diff --git a/src/SPC/builder/BuilderBase.php b/src/SPC/builder/BuilderBase.php
index fdba936d7..3a6c39337 100644
--- a/src/SPC/builder/BuilderBase.php
+++ b/src/SPC/builder/BuilderBase.php
@@ -143,7 +143,7 @@ public function setLibsOnly(bool $status = true): void
      *
      * @internal
      */
-    public function proveExts(array $static_extensions, array $shared_extensions = [], bool $skip_check_deps = false, bool $skip_extract = false): void
+    public function proveExts(array $static_extensions, array $shared_extensions = [], bool $skip_check_deps = false, bool $skip_extract = false, int $build_target = BUILD_TARGET_NONE): void
     {
         // judge ext
         foreach ($static_extensions as $ext) {
@@ -171,7 +171,9 @@ public function proveExts(array $static_extensions, array $shared_extensions = [
             SourceManager::initSource(exts: [...$static_extensions, ...$shared_extensions]);
             $this->emitPatchPoint('after-exts-extract');
             // patch micro
-            SourcePatcher::patchMicro();
+            if (($build_target & BUILD_TARGET_MICRO) === BUILD_TARGET_MICRO) {
+                SourcePatcher::patchMicro();
+            }
         }
 
         foreach ([...$static_extensions, ...$shared_extensions] as $extension) {
diff --git a/src/SPC/builder/Extension.php b/src/SPC/builder/Extension.php
index 63dc31d04..6b56f4e4d 100644
--- a/src/SPC/builder/Extension.php
+++ b/src/SPC/builder/Extension.php
@@ -15,7 +15,6 @@
 use SPC\toolchain\ZigToolchain;
 use SPC\util\GlobalEnvManager;
 use SPC\util\SPCConfigUtil;
-use SPC\util\SPCTarget;
 
 class Extension
 {
@@ -187,14 +186,6 @@ public function patchBeforeWindowsConfigure(): bool
      */
     public function patchBeforeMake(): bool
     {
-        if (SPCTarget::getTargetOS() === 'Linux' && $this->isBuildShared() && ($objs = getenv('SPC_EXTRA_RUNTIME_OBJECTS'))) {
-            FileSystem::replaceFileRegex(
-                SOURCE_PATH . '/php-src/Makefile',
-                "/^(shared_objects_{$this->getName()}\\s*=.*)$/m",
-                "$1 {$objs}",
-            );
-            return true;
-        }
         return false;
     }
 
@@ -244,13 +235,6 @@ public function patchBeforeSharedMake(): bool
             );
         }
 
-        if ($objs = getenv('SPC_EXTRA_RUNTIME_OBJECTS')) {
-            FileSystem::replaceFileRegex(
-                $this->source_dir . '/Makefile',
-                "/^(shared_objects_{$this->getName()}\\s*=.*)$/m",
-                "$1 {$objs}",
-            );
-        }
         return true;
     }
 
diff --git a/src/SPC/builder/linux/LinuxBuilder.php b/src/SPC/builder/linux/LinuxBuilder.php
index ed26d64f3..74702b1f3 100644
--- a/src/SPC/builder/linux/LinuxBuilder.php
+++ b/src/SPC/builder/linux/LinuxBuilder.php
@@ -14,6 +14,7 @@
 use SPC\toolchain\ToolchainManager;
 use SPC\toolchain\ZigToolchain;
 use SPC\util\GlobalEnvManager;
+use SPC\util\PgoManager;
 use SPC\util\SPCConfigUtil;
 use SPC\util\SPCTarget;
 
@@ -22,6 +23,8 @@ class LinuxBuilder extends UnixBuilderBase
     /** @var bool Micro patch phar flag */
     private bool $phar_patched = false;
 
+    private ?PgoManager $pgo = null;
+
     public function __construct(array $options = [])
     {
         $this->options = $options;
@@ -48,6 +51,8 @@ public function __construct(array $options = [])
      */
     public function buildPHP(int $build_target = BUILD_TARGET_NONE): void
     {
+        $this->pgo = PgoManager::fromBuilder($this, $build_target);
+
         $cflags = $this->arch_c_flags;
         f_putenv('CFLAGS=' . $cflags);
 
@@ -129,35 +134,40 @@ public function buildPHP(int $build_target = BUILD_TARGET_NONE): void
 
         $this->emitPatchPoint('before-php-make');
         SourcePatcher::patchBeforeMake($this);
+        PgoManager::patchBeforeMake($this);
 
         $this->cleanMake();
 
