diff --git a/.gitignore b/.gitignore
index 44f7213..346c11d 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,5 @@
 zig-cache/
+zig-out/
 *.mp3
 *.wav
 build_runner.zig
diff --git a/build.zig b/build.zig
index 6858c80..5f2ff5e 100644
--- a/build.zig
+++ b/build.zig
@@ -1,8 +1,6 @@
 const std = @import("std");
-const builds = std.build;
-const Builder = std.build.Builder;
 
-fn setupLinks(step: *builds.LibExeObjStep) void {
+fn setupLinks(step: *std.Build.Step.Compile) void {
     step.linkSystemLibrary("c");
 
     step.linkSystemLibrary("lilv-0");
@@ -12,8 +10,8 @@ fn setupLinks(step: *builds.LibExeObjStep) void {
     step.linkSystemLibrary("GraphicsMagickWand");
     step.linkSystemLibrary("GraphicsMagick");
 
-    step.addIncludeDir("/usr/include/GraphicsMagick");
-    step.addIncludeDir("/usr/include");
+    step.addIncludePath(.{ .path = "/usr/include/GraphicsMagick" });
+    step.addIncludePath(.{ .path = "/usr/include" });
 
     const possible_lilv_include_dirs = [_][]const u8{
         "/usr/include/lilv-0/lilv",
@@ -24,40 +22,52 @@ fn setupLinks(step: *builds.LibExeObjStep) void {
 
     for (possible_lilv_include_dirs) |possible_lilv_dir| {
         var possible_dir = std.fs.cwd().openDir(possible_lilv_dir, .{}) catch |err| {
-            std.debug.warn("possible lilv {} fail: {}\n", .{ possible_lilv_dir, err });
+            std.debug.print("possible lilv {s} fail: {s}\n", .{ possible_lilv_dir, @errorName(err) });
             continue;
         };
 
         possible_dir.close();
         found_any_lilv = true;
 
-        std.debug.warn("found lilv at '{}'\n", .{possible_lilv_dir});
-        step.addIncludeDir(possible_lilv_dir);
+        std.debug.print("found lilv at '{s}'\n", .{possible_lilv_dir});
+        step.addIncludePath(.{ .path = possible_lilv_dir });
     }
 
     if (!found_any_lilv) {
-        std.debug.warn("No LILV library was found :(\n", .{});
+        std.debug.print("No LILV library was found :(\n", .{});
         @panic("no lilv found");
     }
 }
 
-pub fn build(b: *Builder) void {
-    const mode = b.standardReleaseOptions();
-    const exe = b.addExecutable("scritcher", "src/main.zig");
-    exe.setBuildMode(mode);
-    exe.install();
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
 
+    const exe = b.addExecutable(.{
+        .name = "scritcher",
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
     setupLinks(exe);
+    b.installArtifact(exe);
 
-    const test_obj_step = b.addTest("src/main.zig");
-    setupLinks(test_obj_step);
+    const run_cmd = b.addRunArtifact(exe);
 
-    const run_cmd = exe.run();
-    run_cmd.step.dependOn(b.getInstallStep());
+    if (b.args) |args| {
+        run_cmd.addArgs(args);
+    }
 
     const run_step = b.step("run", "Run the app");
     run_step.dependOn(&run_cmd.step);
 
-    const test_step = b.step("test", "Run tests");
-    test_step.dependOn(&test_obj_step.step);
+    const test_step = b.addTest(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    setupLinks(test_step);
+    const run_unit_tests = b.addRunArtifact(test_step);
+    const test_cmd = b.step("test", "run unit tests");
+    test_cmd.dependOn(&run_unit_tests.step);
 }
diff --git a/src/bmp_valid.zig b/src/bmp_valid.zig
index c4f9438..6e256e8 100644
--- a/src/bmp_valid.zig
+++ b/src/bmp_valid.zig
@@ -1,11 +1,10 @@
 const std = @import("std");
-
+const log = std.log.scoped(.scritcher_bmp);
 pub const BMPValidError = error{InvalidMagic};
 
 const VALID_MAGICS = [_][]const u8{
     "BM",
     "BA",
-
     "CI",
     "CP",
     "IC",
@@ -20,7 +19,7 @@ pub fn magicValid(magic: []const u8) !void {
     }
 
     if (!valid) {
-        std.debug.warn("\tINVALID HEADER: '{}'\n", .{magic});
+        log.debug("\tINVALID HEADER: '{s}'", .{magic});
         return BMPValidError.InvalidMagic;
     }
 }
diff --git a/src/custom.zig b/src/custom.zig
index 0420bd3..d942a3b 100644
--- a/src/custom.zig
+++ b/src/custom.zig
@@ -4,6 +4,7 @@ const lv2 = @import("lv2_helpers.zig");
 const plugins = @import("plugin.zig");
 const image = @import("image.zig");
 
+const log = std.log.scoped(.scritcher_custom);
 const c = lv2.c;
 
 const RunBuffers = plugins.RunBuffers;
@@ -11,20 +12,20 @@ const RunBuffers = plugins.RunBuffers;
 pub const RandomNoise = struct {
     r: std.rand.DefaultPrng,
     rand_buf: ?[]f32 = null,
-    allocator: ?*std.mem.Allocator = null,
+    allocator: ?std.mem.Allocator = null,
     cnt: usize = 0,
 
     pub fn init(
-        allocator: *std.mem.Allocator,
-        params: var,
+        allocator: std.mem.Allocator,
+        params: anytype,
     ) ?RandomNoise {
         var r = std.rand.DefaultPrng.init(params.seed);
 
         if (params.fill_bytes > 0) {
             var rand_buf = allocator.alloc(f32, params.fill_bytes) catch return null;
 
-            for (rand_buf) |_, idx| {
-                rand_buf[idx] = r.random.float(f32);
+            for (rand_buf, 0..) |_, idx| {
+                rand_buf[idx] = r.random().float(f32);
             }
 
             return RandomNoise{
@@ -51,7 +52,7 @@ pub const RandomNoise = struct {
             bufs.out[0] = rand_buf[self.cnt];
             self.cnt += 1;
         } else {
-            bufs.out[0] = self.r.random.float(f32);
+            bufs.out[0] = self.r.random().float(f32);
         }
     }
 };
@@ -59,20 +60,20 @@ pub const RandomNoise = struct {
 pub const WildNoise = struct {
     r: std.rand.DefaultPrng,
     rand_buf: ?[]f32 = null,
-    allocator: ?*std.mem.Allocator = null,
+    allocator: ?std.mem.Allocator = null,
     cnt: usize = 0,
 
     pub fn init(
-        allocator: *std.mem.Allocator,
-        params: var,
+        allocator: std.mem.Allocator,
+        params: anytype,
     ) ?WildNoise {
         var r = std.rand.DefaultPrng.init(params.seed);
 
         if (params.fill_bytes > 0) {
             var rand_buf = allocator.alloc(f32, params.fill_bytes) catch return null;
 
-            for (rand_buf) |_, idx| {
-                rand_buf[idx] = @intToFloat(f32, r.random.int(u1));
+            for (rand_buf, 0..) |_, idx| {
+                rand_buf[idx] = @as(f32, @floatFromInt(r.random().int(u1)));
             }
 
             return WildNoise{
@@ -98,7 +99,7 @@ pub const WildNoise = struct {
             bufs.out[0] = rand_buf[self.cnt];
             self.cnt += 1;
         } else {
-            bufs.out[0] = @intToFloat(f32, self.r.random.int(u1));
+            bufs.out[0] = @as(f32, @floatFromInt(self.r.random().int(u1)));
         }
     }
 };
@@ -111,15 +112,18 @@ pub const Write = struct {
     data: f32,
 
     pub fn init(
-        allocator: *std.mem.Allocator,
-        params: var,
+        allocator: std.mem.Allocator,
+        params: anytype,
     ) Write {
+        _ = allocator;
         return Write{
             .data = params.data,
         };
     }
 
-    pub fn deinit(self: *Write) void {}
+    pub fn deinit(self: *Write) void {
+        _ = self;
+    }
 
     pub fn run(self: *Write, bufs: *RunBuffers) void {
         bufs.out[0] = self.data;
@@ -127,13 +131,13 @@ pub const Write = struct {
 };
 
 pub const Embed = struct {
-    allocator: *std.mem.Allocator,
+    allocator: std.mem.Allocator,
     filepath: []const u8,
 
     sndfile: *c.SNDFILE = undefined,
     buf: []f32 = undefined,
 
-    pub fn init(allocator: *std.mem.Allocator, params: var) @This() {
+    pub fn init(allocator: std.mem.Allocator, params: anytype) @This() {
         return Embed{
             .allocator = allocator,
             .filepath = params.path,
@@ -159,10 +163,12 @@ pub const Embed = struct {
 
         image.sseek(self.sndfile, 0);
 
-        self.buf = try self.allocator.alloc(f32, @intCast(usize, in_fmt.channels));
+        self.buf = try self.allocator.alloc(f32, @as(usize, @intCast(in_fmt.channels)));
     }
 
-    pub fn deinit(self: *@This()) void {}
+    pub fn deinit(self: *@This()) void {
+        _ = self;
+    }
 
     pub fn run(self: *@This(), bufs: *RunBuffers) void {
         const read_bytes = c.sf_readf_float(self.sndfile, self.buf.ptr, 1);
@@ -174,7 +180,7 @@ pub const Embed = struct {
 
         if (read_bytes < 0) {
             const st: i32 = c.sf_error(self.sndfile);
-            std.debug.warn("Failed to read {} ({})\n", .{
+            log.debug("Failed to read {s} ({s})", .{
                 self.filepath,
                 c.sf_error_number(st),
             });
diff --git a/src/image.zig b/src/image.zig
index e0fea67..e20cfe7 100644
--- a/src/image.zig
+++ b/src/image.zig
@@ -3,6 +3,7 @@ const lv2 = @import("lv2_helpers.zig");
 const c = lv2.c;
 const bmp = @import("bmp_valid.zig");
 
