Move the pipe's editor side out of pardes.zig into selection_pipe.zig

Pure move, no behaviour change: submitPipe, pipeRequest, pipeFailed,
pipeCut, pipeOutput and pipeResponse, the PendingPipe they share,
pipeMarker, and the eight pipe tests with their nextPipeEffect helper go
verbatim to the end of selection_pipe.zig, so the whole of `|` (runner,
boundary values, prompt, request and atomic edit) is one file. Inside that
file the `selection_pipe.` prefix drops; the file doc now says it holds both
halves.

The methods become free functions taking `p: *Pardes`: the four shells'
`core.pipeRequest(id)` become `selection_pipe.pipeRequest(core, id)`, and
pardes.zig's two calls change the same way. pushUndo becomes pub because
the pipe's edit calls it; PendingPipe.deinit becomes pub for Pardes.deinit.

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

1 files changed, 536 insertions, 5 deletions

diff --git a/src/selection_pipe.zig b/src/selection_pipe.zig
index e1a42962..ea4a4d5b 100644
--- a/src/selection_pipe.zig
+++ b/src/selection_pipe.zig
@@ -1,10 +1,18 @@
-//! Native runner and boundary-owned values for `|`: pipe every editor
-//! selection through one shell command. The core imports only the plain value
-//! types below; native shells call `Job.copy` before starting a worker, then
-//! `runOne` on that worker. No subprocess or borrowed core memory reaches the
-//! editor/event-loop thread.
+//! `|`: pipe every editor selection through one shell command. First the
+//! native runner and its boundary-owned values: native shells call `Job.copy`
+//! before starting a worker, then `runOne` on that worker, so no subprocess or
+//! borrowed core memory reaches the editor/event-loop thread. Then the editor
+//! side: the prompt, the request the core emits, and the atomic edit its
+//! answer makes.
 const std = @import("std");
 const filesystem = @import("fs.zig");
+const pardes = @import("pardes.zig");
+const modal = @import("modal.zig");
+const panes = @import("panes.zig");
+const config = @import("config.zig");
+const Pane = panes.Pane;
+const Key = pardes.Key;
+const Pardes = pardes.Pardes;
 
 /// A deliberately finite answer. One selection cannot retain more than 1 MiB
 /// and a multi-selection command cannot retain more than 4 MiB in total.
@@ -392,3 +400,526 @@ test "native pipe runner preserves stdin/stdout bytes and reports how it failed"
         .failed => return error.EarlyStdinCloseShouldNotFail,
     }
 }
+
+// ---- the pipe inside the editor: the prompt, the request, the atomic edit ----
+
+fn nextPipeEffect(p: *Pardes) ?u32 {
+    while (p.nextEffect()) |effect| switch (effect) {
+        .pipe => |request| return request.id,
+        else => {},
+    };
+    return null;
+}
+
+/// The tag-tail marker each behaviour arms with. One function so the prompt
+/// that is DRAWN and the command that is PARSED can never disagree.
+pub fn pipeMarker(how: modal.Normal.PipeBehavior) []const u8 {
+    return switch (how) {
+        .replace => config.pipe_marker,
+        .ignore => config.pipe_marker_to,
+        .insert => config.pipe_marker_insert,
+        .append => config.pipe_marker_append,
+    };
+}
+
+pub const PendingPipe = struct {
+    id: u32,
+    pane: usize,
+    serial: u32,
+    revision: u32,
+    command: []u8,
+    cwd: []u8,
+    inputs: []Input,
+    ranges: [Pane.max_selections]modal.Selection,
+    primary: u8,
+    explicit: bool,
+    how: modal.Normal.PipeBehavior,
+    nranges: u8,
+
+    pub fn deinit(wait: *PendingPipe, gpa: std.mem.Allocator) void {
+        gpa.free(wait.command);
+        gpa.free(wait.cwd);
+        for (wait.inputs) |input| gpa.free(@constCast(input.bytes));
+        gpa.free(wait.inputs);
+        wait.* = undefined;
+    }
+
+    fn request(wait: *const PendingPipe) Request {
+        return .{
+            .id = wait.id,
+            .command = wait.command,
+            .cwd = wait.cwd,
+            .inputs = wait.inputs,
+        };
+    }
+};
+
+pub fn submitPipe(p: *Pardes, id: usize) void {
+    const pane = p.panes[id] orelse return;
+    const f = pane.file orelse return;
+    if (!panes.Output.fileTraits(f.output).saves) return;
+    const prompt = switch (pane.prompt) {
+        .pipe => |pipe| pipe,
+        else => return,
+    };
+    const tail = pane.tagSlice();
+    const armed = tail[@min(prompt.at, tail.len)..];
+    const marker = pipeMarker(prompt.how);
+    if (!std.mem.startsWith(u8, armed, marker)) return;
+    const command = armed[marker.len..];
+    if (command.len == 0) return;
+
+    var ranges: [Pane.max_selections]modal.Selection = undefined;
+    const got = pane.ranges(f.content, 0, &ranges);
+    // `!`/`A-!` take no stdin and run ONCE — see `PendingPipe.nranges`.
