diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 44716ce..b65c130 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -8,35 +8,68 @@ on:
     branches: [master]
 
 jobs:
-  build-windows:
-    runs-on: windows-latest
+  build-linux:
+    runs-on: ubuntu-24.04
     steps:
       - uses: actions/checkout@v4
 
       - name: Install Zig
         uses: mlugg/setup-zig@v2
         with:
-          version: master # pin to a specific version once stable
+          version: master
+
+      - name: Install LLVM 18
+        run: sudo apt-get update && sudo apt-get install -y llvm-18-dev
+
+      - name: Build
+        run: zig build -Dstatic-llvm -Dllvm-prefix=/usr/lib/llvm-18
+
+      - name: Test
+        run: zig build test -Dstatic-llvm -Dllvm-prefix=/usr/lib/llvm-18 --summary all
+
+      - name: Package
+        run: tar czf sx-linux-x86_64.tar.gz -C zig-out/bin .
+
+      - name: Upload artifact
+        uses: actions/upload-artifact@v4
+        with:
+          name: sx-linux-x86_64
+          path: zig-out/bin/
+
+      - name: Release
+        if: startsWith(github.ref, 'refs/tags/v')
+        uses: softprops/action-gh-release@v2
+        with:
+          files: sx-linux-x86_64.tar.gz
+
+  build-windows:
+    runs-on: windows-latest
+    env:
+      LLVM_PREFIX: C:\LLVM\llvm-18.1.8-windows-amd64-msvc17-msvcrt
+    steps:
+      - uses: actions/checkout@v4
+
+      - name: Install Zig
+        uses: mlugg/setup-zig@v2
+        with:
+          version: master
 
       - name: Download LLVM 18
         run: |
           Invoke-WebRequest -Uri "https://github.com/vovkos/llvm-package-windows/releases/download/llvm-18.1.8/llvm-18.1.8-windows-amd64-msvc17-msvcrt.7z" -OutFile "$env:TEMP\llvm.7z"
           7z x "$env:TEMP\llvm.7z" -oC:\LLVM
 
-      - name: Verify LLVM
-        run: |
-          Get-ChildItem C:\LLVM -Recurse -Name "*.lib" | Select-Object -First 5
-          Get-ChildItem C:\LLVM -Directory
-
       - name: Setup MSVC
         uses: ilammy/msvc-dev-cmd@v1
 
       - name: Build
-        run: zig build -Dstatic-llvm -Dllvm-prefix="C:\LLVM\llvm-18.1.8-windows-amd64-msvc17-msvcrt" -Dtarget=x86_64-windows-msvc
+        shell: cmd
+        run: zig build -Dstatic-llvm -Dllvm-prefix=%LLVM_PREFIX% -Dtarget=x86_64-windows-msvc
 
       - name: Test
+        shell: cmd
         continue-on-error: true
-        run: zig build test -Dstatic-llvm -Dllvm-prefix="C:\LLVM\llvm-18.1.8-windows-amd64-msvc17-msvcrt" -Dtarget=x86_64-windows-msvc --summary all
+        run: zig build test -Dstatic-llvm -Dllvm-prefix=%LLVM_PREFIX% -Dtarget=x86_64-windows-msvc --summary all
 
       - name: Package
         run: Compress-Archive -Path zig-out\bin\* -DestinationPath sx-windows-x86_64.zip
diff --git a/src/codegen.zig b/src/codegen.zig
index 40cda46..7a55985 100644
--- a/src/codegen.zig
+++ b/src/codegen.zig
@@ -12,6 +12,88 @@ const errors = @import("errors.zig");
 const sema = @import("sema.zig");
 const comptime_mod = @import("comptime.zig");
 
