diff --git a/README.md b/README.md
index 8498111..31f1a8b 100644
--- a/README.md
+++ b/README.md
@@ -129,6 +129,7 @@ Defaults inside popup windows:
 - `<C-t>` — promote to new tab
 - `<leader>os` — open stack view
 - `<C-z>` — toggle zoom (maximize top popup)
+- `<C-w>h/j/k/l` — navigate to adjacent split window
 
 Defaults in stack view:
 
diff --git a/doc/peekstack.txt b/doc/peekstack.txt
index 8fe0c06..d55ac17 100644
--- a/doc/peekstack.txt
+++ b/doc/peekstack.txt
@@ -505,6 +505,7 @@ Default keymaps inside popup windows:
     `<C-t>`       Promote to new tab
     `<leader>os`  Toggle the stack view panel
     `<C-z>`       Toggle zoom (maximize top popup)
+    `<C-w>h/j/k/l`  Navigate to the adjacent split window
 
 Stack view keymaps:
 
diff --git a/lua/peekstack/core/stack.lua b/lua/peekstack/core/stack.lua
index f2002ef..e2a2305 100644
--- a/lua/peekstack/core/stack.lua
+++ b/lua/peekstack/core/stack.lua
@@ -37,6 +37,26 @@ local suppress_win_events = false
 local popup_by_id = {}
 ---@type table<integer, PeekstackPopupLookupEntry>
 local popup_by_winid = {}
+---@param winid? integer
+---@return integer
+local get_root_winid
+
+---@param model PeekstackPopupModel
+---@return integer?
+local function resolve_ephemeral_root_winid(model)
+  if not model or not model.origin then
+    return nil
+  end
+  local origin_winid = model.origin.winid
+  if type(origin_winid) ~= "number" or not vim.api.nvim_win_is_valid(origin_winid) then
+    return nil
+  end
+  local ok_root, root_winid = pcall(get_root_winid, origin_winid)
+  if ok_root and type(root_winid) == "number" and vim.api.nvim_win_is_valid(root_winid) then
+    return root_winid
+  end
+  return nil
+end
 
 ---@param model PeekstackPopupModel
 local function unindex_popup(model)
@@ -145,7 +165,7 @@ local function lookup_by_winid(winid)
 
   for _, item in pairs(ephemerals) do
     if item.winid == winid then
-      index_popup(item, nil)
+      index_popup(item, resolve_ephemeral_root_winid(item))
       return popup_by_winid[winid]
     end
   end
@@ -161,7 +181,7 @@ end
 ---@param model PeekstackPopupModel
 local function register_ephemeral(model)
   ephemerals[model.id] = model
-  index_popup(model, nil)
+  index_popup(model, resolve_ephemeral_root_winid(model))
 end
 
 ---@param id integer
@@ -180,7 +200,7 @@ local function find_ephemeral(id)
     return id, ephemerals[id]
   end
   local entry = lookup_by_winid(id)
-  if entry and entry.root_winid == nil then
+  if entry and entry.popup and entry.popup.ephemeral then
     return entry.popup.id, entry.popup
   end
   return nil
@@ -190,7 +210,7 @@ end
 --- floating window, walk through the stacks to find its origin window instead.
 ---@param winid? integer
 ---@return integer
-local function get_root_winid(winid)
+get_root_winid = function(winid)
   local wid = winid or vim.api.nvim_get_current_win()
   local win_cfg = vim.api.nvim_win_get_config(wid)
   if win_cfg.relative == "" then
@@ -988,6 +1008,14 @@ function M.focused_id(winid)
   return stack.focused_id
 end
 
+--- Public wrapper for get_root_winid – used by keymaps to resolve the
+--- non-floating owner window for the current (or given) window.
+---@param winid? integer
+---@return integer
+function M.get_root_winid(winid)
+  return get_root_winid(winid)
+end
+
 --- Reset all stacks (for testing).
 function M._reset()
   stacks = {}
diff --git a/lua/peekstack/ui/keymaps.lua b/lua/peekstack/ui/keymaps.lua
index 2ca0eab..888055f 100644
--- a/lua/peekstack/ui/keymaps.lua
+++ b/lua/peekstack/ui/keymaps.lua
@@ -15,6 +15,19 @@ local function map(bufnr, lhs, rhs, desc)
   vim.keymap.set("n", lhs, rhs, { buffer = bufnr, nowait = true, silent = true, desc = desc })
 end
 
+--- Navigate from a popup to an adjacent split window.
+--- Moves focus back to the root (non-floating) window first, then executes
+--- wincmd in the given direction.
+---@param direction string  one of "h", "j", "k", "l"
+local function nav_to_split(direction)
+  local stack = require("peekstack.core.stack")
+  local root = stack.get_root_winid()
+  if root and vim.api.nvim_win_is_valid(root) then
+    vim.api.nvim_set_current_win(root)
+  end
+  vim.api.nvim_cmd({ cmd = "wincmd", args = { direction } }, {})
+end
+
 --- Resolve the current popup by looking up its id in the stack.
 --- This avoids holding a stale reference to a popup object.
 ---@param popup_id integer
@@ -94,6 +107,22 @@ function M.apply_popup(popup)
     local stack = require("peekstack.core.stack")
     stack.toggle_zoom()
   end, "Peekstack zoom")
+
+  -- Window navigation: <C-w>h/j/k/l to move from popup to adjacent split.
+  -- These are hardcoded (not in ui.keys) because they restore standard Vim
+  -- window-navigation behaviour that floating windows would otherwise break.
+  map(popup.bufnr, "<C-w>h", function()
+    nav_to_split("h")
+  end, "Peekstack navigate left")
+  map(popup.bufnr, "<C-w>j", function()
+    nav_to_split("j")
+  end, "Peekstack navigate down")
+  map(popup.bufnr, "<C-w>k", function()
+    nav_to_split("k")
+  end, "Peekstack navigate up")
+  map(popup.bufnr, "<C-w>l", function()
+    nav_to_split("l")
+  end, "Peekstack navigate right")
 end
 
 return M
diff --git a/tests/popup_source_mode_spec.lua b/tests/popup_source_mode_spec.lua
index dbc2810..b84736a 100644
--- a/tests/popup_source_mode_spec.lua
+++ b/tests/popup_source_mode_spec.lua
@@ -134,6 +134,68 @@ describe("popup source mode", function()
     vim.fn.delete(temp)
   end)
 