+const log = std.log.scoped(.scritcher_image);
 const plugins = @import("plugin.zig");
 
 /// Buffer size for main image copying.
@@ -20,19 +21,19 @@ pub const ImageError = error{
 
 /// Low level integration function with libsndfile.
 pub fn sopen(
-    allocator: *std.mem.Allocator,
+    allocator: std.mem.Allocator,
     path: []const u8,
     mode: i32,
     fmt: *c.SF_INFO,
 ) !*c.SNDFILE {
-    var cstr_path = try std.cstr.addNullByte(allocator, path);
+    const cstr_path = try allocator.dupeZ(u8, path);
     defer allocator.free(cstr_path);
 
-    var file = c.sf_open(cstr_path.ptr, mode, fmt);
+    const file = c.sf_open(cstr_path.ptr, mode, fmt);
     const st: i32 = c.sf_error(file);
 
     if (st != 0) {
-        std.debug.warn("Failed to open {} ({})\n", .{
+        log.debug("Failed to open {s} ({s})", .{
             path,
             c.sf_error_number(st),
         });
@@ -42,12 +43,12 @@ pub fn sopen(
 
     const frames_on_end = c.sf_seek(file, 0, c.SEEK_END);
     _ = c.sf_seek(file, 0, c.SEEK_SET);
-    std.testing.expectEqual(fmt.frames, frames_on_end);
+    try std.testing.expectEqual(fmt.frames, frames_on_end);
 
     const frames_on_end_by_end = c.sf_seek(file, frames_on_end, c.SEEK_SET);
-    std.testing.expectEqual(frames_on_end, frames_on_end_by_end);
+    try std.testing.expectEqual(frames_on_end, frames_on_end_by_end);
 
-    std.debug.warn("frames on end: {}, frame on end (2): {}\n", .{ frames_on_end, frames_on_end_by_end });
+    log.debug("frames on end: {}, frame on end (2): {}", .{ frames_on_end, frames_on_end_by_end });
 
     return file.?;
 }
@@ -56,30 +57,30 @@ pub fn swrite(file: *c.SNDFILE, buf: [*]f32, frames: i64) !void {
     const count = c.sf_writef_float(file, buf, frames);
 
     if (count != frames) {
-        std.debug.warn("Wanted to write {}, got {}\n", .{ frames, count });
+        log.debug("Wanted to write {}, got {}", .{ frames, count });
         return ImageError.WriteFail;
     }
 }
 
 pub fn sseek(file: *c.SNDFILE, offset: usize) void {
-    const offset_i64 = @intCast(i64, offset);
+    const offset_i64 = @as(i64, @intCast(offset));
     const frames = c.sf_seek(file, offset_i64, c.SEEK_SET);
     const frames_current = c.sf_seek(file, 0, c.SEEK_CUR);
-    std.testing.expectEqual(frames, frames_current);
+    std.debug.assert(frames == frames_current);
 
     if (frames != offset_i64) {
-        std.debug.warn("failed to seek to {} (seeked {} frames, offset_i64={})\n", .{ offset, frames, offset_i64 });
+        log.debug("failed to seek to {} (seeked {} frames, offset_i64={})", .{ offset, frames, offset_i64 });
     }
 }
 
 /// Caller owns the returned memory.
-pub fn temporaryName(allocator: *std.mem.Allocator) ![]u8 {
+pub fn temporaryName(allocator: std.mem.Allocator) ![]u8 {
     const template_start = "/temp/temp_";
     const template = "/tmp/temp_XXXXXXXXXXXXXXXXXXXXX";
     var nam = try allocator.alloc(u8, template.len);
-    std.mem.copy(u8, nam, template);
+    std.mem.copyForwards(u8, nam, template);
 
-    const seed = @truncate(u64, @bitCast(u128, std.time.nanoTimestamp()));
+    const seed = @as(u64, @truncate(@as(u128, @bitCast(std.time.nanoTimestamp()))));
     var r = std.rand.DefaultPrng.init(seed);
 
     var fill = nam[template_start.len..nam.len];
@@ -87,17 +88,17 @@ pub fn temporaryName(allocator: *std.mem.Allocator) ![]u8 {
     var i: usize = 0;
     while (i < 100) : (i += 1) {
         // generate a random uppercase letter, that is, 65 + random number.
-        for (fill) |_, f_idx| {
-            var idx = @intCast(u8, r.random.uintLessThan(u5, 24));
-            var letter = @as(u8, 65) + idx;
+        for (fill, 0..) |_, f_idx| {
+            const idx = @as(u8, @intCast(r.random().uintLessThan(u5, 24)));
+            const letter = @as(u8, 65) + idx;
             fill[f_idx] = letter;
         }
 
         // if we fail to access it, we assume it doesn't exist and return it.
         var tmp_file: std.fs.File = std.fs.cwd().openFile(
             nam,
-            .{ .read = true, .write = false },
-        ) catch |err| blk: {
+            .{ .mode = .read_only },
+        ) catch |err| {
             if (err == error.FileNotFound) return nam else continue;
         };
 
@@ -121,7 +122,7 @@ pub fn mkSfInfo() c.SF_INFO {
 }
 
 pub const Image = struct {
-    allocator: *std.mem.Allocator,
+    allocator: std.mem.Allocator,
 
     /// Pointer to the underlying libsndfile's SNDFILE struct.
     sndfile: *c.SNDFILE,
@@ -136,11 +137,11 @@ pub const Image = struct {
     curpath: []const u8,
 
     /// Open a BMP image for later.
-    pub fn open(allocator: *std.mem.Allocator, path: []const u8) !*Image {
+    pub fn open(allocator: std.mem.Allocator, path: []const u8) !*Image {
         var in_fmt = mkSfInfo();
-        var sndfile = try sopen(allocator, path, c.SFM_READ, &in_fmt);
+        const sndfile = try sopen(allocator, path, c.SFM_READ, &in_fmt);
 
-        var image = try allocator.create(Image);
+        const image = try allocator.create(Image);
 
         std.debug.assert(in_fmt.frames > @as(i64, 0));
         std.debug.assert(in_fmt.seekable == @as(i32, 1));
@@ -150,7 +151,7 @@ pub const Image = struct {
             .sndfile = sndfile,
             .path = path,
             .curpath = path,
-            .frames = @intCast(usize, in_fmt.frames),
+            .frames = @as(usize, @intCast(in_fmt.frames)),
         };
 
         return image;
@@ -159,10 +160,10 @@ pub const Image = struct {
     pub fn clone(self: *Image) !*Image {
         var in_fmt = mkSfInfo();
         // clone sndfile
-        var sndfile = try sopen(self.allocator, self.curpath, c.SFM_READ, &in_fmt);
-        std.testing.expectEqual(self.frames, @intCast(usize, in_fmt.frames));
+        const sndfile = try sopen(self.allocator, self.curpath, c.SFM_READ, &in_fmt);
+        std.debug.assert(self.frames == @as(usize, @intCast(in_fmt.frames)));
 
-        var image = try self.allocator.create(Image);
+        const image = try self.allocator.create(Image);
 
         std.debug.assert(in_fmt.frames > @as(i64, 0));
         std.debug.assert(in_fmt.seekable == @as(i32, 1));
@@ -172,35 +173,37 @@ pub const Image = struct {
             .sndfile = sndfile,
             .path = self.path,
             .curpath = self.curpath,
-            .frames = @intCast(usize, in_fmt.frames),
+            .frames = @as(usize, @intCast(in_fmt.frames)),
         };
 
         return image;
     }
 
     pub fn close(self: *Image) void {
-        //self.allocator.free(self.path);
-        //self.allocator.free(self.curpath);
-        var st: i32 = c.sf_close(self.sndfile);
-
+        const st: i32 = c.sf_close(self.sndfile);
         if (st != 0) {
-            std.debug.warn("Failed to close {} ({})\n", .{
+            log.debug("Failed to close {s} ({s})", .{
                 self.path,
                 c.sf_error_number(st),
             });
         }
+
+        self.allocator.free(self.path);
+        self.allocator.free(self.curpath);
+
+        var allocator = self.allocator;
+        self.* = undefined;
+        allocator.destroy(self);
     }
 
     pub fn read(self: *Image, file_chans: c_int, buf: []f32) bool {
-        var file = file_opt.?;
-
-        const n_read: c.sf_count_t = c.sf_readf_float(file, buf.ptr, 1);
-        const buf_chans = @intCast(c_int, buf.len);
+        const n_read: c.sf_count_t = c.sf_readf_float(self.sndfile, buf.ptr, 1);
+        const buf_chans = @as(c_int, @intCast(buf.len));
 
         var i = file_chans - 1;
         while (i < buf_chans) : (i += 1) {
             //buf[@intCast(usize, i)] = buf[i % file_chans];
-            buf[@intCast(usize, i)] = buf[@intCast(usize, @mod(i, file_chans))];
+            buf[@as(usize, @intCast(i))] = buf[@as(usize, @intCast(@mod(i, file_chans)))];
         }
 
         return n_read == 1;
@@ -224,7 +227,7 @@ pub const Image = struct {
         sseek(out_file, start);
 
         while (i <= end) : (i += buf.len) {
-            std.debug.warn("\t\ti={}, buf.len={}, end={}\n", .{ i, buf.len, end });
+            log.debug("\t\ti={d}, buf.len={d}, end={d}", .{ i, buf.len, end });
             sseek(self.sndfile, i);
             sseek(out_file, i);
 
@@ -234,13 +237,13 @@ pub const Image = struct {
             var view: []f32 = buf[0..buf.len];
 
             if (bytes_until_end < buf.len) {
-                read_bytes = c.sf_readf_float(self.sndfile, buf.ptr, @intCast(i64, bytes_until_end));
+                read_bytes = c.sf_readf_float(self.sndfile, buf.ptr, @as(i64, @intCast(bytes_until_end)));
                 view = buf[0..bytes_until_end];
             } else {
-                read_bytes = c.sf_readf_float(self.sndfile, buf.ptr, @intCast(i64, buf.len));
+                read_bytes = c.sf_readf_float(self.sndfile, buf.ptr, @as(i64, @intCast(buf.len)));
             }
 
