diff --git a/src/hqt/cli.py b/src/hqt/cli.py
index 7069f7f..6460e94 100644
--- a/src/hqt/cli.py
+++ b/src/hqt/cli.py
@@ -1,5 +1,6 @@
 import logging
 import os
+import shutil
 import subprocess
 import sys
 import traceback
@@ -105,7 +106,7 @@ def launch(inside_tmux: bool = False):
 @main.command()
 def doctor():
     """Check system requirements."""
-    import shutil
+    from hqt import sandbox
     from hqt.harnesses.registry import discover_harnesses
 
     tmux = shutil.which("tmux")
@@ -119,6 +120,12 @@ def doctor():
         click.echo(f"{name}: ✓")
     if not harnesses:
         click.echo("No harnesses found on PATH")
+    # Use the shared helper so doctor agrees with the New Session dialog and the
+    # spawn backstop (single source of truth: Linux + bwrap on PATH).
+    if sandbox.is_available():
+        click.echo(f"bubblewrap: ✓ {shutil.which('bwrap')}")
+    else:
+        click.echo("bubblewrap: ✗ not found — sandboxed sessions unavailable")
 
 
 @main.command(name="list")
diff --git a/src/hqt/db/migrations.py b/src/hqt/db/migrations.py
index d8b7f02..c91c164 100644
--- a/src/hqt/db/migrations.py
+++ b/src/hqt/db/migrations.py
@@ -36,9 +36,14 @@ def _migrate_v3(conn: Connection) -> None:
     )
 
 
+def _migrate_v4(conn: Connection) -> None:
+    conn.exec_driver_sql("ALTER TABLE sessions ADD COLUMN sandbox_json TEXT")
+
+
 MIGRATIONS: list[tuple[int, Callable[[Connection], None]]] = [
     (2, _migrate_v2),
     (3, _migrate_v3),
+    (4, _migrate_v4),
 ]
 
 BASELINE_VERSION = 1
diff --git a/src/hqt/db/models.py b/src/hqt/db/models.py
index cc70a68..7dcc6bc 100644
--- a/src/hqt/db/models.py
+++ b/src/hqt/db/models.py
@@ -38,6 +38,7 @@ class Session(Base):
     tmux_session_name: Mapped[str] = mapped_column(unique=True)
     harness_session_id: Mapped[str | None] = mapped_column(default=None)
     model: Mapped[str | None] = mapped_column(default=None)
+    sandbox_json: Mapped[str | None] = mapped_column(default=None)
     worktree_path: Mapped[str | None] = mapped_column(default=None)
     worktree_branch: Mapped[str | None] = mapped_column(default=None)
     created_at: Mapped[datetime] = mapped_column(insert_default=func.now())
diff --git a/src/hqt/harnesses/base.py b/src/hqt/harnesses/base.py
index ba03a19..6f49ab9 100644
--- a/src/hqt/harnesses/base.py
+++ b/src/hqt/harnesses/base.py
@@ -2,6 +2,8 @@ from abc import ABC, abstractmethod
 from dataclasses import dataclass, field
 from pathlib import Path
 
+from hqt.sandbox import Bind
+
 
 @dataclass
 class SpawnConfig:
@@ -14,20 +16,34 @@ class HarnessConfigurator(ABC):
     name: str
     display_name: str
     captures_session_id: bool = False
+    # Flags appended to the harness command when the session is sandboxed.
+    sandbox_skip_permission_flags: list[str] = []
 
     @abstractmethod
     def generate_session_id(self, hqt_session_id: int) -> str: ...
 
     @abstractmethod
     def build_spawn_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig: ...
 
     @abstractmethod
     def build_resume_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig: ...
 
