feat(interpreter): run background jobs concurrently

crates/bashkit-js/__test__/security.spec.ts

@@ -106,9 +106,13 @@ test("WB: recursive function depth limited (TM-DOS-020)", (t) => {
 test("WB: fork bomb pattern blocked (TM-DOS-021)", (t) => {
   const bash = new Bash({ maxCommands: 100 });
   const r = bash.executeSync(":(){ :|:& };:");
-  // Should fail — no real process forking and command limit
+  // Background jobs run concurrently, so like real bash the top-level `:`
+  // returns 0 once it has backgrounded the bomb. The bomb itself must hit a
+  // limit (job slots, function depth or command budget) and terminate.
   t.true(
-    r.exitCode !== 0 || r.error !== undefined,
+    r.exitCode !== 0 ||
+      r.error !== undefined ||
+      /limit|fork: retry/.test(r.stderr),
     "fork bomb pattern must not run indefinitely",
   );
 });

crates/bashkit/docs/compatibility.md

@@ -92,7 +92,11 @@ for sandbox security reasons. See the compliance spec for details.
 | `cut` | `-d DELIM`, `-f FIELDS` | Extract fields |
 | `tr` | `-d`, character ranges | Translate/delete chars |
 | `date` | `+FORMAT`, `-u`, `-R`, `-I`, `-r`, `-d`/`--date` (relative, compound, epoch) | Display/format date with sandboxed IANA timezone support |
-| `wait` | `[JOB_ID...]` | Wait for background jobs |
+| `wait` | `[-n] [-p VAR] [-f] [ID...]` (PID or `%jobspec`) | Wait for background jobs |
+| `jobs` | `-l`, `-p` | List running background jobs |
+| `ps` | `-f`, `aux`, `-o`, `-p` | Virtual process list (shell + jobs) |
+| `pgrep`/`pkill` | `-f`, `-l`, `-a`, `-c`, `-x`, `-SIGNAL` | Match jobs by command |
+| `disown`, `fg`, `bg` | `[JOBSPEC]` | `fg` waits; `bg` is a no-op (jobs already run) |
 | `curl` | `-s`, `-o`, `-X`, `-d`/`--data`, `--data-raw`, `--data-binary`, `--data-urlencode`, `-G`/`--get`, `-H`, `-I`, `-f`, `-L`, `-w`, `--compressed`, `-u`, `-A`, `-e`, `-v`, `-m` | HTTP client (requires http_client feature) |
 | `wget` | `-q`, `-O`, `--spider`, `--header`, `-U`, `--post-data`, `-t` | Download files (requires http_client feature) |
 | `time` | `[-p] [-f FORMAT] [-o FILE] [-a] [-v] [--] PIPELINE` | Reserved-word timing; elapsed/status/Bashkit counters are truthful, host CPU/RSS fields say `unavailable` |
@@ -164,7 +168,7 @@ Chrono's validated strftime implementation, plus GNU `%N`, `%3N`, `%6N`, and
 |---------|-------------------|-------|
 | `ln` | `-s`, `-f` | Create links |
 | `chown` | `OWNER[:GROUP] FILE` | Change ownership (virtual) |
-| `kill` | `-SIGNAL PID` | Send signals (virtual) |
+| `kill` | `-l`, `-s SIG`, `-n NUM`, `-SIG`, `PID`/`%job` | Terminate background jobs (exit 128+signal); stop/continue signals are ignored |
 | `trap` | `COMMAND SIGNAL...`, `-p`, `-l` | Signal/event handlers |
 | `type` | `NAME...` | Describe command type |
 | `which` | `NAME...` | Locate a command |
@@ -465,7 +469,7 @@ cargo test --test spec_tests -- bash_comparison_tests --ignored
 - [x] Byte inspection (`strings`, `od`, `xxd`, `hexdump`)
 - [x] `basename`/`dirname` builtins
 - [x] `date` builtin
-- [x] Background execution (`&`, `wait`) - parsed, runs synchronously
+- [x] Background execution (`&`, `wait`) - jobs run concurrently on the session's task (no stop/continue)
 - [x] Network (`curl`, `wget`) - full HTTP implementation with security mitigations
 - [x] `timeout` builtin - stub, requires interpreter-level integration
 - [x] Process substitution (`<(cmd)`, `>(cmd)`)

