diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0884171967..c56de7d253 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -79,6 +79,9 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 * `jj git fetch` and `jj git push` will now use the single defined remote even if it is not named "origin".
 
+* `jj` with no subcommand now invokes `jj log` with the default options, instead
+  of showing help.
+
 ### Fixed bugs
 
 * Modify/delete conflicts now include context lines
diff --git a/src/commands/mod.rs b/src/commands/mod.rs
index e13a540c36..2584507030 100644
--- a/src/commands/mod.rs
+++ b/src/commands/mod.rs
@@ -325,7 +325,7 @@ struct ShowArgs {
 struct StatusArgs {}
 
 /// Show commit history
-#[derive(clap::Args, Clone, Debug)]
+#[derive(clap::Args, Clone, Debug, Default)]
 struct LogArgs {
     /// Which revisions to show. Defaults to the `ui.default-revset` setting,
     /// or `@ | (remote_branches() | tags()).. | ((remote_branches() |
@@ -3474,9 +3474,7 @@ fn cmd_sparse(ui: &mut Ui, command: &CommandHelper, args: &SparseArgs) -> Result
 
 pub fn default_app() -> Command {
     let app: Command = Commands::augment_subcommands(Args::command());
-    app.arg_required_else_help(true)
-        .subcommand_required(true)
-        .version(env!("JJ_VERSION"))
+    app.version(env!("JJ_VERSION"))
 }
 