+    const ninputs = if (prompt.how.pipes()) got.n else 1;
+    const inputs = p.gpa.alloc(Input, ninputs) catch return;
+    var made: usize = 0;
+    for (ranges[0..ninputs], 0..) |range, i| {
+        const bytes = if (prompt.how.pipes()) bytes: {
+            const lo = @min(range.anchor, range.head);
+            const hi = @max(range.anchor, range.head);
+            if (hi > f.content.len) break;
+            break :bytes f.content[lo..hi];
+        } else "";
+        const copy = p.gpa.dupe(u8, bytes) catch break;
+        inputs[i] = .{ .bytes = copy };
+        made += 1;
+    }
+    if (made != ninputs) {
+        for (inputs[0..made]) |input| p.gpa.free(@constCast(input.bytes));
+        p.gpa.free(inputs);
+        return;
+    }
+    const command_copy = p.gpa.dupe(u8, command) catch {
+        for (inputs) |input| p.gpa.free(@constCast(input.bytes));
+        p.gpa.free(inputs);
+        return;
+    };
+    const cwd_copy = p.gpa.dupe(u8, Pardes.paneDir(pane)) catch {
+        p.gpa.free(command_copy);
+        for (inputs) |input| p.gpa.free(@constCast(input.bytes));
+        p.gpa.free(inputs);
+        return;
+    };
+
+    p.pipe_seq +%= 1;
+    if (p.pipe_wait) |*old| old.deinit(p.gpa);
+    p.pipe_wait = .{
+        .id = p.pipe_seq,
+        .pane = id,
+        .serial = pane.serial,
+        .revision = f.revision,
+        .command = command_copy,
+        .cwd = cwd_copy,
+        .inputs = inputs,
+        .ranges = ranges,
+        .primary = @intCast(got.pri),
+        .explicit = (pane.vsel.active and pane.vsel.explicit) or pane.msel.active,
+        .how = prompt.how,
+        .nranges = @intCast(got.n),
+    };
+    p.emit(.{ .pipe = .{ .id = p.pipe_seq } });
+}
+
+/// Frontends call this while draining a .pipe effect, then immediately
+/// copy the borrowed view into a worker-owned selection_pipe.Job.
+pub fn pipeRequest(p: *const Pardes, id: u32) ?Request {
+    if (p.pipe_wait) |*wait| {
+        if (wait.id == id) return wait.request();
+    }
+    return null;
+}
+
+fn pipeFailed(p: *Pardes, wait: *const PendingPipe, failure: ?Failure) void {
+    var out: std.Io.Writer.Allocating = .init(p.gpa);
+    defer out.deinit();
+    const w = &out.writer;
+    w.print("| {s}\n\n", .{wait.command}) catch return;
+    if (failure) |fail| {
+        if (wait.inputs.len > 1)
+            w.print("selection {d} of {d}: ", .{ fail.index + 1, wait.inputs.len }) catch return;
+        switch (fail.kind) {
+            .exit => w.print("exit status {d}\n", .{fail.code}) catch return,
+            .signal => w.writeAll("killed by a signal\n") catch return,
+            .timeout => w.print(
+                "still running after {d} seconds, and stopped\n",
+                .{command_timeout_seconds},
+            ) catch return,
+            .too_large => w.writeAll("produced more output than a filter may return\n") catch return,
+            .spawn => w.writeAll("could not be started\n") catch return,
+            .io => w.writeAll("could not be read\n") catch return,
+        }
+        if (fail.stderr.len > 0) w.print("\n{s}", .{fail.stderr}) catch return;
+    } else {
+        // No diagnosis at all: nobody ran it. The detached daemon, the
+        // browser and the board all leave `pipe` null on purpose.
