diff --git a/src/uu/chmod/src/chmod.rs b/src/uu/chmod/src/chmod.rs
index e5c1f997989..f5867b9c3d3 100644
--- a/src/uu/chmod/src/chmod.rs
+++ b/src/uu/chmod/src/chmod.rs
@@ -319,51 +319,27 @@ impl Chmoder {
         if let Some(mode) = self.fmode {
             Ok((mode, mode))
         } else {
-            let cmode_unwrapped = self.cmode.clone().unwrap();
-            let mut new_mode = current_mode;
-            let mut naively_expected_new_mode = current_mode;
-
-            // Where the clause being parsed starts inside `cmode_unwrapped`, so
-            // that an error can be pointed back at it.
-            let mut offset = 0;
-            for mode in cmode_unwrapped.split(',') {
-                let clause_start = offset;
-                offset += mode.len() + 1; // past the clause and its comma
-
-                let result = if mode.chars().any(|c| c.is_ascii_digit()) {
-                    mode::parse_numeric(new_mode, mode, is_dir).map(|v| (v, v))
-                } else {
-                    mode::parse_symbolic(new_mode, mode, mode::get_umask(), is_dir).map(|m| {
-                        // calculate the new mode as if umask was 0
-                        let naive_mode =
-                            mode::parse_symbolic(naively_expected_new_mode, mode, 0, is_dir)
-                                .unwrap(); // we know that mode must be valid, so this cannot fail
-                        (m, naive_mode)
-                    })
-                };
-
-                match result {
-                    Ok((mode, naive_mode)) => {
-                        new_mode = mode;
-                        naively_expected_new_mode = naive_mode;
+            let cmode = self.cmode.clone().unwrap();
+            // GNU's mode grammar lives in uucore::mode: a bare octal is the
+            // whole string, and a clause list must be all-symbolic and
+            // non-empty. The naive mode is what the clauses would yield with
+            // umask 0, kept here so the umask diagnostic below can compare.
+            mode::parse_chmod_with_naive(current_mode, &cmode, is_dir, mode::get_umask()).map_err(
+                |error| {
+                    if self.quiet {
+                        return ExitCode::new(1);
                     }
-                    Err(error) => {
-                        if self.quiet {
-                            return Err(ExitCode::new(1));
-                        }
-                        if let Some(args) = &self.args
-                            && let Some((index, operand, offset)) =
-                                self.locate_clause(args, &cmode_unwrapped, clause_start)
-                            && error.render_at(args, index, &operand, offset, &error.to_string())
-                        {
-                            // The diagnostic is already on stderr; exit quietly.
-                            return Err(ExitCode::new(1));
-                        }
-                        return Err(USimpleError::new(1, error.to_string()));
+                    if let Some(args) = &self.args
+                        && let Some((index, operand, offset)) =
+                            self.locate_clause(args, &cmode, error.clause_start)
+                        && error.render_at(args, index, &operand, offset, &error.to_string())
+                    {
+                        // The diagnostic is already on stderr; exit quietly.
+                        return ExitCode::new(1);
                     }
-                }
-            }
-            Ok((new_mode, naively_expected_new_mode))
+                    USimpleError::new(1, error.to_string())
+                },
+            )
         }
     }
 
