fix(runtime): contain and supervise detached Bash jobs (ODY-145)

core/atomic_io.py

@@ -16,9 +16,48 @@ from __future__ import annotations
 import json
 import os
 import uuid
+import functools
+import threading
 from typing import Any, Optional
 
 
+_STORE_LOCKS: dict[str, threading.RLock] = {}
+_STORE_LOCKS_GUARD = threading.Lock()
+
+
+def store_transaction(path_factory):
+    """Serialize a JSON read/modify/write across runtime threads and processes."""
+    def decorate(function):
+        @functools.wraps(function)
+        def locked(*args, **kwargs):
+            path = os.path.abspath(str(path_factory())) + ".lock"
+            with _STORE_LOCKS_GUARD:
+                lock = _STORE_LOCKS.setdefault(path, threading.RLock())
+            with lock:
+                os.makedirs(os.path.dirname(path), exist_ok=True)
+                with open(path, "a+b") as handle:
+                    if os.name == "nt":
+                        import msvcrt
+                        if os.fstat(handle.fileno()).st_size == 0:
+                            handle.write(b"0")
+                            handle.flush()
+                        handle.seek(0)
+                        msvcrt.locking(handle.fileno(), msvcrt.LK_LOCK, 1)
+                    else:
+                        import fcntl
+                        fcntl.flock(handle, fcntl.LOCK_EX)
+                    try:
+                        return function(*args, **kwargs)
+                    finally:
+                        if os.name == "nt":
+                            handle.seek(0)
+                            msvcrt.locking(handle.fileno(), msvcrt.LK_UNLCK, 1)
+                        else:
+                            fcntl.flock(handle, fcntl.LOCK_UN)
+        return locked
+    return decorate
+
+
 def atomic_write_json(path: str, data: Any, *, indent: Optional[int] = None) -> None:
     """Atomically persist `data` as JSON at `path`.
 
@@ -64,4 +103,4 @@ def atomic_write_text(path: str, text: str) -> None:
         try:
             os.unlink(tmp)
         except OSError:
-            pass
+            pass

core/platform_compat.py

@@ -124,7 +124,7 @@ def pid_alive(pid: Optional[int]) -> bool:
         return True  # EPERM and other inspection failures are not ESRCH.
 
 
-def kill_process_tree(pid: Optional[int]):
+def kill_process_tree(pid: Optional[int], *, start_token=None, pgid=None, require_identity=False):
     """Use the runtime's shared escalating teardown and return verified death.
 
     Callers retaining durable PIDs must validate their recorded identity before
@@ -140,9 +140,9 @@ def kill_process_tree(pid: Optional[int]):
         id="", mechanism="windows_tree" if IS_WINDOWS else "process_group",
         workspace=spec.workspace, enforced=frozenset(), degraded=(),
         unenforced_required=(), owner="compatibility", mode=containment.CONTAINMENT_MODE,
-        spec=spec, pid=int(pid), pgid=containment._pgid_of(int(pid)),
+        spec=spec, pid=int(pid), pgid=pgid or containment._pgid_of(int(pid)),
     )
-    return containment.release(grant)
+    return containment.release(grant, start_token=start_token, require_identity=require_identity)
 
 
 # ── Shell / executable resolution ───────────────────────────────────────────

src/agent_tools/bg_job_tools.py

@@ -87,6 +87,9 @@ class ManageBgJobsTool:
                 if rec.get("status") != "running":
                     return {"output": f"Job `{job_id}` already {_status_label(rec)}; nothing to kill.", "exit_code": 0}
                 killed = bg_jobs.kill(job_id)
+                if not killed or not killed.get("killed"):
+                    return {"error": f"Could not verify termination of background job `{job_id}`.",
+                            "exit_code": 1, "teardown": (killed or {}).get("teardown")}
                 return {"output": f"Killed background job `{job_id}` ({(killed or {}).get('command', '').splitlines()[0][:80]}).", "exit_code": 0}
 
             out = rec.get("output") or "(no output yet)"

src/bg_jobs.py

@@ -22,18 +22,16 @@ from __future__ import annotations
 
 import json
 import os
-import shlex
+import sys
 import subprocess
 import time
 import uuid
 from pathlib import Path
 from typing import Any, Dict, List, Optional
 
-from core.atomic_io import atomic_write_json
+from core.atomic_io import atomic_write_json, store_transaction
 from core.platform_compat import (
     detached_popen_kwargs,
-    find_bash,
-    git_bash_path,
     kill_process_tree,
     pid_alive,
 )
@@ -53,6 +51,7 @@ _MAX_OUTPUT_CHARS = 16000
 # files) is kept before pruning, so neither the store nor data/bg_jobs/ grows
 # without bound. The agent has already consumed the result by then.
 _RETENTION_S = 3600  # 1 hour after follow-up
+_LIVE_PROCS: dict[int, subprocess.Popen] = {}
 
 
 def _load() -> Dict[str, Dict[str, Any]]:
@@ -79,66 +78,50 @@ def _pid_alive(pid: Optional[int]) -> bool:
     return pid_alive(pid)
 
 
+@store_transaction(lambda: _STORE)
 def launch(command: str, session_id: str, cwd: Optional[str] = None,
-           max_runtime_s: int = DEFAULT_MAX_RUNTIME_S) -> Dict[str, Any]:
+           max_runtime_s: int = DEFAULT_MAX_RUNTIME_S, env: Optional[dict] = None) -> Dict[str, Any]:
     """Launch `command` detached. Returns the job record (status='running').
 
