new panes gain active pwd

src/main/java/com/gregor/jprototerm/LinuxPty.java

@@ -9,6 +9,9 @@ import java.lang.foreign.MemorySegment;
 import java.lang.foreign.SymbolLookup;
 import java.lang.foreign.ValueLayout;
 import java.lang.invoke.MethodHandle;
+import java.io.IOException;
+import java.nio.file.Files;
+import java.nio.file.Path;
 import java.util.ArrayList;
 import java.util.List;
 import java.util.Map;
@@ -74,6 +77,7 @@ public final class LinuxPty implements AutoCloseable {
     private static final long SPAWN_ACTIONS_SIZE = 256;
     private static final long SPAWN_ATTR_SIZE = 512;
 
+    private static final MethodHandle TCGETPGRP = handle("tcgetpgrp", FD_INT_INT);
     private static final MethodHandle POSIX_OPENPT = handle("posix_openpt", FD_INT_INT);
     private static final MethodHandle GRANTPT = handle("grantpt", FD_INT_INT);
     private static final MethodHandle UNLOCKPT = handle("unlockpt", FD_INT_INT);
@@ -205,6 +209,25 @@ public final class LinuxPty implements AutoCloseable {
         }
     }
 
+    /**
+     * Best-effort current working directory of the terminal's foreground process group, read from
+     * {@code /proc}. This tracks the directory the user is actually in (a {@code cd} in the shell,
+     * or a child program that changed dir), so a newly opened pane can start there. Falls back to
+     * the shell's own pid, and returns {@code null} if it cannot be determined.
+     */
+    public String currentWorkingDirectory() {
+        if (closed) {
+            return null;
+        }
+        int pgid = callInt(TCGETPGRP, masterFd);
+        int target = pgid > 0 ? pgid : pid;
+        try {
+            return Files.readSymbolicLink(Path.of("/proc", Integer.toString(target), "cwd")).toString();
+        } catch (IOException | RuntimeException ex) {
+            return null;
+        }
+    }
+
     /** Resizes the terminal window. */
     public void setWinSize(int columns, int rows) {
         if (closed) {

src/main/java/com/gregor/jprototerm/ShellSession.java

@@ -20,7 +20,8 @@ public final class ShellSession implements AutoCloseable {
         });
     }
 
-    public static ShellSession start(String shell, Map<String, String> envOverride, TerminalPane pane, int columns, int rows) {
+    public static ShellSession start(String shell, Map<String, String> envOverride, TerminalPane pane,
+            int columns, int rows, String workingDirectory) {
         try {
             Map<String, String> environment = new HashMap<>(System.getenv());
             environment.put("TERM", "xterm-kitty");
@@ -31,7 +32,7 @@ public final class ShellSession implements AutoCloseable {
             LinuxPty pty = LinuxPty.spawn(
                     new String[] {shell, "-i"},
                     environment,
-                    System.getProperty("user.home"));
+                    workingDirectory != null ? workingDirectory : System.getProperty("user.home"));
             ShellSession session = new ShellSession(pty);
             session.resize(columns, rows);
             return session;
@@ -69,6 +70,11 @@ public final class ShellSession implements AutoCloseable {
         reader.submit(() -> readOutput(pane));
     }
 
+    /** Best-effort current working directory of the running shell, or {@code null} if unknown. */
+    public String currentWorkingDirectory() {
+        return closed ? null : pty.currentWorkingDirectory();
+    }
+
     public void resize(int columns, int rows) {
         if (closed) {
             return;

src/main/java/com/gregor/jprototerm/Tab.java

@@ -308,7 +308,10 @@ final class Tab implements AutoCloseable {
             widthPx = lastWidth / (tiled.size() + 1);
             heightPx = availHeight;
         }
-        return TerminalPane.create(config, metrics, this::markContentChanged, widthPx, heightPx);
+        // Open the new pane in the active pane's working directory, so a split/new pane lands
+        // where the user currently is. null (no active pane yet, or cwd unknown) falls back to home.
+        String workingDirectory = active != null ? active.currentWorkingDirectory() : null;
+        return TerminalPane.create(config, metrics, this::markContentChanged, widthPx, heightPx, workingDirectory);
     }
 
     private static boolean directionFilter(Direction direction, TerminalPane current, TerminalPane candidate) {

src/main/java/com/gregor/jprototerm/TerminalPane.java

@@ -69,9 +69,11 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
      * columns and rows fit, and that grid is handed to ghostty and the shell at start-up. A
      * non-positive size falls back to the configured default grid (used before the first
      * layout, when no rect is known yet). The pane owns the shell session it starts and runs
-     * {@code onContentChange} on every content change.
+     * {@code onContentChange} on every content change. The shell starts in {@code workingDirectory}
+     * (e.g. the active pane's cwd), or the user's home when {@code null}.
      */
-    public static TerminalPane create(AppConfig config, TerminalMetrics metrics, Runnable onContentChange, double widthPx, double heightPx) {
+    public static TerminalPane create(AppConfig config, TerminalMetrics metrics, Runnable onContentChange,
+            double widthPx, double heightPx, String workingDirectory) {
         int columns = widthPx > 0 ? metrics.columnsFor(widthPx) : config.columns();
         int rows = heightPx > 0 ? metrics.rowsFor(heightPx) : config.rows();
         Terminal terminal = Ghostty.open(new TerminalOptions(columns, rows, config.maxScrollback()));
@@ -79,7 +81,7 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
         TerminalPane pane = new TerminalPane(terminal, metrics, config.kittyGraphics(), onContentChange,
                 new GhosttyTerminalRenderer(metrics), columns, rows);
         pane.refresh();
-        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, columns, rows));
+        pane.attach(ShellSession.start(config.shell(), config.envOverride(), pane, columns, rows, workingDirectory));
         return pane;
     }
 
@@ -205,6 +207,12 @@ public final class TerminalPane implements AutoCloseable, RenderTarget {
         }
     }
 
+    /** Best-effort current working directory of this pane's shell, or {@code null} if unknown. */
+    public String currentWorkingDirectory() {
+        ShellSession current = session;
+        return current != null ? current.currentWorkingDirectory() : null;
+    }
+
     /** This pane's own content revision, bumped on every change (see {@link #refresh()}). */
     public long contentVersion() {
         return contentVersion.get();