diff --git a/docs/cli.md b/docs/cli.md
index fb109cf..5c07d44 100644
--- a/docs/cli.md
+++ b/docs/cli.md
@@ -44,6 +44,16 @@ Values are automatically coerced: `true`/`false` to bool, numeric strings to int
 
 Available on both direct task commands (`sputnik deploy -D ...`) and the run command (`sputnik run deploy -D ...`).
 
+### `--format` on `list`
+
+`list` takes Symfony's `--format` (`txt`, `xml`, `json`, `md`) and `--raw`. For
+anything other than the default `txt`, Sputnik leaves the output alone: no
+header, no grouped task section, so the result is exactly what a parser expects.
+
+```bash
+sputnik list --format=json | jq '.commands[].name'
+```
+
 ### `-v` / `--verbose`
 
 Show additional output including log messages and stack traces on errors.
@@ -152,6 +162,12 @@ built-in command - rename the task or give it a group prefix
 The warning appears on every run, not only the one that filled the container
 cache -- the task stays missing until someone renames it.
 
+It is written to **stderr**, along with every other diagnostic Sputnik emits
+about itself. That keeps stdout usable as data: `sputnik completion bash > file`
+writes only the script, and `sputnik list --format=json` parses. Redirect stderr
+if you want it gone -- `--silent` and `-q` are the wrong tool, they suppress the
+payload with it.
+
 `init` is different: a project task may take it, and then the built-in scaffold
 is no longer reachable. Scaffolding a project happens once, while a project
 command called `init` may well be a daily one, so the project wins.
diff --git a/src/Console/Application.php b/src/Console/Application.php
index 25c2179..a19aa1f 100644
--- a/src/Console/Application.php
+++ b/src/Console/Application.php
@@ -8,6 +8,7 @@
 use Sputnik\Task\TaskMetadata;
 use Symfony\Component\Console\Application as BaseApplication;
 use Symfony\Component\Console\Input\InputInterface;
+use Symfony\Component\Console\Output\ConsoleOutputInterface;
 use Symfony\Component\Console\Output\OutputInterface;
 
 final class Application extends BaseApplication
@@ -70,20 +71,33 @@ public function doRun(InputInterface $input, OutputInterface $output): int
         $commandName = $this->getCommandName($input);
         $isList = $commandName === null || $commandName === 'list';
 
-        // Reported here, not while the application is assembled: -v is parsed by
-        // run(), so verbosity is not known any earlier.
+        // Anything else is a format meant for a machine - json, xml, md - or the
+        // raw list used to embed a command runner. Decoration would land in the
+        // middle of it.
+        $isReadableList = $isList
+            && $input->getParameterOption('--format', 'txt') === 'txt'
+            && !$input->hasParameterOption('--raw');
+
+        // Diagnostics go to stderr: `completion bash > file` and
+        // `list --format=json` both put stdout into something that parses it, and
+        // --silent cannot separate the two - it removes the payload as well.
+        //
+        // Reported here rather than while the application is assembled, because
+        // -v is parsed by run() and verbosity is not known any earlier.
+        $diagnostics = $output instanceof ConsoleOutputInterface ? $output->getErrorOutput() : $output;
+
         foreach ($this->discoveryWarnings as $warning) {
-            $output->writeln('<comment>' . $warning . '</comment>');
+            $diagnostics->writeln('<comment>' . $warning . '</comment>');
         }
 
         if ($output->isVerbose()) {
             foreach ($this->discoveryNotices as $notice) {
-                $output->writeln('<comment>' . $notice . '</comment>');
+                $diagnostics->writeln('<comment>' . $notice . '</comment>');
             }
         }
 
         // Show our header instead of Symfony's "AppName version" for list
-        if ($isList) {
+        if ($isReadableList) {
             $output->writeln(\sprintf(
                 "\xF0\x9F\x9B\xB0  <fg=green;options=bold>Sputnik %s</> <fg=gray>│</> %s <fg=gray>│</> %s",
                 self::VERSION,
@@ -95,7 +109,7 @@ public function doRun(InputInterface $input, OutputInterface $output): int
 
         $result = parent::doRun($input, $output);
 
-        if ($isList && $this->taskDiscovery instanceof TaskDiscovery) {
+        if ($isReadableList && $this->taskDiscovery instanceof TaskDiscovery) {
             $this->renderTaskList($output);
         }
 
diff --git a/tests/E2E/SputnikBinaryTest.php b/tests/E2E/SputnikBinaryTest.php
index f38d7dd..19139a3 100644
--- a/tests/E2E/SputnikBinaryTest.php
+++ b/tests/E2E/SputnikBinaryTest.php
@@ -874,6 +874,74 @@ public function testAMissingWorkingDirSaysSoInsteadOfFailingOnItsCache(): void
         $this->assertStringNotContainsString('mkdir', $output, 'The cache is a symptom, not the problem');
     }
 
+    public function testCompletionScriptIsNotPollutedByDiagnostics(): void
+    {
+        // The completion script is written to a file. A warning on stdout landed
+        // in it as line one, and --silent/-q cannot help: they suppress the
+        // script along with the warning.
+        $this->scaffoldProject([
+            'list' => <<<'PHP'
+                #[Task(name: 'list', description: 'Collides with a built-in')]
+                final class ListTask implements TaskInterface
+                {
+                    public function __invoke(TaskContext $ctx): TaskResult
+                    {
+                        return TaskResult::success();
+                    }
+                }
+                PHP,
+        ]);
+
+        $result = $this->sputnik(['completion', 'bash'], $this->tempDir);
+
+        $this->assertStringStartsWith('#', ltrim($result->getOutput()));
+        $this->assertStringNotContainsString('Skipped task', $result->getOutput());
+        $this->assertStringContainsString('Skipped task', $result->getErrorOutput());
+    }
+
+    public function testListInAMachineReadableFormatIsParseable(): void
+    {
+        $this->scaffoldProject([
+            'deploy' => <<<'PHP'
+                #[Task(name: 'deploy', description: 'Deploy it')]
+                final class DeployTask implements TaskInterface
+                {
+                    public function __invoke(TaskContext $ctx): TaskResult
+                    {
+                        return TaskResult::success();
+                    }
+                }
+                PHP,
+        ]);
+
+        $result = $this->sputnik(['list', '--format=json'], $this->tempDir);
+
+        $this->assertSame(0, $result->getExitCode());
+        $this->assertIsArray(json_decode($result->getOutput(), true), 'The header and the task section used to surround the JSON');
+    }
+
+    public function testTheDefaultListKeepsItsHeaderAndTaskSection(): void
+    {
+        $this->scaffoldProject([
+            'deploy' => <<<'PHP'
+                #[Task(name: 'deploy', description: 'Deploy it')]
+                final class DeployTask implements TaskInterface
+                {
+                    public function __invoke(TaskContext $ctx): TaskResult
+                    {
+                        return TaskResult::success();
+                    }
+                }
+                PHP,
+        ]);
+
+        $output = $this->sputnik(['list'], $this->tempDir)->getOutput();
+
+        $this->assertStringContainsString('Sputnik', $output);
+        $this->assertStringContainsString('Available tasks', $output);
+        $this->assertStringContainsString('deploy', $output);
+    }
+
     private function sputnik(array $args, ?string $cwd = null): Process
     {
         $process = new Process(