+pub const TargetConfig = struct {
+    /// Target triple (e.g. "aarch64-apple-darwin"). Null = host default.
+    triple: ?[*:0]const u8 = null,
+    /// CPU name (e.g. "generic", "apple-m1"). Null = "generic".
+    cpu: ?[*:0]const u8 = null,
+    /// CPU features string (e.g. "+avx2"). Null = "".
+    features: ?[*:0]const u8 = null,
+    /// Optimization level.
+    opt_level: OptLevel = .default,
+    /// Library search paths (-L flags).
+    lib_paths: []const []const u8 = &.{},
+    /// Output path override.
+    output_path: ?[]const u8 = null,
+    /// Linker command (null = "cc" on Unix, "link.exe" on Windows).
+    linker: ?[]const u8 = null,
+    /// Sysroot for cross-compilation (passed as --sysroot to linker).
+    sysroot: ?[]const u8 = null,
+
+    pub const OptLevel = enum {
+        none,
+        less,
+        default,
+        aggressive,
+
+        pub fn toLLVM(self: OptLevel) c.LLVMCodeGenOptLevel {
+            return switch (self) {
+                .none => c.LLVMCodeGenLevelNone,
+                .less => c.LLVMCodeGenLevelLess,
+                .default => c.LLVMCodeGenLevelDefault,
+                .aggressive => c.LLVMCodeGenLevelAggressive,
+            };
+        }
+    };
+
+    /// Check if target triple indicates aarch64/arm64 (runtime check, not comptime).
+    pub fn isAarch64(self: TargetConfig) bool {
+        return self.tripleHasPrefix("aarch64", "arm64");
+    }
+
+    /// Check if target triple indicates x86_64/x86-64.
+    pub fn isX86_64(self: TargetConfig) bool {
+        return self.tripleHasPrefix("x86_64", "x86-64");
+    }
+
+    /// Check if target triple indicates Windows (contains "windows" or "win32").
+    pub fn isWindows(self: TargetConfig) bool {
+        return self.tripleContains("windows") or self.tripleContains("win32");
+    }
+
+    fn tripleHasPrefix(self: TargetConfig, prefix1: []const u8, prefix2: []const u8) bool {
+        if (self.triple) |t| {
+            const span = std.mem.span(t);
+            return std.mem.startsWith(u8, span, prefix1) or std.mem.startsWith(u8, span, prefix2);
+        }
+        const dt = c.LLVMGetDefaultTargetTriple();
+        defer c.LLVMDisposeMessage(dt);
+        const span = std.mem.span(dt);
+        return std.mem.startsWith(u8, span, prefix1) or std.mem.startsWith(u8, span, prefix2);
+    }
+
+    fn tripleContains(self: TargetConfig, needle: []const u8) bool {
+        if (self.triple) |t| {
+            return std.mem.indexOf(u8, std.mem.span(t), needle) != null;
+        }
+        const dt = c.LLVMGetDefaultTargetTriple();
+        defer c.LLVMDisposeMessage(dt);
+        return std.mem.indexOf(u8, std.mem.span(dt), needle) != null;
+    }
+
+    pub fn getCpu(self: TargetConfig) [*:0]const u8 {
+        return self.cpu orelse "generic";
+    }
+
+    pub fn getFeatures(self: TargetConfig) [*:0]const u8 {
+        return self.features orelse "";
+    }
+
+    pub fn getLinker(self: TargetConfig) []const u8 {
+        return self.linker orelse "cc";
+    }
+};
+
 pub const CodeGen = struct {
     context: c.LLVMContextRef,
     module: c.LLVMModuleRef,
@@ -95,6 +177,8 @@ pub const CodeGen = struct {
     foreign_libraries: std.ArrayList([]const u8),
     // Set of foreign function names (for ABI lowering at call sites)
     foreign_fns: std.StringHashMap(void),
+    // Target configuration (triple, cpu, opt level, lib paths, linker)
+    target_config: TargetConfig = .{},
 
     const DeferredFn = struct {
         fd: ast.FnDecl,
@@ -167,10 +251,19 @@ pub const CodeGen = struct {
         ty: Type, // sx type
     };
 
-    pub fn init(allocator: std.mem.Allocator, module_name: [*:0]const u8) CodeGen {
+    pub fn init(allocator: std.mem.Allocator, module_name: [*:0]const u8, target_config: TargetConfig) CodeGen {
         const ctx = c.LLVMContextCreate();
         const module = c.LLVMModuleCreateWithNameInContext(module_name, ctx);
         const builder = c.LLVMCreateBuilderInContext(ctx);
+
+        // Set target triple on module so it appears in IR output
+        if (target_config.triple) |t| {
+            c.LLVMSetTarget(module, t);
+        } else {
+            const default_triple = c.LLVMGetDefaultTargetTriple();
+            c.LLVMSetTarget(module, default_triple);
+            c.LLVMDisposeMessage(default_triple);
+        }
         return .{
             .context = ctx,
             .module = module,
@@ -200,6 +293,7 @@ pub const CodeGen = struct {
             .deferred_fn_bodies = std.ArrayList(DeferredFn).empty,
             .foreign_libraries = std.ArrayList([]const u8).empty,
             .foreign_fns = std.StringHashMap(void).init(allocator),
+            .target_config = target_config,
         };
     }
 
