diff --git a/doc/de/weechat_user.de.adoc b/doc/de/weechat_user.de.adoc
index 6e1ab8850..434db8f9c 100644
--- a/doc/de/weechat_user.de.adoc
+++ b/doc/de/weechat_user.de.adoc
@@ -2197,6 +2197,129 @@ Um der Vordergrundfarbe des Terminals das Attribut "fett" zuzuordnen:
 /set weechat.color.status_time *99999
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Themen
+
+A theme is a named bundle of option overrides that can be applied with
+the <<command_weechat_theme,/theme>> command. WeeChat ships a built-in
+`"light"` theme tuned for light-background terminals and supports
+user-defined themes loaded transiently from files.
+
+[[themes_themable_options]]
+==== Themable options
+
+Themes can only set options marked as _themable_. All `*.color.*`
+options are themable by default; a few string options that hold format
+expressions with `+${color:...}+` references (such as
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` or the
+`+buflist.format.*+` formats) are explicitly opted in.
+
+You can list the full themable surface area from the
+<<command_fset_fset,/fset>> buffer with the `+t:themable+` filter.
+
+[[themes_apply]]
+==== Applying a theme
+
+To switch to the built-in light-background theme:
+
+----
+/theme apply light
+----
+
+The current state of every themable option is saved beforehand to a
+backup theme file named like `+backup-YYYYMMDD-HHMMSS-uuuuuu+` in
+directory `+themes+` inside the WeeChat configuration directory, so the
+previous look can be restored at any time with:
+
+----
+/theme apply backup-YYYYMMDD-HHMMSS-uuuuuu
+----
+
+Backup creation can be disabled (not recommended):
+
+----
+/set weechat.look.theme_backup off
+----
+
+If backup is enabled and the backup file cannot be written, the apply
+is aborted before any option is changed.
+
+The name of the last applied theme is stored in
+`+weechat.look.theme+` (informational only; not re-applied at startup).
+
+[[themes_save_delete]]
+==== Saving and deleting user themes
+
+Save the current themable options as a new user theme file:
+
+----
+/theme save mytheme
+----
+
+By default only options whose value differs from their hardcoded
+default are written, keeping the file small and focused. To capture
+every themable option:
+
+----
+/theme save mytheme -full
+----
+
+Reserved names (built-in theme names like `+light+` and any name
+starting with `+backup-+`) are refused. Files live at
+`+${weechat_config_dir}/themes/<name>.theme+`.
+
+Delete a user theme:
+
+----
+/theme delete mytheme
+----
+
+This removes the file on disk; built-in themes cannot be deleted.
+
+[[themes_file_format]]
+==== Theme file format
+
+A theme file is INI-like with two sections:
+
+----
+[info]
+name = "solarized_light"
+description = "Light-background theme inspired by Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` is informational metadata shown by `/theme info`. `+[options]+`
+holds the actual overrides; keys are the full option names that would
+appear in `/set`. String values can be enclosed in double or single
+quotes; quotes are stripped at parse time. Non-themable options listed
+in a theme file are refused at apply time and logged to the core
+buffer (so a `.theme` file imported from an untrusted source cannot
+overwrite passwords, autoload lists, or startup commands).
+
+User theme files are never cached: on every `/theme apply <name>` the
+file is parsed, applied, and freed.
+
+[[themes_resolution]]
+==== Resolution order
+
+When `+/theme apply <name>+` is run:
+
+* If `+${weechat_config_dir}/themes/<name>.theme+` exists, the file
+  is parsed and used (it shadows any built-in with the same name).
+* Otherwise the built-in theme registry is consulted; built-ins are
+  registered programmatically by core, plugins and scripts (see the
+  plugin and scripting documentation for `+weechat_theme_register+`).
+
+If neither source provides the name, the apply is refused.
+
 [[charset]]
 === Charset
 
diff --git a/doc/en/weechat_plugin_api.en.adoc b/doc/en/weechat_plugin_api.en.adoc
index ecdec4cfd..e0beb5e17 100644
--- a/doc/en/weechat_plugin_api.en.adoc
+++ b/doc/en/weechat_plugin_api.en.adoc
@@ -9627,6 +9627,89 @@ elif rc == weechat.WEECHAT_CONFIG_OPTION_UNSET_ERROR:
     # ...
 ----
 