-        if ($enableCli) {
-            logger()->info('building cli');
-            $this->buildCli();
-        }
-        if ($enableFpm) {
-            logger()->info('building fpm');
-            $this->buildFpm();
-        }
-        if ($enableCgi) {
-            logger()->info('building cgi');
-            $this->buildCgi();
-        }
-        if ($enableMicro) {
-            logger()->info('building micro');
-            $this->buildMicro();
-        }
-        if ($enableEmbed) {
-            logger()->info('building embed');
-            if ($enableMicro) {
-                FileSystem::replaceFileStr(SOURCE_PATH . '/php-src/Makefile', 'OVERALL_TARGET =', 'OVERALL_TARGET = libphp.la');
+        $pgo = $this->pgo;
+        $needsClean = false;
+        $sapiBuilds = [
+            ['cli', $enableCli, true, fn () => $this->buildCli()],
+            ['fpm', $enableFpm, true, fn () => $this->buildFpm()],
+            ['cgi', $enableCgi, true, fn () => $this->buildCgi()],
+            ['micro', $enableMicro, true, fn () => $this->buildMicro()],
+            ['embed', $enableEmbed, true, function () use ($enableMicro): void {
+                if ($enableMicro) {
+                    FileSystem::replaceFileStr(SOURCE_PATH . '/php-src/Makefile', 'OVERALL_TARGET =', 'OVERALL_TARGET = libphp.la');
+                }
+                $this->buildEmbed();
+            }],
+            // frankenphp doesn't rebuild php-src; xcaddy links against the deployed libphp.so
+            ['frankenphp', $enableFrankenphp, false, fn () => $this->buildFrankenphp()],
+        ];
+
+        foreach ($sapiBuilds as [$sapi, $enabled, $rebuildsPhpSrc, $build]) {
+            if (!$enabled) {
+                continue;
             }
-            $this->buildEmbed();
-        }
-        if ($enableFrankenphp) {
-            logger()->info('building frankenphp');
-            $this->buildFrankenphp();
+            if ($pgo) {
+                if ($needsClean && $rebuildsPhpSrc) {
+                    $this->cleanMake();
+                }
+                $pgo->applyForSapi($sapi);
+                $needsClean = $needsClean || $rebuildsPhpSrc;
+            }
+            logger()->info('building ' . $sapi);
+            $build();
         }
         $shared_extensions = array_map('trim', array_filter(explode(',', $this->getOption('build-shared'))));
         if (!empty($shared_extensions)) {
@@ -327,11 +337,18 @@ private function getMakeExtraVars(): array
         $config = (new SPCConfigUtil($this, ['libs_only_deps' => true, 'absolute_libs' => true]))->config($this->ext_list, $this->lib_list, $this->getOption('with-suggested-exts'), $this->getOption('with-suggested-libs'));
         $static = SPCTarget::isStatic() ? '-all-static' : '';
         $lib = BUILD_LIB_PATH;
+        $extra_ldflags = (string) getenv('SPC_CMD_VAR_PHP_MAKE_EXTRA_LDFLAGS');
+        if (getenv('SPC_CMD_VAR_PHP_EMBED_TYPE') === 'shared'
+            && !str_contains($extra_ldflags, '-avoid-version')
+            && !preg_match('/-release\s+\S+/', $extra_ldflags)) {
+            $extra_ldflags = trim($extra_ldflags . ' -avoid-version -module');
+        }
+        $extra_ldflags_program = trim("-L{$lib} {$static} -pie " . getenv('SPC_CMD_VAR_PHP_MAKE_EXTRA_LDFLAGS_PROGRAM'));
         return array_filter([
             'EXTRA_CFLAGS' => getenv('SPC_CMD_VAR_PHP_MAKE_EXTRA_CFLAGS'),
             'EXTRA_LIBS' => $config['libs'],
-            'EXTRA_LDFLAGS' => getenv('SPC_CMD_VAR_PHP_MAKE_EXTRA_LDFLAGS'),
-            'EXTRA_LDFLAGS_PROGRAM' => "-L{$lib} {$static} -pie",
+            'EXTRA_LDFLAGS' => $extra_ldflags,
+            'EXTRA_LDFLAGS_PROGRAM' => $extra_ldflags_program,
         ]);
     }
 
diff --git a/src/SPC/builder/linux/library/icu.php b/src/SPC/builder/linux/library/icu.php
index 7b8bcf8e9..3a41cb135 100644
--- a/src/SPC/builder/linux/library/icu.php
+++ b/src/SPC/builder/linux/library/icu.php
@@ -15,9 +15,11 @@ class icu extends LinuxLibraryBase
 
     protected function build(): void
     {
+        $userCxxFlags = trim((string) getenv('SPC_DEFAULT_CXX_FLAGS'));
+        $userLdFlags = trim((string) getenv('SPC_DEFAULT_LD_FLAGS'));
         $cppflags = 'CPPFLAGS="-DU_CHARSET_IS_UTF8=1  -DU_USING_ICU_NAMESPACE=1 -DU_STATIC_IMPLEMENTATION=1 -DPIC -fPIC"';
-        $cxxflags = 'CXXFLAGS="-std=c++17 -DPIC -fPIC -fno-ident"';
-        $ldflags = SPCTarget::isStatic() ? 'LDFLAGS="-static"' : '';
+        $cxxflags = "CXXFLAGS=\"-std=c++17 -DPIC -fPIC -fno-ident {$userCxxFlags}\"";
+        $ldflags = SPCTarget::isStatic() ? "LDFLAGS=\"-static {$userLdFlags}\"" : "LDFLAGS=\"{$userLdFlags}\"";
         shell()->cd($this->source_dir . '/source')->initializeEnv($this)
             ->exec(
                 "{$cppflags} {$cxxflags} {$ldflags} " .
diff --git a/src/SPC/builder/linux/library/openssl.php b/src/SPC/builder/linux/library/openssl.php
index bfc3936ba..c4efdfdf4 100644
--- a/src/SPC/builder/linux/library/openssl.php
+++ b/src/SPC/builder/linux/library/openssl.php
@@ -57,6 +57,11 @@ public function build(): void
         $openssl_dir ??= '/etc/ssl';
         $ex_lib = trim($ex_lib);
 
+        // OpenSSL's Configure ignores env CFLAGS for its target template; pass our flags as extra args after the target.
+        $userCFlags = trim((string) getenv('SPC_DEFAULT_C_FLAGS'));
+        $userLdFlags = trim((string) getenv('SPC_DEFAULT_LD_FLAGS'));
+        $userExtraFlags = trim($userCFlags . ' ' . $userLdFlags);
+
         shell()->cd($this->source_dir)->initializeEnv($this)
             ->exec(
                 "{$env} ./Configure no-shared {$extra} " .
@@ -67,7 +72,8 @@ public function build(): void
                 'enable-pie ' .
                 'no-legacy ' .
                 'no-tests ' .
-                "linux-{$arch}"
+                "linux-{$arch} " .
+                $userExtraFlags
             )
             ->exec('make clean')
             ->exec("make -j{$this->builder->concurrency} CNF_EX_LIBS=\"{$ex_lib}\"")
diff --git a/src/SPC/builder/unix/UnixBuilderBase.php b/src/SPC/builder/unix/UnixBuilderBase.php
index fd16656ce..37127f24a 100644
--- a/src/SPC/builder/unix/UnixBuilderBase.php
+++ b/src/SPC/builder/unix/UnixBuilderBase.php
@@ -145,7 +145,7 @@ public function deployBinary(string $src, string $dst, bool $executable = true):
             throw new SPCInternalException("Deploy failed. Cannot find file after copy: {$dst}");
         }
 
