@@ -84,6 +84,7 @@ jobs:
           - python-uv
           - react
           - rust
+          - scala
           - typescript
           - zig-js
           - zig
 
@@ -40,6 +40,7 @@
 from ._pipeline import pipeline_to_json
 from ._python import python
 from ._rust import RustProject, rust
+from ._scala import ScalaProject, scala
 from ._step import Step, scratch, wait
 from ._target import clear_target_cache, target  # noqa: F401  clear_target_cache used by tests
 from ._toolchain import apt_base
@@ -309,6 +310,7 @@ def group(steps: list[Step] | tuple[Step, ...]) -> tuple[Step, ...]:
     "JsProject",
     "Pipeline",
     "RustProject",
+    "ScalaProject",
     "Step",
     "Target",
     "apt_base",
@@ -329,6 +331,7 @@ def group(steps: list[Step] | tuple[Step, ...]) -> tuple[Step, ...]:
     "py",
     "python",
     "rust",
+    "scala",
     "scratch",
     "sh",
     "target",
 
@@ -0,0 +1,337 @@
+"""Scala toolchain and CI-pipeline DSL.
+
+Public surface is the module-level ``scala`` namespace:
+
+    hm.scala.toolchain(...)  -> ScalaToolchain  (install-only)
+    hm.scala.project(...)    -> ScalaProject    (full CI DAG)
+"""
+
+from __future__ import annotations
+
+import re
+import shlex
+from dataclasses import dataclass
+from typing import TYPE_CHECKING, Any, Self
+
+from ._toolchain import advance_install, make_install_chain
+from .cache import CacheForever, CacheOnChange
+
+if TYPE_CHECKING:
+    from ._step import Step
+    from .cache import CachePolicy
+
+APT_PACKAGES = ("curl", "ca-certificates", "openjdk-17-jdk-headless")
+_VERSION_RE = re.compile(r"^[0-9]+\.[0-9]+\.[0-9]+$")  # e.g. 3.3.8
+_MIN_VERSION = (2, 13, 0)
+
+
+def _parse_version(version: str) -> tuple[int, ...]:
+    return tuple(int(p) for p in version.split("."))
+
+
+def coursier_install_cmd(version: str = "3.3.8") -> str:
+    return (
+        "curl -fL https://github.com/coursier/launchers/raw/master/cs-x86_64-pc-linux.gz "
+        "| gzip -d > cs && "
+        "chmod +x cs && "
+        "./cs setup --yes && "
+        f"./cs install scala:{version} && "
+        "ln -sf /root/.local/share/coursier/bin/* /usr/local/bin/"
+    )
+
+
+def _compile_cmd(*, query: str | None = None, test: bool = False) -> str:
+    scope = ""
+    if query:
+        scope += f"{query} / "
+    if test:
+        scope += "Test / "
+    return f"sbt {scope}compile"
+
+
+# sbt [<query> / ] test [<testname> …] [ -- <options> ]
+def _test_cmd(
+    *,
+    query: str | None = None,
+    testnames: tuple[str, ...] = (),
+    options: dict[str, Any] | None = None,
+) -> str:
+    scope = f"{query} / " if query else ""
+    names = (" " + " ".join(testnames)) if testnames else ""
+    opts = ""
+    if options:
+        rendered = " ".join(f"{key} {shlex.quote(str(value))}" for key, value in options.items())
+        opts = f" -- {rendered}"
+    return f"sbt {scope}test{names}{opts}"
+
+
+def _fmt_cmd(*, check: bool = True) -> str:
+    return "sbt scalafmtCheckAll" if check else "sbt scalafmtAll"
+
+
+@dataclass(frozen=True)
+class ScalaToolchain:
+    """Scala install chain built by ``hm.scala.toolchain()``.
+
+    Holds the coursier install step. Action methods (``compile``, ``test``,
+    ``fmt``, ``warmup``) attach leaves to ``installed`` and forward Step kwargs
+    (``label``, ``cache``, ``env``, ``image`` …) unchanged.
+    """
+
+    path: str
+    installed: Step
+
+    def setup(
+        self,
+        cmd: str,
+        *,
+        cwd: str | None = None,
+        label: str | None = None,
+        cache: CachePolicy | None = None,
+        env: dict[str, str] | None = None,
+    ) -> Self:
+        """Append a post-install command and return an advanced toolchain; chainable.
+
+        Use for prep steps the toolchain's actions must depend on but that the SDK
+        does not model natively — code generation, fixtures, extra tooling. The
+        returned object's action methods fork from this step.