+[[themes]]
+=== Themes
+
+Functions to contribute color (and other themable option) overrides to
+built-in themes. See the
+link:weechat_user.en.html#themes[user's guide / Themes] section for the
+end-user side and the `+/theme+` command.
+
+==== theme_register
+
+_WeeChat ≥ 4.10.0._
+
+Register a contribution of option overrides under a named theme. The
+caller's plugin is the owner of the contribution; subsequent calls
+with the same theme name from the same plugin merge into the existing
+contribution (later keys win for duplicates).
+
+When the calling plugin is unloaded, all its contributions are
+automatically dropped from every theme.
+
+Prototype:
+
+[source,c]
+----
+struct t_theme *weechat_theme_register (const char *name,
+                                        struct t_hashtable *overrides);
+----
+
+Arguments:
+
+* _name_: theme name (for example `+light+` or a custom name)
+* _overrides_: hashtable mapping full option names
+  (e.g. `+irc.color.input_nick+`) to their string values; the caller
+  retains ownership and may free the hashtable right after the call
+
+Return value:
+
+* pointer to the registered theme (existing or newly created), NULL on
+  error
+
+C example:
+
+[source,c]
+----
+struct t_hashtable *overrides = weechat_hashtable_new (
+    8,
+    WEECHAT_HASHTABLE_STRING,
+    WEECHAT_HASHTABLE_STRING,
+    NULL, NULL);
+if (overrides)
+{
+    weechat_hashtable_set (overrides, "irc.color.input_nick", "cyan");
+    weechat_hashtable_set (overrides, "irc.color.topic_old",  "darkgray");
+    weechat_theme_register ("light", overrides);
+    weechat_hashtable_free (overrides);
+}
+----
+
+Script (Python):
+
+[source,python]
+----
+# prototype
+def theme_register(name: str, overrides: Dict[str, str]) -> str: ...
+
+# example
+weechat.theme_register("light", {
+    "irc.color.input_nick": "cyan",
+    "irc.color.topic_old": "darkgray",
+})
+----
+
+[NOTE]
+Only options that have the _themable_ flag will be set by `/theme apply`.
+All `*.color.*` options are themable by default; string options that
+hold `+${color:...}+` references are explicitly opted in. Entries
+targeting non-themable options are silently skipped at apply-time with
+a warning logged to the _core_ buffer.
+
+[NOTE]
+When called from a script, the contribution is automatically dropped
+when the script unloads (no manual cleanup is needed).
+
 [[key_bindings]]
 === Key bindings
 
diff --git a/doc/en/weechat_user.en.adoc b/doc/en/weechat_user.en.adoc
index 183dc87ba..407800c22 100644
--- a/doc/en/weechat_user.en.adoc
+++ b/doc/en/weechat_user.en.adoc
@@ -2185,6 +2185,128 @@ Example of bold with terminal foreground color:
 /set weechat.color.status_time *99999
 ----
 
+[[themes]]
+=== Themes
+
+A theme is a named bundle of option overrides that can be applied with
+the <<command_weechat_theme,/theme>> command. WeeChat ships a built-in
+`"light"` theme tuned for light-background terminals and supports
+user-defined themes loaded transiently from files.
+
+[[themes_themable_options]]
+==== Themable options
+
+Themes can only set options marked as _themable_. All `*.color.*`
+options are themable by default; a few string options that hold format
+expressions with `+${color:...}+` references (such as
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` or the
+`+buflist.format.*+` formats) are explicitly opted in.
+
+You can list the full themable surface area from the
+<<command_fset_fset,/fset>> buffer with the `+t:themable+` filter.
+
+[[themes_apply]]
+==== Applying a theme
+
+To switch to the built-in light-background theme:
+
+----
+/theme apply light
+----
+
+The current state of every themable option is saved beforehand to a
+backup theme file named like `+backup-YYYYMMDD-HHMMSS-uuuuuu+` in
+directory `+themes+` inside the WeeChat configuration directory, so the
+previous look can be restored at any time with:
+
+----
+/theme apply backup-YYYYMMDD-HHMMSS-uuuuuu
+----
+
+Backup creation can be disabled (not recommended):
+
+----
+/set weechat.look.theme_backup off
+----
+
+If backup is enabled and the backup file cannot be written, the apply
+is aborted before any option is changed.
+
+The name of the last applied theme is stored in
+`+weechat.look.theme+` (informational only; not re-applied at startup).
+
+[[themes_save_delete]]
+==== Saving and deleting user themes
+
+Save the current themable options as a new user theme file:
+
+----
+/theme save mytheme
+----
+
+By default only options whose value differs from their hardcoded
+default are written, keeping the file small and focused. To capture
+every themable option:
+
+----
+/theme save mytheme -full
+----
+
+Reserved names (built-in theme names like `+light+` and any name
+starting with `+backup-+`) are refused. Files live at
+`+${weechat_config_dir}/themes/<name>.theme+`.
+
+Delete a user theme:
+
+----
+/theme delete mytheme
+----
+
+This removes the file on disk; built-in themes cannot be deleted.
+
+[[themes_file_format]]
+==== Theme file format
+
+A theme file is INI-like with two sections:
+
+----
+[info]
+name = "solarized_light"
+description = "Light-background theme inspired by Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` is informational metadata shown by `/theme info`. `+[options]+`
+holds the actual overrides; keys are the full option names that would
+appear in `/set`. String values can be enclosed in double or single
+quotes; quotes are stripped at parse time. Non-themable options listed
+in a theme file are refused at apply time and logged to the core
+buffer (so a `.theme` file imported from an untrusted source cannot
+overwrite passwords, autoload lists, or startup commands).
+
+User theme files are never cached: on every `/theme apply <name>` the
+file is parsed, applied, and freed.
+
+[[themes_resolution]]
+==== Resolution order
+
+When `+/theme apply <name>+` is run:
+
+* If `+${weechat_config_dir}/themes/<name>.theme+` exists, the file
+  is parsed and used (it shadows any built-in with the same name).
+* Otherwise the built-in theme registry is consulted; built-ins are
+  registered programmatically by core, plugins and scripts (see the
+  plugin and scripting documentation for `+weechat_theme_register+`).
+
+If neither source provides the name, the apply is refused.
+
 [[charset]]
 === Charset
 
diff --git a/doc/fr/weechat_plugin_api.fr.adoc b/doc/fr/weechat_plugin_api.fr.adoc
index 49f43569a..37cc42ffb 100644
--- a/doc/fr/weechat_plugin_api.fr.adoc
+++ b/doc/fr/weechat_plugin_api.fr.adoc
@@ -9771,6 +9771,95 @@ elif rc == weechat.WEECHAT_CONFIG_OPTION_UNSET_ERROR:
     # ...
 ----
 