+        w.writeAll("this session cannot run filters\n") catch return;
+    }
+    const content = out.toOwnedSlice() catch return;
+    const was = p.active;
+    panes.Output.openErrors(p, wait.pane, content) catch |err| {
+        p.gpa.free(content);
+        // Nowhere to put the report is itself worth one line.
+        p.reportError(wait.pane, "pipe", err);
+        return;
+    };
+    if (p.panes[was] != null) p.active = was;
+}
+
+fn pipeCut(wait: *const PendingPipe, content: []const u8, i: usize) ?struct { lo: usize, hi: usize } {
+    const range = wait.ranges[i];
+    const lo = @min(range.anchor, range.head);
+    const hi = @max(range.anchor, range.head);
+    if (hi > content.len) return null;
+    return switch (wait.how) {
+        .replace, .ignore => .{ .lo = lo, .hi = hi },
+        .insert => .{ .lo = lo, .hi = lo },
+        .append => .{ .lo = hi, .hi = hi },
+    };
+}
+
+fn pipeOutput(
+    wait: *const PendingPipe,
+    outputs: []const []const u8,
+    content: []const u8,
+    i: usize,
+) []const u8 {
+    var out = if (wait.how.pipes()) outputs[i] else outputs[0];
+    const range = wait.ranges[i];
+    const lo = @min(range.anchor, range.head);
+    const hi = @max(range.anchor, range.head);
+    const selected = if (hi <= content.len) content[lo..hi] else "";
+    if (!std.mem.endsWith(u8, selected, "\n") and std.mem.endsWith(u8, out, "\n")) {
+        out = out[0 .. out.len - 1];
+        if (std.mem.endsWith(u8, out, "\r")) out = out[0 .. out.len - 1];
+    }
+    return out;
+}
+
+pub fn pipeResponse(
+    p: *Pardes,
+    id: u32,
+    success: bool,
+    outputs: []const []const u8,
+    failure: ?Failure,
+) void {
+    // A SUPERSEDED OR UNKNOWN id is the one silence worth keeping: it is
+    // the answer to a question nobody is still asking.
+    if (p.pipe_wait == null or p.pipe_wait.?.id != id) return;
+    var wait = p.pipe_wait.?;
+    p.pipe_wait = null;
+    defer wait.deinit(p.gpa);
+
+    if (!success or outputs.len != wait.inputs.len) return pipeFailed(p, &wait, failure);
+
+    const pane = p.panes[wait.pane] orelse return;
+    if (pane.serial != wait.serial) return;
+    const f = if (pane.file) |*file| file else return;
+    if (!panes.Output.fileTraits(f.output).saves) return;
+    if (f.revision != wait.revision)
+        return p.reportError(wait.pane, "pipe", error.FileChangedWhileFiltering);
+
+    if (wait.how == .ignore) return;
+
+    const n = wait.nranges;
+    var total_output: usize = 0;
+    var removed: usize = 0;
+    var previous_end: usize = 0;
+    for (0..n) |i| {
+        const cut = pipeCut(&wait, f.content, i) orelse return;
+        const output = pipeOutput(&wait, outputs, f.content, i);
+        if (output.len > max_stdout_bytes) return;
+        total_output = std.math.add(usize, total_output, output.len) catch return;
+        if (total_output > max_total_stdout_bytes) return;
+        if (cut.lo < previous_end) return;
+        removed = std.math.add(usize, removed, cut.hi - cut.lo) catch return;
+        previous_end = cut.hi;
+    }
+    const kept = f.content.len - removed;
+    const final_len = std.math.add(usize, kept, total_output) catch return;
+    const replacement = p.gpa.alloc(u8, final_len) catch return;
+
+    var new_ranges: [Pane.max_selections]modal.Selection = undefined;
+    var read_at: usize = 0;
+    var write_at: usize = 0;
+    for (0..n) |i| {
+        const range = wait.ranges[i];
+        const cut = pipeCut(&wait, f.content, i).?;
+        const output = pipeOutput(&wait, outputs, f.content, i);
+        @memcpy(replacement[write_at .. write_at + (cut.lo - read_at)], f.content[read_at..cut.lo]);
+        write_at += cut.lo - read_at;
+        const out_start = write_at;
+        @memcpy(replacement[write_at .. write_at + output.len], output);
+        write_at += output.len;
+        const out_end = write_at;
+        new_ranges[i] = if (range.anchor > range.head)
+            .{ .anchor = out_end, .head = out_start }
+        else
+            .{ .anchor = out_start, .head = out_end };
+        read_at = cut.hi;
+    }
+    @memcpy(replacement[write_at..], f.content[read_at..]);
+
+    // One async request is one history transaction, even at 64 cursors.
