diff --git a/src/uu/chmod/src/chmod.rs b/src/uu/chmod/src/chmod.rs
index c98e4af89e5..4e6b62cb7fb 100644
--- a/src/uu/chmod/src/chmod.rs
+++ b/src/uu/chmod/src/chmod.rs
@@ -326,6 +326,16 @@ impl Chmoder {
             let mut new_mode = current_mode;
             let mut naively_expected_new_mode = current_mode;
 
+            if let Err(error) = mode::check_clauses(&cmode_unwrapped) {
+                // Report it like a clause error, from where the fault starts
+                let clause_start = error.span.start;
+                let error = mode::ModeError {
+                    span: 0..error.span.len(),
+                    ..error
+                };
+                return Err(self.mode_error(&cmode_unwrapped, clause_start, &error));
+            }
+
             // Where the clause being parsed starts inside `cmode_unwrapped`, so
             // that an error can be pointed back at it.
             let mut offset = 0;
@@ -351,18 +361,7 @@ impl Chmoder {
                         naively_expected_new_mode = naive_mode;
                     }
                     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()));
+                        return Err(self.mode_error(&cmode_unwrapped, clause_start, &error));
                     }
                 }
             }
@@ -370,6 +369,27 @@ impl Chmoder {
         }
     }
 
+    /// The error to return for `error`, found in the clause that starts at
+    /// `clause_start` inside `cmode`. Its span is relative to that clause.
+    fn mode_error(
+        &self,
+        cmode: &str,
+        clause_start: usize,
+        error: &mode::ModeError,
+    ) -> Box<dyn UError> {
+        if self.quiet {
+            return ExitCode::new(1);
+        }
+        if let Some(args) = &self.args
+            && let Some((index, operand, offset)) = self.locate_clause(args, cmode, clause_start)
+            && error.render_at(args, index, &operand, offset, &error.to_string())
+        {
+            // The diagnostic is already on stderr; exit quietly.
+            return ExitCode::new(1);
+        }
+        USimpleError::new(1, error.to_string())
+    }
+
     /// Map `clause_start` — an offset into `cmode`, the joined mode string —
     /// back to the argument the failing clause came from.
     ///
diff --git a/src/uucore/src/lib/features/mode.rs b/src/uucore/src/lib/features/mode.rs
index b6ce07aa9d5..498ec32c6cf 100644
--- a/src/uucore/src/lib/features/mode.rs
+++ b/src/uucore/src/lib/features/mode.rs
@@ -38,6 +38,10 @@ pub enum ModeErrorKind {
     MissingOperator,
     /// A numeric mode that is not octal, or is out of range.
     InvalidNumber,
+    /// Nothing between two commas, or at either end of the mode.
+    EmptyClause,
+    /// An octal mode without an operator, next to other clauses.
+    OctalInList,
 }
 
 impl ModeError {
@@ -177,8 +181,10 @@ 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 is wrong.
+            ModeErrorKind::InvalidOperator
+            | ModeErrorKind::EmptyClause
+            | ModeErrorKind::OctalInList => None,
             ModeErrorKind::MissingOperator => Some("mode-diag-label-missing-operator"),
             ModeErrorKind::InvalidNumber => Some("mode-diag-label-invalid-number"),
         };
@@ -359,6 +365,44 @@ fn parse_change(mode: &str, fperm: u32, considering_dir: bool) -> (u32, usize) {
     (srwx, pos)
 }
 
