diff --git a/java/com/google/turbine/binder/ClassPathBinder.java b/java/com/google/turbine/binder/ClassPathBinder.java
index af59bca..b499fa2 100644
--- a/java/com/google/turbine/binder/ClassPathBinder.java
+++ b/java/com/google/turbine/binder/ClassPathBinder.java
@@ -17,7 +17,6 @@
 package com.google.turbine.binder;
 
 import com.google.common.base.Supplier;
-import com.google.common.base.Suppliers;
 import com.google.common.collect.ImmutableMap;
 import com.google.turbine.binder.bound.ModuleInfo;
 import com.google.turbine.binder.bytecode.BytecodeBinder;
@@ -35,7 +34,6 @@
 import java.util.HashMap;
 import java.util.LinkedHashMap;
 import java.util.Map;
-import java.util.function.Function;
 import org.jspecify.annotations.Nullable;
 
 /** Sets up an environment for symbols on the classpath. */
@@ -55,33 +53,31 @@ public final class ClassPathBinder {
 
   /** Creates an environment containing symbols in the given classpath. */
   public static ClassPath bindClasspath(Collection<Path> paths) throws IOException {
-    // TODO(cushon): this is going to require an env eventually,
-    // e.g. to look up type parameters in enclosing declarations
-    Map<ClassSymbol, BytecodeBoundClass> transitive = new LinkedHashMap<>();
-    Map<ClassSymbol, BytecodeBoundClass> map = new HashMap<>();
+    Map<ClassSymbol, Supplier<BytecodeBoundClass>> transitive = new LinkedHashMap<>();
+    Map<ClassSymbol, Supplier<BytecodeBoundClass>> map = new HashMap<>();
     Map<ModuleSymbol, ModuleInfo> modules = new HashMap<>();
     Map<String, Supplier<byte[]>> resources = new HashMap<>();
-    Env<ClassSymbol, BytecodeBoundClass> benv =
+    Env<ClassSymbol, BytecodeBoundClass> env =
         new Env<ClassSymbol, BytecodeBoundClass>() {
           @Override
           public @Nullable BytecodeBoundClass get(ClassSymbol sym) {
-            return map.get(sym);
+            Supplier<BytecodeBoundClass> supplier = map.get(sym);
+            return supplier == null ? null : supplier.get();
           }
         };
     for (Path path : paths) {
       try {
-        bindJar(path, map, modules, benv, transitive, resources);
+        bindJar(path, map, modules, env, transitive, resources);
       } catch (IOException e) {
         throw new IOException("error reading " + path, e);
       }
     }
-    for (Map.Entry<ClassSymbol, BytecodeBoundClass> entry : transitive.entrySet()) {
+    for (Map.Entry<ClassSymbol, Supplier<BytecodeBoundClass>> entry : transitive.entrySet()) {
       ClassSymbol symbol = entry.getKey();
       map.putIfAbsent(symbol, entry.getValue());
     }
-    SimpleEnv<ClassSymbol, BytecodeBoundClass> env = new SimpleEnv<>(ImmutableMap.copyOf(map));
     SimpleEnv<ModuleSymbol, ModuleInfo> moduleEnv = new SimpleEnv<>(ImmutableMap.copyOf(modules));
-    TopLevelIndex index = SimpleTopLevelIndex.of(env.asMap().keySet());
+    TopLevelIndex index = SimpleTopLevelIndex.of(map.keySet());
     return new ClassPath() {
       @Override
       public Env<ClassSymbol, BytecodeBoundClass> env() {
@@ -107,10 +103,10 @@ public TopLevelIndex index() {
 
   private static void bindJar(
       Path path,
-      Map<ClassSymbol, BytecodeBoundClass> env,
+      Map<ClassSymbol, Supplier<BytecodeBoundClass>> env,
       Map<ModuleSymbol, ModuleInfo> modules,
       Env<ClassSymbol, BytecodeBoundClass> benv,
-      Map<ClassSymbol, BytecodeBoundClass> transitive,
+      Map<ClassSymbol, Supplier<BytecodeBoundClass>> transitive,
       Map<String, Supplier<byte[]>> resources)
       throws IOException {
     // TODO(cushon): don't leak file descriptors
@@ -124,41 +120,22 @@ private static void bindJar(
             new ClassSymbol(
                 name.substring(
                     TRANSITIVE_PREFIX.length(), name.length() - TRANSITIVE_SUFFIX.length()));
-        transitive.computeIfAbsent(
-            sym,
-            new Function<ClassSymbol, BytecodeBoundClass>() {
-              @Override
-              public BytecodeBoundClass apply(ClassSymbol sym) {
-                return new BytecodeBoundClass(sym, toByteArrayOrDie(ze), benv, path.toString());
-              }
-            });
+        transitive.putIfAbsent(sym, BytecodeBoundClass.lazy(sym, ze, benv, path));
         continue;
       }
       if (!name.endsWith(".class")) {
-        resources.put(name, toByteArrayOrDie(ze));
+        resources.put(name, ze);
         continue;
       }
       if (name.substring(name.lastIndexOf('/') + 1).equals("module-info.class")) {
-        ModuleInfo moduleInfo =
-            BytecodeBinder.bindModuleInfo(path.toString(), toByteArrayOrDie(ze));
+        ModuleInfo moduleInfo = BytecodeBinder.bindModuleInfo(path.toString(), ze);
         modules.put(new ModuleSymbol(moduleInfo.name()), moduleInfo);
         continue;
       }
       ClassSymbol sym = new ClassSymbol(name.substring(0, name.length() - ".class".length()));
-      env.putIfAbsent(
-          sym, new BytecodeBoundClass(sym, toByteArrayOrDie(ze), benv, path.toString()));
+      env.putIfAbsent(sym, BytecodeBoundClass.lazy(sym, ze, benv, path));
     }
   }
 