+[[themes]]
+=== Thèmes
+
+Fonctions permettant de contribuer des surcharges d'options de couleur
+(et autres options modifiables par un thème) à des thèmes intégrés.
+Voir la section
+link:weechat_user.fr.html#themes[guide utilisateur / Thèmes] pour le
+côté utilisateur final et la commande `+/theme+`.
+
+==== theme_register
+
+_WeeChat ≥ 4.10.0._
+
+Enregistrer une contribution de surcharges d'options sous un thème
+nommé. L'extension appelante est le propriétaire de la contribution ;
+les appels suivants avec le même nom de thème depuis la même extension
+sont fusionnés dans la contribution existante (en cas de doublons, les
+dernières clés gagnent).
+
+Lorsque l'extension appelante est déchargée, toutes ses contributions
+sont automatiquement retirées de tous les thèmes.
+
+Prototype :
+
+[source,c]
+----
+struct t_theme *weechat_theme_register (const char *name,
+                                        struct t_hashtable *overrides);
+----
+
+Paramètres :
+
+* _name_ : nom du thème (par exemple `+light+` ou un nom personnalisé)
+* _overrides_ : table de hachage associant des noms d'options complets
+  (par exemple `+irc.color.input_nick+`) à leurs valeurs chaîne ;
+  l'appelant en conserve la propriété et peut la libérer juste après
+  l'appel
+
+Valeur de retour :
+
+* pointeur vers le thème enregistré (existant ou nouvellement créé),
+  NULL en cas d'erreur
+
+Exemple en C :
+
+[source,c]
+----
+struct t_hashtable *overrides = weechat_hashtable_new (
+    8,
+    WEECHAT_HASHTABLE_STRING,
+    WEECHAT_HASHTABLE_STRING,
+    NULL, NULL);
+if (overrides)
+{
+    weechat_hashtable_set (overrides, "irc.color.input_nick", "cyan");
+    weechat_hashtable_set (overrides, "irc.color.topic_old",  "darkgray");
+    weechat_theme_register ("light", overrides);
+    weechat_hashtable_free (overrides);
+}
+----
+
+Script (Python) :
+
+[source,python]
+----
+# prototype
+def theme_register(name: str, overrides: Dict[str, str]) -> str: ...
+
+# exemple
+weechat.theme_register("light", {
+    "irc.color.input_nick": "cyan",
+    "irc.color.topic_old": "darkgray",
+})
+----
+
+[NOTE]
+Seules les options possédant le flag _themable_ seront modifiées par
+`/theme apply`. Toutes les options `*.color.*` sont modifiables par
+défaut ; les options de type chaîne contenant des références
+`+${color:...}+` sont explicitement déclarées comme modifiables. Les
+entrées ciblant des options non modifiables sont silencieusement
+ignorées au moment de l'application avec un avertissement écrit sur
+le tampon _core_.
+
+[NOTE]
+Lorsqu'elle est appelée depuis un script, la contribution est
+automatiquement retirée lorsque le script est déchargé (aucun nettoyage
+manuel n'est nécessaire).
+
 [[key_bindings]]
 === Associations de touches
 
diff --git a/doc/fr/weechat_user.fr.adoc b/doc/fr/weechat_user.fr.adoc
index 658f2a98c..c38c29948 100644
--- a/doc/fr/weechat_user.fr.adoc
+++ b/doc/fr/weechat_user.fr.adoc
@@ -2227,6 +2227,141 @@ Exemple de gras avec la couleur de texte du terminal :
 /set weechat.color.status_time *99999
 ----
 
