diff --git a/disag.js b/disag.js
index 2050613..721eb7c 100755
--- a/disag.js
+++ b/disag.js
@@ -4,7 +4,8 @@ import fs from "node:fs";
 import { spawn } from "node:child_process";
 import process from "node:process";
 
-const colors = [31, 32, 33, 34, 35, 36, 91, 92, 93, 94, 95, 96];
+const systemColor = "31";
+const commandColors = ["32", "33", "34", "35", "36", "92", "93", "94", "95", "96"];
 const signalCodes = {
   SIGINT: 130,
   SIGTERM: 143,
@@ -14,14 +15,14 @@ const signalCodes = {
 
 function usage() {
   process.stderr.write(
-    "usage: diag [-z|--no-color] command [-f|--file file] [-n|--name name] [-s|--shell] ...\n",
+    "usage: diag [-z|--no-color] command [-f|--file file] [-n|--name name] [-r|--retry] [-s|--shell] ...\n",
   );
   process.stderr.write("try: diag --help\n");
   process.exit(1);
 }
 
 function help() {
-  process.stdout.write(`usage: diag [-z|--no-color] command [-f|--file file] [-n|--name name] [-s|--shell] ...
+  process.stdout.write(`usage: diag [-z|--no-color] command [-f|--file file] [-n|--name name] [-r|--retry] [-s|--shell] ...
        diag -h|--help
 
 Run one or more commands at the same time and mirror their output.
@@ -36,16 +37,19 @@ Options:
                      to file; if repeated for that command, the last value wins
   -n, --name name     prefix displayed lines for the immediately preceding
                      command with [name]; not written to log files
+  -r, --retry         retry the immediately preceding command until it exits
+                     with code 0
   -s, --shell         execute the immediately preceding command with sh -c
   -z, --no-color      disable ANSI colors even when stdout is a terminal
   -h, --help          show this help text
 
 Notes:
-  -f, -n, and -s always apply to the command immediately before them.
+  -f, -n, -r, and -s always apply to the command immediately before them.
   If no -f is specified for a command, its output is only displayed.
   Display prefixes and ANSI colors are never written to log files.
   Colors are used only when stdout is a terminal.
   Each command prints a [DISAG] exit-code line to stderr when it exits.
+  Retried commands print a [DISAG] retry line before each retry.
   diag-js only writes paths named with -f.
   Signals are forwarded to child processes with kill.
 
@@ -56,6 +60,8 @@ Examples:
 
   diag 'echo out; echo err >&2' -s -f ./command.log -n CMD
 
+  diag 'flaky_command' -r -n FLAKY
+
   diag \\
     'while true; do echo hello; sleep 1; done' -s -f ./hello.log -n HELLO \\
     'some_command' -f ./some_command.log
@@ -110,8 +116,15 @@ function parseArgs(args) {
       current.shell = true;
       continue;
     }
+    if (arg === "-r" || arg === "--retry") {
+      if (current === null) {
+        usage();
+      }
+      current.retry = true;
+      continue;
+    }
     finishCurrent();
-    current = { command: arg, file: "", name: "", shell: false };
+    current = { command: arg, file: "", name: "", retry: false, shell: false };
   }
 
   finishCurrent();
@@ -190,17 +203,24 @@ function decorate(line, spec) {
   return out;
 }
 
-function colorize(line, spec) {
-  if (spec.color === "") {
+function colorize(line, color) {
+  if (color === "") {
     return line;
   }
-  return `\x1b[${spec.color}m${line}\x1b[0m`;
+  return `\x1b[${color}m${line}\x1b[0m`;
 }
 
 function reportExit(spec, status) {
   const label = spec.name !== "" ? spec.name : spec.command;
   process.stderr.write(
-    `${colorize(`[DISAG] ${label} exited with exit code ${status}`, spec)}\n`,
+    `${colorize(`[DISAG] ${label} exited with exit code ${status}`, spec.systemColor)}\n`,
+  );
+}
+
+function reportRetry(spec, status) {
+  const label = spec.name !== "" ? spec.name : spec.command;
+  process.stderr.write(
+    `${colorize(`[DISAG] ${label} retrying after exit code ${status}`, spec.systemColor)}\n`,
   );
 }
 