-            try swrite(out_file, view.ptr, @intCast(i64, view.len));
+            try swrite(out_file, view.ptr, @as(i64, @intCast(view.len)));
         }
 
         sseek(self.sndfile, end);
@@ -249,8 +252,8 @@ pub const Image = struct {
 
     fn getSeekPos(self: *Image, position: plugins.Position) plugins.SeekPos {
         const file_end = self.frames;
-        var seek_pos = position.seekPos(file_end);
-        std.debug.warn("\tstart {} end {}\n", .{ seek_pos.start, seek_pos.end });
+        const seek_pos = position.seekPos(file_end);
+        log.debug("\tstart {d} end {d}", .{ seek_pos.start, seek_pos.end });
         return seek_pos;
     }
 
@@ -261,9 +264,9 @@ pub const Image = struct {
         // std.testing.expectEqual(self.frames, @intCast(usize, in_fmt.frames));
 
         self.curpath = path;
-        self.frames = @intCast(usize, in_fmt.frames);
+        self.frames = @as(usize, @intCast(in_fmt.frames));
 
-        std.debug.warn("\timage: reopened on '{}' (frames={}, fmt.frames={})\n", .{
+        log.debug("\timage: reopened on '{s}' (frames={d}, fmt.frames={d})", .{
             self.curpath,
             self.frames,
             in_fmt.frames,
@@ -271,7 +274,7 @@ pub const Image = struct {
     }
 
     pub fn checkValid(self: *Image) !void {
-        var file = try std.fs.cwd().openFile(self.path, .{ .read = true });
+        var file = try std.fs.cwd().openFile(self.path, .{ .mode = .read_only });
         defer file.close();
 
         // main bmp header:
@@ -303,33 +306,34 @@ pub const Image = struct {
         defer ctx.deinit();
 
         var ports = try lv2.setupPorts(&ctx);
+        defer ctx.allocator.free(ports);
 
         if (ctx.n_audio_in > 2) {
-            std.debug.warn("plugin <{}> has more than two inputs.\n", .{plugin_uri});
+            log.debug("plugin <{s}> has more than two inputs.", .{plugin_uri});
             return ImageError.InvalidPlugin;
         }
 
         if (ctx.n_audio_out > 2) {
-            std.debug.warn("plugin <{}> has more than two outputs.\n", .{plugin_uri});
+            log.debug("plugin <{s}> has more than two outputs.", .{plugin_uri});
             return ImageError.InvalidPlugin;
         }
 
         // now, for each param for the plugin, we find its port, and set
         // the value for the port there.
         for (params.items) |param| {
-            var sym_cstr = try std.cstr.addNullByte(self.allocator, param.sym);
+            const sym_cstr = try self.allocator.dupeZ(u8, param.sym);
             defer self.allocator.free(sym_cstr);
 
-            var sym = c.lilv_new_string(ctx.world, sym_cstr.ptr);
-            const port = c.lilv_plugin_get_port_by_symbol(ctx.plugin, sym) orelse blk: {
-                std.debug.warn("assert fail: symbol {} not found on port\n", .{param.sym});
+            const sym = c.lilv_new_string(ctx.world, sym_cstr.ptr);
+            const port = c.lilv_plugin_get_port_by_symbol(ctx.plugin, sym) orelse {
+                log.debug("assert fail: symbol {s} not found on port", .{param.sym});
                 return ImageError.InvalidSymbol;
             };
 
             c.lilv_node_free(sym);
 
-            var idx = c.lilv_port_get_index(ctx.plugin, port);
-            std.debug.warn("\tset sym={}, idx={} to val={}\n", .{
+            const idx = c.lilv_port_get_index(ctx.plugin, port);
+            log.debug("\tset sym={s}, idx={d} to val={}", .{
                 param.sym,
                 idx,
                 param.value,
@@ -339,11 +343,11 @@ pub const Image = struct {
 
         // now we need to generate a temporary file and put the output of
         // running the plugin on that file
-        var tmpnam = try temporaryName(self.allocator);
-        std.debug.warn("\trunning plugin from '{}' to '{}'\n", .{ self.curpath, tmpnam });
+        const tmpnam = try temporaryName(self.allocator);
+        log.debug("\trunning plugin from '{s}' to '{s}'", .{ self.curpath, tmpnam });
 
         var out_fmt = mkSfInfo();
-        var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
+        const out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
 
         var rctx = try plugins.RunContext.init(self.allocator, ctx.plugin);
         defer rctx.deinit();
@@ -373,10 +377,10 @@ pub const Image = struct {
         sseek(self.sndfile, seek_pos.start);
 
         var i: usize = seek_pos.start;
-        std.debug.warn("\tseek pos start: {} end: {}\n", .{ seek_pos.start, seek_pos.end });
+        log.debug("\tseek pos start: {d} end: {d}", .{ seek_pos.start, seek_pos.end });
 
         var inbuf = &rctx.buffers.in;
-        var outbuf = &rctx.buffers.out;
+        const outbuf = &rctx.buffers.out;
 
         while (i <= seek_pos.end) : (i += 1) {
             inbuf[0] = 0;
@@ -384,7 +388,7 @@ pub const Image = struct {
 
             const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
             if (read_bytes == 0) {
-                std.debug.warn("WARN! reached EOF at idx={}\n", .{i});
+                log.debug("WARN! reached EOF at idx={d}", .{i});
                 break;
             }
 
@@ -412,12 +416,12 @@ pub const Image = struct {
         try self.reopen(tmpnam);
         try self.checkValid();
 
-        var time_taken = timer.read();
-        std.debug.warn("\ttook {d:.2}ms running plugin\n", .{time_taken / std.time.us_per_ms});
+        const time_taken = timer.read();
+        log.debug("\ttook {d:.2}ms running plugin", .{time_taken / std.time.us_per_ms});
     }
 
     pub fn saveTo(self: *Image, out_path: []const u8) !void {
-        std.debug.warn("\timg: copy from '{}' to '{}'\n", .{ self.curpath, out_path });
+        log.debug("\timg: copy from '{s}' to '{s}'", .{ self.curpath, out_path });
         try std.fs.copyFileAbsolute(self.curpath, out_path, .{});
     }
 
@@ -425,9 +429,9 @@ pub const Image = struct {
         self: *Image,
         comptime Plugin: type,
         position: plugins.Position,
-        extra: var,
+        extra: anytype,
     ) !void {
-        var plugin_opt: ?Plugin = Plugin.init(self.allocator, extra);
+        const plugin_opt: ?Plugin = Plugin.init(self.allocator, extra);
         if (plugin_opt == null) {
             return ImageError.PluginLoadFail;
         }
@@ -444,11 +448,11 @@ pub const Image = struct {
 
         // the code here is a copypaste of runPlugin() without the specific
         // lilv things.
-        var tmpnam = try temporaryName(self.allocator);
-        std.debug.warn("\trunning CUSTOM plugin from '{}' to '{}'\n", .{ self.curpath, tmpnam });
+        const tmpnam = try temporaryName(self.allocator);
+        log.debug("\trunning CUSTOM plugin from '{s}' to '{s}'", .{ self.curpath, tmpnam });
 
         var out_fmt = mkSfInfo();
-        var out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
+        const out_file = try sopen(self.allocator, tmpnam, c.SFM_WRITE, &out_fmt);
 
         var bufs = plugins.RunBuffers{};
         const seek_pos = self.getSeekPos(position);
@@ -472,15 +476,15 @@ pub const Image = struct {
         sseek(self.sndfile, seek_pos.start);
 
         var i: usize = seek_pos.start;
-        std.debug.warn("\tseek pos start: {} end: {}\n", .{ seek_pos.start, seek_pos.end });
+        log.debug("\tseek pos start: {d} end: {d}", .{ seek_pos.start, seek_pos.end });
 
-        var inbuf = &bufs.in;
-        var outbuf = &bufs.out;
+        const inbuf = &bufs.in;
+        const outbuf = &bufs.out;
 
         while (i <= seek_pos.end) : (i += 1) {
             const read_bytes = c.sf_readf_float(self.sndfile, inbuf, 1);
             if (read_bytes == 0) {
-                std.debug.warn("WARN! reached EOF at idx={}\n", .{i});
+                log.debug("WARN! reached EOF at idx={d}", .{i});
                 break;
             }
 
diff --git a/src/lang.zig b/src/lang.zig
index 305eb4a..31e5a73 100644
--- a/src/lang.zig
+++ b/src/lang.zig
@@ -3,6 +3,7 @@ const std = @import("std");
 const plugin = @import("plugin.zig");
 const custom = @import("custom.zig");
 
+const log = std.log.scoped(.scritcher_lang);
 pub const ParseError = error{ParseFail};
 
 pub const CommandType = enum {
@@ -93,7 +94,7 @@ pub const Command = struct {
         rotate,
     };
 
-    pub fn tagToType(tag: Tag) type {
+    pub fn tagToType(comptime tag: Tag) type {
         return switch (tag) {
             .noop => Noop,
             .load => Load,
@@ -135,8 +136,6 @@ pub const Command = struct {
             .embed => Embed,
 
             .rotate => Rotate,
-
-            else => @panic("TODO"),
         };
     }
 
@@ -144,11 +143,23 @@ pub const Command = struct {
         if (base.tag != T.base_tag)
             return null;
 