-    Output + the final exit code are written to files so status survives a
-    server restart. The process is put in its own session (setsid) so it
-    outlives the request/stream that started it.
+    A trusted detached supervisor owns the shared containment runner, output,
+    wall clock and exit metadata, independently of the request/server lifetime.
     """
     _JOBS_DIR.mkdir(parents=True, exist_ok=True)
     job_id = uuid.uuid4().hex[:12]
     log_path = _JOBS_DIR / f"{job_id}.log"
     exit_path = _JOBS_DIR / f"{job_id}.exit"
 
-    # The user command goes in its OWN script file, run as a child `bash`. This
-    # is what isolates it: an `exit` inside it only ends that child (so the
-    # wrapper still records the exit code), and — unlike textually wrapping the
-    # command in `( … )` — the wrapper can't be broken by an unbalanced paren or
-    # a trailing line-continuation in the command. `$?` is the child's real
-    # exit status.
-    bash = find_bash()
-    if bash:
-        # POSIX, or Windows with Git Bash/WSL. The user command goes in its OWN
-        # script file, run as a child `bash` — an `exit` inside it only ends
-        # that child (so the wrapper still records the exit code), and an
-        # unbalanced paren / trailing line-continuation in the command can't
-        # break the wrapper. `$?` is the child's real exit status. Paths are
-        # emitted as POSIX (forward-slash) + shell-quoted so Git Bash on Windows
-        # handles drive paths and spaces correctly.
-        cmd_path = _JOBS_DIR / f"{job_id}.cmd.sh"
-        cmd_path.write_text(command + "\n", encoding="utf-8")
-        lp, xp, cp = (shlex.quote(git_bash_path(p)) for p in (log_path, exit_path, cmd_path))
-        script_path = _JOBS_DIR / f"{job_id}.sh"
-        script_path.write_text(
-            f"bash {cp} > {lp} 2>&1\n"
-            f"echo $? > {xp}\n",
-            encoding="utf-8",
-        )
-        argv = [bash, str(script_path)]
-    else:
-        # Windows without any bash installed: cmd.exe wrapper. The command runs
-        # in its own child .cmd so %ERRORLEVEL% is the command's real exit code.
-        child_path = _JOBS_DIR / f"{job_id}.child.cmd"
-        child_path.write_text("@echo off\r\n" + command + "\r\n", encoding="utf-8")
-        script_path = _JOBS_DIR / f"{job_id}.cmd"
-        script_path.write_text(
-            "@echo off\r\n"
-            f'call "{child_path}" > "{log_path}" 2>&1\r\n'
-            f'echo %ERRORLEVEL%> "{exit_path}"\r\n',
-            encoding="utf-8",
-        )
-        argv = [os.environ.get("ComSpec", "cmd.exe"), "/c", str(script_path)]
-
-    proc = subprocess.Popen(
-        argv,
-        stdout=subprocess.DEVNULL,
-        stderr=subprocess.DEVNULL,
-        stdin=subprocess.DEVNULL,
-        cwd=cwd or None,
-        **detached_popen_kwargs(),  # detach from the request lifecycle (setsid / DETACHED_PROCESS)
-    )
+    from src import containment
+    from src.agent_tools.subprocess_tools import _owned_spec, _replace_workspace_alias
+    spec = _owned_spec(cwd or os.getcwd(), env, max_runtime_s)
+    grant = containment.acquire(spec, owner=f"bg:{session_id}")
+    bounded_command = command
+    if containment.FILESYSTEM not in grant.enforced:
+        bounded_command = _replace_workspace_alias(command, grant.workspace)
+    result_path = _JOBS_DIR / f"{job_id}.result.json"
+    payload = {
+        "store_path": str(containment._store_path().resolve()),
+        "grant": {**grant.to_dict(), "owner": grant.owner},
+        "spec": {
+            "workspace": spec.workspace, "env": dict(spec.env), "wall_clock_s": spec.wall_clock_s,
+            "required": sorted(spec.required), "network": spec.network,
+            "readonly_extra": list(spec.readonly_extra), "writable_extra": list(spec.writable_extra),
+            "max_output_bytes": spec.max_output_bytes,
+        },
+        "command": bounded_command, "log_path": str(log_path.resolve()),
+        "result_path": str(result_path.resolve()), "exit_path": str(exit_path.resolve()),
+    }
+    try:
+        with open(log_path, "ab") as bootstrap_log:
+            proc = subprocess.Popen(
+                [sys.executable, str(Path(containment.__file__).with_name("containment_worker.py"))],
+                stdin=subprocess.PIPE, stdout=subprocess.DEVNULL, stderr=bootstrap_log,
+                cwd=str(Path(containment.__file__).resolve().parent.parent),
+                **detached_popen_kwargs(),
+            )
+    except BaseException:
+        containment.release(grant, grace_s=0)
+        raise
 
