V0.7 to V0.8 Migration (Draft)

Status: draft. V0.8 is in active development. Nothing on this page is final. This stub exists so you can plan ahead — concrete migration steps will land alongside the V0.8 RC1 release.

V0.7 will remain the supported stable line through the V0.8 RC cycle. You do not need to migrate immediately — but if you are starting a new project today and will ship after V0.8, reading this page now will save a rewrite.

Tracking V0.8

Follow progress on the GitHub milestone:

https://github.com/covenant-lang/covenant/milestone/8

The milestone tracks every breaking change, design discussion, and RC ship date. When V0.8 RC1 is tagged, this page will be rewritten with precise migration steps, a covenant migrate --target 0.8 command, and test-suite updates. Until then, treat the section below as directional.

What the V0.8 migration will cover

The release themes driving this version:

1. WASM target stabilization

V0.7 shipped WASM codegen as experimental behind --target wasm32-covenant --unstable. V0.8 stabilizes the target and wires it into covenant build without the unstable flag. Expected migration work:

Remove --unstable from CI scripts.
Update covenant.toml [build.target] entries — the stable target name will be wasm32-covenant.
Re-generate client bindings; the ABI layout for bytes parameters is changing slightly to match the ABI stability guarantees.

2. New `@async_action` keyword

V0.8 introduces a first-class notion of asynchronous actions — actions that span multiple blocks, receive callbacks from cross-chain messages, or await off-chain computation such as ZK proofs or FHE decryption results. Today these patterns are expressed by hand using state machines; V0.8 replaces them with:

@async_action
action redeem(id: u64) {
    let proof = await zk_prover.verify(id)
    given proof.valid or revert_with InvalidProof()
    _settle(id)
}

Code that currently implements the state-machine-by-hand pattern will be convertible via covenant migrate --rewrite async_pattern.

3. Revised FHE API for BFV parameter selection

V0.7 requires BFV parameter selection (polynomial degree, modulus chain, plaintext modulus) to be specified up-front per contract. V0.8 introduces:

A fhe_params language-level declaration that the compiler validates against the set of operations the contract performs.
Automatic parameter upgrade paths when a contract adds an operation that exceeds the current depth budget.
Deprecation of the fhe::bfv::manual_params(...) intrinsic in favor of the declarative form.

Contracts that use only the standard encrypted<T> operators and do not call manual_params(...) will migrate without changes.

4. Compiler diagnostic format changes

V0.8 replaces V0.7’s plain-text diagnostic output with a structured format compatible with the Language Server Protocol, and emits machine-readable JSON under --message-format=json. CI pipelines parsing compiler output will need updates — the covenant migrate tool will emit a hint whenever it detects the legacy format being grepped.

Placeholder: likely breaking changes

The following table is indicative, not final. Treat it as the shape of things to expect.

Area	V0.7	V0.8 (planned)	Notes
WASM build target	`wasm32-covenant-experimental`	`wasm32-covenant`	Flag rename; same binary layout
Async patterns	hand-written state machine	`@async_action` + `await`	Auto-rewriter in `covenant migrate`
FHE param selection	`fhe::bfv::manual_params(...)`	`fhe_params { ... }` declaration	Manual form deprecated, not removed
Compiler output	plain text	structured JSON via `--message-format`	CI grep will need updating

What is not changing

To set expectations for existing V0.7 code:

Core syntax — contract, action, field, guard, given, revert_with — is stable.
The ERC-20 token { ... } block shape is stable.
Decorators (@nonreentrant, @pausable, @upgradeable) are stable.
amount, u256, timestamp, encrypted<T> remain first-class and source-compatible.

In practice, most V0.7 contracts will compile on V0.8 unchanged. The migration work is concentrated in CI scripts, build configs, and FHE-heavy contracts that opted out of the default parameter path.

What you can do now

Pin language = "0.7" in covenant.toml if you want to freeze behavior while V0.8 stabilizes.
Avoid fhe::bfv::manual_params(...) for new code — use the default encrypted<T> operators.
Keep custom async/state-machine code isolated so the V0.8 rewriter can find it.
Subscribe to the V0.8 milestone (link above) for RC announcements.

This page will be fully rewritten with concrete steps and a covenant migrate --target 0.8 walkthrough when V0.8 RC1 ships. Check back then, or watch the milestone for the migration-guide label.