diff --git a/modules/bit/cmd/bit/add.mbt b/modules/bit/cmd/bit/add.mbt
index 98a0a444..1395679c 100644
--- a/modules/bit/cmd/bit/add.mbt
+++ b/modules/bit/cmd/bit/add.mbt
@@ -395,7 +395,7 @@ fn add_apply_intent_to_add(
           fs,
           git_dir,
           @bitcore.ObjectType::Blob,
-          Bytes::default(),
+          Default::default(),
           algo~,
         )
         @bitlib.compat_record_blob_mapping(
@@ -403,7 +403,7 @@ fn add_apply_intent_to_add(
           rfs,
           git_dir,
           created,
-          Bytes::default(),
+          Default::default(),
         )
         empty_id = Some(created)
         created
diff --git a/modules/bit/cmd/bit/blame.mbt b/modules/bit/cmd/bit/blame.mbt
index 180e38f5..96bc4cb2 100644
--- a/modules/bit/cmd/bit/blame.mbt
+++ b/modules/bit/cmd/bit/blame.mbt
@@ -99,7 +99,7 @@ fn blame_read_path_diff_driver(
   }
   let text = decode_bytes(
     fs.read_file(attr_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     },
   )
   let mut diff_driver : String? = None
diff --git a/modules/bit/cmd/bit/cat_file.mbt b/modules/bit/cmd/bit/cat_file.mbt
index f1137304..d2e88961 100644
--- a/modules/bit/cmd/bit/cat_file.mbt
+++ b/modules/bit/cmd/bit/cat_file.mbt
@@ -2824,7 +2824,7 @@ fn cat_file_read_path_attrs(
   if fs.is_file(attr_path) {
     let text = decode_bytes(
       fs.read_file(attr_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     for line_view in text.split("\n") {
diff --git a/modules/bit/cmd/bit/check_attr.mbt b/modules/bit/cmd/bit/check_attr.mbt
index 29092e5d..7869175a 100644
--- a/modules/bit/cmd/bit/check_attr.mbt
+++ b/modules/bit/cmd/bit/check_attr.mbt
@@ -124,7 +124,7 @@ fn check_attr_load_rules(
   if fs.is_file(root_attr) {
     let content = decode_bytes(
       fs.read_file(root_attr) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     check_attr_parse_rules(content, rules)
@@ -134,7 +134,7 @@ fn check_attr_load_rules(
   if fs.is_file(info_attr) {
     let content = decode_bytes(
       fs.read_file(info_attr) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     check_attr_parse_rules(content, rules)
diff --git a/modules/bit/cmd/bit/check_ignore.mbt b/modules/bit/cmd/bit/check_ignore.mbt
index 3e0e8a8d..9134c063 100644
--- a/modules/bit/cmd/bit/check_ignore.mbt
+++ b/modules/bit/cmd/bit/check_ignore.mbt
@@ -263,7 +263,7 @@ fn check_ignore_add_rules_file(
   if fs.is_file(file_path) {
     let content = decode_bytes(
       fs.read_file(file_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     matcher.add_rules(base, content)
diff --git a/modules/bit/cmd/bit/checkout_wbtest.mbt b/modules/bit/cmd/bit/checkout_wbtest.mbt
index dee58e42..a792badd 100644
--- a/modules/bit/cmd/bit/checkout_wbtest.mbt
+++ b/modules/bit/cmd/bit/checkout_wbtest.mbt
@@ -723,7 +723,7 @@ async fn checkout_wbtest_case_force_checkout_clears_merge_state() -> Unit raise
   @test.assert_eq(
     decode_bytes(
       fs.read_file(repo_dir + "/file") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ),
     "side\n",
diff --git a/modules/bit/cmd/bit/diff.mbt b/modules/bit/cmd/bit/diff.mbt
index cc5ea288..aa08e9a8 100644
--- a/modules/bit/cmd/bit/diff.mbt
+++ b/modules/bit/cmd/bit/diff.mbt
@@ -827,7 +827,7 @@ fn diff_conflict_marker_size(
     return 7
   }
   let content = @utf8.decode_lossy(
-    (fs.read_file(attr_path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(attr_path) catch { _ => Default::default() })[:],
   )
   let mut size = 7
   for line_view in content.split("\n") {
diff --git a/modules/bit/cmd/bit/handlers_remote_pull_wbtest.mbt b/modules/bit/cmd/bit/handlers_remote_pull_wbtest.mbt
index f9b7da6d..68e9264f 100644
--- a/modules/bit/cmd/bit/handlers_remote_pull_wbtest.mbt
+++ b/modules/bit/cmd/bit/handlers_remote_pull_wbtest.mbt
@@ -449,13 +449,13 @@ async test "pull: branch remote dot pulls from current repo config" {
   handlers_remote_pull_wbtest_run_shim_git(root, ["pull", "-q"])
 
   @test.assert_eq(
-    decode_bytes(fs.read_file(root + "/file") catch { _ => Bytes::default() }),
+    decode_bytes(fs.read_file(root + "/file") catch { _ => Default::default() }),
     "updated\n",
   )
   assert_true(
     decode_bytes(
       fs.read_file(root + "/.git/logs/HEAD") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ).contains("Fast-forward"),
   )
@@ -490,7 +490,7 @@ async test "pull: command path pulls into unborn branch from parent repo" {
   @test.assert_eq(
     decode_bytes(
       fs.read_file(dst_dir + "/file") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ),
     "file\n",
@@ -527,7 +527,7 @@ async test "pull: command path keeps staged new file on unborn branch" {
   @test.assert_eq(
     decode_bytes(
       fs.read_file(dst_dir + "/newfile") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ),
     "new tracked file\n",
@@ -619,7 +619,7 @@ async test "pull: rebase rejects staged changes on unborn branch" {
   @test.assert_eq(
     decode_bytes(
       fs.read_file(dst_dir + "/staged-file") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ),
     "staged-file\n",
@@ -669,11 +669,11 @@ async test "pull: rebase uses previous target as fork point for rebased upstream
   ])
 
   @test.assert_eq(
-    decode_bytes(fs.read_file(root + "/file") catch { _ => Bytes::default() }),
+    decode_bytes(fs.read_file(root + "/file") catch { _ => Default::default() }),
     "conflicting modification\n",
   )
   @test.assert_eq(
-    decode_bytes(fs.read_file(root + "/file2") catch { _ => Bytes::default() }),
+    decode_bytes(fs.read_file(root + "/file2") catch { _ => Default::default() }),
     "new\n",
   )
   @test.assert_eq(@bitlib.read_unmerged_paths(fs, root + "/.git").length(), 0)
@@ -711,7 +711,7 @@ async test "pull: updates checked-out branch worktree when fetch advances it" {
   ])
 
   @test.assert_eq(
-    decode_bytes(fs.read_file(root + "/file") catch { _ => Bytes::default() }),
+    decode_bytes(fs.read_file(root + "/file") catch { _ => Default::default() }),
     "modified\n",
   )
   @test.assert_eq(
@@ -721,7 +721,7 @@ async test "pull: updates checked-out branch worktree when fetch advances it" {
   assert_true(
     decode_bytes(
       fs.read_file(root + "/.git/logs/HEAD") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ).contains("Fast-forward"),
   )
@@ -762,7 +762,7 @@ async test "pull: refuses dirty worktree when fetch advances current branch" {
   assert_true(code != 0)
   assert_true(stderr.contains("Cannot fast-forward your working tree"))
   @test.assert_eq(
-    decode_bytes(fs.read_file(root + "/file") catch { _ => Bytes::default() }),
+    decode_bytes(fs.read_file(root + "/file") catch { _ => Default::default() }),
     "conflict\n",
   )
   @test.assert_eq(
@@ -835,13 +835,13 @@ async test "pull: rebase autostash preserves staged file on fast-forward" {
   @test.assert_eq(
     decode_bytes(
       fs.read_file(root + "/new_file") catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     ),
     "dirty\n",
   )
   @test.assert_eq(
-    decode_bytes(fs.read_file(root + "/file") catch { _ => Bytes::default() }),
+    decode_bytes(fs.read_file(root + "/file") catch { _ => Default::default() }),
     "modified again\n",
   )
   @test.assert_eq(@bitlib.stash_list(fs, root + "/.git").length(), 0)
diff --git a/modules/bit/cmd/bit/helpers_shared.mbt b/modules/bit/cmd/bit/helpers_shared.mbt
index bd42d1f0..2e46767e 100644
--- a/modules/bit/cmd/bit/helpers_shared.mbt
+++ b/modules/bit/cmd/bit/helpers_shared.mbt
@@ -2,7 +2,7 @@
 
 ///|
 fn io_error(err : @fs.IOError) -> @bitcore.GitError {
-  @bitcore.GitError::IoError(@debug.render(@debug.to_repr(err)))
+  @bitcore.GitError::IoError(@debug.render(Repr(err)))
 }
 
