diff --git a/source/compose.manager/include/ComposeList.php b/source/compose.manager/include/ComposeList.php
index a41c4c6d..75b8064e 100755
--- a/source/compose.manager/include/ComposeList.php
+++ b/source/compose.manager/include/ComposeList.php
@@ -176,11 +176,16 @@ function composeRowBuildFailurePayload(string $composeRoot, string $project, str
         exit;
     }
     try {
-        $stackInfos = [StackInfo::fromProject($compose_root, $project)];
+        $stackInfo = StackInfo::fromProject($compose_root, $project);
     } catch (\Throwable $e) {
         echo json_encode(composeRowBuildFailurePayload($compose_root, $project, $e->getMessage()));
         exit;
     }
+    // The stack's containers from one docker ps call, as the full list gets them
+    // (StackInfo::allFromRoot()), rather than docker compose ps, which reads the
+    // compose files first and takes several times as long for every row.
+    $stackInfo->setContainerList(StackInfo::containersByProject($stackInfo->projectName)[$stackInfo->projectName] ?? []);
+    $stackInfos = [$stackInfo];
 } else {
     $stackInfos = StackInfo::allFromRoot($compose_root);
 }
diff --git a/source/compose.manager/include/Util.php b/source/compose.manager/include/Util.php
index e4f9fe8d..3b9eb32a 100644
--- a/source/compose.manager/include/Util.php
+++ b/source/compose.manager/include/Util.php
@@ -3395,8 +3395,8 @@ private function isProfilesCacheStale(): bool
      * Extract available profiles via `docker compose config --profiles`.
      *
      * Mirrors the approach used by {@see getDefinedServices()}.  On success
-     * the result is written back to the profiles metadata file so subsequent
-     * reads hit the fast-path cache.
+     * the result, even an empty one, is written back to the profiles metadata
+     * file so subsequent reads hit the fast-path cache.
      *
      * @return string[]
      */
@@ -3413,17 +3413,23 @@ private function extractProfilesFromCompose(): array
         }
         $cmd .= " config --profiles 2>/dev/null";
 
-        $output = shell_exec($cmd);
-        if (!is_string($output) || trim($output) === '') {
+        $output = [];
+        $exitCode = 0;
+        exec($cmd, $output, $exitCode);
+        if ($exitCode !== 0) {
+            // Compose could not read the stack (a broken compose file, say): nothing is
+            // cached, so the next read asks again once it is fixed.
             return [];
         }
 
         $profiles = array_values(array_filter(
-            array_map('trim', explode("\n", trim($output))),
+            array_map('trim', $output),
             fn(string $p): bool => $p !== ''
         ));
 
-        // Write-through: persist so future reads hit the cache.
+        // Write-through: persist so future reads hit the cache. An empty list is cached
+        // too: most stacks have no profiles, and asking compose again costs about 0.1 s
+        // per stack on every load of the stack list.
         $this->writeMetadata('profiles', json_encode($profiles));
 
         return $profiles;
@@ -4197,8 +4203,31 @@ public static function allFromRoot(string $composeRoot, bool $skipDocker = false
 
         // Batch-preload container data with a single docker ps call to avoid
         // O(n) docker invocations when callers iterate getContainerList().
+        $containersByProject = self::containersByProject();
+        foreach ($stacks as $stack) {
+            $key = $stack->projectName;
+            $stack->setContainerList($containersByProject[$key] ?? []);
+        }
+
+        return $stacks;
+    }
+
+    /**
+     * The containers of compose projects, from a single `docker ps` call, by project name.
+     *
+     * Rows are `docker ps --format json` rows, filtered on the compose project label.
+     * That is much quicker than `docker compose ps` for each stack, which has to read
+     * the stack's compose files first. Pass a project name to get only that project's
+     * containers.
+     *
+     * @param string|null $projectName One project, or null for every compose project
+     * @return array<string, array[]> Rows by project name
+     */
+    public static function containersByProject(?string $projectName = null): array
+    {
+        $filter = 'label=com.docker.compose.project' . ($projectName === null ? '' : '=' . $projectName);
         $containersByProject = [];
-        $psOutput = shell_exec("docker ps -a --filter label=com.docker.compose.project --format json 2>/dev/null");
+        $psOutput = shell_exec('docker ps -a --filter ' . escapeshellarg($filter) . ' --format json 2>/dev/null');
         if ($psOutput) {
             foreach (explode("\n", trim($psOutput)) as $line) {
                 if ($line === '') {
@@ -4215,12 +4244,7 @@ public static function allFromRoot(string $composeRoot, bool $skipDocker = false
                 }
             }
         }
-        foreach ($stacks as $stack) {
-            $key = $stack->projectName;
-            $stack->setContainerList($containersByProject[$key] ?? []);
-        }
-
-        return $stacks;
+        return $containersByProject;
     }
 
     /**
diff --git a/tests/unit/StackInfoTest.php b/tests/unit/StackInfoTest.php
index 2496f44e..d7a9a436 100644
--- a/tests/unit/StackInfoTest.php
+++ b/tests/unit/StackInfoTest.php
@@ -1011,6 +1011,99 @@ public function testGetProfilesEmptyWhenNoFile(): void
         $this->assertSame([], $info->getProfiles());
     }
 
