Columns are named by stable serials over 9P, as panes are

/col/<n> named a column by its index, which shifts when a column left of it
closes: exactly what scripts trip on. A column is now /col/<serial>, its
serial kept while it lives and never reused; /layout lines give serial and
index (`<serial> <index> ...`), active names the serial, /index's last
field is the column's serial, and the log says newcol and delcol with
serials. Docs, the skill and the tree's README say so.

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

1 files changed, 27 insertions, 22 deletions

diff --git a/src/ninep/tree.zig b/src/ninep/tree.zig
index 9459be4f..3be75960 100644
--- a/src/ninep/tree.zig
+++ b/src/ninep/tree.zig
@@ -19,6 +19,7 @@ pub const pane = @import("pane.zig");
 pub const addr = @import("addr.zig");
 pub const ctl = @import("ctl.zig");
 pub const cols = @import("cols.zig");
+const layout = pardes.layout;
 pub const pty = @import("pty.zig");
 pub const sources = @import("sources.zig");
 pub const screen = @import("screen.zig");
@@ -268,8 +269,9 @@ pub const PaneFile = enum(u5) {
     }
 };
 
-/// /col/<n> and its tag: a column is named by its index, which a serial
-/// never is (serials are 32 bits; this bit is past them).
+/// /col/<serial> and its tag: a column is named by its serial, which stays
+/// while it lives as a pane's does; this bit, past a pane serial's 32, keeps
+/// the two apart.
 pub const ColFile = enum(u5) { dir = 0, tag = 1 };
 const col_bit: u59 = 1 << 58;
 
@@ -282,8 +284,8 @@ pub const Node = packed struct(u64) {
         return @bitCast(Node{ .file = @intFromEnum(file), .serial = serial });
     }
 
-    pub fn ofCol(index: usize, file: ColFile) u64 {
-        return @bitCast(Node{ .file = @intFromEnum(file), .serial = col_bit | @as(u59, @intCast(index)) });
+    pub fn ofCol(serial: u32, file: ColFile) u64 {
+        return @bitCast(Node{ .file = @intFromEnum(file), .serial = col_bit | @as(u59, serial) });
     }
 
     pub fn target(node: u64) ?Target {
@@ -292,7 +294,7 @@ pub const Node = packed struct(u64) {
             return .{ .top = std.enums.fromInt(TopFile, n.file) orelse return null };
         }
         if (n.serial & col_bit != 0) return .{ .col = .{
-            .index = std.math.cast(u32, n.serial & ~col_bit) orelse return null,
+            .serial = std.math.cast(u32, n.serial & ~col_bit) orelse return null,
             .file = std.enums.fromInt(ColFile, n.file) orelse return null,
         } };
         return .{ .pane = .{
@@ -305,7 +307,7 @@ pub const Node = packed struct(u64) {
 pub const Target = union(enum) {
     top: TopFile,
     pane: struct { serial: u32, file: PaneFile },
-    col: struct { index: u32, file: ColFile },
+    col: struct { serial: u32, file: ColFile },
 };
 