-  private static Supplier<byte[]> toByteArrayOrDie(Zip.Entry ze) {
-    return Suppliers.memoize(
-        new Supplier<byte[]>() {
-          @Override
-          public byte[] get() {
-            return ze.data();
-          }
-        });
-  }
-
   private ClassPathBinder() {}
 }
diff --git a/java/com/google/turbine/binder/CtSymClassBinder.java b/java/com/google/turbine/binder/CtSymClassBinder.java
index a04366f..8b374a3 100644
--- a/java/com/google/turbine/binder/CtSymClassBinder.java
+++ b/java/com/google/turbine/binder/CtSymClassBinder.java
@@ -21,7 +21,6 @@
 
 import com.google.common.annotations.VisibleForTesting;
 import com.google.common.base.Supplier;
-import com.google.common.base.Suppliers;
 import com.google.common.collect.ImmutableMap;
 import com.google.turbine.binder.bound.ModuleInfo;
 import com.google.turbine.binder.bytecode.BytecodeBinder;
@@ -86,13 +85,12 @@ public final class CtSymClassBinder {
       // JDK >= 12 includes the module name as a prefix
       idx = name.indexOf('/', idx + 1);
       if (name.substring(name.lastIndexOf('/') + 1).equals("module-info.sig")) {
-        ModuleInfo moduleInfo = BytecodeBinder.bindModuleInfo(name, toByteArrayOrDie(ze));
+        ModuleInfo moduleInfo = BytecodeBinder.bindModuleInfo(name, ze);
         modules.put(new ModuleSymbol(moduleInfo.name()), moduleInfo);
         continue;
       }
       ClassSymbol sym = new ClassSymbol(name.substring(idx + 1, name.length() - ".sig".length()));
-      map.putIfAbsent(
-          sym, new BytecodeBoundClass(sym, toByteArrayOrDie(ze), benv, ctSym + "!" + ze.name()));
+      map.putIfAbsent(sym, new BytecodeBoundClass(sym, ze, benv, ctSym + "!" + ze.name()));
     }
     if (map.isEmpty()) {
       // we didn't find any classes for the desired release
@@ -124,16 +122,6 @@ public TopLevelIndex index() {
     };
   }
 
-  private static Supplier<byte[]> toByteArrayOrDie(Zip.Entry ze) {
-    return Suppliers.memoize(
-        new Supplier<byte[]>() {
-          @Override
-          public byte[] get() {
-            return ze.data();
-          }
-        });
-  }
-
   // ct.sym contains directories whose names are the concatenation of a list of target versions
   // formatted as a single character 0-9 or A-Z (e.g. 789A) and which contain interface class
   // files with a .sig extension.
diff --git a/java/com/google/turbine/binder/bytecode/BytecodeBoundClass.java b/java/com/google/turbine/binder/bytecode/BytecodeBoundClass.java
index fad5716..b86d0c4 100644
--- a/java/com/google/turbine/binder/bytecode/BytecodeBoundClass.java
+++ b/java/com/google/turbine/binder/bytecode/BytecodeBoundClass.java
@@ -58,6 +58,7 @@
 import com.google.turbine.type.Type.ClassTy;
 import com.google.turbine.type.Type.IntersectionTy;
 import java.lang.annotation.RetentionPolicy;
+import java.nio.file.Path;
 import java.util.List;
 import java.util.Map;
 import org.jspecify.annotations.Nullable;
@@ -72,6 +73,20 @@
  */
 public class BytecodeBoundClass implements TypeBoundClass {
 
+  public static Supplier<BytecodeBoundClass> lazy(
+      ClassSymbol sym,
+      Supplier<byte[]> bytes,
+      Env<ClassSymbol, BytecodeBoundClass> env,
+      Path path) {
+    return Suppliers.memoize(
+        new Supplier<BytecodeBoundClass>() {
+          @Override
+          public BytecodeBoundClass get() {
+            return new BytecodeBoundClass(sym, bytes, env, path.toString());
+          }
+        });
+  }
+
   private final ClassSymbol sym;
   private final Env<ClassSymbol, BytecodeBoundClass> env;
   private final Supplier<ClassFile> classFile;
diff --git a/java/com/google/turbine/zip/Zip.java b/java/com/google/turbine/zip/Zip.java
index bf0365b..95ebb3f 100644
--- a/java/com/google/turbine/zip/Zip.java
+++ b/java/com/google/turbine/zip/Zip.java
@@ -18,6 +18,7 @@
 
 import static java.nio.charset.StandardCharsets.UTF_8;
 
+import com.google.common.base.Supplier;
 import com.google.common.primitives.UnsignedInts;
 import java.io.ByteArrayInputStream;
 import java.io.Closeable;
@@ -251,7 +252,7 @@ public void close() throws IOException {
   }
 
   /** An entry in a zip archive. */
-  public static class Entry {
+  public static class Entry implements Supplier<byte[]> {
 
     private final Path path;
     private final FileChannel chan;
@@ -351,6 +352,11 @@ private byte[] getBytes(
         throw new IOError(e);
       }
     }
+
+    @Override
+    public byte[] get() {
+      return data();
+    }
   }
 
   static void checkSignature(