diff --git a/tests/dsv_cli_tests.rs b/tests/dsv_cli_tests.rs
index c9c6ab65c..9f702e2ca 100644
--- a/tests/dsv_cli_tests.rs
+++ b/tests/dsv_cli_tests.rs
@@ -36,11 +36,7 @@ fn succinctly_bin() -> &'static Path {
             String::from_utf8_lossy(&output.stderr)
         );
 
-        let mut path = std::env::current_exe().expect("resolve current_exe");
-        path.pop(); // drop the test executable's file name -> `.../deps`
-        if path.file_name().and_then(|s| s.to_str()) == Some("deps") {
-            path.pop(); // drop `deps` -> `.../<profile>`
-        }
+        let mut path = target_profile_dir_from_test_exe();
         path.push(format!("succinctly{}", std::env::consts::EXE_SUFFIX));
         assert!(
             path.is_file(),
@@ -51,6 +47,24 @@ fn succinctly_bin() -> &'static Path {
     })
 }
 
+/// Derive `<target>/<profile>/` from this test executable's own path.
+///
+/// The classic flat layout places the test exe at
+/// `<target>/<profile>/deps/<test>-<hash>`, but nightly's build-dir-layout-v2
+/// (rust-lang/cargo#17258, defaulted on nightly toolchains from ~2026-07)
+/// instead nests it at `<target>/<profile>/build/<pkg>/<hash>/out/<test>-<hash>`.
+/// Both layouts keep `<profile>` as the path component immediately after
+/// `target`, so locate it that way instead of assuming a fixed depth.
+fn target_profile_dir_from_test_exe() -> PathBuf {
+    let current_exe = std::env::current_exe().expect("resolve current_exe");
+    let components: Vec<_> = current_exe.components().collect();
+    let target_idx = components
+        .iter()
+        .rposition(|c| c.as_os_str() == "target")
+        .expect("test executable path has no `target` component");
+    components[..=target_idx + 1].iter().collect()
+}
+
 /// Run `dsv generate` and capture stdout, stderr, and exit code.
 fn run_generate(size: &str, extra_args: &[&str]) -> Result<(String, String, i32)> {
     let output = Command::new(succinctly_bin())
diff --git a/tests/json_validate_tests.rs b/tests/json_validate_tests.rs
index 6aabab04d..c58dcd474 100644
--- a/tests/json_validate_tests.rs
+++ b/tests/json_validate_tests.rs
@@ -38,13 +38,9 @@ fn succinctly_bin() -> &'static Path {
             String::from_utf8_lossy(&output.stderr)
         );
 
-        // The test executable lives at `<target>/<profile>/deps/<test>-<hash>`;
-        // the CLI binary is its sibling at `<target>/<profile>/succinctly`.
-        let mut path = std::env::current_exe().expect("resolve current_exe");
-        path.pop(); // drop the test executable's file name -> `.../deps`
-        if path.file_name().and_then(|s| s.to_str()) == Some("deps") {
-            path.pop(); // drop `deps` -> `.../<profile>`
-        }
+        // The CLI binary is `<target>/<profile>/succinctly`, a sibling of the
+        // test executable's own `<target>/<profile>/` ancestor.
+        let mut path = target_profile_dir_from_test_exe();
         path.push(format!("succinctly{}", std::env::consts::EXE_SUFFIX));
         assert!(
             path.is_file(),
@@ -55,6 +51,24 @@ fn succinctly_bin() -> &'static Path {
     })
 }
 
+/// Derive `<target>/<profile>/` from this test executable's own path.
+///
+/// The classic flat layout places the test exe at
+/// `<target>/<profile>/deps/<test>-<hash>`, but nightly's build-dir-layout-v2
+/// (rust-lang/cargo#17258, defaulted on nightly toolchains from ~2026-07)
+/// instead nests it at `<target>/<profile>/build/<pkg>/<hash>/out/<test>-<hash>`.
+/// Both layouts keep `<profile>` as the path component immediately after
+/// `target`, so locate it that way instead of assuming a fixed depth.
+fn target_profile_dir_from_test_exe() -> PathBuf {
+    let current_exe = std::env::current_exe().expect("resolve current_exe");
+    let components: Vec<_> = current_exe.components().collect();
+    let target_idx = components
+        .iter()
+        .rposition(|c| c.as_os_str() == "target")
+        .expect("test executable path has no `target` component");
+    components[..=target_idx + 1].iter().collect()
+}
+
 /// Helper to run `json validate` with input from stdin.
 fn run_validate_stdin(input: &str, extra_args: &[&str]) -> Result<(String, String, i32)> {
     let mut cmd = Command::new(succinctly_bin())
diff --git a/tests/text_cli_tests.rs b/tests/text_cli_tests.rs
index 20bd55272..7c3da359e 100644
--- a/tests/text_cli_tests.rs
+++ b/tests/text_cli_tests.rs
@@ -38,11 +38,7 @@ fn succinctly_bin() -> &'static Path {
             String::from_utf8_lossy(&output.stderr)
         );
 