+    public function testAStackWithoutProfilesAsksComposeOnlyOnce(): void
+    {
+        $stackDir = $this->tempRoot . '/no-profiles';
+        mkdir($stackDir);
+        file_put_contents($stackDir . '/compose.yaml', "services:\n  web:\n    image: nginx\n");
+        // docker compose config --profiles prints nothing for a stack without profiles.
+        $calls = $this->withDockerStandIn(0, function () use ($stackDir): void {
+            $this->assertSame([], \StackInfo::fromProject($this->tempRoot, 'no-profiles')->getProfiles());
+            \StackInfo::clearCache();
+            $this->assertSame([], \StackInfo::fromProject($this->tempRoot, 'no-profiles')->getProfiles());
+        });
+
+        $this->assertCount(1, $calls);
+        $this->assertSame('[]', file_get_contents($stackDir . '/profiles'));
+    }
+
+    public function testProfilesAreNotCachedWhenComposeCannotReadTheStack(): void
+    {
+        $stackDir = $this->tempRoot . '/broken';
+        mkdir($stackDir);
+        file_put_contents($stackDir . '/compose.yaml', "services:\n  web:\n    image: nginx\n");
+        $calls = $this->withDockerStandIn(1, function (): void {
+            $this->assertSame([], \StackInfo::fromProject($this->tempRoot, 'broken')->getProfiles());
+            \StackInfo::clearCache();
+            $this->assertSame([], \StackInfo::fromProject($this->tempRoot, 'broken')->getProfiles());
+        });
+
+        // Asked again, since the failure might be fixed by the next read.
+        $this->assertCount(2, $calls);
+        $this->assertFileDoesNotExist($stackDir . '/profiles');
+    }
+
+    public function testContainersByProjectGroupsEveryProjectsContainersByItsLabel(): void
+    {
+        // docker ps --format json prints one row per line; Labels is one comma-separated string.
+        $psOutput = implode("\n", [
+            json_encode(['Names' => 'web-app-1', 'Labels' => 'com.docker.compose.project=web,com.docker.compose.service=app']),
+            // The project label is not always first, and other compose labels start the same way.
+            json_encode(['Names' => 'web-db-1', 'Labels' => 'com.docker.compose.project.working_dir=/mnt/web,com.docker.compose.project=web,com.docker.compose.service=db']),
+            json_encode(['Names' => 'media-plex-1', 'Labels' => 'com.docker.compose.service=plex,com.docker.compose.project=media']),
+        ]) . "\n";
+        $byProject = [];
+        $calls = $this->withDockerStandIn(0, function () use (&$byProject): void {
+            $byProject = \StackInfo::containersByProject();
+        }, $psOutput);
+
+        $this->assertSame(['web', 'media'], array_keys($byProject));
+        $this->assertSame(['web-app-1', 'web-db-1'], array_column($byProject['web'], 'Names'));
+        $this->assertSame(['media-plex-1'], array_column($byProject['media'], 'Names'));
+        // Every compose project: the label filter has no value.
+        $this->assertSame(['ps -a --filter label=com.docker.compose.project --format json'], $calls);
+    }
+
+    public function testContainersByProjectAsksDockerForOneProjectOnly(): void
+    {
+        $psOutput = json_encode(['Names' => 'web-app-1', 'Labels' => 'com.docker.compose.project=web']) . "\n";
+        $byProject = [];
+        $calls = $this->withDockerStandIn(0, function () use (&$byProject): void {
+            $byProject = \StackInfo::containersByProject('web');
+        }, $psOutput);
+
+        $this->assertSame(['web'], array_keys($byProject));
+        $this->assertSame(['ps -a --filter label=com.docker.compose.project=web --format json'], $calls);
+    }
+
+    /**
+     * Run $work with a docker on PATH that prints $output and exits with $exitCode,
+     * and return the arguments of every call made to it, one line per call.
+     *
+     * @return string[]
+     */
+    private function withDockerStandIn(int $exitCode, callable $work, string $output = ''): array
+    {
+        $binDir = $this->tempRoot . '/bin';
+        $callsFile = $this->tempRoot . '/docker-calls';
+        $outputFile = $this->tempRoot . '/docker-output';
+        mkdir($binDir);
+        file_put_contents($outputFile, $output);
+        file_put_contents(
+            $binDir . '/docker',
+            "#!/bin/sh\necho \"\$*\" >> " . escapeshellarg($callsFile) . "\ncat " . escapeshellarg($outputFile) . "\nexit $exitCode\n"
+        );
+        chmod($binDir . '/docker', 0755);
+        $originalPath = (string) getenv('PATH');
+        putenv('PATH=' . $binDir . ':' . $originalPath);
+        try {
+            $work();
+        } finally {
+            putenv('PATH=' . $originalPath);
+        }
+        return is_file($callsFile) ? file($callsFile, FILE_IGNORE_NEW_LINES) : [];
+    }
+
     public function testGetProfilesEmptyForInvalidJson(): void
     {
         $stack = 'bad-json';