     rec = {
         "id": job_id,
@@ -153,15 +136,31 @@ def launch(command: str, session_id: str, cwd: Optional[str] = None,
         "followed_up": False,       # has the agent been re-invoked with the result?
         "log_path": str(log_path),
         "exit_path": str(exit_path),
+        "result_path": str(result_path),
+        "containment_id": grant.id,
+        "containment": {**grant.to_dict(), "contained": False, "enforced": [], "pending": True, "executed": False},
+        "pgid": None if os.name == "nt" else proc.pid,
         # Identity, not just a slot. The pid above is reused by the kernel, and
         # this record outlives the process and the server; the token is what a
         # later run compares before it signals anything. See
         # src/process_ownership.py.
         "start_token": process_ownership.capture(proc.pid)["start_token"],
     }
-    jobs = _load()
-    jobs[job_id] = rec
-    _save(jobs)
+    try:
+        containment._update_record(grant.id, lifetime="background", supervisor_pid=proc.pid,
+                                   supervisor_token=rec["start_token"])
+        jobs = _load()
+        jobs[job_id] = rec
+        _save(jobs)
+        # The supervisor cannot execute until the identity and job record are durable.
+        proc.stdin.write(json.dumps(payload).encode("utf-8"))
+        proc.stdin.close()
+    except BaseException:
+        kill_process_tree(proc.pid)
+        proc.wait(timeout=5)
+        containment.release(grant, grace_s=0)
+        raise
+    _LIVE_PROCS[proc.pid] = proc
     return rec
 
 
@@ -194,10 +193,14 @@ def _prune(jobs: Dict[str, Dict[str, Any]], now: float) -> bool:
     return bool(stale)
 
 
+@store_transaction(lambda: _STORE)
 def refresh() -> Dict[str, Dict[str, Any]]:
     """Reconcile every running job against disk. Marks done/failed (incl.
     timeout). Idempotent — safe to call from a poll loop. Returns the store."""
     jobs = _load()
+    for pid, proc in list(_LIVE_PROCS.items()):
+        if proc.poll() is not None:
+            _LIVE_PROCS.pop(pid, None)
     changed = False
     now = time.time()
     for rec in jobs.values():
@@ -212,13 +215,24 @@ def refresh() -> Dict[str, Dict[str, Any]]:
             rec["exit_code"] = code
             rec["status"] = "done" if code == 0 else "failed"
             rec["ended_at"] = now
+            if rec.get("result_path"):
+                try:
+                    report = json.loads(Path(rec["result_path"]).read_text(encoding="utf-8"))
+                    rec.update(report)
+                except (OSError, ValueError):
+                    rec["status"], rec["exit_code"] = "failed", 1
+                    rec["result_unavailable"] = True
             changed = True
         elif (now - rec.get("started_at", now)) > rec.get("max_runtime_s", DEFAULT_MAX_RUNTIME_S):
             # Runaway / stuck — reap it but STILL surface a follow-up.
-            _kill(rec.get("pid"))
-            rec["status"] = "failed"
-            rec["exit_code"] = -1
-            rec["ended_at"] = now
+            outcome = _kill_record(rec)
+            rec["teardown"] = outcome.to_dict()
+            if outcome.dead:
+                rec["status"] = "failed"
+                rec["exit_code"] = -1
+                rec["ended_at"] = now
+            else:
+                rec["kill_failed"] = True
             rec["timed_out"] = True
             changed = True
         elif not _pid_alive(rec.get("pid")) and not exit_path.exists():
@@ -236,9 +250,33 @@ def refresh() -> Dict[str, Dict[str, Any]]:
     return jobs
 