+/// The comma-separated clauses of `mode`, trimmed, each with where it starts
+/// inside `mode`.
+fn clauses(mode: &str) -> impl Iterator<Item = (usize, &str)> {
+    let mut offset = 0;
+    mode.split(',').map(move |raw| {
+        let start = offset + (raw.len() - raw.trim_start().len());
+        // Past the clause and the comma that followed it.
+        offset += raw.len() + 1;
+        (start, raw.trim())
+    })
+}
+
+/// Check how the comma-separated clauses of `mode` fit together: `+644,u+x`
+/// is valid, `u+x,` and `644,u+x` are not. The error's span is inside `mode`.
+///
+/// Empty clauses are looked for first, so `644,` points at the missing
+/// clause rather than at `644`. A blank clause counts as empty.
+pub fn check_clauses(mode: &str) -> Result<(), ModeError> {
+    if let Some((start, _)) = clauses(mode).find(|(_, clause)| clause.is_empty()) {
+        return Err(ModeError::new(
+            format!("invalid mode ({mode})"),
+            start..start,
+            ModeErrorKind::EmptyClause,
+        ));
+    }
+    if mode.contains(',')
+        && let Some((start, clause)) =
+            clauses(mode).find(|(_, clause)| clause.starts_with(|c: char| c.is_ascii_digit()))
+    {
+        return Err(ModeError::new(
+            format!("invalid mode ({mode})"),
+            start..start + clause.len(),
+            ModeErrorKind::OctalInList,
+        ));
+    }
+    Ok(())
+}
+
 /// 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(
@@ -367,20 +411,11 @@ pub fn parse_chmod(
     considering_dir: bool,
     umask: u32,
 ) -> Result<u32, ModeError> {
+    check_clauses(mode_string)?;
     let mut new_mode: u32 = current_mode;
 
-    // Split by commas and process each mode part sequentially
-    let mut offset = 0;
-    for raw_part in mode_string.split(',') {
-        let start = offset + (raw_part.len() - raw_part.trim_start().len());
-        // Past the part and the comma that followed it.
-        offset += raw_part.len() + 1;
-
-        let mode_part = raw_part.trim();
-        if mode_part.is_empty() {
-            continue;
-        }
-
+    // Process each mode part sequentially
+    for (start, mode_part) in clauses(mode_string) {
         new_mode = if mode_part.chars().any(|c| c.is_ascii_digit()) {
             parse_numeric(new_mode, mode_part, considering_dir)
         } else {
@@ -494,6 +529,7 @@ pub fn with_umask<T>(mask: u32, operation: impl FnOnce() -> T) -> T {
 #[cfg(test)]
 mod tests {
 
+    use super::ModeErrorKind;
     use super::parse;
     use super::parse_chmod;
 
@@ -530,7 +566,7 @@ 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);
+        assert_eq!(parse("=644,-4", false, 0).unwrap(), 0o640);
     }
 
     #[test]
@@ -567,17 +603,51 @@ 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);
+        // An octal mode next to other clauses needs an operator
+        assert_eq!(parse("+644,u+x", false, 0).unwrap(), 0o744);
+        assert_eq!(parse("u+rw,=755", false, 0).unwrap(), 0o755);
+        assert_eq!(
+            parse("644,u+x", false, 0).unwrap_err().kind,
+            ModeErrorKind::OctalInList
+        );
+        assert_eq!(
+            parse("u+rw,755", false, 0).unwrap_err().kind,
+            ModeErrorKind::OctalInList
+        );
+        assert_eq!(
+            parse("+644,644", false, 0).unwrap_err().kind,
+            ModeErrorKind::OctalInList
+        );
+    }
+
+    #[test]
+    fn test_parse_empty_clauses() {
+        for mode in [
+            "",
+            "   ",
+            ",",
+            ",,",
+            "u+x,",
+            ",u+x",
+            "u+x,,g+x",
+            "u+x, ,g+x",
+            ",644",
+            "644,",
+            "644,,u+x",
+        ] {
+            let err = parse(mode, false, 0).unwrap_err();
+            assert_eq!(err.kind, ModeErrorKind::EmptyClause, "{mode:?}");
+        }
+        // The caret goes under the missing clause, not under the octal
+        assert_eq!(parse("644,", false, 0).unwrap_err().span, 4..4);
     }
 
     #[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_error_spans() {
+        // The span is inside the whole mode, not the clause
+        assert_eq!(parse("u+x,,g+x", false, 0).unwrap_err().span, 4..4);
+        assert_eq!(parse("u+x,644", false, 0).unwrap_err().span, 4..7);
+        assert_eq!(parse("u+x, ,g+x", false, 0).unwrap_err().span, 5..5);
     }
 
     #[test]
@@ -617,18 +687,18 @@ mod tests {
         // 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);
+        assert_eq!(parse("=644,a-w", false, 0).unwrap(), 0o444);
+        assert_eq!(parse("=644,g-r", false, 0).unwrap(), 0o604);
     }
 