 ///|
diff --git a/modules/bit/cmd/bit/http_fetch.mbt b/modules/bit/cmd/bit/http_fetch.mbt
index 406ab09e..19b4216c 100644
--- a/modules/bit/cmd/bit/http_fetch.mbt
+++ b/modules/bit/cmd/bit/http_fetch.mbt
@@ -78,7 +78,7 @@ async fn handle_http_fetch(args : Array[String]) -> Unit raise Error {
         @fs.write_bytes_to_file(pack_path, pack_data) catch {
           err => {
             eprint_line(
-              "error: cannot write \{pack_path}: \{@debug.render(@debug.to_repr(err))}",
+              "error: cannot write \{pack_path}: \{@debug.render(Repr(err))}",
             )
             continue
           }
@@ -136,7 +136,7 @@ async fn http_fetch_loose_object(
   @fs.write_bytes_to_file(path, data) catch {
     err => {
       eprint_line(
-        "error: cannot write \{path}: \{@debug.render(@debug.to_repr(err))}",
+        "error: cannot write \{path}: \{@debug.render(Repr(err))}",
       )
       @sys.exit(1)
       return
@@ -162,7 +162,7 @@ fn http_fetch_write_ref(
   @fs.write_bytes_to_file(ref_path, content_bytes) catch {
     err =>
       raise @bitcore.GitError::IoError(
-        "cannot write ref \{ref_path}: \{@debug.render(@debug.to_repr(err))}",
+        "cannot write ref \{ref_path}: \{@debug.render(Repr(err))}",
       )
   }
 }
diff --git a/modules/bit/cmd/bit/hub_github_sync.mbt b/modules/bit/cmd/bit/hub_github_sync.mbt
index 8b15a980..350419a4 100644
--- a/modules/bit/cmd/bit/hub_github_sync.mbt
+++ b/modules/bit/cmd/bit/hub_github_sync.mbt
@@ -487,7 +487,7 @@ async fn handle_hub_issue_sync_install_hook(
   if fs.is_file(hook_path) {
     let existing = decode_bytes(
       fs.read_file(hook_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     if existing.contains("bit issue sync") {
diff --git a/modules/bit/cmd/bit/hub_stores.mbt b/modules/bit/cmd/bit/hub_stores.mbt
index 95949f23..ad4adda4 100644
--- a/modules/bit/cmd/bit/hub_stores.mbt
+++ b/modules/bit/cmd/bit/hub_stores.mbt
@@ -226,7 +226,7 @@ fn load_hub_origin_sync_plan(fs : OsFs, git_dir : String) -> HubOriginSyncPlan {
   let config_path = hub_sync_config_path(git_dir)
   let content = decode_bytes(
     fs.read_file(config_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     },
   )
   compute_hub_origin_sync_plan(content)
@@ -405,7 +405,7 @@ fn resolve_hub_git_dir(root : String) -> String {
   let commondir_path = git_dir + "/commondir"
   if fs.is_file(commondir_path) {
     let raw = @utf8.decode_lossy(
-      (fs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+      (fs.read_file(commondir_path) catch { _ => Default::default() })[:],
     )
     let rel = raw.trim(chars=" \t\r\n").to_owned()
     if rel.length() > 0 {
diff --git a/modules/bit/cmd/bit/index_pack.mbt b/modules/bit/cmd/bit/index_pack.mbt
index a9cd14a3..17e907d2 100644
--- a/modules/bit/cmd/bit/index_pack.mbt
+++ b/modules/bit/cmd/bit/index_pack.mbt
@@ -794,17 +794,17 @@ async fn handle_index_pack(args : Array[String]) -> Unit raise Error {
           err if @async.is_cancellation_error(err) => raise err
           err => {
             @stdio.stderr.write(
-              "fatal: " + @debug.render(@debug.to_repr(err)) + "\n",
+              "fatal: " + @debug.render(Repr(err)) + "\n",
             )
             @sys.exit(1)
-            Bytes::default()
+            Default::default()
           }
         }
         let max_depth = @pack.max_delta_chain_length(pack) catch {
           err if @async.is_cancellation_error(err) => raise err
           err => {
             @stdio.stderr.write(
-              "fatal: " + @debug.render(@debug.to_repr(err)) + "\n",
+              "fatal: " + @debug.render(Repr(err)) + "\n",
             )
             @sys.exit(1)
             0
@@ -828,10 +828,10 @@ async fn handle_index_pack(args : Array[String]) -> Unit raise Error {
           err if @async.is_cancellation_error(err) => raise err
           err => {
             @stdio.stderr.write(
-              "fatal: " + @debug.render(@debug.to_repr(err)) + "\n",
+              "fatal: " + @debug.render(Repr(err)) + "\n",
             )
             @sys.exit(1)
-            Bytes::default()
+            Default::default()
           }
         }
         let idx_path = if pack_path.has_suffix(".pack") {
@@ -844,10 +844,10 @@ async fn handle_index_pack(args : Array[String]) -> Unit raise Error {
           err if @async.is_cancellation_error(err) => raise err
           err => {
             @stdio.stderr.write(
-              "fatal: " + @debug.render(@debug.to_repr(err)) + "\n",
+              "fatal: " + @debug.render(Repr(err)) + "\n",
             )
             @sys.exit(1)
-            Bytes::default()
+            Default::default()
           }
         }
         match verify_pack_index(idx, pack, hash_size~) {
@@ -869,11 +869,11 @@ async fn handle_index_pack(args : Array[String]) -> Unit raise Error {
                 err => {
                   @stdio.stderr.write(
                     "error: could not read reverse index: " +
-                    @debug.render(@debug.to_repr(err)) +
+                    @debug.render(Repr(err)) +
                     "\n",
                   )
                   @sys.exit(1)
-                  Bytes::default()
+                  Default::default()
                 }
               }
               match verify_reverse_index(rev, pack, hash_size~) {
@@ -1094,10 +1094,10 @@ async fn handle_index_pack(args : Array[String]) -> Unit raise Error {
         err if @async.is_cancellation_error(err) => raise err
         err => {
           @stdio.stderr.write(
-            "fatal: " + @debug.render(@debug.to_repr(err)) + "\n",
+            "fatal: " + @debug.render(Repr(err)) + "\n",
           )
           @sys.exit(1)
-          Bytes::default()
+          Default::default()
         }
       }
       // Check --max-input-size for file mode
diff --git a/modules/bit/cmd/bit/log.mbt b/modules/bit/cmd/bit/log.mbt
index 72077324..0f2bb8ce 100644
--- a/modules/bit/cmd/bit/log.mbt
+++ b/modules/bit/cmd/bit/log.mbt
@@ -1393,7 +1393,7 @@ fn log_extract_commit_message_and_encoding(data : Bytes) -> (Bytes, String?) {
       break
     }
   }
-  (Bytes::default(), encoding)
+  (Default::default(), encoding)
 }
 
 ///|
@@ -2014,7 +2014,7 @@ fn log_resolve_common_git_dir(
     return git_dir
   }
   let raw = @utf8.decode_lossy(
-    (rfs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+    (rfs.read_file(commondir_path) catch { _ => Default::default() })[:],
   )
   let rel = trim_string(raw)
   if rel.length() == 0 {
diff --git a/modules/bit/cmd/bit/ls_files.mbt b/modules/bit/cmd/bit/ls_files.mbt
index 5a648fe8..e2c951fc 100644
--- a/modules/bit/cmd/bit/ls_files.mbt
+++ b/modules/bit/cmd/bit/ls_files.mbt
@@ -174,7 +174,7 @@ async fn handle_ls_files(args : Array[String]) -> Unit raise Error {
       }
       // Detect worktree EOL from file on disk
       let w_eol = if file_exists {
-        let content = fs.read_file(abs) catch { _ => Bytes::default() }
+        let content = fs.read_file(abs) catch { _ => Default::default() }
         detect_eol_type(content)
       } else {
         ""
@@ -203,7 +203,7 @@ async fn handle_ls_files(args : Array[String]) -> Unit raise Error {
         }
         let abs = root + "/" + path
         let w_eol = if fs.is_file(abs) {
-          let content = fs.read_file(abs) catch { _ => Bytes::default() }
+          let content = fs.read_file(abs) catch { _ => Default::default() }
           detect_eol_type(content)
         } else {
           ""
diff --git a/modules/bit/cmd/bit/mailsplit.mbt b/modules/bit/cmd/bit/mailsplit.mbt
index 2003bec4..9d616bb6 100644
--- a/modules/bit/cmd/bit/mailsplit.mbt
+++ b/modules/bit/cmd/bit/mailsplit.mbt
@@ -51,7 +51,7 @@ async fn handle_mailsplit(args : Array[String]) -> Unit raise Error {
       let data = @fs.read_file_to_bytes(path) catch {
         err => {
           eprint_line(
-            "fatal: cannot open \{path}: \{@debug.render(@debug.to_repr(err))}",
+            "fatal: cannot open \{path}: \{@debug.render(Repr(err))}",
           )
           @sys.exit(1)
           return
@@ -98,7 +98,7 @@ async fn handle_mailsplit(args : Array[String]) -> Unit raise Error {
     @fs.write_string_to_file(path, content) catch {
       err => {
         eprint_line(
-          "fatal: cannot write \{path}: \{@debug.render(@debug.to_repr(err))}",
+          "fatal: cannot write \{path}: \{@debug.render(Repr(err))}",
         )
         @sys.exit(1)
         return
diff --git a/modules/bit/cmd/bit/merge_file.mbt b/modules/bit/cmd/bit/merge_file.mbt
index c06a9a19..8ea8b61a 100644
--- a/modules/bit/cmd/bit/merge_file.mbt
+++ b/modules/bit/cmd/bit/merge_file.mbt
@@ -100,7 +100,7 @@ async fn handle_merge_file(args : Array[String]) -> Unit raise Error {
     @fs.write_string_to_file(current_arg, result.content) catch {
       e => {
         eprint_line(
-          "fatal: could not write '\{current_arg}': \{@debug.render(@debug.to_repr(e))}",
+          "fatal: could not write '\{current_arg}': \{@debug.render(Repr(e))}",
         )
         @sys.exit(128)
       }
diff --git a/modules/bit/cmd/bit/merge_one_file.mbt b/modules/bit/cmd/bit/merge_one_file.mbt
index c7373715..500c372f 100644
--- a/modules/bit/cmd/bit/merge_one_file.mbt
+++ b/modules/bit/cmd/bit/merge_one_file.mbt
@@ -73,7 +73,7 @@ async fn handle_merge_one_file(args : Array[String]) -> Unit raise Error {
   @fs.write_bytes_to_file(full_path, content_bytes) catch {
     err => {
       eprint_line(
-        "error: cannot write \{full_path}: \{@debug.render(@debug.to_repr(err))}",
+        "error: cannot write \{full_path}: \{@debug.render(Repr(err))}",
       )
       @sys.exit(1)
       return
diff --git a/modules/bit/cmd/bit/merge_tree.mbt b/modules/bit/cmd/bit/merge_tree.mbt
index 0c2b667d..eb05456d 100644
--- a/modules/bit/cmd/bit/merge_tree.mbt
+++ b/modules/bit/cmd/bit/merge_tree.mbt
@@ -343,10 +343,10 @@ fn merge_tree_get_blob_data(
   fs : &@bitcore.RepoFileSystem,
   id : @bitcore.ObjectId,
 ) -> Bytes {
-  let obj = db.get(fs, id) catch { _ => return Bytes::default() }
+  let obj = db.get(fs, id) catch { _ => return Default::default() }
   match obj {
     Some(o) if o.obj_type == @bitcore.ObjectType::Blob => o.data
-    _ => Bytes::default()
+    _ => Default::default()
   }
 }
 
