diff --git a/third_party/make/README.cosmo b/third_party/make/README.cosmo
index 17e3a479a..2f9ca417e 100644
--- a/third_party/make/README.cosmo
+++ b/third_party/make/README.cosmo
@@ -15,6 +15,7 @@ LICENSE
 
 LOCAL CHANGES
 
+  - Introduce -T FILE, --time-log=FILE flag
   - Introduce $(uniq token...) native function
   - Remove code that forces slow path if not using /bin/sh
 
diff --git a/third_party/make/function.c b/third_party/make/function.c
index 8608b4604..64bd61035 100644
--- a/third_party/make/function.c
+++ b/third_party/make/function.c
@@ -1949,6 +1949,7 @@ func_shell_base (char *o, char **argv, int trim_newlines)
   child.output.out = pipedes[1];
   child.output.err = errfd;
 
+  child.timelog = timelog_begin (command_argv);
   pid = child_execute_job (&child, 1, command_argv);
 
   if (pid < 0)
diff --git a/third_party/make/job.c b/third_party/make/job.c
index 9b54489dc..9b0399d98 100644
--- a/third_party/make/job.c
+++ b/third_party/make/job.c
@@ -1104,6 +1104,8 @@ reap_children (int block, int err)
 void
 free_childbase (struct childbase *child)
 {
+  timelog_end (child->timelog);
+
   if (child->environment != 0)
     {
       char **ep = child->environment;
@@ -1463,6 +1465,7 @@ start_job_command (struct child *child)
 
       jobserver_pre_child (ANY_SET (flags, COMMANDS_RECURSE));
 
+      child->timelog = timelog_begin (argv);
       child->pid = child_execute_job ((struct childbase *)child,
                                       child->good_stdin, argv);
 
diff --git a/third_party/make/job.h b/third_party/make/job.h
index 00fac9984..daf414565 100644
--- a/third_party/make/job.h
+++ b/third_party/make/job.h
@@ -15,6 +15,7 @@ You should have received a copy of the GNU General Public License along with
 this program.  If not, see <https://www.gnu.org/licenses/>.  */
 
 #include "output.h"
+#include "timelog.h"
 
 /* Structure describing a running or dead child process.  */
 
@@ -31,6 +32,7 @@ this program.  If not, see <https://www.gnu.org/licenses/>.  */
 #define CHILDBASE                                               \
     char *cmd_name;       /* Allocated copy of command run.  */ \
     char **environment;   /* Environment for commands. */       \
+    struct timelog *timelog; /* [jart] the lorde of all time.  */ \
     VMSCHILD                                                    \
     struct output output  /* Output for this child.  */
 
diff --git a/third_party/make/main.c b/third_party/make/main.c
index 8a367f766..0bd269481 100644
--- a/third_party/make/main.c
+++ b/third_party/make/main.c
@@ -27,6 +27,7 @@ this program.  If not, see <https://www.gnu.org/licenses/>.  */
 #include "getopt.h"
 #include "libc/runtime/runtime.h"
 #include "shuffle.h"
+#include "timelog.h"
 
 #include <assert.h>
 #ifdef HAVE_FCNTL_H
@@ -374,6 +375,8 @@ static const char *const usage[] =
     N_("\
   --trace                     Print tracing information.\n"),
     N_("\
+  -T FILE, --time-log=FILE    Log command invocation microseconds to FILE.\n"),
+    N_("\
   -v, --version               Print the version number of make and exit.\n"),
     N_("\
   -w, --print-directory       Print the current directory.\n"),
@@ -471,6 +474,7 @@ static struct command_switch switches[] =
     { 'o', filename, &old_files, 0, 0, 0, 0, 0, 0, "old-file", 0 },
     { 'O', string, &output_sync_option, 1, 1, 0, 0, "target", 0, "output-sync", 0 },
     { 'W', filename, &new_files, 0, 0, 0, 0, 0, 0, "what-if", 0 },
+    { 'T', string, &timelog_path, 0, 0, 0, 0, 0, 0, "timelog", 0 }, // [jart]
 
     /* These are long-style options.  */
     { CHAR_MAX+1, strlist, &db_flags, 1, 1, 0, 0, "basic", 0, "debug", 0 },
@@ -2258,6 +2262,10 @@ main (int argc, char **argv, char **envp)
     }
 #endif
 