     #[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);
+        assert_eq!(parse("=644,u+x", false, 0).unwrap(), 0o744);
 
         // First add user write, then set to 755 (should override)
-        assert_eq!(parse("u+w,755", false, 0).unwrap(), 0o755);
+        assert_eq!(parse("u+w,=755", false, 0).unwrap(), 0o755);
     }
 
     /// Reads the umask without going through the helpers under test.
diff --git a/tests/by-util/test_chmod.rs b/tests/by-util/test_chmod.rs
index afbf7e23e1e..eb8c15f819f 100644
--- a/tests/by-util/test_chmod.rs
+++ b/tests/by-util/test_chmod.rs
@@ -984,6 +984,59 @@ fn test_chmod_invalid_mode_checked_before_any_file() {
         .stderr_only("chmod: invalid operator (expected +, -, or =, but found ?)\n");
 }
 
+#[test]
+fn test_mode_list_with_empty_clause_or_bare_octal() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.touch("file");
+    set_permissions(at.plus("file"), Permissions::from_mode(0o640)).unwrap();
+
+    for mode in [
+        "", ",", "u+x,", ",u+x", "u+x,,g+w", "u+x, ", "644,", "644,u+x", "u+x,644", "+644,644",
+        " 644,u+x",
+    ] {
+        scene
+            .ucmd()
+            .arg(mode)
+            .arg("file")
+            .fails_with_code(1)
+            .no_stdout()
+            .stderr_is(format!("chmod: invalid mode ({mode})\n"));
+        assert_eq!(
+            at.metadata("file").permissions().mode(),
+            0o100_640,
+            "{mode:?}"
+        );
+    }
+
+    scene.ucmd().arg("=644,u+x").arg("file").succeeds();
+    assert_eq!(at.metadata("file").permissions().mode(), 0o100_744);
+}
+
+#[test]
+fn test_mode_list_rejected_before_files() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+    at.symlink_file("nowhere", "dangling");
+
+    for mode in [",", "u+x,", "644,u+x"] {
+        scene
+            .ucmd()
+            .arg(mode)
+            .arg("missing")
+            .fails_with_code(1)
+            .stderr_is(format!("chmod: invalid mode ({mode})\n"));
+    }
+
+    scene
+        .ucmd()
+        .arg("-h")
+        .arg("u+x,")
+        .arg("dangling")
+        .fails_with_code(1)
+        .stderr_is("chmod: invalid mode (u+x,)\n");
+}
+
 #[test]
 #[cfg(not(target_os = "android"))]
 fn test_gnu_options() {
diff --git a/tests/by-util/test_install.rs b/tests/by-util/test_install.rs
index a3b9c5657d4..932b9daa857 100644
--- a/tests/by-util/test_install.rs
+++ b/tests/by-util/test_install.rs
@@ -304,6 +304,38 @@ fn test_install_mode_comma_separated_directory() {
     assert_eq!(0o040_775_u32, PermissionsExt::mode(&permissions));
 }
 
+#[test]
+fn test_install_mode_list_with_empty_clause_or_bare_octal() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    for mode in [
+        "", ",", "u+x,", ",u+x", "u+x,,g+w", "644,u+x", "u+x,644", "+644,644", " 644,u+x",
+    ] {
+        scene
+            .ucmd()
+            .arg("-d")
+            .arg("-m")
+            .arg(mode)
+            .arg("test_dir")
+            .fails_with_code(1)
+            .stderr_is(format!(
+                "install: Invalid mode string: invalid mode ({mode})\n"
+            ));
+        assert!(!at.dir_exists("test_dir"), "{mode:?}");
+    }
+
+    scene
+        .ucmd()
+        .arg("-d")
+        .arg("-m")
+        .arg("=644,u+x")
+        .arg("test_dir")
+        .succeeds();
+    let permissions = at.metadata("test_dir").permissions();
+    assert_eq!(0o040_744_u32, PermissionsExt::mode(&permissions));
+}
+
 #[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 4d2722a858a..0701c64250d 100644
--- a/tests/by-util/test_mkdir.rs
+++ b/tests/by-util/test_mkdir.rs
@@ -260,6 +260,35 @@ fn test_symbolic_mode() {
     assert_eq!(perms, 0o40777);
 }
 