-        if (!$this->getOption('no-strip')) {
+        if (!$this->getOption('no-strip') && !$this->getOption('pgi') && !$this->getOption('cs-pgi')) {
             // extract debug info
             $this->extractDebugInfo($dst);
             // extra strip
@@ -450,10 +450,11 @@ protected function buildFrankenphp(): void
             $cflags .= ' -Wno-error=missing-profile';
             $libs .= ' -lgcov';
         }
+        $extraLdProgram = (string) getenv('SPC_CMD_VAR_PHP_MAKE_EXTRA_LDFLAGS_PROGRAM');
         $env = [...[
             'CGO_ENABLED' => '1',
             'CGO_CFLAGS' => clean_spaces($cflags),
-            'CGO_LDFLAGS' => "{$this->arch_ld_flags} {$staticFlags} {$config['ldflags']} {$libs}",
+            'CGO_LDFLAGS' => trim("{$this->arch_ld_flags} {$staticFlags} {$config['ldflags']} {$libs} {$extraLdProgram}"),
             'XCADDY_GO_BUILD_FLAGS' => '-buildmode=pie ' .
                 '-ldflags \"-linkmode=external ' . $extLdFlags . ' ' .
                 '-X \'github.com/caddyserver/caddy/v2/modules/caddyhttp.ServerHeader=FrankenPHP Caddy\' ' .
diff --git a/src/SPC/builder/unix/library/bzip2.php b/src/SPC/builder/unix/library/bzip2.php
index 32d87270c..4ed3b46a2 100644
--- a/src/SPC/builder/unix/library/bzip2.php
+++ b/src/SPC/builder/unix/library/bzip2.php
@@ -10,7 +10,8 @@ trait bzip2
 {
     public function patchBeforeBuild(): bool
     {
-        FileSystem::replaceFileStr($this->source_dir . '/Makefile', 'CFLAGS=-Wall', 'CFLAGS=-fPIC -Wall');
+        $extra = trim((string) getenv('SPC_DEFAULT_C_FLAGS'));
+        FileSystem::replaceFileStr($this->source_dir . '/Makefile', 'CFLAGS=-Wall', "CFLAGS=-Wall {$extra}");
         return true;
     }
 
diff --git a/src/SPC/command/BuildPHPCommand.php b/src/SPC/command/BuildPHPCommand.php
index ad884b3ba..58be9087e 100644
--- a/src/SPC/command/BuildPHPCommand.php
+++ b/src/SPC/command/BuildPHPCommand.php
@@ -49,6 +49,9 @@ public function configure(): void
         $this->addOption('with-micro-logo', null, InputOption::VALUE_REQUIRED, 'Use custom .ico for micro.sfx (windows only)');
         $this->addOption('enable-micro-win32', null, null, 'Enable win32 mode for phpmicro (Windows only)');
         $this->addOption('with-frankenphp-app', null, InputOption::VALUE_REQUIRED, 'Path to a folder to be embedded in FrankenPHP');
+        $this->addOption('pgi', null, null, 'Build instrumented binaries (-fprofile-generate). Run them to collect .profraw files, then re-run with --pgo.');
+        $this->addOption('cs-pgi', null, null, 'Build cs-instrumented binaries (-fprofile-use=<existing.profdata> -fcs-profile-generate). Requires a prior --pgi+--pgo cycle.');
+        $this->addOption('pgo', null, null, 'Build optimised binaries (-fprofile-use) from .profraw collected by a previous --pgi run.');
     }
 
     public function handle(): int
@@ -177,7 +180,7 @@ public function handle(): int
         // compile libraries
         $builder->proveLibs($libraries);
         // check extensions
-        $builder->proveExts($static_extensions, $shared_extensions);
+        $builder->proveExts($static_extensions, $shared_extensions, build_target: $rule);
         // validate libs and extensions
         $builder->validateLibsAndExts();
 
@@ -210,9 +213,8 @@ public function handle(): int
 
         // clean old modules that may conflict with the new php build
         FileSystem::removeDir(BUILD_MODULES_PATH);
-        // start to build
-        $builder->buildPHP($rule);
 
+        $builder->buildPHP($rule);
         $builder->testPHP($rule);
 
         // compile stopwatch :P
diff --git a/src/SPC/command/CraftCommand.php b/src/SPC/command/CraftCommand.php
index 6c40133d1..7a4765acf 100644
--- a/src/SPC/command/CraftCommand.php
+++ b/src/SPC/command/CraftCommand.php
@@ -19,6 +19,9 @@ class CraftCommand extends BuildCommand
     public function configure(): void
     {
         $this->addArgument('craft', null, 'Path to craft.yml file', WORKING_DIR . '/craft.yml');
+        $this->addOption('pgi', null, null, 'Forward --pgi to the inner build (instrumented binaries).');
+        $this->addOption('cs-pgi', null, null, 'Forward --cs-pgi to the inner build (cs-instrumented binaries).');
+        $this->addOption('pgo', null, null, 'Forward --pgo to the inner build (use collected profile data).');
     }
 