+[[themes]]
+=== Thèmes
+
+Un thème est un ensemble nommé de surcharges d'options qui peut être
+appliqué par la commande <<command_weechat_theme,/theme>>. WeeChat est
+livré avec un thème intégré `"light"` adapté aux terminaux à fond clair
+et permet de charger temporairement des thèmes utilisateur depuis des
+fichiers.
+
+[[themes_themable_options]]
+==== Options modifiables par un thème
+
+Les thèmes ne peuvent modifier que les options marquées comme
+_themable_ (modifiables par un thème). Toutes les options `*.color.*`
+le sont par défaut ; certaines options de type chaîne contenant des
+références `+${color:...}+` (par exemple
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` ou les
+formats `+buflist.format.*+`) sont explicitement déclarées comme
+modifiables.
+
+La liste complète des options modifiables peut être affichée depuis le
+tampon <<command_fset_fset,/fset>> avec le filtre `+t:themable+`.
+
+[[themes_apply]]
+==== Appliquer un thème
+
+Pour basculer vers le thème intégré pour fond clair :
+
+----
+/theme apply light
+----
+
+L'état actuel de toutes les options modifiables est sauvegardé au
+préalable dans un fichier de sauvegarde nommé
+`+backup-AAAAMMJJ-HHMMSS-uuuuuu+` dans le répertoire `+themes+` du
+répertoire de configuration de WeeChat. L'apparence précédente peut
+ainsi être restaurée à tout moment avec :
+
+----
+/theme apply backup-AAAAMMJJ-HHMMSS-uuuuuu
+----
+
+La création de la sauvegarde peut être désactivée (déconseillé) :
+
+----
+/set weechat.look.theme_backup off
+----
+
+Si la sauvegarde est activée et que le fichier ne peut pas être écrit,
+l'application est annulée avant qu'aucune option ne soit modifiée.
+
+Le nom du dernier thème appliqué est conservé dans
+`+weechat.look.theme+` (à titre informatif uniquement ; il n'est pas
+ré-appliqué au démarrage).
+
+[[themes_save_delete]]
+==== Sauvegarder et supprimer des thèmes utilisateur
+
+Sauvegarder l'état actuel des options modifiables en tant que nouveau
+thème utilisateur :
+
+----
+/theme save monTheme
+----
+
+Par défaut, seules les options dont la valeur diffère de la valeur par
+défaut codée en dur sont écrites, ce qui garde le fichier compact et
+ciblé. Pour capturer toutes les options modifiables :
+
+----
+/theme save monTheme -full
+----
+
+Les noms réservés (noms de thèmes intégrés comme `+light+` et tout nom
+commençant par `+backup-+`) sont refusés. Les fichiers sont placés
+dans `+${weechat_config_dir}/themes/<nom>.theme+`.
+
+Supprimer un thème utilisateur :
+
+----
+/theme delete monTheme
+----
+
+Cela supprime le fichier sur le disque ; les thèmes intégrés ne
+peuvent pas être supprimés.
+
+[[themes_file_format]]
+==== Format du fichier de thème
+
+Un fichier de thème est de type INI avec deux sections :
+
+----
+[info]
+name = "solarized_light"
+description = "Thème fond clair inspiré de Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` est une section de métadonnées informatives affichées par
+`/theme info`. `+[options]+` contient les surcharges réelles ; les clés
+sont les noms complets d'options tels qu'affichés par `/set`. Les
+valeurs de type chaîne peuvent être encadrées par des guillemets
+simples ou doubles ; les guillemets sont retirés à l'analyse. Les
+options non modifiables par un thème listées dans un fichier sont
+refusées au moment de l'application et signalées sur le tampon _core_
+(ainsi, un fichier `.theme` importé depuis une source non fiable ne
+peut pas écraser des mots de passe, des listes d'auto-chargement ou
+des commandes de démarrage).
+
+Les fichiers de thème utilisateur ne sont jamais mis en cache : à
+chaque `/theme apply <nom>`, le fichier est analysé, appliqué, puis
+libéré.
+
+[[themes_resolution]]
+==== Ordre de résolution
+
+Lors de l'exécution de `+/theme apply <nom>+` :
+
+* Si `+${weechat_config_dir}/themes/<nom>.theme+` existe, le fichier
+  est analysé et utilisé (il masque tout thème intégré du même nom).
+* Sinon, le registre des thèmes intégrés est consulté ; les thèmes
+  intégrés sont enregistrés par programmation par le cœur, les
+  extensions et les scripts (voir la documentation des extensions et
+  des scripts pour `+weechat_theme_register+`).
+
+Si aucune des deux sources ne fournit le nom, l'application est
+refusée.
+
 [[charset]]
 === Charset
 
diff --git a/doc/it/weechat_plugin_api.it.adoc b/doc/it/weechat_plugin_api.it.adoc
index a490dd8a6..e25b5d8f7 100644
--- a/doc/it/weechat_plugin_api.it.adoc
+++ b/doc/it/weechat_plugin_api.it.adoc
@@ -9967,6 +9967,90 @@ elif rc == weechat.WEECHAT_CONFIG_OPTION_UNSET_ERROR:
     # ...
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Themes
+
+Functions to contribute color (and other themable option) overrides to
+built-in themes. See the
+link:weechat_user.it.html#themes[user's guide / Themes] section for the
+end-user side and the `+/theme+` command.
+
+==== theme_register
+
+_WeeChat ≥ 4.10.0._
+
+Register a contribution of option overrides under a named theme. The
+caller's plugin is the owner of the contribution; subsequent calls
+with the same theme name from the same plugin merge into the existing
+contribution (later keys win for duplicates).
+
+When the calling plugin is unloaded, all its contributions are
+automatically dropped from every theme.
+
+Prototype:
+
+[source,c]
+----
+struct t_theme *weechat_theme_register (const char *name,
+                                        struct t_hashtable *overrides);
+----
+
+Arguments:
+
+* _name_: theme name (for example `+light+` or a custom name)
+* _overrides_: hashtable mapping full option names
+  (e.g. `+irc.color.input_nick+`) to their string values; the caller
+  retains ownership and may free the hashtable right after the call
+
+Return value:
+
+* pointer to the registered theme (existing or newly created), NULL on
+  error
+
+C example:
+
+[source,c]
+----
+struct t_hashtable *overrides = weechat_hashtable_new (
+    8,
+    WEECHAT_HASHTABLE_STRING,
+    WEECHAT_HASHTABLE_STRING,
+    NULL, NULL);
+if (overrides)
+{
+    weechat_hashtable_set (overrides, "irc.color.input_nick", "cyan");
+    weechat_hashtable_set (overrides, "irc.color.topic_old",  "darkgray");
+    weechat_theme_register ("light", overrides);
+    weechat_hashtable_free (overrides);
+}
+----
+
+Script (Python):
+
+[source,python]
+----
+# prototype
+def theme_register(name: str, overrides: Dict[str, str]) -> str: ...
+
+# example
+weechat.theme_register("light", {
+    "irc.color.input_nick": "cyan",
+    "irc.color.topic_old": "darkgray",
+})
+----
+
+[NOTE]
+Only options that have the _themable_ flag will be set by `/theme apply`.
+All `*.color.*` options are themable by default; string options that
+hold `+${color:...}+` references are explicitly opted in. Entries
+targeting non-themable options are silently skipped at apply-time with
+a warning logged to the _core_ buffer.
+
+[NOTE]
+When called from a script, the contribution is automatically dropped
+when the script unloads (no manual cleanup is needed).
+
 [[key_bindings]]
 === Combinazione tasti
 
