diff --git a/runtime/doc/api.txt b/runtime/doc/api.txt
index 31fc1ab32a..1cdaa4b571 100644
--- a/runtime/doc/api.txt
+++ b/runtime/doc/api.txt
@@ -4231,6 +4231,34 @@ nvim_win_is_valid({win})                                 *nvim_win_is_valid()*
     Return: ~
         (`boolean`) true if the window is valid, false otherwise
 
+nvim_win_resize({win}, {width}, {height}, {opts})          *nvim_win_resize()*
+    Resize a window, choosing which edge stays anchored.
+
+    The window first takes space from the non-anchored side (the window below
+    or to the right by default), and only then from the anchored side. The
+    "anchor" selects the fixed edge, so a window can also grow upwards or
+    leftwards.
+
+    Can set the height, the width, or both in a single call. "anchor" applies
+    to the matching axis ("top"/"bottom" for height, "left"/"right" for
+    width); the other axis, if also resized, uses its default anchor.
+
+    Attributes: ~
+        Since: 0.13.0
+
+    Parameters: ~
+      • {win}     (`integer`) |window-ID|, or 0 for current window
+      • {width}   (`integer`) New width as a count of columns, set -1 as "no
+                  change"
+      • {height}  (`integer`) New height as a count of rows, set -1 as "no
+                  change"
+      • {opts}    (`vim.api.keyset.win_resize`) Optional parameters.
+                  • anchor: Edge that stays fixed while the opposite edge
+                    moves; the neighbor on the moving side is resized first.
+                    One of:
+                    • "top" (default for height) or "bottom"
+                    • "left" (default for width) or "right"
+
 nvim_win_set_buf({win}, {buf})                            *nvim_win_set_buf()*
     Sets the current buffer in a window.
 
@@ -4257,16 +4285,6 @@ nvim_win_set_cursor({win}, {pos})                      *nvim_win_set_cursor()*
       • {pos}  (`[integer, integer]`) (row, col) tuple representing the new
                position
 
-nvim_win_set_height({win}, {height})                   *nvim_win_set_height()*
-    Sets the window height.
-
-    Attributes: ~
-        Since: 0.1.0
-
-    Parameters: ~
-      • {win}     (`integer`) |window-ID|, or 0 for current window
-      • {height}  (`integer`) Height as a count of rows
-
 nvim_win_set_hl_ns({win}, {ns_id})                      *nvim_win_set_hl_ns()*
     Set highlight namespace for a window. This will use highlights defined
     with |nvim_set_hl()| for this namespace, but fall back to global
@@ -4292,17 +4310,6 @@ nvim_win_set_var({win}, {name}, {value})                  *nvim_win_set_var()*
       • {name}   (`string`) Variable name
       • {value}  (`any`) Variable value
 
-nvim_win_set_width({win}, {width})                      *nvim_win_set_width()*
-    Sets the window width. This will only succeed if the screen is split
-    vertically.
-
-    Attributes: ~
-        Since: 0.1.0
-
-    Parameters: ~
-      • {win}    (`integer`) |window-ID|, or 0 for current window
-      • {width}  (`integer`) Width as a count of columns
-
 nvim_win_text_height({win}, {opts})                   *nvim_win_text_height()*
     Computes the number of screen lines occupied by a range of text in a given
     window. Works for off-screen text and takes folds into account.
diff --git a/runtime/doc/deprecated.txt b/runtime/doc/deprecated.txt
index 959ac3dedc..158491d8a9 100644
--- a/runtime/doc/deprecated.txt
+++ b/runtime/doc/deprecated.txt
@@ -17,6 +17,8 @@ DEPRECATED IN 0.13					*deprecated-0.13*
 
 API
 
+• *nvim_win_set_height()*	Use |nvim_win_resize()| instead.
+• *nvim_win_set_width()*	Use |nvim_win_resize()| instead.
 • The "buffer" key accepted and/or returned by these functions, was renamed to
   "buf":
   • |nvim_create_autocmd()|
diff --git a/runtime/doc/news.txt b/runtime/doc/news.txt
index 87b3ea9d1c..403c2b67eb 100644
--- a/runtime/doc/news.txt
+++ b/runtime/doc/news.txt
@@ -119,6 +119,9 @@ The following new features were added.
 
 API
 
+• |nvim_win_resize()| resizes a window with a choosable anchor edge, letting a
+  window grow upwards or leftwards by taking space from the window above or to
+  the left first. |nvim_win_set_height()| and |nvim_win_set_width()| are now deprecated.
 • |nvim_buf_call()| and |nvim_win_call()| now preserve multiple return values.
 • |nvim_set_hl()| supports "font" key.
 • |nvim_open_win()| `zindex` controls whether the UI will use a dimmed cursor
diff --git a/runtime/lua/vim/_core/ui2/cmdline.lua b/runtime/lua/vim/_core/ui2/cmdline.lua
index 81f089c7e3..ec06550455 100644
--- a/runtime/lua/vim/_core/ui2/cmdline.lua
+++ b/runtime/lua/vim/_core/ui2/cmdline.lua
@@ -22,7 +22,7 @@ local function win_config(win, hide, height)
   if ui.cmdheight == 0 and api.nvim_win_get_config(win).hide ~= hide then
     api.nvim_win_set_config(win, { hide = hide, height = not hide and height or nil })
   elseif api.nvim_win_get_height(win) ~= height then
-    api.nvim_win_set_height(win, height)
+    api.nvim_win_resize(win, -1, height, {})
   end
   if vim.o.cmdheight ~= height then
     -- Avoid moving the cursor with 'splitkeep' = "screen", and altering the user
diff --git a/runtime/lua/vim/_core/ui2/messages.lua b/runtime/lua/vim/_core/ui2/messages.lua
index 46233e2900..9b081999a9 100644
--- a/runtime/lua/vim/_core/ui2/messages.lua
+++ b/runtime/lua/vim/_core/ui2/messages.lua
@@ -139,7 +139,7 @@ local function set_virttext(type, tgt)
       -- Check if adding the virt_text on this line will exceed the current window width.
       local maxwidth = math.max(M.msg.width, math.min(o.columns, scol - offset + width))
       if tgt == 'msg' and api.nvim_win_get_width(win) < maxwidth then
-        api.nvim_win_set_width(win, maxwidth)
+        api.nvim_win_resize(win, maxwidth, -1, {})
         M.msg.width = maxwidth
       end
 