@@ -1143,6 +1237,8 @@ pub const CodeGen = struct {
         const is_main = std.mem.eql(u8, name, "main");
         const ret_llvm_type = if (is_main)
             c.LLVMInt32TypeInContext(self.context)
+        else if (is_foreign and ret_sx_type.isStruct())
+            self.getForeignReturnABIType(ret_sx_type)
         else
             self.typeToLLVM(ret_sx_type);
 
@@ -1175,19 +1271,33 @@ pub const CodeGen = struct {
         );
     }
 
-    /// For foreign (C ABI) functions on ARM64, struct parameters must be lowered
-    /// to their ABI-equivalent types. LLVM does NOT do this automatically.
-    /// - HFA (1-4 same float/double fields): [N x float/double]
-    /// - Non-HFA ≤ 8 bytes: i64
-    /// - Non-HFA 9-16 bytes: [2 x i64]
+    /// For foreign (C ABI) functions, struct parameters must be lowered to their
+    /// ABI-equivalent types. LLVM does NOT do this automatically on all targets.
+    /// Dispatches to architecture-specific lowering based on target config.
     fn getForeignParamABIType(self: *CodeGen, sx_ty: Type) c.LLVMTypeRef {
-        const is_aarch64 = comptime @import("builtin").cpu.arch == .aarch64;
-        if (!is_aarch64) return self.typeToLLVM(sx_ty);
         if (!sx_ty.isStruct()) return self.typeToLLVM(sx_ty);
 
         const sname = self.type_aliases.get(sx_ty.struct_type) orelse sx_ty.struct_type;
         const info = self.struct_types.get(sname) orelse return self.typeToLLVM(sx_ty);
 
+        if (self.target_config.isAarch64()) {
+            return self.aarch64ParamABI(info);
+        } else if (self.target_config.isX86_64()) {
+            if (self.target_config.isWindows()) {
+                return self.win64ParamABI(info);
+            }
+            return self.x86_64SysVParamABI(info);
+        }
+        // Unknown architecture: pass struct type as-is (let LLVM backend handle it)
+        return info.llvm_type;
+    }
+
+    /// AArch64 ABI: struct parameter lowering.
+    /// - HFA (1-4 same float/double fields): [N x float/double]
+    /// - Non-HFA ≤ 8 bytes: i64
+    /// - Non-HFA 9-16 bytes: [2 x i64]
+    /// - > 16 bytes: pass as-is (indirect, not yet fully handled)
+    fn aarch64ParamABI(self: *CodeGen, info: StructInfo) c.LLVMTypeRef {
         // Check HFA: 1-4 fields all of the same float type
         const field_types = info.field_types;
         if (field_types.len >= 1 and field_types.len <= 4) {
@@ -1215,10 +1325,119 @@ pub const CodeGen = struct {
         const size = c.LLVMStoreSizeOfType(data_layout, info.llvm_type);
         if (size <= 8) return c.LLVMInt64TypeInContext(self.context);
         if (size <= 16) return c.LLVMArrayType2(c.LLVMInt64TypeInContext(self.context), 2);
-        // > 16 bytes: pass by pointer (indirect) — not yet handled, fall back to struct type
         return info.llvm_type;
     }
 