diff --git a/src/uu/install/src/install.rs b/src/uu/install/src/install.rs
index 615791c5a0a..9ed82efcd50 100644
--- a/src/uu/install/src/install.rs
+++ b/src/uu/install/src/install.rs
@@ -376,7 +376,9 @@ fn behavior(matches: &ArgMatches, diag_args: Option<&[OsString]>) -> UResult<Beh
         Some(uucore::mode::parse(x, considering_dir, 0).map_err(|err| {
             let message = translate!("install-error-invalid-mode", "error" => err.to_string());
             // When the diagnostic is rendered it is already on stderr; exit quietly.
-            if !diag_args.is_some_and(|args| err.render_mode_value(args, x, 0, &message)) {
+            if !diag_args
+                .is_some_and(|args| err.render_mode_value(args, x, err.clause_start, &message))
+            {
                 show_error!("{message}");
             }
             1
diff --git a/src/uu/mkdir/src/mkdir.rs b/src/uu/mkdir/src/mkdir.rs
index 0cb71395ae0..717f7ac3a4b 100644
--- a/src/uu/mkdir/src/mkdir.rs
+++ b/src/uu/mkdir/src/mkdir.rs
@@ -70,7 +70,9 @@ fn get_mode(matches: &ArgMatches, diag_args: Option<&[OsString]>) -> UResult<Opt
     mode::parse_chmod(DEFAULT_PERM, m, true, mode::get_umask())
         .map(Some)
         .map_err(|err| {
-            if diag_args.is_some_and(|args| err.render_mode_value(args, m, 0, &err.to_string())) {
+            if diag_args.is_some_and(|args| {
+                err.render_mode_value(args, m, err.clause_start, &err.to_string())
+            }) {
                 // The diagnostic is already on stderr; exit quietly.
                 ExitCode::new(1)
             } else {
diff --git a/src/uu/mknod/src/mknod.rs b/src/uu/mknod/src/mknod.rs
index 2a91f98ba0d..132c915f7db 100644
--- a/src/uu/mknod/src/mknod.rs
+++ b/src/uu/mknod/src/mknod.rs
@@ -158,7 +158,7 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
                     let message =
                         translate!("mknod-error-invalid-mode", "error" => err.to_string());
                     if let Some(args) = &diag_args
-                        && err.render_mode_value(args, str_mode, 0, &message)
+                        && err.render_mode_value(args, str_mode, err.clause_start, &message)
                     {
                         // The diagnostic is already on stderr; exit quietly.
                         return ExitCode::new(1);
diff --git a/src/uucore/src/lib/features/mode.rs b/src/uucore/src/lib/features/mode.rs
index 8dfeccb4c94..9cc9a1cf8b8 100644
--- a/src/uucore/src/lib/features/mode.rs
+++ b/src/uucore/src/lib/features/mode.rs
@@ -17,14 +17,18 @@ use crate::translate;
 
 /// A mode string that does not parse, and the part of it that is at fault.
 ///
-/// `span` is a byte range inside the mode string that was handed to the parser,
-/// so that a caller can point a caret at the one clause — often the one
-/// character — that broke it.
+/// `span` is a byte range inside the clause that broke the parse, so that a
+/// caller can point a caret at the offending characters. `clause_start` is
+/// where that clause begins inside the whole mode string, which the parser
+/// knows but a caller may not; together they let the caret find its spot.
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ModeError {
     pub message: String,
     pub span: Range<usize>,
     pub kind: ModeErrorKind,
+    /// Offset of the clause that failed inside the mode string handed to the
+    /// parser. Zero for a bare mode, which is its own single clause.
+    pub clause_start: usize,
 }
 
 /// What went wrong, for callers that want to say more than the message does.
@@ -36,6 +40,11 @@ pub enum ModeErrorKind {
     MissingOperator,
     /// A numeric mode that is not octal, or is out of range.
     InvalidNumber,
+    /// A digit-bearing clause inside a symbolic list, where GNU only accepts
+    /// a bare octal as the whole mode string.
+    NumericClauseInList,
+    /// An empty clause in a comma-separated list.
+    EmptyClause,
 }
 
 impl ModeError {
@@ -44,6 +53,7 @@ impl ModeError {
             message,
             span,
             kind,
+            clause_start: 0,
         }
     }
 