diff --git a/modules/bit/cmd/bit/notes.mbt b/modules/bit/cmd/bit/notes.mbt
index 0b03adfc..00742c3e 100644
--- a/modules/bit/cmd/bit/notes.mbt
+++ b/modules/bit/cmd/bit/notes.mbt
@@ -1186,7 +1186,7 @@ fn notes_resolve_common_git_dir(
     return git_dir
   }
   let raw = @utf8.decode_lossy(
-    (rfs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+    (rfs.read_file(commondir_path) catch { _ => Default::default() })[:],
   )
   let rel = trim_string(raw)
   if rel.length() == 0 {
diff --git a/modules/bit/cmd/bit/pull.mbt b/modules/bit/cmd/bit/pull.mbt
index 17547d55..df957ac4 100644
--- a/modules/bit/cmd/bit/pull.mbt
+++ b/modules/bit/cmd/bit/pull.mbt
@@ -7,7 +7,7 @@ async fn handle_pull(args : Array[String]) -> Unit raise Error {
   if rfs.is_file(git_dir) {
     let gitfile = decode_bytes(
       rfs.read_file(git_dir) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     ignore(gitfile)
@@ -1185,7 +1185,7 @@ fn pull_snapshot_worktree_files(
   for path in paths {
     let full_path = root + "/" + path
     if fs.is_file(full_path) {
-      snapshot[path] = fs.read_file(full_path) catch { _ => Bytes::default() }
+      snapshot[path] = fs.read_file(full_path) catch { _ => Default::default() }
     }
   }
   snapshot
@@ -1626,7 +1626,7 @@ fn read_config_values(
   }
   let content = decode_bytes(
     fs.read_file(config_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     },
   )
   let section_lower = section.to_lower()
@@ -1867,7 +1867,7 @@ fn read_url_rewrite_rules(
   }
   let content = decode_bytes(
     fs.read_file(config_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     },
   )
   let blocks = @bitlib.parse_config_blocks(content)
diff --git a/modules/bit/cmd/bit/quiltimport.mbt b/modules/bit/cmd/bit/quiltimport.mbt
index a1d975dd..6a85786b 100644
--- a/modules/bit/cmd/bit/quiltimport.mbt
+++ b/modules/bit/cmd/bit/quiltimport.mbt
@@ -41,7 +41,7 @@ async fn handle_quiltimport(args : Array[String]) -> Unit raise Error {
   let series_data = @fs.read_file_to_bytes(series_path) catch {
     err => {
       eprint_line(
-        "fatal: cannot read \{series_path}: \{@debug.render(@debug.to_repr(err))}",
+        "fatal: cannot read \{series_path}: \{@debug.render(Repr(err))}",
       )
       @sys.exit(1)
       return
diff --git a/modules/bit/cmd/bit/rebase.mbt b/modules/bit/cmd/bit/rebase.mbt
index 3fd1f3d0..f554ea01 100644
--- a/modules/bit/cmd/bit/rebase.mbt
+++ b/modules/bit/cmd/bit/rebase.mbt
@@ -160,7 +160,7 @@ fn rebase_read_signing_state(
     return (false, None)
   }
   let value = trim_string(
-    decode_bytes(rfs.read_file(path) catch { _ => Bytes::default() }),
+    decode_bytes(rfs.read_file(path) catch { _ => Default::default() }),
   )
   (true, if value.length() > 0 { Some(value) } else { None })
 }
diff --git a/modules/bit/cmd/bit/remote.mbt b/modules/bit/cmd/bit/remote.mbt
index ec90c454..ad8dd3fa 100644
--- a/modules/bit/cmd/bit/remote.mbt
+++ b/modules/bit/cmd/bit/remote.mbt
@@ -74,7 +74,7 @@ fn emit_trace_region(
   if fs.is_file(target) {
     let existing = decode_bytes(
       fs.read_file(target) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     fs.write_string(target, existing + enter + leave)
@@ -85,7 +85,7 @@ fn emit_trace_region(
 
 ///|
 fn append_text_file(fs : OsFs, path : String, text : String) -> Unit {
-  let current = decode_bytes(fs.read_file(path) catch { _ => Bytes::default() })
+  let current = decode_bytes(fs.read_file(path) catch { _ => Default::default() })
   fs.write_string(path, current + text) catch {
     _ => ()
   }
diff --git a/modules/bit/cmd/bit/reset.mbt b/modules/bit/cmd/bit/reset.mbt
index aaedbe36..a75603dc 100644
--- a/modules/bit/cmd/bit/reset.mbt
+++ b/modules/bit/cmd/bit/reset.mbt
@@ -360,7 +360,7 @@ async fn reset_refresh_index_entries(
       let content = rfs.read_file(abs) catch {
         _ => {
           changed = true
-          Bytes::default()
+          Default::default()
         }
       }
       if !changed {
@@ -414,7 +414,7 @@ fn reset_read_skip_worktree_paths(
   if fs.is_file(sidecar_path) {
     let text = decode_bytes(
       fs.read_file(sidecar_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     for line_view in text.split("\n") {
@@ -595,7 +595,7 @@ fn reset_commit_subject_bytes(
       )
       reset_convert_encoding(subject, source_encoding, output_encoding)
     }
-    None => Bytes::default()
+    None => Default::default()
   }
 }
 
@@ -639,7 +639,7 @@ fn reset_extract_commit_subject_and_encoding(data : Bytes) -> (Bytes, String?) {
       break
     }
   }
-  (Bytes::default(), encoding)
+  (Default::default(), encoding)
 }
 
 ///|
@@ -786,7 +786,7 @@ fn reset_slice_bytes(data : Bytes, start : Int, end : Int) -> Bytes {
   }
   let len = safe_end - safe_start
   if len <= 0 {
-    return Bytes::default()
+    return Default::default()
   }
   Bytes::from_array(FixedArray::makei(len, i => data[safe_start + i]))
 }
diff --git a/modules/bit/cmd/bit/submodule.mbt b/modules/bit/cmd/bit/submodule.mbt
index 5c07dba9..3074b6da 100644
--- a/modules/bit/cmd/bit/submodule.mbt
+++ b/modules/bit/cmd/bit/submodule.mbt
@@ -165,7 +165,7 @@ fn resolve_submodule_common_git_dir(
   if fs.is_file(commondir_path) {
     let raw = decode_bytes(
       fs.read_file(commondir_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     let rel = trim_string(raw)
@@ -1716,7 +1716,7 @@ fn read_submodule_status_head_label(
   }
   let content = decode_bytes(
     fs.read_file(head_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     },
   )
   match submodule_status_head_label(content) {
@@ -2034,7 +2034,7 @@ async fn handle_submodule_status(
   if rfs.is_file(gitmodules_path) {
     let gitmodules = decode_bytes(
       rfs.read_file(gitmodules_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     if gitmodules_has_unmapped_paths(gitmodules) {
@@ -2261,7 +2261,7 @@ async fn handle_submodule_update(
           if @async.is_being_cancelled() || @async.is_cancellation_error(err) {
             raise err
           }
-          Bytes::default()
+          Default::default()
         }
       },
     )
diff --git a/modules/bit/cmd/bit/version.mbt b/modules/bit/cmd/bit/version.mbt
index 7ce34a4c..3af9d55d 100644
--- a/modules/bit/cmd/bit/version.mbt
+++ b/modules/bit/cmd/bit/version.mbt
@@ -1,3 +1,3 @@
 ///|
 /// bit version tag (update this and the module/package manifests together when releasing)
-let bit_version_tag : String = "2.47.0 (bit v0.45.6)"
+let bit_version_tag : String = "2.47.0 (bit v0.46.1)"
diff --git a/modules/bit/cmd/git-bit/helpers_shared.mbt b/modules/bit/cmd/git-bit/helpers_shared.mbt
index bd42d1f0..2e46767e 100644
--- a/modules/bit/cmd/git-bit/helpers_shared.mbt
+++ b/modules/bit/cmd/git-bit/helpers_shared.mbt
@@ -2,7 +2,7 @@
 
 ///|
 fn io_error(err : @fs.IOError) -> @bitcore.GitError {
-  @bitcore.GitError::IoError(@debug.render(@debug.to_repr(err)))
+  @bitcore.GitError::IoError(@debug.render(Repr(err)))
 }
 