     public function handle(): int
@@ -105,6 +108,11 @@ public function handle(): int
         if ($craft['craft-options']['build']) {
             $args = [$static_extensions, "--with-libs={$libs}", "--build-shared={$shared_extensions}", ...array_map(fn ($x) => "--build-{$x}", $craft['sapi'])];
             $this->optionsToArguments($craft['build-options'], $args);
+            foreach (['pgi', 'cs-pgi', 'pgo'] as $pgoFlag) {
+                if ($this->getOption($pgoFlag)) {
+                    $args[] = "--{$pgoFlag}";
+                }
+            }
             $retcode = $this->runCommand('build', ...$args);
             if ($retcode !== 0) {
                 $this->output->writeln('<error>craft build failed</error>');
diff --git a/src/SPC/store/pkg/Zig.php b/src/SPC/store/pkg/Zig.php
index c2a81c0da..ffe46657c 100644
--- a/src/SPC/store/pkg/Zig.php
+++ b/src/SPC/store/pkg/Zig.php
@@ -116,18 +116,17 @@ public function extract(string $name): void
                 break;
             }
         }
-        if ($all_exist) {
-            return;
-        }
-
-        $lock = json_decode(FileSystem::readFile(LockFile::LOCK_FILE), true);
-        $source_type = $lock[$name]['source_type'];
-        $filename = DOWNLOAD_PATH . '/' . ($lock[$name]['filename'] ?? $lock[$name]['dirname']);
-        $extract = "{$pkgroot}/zig";
+        if (!$all_exist) {
+            $lock = json_decode(FileSystem::readFile(LockFile::LOCK_FILE), true);
+            $source_type = $lock[$name]['source_type'];
+            $filename = DOWNLOAD_PATH . '/' . ($lock[$name]['filename'] ?? $lock[$name]['dirname']);
+            $extract = "{$pkgroot}/zig";
 
-        FileSystem::extractPackage($name, $source_type, $filename, $extract);
+            FileSystem::extractPackage($name, $source_type, $filename, $extract);
 
-        $this->createZigCcScript($zig_bin_dir);
+            $this->createZigCcScript($zig_bin_dir);
+        }
+        $this->buildClangRuntimeBits($zig_bin_dir);
     }
 
     public static function getEnvironment(): array
@@ -140,6 +139,144 @@ public static function getPath(): ?string
         return PKG_ROOT_PATH . '/zig';
     }
 