-        return @fieldParentPtr(T, "base", base);
+        //const baseInt = @intFromPtr(base);
+
+        //log.debug("casting from {d}", .{baseInt});
+        //log.debug("aligns from 8? {d}", .{baseInt % 8});
+        //log.debug("align T: {d} {s}", .{ @alignOf(*T), @typeName(T) });
+        //log.debug("align base: {d} {s}", .{ @alignOf(*const @This()), @typeName(@This()) });
+        const base_aligned: *const @This() = @alignCast(base);
+
+        const parented = @as(*const T, @alignCast(@fieldParentPtr("base", base_aligned)));
+
+        const ptr: *const T = @alignCast(parented);
+        //log.debug("align: {d}\n", .{@alignOf(@TypeOf(ptr))});
+        return ptr;
     }
 
     pub fn print(base: *const @This()) void {
-        std.debug.warn("tag: {}\n", .{base.tag});
+        log.debug("tag: {}", .{base.tag});
     }
 
     pub const Noop = struct {
@@ -159,7 +170,7 @@ pub const Command = struct {
     pub const Load = struct {
         pub const base_tag = Tag.load;
         base: Command,
-        path: []u8,
+        path: []const u8,
     };
 
     pub const Quicksave = struct {
@@ -201,33 +212,25 @@ pub const Command = struct {
     pub const Amp = LV2Command(
         .amp,
         "http://lv2plug.in/plugins/eg-amp",
-        struct {
-            gain: f32
-        },
+        struct { gain: f32 },
     );
 
     pub const RFlanger = LV2Command(
         .rflanger,
         "http://plugin.org.uk/swh-plugins/retroFlange",
-        struct {
-            delay_depth_avg: f32, law_freq: f32
-        },
+        struct { delay_depth_avg: f32, law_freq: f32 },
     );
 
     pub const Eq = LV2Command(
         .rflanger,
         "http://plugin.org.uk/swh-plugins/dj_eq_mono",
-        struct {
-            lo: f32, mid: f32, hi: f32
-        },
+        struct { lo: f32, mid: f32, hi: f32 },
     );
 
     pub const Phaser = LV2Command(
         .phaser,
         "http://plugin.org.uk/swh-plugins/lfoPhaser",
-        struct {
-            lfo_rate: f32, lfo_depth: f32, fb: f32, spread: f32
-        },
+        struct { lfo_rate: f32, lfo_depth: f32, fb: f32, spread: f32 },
     );
 
     pub const Mbeq = LV2Command(
@@ -380,9 +383,7 @@ pub const Command = struct {
     pub const Foverdrive = LV2Command(.foverdrive, "http://plugin.org.uk/swh-plugins/foverdrive", struct {
         drive: f32,
     });
-    pub const Thruzero = LV2Command(.thruzero, "http://drobilla.net/plugins/mda/ThruZero", struct {
-        rate: f32, mix: f32, feedback: f32, depth_mod: f32
-    });
+    pub const Thruzero = LV2Command(.thruzero, "http://drobilla.net/plugins/mda/ThruZero", struct { rate: f32, mix: f32, feedback: f32, depth_mod: f32 });
 
     pub const Gverb = LV2Command(.gverb, "http://plugin.org.uk/swh-plugins/gverb", struct {
         roomsize: f32,
@@ -476,50 +477,94 @@ pub const Command = struct {
     });
 };
 
-pub const CommandList = std.ArrayList(*Command);
+const CmdArrayList = std.ArrayList(*Command);
+
+pub const CommandList = struct {
+    list: CmdArrayList,
+    const Self = @This();
+
+    pub fn init(allocator: std.mem.Allocator) Self {
+        return .{
+            .list = CmdArrayList.init(allocator),
+        };
+    }
+
+    pub fn deinit(self: *Self) void {
+        for (self.list.items) |cmd_ptr| {
+            inline for (@typeInfo(Command.Tag).Enum.fields) |field| {
+                if (cmd_ptr.tag == @field(Command.Tag, field.name)) {
+                    const actual_tag =
+                        @field(Command.Tag, field.name);
+                    // if we find a match on the tag, we can get the type
+                    const typ = Command.tagToType(actual_tag);
+
+                    const inner_command = cmd_ptr.cast(typ).?;
+                    inline for (@typeInfo(typ).Struct.fields) |cmd_field| {
+                        switch (cmd_field.type) {
+                            []u8, []const u8 => self.list.allocator.free(@field(inner_command, cmd_field.name)),
+                            else => {},
+                        }
+                    }
+                }
+            }
+
+            //TODO this is ian invalid free
+            //self.list.allocator.destroy(cmd_ptr);
+        }
+        self.list.deinit();
+    }
+
+    pub fn append(self: *Self, cmd: *Command) !void {
+        return try self.list.append(cmd);
+    }
+};
 
 /// A parser.
 pub const Lang = struct {
-    allocator: *std.mem.Allocator,
+    allocator: std.mem.Allocator,
 
     has_error: bool = false,
     line: usize = 0,
 
-    pub fn init(allocator: *std.mem.Allocator) Lang {
+    pub fn init(allocator: std.mem.Allocator) Lang {
         return Lang{
             .allocator = allocator,
         };
     }
 
-    pub fn deinit(self: *Lang) void {}
+    pub fn deinit(self: *Lang) void {
+        _ = self;
+    }
 
     pub fn reset(self: *Lang) void {
         self.has_error = false;
         self.line = 0;
     }
-    fn doError(self: *Lang, comptime fmt: []const u8, args: var) void {
-        std.debug.warn("ERROR! at line {}: ", .{self.line});
-        std.debug.warn(fmt, args);
-        std.debug.warn("\n", .{});
+
+    fn doError(self: *Lang, comptime fmt: []const u8, args: anytype) void {
+        log.warn("ERROR! at line {}: ", .{self.line});
+        log.warn(fmt, args);
         self.has_error = true;
     }
 
     fn parseCommandArguments(
         self: *@This(),
         comptime command_struct: type,
-        tok_it: *std.mem.TokenIterator,
+        tok_it: *std.mem.SplitIterator(u8, .sequence),
         commands: *CommandList,
     ) !void {
         // Based on the command struct fields, we can parse the arguments.
         var cmd = try self.allocator.create(command_struct);
+
+        // we already add the command to the list to prevent memory leaks
+        // by commands that error out
+        try commands.append(&cmd.base);
+
         const is_lv2_command = switch (command_struct.base_tag) {
             .noop, .load, .quicksave, .runqs, .rotate => false,
             else => true,
         };
 
-        // TODO: crash when no arguments are left but we still need
-        // arguments...
-
         if (is_lv2_command) {
             const split = tok_it.next();
             if (split == null) {
@@ -539,16 +584,16 @@ pub const Lang = struct {
             inline for (@typeInfo(@TypeOf(cmd.parameters)).Struct.fields) |cmd_field| {
                 const maybe_arg = tok_it.next();
                 if (maybe_arg == null) {
-                    self.doError("Expected parameter for {}, got nothing", .{cmd_field.name});
+                    self.doError("Expected parameter for {s}, got nothing", .{cmd_field.name});
                     return;
                 }
 
                 const arg = maybe_arg.?;
-                const arg_value = switch (cmd_field.field_type) {
+                const arg_value = switch (cmd_field.type) {
                     f32 => try std.fmt.parseFloat(f32, arg),
                     u64 => try std.fmt.parseInt(u64, arg, 10),
                     usize => try std.fmt.parseInt(usize, arg, 10),
-                    []const u8 => try self.allocator.dupe(u8, arg),
+                    []const u8 => @as([]const u8, try self.allocator.dupe(u8, arg)),
                     else => @compileError("parameter struct has unsupported type " ++ @typeName(cmd_field.field_type)),
                 };
 
@@ -561,17 +606,23 @@ pub const Lang = struct {
                         continue;
                     }
                 }
-                const arg = tok_it.next().?;
-                const argument_value = switch (cmd_field.field_type) {
+
+                const arg_opt = tok_it.next();
+                if (arg_opt == null) {
+                    self.doError("Expected parameter for {s}, got nothing", .{cmd_field.name});
+                    return;
+                }
+                const arg = arg_opt.?;
+
+                const argument_value = switch (cmd_field.type) {
                     usize => try std.fmt.parseInt(usize, arg, 10),
                     i32 => try std.fmt.parseInt(i32, arg, 10),
                     f32 => try std.fmt.parseFloat(f32, arg),
-                    []u8 => try self.allocator.dupe(u8, arg),
-                    []const u8 => try self.allocator.dupe(u8, arg),
+                    []const u8 => @as([]const u8, try self.allocator.dupe(u8, arg)),
                     else => @compileError("Invalid parameter type (" ++ @typeName(cmd_field.field_type) ++ ") left on command struct " ++ @typeName(command_struct) ++ "."),
                 };
 
-                std.debug.warn("parsing {}, arg of type {} => {}\n", .{
+                log.debug("parsing {s}, arg of type {s} => {any}", .{
                     @typeName(command_struct),
                     @typeName(@TypeOf(argument_value)),
                     argument_value,
@@ -583,14 +634,13 @@ pub const Lang = struct {
 
         cmd.base.tag = command_struct.base_tag;
         const command = cmd.base.cast(command_struct).?;
-        std.debug.warn("cmd: {}\n", .{command});
-
-        try commands.append(&cmd.base);
+        log.debug("cmd: {}", .{command});
     }
 
     pub fn parse(self: *Lang, data: []const u8) !CommandList {
-        var splitted_it = std.mem.split(data, ";");
+        var splitted_it = std.mem.split(u8, data, ";");
         var cmds = CommandList.init(self.allocator);
+        errdefer cmds.deinit();
 
         while (splitted_it.next()) |stmt_orig| {
             self.line += 1;
@@ -601,9 +651,9 @@ pub const Lang = struct {
             if (std.mem.startsWith(u8, stmt, "#")) continue;
 
             // TODO better tokenizer instead of just tokenize(" ")...maybe????
-            var tok_it = std.mem.tokenize(stmt, " ");
+            var tok_it = std.mem.splitSequence(u8, stmt, " ");
 
-            var cmd_opt = tok_it.next();
+            const cmd_opt = tok_it.next();
             if (cmd_opt == null) {
                 self.doError("No command given", .{});
                 continue;
@@ -613,38 +663,51 @@ pub const Lang = struct {
             var found: bool = false;
 
             inline for (@typeInfo(Command).Struct.decls) |cmd_struct_decl| {
-                switch (cmd_struct_decl.data) {
-                    .Type => |typ| switch (@typeInfo(typ)) {
-                        .Struct => {},
-                        else => continue,
-                    },
+                const struct_name = cmd_struct_decl.name;
+                const cmd_struct_type = @field(Command, struct_name);
+
+                const info_of_info = @typeInfo(@TypeOf(cmd_struct_type));
+
+                switch (info_of_info) {
+                    .Type => {},
+                    else => continue,
+                }
+
+                const info = @typeInfo(cmd_struct_type);
+
+                switch (info) {
+                    .Struct => {},
                     else => continue,
                 }
 
-                const struct_name = cmd_struct_decl.name;
                 comptime var lowered_command_name = [_]u8{0} ** struct_name.len;
+                var runtime_lowered_command_name = [_]u8{0} ** struct_name.len;
                 comptime {
-                    for (struct_name) |c, i| {
+                    for (struct_name, 0..) |c, i| {
                         lowered_command_name[i] = std.ascii.toLower(c);
                     }
                 }
+                const c_l = lowered_command_name;
+                std.mem.copyForwards(u8, &runtime_lowered_command_name, &c_l);
 
                 // if we have a match, we know the proper struct type
                 // to use. this actually works compared to storing command_struct
                 // in a variable because then that variable must be comptime.
 