+    /// x86-64 SysV ABI: struct parameter lowering.
+    /// Each 8-byte "eightbyte" is classified as INTEGER or SSE:
+    /// - If all fields in the eightbyte are float/double: SSE (passed in XMM register)
+    /// - If any field is integer/pointer: INTEGER (passed in GPR)
+    /// - Structs > 16 bytes: passed in memory (by pointer)
+    fn x86_64SysVParamABI(self: *CodeGen, info: StructInfo) c.LLVMTypeRef {
+        const data_layout = c.LLVMGetModuleDataLayout(self.module);
+        const size = c.LLVMStoreSizeOfType(data_layout, info.llvm_type);
+
+        // > 16 bytes: MEMORY class (passed by pointer, handled by LLVM backend)
+        if (size > 16) return info.llvm_type;
+
+        // Single eightbyte (≤ 8 bytes)
+        if (size <= 8) {
+            return self.classifyEightbyte(info.field_types, size);
+        }
+
+        // Two eightbytes (9-16 bytes): classify each half independently
+        // Split fields into first eightbyte (offset < 8) and second eightbyte (offset >= 8)
+        var first_eb_types = std.ArrayList(Type).empty;
+        var second_eb_types = std.ArrayList(Type).empty;
+        var second_eb_size: u64 = 0;
+
+        const struct_ty = info.llvm_type;
+        for (info.field_types, 0..) |ft, idx| {
+            const offset = c.LLVMOffsetOfElement(data_layout, struct_ty, @intCast(idx));
+            if (offset < 8) {
+                first_eb_types.append(self.allocator, ft) catch return info.llvm_type;
+            } else {
+                second_eb_types.append(self.allocator, ft) catch return info.llvm_type;
+                const field_llvm = self.typeToLLVM(ft);
+                second_eb_size += c.LLVMStoreSizeOfType(data_layout, field_llvm);
+            }
+        }
+
+        const eb1 = self.classifyEightbyte(first_eb_types.items, 8);
+        const eb2 = self.classifyEightbyte(second_eb_types.items, if (second_eb_size > 0) second_eb_size else size - 8);
+
+        // Compose the two eightbytes into a struct type
+        var members: [2]c.LLVMTypeRef = .{ eb1, eb2 };
+        return c.LLVMStructTypeInContext(self.context, &members, 2, 0);
+    }
+
+    /// Classify a single x86-64 eightbyte: if all fields are float, return SSE type;
+    /// otherwise return an integer type matching the byte size.
+    fn classifyEightbyte(self: *CodeGen, field_types_in_eb: []const Type, byte_size: u64) c.LLVMTypeRef {
+        if (field_types_in_eb.len == 0) {
+            // No fields in this chunk — use integer padding
+            return c.LLVMIntTypeInContext(self.context, @intCast(byte_size * 8));
+        }
+
+        // Check if all fields are SSE (float/double)
+        var all_sse = true;
+        var float_count: u32 = 0;
+        var double_count: u32 = 0;
+        for (field_types_in_eb) |ft| {
+            if (ft == .f32) {
+                float_count += 1;
+            } else if (ft == .f64) {
+                double_count += 1;
+            } else {
+                all_sse = false;
+                break;
+            }
+        }
+
+        if (all_sse) {
+            // SSE class: return appropriate float type
+            if (double_count > 0 and float_count == 0) {
+                if (double_count == 1) return c.LLVMDoubleTypeInContext(self.context);
+                // Multiple doubles shouldn't fit in one eightbyte (double = 8 bytes)
+                return c.LLVMDoubleTypeInContext(self.context);
+            }
+            if (float_count > 0 and double_count == 0) {
+                if (float_count == 1) return c.LLVMFloatTypeInContext(self.context);
+                // 2 floats = 8 bytes, fits in one eightbyte
+                return c.LLVMArrayType2(c.LLVMFloatTypeInContext(self.context), @intCast(float_count));
+            }
+            // Mixed float/double in one eightbyte shouldn't happen (float=4, double=8)
+            // but fall through to integer just in case
+        }
+
+        // INTEGER class: coerce to integer matching the byte size
+        return c.LLVMIntTypeInContext(self.context, @intCast(byte_size * 8));
+    }
+
+    /// Windows x64 ABI: struct parameter lowering.
+    /// Only structs of exactly 1, 2, 4, or 8 bytes are passed in a register.
+    /// Everything else is passed by pointer (handled by LLVM backend).
+    fn win64ParamABI(self: *CodeGen, info: StructInfo) c.LLVMTypeRef {
+        const data_layout = c.LLVMGetModuleDataLayout(self.module);
+        const size = c.LLVMStoreSizeOfType(data_layout, info.llvm_type);
+
+        // Windows x64: only power-of-2 sizes ≤ 8 passed in register
+        if (size == 1 or size == 2 or size == 4 or size == 8) {
+            return c.LLVMIntTypeInContext(self.context, @intCast(size * 8));
+        }
+        // All other sizes: passed by pointer (LLVM handles byval)
+        return info.llvm_type;
+    }
+
+    /// For foreign functions returning structs, apply the same ABI lowering as parameters.
+    /// The rules for return values match parameter rules on both AArch64 and x86-64 SysV
+    /// for small structs (≤ 16 bytes). Larger structs use sret (handled by LLVM).
+    fn getForeignReturnABIType(self: *CodeGen, sx_ty: Type) c.LLVMTypeRef {
+        // Reuse the same classification as parameters — the rules are identical
+        // for small struct returns on both AArch64 and x86-64 SysV.
+        return self.getForeignParamABIType(sx_ty);
+    }
+
     /// Convert a struct value to its C ABI representation for a foreign call.
     /// Stores the struct to memory, then loads as the ABI type.
     fn convertStructToABI(self: *CodeGen, struct_val: c.LLVMValueRef, struct_ty: c.LLVMTypeRef, abi_ty: c.LLVMTypeRef) c.LLVMValueRef {
@@ -5894,11 +6113,13 @@ pub const CodeGen = struct {
         std.debug.print("{s}\n", .{ir[0..len]});
     }
 