+#[test]
+#[cfg(not(windows))]
+#[cfg_attr(wasi_runner, ignore = "WASI: st_mode has no real permission bits")]
+fn test_mode_list_with_empty_clause_or_bare_octal() {
+    let scene = TestScenario::new(util_name!());
+    let at = &scene.fixtures;
+
+    for mode in [
+        "", ",", "u+x,", ",u+x", "u+x,,g+w", "644,u+x", "u+x,644", " 644,u+x",
+    ] {
+        scene
+            .ucmd()
+            .arg("-m")
+            .arg(mode)
+            .arg("test_dir")
+            .fails_with_code(1)
+            .stderr_is(format!("mkdir: invalid mode '{mode}'\n"));
+        assert!(!at.dir_exists("test_dir"), "{mode:?}");
+    }
+
+    scene
+        .ucmd()
+        .arg("-m")
+        .arg("=644,u+x")
+        .arg("test_dir")
+        .succeeds();
+    assert_eq!(at.metadata("test_dir").permissions().mode(), 0o40744);
+}
+
 #[test]
 #[cfg(not(windows))]
 #[cfg_attr(wasi_runner, ignore = "WASI: st_mode has no real permission bits")]
diff --git a/tests/by-util/test_mkfifo.rs b/tests/by-util/test_mkfifo.rs
index 58b93d358f1..215b3a74c05 100644
--- a/tests/by-util/test_mkfifo.rs
+++ b/tests/by-util/test_mkfifo.rs
@@ -43,6 +43,32 @@ fn test_create_one_fifo_with_invalid_mode() {
         .stderr_contains("invalid mode");
 }
 
+#[test]
+fn test_create_fifo_with_empty_clause_or_bare_octal() {
+    let scene = TestScenario::new(util_name!());
+
+    for mode in [
+        "", ",", "u+x,", ",u+x", "u+x,,g+w", "644,u+x", "u+x,644", "+644,644", " 644,u+x",
+    ] {
+        scene
+            .ucmd()
+            .arg("-m")
+            .arg(mode)
+            .arg("abcd")
+            .fails_with_code(1)
+            .stderr_is(format!("mkfifo: invalid mode: invalid mode ({mode})\n"));
+        assert!(!scene.fixtures.file_exists("abcd"), "{mode:?}");
+    }
+
+    scene
+        .ucmd()
+        .arg("-m")
+        .arg("=644,u+x")
+        .arg("abcd")
+        .succeeds();
+    assert!(scene.fixtures.is_fifo("abcd"));
+}
+
 #[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 9c9bc9730a3..6515a14ba41 100644
--- a/tests/by-util/test_mknod.rs
+++ b/tests/by-util/test_mknod.rs
@@ -257,6 +257,35 @@ fn test_mknod_fifo_with_umask() {
     test_fifo_creation(0o777, "p---------"); // spell-checker:disable-line
 }
 
+#[test]
+fn test_mknod_mode_list_with_empty_clause_or_bare_octal() {
+    let ts = TestScenario::new(util_name!());
+
+    for mode in [
+        "", ",", "u+x,", ",u+x", "u+x,,g+w", "644,u+x", "u+x,644", "+644,644", " 644,u+x",
+    ] {
+        ts.ucmd()
+            .arg("-m")
+            .arg(mode)
+            .arg("test_file")
+            .arg("p")
+            .fails_with_code(1)
+            .stderr_is(format!("mknod: invalid mode (invalid mode ({mode}))\n"));
+        assert!(!ts.fixtures.file_exists("test_file"), "{mode:?}");
+    }
+
+    ts.ucmd()
+        .arg("-m")
+        .arg("=644,u+x")
+        .arg("test_file")
+        .arg("p")
+        .succeeds();
+    assert_eq!(
+        ts.fixtures.metadata("test_file").permissions().mode() & 0o777,
+        0o744
+    );
+}
+
 #[test]
 #[cfg(all(feature = "selinux", any(target_os = "linux", target_os = "android")))]
 fn test_mknod_selinux() {