@@ -135,8 +145,11 @@ impl ModeError {
     /// convention in [`crate::diagnostics`].
     fn describe(&self) -> (Option<String>, Option<String>) {
         let label = match self.kind {
-            // The message already names the expected operators.
-            ModeErrorKind::InvalidOperator => None,
+            // The message already says what the clause is and how the grammar
+            // treats it; a label would only repeat it.
+            ModeErrorKind::InvalidOperator
+            | ModeErrorKind::NumericClauseInList
+            | ModeErrorKind::EmptyClause => None,
             ModeErrorKind::MissingOperator => Some("mode-diag-label-missing-operator"),
             ModeErrorKind::InvalidNumber => Some("mode-diag-label-invalid-number"),
         };
@@ -317,17 +330,25 @@ fn parse_change(mode: &str, fperm: u32, considering_dir: bool) -> (u32, usize) {
     (srwx, pos)
 }
 
-/// Modify a file mode based on a user-supplied string.
-/// Supports comma-separated mode strings like "ug+rwX,o+rX" (same as chmod).
-pub fn parse_chmod(
+/// Apply a mode string to `current_mode`, returning both the result and the
+/// mode the same clauses would have produced with umask 0 — what the user
+/// asked for before the umask curtailed it, which drives chmod's diagnostic.
+fn parse_chmod_inner(
     current_mode: u32,
     mode_string: &str,
     considering_dir: bool,
     umask: u32,
-) -> Result<u32, ModeError> {
-    let mut new_mode: u32 = current_mode;
+) -> Result<(u32, u32), ModeError> {
+    // A digit makes GNU read the whole string as one bare numeric mode, which
+    // is only valid without commas; everything else is a list of symbolic
+    // clauses, and no clause in such a list may be numeric or empty.
+    if !mode_string.contains(',') && mode_string.chars().any(|c| c.is_ascii_digit()) {
+        let mode = parse_numeric(current_mode, mode_string, considering_dir)?;
+        return Ok((mode, mode));
+    }
 
-    // Split by commas and process each mode part sequentially
+    let mut new_mode = current_mode;
+    let mut naive_mode = current_mode;
     let mut offset = 0;
     for raw_part in mode_string.split(',') {
         let start = offset + (raw_part.len() - raw_part.trim_start().len());
@@ -336,18 +357,65 @@ pub fn parse_chmod(
 
         let mode_part = raw_part.trim();
         if mode_part.is_empty() {
-            continue;
+            return Err(ModeError {
+                clause_start: start,
+                ..ModeError::new(
+                    format!("invalid mode ({raw_part})"),
+                    0..0,
+                    ModeErrorKind::EmptyClause,
+                )
+            });
         }
-
-        new_mode = if mode_part.chars().any(|c| c.is_ascii_digit()) {
-            parse_numeric(new_mode, mode_part, considering_dir)
-        } else {
-            parse_symbolic(new_mode, mode_part, umask, considering_dir)
+        if mode_part.chars().any(|c| c.is_ascii_digit()) {
+            return Err(ModeError {
+                clause_start: start,
+                ..ModeError::new(
+                    format!("invalid mode ({mode_part})"),
+                    0..mode_part.len(),
+                    ModeErrorKind::NumericClauseInList,
+                )
+            });
         }
-        .map_err(|err| err.shift(start))?;
+
+        new_mode = parse_symbolic(new_mode, mode_part, umask, considering_dir).map_err(|err| {
+            ModeError {
+                clause_start: start,
+                ..err
+            }
+        })?;
+        // The umask only masks bits, so the same clause parses with umask 0:
+        // it yields the mode the user asked for, before the umask curtailed it.
+        naive_mode = parse_symbolic(naive_mode, mode_part, 0, considering_dir)
+            .expect("the clause parsed above with the caller's umask");
     }
+    Ok((new_mode, naive_mode))
+}
+
+/// Modify a file mode based on a user-supplied string.
+///
+/// GNU accepts either a bare numeric (octal) mode, optionally with a leading
+/// `+`, `-` or `=`, or a comma-separated list of symbolic clauses such as
+/// "ug+rwX,o+rX". A numeric mode can only be the whole string: a list whose
+/// clause contains a digit, or that has an empty clause, is rejected.
+pub fn parse_chmod(
+    current_mode: u32,
+    mode_string: &str,
+    considering_dir: bool,
+    umask: u32,
+) -> Result<u32, ModeError> {
+    parse_chmod_inner(current_mode, mode_string, considering_dir, umask).map(|(mode, _)| mode)
+}
 