 pub fn run_command(
@@ -3484,47 +3482,55 @@ pub fn run_command(
     command_helper: &CommandHelper,
     matches: &ArgMatches,
 ) -> Result<(), CommandError> {
-    let derived_subcommands: Commands = Commands::from_arg_matches(matches).unwrap();
+    let derived_subcommands: Option<Commands> = Commands::from_arg_matches(matches).ok();
     match &derived_subcommands {
-        Commands::Version(sub_args) => cmd_version(ui, command_helper, sub_args),
-        Commands::Init(sub_args) => cmd_init(ui, command_helper, sub_args),
-        Commands::Config(sub_args) => cmd_config(ui, command_helper, sub_args),
-        Commands::Checkout(sub_args) => cmd_checkout(ui, command_helper, sub_args),
-        Commands::Untrack(sub_args) => cmd_untrack(ui, command_helper, sub_args),
-        Commands::Files(sub_args) => cmd_files(ui, command_helper, sub_args),
-        Commands::Cat(sub_args) => cmd_cat(ui, command_helper, sub_args),
-        Commands::Diff(sub_args) => cmd_diff(ui, command_helper, sub_args),
-        Commands::Show(sub_args) => cmd_show(ui, command_helper, sub_args),
-        Commands::Status(sub_args) => cmd_status(ui, command_helper, sub_args),
-        Commands::Log(sub_args) => cmd_log(ui, command_helper, sub_args),
-        Commands::Interdiff(sub_args) => cmd_interdiff(ui, command_helper, sub_args),
-        Commands::Obslog(sub_args) => cmd_obslog(ui, command_helper, sub_args),
-        Commands::Describe(sub_args) => cmd_describe(ui, command_helper, sub_args),
-        Commands::Commit(sub_args) => cmd_commit(ui, command_helper, sub_args),
-        Commands::Duplicate(sub_args) => cmd_duplicate(ui, command_helper, sub_args),
-        Commands::Abandon(sub_args) => cmd_abandon(ui, command_helper, sub_args),
-        Commands::Edit(sub_args) => cmd_edit(ui, command_helper, sub_args),
-        Commands::New(sub_args) => cmd_new(ui, command_helper, sub_args),
-        Commands::Move(sub_args) => cmd_move(ui, command_helper, sub_args),
-        Commands::Squash(sub_args) => cmd_squash(ui, command_helper, sub_args),
-        Commands::Unsquash(sub_args) => cmd_unsquash(ui, command_helper, sub_args),
-        Commands::Restore(sub_args) => cmd_restore(ui, command_helper, sub_args),
-        Commands::Diffedit(sub_args) => cmd_diffedit(ui, command_helper, sub_args),
-        Commands::Split(sub_args) => cmd_split(ui, command_helper, sub_args),
-        Commands::Merge(sub_args) => cmd_merge(ui, command_helper, sub_args),
-        Commands::Rebase(sub_args) => cmd_rebase(ui, command_helper, sub_args),
-        Commands::Backout(sub_args) => cmd_backout(ui, command_helper, sub_args),
-        Commands::Resolve(sub_args) => cmd_resolve(ui, command_helper, sub_args),
-        Commands::Branch(sub_args) => branch::cmd_branch(ui, command_helper, sub_args),
-        Commands::Undo(sub_args) => operation::cmd_op_undo(ui, command_helper, sub_args),
-        Commands::Operation(sub_args) => operation::cmd_operation(ui, command_helper, sub_args),
-        Commands::Workspace(sub_args) => cmd_workspace(ui, command_helper, sub_args),
-        Commands::Sparse(sub_args) => cmd_sparse(ui, command_helper, sub_args),
-        Commands::Git(sub_args) => git::cmd_git(ui, command_helper, sub_args),
-        Commands::Util(sub_args) => cmd_util(ui, command_helper, sub_args),
+        Some(Commands::Version(sub_args)) => cmd_version(ui, command_helper, sub_args),
+        Some(Commands::Init(sub_args)) => cmd_init(ui, command_helper, sub_args),
+        Some(Commands::Config(sub_args)) => cmd_config(ui, command_helper, sub_args),
+        Some(Commands::Checkout(sub_args)) => cmd_checkout(ui, command_helper, sub_args),
+        Some(Commands::Untrack(sub_args)) => cmd_untrack(ui, command_helper, sub_args),
+        Some(Commands::Files(sub_args)) => cmd_files(ui, command_helper, sub_args),
+        Some(Commands::Cat(sub_args)) => cmd_cat(ui, command_helper, sub_args),
+        Some(Commands::Diff(sub_args)) => cmd_diff(ui, command_helper, sub_args),
+        Some(Commands::Show(sub_args)) => cmd_show(ui, command_helper, sub_args),
+        Some(Commands::Status(sub_args)) => cmd_status(ui, command_helper, sub_args),
+        Some(Commands::Log(sub_args)) => cmd_log(ui, command_helper, sub_args),
+        Some(Commands::Interdiff(sub_args)) => cmd_interdiff(ui, command_helper, sub_args),
+        Some(Commands::Obslog(sub_args)) => cmd_obslog(ui, command_helper, sub_args),
+        Some(Commands::Describe(sub_args)) => cmd_describe(ui, command_helper, sub_args),
+        Some(Commands::Commit(sub_args)) => cmd_commit(ui, command_helper, sub_args),
+        Some(Commands::Duplicate(sub_args)) => cmd_duplicate(ui, command_helper, sub_args),
+        Some(Commands::Abandon(sub_args)) => cmd_abandon(ui, command_helper, sub_args),
+        Some(Commands::Edit(sub_args)) => cmd_edit(ui, command_helper, sub_args),
+        Some(Commands::New(sub_args)) => cmd_new(ui, command_helper, sub_args),
+        Some(Commands::Move(sub_args)) => cmd_move(ui, command_helper, sub_args),
+        Some(Commands::Squash(sub_args)) => cmd_squash(ui, command_helper, sub_args),
+        Some(Commands::Unsquash(sub_args)) => cmd_unsquash(ui, command_helper, sub_args),
+        Some(Commands::Restore(sub_args)) => cmd_restore(ui, command_helper, sub_args),
+        Some(Commands::Diffedit(sub_args)) => cmd_diffedit(ui, command_helper, sub_args),
+        Some(Commands::Split(sub_args)) => cmd_split(ui, command_helper, sub_args),
+        Some(Commands::Merge(sub_args)) => cmd_merge(ui, command_helper, sub_args),
+        Some(Commands::Rebase(sub_args)) => cmd_rebase(ui, command_helper, sub_args),
+        Some(Commands::Backout(sub_args)) => cmd_backout(ui, command_helper, sub_args),
+        Some(Commands::Resolve(sub_args)) => cmd_resolve(ui, command_helper, sub_args),
+        Some(Commands::Branch(sub_args)) => branch::cmd_branch(ui, command_helper, sub_args),
+        Some(Commands::Undo(sub_args)) => operation::cmd_op_undo(ui, command_helper, sub_args),
+        Some(Commands::Operation(sub_args)) => {
+            operation::cmd_operation(ui, command_helper, sub_args)
+        }
+        Some(Commands::Workspace(sub_args)) => cmd_workspace(ui, command_helper, sub_args),
+        Some(Commands::Sparse(sub_args)) => cmd_sparse(ui, command_helper, sub_args),
+        Some(Commands::Git(sub_args)) => git::cmd_git(ui, command_helper, sub_args),
+        Some(Commands::Util(sub_args)) => cmd_util(ui, command_helper, sub_args),
         #[cfg(feature = "bench")]
-        Commands::Bench(sub_args) => bench::cmd_bench(ui, command_helper, sub_args),
-        Commands::Debug(sub_args) => cmd_debug(ui, command_helper, sub_args),
+        Some(Commands::Bench(sub_args)) => bench::cmd_bench(ui, command_helper, sub_args),
+        Some(Commands::Debug(sub_args)) => cmd_debug(ui, command_helper, sub_args),
+        None => {
+            let sub_args = LogArgs {
+                ..Default::default()
+            };
+            cmd_log(ui, command_helper, &sub_args)
+        }
     }
 }
 
