, job 0
…
remote: settled (done): charged 0.0009 ICP, refunded 0.3489 ICP
compiled by … (sha256 …), moxzi 0.1.0-alpha.5

Useful with it: --progress N (report every N steps), --status-secs S (name the compiler's phase, coarsely — it costs a query), --max-steps N (give up), moxzi deps entry.mo (preview exactly which files would be uploaded, with VFS paths).

The driver dies; the job does not. The job is a state machine on the canister — a network blip, laptop sleep, or killed terminal loses nothing on-chain. The CLI retries transport errors automatically (up to 5, with backoff); if the driver still dies, resume the SAME job instead of paying to rebuild:

moxzi build src/main.mo --remote <url> --canister <id> --resume-job <N>

Find the job id in the CLI's own output (escrow pulled, job N) or with moxzi verify --remote <url> --canister <id> --list. Resume skips upload and start entirely and drives the existing job to completion — measured in anger: a build stranded at message 3,034 of ~4,100 finished with 1,104 more instead of starting over.

The registry pulls the attestation (how "built on-chain" is decided)#

The compiler links its own output (linkArtifact) and indexes the LINKED sha256 (attestLinked(hex) : ?{ job; build; link }, a query). A registry that holds those bytes asks that question itself -- astroflora's icrc118_attest_wasm(hash) -- and files the answer as the compiler's ICRC-126 attestation with the build evidence (sourcesDigest, optionsDigest, compilerVersion, jobId, linkOptions). Nobody pushes an attestation on the compiler's behalf; a byte-modified wasm gets null, and stays unverified. moxzi publish triggers the pull and prints the verdict. Mainnet compiler: xcn6l-iqaaa-aaaai-raq6q-cai; registry: l55bi-3aaaa-aaaai-atk4a-cai; UI: https://registry.astroflora.xyz.

The payment model (escrow → measure → 3× actual → refund)#

• quoteEscrow() (an update — the rate comes from the CMC live) returns exactly what startEscrowed will pull: escrow cycles at the CMC's ICP↔XDR rate plus the ledger fee. Pricing is server-side so clients cannot drift.
• startEscrowed pulls escrow via icrc2_transfer_from and samples the cycle balance; the delta at completion is what the compile actually consumed.
• settleStep(id) is an idempotent machine: measure → refund unused escrow → convert 1× actual back to cycles (self-funding top-up) → donations → done.
• A flat-fee path also exists (startPaid, getPrice); the CLI prefers escrow because it charges what a build costs, not what the worst build costs.

Operator: deploy and arm#

1. Build reproducibly: make compiler-canister-wasm and make moxzi-linker; pin the mops toolchain moc version; record both SHA-256s — they are the provenance every build cites.
2. Deploy both canisters: compiler with wasm_memory_limit = 6 GiB (big compiles really peak near it) and generous cycles; linker > 3 GiB.
3. Bootstrap operators: call syncOperators() — callable by anyone, grants nothing new: it copies the controller list into the operator set. A fresh deployment is LOCKED (empty operator set fails closed) until this runs.
4. Arm payment (operator): setLedger(ryjl3-tyaaa-aaaaa-aaaba-cai) (mainnet ICP), setCmc(rkp4c-7iaaa-aaaaa-aaaca-cai), optionally setEscrowCycles(n), setPrice(e8s), setChargeMultiplier(n).
5. Smoke it: an unfunded identity must be refused with "insufficient balance" BEFORE any transfer; a funded hello-world must compile, settle, and refund most of its escrow.
6. Watch it: sdStatus() (heartbeat), jobStats() (jobs/finished/artifact bytes), revenue() (flat-path e8s), the canister's ledger account, and the cycle balance — top-ups convert 1× actual back to cycles, so a busy canister partially self-funds.

Abuse posture (what a stranger can and cannot do)#

Error → cause → fix#

Prove what was built#

Every finished build leaves a stable record on the canister (sources digest, options digest, compiler version, artifact sha256) that outlives the job and canister upgrades:

moxzi verify --remote <url> --canister <id> [--job N] [--entry main.mo] [--artifact out.wasm]

It recomputes the sources digest locally and reads the canister's module hash FROM THE IC (not from the canister's own methods), so the claims are checked rather than believed. Exits non-zero on any mismatch. --list shows recent builds.

Related skills: local builds → moxzi-cli; running artifacts → moxzid-server / moxzi-web.