diff --git a/.claude/CLAUDE.md b/.claude/CLAUDE.md
index 127f7b0..32a7764 100644
--- a/.claude/CLAUDE.md
+++ b/.claude/CLAUDE.md
@@ -8,6 +8,7 @@ tmux-binding-help is a tmux plugin that displays an interactive popup showing al
 
 Tests use [Scrut](https://github.com/facebookincubator/scrut), a snapshot testing tool:
 
+```
 make test
 ```
 
diff --git a/.github/shell.instructions.md b/.github/shell.instructions.md
index b2ee38e..6e7c03b 100644
--- a/.github/shell.instructions.md
+++ b/.github/shell.instructions.md
@@ -6,3 +6,4 @@ applyTo: "**/*.sh"
 - **Single-quoted path interpolation in tmux commands**: Embedding `$CURRENT_DIR` inside single-quoted segments of tmux `display-popup` command strings is intentional. The variable is expanded by the outer shell before tmux receives the command. This is the conventional tmux plugin approach.
 - **Repeated simple function calls over loop abstractions**: When a function like `move_up` or `move_down` is called a small fixed number of times (e.g., 3), repeating the call is preferred over a loop or helper. This is more readable in Bash and avoids unnecessary abstraction for trivial repetition. Do not suggest extracting loops or helpers for small fixed-count call sequences.
 - **Parsed-but-not-persisted variables are intentional**: When a parsed value (e.g., a mouse column coordinate) is used only for validation and not stored in a global, this is intentional. Do not flag it as unused. The variable serves its purpose during parsing/validation and does not need to be persisted if no downstream code requires it.
+- **POPUP_WIDTH - 2 for TERM_COLS is intentional**: In `viewer.sh`, `TERM_COLS` is preferentially set to `POPUP_WIDTH - 2` (outer popup width minus border) rather than `stty size` columns. Both values represent the same inner content width inside a tmux popup. Using the passed-in `POPUP_WIDTH` is preferred because it is a known value from `popup.sh`; `stty size` is the fallback when `POPUP_WIDTH` is not available. Do not suggest replacing `POPUP_WIDTH - 2` with `stty size` columns.
diff --git a/docs/plans/done/2026-02-08-close-popup-on-outside-click.md b/docs/plans/done/2026-02-08-close-popup-on-outside-click.md
new file mode 100644
index 0000000..7e1c692
--- /dev/null
+++ b/docs/plans/done/2026-02-08-close-popup-on-outside-click.md
@@ -0,0 +1,69 @@
+# Close Popup by Clicking Outside
+
+## Context
+
+The tmux-binding-help popup currently only closes via keyboard (`q` or `Escape`). Users expect to be able to click outside the popup to dismiss it, as is standard for overlay/popup UIs. In tmux 3.4+, the popup may already close on outside click at the tmux level, but for tmux 3.2-3.3 the click may be forwarded to the viewer's PTY with out-of-bounds coordinates. Adding viewer-level detection of these out-of-bounds coordinates provides coverage across tmux versions.
+
+## Changes
+
+All changes are in **`scripts/viewer.sh`** (3 edits, ~10 lines changed).
+
+### 1. Include column in the MOUSE_LEFT token (line 523)
+
+```bash
+# Before:
+0) printf 'MOUSE_LEFT:%d' "$mouse_row" ;;
+
+# After:
+0) printf 'MOUSE_LEFT:%d:%d' "$mouse_row" "$mouse_col" ;;
+```
+
+The column is already parsed and validated at line 510-518 but currently discarded. This makes it available to the main loop.
+
+### 2. Extract both row and column in the main loop (lines 589-594)
+
+```bash
+# Before:
+    # Extract mouse row from MOUSE_LEFT:ROW token
+    local mouse_row=0
+    if [[ "$key" == MOUSE_LEFT:* ]]; then
+      mouse_row="${key#MOUSE_LEFT:}"
+      key="MOUSE_LEFT"
+    fi
+
+# After:
+    # Extract mouse row and column from MOUSE_LEFT:ROW:COL token
+    local mouse_row=0 mouse_col=0
+    if [[ "$key" == MOUSE_LEFT:* ]]; then
+      local mouse_coords="${key#MOUSE_LEFT:}"
+      mouse_row="${mouse_coords%%:*}"
+      mouse_col="${mouse_coords#*:}"
+      key="MOUSE_LEFT"
+    fi
+```
+
+### 3. Add boundary check before mode dispatch (insert after line 594, before line 596)
+
+```bash
+    # Close popup on click outside content area
+    if [[ "$key" == "MOUSE_LEFT" ]] && ((mouse_row > TERM_ROWS || mouse_col > TERM_COLS)); then
+      break
+    fi
+```
+
+Placed before the search-mode/normal-mode `if`, so it applies regardless of current mode. The `break` exits the main loop, triggering `cleanup()` via the EXIT trap, and the popup closes via `-E`.
+
+Coordinates < 1 are already rejected as `MOUSE_OTHER` in `read_key()` (line 516), so only the upper-bound check is needed here.
+
+## What does not change
+
+- `click_select()`, scroll events, `popup.sh`, `cleanup()`, release/other mouse events
+- No new dependencies or version requirements
+
+## Verification
+
+1. Open the popup, click outside it -- popup should close
+2. Click inside on bindings, group headers, search bar, footer, empty area -- all should work as before
+3. Enter search mode, click outside -- popup should close
+4. Scroll inside popup -- should work as before
+5. `make test` -- existing parser tests should pass
diff --git a/scripts/viewer.sh b/scripts/viewer.sh
index 2809741..cce53aa 100755
--- a/scripts/viewer.sh
+++ b/scripts/viewer.sh
@@ -504,7 +504,7 @@ read_key() {
         # Strip modifier bits (shift=4, meta=8, ctrl=16)
         mouse_button=$((mouse_button & ~(4 | 8 | 16)))
         case "$mouse_button" in
-        0) printf 'MOUSE_LEFT:%d' "$mouse_row" ;;
+        0) printf 'MOUSE_LEFT:%d:%d' "$mouse_row" "$mouse_col" ;;
         64) printf 'MOUSE_SCROLL_UP' ;;
         65) printf 'MOUSE_SCROLL_DOWN' ;;
         *) printf 'MOUSE_OTHER' ;;
@@ -570,13 +570,20 @@ main() {
 
     key="$(read_key)" || continue
 
-    # Extract mouse row from MOUSE_LEFT:ROW token
-    local mouse_row=0
+    # Extract mouse row and column from MOUSE_LEFT:ROW:COL token
+    local mouse_row=0 mouse_col=0
     if [[ "$key" == MOUSE_LEFT:* ]]; then
-      mouse_row="${key#MOUSE_LEFT:}"
+      local mouse_coords="${key#MOUSE_LEFT:}"
+      mouse_row="${mouse_coords%%:*}"
+      mouse_col="${mouse_coords#*:}"
       key="MOUSE_LEFT"
     fi
 
+    # Close popup on click outside content area
+    if [[ "$key" == "MOUSE_LEFT" ]] && ((mouse_row > TERM_ROWS || mouse_col > TERM_COLS)); then
+      break
+    fi
+
     if ((SEARCH_MODE)); then
       case "$key" in
       ENTER | DOWN)