A new contender has entered the complex world of software build automation with the release of Toast 1.0. Developed by Mixedbread, Toast is a language-agnostic build system designed to bring correctness, reproducibility, and high performance to projects of any scale. The official announcement of the 1.0 release positions the tool as a universal solution for modern, polyglot codebases, and its debut has garnered significant developer interest, sparking a lengthy discussion on Hacker News.
In an ecosystem saturated with tools like Make, Maven, Gradle, Cargo, and npm, the launch of another build system begs the question of necessity. Toast’s answer lies in its ambition to unify the disparate tooling that plagues projects using multiple programming languages. Instead of stitching together language-specific build tools with brittle shell scripts, Toast provides a single, coherent interface for building, testing, and deploying an entire repository.
A Unified Approach to Building Software
At its core, Toast is engineered to solve the challenges that arise when a single project contains code written in C++, Rust, Go, and TypeScript. Managing dependencies, compilers, and build steps across these ecosystems is a common source of complexity and errors. Toast abstracts this away, allowing developers to define build targets in a consistent manner, regardless of the underlying language.
Its design philosophy is heavily inspired by Google's Bazel, borrowing several key principles:
- Hermetic Builds: Toast executes build steps in a sandboxed environment with no network access and access only to explicitly declared inputs. This ensures that a build will produce the same output every time, on any machine, eliminating “it works on my machine” problems.
- Language Agnosticism: The system is not tied to any single language. Through a system of rules, it can be extended to support virtually any toolchain.
- Distributed Caching and Execution: For large teams and continuous integration pipelines, Toast offers local and remote caching to avoid rebuilding unchanged code. It also supports remote execution, allowing build tasks to be distributed across a cluster of machines for significant speed improvements.
Configuration is handled through TOAST files written in Starlark, a dialect of Python. This makes build definitions programmable and easier to manage than static formats like XML or JSON. A developer defines a target, which is the fundamental unit of work, such as compiling a binary or running a test.
For example, building a simple C++ executable is straightforward. A TOAST file in the source directory would contain:
# src/hello/TOAST
load("@rules_cc//:rules.bzl", "cc_binary")
cc_binary(
name = "hello",
srcs = ["hello.cpp"],
)
A developer can then build this target from anywhere in the project with a single command:
toast build //src/hello:hello
This command invokes the C++ compiler with the correct flags, links the binary, and places the output in a predictable location, all without the developer needing to manage the compiler installation or environment variables directly.
Differentiating from Bazel
While Toast shares its conceptual foundation with Bazel, its creators emphasize a focus on improved user experience and a lower barrier to entry. Bazel is notoriously powerful but also famously difficult to configure and debug. The Toast announcement post highlights several key areas where it aims to be simpler.
One of the most significant differences is toolchain management. Setting up compilers, linkers, and interpreters in Bazel can be a complex and manual process. Toast automates this by default, fetching and managing required toolchains for the host platform. This approach simplifies initial setup and ensures a consistent build environment for all developers on a project.
Another major differentiator is first-party support for remote caching. Toast is developed alongside a managed service, Mixedbread Cache, which provides a zero-configuration remote build cache. While Bazel supports remote caching, teams are typically responsible for deploying and maintaining their own caching infrastructure, a non-trivial engineering task. By offering an integrated solution, Toast aims to make the benefits of distributed caching accessible to a wider range of teams.
The project also promises more helpful error messages and sane defaults, addressing common complaints from developers new to Bazel-style build systems. The goal is to provide the power of hermetic, scalable builds without the steep learning curve.
Performance Through Caching and Parallelism
Modern software development demands fast feedback loops. Toast is designed for speed, using a multi-layered caching system to ensure that work is never repeated unnecessarily. It maintains an in-memory cache for the duration of a single command, a persistent on-disk cache for subsequent commands on the same machine, and the optional remote cache for sharing build artifacts across a team.
When a toast build command is run, the system first constructs a directed acyclic graph (DAG) of all targets and their dependencies. It then checks the cache for the outputs of each step. If a valid artifact is found, it is reused instantly. Any steps that do need to be executed are run in parallel, taking full advantage of multi-core processors. This combination of fine-grained dependency tracking and aggressive caching can reduce build times from minutes to seconds, especially for incremental changes.
The Path to Adoption
The release of version 1.0 marks a significant milestone, signaling API stability and readiness for production use. The initial reception from the developer community suggests a strong appetite for a tool that promises the power of Bazel with the usability of simpler, language-specific tools. Discussions often center on the pain points of maintaining polyglot repositories and the operational overhead of existing enterprise-grade build systems.
However, the success of any build system depends heavily on its ecosystem. Toast's utility will be determined by the quality and breadth of its available rules—the plugins that provide support for different languages, frameworks, and tools. While Toast ships with core rules for languages like C++, Rust, and Go, its long-term viability hinges on the community's willingness to build and maintain rules for the vast landscape of modern development tools.
What to Watch Next
The immediate future for Toast will likely focus on expanding its ecosystem of rules and proving its claims of simplicity in real-world, complex projects. Its ability to carve out a space between single-language tools like Cargo and the industrial-strength complexity of Bazel will be its primary test. Key indicators to watch will be the adoption of Toast by notable open-source projects, the growth of third-party rule sets, and the uptake of its commercial caching service. For now, Toast stands as a promising and well-timed effort to bring order to the controlled chaos of modern software development.