-    Ok(new_mode)
+/// Like [`parse_chmod`], but also returns the mode the symbolic clauses would
+/// have produced with umask 0, which callers such as chmod need to report a
+/// mode curtailed by the umask.
+pub fn parse_chmod_with_naive(
+    current_mode: u32,
+    mode_string: &str,
+    considering_dir: bool,
+    umask: u32,
+) -> Result<(u32, u32), ModeError> {
+    parse_chmod_inner(current_mode, mode_string, considering_dir, umask)
 }
 
 /// Takes a user-supplied string and tries to parse to u32 mode bitmask.
@@ -425,8 +493,6 @@ mod tests {
 
         // Numeric mode with - operator (starting from 0, so nothing to remove)
         assert_eq!(parse("-4", false, 0).unwrap(), 0);
-        // But if we first set a mode, then remove bits
-        assert_eq!(parse("644,-4", false, 0).unwrap(), 0o640);
     }
 
     #[test]
@@ -462,18 +528,26 @@ mod tests {
     }
 
     #[test]
-    fn test_parse_mixed_numeric_and_symbolic() {
-        // Mix of numeric and symbolic modes
-        assert_eq!(parse("644,u+x", false, 0).unwrap(), 0o744);
-        assert_eq!(parse("u+rw,755", false, 0).unwrap(), 0o755);
+    fn test_parse_rejects_numeric_clause_in_list() {
+        // GNU only accepts a bare octal as the whole mode; a comma-separated
+        // list must consist entirely of symbolic clauses.
+        assert!(parse("644,u+x", false, 0).is_err());
+        assert!(parse("u+x,644", false, 0).is_err());
+        assert!(parse("a-w,644", false, 0).is_err());
+        assert!(parse("644,644", false, 0).is_err());
+        assert!(parse("g+s,755", false, 0).is_err());
+        assert!(parse("755,g+s", false, 0).is_err());
     }
 
     #[test]
-    fn test_parse_empty_string() {
-        // Empty string should return 0
-        assert_eq!(parse("", false, 0).unwrap(), 0);
-        assert_eq!(parse("   ", false, 0).unwrap(), 0);
-        assert_eq!(parse(",,", false, 0).unwrap(), 0);
+    fn test_parse_rejects_empty_clauses() {
+        // GNU rejects an empty mode and any list with an empty clause in it.
+        assert!(parse("", false, 0).is_err());
+        assert!(parse("   ", false, 0).is_err());
+        assert!(parse(",,", false, 0).is_err());
+        assert!(parse("644,", false, 0).is_err());
+        assert!(parse(",644", false, 0).is_err());
+        assert!(parse("u+x,,g+x", false, 0).is_err());
     }
 
     #[test]
@@ -512,18 +586,19 @@ mod tests {
     fn test_parse_complex_combinations() {
         // Complex real-world examples
         assert_eq!(parse("u=rwx,g=rx,o=r", false, 0).unwrap(), 0o754);
-        // To test removal, we need to first set permissions, then remove them
-        assert_eq!(parse("644,a-w", false, 0).unwrap(), 0o444);
-        assert_eq!(parse("644,g-r", false, 0).unwrap(), 0o604);
+        // Symbolic clauses apply in order, so a later one can remove bits
+        // that an earlier one added.
+        assert_eq!(parse("a=rw,u-w", false, 0).unwrap(), 0o466);
+        assert_eq!(parse("a=rw,g-r", false, 0).unwrap(), 0o626);
     }
 