+    /**
+     * Build the bits of clang's runtime that zig 0.16 doesn't ship: the
+     * profile runtime (so -fprofile-generate actually emits .profraw) and
+     * crtbegin.o/crtend.o (so shared libraries get __dso_handle and the
+     * __cxa_finalize atexit hook).
+     *
+     * Build from 2mb compiler-rt-<llvm>.src tar
+     * to avoid downloading 2gb full prebuilt tarball.
+     */
+    private function buildClangRuntimeBits(string $zig_bin_dir): void
+    {
+        if (PHP_OS_FAMILY !== 'Linux') {
+            return;
+        }
+        $libDir = "{$zig_bin_dir}/lib";
+        $profileLib = "{$libDir}/libclang_rt.profile.a";
+        $crtBegin = "{$libDir}/clang_rt.crtbegin.o";
+        $crtEnd = "{$libDir}/clang_rt.crtend.o";
+        if (file_exists($profileLib) && file_exists($crtBegin) && file_exists($crtEnd)) {
+            return;
+        }
+
+        $zig = "{$zig_bin_dir}/zig";
+        $verLine = trim((string) shell_exec(escapeshellarg($zig) . ' cc --version 2>/dev/null'));
+        if (!preg_match('/clang version (\d+\.\d+\.\d+)/', $verLine, $m)) {
+            logger()->warning('[zig] could not detect bundled clang version; skipping runtime bit build (--pgo + shared libs without __dso_handle)');
+            return;
+        }
+        $llvmVersion = $m[1];
+        logger()->info("Building clang runtime bits for LLVM {$llvmVersion} (zig's bundled clang)");
+
+        $srcRoot = $this->fetchCompilerRtSource($llvmVersion);
+        if ($srcRoot === null) {
+            return;
+        }
+
+        f_mkdir($libDir, recursive: true);
+        if (!file_exists($profileLib)) {
+            $this->buildProfileRuntime($zig, $srcRoot, $profileLib);
+        }
+        if (!file_exists($crtBegin) || !file_exists($crtEnd)) {
+            $this->buildCrtObjects($zig, $srcRoot, $crtBegin, $crtEnd);
+        }
+        FileSystem::removeDir($srcRoot);
+    }
+
+    private function fetchCompilerRtSource(string $llvmVersion): ?string
+    {
+        $pkgName = "compiler-rt-{$llvmVersion}";
+        $tarball = "compiler-rt-{$llvmVersion}.src.tar.xz";
+        $url = "https://github.com/llvm/llvm-project/releases/download/llvmorg-{$llvmVersion}/{$tarball}";
+        try {
+            Downloader::downloadPackage($pkgName, [
+                'type' => 'url',
+                'url' => $url,
+                'filename' => $tarball,
+            ]);
+        } catch (\Throwable $e) {
+            logger()->warning("[zig] failed to download {$tarball}: {$e->getMessage()}");
+            return null;
+        }
+        $srcRoot = PKG_ROOT_PATH . "/compiler-rt-src-{$llvmVersion}";
+        FileSystem::removeDir($srcRoot);
+        FileSystem::extractPackage($pkgName, SPC_SOURCE_ARCHIVE, DOWNLOAD_PATH . '/' . $tarball, $srcRoot);
+        return $srcRoot;
+    }
+
+    private function buildProfileRuntime(string $zig, string $srcRoot, string $libPath): void
+    {
+        $profileSrc = "{$srcRoot}/lib/profile";
+        $profileInc = "{$srcRoot}/include";
+        if (!is_dir($profileSrc)) {
+            logger()->warning("[zig] profile src dir missing at {$profileSrc} — --pgo will not work");
+            return;
+        }
+        $sources = array_merge(
+            glob("{$profileSrc}/*.c") ?: [],
+            glob("{$profileSrc}/*.cpp") ?: []
+        );
+        $skip = ['/PlatformAIX', '/PlatformDarwin', '/PlatformFuchsia', '/PlatformOther', '/PlatformWindows', '/WindowsMMap'];
+        $sources = array_filter($sources, function ($f) use ($skip) {
+            foreach ($skip as $s) {
+                if (str_contains($f, $s)) {
+                    return false;
+                }
+            }
+            return true;
+        });
+
+        $objDir = "{$srcRoot}/obj-profile";
+        f_mkdir($objDir, recursive: true);
+        $cflags = '-c -O2 -fPIC -fvisibility=hidden ' .
+            '-I' . escapeshellarg($profileInc) . ' ' .
+            '-DCOMPILER_RT_HAS_ATOMICS=1 -DCOMPILER_RT_HAS_FCNTL_LCK=1 -DCOMPILER_RT_HAS_UNAME=1';
+        $objs = [];
+        foreach ($sources as $src) {
+            $obj = $objDir . '/' . pathinfo($src, PATHINFO_FILENAME) . '.o';
+            $cmd = escapeshellarg($zig) . ' cc ' . $cflags . ' -o ' . escapeshellarg($obj) . ' ' . escapeshellarg($src) . ' 2>&1';
+            if (!$this->runZigCmd($cmd, $obj, "failed to compile {$src}")) {
+                return;
+            }
+            $objs[] = $obj;
+        }
+        $arCmd = escapeshellarg($zig) . ' ar rcs ' . escapeshellarg($libPath) . ' ' . implode(' ', array_map('escapeshellarg', $objs)) . ' 2>&1';
+        if (!$this->runZigCmd($arCmd, $libPath, 'zig ar failed')) {
+            return;
+        }
+        logger()->info('[zig] libclang_rt.profile.a installed (' . filesize($libPath) . ' bytes)');
+    }
+
+    private function buildCrtObjects(string $zig, string $srcRoot, string $crtBegin, string $crtEnd): void
+    {
+        $beginSrc = "{$srcRoot}/lib/builtins/crtbegin.c";
+        $endSrc = "{$srcRoot}/lib/builtins/crtend.c";
+        if (!is_file($beginSrc) || !is_file($endSrc)) {
+            logger()->error("[zig] crtbegin/crtend source missing under {$srcRoot}/lib/builtins — shared libs will lack __dso_handle");
+            return;
+        }
+        $cflags = '-c -O2 -fPIC -fvisibility=hidden -DCRT_HAS_INITFINI_ARRAY';
+        foreach ([[$beginSrc, $crtBegin], [$endSrc, $crtEnd]] as [$src, $dst]) {
+            $cmd = escapeshellarg($zig) . ' cc ' . $cflags . ' -o ' . escapeshellarg($dst) . ' ' . escapeshellarg($src) . ' 2>&1';
+            if (!$this->runZigCmd($cmd, $dst, "failed to compile {$src}")) {
+                return;
+            }
+        }
+        logger()->info('[zig] clang_rt.crtbegin.o + clang_rt.crtend.o installed (' . filesize($crtBegin) . ' + ' . filesize($crtEnd) . ' bytes)');
+    }
+
+    private function runZigCmd(string $cmd, string $dst, string $errPrefix): bool
+    {
+        exec($cmd, $out, $rc);
+        if ($rc !== 0 || !is_file($dst)) {
+            logger()->warning("[zig] {$errPrefix}: " . implode("\n", $out));
+            return false;
+        }
+        return true;
+    }
+
     private function createZigCcScript(string $bin_dir): void
     {
         $script_path = __DIR__ . '/../scripts/zig-cc.sh';
diff --git a/src/SPC/store/scripts/zig-cc.sh b/src/SPC/store/scripts/zig-cc.sh
index 6b340bc1d..586c828c3 100644
--- a/src/SPC/store/scripts/zig-cc.sh
+++ b/src/SPC/store/scripts/zig-cc.sh
@@ -39,6 +39,24 @@ while [[ $# -gt 0 ]]; do
     esac
 done
 
+IS_LINK=1
+NEED_PROFILE_RT=0 # https://codeberg.org/ziglang/zig/issues/32066
+NEED_CRT=0 # https://codeberg.org/ziglang/zig/issues/32064
+for _a in "${PARSED_ARGS[@]}"; do
+    case "$_a" in
+        -c|-S|-E|-M|-MM) IS_LINK=0 ;;
+        -fprofile-generate*|-fprofile-instr-generate*|-fcs-profile-generate*) NEED_PROFILE_RT=1 ;;
+        -shared) NEED_CRT=1 ;;
+    esac
+done
+[[ "$SPC_COMPILER_EXTRA" == *-fprofile-generate* || "$SPC_COMPILER_EXTRA" == *-fcs-profile-generate* ]] && NEED_PROFILE_RT=1
+if [[ $IS_LINK -eq 1 && $NEED_PROFILE_RT -eq 1 && -f "$SCRIPT_DIR/lib/libclang_rt.profile.a" ]]; then
+    PARSED_ARGS+=("$SCRIPT_DIR/lib/libclang_rt.profile.a" "-Wl,-u,__llvm_profile_runtime")
+fi
+if [[ $IS_LINK -eq 1 && $NEED_CRT -eq 1 && -f "$SCRIPT_DIR/lib/clang_rt.crtbegin.o" && -f "$SCRIPT_DIR/lib/clang_rt.crtend.o" ]]; then
+    PARSED_ARGS+=("$SCRIPT_DIR/lib/clang_rt.crtbegin.o" "$SCRIPT_DIR/lib/clang_rt.crtend.o")
+fi
+
 [[ -n "$SPC_TARGET" ]] && TARGET="-target $SPC_TARGET" || TARGET=""
 
