diff --git a/lib/BUILD b/lib/BUILD
new file mode 100644
index 0000000000..0667358cbc
--- /dev/null
+++ b/lib/BUILD
@@ -0,0 +1,117 @@
+
+load("//buck/shims/jj.bzl", "jj")
+
+[
+    # set an alias for 'lib' which is the default for this package, and jj-lib
+    # which other crates may set dependencies on. defaults to the full build
+    alias(
+        name = name,
+        actual = ':jj-lib-full',
+    ) for name in [ 'lib', 'jj-lib' ]
+]
+
+filegroup(
+    name = 'protos.pb',
+    srcs = glob(['src/protos/*.proto']),
+    visibility = [ '//lib/...' ],
+)
+
+# extra dependencies for the full build of jj-lib
+FULL_DEPS = [
+    'third-party//rust:git2',
+    'third-party//rust:gix',
+    'third-party//rust:watchman_client',
+]
+
+# these deps are shared between all versions
+# of jj-lib. filter out FULL_DEPS from this list
+COMMON_DEPS = filter(lambda x: x not in FULL_DEPS, [
+    # CARGO-SYNC-START: dependencies
+    '//lib/proc-macros:jj-lib-proc-macros',
+    'third-party//rust:async-trait',
+    'third-party//rust:backoff',
+    'third-party//rust:blake2',
+    'third-party//rust:bstr',
+    'third-party//rust:chrono',
+    'third-party//rust:chrono-english',
+    'third-party//rust:config',
+    'third-party//rust:digest',
+    'third-party//rust:either',
+    'third-party//rust:futures',
+    'third-party//rust:git2',
+    'third-party//rust:gix',
+    'third-party//rust:gix-filter',
+    'third-party//rust:glob',
+    'third-party//rust:hex',
+    'third-party//rust:ignore',
+    'third-party//rust:itertools',
+    'third-party//rust:maplit',
+    'third-party//rust:once_cell',
+    'third-party//rust:pest',
+    'third-party//rust:pest_derive',
+    'third-party//rust:pollster',
+    'third-party//rust:prost',
+    'third-party//rust:rand',
+    'third-party//rust:rand_chacha',
+    'third-party//rust:rayon',
+    'third-party//rust:ref-cast',
+    'third-party//rust:regex',
+    'third-party//rust:serde',
+    'third-party//rust:serde_json',
+    'third-party//rust:smallvec',
+    'third-party//rust:strsim',
+    'third-party//rust:tempfile',
+    'third-party//rust:thiserror',
+    'third-party//rust:tokio',
+    'third-party//rust:tracing',
+    'third-party//rust:watchman_client',
+    'third-party//rust:whoami',
+    'third-party//rust:zstd',
+    # CARGO-SYNC-END
+]) + select({
+    "config//os:windows": [
+        # CARGO-SYNC-START: dependencies@cfg(windows)
+        'third-party//rust:winreg',
+        # CARGO-SYNC-END
+    ],
+    "DEFAULT": [
+        # CARGO-SYNC-START: dependencies@cfg(unix)
+        'third-party//rust:rustix',
+        # CARGO-SYNC-END
+    ],
+})
+
+jj.rust_library(
+    name = "jj-lib-full",
+    crate = "jj_lib",
+    srcs = glob([
+        "src/**/*.pest",
+        "src/**/*.rs",
+    ], exclude = [
+        "src/protos/*.rs"
+    ]),
+    mapped_srcs = {
+        "//lib/gen-protos:protos.rs": "src/protos",
+    },
+    features = [
+        "watchman",
+        "git",
+    ],
+    deps = COMMON_DEPS + FULL_DEPS,
+)
+
+jj.rust_library(
+    name = "jj-lib-core",
+    crate = "jj_lib",
+    srcs = glob([
+        "src/**/*.pest",
+        "src/**/*.rs",
+    ], exclude = [
+        "src/protos/*.rs"
+    ]),
+    mapped_srcs = {
+        "//lib/gen-protos:protos.rs": "src/protos",
+    },
+
+    deps = COMMON_DEPS,
+)
diff --git a/lib/PACKAGE b/lib/PACKAGE
new file mode 100644
index 0000000000..9bf0691b15
--- /dev/null
+++ b/lib/PACKAGE
@@ -0,0 +1,5 @@
+
+package(
+    inherit = True,
+    visibility = [ 'PUBLIC' ],
+)
diff --git a/lib/src/fileset_parser.rs b/lib/src/fileset_parser.rs
index 4274f7c9fd..e4a459bf82 100644
--- a/lib/src/fileset_parser.rs
+++ b/lib/src/fileset_parser.rs
@@ -26,6 +26,12 @@ use thiserror::Error;
 
 use crate::dsl_util::{self, InvalidArguments, StringLiteralParser};
 
+#[cfg(buck_build)]
+#[derive(Parser)]
+#[grammar = "lib/src/fileset.pest"]
+struct FilesetParser;
+
+#[cfg(not(buck_build))]
 #[derive(Parser)]
 #[grammar = "fileset.pest"]
 struct FilesetParser;
diff --git a/lib/src/revset_parser.rs b/lib/src/revset_parser.rs
index 234aa0eda3..163c1b32ff 100644
--- a/lib/src/revset_parser.rs
+++ b/lib/src/revset_parser.rs
@@ -32,6 +32,12 @@ use crate::dsl_util::{
     FoldableExpression, InvalidArguments, KeywordArgument, StringLiteralParser,
 };
 
+#[cfg(buck_build)]
+#[derive(Parser)]
+#[grammar = "lib/src/revset.pest"]
+struct RevsetParser;
+
+#[cfg(not(buck_build))]
 #[derive(Parser)]
 #[grammar = "revset.pest"]
 struct RevsetParser;