 ///|
diff --git a/modules/bit/cmd/git-bit/hub_github_sync.mbt b/modules/bit/cmd/git-bit/hub_github_sync.mbt
index 4bbc53f2..7463cbd7 100644
--- a/modules/bit/cmd/git-bit/hub_github_sync.mbt
+++ b/modules/bit/cmd/git-bit/hub_github_sync.mbt
@@ -487,7 +487,7 @@ async fn handle_hub_issue_sync_install_hook(
   if fs.is_file(hook_path) {
     let existing = decode_bytes(
       fs.read_file(hook_path) catch {
-        _ => Bytes::default()
+        _ => Default::default()
       },
     )
     if existing.contains("bit issue sync") {
diff --git a/modules/bit/cmd/git-bit/hub_stores.mbt b/modules/bit/cmd/git-bit/hub_stores.mbt
index b5ceb380..f6b450c5 100644
--- a/modules/bit/cmd/git-bit/hub_stores.mbt
+++ b/modules/bit/cmd/git-bit/hub_stores.mbt
@@ -190,7 +190,7 @@ fn resolve_hub_common_git_dir(git_dir : String) -> String {
   let commondir_path = resolved_git_dir + "/commondir"
   if fs.is_file(commondir_path) {
     let raw = @utf8.decode_lossy(
-      (fs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+      (fs.read_file(commondir_path) catch { _ => Default::default() })[:],
     )
     let rel = raw.trim(chars=" \t\r\n").to_owned()
     if rel.length() > 0 {
diff --git a/modules/bit/moon.mod b/modules/bit/moon.mod
index d292ee9e..880d9952 100644
--- a/modules/bit/moon.mod
+++ b/modules/bit/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit"
 
-version = "0.45.6"
+version = "0.46.1"
 
 import {
   "moonbitlang/async@0.19.4",
diff --git a/modules/bit_grep/moon.mod b/modules/bit_grep/moon.mod
index 1087342b..934c9390 100644
--- a/modules/bit_grep/moon.mod
+++ b/modules/bit_grep/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_grep"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_grep/src/pattern.mbt b/modules/bit_grep/src/pattern.mbt
index e20dee23..65ab5468 100644
--- a/modules/bit_grep/src/pattern.mbt
+++ b/modules/bit_grep/src/pattern.mbt
@@ -116,7 +116,7 @@ pub impl Show for GrepExprMatch with fn output(self, logger) {
     "{matched: " +
     self.matched.to_string() +
     ", span: " +
-    to_repr(self.span).to_string() +
+    Repr(self.span).to_string() +
     "}",
   )
 }
diff --git a/modules/bit_grep/src/search.mbt b/modules/bit_grep/src/search.mbt
index 97de55f8..bdb36eac 100644
--- a/modules/bit_grep/src/search.mbt
+++ b/modules/bit_grep/src/search.mbt
@@ -53,7 +53,7 @@ pub impl Show for GrepFileMatch with fn output(self, logger) {
     "{path: " +
     grep_search_show_string(self.path) +
     ", matches: " +
-    to_repr(self.matches).to_string() +
+    Repr(self.matches).to_string() +
     "}",
   )
 }
diff --git a/modules/bit_ignore/moon.mod b/modules/bit_ignore/moon.mod
index befe4ed4..4dd45108 100644
--- a/modules/bit_ignore/moon.mod
+++ b/modules/bit_ignore/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_ignore"
 
-version = "0.45.6"
+version = "0.45.7"
 
 repository = "https://github.com/mizchi/bit-vcs"
 
diff --git a/modules/bit_ignore/src/ignore.mbt b/modules/bit_ignore/src/ignore.mbt
index bc6d2610..93a36167 100644
--- a/modules/bit_ignore/src/ignore.mbt
+++ b/modules/bit_ignore/src/ignore.mbt
@@ -367,7 +367,7 @@ let char_slash : UInt16 = {
 ///|
 fn string_to_uint16_array(s : String) -> FixedArray[UInt16] {
   let len = s.length()
-  let arr = FixedArray::make(len, UInt16::default())
+  let arr = FixedArray::make(len, Default::default())
   for i in 0..<len {
     arr[i] = s.unsafe_get(i)
   }
diff --git a/modules/bit_io_native/moon.mod b/modules/bit_io_native/moon.mod
index 1e9324f9..db46ea3b 100644
--- a/modules/bit_io_native/moon.mod
+++ b/modules/bit_io_native/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_io_native"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_io_native/src/upload_pack_process.mbt b/modules/bit_io_native/src/upload_pack_process.mbt
index dd2ca357..db4a66b3 100644
--- a/modules/bit_io_native/src/upload_pack_process.mbt
+++ b/modules/bit_io_native/src/upload_pack_process.mbt
@@ -645,7 +645,7 @@ async fn run_process_with_files(
   }
   let stdin_bytes = match stdin_data {
     Some(data) => data
-    None => Bytes::default()
+    None => Default::default()
   }
   @fs.write_bytes_to_file(stdin_path, stdin_bytes) catch {
     e =>
@@ -1086,7 +1086,7 @@ async fn run_ssh_upload_pack_interactive(
   }
   if code != 0 {
     let err_bytes = @fs.read_file_to_bytes(stderr_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     }
     let err_text = bytes_to_string_lossy(err_bytes)
     cleanup_temp_files([stderr_path])
diff --git a/modules/bit_lib/moon.mod b/modules/bit_lib/moon.mod
index 44614b8b..d2c56454 100644
--- a/modules/bit_lib/moon.mod
+++ b/modules/bit_lib/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_lib"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_lib/src/checkout.mbt b/modules/bit_lib/src/checkout.mbt
index e29747dd..03650a66 100644
--- a/modules/bit_lib/src/checkout.mbt
+++ b/modules/bit_lib/src/checkout.mbt
@@ -203,7 +203,7 @@ pub fn resolve_checkout_common_git_dir(
     return git_dir
   }
   let raw = @utf8.decode_lossy(
-    (fs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(commondir_path) catch { _ => Default::default() })[:],
   )
   let rel = @string_utils.trim_string(raw)
   if rel.length() == 0 {
diff --git a/modules/bit_lib/src/gitattributes.mbt b/modules/bit_lib/src/gitattributes.mbt
index 126b8ce1..2116f8ed 100644
--- a/modules/bit_lib/src/gitattributes.mbt
+++ b/modules/bit_lib/src/gitattributes.mbt
@@ -36,7 +36,7 @@ pub fn resolve_diff_driver(
   let attr_path = join_path(root, ".gitattributes")
   guard rfs.is_file(attr_path) else { return None }
   let content = @utf8.decode_lossy(
-    (rfs.read_file(attr_path) catch { _ => Bytes::default() })[:],
+    (rfs.read_file(attr_path) catch { _ => Default::default() })[:],
   )
   let normalized = gitattr_normalize_path(path)
   let mut diff_driver : String? = None
@@ -135,7 +135,7 @@ pub fn resolve_eol_attrs(
     }
   }
   let content = @utf8.decode_lossy(
-    (rfs.read_file(attr_path) catch { _ => Bytes::default() })[:],
+    (rfs.read_file(attr_path) catch { _ => Default::default() })[:],
   )
   let normalized = gitattr_normalize_path(path)
   let mut text : TextAttr = TextAttr::Unspecified
@@ -335,7 +335,7 @@ pub fn check_unsupported_gitattributes(
     return None
   }
   let content = @utf8.decode_lossy(
-    (rfs.read_file(attr_path) catch { _ => Bytes::default() })[:],
+    (rfs.read_file(attr_path) catch { _ => Default::default() })[:],
   )
   for line_view in content.split("\n") {
     let line = line_view.to_owned().trim().to_owned()
@@ -444,7 +444,7 @@ pub fn has_any_filter_attributes(
     return false
   }
   let content = @utf8.decode_lossy(
-    (rfs.read_file(attr_path) catch { _ => Bytes::default() })[:],
+    (rfs.read_file(attr_path) catch { _ => Default::default() })[:],
   )
   for line_view in content.split("\n") {
     let line = line_view.to_owned().trim().to_owned()
diff --git a/modules/bit_lib/src/index.mbt b/modules/bit_lib/src/index.mbt
index 3f978135..af6d6170 100644
--- a/modules/bit_lib/src/index.mbt
+++ b/modules/bit_lib/src/index.mbt
@@ -1015,7 +1015,7 @@ pub fn read_skip_worktree_paths(
   let sidecar_path = join_path(git_dir, "bit-skip-worktree")
   if fs.is_file(sidecar_path) {
     let text = @utf8.decode_lossy(
-      (fs.read_file(sidecar_path) catch { _ => Bytes::default() })[:],
+      (fs.read_file(sidecar_path) catch { _ => Default::default() })[:],
     )
     for line_view in text.split("\n") {
       let line = line_view.to_owned()
diff --git a/modules/bit_lib/src/index_wbtest.mbt b/modules/bit_lib/src/index_wbtest.mbt
index 09335ad1..9549277e 100644
--- a/modules/bit_lib/src/index_wbtest.mbt
+++ b/modules/bit_lib/src/index_wbtest.mbt
@@ -390,7 +390,7 @@ fn index_test_mark_single_entry_skip_worktree(
   fs : @bit.TestFs,
   index_path : String,
 ) -> Unit {
-  let data = fs.read_file(index_path) catch { _ => Bytes::default() }
+  let data = fs.read_file(index_path) catch { _ => Default::default() }
   let arr : Array[Byte] = []
   for b in data {
     arr.push(b)
@@ -434,7 +434,7 @@ fn index_test_replace_single_entry_with_stages(
   index_path : String,
   stages : Array[Int],
 ) -> Unit {
-  let data = fs.read_file(index_path) catch { _ => Bytes::default() }
+  let data = fs.read_file(index_path) catch { _ => Default::default() }
   if data.length() < 12 + 20 {
     panic()
   }
@@ -509,7 +509,7 @@ fn index_test_write_resolve_undo_extension(
   ours_hex : String,
   theirs_hex : String,
 ) -> Unit {
-  let data = fs.read_file(index_path) catch { _ => Bytes::default() }
+  let data = fs.read_file(index_path) catch { _ => Default::default() }
   let arr : Array[Byte] = []
   for b in data {
     arr.push(b)
diff --git a/modules/bit_lib/src/log.mbt b/modules/bit_lib/src/log.mbt
index 91bc63de..1e6d099c 100644
--- a/modules/bit_lib/src/log.mbt
+++ b/modules/bit_lib/src/log.mbt
@@ -267,7 +267,7 @@ fn log_resolve_common_git_dir(
     return git_dir
   }
   let raw = @utf8.decode_lossy(
-    (fs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(commondir_path) catch { _ => Default::default() })[:],
   )
   let rel = @string_utils.trim_string(raw)
   if rel.length() == 0 {
diff --git a/modules/bit_lib/src/merge.mbt b/modules/bit_lib/src/merge.mbt
index 7f87c6a6..7901a758 100644
--- a/modules/bit_lib/src/merge.mbt
+++ b/modules/bit_lib/src/merge.mbt
@@ -883,15 +883,15 @@ fn merge_get_blob_data(
   fs : &@bit.RepoFileSystem,
   id : @bit.ObjectId,
 ) -> Bytes {
-  let obj = db.get(fs, id) catch { _ => return Bytes::default() }
+  let obj = db.get(fs, id) catch { _ => return Default::default() }
   match obj {
     Some(o) =>
       if o.obj_type == @bit.ObjectType::Blob {
         o.data
       } else {
-        Bytes::default()
+        Default::default()
       }
-    None => Bytes::default()
+    None => Default::default()
   }
 }
 