+
+        Examples:
+            >>> import harmont as hm
+            >>> tc = hm.scala.toolchain(path=".").setup("cs install scalafix")
+        """
+        return advance_install(self, cmd, cwd=cwd, label=label, cache=cache, env=env)
+
+    def _wrap(self, sbt_cmd: str) -> str:
+        return (
+            f'export PATH="$PATH:$HOME/.local/share/coursier/bin" && cd {self.path} && {sbt_cmd}'
+        )
+
+    def _emit(self, sbt_cmd: str, default_label: str, **kw: Any) -> Step:
+        if kw.get("label") is None:
+            kw["label"] = default_label
+        return self.installed.sh(self._wrap(sbt_cmd), **kw)
+
+    def compile(self, *, query: str | None = None, test: bool = False, **kw: Any) -> Step:
+        """Compile the project (``sbt compile``); ``test=True`` compiles the test
+        sources (``sbt Test / compile``)."""
+        cmd = _compile_cmd(query=query, test=test)
+        return self._emit(cmd, f":scala: {self.path} compile", **kw)
+
+    def test(
+        self,
+        *,
+        query: str | None = None,
+        testnames: tuple[str, ...] = (),
+        options: dict[str, Any] | None = None,
+        **kw: Any,
+    ) -> Step:
+        """Run the test suite (``sbt test``). ``query`` scopes to a subproject,
+        ``testnames`` selects specific suites, ``options`` pass through after ``--``."""
+        cmd = _test_cmd(query=query, testnames=testnames, options=options)
+        return self._emit(cmd, f":scala: {self.path} test", **kw)
+
+    def fmt(self, *, check: bool = True, **kw: Any) -> Step:
+        """Format Scala sources. ``check=True`` (default) verifies formatting via
+        ``sbt scalafmtCheckAll`` and fails on drift; ``check=False`` rewrites in
+        place via ``sbt scalafmtAll``."""
+        cmd = _fmt_cmd(check=check)
+        return self._emit(cmd, f":scala: {self.path} format", **kw)
+
+    def warmup(self, **kw: Any) -> Step:
+        """Pre-resolve dependencies (``sbt update``) so later steps reuse the cache.
+        Used internally by ``hm.scala.project()``."""
+        return self._emit("sbt update", ":scala: warmup", **kw)
+
+
+@dataclass(frozen=True)
+class ScalaProject:
+    """High-level Scala CI DAG built by ``hm.scala.project()``.
+
+    ``compile`` and ``test`` attach to a shared ``warmup`` step so dependency
+    resolution is reused; ``fmt`` forks off the toolchain install to run in
+    parallel. ``ci()`` returns the standard DAG in one call.
+    """
+
+    path: str
+    toolchain: ScalaToolchain
+    warmup: Step
+
+    def _emit(self, cmd: str, default_label: str, **kw: Any) -> Step:
+        if kw.get("label") is None:
+            kw["label"] = default_label
+        return self.warmup.sh(self.toolchain._wrap(cmd), **kw)  # noqa: SLF001
+
+    def compile(self, *, query: str | None = None, test: bool = False, **kw: Any) -> Step:
+        """Compile the project (``sbt compile``); ``test=True`` compiles the test
+        sources (``sbt Test / compile``)."""
+        cmd = _compile_cmd(query=query, test=test)
+        return self._emit(cmd, f":scala: {self.path} sbt compile", **kw)
+
+    def test(
+        self,
+        *,
+        query: str | None = None,
+        testnames: tuple[str, ...] = (),
+        options: dict[str, Any] | None = None,
+        **kw: Any,
+    ) -> Step:
+        """Run the test suite (``sbt test``). ``query`` scopes to a subproject,
+        ``testnames`` selects specific suites, ``options`` pass through after ``--``."""
+        cmd = _test_cmd(query=query, testnames=testnames, options=options)
+        return self._emit(cmd, f":scala: {self.path} sbt test", **kw)
+
+    def fmt(self, *, check: bool = True, **kw: Any) -> Step:
+        """Format Scala sources (``sbt scalafmtCheckAll`` when ``check=True``,
+        default). Forks off the toolchain install so it runs in parallel with the
+        warmup rather than waiting on dependency resolution."""
+        return self.toolchain.fmt(check=check, **kw)
+
+    def ci(self) -> tuple[Step, ...]:
+        """Zero-config Scala CI DAG: ``compile`` and ``test`` off the shared warmup,
+        ``fmt`` (verify) in parallel off the install.