     #[test]
     fn test_parse_sequential_application() {
-        // Test that comma-separated modes are applied sequentially
-        // First set to 644, then add execute for user
-        assert_eq!(parse("644,u+x", false, 0).unwrap(), 0o744);
+        // Test that comma-separated symbolic clauses are applied sequentially
+        // (a numeric clause in a list is rejected, so relative effects chain).
+        assert_eq!(parse("u+w,g+r", false, 0).unwrap(), 0o240);
 
-        // First add user write, then set to 755 (should override)
-        assert_eq!(parse("u+w,755", false, 0).unwrap(), 0o755);
+        // A later clause overrides the bits an earlier one set
+        assert_eq!(parse("u=rw,u+x", false, 0).unwrap(), 0o700);
     }
 }
diff --git a/tests/by-util/test_chmod.rs b/tests/by-util/test_chmod.rs
index a9ab8403769..0f4abb06db9 100644
--- a/tests/by-util/test_chmod.rs
+++ b/tests/by-util/test_chmod.rs
@@ -913,6 +913,28 @@ fn test_gnu_invalid_mode() {
     scene.ucmd().arg("u+gr").arg("file").fails();
 }
 
+#[test]
+fn test_gnu_rejects_octal_clause_in_list() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.touch("file");
+    for mode in [
+        "644,u+x", "u+x,644", "a-w,644", "644,644", "g+s,755", "755,g+s",
+    ] {
+        scene.ucmd().arg(mode).arg("file").fails();
+    }
+}
+
+#[test]
+fn test_gnu_rejects_empty_mode() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.touch("file");
+    for mode in ["", " ", ",", "644,", ",644", "u+x,,g+x"] {
+        scene.ucmd().arg(mode).arg("file").fails();
+    }
+}
+
 #[test]
 #[cfg(not(target_os = "android"))]
 fn test_gnu_options() {
@@ -1757,6 +1779,23 @@ mod diagnostics {
         assert_eq!(result.caret_column(), Some(7), "{stderr}");
     }
 
+    #[cfg(unix)]
+    #[test]
+    fn test_snippet_points_into_a_numeric_clause_in_a_list() {
+        let (at, mut ucmd) = at_and_ucmd!();
+        at.touch("probe");
+
+        let result = ucmd
+            .terminal_sim_stderr()
+            .args(&["u+x,644", "probe"])
+            .fails_with_code(1);
+        let stderr = result.stderr_str();
+
+        assert!(stderr.contains("invalid mode"), "{stderr}");
+        // The caret lands on the octal clause: `6` is its fifth character.
+        assert_eq!(result.caret_column(), Some(5), "{stderr}");
+    }
+
     #[cfg(unix)]
     #[test]
     fn test_snippet_marks_a_clause_with_no_operator() {
diff --git a/tests/by-util/test_install.rs b/tests/by-util/test_install.rs
index da638746b56..0c6d6569658 100644
--- a/tests/by-util/test_install.rs
+++ b/tests/by-util/test_install.rs
@@ -304,6 +304,50 @@ fn test_install_mode_comma_separated_directory() {
     assert_eq!(0o040_775_u32, PermissionsExt::mode(&permissions));
 }
 