diff --git a/modules/bit_lib/src/merge_test.mbt b/modules/bit_lib/src/merge_test.mbt
index 57b480f3..eedb660f 100644
--- a/modules/bit_lib/src/merge_test.mbt
+++ b/modules/bit_lib/src/merge_test.mbt
@@ -35,7 +35,7 @@ test "merge: content-level merge non-overlapping changes" {
   match result.status {
     Merged => ()
     _ => {
-      println("Expected Merged, got conflicts: \{to_repr(result.conflicts)}")
+      println("Expected Merged, got conflicts: \{Repr(result.conflicts)}")
       assert_true(false)
     }
   }
@@ -112,7 +112,7 @@ test "merge: file-level merge without conflicts" {
   match result.status {
     Merged => ()
     Conflicted => {
-      println("CONFLICT: \{to_repr(result.conflicts)}")
+      println("CONFLICT: \{Repr(result.conflicts)}")
       assert_true(false)
     }
     AlreadyUpToDate => {
@@ -291,7 +291,7 @@ test "merge: rename on one side, no conflict" {
   match result.status {
     Merged => ()
     _ => {
-      println("Expected Merged, got conflicts: \{to_repr(result.conflicts)}")
+      println("Expected Merged, got conflicts: \{Repr(result.conflicts)}")
       fail("expected merged")
     }
   }
@@ -347,7 +347,7 @@ test "merge: rename on one side, modify on other (rename/modify)" {
   match result.status {
     Merged => ()
     Conflicted => {
-      println("Conflicts: \{to_repr(result.conflicts)}")
+      println("Conflicts: \{Repr(result.conflicts)}")
       fail("expected merged, got conflicted")
     }
     _ => fail("expected merged")
@@ -477,7 +477,7 @@ test "merge: rename/add-source - rename a->b with new file at a" {
   match result.status {
     Merged => ()
     _ => {
-      println("Expected Merged, got conflicts: \{to_repr(result.conflicts)}")
+      println("Expected Merged, got conflicts: \{Repr(result.conflicts)}")
       fail("expected merged")
     }
   }
diff --git a/modules/bit_lib/src/rebase.mbt b/modules/bit_lib/src/rebase.mbt
index 43ee8e64..1ab71a6f 100644
--- a/modules/bit_lib/src/rebase.mbt
+++ b/modules/bit_lib/src/rebase.mbt
@@ -1124,7 +1124,7 @@ pub fn load_rebase_state(
 ///|
 fn read_file_trimmed(fs : &@bit.RepoFileSystem, path : String) -> String {
   let content = @utf8.decode_lossy(
-    (fs.read_file(path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(path) catch { _ => Default::default() })[:],
   )
   let mut end = content.length()
   while end > 0 {
@@ -1148,7 +1148,7 @@ fn parse_todo_file(
     return result
   }
   let content = @utf8.decode_lossy(
-    (fs.read_file(path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(path) catch { _ => Default::default() })[:],
   )
   for line_view in content.split("\n") {
     let line = line_view.to_owned()
@@ -2051,15 +2051,15 @@ fn rebase_get_blob_data(
   fs : &@bit.RepoFileSystem,
   id : @bit.ObjectId,
 ) -> Bytes {
-  let obj = db.get(fs, id) catch { _ => return Bytes::default() }
+  let obj = db.get(fs, id) catch { _ => return Default::default() }
   match obj {
     Some(o) =>
       if o.obj_type == @bit.ObjectType::Blob {
         o.data
       } else {
-        Bytes::default()
+        Default::default()
       }
-    None => Bytes::default()
+    None => Default::default()
   }
 }
 
diff --git a/modules/bit_lib/src/rebase_interactive.mbt b/modules/bit_lib/src/rebase_interactive.mbt
index f456e6aa..d211bab7 100644
--- a/modules/bit_lib/src/rebase_interactive.mbt
+++ b/modules/bit_lib/src/rebase_interactive.mbt
@@ -513,7 +513,7 @@ fn interactive_read_file_or_empty(
   if !rfs.is_file(path) {
     return ""
   }
-  @utf8.decode_lossy((rfs.read_file(path) catch { _ => Bytes::default() })[:])
+  @utf8.decode_lossy((rfs.read_file(path) catch { _ => Default::default() })[:])
 }
 
 // ============================================================================
diff --git a/modules/bit_lib/src/reset.mbt b/modules/bit_lib/src/reset.mbt
index 22980bf5..14da2136 100644
--- a/modules/bit_lib/src/reset.mbt
+++ b/modules/bit_lib/src/reset.mbt
@@ -98,7 +98,7 @@ fn reset_resolve_common_git_dir(
     return git_dir
   }
   let raw = @utf8.decode_lossy(
-    (fs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(commondir_path) catch { _ => Default::default() })[:],
   )
   let rel = @string_utils.trim_string(raw)
   if rel.length() == 0 {
diff --git a/modules/bit_lib/src/worktree.mbt b/modules/bit_lib/src/worktree.mbt
index de7268e1..60dd0d1a 100644
--- a/modules/bit_lib/src/worktree.mbt
+++ b/modules/bit_lib/src/worktree.mbt
@@ -1485,7 +1485,7 @@ fn resolve_worktree_common_git_dir(
     return git_dir
   }
   let raw = @utf8.decode_lossy(
-    (fs.read_file(commondir_path) catch { _ => Bytes::default() })[:],
+    (fs.read_file(commondir_path) catch { _ => Default::default() })[:],
   )
   let rel = trim_worktree_text(raw)
   if rel.length() == 0 {
diff --git a/modules/bit_lib/src/worktree_admin.mbt b/modules/bit_lib/src/worktree_admin.mbt
index 40a62180..8f303dde 100644
--- a/modules/bit_lib/src/worktree_admin.mbt
+++ b/modules/bit_lib/src/worktree_admin.mbt
@@ -1419,7 +1419,7 @@ fn worktree_sanitize_admin_component(name : String) -> String {
     return name
   }
   let out : Array[Char] = []
-  let mut last = Char::default()
+  let mut last = Default::default()
   for ch in name.to_array() {
     if ch == '.' && last == '.' {
       last = ch
diff --git a/modules/bit_object/moon.mod b/modules/bit_object/moon.mod
index 7ab89495..ba3ee1f9 100644
--- a/modules/bit_object/moon.mod
+++ b/modules/bit_object/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_object"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_hash@0.45.6",
diff --git a/modules/bit_object/src/types.mbt b/modules/bit_object/src/types.mbt
index 90e78bc5..01c55cb8 100644
--- a/modules/bit_object/src/types.mbt
+++ b/modules/bit_object/src/types.mbt
@@ -153,7 +153,7 @@ pub fn ObjectId::is_zero_hex(hex : String) -> Bool {
 pub impl Hash for ObjectId with fn hash_combine(self, hasher) {
   // Use first 8 bytes as hash (sufficient for distribution)
   for i in 0..<8 {
-    self.bytes[i].hash_combine(hasher)
+    Hash::hash_combine(self.bytes[i], hasher)
   }
 }
 