-    pub fn emitObject(self: *CodeGen, output_path: [*:0]const u8) !void {
+    fn emitToFile(self: *CodeGen, output_path: [*:0]const u8, file_type: c.LLVMCodeGenFileType) !void {
         llvm.initAllTargets();
 
-        const triple = c.LLVMGetDefaultTargetTriple();
-        defer c.LLVMDisposeMessage(triple);
+        const cfg = self.target_config;
+        const triple_owned = cfg.triple == null;
+        const triple = cfg.triple orelse c.LLVMGetDefaultTargetTriple();
+        defer if (triple_owned) c.LLVMDisposeMessage(@constCast(triple));
 
         var target: c.LLVMTargetRef = null;
         var err_msg: [*c]u8 = null;
@@ -5912,9 +6133,9 @@ pub const CodeGen = struct {
         const tm = c.LLVMCreateTargetMachine(
             target,
             triple,
-            "generic",
-            "",
-            c.LLVMCodeGenLevelDefault,
+            cfg.getCpu(),
+            cfg.getFeatures(),
+            cfg.opt_level.toLLVM(),
             c.LLVMRelocPIC,
             c.LLVMCodeModelDefault,
         );
@@ -5923,24 +6144,58 @@ pub const CodeGen = struct {
         c.LLVMSetTarget(self.module, triple);
 
         var err_msg2: [*c]u8 = null;
-        if (c.LLVMTargetMachineEmitToFile(tm, self.module, output_path, c.LLVMObjectFile, &err_msg2) != 0) {
+        if (c.LLVMTargetMachineEmitToFile(tm, self.module, output_path, file_type, &err_msg2) != 0) {
             defer c.LLVMDisposeMessage(err_msg2);
             const msg = std.mem.span(err_msg2);
-            return self.emitErrorFmt("failed to emit object file: {s}", .{msg});
+            return self.emitErrorFmt("failed to emit file: {s}", .{msg});
         }
     }
 
-    pub fn link(allocator: std.mem.Allocator, io: std.Io, output_obj: []const u8, output_bin: []const u8, libraries: []const []const u8) !void {
-        var argv = std.ArrayList([]const u8).empty;
-        try argv.appendSlice(allocator, &.{ "cc", output_obj, "-o", output_bin });
+    pub fn emitObject(self: *CodeGen, output_path: [*:0]const u8) !void {
+        return self.emitToFile(output_path, c.LLVMObjectFile);
+    }
 
-        if (libraries.len > 0) {
-            // Add Homebrew library path on macOS
-            try argv.append(allocator, "-L/opt/homebrew/lib");
+    pub fn emitAssembly(self: *CodeGen, output_path: [*:0]const u8) !void {
+        return self.emitToFile(output_path, c.LLVMAssemblyFile);
+    }
+
+    pub fn link(allocator: std.mem.Allocator, io: std.Io, output_obj: []const u8, output_bin: []const u8, libraries: []const []const u8, target_config: TargetConfig) !void {
+        var argv = std.ArrayList([]const u8).empty;
+
+        if (target_config.isWindows()) {
+            // Windows: MSVC-style linker flags
+            const linker = target_config.linker orelse "link.exe";
+            try argv.appendSlice(allocator, &.{ linker, output_obj });
+            try argv.append(allocator, try std.fmt.allocPrint(allocator, "/OUT:{s}", .{output_bin}));
+
+            for (target_config.lib_paths) |lp| {
+                try argv.append(allocator, try std.fmt.allocPrint(allocator, "/LIBPATH:{s}", .{lp}));
+            }
+            for (libraries) |lib| {
+                try argv.append(allocator, try std.fmt.allocPrint(allocator, "{s}.lib", .{lib}));
+            }
+        } else {
+            // Unix: cc-style linker flags
+            try argv.appendSlice(allocator, &.{ target_config.getLinker(), output_obj, "-o", output_bin });
+
+            if (target_config.sysroot) |sr| {
+                try argv.append(allocator, try std.fmt.allocPrint(allocator, "--sysroot={s}", .{sr}));
+            }
+
+            // User-supplied library paths first
+            for (target_config.lib_paths) |lp| {
+                try argv.append(allocator, try std.fmt.allocPrint(allocator, "-L{s}", .{lp}));
+            }
+
+            // Auto-detect host OS library paths when linking foreign libraries
+            if (libraries.len > 0 and target_config.triple == null) {
+                for (host_lib_paths) |path| {
+                    try argv.append(allocator, try std.fmt.allocPrint(allocator, "-L{s}", .{path}));
+                }
+            }
 
