diff --git a/codegen/codecVisitor.ts b/codegen/codecVisitor.ts
index 585dcaed6..884b8b7a7 100644
--- a/codegen/codecVisitor.ts
+++ b/codegen/codecVisitor.ts
@@ -1,7 +1,29 @@
 import * as M from "../frame_metadata/mod.ts";
-import { Decl, getCodecPath, getName, getRawCodecPath, S } from "./utils.ts";
+import { Decl, Files, getCodecPath, getName, getRawCodecPath, importSource, S } from "./utils.ts";
+
+export function createCodecVisitor(
+  tys: M.Ty[],
+  decls: Decl[],
+  typeVisitor: M.TyVisitor<S>,
+  files: Files,
+) {
+  ["import { $, $null, $era } from", S.string(importSource)];
+  const namespaceImports = new Set<string>();
+  const codecs: S[] = [];
+
+  files.set("codecs.ts", {
+    getContent: () => [
+      "\n",
+      ["import { ChainError, BitSequence, Era, $, $era, $null } from", S.string(importSource)],
+      [`import type * as t from "./mod.ts"`],
+      ...codecs,
+      [
+        "export const _all: $.AnyCodec[] =",
+        S.array(tys.map((ty) => getName(getRawCodecPath(ty)))),
+      ],
+    ],
+  });
 
-export function createCodecVisitor(tys: M.Ty[], decls: Decl[], typeVisitor: M.TyVisitor<S>) {
   const compactCodecVisitor = new M.TyVisitor<string | null>(tys, {
     unitStruct: () => "$null",
     wrapperStruct(_, inner) {
@@ -59,7 +81,9 @@ export function createCodecVisitor(tys: M.Ty[], decls: Decl[], typeVisitor: M.Ty
     },
     result(ty, ok, err) {
       return addCodecDecl(ty, ["$.result(", this.visit(ok), ",", [
-        `$.instance(ChainError<${typeVisitor.visit(err)}>, ["value", `,
+        "$.instance(ChainError<",
+        fixType(typeVisitor.visit(err)),
+        `>, ["value", `,
         this.visit(err),
         "])",
       ], ")"]);
@@ -141,22 +165,22 @@ export function createCodecVisitor(tys: M.Ty[], decls: Decl[], typeVisitor: M.Ty
       return addCodecDecl(ty, "$era");
     },
     circular(ty) {
-      return ["$.deferred(() =>", getRawCodecPath(ty), ")"];
+      return ["$.deferred(() =>", getName(getRawCodecPath(ty)), ")"];
     },
   });
 
   function addCodecDecl(ty: M.Ty, value: S) {
     const rawPath = getRawCodecPath(ty);
-    decls.push({
-      path: "_codec.", // no sorting
-      code: [
-        ["export const", getName(rawPath)],
-        ": $.Codec<",
-        typeVisitor.visit(ty),
-        "> =",
-        value,
-      ],
-    });
+    if (ty.path.length > 1) {
+      namespaceImports.add(ty.path[0]!);
+    }
+    codecs.push([
+      ["export const", getName(rawPath)],
+      ": $.Codec<",
+      fixType(typeVisitor.visit(ty)),
+      "> =",
+      value,
+    ]);
     const path = getCodecPath(tys, ty);
     if (path !== rawPath && path !== value && !decls.some((x) => x.path === path)) {
       decls.push({
@@ -170,6 +194,13 @@ export function createCodecVisitor(tys: M.Ty[], decls: Decl[], typeVisitor: M.Ty
         ],
       });
     }
-    return rawPath;
+    return getName(rawPath);
+  }
+
+  function fixType(type: S) {
+    return S.toString(type).replace(
+      /\b([\w\$]+\.[\w\.$]+|u\d+|Compact)\b/g,
+      (x) => "t." + x,
+    );
   }
 }
diff --git a/codegen/codegen.ts b/codegen/codegen.ts
index 203f702af..0c3d4bae8 100644
--- a/codegen/codegen.ts
+++ b/codegen/codegen.ts
@@ -1,55 +1,69 @@
 import { tsFormatter } from "../deps/dprint.ts";
 import { parse } from "../deps/std/flags.ts";
+import * as path from "../deps/std/path.ts";
 import * as M from "../frame_metadata/mod.ts";
 import { createCodecVisitor } from "./codecVisitor.ts";
 import { genMetadata } from "./genMetadata.ts";
 import { createTypeVisitor } from "./typeVisitor.ts";
-import { Decl, printDecls, S } from "./utils.ts";
-
-const importSource = new URL("../mod.ts", import.meta.url).toString();
+import { Decl, Files, importSource, printDecls, S } from "./utils.ts";
 