+    p.pushUndo(pane);
+    panes.File.setContent(p, f, replacement);
+    pane.setRanges(f.content, new_ranges[0..n], &.{}, wait.primary, wait.explicit);
+    pane.select = false;
+    pane.ensureCursorVisible();
+}
+
+test "selection pipe prompt submits exact request and Escape cancels" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = try p.setTestFile("one\ntwo\n");
+    pane.cur_row = 0;
+    pane.cur_col = 2;
+    pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
+
+    p.update(.{ .key = .{ .cp = '|' } });
+    try std.testing.expect(pane.tag_edit and pane.prompt == .pipe);
+    try std.testing.expect(std.mem.endsWith(u8, pane.tagSlice(), config.pipe_marker));
+    try std.testing.expect(nextPipeEffect(p) == null);
+    p.update(.{ .key = .{ .cp = 't', .text = "tr a-z A-Z" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    try std.testing.expect(!pane.tag_edit and pane.prompt != .pipe);
+    const id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    const request = pipeRequest(p, id) orelse return error.MissingPipeRequest;
+    try std.testing.expectEqualStrings("tr a-z A-Z", request.command);
+    try std.testing.expectEqualStrings("/", request.cwd);
+    try std.testing.expectEqual(@as(usize, 1), request.inputs.len);
+    try std.testing.expectEqualSlices(u8, "one", request.inputs[0].bytes);
+
+    const before = pane.file.?.content;
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
+    p.update(.{ .key = .{ .cp = Key.escape } });
+    try std.testing.expect(!pane.tag_edit and pane.prompt != .pipe);
+    try std.testing.expectEqualSlices(u8, before, pane.file.?.content);
+    try std.testing.expect(nextPipeEffect(p) == null);
+}
+
+test "selection pipe replaces all ranges atomically and undo restores them" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = try p.setTestFile("aa bb cc\n");
+    const ranges = [_]modal.Selection{
+        .{ .anchor = 0, .head = 2 },
+        .{ .anchor = 6, .head = 8 },
+    };
+    pane.setRanges(pane.file.?.content, &ranges, &.{}, 0, true);
+
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    const request = pipeRequest(p, id) orelse return error.MissingPipeRequest;
+    try std.testing.expectEqual(@as(usize, 2), request.inputs.len);
+    try std.testing.expectEqualSlices(u8, "aa", request.inputs[0].bytes);
+    try std.testing.expectEqualSlices(u8, "cc", request.inputs[1].bytes);
+
+    var denied = std.testing.FailingAllocator.init(gpa, .{ .fail_index = 0 });
+    p.scratch.deinit();
+    p.scratch = .init(denied.allocator());
+    const outputs: []const []const u8 = &.{ "AA\n", "" };
+    p.update(.{ .pipe_resp = .{ .id = id, .success = true, .outputs = outputs } });
+    try std.testing.expectEqualSlices(u8, "AA bb \n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 1), pane.file.?.history.undo_len);
+    try std.testing.expectEqual(@as(u8, 1), pane.nsel);
+    try std.testing.expectEqual(@as(i32, 1), pane.cur_col);
+    try std.testing.expectEqual(@as(i32, 6), pane.sels[0].col);
+    try std.testing.expect(!denied.has_induced_failure);
+
+    p.update(.{ .key = .{ .cp = 'u' } });
+    try std.testing.expectEqualSlices(u8, "aa bb cc\n", pane.file.?.content);
+}
+
+test "the four shell behaviours put their output where helix puts it" {
+    const gpa = std.testing.allocator;
+    const Case = struct {
+        key: Key,
+        outputs: []const []const u8,
+        want: []const u8,
+        want_effect: bool = true,
+    };
+    // One selection, `bb`, in `aa bb cc\n` — bytes 3..5.
