diff --git a/CHANGELOG.md b/CHANGELOG.md
index 4296da09..5c40b8cf 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -71,6 +71,11 @@
   `key-bindings.color-theme-toggle` key bindings. These can be used to
   switch between the primary and alternative color themes. They are
   not bound by default.
+* Support for private mode 2031 - [_Dark and Light Mode
+  Detection_](https://contour-terminal.org/vt-extensions/color-palette-update-notifications/)
+  ([#2025][2025])
+
+[2025]: https://codeberg.org/dnkl/foot/issues/2025
 
 
 ### Changed
diff --git a/csi.c b/csi.c
index b66fda21..e8b2c492 100644
--- a/csi.c
+++ b/csi.c
@@ -563,6 +563,10 @@ decset_decrst(struct terminal *term, unsigned param, bool enable)
 #endif
         break;
 
+    case 2031:
+        term->report_theme_changes = enable;
+        break;
+
     case 2048:
         if (enable)
             term_enable_size_notifications(term);
@@ -657,6 +661,7 @@ decrqm(const struct terminal *term, unsigned param)
     case 2027: return term->conf->tweak.grapheme_width_method != GRAPHEME_WIDTH_DOUBLE
         ? DECRPM_PERMANENTLY_RESET
         : decrpm(term->grapheme_shaping);
+    case 2031: return decrpm(term->report_theme_changes);
     case 2048: return decrpm(term->size_notifications);
     case 8452: return decrpm(term->sixel.cursor_right_of_graphics);
     case 737769: return decrpm(term_ime_is_enabled(term));
@@ -702,6 +707,7 @@ xtsave(struct terminal *term, unsigned param)
     case 2004: term->xtsave.bracketed_paste = term->bracketed_paste; break;
     case 2026: term->xtsave.app_sync_updates = term->render.app_sync_updates.enabled; break;
     case 2027: term->xtsave.grapheme_shaping = term->grapheme_shaping; break;
+    case 2031: term->xtsave.report_theme_changes = term->report_theme_changes; break;
     case 2048: term->xtsave.size_notifications = term->size_notifications; break;
     case 8452: term->xtsave.sixel_cursor_right_of_graphics = term->sixel.cursor_right_of_graphics; break;
     case 737769: term->xtsave.ime = term_ime_is_enabled(term); break;
@@ -746,6 +752,7 @@ xtrestore(struct terminal *term, unsigned param)
     case 2004: enable = term->xtsave.bracketed_paste; break;
     case 2026: enable = term->xtsave.app_sync_updates; break;
     case 2027: enable = term->xtsave.grapheme_shaping; break;
+    case 2031: enable = term->xtsave.report_theme_changes; break;
     case 2048: enable = term->xtsave.size_notifications; break;
     case 8452: enable = term->xtsave.sixel_cursor_right_of_graphics; break;
     case 737769: enable = term->xtsave.ime; break;
@@ -1539,6 +1546,32 @@ csi_dispatch(struct terminal *term, uint8_t final)
             break;
         }
 
+        case 'n': {
+            const int param = vt_param_get(term, 0, 0);
+
+            switch (param) {
+            case 996: {  /* Query current theme mode (see private mode 2031) */
+                /*
+                 * 1 - dark mode
+                 * 2 - light mode
+                 *
+                 * In foot, the themes aren't necessarily light/dark,
+                 * but by convention, the primary theme is dark, and
+                 * the alternative theme is light.
+                 */
+                char reply[16] = {0};
+                int chars = snprintf(
+                    reply, sizeof(reply),
+                    "\033[?997;%dn",
+                    term->colors.active_theme == COLOR_THEME1 ? 1 : 2);
+
+                term_to_slave(term, reply, chars);
+                break;
+            }
+            }
+            break;
+        }
+
         case 'p': {
             /*
              * Request status of ECMA-48/"ANSI" private mode (DECRQM
diff --git a/doc/foot-ctlseqs.7.scd b/doc/foot-ctlseqs.7.scd
index 6c702738..40906ebf 100644
--- a/doc/foot-ctlseqs.7.scd
+++ b/doc/foot-ctlseqs.7.scd
@@ -337,6 +337,9 @@ that corresponds to one of the following modes:
 |  2027
 :  contour
 :  Grapheme cluster processing
+|  2031
+:  contour
+:  Request color theme updates
 |  2048
 :  TODO
 :  In-band window resize notifications
@@ -657,6 +660,13 @@ manipulation sequences. The generic format is:
 :  xterm
 :  Report the current entry on the palette stack, and the number of
    palettes stored on the stack.
+|  \\E[ ? 996 n
+:  Query the current (color) theme mode
+:  contour
+:  The current color theme mode (light or dark) is reported as *CSI ?
+   997 ; 1|2 n*, where *1* means dark and *2* light. By convention, the
+   primary theme in foot is considered dark, and the alternative theme
+   light.
 