+    def sandbox_binds(self) -> list[Bind]:
+        """Host paths this harness needs inside the jail (credentials, config)."""
+        return []
+
     def capture_session_id(self, project_path: Path, since: float) -> str | None:
         return None
 
diff --git a/src/hqt/harnesses/configurators/claude.py b/src/hqt/harnesses/configurators/claude.py
index 3adbded..d9e08a5 100644
--- a/src/hqt/harnesses/configurators/claude.py
+++ b/src/hqt/harnesses/configurators/claude.py
@@ -2,6 +2,7 @@ import uuid
 from pathlib import Path
 
 from hqt.harnesses.base import HarnessConfigurator, SpawnConfig
+from hqt.sandbox import Bind
 
 NAMESPACE = uuid.UUID("a1b2c3d4-e5f6-7890-abcd-ef1234567890")
 
@@ -9,6 +10,7 @@ NAMESPACE = uuid.UUID("a1b2c3d4-e5f6-7890-abcd-ef1234567890")
 class ClaudeConfigurator(HarnessConfigurator):
     name = "claude"
     display_name = "Claude Code"
+    sandbox_skip_permission_flags = ["--dangerously-skip-permissions"]
 
     # Markers for parse_status — conservative, case-insensitive substring checks.
     # None returned when none match; caller falls back to activity-based status.
@@ -21,20 +23,35 @@ class ClaudeConfigurator(HarnessConfigurator):
     def generate_session_id(self, hqt_session_id: int) -> str:
         return str(uuid.uuid5(NAMESPACE, str(hqt_session_id)))
 
+    def sandbox_binds(self) -> list[Bind]:
+        return [Bind(Path.home() / ".claude", writable=True)]
+
     def build_spawn_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         cmd = ["claude", "--session-id", harness_session_id]
         if model:
             cmd += ["--model", model]
+        if sandboxed:
+            cmd += self.sandbox_skip_permission_flags
         return SpawnConfig(command=cmd, cwd=project_path)
 
     def build_resume_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         cmd = ["claude", "--resume", harness_session_id]
         if model:
             cmd += ["--model", model]
+        if sandboxed:
+            cmd += self.sandbox_skip_permission_flags
         return SpawnConfig(command=cmd, cwd=project_path)
 
     def parse_status(self, pane_text: str) -> str | None:
diff --git a/src/hqt/harnesses/configurators/codex.py b/src/hqt/harnesses/configurators/codex.py
index 10107f4..8555fa0 100644
--- a/src/hqt/harnesses/configurators/codex.py
+++ b/src/hqt/harnesses/configurators/codex.py
@@ -4,6 +4,7 @@ from datetime import datetime
 from pathlib import Path
 
 from hqt.harnesses.base import HarnessConfigurator, SpawnConfig
+from hqt.sandbox import Bind
 
 log = logging.getLogger(__name__)
 
@@ -12,6 +13,7 @@ class CodexConfigurator(HarnessConfigurator):
     name = "codex"
     display_name = "Codex"
     captures_session_id = True
+    sandbox_skip_permission_flags = ["--dangerously-bypass-approvals-and-sandbox"]
 
     # Markers for parse_status — conservative, case-insensitive substring checks.
     _WORKING_MARKERS = ("esc to interrupt",)
@@ -19,20 +21,35 @@ class CodexConfigurator(HarnessConfigurator):
     def generate_session_id(self, hqt_session_id: int) -> str:
         return str(hqt_session_id)
 
+    def sandbox_binds(self) -> list[Bind]:
+        return [Bind(Path.home() / ".codex", writable=True)]
+
     def build_spawn_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         cmd = ["codex"]
         if model:
             cmd += ["-m", model]
+        if sandboxed:
+            cmd += self.sandbox_skip_permission_flags
         return SpawnConfig(command=cmd, cwd=project_path)
 
     def build_resume_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         cmd = ["codex", "resume", harness_session_id]
         if model:
             cmd += ["-m", model]
+        if sandboxed:
+            cmd += self.sandbox_skip_permission_flags
         return SpawnConfig(command=cmd, cwd=project_path)
 
     def parse_status(self, pane_text: str) -> str | None:
diff --git a/src/hqt/harnesses/configurators/generic.py b/src/hqt/harnesses/configurators/generic.py
index 505ea61..28b48e4 100644
--- a/src/hqt/harnesses/configurators/generic.py
+++ b/src/hqt/harnesses/configurators/generic.py
@@ -14,11 +14,19 @@ class GenericConfigurator(HarnessConfigurator):
         return str(hqt_session_id)
 
     def build_spawn_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         return SpawnConfig(command=self._command, cwd=project_path)
 