 
-def _kill(pid: Optional[int]) -> None:
+def _kill(pid: Optional[int], **kwargs):
     # Cross-platform process-tree teardown (POSIX killpg / Windows taskkill /T).
-    kill_process_tree(pid)
+    return kill_process_tree(pid, **kwargs)
+
+
+def _kill_record(rec):
+    from src import containment
+    verdict = process_ownership.verify(rec.get("pid"), rec.get("start_token"))
+    if verdict in (process_ownership.FOREIGN, process_ownership.UNVERIFIABLE):
+        return containment.ReleaseOutcome(dead=False, escalated=False, ownership=verdict)
+    if rec.get("containment_id"):
+        record = containment._load_records().get(rec["containment_id"])
+        if record and record.get("pid"):
+            outcome = containment.reap_record(record)
+            if not outcome.dead:
+                return outcome
+    outcome = _kill(rec.get("pid"), start_token=rec.get("start_token"),
+                    pgid=rec.get("pgid"), require_identity=True)
+    proc = _LIVE_PROCS.get(rec.get("pid"))
+    if proc and outcome.dead:
+        proc.wait(timeout=5)
+        _LIVE_PROCS.pop(proc.pid, None)
+    if outcome.dead and rec.get("containment_id"):
+        record = containment._load_records().get(rec["containment_id"])
+        if record and not record.get("pid"):
+            containment.reap_record(record)
+    return outcome
 
 
 def pending_followups() -> List[Dict[str, Any]]:
@@ -249,6 +287,7 @@ def pending_followups() -> List[Dict[str, Any]]:
             if r.get("status") in ("done", "failed") and not r.get("followed_up")]
 
 
+@store_transaction(lambda: _STORE)
 def mark_followed_up(job_id: str) -> None:
     jobs = _load()
     if job_id in jobs:
@@ -269,6 +308,7 @@ def list_for_session(session_id: str) -> List[Dict[str, Any]]:
     return [r for r in refresh().values() if r.get("session_id") == session_id]
 
 
+@store_transaction(lambda: _STORE)
 def kill(job_id: str) -> Optional[Dict[str, Any]]:
     """Terminate a running job's process tree and mark it killed. Returns the
     updated record, or None if the id is unknown. Idempotent: a job that already
@@ -279,16 +319,21 @@ def kill(job_id: str) -> Optional[Dict[str, Any]]:
     if rec is None:
         return None
     if rec.get("status") == "running":
-        _kill(rec.get("pid"))
-        rec["status"] = "failed"
-        rec["exit_code"] = -1
-        rec["ended_at"] = time.time()
-        rec["killed"] = True
-        rec["followed_up"] = True
+        outcome = _kill_record(rec)
+        rec["teardown"] = outcome.to_dict()
+        if outcome.dead:
+            rec["status"] = "failed"
+            rec["exit_code"] = -1
+            rec["ended_at"] = time.time()
+            rec["killed"] = True
+            rec["followed_up"] = True
+        else:
+            rec["kill_failed"] = True
         _save(jobs)
     return rec
 
 
+@store_transaction(lambda: _STORE)
 def disown_unverified() -> Dict[str, Any]:
     """Stop tracking running jobs whose process can no longer be proven ours.
 

src/containment.py

@@ -49,6 +49,7 @@ constant is reversible in a way that breaking every host is not.
 from __future__ import annotations
 
 import asyncio
+import codecs
 import json
 import logging
 import os
@@ -63,7 +64,7 @@ from pathlib import Path, PurePosixPath
 from types import MappingProxyType
 from typing import Any, Awaitable, Callable, Mapping, Optional
 
-from core.atomic_io import atomic_write_json
+from core.atomic_io import atomic_write_json, store_transaction
 from core.platform_compat import IS_WINDOWS, find_bash, pid_alive
 
 from src import process_ownership
@@ -439,6 +440,7 @@ def _prune(records: dict[str, dict[str, Any]]) -> dict[str, dict[str, Any]]:
     return kept
 
 
+@store_transaction(lambda: _store_path())
 def _write_record(grant: ContainmentGrant) -> None:
     records = _prune(_load_records())
     records[grant.id] = {
@@ -465,6 +467,7 @@ def _write_record(grant: ContainmentGrant) -> None:
     _save_records(records)
 
 
+@store_transaction(lambda: _store_path())
 def _update_record(grant_id: str, **fields: Any) -> None:
     records = _load_records()
     record = records.get(grant_id)
@@ -487,6 +490,7 @@ def active_grants() -> list[dict[str, Any]]:
     ]
 
 
+@store_transaction(lambda: _store_path())
 def forget(grant_id: str) -> None:
     """Drop a record outright. For a reaper that has finished with it."""
     records = _load_records()
@@ -908,7 +912,7 @@ def _spawn_kwargs(grant: ContainmentGrant) -> dict[str, Any]:
     return kwargs
 
 
-async def _drain(stream, buffer: list[str], budget: list[int]) -> None:
+async def _drain(stream, buffer: list[str], budget: list[int], output_cb=None) -> None:
     """Read a stream to EOF, keeping at most ``budget[0]`` bytes.
 