@@ -293,7 +293,7 @@ function M.show_msg(tgt, kind, content, replace_last, append, id)
     if tgt == 'msg' then
       local width_cmd = [[echo max(map(range(1, line('$')), 'virtcol([v:val, "$"])'))]]
       local width = tonumber(fn.win_execute(ui.wins.msg, width_cmd)) - 1
-      api.nvim_win_set_width(ui.wins.msg, width)
+      api.nvim_win_resize(ui.wins.msg, width, -1, {})
       local texth = api.nvim_win_text_height(ui.wins.msg, { start_row = start_row, end_row = row })
       if texth.all > math.ceil(lines * 0.5) then
         tgt, buf = M.expand_msg(tgt)
diff --git a/runtime/lua/vim/_meta/api.gen.lua b/runtime/lua/vim/_meta/api.gen.lua
index e3a4fda5c6..bd8821d7f9 100644
--- a/runtime/lua/vim/_meta/api.gen.lua
+++ b/runtime/lua/vim/_meta/api.gen.lua
@@ -2492,6 +2492,26 @@ function vim.api.nvim_win_hide(win) end
 --- @return boolean # true if the window is valid, false otherwise
 function vim.api.nvim_win_is_valid(win) end
 
+--- Resize a window, choosing which edge stays anchored.
+---
+--- The window first takes space from the non-anchored side (the window below or
+--- to the right by default), and only then from the anchored side. The "anchor"
+--- selects the fixed edge, so a window can also grow upwards or leftwards.
+---
+--- Can set the height, the width, or both in a single call. "anchor" applies to the
+--- matching axis ("top"/"bottom" for height, "left"/"right" for width); the other
+--- axis, if also resized, uses its default anchor.
+---
+--- @param win integer `window-ID`, or 0 for current window
+--- @param width integer New width as a count of columns, set -1 as "no change"
+--- @param height integer New height as a count of rows, set -1 as "no change"
+--- @param opts vim.api.keyset.win_resize Optional parameters.
+--- - anchor: Edge that stays fixed while the opposite edge moves; the
+---   neighbor on the moving side is resized first. One of:
+---   - "top" (default for height) or "bottom"
+---   - "left" (default for width) or "right"
+function vim.api.nvim_win_resize(win, width, height, opts) end
+
 --- Sets the current buffer in a window.
 ---
 --- Note: As a side-effect, this executes `BufEnter` and `BufLeave` autocommands.
@@ -2526,10 +2546,9 @@ function vim.api.nvim_win_set_config(win, config) end
 --- @param pos [integer, integer] (row, col) tuple representing the new position
 function vim.api.nvim_win_set_cursor(win, pos) end
 
---- Sets the window height.
----
---- @param win integer `window-ID`, or 0 for current window
---- @param height integer Height as a count of rows
+--- @deprecated
+--- @param win integer
+--- @param height integer
 function vim.api.nvim_win_set_height(win, height) end
 
 --- Set highlight namespace for a window. This will use highlights defined with
@@ -2555,11 +2574,9 @@ function vim.api.nvim_win_set_option(window, name, value) end
 --- @param value any Variable value
 function vim.api.nvim_win_set_var(win, name, value) end
 
---- Sets the window width. This will only succeed if the screen is split
---- vertically.
----
---- @param win integer `window-ID`, or 0 for current window
---- @param width integer Width as a count of columns
+--- @deprecated
+--- @param win integer
+--- @param width integer
 function vim.api.nvim_win_set_width(win, width) end
 
 --- Computes the number of screen lines occupied by a range of text in a given window.
diff --git a/runtime/lua/vim/_meta/api_keysets.gen.lua b/runtime/lua/vim/_meta/api_keysets.gen.lua
index 3f5a465984..d16983615b 100644
--- a/runtime/lua/vim/_meta/api_keysets.gen.lua
+++ b/runtime/lua/vim/_meta/api_keysets.gen.lua
@@ -493,6 +493,9 @@ error('Cannot require a meta file')
 --- @field zindex? integer
 --- @field _cmdline_offset? integer
 
+--- @class vim.api.keyset.win_resize
+--- @field anchor? string
+
 --- @class vim.api.keyset.win_text_height
 --- @field end_row? integer
 --- @field end_vcol? integer
diff --git a/runtime/lua/vim/lsp/completion.lua b/runtime/lua/vim/lsp/completion.lua
index a77c06075d..ad258e4363 100644
--- a/runtime/lua/vim/lsp/completion.lua
+++ b/runtime/lua/vim/lsp/completion.lua
@@ -677,7 +677,7 @@ local function update_popup_window(winid, bufnr, kind)
       vim.treesitter.start(bufnr, kind)
     end
     local all = api.nvim_win_text_height(winid, {}).all
-    api.nvim_win_set_height(winid, all)
+    api.nvim_win_resize(winid, -1, all, {})
   end
 end
 
diff --git a/runtime/lua/vim/lsp/util.lua b/runtime/lua/vim/lsp/util.lua
index a31c1af1b3..6dd4c6f0bb 100644
--- a/runtime/lua/vim/lsp/util.lua
+++ b/runtime/lua/vim/lsp/util.lua
@@ -1625,7 +1625,7 @@ function M.open_floating_preview(contents, syntax, opts)
       local win_height = api.nvim_win_get_height(floating_winnr)
       local text_height = api.nvim_win_text_height(floating_winnr, { max_height = win_height }).all
       if text_height < win_height then
-        api.nvim_win_set_height(floating_winnr, text_height)
+        api.nvim_win_resize(floating_winnr, -1, text_height, {})
       end
     end
   end
diff --git a/src/nvim/api/deprecated.c b/src/nvim/api/deprecated.c
index 16df5aae18..3ed1ce15fc 100644
--- a/src/nvim/api/deprecated.c
+++ b/src/nvim/api/deprecated.c
@@ -31,6 +31,7 @@
 #include "nvim/pos_defs.h"
 #include "nvim/strings.h"
 #include "nvim/types_defs.h"
+#include "nvim/window.h"
 
