# Build Tool Alternatives to Gradle (2026)
Quick comparison of JVM build tools with **faster startup and iteration** for AI-assisted development. Goal: less wait between “run tests” / “compile” and feedback.
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## TL;DR
| Tool | Cold start | Incremental | Best for |
|------|------------|-------------|----------|
| **Mill** | **~0.1s no-op** (vs Gradle ~0.9s) | **3–7x faster** than Gradle | **Primary recommendation** for Java/Spring Boot |
| **saker.build** | Faster than Gradle | ~50–60% faster (claimed) | Experimental / niche |
| **mvnd** | Maven with daemon | Faster than plain Maven | If you must stay on Maven |
| **Bazel / Pants** | Heavy | Great at scale | Large monorepos, not this project |
**Recommendation:** **Mill** — best balance of fast startup, fast incremental builds, and Spring Boot–friendly setup.
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## 1. Mill
- **Site:** https://mill-build.org
- **Status:** Active (1.x, 0.12.x).
**Why it fits “faster startup + AI vibe coding”:**
- **No-op run:** ~**0.1s** vs Gradle ~**0.9s** (Mockito-style project) — ~**8.5x** less overhead when nothing to do.
- **Incremental compile (single module):** ~**0.2s** vs Gradle ~**1.3s** — ~**6–7x** faster.
- **Clean compile (single module):** ~**1.2s** vs Gradle ~**4.4s** — ~**3–4x** faster.
- No daemon by default → **predictable cold start**; no “first run vs daemon warm” surprise.
- Build is **programmatic** (Scala in `build.sc` / `build.mill`); IDE jump-to-def and find-usages work well.
- **Spring Boot:** Examples and patterns exist (e.g. fat JAR via `.assembly` or Spring Boot repackaging); no official plugin but community usage.
**Tradeoffs:**
- You maintain dependency versions (no Spring BOM out of the box; you can mirror Gradle’s versions).
- Less ecosystem than Gradle (fewer “official” plugins); for compile + test + fat JAR it’s enough.
**Commands (conceptually):** `mill compile`, `mill test`, `mill run`, `mill assembly` (fat JAR).
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## 2. saker.build
- **Site:** https://saker.build
- **Status:** Niche / experimental in adoption.
**Why it’s interesting:**
- Claims **~50% faster** than Gradle for clean Java compile, **~60%** for incremental (their benchmarks).
- Uses Java Compiler API + custom handling; different from “Gradle/Maven over javac”.
**Tradeoffs:**
- Smaller community and fewer examples (e.g. Spring Boot).
- Migration and debugging may be harder for a full Spring Boot + MCP stack.
**Verdict:** Only consider if you’re willing to experiment and possibly maintain more custom build logic.
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## 3. mvnd (Maven Daemon)
- **Site:** https://maven.apache.org/tools/mvnd.html
- **Status:** Official Apache Maven tool.
**What it does:**
- Runs **Maven** in a **long-lived daemon** (like Gradle’s daemon).
- **Native client** (e.g. GraalVM) for fast CLI startup.
- Reuses JVM and classloaders across builds → **much faster** than “cold” `mvn` every time.
**Tradeoffs:**
- Still **Maven**: dependency model, lifecycle, and plugin UX unchanged. Gradle is often 2–7x+ faster than Maven for incremental and cached builds.
- Helps “Maven users who want less cold start,” not “Gradle users who want Mill-like speed.”
**Verdict:** Good if you prefer Maven; not the best way to get “fastest possible” startup vs Mill.
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## 4. Bazel / Pants
- **Bazel:** https://bazel.build
- **Pants:** https://pantsbuild.org
**Strengths:**
- Hermetic, cacheable, scalable; great for **very large** repos and polyglot monorepos.
- **Persistent workers** reduce JVM startup cost per action.
**Tradeoffs:**
- **Heavy** setup and concepts (WORKSPACE, BUILD files, toolchains).
- **Cold / first-time** invocations can still be slower than Mill for a single Java app.
- Overkill for a single Jakarta Migration MCP–style service.
**Verdict:** Not recommended for “faster startup for AI vibe coding” on this project.
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## 5. Stay on Gradle, but optimize
If you don’t switch tools yet:
- **Keep daemon on** for repeated runs (`org.gradle.daemon=true`).
- **Use JDK 21** for running Gradle (avoids JDK 25 + Kotlin DSL issues).
- **Configuration cache:** `--configuration-cache` (Gradle 8+) can reduce configuration time.
- **Build cache:** `--build-cache` for reuse across clean builds.
Even then, Mill’s **no-op and incremental** numbers are much lower than Gradle’s, so for “run again as fast as possible” Mill is still the better bet.
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## Recommendation for this repo
- **Try Mill** for faster startup and incremental compile/test cycles with AI.
- Keep **Gradle** in parallel until Mill is proven (e.g. `build.sc` + CI + release JAR and tests passing).
- If you want minimal change and are on Maven already, **mvnd** is an option; for “fastest feedback,” **Mill** is the better alternative to Gradle.
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## References
- Mill vs Gradle (Mockito case study): https://mill-build.org/mill/main-branch/comparisons/gradle.html
- Mill executable JARs: https://mill-build.org/blog/5-executable-jars.html
- saker.build Java compiler performance: https://saker.build/saker.java.compiler/doc/performancecomparison.html
- Gradle vs Maven: https://gradle.org/gradle-and-maven-performance
- mvnd: https://maven.apache.org/tools/mvnd.html
