diff --git a/.claude/skills/test-forestui/SKILL.md b/.claude/skills/test-forestui/SKILL.md
index 90460d5..0cf1853 100644
--- a/.claude/skills/test-forestui/SKILL.md
+++ b/.claude/skills/test-forestui/SKILL.md
@@ -1,6 +1,6 @@
 ---
 name: test-forestui
-description: Use tu to visually drive and test forestui in headless terminals. Invoke when developing forestui features, debugging UI issues, or verifying changes — lets you see and interact with the running app yourself.
+description: Use tu to visually drive and test forestui in headless terminals. Invoke PROACTIVELY when fixing behavioral/visual bugs or developing new features — don't wait to be asked. Lint and typecheck can't catch UI regressions, wrong window names, or broken interactions.
 allowed-tools: Bash, Read
 argument-hint: "[what to test or verify]"
 ---
@@ -35,9 +35,10 @@ If no `.tmux.conf`: defaults are prefix `Ctrl+B`, next `Ctrl+B n`, prev `Ctrl+B
 ## How to launch forestui
 
 **NEVER run `uv run forestui` or any tmux command without `TMUX_TMPDIR` isolation.**
-The user is likely running their own tmux/forestui session right now. If you
-connect to the default tmux server you will interfere with their live session —
-creating windows, switching their active view, or corrupting their session state.
+**NEVER call `tmux` directly from Bash** — not even with `TMUX_TMPDIR` set. The
+user is likely running their own tmux/forestui session right now. Any direct
+`tmux` call risks connecting to (and corrupting) their live session. ALL
+interaction with the test tmux must go through `tu` commands.
 
 ```bash
 FUI_TEST_DIR=$(mktemp -d)
@@ -48,6 +49,32 @@ tu run --name fui --env TMUX_TMPDIR=$FUI_TEST_DIR \
 tu wait --name fui --text "forestui" --timeout 15000
 ```
 
+### When you need to detach and reattach
+
+If your test involves detaching from tmux and re-running `forestui` (e.g.,
+testing reattach behavior), do NOT launch forestui directly as the `tu` process.
+Instead, launch a **bash shell** inside `tu` and run forestui from it. This way,
+when tmux detaches, bash gets its prompt back and you can run forestui again:
+
+```bash
+tu run --name fui --env TMUX_TMPDIR=$FUI_TEST_DIR \
+  --cwd <project-root> -- env -u TMUX bash -l
+
+# Wait for bash prompt, then start forestui
+tu wait --name fui --text "\\$" --timeout 5000
+tu type --name fui "uv run forestui"
+tu press --name fui Enter
+
+# ... do your test, detach with Ctrl+A d ...
+# After detach, bash prompt returns. Run forestui again:
+tu wait --name fui --text "\\$" --timeout 5000
+tu type --name fui "uv run forestui"
+tu press --name fui Enter
+```
+
+Why: forestui calls `os.execvp("tmux", ...)` to enter tmux. If forestui IS the
+`tu` process, detaching kills the tu session (no shell to return to).
+
 Need multiple terminals (e.g., testing grouped sessions)? Use the same
 `TMUX_TMPDIR` so they share the same isolated tmux server:
 
@@ -85,6 +112,11 @@ each session is viewing.
 
 Use the bindings from `.tmux.conf`. Translate to `tu press` yourself.
 
