---
name: sails-ethexe-implementer-93969a0740e1
description: Use when approved tasks require Rust code changes in a Sails ethexe workspace with the ethexe feature enabled. Do not use for standard Gear/Vara Sails apps without ethexe, or when the spec or architecture is still unsettled.
---

# Sails Ethexe Implementer

## Overview

Implement approved tasks in Sails ethexe workspaces where the `ethexe` feature is enabled and methods may be exported via ethabi transport, accept value (payable), or emit Ethereum-style events.

If the task does NOT need the ethexe feature, use `../sails-rust-implementer/SKILL.md` instead.

## Inputs

- `../../references/sails-ethexe-patterns.md` — ethexe diff table, type requirements, transport rules, event patterns
- `../../references/sails-syscall-mapping.md` — `Syscall::*` API (note gated syscalls)
- `../../references/sails-cheatsheet.md` — core Sails patterns
- `../../references/sails-rs-imports.md` — import paths
- `../../references/sails-idl-v2-syntax.md` — IDL v2 annotations
- `../../references/sails-header-wire-format.md` — Sails Header routing

Consume the approved `spec`, `architecture`, and `tasks` artifacts before changing code.

## Workflow

1. Confirm the task is specified and architecture-approved.
2. Confirm the crate has `sails-rs` with `features = ["ethexe"]` in `Cargo.toml`.
3. Identify the smallest code change that satisfies the task.
4. Use `#[sails_type]` for all custom types. Types used in ethabi-exported methods must also be ABI-encodable as Solidity tuples (`SolValue`).
5. Choose the correct transport per method:
   - `#[export]` — both scale + ethabi (default with ethexe)
   - `#[export(scale)]` — scale only, no ethabi
   - `#[export(ethabi)]` — ethabi only
   - `#[export(ethabi, payable)]` — ethabi with value acceptance
6. Use `emit_eth_event()` for Ethereum-style events, `emit_event()` for standard Gear events. Do not mix them on the same event type without explicit architecture guidance.
7. Mark `#[indexed]` on up to 3 event fields per variant for Ethereum topic indexing.
8. Use `Syscall::*` for runtime accessors. Three syscalls are unavailable: `signal_from`, `signal_code`, `system_reserve_gas`.
9. Hand verification to the gtest loop before claiming done.

## Transport Decision Guide

| Scenario | Attribute |
|----------|-----------|
| Standard method, both transports | `#[export]` |
| Method only callable from Gear programs (no EVM) | `#[export(scale)]` |
| Method only callable from EVM | `#[export(ethabi)]` |
| Method that accepts value from EVM | `#[export(ethabi, payable)]` or `#[export(scale, ethabi, payable)]` |
| Query (read-only) | `#[export]` (transport flags orthogonal to query semantics) |

## Payable Methods

Non-payable methods panic at runtime if `msg::value() > 0`. To accept value:

```rust
#[export(payable)]
pub fn deposit(&mut self) -> u64 {
    let value = Syscall::message_value();
    // handle deposit...
    value as u64
}
```

Constructors can also be payable: `#[export(payable)] pub fn create() -> Self { ... }`

## Eth Events

```rust
#[event]
pub enum MyEvent {
    Transfer {
        #[indexed]
        from: ActorId,
        #[indexed]
        to: ActorId,
        value: u64,
    },
    Paused,
}

// In service method:
self.emit_eth_event(MyEvent::Transfer { from, to, value });
```

- Max 3 `#[indexed]` fields per variant
- Forbidden variant names: ExecutableBalanceTopUpRequested, Message, MessageQueueingRequested, Reply, ReplyQueueingRequested, StateChanged, ValueClaimed, ValueClaimingRequested

## Guardrails

- Do not use `signal_from()`, `signal_code()`, or `system_reserve_gas()` — they are gated out under ethexe.
- Do not use raw `gcore::*`, `msg::*`, or `exec::*` calls — use `Syscall::*`.
- Do not mark more than 3 fields as `#[indexed]` per event variant.
- Do not use reserved event variant names.
- Do not assume `payable` works with scale-only transport — it requires ethabi.
- Service names must be PascalCase and must not collide with Solidity reserved keywords.
- Preserve released routes, reply shapes, and events unless the task explicitly changes them.
- Use `Syscall::message_source() == Syscall::program_id()` for self-message guards.
- Hand verification to the gtest loop before claiming done.


---
Source attribution: gear-foundation
Original project: https://github.com/gear-foundation/vara-skills/blob/44c1454141ececc8ef3a88903b625260f370c4de/skills/sails-ethexe-implementer/SKILL.md
License: MIT
License information: https://opensource.org/license/mit
Original upstream instructions; downloaded from Mega AI Hub.

## Upstream license notice

MIT License

Copyright (c) 2026 Gear Foundation

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all
copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
SOFTWARE.



# Mega AI Hub resource metadata

Creator / publisher: gear-foundation
Original project: https://github.com/gear-foundation/vara-skills/blob/44c1454141ececc8ef3a88903b625260f370c4de/skills/sails-ethexe-implementer/SKILL.md
Attribution basis: Source repository record

Fields of work: Development & Engineering
Roles: Backend Developer, ML / AI Engineer
Specialties: Backend
Tools: Sails
Country applicability: Country not specified
Classification basis: Source catalog labels
Instruction SHA-256: 2f7f20d1248b4aeee9d03b91b5d8bc5bc5036fe352215d9d20f7e4487e31bf21