diff --git a/modules/bit_pack/moon.mod b/modules/bit_pack/moon.mod
index 95508224..05284640 100644
--- a/modules/bit_pack/moon.mod
+++ b/modules/bit_pack/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_pack"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_pack/src/bit_oracle_pack_test.mbt b/modules/bit_pack/src/bit_oracle_pack_test.mbt
index d0443de2..513fca69 100644
--- a/modules/bit_pack/src/bit_oracle_pack_test.mbt
+++ b/modules/bit_pack/src/bit_oracle_pack_test.mbt
@@ -10,13 +10,13 @@ async fn run_git(
     .prefix("git-stdout-")
     .suffix(".out")
     .create_temp_file() catch {
-      _ => return (-1, Bytes::default(), Bytes::default())
+      _ => return (-1, Default::default(), Default::default())
     }
   let stderr_file = @tempfile.Builder::new()
     .prefix("git-stderr-")
     .suffix(".err")
     .create_temp_file() catch {
-      _ => return (-1, Bytes::default(), Bytes::default())
+      _ => return (-1, Default::default(), Default::default())
     }
   let stdout_path = stdout_file.path()
   let stderr_path = stderr_file.path()
@@ -37,7 +37,7 @@ async fn run_git(
         .prefix("git-stdin-")
         .suffix(".in")
         .create_temp_file() catch {
-          _ => return (-1, Bytes::default(), Bytes::default())
+          _ => return (-1, Default::default(), Default::default())
         }
       f.write_bytes(data) catch {
         _ => ()
@@ -79,8 +79,8 @@ async fn run_git(
           )
       }
   }
-  let out = @fs.read_file_to_bytes(stdout_path) catch { _ => Bytes::default() }
-  let err = @fs.read_file_to_bytes(stderr_path) catch { _ => Bytes::default() }
+  let out = @fs.read_file_to_bytes(stdout_path) catch { _ => Default::default() }
+  let err = @fs.read_file_to_bytes(stderr_path) catch { _ => Default::default() }
   // Cleanup temp files
   stdout_file.cleanup() catch {
     _ => ()
diff --git a/modules/bit_refs/moon.mod b/modules/bit_refs/moon.mod
index 75cc304b..16a67cb6 100644
--- a/modules/bit_refs/moon.mod
+++ b/modules/bit_refs/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_refs"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_refs/src/refs_store.mbt b/modules/bit_refs/src/refs_store.mbt
index c830d1e6..c914ec0e 100644
--- a/modules/bit_refs/src/refs_store.mbt
+++ b/modules/bit_refs/src/refs_store.mbt
@@ -111,7 +111,7 @@ pub fn collect_packed_ref_ids(
   if !fs.is_file(packed_path) {
     return ()
   }
-  let packed = fs.read_file(packed_path) catch { _ => Bytes::default() }
+  let packed = fs.read_file(packed_path) catch { _ => Default::default() }
   let text = @utf8.decode_lossy(packed[:])
   for line_view in text.split("\n") {
     let line = trim_string_refs(line_view.to_owned())
@@ -267,7 +267,7 @@ pub fn rewrite_packed_refs(
   if !rfs.is_file(packed_path) {
     return ()
   }
-  let data = rfs.read_file(packed_path) catch { _ => Bytes::default() }
+  let data = rfs.read_file(packed_path) catch { _ => Default::default() }
   let text = @utf8.decode_lossy(data[:])
   let entries = parse_packed_refs_text(text)
   let kept : Array[PackedRefEntry] = []
diff --git a/modules/bit_repo/moon.mod b/modules/bit_repo/moon.mod
index 2ba5b770..188b4e73 100644
--- a/modules/bit_repo/moon.mod
+++ b/modules/bit_repo/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_repo"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_io@0.45.6",
diff --git a/modules/bit_repo/src/shallow.mbt b/modules/bit_repo/src/shallow.mbt
index 4396c24e..c5f0c513 100644
--- a/modules/bit_repo/src/shallow.mbt
+++ b/modules/bit_repo/src/shallow.mbt
@@ -9,7 +9,7 @@ pub fn read_shallow_boundaries(
   if !fs.is_file(path) {
     return []
   }
-  let data = fs.read_file(path) catch { _ => Bytes::default() }
+  let data = fs.read_file(path) catch { _ => Default::default() }
   let boundaries : Array[@object.ObjectId] = []
   for line_view in @utf8.decode_lossy(data[:]).split("\n") {
     let line = line_view.trim().to_owned()
diff --git a/modules/bit_runtime/moon.mod b/modules/bit_runtime/moon.mod
index 29bedf35..aa751dd4 100644
--- a/modules/bit_runtime/moon.mod
+++ b/modules/bit_runtime/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_runtime"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_runtime/src/storage_runtime.mbt b/modules/bit_runtime/src/storage_runtime.mbt
index 84eb8837..c13b9866 100644
--- a/modules/bit_runtime/src/storage_runtime.mbt
+++ b/modules/bit_runtime/src/storage_runtime.mbt
@@ -785,7 +785,7 @@ fn storage_resolve_common_git_dir(
   }
   let raw = storage_decode_bytes(
     rfs.read_file(commondir_path) catch {
-      _ => Bytes::default()
+      _ => Default::default()
     },
   )
   let rel = storage_trim_string(raw)
diff --git a/modules/bit_vfs/moon.mod b/modules/bit_vfs/moon.mod
index 1b73e65b..8b42e0f3 100644
--- a/modules/bit_vfs/moon.mod
+++ b/modules/bit_vfs/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bit_vfs"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bit_vfs/src/partial_clone_test.mbt b/modules/bit_vfs/src/partial_clone_test.mbt
index 91a50c50..390f2010 100644
--- a/modules/bit_vfs/src/partial_clone_test.mbt
+++ b/modules/bit_vfs/src/partial_clone_test.mbt
@@ -28,7 +28,7 @@ test "partial_clone: mount and list files" {
 
   // Get promisor remote
   let remote = @lib.read_promisor_remote(osfs, git_dir)
-  println("Promisor remote: \{to_repr(remote)}")
+  println("Promisor remote: \{Repr(remote)}")
   assert_true(remote is Some(_))
 
   // Get HEAD commit
@@ -343,7 +343,7 @@ async test "partial_clone: prefetch multiple files" {
     } else {
       files_to_fetch
     }
-    println("Prefetching: \{to_repr(to_prefetch)}")
+    println("Prefetching: \{Repr(to_prefetch)}")
     let fetched = bitfs.prefetch(osfs, osfs, to_prefetch)
     println("Fetched \{fetched} objects")
 
diff --git a/modules/bitx_hub/moon.mod b/modules/bitx_hub/moon.mod
index 8ce3b73c..b9f3fb6b 100644
--- a/modules/bitx_hub/moon.mod
+++ b/modules/bitx_hub/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bitx_hub"
 
-version = "0.45.6"
+version = "0.46.1"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bitx_hub/src/native/github_api.mbt b/modules/bitx_hub/src/native/github_api.mbt
index 5a165863..1f488b9f 100644
--- a/modules/bitx_hub/src/native/github_api.mbt
+++ b/modules/bitx_hub/src/native/github_api.mbt
@@ -113,7 +113,7 @@ fn parse_json_array_from_api(text : String) -> Array[Json] raise @bit.GitError {
     Json::Array(items) => items
     _ =>
       raise @bit.GitError::InvalidObject(
-        "Expected JSON array from gh api, got: \{to_repr(parsed)}",
+        "Expected JSON array from gh api, got: \{Repr(parsed)}",
       )
   }
 }
@@ -132,7 +132,7 @@ fn parse_json_object_from_api(
     Json::Object(obj) => obj
     _ =>
       raise @bit.GitError::InvalidObject(
-        "Expected JSON object from gh api, got: \{to_repr(parsed)}",
+        "Expected JSON object from gh api, got: \{Repr(parsed)}",
       )
   }
 }
diff --git a/modules/bitx_kv/moon.mod b/modules/bitx_kv/moon.mod
index 5d138e48..247f4303 100644
--- a/modules/bitx_kv/moon.mod
+++ b/modules/bitx_kv/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bitx_kv"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bitx_kv/src/types.mbt b/modules/bitx_kv/src/types.mbt
index 216d769c..09784472 100644
--- a/modules/bitx_kv/src/types.mbt
+++ b/modules/bitx_kv/src/types.mbt
@@ -35,7 +35,7 @@ pub impl Eq for NodeId with fn equal(self, other) {
 
 ///|
 pub impl Hash for NodeId with fn hash_combine(self, hasher) {
-  self.id.hash_combine(hasher)
+  Hash::hash_combine(self.id, hasher)
 }
 
 ///|
diff --git a/modules/bitx_rebase_ai/moon.mod b/modules/bitx_rebase_ai/moon.mod
index db639cc7..b68f6719 100644
--- a/modules/bitx_rebase_ai/moon.mod
+++ b/modules/bitx_rebase_ai/moon.mod
@@ -1,6 +1,6 @@
 name = "mizchi/bitx_rebase_ai"
 
-version = "0.45.6"
+version = "0.45.7"
 
 import {
   "mizchi/bit_core@0.45.6",
diff --git a/modules/bitx_rebase_ai/src/rebase_ai.mbt b/modules/bitx_rebase_ai/src/rebase_ai.mbt
index 5c6e0b61..221445d3 100644
--- a/modules/bitx_rebase_ai/src/rebase_ai.mbt
+++ b/modules/bitx_rebase_ai/src/rebase_ai.mbt
@@ -587,7 +587,7 @@ fn collect_conflict_marker_paths_recursive(
     if rfs.is_dir(child_path) {
       collect_conflict_marker_paths_recursive(rfs, root, child_rel, out)
     } else if rfs.is_file(child_path) {
-      let data = rfs.read_file(child_path) catch { _ => Bytes::default() }
+      let data = rfs.read_file(child_path) catch { _ => Default::default() }
       let text = decode_bytes(data)
       if has_conflict_markers(text) {
         out.push(child_rel)
diff --git a/npm/package.json b/npm/package.json
index 19406b3f..42febb84 100644
--- a/npm/package.json
+++ b/npm/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@mizchi/bit",
-  "version": "0.45.6",
+  "version": "0.46.1",
   "description": "Pure MoonBit Git implementation (JS target)",
   "type": "module",
   "sideEffects": false,
diff --git a/tools/module-publish-graph.test.mjs b/tools/module-publish-graph.test.mjs
index 92bf4d70..401595cb 100644
--- a/tools/module-publish-graph.test.mjs
+++ b/tools/module-publish-graph.test.mjs
@@ -8,7 +8,7 @@ import {
   topologicalPublishOrder,
 } from "./module-publish-graph.mjs";
 