     Reading past the cap and discarding is deliberate: stopping the read would
@@ -921,20 +925,30 @@ async def _drain(stream, buffer: list[str], budget: list[int]) -> None:
     """
     if stream is None:
         return
+    decoder = codecs.getincrementaldecoder("utf-8")(errors="replace")
+    def emit(text):
+        if not text:
+            return
+        buffer.append(text)
+        if output_cb:
+            try:
+                output_cb(text)
+            except OSError:
+                budget[0] = -1
+                logger.warning("containment: output sink failed", exc_info=True)
     while True:
         line = await stream.read(65536)
         if not line:
+            emit(decoder.decode(b"", final=True))
             break
         if budget[0] < 0:
             continue
-        if len(line) <= budget[0]:
-            budget[0] -= len(line)
-            buffer.append(line.decode("utf-8", errors="replace"))
-            continue
-        chunk = line[: budget[0]]
+        chunk = line[:budget[0]]
         if chunk:
-            buffer.append(chunk.decode("utf-8", errors="replace"))
-        budget[0] = -1
+            emit(decoder.decode(chunk))
+            if budget[0] < 0:
+                continue
+        budget[0] = budget[0] - len(line) if len(line) <= budget[0] else -1
 
 
 async def run(
@@ -944,6 +958,7 @@ async def run(
     argv: bool = False,
     stdin: Optional[bytes] = None,
     progress_cb: Optional[Callable[[dict], Awaitable[None]]] = None,
+    output_cb: Optional[Callable[[str], None]] = None,
 ) -> ContainmentResult:
     """Execute inside an existing grant.
 
@@ -1006,8 +1021,8 @@ async def run(
     err_budget = [int(spec.max_output_bytes)]
     started = time.time()
     readers = [
-        asyncio.create_task(_drain(proc.stdout, out_buf, out_budget)),
-        asyncio.create_task(_drain(proc.stderr, err_buf, err_budget)),
+        asyncio.create_task(_drain(proc.stdout, out_buf, out_budget, output_cb)),
+        asyncio.create_task(_drain(proc.stderr, err_buf, err_budget, output_cb)),
     ]
     async def _wait() -> None:
         # Pipe backpressure is execution time too. Feeding a child that never
@@ -1027,7 +1042,8 @@ async def run(
             await asyncio.sleep(2.0)
             if progress_cb:
                 try:
-                    await progress_cb({"elapsed_s": round(time.time() - started, 1)})
+                    tail = "\n".join(("".join(out_buf) + "".join(err_buf)).splitlines()[-12:])[-8192:]
+                    await progress_cb({"elapsed_s": round(time.time() - started, 1), "tail": tail})
                 except Exception:
                     pass
 
@@ -1257,7 +1273,8 @@ def _ownership_gate(
     )
 
 
-def release(grant: ContainmentGrant, *, grace_s: float = 2.0) -> ReleaseOutcome:
+def release(grant: ContainmentGrant, *, grace_s: float = 2.0,
+            start_token: Optional[str] = None, require_identity: bool = False) -> ReleaseOutcome:
     """Authoritative teardown: signal the group, escalate, then verify.
 
     Returns whether the tree is **observed** gone. A caller must not record a
@@ -1276,12 +1293,12 @@ def release(grant: ContainmentGrant, *, grace_s: float = 2.0) -> ReleaseOutcome:
     # pid had to be recovered from the durable store is the restart case, and
     # there the pid is a *claim* about a process this run never started.
     recovered = pid is None
-    token: Optional[str] = None
+    token: Optional[str] = start_token
     if pid is None or (pgid is None and not IS_WINDOWS):
         record = _load_records().get(grant.id) or {}
         pid = pid if pid is not None else record.get("pid")
         pgid = pgid if pgid is not None else record.get("pgid")
-        token = record.get("start_token")
+        token = token or record.get("start_token")
     try:
         pid = int(pid) if pid else 0
     except (TypeError, ValueError):
@@ -1301,7 +1318,7 @@ def release(grant: ContainmentGrant, *, grace_s: float = 2.0) -> ReleaseOutcome:
         _finish_release(grant, outcome)
         return outcome
 
-    if recovered:
+    if recovered or require_identity:
         refusal = _ownership_gate(grant, pid, pgid, token)
         if refusal is not None:
             _finish_release(grant, refusal)
@@ -1336,6 +1353,11 @@ def release(grant: ContainmentGrant, *, grace_s: float = 2.0) -> ReleaseOutcome:
         time.sleep(_DEATH_POLL_S)
     if not _tree_gone(pid, pgid, reap=True):
         escalated = True
+        if recovered or require_identity:
+            refusal = _ownership_gate(grant, pid, pgid, token)
+            if refusal is not None:
+                _finish_release(grant, refusal)
+                return refusal
         _signal_tree(pid, pgid, signal.SIGKILL)
         # SIGKILL cannot be caught, so a short verification window is enough.
         # Anything still here is out of our reach — a zombie whose parent is