 if [[ "$SPC_TARGET" =~ \.[0-9]+\.[0-9]+ ]]; then
diff --git a/src/SPC/toolchain/ZigToolchain.php b/src/SPC/toolchain/ZigToolchain.php
index 1b7cc70dc..8d121db53 100644
--- a/src/SPC/toolchain/ZigToolchain.php
+++ b/src/SPC/toolchain/ZigToolchain.php
@@ -17,27 +17,6 @@ public function initEnv(): void
         GlobalEnvManager::putenv('SPC_LINUX_DEFAULT_CXX=zig-c++');
         GlobalEnvManager::putenv('SPC_LINUX_DEFAULT_AR=zig-ar');
         GlobalEnvManager::putenv('SPC_LINUX_DEFAULT_LD=zig-ld.lld');
-
-        // Generate additional objects needed for zig toolchain
-        $paths = ['/usr/lib/gcc', '/usr/local/lib/gcc'];
-        $objects = ['crtbeginS.o', 'crtendS.o'];
-        $found = [];
-
-        foreach ($objects as $obj) {
-            $located = null;
-            foreach ($paths as $base) {
-                $output = shell_exec("find {$base} -name {$obj} 2>/dev/null | grep -v '/32/' | head -n 1");
-                $line = trim((string) $output);
-                if ($line !== '') {
-                    $located = $line;
-                    break;
-                }
-            }
-            if ($located) {
-                $found[] = $located;
-            }
-        }
-        GlobalEnvManager::putenv('SPC_EXTRA_RUNTIME_OBJECTS=' . implode(' ', $found));
     }
 