+#[test]
+fn test_install_mode_rejects_octal_clause_in_list() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.touch("source_file");
+    at.mkdir("target_dir");
+    for mode in [
+        "--mode=644,u+x",
+        "--mode=u+x,644",
+        "--mode=a-w,644",
+        "--mode=644,644",
+        "--mode=g+s,755",
+        "--mode=755,g+s",
+    ] {
+        scene
+            .ucmd()
+            .args(&["source_file", "target_dir"])
+            .arg(mode)
+            .fails();
+    }
+}
+
+#[test]
+fn test_install_mode_rejects_empty_mode() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.touch("source_file");
+    at.mkdir("target_dir");
+    for mode in [
+        "--mode=",
+        "--mode=  ",
+        "--mode=,,",
+        "--mode=644,",
+        "--mode=,644",
+        "--mode=u+x,,g+x",
+    ] {
+        scene
+            .ucmd()
+            .args(&["source_file", "target_dir"])
+            .arg(mode)
+            .fails();
+    }
+}
+
 #[test]
 fn test_install_mode_symbolic_ignore_umask() {
     let (at, mut ucmd) = at_and_ucmd!();
diff --git a/tests/by-util/test_mkdir.rs b/tests/by-util/test_mkdir.rs
index c0601a850d8..90e7db73338 100644
--- a/tests/by-util/test_mkdir.rs
+++ b/tests/by-util/test_mkdir.rs
@@ -1083,6 +1083,24 @@ fn test_mkdir_inside_inexistent_dir() {
 }
 
 // The mode is only parsed where a mode means something.
+#[cfg(unix)]
+#[test]
+fn test_mkdir_rejects_octal_clause_in_list() {
+    for mode in [
+        "644,u+x", "u+x,644", "a-w,644", "644,644", "g+s,755", "755,g+s",
+    ] {
+        new_ucmd!().args(&["-m", mode, "some_dir"]).fails();
+    }
+}
+
+#[cfg(unix)]
+#[test]
+fn test_mkdir_rejects_empty_mode() {
+    for mode in ["", " ", ",", "644,", ",644", "u+x,,g+x"] {
+        new_ucmd!().args(&["-m", mode, "some_dir"]).fails();
+    }
+}
+
 #[cfg(unix)]
 #[cfg(all(feature = "feat_diagnostics", not(wasi_runner)))]
 mod diagnostics {
diff --git a/tests/by-util/test_mkfifo.rs b/tests/by-util/test_mkfifo.rs
index 13d43f5a59a..3cb91a1f855 100644
--- a/tests/by-util/test_mkfifo.rs
+++ b/tests/by-util/test_mkfifo.rs
@@ -43,6 +43,21 @@ fn test_create_one_fifo_with_invalid_mode() {
         .stderr_contains("invalid mode");
 }
 
+#[test]
+fn test_create_one_fifo_rejects_octal_clause_in_list_and_empty_modes() {
+    for mode in [
+        "644,u+x", "u+x,644", "a-w,644", "644,644", "g+s,755", "755,g+s", "u+x,,g+x", "644,",
+        ",644",
+    ] {
+        new_ucmd!()
+            .arg("abcd")
+            .arg("-m")
+            .arg(mode)
+            .fails()
+            .stderr_contains("invalid mode");
+    }
+}
+
 #[test]
 fn test_create_one_fifo_with_non_file_permission_mode() {
     new_ucmd!()
diff --git a/tests/by-util/test_mknod.rs b/tests/by-util/test_mknod.rs
index 49fdbc243f9..3ac2ec4f204 100644
--- a/tests/by-util/test_mknod.rs
+++ b/tests/by-util/test_mknod.rs
@@ -138,6 +138,23 @@ fn test_mknod_invalid_mode() {
         .stderr_contains("invalid mode");
 }
 
+#[test]
+fn test_mknod_rejects_octal_clause_in_list_and_empty_modes() {
+    for mode in [
+        "644,u+x", "u+x,644", "a-w,644", "644,644", "g+s,755", "755,g+s", "u+x,,g+x", "644,",
+        ",644",
+    ] {
+        new_ucmd!()
+            .arg("--mode")
+            .arg(mode)
+            .arg("test_file")
+            .arg("p")
+            .fails()
+            .code_is(1)
+            .stderr_contains("invalid mode");
+    }
+}
+
 #[test]
 fn test_mknod_mode_permissions() {
     for test_mode in [0o0666, 0o0000, 0o0444, 0o0004, 0o0040, 0o0400, 0o0644] {