+    for ([_]Case{
+        // `|` replaces the selection with what the command wrote.
+        .{ .key = .{ .cp = '|' }, .outputs = &.{"XX"}, .want = "aa XX cc\n" },
+        // `!` inserts BEFORE it, and the selection survives to its right.
+        .{ .key = .{ .cp = '!' }, .outputs = &.{"XX"}, .want = "aa XXbb cc\n" },
+        // `A-!` appends AFTER it.
+        .{ .key = .{ .cp = '!', .alt = true }, .outputs = &.{"XX"}, .want = "aa bbXX cc\n" },
+        // `A-|` runs the command and leaves the text completely alone: the
+        // point is the side effect, not the output.
+        .{ .key = .{ .cp = '|', .alt = true }, .outputs = &.{"XX"}, .want = "aa bb cc\n" },
+    }) |case| {
+        const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 100, .rows = 30 });
+        defer p.deinit();
+        while (p.nextEffect()) |_| {}
+        const pane = try p.setTestFile("aa bb cc\n");
+        pane.setRanges(pane.file.?.content, &.{.{ .anchor = 3, .head = 5 }}, &.{}, 0, true);
+
+        p.update(.{ .key = case.key });
+        for ("cmd") |c| p.update(.{ .key = .{ .cp = c, .text = &.{c} } });
+        p.update(.{ .key = .{ .cp = Key.enter } });
+        const id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+        p.update(.{ .pipe_resp = .{ .id = id, .success = true, .outputs = case.outputs } });
+        try std.testing.expectEqualSlices(u8, case.want, pane.file.?.content);
+    }
+}
+
+test "a command with no stdin runs once and every cursor gets that one answer" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 100, .rows = 30 });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = try p.setTestFile("aa bb cc\n");
+    const ranges = [_]modal.Selection{
+        .{ .anchor = 0, .head = 2 },
+        .{ .anchor = 6, .head = 8 },
+    };
+    pane.setRanges(pane.file.?.content, &ranges, &.{}, 0, true);
+
+    p.update(.{ .key = .{ .cp = '!' } }); // insert-output: no stdin
+    for ("date") |c| p.update(.{ .key = .{ .cp = c, .text = &.{c} } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    const request = pipeRequest(p, id) orelse return error.MissingPipeRequest;
+
+    try std.testing.expectEqual(@as(usize, 1), request.inputs.len);
+    try std.testing.expectEqualSlices(u8, "", request.inputs[0].bytes);
+
+    p.update(.{ .pipe_resp = .{ .id = id, .success = true, .outputs = &.{"T"} } });
+    try std.testing.expectEqualSlices(u8, "Taa bb Tcc\n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 1), pane.file.?.history.undo_len);
+}
+
+test "selection pipe failure and stale completion never mutate the file" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = try p.setTestFile("abc\n");
+    pane.cur_col = 2;
+    pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
+
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const failed_id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    p.update(.{ .pipe_resp = .{ .id = failed_id, .success = false, .outputs = &.{} } });
+    try std.testing.expectEqualSlices(u8, "abc\n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.undo_len);
+
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const stale_id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    panes.File.setContent(p, &pane.file.?, try gpa.dupe(u8, "changed\n"));
+    p.update(.{ .pipe_resp = .{ .id = stale_id, .success = true, .outputs = &.{"ABC"} } });
+    try std.testing.expectEqualSlices(u8, "changed\n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.undo_len);
+}
+
+test "a failed filter opens an errors buffer carrying the command's own words" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true, .cols = 100, .rows = 30 });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = try p.setTestFile("abc\n");
+    pane.cur_col = 2;
+    pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
+
+    p.update(.{ .key = .{ .cp = '|' } });
+    for ("trr") |c| p.update(.{ .key = .{ .cp = c, .text = &.{c} } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+
+    // The shape a real runner brings home for `| trr`: nonzero exit, and the
+    // shell's own sentence about it.
