diff --git a/src/ephapax-cli/Cargo.toml b/src/ephapax-cli/Cargo.toml
index 0ea87ac..141f1dc 100644
--- a/src/ephapax-cli/Cargo.toml
+++ b/src/ephapax-cli/Cargo.toml
@@ -36,4 +36,5 @@ serde_json.workspace = true
 [dev-dependencies]
 wasmtime.workspace = true
 proptest = { workspace = true }
+wasmparser = "0.221"
 tempfile = "3"
diff --git a/src/ephapax-cli/src/main.rs b/src/ephapax-cli/src/main.rs
index fa4c1e6..b4a12eb 100644
--- a/src/ephapax-cli/src/main.rs
+++ b/src/ephapax-cli/src/main.rs
@@ -73,7 +73,14 @@ enum Commands {
         mode: String,
     },
 
-    /// Compile to WebAssembly
+    /// Compile to WebAssembly.
+    ///
+    /// Aliased as `compile-eph` and `compile-affine` for downstream
+    /// consumers (notably hypatia's `build-gossamer-gui` workflow, which
+    /// probes for these names in order). All three names route to the same
+    /// surface-parse → desugar → typecheck → wasm pipeline.
+    /// Closes hyperpolymath/ephapax#36.
+    #[command(alias = "compile-eph", alias = "compile-affine")]
     Compile {
         /// Input file
         file: PathBuf,
diff --git a/src/ephapax-cli/tests/v2_grammar_phase_d_aliases.rs b/src/ephapax-cli/tests/v2_grammar_phase_d_aliases.rs
new file mode 100644
index 0000000..46513a2
--- /dev/null
+++ b/src/ephapax-cli/tests/v2_grammar_phase_d_aliases.rs
@@ -0,0 +1,61 @@
+// SPDX-License-Identifier: PMPL-1.0-or-later
+//
+// Phase D: clap aliases for the `compile` subcommand. Closes #36.
+// Asserts that invoking the CLI as `compile-eph` and `compile-affine`
+// both route to the same `Compile` subcommand. Probed by hypatia's
+// `build-gossamer-gui.yml` workflow (see #36 for the probe order).
+
+use std::process::Command;
+
+fn ephapax_bin() -> String {
+    // CARGO_BIN_EXE_ephapax is set by cargo for integration tests.
+    env!("CARGO_BIN_EXE_ephapax").to_string()
+}
+
+fn fixture(name: &str) -> String {
+    format!(
+        "{}/../../tests/v2-grammar/fixtures/{}",
+        env!("CARGO_MANIFEST_DIR"),
+        name
+    )
+}
+
+#[test]
+fn compile_eph_alias_routes_to_compile() {
+    let out = tempfile::NamedTempFile::new().expect("temp file");
+    let status = Command::new(ephapax_bin())
+        .arg("compile-eph")
+        .arg(fixture("extern-callsite.eph"))
+        .arg("-o")
+        .arg(out.path())
+        .output()
+        .expect("ephapax compile-eph must run");
+    assert!(
+        status.status.success(),
+        "compile-eph alias failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&status.stdout),
+        String::from_utf8_lossy(&status.stderr)
+    );
+    let bytes = std::fs::read(out.path()).expect("output wasm exists");
+    assert!(bytes.starts_with(b"\0asm"), "wasm magic bytes present");
+}
+
+#[test]
+fn compile_affine_alias_routes_to_compile() {
+    let out = tempfile::NamedTempFile::new().expect("temp file");
+    let status = Command::new(ephapax_bin())
+        .arg("compile-affine")
+        .arg(fixture("extern-callsite.eph"))
+        .arg("-o")
+        .arg(out.path())
+        .output()
+        .expect("ephapax compile-affine must run");
+    assert!(
+        status.status.success(),
+        "compile-affine alias failed: stdout={} stderr={}",
+        String::from_utf8_lossy(&status.stdout),
+        String::from_utf8_lossy(&status.stderr)
+    );
+    let bytes = std::fs::read(out.path()).expect("output wasm exists");
+    assert!(bytes.starts_with(b"\0asm"), "wasm magic bytes present");
+}
diff --git a/tests/v2-grammar/fixtures/extern-callsite.eph b/tests/v2-grammar/fixtures/extern-callsite.eph
new file mode 100644
index 0000000..b1bf26f
--- /dev/null
+++ b/tests/v2-grammar/fixtures/extern-callsite.eph
@@ -0,0 +1,17 @@
+// SPDX-License-Identifier: PMPL-1.0-or-later
+// Extern fn callsite — proves Phase B of #43: the extern signature is
+// in scope from the function body. `entry()` returns the result of an
+// `extern "wasm"`-declared identity function on a literal.
+//
+// The `type` extern item is currently dropped by desugar (Phase B+ will
+// register it as an abstract type). The `fn` extern item desugars to
+// `Decl::Extern`, gets registered in the typechecker env by the
+// pre-pass, and the call resolves cleanly.
+
+module hyperpolymath/ephapax/test
+
+extern "wasm" {
+  fn host_identity(x: I32): I32
+}
+
+fn entry(): I32 = host_identity(7)