diff --git a/Documentation/config/extensions.adoc b/Documentation/config/extensions.adoc
index a13b287d4b..934fc080ab 100644
--- a/Documentation/config/extensions.adoc
+++ b/Documentation/config/extensions.adoc
@@ -116,6 +116,21 @@ The extension can be enabled automatically for new repositories by setting
 `init.defaultSubmodulePathConfig` to `true`, for example by running
 `git config --global init.defaultSubmodulePathConfig true`.
 
+hookStdoutToStderr:::
+	If enabled, the stdout of all hooks is redirected to stderr. This
+	enforces consistency, since by default most hooks already behave
+	this way, with pre-push being the only known exception.
++
+This is useful for parallel hook execution (see the `hook.jobs` config in
+linkgit:git-config[1]), as it allows the output of multiple hooks running
+in parallel to be grouped (de-interleaved) correctly.
++
+Defaults to disabled. When disabled, `hook.jobs` has no effect for pre-push
+hooks, which will always be run sequentially.
++
+The extension can also be enabled by setting `hook.forceStdoutToStderr`
+to `true` in the global configuration.
+
 worktreeConfig:::
 	If enabled, then worktrees will load config settings from the
 	`$GIT_DIR/config.worktree` file in addition to the
diff --git a/Documentation/config/hook.adoc b/Documentation/config/hook.adoc
index 64e845a260..7b81d2b615 100644
--- a/Documentation/config/hook.adoc
+++ b/Documentation/config/hook.adoc
@@ -22,3 +22,52 @@ hook.<name>.enabled::
 	configuration. This is particularly useful when a hook is defined
 	in a system or global config file and needs to be disabled for a
 	specific repository. See linkgit:git-hook[1].
+
+hook.<name>.parallel::
+	Whether the hook `hook.<name>` may run in parallel with other hooks
+	for the same event. Defaults to `false`. Set to `true` only when the
+	hook script is safe to run concurrently with other hooks for the same
+	event. If any hook for an event does not have this set to `true`,
+	all hooks for that event run sequentially regardless of `hook.jobs`.
+	Only configured (named) hooks need to declare this. Traditional hooks
+	found in the hooks directory do not need to, and run in parallel when
+	the effective job count is greater than 1. See linkgit:git-hook[1].
+
+hook.<event>.jobs::
+	Specifies how many hooks can be run simultaneously for the `<event>`
+	hook event (e.g. `hook.post-receive.jobs = 4`). Overrides `hook.jobs`
+	for this specific event. The same parallelism restrictions apply: this
+	setting has no effect unless all configured hooks for the event have
+	`hook.<friendly-name>.parallel` set to `true`. Must be a positive int,
+	zero is rejected with a warning. See linkgit:git-hook[1].
++
+Note on naming: although this key resembles `hook.<friendly-name>.*`
+(a per-hook setting), `<event>` must be the event name, not a hook
+friendly name. The key component is stored literally and looked up by
+event name at runtime with no translation between the two namespaces.
+A key like `hook.my-hook.jobs` is stored under `"my-hook"` but the
+lookup at runtime uses the event name (e.g. `"post-receive"`), so
+`hook.my-hook.jobs` is silently ignored even when `my-hook` is
+registered for that event. Use `hook.post-receive.jobs` or any other
+valid event name when setting `hook.<event>.jobs`.
+
+hook.jobs::
+	Specifies how many hooks can be run simultaneously during parallelized
+	hook execution. If unspecified, defaults to 1 (serial execution).
+	Can be overridden on a per-event basis with `hook.<event>.jobs`.
+	Some hooks always run sequentially regardless of this setting because
+	git knows they cannot safely be parallelized: `applypatch-msg`,
+	`pre-commit`, `prepare-commit-msg`, `commit-msg`, `post-commit`,
+	`post-checkout`, and `push-to-checkout`.
++
+This setting has no effect unless all configured hooks for the event have
+`hook.<name>.parallel` set to `true`.
++
+This has no effect for hooks requiring separate output streams (like `pre-push`)
+unless `extensions.hookStdoutToStderr` is enabled.
+
+hook.forceStdoutToStderr::
+	A boolean that enables the `extensions.hookStdoutToStderr` behavior
+	(merging stdout to stderr for all hooks) globally. This effectively
+	forces all hooks to behave as if the extension was enabled, allowing
+	parallel execution for hooks like `pre-push`.
diff --git a/Documentation/git-hook.adoc b/Documentation/git-hook.adoc
index 12d2701b52..c9492f6f8e 100644
--- a/Documentation/git-hook.adoc
+++ b/Documentation/git-hook.adoc
@@ -8,7 +8,8 @@ git-hook - Run git hooks
 SYNOPSIS
 --------
 [verse]
-'git hook' run [--ignore-missing] [--to-stdin=<path>] <hook-name> [-- <hook-args>]
+'git hook' run [--ignore-missing] [--to-stdin=<path>] [(-j|--jobs) <n>]
+	<hook-name> [-- <hook-args>]
 'git hook' list [-z] <hook-name>
 
 DESCRIPTION
@@ -134,6 +135,18 @@ OPTIONS
 -z::
 	Terminate "list" output lines with NUL instead of newlines.
 
+-j::
+--jobs::
+	Only valid for `run`.
++
+Specify how many hooks to run simultaneously. If this flag is not specified,
+the value of the `hook.jobs` config is used, see linkgit:git-config[1]. If
+neither is specified, defaults to 1 (serial execution). Some hooks always run
+sequentially regardless of this flag or the `hook.jobs` config, because git
+knows they cannot safely run in parallel: `applypatch-msg`, `pre-commit`,
+`prepare-commit-msg`, `commit-msg`, `post-commit`, `post-checkout`, and
+`push-to-checkout`.
+
 WRAPPERS
 --------
 
@@ -156,7 +169,8 @@ running:
 git hook run mywrapper-start-tests \
   # providing something to stdin
   --stdin some-tempfile-123 \
-  # execute hooks in serial
+  # execute multiple hooks in parallel
+  --jobs 3 \
   # plus some arguments of your own...
   -- \
   --testname bar \
diff --git a/builtin/am.c b/builtin/am.c
index c439f868dc..4d4c8ae9fd 100644
--- a/builtin/am.c
+++ b/builtin/am.c
@@ -490,9 +490,11 @@ static int run_applypatch_msg_hook(struct am_state *state)
 
 	assert(state->msg);
 