 #include "api/deprecated.c.generated.h"
 
@@ -1006,3 +1007,50 @@ Object nvim_notify(String msg, Integer log_level, Dict opts, Arena *arena, Error
 
   return NLUA_EXEC_STATIC("return vim.notify(...)", args, kRetObject, arena, err);
 }
+
+/// @deprecated
+///
+/// Use |nvim_win_resize()| instead, e.g., nvim_win_resize(win, -1, height, {})
+///
+/// Sets the window height.
+///
+/// @param win   |window-ID|, or 0 for current window
+/// @param height   Height as a count of rows
+/// @param[out] err Error details, if any
+void nvim_win_set_height(Window win, Integer height, Error *err)
+  FUNC_API_SINCE(1) FUNC_API_DEPRECATED_SINCE(15)
+{
+  win_T *w = find_window_by_handle(win, err);
+
+  if (!w) {
+    return;
+  }
+
+  TRY_WRAP(err, {
+    win_setheight_win((int)height, w, true);
+  });
+}
+
+/// @deprecated
+///
+/// Use |nvim_win_resize()| instead, e.g., nvim_win_resize(win, width, -1, {})
+///
+/// Sets the window width. This will only succeed if the screen is split
+/// vertically.
+///
+/// @param win   |window-ID|, or 0 for current window
+/// @param width    Width as a count of columns
+/// @param[out] err Error details, if any
+void nvim_win_set_width(Window win, Integer width, Error *err)
+  FUNC_API_SINCE(1) FUNC_API_DEPRECATED_SINCE(15)
+{
+  win_T *w = find_window_by_handle(win, err);
+
+  if (!w) {
+    return;
+  }
+
+  TRY_WRAP(err, {
+    win_setwidth_win((int)width, w, true);
+  });
+}
diff --git a/src/nvim/api/keysets_defs.h b/src/nvim/api/keysets_defs.h
index 2f3049d731..7ac3ad929d 100644
--- a/src/nvim/api/keysets_defs.h
+++ b/src/nvim/api/keysets_defs.h
@@ -253,6 +253,11 @@ typedef struct {
   Integer max_height;
 } Dict(win_text_height);
 
+typedef struct {
+  OptionalKeys is_set__win_resize_;
+  String anchor;
+} Dict(win_resize);
+
 typedef struct {
   OptionalKeys is_set__clear_autocmds_;
   Buffer buffer;  // deprecated - use buf
diff --git a/src/nvim/api/win_config.c b/src/nvim/api/win_config.c
index 880b716e03..8a1f7e2f8e 100644
--- a/src/nvim/api/win_config.c
+++ b/src/nvim/api/win_config.c
@@ -272,9 +272,9 @@ Window nvim_open_win(Buffer buf, Boolean enter, Dict(win_config) *config, Error
         // Without room for the requested size, window sizes may have been equalized instead.
         // If the size differs from what was requested, try to set it again now.
         if ((flags & WSP_VERT) && wp->w_width != size) {
-          win_setwidth_win(size, wp);
+          win_setwidth_win(size, wp, true);
         } else if (!(flags & WSP_VERT) && wp->w_height != size) {
-          win_setheight_win(size, wp);
+          win_setheight_win(size, wp, true);
         }
       }
     }
@@ -627,10 +627,10 @@ restore_curwin:
 
 resize:
   if (HAS_KEY_X(config, width)) {
-    win_setwidth_win(fconfig->width, win);
+    win_setwidth_win(fconfig->width, win, true);
   }
   if (HAS_KEY_X(config, height)) {
-    win_setheight_win(fconfig->height, win);
+    win_setheight_win(fconfig->height, win, true);
   }
 
   // Merge configs now. If previously a float, clear fields irrelevant to splits that `fconfig` may
diff --git a/src/nvim/api/window.c b/src/nvim/api/window.c
index bdca9111bf..667ecf4eaa 100644
--- a/src/nvim/api/window.c
+++ b/src/nvim/api/window.c
@@ -162,25 +162,6 @@ Integer nvim_win_get_height(Window win, Error *err)
   return w->w_height;
 }
 
-/// Sets the window height.
-///
-/// @param win   |window-ID|, or 0 for current window
-/// @param height   Height as a count of rows
-/// @param[out] err Error details, if any
-void nvim_win_set_height(Window win, Integer height, Error *err)
-  FUNC_API_SINCE(1)
-{
-  win_T *w = find_window_by_handle(win, err);
-
-  if (!w) {
-    return;
-  }
-
-  TRY_WRAP(err, {
-    win_setheight_win((int)height, w);
-  });
-}
-
 /// Gets the window width
 ///
 /// @param win   |window-ID|, or 0 for current window
@@ -198,26 +179,6 @@ Integer nvim_win_get_width(Window win, Error *err)
   return w->w_width;
 }
 