                 // the drawback of this approach is that our emitted code is basically linear
-                // because we don't use the hashmap anymore. maybe #5359 can help.
+                // because we don't use the hashmap anymore.
+                //
+                // Attempting to use ComptimeHashMap hits compiler bugs and I'm
+                // not sure if we can map strings to *types* in it.
 
-                if (std.mem.eql(u8, &lowered_command_name, command_string)) {
+                if ((!found) and std.mem.eql(u8, &runtime_lowered_command_name, command_string)) {
                     found = true;
-                    const cmd_struct_type = cmd_struct_decl.data.Type;
                     try self.parseCommandArguments(cmd_struct_type, &tok_it, &cmds);
                 }
             }
 
             if (!found) {
-                self.doError("Unknown command '{}' ({})", .{ command_string, command_string.len });
+                self.doError("Unknown command '{s}' ({d} bytes)", .{ command_string, command_string.len });
                 continue;
             }
         }
@@ -656,18 +719,18 @@ pub const Lang = struct {
 };
 
 test "noop" {
-    var lang = Lang.init(std.heap.direct_allocator);
+    var lang = Lang.init(std.testing.allocator);
     defer lang.deinit();
 
     var cmds = try lang.parse("noop;");
     defer cmds.deinit();
 
-    std.testing.expectEqual(cmds.len, 1);
-    std.testing.expectEqual(cmds.items[0].command, .Noop);
+    try std.testing.expectEqual(cmds.list.items.len, 1);
+    try std.testing.expectEqual(cmds.list.items[0].tag, .noop);
 }
 
 test "load, phaser, quicksave" {
-    var lang = Lang.init(std.heap.direct_allocator);
+    var lang = Lang.init(std.testing.allocator);
     defer lang.deinit();
 
     const prog =
@@ -679,8 +742,21 @@ test "load, phaser, quicksave" {
     var cmds = try lang.parse(prog);
     defer cmds.deinit();
 
-    std.testing.expectEqual(cmds.len, 3);
-    std.testing.expectEqual(cmds.items[0].command, .Load);
-    std.testing.expectEqual(cmds.items[1].command, .Phaser);
-    std.testing.expectEqual(cmds.items[2].command, .Quicksave);
+    try std.testing.expectEqual(cmds.list.items.len, 3);
+    try std.testing.expectEqual(cmds.list.items[0].tag, .load);
+    try std.testing.expectEqual(cmds.list.items[1].tag, .phaser);
+    try std.testing.expectEqual(cmds.list.items[2].tag, .quicksave);
+}
+
+test "load, phaser with errors, quicksave" {
+    var lang = Lang.init(std.testing.allocator);
+    defer lang.deinit();
+
+    const prog =
+        \\load :0;
+        \\phaser 3 1 25;
+        \\quicksave;
+    ;
+
+    try std.testing.expectError(error.ParseFail, lang.parse(prog));
 }
diff --git a/src/lv2_helpers.zig b/src/lv2_helpers.zig
index a72e07d..a59babd 100644
--- a/src/lv2_helpers.zig
+++ b/src/lv2_helpers.zig
@@ -1,6 +1,8 @@
 const std = @import("std");
 const plugin = @import("plugin.zig");
 
+const log = std.log.scoped(.scritcher_lv2);
+
 pub const c = @cImport({
     @cInclude("sndfile.h");
     @cInclude("lilv/lilv.h");
@@ -21,7 +23,7 @@ const LV2_CORE__connectionOptional = Lv2Core("#connectionOptional");
 pub fn lilv_instance_connect_port(
     instance: [*c]c.LilvInstance,
     port_index: u32,
-    data_location: ?*c_void,
+    data_location: ?*anyopaque,
 ) void {
     instance.?.*.lv2_descriptor.?.*.connect_port.?(instance.?.*.lv2_handle, port_index, data_location);
 }
@@ -59,14 +61,16 @@ pub const Port = struct {
 /// Setup ports for a given plugin. Gives an array to pointers of Port structs.
 /// This setup is required so we link the plugin to the ports later on, and
 /// also link our buffers, and control values.
+///
+/// Caller owns returned memory.
 pub fn setupPorts(ctx: *plugin.Context) ![]Port {
-    var world = ctx.world;
+    const world = ctx.world;
     const n_ports: u32 = c.lilv_plugin_get_num_ports(ctx.plugin);
 
     var ports = try ctx.allocator.alloc(Port, n_ports);
 
-    for (ports) |_, idx| {
-        var port: *Port = &ports[idx];
+    for (ports, 0..) |_, idx| {
+        const port: *Port = &ports[idx];
         port.* = Port{
             .lilv_port = null,
             .ptype = .Control,
@@ -77,24 +81,24 @@ pub fn setupPorts(ctx: *plugin.Context) ![]Port {
         };
     }
 
-    var values: []f32 = try ctx.allocator.alloc(f32, n_ports);
+    const values: []f32 = try ctx.allocator.alloc(f32, n_ports);
     defer ctx.allocator.free(values);
 
     c.lilv_plugin_get_port_ranges_float(ctx.plugin, null, null, values.ptr);
-    var lv2_InputPort = c.lilv_new_uri(world, LV2_CORE__InputPort.ptr);
-    defer std.heap.c_allocator.destroy(lv2_InputPort);
+    const lv2_InputPort = c.lilv_new_uri(world, LV2_CORE__InputPort.ptr).?;
+    //defer std.heap.c_allocator.destroy(lv2_InputPort);
 
-    var lv2_OutputPort = c.lilv_new_uri(world, LV2_CORE__OutputPort.ptr);
-    defer std.heap.c_allocator.destroy(lv2_OutputPort);
+    const lv2_OutputPort = c.lilv_new_uri(world, LV2_CORE__OutputPort.ptr).?;
+    //defer std.heap.c_allocator.destroy(lv2_OutputPort);
 
-    var lv2_AudioPort = c.lilv_new_uri(world, LV2_CORE__AudioPort.ptr);
-    defer std.heap.c_allocator.destroy(lv2_AudioPort);
+    const lv2_AudioPort = c.lilv_new_uri(world, LV2_CORE__AudioPort.ptr).?;
+    //defer std.heap.c_allocator.destroy(lv2_AudioPort);
 
-    var lv2_ControlPort = c.lilv_new_uri(world, LV2_CORE__ControlPort.ptr);
-    defer std.heap.c_allocator.destroy(lv2_ControlPort);
+    const lv2_ControlPort = c.lilv_new_uri(world, LV2_CORE__ControlPort.ptr).?;
+    //defer std.heap.c_allocator.destroy(lv2_ControlPort);
 
-    var lv2_connectionOptional = c.lilv_new_uri(world, LV2_CORE__connectionOptional.ptr);
-    defer std.heap.c_allocator.destroy(lv2_connectionOptional);
+    const lv2_connection_string = c.lilv_new_uri(world, LV2_CORE__connectionOptional.ptr).?;
+    //defer std.heap.c_allocator.destroy(lv2_connection_string);
 
     var i: u32 = 0;
     while (i < n_ports) : (i += 1) {
@@ -111,12 +115,12 @@ pub fn setupPorts(ctx: *plugin.Context) ![]Port {
             port.value = values[i];
         }
 
-        port.optional = c.lilv_port_has_property(ctx.plugin, lport, lv2_connectionOptional);
+        port.optional = c.lilv_port_has_property(ctx.plugin, lport, lv2_connection_string);
 
         if (c.lilv_port_is_a(ctx.plugin, lport, lv2_InputPort)) {
             port.is_input = true;
         } else if (!c.lilv_port_is_a(ctx.plugin, lport, lv2_OutputPort) and !port.optional) {
-            std.debug.warn("Port {} is neither input or output\n", .{i});
+            log.debug("Port {d} is neither input or output", .{i});
             return error.UnassignedIOPort;
         }
 
@@ -132,7 +136,7 @@ pub fn setupPorts(ctx: *plugin.Context) ![]Port {
                 ctx.n_audio_out += 1;
             }
         } else if (!port.optional) {
-            std.debug.warn("Port {} has unsupported type\n", .{i});
+            log.debug("Port {d} has unsupported type", .{i});
             return error.UnsupportedPortType;
         }
     }
diff --git a/src/magick.zig b/src/magick.zig
index 33ba882..ab59f0a 100644
--- a/src/magick.zig
+++ b/src/magick.zig
@@ -2,6 +2,7 @@
 const std = @import("std");
 const images = @import("image.zig");
 
+const log = std.log.scoped(.scritcher_magick);
 const Image = images.Image;
 
 const mc = @cImport({
@@ -14,7 +15,7 @@ pub const MagickContext = struct {
     pub fn init() !MagickContext {
         mc.InitializeMagick(null);
 