+  /* [jart] Setup command latency log.  */
+
+  timelog_init ();
+
   /* Set up MAKEFLAGS and MFLAGS again, so they will be right.  */
 
   define_makeflags (0);
diff --git a/third_party/make/timelog.c b/third_party/make/timelog.c
new file mode 100644
index 000000000..b6be15c8c
--- /dev/null
+++ b/third_party/make/timelog.c
@@ -0,0 +1,186 @@
+/* Copyright 2024 Justine Alexandra Roberts Tunney
+
+   Permission to use, copy, modify, and/or distribute this software for
+   any purpose with or without fee is hereby granted, provided that the
+   above copyright notice and this permission notice appear in all copies.
+
+   THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL
+   WARRANTIES WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED
+   WARRANTIES OF MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE
+   AUTHOR BE LIABLE FOR ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL
+   DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR
+   PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR OTHER
+   TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
+   PERFORMANCE OF THIS SOFTWARE.  */
+
+#include "timelog.h"
+
+#include <time.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/uio.h>
+
+struct timelog
+  {
+    struct timespec started;
+    size_t command_length;
+    char command[4000];
+  };
+
+char *timelog_path;
+int timelog_fd = -1;
+
+void timelog_init (void)
+{
+  if (!timelog_path)
+    return;
+  if ((timelog_fd = open (timelog_path, O_APPEND | O_WRONLY | O_CREAT, 0644)) == -1)
+    {
+      perror (timelog_path);
+      exit (1);
+    }
+}
+
+static int is_shell_safe (int c)
+{
+  if (c > 127)
+    return true;
+  if (isalnum(c))
+    return true;
+  switch (c)
+    {
+    case '+':
+    case '-':
+    case '.':
+    case '/':
+    case '_':
+    case '=':
+    case ':':
+      return true;
+    default:
+      return false;
+    }
+}
+
+static int needs_quotes (const char *s)
+{
+  int c;
+  if (!*s)
+    return true;
+  while ((c = *s++ & 255))
+    if (!is_shell_safe (c))
+      return true;
+  return false;
+}
+
+static long long get_microseconds (struct timespec beg, struct timespec end)
+{
+  end.tv_sec -= beg.tv_sec;
+  if (end.tv_nsec < beg.tv_nsec)
+    {
+      end.tv_nsec += 1000000000;
+      end.tv_sec--;
+    }
+  end.tv_nsec -= beg.tv_nsec;
+  return end.tv_sec * 1000000ll + end.tv_nsec / 1000ll;
+}
+
+struct timelog *timelog_begin (char **argv)
+{
+  int i, j, q;
+  char *p, *pe;
+
+  /* don't bother if disabled */
+  if (timelog_fd == -1)
+    return NULL;
+
+  /* allocate object */
+  struct timelog *tl;
+  if (!(tl = malloc (sizeof (struct timelog))))
+    return NULL;
+
+  /* stringify command */
+  p = tl->command;
+  pe = tl->command + sizeof (tl->command) - 1;
+  for (i = 0; argv[i]; ++i)
+    {
+      if (i && p < pe)
+        *p++ = ' ';
+      q = needs_quotes (argv[i]);
+      if (q && p < pe)
+        *p++ = '\'';
+      for (j = 0; argv[i][j]; ++j)
+        {
+          if (isspace(argv[i][j]) ||
+              iscntrl(argv[i][j]))
+            {
+              if (p < pe)
+                *p++ = ' ';
+            }
+          else if (argv[i][j] == '\'')
+            {
+              if (p < pe)
+                *p++ = '\'';
+              if (p < pe)
+                *p++ = '"';
+              if (p < pe)
+                *p++ = '\'';
+              if (p < pe)
+                *p++ = '"';
+              if (p < pe)
+                *p++ = '\'';
+            }
+          else
+            {
+              if (p < pe)
+                *p++ = argv[i][j];
+            }
+        }
+      if (q && p < pe)
+        *p++ = '\'';
+    }
+  if (p == pe)
+    {
+      p[-3] = '.';
+      p[-2] = '.';
+      p[-1] = '.';
+    }
+  *p++ = '\n';
+  tl->command_length = p - tl->command;
+
+  /* record starting timestamp */
+  clock_gettime (CLOCK_REALTIME, &tl->started);
+
+  /* return object */
+  return tl;
+}
+
+void timelog_end (struct timelog *tl)
+{
+  long long us;
+  char ibuf[22];
+  struct iovec iov[2];
+  struct timespec ended;
+
+  /* don't bother if disabled */
+  if (tl == NULL)
+    return;
+
+  /* get elapsed microseconds string */
+  clock_gettime (CLOCK_REALTIME, &ended);
+  us = get_microseconds (tl->started, ended);
+  snprintf (ibuf, sizeof(ibuf), "% 20lld ", us);
+
+  // write to log
+  iov[0].iov_base = ibuf;
+  iov[0].iov_len = 21;
+  iov[1].iov_base = tl->command;
+  iov[1].iov_len = tl->command_length;
+  writev (timelog_fd, iov, 2);
+
+  // free object
+  free (tl);
+}
diff --git a/third_party/make/timelog.h b/third_party/make/timelog.h
new file mode 100644
index 000000000..72d2af31b
--- /dev/null
+++ b/third_party/make/timelog.h
@@ -0,0 +1,13 @@
+#ifndef MAKE_TIMELOG_H_
+#define MAKE_TIMELOG_H_
+
+struct timelog;
+
+extern int timelog_fd;
+extern char *timelog_path;
+
+void timelog_init (void);
+struct timelog *timelog_begin (char **);
+void timelog_end (struct timelog *);
+
+#endif /* MAKE_TIMELOG_H_ */