-	if (!state->no_verify)
-		ret = run_hooks_l(the_repository, "applypatch-msg",
-				  am_path(state, "final-commit"), NULL);
+	if (!state->no_verify) {
+		struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT_FORCE_SERIAL;
+		strvec_push(&opt.args, am_path(state, "final-commit"));
+		ret = run_hooks_opt(the_repository, "applypatch-msg", &opt);
+	}
 
 	if (!ret) {
 		FREE_AND_NULL(state->msg);
diff --git a/builtin/checkout.c b/builtin/checkout.c
index 1d1667fa4c..ddbe8474d2 100644
--- a/builtin/checkout.c
+++ b/builtin/checkout.c
@@ -31,6 +31,7 @@
 #include "resolve-undo.h"
 #include "revision.h"
 #include "setup.h"
+#include "strvec.h"
 #include "submodule.h"
 #include "symlinks.h"
 #include "trace2.h"
@@ -123,13 +124,19 @@ static void branch_info_release(struct branch_info *info)
 static int post_checkout_hook(struct commit *old_commit, struct commit *new_commit,
 			      int changed)
 {
-	return run_hooks_l(the_repository, "post-checkout",
-			   oid_to_hex(old_commit ? &old_commit->object.oid : null_oid(the_hash_algo)),
-			   oid_to_hex(new_commit ? &new_commit->object.oid : null_oid(the_hash_algo)),
-			   changed ? "1" : "0", NULL);
-	/* "new_commit" can be NULL when checking out from the index before
-	   a commit exists. */
+	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT_FORCE_SERIAL;
 
+	/*
+	 * "new_commit" can be NULL when checking out from the index before
+	 * a commit exists.
+	 */
+	strvec_pushl(&opt.args,
+		     oid_to_hex(old_commit ? &old_commit->object.oid : null_oid(the_hash_algo)),
+		     oid_to_hex(new_commit ? &new_commit->object.oid : null_oid(the_hash_algo)),
+		     changed ? "1" : "0",
+		     NULL);
+
+	return run_hooks_opt(the_repository, "post-checkout", &opt);
 }
 
 static int update_some(const struct object_id *oid, struct strbuf *base,
diff --git a/builtin/clone.c b/builtin/clone.c
index fba3c9c508..d23b0cafcf 100644
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -647,6 +647,7 @@ static int checkout(int submodule_progress,
 	struct tree *tree;
 	struct tree_desc t;
 	int err = 0;
+	struct run_hooks_opt hook_opt = RUN_HOOKS_OPT_INIT_FORCE_SERIAL;
 
 	if (option_no_checkout)
 		return 0;
@@ -697,8 +698,9 @@ static int checkout(int submodule_progress,
 	if (write_locked_index(the_repository->index, &lock_file, COMMIT_LOCK))
 		die(_("unable to write new index file"));
 
-	err |= run_hooks_l(the_repository, "post-checkout", oid_to_hex(null_oid(the_hash_algo)),
-			   oid_to_hex(&oid), "1", NULL);
+	strvec_pushl(&hook_opt.args, oid_to_hex(null_oid(the_hash_algo)),
+		     oid_to_hex(&oid), "1", NULL);
+	err |= run_hooks_opt(the_repository, "post-checkout", &hook_opt);
 
 	if (!err && (option_recurse_submodules.nr > 0)) {
 		struct child_process cmd = CHILD_PROCESS_INIT;
diff --git a/builtin/hook.c b/builtin/hook.c
index 83020dfb4f..1fdde80113 100644
--- a/builtin/hook.c
+++ b/builtin/hook.c
@@ -9,7 +9,8 @@
 #include "abspath.h"
 
 #define BUILTIN_HOOK_RUN_USAGE \
-	N_("git hook run [--ignore-missing] [--to-stdin=<path>] <hook-name> [-- <hook-args>]")
+	N_("git hook run [--ignore-missing] [--to-stdin=<path>] [(-j|--jobs) <n>]\n" \
+	   "<hook-name> [-- <hook-args>]")
 #define BUILTIN_HOOK_LIST_USAGE \
 	N_("git hook list [-z] <hook-name>")
 
@@ -97,6 +98,8 @@ static int run(int argc, const char **argv, const char *prefix,
 			 N_("silently ignore missing requested <hook-name>")),
 		OPT_STRING(0, "to-stdin", &opt.path_to_stdin, N_("path"),
 			   N_("file to read into hooks' stdin")),
+		OPT_UNSIGNED('j', "jobs", &opt.jobs,
+			    N_("run up to <n> hooks simultaneously")),
 		OPT_END(),
 	};
 	int ret;
diff --git a/builtin/receive-pack.c b/builtin/receive-pack.c
index 519f6597b0..b5300f77ac 100644
--- a/builtin/receive-pack.c
+++ b/builtin/receive-pack.c
@@ -1453,7 +1453,8 @@ static const char *push_to_checkout(unsigned char *hash,
 				    struct strvec *env,
 				    const char *work_tree)
 {
-	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
+	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT_FORCE_SERIAL;
+
 	opt.invoked_hook = invoked_hook;
 
 	strvec_pushf(env, "GIT_WORK_TREE=%s", absolute_path(work_tree));
diff --git a/builtin/worktree.c b/builtin/worktree.c
index bc2d0d645b..d4e7c33205 100644
--- a/builtin/worktree.c
+++ b/builtin/worktree.c
@@ -609,7 +609,7 @@ done:
 	 * is_junk is cleared, but do return appropriate code when hook fails.
 	 */
 	if (!ret && opts->checkout && !opts->orphan) {
-		struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
+		struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT_FORCE_SERIAL;
 
 		strvec_pushl(&opt.env, "GIT_DIR", "GIT_WORK_TREE", NULL);
 		strvec_pushl(&opt.args,
diff --git a/commit.c b/commit.c
index 0ffdd6679e..a2c4ffaac5 100644
--- a/commit.c
+++ b/commit.c
@@ -1979,7 +1979,7 @@ size_t ignored_log_message_bytes(const char *buf, size_t len)
 int run_commit_hook(int editor_is_used, const char *index_file,
 		    int *invoked_hook, const char *name, ...)
 {
-	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT;
+	struct run_hooks_opt opt = RUN_HOOKS_OPT_INIT_FORCE_SERIAL;
 	va_list args;
 	const char *arg;
 
diff --git a/config.c b/config.c
index 156f2a24fa..a1b92fe083 100644
--- a/config.c
+++ b/config.c
@@ -1212,6 +1212,15 @@ int git_config_int(const char *name, const char *value,
 	return ret;
 }
 
+unsigned int git_config_uint(const char *name, const char *value,
+			     const struct key_value_info *kvi)
+{
+	unsigned int ret;
+	if (!git_parse_uint(value, &ret))
+		die_bad_number(name, value, kvi);
+	return ret;
+}
+
 int64_t git_config_int64(const char *name, const char *value,
 			 const struct key_value_info *kvi)
 {
@@ -1907,6 +1916,18 @@ int git_configset_get_int(struct config_set *set, const char *key, int *dest)
 		return 1;
 }
 
+int git_configset_get_uint(struct config_set *set, const char *key, unsigned int *dest)
+{
+	const char *value;
+	struct key_value_info kvi;
+
+	if (!git_configset_get_value(set, key, &value, &kvi)) {
+		*dest = git_config_uint(key, value, &kvi);
+		return 0;
+	} else
+		return 1;
+}
+
 int git_configset_get_ulong(struct config_set *set, const char *key, unsigned long *dest)
 {
 	const char *value;
@@ -2356,6 +2377,13 @@ int repo_config_get_int(struct repository *repo,
 	return git_configset_get_int(repo->config, key, dest);
 }
 