diff --git a/doc/it/weechat_user.it.adoc b/doc/it/weechat_user.it.adoc
index e758d66a0..4e372000a 100644
--- a/doc/it/weechat_user.it.adoc
+++ b/doc/it/weechat_user.it.adoc
@@ -2439,6 +2439,129 @@ Esempio di grassetto con il colore di primo piano del terminale:
 /set weechat.color.status_time *99999
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Themes
+
+A theme is a named bundle of option overrides that can be applied with
+the <<command_weechat_theme,/theme>> command. WeeChat ships a built-in
+`"light"` theme tuned for light-background terminals and supports
+user-defined themes loaded transiently from files.
+
+[[themes_themable_options]]
+==== Themable options
+
+Themes can only set options marked as _themable_. All `*.color.*`
+options are themable by default; a few string options that hold format
+expressions with `+${color:...}+` references (such as
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` or the
+`+buflist.format.*+` formats) are explicitly opted in.
+
+You can list the full themable surface area from the
+<<command_fset_fset,/fset>> buffer with the `+t:themable+` filter.
+
+[[themes_apply]]
+==== Applying a theme
+
+To switch to the built-in light-background theme:
+
+----
+/theme apply light
+----
+
+The current state of every themable option is saved beforehand to a
+backup theme file named like `+backup-YYYYMMDD-HHMMSS-uuuuuu+` in
+directory `+themes+` inside the WeeChat configuration directory, so the
+previous look can be restored at any time with:
+
+----
+/theme apply backup-YYYYMMDD-HHMMSS-uuuuuu
+----
+
+Backup creation can be disabled (not recommended):
+
+----
+/set weechat.look.theme_backup off
+----
+
+If backup is enabled and the backup file cannot be written, the apply
+is aborted before any option is changed.
+
+The name of the last applied theme is stored in
+`+weechat.look.theme+` (informational only; not re-applied at startup).
+
+[[themes_save_delete]]
+==== Saving and deleting user themes
+
+Save the current themable options as a new user theme file:
+
+----
+/theme save mytheme
+----
+
+By default only options whose value differs from their hardcoded
+default are written, keeping the file small and focused. To capture
+every themable option:
+
+----
+/theme save mytheme -full
+----
+
+Reserved names (built-in theme names like `+light+` and any name
+starting with `+backup-+`) are refused. Files live at
+`+${weechat_config_dir}/themes/<name>.theme+`.
+
+Delete a user theme:
+
+----
+/theme delete mytheme
+----
+
+This removes the file on disk; built-in themes cannot be deleted.
+
+[[themes_file_format]]
+==== Theme file format
+
+A theme file is INI-like with two sections:
+
+----
+[info]
+name = "solarized_light"
+description = "Light-background theme inspired by Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` is informational metadata shown by `/theme info`. `+[options]+`
+holds the actual overrides; keys are the full option names that would
+appear in `/set`. String values can be enclosed in double or single
+quotes; quotes are stripped at parse time. Non-themable options listed
+in a theme file are refused at apply time and logged to the core
+buffer (so a `.theme` file imported from an untrusted source cannot
+overwrite passwords, autoload lists, or startup commands).
+
+User theme files are never cached: on every `/theme apply <name>` the
+file is parsed, applied, and freed.
+
+[[themes_resolution]]
+==== Resolution order
+
+When `+/theme apply <name>+` is run:
+
+* If `+${weechat_config_dir}/themes/<name>.theme+` exists, the file
+  is parsed and used (it shadows any built-in with the same name).
+* Otherwise the built-in theme registry is consulted; built-ins are
+  registered programmatically by core, plugins and scripts (see the
+  plugin and scripting documentation for `+weechat_theme_register+`).
+
+If neither source provides the name, the apply is refused.
+
 [[charset]]
 === Charset
 