     public function afterInit(): void
diff --git a/src/SPC/util/PgoManager.php b/src/SPC/util/PgoManager.php
new file mode 100644
index 000000000..d1564c886
--- /dev/null
+++ b/src/SPC/util/PgoManager.php
@@ -0,0 +1,313 @@
+<?php
+
+declare(strict_types=1);
+
+namespace SPC\util;
+
+use SPC\builder\BuilderBase;
+use SPC\exception\WrongUsageException;
+use SPC\store\FileSystem;
+use SPC\store\SourcePatcher;
+
+/**
+ * Two-call PGO driver: --pgi instruments, --pgo uses the .profraw the user
+ * collected by running the instrumented binaries.
+ */
+class PgoManager
+{
+    public const MODE_INSTRUMENT = 'instrument';
+
+    public const MODE_CS_INSTRUMENT = 'cs-instrument';
+
+    public const MODE_USE = 'use';
+
+    private const TRAINABLE = [
+        'cli' => BUILD_TARGET_CLI,
+        'micro' => BUILD_TARGET_MICRO,
+        'cgi' => BUILD_TARGET_CGI,
+        'fpm' => BUILD_TARGET_FPM,
+        'embed' => BUILD_TARGET_EMBED,
+        'frankenphp' => BUILD_TARGET_FRANKENPHP,
+    ];
+
+    /**
+     * Applied during --pgi only: explicit __llvm_profile_write_file() at
+     * shutdown, since Go/frankenphp exits skip libc atexit.
+     */
+    private const SHUTDOWN_PATCHES = [
+        'php-src' => 'spc_pgo_flush_php_main.patch',
+        'frankenphp' => 'spc_pgo_flush_frankenphp.patch',
+    ];
+
+    private string $profileRoot;
+
+    private string $mode;
+
+    private function __construct()
+    {
+        $this->profileRoot = BUILD_ROOT_PATH . '/pgo-data';
+    }
+
+    /** Build a PgoManager for the active --pgi/--cs-pgi/--pgo option, or null if none set. */
+    public static function fromBuilder(BuilderBase $builder, int $rule): ?self
+    {
+        $modes = array_filter(['pgi', 'cs-pgi', 'pgo'], fn ($m) => (bool) $builder->getOption($m));
+        if (count($modes) > 1) {
+            throw new WrongUsageException('--pgi, --cs-pgi, and --pgo are mutually exclusive');
+        }
+        $mode = array_values($modes)[0] ?? null;
+        if ($mode === null) {
+            return null;
+        }
+        $instance = new self();
+        match ($mode) {
+            'pgi' => $instance->setupInstrument($rule),
+            'cs-pgi' => $instance->setupCsInstrument($rule),
+            'pgo' => $instance->setupUse($rule),
+        };
+        return $instance;
+    }
+
+    /** Patches php-src/libtool to passthrough -fcs-profile-* flags (otherwise dropped during shared lib link). */
+    public static function patchBeforeMake(BuilderBase $builder): void
+    {
+        if (!$builder->getOption('cs-pgi')) {
+            return;
+        }
+        $libtool = SOURCE_PATH . '/php-src/libtool';
+        if (!is_file($libtool)) {
+            return;
+        }
+        $contents = file_get_contents($libtool);
+        if (str_contains($contents, '-fcs-profile-*')) {
+            return;
+        }
+        $patched = str_replace('-fprofile-*|-F*', '-fprofile-*|-fcs-profile-*|-F*', $contents);
+        if ($patched === $contents) {
+            logger()->warning('pgo --cs-pgi: could not patch libtool for -fcs-profile-* passthrough');
+            return;
+        }
+        file_put_contents($libtool, $patched);
+        logger()->info('pgo --cs-pgi: patched libtool for -fcs-profile-* passthrough');
+    }
+
+    public function applyForSapi(string $sapi): void
+    {
+        $sapi = $this->resolveSapi($sapi);
+        if (!isset(self::TRAINABLE[$sapi])) {
+            return;
+        }
+        if ($this->mode === self::MODE_USE && !is_file($this->profDataFile($sapi))) {
+            logger()->warning("pgo --pgo: no profdata for {$sapi}, building without PGO for this sapi");
+            $this->setFlag('SPC_CMD_VAR_PHP_MAKE_EXTRA_CFLAGS', '');
+            $this->setFlag('SPC_CMD_VAR_PHP_MAKE_EXTRA_LDFLAGS_PROGRAM', '');
+            return;
+        }
+        $flags = match ($this->mode) {
+            self::MODE_INSTRUMENT => '-fprofile-generate=' . $this->rawDir($sapi)
+                . ' -fprofile-update=atomic',
+            self::MODE_CS_INSTRUMENT => '-fprofile-use=' . $this->profDataFile($sapi)
+                . ' -fcs-profile-generate=' . $this->csRawDir($sapi)
+                . ' -fprofile-update=atomic'
+                . ' -Wno-error=profile-instr-unprofiled'
+                . ' -Wno-error=profile-instr-out-of-date'
+                . ' -Wno-backend-plugin',
+            default => '-fprofile-use=' . $this->profDataFile($sapi)
+                . ' -Wno-error=profile-instr-unprofiled'
+                . ' -Wno-error=profile-instr-out-of-date'
+                . ' -Wno-backend-plugin',
+        };
+        $this->setFlag('SPC_CMD_VAR_PHP_MAKE_EXTRA_CFLAGS', $flags);
+        $this->setFlag('SPC_CMD_VAR_PHP_MAKE_EXTRA_LDFLAGS_PROGRAM', $this->ldOnly($flags, $sapi));
+        logger()->info("pgo {$this->mode} ({$sapi})");
+    }
+
+    /** Setup --pgi: build with -fprofile-generate=<sapi-dir>. */
+    private function setupInstrument(int $rule): void
+    {
+        $this->validateRule($rule);
+        FileSystem::removeDir($this->profileRoot);
+        f_mkdir($this->profileRoot, recursive: true);
+        foreach ($this->trainableIn($rule) as $sapi) {
+            f_mkdir($this->rawDir($sapi), recursive: true);
+        }
+        $this->mode = self::MODE_INSTRUMENT;
+        $this->applyShutdownPatches();
+        $this->applyForSapi($this->trainableIn($rule)[0]);
+        logger()->info('pgo --pgi: instrumented build, profraw will land under ' . $this->profileRoot . '/<sapi>/');
+    }
+
+    /** Setup --cs-pgi: build with -fprofile-use=<sapi.profdata> -fcs-profile-generate=<cs-dir>. Requires existing .profdata. */
+    private function setupCsInstrument(int $rule): void
+    {
+        $this->validateRule($rule);
+        foreach ($this->trainableIn($rule) as $sapi) {
+            if (!is_file($this->profDataFile($sapi))) {
+                throw new WrongUsageException("--cs-pgi: missing {$sapi}.profdata; run --pgi + --pgo first");
+            }
+            f_mkdir($this->csRawDir($sapi), recursive: true);
+        }
+        $this->mode = self::MODE_CS_INSTRUMENT;
+        $this->applyShutdownPatches();
+        $this->applyForSapi($this->trainableIn($rule)[0]);
+        logger()->info('pgo --cs-pgi: cs-instrumented build, cs-profraw under ' . $this->profileRoot . '/cs-<sapi>/');
+    }
+
+    /** Setup --pgo: merge collected .profraw, then build with -fprofile-use=<sapi.profdata>. */
+    private function setupUse(int $rule): void
+    {
+        $this->validateRule($rule);
+        if (trim((string) shell_exec('command -v llvm-profdata 2>/dev/null')) === '') {
+            throw new WrongUsageException('--pgo: llvm-profdata not on PATH');
+        }
+        foreach ($this->trainableIn($rule) as $sapi) {
+            $this->mergeSapi($sapi);
+        }
+        $this->mode = self::MODE_USE;
+        $this->applyForSapi($this->trainableIn($rule)[0]);
+    }
+
+    /**
+     * Static-embed mode links libphp.a into frankenphp; both end up in one
+     * binary so must share one profdata. Shared-embed mode keeps libphp.so
