Executive Summary

This proposal funds 16 months of maintenance for the open-source substrate-api-client, a Rust RPC client library for interacting with Substrate/Polkadot-based chains, with a particular focus on no_std environments such as trusted execution environments, embedded systems, and constrained devices.

The library is actively used by ecosystem teams and fills an important gap alongside other Rust clients, such as subxt by enabling lightweight, no-std-compatible chain interaction.

The requested funding covers:

Keeping the library aligned with Polkadot/Substrate releases
Supporting users and contributors
Delivering small improvements

This is a continuation of previous maintenance efforts and aims to ensure that the library remains reliable, compatible, and accessible.

Why this matters to Polkadot

The Polkadot ecosystem depends on shared infrastructure libraries that many teams use. The substrate-api-client is one of these pieces of infrastructure:

It enables programmatic interaction with Substrate-based chains via RPC
It is especially relevant for environments where subxt is too heavy or unavailable
It reduces duplicated effort across multiple ecosystem teams
It helps sustain developer choice in the Rust tooling stack

This makes the library a common good: useful across the ecosystem, open source, and maintained for broad benefit rather than a single product.

Scope of work

This proposal covers maintenance work for the period:
September 2026 - Dec 2027

1. Stay up to date with the ecosystem

Polkadot SDK and related dependencies evolve quickly. To keep the library usable, we will:

track relevant Polkadot/Substrate releases
update dependencies when required
adapt the client to upstream breaking changes
replace or remove unmaintained dependencies where needed

2. Support users and contributors

Maintenance is not only code updates; it also includes direct developer support. We will:

respond to usage questions and integration issues
investigate bug reports
document known issues and workarounds
review incoming community pull requests
help new teams onboard to the library

3. Deliver small improvements

In addition to maintenance, we plan to implement a selected set of smaller improvements and fixes.
Candidate items include:

Final prioritization may depend on urgency, compatibility requirements, and ecosystem demand.

Deliverables

By the end of the proposal period, we commit to delivering:

continued compatibility maintenance for relevant upstream changes
issue triage and user support throughout the support period
implementation of small improvements within the allocated budget
public progress reports every 3 months in the polkadot forum
visible work tracking through GitHub issues, PRs, releases, and changelogs

Team

Supercomputing Systems AG (SCS), Zurich, Switzerland

SCS is an engineering company with approximately 140 engineers working across software, electronics, and system design. Within SCS, a dedicated blockchain team has been contributing to the Polkadot ecosystem since 2019.

In 2022–2026, the team’s primary ecosystem contribution has been the ongoing maintenance and improvement of the substrate-api-client.
GitHub contributors:

Budget

This proposal requests $38,500 in USDT. SCS bills engineering work at 185 CHF/hour.

Work Package	Deliverables	Cost
Ecosystem updates	Dependency updates, release tracking, compatibility maintenance	$18,400
User support	Issue triage, user support, PR review, bug investigation	$7,300
Small improvements	Implementation, code review, documentation, release notes	$12,800
Total		$38,500

Track Record

2025:
- https://polkadot.polkassembly.io/referenda/1355 (the support was extended to one year due to less frequent polkadot updates than expected)
2024:
- https://polkadot.polkassembly.io/referenda/792
- https://polkadot-old.polkassembly.io/treasury/546
2023:
2022:
- https://kusama.polkassembly.io/referenda/26

Forum Discussion

Corresponding Forum post and discussion: https://forum.polkadot.network/t/pre-proposal-discussion-maintenance-for-the-substrate-api-client/18148