@@ -240,6 +260,9 @@ function attachLineStream(readable, display, log, spec) {
 }
 
 function killChild(child, signal) {
+  if (child === null) {
+    return;
+  }
   if (child.exitCode !== null || child.signalCode !== null) {
     return;
   }
@@ -257,65 +280,77 @@ function killChild(child, signal) {
 
 function runCommand(spec) {
   const argv = spec.shell ? ["sh", "-c", spec.command] : splitCommand(spec.command);
-  let log = null;
-  if (spec.file !== "") {
-    log = fs.openSync(spec.file, "w");
-  }
+  const run = { child: null, done: null };
 
-  const child = spawn(argv[0], argv.slice(1), {
-    detached: true,
-    stdio: ["ignore", "pipe", "pipe"],
-  });
+  run.done = (async () => {
+    for (;;) {
+      let log = null;
+      if (spec.file !== "") {
+        log = fs.openSync(spec.file, "w");
+      }
 
-  if (child.stdout !== null) {
-    attachLineStream(child.stdout, process.stdout, log, spec);
-  }
-  if (child.stderr !== null) {
-    attachLineStream(child.stderr, process.stderr, log, spec);
-  }
+      const child = spawn(argv[0], argv.slice(1), {
+        detached: true,
+        stdio: ["ignore", "pipe", "pipe"],
+      });
+      run.child = child;
 
-  const done = new Promise((resolve) => {
-    child.on("error", (err) => {
-      if (log !== null) {
-        fs.closeSync(log);
+      if (child.stdout !== null) {
+        attachLineStream(child.stdout, process.stdout, log, spec);
       }
-      process.stderr.write(`diag-js: ${err.message}\n`);
-      resolve(1);
-    });
-
-    child.on("close", (code, signal) => {
-      if (log !== null) {
-        fs.closeSync(log);
+      if (child.stderr !== null) {
+        attachLineStream(child.stderr, process.stderr, log, spec);
       }
-      if (code !== null) {
-        reportExit(spec, code);
-        resolve(code);
-      } else if (signal !== null && signal in signalCodes) {
-        const status = signalCodes[signal];
-        reportExit(spec, status);
-        resolve(status);
-      } else {
-        reportExit(spec, 1);
-        resolve(1);
+
+      const status = await new Promise((resolve) => {
+        child.on("error", (err) => {
+          if (log !== null) {
+            fs.closeSync(log);
+          }
+          process.stderr.write(`diag-js: ${err.message}\n`);
+          resolve(1);
+        });
+
+        child.on("close", (code, signal) => {
+          if (log !== null) {
+            fs.closeSync(log);
+          }
+          if (code !== null) {
+            resolve(code);
+          } else if (signal !== null && signal in signalCodes) {
+            resolve(signalCodes[signal]);
+          } else {
+            resolve(1);
+          }
+        });
+      });
+
+      run.child = null;
+      reportExit(spec, status);
+      if (!spec.retry || status === 0 || spec.stopping()) {
+        return status;
       }
-    });
-  });
+      reportRetry(spec, status);
+    }
+  })();
 
-  return { child, done };
+  return run;
 }
 
 async function main() {
   const { commands, noColor } = parseArgs(process.argv.slice(2));
   const useColor = !noColor && process.stdout.isTTY;
+  let stopping = false;
+  let stopCode = null;
   const runs = commands.map((command, index) =>
     runCommand({
       ...command,
-      color: useColor ? String(colors[index % colors.length]) : "",
+      color: useColor ? commandColors[index % commandColors.length] : "",
+      systemColor: useColor ? systemColor : "",
+      stopping: () => stopping,
     }),
   );
 
-  let stopping = false;
-  let stopCode = null;
   for (const signal of Object.keys(signalCodes)) {
     process.on(signal, () => {
       if (stopping) {
diff --git a/tests/disag-js.rc b/tests/disag-js.rc
index 1c239cb..b6f45a3 100755
--- a/tests/disag-js.rc
+++ b/tests/disag-js.rc
@@ -83,11 +83,35 @@ printf '%s\n' '[DISAG] echo command-label exited with exit code 0' > $tmp/comman
 assert_file $tmp/command-label.out $tmp/command-label.out.want command-label-stdout
 assert_file $tmp/command-label.err $tmp/command-label.err.want command-label-stderr
 