 if (import.meta.main) {
   const args = parse(Deno.args, {
     string: ["metadata", "output"],
   });
   if (args.help || args["?"]) {
-    console.log("Usage: codegen --metadata <file> --output <file>");
+    console.log("Usage: codegen --metadata <file> --output <dir>");
     Deno.exit(0);
   }
   if (!args.metadata) throw new Error("Must specify metadata file");
-  if (!args.output) throw new Error("Must specify output file");
-  const { metadata: metadataFile, output: outputFile } = args;
-  const metadata = M.fromPrefixedHex(await Deno.readTextFile(metadataFile!));
+  if (!args.output) throw new Error("Must specify output dir");
+  const { metadata: metadataFile, output: outputDir } = args;
+  const metadata = M.fromPrefixedHex(await Deno.readTextFile(metadataFile));
   const output = codegen(metadata);
-  try {
-    const formatted = tsFormatter.formatText("gen.ts", output);
-    await Deno.writeTextFile(outputFile!, formatted);
-  } catch (e) {
-    await Deno.writeTextFile(outputFile!, output);
-    throw e;
+  const errors = [];
+  await Deno.mkdir(outputDir, { recursive: true });
+  for (const [relativePath, file] of output.entries()) {
+    const outputPath = path.join(outputDir, relativePath);
+    const content = S.toString(file.getContent());
+    try {
+      const formatted = tsFormatter.formatText("gen.ts", content);
+      await Deno.writeTextFile(outputPath, formatted);
+    } catch (e) {
+      await Deno.writeTextFile(outputPath, content);
+      errors.push(e);
+    }
+  }
+  if (errors.length) {
+    console.error(errors);
+    Deno.exit(1);
   }
 }
 
-export function codegen(metadata: M.Metadata) {
+export function codegen(metadata: M.Metadata): Files {
   const decls: Decl[] = [];
 
   const { tys } = metadata;
 
+  const files: Files = new Map();
+
   decls.push({
     path: "_",
     code: [
-      "import { ChainError, BitSequence, Era, $, $null, $era } from",
-      S.string(importSource),
+      "\n",
+      ["import { ChainError, BitSequence, Era, $ } from", S.string(importSource)],
+      [`import * as _codec from "./codecs.ts"`],
     ],
   });
 
   const typeVisitor = createTypeVisitor(tys, decls);
-  const codecVisitor = createCodecVisitor(tys, decls, typeVisitor);
+  const codecVisitor = createCodecVisitor(tys, decls, typeVisitor, files);
 
   typeVisitor.tys.map((x) => typeVisitor.visit(x));
   codecVisitor.tys.map((x) => codecVisitor.visit(x));
 
-  genMetadata(metadata, decls, codecVisitor);
+  genMetadata(metadata, decls);
+
+  files.set("mod.ts", { getContent: () => printDecls(decls) });
 
-  return printDecls(decls);
+  return files;
 }
diff --git a/codegen/genMetadata.ts b/codegen/genMetadata.ts
index 8bbdd1d8f..96764db44 100644
--- a/codegen/genMetadata.ts
+++ b/codegen/genMetadata.ts
@@ -1,7 +1,7 @@
 import * as M from "../frame_metadata/mod.ts";
 import { Decl, getPath, getRawCodecPath, makeDocComment, S } from "./utils.ts";
 
-export function genMetadata(metadata: M.Metadata, decls: Decl[], codecVisitor: M.TyVisitor<S>) {
+export function genMetadata(metadata: M.Metadata, decls: Decl[]) {
   const { tys, extrinsic, pallets } = metadata;
 
   const isUnitVisitor = new M.TyVisitor<boolean>(tys, {
@@ -56,11 +56,11 @@ export function genMetadata(metadata: M.Metadata, decls: Decl[], codecVisitor: M
               "key",
               entry.type === "Map"
                 ? entry.hashers.length === 1
-                  ? ["$.tuple(", codecVisitor.visit(entry.key), ")"]
-                  : codecVisitor.visit(entry.key)
+                  ? ["$.tuple(", getRawCodecPath(tys[entry.key]!), ")"]
+                  : getRawCodecPath(tys[entry.key]!)
                 : "[]",
             ],
-            ["value", codecVisitor.visit(entry.value)],
+            ["value", getRawCodecPath(tys[entry.value]!)],
           ),
         ],
       });
@@ -96,15 +96,12 @@ export function genMetadata(metadata: M.Metadata, decls: Decl[], codecVisitor: M
 
   decls.push({
     path: "_metadata.types",
-    code: [
-      "export const types: $.AnyCodec[] =",
-      S.array(codecVisitor.tys.map((ty) => getRawCodecPath(ty))),
-    ],
+    code: "export const types = _codec._all",
   });
 
   function getExtrasCodec(xs: [string, number][]) {
     return S.array(
-      xs.filter((x) => !isUnitVisitor.visit(x[1])).map((x) => codecVisitor.visit(x[1])),
+      xs.filter((x) => !isUnitVisitor.visit(x[1])).map((x) => getRawCodecPath(tys[x[1]]!)),
     );
   }
 }
diff --git a/codegen/utils.ts b/codegen/utils.ts
index 2c5e81ce8..7b940d26b 100644
--- a/codegen/utils.ts
+++ b/codegen/utils.ts
@@ -1,4 +1,10 @@
 import * as M from "../frame_metadata/mod.ts";
+
+export const importSource = new URL("../mod.ts", import.meta.url).toString();
+
+export type File = { getContent: () => S };
+export type Files = Map<string, File>;
+
 export type S = string | number | S[];
 
 export namespace S {