+     * standalone — embed and frankenphp keep separate profiles.
+     */
+    private function resolveSapi(string $sapi): string
+    {
+        if ($sapi === 'embed' && getenv('SPC_CMD_VAR_PHP_EMBED_TYPE') === 'static') {
+            return 'frankenphp';
+        }
+        return $sapi;
+    }
+
+    private function validateRule(int $rule): void
+    {
+        if (empty($this->trainableIn($rule))) {
+            throw new WrongUsageException('--pgi/--pgo: no trainable SAPI in build rule (need one of: ' . implode(', ', array_keys(self::TRAINABLE)) . ')');
+        }
+    }
+
+    private function mergeSapi(string $sapi): void
+    {
+        $raws = glob($this->rawDir($sapi) . '/*.profraw') ?: [];
+        $csRaws = glob($this->csRawDir($sapi) . '/*.profraw') ?: [];
+        if (empty($raws) && empty($csRaws)) {
+            if ($sapi === 'frankenphp') {
+                logger()->warning('pgo --pgo: no .profraw for frankenphp (cgo glue PGO will be skipped); run --pgi, exercise frankenphp longer, then re-run --pgo to include it');
+                return;
+            }
+            throw new WrongUsageException("--pgo: no .profraw for {$sapi}; run --pgi, exercise the binary, then re-run --pgo");
+        }
+        $out = $this->profDataFile($sapi);
+        $inputs = array_merge($raws, $csRaws);
+        $argv = implode(' ', array_map('escapeshellarg', $inputs));
+        shell()->exec('llvm-profdata merge --failure-mode=warn -output=' . escapeshellarg($out) . ' ' . $argv);
+        if (!is_file($out) || filesize($out) === 0) {
+            throw new WrongUsageException("--pgo: empty merge output for {$sapi}");
+        }
+        logger()->info("pgo merged {$sapi}: " . filesize($out) . ' bytes');
+    }
+
+    private function rawDir(string $sapi): string
+    {
+        return $this->profileRoot . '/' . $sapi;
+    }
+
+    private function csRawDir(string $sapi): string
+    {
+        return $this->profileRoot . '/cs-' . $sapi;
+    }
+
+    private function profDataFile(string $sapi): string
+    {
+        return $this->profileRoot . '/' . $sapi . '.profdata';
+    }
+
+    /** @return list<string> */
+    private function trainableIn(int $rule): array
+    {
+        $out = [];
+        foreach (self::TRAINABLE as $sapi => $mask) {
+            if (($rule & $mask) !== $mask) {
+                continue;
+            }
+            $resolved = $this->resolveSapi($sapi);
+            if (!in_array($resolved, $out, true)) {
+                $out[] = $resolved;
+            }
+        }
+        return $out;
+    }
+
+    /** Strip the previous PGO flags from $var and append the new ones. */
+    private function setFlag(string $var, string $append): void
+    {
+        $cur = (string) getenv($var);
+        $cur = preg_replace('/\s*-f(cs-)?profile-(generate|use)=\S+/', '', $cur) ?? $cur;
+        $cur = preg_replace('/\s*-Wno-error=profile-instr-\S+/', '', $cur) ?? $cur;
+        $cur = preg_replace('/\s*-Wno-backend-plugin/', '', $cur) ?? $cur;
+        f_putenv($var . '=' . trim($cur . ' ' . $append));
+    }
+
+    /**
+     * Linker flags: cli wants -fprofile-use= at link too (LTO does its
+     * profile-driven inlining/reordering at link time). Strip -Wno-error
+     * flags (linker doesn't accept them).
+     */
+    private function ldOnly(string $flags, string $sapi = ''): string
+    {
+        $patterns = ['/\s*-Wno-error=\S+/', '/\s*-Wno-backend-plugin/'];
+        if ($sapi === 'frankenphp') {
+            $patterns[] = '/\s*-fprofile-use=\S+/';
+            $patterns[] = '/\s*-fcs-profile-generate=\S+/';
+        }
+        return trim(preg_replace($patterns, '', $flags) ?? $flags);
+    }
+
+    /** --pgi patch: inject __llvm_profile_write_file() flush handler to php and frankenphp sources. */
+    private function applyShutdownPatches(): void
+    {
+        $applied = [];
+        foreach (self::SHUTDOWN_PATCHES as $dir => $patch) {
+            $cwd = SOURCE_PATH . '/' . $dir;
+            if (!is_dir($cwd)) {
+                continue;
+            }
+            if (!SourcePatcher::patchFile($patch, $cwd)) {
+                throw new WrongUsageException("--pgi: patch {$patch} failed to apply in {$cwd}");
+            }
+            $applied[] = ['cwd' => $cwd, 'patch' => $patch];
+            logger()->info("pgo --pgi: applied {$patch}");
+        }
+        if ($applied === []) {
+            return;
+        }
+        register_shutdown_function(static function () use ($applied): void {
+            foreach ($applied as $entry) {
+                $cwd = $entry['cwd'];
+                $patch = $entry['patch'];
+                if (!is_dir($cwd)) {
+                    continue;
+                }
+                $patch_file = ROOT_DIR . "/src/globals/patch/{$patch}";
+                if (!is_file($patch_file)) {
+                    continue;
+                }
+                $args = ' -p1 -s -R -F0 ';
+                exec('cd ' . escapeshellarg($cwd) . ' && patch --dry-run' . $args
+                    . ' < ' . escapeshellarg($patch_file) . ' >/dev/null 2>&1', $_, $detect_status);
+                if ($detect_status !== 0) {
+                    logger()->info("pgo --pgi: {$patch} already clean, skipping revert");
+                    continue;
+                }
+                exec('cd ' . escapeshellarg($cwd) . ' && patch' . $args
+                    . ' < ' . escapeshellarg($patch_file), $out, $apply_status);
+                if ($apply_status === 0) {
+                    logger()->info("pgo --pgi: reverted {$patch}");
+                } else {
+                    logger()->warning("pgo --pgi: failed to revert {$patch} (status {$apply_status}): " . implode("\n", $out));
+                }
+            }
+        });
+    }
+}
diff --git a/src/globals/patch/spc_pgo_flush_frankenphp.patch b/src/globals/patch/spc_pgo_flush_frankenphp.patch
new file mode 100644
index 000000000..7c58fafff
--- /dev/null
+++ b/src/globals/patch/spc_pgo_flush_frankenphp.patch
@@ -0,0 +1,15 @@
+--- a/frankenphp.c
++++ b/frankenphp.c
+@@ -1254,6 +1254,12 @@
+
+   go_frankenphp_shutdown_main_thread();
+
++  /* spc-pgo: explicit profile flush so the cgo-instrumented frankenphp
++   * still writes .profraw on Go-runtime exit (which bypasses libc atexit).
++   * Weak symbol → no-op in non-PGO builds. */
++  { extern int __llvm_profile_write_file(void) __attribute__((weak));
++    if (__llvm_profile_write_file) __llvm_profile_write_file(); }
++
+   return NULL;
+ }
+
diff --git a/src/globals/patch/spc_pgo_flush_php_main.patch b/src/globals/patch/spc_pgo_flush_php_main.patch
new file mode 100644
index 000000000..6bf905bf0
--- /dev/null
+++ b/src/globals/patch/spc_pgo_flush_php_main.patch
@@ -0,0 +1,12 @@
+--- a/main/main.c
++++ b/main/main.c
+@@ -2563,6 +2563,9 @@
+ #endif
+
+ 	zend_observer_shutdown();
++
++	{ extern int __llvm_profile_write_file(void) __attribute__((weak));
++	  if (__llvm_profile_write_file) __llvm_profile_write_file(); }
+ }
+ /* }}} */
+