From 9d25965adf0e0f132d10a0c9fbc545d595b8a31a Mon Sep 17 00:00:00 2001
From: Seong Yong-ju <sei40kr@gmail.com>
Date: Mon, 20 Apr 2026 14:04:26 +0900
Subject: [PATCH] fix(cli): apply focus to tmux pane for external sessions
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Adds `Session:focus()`, `Session:is_focused()`, and `Session:blur()`
backend hooks with tmux implementations, and unifies the UI layer to
dispatch through `state.session:*`. `Terminal` is already a `Session`
backend so `state.terminal === state.session` for terminal-backed
sessions — the same calls cover both paths.

tmux:
- focus: select-window then select-pane (window switch handles
  create="window", select-pane handles the pane within the window)
- is_focused: compare client_active_pane with the pane id
- blur: switch back to the editor pane via $TMUX_PANE

Also fixes the default-focus asymmetry in `M.attach`: external focus
now fires on `opts.show and opts.focus ~= false` to match terminal,
so `send()` and `toggle()` (no args) focus external panes the same
way they focus terminals.

Closes folke/sidekick.nvim#179.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
---
 lua/sidekick/cli/init.lua         | 21 +++++++--------
 lua/sidekick/cli/session/init.lua | 12 +++++++++
 lua/sidekick/cli/session/tmux.lua | 43 +++++++++++++++++++++++++++++++
 lua/sidekick/cli/state.lua        | 16 ++++++------
 4 files changed, 72 insertions(+), 20 deletions(-)

diff --git a/lua/sidekick/cli/init.lua b/lua/sidekick/cli/init.lua
index 9c0e9b50..5cfa62cd 100644
--- a/lua/sidekick/cli/init.lua
+++ b/lua/sidekick/cli/init.lua
@@ -100,14 +100,14 @@ end
 function M.toggle(opts)
   opts = filter_opts(opts)
   State.with(function(state, attached)
-    if not state.terminal then
-      return
-    end
-    if not attached then
+    if state.terminal and not attached then
       state.terminal:toggle()
     end
-    if state.terminal:is_open() and opts.focus ~= false then
-      state.terminal:focus()
+    if opts.focus == false then
+      return
+    end
+    if state.external or (state.terminal and state.terminal:is_open()) then
+      state.session:focus()
     end
   end, {
     attach = true,
@@ -121,13 +121,10 @@ end
 function M.focus(opts)
   opts = filter_opts(opts)
   State.with(function(state)
-    if not state.terminal then
-      return
-    end
-    if state.terminal:is_focused() then
-      state.terminal:blur()
+    if state.session:is_focused() then
+      state.session:blur()
     else
-      state.terminal:focus()
+      state.session:focus()
     end
   end, {
     attach = true,
diff --git a/lua/sidekick/cli/session/init.lua b/lua/sidekick/cli/session/init.lua
index 1c598924..78701748 100644
--- a/lua/sidekick/cli/session/init.lua
+++ b/lua/sidekick/cli/session/init.lua
@@ -52,6 +52,18 @@ function B:attach() end
 --- Detach from an existing session
 function B:detach() end
 
+--- Focus the session
+function B:focus() end
+
+--- Whether the session currently has user focus
+---@return boolean
+function B:is_focused()
+  return false
+end
+
+--- Move focus away from the session
+function B:blur() end
+
 --- Start a new session
 --- If the backend returns a Cmd, a new terminal session will be spawned
 ---@return sidekick.cli.terminal.Cmd?
diff --git a/lua/sidekick/cli/session/tmux.lua b/lua/sidekick/cli/session/tmux.lua
index 942ed7d1..788f4472 100644
--- a/lua/sidekick/cli/session/tmux.lua
+++ b/lua/sidekick/cli/session/tmux.lua
@@ -195,4 +195,47 @@ function M:dump()
   return ret
 end
 
+---Focus the tmux pane
+function M:focus()
+  local pane_id = self:pane_id()
+  if not pane_id then
+    return
+  end
+  -- select-window first so create="window" switches the client to the pane's window;
+  -- no-op for create="split" where the pane is already in the current window.
+  Util.exec({ "tmux", "select-window", "-t", pane_id })
+  Util.exec({ "tmux", "select-pane", "-t", pane_id })
+end
+
+---Whether this tmux pane is the active pane of the calling client
+---@return boolean
+function M:is_focused()
+  local pane_id = self:pane_id()
+  if not pane_id then
+    return false
+  end
+  local lines = Util.exec({
+    "tmux",
+    "display-message",
+    "-p",
+    "-t",
+    pane_id,
+    "#{==:#{client_active_pane},#{pane_id}}",
+  }, { notify = false })
+  return lines ~= nil and lines[1] == "1"
+end
+
+---Send focus back to the editor pane (identified via $TMUX_PANE)
+function M:blur()
+  if not self:is_focused() then
+    return
+  end
+  local editor_pane = vim.env.TMUX_PANE
+  if not editor_pane then
+    return
+  end
+  Util.exec({ "tmux", "select-window", "-t", editor_pane }, { notify = false })
+  Util.exec({ "tmux", "select-pane", "-t", editor_pane }, { notify = false })
+end
+
 return M
diff --git a/lua/sidekick/cli/state.lua b/lua/sidekick/cli/state.lua
index 01f1f3e3..3c996d04 100644
--- a/lua/sidekick/cli/state.lua
+++ b/lua/sidekick/cli/state.lua
@@ -187,14 +187,14 @@ function M.attach(state, opts)
 
   state = M.get_state(session) -- update state
   local terminal = state.terminal
-  if terminal then
-    if opts.show then
-      terminal:show()
-      if opts.focus ~= false and terminal:is_running() then
-        terminal:focus()
-      end
-    end
-  elseif attached then
+  if terminal and opts.show then
+    terminal:show()
+  end
+  local visible = state.external or (terminal and terminal:is_running())
+  if opts.show and opts.focus ~= false and visible then
+    session:focus()
+  end
+  if not terminal and attached then
     Util.info("Attached to `" .. state.tool.name .. "`")
   end
   return state, attached