+int repo_config_get_uint(struct repository *repo,
+			 const char *key, unsigned int *dest)
+{
+	git_config_check_init(repo);
+	return git_configset_get_uint(repo->config, key, dest);
+}
+
 int repo_config_get_ulong(struct repository *repo,
 			  const char *key, unsigned long *dest)
 {
diff --git a/config.h b/config.h
index ba426a960a..bf47fb3afc 100644
--- a/config.h
+++ b/config.h
@@ -267,6 +267,12 @@ int git_config_int(const char *, const char *, const struct key_value_info *);
 int64_t git_config_int64(const char *, const char *,
 			 const struct key_value_info *);
 
+/**
+ * Identical to `git_config_int`, but for unsigned ints.
+ */
+unsigned int git_config_uint(const char *, const char *,
+			     const struct key_value_info *);
+
 /**
  * Identical to `git_config_int`, but for unsigned longs.
  */
@@ -560,6 +566,7 @@ int git_configset_get_value(struct config_set *cs, const char *key,
 
 int git_configset_get_string(struct config_set *cs, const char *key, char **dest);
 int git_configset_get_int(struct config_set *cs, const char *key, int *dest);
+int git_configset_get_uint(struct config_set *cs, const char *key, unsigned int *dest);
 int git_configset_get_ulong(struct config_set *cs, const char *key, unsigned long *dest);
 int git_configset_get_bool(struct config_set *cs, const char *key, int *dest);
 int git_configset_get_bool_or_int(struct config_set *cs, const char *key, int *is_bool, int *dest);
@@ -650,6 +657,12 @@ int repo_config_get_string_tmp(struct repository *r,
  */
 int repo_config_get_int(struct repository *r, const char *key, int *dest);
 
+/**
+ * Similar to `repo_config_get_int` but for unsigned ints.
+ */
+int repo_config_get_uint(struct repository *r,
+			 const char *key, unsigned int *dest);
+
 /**
  * Similar to `repo_config_get_int` but for unsigned longs.
  */
diff --git a/hook.c b/hook.c
index 2c8252b2c4..d5675df238 100644
--- a/hook.c
+++ b/hook.c
@@ -118,16 +118,34 @@ static void unsorted_string_list_remove(struct string_list *list,
 		unsorted_string_list_delete_item(list, item - list->items, 0);
 }
 
+/*
+ * Cache entry stored as the .util pointer of string_list items inside the
+ * hook config cache. Carries both the resolved command and the parallel flag.
+ */
+struct hook_config_cache_entry {
+	char *command;
+	unsigned int parallel:1;
+};
+
 /*
  * Callback struct to collect all hook.* keys in a single config pass.
  * commands: friendly-name to command map.
  * event_hooks: event-name to list of friendly-names map.
  * disabled_hooks: set of friendly-names with hook.name.enabled = false.
+ * parallel_hooks: friendly-name to parallel flag.
+ * event_jobs: event-name to per-event jobs count (heap-allocated unsigned int *,
+ *             where NULL == unset).
+ * jobs: value of the global hook.jobs key. Defaults to 0 if unset.
+ * force_stdout_to_stderr: value of hook.forceStdoutToStderr. Defaults to 0.
  */
 struct hook_all_config_cb {
 	struct strmap commands;
 	struct strmap event_hooks;
 	struct string_list disabled_hooks;
+	struct strmap parallel_hooks;
+	struct strmap event_jobs;
+	unsigned int jobs;
+	int force_stdout_to_stderr;
 };
 
 /* repo_config() callback that collects all hook.* configuration in one pass. */
@@ -143,6 +161,24 @@ static int hook_config_lookup_all(const char *key, const char *value,
 	if (parse_config_key(key, "hook", &name, &name_len, &subkey))
 		return 0;
 
+	/* Handle plain hook.<key> entries that have no hook name component. */
+	if (!name) {
+		if (!strcmp(subkey, "jobs") && value) {
+			unsigned int v;
+			if (!git_parse_uint(value, &v))
+				warning(_("hook.jobs must be a positive integer, ignoring: '%s'"), value);
+			else if (!v)
+				warning(_("hook.jobs must be positive, ignoring: 0"));
+			else
+				data->jobs = v;
+		} else if (!strcmp(subkey, "forcestdouttostderr") && value) {
+			int v = git_parse_maybe_bool(value);
+			if (v >= 0)
+				data->force_stdout_to_stderr = v;
+		}
+		return 0;
+	}
+
 	if (!value)
 		return config_error_nonbool(key);
 
@@ -191,6 +227,24 @@ static int hook_config_lookup_all(const char *key, const char *value,
 		default:
 			break; /* ignore unrecognised values */
 		}
+	} else if (!strcmp(subkey, "parallel")) {
+		int v = git_parse_maybe_bool(value);
+		if (v >= 0)
+			strmap_put(&data->parallel_hooks, hook_name, (void *)(uintptr_t)v);
+	} else if (!strcmp(subkey, "jobs")) {
+		unsigned int v;
+		if (!git_parse_uint(value, &v))
+			warning(_("hook.%s.jobs must be a positive integer, ignoring: '%s'"),
+				hook_name, value);
+		else if (!v)
+			warning(_("hook.%s.jobs must be positive, ignoring: 0"), hook_name);
+		else {
+			unsigned int *old;
+			unsigned int *p = xmalloc(sizeof(*p));
+			*p = v;
+			old = strmap_put(&data->event_jobs, hook_name, p);
+			free(old);
+		}
 	}
 
 	free(hook_name);
@@ -205,31 +259,40 @@ static int hook_config_lookup_all(const char *key, const char *value,
  * Disabled hooks and hooks missing a command are already filtered out at
  * parse time, so callers can iterate the list directly.
  */
-void hook_cache_clear(struct strmap *cache)
+void hook_cache_clear(struct hook_config_cache *cache)
 {
 	struct hashmap_iter iter;
 	struct strmap_entry *e;
 
-	strmap_for_each_entry(cache, &iter, e) {
+	strmap_for_each_entry(&cache->hooks, &iter, e) {
 		struct string_list *hooks = e->value;
-		string_list_clear(hooks, 1); /* free util (command) pointers */
+		for (size_t i = 0; i < hooks->nr; i++) {
+			struct hook_config_cache_entry *entry = hooks->items[i].util;
+			free(entry->command);
+			free(entry);
+		}
+		string_list_clear(hooks, 0);
 		free(hooks);
 	}
-	strmap_clear(cache, 0);
+	strmap_clear(&cache->hooks, 0);
+	strmap_clear(&cache->event_jobs, 1); /* free heap-allocated unsigned int * values */
 }
 
 /* Populate `cache` with the complete hook configuration */
-static void build_hook_config_map(struct repository *r, struct strmap *cache)
+static void build_hook_config_map(struct repository *r,
+				  struct hook_config_cache *cache)
 {
-	struct hook_all_config_cb cb_data;
+	struct hook_all_config_cb cb_data = { 0 };
 	struct hashmap_iter iter;
 	struct strmap_entry *e;
 
 	strmap_init(&cb_data.commands);
 	strmap_init(&cb_data.event_hooks);
 	string_list_init_dup(&cb_data.disabled_hooks);
+	strmap_init(&cb_data.parallel_hooks);
+	strmap_init(&cb_data.event_jobs);
 