+script -q $tmp/color.tty $diag 'echo color-test' -n COLOR >/dev/null || fail color-run
+awk 'BEGIN { ok = 0; pat = sprintf("%c[31m[DISAG]", 27) } index($0, pat) { ok = 1 } END { exit ok ? 0 : 1 }' $tmp/color.tty || fail color-system-red
+awk 'BEGIN { ok = 0; pat = sprintf("%c[32m[COLOR]", 27) } index($0, pat) { ok = 1 } END { exit ok ? 0 : 1 }' $tmp/color.tty || fail color-command-non-red
+awk 'BEGIN { bad = 0; pat = sprintf("%c[31m[COLOR]", 27) } index($0, pat) { bad = 1 } END { exit bad ? 1 : 0 }' $tmp/color.tty || fail color-command-red
+
+script -q $tmp/color-rotation.tty $diag 'echo one' -n C1 'echo two' -n C2 'echo three' -n C3 'echo four' -n C4 'echo five' -n C5 'echo six' -n C6 >/dev/null || fail color-rotation-run
+awk 'BEGIN { bad = 0; red = sprintf("%c[31m[C", 27); brightred = sprintf("%c[91m[C", 27) } index($0, red) || index($0, brightred) { bad = 1 } END { exit bad ? 1 : 0 }' $tmp/color-rotation.tty || fail color-rotation-red-command
+
+script -q $tmp/no-color.tty $diag -z 'echo color-test' -n COLOR >/dev/null || fail no-color-run
+awk 'BEGIN { bad = 0; pat = sprintf("%c[", 27) } index($0, pat) { bad = 1 } END { exit bad ? 1 : 0 }' $tmp/no-color.tty || fail no-color-has-ansi
+
 $diag 'node tests/fixtures/diag-helper.js exit 7' > $tmp/status.out >[2=1]
 s=$status
 if(~ $s 0)
 	fail status-zero
 
+$diag 'node tests/fixtures/diag-helper.js flaky '^$tmp^'/retry.count' -r -n RETRY -f $tmp/retry.log > $tmp/retry.out >[2]$tmp/retry.err || fail retry-run
+printf '%s\n' '[RETRY] attempt 1' '[RETRY] attempt 2' > $tmp/retry.out.want
+printf '%s\n' '[DISAG] RETRY exited with exit code 7' '[DISAG] RETRY retrying after exit code 7' '[DISAG] RETRY exited with exit code 0' > $tmp/retry.err.want
+printf '%s\n' 'attempt 2' > $tmp/retry.log.want
+printf '%s\n' 2 > $tmp/retry.count.want
+assert_file $tmp/retry.out $tmp/retry.out.want retry-stdout
+assert_file $tmp/retry.err $tmp/retry.err.want retry-stderr
+assert_file $tmp/retry.log $tmp/retry.log.want retry-log-last-attempt
+assert_file $tmp/retry.count $tmp/retry.count.want retry-count
+
+script -q $tmp/retry-color.tty $diag 'node tests/fixtures/diag-helper.js flaky '^$tmp^'/retry-color.count' -r -n RETRYCOLOR >/dev/null || fail retry-color-run
+awk 'BEGIN { ok = 0; pat = sprintf("%c[31m[DISAG] RETRYCOLOR retrying after exit code 7", 27) } index($0, pat) { ok = 1 } END { exit ok ? 0 : 1 }' $tmp/retry-color.tty || fail retry-color-red
+
 sigcmd='node tests/fixtures/diag-helper.js signal '^$tmp
 $diag $sigcmd -f $tmp/signal.log > $tmp/signal.out >[2=1] &
 pid=$apid
diff --git a/tests/fixtures/diag-helper.js b/tests/fixtures/diag-helper.js
index 5ac8e7f..964f973 100644
--- a/tests/fixtures/diag-helper.js
+++ b/tests/fixtures/diag-helper.js
@@ -9,6 +9,18 @@ if (mode === "emit") {
   process.stderr.write(`${args[1]}\n`);
 } else if (mode === "exit") {
   process.exit(Number(args[0]));
+} else if (mode === "flaky") {
+  const counter = args[0];
+  let attempts = 0;
+  try {
+    attempts = Number(fs.readFileSync(counter, "utf8"));
+  } catch {
+    attempts = 0;
+  }
+  attempts += 1;
+  fs.writeFileSync(counter, `${attempts}\n`);
+  process.stdout.write(`attempt ${attempts}\n`);
+  process.exit(attempts < 2 ? 7 : 0);
 } else if (mode === "signal") {
   const dir = args[0];
   process.on("SIGTERM", () => {