diff --git a/doc/ja/weechat_plugin_api.ja.adoc b/doc/ja/weechat_plugin_api.ja.adoc
index aa9eb0ca0..6778f5228 100644
--- a/doc/ja/weechat_plugin_api.ja.adoc
+++ b/doc/ja/weechat_plugin_api.ja.adoc
@@ -9746,6 +9746,90 @@ elif rc == weechat.WEECHAT_CONFIG_OPTION_UNSET_ERROR:
     # ...
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Themes
+
+Functions to contribute color (and other themable option) overrides to
+built-in themes. See the
+link:weechat_user.ja.html#themes[user's guide / Themes] section for the
+end-user side and the `+/theme+` command.
+
+==== theme_register
+
+_WeeChat ≥ 4.10.0._
+
+Register a contribution of option overrides under a named theme. The
+caller's plugin is the owner of the contribution; subsequent calls
+with the same theme name from the same plugin merge into the existing
+contribution (later keys win for duplicates).
+
+When the calling plugin is unloaded, all its contributions are
+automatically dropped from every theme.
+
+Prototype:
+
+[source,c]
+----
+struct t_theme *weechat_theme_register (const char *name,
+                                        struct t_hashtable *overrides);
+----
+
+Arguments:
+
+* _name_: theme name (for example `+light+` or a custom name)
+* _overrides_: hashtable mapping full option names
+  (e.g. `+irc.color.input_nick+`) to their string values; the caller
+  retains ownership and may free the hashtable right after the call
+
+Return value:
+
+* pointer to the registered theme (existing or newly created), NULL on
+  error
+
+C example:
+
+[source,c]
+----
+struct t_hashtable *overrides = weechat_hashtable_new (
+    8,
+    WEECHAT_HASHTABLE_STRING,
+    WEECHAT_HASHTABLE_STRING,
+    NULL, NULL);
+if (overrides)
+{
+    weechat_hashtable_set (overrides, "irc.color.input_nick", "cyan");
+    weechat_hashtable_set (overrides, "irc.color.topic_old",  "darkgray");
+    weechat_theme_register ("light", overrides);
+    weechat_hashtable_free (overrides);
+}
+----
+
+Script (Python):
+
+[source,python]
+----
+# prototype
+def theme_register(name: str, overrides: Dict[str, str]) -> str: ...
+
+# example
+weechat.theme_register("light", {
+    "irc.color.input_nick": "cyan",
+    "irc.color.topic_old": "darkgray",
+})
+----
+
+[NOTE]
+Only options that have the _themable_ flag will be set by `/theme apply`.
+All `*.color.*` options are themable by default; string options that
+hold `+${color:...}+` references are explicitly opted in. Entries
+targeting non-themable options are silently skipped at apply-time with
+a warning logged to the _core_ buffer.
+
+[NOTE]
+When called from a script, the contribution is automatically dropped
+when the script unloads (no manual cleanup is needed).
+
 [[key_bindings]]
 === キー割り当て
 
diff --git a/doc/ja/weechat_user.ja.adoc b/doc/ja/weechat_user.ja.adoc
index 0e72c9733..d5073e594 100644
--- a/doc/ja/weechat_user.ja.adoc
+++ b/doc/ja/weechat_user.ja.adoc
@@ -2375,6 +2375,129 @@ WeeChat は画面に色が表示された時点で色ペアを動的に割り当
 /set weechat.color.status_time *99999
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Themes
+
+A theme is a named bundle of option overrides that can be applied with
+the <<command_weechat_theme,/theme>> command. WeeChat ships a built-in
+`"light"` theme tuned for light-background terminals and supports
+user-defined themes loaded transiently from files.
+
+[[themes_themable_options]]
+==== Themable options
+
+Themes can only set options marked as _themable_. All `*.color.*`
+options are themable by default; a few string options that hold format
+expressions with `+${color:...}+` references (such as
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` or the
+`+buflist.format.*+` formats) are explicitly opted in.
+
+You can list the full themable surface area from the
+<<command_fset_fset,/fset>> buffer with the `+t:themable+` filter.
+
+[[themes_apply]]
+==== Applying a theme
+
+To switch to the built-in light-background theme:
+
+----
+/theme apply light
+----
+
+The current state of every themable option is saved beforehand to a
+backup theme file named like `+backup-YYYYMMDD-HHMMSS-uuuuuu+` in
+directory `+themes+` inside the WeeChat configuration directory, so the
+previous look can be restored at any time with:
+
+----
+/theme apply backup-YYYYMMDD-HHMMSS-uuuuuu
+----
+
+Backup creation can be disabled (not recommended):
+
+----
+/set weechat.look.theme_backup off
+----
+
+If backup is enabled and the backup file cannot be written, the apply
+is aborted before any option is changed.
+
+The name of the last applied theme is stored in
+`+weechat.look.theme+` (informational only; not re-applied at startup).
+
+[[themes_save_delete]]
+==== Saving and deleting user themes
+
+Save the current themable options as a new user theme file:
+
+----
+/theme save mytheme
+----
+
+By default only options whose value differs from their hardcoded
+default are written, keeping the file small and focused. To capture
+every themable option:
+
+----
+/theme save mytheme -full
+----
+
+Reserved names (built-in theme names like `+light+` and any name
+starting with `+backup-+`) are refused. Files live at
+`+${weechat_config_dir}/themes/<name>.theme+`.
+
+Delete a user theme:
+
+----
+/theme delete mytheme
+----
+
+This removes the file on disk; built-in themes cannot be deleted.
+
+[[themes_file_format]]
+==== Theme file format
+
+A theme file is INI-like with two sections:
+
+----
+[info]
+name = "solarized_light"
+description = "Light-background theme inspired by Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` is informational metadata shown by `/theme info`. `+[options]+`
+holds the actual overrides; keys are the full option names that would
+appear in `/set`. String values can be enclosed in double or single
+quotes; quotes are stripped at parse time. Non-themable options listed
+in a theme file are refused at apply time and logged to the core
+buffer (so a `.theme` file imported from an untrusted source cannot
+overwrite passwords, autoload lists, or startup commands).
+
+User theme files are never cached: on every `/theme apply <name>` the
+file is parsed, applied, and freed.
+
+[[themes_resolution]]
+==== Resolution order
+
+When `+/theme apply <name>+` is run:
+
+* If `+${weechat_config_dir}/themes/<name>.theme+` exists, the file
+  is parsed and used (it shadows any built-in with the same name).
+* Otherwise the built-in theme registry is consulted; built-ins are
+  registered programmatically by core, plugins and scripts (see the
+  plugin and scripting documentation for `+weechat_theme_register+`).
+
+If neither source provides the name, the apply is refused.
+
 [[charset]]
 === Charset
 