+**Gotcha — renaming windows.** Check `.tmux.conf` for the rename-window binding.
+If it uses `command-prompt -I "#W"`, the prompt is pre-filled with the current
+window name — press `Ctrl+U` to clear before typing. If it uses
+`command-prompt` without `-I`, the prompt starts empty and you can type directly.
+
 ### Text input
 
 ```bash
diff --git a/.github/workflows/check.yml b/.github/workflows/check.yml
new file mode 100644
index 0000000..bc8c745
--- /dev/null
+++ b/.github/workflows/check.yml
@@ -0,0 +1,24 @@
+name: Check
+
+on:
+  push:
+    branches: [main]
+  pull_request:
+
+jobs:
+  check:
+    name: Lint & Typecheck
+    runs-on: ubuntu-latest
+
+    steps:
+      - name: Check out repository
+        uses: actions/checkout@v6
+
+      - name: Install uv
+        uses: astral-sh/setup-uv@v7
+
+      - name: Set up Python
+        run: uv python install
+
+      - name: Run checks
+        run: make check
diff --git a/CLAUDE.md b/CLAUDE.md
index 6faf046..10c445f 100644
--- a/CLAUDE.md
+++ b/CLAUDE.md
@@ -153,7 +153,14 @@ Each forest has its own `.forestui-config.json` state file.
 
 ## Testing
 
-Currently no test suite. When adding tests:
+**Visual/behavioral verification:** forestui is a TUI app — lint and typecheck
+alone cannot catch visual bugs, wrong window names, broken interactions, or
+UI regressions. When fixing behavioral/visual bugs or developing new features,
+use the `test-forestui` skill to launch forestui in a headless terminal and
+visually verify the fix or feature works. Do this proactively, not only when
+asked.
+
+Currently no unit test suite. When adding tests:
 - Use pytest
 - Place tests in `tests/` directory
 - Add pytest to dev dependencies
@@ -165,7 +172,8 @@ Version is `0.0.0` in source code. Actual versions are derived from git tags at
 ### Development
 
 1. Create a branch, make changes
-2. Run `make check` and test locally
+2. **Always run `make check` before committing, pushing, or opening a PR.** Do not
+   push code that fails lint or typecheck — fix issues first.
 3. Open a PR and merge to `main`
 
 Running from source (`uv run forestui`) shows version `0.0.0` and auto-enables dev mode.
diff --git a/Makefile b/Makefile
index 5cd0cc5..6843330 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,4 @@
-.PHONY: lint typecheck check format install dev clean
+.PHONY: lint typecheck format-check check format install dev clean
 
 # Run ruff linter
 lint:
@@ -8,8 +8,12 @@ lint:
 typecheck:
 	uv run mypy forestui/
 
-# Run all checks (lint + typecheck)
-check: lint typecheck
+# Check formatting without modifying files
+format-check:
+	uv run ruff format --check forestui/
+
+# Run all checks (lint + typecheck + format)
+check: lint typecheck format-check
 
 # Format code with ruff
 format:
diff --git a/forestui/cli.py b/forestui/cli.py
index a794944..4868629 100644
--- a/forestui/cli.py
+++ b/forestui/cli.py
@@ -112,7 +112,7 @@ def ensure_tmux(
                     "-t",
                     f"={session_name}",
                     "-n",
-                    "forestui",
+                    get_window_name(dev_mode),
                     forestui_cmd,
                 ],
             )
diff --git a/forestui/services/tmux.py b/forestui/services/tmux.py
index 17ea528..06db049 100644
--- a/forestui/services/tmux.py
+++ b/forestui/services/tmux.py
@@ -108,13 +108,26 @@ def session(self) -> Session | None:
 
     @property
     def current_window(self) -> Window | None:
-        """Get the current tmux window."""
-        if self.session is None:
+        """Get the tmux window this process is running in.
+
+        Uses the TMUX_PANE environment variable to find our own window,
+        rather than the session's active window — which may be a different
+        window when forestui is starting up in a background window.
+        """
+        if self.server is None:
+            return None
+        pane_id = os.environ.get("TMUX_PANE")
+        if not pane_id:
             return None
         try:
-            return self.session.active_window
+            for sess in self.server.sessions:
+                for window in sess.windows:
+                    for pane in window.panes:
+                        if pane.pane_id == pane_id:
+                            return window
         except LibTmuxException:
             return None
+        return None
 
     def rename_window(self, name: str) -> bool:
         """Rename the current tmux window."""