             for (libraries) |lib| {
-                const flag = try std.fmt.allocPrint(allocator, "-l{s}", .{lib});
-                try argv.append(allocator, flag);
+                try argv.append(allocator, try std.fmt.allocPrint(allocator, "-l{s}", .{lib}));
             }
         }
 
@@ -5952,4 +6207,22 @@ pub const CodeGen = struct {
         if (result != .exited) return error.LinkError;
         if (result.exited != 0) return error.LinkError;
     }
+
+    /// Common library paths for the host OS, computed at comptime.
+    const host_lib_paths = blk: {
+        const builtin = @import("builtin");
+        var paths: []const []const u8 = &.{};
+        if (builtin.os.tag == .macos) {
+            if (builtin.cpu.arch == .aarch64) {
+                // Apple Silicon Homebrew
+                paths = &.{ "/opt/homebrew/lib", "/usr/local/lib" };
+            } else {
+                // Intel Mac Homebrew
+                paths = &.{"/usr/local/lib"};
+            }
+        } else if (builtin.os.tag == .linux) {
+            paths = &.{ "/usr/local/lib", "/usr/lib" };
+        }
+        break :blk paths;
+    };
 };
diff --git a/src/core.zig b/src/core.zig
index 0bbb955..c0d2c78 100644
--- a/src/core.zig
+++ b/src/core.zig
@@ -7,12 +7,15 @@ const codegen = @import("codegen.zig");
 const errors = @import("errors.zig");
 const Node = ast.Node;
 
+pub const TargetConfig = codegen.TargetConfig;
+
 pub const Compilation = struct {
     allocator: std.mem.Allocator,
     io: std.Io,
     file_path: []const u8,
     source: [:0]const u8,
     diagnostics: errors.DiagnosticList,
+    target_config: TargetConfig,
 
     // Pipeline results
     root: ?*Node = null,
@@ -21,7 +24,7 @@ pub const Compilation = struct {
     sema_result: ?sema.SemaResult = null,
     cg: ?codegen.CodeGen = null,
 
-    pub fn init(allocator: std.mem.Allocator, io: std.Io, file_path: []const u8, source: [:0]const u8) Compilation {
+    pub fn init(allocator: std.mem.Allocator, io: std.Io, file_path: []const u8, source: [:0]const u8, target_config: TargetConfig) Compilation {
         return .{
             .allocator = allocator,
             .io = io,
@@ -29,6 +32,7 @@ pub const Compilation = struct {
             .source = source,
             .diagnostics = errors.DiagnosticList.init(allocator, source, file_path),
             .import_sources = std.StringHashMap([:0]const u8).init(allocator),
+            .target_config = target_config,
         };
     }
 
@@ -83,7 +87,7 @@ pub const Compilation = struct {
 
     pub fn generateCode(self: *Compilation) !void {
         const root = self.resolved_root orelse self.root orelse return error.CompileError;
-        var cg = codegen.CodeGen.init(self.allocator, "sx_module");
+        var cg = codegen.CodeGen.init(self.allocator, "sx_module", self.target_config);
         cg.diagnostics = &self.diagnostics;
         if (self.sema_result) |*sr| {
             cg.sema_result = sr;
diff --git a/src/lsp/server.zig b/src/lsp/server.zig
index 12029ad..82e4ca3 100644
--- a/src/lsp/server.zig
+++ b/src/lsp/server.zig
@@ -893,7 +893,7 @@ pub const Server = struct {
         const source = try self.allocator.dupeZ(u8, text);
         const file_path = uriToFilePath(uri) orelse "";
 
-        var comp = sx.core.Compilation.init(self.allocator, self.io, file_path, source);
+        var comp = sx.core.Compilation.init(self.allocator, self.io, file_path, source, .{});
         defer comp.deinit();
 
         comp.parse() catch {
diff --git a/src/main.zig b/src/main.zig
index dbe6362..96788b6 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -19,22 +19,75 @@ pub fn main(init: std.process.Init) !void {
         return;
     }
 
