diff --git a/src/header/sched/mod.rs b/src/header/sched/mod.rs
--- a/src/header/sched/mod.rs
+++ b/src/header/sched/mod.rs
@@ -2,9 +2,11 @@
 //!
 //! See <https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/sched.h.html>.
 
 use crate::{
     error::ResultExt,
-    header::bits_timespec::timespec,
+    header::{bits_timespec::timespec, errno},
     platform::{
-        Pal, Sys,
+        self, Pal, Sys,
         types::{c_int, pid_t},
     },
 };
@@ -29,42 +31,67 @@
 pub const SCHED_OTHER: c_int = 2;
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_get_priority_max.html>.
 // #[unsafe(no_mangle)]
 pub extern "C" fn sched_get_priority_max(policy: c_int) -> c_int {
-    todo!()
+    match policy {
+        SCHED_FIFO | SCHED_RR => 99,
+        SCHED_OTHER => 0,
+        _ => {
+            platform::ERRNO.set(errno::EINVAL);
+            -1
+        }
+    }
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_get_priority_max.html>.
 // #[unsafe(no_mangle)]
 pub extern "C" fn sched_get_priority_min(policy: c_int) -> c_int {
-    todo!()
+    match policy {
+        SCHED_FIFO | SCHED_RR => 0,
+        SCHED_OTHER => 0,
+        _ => {
+            platform::ERRNO.set(errno::EINVAL);
+            -1
+        }
+    }
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_getparam.html>.
 // #[unsafe(no_mangle)]
 pub unsafe extern "C" fn sched_getparam(pid: pid_t, param: *mut sched_param) -> c_int {
-    todo!()
+    if param.is_null() {
+        platform::ERRNO.set(errno::EINVAL);
+        return -1;
+    }
+    // Redox has no real-time scheduler; return default params
+    (*param).sched_priority = 0;
+    0
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_rr_get_interval.html>.
 // #[unsafe(no_mangle)]
 pub extern "C" fn sched_rr_get_interval(pid: pid_t, time: *const timespec) -> c_int {
-    todo!()
+    if time.is_null() {
+        platform::ERRNO.set(errno::EINVAL);
+        return -1;
+    }
+    // Redox has no real-time scheduler; report a nominal 1-second round-robin interval
+    unsafe {
+        (*(time as *mut timespec)).tv_sec = 1;
+        (*(time as *mut timespec)).tv_nsec = 0;
+    }
+    0
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_setparam.html>.
 // #[unsafe(no_mangle)]
 pub unsafe extern "C" fn sched_setparam(pid: pid_t, param: *const sched_param) -> c_int {
-    todo!()
+    if param.is_null() {
+        platform::ERRNO.set(errno::EINVAL);
+        return -1;
+    }
+    let priority = (*param).sched_priority;
+    if priority < 0 || priority > 99 {
+        platform::ERRNO.set(errno::EINVAL);
+        return -1;
+    }
+    // Redox has no real-time scheduler; validate and succeed as a no-op
+    0
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_setscheduler.html>.
 // #[unsafe(no_mangle)]
 pub extern "C" fn sched_setscheduler(
     pid: pid_t,
     policy: c_int,
     param: *const sched_param,
 ) -> c_int {
-    todo!()
+    if param.is_null() {
+        platform::ERRNO.set(errno::EINVAL);
+        return -1;
+    }
+    match policy {
+        SCHED_FIFO | SCHED_RR | SCHED_OTHER => {
+            let priority = unsafe { (*param).sched_priority };
+            if priority < 0 || priority > 99 {
+                platform::ERRNO.set(errno::EINVAL);
+                return -1;
+            }
+            // Redox has no real-time scheduler; validate and succeed as a no-op
+            0
+        }
+        _ => {
+            platform::ERRNO.set(errno::EINVAL);
+            -1
+        }
+    }
 }
 
 /// See <https://pubs.opengroup.org/onlinepubs/9799919799/functions/sched_yield.html>.