-/// Sets the window width. This will only succeed if the screen is split
-/// vertically.
-///
-/// @param win   |window-ID|, or 0 for current window
-/// @param width    Width as a count of columns
-/// @param[out] err Error details, if any
-void nvim_win_set_width(Window win, Integer width, Error *err)
-  FUNC_API_SINCE(1)
-{
-  win_T *w = find_window_by_handle(win, err);
-
-  if (!w) {
-    return;
-  }
-
-  TRY_WRAP(err, {
-    win_setwidth_win((int)width, w);
-  });
-}
-
 /// Gets a window-scoped (w:) variable
 ///
 /// @param win   |window-ID|, or 0 for current window
@@ -575,3 +536,75 @@ DictAs(win_text_height_ret) nvim_win_text_height(Window win, Dict(win_text_heigh
   PUT_C(rv, "end_vcol", INTEGER_OBJ(end_vcol));
   return rv;
 }
+
+/// Resize a window, choosing which edge stays anchored.
+///
+/// The window first takes space from the non-anchored side (the window below or
+/// to the right by default), and only then from the anchored side. The "anchor"
+/// selects the fixed edge, so a window can also grow upwards or leftwards.
+///
+/// Can set the height, the width, or both in a single call. "anchor" applies to the
+/// matching axis ("top"/"bottom" for height, "left"/"right" for width); the other
+/// axis, if also resized, uses its default anchor.
+///
+/// @param win        |window-ID|, or 0 for current window
+/// @param width      New width as a count of columns, set -1 as "no change"
+/// @param height     New height as a count of rows, set -1 as "no change"
+/// @param opts       Optional parameters.
+///                     - anchor: Edge that stays fixed while the opposite edge moves; the
+///                       neighbor on the moving side is resized first. One of:
+///                       - "top" (default for height) or "bottom"
+///                       - "left" (default for width) or "right"
+/// @param[out] err Error details, if any
+void nvim_win_resize(Window win, Integer width, Integer height, Dict(win_resize) *opts, Error *err)
+  FUNC_API_SINCE(15)
+{
+  win_T *w = find_window_by_handle(win, err);
+
+  if (!w) {
+    return;
+  }
+
+  VALIDATE_EXP((height >= 0 || height == -1), "height",
+               "a non-negative count of rows, or -1 for no change", NULL, {
+    return;
+  });
+  VALIDATE_EXP((width >= 0 || width == -1), "width",
+               "a non-negative count of columns, or -1 for no change", NULL, {
+    return;
+  });
+
+  VALIDATE_R((height >= 0 || width >= 0), "must set at least one of 'height', 'width'", {
+    return;
+  });
+
+  // default anchors
+  bool from_top = true;
+  bool from_left = true;
+
+  if (HAS_KEY(opts, win_resize, anchor)) {
+    char *anchor = opts->anchor.data;
+    bool is_height = strequal("top", anchor) || strequal("bottom", anchor);
+    bool is_width = strequal("left", anchor) || strequal("right", anchor);
+
+    VALIDATE_EXP(is_height || is_width, "anchor", "\"top\", \"bottom\", \"left\" or \"right\"",
+                 anchor, { return; });
+    // anchor must match a dimension that is actually being resized.
+    VALIDATE_CON(!(is_height && height == -1) && !(is_width && width == -1), anchor,
+                 "this dimension", {
+      return;
+    });
+
+    if (is_height) {
+      from_top = strequal("top", anchor);
+    } else {
+      from_left = strequal("left", anchor);
+    }
+  }
+  if (height >= 0) {
+    TRY_WRAP(err, win_setheight_win((int)height, w, from_top));
+  }
+  if (!ERROR_SET(err) && width >= 0) {
+    TRY_WRAP(err, win_setwidth_win((int)width, w, from_left));
+  }
+}
diff --git a/src/nvim/ex_docmd.c b/src/nvim/ex_docmd.c
index cda4353484..b85b6caf53 100644
--- a/src/nvim/ex_docmd.c
+++ b/src/nvim/ex_docmd.c
@@ -6079,14 +6079,14 @@ static void ex_resize(exarg_T *eap)
     } else if (n == 0 && eap->arg[0] == NUL) {  // default is very wide
       n = Columns;
     }
-    win_setwidth_win(n, wp);
+    win_setwidth_win(n, wp, true);
   } else {
     if (*eap->arg == '-' || *eap->arg == '+') {
       n += wp->w_height;
     } else if (n == 0 && eap->arg[0] == NUL) {  // default is very high
       n = Rows - 1;
     }
-    win_setheight_win(n, wp);
+    win_setheight_win(n, wp, true);
   }
 }
 
diff --git a/src/nvim/window.c b/src/nvim/window.c
index 13c038fb88..b6b8dc7a44 100644
--- a/src/nvim/window.c
+++ b/src/nvim/window.c
@@ -1259,7 +1259,7 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir, frame_T *to_fl
     // 'winfixwidth' window.  Take them from a window to the left or right
     // instead, if possible. Add one for the separator.
     if (oldwin->w_p_wfw) {
-      win_setwidth_win(oldwin->w_width + new_size + 1, oldwin);
+      win_setwidth_win(oldwin->w_width + new_size + 1, oldwin, true);
     }
 
     // Only make all windows the same width if one of them (except oldwin)
@@ -1346,7 +1346,7 @@ win_T *win_split_ins(int size, int flags, win_T *new_wp, int dir, frame_T *to_fl
       did_set_fraction = true;
 
       win_setheight_win(oldwin->w_height + new_size + STATUS_HEIGHT,
-                        oldwin);
+                        oldwin, true);
       oldwin_height = oldwin->w_height;
       if (need_status) {
         oldwin_height -= STATUS_HEIGHT;
@@ -2110,7 +2110,7 @@ int win_splitmove(win_T *wp, int size, int flags)
   // If splitting horizontally, try to preserve height.
   // Note that win_split_ins autocommands may have immediately closed "wp", or made it floating!
   if (size == 0 && !(flags & WSP_VERT) && win_valid(wp) && !wp->w_floating) {
-    win_setheight_win(height, wp);
+    win_setheight_win(height, wp, true);
     if (p_ea) {
       // Equalize windows.  Note that win_split_ins autocommands may have
       // made a window other than "wp" current.
@@ -6183,8 +6183,8 @@ void win_size_restore(garray_T *gap)
         int width = ((int *)gap->ga_data)[i++];
         int height = ((int *)gap->ga_data)[i++];
         if (!wp->w_floating) {
-          frame_setwidth(wp->w_frame, width);
-          win_setheight_win(height, wp);
+          frame_setwidth(wp->w_frame, width, true);
+          win_setheight_win(height, wp, true);
         }
       }
     }
@@ -6251,12 +6251,13 @@ static void frame_comp_pos(frame_T *topfrp, int *row, int *col)
 // fit around it.
 void win_setheight(int height)
 {
-  win_setheight_win(height, curwin);
+  win_setheight_win(height, curwin, true);
 }
 