src/containment_worker.py

@@ -0,0 +1,77 @@
+"""Trusted detached supervisor; command execution stays in containment.run."""
+from __future__ import annotations
+
+import asyncio
+import json
+import signal
+import sys
+import types
+from pathlib import Path
+
+# Launch by absolute script path, so a task workspace cannot shadow src.
+sys.path.insert(0, str(Path(__file__).resolve().parent.parent))
+# This supervisor needs atomic I/O and platform primitives, not core's chat
+# facade (auth, database, LLM startup). Keep that facade out of the detached
+# process without changing the application's normal imports.
+core_package = types.ModuleType("core")
+core_package.__path__ = [str(Path(__file__).resolve().parent.parent / "core")]
+sys.modules["core"] = core_package
+
+from core.atomic_io import atomic_write_json, atomic_write_text
+from src import containment
+
+
+async def supervise(payload: dict) -> None:
+    containment._store_path = lambda: Path(payload["store_path"])
+    data = payload["spec"]
+    data["required"] = frozenset(data["required"])
+    spec = containment.ContainmentSpec(**data)
+    info = payload["grant"]
+    grant = containment.ContainmentGrant(
+        id=info["id"], mechanism=info["mechanism"], workspace=spec.workspace,
+        enforced=frozenset(info["enforced"]), degraded=tuple(info["degraded"]),
+        unenforced_required=tuple(info["unenforced_required"]), owner=info["owner"],
+        mode=info["mode"], spec=spec,
+    )
+    task = asyncio.current_task()
+    loop = asyncio.get_running_loop()
+    if sys.platform != "win32":
+        loop.add_signal_handler(signal.SIGTERM, task.cancel)
+        loop.add_signal_handler(signal.SIGINT, task.cancel)
+    try:
+        with open(payload["log_path"], "w", encoding="utf-8") as log:
+            def capture(text):
+                log.write(text)
+                log.flush()
+            result = await containment.run(grant, payload["command"], output_cb=capture)
+        output = ""
+        code = 124 if result.timed_out else result.exit_code
+        if not result.release or not result.release.dead:
+            code = 1
+        report = {"containment": result.grant.to_dict(),
+                  "teardown": result.release.to_dict() if result.release else {"dead": False},
+                  "output_truncated": result.output_truncated,
+                  "timed_out": result.timed_out}
+        report["containment"]["executed"] = True
+        if result.output_truncated:
+            output = "\n…[output truncated by containment capture limit]…\n"
+    except BaseException as exc:
+        record = containment._load_records().get(grant.id, {})
+        output, code = f"background execution failed: {type(exc).__name__}: {exc}\n", 1
+        report = {"containment": grant.to_dict(), "teardown": record.get("release") or {"dead": False},
+                  "output_truncated": False}
+        report["containment"]["executed"] = bool(record.get("pid"))
+        if not record.get("pid"):
+            report["containment"].update(contained=False, enforced=[])
+        if isinstance(exc, containment.ContainmentUnavailable):
+            report.update(containment.unavailable_tool_result(exc, tool="bash"))
+    if output:
+        with open(payload["log_path"], "a", encoding="utf-8") as log:
+            log.write(output)
+    atomic_write_json(payload["result_path"], report)
+    # Publish completion last: refresh must never see an exit without metadata.
+    atomic_write_text(payload["exit_path"], str(code if code is not None else 1))
+
+
+if __name__ == "__main__":
+    asyncio.run(supervise(json.load(sys.stdin)))

src/process_reaper.py

@@ -71,6 +71,13 @@ def reap_containment_grants() -> Dict[str, Any]:
             containment.forget(grant_id)
             report["already_gone"] += 1
             continue
+        if record.get("lifetime") == "background" and process_ownership.verify(
+            record.get("supervisor_pid"), record.get("supervisor_token"),
+        ) == process_ownership.OWNED:
+            # Detached jobs deliberately survive a server restart. Their
+            # supervisor owns the wall clock and teardown, independently.
+            report["background_kept"] = report.get("background_kept", 0) + 1
+            continue
         verdict = process_ownership.verify_record(record)
         if verdict == process_ownership.GONE:
             if containment._group_present(record.get("pgid")):

src/tool_execution.py

@@ -1187,6 +1187,10 @@ def _split_bg_marker(content: str):
     return False, content
 