diff --git a/doc/pl/weechat_user.pl.adoc b/doc/pl/weechat_user.pl.adoc
index a31903f85..9494b1529 100644
--- a/doc/pl/weechat_user.pl.adoc
+++ b/doc/pl/weechat_user.pl.adoc
@@ -2191,6 +2191,129 @@ Przykład pogrubienia z domyślnym kolorem terminala:
 /set weechat.color.status_time *99999
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Motywy
+
+A theme is a named bundle of option overrides that can be applied with
+the <<command_weechat_theme,/theme>> command. WeeChat ships a built-in
+`"light"` theme tuned for light-background terminals and supports
+user-defined themes loaded transiently from files.
+
+[[themes_themable_options]]
+==== Themable options
+
+Themes can only set options marked as _themable_. All `*.color.*`
+options are themable by default; a few string options that hold format
+expressions with `+${color:...}+` references (such as
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` or the
+`+buflist.format.*+` formats) are explicitly opted in.
+
+You can list the full themable surface area from the
+<<command_fset_fset,/fset>> buffer with the `+t:themable+` filter.
+
+[[themes_apply]]
+==== Applying a theme
+
+To switch to the built-in light-background theme:
+
+----
+/theme apply light
+----
+
+The current state of every themable option is saved beforehand to a
+backup theme file named like `+backup-YYYYMMDD-HHMMSS-uuuuuu+` in
+directory `+themes+` inside the WeeChat configuration directory, so the
+previous look can be restored at any time with:
+
+----
+/theme apply backup-YYYYMMDD-HHMMSS-uuuuuu
+----
+
+Backup creation can be disabled (not recommended):
+
+----
+/set weechat.look.theme_backup off
+----
+
+If backup is enabled and the backup file cannot be written, the apply
+is aborted before any option is changed.
+
+The name of the last applied theme is stored in
+`+weechat.look.theme+` (informational only; not re-applied at startup).
+
+[[themes_save_delete]]
+==== Saving and deleting user themes
+
+Save the current themable options as a new user theme file:
+
+----
+/theme save mytheme
+----
+
+By default only options whose value differs from their hardcoded
+default are written, keeping the file small and focused. To capture
+every themable option:
+
+----
+/theme save mytheme -full
+----
+
+Reserved names (built-in theme names like `+light+` and any name
+starting with `+backup-+`) are refused. Files live at
+`+${weechat_config_dir}/themes/<name>.theme+`.
+
+Delete a user theme:
+
+----
+/theme delete mytheme
+----
+
+This removes the file on disk; built-in themes cannot be deleted.
+
+[[themes_file_format]]
+==== Theme file format
+
+A theme file is INI-like with two sections:
+
+----
+[info]
+name = "solarized_light"
+description = "Light-background theme inspired by Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` is informational metadata shown by `/theme info`. `+[options]+`
+holds the actual overrides; keys are the full option names that would
+appear in `/set`. String values can be enclosed in double or single
+quotes; quotes are stripped at parse time. Non-themable options listed
+in a theme file are refused at apply time and logged to the core
+buffer (so a `.theme` file imported from an untrusted source cannot
+overwrite passwords, autoload lists, or startup commands).
+
+User theme files are never cached: on every `/theme apply <name>` the
+file is parsed, applied, and freed.
+
+[[themes_resolution]]
+==== Resolution order
+
+When `+/theme apply <name>+` is run:
+
+* If `+${weechat_config_dir}/themes/<name>.theme+` exists, the file
+  is parsed and used (it shadows any built-in with the same name).
+* Otherwise the built-in theme registry is consulted; built-ins are
+  registered programmatically by core, plugins and scripts (see the
+  plugin and scripting documentation for `+weechat_theme_register+`).
+
+If neither source provides the name, the apply is refused.
+
 [[charset]]
 === Charset
 
diff --git a/doc/sr/weechat_plugin_api.sr.adoc b/doc/sr/weechat_plugin_api.sr.adoc
index 51fb0670e..d131eb923 100644
--- a/doc/sr/weechat_plugin_api.sr.adoc
+++ b/doc/sr/weechat_plugin_api.sr.adoc
@@ -9436,6 +9436,90 @@ elif rc == weechat.WEECHAT_CONFIG_OPTION_UNSET_ERROR:
     # ...
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Теме
+
+Functions to contribute color (and other themable option) overrides to
+built-in themes. See the
+link:weechat_user.sr.html#themes[user's guide / Themes] section for the
+end-user side and the `+/theme+` command.
+
+==== theme_register
+
+_WeeChat ≥ 4.10.0._
+
+Register a contribution of option overrides under a named theme. The
+caller's plugin is the owner of the contribution; subsequent calls
+with the same theme name from the same plugin merge into the existing
+contribution (later keys win for duplicates).
+
+When the calling plugin is unloaded, all its contributions are
+automatically dropped from every theme.
+
+Prototype:
+
+[source,c]
+----
+struct t_theme *weechat_theme_register (const char *name,
+                                        struct t_hashtable *overrides);
+----
+
+Arguments:
+
+* _name_: theme name (for example `+light+` or a custom name)
+* _overrides_: hashtable mapping full option names
+  (e.g. `+irc.color.input_nick+`) to their string values; the caller
+  retains ownership and may free the hashtable right after the call
+
+Return value:
+
+* pointer to the registered theme (existing or newly created), NULL on
+  error
+
+C example:
+
+[source,c]
+----
+struct t_hashtable *overrides = weechat_hashtable_new (
+    8,
+    WEECHAT_HASHTABLE_STRING,
+    WEECHAT_HASHTABLE_STRING,
+    NULL, NULL);
+if (overrides)
+{
+    weechat_hashtable_set (overrides, "irc.color.input_nick", "cyan");
+    weechat_hashtable_set (overrides, "irc.color.topic_old",  "darkgray");
+    weechat_theme_register ("light", overrides);
+    weechat_hashtable_free (overrides);
+}
+----
+
+Script (Python):
+
+[source,python]
+----
+# prototype
+def theme_register(name: str, overrides: Dict[str, str]) -> str: ...
+
+# example
+weechat.theme_register("light", {
+    "irc.color.input_nick": "cyan",
+    "irc.color.topic_old": "darkgray",
+})
+----
+
+[NOTE]
+Only options that have the _themable_ flag will be set by `/theme apply`.
+All `*.color.*` options are themable by default; string options that
+hold `+${color:...}+` references are explicitly opted in. Entries
+targeting non-themable options are silently skipped at apply-time with
+a warning logged to the _core_ buffer.
+
+[NOTE]
+When called from a script, the contribution is automatically dropped
+when the script unloads (no manual cleanup is needed).
+
 [[key_bindings]]
 === Тастерске пречице
 