 /// Opening /pane/new makes a pane and reading the open fid answers its
@@ -450,13 +452,13 @@ fn attrOf(p: *Pardes, target: Target) ?Reply.Attr {
             .append = f == .tag,
         },
         .col => |c| {
-            if (c.index >= p.ncol) return null;
+            if (layout.columnBySerial(p, c.serial) == null) return null;
             return .{
-                .name = if (c.file == .dir) (std.fmt.bufPrint(&p.fs.node_name, "{d}", .{c.index}) catch unreachable) else "tag",
-                .node = Node.ofCol(c.index, c.file),
+                .name = if (c.file == .dir) (std.fmt.bufPrint(&p.fs.node_name, "{d}", .{c.serial}) catch unreachable) else "tag",
+                .node = Node.ofCol(c.serial, c.file),
                 .dir = c.file == .dir,
                 .mode = if (c.file == .dir) 0o755 else 0o666,
-                .size = if (c.file == .tag) cols.headerText(p, c.index).?.len + 1 else 0,
+                .size = if (c.file == .tag) cols.headerText(p, c.serial).?.len + 1 else 0,
                 .mtime = p.fs.started,
                 .append = c.file == .tag,
             };
@@ -548,18 +550,20 @@ fn lookup(p: *Pardes, req: Req, target: Target) Reply {
                 if (serial == 0) return Reply.fail(req.tag, E.NOENT);
                 break :pane Node.of(serial, .dir);
             },
-            // A column is its index, in decimal digits.
+            // A column is its serial, in decimal digits and never 0.
             .col => col: {
-                if (name.len > 4) return Reply.fail(req.tag, E.NOENT);
+                if (name.len > 10) return Reply.fail(req.tag, E.NOENT);
                 for (name) |c| if (c < '0' or c > '9') return Reply.fail(req.tag, E.NOENT);
-                break :col Node.ofCol(std.fmt.parseInt(u32, name, 10) catch return Reply.fail(req.tag, E.NOENT), .dir);
+                const serial = std.fmt.parseInt(u32, name, 10) catch return Reply.fail(req.tag, E.NOENT);
+                if (serial == 0) return Reply.fail(req.tag, E.NOENT);
+                break :col Node.ofCol(serial, .dir);
             },
             else => return Reply.fail(req.tag, E.NOTDIR),
         },
         .col => |c| col: {
             if (c.file != .dir) return Reply.fail(req.tag, E.NOTDIR);
             if (!std.mem.eql(u8, name, "tag")) return Reply.fail(req.tag, E.NOENT);
-            break :col Node.ofCol(c.index, .tag);
+            break :col Node.ofCol(c.serial, .tag);
         },
         .pane => |t| pane: {
             _ = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
@@ -626,14 +630,15 @@ fn readdir(p: *Pardes, req: Req, target: Target) Reply {
                     continue;
                 }
                 var buf: [16]u8 = undefined;
-                stageDirent(out, p.gpa, Node.ofCol(c, .dir), true, std.fmt.bufPrint(&buf, "{d}", .{c}) catch unreachable);
+                const serial = layout.columnSerial(p, c);
+                stageDirent(out, p.gpa, Node.ofCol(serial, .dir), true, std.fmt.bufPrint(&buf, "{d}", .{serial}) catch unreachable);
             },
             else => return Reply.fail(req.tag, E.NOTDIR),
         },
         .col => |c| {
-            if (c.index >= p.ncol) return Reply.fail(req.tag, E.NOENT);
+            if (layout.columnBySerial(p, c.serial) == null) return Reply.fail(req.tag, E.NOENT);
             if (c.file != .dir) return Reply.fail(req.tag, E.NOTDIR);
-            if (skip > 0) skip -= 1 else stageDirent(out, p.gpa, Node.ofCol(c.index, .tag), false, "tag");
+            if (skip > 0) skip -= 1 else stageDirent(out, p.gpa, Node.ofCol(c.serial, .tag), false, "tag");
         },
         .pane => |t| {
             const id = p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT);
@@ -668,7 +673,7 @@ fn open(p: *Pardes, req: Req, target: Target) Reply {
             .log => .{ .log = .{} },
             else => return .{ .tag = req.tag },
         },
-        .col => |c| return if (c.index < p.ncol) .{ .tag = req.tag } else Reply.fail(req.tag, E.NOENT),
+        .col => |c| return if (layout.columnBySerial(p, c.serial) != null) .{ .tag = req.tag } else Reply.fail(req.tag, E.NOENT),
         .pane => |t| what: {
             const pn = p.panes[p.paneBySerial(t.serial) orelse return Reply.fail(req.tag, E.NOENT)].?;
             if (t.file.inPty() and !pn.isTerminal()) return Reply.fail(req.tag, E.NOENT);
@@ -749,7 +754,7 @@ fn releaseHandle(p: *Pardes, req: Req) void {
         p.panes[id].?.fs.tag_rewrite = false;
         p.panes[id].?.fs.tag_held_newline = false;
     };
-    if (t == .col and t.col.file == .tag) cols.released(p, t.col.index);
+    if (t == .col and t.col.file == .tag) cols.released(p, t.col.serial);
     if (t == .top and t.top == .tag) cols.released(p, null);
     const o = openOf(p, req) orelse return;
     const of: ?*Pane = if (t == .pane) (if (p.paneBySerial(t.pane.serial)) |id| p.panes[id] else null) else null;
@@ -786,7 +791,7 @@ fn setattr(p: *Pardes, req: Req, target: Target) Reply {
                 return failText(req.tag, E.INVAL, pane.e_addr_failed);
             if (pane.truncate(p, p.panes[id].?, t.file) != .ok) return Reply.fail(req.tag, E.NOMEM);
         },
-        .col => |c| if (c.file == .tag and cols.truncate(p, c.index) != .ok) return Reply.fail(req.tag, E.NOENT),
+        .col => |c| if (c.file == .tag and cols.truncate(p, c.serial) != .ok) return Reply.fail(req.tag, E.NOENT),
         .top => |f| if (f == .tag and cols.truncate(p, null) != .ok) return Reply.fail(req.tag, E.NOMEM),
     };
     return .{ .tag = req.tag, .attr = attrOf(p, target) orelse return Reply.fail(req.tag, E.NOENT) };
@@ -877,7 +882,7 @@ fn readFile(p: *Pardes, req: Req, target: Target) Reply {
             if (t.file.inPty() and !pn.isTerminal()) return Reply.fail(req.tag, E.NOENT);
             return pane.read(p, req, id, pn, t.file);
         },
-        .col => |c| return if (c.file == .tag) cols.read(p, req, c.index) else Reply.fail(req.tag, E.PERM),
+        .col => |c| return if (c.file == .tag) cols.read(p, req, c.serial) else Reply.fail(req.tag, E.PERM),
     }
 }
 
@@ -897,7 +902,7 @@ fn write(p: *Pardes, req: Req, target: Target) Reply {
             if (t.file.inPty() and !pn.isTerminal()) return Reply.fail(req.tag, E.NOENT);
             return pane.write(p, req, id, pn, t.file);
         },
-        .col => |c| return if (c.file == .tag) cols.write(p, req, c.index) else Reply.fail(req.tag, E.PERM),
+        .col => |c| return if (c.file == .tag) cols.write(p, req, c.serial) else Reply.fail(req.tag, E.PERM),
     }
 }