-    if (args.len < 3) {
-        printUsage();
-        return;
+    // Parse flags and positional arguments
+    var input_path: ?[]const u8 = null;
+    var target_config = sx.codegen.TargetConfig{};
+    var lib_paths = std.ArrayList([]const u8).empty;
+
+    var i: usize = 2;
+    while (i < args.len) : (i += 1) {
+        const arg = args[i];
+        if (std.mem.eql(u8, arg, "--target")) {
+            i += 1;
+            if (i >= args.len) { std.debug.print("error: --target requires a value\n", .{}); return; }
+            target_config.triple = (try allocator.dupeZ(u8, args[i])).ptr;
+        } else if (std.mem.eql(u8, arg, "--cpu")) {
+            i += 1;
+            if (i >= args.len) { std.debug.print("error: --cpu requires a value\n", .{}); return; }
+            target_config.cpu = (try allocator.dupeZ(u8, args[i])).ptr;
+        } else if (std.mem.eql(u8, arg, "--opt")) {
+            i += 1;
+            if (i >= args.len) { std.debug.print("error: --opt requires a value\n", .{}); return; }
+            target_config.opt_level = parseOptLevel(args[i]) orelse {
+                std.debug.print("error: invalid --opt value '{s}' (expected: none/0, less/1, default/2, aggressive/3)\n", .{args[i]});
+                return;
+            };
+        } else if (std.mem.eql(u8, arg, "-o")) {
+            i += 1;
+            if (i >= args.len) { std.debug.print("error: -o requires a value\n", .{}); return; }
+            target_config.output_path = args[i];
+        } else if (std.mem.eql(u8, arg, "--linker")) {
+            i += 1;
+            if (i >= args.len) { std.debug.print("error: --linker requires a value\n", .{}); return; }
+            target_config.linker = args[i];
+        } else if (std.mem.eql(u8, arg, "--sysroot")) {
+            i += 1;
+            if (i >= args.len) { std.debug.print("error: --sysroot requires a value\n", .{}); return; }
+            target_config.sysroot = args[i];
+        } else if (std.mem.startsWith(u8, arg, "-L")) {
+            if (arg.len > 2) {
+                try lib_paths.append(allocator, arg[2..]);
+            } else {
+                i += 1;
+                if (i >= args.len) { std.debug.print("error: -L requires a value\n", .{}); return; }
+                try lib_paths.append(allocator, args[i]);
+            }
+        } else if (!std.mem.startsWith(u8, arg, "-")) {
+            input_path = arg;
+        } else {
+            std.debug.print("error: unknown flag '{s}'\n", .{arg});
+            return;
+        }
     }
 
-    const input_path = args[2];
+    target_config.lib_paths = try lib_paths.toOwnedSlice(allocator);
+
+    const path = input_path orelse {
+        printUsage();
+        return;
+    };
 
     if (std.mem.eql(u8, command, "build")) {
-        const output_name = deriveOutputName(input_path);
-        compile(allocator, io, input_path, output_name) catch return;
+        const output_name = target_config.output_path orelse deriveOutputName(path);
+        compile(allocator, io, path, output_name, target_config) catch return;
         std.debug.print("compiled: {s}\n", .{output_name});
     } else if (std.mem.eql(u8, command, "ir")) {
-        emitIR(allocator, io, input_path) catch return;
+        emitIR(allocator, io, path, target_config) catch return;
+    } else if (std.mem.eql(u8, command, "asm")) {
+        emitAsm(allocator, io, path, target_config) catch return;
     } else if (std.mem.eql(u8, command, "run")) {
-        const tmp_bin = "/tmp/sx_run_tmp";
-        compile(allocator, io, input_path, tmp_bin) catch return;
+        const tmp_bin = if (comptime @import("builtin").os.tag == .windows) "sx_run_tmp.exe" else "/tmp/sx_run_tmp";
+        compile(allocator, io, path, tmp_bin, target_config) catch return;
         defer {
             std.Io.Dir.deleteFile(.cwd(), io, tmp_bin) catch {};
         }
@@ -53,16 +106,34 @@ pub fn main(init: std.process.Init) !void {
     }
 }
 