diff --git a/doc/sr/weechat_user.sr.adoc b/doc/sr/weechat_user.sr.adoc
index 484b63650..b25544cd5 100644
--- a/doc/sr/weechat_user.sr.adoc
+++ b/doc/sr/weechat_user.sr.adoc
@@ -2093,6 +2093,129 @@ include::{autogendir}/autogen_user_options.sr.adoc[tag=fset_options]
 /set weechat.color.status_time *99999
 ----
 
+// TRANSLATION MISSING
+[[themes]]
+=== Теме
+
+A theme is a named bundle of option overrides that can be applied with
+the <<command_weechat_theme,/theme>> command. WeeChat ships a built-in
+`"light"` theme tuned for light-background terminals and supports
+user-defined themes loaded transiently from files.
+
+[[themes_themable_options]]
+==== Themable options
+
+Themes can only set options marked as _themable_. All `*.color.*`
+options are themable by default; a few string options that hold format
+expressions with `+${color:...}+` references (such as
+`+weechat.color.chat_nick_colors+`, `+weechat.look.prefix_error+` or the
+`+buflist.format.*+` formats) are explicitly opted in.
+
+You can list the full themable surface area from the
+<<command_fset_fset,/fset>> buffer with the `+t:themable+` filter.
+
+[[themes_apply]]
+==== Applying a theme
+
+To switch to the built-in light-background theme:
+
+----
+/theme apply light
+----
+
+The current state of every themable option is saved beforehand to a
+backup theme file named like `+backup-YYYYMMDD-HHMMSS-uuuuuu+` in
+directory `+themes+` inside the WeeChat configuration directory, so the
+previous look can be restored at any time with:
+
+----
+/theme apply backup-YYYYMMDD-HHMMSS-uuuuuu
+----
+
+Backup creation can be disabled (not recommended):
+
+----
+/set weechat.look.theme_backup off
+----
+
+If backup is enabled and the backup file cannot be written, the apply
+is aborted before any option is changed.
+
+The name of the last applied theme is stored in
+`+weechat.look.theme+` (informational only; not re-applied at startup).
+
+[[themes_save_delete]]
+==== Saving and deleting user themes
+
+Save the current themable options as a new user theme file:
+
+----
+/theme save mytheme
+----
+
+By default only options whose value differs from their hardcoded
+default are written, keeping the file small and focused. To capture
+every themable option:
+
+----
+/theme save mytheme -full
+----
+
+Reserved names (built-in theme names like `+light+` and any name
+starting with `+backup-+`) are refused. Files live at
+`+${weechat_config_dir}/themes/<name>.theme+`.
+
+Delete a user theme:
+
+----
+/theme delete mytheme
+----
+
+This removes the file on disk; built-in themes cannot be deleted.
+
+[[themes_file_format]]
+==== Theme file format
+
+A theme file is INI-like with two sections:
+
+----
+[info]
+name = "solarized_light"
+description = "Light-background theme inspired by Solarized"
+date = "2026-05-25 09:42:10"
+weechat = "4.10.0-dev"
+
+[options]
+weechat.color.chat = "darkgray"
+weechat.color.separator = "blue"
+irc.color.input_nick = "magenta"
+buflist.format.number = "${color:28}${number}${if:${number_displayed}?.: }"
+----
+
+`+[info]+` is informational metadata shown by `/theme info`. `+[options]+`
+holds the actual overrides; keys are the full option names that would
+appear in `/set`. String values can be enclosed in double or single
+quotes; quotes are stripped at parse time. Non-themable options listed
+in a theme file are refused at apply time and logged to the core
+buffer (so a `.theme` file imported from an untrusted source cannot
+overwrite passwords, autoload lists, or startup commands).
+
+User theme files are never cached: on every `/theme apply <name>` the
+file is parsed, applied, and freed.
+
+[[themes_resolution]]
+==== Resolution order
+
+When `+/theme apply <name>+` is run:
+
+* If `+${weechat_config_dir}/themes/<name>.theme+` exists, the file
+  is parsed and used (it shadows any built-in with the same name).
+* Otherwise the built-in theme registry is consulted; built-ins are
+  registered programmatically by core, plugins and scripts (see the
+  plugin and scripting documentation for `+weechat_theme_register+`).
+
+If neither source provides the name, the apply is refused.
+
 [[charset]]
 === Charset