+    var stderr = "sh: line 1: trr: command not found\n".*;
+    p.update(.{ .pipe_resp = .{
+        .id = id,
+        .success = false,
+        .outputs = &.{},
+        .failure = .{ .kind = .exit, .code = 127, .stderr = &stderr },
+    } });
+
+    // The text is untouched — a failed filter is not an edit...
+    try std.testing.expectEqualSlices(u8, "abc\n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.undo_len);
+    // ...and the cursor did not go anywhere, so `|` again edits the same file.
+    try std.testing.expectEqual(@as(usize, 0), p.active);
+
+    var found: ?[]const u8 = null;
+    for (p.panes) |slot| {
+        const q = slot orelse continue;
+        const qf = q.file orelse continue;
+        const o = qf.output orelse continue;
+        if (std.meta.activeTag(o.from) == .errors) found = qf.content;
+    }
+    const report = found orelse return error.NoErrorsBuffer;
+    try std.testing.expect(std.mem.indexOf(u8, report, "| trr") != null);
+    try std.testing.expect(std.mem.indexOf(u8, report, "exit status 127") != null);
+    try std.testing.expect(std.mem.indexOf(u8, report, "command not found") != null);
+}
+
+test "selection pipe rejects a reused pane slot and a superseded request" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    var pane = try p.setTestFile("old\n");
+    pane.cur_col = 2;
+    pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
+
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const replaced_id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    pane = try p.setTestFile("new\n"); // same slot, different serial
+    p.update(.{ .pipe_resp = .{ .id = replaced_id, .success = true, .outputs = &.{"OLD"} } });
+    try std.testing.expectEqualSlices(u8, "new\n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 0), pane.file.?.history.undo_len);
+
+    pane.cur_col = 2;
+    pane.vsel = .{ .active = true, .row = 0, .col = 0, .explicit = true };
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "cat" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const first_id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    p.update(.{ .key = .{ .cp = '|' } });
+    p.update(.{ .key = .{ .cp = 'c', .text = "tr a-z A-Z" } });
+    p.update(.{ .key = .{ .cp = Key.enter } });
+    const latest_id = nextPipeEffect(p) orelse return error.MissingPipeEffect;
+    try std.testing.expect(first_id != latest_id);
+
+    p.update(.{ .pipe_resp = .{ .id = first_id, .success = true, .outputs = &.{"BAD"} } });
+    try std.testing.expectEqualSlices(u8, "new\n", pane.file.?.content);
+    p.update(.{ .pipe_resp = .{ .id = latest_id, .success = true, .outputs = &.{"NEW"} } });
+    try std.testing.expectEqualSlices(u8, "NEW\n", pane.file.?.content);
+    try std.testing.expectEqual(@as(usize, 1), pane.file.?.history.undo_len);
+}
+
+test "selection pipe binding is file-normal-only" {
+    const gpa = std.testing.allocator;
+    const p = try Pardes.init(gpa, .{ .tty_only = true });
+    defer p.deinit();
+    while (p.nextEffect()) |_| {}
+    const pane = try p.setTestFile("x");
+
+    pane.file.?.output = .{ .from = .search };
+    p.update(.{ .key = .{ .cp = '|' } });
+    try std.testing.expect(pane.prompt != .pipe);
+    pane.file.?.output = null;
+    pane.mode = .insert;
+    p.update(.{ .key = .{ .cp = '|', .text = "|" } });
+    try std.testing.expect(pane.prompt != .pipe);
+    try std.testing.expectEqualSlices(u8, "|x", pane.file.?.content);
+}