diff --git a/AGENTS.md b/AGENTS.md
index 1378a13c8a..1222bf94e5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -105,7 +105,8 @@ on `master`. CI runs on every PR in the stack.
 For compiler or standard-library changes, run `make test`. For syntax changes,
 also run `make test-syntax`; use `make test-syntax-roundtrip` when parsing or
 printing changes. Other focused suites are `make test-gentype`,
-`make test-analysis`, `make test-tools`, and `make test-rewatch`.
+`make test-analysis`, `make test-tools`, `make test-rewatch` (OCaml build
+system), and `make test-rewatch-rust` (Rust build system).
 
 ### Testing Requirements
 
diff --git a/Makefile b/Makefile
index 46b3413003..a49799ae4b 100644
--- a/Makefile
+++ b/Makefile
@@ -188,6 +188,9 @@ test-gentype: lib
 test-rewatch: lib
 	./rewatch/tests/suite.sh $(RESCRIPT_EXE)
 
+test-rewatch-rust: lib rewatch
+	./rewatch/tests/suite.sh $(RESCRIPT_RUST_EXE)
+
 test-all: test test-gentype test-analysis test-tools test-rewatch
 
 # Playground
@@ -382,4 +385,4 @@ clean: clean-lib clean-compiler clean-rewatch clean-coverage
 
 .DEFAULT_GOAL := build
 
-.PHONY: yarn-install build rewatch compiler lib artifacts bench test test-analysis test-reanalyze benchmark-reanalyze test-tools test-syntax test-syntax-roundtrip test-gentype test-rewatch test-all playground playground-compiler playground-test playground-cmijs playground-release format checkformat semantic-diff clean-rewatch clean-compiler clean-lib clean-gentype clean-tests clean
+.PHONY: yarn-install build rewatch compiler lib artifacts bench test test-analysis test-reanalyze benchmark-reanalyze test-tools test-syntax test-syntax-roundtrip test-gentype test-rewatch test-rewatch-rust test-all playground playground-compiler playground-test playground-cmijs playground-release format checkformat semantic-diff clean-rewatch clean-compiler clean-lib clean-gentype clean-tests clean
diff --git a/changes/test-rewatch-rust.internal.md b/changes/test-rewatch-rust.internal.md
new file mode 100644
index 0000000000..83f8e6c2c7
--- /dev/null
+++ b/changes/test-rewatch-rust.internal.md
@@ -0,0 +1 @@
+- Add `make test-rewatch-rust`, which runs the build system suite against the Rust implementation, and document that `make test-rewatch` tests the OCaml one.
diff --git a/rewatch/AGENTS.md b/rewatch/AGENTS.md
index d9c16dfaca..9cb7abd59f 100644
--- a/rewatch/AGENTS.md
+++ b/rewatch/AGENTS.md
@@ -72,13 +72,13 @@ cargo fmt --check --manifest-path rewatch/Cargo.toml
 cargo build --manifest-path rewatch/Cargo.toml --release
 
 # Or use the Makefile shortcuts
-make rewatch          # Build rewatch
-make test-rewatch     # Run integration tests
+make rewatch            # Build rewatch
+make test-rewatch-rust  # Build rewatch and run the integration tests against it
 ```
 
 **Note**: The rewatch project is located in the `rewatch/` directory with its own `Cargo.toml` file. All cargo commands should be run from the project root using the `--manifest-path rewatch/Cargo.toml` flag, as shown in the CI workflow.
 
-**Integration Tests**: The `make test-rewatch` command runs bash-based integration tests located in `rewatch/tests/suite.sh`. These tests use the `rewatch/testrepo/` directory as a test workspace with various package configurations to verify rewatch's behavior across different scenarios.
+**Integration Tests**: The `make test-rewatch-rust` command runs bash-based integration tests located in `rewatch/tests/suite.sh` against the Rust binary, `rescript-rust`. `make test-rewatch` runs the same suite against `rescript`, the OCaml implementation in `rewatch-ocaml/`, so it neither rebuilds nor tests this code. These tests use the `rewatch/testrepo/` directory as a test workspace with various package configurations to verify rewatch's behavior across different scenarios.
 
 **Running Individual Integration Tests**: You can run individual test scripts directly by setting up the environment manually:
 
diff --git a/rewatch/README.md b/rewatch/README.md
index 1457fc1d07..e5e19871f2 100644
--- a/rewatch/README.md
+++ b/rewatch/README.md
@@ -37,12 +37,16 @@ Run commands from the repository root:
 
 ```sh
 make rewatch
-make test-rewatch
+make test-rewatch-rust
 cargo test --manifest-path rewatch/Cargo.toml
 cargo clippy --manifest-path rewatch/Cargo.toml --all-targets --all-features
 cargo fmt --check --manifest-path rewatch/Cargo.toml
 ```
 
+`make test-rewatch-rust` builds this implementation and runs the integration
+suite against it; `make test-rewatch` runs the same suite against `rescript`,
+the OCaml implementation.
+
 The integration suite is [`tests/suite.sh`](tests/suite.sh). It creates and
 modifies projects under `testrepo/`; use its helpers for portable path and file
 operations rather than adding platform-specific `sed` commands or fixed