+
+        Examples:
+            >>> import harmont as hm
+            >>> proj = hm.scala.project()
+            >>> hm.pipeline(list(proj.ci()))
+        """
+        return self.compile(), self.test(), self.fmt()
+
+
+def _make_scala(
+    *,
+    path: str = ".",
+    version: str = "3.3.8",
+    image: str | None = None,
+    base: Step | None = None,
+) -> ScalaToolchain:
+    if not _VERSION_RE.match(version):
+        msg = f"hm.scala: invalid version {version!r}\n -> use a valid X.Y.Z Scala version"
+        raise ValueError(msg)
+
+    if _parse_version(version) < _MIN_VERSION:
+        msg = f"hm.scala: unsupported version {version!r}\n -> use Scala 2.13.0 or newer"
+        raise ValueError(msg)
+
+    installed = make_install_chain(
+        apt_packages=APT_PACKAGES,
+        install_cmd=coursier_install_cmd(version),
+        install_cache=CacheForever(env_keys=()),
+        lang_tag="scala",
+        install_tag="install",
+        image=image,
+        base=base,
+    )
+    return ScalaToolchain(path=path, installed=installed)
+
+
+def _make_scala_project(
+    *,
+    path: str = ".",
+    version: str = "3.3.8",
+    image: str | None = None,
+    base: Step | None = None,
+    cache: CachePolicy | None = None,
+) -> ScalaProject:
+    tc = _make_scala(path=path, version=version, image=image, base=base)
+
+    if not path:
+        path = "."
+
+    prefix = "" if path == "." else f"{path}/"
+    build_file = f"{prefix}build.sbt"
+    properties_file = f"{prefix}project/build.properties"
+    main_glob = f"{prefix}**/src/main/*.scala"
+    test_glob = f"{prefix}**/src/test/*.scala"
+
+    warmup_cache = cache or CacheOnChange(
+        paths=(build_file, main_glob, test_glob, properties_file)
+    )
+
+    warm = tc._emit("sbt update", ":scala: sbt warmup", cache=warmup_cache)  # noqa: SLF001
+    return ScalaProject(path=path, toolchain=tc, warmup=warm)
+
+
+class ScalaEntry:
+    """Namespace for ``hm.scala.toolchain()`` and ``hm.scala.project()``."""
+
+    @staticmethod
+    def toolchain(
+        *,
+        path: str = ".",
+        scala_version: str = "3.3.8",
+        image: str | None = None,
+        base: Step | None = None,
+    ) -> ScalaToolchain:
+        """Install the Scala toolchain via coursier.
+
+        Produces a ``ScalaToolchain`` whose ``installed`` step runs coursier;
+        action methods attach leaves to it. Use ``project()`` instead when you
+        want a shared warmup step across compile/test/fmt.
+
+        Args:
+            path: Path to the workspace root.
+            scala_version: Pinned Scala version, e.g. ``"3.3.8"`` (2.13.0 or newer).
+            image: Local-mode Docker base image override.
+            base: Existing ``Step`` to attach the install to instead of emitting
+                a fresh apt-base step. Use to share one apt-base across toolchains.
+
+        Returns:
+            A ``ScalaToolchain`` ready for action methods.
+
+        Raises:
+            ValueError: If ``scala_version`` is malformed or older than 2.13.0.
+
+        Examples:
+            >>> import harmont as hm
+            >>> tc = hm.scala.toolchain(scala_version="3.3.8")
+            >>> hm.pipeline([tc.compile(), tc.test()])
+        """
+        return _make_scala(path=path, version=scala_version, image=image, base=base)
+
+    @staticmethod
+    def project(
+        *,
+        path: str = ".",
+        scala_version: str = "3.3.8",
+        image: str | None = None,
+        base: Step | None = None,
+        cache: CachePolicy | None = None,
+    ) -> ScalaProject:
+        """Build a high-level Scala CI DAG.
+
+        Installs the toolchain via coursier, warms a dependency cache keyed on
+        ``build.sbt``/``project/build.properties``/``**/*.scala``, and returns a
+        ``ScalaProject`` whose ``compile``/``test``/``fmt`` build on that warmup.
+
+        Args:
+            path: Path to the workspace root.
+            scala_version: Pinned Scala version, e.g. ``"3.3.8"`` (2.13.0 or newer).
+            image: Local-mode Docker base image override.
+            base: Existing ``Step`` to attach the install to instead of emitting
+                a fresh apt-base step.
+            cache: Override the warmup cache policy. Defaults to ``CacheOnChange``
+                keyed on the build files and ``**/*.scala`` sources.
+
+        Returns:
+            A ``ScalaProject`` exposing the common CI steps.
+
+        Raises:
+            ValueError: If ``scala_version`` is malformed or older than 2.13.0.
+
+        Examples:
+            >>> import harmont as hm
+            >>> proj = hm.scala.project()
+            >>> hm.pipeline(list(proj.ci()))
+        """
+        return _make_scala_project(
+            path=path,
+            version=scala_version,
+            image=image,
+            base=base,
+            cache=cache,
+        )
+
+
+scala: ScalaEntry = ScalaEntry()