+  it("installs <C-w>hjkl navigation keymaps on copy-mode popups", function()
+    local loc = make_location()
+    local model = popup.create(loc, { buffer_mode = "copy" })
+    assert.is_not_nil(model)
+    assert.is_true(has_buffer_map(model.bufnr, "<C-W>h"))
+    assert.is_true(has_buffer_map(model.bufnr, "<C-W>j"))
+    assert.is_true(has_buffer_map(model.bufnr, "<C-W>k"))
+    assert.is_true(has_buffer_map(model.bufnr, "<C-W>l"))
+    popup.close(model)
+  end)
+
+  it("<C-w>l navigates from popup to adjacent split", function()
+    -- Create a vertical split so there are two windows.
+    vim.api.nvim_cmd({ cmd = "vsplit" }, {})
+    local left_win = vim.api.nvim_get_current_win()
+    -- Move to the right split.
+    vim.api.nvim_cmd({ cmd = "wincmd", args = { "l" } }, {})
+    local right_win = vim.api.nvim_get_current_win()
+    assert.is_not.equals(left_win, right_win)
+
+    -- Open a popup anchored to the right split.
+    local loc = make_location()
+    local model = stack.push(loc)
+    assert.is_not_nil(model)
+    -- Focus the popup (simulates user entering the floating window).
+    vim.api.nvim_set_current_win(model.winid)
+    assert.equals(model.winid, vim.api.nvim_get_current_win())
+
+    -- Execute the <C-w>h keymap callback: should land on the left split.
+    vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<C-w>h", true, false, true), "x", false)
+    assert.equals(left_win, vim.api.nvim_get_current_win())
+
+    -- Cleanup
+    stack.close(model.id)
+    vim.api.nvim_set_current_win(right_win)
+    vim.api.nvim_cmd({ cmd = "close" }, {})
+  end)
+
+  it("does not install <C-w>hjkl navigation keymaps on source-mode popups", function()
+    local temp = vim.fn.tempname() .. ".lua"
+    vim.fn.writefile({ "print('peekstack')" }, temp)
+    vim.api.nvim_cmd({ cmd = "edit", args = { temp } }, {})
+    local source_bufnr = vim.api.nvim_get_current_buf()
+
+    local model = popup.create({
+      uri = vim.uri_from_fname(temp),
+      range = { start = { line = 0, character = 0 }, ["end"] = { line = 0, character = 0 } },
+      provider = "test",
+    }, {
+      buffer_mode = "source",
+    })
+
+    assert.is_not_nil(model)
+    assert.is_false(has_buffer_map(source_bufnr, "<C-W>h"))
+    assert.is_false(has_buffer_map(source_bufnr, "<C-W>j"))
+    assert.is_false(has_buffer_map(source_bufnr, "<C-W>k"))
+    assert.is_false(has_buffer_map(source_bufnr, "<C-W>l"))
+
+    popup.close(model)
+    vim.fn.delete(temp)
+  end)
+
   it("deletes copy-mode scratch buffer when render.open fails", function()
     local render = require("peekstack.ui.render")
     local loc = make_location()
diff --git a/tests/quick_peek_spec.lua b/tests/quick_peek_spec.lua
index a6e8052..35f08d8 100644
--- a/tests/quick_peek_spec.lua
+++ b/tests/quick_peek_spec.lua
@@ -113,6 +113,34 @@ describe("peekstack.quick_peek", function()
     assert.is_nil(stack._ephemerals()[model.id])
   end)
 
+  it("keeps split navigation root for quick peek popups", function()
+    local location = {
+      uri = vim.uri_from_bufnr(0),
+      range = { start = { line = 0, character = 0 }, ["end"] = { line = 0, character = 10 } },
+      provider = "test",
+    }
+
+    vim.api.nvim_cmd({ cmd = "vsplit" }, {})
+    vim.api.nvim_cmd({ cmd = "vsplit" }, {})
+    vim.api.nvim_cmd({ cmd = "wincmd", args = { "h" } }, {})
+    vim.api.nvim_cmd({ cmd = "wincmd", args = { "h" } }, {})
+    vim.api.nvim_cmd({ cmd = "wincmd", args = { "l" } }, {})
+    local middle_win = vim.api.nvim_get_current_win()
+    vim.api.nvim_cmd({ cmd = "wincmd", args = { "l" } }, {})
+    local right_win = vim.api.nvim_get_current_win()
+
+    vim.api.nvim_set_current_win(middle_win)
+    local model = stack.push(location, { stack = false })
+    assert.is_not_nil(model)
+    vim.api.nvim_set_current_win(model.winid)
+
+    vim.api.nvim_feedkeys(vim.api.nvim_replace_termcodes("<C-w>l", true, false, true), "x", false)
+    assert.equals(right_win, vim.api.nvim_get_current_win())
+
+    assert.is_true(stack.close(model.id))
+    vim.api.nvim_cmd({ cmd = "only" }, {})
+  end)
+
   it("should handle normal peek mode", function()
     local location = {
       uri = vim.uri_from_bufnr(0),