-	/* Parse all configs in one run. */
+	/* Parse all configs in one run, capturing hook.* including hook.jobs. */
 	repo_config(r, hook_config_lookup_all, &cb_data);
 
 	/* Construct the cache from parsed configs. */
@@ -241,6 +304,8 @@ static void build_hook_config_map(struct repository *r, struct strmap *cache)
 
 		for (size_t i = 0; i < hook_names->nr; i++) {
 			const char *hname = hook_names->items[i].string;
+			struct hook_config_cache_entry *entry;
+			void *par = strmap_get(&cb_data.parallel_hooks, hname);
 			char *command;
 
 			/* filter out disabled hooks */
@@ -254,15 +319,22 @@ static void build_hook_config_map(struct repository *r, struct strmap *cache)
 				      "'hook.%s.event' must be removed;"
 				      " aborting."), hname, hname);
 
-			/* util stores the command; owned by the cache. */
-			string_list_append(hooks, hname)->util =
-				xstrdup(command);
+			/* util stores a cache entry; owned by the cache. */
+			CALLOC_ARRAY(entry, 1);
+			entry->command = xstrdup(command);
+			entry->parallel = par ? (int)(uintptr_t)par : 0;
+			string_list_append(hooks, hname)->util = entry;
 		}
 
-		strmap_put(cache, e->key, hooks);
+		strmap_put(&cache->hooks, e->key, hooks);
 	}
 
+	cache->jobs = cb_data.jobs;
+	cache->event_jobs = cb_data.event_jobs;
+	cache->force_stdout_to_stderr = cb_data.force_stdout_to_stderr;
+
 	strmap_clear(&cb_data.commands, 1);
+	strmap_clear(&cb_data.parallel_hooks, 0); /* values are uintptr_t, not heap ptrs */
 	string_list_clear(&cb_data.disabled_hooks, 0);
 	strmap_for_each_entry(&cb_data.event_hooks, &iter, e) {
 		string_list_clear(e->value, 0);
@@ -272,35 +344,35 @@ static void build_hook_config_map(struct repository *r, struct strmap *cache)
 }
 
 /*
- * Return the hook config map for `r`, populating it first if needed.
+ * Return the hook config cache for `r`, populating it first if needed.
  *
  * Out-of-repo calls (r->gitdir == NULL) allocate and return a temporary
- * cache map; the caller is responsible for freeing it with
+ * cache; the caller is responsible for freeing it with
  * hook_cache_clear() + free().
  */
-static struct strmap *get_hook_config_cache(struct repository *r)
+static struct hook_config_cache *get_hook_config_cache(struct repository *r)
 {
-	struct strmap *cache = NULL;
+	struct hook_config_cache *cache = NULL;
 
 	if (r && r->gitdir) {
 		/*
-		 * For in-repo calls, the map is stored in r->hook_config_cache,
-		 * so repeated invocations don't parse the configs, so allocate
+		 * For in-repo calls, the cache is stored in r->hook_config_cache,
+		 * so repeated invocations don't parse the configs; allocate
 		 * it just once on the first call.
 		 */
 		if (!r->hook_config_cache) {
-			r->hook_config_cache = xcalloc(1, sizeof(*cache));
-			strmap_init(r->hook_config_cache);
+			CALLOC_ARRAY(r->hook_config_cache, 1);
+			strmap_init(&r->hook_config_cache->hooks);
 			build_hook_config_map(r, r->hook_config_cache);
 		}
 		cache = r->hook_config_cache;
 	} else {
 		/*
 		 * Out-of-repo calls (no gitdir) allocate and return a temporary
-		 * map cache which gets free'd immediately by the caller.
+		 * cache which gets freed immediately by the caller.
 		 */
-		cache = xcalloc(1, sizeof(*cache));
-		strmap_init(cache);
+		CALLOC_ARRAY(cache, 1);
+		strmap_init(&cache->hooks);
 		build_hook_config_map(r, cache);
 	}
 
@@ -312,13 +384,13 @@ static void list_hooks_add_configured(struct repository *r,
 				      struct string_list *list,
 				      struct run_hooks_opt *options)
 {
-	struct strmap *cache = get_hook_config_cache(r);
-	struct string_list *configured_hooks = strmap_get(cache, hookname);
+	struct hook_config_cache *cache = get_hook_config_cache(r);
+	struct string_list *configured_hooks = strmap_get(&cache->hooks, hookname);
 
 	/* Iterate through configured hooks and initialize internal states */
 	for (size_t i = 0; configured_hooks && i < configured_hooks->nr; i++) {
 		const char *friendly_name = configured_hooks->items[i].string;
-		const char *command = configured_hooks->items[i].util;
+		struct hook_config_cache_entry *entry = configured_hooks->items[i].util;
 		struct hook *hook = xcalloc(1, sizeof(struct hook));
 
 		if (options && options->feed_pipe_cb_data_alloc)
@@ -328,7 +400,8 @@ static void list_hooks_add_configured(struct repository *r,
 
 		hook->kind = HOOK_CONFIGURED;
 		hook->u.configured.friendly_name = xstrdup(friendly_name);
-		hook->u.configured.command = xstrdup(command);
+		hook->u.configured.command = xstrdup(entry->command);
+		hook->parallel = entry->parallel;
 
 		string_list_append(list, friendly_name)->util = hook;
 	}
@@ -464,21 +537,101 @@ static void run_hooks_opt_clear(struct run_hooks_opt *options)
 	strvec_clear(&options->args);
 }
 