-        let mut path = std::env::current_exe().expect("resolve current_exe");
-        path.pop(); // drop the test executable's file name -> `.../deps`
-        if path.file_name().and_then(|s| s.to_str()) == Some("deps") {
-            path.pop(); // drop `deps` -> `.../<profile>`
-        }
+        let mut path = target_profile_dir_from_test_exe();
         path.push(format!("succinctly{}", std::env::consts::EXE_SUFFIX));
         assert!(
             path.is_file(),
@@ -53,6 +49,24 @@ fn succinctly_bin() -> &'static Path {
     })
 }
 
+/// Derive `<target>/<profile>/` from this test executable's own path.
+///
+/// The classic flat layout places the test exe at
+/// `<target>/<profile>/deps/<test>-<hash>`, but nightly's build-dir-layout-v2
+/// (rust-lang/cargo#17258, defaulted on nightly toolchains from ~2026-07)
+/// instead nests it at `<target>/<profile>/build/<pkg>/<hash>/out/<test>-<hash>`.
+/// Both layouts keep `<profile>` as the path component immediately after
+/// `target`, so locate it that way instead of assuming a fixed depth.
+fn target_profile_dir_from_test_exe() -> PathBuf {
+    let current_exe = std::env::current_exe().expect("resolve current_exe");
+    let components: Vec<_> = current_exe.components().collect();
+    let target_idx = components
+        .iter()
+        .rposition(|c| c.as_os_str() == "target")
+        .expect("test executable path has no `target` component");
+    components[..=target_idx + 1].iter().collect()
+}
+
 /// Run `text validate utf8` with raw bytes piped on stdin.
 fn run_validate_stdin(input: &[u8], extra_args: &[&str]) -> Result<(Vec<u8>, String, i32)> {
     let mut cmd = Command::new(succinctly_bin())
diff --git a/tests/yaml_validate_tests.rs b/tests/yaml_validate_tests.rs
index 52d79c1d4..7cf52f6bb 100644
--- a/tests/yaml_validate_tests.rs
+++ b/tests/yaml_validate_tests.rs
@@ -28,11 +28,7 @@ fn succinctly_bin() -> &'static Path {
             String::from_utf8_lossy(&output.stderr)
         );
 
-        let mut path = std::env::current_exe().expect("resolve current_exe");
-        path.pop();
-        if path.file_name().and_then(|s| s.to_str()) == Some("deps") {
-            path.pop();
-        }
+        let mut path = target_profile_dir_from_test_exe();
         path.push(format!("succinctly{}", std::env::consts::EXE_SUFFIX));
         assert!(
             path.is_file(),
@@ -43,6 +39,24 @@ fn succinctly_bin() -> &'static Path {
     })
 }
 
+/// Derive `<target>/<profile>/` from this test executable's own path.
+///
+/// The classic flat layout places the test exe at
+/// `<target>/<profile>/deps/<test>-<hash>`, but nightly's build-dir-layout-v2
+/// (rust-lang/cargo#17258, defaulted on nightly toolchains from ~2026-07)
+/// instead nests it at `<target>/<profile>/build/<pkg>/<hash>/out/<test>-<hash>`.
+/// Both layouts keep `<profile>` as the path component immediately after
+/// `target`, so locate it that way instead of assuming a fixed depth.
+fn target_profile_dir_from_test_exe() -> PathBuf {
+    let current_exe = std::env::current_exe().expect("resolve current_exe");
+    let components: Vec<_> = current_exe.components().collect();
+    let target_idx = components
+        .iter()
+        .rposition(|c| c.as_os_str() == "target")
+        .expect("test executable path has no `target` component");
+    components[..=target_idx + 1].iter().collect()
+}
+
 fn run_validate_stdin(input: &str, extra_args: &[&str]) -> Result<(String, String, i32)> {
     let mut cmd = Command::new(succinctly_bin())
         .args(["yaml", "validate"])