fix(parser): accept {arr[i]} as an fd-variable redirect

crates/bashkit/src/interpreter/mod.rs

@@ -7392,10 +7392,10 @@ impl Interpreter {
         for redirect in redirects {
             // Resolve fd from either explicit fd or {var} fd-variable syntax
             let resolved_fd_var: Option<i32> = redirect.fd_var.as_ref().and_then(|var_name| {
-                self.scoped
-                    .variables
-                    .get(var_name)
-                    .and_then(|val| val.parse::<i32>().ok())
+                self.expand_name_or_array_element(var_name)
+                    .trim()
+                    .parse::<i32>()
+                    .ok()
             });
             match redirect.kind {
                 RedirectKind::Input => {

crates/bashkit/src/parser/mod.rs

@@ -2749,9 +2749,12 @@ impl<'a> Parser<'a> {
             && s.starts_with('{')
             && s.ends_with('}')
             && s.len() > 2
+            // `{fd}` or `{arr[i]}` (a coproc hands its descriptors out as
+            // `${NAME[0]}` / `${NAME[1]}`, and `exec {NAME[1]}>&-` closes one).
             && s[1..s.len() - 1]
                 .chars()
-                .all(|c| c.is_alphanumeric() || c == '_')
+                .all(|c| c.is_alphanumeric() || matches!(c, '_' | '[' | ']'))
+            && s[1..s.len() - 1].starts_with(|c: char| c.is_alphabetic() || c == '_')
         {
             let var_name = s[1..s.len() - 1].to_string();
             words.pop();

crates/bashkit/tests/spec_cases/bash/fdvar-array.test.sh

@@ -0,0 +1,21 @@
+### fd_var_array_subscript_closes
+exec {fd}>/tmp/fv.txt
+echo one >&$fd
+exec {fd}>&-
+cat /tmp/fv.txt
+coproc UP { echo from_coproc; }
+exec {UP[1]}>&-
+read -r line <&"${UP[0]}"
+echo "[$line]"
+### expect
+one
+[from_coproc]
+### end
+
+### fd_var_array_is_not_a_command
+coproc C { echo x; }
+exec {C[1]}>&- 2>&1
+echo "rc=$?"
+### expect
+rc=0
+### end

knowledge/log.md

@@ -22,6 +22,7 @@
 * **Fix**: parameter expansion and `mapfile` gaps from the Debian oracle. `${v~}`/`${v~~}` toggle case (also per array element). `\/` in a `${v/pat/rep}` replacement is a plain `/`. Unquoted `${!prefix@}`, `${!ref}`, `${v:off:len}`, `${a[@]:o:n}` and `${v@op}` now undergo field splitting like other expansions, so `for v in ${!cfg_@}` loops per name. `mapfile` gained `-d DELIM` (`''` is NUL), `-n`, `-s`, `-O` (keeps other elements) and grouped options; `-u` other than 0 and `-C`/`-c` exit 2 (L-MAPFILE-001).
 * **Fix**: `[[ a < b ]]` and `[[ a > b ]]` compare strings instead of being swallowed as redirections (the conditional grammar has no redirects), so `[[ a < B ]]` is false in byte order like bash. `shopt` listings pad the name to 15 columns and separate the state with a tab, matching bash.
 * **Fix**: arithmetic evaluation reports errors instead of yielding 0. `$((1/0))` and `$((08))` now print bash's `line N: EXPR: division by 0 (error token is "0")` / `value too great for base` and abort the command with status 1; `(( ))` and `let` print the same with their `((: ` / `let: ` prefix and fail without aborting the script. A new `arith_error` channel on the interpreter carries the failure out of the `&self` evaluator, reported where `set -u` errors are. Error lines say `bash: line N:` because the interpreter does not track the running script's path (see architecture).
+* **Fix**: `{name[i]}` is accepted as an fd-variable redirect, so `exec {COPROC[1]}>&-` closes that descriptor instead of running `{COPROC[1]}` as a command. Fd-variable values resolve through array elements, which is how a coproc hands its descriptors out.
 * **Decision**: CPython's workload priority is agents running `python3` for scripted logic (processing a file, transforming data). Low-use stdlib modules are no longer shipped: `unittest`, `doctest`, profilers, `compileall`/`zipapp`, `dbm`/`shelve`, `plistlib`, `wave`, `netrc`, `cmd`, `tty`/`pty`, and `bz2`/`lzma`/`compression.zstd` (no C codec in the guest anyway). Stdlib zip 3.58 to 3.16 MB. L-CPY-009 updated. See [CPython WebAssembly Runtime](runtimes/cpython-wasm.md#workload-priority).
 * **Feature**: `yes` and `seq` stream into pipelines. As a producer stage they write chunks into the pipe as they go (`Context::stdout_stream`), so `yes | head -1` and `seq 1000000 | head -1` stop after the first chunk with `PIPESTATUS` `141 0` instead of running to the output cap and printing a truncation notice. Step 2 of the roadmap (streaming builtin I/O), starting with the generators.
 * **Feature**: `sudo` and `busybox`, the top missing commands in the gap replay (`sudo tee /etc/x <<EOF`, `busybox tar --help`). `sudo` skips its options and runs the command (leading `VAR=VALUE` through `env`, `-s`/`-i` through `bash -c`; `-v`/`-k` succeed, `-l` lists ALL); `busybox APPLET` runs the builtin of that name, `--list` lists them (L-SUDO-001). `nohup`/`nice`/`flock` no longer steal the inner command's `--help`.