-        var wand = mc.NewMagickWand();
+        const wand = mc.NewMagickWand();
         if (wand == null) return error.WandCreateFail;
 
         return MagickContext{
@@ -28,6 +29,7 @@ pub const MagickContext = struct {
     }
 
     pub fn doErr(self: *MagickContext) !void {
+        _ = self;
         return error.WandError;
     }
 };
@@ -36,10 +38,10 @@ fn magickLoad(image: *Image) !MagickContext {
     var mctx = try MagickContext.init();
     errdefer mctx.deinit();
 
-    var curpath = try std.cstr.addNullByte(image.allocator, image.curpath);
+    const curpath = try image.allocator.dupeZ(u8, image.curpath);
     defer image.allocator.free(curpath);
 
-    std.debug.warn("loading '{}'\n", .{curpath});
+    log.debug("loading '{s}'", .{curpath});
 
     if (mc.MagickReadImage(mctx.wand, curpath.ptr) != 1)
         return error.MagickReadFail;
@@ -50,16 +52,16 @@ fn magickLoad(image: *Image) !MagickContext {
 fn magickSave(image: *Image, wand: *mc.MagickWand) !void {
     const allocator = image.allocator;
 
-    var tmpnam = try images.temporaryName(allocator);
-    var c_tmpnam = try std.cstr.addNullByte(allocator, tmpnam);
+    const tmpnam = try images.temporaryName(allocator);
+    const c_tmpnam = try allocator.dupeZ(u8, tmpnam);
     defer allocator.free(c_tmpnam);
 
-    std.debug.warn("\tmagick: saving to '{}'..", .{c_tmpnam});
+    log.debug("\tmagick: saving to '{s}'..", .{c_tmpnam});
 
     if (mc.MagickWriteImage(wand, c_tmpnam.ptr) != 1)
         return error.MagickWriteFail;
 
-    std.debug.warn("OK\n", .{});
+    log.debug("OK", .{});
 
     try image.reopen(tmpnam);
 }
@@ -70,7 +72,7 @@ pub fn runRotate(image: *Image, deg: f32, bgfill: []const u8) !void {
     var mctx = try magickLoad(image);
     defer mctx.deinit();
 
-    var bg = mc.NewPixelWand();
+    const bg = mc.NewPixelWand();
     defer mc.DestroyPixelWand(bg);
 
     if (mc.PixelSetColor(bg, bgfill.ptr) != 1)
diff --git a/src/main.zig b/src/main.zig
index be1b672..f21087e 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -3,6 +3,8 @@ const langs = @import("lang.zig");
 const runners = @import("runner.zig");
 const printer = @import("printer.zig");
 
+const log = std.log.scoped(.scritcher);
+
 test "scritcher" {
     _ = @import("lang.zig");
     _ = @import("runner.zig");
@@ -16,30 +18,30 @@ const readline = @cImport({
     @cInclude("readline/history.h");
 });
 
-fn wrapInCmdList(allocator: *std.mem.Allocator, cmd: *langs.Command) !langs.CommandList {
+fn wrapInCmdList(allocator: std.mem.Allocator, cmd: *langs.Command) !langs.CommandList {
     var cmds = langs.CommandList.init(allocator);
     try cmds.append(cmd);
     return cmds;
 }
 
-fn copyCommandToHeap(allocator: *std.mem.Allocator, command: langs.Command, comptime tag: langs.Command.Tag) !*langs.Command {
+fn copyCommandToHeap(allocator: std.mem.Allocator, command: langs.Command, comptime tag: langs.Command.Tag) !*langs.Command {
     const CommandStruct = langs.Command.tagToType(tag);
     const casted = command.cast(CommandStruct).?;
     var heap_cmd = try allocator.create(CommandStruct);
 
-    @memcpy(
-        @ptrCast([*]u8, &heap_cmd),
-        @ptrCast([*]const u8, &casted),
-        @sizeOf(CommandStruct),
-    );
+    heap_cmd.* = casted.*;
+    log.debug("casted: {}", .{casted});
+    log.debug("heap_cmd: {}", .{heap_cmd});
 
     return &heap_cmd.base;
 }
 
-pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
+pub fn doRepl(allocator: std.mem.Allocator, args_it: anytype) !void {
     var stdout_file = std.io.getStdOut();
-    const stdout = &stdout_file.outStream();
-    const scri_path = try (args_it.next(allocator) orelse @panic("expected scri path"));
+    const stdout = &stdout_file.writer();
+    const scri_path = (args_it.next() orelse @panic("expected scri path"));
+    errdefer allocator.free(scri_path);
+    defer allocator.free(scri_path);
 
     var file_read_opt: ?std.fs.File = std.fs.cwd().openFile(scri_path, .{}) catch |err| blk: {
         if (err == error.FileNotFound) break :blk null;
@@ -54,18 +56,18 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
     defer lang.deinit();
 
     if (total_bytes > 0) {
-        // this MUST BE long lived (a reference to it is kept inside
-        // existing_cmds, and then passed along to cmds),
-        // we can't defer them here
-        var scri_existing = try allocator.alloc(u8, total_bytes);
+        const scri_existing = try allocator.alloc(u8, total_bytes);
         _ = try file_read_opt.?.read(scri_existing);
+        defer allocator.free(scri_existing);
 
-        // we can defer this because we copy the Command structs back to cmds
+        // we can't defer this directly because we copy the
+        // Command pointers to the cmds list. running deinit() directly
+        // would cause those pointers to be freed.
         var existing_cmds = try lang.parse(scri_existing);
-        defer existing_cmds.deinit();
+        defer existing_cmds.list.deinit();
 
         // copy the existing command list into the repl's command list
-        for (existing_cmds.items) |existing_cmd| {
+        for (existing_cmds.list.items) |existing_cmd| {
             try cmds.append(existing_cmd);
         }
     } else {
@@ -75,7 +77,7 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
         // TODO: deliberate memleak here. we only allocate this
         // command once, for the start of the file, so.
         var load_cmd = try allocator.create(langs.Command.Load);
-        std.mem.copy(u8, load_cmd.path, ":0");
+        load_cmd.path = ":0";
         load_cmd.base.tag = langs.Command.Tag.load;
 
         // taking address is fine, because load_cmd lives in the lifetime
@@ -87,14 +89,14 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
         file_read.close();
     }
 
-    var file = try std.fs.cwd().openFile(scri_path, .{
-        .write = true,
+    var file = try std.fs.cwd().createFile(scri_path, .{
         .read = false,
+        .truncate = true,
     });
     defer file.close();
 
-    var out = file.outStream();
-    var stream = &out;
+    var out = file.writer();
+    const stream = &out;
 
     // since we opened the file for writing, it becomes empty, so, to ensure
     // we don't fuck up later on, we print cmds before starting the repl
@@ -118,7 +120,7 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
     // run the load command
     try runner.runCommands(cmds, true);
 
-    const wanted_runner: []const u8 = std.os.getenv("SCRITCHER_RUNNER") orelse "ristretto";
+    const wanted_runner: []const u8 = std.posix.getenv("SCRITCHER_RUNNER") orelse "ristretto";
 
     var runqs_cmd = langs.Command.RunQS{
         .base = langs.Command{ .tag = langs.Command.Tag.runqs },
@@ -130,13 +132,13 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
 
         var rd_line = readline.readline("> ");
         if (rd_line == null) {
-            std.debug.warn("leaving from eof\n", .{});
+            log.debug("leaving from eof", .{});
             break;
         }
         readline.add_history(rd_line);
         //defer std.heap.c_allocator.destroy(rd_line);
 
-        var line = rd_line[0..std.mem.len(rd_line)];
+        const line = rd_line[0..std.mem.len(rd_line)];
 
         if (std.mem.eql(u8, line, "push")) {
             const heap_cmd = switch (current.tag) {
@@ -198,21 +200,20 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
             try printer.printList(cmds, stream);
             continue;
         } else if (std.mem.eql(u8, line, "quit") or std.mem.eql(u8, line, "q")) {
-            std.debug.warn("leaving\n", .{});
+            log.debug("leaving", .{});
             break;
         } else if (std.mem.startsWith(u8, line, "#")) {
             continue;
         }
 
         var cmds_parsed = lang.parse(line) catch |err| {
-            std.debug.warn("repl: error while parsing: {}\n", .{err});
+            log.debug("repl: error while parsing: {}", .{err});
             continue;
         };
 
         // no command? ignore!
-        if (cmds_parsed.items.len == 0) continue;
-
-        current = cmds_parsed.items[0].*;
+        if (cmds_parsed.list.items.len == 0) continue;
+        current = cmds_parsed.list.items[0].*;
 
         // by cloning the parent runner, we can iteratively write
         // whatever command we want and only commit the good results
@@ -229,25 +230,21 @@ pub fn doRepl(allocator: *std.mem.Allocator, args_it: var) !void {
     }
 }
 
-pub fn main() !void {
-    const allocator = std.heap.page_allocator;
+fn doHelp() void {
+    log.debug("scritcher!", .{});
+    log.debug("usage: scritcher [run|help|repl]", .{});
+    log.debug("\tscritcher run path_to_script.scri path_to_input_file.bmp", .{});
+    log.debug("\tscritcher repl path_to_script.scri path_to_input_file.bmp", .{});
+}
 
+fn doRun(allocator: std.mem.Allocator, args_it: anytype) !void {
     var lang = langs.Lang.init(allocator);
     defer lang.deinit();
 
     var runner = runners.Runner.init(allocator, false);
     defer runner.deinit();
 
-    var args_it = std.process.args();
-
-    // TODO print help
-
-    _ = try (args_it.next(allocator) orelse @panic("expected exe name"));
-    const scri_path = try (args_it.next(allocator) orelse @panic("expected scri path or 'repl'"));
-
-    if (std.mem.eql(u8, scri_path, "repl")) {
-        return try doRepl(allocator, &args_it);
-    }
+    const scri_path = (args_it.next() orelse @panic("run: expected scri path"));
 
     var file = try std.fs.cwd().openFile(scri_path, .{});
     defer file.close();
@@ -255,7 +252,7 @@ pub fn main() !void {
     // sadly, we read it all into memory. such is life
     const total_bytes = try file.getEndPos();
 