 
+def _agent_subprocess_env() -> dict:
+    return {**os.environ, "TERM": "xterm-256color", "COLUMNS": "120", "LINES": "40", "HOME": _AGENT_WORKDIR}
+
+
 async def _direct_fallback(
     tool: str,
     content: str,
@@ -1197,13 +1201,7 @@ async def _direct_fallback(
     disabled_tools: Optional[set] = None,
     tool_policy: Optional[ToolPolicy] = None,
 ) -> Optional[Dict]:
-    _subproc_env = {
-        **os.environ,
-        "TERM": "xterm-256color",
-        "COLUMNS": "120",
-        "LINES": "40",
-        "HOME": _AGENT_WORKDIR,
-    }
+    _subproc_env = _agent_subprocess_env()
 
     try:
         ctx = {
@@ -1663,7 +1661,11 @@ async def _execute_tool_block_impl(
         if _is_bg and _bg_cmd:
             from src import bg_jobs
             mark_dispatch()
-            rec = bg_jobs.launch(_bg_cmd, session_id=session_id, cwd=agent_cwd())
+            from src import containment
+            try:
+                rec = bg_jobs.launch(_bg_cmd, session_id=session_id, cwd=agent_cwd(), env=_agent_subprocess_env())
+            except containment.ContainmentUnavailable as exc:
+                return "bash (background): containment unavailable", containment.unavailable_tool_result(exc, tool="bash")
             # Only this server launch may seal detached-job authority; a
             # handler/bridge output carrying a job id is not a grant source.
             save_background_authority(rec["id"], active_request_authority())
@@ -1673,7 +1675,7 @@ async def _execute_tool_block_impl(
                 "output": (
                     f"Started background job `{rec['id']}`. It is running detached; "
                     f"do NOT wait for it or poll it. You will be automatically re-invoked "
-                    f"with its full output when it finishes. Continue with other work, or "
+                    f"with its captured output and any capture limit when it finishes. Continue with other work, or "
                     f"end your turn now and resume when the result arrives. If the user "
                     f"later asks to check progress or stop it, call the manage_bg_jobs "
                     f"tool yourself (output or kill); do not tell them to run a tool "
@@ -1681,6 +1683,7 @@ async def _execute_tool_block_impl(
                 ),
                 "exit_code": 0,
                 "bg_job_id": rec["id"],
+                "containment": rec.get("containment"),
             }
             logger.info(f"Tool executed: {desc} -> bg job {rec['id']}")
             return desc, result

tests/test_background_containment.py

@@ -0,0 +1,126 @@
+"""Detached Bash uses the same boundary; restart and kill retain ownership."""
+import asyncio
+import os
+import time
+from collections import namedtuple
+
+import pytest
+
+from src import bg_jobs, containment, process_ownership, process_reaper, tool_execution
+from src.tool_execution import NO_TOOL_SECURITY_CONTEXT
+from tests.runtime_evidence_helpers import server_authorized_executor
+
+
+@pytest.fixture
+def jobs(tmp_path, monkeypatch):
+    monkeypatch.setattr(bg_jobs, "_JOBS_DIR", tmp_path / "jobs")
+    monkeypatch.setattr(bg_jobs, "_STORE", tmp_path / "jobs.json")
+    monkeypatch.setattr(containment, "_store_path", lambda: tmp_path / "grants.json")
+    monkeypatch.setattr(containment, "CONTAINMENT_MODE", containment.MODE_REPORT_ONLY)
+    monkeypatch.setattr(containment, "MECHANISMS", tuple(m for m in containment.MECHANISMS if m.name == "process_group"))
+    monkeypatch.setattr(tool_execution, "_owner_is_admin", lambda owner: True)
+    launched = []
+    yield tmp_path, launched
+    for record in launched:
+        current = bg_jobs.get(record["id"])
+        if current and current["status"] == "running":
+            bg_jobs.kill(record["id"])
+        proc = bg_jobs._LIVE_PROCS.pop(record["pid"], None)
+        if proc:
+            proc.wait(timeout=8)
+
+
+def finished(job_id):
+    deadline = time.monotonic() + 10
+    while time.monotonic() < deadline:
+        record = bg_jobs.get(job_id)
+        if record["status"] != "running":
+            return record
+        time.sleep(0.03)
+    pytest.fail("background job did not finish")
+
+
+def test_detached_execution_owns_boundary_and_reports_death(jobs):
+    path, launched = jobs
+    record = bg_jobs.launch("printf captured", "chat", cwd=str(path))
+    launched.append(record)
+    result = finished(record["id"])
+    assert result["output"] == "captured"
+    assert result["exit_code"] == 0
+    assert result["containment"]["mechanism"] == "process_group"
+    assert result["containment"]["contained"] is False
+    assert result["teardown"]["dead"] is True
+
+
+async def test_bg_marker_refuses_without_spawning_and_authority_still_gates(jobs, monkeypatch):
+    path, _ = jobs
+    monkeypatch.setattr(containment, "CONTAINMENT_MODE", containment.MODE_ENFORCING)
+    monkeypatch.setattr(bg_jobs.subprocess, "Popen", lambda *args, **kwargs: pytest.fail("uncontained bg spawn"))
+    block = namedtuple("Block", "tool_type content")("bash", "#!bg\nprintf unsafe")
+    execute = server_authorized_executor(tool_execution.execute_tool_block)
+    _, result = await execute(block, session_id="chat", owner="alice", workspace=str(path),
+                              security_context=NO_TOOL_SECURITY_CONTEXT)
+    assert result["containment"]["executed"] is False
+    assert "bg_job_id" not in result
+    _, denied = await tool_execution.execute_tool_block(
+        block, session_id="chat", owner="alice", workspace=str(path),
+        security_context=NO_TOOL_SECURITY_CONTEXT, request_authority=None,
+    )
+    assert denied["failure_kind"] == "request_authority_denied"
+
+
+def test_detached_supervisor_enforces_timeout(jobs):
+    path, launched = jobs
+    record = bg_jobs.launch("sleep 60", "chat", cwd=str(path), max_runtime_s=1)
+    launched.append(record)
+    result = finished(record["id"])
+    assert result["timed_out"] is True
+    assert result["teardown"]["dead"] is True
+
+
+def test_restart_keeps_verified_background_supervisor(jobs):
+    path, launched = jobs
+    record = bg_jobs.launch("sleep 60", "chat", cwd=str(path))
+    launched.append(record)
+    report = process_reaper.reap_containment_grants()
+    assert report["background_kept"] == 1
+    killed = bg_jobs.kill(record["id"])
+    assert killed["killed"] is True
+    assert killed["teardown"]["dead"] is True
+
+
+def test_kill_never_marks_a_foreign_pid_killed(jobs, monkeypatch):
+    record = {"id": "stale", "status": "running", "pid": 12345, "start_token": "old",
+              "session_id": "chat", "started_at": time.time(), "exit_path": "missing"}
+    bg_jobs._save({"stale": record})
+    monkeypatch.setattr(process_ownership, "verify", lambda *args: process_ownership.FOREIGN)
+    monkeypatch.setattr(bg_jobs, "_kill", lambda *args, **kwargs: pytest.fail("foreign process signalled"))
+    result = bg_jobs.kill("stale")
+    assert result["status"] == "running"
+    assert result.get("killed") is not True
+    assert result["teardown"]["dead"] is False
+
+
+def test_running_detached_output_and_concurrent_grants_are_preserved(jobs):
+    path, launched = jobs
+    for number in range(3):
+        launched.append(bg_jobs.launch(f"printf job-{number}; sleep 0.3", "chat", cwd=str(path)))
+    for number, record in enumerate(launched):
+        assert finished(record["id"])["output"] == f"job-{number}"
+    grants = containment._load_records()
+    assert {record["containment_id"] for record in launched} <= grants.keys()
+    assert all(grants[record["containment_id"]]["release"]["dead"] for record in launched)
+
+
+def test_detached_output_is_available_while_running(jobs):
+    path, launched = jobs
+    record = bg_jobs.launch("printf progress; sleep 5", "chat", cwd=str(path))
+    launched.append(record)
+    deadline = time.monotonic() + 3
+    while time.monotonic() < deadline:
+        current = bg_jobs.get(record["id"])
+        if "progress" in current["output"]:
+            assert current["status"] == "running"
+            return
+        time.sleep(0.03)
+    pytest.fail("detached stdout was unavailable until completion")

