diff --git a/src/help-generator_.toit b/src/help-generator_.toit
index 6364b7f..77b3681 100644
--- a/src/help-generator_.toit
+++ b/src/help-generator_.toit
@@ -16,12 +16,17 @@ It finds the selected command and prints its help.
 */
 help-command_ path/Path arguments/List --ui/Ui:
   command/Command := path.last
+  show-all := false
 
   for i := 0; i < arguments.size; i++:
     argument := arguments[i]
     if argument == "--": break
 
-    // Simply drop all options.
+    if argument == "--all":
+      show-all = true
+      continue
+
+    // Simply drop all other options.
     if argument.starts-with "-":
       continue
 
@@ -32,7 +37,24 @@ help-command_ path/Path arguments/List --ui/Ui:
     command = subcommand
     path += command
 
-  emit-help_ path --ui=ui
+  if show-all:
+    emit-help-all_ path --ui=ui
+  else:
+    emit-help_ path --ui=ui
+
+/**
+Emits the help for all commands in the subtree rooted at the given command.
+
+The command is identified by the $path where the command is the last element.
+*/
+emit-help-all_ path/Path --ui/Ui:
+  ui.emit --kind=Ui.RESULT
+      --structured=:
+        build-json-help-all_ path
+      --text=:
+        generator := HelpGenerator path
+        generator.build-all-commands
+        generator.to-string
 
 /**
 Emits the help for the given command.
@@ -48,6 +70,35 @@ emit-help_ path/Path --ui/Ui:
         generator.build-all
         generator.to-string
 
+build-json-help-all_ path/Path -> Map:
+  return build-json-command-tree_ path.last --is-root=(path.size == 1)
+
+build-json-command-tree_ command/Command --is-root/bool=false -> Map:
+  sub-list := []
+  sorted := command.subcommands_.sort: | a/Command b/Command | a.name.compare-to b.name
+  sorted.do: | sub/Command |
+    if sub.is-hidden_: continue.do
+    sub-list.add (build-json-command-tree_ sub)
+
+  if is-root:
+    has-help := false
+    has-completion := false
+    command.subcommands_.do: | sub/Command |
+      if sub.name == "help": has-help = true
+      sub.aliases_.do: if it == "help": has-help = true
+      if sub.name == "completion": has-completion = true
+      sub.aliases_.do: if it == "completion": has-completion = true
+    if not has-help:
+      sub-list.add {"name": "help", "help": "Show help for a command.", "subcommands": []}
+    if not has-completion:
+      sub-list.add {"name": "completion", "help": "Generate shell completion scripts.", "subcommands": []}
+
+  return {
+    "name": command.name,
+    "help": command.short-help,
+    "subcommands": sub-list,
+  }
+
 build-json-help_ path/Path -> Map:
   // Local block to build json objects for the given command.
   // Adds the converted json object to the out-map.
@@ -254,6 +305,53 @@ class HelpGenerator:
     sorted-commands := commands-and-help.sort: | a/List b/List | a[0].compare-to b[0]
     write-table_ sorted-commands --indentation=2
 
+  /**
+  Builds a hierarchical summary of all commands in the subtree.
+
+  Recursively lists all subcommands with indentation showing nesting.
+  Hidden commands are excluded. At root level, auto-added 'help' and
+    'completion' entries are included.
+  */
+  build-all-commands -> none:
+    rows := []
+    collect-commands-recursive_ command_ rows --indent=0 --is-root=is-root-command_
+    if rows.is-empty: return
+    write-table_ rows
+
+  /**
+  Collects all commands recursively into $rows as [indented-name, short-help] pairs.
+  */
+  collect-commands-recursive_ command/Command rows/List --indent/int --is-root/bool=false -> none:
+    // Each entry is [name, help, subcommand-or-null].
+    entries := []
+    command.subcommands_.do: | subcommand/Command |
+      if subcommand.is-hidden_: continue.do
+      entries.add [subcommand.name, subcommand.short-help, subcommand]
+
+    if is-root:
+      has-help := false
+      has-completion := false
+      command.subcommands_.do: | sub/Command |
+        if sub.name == "help": has-help = true
+        sub.aliases_.do: if it == "help": has-help = true
+        if sub.name == "completion": has-completion = true
+        sub.aliases_.do: if it == "completion": has-completion = true
+      if not has-help:
+        entries.add ["help", "Show help for a command.", null]
+      if not has-completion:
+        entries.add ["completion", "Generate shell completion scripts.", null]
+
+    sorted := entries.sort: | a/List b/List |
+      (a[0] as string).compare-to (b[0] as string)
+
+    prefix := " " * indent
+    sorted.do: | entry/List |
+      name := entry[0] as string
+      help-str := entry[1] as string
+      rows.add ["$prefix$name", help-str]
+      if entry[2]:
+        collect-commands-recursive_ (entry[2] as Command) rows --indent=(indent + 2)
+
   /**
   Builds the local options section.
 
diff --git a/tests/help_test.toit b/tests/help_test.toit
index c27172c..4b6ea49 100644
--- a/tests/help_test.toit
+++ b/tests/help_test.toit
@@ -16,6 +16,7 @@ main:
   test-options
   test-examples
   test-short-help
+  test-help-all
 
 check-output expected/string [block]:
   ui := TestUi
@@ -870,3 +871,66 @@ test-short-help:
   expected = "Test command."
   actual = cmd.short-help
   expect-equals expected actual
+
+test-help-all:
+  sub-sub := cli.Command "sub2"
+      --help="Even more nested info."
+      --run=:: null
+
+  sub1 := cli.Command "sub1"
+      --help="Sub info."
+      --subcommands=[sub-sub]
+
+  tool-foo := cli.Command "foo"
+      --help="The foo tool."
+      --run=:: null
+
+  tool-bar := cli.Command "bar"
+      --help="The bar tool."
+      --run=:: null
+
+  tool := cli.Command "tool"
+      --help="Tools for xyz."
+      --subcommands=[tool-foo, tool-bar]
+
+  hidden-cmd := cli.Command "secret"
+      --help="Secret command."
+      --hidden
+      --run=:: null
+
+  execute := cli.Command "execute"
+      --help="Runs toto."
+      --run=:: null
+
+  root := cli.Command "root"
+      --help="Root command."
+      --subcommands=[tool, execute, sub1, hidden-cmd]
+
+  expected := """
+    completion  Generate shell completion scripts.
+    execute     Runs toto.
+    help        Show help for a command.
+    sub1        Sub info.
+      sub2      Even more nested info.
+    tool        Tools for xyz.
+      bar       The bar tool.
+      foo       The foo tool.
+    """
+  check-output expected: | cli/cli.Cli |
+    root.run ["help", "--all"] --cli=cli --invoked-command="bin/app"
+
+  // Test --all on a subcommand.
+  expected = """
+    bar  The bar tool.
+    foo  The foo tool.
+    """
+  check-output expected: | cli/cli.Cli |
+    root.run ["help", "--all", "tool"] --cli=cli --invoked-command="bin/app"
+
+  // Test --all on a leaf command (no subcommands).
+  expected = ""
+  ui := TestUi
+  cli-obj := cli.Cli "test" --ui=ui
+  root.run ["help", "--all", "execute"] --cli=cli-obj --invoked-command="bin/app"
+  all-output := ui.stdout + ui.stderr
+  expect-equals (expected + "\n") all-output