-    var data = try allocator.alloc(u8, total_bytes);
+    const data = try allocator.alloc(u8, total_bytes);
     defer allocator.free(data);
     _ = try file.read(data);
 
@@ -264,3 +261,33 @@ pub fn main() !void {
 
     try runner.runCommands(cmds, true);
 }
+
+pub fn main() !void {
+    var allocator_instance = std.heap.GeneralPurposeAllocator(.{}){};
+    defer {
+        _ = allocator_instance.deinit();
+    }
+    const allocator = allocator_instance.allocator();
+
+    var args_it = try std.process.argsWithAllocator(allocator);
+    defer args_it.deinit();
+
+    _ = args_it.skip();
+    const cli_command_opt = args_it.next();
+    if (cli_command_opt == null) {
+        return doHelp();
+    }
+
+    const cli_command = cli_command_opt.?;
+
+    if (std.mem.eql(u8, cli_command, "help")) {
+        return doHelp();
+    } else if (std.mem.eql(u8, cli_command, "repl")) {
+        return try doRepl(allocator, &args_it);
+    } else if (std.mem.eql(u8, cli_command, "run")) {
+        return try doRun(allocator, &args_it);
+    } else {
+        log.debug("unknown command: '{s}'", .{cli_command});
+        return error.UnknownCommand;
+    }
+}
diff --git a/src/plugin.zig b/src/plugin.zig
index b979833..29ec224 100644
--- a/src/plugin.zig
+++ b/src/plugin.zig
@@ -3,6 +3,7 @@ const std = @import("std");
 const lv2 = @import("lv2_helpers.zig");
 const c = lv2.c;
 
+const log = std.log.scoped(.scritcher_plugin);
 const ImageError = @import("image.zig").ImageError;
 
 /// Control port
@@ -35,7 +36,7 @@ pub const Position = struct {
 
     pub fn seekPos(self: Position, total_size: usize) SeekPos {
         std.debug.assert(self.index <= self.split);
-        var tot = total_size / self.split;
+        const tot = total_size / self.split;
 
         return SeekPos{
             .start = self.index * tot,
@@ -46,7 +47,7 @@ pub const Position = struct {
 
 /// Represents the starting context for a single plugin run.
 pub const Context = struct {
-    allocator: *std.mem.Allocator,
+    allocator: std.mem.Allocator,
     world: *c.LilvWorld,
     plugin: *const c.LilvPlugin,
 
@@ -74,10 +75,12 @@ pub const RunContext = struct {
     instance: *c.LilvInstance,
 
     pub fn init(
-        allocator: *std.mem.Allocator,
+        allocator: std.mem.Allocator,
         plugin: *const c.LilvPlugin,
     ) !RunContext {
-        var instance = c.lilv_plugin_instantiate(plugin, @as(f64, 44100), null);
+        _ = allocator; // TODO batch RunBuffers?
+
+        const instance = c.lilv_plugin_instantiate(plugin, @as(f64, 44100), null);
         errdefer c.lilv_instance_free(instance);
 
         if (instance == null) {
@@ -98,13 +101,13 @@ pub const RunContext = struct {
         var i: usize = 0;
         var o: usize = 0;
 
-        for (ports) |_, p_idx| {
-            var p = @intCast(u32, p_idx);
+        for (ports, 0..) |_, p_idx| {
+            const p = @as(u32, @intCast(p_idx));
             var port: *lv2.Port = &ports[p_idx];
 
             switch (port.ptype) {
                 .Control => lv2.lilv_instance_connect_port(self.instance, p, &port.value),
-                .Audio => blk: {
+                .Audio => {
                     if (port.is_input) {
                         lv2.lilv_instance_connect_port(
                             self.instance,
@@ -121,31 +124,31 @@ pub const RunContext = struct {
                         o += 1;
                     }
                 },
-                else => lv2.lilv_instance_connect_port(self.instance, p, null),
+                // else => lv2.lilv_instance_connect_port(self.instance, p, null),
             }
         }
     }
 };
 
-pub fn makeContext(allocator: *std.mem.Allocator, plugin_uri: []const u8) !Context {
-    const cstr_plugin_uri = try std.cstr.addNullByte(allocator, plugin_uri);
+pub fn makeContext(allocator: std.mem.Allocator, plugin_uri: []const u8) !Context {
+    const cstr_plugin_uri = try allocator.dupeZ(u8, plugin_uri);
     defer allocator.free(cstr_plugin_uri);
 
-    var world: *c.LilvWorld = c.lilv_world_new().?;
+    const world: *c.LilvWorld = c.lilv_world_new().?;
     errdefer c.lilv_world_free(world);
 
     c.lilv_world_load_all(world);
 
-    var uri: *c.LilvNode = c.lilv_new_uri(world, cstr_plugin_uri.ptr) orelse blk: {
-        std.debug.warn("Invalid plugin URI <{}>\n", .{plugin_uri});
+    const uri: *c.LilvNode = c.lilv_new_uri(world, cstr_plugin_uri.ptr) orelse {
+        log.debug("Invalid plugin URI <{s}>", .{plugin_uri});
         return ImageError.InvalidPlugin;
     };
     defer c.lilv_node_free(uri);
 
-    const plugins: *const c.LilvPlugins = c.lilv_world_get_all_plugins(world);
+    const plugins: *const c.LilvPlugins = c.lilv_world_get_all_plugins(world).?;
 
-    var plugin: *const c.LilvPlugin = c.lilv_plugins_get_by_uri(plugins, uri) orelse blk: {
-        std.debug.warn("Plugin <{}> not found\n", .{plugin_uri});
+    const plugin: *const c.LilvPlugin = c.lilv_plugins_get_by_uri(plugins, uri) orelse {
+        log.debug("Plugin <{s}> not found", .{plugin_uri});
         return ImageError.UnknownPlugin;
     };
 
diff --git a/src/printer.zig b/src/printer.zig
index bf32f76..b3da89b 100644
--- a/src/printer.zig
+++ b/src/printer.zig
@@ -1,54 +1,51 @@
 const std = @import("std");
 const langs = @import("lang.zig");
 
-fn printCommandWithParams(stream: var, command: var) !void {
+const log = std.log.scoped(.scritcher_printer);
+
+fn printCommandWithParams(stream: anytype, command: anytype) !void {
     const Parameters = @TypeOf(command.parameters);
-    try stream.print(" {} {}", .{ command.split, command.index });
+    try stream.print(" {d} {d}", .{ command.split, command.index });
     inline for (@typeInfo(Parameters).Struct.fields) |field| {
-        if (field.field_type == f32 or field.field_type == f64) {
+        if (field.type == f32 or field.type == f64) {
+            try stream.print(" {}", .{@field(command.parameters, field.name)});
+        } else if (field.type == usize or field.type == u64) {
             try stream.print(" {d}", .{@field(command.parameters, field.name)});
         } else {
-            try stream.print(" {}", .{@field(command.parameters, field.name)});
+            try stream.print(" {s}", .{@field(command.parameters, field.name)});
         }
     }
 }
 
-fn printCommand(stream: var, cmd: *langs.Command, comptime tag: langs.Command.Tag) !void {
+fn printCommand(stream: anytype, cmd: *langs.Command, comptime tag: langs.Command.Tag) !void {
     const CommandStruct = langs.Command.tagToType(tag);
     const casted = cmd.cast(CommandStruct).?;
 
-    // TODO move this to Tag method?
-    const is_typed = switch (tag) {
-        .noop, .load, .quicksave, .runqs, .rotate => false,
-        else => true,
-    };
-
     const ctype = CommandStruct.command_type;
     switch (ctype) {
         .lv2_command => try printCommandWithParams(stream, casted),
         .custom_command => try printCommandWithParams(stream, casted),
-        else => @panic("TODO support command type"),
     }
 }
 
-pub fn printList(list: langs.CommandList, stream: var) !void {
-    for (list.items) |cmd| {
+pub fn printList(list: langs.CommandList, stream: anytype) !void {
+    for (list.list.items) |cmd| {
         const command = @tagName(cmd.tag);
-        try stream.print("{}", .{command});
+        try stream.print("{s}", .{command});
 
         switch (cmd.tag) {
             .load => {
                 const load = cmd.cast(langs.Command.Load).?;
-                try stream.print(" {}", .{load.path});
+                try stream.print(" {s}", .{load.path});
             },
             .runqs => {
                 const runqs = cmd.cast(langs.Command.RunQS).?;
-                try stream.print(" {}", .{runqs.program});
+                try stream.print(" {s}", .{runqs.program});
             },
             .noop, .quicksave => {},
             .rotate => {
                 const rotate = cmd.cast(langs.Command.Rotate).?;
-                try stream.print(" {d} {}", .{ rotate.deg, rotate.bgfill });
+                try stream.print(" {d} {s}", .{ rotate.deg, rotate.bgfill });
             },
 
             .amp => try printCommand(stream, cmd, .amp),
diff --git a/src/runner.zig b/src/runner.zig
index a089a67..85b8d79 100644
--- a/src/runner.zig
+++ b/src/runner.zig
@@ -5,6 +5,8 @@ const plugin = @import("plugin.zig");
 const custom = @import("custom.zig");
 const magick = @import("magick.zig");
 
+const log = std.log.scoped(.scritcher_runner);
+
 const Position = plugin.Position;
 const ParamList = plugin.ParamList;
 const ParamMap = plugin.ParamMap;
@@ -18,7 +20,7 @@ pub const RunError = error{
 };
 
 pub const Runner = struct {
-    allocator: *std.mem.Allocator,
+    allocator: std.mem.Allocator,
 
     /// The currently opened image in the runner
     image: ?*Image = null,
@@ -26,9 +28,9 @@ pub const Runner = struct {
     /// If the runner is in REPL mode
     repl: bool,
 