-test("workspace modules form a publish DAG with resolvable internal versions", () => {
+test("workspace modules form a publish DAG with valid internal dependency versions", () => {
   const modules = loadWorkspaceModules();
   const byName = new Map(modules.map((module) => [module.name, module]));
 
@@ -18,10 +18,10 @@ test("workspace modules form a publish DAG with resolvable internal versions", (
   for (const module of modules) {
     for (const [dependency, version] of Object.entries(module.deps ?? {})) {
       if (byName.has(dependency)) {
-        assert.equal(
+        assert.match(
           version,
-          byName.get(dependency).version,
-          `${module.name} must use ${dependency}'s workspace version`,
+          /^\d+\.\d+\.\d+$/,
+          `${module.name} must pin ${dependency} to a semantic version`,
         );
       }
     }
diff --git a/tools/publish-changed.mbtx b/tools/publish-changed.mbtx
index 9e096b90..085edd61 100644
--- a/tools/publish-changed.mbtx
+++ b/tools/publish-changed.mbtx
@@ -1,5 +1,5 @@
 // Lerna-style selective publish for the bit workspace's many `modules/*`
-// packages: diff each package's directory against the last "Release vX.Y.Z"
+// packages: diff each package's directory against the last "Release" marker
 // commit and only `moon publish` the ones that actually changed, in
 // dependency order.
 //
@@ -9,7 +9,14 @@
 //   moon run --target native tools/publish-changed.mbtx -- --apply
 //     -- actually run `moon publish` for the changed modules
 //   moon run --target native tools/publish-changed.mbtx -- --since <git-ref> [--apply]
-//     -- compare against an explicit ref instead of the last Release commit
+//     -- compare against an explicit ref instead of the last Release marker
+//   moon run --target native tools/publish-changed.mbtx -- patch
+//   moon run --target native tools/publish-changed.mbtx -- minor
+//     -- prepare independent releases by updating only packages with changes
+//        since the last release. npm and the CLI version update only when the
+//        installable `mizchi/bit` package itself changed. Commit the resulting
+//        metadata with a subject beginning `Release`, then tag/push it and run
+//        the script again with `--apply` to publish the changed packages.
 
 import {
   "moonbitlang/async@0.19.4",
@@ -40,6 +47,27 @@ struct ModuleInfo {
   deps : Array[String]
 }
 
+///|
+enum ReleaseBump {
+  Patch
+  Minor
+}
+
+///|
+struct AnchorInfo {
+  sha : String
+  subject : String
+}
+
+///|
+struct VersionUpdate {
+  name : String
+  current : String
+  next : String
+  manifest_path : String
+  manifest_content : String
+}
+
 // -- tiny moon.mod parsing -------------------------------------------------
 
 ///|
@@ -162,13 +190,146 @@ fn load_workspace_modules(root : String) -> Array[ModuleInfo] raise ScriptError
   result
 }
 
+// -- version updates -------------------------------------------------------
+
+///|
+fn parse_decimal_component(value : String) -> Int? {
+  if value.length() == 0 {
+    return None
+  }
+  let mut result = 0
+  for c in value {
+    if c < '0' || c > '9' {
+      return None
+    }
+    result = result * 10 + c.to_int() - '0'.to_int()
+  }
+  Some(result)
+}
+
+///|
+fn next_version(current : String, bump : ReleaseBump) -> String raise ScriptError {
+  let parts : Array[String] = []
+  for part in current.split(".") {
+    parts.push(part.to_owned())
+  }
+  if parts.length() != 3 {
+    raise ScriptError::Fail("expected MAJOR.MINOR.PATCH version, got \{current}")
+  }
+  let major = match parse_decimal_component(parts[0]) {
+    Some(value) => value
+    None => raise ScriptError::Fail("invalid major version in \{current}")
+  }
+  let minor = match parse_decimal_component(parts[1]) {
+    Some(value) => value
+    None => raise ScriptError::Fail("invalid minor version in \{current}")
+  }
+  let patch = match parse_decimal_component(parts[2]) {
+    Some(value) => value
+    None => raise ScriptError::Fail("invalid patch version in \{current}")
+  }
+  match bump {
+    Patch => "\{major}.\{minor}.\{patch + 1}"
+    Minor => "\{major}.\{minor + 1}.0"
+  }
+}
+
+///|
+fn replace_required(
+  content : String,
+  old : String,
+  new : String,
+  path : String,
+) -> String raise ScriptError {
+  match content.find(old) {
+    Some(_) => content.replace(old=old, new=new)
+    None => raise ScriptError::Fail("\{path}: expected to find \{old}")
+  }
+}
+
+///|
+fn read_text(path : String) -> String raise ScriptError {
+  try @fs.read_file_to_string(path) catch {
+    err => raise ScriptError::Fail("cannot read \{path}: \{err}")
+  }
+}
+
+///|
+fn write_text(path : String, content : String) -> Unit raise ScriptError {
+  try @fs.write_string_to_file(path, content) catch {
+    err => raise ScriptError::Fail("cannot write \{path}: \{err}")
+  }
+}
+
+///|
+fn prepare_release_versions(
+  root : String,
+  modules : Array[ModuleInfo],
+  changed_dirs : Array[String],
+  bump : ReleaseBump,
+) -> Array[VersionUpdate] raise ScriptError {
+  // Build and validate every change before writing any file.
+  let updates : Array[VersionUpdate] = []
+  let mut npm_updated : String? = None
+  let mut cli_version_updated : String? = None
+  for m in modules {
+    if !changed_dirs.contains(m.dir_basename) {
+      continue
+    }
+    let current = m.version
+    let next = next_version(current, bump)
+    let manifest_path = m.dir + "/moon.mod"
+    let manifest_content = replace_required(
+      read_text(manifest_path),
+      "version = \"\{current}\"",
+      "version = \"\{next}\"",
+      manifest_path,
+    )
+    updates.push({
+      name: m.name,
+      current,
+      next,
+      manifest_path,
+      manifest_content,
+    })
+    if m.dir_basename == "bit" {
+      let npm_path = root + "/npm/package.json"
+      npm_updated = Some(replace_required(
+        read_text(npm_path),
+        "\"version\": \"\{current}\"",
+        "\"version\": \"\{next}\"",
+        npm_path,
+      ))
+      let cli_version_path = root + "/modules/bit/cmd/bit/version.mbt"
+      cli_version_updated = Some(replace_required(
+        read_text(cli_version_path),
+        "bit v\{current}",
+        "bit v\{next}",
+        cli_version_path,
+      ))
+    }
+  }
+  for update in updates {
+    write_text(update.manifest_path, update.manifest_content)
+  }
+  match npm_updated {
+    Some(content) => write_text(root + "/npm/package.json", content)
+    None => ()
+  }
+  match cli_version_updated {
+    Some(content) => write_text(root + "/modules/bit/cmd/bit/version.mbt", content)
+    None => ()
+  }
+  updates
+}
+
 // -- dependency ordering ----------------------------------------------------
 
 ///|
 fn topological_layers(
   modules : Array[ModuleInfo],
 ) -> Array[Array[ModuleInfo]] raise ScriptError {
-  let by_name : Map[String, ModuleInfo] = Map::new()
+  let by_name : Map[String, ModuleInfo] = Map([], capacity=modules.length())
   for m in modules {
     by_name.set(m.name, m)
   }
@@ -196,7 +357,7 @@ fn topological_layers(
       for m in remaining {
         names.push(m.name)
       }
-      raise ScriptError::Fail("workspace module dependency cycle: \{names}")
+      raise ScriptError::Fail("workspace module dependency cycle: \{Repr(names)}")
     }
     ready.sort_by(fn(a, b) { String::compare(a.name, b.name) })
     for m in ready {
@@ -213,13 +374,13 @@ fn topological_layers(
 ///|
 async fn git_output(args : Array[String]) -> String raise ScriptError {
   let (code, stdout, stderr) = try @process.collect_output("git", args) catch {
-    err => raise ScriptError::Fail("failed to spawn git \{args}: \{err}")
+    err => raise ScriptError::Fail("failed to spawn git \{Repr(args)}: \{err}")
   }
   let out = try stdout.text() catch { _ => "" }
   if code != 0 {
     let err_text = try stderr.text() catch { _ => "" }
     raise ScriptError::Fail(
-      "git \{args} failed (\{code}): \{err_text.trim().to_owned()}",
+      "git \{Repr(args)} failed (\{code}): \{err_text.trim().to_owned()}",
     )
   }
   out
@@ -234,33 +395,63 @@ fn first_line(s : String) -> String {
 }
 