+static void hook_force_apply_stdout_to_stderr(struct repository *r,
+					      struct run_hooks_opt *options)
+{
+	int force = 0;
+
+	if (r && r->gitdir && r->hook_config_cache)
+		force = r->hook_config_cache->force_stdout_to_stderr;
+	else
+		repo_config_get_bool(r, "hook.forceStdoutToStderr", &force);
+
+	if (force)
+		options->stdout_to_stderr = 1;
+}
+
+/* Determine how many jobs to use for hook execution. */
+static unsigned int get_hook_jobs(struct repository *r,
+				  struct run_hooks_opt *options,
+				  const char *hook_name,
+				  struct string_list *hook_list)
+{
+	unsigned int jobs;
+
+	/*
+	 * Apply hook.forceStdoutToStderr before anything else: it affects
+	 * whether we can run in parallel or not.
+	 */
+	hook_force_apply_stdout_to_stderr(r, options);
+
+	/* Hooks needing separate output streams must run sequentially. */
+	if (!options->stdout_to_stderr)
+		return 1;
+
+	/* Pinned serial: FORCE_SERIAL (internal) or explicit -j1 from CLI. */
+	if (options->jobs == 1)
+		return 1;
+
+	/*
+	 * Resolve effective job count: -j N (when given) overrides config.
+	 * hook.<event>.jobs overrides hook.jobs.
+	 * Unset configs and -jN default to 1.
+	 */
+	if (options->jobs > 1) {
+		jobs = options->jobs;
+	} else if (r && r->gitdir && r->hook_config_cache) {
+		/* Use the already-parsed cache (in-repo) */
+		unsigned int *event_jobs = strmap_get(&r->hook_config_cache->event_jobs,
+						      hook_name);
+		jobs = r->hook_config_cache->jobs ? r->hook_config_cache->jobs : 1;
+		if (event_jobs)
+			jobs = *event_jobs;
+	} else {
+		/* No cache present (out-of-repo call), use direct cfg lookup */
+		unsigned int event_jobs;
+		char *key;
+		jobs = repo_config_get_uint(r, "hook.jobs", &jobs) ? 1 : jobs;
+		key = xstrfmt("hook.%s.jobs", hook_name);
+		if (!repo_config_get_uint(r, key, &event_jobs) && event_jobs)
+			jobs = event_jobs;
+		free(key);
+	}
+
+	/*
+	 * Cap to serial any configured hook not marked as parallel = true.
+	 * This enforces the parallel = false default, even for "traditional"
+	 * hooks from the hookdir which cannot be marked parallel = true.
+	 * The same restriction applies whether jobs came from hook.jobs or
+	 * hook.<event>.jobs.
+	 */
+	for (size_t i = 0; jobs > 1 && i < hook_list->nr; i++) {
+		struct hook *h = hook_list->items[i].util;
+		if (h->kind == HOOK_CONFIGURED && !h->parallel)
+			jobs = 1;
+	}
+
+	return jobs;
+}
+
 int run_hooks_opt(struct repository *r, const char *hook_name,
 		  struct run_hooks_opt *options)
 {
+	struct string_list *hook_list = list_hooks(r, hook_name, options);
 	struct hook_cb_data cb_data = {
 		.rc = 0,
 		.hook_name = hook_name,
+		.hook_command_list = hook_list,
 		.options = options,
 	};
 	int ret = 0;
+	unsigned int jobs = get_hook_jobs(r, options, hook_name, hook_list);
 	const struct run_process_parallel_opts opts = {
 		.tr2_category = "hook",
 		.tr2_label = hook_name,
 
-		.processes = options->jobs,
-		.ungroup = options->jobs == 1,
+		.processes = jobs,
+		.ungroup = jobs == 1,
 
 		.get_next_task = pick_next_hook,
 		.start_failure = notify_start_failure,
@@ -494,9 +647,6 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 	if (options->path_to_stdin && options->feed_pipe)
 		BUG("options path_to_stdin and feed_pipe are mutually exclusive");
 
-	if (!options->jobs)
-		BUG("run_hooks_opt must be called with options.jobs >= 1");
-
 	/*
 	 * Ensure cb_data copy and free functions are either provided together,
 	 * or neither one is provided.
@@ -508,7 +658,6 @@ int run_hooks_opt(struct repository *r, const char *hook_name,
 	if (options->invoked_hook)
 		*options->invoked_hook = 0;
 
-	cb_data.hook_command_list = list_hooks(r, hook_name, options);
 	if (!cb_data.hook_command_list->nr) {
 		if (options->error_if_missing)
 			ret = error("cannot find a hook named %s", hook_name);
diff --git a/hook.h b/hook.h
index e949f5d488..6ea6dbca40 100644
--- a/hook.h
+++ b/hook.h
@@ -29,6 +29,13 @@ struct hook {
 		} configured;
 	} u;
 
+	/**
+	 * Whether this hook may run in parallel with other hooks for the same
+	 * event. Only useful for configured (named) hooks. Traditional hooks
+	 * always default to 0 (serial). Set via `hook.<name>.parallel = true`.
+	 */
+	unsigned int parallel:1;
+
 	/**
 	 * Opaque data pointer used to keep internal state across callback calls.
 	 *
@@ -62,6 +69,8 @@ struct run_hooks_opt
 	 *
 	 * If > 1, output will be buffered and de-interleaved (ungroup=0).
 	 * If == 1, output will be real-time (ungroup=1).
+	 * If == 0, the 'hook.jobs' config is used or, if the config is unset,
+	 * defaults to 1 (serial execution).
 	 */
 	unsigned int jobs;
 
@@ -142,7 +151,23 @@ struct run_hooks_opt
 	cb_data_free_fn feed_pipe_cb_data_free;
 };
 
+/**
+ * Default initializer for hooks. Parallelism is opt-in: .jobs = 0 defers to
+ * the 'hook.jobs' config, falling back to serial (1) if unset.
+ */
 #define RUN_HOOKS_OPT_INIT { \
+	.env = STRVEC_INIT, \
+	.args = STRVEC_INIT, \
+	.stdout_to_stderr = 1, \
+	.jobs = 0, \
+}
+
+/**
+ * Initializer for hooks that must always run sequentially regardless of
+ * 'hook.jobs'. Use this when git knows the hook cannot safely be parallelized
+ * .jobs = 1 is non-overridable.
+ */
+#define RUN_HOOKS_OPT_INIT_FORCE_SERIAL { \
 	.env = STRVEC_INIT, \
 	.args = STRVEC_INIT, \
 	.stdout_to_stderr = 1, \
@@ -191,11 +216,22 @@ struct string_list *list_hooks(struct repository *r, const char *hookname,
  */
 void hook_list_clear(struct string_list *hooks, cb_data_free_fn cb_data_free);
 
+/**
+ * Persistent cache for hook configuration, stored on `struct repository`.
+ * Populated lazily on first hook use and freed by repo_clear().
+ */
+struct hook_config_cache {
+	struct strmap hooks; /* maps event name -> string_list of hooks */
+	struct strmap event_jobs; /* maps event name -> heap-allocated unsigned int * */
+	unsigned int jobs; /* hook.jobs config value; 0 if unset (defaults to serial) */
+	int force_stdout_to_stderr; /* hook.forceStdoutToStderr config value */
+};
+
 /**
  * Frees the hook configuration cache stored in `struct repository`.
  * Called by repo_clear().
  */
-void hook_cache_clear(struct strmap *cache);
+void hook_cache_clear(struct hook_config_cache *cache);
 
 /**
  * Returns the path to the hook file, or NULL if the hook is missing
diff --git a/parse.c b/parse.c
index 48313571aa..d77f28046a 100644
--- a/parse.c
+++ b/parse.c
@@ -107,6 +107,15 @@ int git_parse_int64(const char *value, int64_t *ret)
 	return 1;
 }
 
+int git_parse_uint(const char *value, unsigned int *ret)
+{
+	uintmax_t tmp;
+	if (!git_parse_unsigned(value, &tmp, maximum_unsigned_value_of_type(unsigned int)))
+		return 0;
+	*ret = tmp;
+	return 1;
+}
+
 int git_parse_ulong(const char *value, unsigned long *ret)
 {
 	uintmax_t tmp;
diff --git a/parse.h b/parse.h
index ea32de9a91..a6dd37c4cb 100644
--- a/parse.h
+++ b/parse.h
@@ -5,6 +5,7 @@ int git_parse_signed(const char *value, intmax_t *ret, intmax_t max);
 int git_parse_unsigned(const char *value, uintmax_t *ret, uintmax_t max);
 int git_parse_ssize_t(const char *, ssize_t *);
 int git_parse_ulong(const char *, unsigned long *);
+int git_parse_uint(const char *value, unsigned int *ret);
 int git_parse_int(const char *value, int *ret);
 int git_parse_int64(const char *value, int64_t *ret);
 int git_parse_double(const char *value, double *ret);
diff --git a/repository.c b/repository.c
index 0b8f7ec200..aecd1cbb0b 100644
--- a/repository.c
+++ b/repository.c
@@ -307,6 +307,7 @@ int repo_init(struct repository *repo,
 	repo->repository_format_relative_worktrees = format.relative_worktrees;
 	repo->repository_format_precious_objects = format.precious_objects;
 	repo->repository_format_submodule_path_cfg = format.submodule_path_cfg;
+	repo->repository_format_hook_stdout_to_stderr = format.hook_stdout_to_stderr;
 