-    args: [][]u8,
+    args: []const [:0]u8,
 
-    pub fn init(allocator: *std.mem.Allocator, repl: bool) Runner {
+    pub fn init(allocator: std.mem.Allocator, repl: bool) Runner {
         return Runner{
             .allocator = allocator,
             .repl = repl,
@@ -40,10 +42,12 @@ pub const Runner = struct {
         if (self.image) |image| {
             image.close();
         }
+
+        std.process.argsFree(self.allocator, self.args);
     }
 
     pub fn clone(self: *Runner) !Runner {
-        var cloned_image = if (self.image) |image| try image.clone() else null;
+        const cloned_image = if (self.image) |image| try image.clone() else null;
         return Runner{
             .allocator = self.allocator,
             .image = cloned_image,
@@ -53,6 +57,7 @@ pub const Runner = struct {
     }
 
     fn resolveArg(self: *Runner, load_path: []const u8) ![]const u8 {
+        std.debug.assert(load_path.len > 0);
         if (load_path[0] == ':') {
             // parse the index from 1 to end
             var index = try std.fmt.parseInt(usize, load_path[1..], 10);
@@ -63,19 +68,20 @@ pub const Runner = struct {
             // 'scritcher repl ./script ./image'
 
             // ':0' should ALWAYS point to the image.
-            if (self.repl) index += 3 else index += 2;
+            if (self.repl) index += 3 else index += 3;
 
-            std.debug.warn("ARGS!! {} \n", .{self.args.len});
-            for (self.args) |arg, idx| {
-                std.debug.warn("arg{} = {}\n", .{ idx, arg });
+            for (self.args, 0..) |arg, idx| {
+                log.debug("arg{d} = {s}", .{ idx, arg });
             }
-            std.debug.warn("fetch arg idx={}, val={}\n", .{ index, self.args[index] });
+            log.debug("fetch arg idx={d}", .{index});
+            log.debug("fetch arg val={s}", .{self.args[index]});
             return self.args[index];
         } else {
             return load_path;
         }
     }
 
+    // Caller owns returned memory.
     fn resolveArgPath(self: *Runner, path_or_argidx: []const u8) ![]const u8 {
         const path = try self.resolveArg(path_or_argidx);
         const resolved_path = try std.fs.path.resolve(
@@ -87,8 +93,8 @@ pub const Runner = struct {
     }
 
     fn loadCmd(self: *Runner, path_or_argidx: []const u8) !void {
-        var load_path = try self.resolveArgPath(path_or_argidx);
-        std.debug.warn("\tload path: {}\n", .{load_path});
+        const load_path = try self.resolveArgPath(path_or_argidx);
+        log.debug("\tload path: {s}", .{load_path});
 
         // we could use ImageMagick to convert from X to BMP
         // but i can't find an easy way to do things in memory.
@@ -98,13 +104,14 @@ pub const Runner = struct {
         // krita/gimp and make it export a bmp and while in the program you can
         // apply filters, etc.
         if (!std.mem.endsWith(u8, load_path, ".bmp") and !std.mem.endsWith(u8, load_path, ".ppm")) {
-            std.debug.warn("Only BMP files are allowed to be loaded. Got path '{}'\n", .{load_path});
+            log.debug("Only BMP files are allowed to be loaded. Got path '{s}'", .{load_path});
             return RunError.NoBMP;
         }
 
         // we don't copy load_path into a temporary file because we're already
         // loading it under the SFM_READ mode, which won't cause any destructive
         // operations on the file.
+        if (self.image) |image| image.close();
         self.image = try Image.open(self.allocator, load_path);
     }
 
@@ -112,15 +119,16 @@ pub const Runner = struct {
         if (self.image) |image| {
             return image;
         } else {
-            std.debug.warn("image is required!\n", .{});
+            log.debug("image is required!", .{});
             return RunError.ImageRequired;
         }
     }
 
+    /// Caller owns returned memory.
     fn makeGlitchedPath(self: *Runner) ![]const u8 {
         // we want to transform basename, if it is "x.bmp" to "x_gN.bmp", where
         // N is the maximum non-used integer.
-        var image = try self.getImage();
+        const image = try self.getImage();
 
         const basename = std.fs.path.basename(image.path);
         const dirname = std.fs.path.dirname(image.path).?;
@@ -133,7 +141,7 @@ pub const Runner = struct {
 
         // starts_with would be "x_g", we want to find all files in the directory
         // that start with that name.
-        const starts_with = try std.fmt.allocPrint(self.allocator, "{}_g", .{
+        const starts_with = try std.fmt.allocPrint(self.allocator, "{s}_g", .{
             basename[0..period_idx],
         });
         defer self.allocator.free(starts_with);
@@ -144,7 +152,7 @@ pub const Runner = struct {
 
         while (try it.next()) |entry| {
             switch (entry.kind) {
-                .File => blk: {
+                .file => blk: {
                     if (!std.mem.startsWith(u8, entry.name, starts_with)) break :blk {};
 
                     // we want to get the N in x_gN.ext
@@ -158,6 +166,8 @@ pub const Runner = struct {
                     // if N isn't a number, we just ignore that file
                     const idx_str = entry.name[entry_gidx + 2 .. entry_pidx];
                     const idx = std.fmt.parseInt(usize, idx_str, 10) catch |err| {
+                        log.debug("ignoring file {s}", .{@errorName(err)});
+
                         break :blk {};
                     };
 
@@ -167,7 +177,7 @@ pub const Runner = struct {
             }
         }
 
-        const out_path = try std.fmt.allocPrint(self.allocator, "{}/{}{}{}", .{
+        const out_path = try std.fmt.allocPrint(self.allocator, "{s}/{s}{d}{s}", .{
             dirname,
             starts_with,
             max + 1,
@@ -180,36 +190,38 @@ pub const Runner = struct {
     fn quicksaveCmd(self: *Runner) !void {
         var image = try self.getImage();
         const out_path = try self.makeGlitchedPath();
+        defer self.allocator.free(out_path);
         try image.saveTo(out_path);
     }
 
-    fn runQSCmd(self: *Runner, cmd: lang.Command) !void {
+    fn runQSCmd(self: *Runner, cmd: *lang.Command) !void {
         const runqs = cmd.cast(lang.Command.RunQS).?;
         var image = try self.getImage();
         const out_path = try self.makeGlitchedPath();
+        defer self.allocator.free(out_path);
         try image.saveTo(out_path);
 
-        var proc = try std.ChildProcess.init(
+        var proc = std.ChildProcess.init(
             &[_][]const u8{ runqs.program, out_path },
             self.allocator,
         );
-        defer proc.deinit();
+        //defer proc.deinit();
 
-        std.debug.warn("running '{} {}'\n", .{ runqs.program, out_path });
+        log.debug("running '{s} {s}'", .{ runqs.program, out_path });
         _ = try proc.spawnAndWait();
     }
 
-    fn rotateCmd(self: *Runner, cmd: lang.Command) !void {
+    fn rotateCmd(self: *Runner, cmd: *lang.Command) !void {
         const rotate_cmd = cmd.cast(lang.Command.Rotate).?;
 
-        var image = try self.getImage();
-        var c_bgfill = try std.cstr.addNullByte(self.allocator, rotate_cmd.bgfill);
+        const image = try self.getImage();
+        const c_bgfill = try self.allocator.dupeZ(u8, rotate_cmd.bgfill);
         defer self.allocator.free(c_bgfill);
 
         try magick.runRotate(image, rotate_cmd.deg, c_bgfill);
     }
 
-    fn executeLV2Command(self: *@This(), command: var) !void {
+    fn executeLV2Command(self: *@This(), command: anytype) !void {
         const pos = plugin.Position{
             .split = command.split,
             .index = command.index,
@@ -231,7 +243,7 @@ pub const Runner = struct {
         try image.runPlugin(typ.lv2_url, pos, params);
     }
 
-    fn executeCustomCommand(self: *@This(), command: var) !void {
+    fn executeCustomCommand(self: *@This(), command: anytype) !void {
         const pos = plugin.Position{
             .split = command.split,
             .index = command.index,
@@ -243,20 +255,19 @@ pub const Runner = struct {
 
     fn runSingleCommand(
         self: *@This(),
-        cmd: lang.Command,
+        cmd: *lang.Command,
         comptime tag: lang.Command.Tag,
     ) !void {
-        comptime const typ = lang.Command.tagToType(tag);
+        const typ = lang.Command.tagToType(tag);
         const command = cmd.cast(typ).?;
         const ctype = typ.command_type;
         switch (ctype) {
             .lv2_command => try self.executeLV2Command(command.*),
             .custom_command => try self.executeCustomCommand(command.*),
-            else => @panic("TODO support command type"),
         }
     }
 
-    fn runCommand(self: *@This(), cmd: lang.Command) !void {
+    fn runCommand(self: *@This(), cmd: *lang.Command) !void {
         switch (cmd.tag) {
             .noop => {},
             .load => {
@@ -308,26 +319,26 @@ pub const Runner = struct {
         cmds: lang.CommandList,
         debug_flag: bool,
     ) !void {
-        for (cmds.items) |cmd| {
+        _ = debug_flag;
+        for (cmds.list.items) |cmd| {
             cmd.print();
-            try self.runCommand(cmd.*);
+            try self.runCommand(cmd);
         }
     }
 };
 
 test "running noop" {
-    const allocator = std.heap.direct_allocator;
+    const allocator = std.testing.allocator;
     var cmds = lang.CommandList.init(allocator);
     defer cmds.deinit();
 
-    var cmd_ptr = try allocator.create(lang.Command);
-    cmd_ptr.* = lang.Command{
-        .command = .Noop,
-        .args = lang.ArgList.init(allocator),
-    };
-    try cmds.append(cmd_ptr);
+    const command = lang.Command{ .tag = .noop };
 
-    var runner = Runner.init(allocator);
+    var noop = try allocator.create(lang.Command.Noop);
+    noop.* = lang.Command.Noop{ .base = command };
+    try cmds.append(&noop.base);
+
+    var runner = Runner.init(allocator, false);
     defer runner.deinit();
 
     try runner.runCommands(cmds, false);