 // Set the window height of window "win" and take care of repositioning other
 // windows to fit around it.
-void win_setheight_win(int height, win_T *win)
+// from_top: keep the top edge anchored (take space from the window below first).
+void win_setheight_win(int height, win_T *win, bool from_top)
 {
   // Always keep current window at least one line high, even when 'winminheight' is zero.
   // Keep window at least two lines high if 'winbar' is enabled.
@@ -6267,7 +6268,8 @@ void win_setheight_win(int height, win_T *win)
     win_config_float(win, win->w_config);
     redraw_later(win, UPD_VALID);
   } else {
-    frame_setheight(win->w_frame, height + win->w_hsep_height + win->w_status_height);
+    frame_setheight(win->w_frame, height + win->w_hsep_height + win->w_status_height,
+                    from_top);
 
     // recompute the window positions
     win_comp_pos();
@@ -6289,7 +6291,7 @@ void win_setheight_win(int height, win_T *win)
 // If the frame is part of a FR_ROW frame, all frames must be resized as well.
 // Check for the minimal height of the FR_ROW frame.
 // At the top level we can also use change the command line height.
-static void frame_setheight(frame_T *curfrp, int height)
+static void frame_setheight(frame_T *curfrp, int height, bool from_top)
 {
   // If the height already is the desired value, nothing to do.
   if (curfrp->fr_height == height) {
@@ -6306,7 +6308,7 @@ static void frame_setheight(frame_T *curfrp, int height)
     // one.  First check for the minimal height of these.
     int h = frame_minheight(curfrp->fr_parent, NULL);
     height = MAX(height, h);
-    frame_setheight(curfrp->fr_parent, height);
+    frame_setheight(curfrp->fr_parent, height, from_top);
   } else {
     // Column of frames: try to change only frames in this column.
 
@@ -6334,7 +6336,8 @@ static void frame_setheight(frame_T *curfrp, int height)
           room -= frame_minheight(frp, NULL);
         }
       }
-      if (curfrp->fr_width != Columns) {
+      // For bottom-anchored resize, treat cmdline room as zero.
+      if (!from_top || curfrp->fr_width != Columns) {
         room_cmdline = 0;
       } else {
         win_T *wp = lastwin_nofloating(NULL);
@@ -6351,7 +6354,8 @@ static void frame_setheight(frame_T *curfrp, int height)
         break;
       }
       frame_setheight(curfrp->fr_parent, height
-                      + frame_minheight(curfrp->fr_parent, NOWIN) - (int)p_wmh - 1);
+                      + frame_minheight(curfrp->fr_parent, NOWIN) - (int)p_wmh - 1,
+                      from_top);
       // NOTREACHED
     }
 
@@ -6384,9 +6388,10 @@ static void frame_setheight(frame_T *curfrp, int height)
     // that is not enough, takes lines from frames above the current
     // frame.
     for (int run = 0; run < 2; run++) {
-      // 1st run: start with next window
-      // 2nd run: start with prev window
-      frame_T *frp = run == 0 ? curfrp->fr_next : curfrp->fr_prev;
+      // 1st run: from the non-anchored side
+      // 2nd run: the anchored side
+      bool forward = (run == 0) == from_top;
+      frame_T *frp = forward ? curfrp->fr_next : curfrp->fr_prev;
 
       while (frp != NULL && take != 0) {
         int h = frame_minheight(frp, NULL);
@@ -6412,11 +6417,7 @@ static void frame_setheight(frame_T *curfrp, int height)
             take = 0;
           }
         }
-        if (run == 0) {
-          frp = frp->fr_next;
-        } else {
-          frp = frp->fr_prev;
-        }
+        frp = forward ? frp->fr_next : frp->fr_prev;
       }
     }
   }
@@ -6426,10 +6427,10 @@ static void frame_setheight(frame_T *curfrp, int height)
 // fit around it.
 void win_setwidth(int width)
 {
-  win_setwidth_win(width, curwin);
+  win_setwidth_win(width, curwin, true);
 }
 
-void win_setwidth_win(int width, win_T *wp)
+void win_setwidth_win(int width, win_T *wp, bool from_left)
 {
   // Always keep current window at least one column wide, even when
   // 'winminwidth' is zero.
@@ -6443,7 +6444,7 @@ void win_setwidth_win(int width, win_T *wp)
     win_config_float(wp, wp->w_config);
     redraw_later(wp, UPD_NOT_VALID);
   } else {
-    frame_setwidth(wp->w_frame, width + wp->w_vsep_width);
+    frame_setwidth(wp->w_frame, width + wp->w_vsep_width, from_left);
 
     // recompute the window positions
     win_comp_pos();
@@ -6456,7 +6457,7 @@ void win_setwidth_win(int width, win_T *wp)
 // are in the same FR_ROW frame.
 //
 // Strategy is similar to frame_setheight().
-static void frame_setwidth(frame_T *curfrp, int width)
+static void frame_setwidth(frame_T *curfrp, int width, bool from_left)
 {
   // If the width already is the desired value, nothing to do.
   if (curfrp->fr_width == width) {
@@ -6473,7 +6474,7 @@ static void frame_setwidth(frame_T *curfrp, int width)
     // this one.  First check for the minimal width of these.
     int w = frame_minwidth(curfrp->fr_parent, NULL);
     width = MAX(width, w);
-    frame_setwidth(curfrp->fr_parent, width);
+    frame_setwidth(curfrp->fr_parent, width, from_left);
   } else {
     // Row of frames: try to change only frames in this row.
     //
@@ -6508,7 +6509,7 @@ static void frame_setwidth(frame_T *curfrp, int width)
         break;
       }
       frame_setwidth(curfrp->fr_parent, width
-                     + frame_minwidth(curfrp->fr_parent, NOWIN) - (int)p_wmw - 1);
+                     + frame_minwidth(curfrp->fr_parent, NOWIN) - (int)p_wmw - 1, from_left);
     }
 