 	/* take ownership of format.partial_clone */
 	repo->repository_format_partial_clone = format.partial_clone;
@@ -322,6 +323,7 @@ int repo_init(struct repository *repo,
 	return 0;
 
 error:
+	clear_repository_format(&format);
 	repo_clear(repo);
 	return -1;
 }
diff --git a/repository.h b/repository.h
index 078059a6e0..daa7ae7d16 100644
--- a/repository.h
+++ b/repository.h
@@ -12,6 +12,7 @@ struct lock_file;
 struct pathspec;
 struct object_database;
 struct submodule_cache;
+struct hook_config_cache;
 struct promisor_remote_config;
 struct remote_state;
 
@@ -170,7 +171,7 @@ struct repository {
 	 * Lazily-populated cache mapping hook event names to configured hooks.
 	 * NULL until first hook use.
 	 */
-	struct strmap *hook_config_cache;
+	struct hook_config_cache *hook_config_cache;
 
 	/* Configurations related to promisor remotes. */
 	char *repository_format_partial_clone;
@@ -181,6 +182,7 @@ struct repository {
 	int repository_format_relative_worktrees;
 	int repository_format_precious_objects;
 	int repository_format_submodule_path_cfg;
+	int repository_format_hook_stdout_to_stderr;
 
 	/* Indicate if a repository has a different 'commondir' from 'gitdir' */
 	unsigned different_commondir:1;
diff --git a/setup.c b/setup.c
index 02e5a71779..cce48a4bcf 100644
--- a/setup.c
+++ b/setup.c
@@ -710,6 +710,9 @@ static enum extension_result handle_extension(const char *var,
 	} else if (!strcmp(ext, "submodulepathconfig")) {
 		data->submodule_path_cfg = git_config_bool(var, value);
 		return EXTENSION_OK;
+	} else if (!strcmp(ext, "hookstdouttostderr")) {
+		data->hook_stdout_to_stderr = git_config_bool(var, value);
+		return EXTENSION_OK;
 	}
 	return EXTENSION_UNKNOWN;
 }
@@ -1997,6 +2000,8 @@ const char *setup_git_directory_gently(int *nongit_ok)
 				repo_fmt.relative_worktrees;
 			the_repository->repository_format_submodule_path_cfg =
 				repo_fmt.submodule_path_cfg;
+			the_repository->repository_format_hook_stdout_to_stderr =
+				repo_fmt.hook_stdout_to_stderr;
 			/* take ownership of repo_fmt.partial_clone */
 			the_repository->repository_format_partial_clone =
 				repo_fmt.partial_clone;
@@ -2119,6 +2124,8 @@ void check_repository_format(struct repository_format *fmt)
 		fmt->submodule_path_cfg;
 	the_repository->repository_format_relative_worktrees =
 		fmt->relative_worktrees;
+	the_repository->repository_format_hook_stdout_to_stderr =
+		fmt->hook_stdout_to_stderr;
 	the_repository->repository_format_partial_clone =
 		xstrdup_or_null(fmt->partial_clone);
 	clear_repository_format(&repo_fmt);
@@ -2376,6 +2383,7 @@ void initialize_repository_version(int hash_algo,
 	struct strbuf repo_version = STRBUF_INIT;
 	int target_version = GIT_REPO_VERSION;
 	int default_submodule_path_config = 0;
+	int default_hook_stdout_to_stderr = 0;
 
 	/*
 	 * Note that we initialize the repository version to 1 when the ref
@@ -2433,6 +2441,15 @@ void initialize_repository_version(int hash_algo,
 		repo_config_set(the_repository, "extensions.submodulepathconfig", "true");
 	}
 
+	repo_config_get_bool(the_repository, "hook.forceStdoutToStderr",
+			     &default_hook_stdout_to_stderr);
+	if (default_hook_stdout_to_stderr) {
+		/* extensions.hookstdouttostderr requires at least version 1 */
+		if (target_version == 0)
+			target_version = 1;
+		repo_config_set(the_repository, "extensions.hookstdouttostderr", "true");
+	}
+
 	strbuf_addf(&repo_version, "%d", target_version);
 	repo_config_set(the_repository, "core.repositoryformatversion", repo_version.buf);
 
diff --git a/setup.h b/setup.h
index 80bc6e5f07..b2a4ee3260 100644
--- a/setup.h
+++ b/setup.h
@@ -170,6 +170,7 @@ struct repository_format {
 	int worktree_config;
 	int relative_worktrees;
 	int submodule_path_cfg;
+	int hook_stdout_to_stderr;
 	int is_bare;
 	int hash_algo;
 	int compat_hash_algo;
diff --git a/t/t1800-hook.sh b/t/t1800-hook.sh
index b1583e9ef9..d8f60f2ced 100755
--- a/t/t1800-hook.sh
+++ b/t/t1800-hook.sh
@@ -21,6 +21,57 @@ setup_hookdir () {
 	test_when_finished rm -rf .git/hooks
 }
 
+# write_sentinel_hook <path> [sentinel]
+#
+# Writes a hook that marks itself as started, sleeps for a few seconds, then
+# marks itself done. The sleep must be long enough that sentinel_detector can
+# observe <sentinel>.started before <sentinel>.done appears when both hooks
+# run concurrently in parallel mode.
+write_sentinel_hook () {
+	sentinel="${2:-sentinel}"
+	write_script "$1" <<-EOF
+	touch ${sentinel}.started &&
+	sleep 2 &&
+	touch ${sentinel}.done
+	EOF
+}
+
+# sentinel_detector <sentinel> <output>
+#
+# Returns a shell command string suitable for use as hook.<name>.command.
+# The detector must be registered after the sentinel:
+# 1. In serial mode, the sentinel has completed (and <sentinel>.done exists)
+#    before the detector starts.
+# 2. In parallel mode, both run concurrently so <sentinel>.done has not appeared
+#    yet and the detector just sees <sentinel>.started.
+#
+# At start, poll until <sentinel>.started exists to absorb startup jitter, then
+# write to <output>:
+# 1. 'serial'   if <sentinel>.done exists (sentinel finished before we started),
+# 2. 'parallel' if only <sentinel>.started exists (sentinel still running),
+# 3. 'timeout'  if <sentinel>.started never appeared.
+#
+# The command ends with ':' so when git appends "$@" for hooks that receive
+# positional arguments (e.g. pre-push), the result ': "$@"' is valid shell
+# rather than a syntax error 'fi "$@"'.
+sentinel_detector () {
+	cat <<-EOF
+	i=0
+	while ! test -f ${1}.started && test \$i -lt 10; do
+	    sleep 1
+	    i=\$((i+1))
+	done
+	if test -f ${1}.done; then
+	    echo serial >${2}
+	elif test -f ${1}.started; then
+	    echo parallel >${2}
+	else
+	    echo timeout >${2}
+	fi
+	:
+	EOF
+}
+
 test_expect_success 'git hook usage' '
 	test_expect_code 129 git hook &&
 	test_expect_code 129 git hook run &&
@@ -188,10 +239,20 @@ test_expect_success 'git -c core.hooksPath=<PATH> hook run' '
 '
 
