A terminal's Tty word names its shell, Tty+fish, and a click on it opens another

A terminal's tag said Tty whatever shell it ran. The host's acknowledgement
of the shell it forked now sets the word to Tty+<shell>, tinted like the tag's
name. Word+arg is taken as Word arg, one word a tag can hold and a click can
take whole (+ is a word character), so Tty+fish opens a terminal on fish, as
Tty fish does; Tty takes the shell as its argument, which the host forks for
that pane instead of the configured one. Every snapshot whose screen shows a
terminal's tag changes: 69 goldens, re-recorded by name, whose 297 changed
lines are all Tty becoming Tty+bash (the harness runs bash), the cursor
columns and style spans that moved with it, or that text cut at a pane's
width.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

1 files changed, 3 insertions, 1 deletions

diff --git a/src/host_io.zig b/src/host_io.zig
index 820cb2b6..63b907ac 100644
--- a/src/host_io.zig
+++ b/src/host_io.zig
@@ -976,7 +976,9 @@ pub fn forkShell(
     };
     var master: c_int = -1;
     var path_buf: [std.fs.max_path_bytes]u8 = undefined;
-    var spawn = Shell.resolve(bin, &path_buf, prompt_rcs);
+    // A terminal opened on a shell of its own (`Tty fish`) runs that one.
+    const own = if (core) |c| if (c.panes[pane]) |pn| pn.shell else null else null;
+    var spawn = Shell.resolve(own orelse bin, &path_buf, prompt_rcs);
     // A command pane's child is the shell running its one line, which has
     // no prompt to mark (exec.zig runCommand).
     const one_line = if (core) |c| if (c.panes[pane]) |pn| pn.command else null else null;