     // Compute the number of lines we will take from others frames (can be
@@ -6533,9 +6534,10 @@ static void frame_setwidth(frame_T *curfrp, int width)
     // that is not enough, takes lines from frames left of the current
     // frame.
     for (int run = 0; run < 2; run++) {
-      // 1st run: start with next window
-      // 2nd run: start with prev window
-      frame_T *frp = run == 0 ? curfrp->fr_next : curfrp->fr_prev;
+      // 1st run: from the non-anchored side
+      // 2nd run: the anchored side
+      bool forward = (run == 0) == from_left;
+      frame_T *frp = forward ? curfrp->fr_next : curfrp->fr_prev;
 
       while (frp != NULL && take != 0) {
         int w = frame_minwidth(frp, NULL);
@@ -6561,11 +6563,7 @@ static void frame_setwidth(frame_T *curfrp, int width)
             take = 0;
           }
         }
-        if (run == 0) {
-          frp = frp->fr_next;
-        } else {
-          frp = frp->fr_prev;
-        }
+        frp = forward ? frp->fr_next : frp->fr_prev;
       }
     }
   }
diff --git a/test/functional/api/deprecated_spec.lua b/test/functional/api/deprecated_spec.lua
index 976e093c53..8a941e7af7 100644
--- a/test/functional/api/deprecated_spec.lua
+++ b/test/functional/api/deprecated_spec.lua
@@ -7,6 +7,7 @@ local Screen = require('test.functional.ui.screen')
 local clear, eval, eq, ok = n.clear, n.eval, t.eq, t.ok
 local api, command, fn = n.api, n.command, n.fn
 local pcall_err, assert_alive = t.pcall_err, n.assert_alive
+local insert, exec, feed = n.insert, n.exec, n.feed
 
 describe('deprecated', function()
   before_each(n.clear)
@@ -204,4 +205,106 @@ describe('deprecated', function()
       assert_alive()
     end)
   end)
+
+  describe('{get,set}_height', function()
+    it('works', function()
+      command('vsplit')
+      eq(
+        api.nvim_win_get_height(api.nvim_list_wins()[2]),
+        api.nvim_win_get_height(api.nvim_list_wins()[1])
+      )
+      api.nvim_set_current_win(api.nvim_list_wins()[2])
+      command('split')
+      eq(
+        api.nvim_win_get_height(api.nvim_list_wins()[2]),
+        math.floor(api.nvim_win_get_height(api.nvim_list_wins()[1]) / 2)
+      )
+      api.nvim_win_set_height(api.nvim_list_wins()[2], 2)
+      eq(2, api.nvim_win_get_height(api.nvim_list_wins()[2]))
+    end)
+
+    it('failure modes', function()
+      command('split')
+      eq('Invalid window id: 999999', pcall_err(api.nvim_win_set_height, 999999, 10))
+      eq(
+        'Wrong type for argument 2 when calling nvim_win_set_height, expecting Integer',
+        pcall_err(api.nvim_win_set_height, 0, 0.9)
+      )
+    end)
+
+    it('correctly handles height=1', function()
+      command('split')
+      api.nvim_set_current_win(api.nvim_list_wins()[1])
+      api.nvim_win_set_height(api.nvim_list_wins()[2], 1)
+      eq(1, api.nvim_win_get_height(api.nvim_list_wins()[2]))
+    end)
+
+    it('correctly handles height=1 with a winbar', function()
+      command('set winbar=foobar')
+      command('set winminheight=0')
+      command('split')
+      api.nvim_set_current_win(api.nvim_list_wins()[1])
+      api.nvim_win_set_height(api.nvim_list_wins()[2], 1)
+      eq(1, api.nvim_win_get_height(api.nvim_list_wins()[2]))
+    end)
+
+    it('do not cause ml_get errors with foldmethod=expr #19989', function()
+      insert([[
+        aaaaa
+        bbbbb
+        ccccc]])
+      command('set foldmethod=expr')
+      exec([[
+        new
+        let w = nvim_get_current_win()
+        wincmd w
+        call nvim_win_set_height(w, 5)
+      ]])
+      feed('l')
+      eq('', api.nvim_get_vvar('errmsg'))
+    end)
+  end)
+
+  describe('{get,set}_width', function()
+    it('works', function()
+      command('split')
+      eq(
+        api.nvim_win_get_width(api.nvim_list_wins()[2]),
+        api.nvim_win_get_width(api.nvim_list_wins()[1])
+      )
+      api.nvim_set_current_win(api.nvim_list_wins()[2])
+      command('vsplit')
+      eq(
+        api.nvim_win_get_width(api.nvim_list_wins()[2]),
+        math.floor(api.nvim_win_get_width(api.nvim_list_wins()[1]) / 2)
+      )
+      api.nvim_win_set_width(api.nvim_list_wins()[2], 2)
+      eq(2, api.nvim_win_get_width(api.nvim_list_wins()[2]))
+    end)
+
+    it('failure modes', function()
+      command('vsplit')
+      eq('Invalid window id: 999999', pcall_err(api.nvim_win_set_width, 999999, 10))
+      eq(
+        'Wrong type for argument 2 when calling nvim_win_set_width, expecting Integer',
+        pcall_err(api.nvim_win_set_width, 0, 0.9)
+      )
+    end)
+
+    it('do not cause ml_get errors with foldmethod=expr #19989', function()
+      insert([[
+        aaaaa
+        bbbbb
+        ccccc]])
+      command('set foldmethod=expr')
+      exec([[
+        vnew
+        let w = nvim_get_current_win()
+        wincmd w
+        call nvim_win_set_width(w, 5)
+      ]])
+      feed('l')
+      eq('', api.nvim_get_vvar('errmsg'))
+    end)
+  end)
 end)
diff --git a/test/functional/api/window_spec.lua b/test/functional/api/window_spec.lua
index fa2f9ead36..489f54401b 100644
--- a/test/functional/api/window_spec.lua
+++ b/test/functional/api/window_spec.lua
@@ -321,36 +321,172 @@ describe('API/win', function()
     end)
   end)
 