 test_hook_tty () {
-	cat >expect <<-\EOF
-	STDOUT TTY
-	STDERR TTY
-	EOF
+	expect_tty=$1
+	shift
+
+	if test "$expect_tty" != "no_tty"; then
+		cat >expect <<-\EOF
+		STDOUT TTY
+		STDERR TTY
+		EOF
+	else
+		cat >expect <<-\EOF
+		STDOUT NO TTY
+		STDERR NO TTY
+		EOF
+	fi
 
 	test_when_finished "rm -rf repo" &&
 	git init repo &&
@@ -209,12 +270,21 @@ test_hook_tty () {
 	test_cmp expect repo/actual
 }
 
-test_expect_success TTY 'git hook run: stdout and stderr are connected to a TTY' '
-	test_hook_tty hook run pre-commit
+test_expect_success TTY 'git hook run -j1: stdout and stderr are connected to a TTY' '
+	# hooks running sequentially (-j1) are always connected to the tty for
+	# optimum real-time performance.
+	test_hook_tty tty hook run -j1 pre-commit
+'
+
+test_expect_success TTY 'git hook run -jN: stdout and stderr are not connected to a TTY' '
+	# Hooks are not connected to the tty when run in parallel, instead they
+	# output to a pipe through which run-command collects and de-interlaces
+	# their outputs, which then gets passed either to the tty or a sideband.
+	test_hook_tty no_tty hook run -j2 pre-commit
 '
 
 test_expect_success TTY 'git commit: stdout and stderr are connected to a TTY' '
-	test_hook_tty commit -m"B.new"
+	test_hook_tty tty commit -m"B.new"
 '
 
 test_expect_success 'git hook list orders by config order' '
@@ -462,6 +532,43 @@ test_expect_success 'client hooks: pre-push expects separate stdout and stderr'
 	check_stdout_separate_from_stderr pre-push
 '
 
+test_expect_success 'client hooks: extension makes pre-push merge stdout to stderr' '
+	test_when_finished "rm -rf remote2 stdout.actual stderr.actual" &&
+	git init --bare remote2 &&
+	git remote add origin2 remote2 &&
+	test_commit B &&
+	git config set core.repositoryformatversion 1 &&
+	test_config extensions.hookStdoutToStderr true &&
+	setup_hooks pre-push &&
+	git push origin2 HEAD:main >stdout.actual 2>stderr.actual &&
+	check_stdout_merged_to_stderr pre-push
+'
+
+test_expect_success 'client hooks: pre-push defaults to serial execution' '
+	test_when_finished "rm -rf remote-serial repo-serial" &&
+	git init --bare remote-serial &&
+	git init repo-serial &&
+	git -C repo-serial remote add origin ../remote-serial &&
+	test_commit -C repo-serial A &&
+
+	# Setup 2 pre-push hooks; no parallel=true so they must run serially.
+	# Use sentinel/detector pattern: hook-1 (sentinel, configured) runs first
+	# because configured hooks precede traditional hooks in list order; hook-2
+	# (detector) runs second and checks whether hook-1 has finished.
+	git -C repo-serial config hook.hook-1.event pre-push &&
+	git -C repo-serial config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	git -C repo-serial config hook.hook-2.event pre-push &&
+	git -C repo-serial config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+
+	git -C repo-serial config hook.jobs 2 &&
+
+	git -C repo-serial push origin HEAD >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect repo-serial/hook.order
+'
+
 test_expect_success 'client hooks: commit hooks expect stdout redirected to stderr' '
 	hooks="pre-commit prepare-commit-msg \
 		commit-msg post-commit \
@@ -553,4 +660,329 @@ test_expect_success 'server push-to-checkout hook expects stdout redirected to s
 	check_stdout_merged_to_stderr push-to-checkout
 '
 