crates/bashkit/docs/threat-model.md

@@ -87,7 +87,8 @@ through configurable limits.
 | Builtin parser depth (TM-DOS-027) | Deeply nested awk/jq | `MAX_AWK_PARSER_DEPTH` (100) + `MAX_JQ_JSON_DEPTH` (100) | MITIGATED |
 | Collect dirs recursion (TM-DOS-049) | Deep VFS tree | Mitigated by `max_path_depth` | MITIGATED |
 | Python read-only self-mount recursion (TM-DOS-118) | `bash.mount("/", bash.fs(), read_only=True)` hides the live filesystem identity behind a wrapper | Python validates the resolved filesystem identity before wrapping it | MITIGATED |
-| find traversal amplification (TM-DOS-121) | `find -L` over a symlink cycle, unbounded `-exec ... {} +` batches, or `*`-heavy `-name` patterns | Canonical-path loop detection with a 40-hop symlink cap, budget-charged directory listings, capped output, batches flushed every 4096 paths, linear-time glob matching |
+| find traversal amplification (TM-DOS-121) | `find -L` over a symlink cycle, unbounded `-exec ... {} +` batches, or `*`-heavy `-name` patterns | Canonical-path loop detection with a 40-hop symlink cap, budget-charged directory listings, capped output, batches flushed every 4096 paths, linear-time glob matching | MITIGATED |
+| Background job flooding (TM-DOS-122) | `while :; do sleep 99 & done` holds unbounded concurrent interpreters | `max_background_jobs` (64 default, 16 hardened) caps live jobs; extra `&` fails like bash's fork EAGAIN; jobs share the session budget, timeout and cancellation; every job is reaped when `exec()` returns | MITIGATED |
 
 **Parser and Arithmetic:**
 

crates/bashkit/src/builtins/fileops.rs

@@ -992,54 +992,6 @@ impl Builtin for Chown {
     }
 }
 
-/// The kill builtin - send signal to process (no-op in VFS).
-///
-/// Usage: kill [-s SIGNAL] [-SIGNAL] PID...
-///
-/// Since there are no real processes in the virtual environment, kill is a no-op
-/// that accepts the command syntax for compatibility.
-pub struct Kill;
-
-#[async_trait]
-impl Builtin for Kill {
-    async fn execute(&self, ctx: Context<'_>) -> Result<ExecResult> {
-        if let Some(r) = super::check_help_version(
-            ctx.args,
-            "Usage: kill [-s SIGNAL | -SIGNAL] PID...\nSend a signal to a process.\n\n  -s SIGNAL\tspecify the signal to send\n  -l, -L\tlist signal names\n      --help\tdisplay this help and exit\n      --version\toutput version information and exit\n",
-            Some("kill (bashkit) 0.1"),
-        ) {
-            return Ok(r);
-        }
-
-        let mut pids: Vec<&str> = Vec::new();
-
-        for arg in ctx.args {
-            if arg == "-l" || arg == "-L" {
-                // List signal names
-                return Ok(ExecResult::ok(
-                    "HUP INT QUIT ILL TRAP ABRT BUS FPE KILL USR1 SEGV USR2 PIPE ALRM TERM\n"
-                        .to_string(),
-                ));
-            }
-            if arg.starts_with('-') {
-                continue; // skip signal spec
-            }
-            pids.push(arg);
-        }
-
-        if pids.is_empty() {
-            return Ok(ExecResult::err(
-                "kill: usage: kill [-s sigspec | -n signum | -sigspec] pid | jobspec ...\n"
-                    .to_string(),
-                2,
-            ));
-        }
-
-        // In VFS, no real processes exist — just succeed silently
-        Ok(ExecResult::ok(String::new()))
-    }
-}
-
 /// The mktemp builtin - create temporary files or directories.
 ///
 /// Argument surface is generated from uutils/coreutils' `uu_app()` via