+fn parseOptLevel(s: []const u8) ?sx.codegen.TargetConfig.OptLevel {
+    if (std.mem.eql(u8, s, "none") or std.mem.eql(u8, s, "0")) return .none;
+    if (std.mem.eql(u8, s, "less") or std.mem.eql(u8, s, "1")) return .less;
+    if (std.mem.eql(u8, s, "default") or std.mem.eql(u8, s, "2")) return .default;
+    if (std.mem.eql(u8, s, "aggressive") or std.mem.eql(u8, s, "3")) return .aggressive;
+    return null;
+}
+
 fn printUsage() void {
     std.debug.print(
-        \\Usage: sx <command> [file.sx]
+        \\Usage: sx <command> [options] <file.sx>
         \\
         \\Commands:
         \\  run    Build and run immediately
         \\  build  Build binary in current directory
         \\  ir     Print LLVM IR to stdout
+        \\  asm    Emit assembly (.s) file
         \\  lsp    Start language server (LSP)
         \\
+        \\Options:
+        \\  --target <triple>   Target triple (default: host)
+        \\  --cpu <name>        CPU name (default: generic)
+        \\  --opt <level>       Optimization: none/0, less/1, default/2, aggressive/3
+        \\  -o <path>           Output path
+        \\  -L <path>           Library search path (repeatable)
+        \\  --linker <cmd>      Linker command (default: cc)
+        \\  --sysroot <path>    Sysroot for cross-compilation
+        \\
     , .{});
 }
 
@@ -96,7 +167,7 @@ fn deriveOutputName(input_path: []const u8) []const u8 {
     // Get basename (strip directory)
     var start: usize = 0;
     for (input_path, 0..) |ch, i| {
-        if (ch == '/') start = i + 1;
+        if (ch == '/' or ch == '\\') start = i + 1;
     }
     const basename = input_path[start..];
     // Strip .sx extension
@@ -115,10 +186,10 @@ fn readSource(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8)
     return try allocator.dupeZ(u8, source_bytes);
 }
 
-fn compilePipeline(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8) !sx.core.Compilation {
+fn compilePipeline(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8, target_config: sx.codegen.TargetConfig) !sx.core.Compilation {
     const source = try readSource(allocator, io, input_path);
 
-    var comp = sx.core.Compilation.init(allocator, io, input_path, source);
+    var comp = sx.core.Compilation.init(allocator, io, input_path, source, target_config);
     errdefer comp.deinit();
 
     comp.parse() catch { comp.renderErrors(); return error.CompileError; };
@@ -131,14 +202,26 @@ fn compilePipeline(allocator: std.mem.Allocator, io: std.Io, input_path: []const
     return comp;
 }
 
-fn emitIR(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8) !void {
-    var comp = try compilePipeline(allocator, io, input_path);
+fn emitIR(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8, target_config: sx.codegen.TargetConfig) !void {
+    var comp = try compilePipeline(allocator, io, input_path, target_config);
     defer comp.deinit();
     comp.cg.?.printIR();
 }
 
-fn compile(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8, output_path: []const u8) !void {
-    var comp = try compilePipeline(allocator, io, input_path);
+fn emitAsm(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8, target_config: sx.codegen.TargetConfig) !void {
+    var comp = try compilePipeline(allocator, io, input_path, target_config);
+    defer comp.deinit();
+    const asm_path = target_config.output_path orelse blk: {
+        const name = deriveOutputName(input_path);
+        break :blk try std.fmt.allocPrint(allocator, "{s}.s", .{name});
+    };
+    const asm_path_z = try allocator.dupeZ(u8, asm_path);
+    comp.cg.?.emitAssembly(asm_path_z.ptr) catch { comp.renderErrors(); return error.CompileError; };
+    std.debug.print("emitted: {s}\n", .{asm_path});
+}
+
+fn compile(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8, output_path: []const u8, target_config: sx.codegen.TargetConfig) !void {
+    var comp = try compilePipeline(allocator, io, input_path, target_config);
     defer comp.deinit();
 
     var cg = &comp.cg.?;
@@ -148,7 +231,7 @@ fn compile(allocator: std.mem.Allocator, io: std.Io, input_path: []const u8, out
     cg.emitObject(obj_path.ptr) catch { comp.renderErrors(); return error.CompileError; };
 
     // Link
-    sx.codegen.CodeGen.link(allocator, io, obj_path, output_path, cg.foreign_libraries.items) catch {
+    sx.codegen.CodeGen.link(allocator, io, obj_path, output_path, cg.foreign_libraries.items, target_config) catch {
         std.debug.print("error: linking failed\n", .{});
         return error.CompileError;
     };