+test_expect_success 'parallel hook output is not interleaved' '
+	test_when_finished "rm -rf .git/hooks" &&
+
+	write_script .git/hooks/test-hook <<-EOF &&
+	echo "Hook 1 Start"
+	sleep 1
+	echo "Hook 1 End"
+	EOF
+
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+		    "echo \"Hook 2 Start\"; sleep 2; echo \"Hook 2 End\"" &&
+	test_config hook.hook-2.parallel true &&
+	test_config hook.hook-3.event test-hook &&
+	test_config hook.hook-3.command \
+		    "echo \"Hook 3 Start\"; sleep 3; echo \"Hook 3 End\"" &&
+	test_config hook.hook-3.parallel true &&
+
+	git hook run -j3 test-hook >out 2>err.parallel &&
+
+	# Verify Hook 1 output is grouped
+	sed -n "/Hook 1 Start/,/Hook 1 End/p" err.parallel >hook1_out &&
+	test_line_count = 2 hook1_out &&
+
+	# Verify Hook 2 output is grouped
+	sed -n "/Hook 2 Start/,/Hook 2 End/p" err.parallel >hook2_out &&
+	test_line_count = 2 hook2_out &&
+
+	# Verify Hook 3 output is grouped
+	sed -n "/Hook 3 Start/,/Hook 3 End/p" err.parallel >hook3_out &&
+	test_line_count = 2 hook3_out
+'
+
+test_expect_success 'git hook run -j1 runs hooks in series' '
+	test_when_finished "rm -rf .git/hooks" &&
+
+	test_config hook.series-1.event "test-hook" &&
+	test_config hook.series-1.command "echo 1" --add &&
+	test_config hook.series-2.event "test-hook" &&
+	test_config hook.series-2.command "echo 2" --add &&
+
+	mkdir -p .git/hooks &&
+	write_script .git/hooks/test-hook <<-EOF &&
+	echo 3
+	EOF
+
+	cat >expected <<-\EOF &&
+	1
+	2
+	3
+	EOF
+
+	git hook run -j1 test-hook 2>actual &&
+	test_cmp expected actual
+'
+
+test_expect_success 'git hook run -j2 runs hooks in parallel' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_when_finished "rm -rf .git/hooks" &&
+
+	mkdir -p .git/hooks &&
+	write_sentinel_hook .git/hooks/test-hook &&
+
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	test_config hook.hook-2.parallel true &&
+
+	git hook run -j2 test-hook >out 2>err &&
+	echo parallel >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'git hook run -j2 is blocked by parallel=false' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	# hook-1 intentionally has no parallel=true
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	# hook-2 also has no parallel=true
+
+	# -j2 must not override parallel=false on configured hooks.
+	git hook run -j2 test-hook >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.jobs=1 config runs hooks in series' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+
+	# Use two configured hooks so the execution order is deterministic:
+	# hook-1 (sentinel) is listed before hook-2 (detector), so hook-1
+	# always runs first even in serial mode.
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+
+	test_config hook.jobs 1 &&
+
+	git hook run test-hook >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.jobs=2 config runs hooks in parallel' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_when_finished "rm -rf .git/hooks" &&
+
+	mkdir -p .git/hooks &&
+	write_sentinel_hook .git/hooks/test-hook &&
+
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	test_config hook.hook-2.parallel true &&
+
+	test_config hook.jobs 2 &&
+
+	git hook run test-hook >out 2>err &&
+	echo parallel >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.<name>.parallel=true enables parallel execution' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-1.parallel true &&
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	test_config hook.hook-2.parallel true &&
+
+	test_config hook.jobs 2 &&
+
+	git hook run test-hook >out 2>err &&
+	echo parallel >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.<name>.parallel=false (default) forces serial execution' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+
+	test_config hook.jobs 2 &&
+
+	git hook run test-hook >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'one non-parallel hook forces the whole event to run serially' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-1.parallel true &&
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	# hook-2 has no parallel=true: should force serial for all
+
+	test_config hook.jobs 2 &&
+
+	git hook run test-hook >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.jobs=2 is ignored for force-serial hooks (pre-commit)' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event pre-commit &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-1.parallel true &&
+	test_config hook.hook-2.event pre-commit &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	test_config hook.hook-2.parallel true &&
+	test_config hook.jobs 2 &&
+	git commit --allow-empty -m "test: verify force-serial on pre-commit" &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.<event>.jobs overrides hook.jobs for that event' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-1.parallel true &&
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	test_config hook.hook-2.parallel true &&
+
+	# Global hook.jobs=1 (serial), but per-event override allows parallel.
+	test_config hook.jobs 1 &&
+	test_config hook.test-hook.jobs 2 &&
+
+	git hook run test-hook >out 2>err &&
+	echo parallel >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.<event>.jobs=1 forces serial even when hook.jobs>1' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	test_config hook.hook-1.parallel true &&
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	test_config hook.hook-2.parallel true &&
+
+	# Global hook.jobs=4 allows parallel, but per-event override forces serial.
+	test_config hook.jobs 4 &&
+	test_config hook.test-hook.jobs 1 &&
+
+	git hook run test-hook >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success 'hook.<event>.jobs still requires hook.<name>.parallel=true' '
+	test_when_finished "rm -f sentinel.started sentinel.done hook.order" &&
+	test_config hook.hook-1.event test-hook &&
+	test_config hook.hook-1.command \
+	    "touch sentinel.started; sleep 2; touch sentinel.done" &&
+	# hook-1 intentionally has no parallel=true
+	test_config hook.hook-2.event test-hook &&
+	test_config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	# hook-2 also has no parallel=true
+
+	# Per-event jobs=2 but no hook has parallel=true: must still run serially.
+	test_config hook.test-hook.jobs 2 &&
+
+	git hook run test-hook >out 2>err &&
+	echo serial >expect &&
+	test_cmp expect hook.order
+'
+
+test_expect_success '`git init` respects hook.forceStdoutToStderr' '
+	test_when_finished "rm -rf repo-init" &&
+	test_config_global hook.forceStdoutToStderr true &&
+	git init repo-init &&
+	git -C repo-init config extensions.hookStdoutToStderr >actual &&
+	echo true >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success '`git init` does not set extensions.hookStdoutToStderr by default' '
+	test_when_finished "rm -rf upstream" &&
+	git init upstream &&
+	test_must_fail git -C upstream config extensions.hookStdoutToStderr
+'
+
+test_expect_success '`git clone` does not set extensions.hookStdoutToStderr by default' '
+	test_when_finished "rm -rf upstream repo-clone-no-ext" &&
+	git init upstream &&
+	git clone upstream repo-clone-no-ext &&
+	test_must_fail git -C repo-clone-no-ext config extensions.hookStdoutToStderr
+'
+
+test_expect_success '`git clone` respects hook.forceStdoutToStderr' '
+	test_when_finished "rm -rf upstream repo-clone" &&
+	git init upstream &&
+	test_config_global hook.forceStdoutToStderr true &&
+	git clone upstream repo-clone &&
+	git -C repo-clone config extensions.hookStdoutToStderr >actual &&
+	echo true >expect &&
+	test_cmp expect actual
+'
+
+test_expect_success 'hook.forceStdoutToStderr enables extension for existing repos' '
+	test_when_finished "rm -rf remote-repo existing-repo" &&
+	git init --bare remote-repo &&
+	git init -b main existing-repo &&
+	# No local extensions.hookStdoutToStderr config set here
+	# so global config should apply
+	test_config_global hook.forceStdoutToStderr true &&
+	cd existing-repo &&
+	test_commit A &&
+	git remote add origin ../remote-repo &&
+	setup_hooks pre-push &&
+	git push origin HEAD >stdout.actual 2>stderr.actual &&
+	check_stdout_merged_to_stderr pre-push &&
+	cd ..
+'
+
+test_expect_success 'hook.forceStdoutToStderr enables pre-push parallel runs' '
+	test_when_finished "rm -rf repo-parallel remote-parallel" &&
+	git init --bare remote-parallel &&
+	git init repo-parallel &&
+	git -C repo-parallel remote add origin ../remote-parallel &&
+	test_commit -C repo-parallel A &&
+
+	write_sentinel_hook repo-parallel/.git/hooks/pre-push &&
+	git -C repo-parallel config hook.hook-2.event pre-push &&
+	git -C repo-parallel config hook.hook-2.command \
+	    "$(sentinel_detector sentinel hook.order)" &&
+	git -C repo-parallel config hook.hook-2.parallel true &&
+
+	git -C repo-parallel config hook.jobs 2 &&
+	git -C repo-parallel config hook.forceStdoutToStderr true &&
+
+	git -C repo-parallel push origin HEAD >out 2>err &&
+	echo parallel >expect &&
+	test_cmp expect repo-parallel/hook.order
+'
+
 test_done
diff --git a/transport.c b/transport.c
index 259e9d7b70..02d514e567 100644
--- a/transport.c
+++ b/transport.c
@@ -1392,11 +1392,8 @@ static int run_pre_push_hook(struct transport *transport,
 	opt.feed_pipe_cb_data_alloc = pre_push_hook_data_alloc;
 	opt.feed_pipe_cb_data_free = pre_push_hook_data_free;
 
-	/*
-	 * pre-push hooks expect stdout & stderr to be separate, so don't merge
-	 * them to keep backwards compatibility with existing hooks.
-	 */
-	opt.stdout_to_stderr = 0;
+	/* merge stdout to stderr only when extensions.hookStdoutToStderr is enabled */
+	opt.stdout_to_stderr = the_repository->repository_format_hook_stdout_to_stderr;
 
 	ret = run_hooks_opt(the_repository, "pre-push", &opt);