 
 # OSC
diff --git a/doc/foot.ini.5.scd b/doc/foot.ini.5.scd
index af6f7875..85a7cf7b 100644
--- a/doc/foot.ini.5.scd
+++ b/doc/foot.ini.5.scd
@@ -958,6 +958,10 @@ The colors are in RRGGBB format (i.e. plain old 6-digit hex values,
 without prefix). That is, they do *not* have an alpha component. You
 can configure the background transparency with the _alpha_ option.
 
+In the context of private mode 2031 (Dark and Light Mode detection),
+the primary theme (i.e. the *colors* section) is considered to be the
+dark theme (since the default theme is dark).
+
 *cursor*
 	Two space separated RRGGBB values (i.e. plain old 6-digit hex
 	values, without prefix) specifying the foreground (text) and
@@ -1093,6 +1097,10 @@ Note that values are not inherited. That is, if you set a value in
 *colors*, but not in *colors2*, the value from *colors* is not
 inherited by *colors2*.
 
+In the context of private mode 2031 (Dark and Light Mode detection),
+the primary theme (i.e. the *colors2* section) is considered to be the
+light theme (since the default theme is dark).
+
 # SECTION: csd
 
 This section controls the look of the _CSDs_ (Client Side
diff --git a/input.c b/input.c
index ebb646c6..b6c56fde 100644
--- a/input.c
+++ b/input.c
@@ -492,6 +492,9 @@ execute_binding(struct seat *seat, struct terminal *term,
             wayl_win_alpha_changed(term->window);
             term_font_subpixel_changed(term);
 
+            if (term->report_theme_changes)
+                term_to_slave(term, "\033[?997;1n", 9);
+
             term_damage_view(term);
             term_damage_margins(term);
             render_refresh(term);
@@ -506,6 +509,9 @@ execute_binding(struct seat *seat, struct terminal *term,
             wayl_win_alpha_changed(term->window);
             term_font_subpixel_changed(term);
 
+            if (term->report_theme_changes)
+                term_to_slave(term, "\033[?997;2n", 9);
+
             term_damage_view(term);
             term_damage_margins(term);
             render_refresh(term);
@@ -516,9 +522,15 @@ execute_binding(struct seat *seat, struct terminal *term,
         if (term->colors.active_theme == COLOR_THEME1) {
             term_theme_apply(term, &term->conf->colors2);
             term->colors.active_theme = COLOR_THEME2;
+
+            if (term->report_theme_changes)
+                term_to_slave(term, "\033[?997;2n", 9);
         } else {
             term_theme_apply(term, &term->conf->colors);
             term->colors.active_theme = COLOR_THEME1;
+
+            if (term->report_theme_changes)
+                term_to_slave(term, "\033[?997;1n", 9);
         }
 
         wayl_win_alpha_changed(term->window);
diff --git a/terminal.h b/terminal.h
index 45e13925..e6499ef7 100644
--- a/terminal.h
+++ b/terminal.h
@@ -518,6 +518,7 @@ struct terminal {
 
     bool num_lock_modifier;
     bool bell_action_enabled;
+    bool report_theme_changes;
 
     /* Saved DECSET modes - we save the SET state */
     struct {
@@ -548,6 +549,7 @@ struct terminal {
         bool ime:1;
         bool app_sync_updates:1;
         bool grapheme_shaping:1;
+        bool report_theme_changes:1;
 
         bool size_notifications:1;