diff --git a/src/diff_util.rs b/src/diff_util.rs
index 55e3991e60..b61916418b 100644
--- a/src/diff_util.rs
+++ b/src/diff_util.rs
@@ -32,7 +32,7 @@ use jujutsu_lib::{conflicts, diff, files, rewrite, tree};
 use crate::cli_util::{CommandError, WorkspaceCommandHelper};
 use crate::formatter::Formatter;
 
-#[derive(clap::Args, Clone, Debug)]
+#[derive(clap::Args, Clone, Debug, Default)]
 #[command(group(clap::ArgGroup::new("short-format").args(&["summary", "types"])))]
 #[command(group(clap::ArgGroup::new("long-format").args(&["git", "color_words"])))]
 pub struct DiffFormatArgs {
diff --git a/tests/test_alias.rs b/tests/test_alias.rs
index 546dc64c15..86bdac4030 100644
--- a/tests/test_alias.rs
+++ b/tests/test_alias.rs
@@ -69,7 +69,7 @@ fn test_alias_bad_name() {
     insta::assert_snapshot!(stderr, @r###"
     error: unrecognized subcommand 'foo.'
 
-    Usage: jj [OPTIONS] <COMMAND>
+    Usage: jj [OPTIONS] [COMMAND]
 
     For more information, try '--help'.
     "###);
@@ -86,7 +86,7 @@ fn test_alias_calls_unknown_command() {
     insta::assert_snapshot!(stderr, @r###"
     error: unrecognized subcommand 'nonexistent'
 
-    Usage: jj [OPTIONS] <COMMAND>
+    Usage: jj [OPTIONS] [COMMAND]
 
     For more information, try '--help'.
     "###);
@@ -123,7 +123,7 @@ fn test_alias_calls_help() {
 
     To get started, see the tutorial at https://github.com/martinvonz/jj/blob/main/docs/tutorial.md.
 
-    Usage: jj [OPTIONS] <COMMAND>
+    Usage: jj [OPTIONS] [COMMAND]
     "###);
 }
 
diff --git a/tests/test_global_opts.rs b/tests/test_global_opts.rs
index fca8012696..a79aacdc4b 100644
--- a/tests/test_global_opts.rs
+++ b/tests/test_global_opts.rs
@@ -47,23 +47,11 @@ fn test_non_utf8_arg() {
 #[test]
 fn test_no_subcommand() {
     let test_env = TestEnvironment::default();
+    test_env.jj_cmd_success(test_env.env_root(), &["init", "repo", "--git"]);
+    let repo_path = test_env.env_root().join("repo");
 
-    let stderr = test_env.jj_cmd_cli_error(test_env.env_root(), &[]);
-    insta::assert_snapshot!(stderr.lines().next().unwrap(), @"Jujutsu (An experimental VCS)");
-
-    let stderr = test_env.jj_cmd_cli_error(test_env.env_root(), &["-R."]);
-    insta::assert_snapshot!(stderr.lines().next().unwrap(), @"error: 'jj' requires a subcommand but one was not provided");
-
-    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["--version"]);
-    let sanitized = stdout.replace(|c: char| c.is_ascii_hexdigit(), "?");
-    assert!(
-        sanitized == "jj ?.?.?\n"
-            || sanitized == "jj ?.?.?-????????????????????????????????????????\n",
-        "{sanitized}"
-    );
-
-    let stdout = test_env.jj_cmd_success(test_env.env_root(), &["--help"]);
-    insta::assert_snapshot!(stdout.lines().next().unwrap(), @"Jujutsu (An experimental VCS)");
+    let stdout = test_env.jj_cmd_success(&repo_path, &[]);
+    assert_eq!(stdout, test_env.jj_cmd_success(&repo_path, &["log"]));
 }
 
 #[test]