-  describe('{get,set}_height', function()
-    it('works', function()
-      command('vsplit')
-      eq(
-        api.nvim_win_get_height(api.nvim_list_wins()[2]),
-        api.nvim_win_get_height(api.nvim_list_wins()[1])
-      )
-      api.nvim_set_current_win(api.nvim_list_wins()[2])
-      command('split')
-      eq(
-        api.nvim_win_get_height(api.nvim_list_wins()[2]),
-        math.floor(api.nvim_win_get_height(api.nvim_list_wins()[1]) / 2)
-      )
-      api.nvim_win_set_height(api.nvim_list_wins()[2], 2)
-      eq(2, api.nvim_win_get_height(api.nvim_list_wins()[2]))
+  describe('resize', function()
+    local function heights(wins)
+      return vim.tbl_map(api.nvim_win_get_height, wins)
+    end
+    local function widths(wins)
+      return vim.tbl_map(api.nvim_win_get_width, wins)
+    end
+
+    it('height: default anchor="top"', function()
+      command('split | split')
+      local wins = api.nvim_list_wins()
+      local before = heights(wins)
+      api.nvim_win_resize(wins[2], -1, before[2] + 2, {})
+      -- default anchor top.
+      local after = heights(wins)
+      eq(before[1], after[1])
+      eq(before[2] + 2, after[2])
+      eq(before[3] - 2, after[3])
     end)
 
-    it('failure modes', function()
-      command('split')
-      eq('Invalid window id: 999999', pcall_err(api.nvim_win_set_height, 999999, 10))
-      eq(
-        'Wrong type for argument 2 when calling nvim_win_set_height, expecting Integer',
-        pcall_err(api.nvim_win_set_height, 0, 0.9)
-      )
+    it('height: anchor="bottom"', function()
+      command('split | split')
+      local wins = api.nvim_list_wins()
+      local before = heights(wins)
+      api.nvim_win_resize(wins[2], -1, before[2] + 2, { anchor = 'bottom' })
+      local after = heights(wins)
+      -- bottom anchor unchanged.
+      eq(before[1] - 2, after[1])
+      eq(before[2] + 2, after[2])
+      eq(before[3], after[3])
+    end)
+
+    it('height: anchor="bottom" in a nested frame', function()
+      -- layout: column[ Top, row[ML|MR], Bottom ]; current window = ML
+      command('split | split | 2wincmd w | vsplit')
+      local ml = api.nvim_get_current_win()
+      local function row_of(w)
+        return fn.win_screenpos(fn.win_id2win(w))[1]
+      end
+      local top, bottom
+      for _, w in ipairs(api.nvim_list_wins()) do
+        if row_of(w) == 1 then
+          top = w
+        end
+        if not bottom or row_of(w) > row_of(bottom) then
+          bottom = w
+        end
+      end
+      local top_h = api.nvim_win_get_height(top)
+      local bottom_h = api.nvim_win_get_height(bottom)
+      api.nvim_win_resize(ml, -1, api.nvim_win_get_height(ml) + 3, { anchor = 'bottom' })
+      -- "bottom" grow the row upward, taking from Top, not Bottom
+      eq(top_h - 3, api.nvim_win_get_height(top))
+      eq(bottom_h, api.nvim_win_get_height(bottom))
+    end)
+
+    it('height: anchor="bottom" with borrowing', function()
+      -- column[ Wupper, row[ col[Ltop|Ltarget], Right ], Wlower ]; current = Ltarget.
+      -- Growing Ltarget more than Ltop can supply forces us to borrow from row
+      -- and row's growth must respect given anchor.
+      command('split | split | 2wincmd w | vsplit | split | wincmd j')
+      local target = api.nvim_get_current_win()
+      local function row_of(w)
+        return fn.win_screenpos(fn.win_id2win(w))[1]
+      end
+      local wupper, wlower
+      for _, w in ipairs(api.nvim_list_wins()) do
+        if row_of(w) == 1 then
+          wupper = w
+        end
+        if not wlower or row_of(w) > row_of(wlower) then
+          wlower = w
+        end
+      end
+      local wupper_h = api.nvim_win_get_height(wupper)
+      local wlower_h = api.nvim_win_get_height(wlower)
+      api.nvim_win_resize(target, -1, api.nvim_win_get_height(target) + 6, { anchor = 'bottom' })
+      -- must borrow from above.
+      ok(api.nvim_win_get_height(wupper) < wupper_h)
+      eq(wlower_h, api.nvim_win_get_height(wlower))
+    end)
+
+    it('width: default anchor="left"', function()
+      command('vsplit | vsplit')
+      local wins = api.nvim_list_wins()
+      local before = widths(wins)
+      api.nvim_win_resize(wins[2], before[2] + 4, -1, {})
+      local after = widths(wins)
+      eq(before[1], after[1])
+      eq(before[2] + 4, after[2])
+      eq(before[3] - 4, after[3])
+    end)
+
+    it('width: anchor="right"', function()
+      command('vsplit | vsplit')
+      local wins = api.nvim_list_wins()
+      local before = widths(wins)
+      api.nvim_win_resize(wins[2], before[2] + 4, -1, { anchor = 'right' })
+      local after = widths(wins)
+      eq(before[1] - 4, after[1])
+      eq(before[2] + 4, after[2])
+      eq(before[3], after[3])
+    end)
+
+    it('width: anchor="right" a nested frame', function()
+      -- layout: row[ Left, col[MT|MB], Right ]; current window = MT
+      command('vsplit | vsplit | 2wincmd w | split')
+      local mt = api.nvim_get_current_win()
+      local function col_of(w)
+        return fn.win_screenpos(fn.win_id2win(w))[2]
+      end
+      local left, right
+      for _, w in ipairs(api.nvim_list_wins()) do
+        if col_of(w) == 1 then
+          left = w
+        end
+        if not right or col_of(w) > col_of(right) then
+          right = w
+        end
+      end
+      local left_w = api.nvim_win_get_width(left)
+      local right_w = api.nvim_win_get_width(right)
+      api.nvim_win_resize(mt, api.nvim_win_get_width(mt) + 3, -1, { anchor = 'right' })
+      -- "right" must grow the column leftward, taking from Left, not Right
+      eq(left_w - 3, api.nvim_win_get_width(left))
+      eq(right_w, api.nvim_win_get_width(right))
+    end)
+
+    it('sets both height and width in a single call', function()
+      -- layout: column[ Top, row[ML|MR], Bottom ]; current = ML.
+      command('split | split | 2wincmd w | vsplit')
+      local ml = api.nvim_get_current_win()
+      local function row_of(w)
+        return fn.win_screenpos(fn.win_id2win(w))[1]
+      end
+      local top, bottom, mr
+      for _, w in ipairs(api.nvim_list_wins()) do
+        if row_of(w) == 1 then
+          top = w
+        end
+        if not bottom or row_of(w) > row_of(bottom) then
+          bottom = w
+        end
+        if row_of(w) == row_of(ml) and w ~= ml then
+          mr = w
+        end
+      end
+      local top_h = api.nvim_win_get_height(top)
+      local bottom_h = api.nvim_win_get_height(bottom)
+      local mr_w = api.nvim_win_get_width(mr)
+      local h, w = api.nvim_win_get_height(ml), api.nvim_win_get_width(ml)
+      -- "bottom" anchors the height axis; width has no matching anchor so it defaults to "left"
+      api.nvim_win_resize(ml, w - 4, h + 2, { anchor = 'bottom' })
+      eq(h + 2, api.nvim_win_get_height(ml))
+      eq(w - 4, api.nvim_win_get_width(ml))
+      -- height took from above
+      eq(top_h - 2, api.nvim_win_get_height(top))
+      eq(bottom_h, api.nvim_win_get_height(bottom))
+      -- width default to "left"
+      eq(mr_w + 4, api.nvim_win_get_width(mr))
     end)
 