 ///|
-/// Returns (sha, subject) of the last commit that looks like a release, or
-/// the repo's root commit if no such commit exists yet.
-async fn find_anchor_commit() -> (String, String) raise ScriptError {
+fn parse_release_log_line(output : String) -> (String, String)? {
+  let trimmed = output.trim().to_owned()
+  if trimmed.length() == 0 {
+    return None
+  }
+  match trimmed.find("\t") {
+    Some(i) =>
+      Some((
+        String::unsafe_substring(trimmed, start=0, end=i),
+        String::unsafe_substring(trimmed, start=i + 1, end=trimmed.length()),
+      ))
+    None => Some((trimmed, ""))
+  }
+}
+
+///|
+/// Returns the release anchor. When HEAD itself is a Release commit, use its
+/// predecessor so `--apply` sees the feature diff contained by that release.
+async fn find_anchor_commit() -> AnchorInfo raise ScriptError {
   let out = git_output([
-    "log", "-n", "1", "--format=%H\t%s", "--grep=^Release v", "-i", "HEAD",
+    "log", "-n", "1", "--format=%H\t%s", "--grep=^Release", "-i", "HEAD",
   ])
-  let trimmed = out.trim().to_owned()
-  if trimmed.length() > 0 {
-    match trimmed.find("\t") {
-      Some(i) =>
-        return (
-          String::unsafe_substring(trimmed, start=0, end=i),
-          String::unsafe_substring(trimmed, start=i + 1, end=trimmed.length()),
-        )
-      None => return (trimmed, "")
+  match parse_release_log_line(out) {
+    Some((latest_sha, latest_subject)) => {
+      let head_sha = first_line(git_output(["rev-parse", "HEAD"]).trim().to_owned())
+      if latest_sha != head_sha {
+        return {
+          sha: latest_sha,
+          subject: latest_subject,
+        }
+      }
+      let previous = git_output([
+        "log", "-n", "1", "--skip=1", "--format=%H\t%s", "--grep=^Release", "-i", "HEAD",
+      ])
+      match parse_release_log_line(previous) {
+        Some((sha, subject)) =>
+          return {
+            sha,
+            subject: "\{subject} (previous release for current HEAD)",
+          }
+        None => ()
+      }
     }
+    None => ()
   }
   let root_out = git_output(["rev-list", "--max-parents=0", "HEAD"])
   let root_sha = first_line(root_out.trim().to_owned())
-  (root_sha, "(root commit, no prior release found)")
+  {
+    sha: root_sha,
+    subject: "(root commit, no prior release found)",
+  }
 }
 
 ///|
-/// Names of `modules/*` directories with content changes (excluding the
-/// `moon.mod` file itself, since a release commit bumps every module's
-/// `moon.mod` in lockstep regardless of whether that module's own code
-/// changed).
+/// Names of `modules/*` directories with changes. A `moon.mod` dependency
+/// update is a package change too, while independently versioned release
+/// metadata only touches the modules selected for that release.
 async fn changed_module_dirs(anchor : String) -> Array[String] raise ScriptError {
   let out = git_output(["diff", "--name-only", anchor, "HEAD", "--", "modules"])
   let changed : Array[String] = []
@@ -274,8 +465,7 @@ async fn changed_module_dirs(anchor : String) -> Array[String] raise ScriptError
       None => continue
       Some(si) => {
         let mod_dir = String::unsafe_substring(rest, start=0, end=si)
-        let sub = String::unsafe_substring(rest, start=si + 1, end=rest.length())
-        if sub != "moon.mod" && !changed.contains(mod_dir) {
+        if !changed.contains(mod_dir) {
           changed.push(mod_dir)
         }
       }
@@ -359,7 +549,7 @@ async fn wait_for_layer(layer : Array[ModuleInfo]) -> Unit raise ScriptError {
     }
   }
   raise ScriptError::Fail(
-    "published modules did not reach the registry index: \{missing}",
+    "published modules did not reach the registry index: \{Repr(missing)}",
   )
 }
 
@@ -377,10 +567,56 @@ fn arg_value_after(args : Array[String], flag : String) -> String? {
   None
 }
 
+///|
+fn release_bump_from_args(args : Array[String]) -> ReleaseBump? raise ScriptError {
+  let mut bump : ReleaseBump? = None
+  // get_cli_args includes the executable path at index zero.
+  let mut i = 1
+  while i < args.length() {
+    let arg = args[i]
+    if arg == "--apply" {
+      i += 1
+      continue
+    }
+    if arg == "--since" {
+      if i + 1 >= args.length() {
+        raise ScriptError::Fail("--since requires a git ref")
+      }
+      i += 2
+      continue
+    }
+    let requested = match arg {
+      "patch" => Patch
+      "minor" => Minor
+      _ => raise ScriptError::Fail(
+        "unknown argument `\{arg}`; expected `patch` or `minor`",
+      )
+    }
+    match bump {
+      Some(_) => raise ScriptError::Fail("only one of `patch` or `minor` may be given")
+      None => bump = Some(requested)
+    }
+    i += 1
+  }
+  bump
+}
+
 ///|
 async fn main_async() -> Unit {
   let args = @sys.get_cli_args()
   let apply = args.contains("--apply")
+  let bump = try release_bump_from_args(args) catch {
+    err => {
+      println("error: \{err}")
+      @sys.exit(1)
+      return
+    }
+  }
+  if apply && bump is Some(_) {
+    println("error: `patch`/`minor` prepares release metadata; commit and tag it before --apply")
+    @sys.exit(1)
+    return
+  }
   let root = "."
   let modules = try load_workspace_modules(root) catch {
     err => {
@@ -389,9 +625,12 @@ async fn main_async() -> Unit {
       return
     }
   }
-  let (anchor_sha, anchor_subject) = try (
+  let anchor = try (
     match arg_value_after(args, "--since") {
-      Some(refname) => (refname, "(explicit --since ref)")
+      Some(refname) => {
+        sha: refname,
+        subject: "(explicit --since ref)",
+      }
       None => find_anchor_commit()
     }
   ) catch {
@@ -401,15 +640,52 @@ async fn main_async() -> Unit {
       return
     }
   }
-  let changed_dirs = try changed_module_dirs(anchor_sha) catch {
+  let changed_dirs = try changed_module_dirs(anchor.sha) catch {
     err => {
       println("error: \{err}")
       @sys.exit(1)
       return
     }
   }
-  println("comparing against \{anchor_sha} \{anchor_subject}")
+  println("comparing against \{anchor.sha} \{anchor.subject}")
   println("")
+  if bump is Some(_) {
+    if changed_dirs.length() == 0 {
+      println("no modules changed since \{anchor.sha} — release metadata was not updated")
+      return
+    }
+    let dirty = try git_output(["status", "--porcelain"]) catch {
+      err => {
+        println("error: \{err}")
+        @sys.exit(1)
+        return
+      }
+    }
+    if dirty.trim().to_owned().length() > 0 {
+      println("error: refusing to bump a dirty worktree; commit source changes first")
+      @sys.exit(1)
+      return
+    }
+    let updates = try (
+      match bump {
+        Some(kind) => prepare_release_versions(root, modules, changed_dirs, kind)
+        None => raise ScriptError::Fail("unreachable: missing release bump")
+      }
+    ) catch {
+      err => {
+        println("error: \{err}")
+        @sys.exit(1)
+        return
+      }
+    }
+    println("prepared \{updates.length()} independent release(s):")
+    for update in updates {
+      println("  \{update.name}: v\{update.current} -> v\{update.next}")
+    }
+    println("updated only changed module manifests (and npm/CLI if mizchi/bit changed)")
+    println("next: commit the release metadata, tag/push it, then run with --apply")
+    return
+  }
   let layers = try topological_layers(modules) catch {
     err => {
       println("error: \{err}")
@@ -435,7 +711,7 @@ async fn main_async() -> Unit {
   println("")
   let total_changed = changed_dirs.length()
   if total_changed == 0 {
-    println("no modules changed since \{anchor_sha} — nothing to publish")
+    println("no modules changed since \{anchor.sha} — nothing to publish")
     return
   }
   println("\{total_changed} module(s) changed; publish order:")
diff --git a/tools/publish-changed.test.mjs b/tools/publish-changed.test.mjs
index a38ecdd8..05d180a6 100644
--- a/tools/publish-changed.test.mjs
+++ b/tools/publish-changed.test.mjs
@@ -26,3 +26,58 @@ test("reports no changes when compared against HEAD itself", () => {
   assert.equal(result.status, 0, result.stderr);
   assert.match(result.stdout, /no modules changed since HEAD — nothing to publish/);
 });
+
+test("rejects an unknown release bump argument", () => {
+  const result = runScript(["major", "--since", "HEAD"]);
+
+  assert.notEqual(result.status, 0);
+  assert.match(result.stdout, /unknown argument `major`; expected `patch` or `minor`/);
+});
+
+test("patch leaves release metadata untouched when its diff is empty", () => {
+  const result = runScript(["patch", "--since", "HEAD"]);
+
+  assert.equal(result.status, 0, result.stderr);
+  assert.match(
+    result.stdout,
+    /no modules changed since HEAD — release metadata was not updated/,
+  );
+});
+
+test("minor leaves release metadata untouched when its diff is empty", () => {
+  const result = runScript(["minor", "--since", "HEAD"]);
+
+  assert.equal(result.status, 0, result.stderr);
+  assert.match(
+    result.stdout,
+    /no modules changed since HEAD — release metadata was not updated/,
+  );
+});
+
+test("release preparation cannot publish from its dirty prepared worktree", () => {
+  const result = runScript(["patch", "--apply", "--since", "HEAD"]);
+
+  assert.notEqual(result.status, 0);
+  assert.match(
+    result.stdout,
+    /prepares release metadata; commit and tag it before --apply/,
+  );
+});
+
+test("release preparation updates only modules changed since its anchor", () => {
+  const source = readFileSync(
+    new URL("./publish-changed.mbtx", import.meta.url),
+    "utf8",
+  );
+
+  assert.match(source, /"patch" => Patch/);
+  assert.match(source, /"minor" => Minor/);
+  assert.match(source, /prepare_release_versions\(root, modules, changed_dirs, kind\)/);
+  assert.match(source, /if !changed_dirs\.contains\(m\.dir_basename\)/);
+  assert.match(source, /if m\.dir_basename == "bit"/);
+  assert.doesNotMatch(source, /workspace versions must match/);
+  assert.doesNotMatch(source, /sub != "moon\.mod"/);
+  assert.match(source, /"--grep=\^Release"/);
+  assert.match(source, /"--skip=1"/);
+  assert.doesNotMatch(source, /publishing the full workspace version/);
+});