tests/test_bg_job_tools.py

@@ -11,7 +11,7 @@ import time
 
 import pytest
 
-from src import bg_jobs
+from src import bg_jobs, containment, process_ownership
 from src.agent_tools.bg_job_tools import ManageBgJobsTool
 
 
@@ -23,7 +23,11 @@ def store(tmp_path, monkeypatch):
     monkeypatch.setattr(bg_jobs, "_JOBS_DIR", jobs_dir)
     monkeypatch.setattr(bg_jobs, "_pid_alive", lambda pid: True)
     killed: list = []
-    monkeypatch.setattr(bg_jobs, "_kill", lambda pid: killed.append(pid))
+    monkeypatch.setattr(process_ownership, "verify", lambda *args: process_ownership.OWNED)
+    def fake_kill(pid, **kwargs):
+        killed.append(pid)
+        return containment.ReleaseOutcome(dead=True, escalated=False)
+    monkeypatch.setattr(bg_jobs, "_kill", fake_kill)
     return {"dir": jobs_dir, "killed": killed}
 
 

tests/test_native_execution_containment.py

@@ -140,3 +140,14 @@ async def test_python_final_expression_and_opt_in_imports(native_boundary):
     })
     assert result["output"] == "42"
     assert result["teardown"]["dead"] is True
+
+
+async def test_capture_preserves_multibyte_text_across_chunks(native_boundary):
+    spec = containment.ContainmentSpec(
+        workspace=str(native_boundary), env=dict(os.environ), wall_clock_s=5,
+        required=frozenset({containment.PROCESS_TREE, containment.WALL_CLOCK}), max_output_bytes=200000,
+    )
+    result = await containment.run(containment.acquire(spec, owner="unicode"),
+        [sys.executable, "-c", "import sys; sys.stdout.write('€' * 30000)"], argv=True)
+    assert result.stdout == "€" * 30000
+    assert result.output_truncated is False