     it('correctly handles height=1', function()
       command('split')
       api.nvim_set_current_win(api.nvim_list_wins()[1])
-      api.nvim_win_set_height(api.nvim_list_wins()[2], 1)
+      api.nvim_win_resize(api.nvim_list_wins()[2], -1, 1, {})
       eq(1, api.nvim_win_get_height(api.nvim_list_wins()[2]))
     end)
 
@@ -359,11 +495,11 @@ describe('API/win', function()
       command('set winminheight=0')
       command('split')
       api.nvim_set_current_win(api.nvim_list_wins()[1])
-      api.nvim_win_set_height(api.nvim_list_wins()[2], 1)
+      api.nvim_win_resize(api.nvim_list_wins()[2], -1, 1, {})
       eq(1, api.nvim_win_get_height(api.nvim_list_wins()[2]))
     end)
 
-    it('do not cause ml_get errors with foldmethod=expr #19989', function()
+    it('does not cause ml_get errors with foldmethod=expr #19989', function()
       insert([[
         aaaaa
         bbbbb
@@ -373,53 +509,48 @@ describe('API/win', function()
         new
         let w = nvim_get_current_win()
         wincmd w
-        call nvim_win_set_height(w, 5)
+        call nvim_win_resize(w, -1, 5, #{})
       ]])
       feed('l')
       eq('', api.nvim_get_vvar('errmsg'))
     end)
-  end)
 
-  describe('{get,set}_width', function()
-    it('works', function()
-      command('split')
-      eq(
-        api.nvim_win_get_width(api.nvim_list_wins()[2]),
-        api.nvim_win_get_width(api.nvim_list_wins()[1])
-      )
-      api.nvim_set_current_win(api.nvim_list_wins()[2])
-      command('vsplit')
-      eq(
-        api.nvim_win_get_width(api.nvim_list_wins()[2]),
-        math.floor(api.nvim_win_get_width(api.nvim_list_wins()[1]) / 2)
-      )
-      api.nvim_win_set_width(api.nvim_list_wins()[2], 2)
-      eq(2, api.nvim_win_get_width(api.nvim_list_wins()[2]))
-    end)
+    it(
+      'accepts size = 0 (clamp to minimum size). Compatible with deprecated set_height/width',
+      function()
+        command('set winminheight=1')
+        command('split')
+        api.nvim_set_current_win(api.nvim_list_wins()[1])
+        api.nvim_win_resize(api.nvim_list_wins()[2], -1, 0, {})
+        eq(1, api.nvim_win_get_height(api.nvim_list_wins()[2]))
+      end
+    )
 
     it('failure modes', function()
-      command('vsplit')
-      eq('Invalid window id: 999999', pcall_err(api.nvim_win_set_width, 999999, 10))
+      command('split')
       eq(
-        'Wrong type for argument 2 when calling nvim_win_set_width, expecting Integer',
-        pcall_err(api.nvim_win_set_width, 0, 0.9)
+        "Required: must set at least one of 'height', 'width'",
+        pcall_err(api.nvim_win_resize, 0, -1, -1, {})
       )
-    end)
-
-    it('do not cause ml_get errors with foldmethod=expr #19989', function()
-      insert([[
-        aaaaa
-        bbbbb
-        ccccc]])
-      command('set foldmethod=expr')
-      exec([[
-        vnew
-        let w = nvim_get_current_win()
-        wincmd w
-        call nvim_win_set_width(w, 5)
-      ]])
-      feed('l')
-      eq('', api.nvim_get_vvar('errmsg'))
+      eq(
+        "Invalid 'width': expected a non-negative count of columns, or -1 for no change",
+        pcall_err(api.nvim_win_resize, 0, -2, 5, {})
+      )
+      eq(
+        "Invalid 'height': expected a non-negative count of rows, or -1 for no change",
+        pcall_err(api.nvim_win_resize, 0, 5, -2, {})
+      )
+      -- anchor not applicable to the dimension(s) being changed
+      eq(
+        "Conflict: 'left' not allowed with this dimension",
+        pcall_err(api.nvim_win_resize, 0, -1, 5, { anchor = 'left' })
+      )
+      -- unrecognized anchor value
+      eq(
+        [[Invalid 'anchor': expected "top", "bottom", "left" or "right", got garbage]],
+        pcall_err(api.nvim_win_resize, 0, -1, 5, { anchor = 'garbage' })
+      )
+      eq('Invalid window id: 999999', pcall_err(api.nvim_win_resize, 999999, 5, -1, {}))
     end)
   end)