     def build_resume_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         return SpawnConfig(command=self._command, cwd=project_path)
diff --git a/src/hqt/harnesses/configurators/kiro.py b/src/hqt/harnesses/configurators/kiro.py
index c652aff..2b30a87 100644
--- a/src/hqt/harnesses/configurators/kiro.py
+++ b/src/hqt/harnesses/configurators/kiro.py
@@ -1,6 +1,7 @@
 from pathlib import Path
 
 from hqt.harnesses.base import HarnessConfigurator, SpawnConfig
+from hqt.sandbox import Bind
 
 
 class KiroConfigurator(HarnessConfigurator):
@@ -10,12 +11,23 @@ class KiroConfigurator(HarnessConfigurator):
     def generate_session_id(self, hqt_session_id: int) -> str:
         return str(hqt_session_id)
 
+    def sandbox_binds(self) -> list[Bind]:
+        return [Bind(Path.home() / ".kiro", writable=True)]
+
     def build_spawn_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         return SpawnConfig(command=["kiro-cli", "chat"], cwd=project_path)
 
     def build_resume_config(
-        self, project_path: Path, harness_session_id: str, model: str | None = None
+        self,
+        project_path: Path,
+        harness_session_id: str,
+        model: str | None = None,
+        sandboxed: bool = False,
     ) -> SpawnConfig:
         return SpawnConfig(command=["kiro-cli", "chat"], cwd=project_path)
diff --git a/src/hqt/sandbox.py b/src/hqt/sandbox.py
new file mode 100644
index 0000000..0dbca8a
--- /dev/null
+++ b/src/hqt/sandbox.py
@@ -0,0 +1,81 @@
+import os
+import shutil
+import sys
+from dataclasses import dataclass
+from pathlib import Path
+
+
+@dataclass(frozen=True)
+class Bind:
+    """A host path to expose inside the sandbox (read-only unless writable)."""
+
+    src: Path
+    writable: bool = False
+
+
+@dataclass(frozen=True)
+class SandboxPolicy:
+    """Per-session sandbox settings.
+
+    fs:  "rw" binds the project dir writable; "ro" binds it read-only.
+    net: True shares the host network namespace; False = no connectivity.
+    """
+
+    fs: str
+    net: bool
+
+
+def is_available() -> bool:
+    """True when bubblewrap can be used: Linux with `bwrap` on PATH.
+
+    The single source of truth for both `hqt doctor` and the New Session dialog.
+    """
+    return sys.platform.startswith("linux") and shutil.which("bwrap") is not None
+
+
+# System paths bound read-only so binaries and shared libraries resolve.
+_SYSTEM_RO_PATHS = ["/usr", "/bin", "/sbin", "/lib", "/lib64", "/etc", "/opt"]
+
+# Environment variables passed through into the jail.
+_PASSTHROUGH_ENV = ["PATH", "HOME", "TERM", "LANG", "LC_ALL", "USER", "SHELL"]
+
+
+def wrap(
+    command: list[str],
+    cwd: Path,
+    policy: SandboxPolicy,
+    binds: list[Bind],
+) -> list[str]:
+    """Build the `bwrap … -- <command>` argv for a sandboxed harness.
+
+    Minimal-allowlist model: $HOME and other user data are NOT exposed. System
+    dirs are read-only; the project dir (cwd) and each existing harness bind are
+    bound explicitly. Network is all-or-nothing: shared only when policy.net.
+    Binds whose source does not exist are skipped (bwrap would otherwise error).
+    """
+    args: list[str] = ["bwrap", "--die-with-parent", "--unshare-all"]
+    if policy.net:
+        args.append("--share-net")
+    for path in _SYSTEM_RO_PATHS:
+        if Path(path).exists():
+            args += ["--ro-bind", path, path]
+    # Git reads user.name/email from ~/.gitconfig; without it `git commit` fails
+    # inside the jail. Bound read-only since $HOME itself is hidden.
+    gitconfig = Path.home() / ".gitconfig"
+    if gitconfig.exists():
+        args += ["--ro-bind", str(gitconfig), str(gitconfig)]
+    args += ["--proc", "/proc", "--dev", "/dev", "--tmpfs", "/tmp"]
+    for bind in binds:
+        if not bind.src.exists():
+            continue
+        flag = "--bind" if bind.writable else "--ro-bind"
+        args += [flag, str(bind.src), str(bind.src)]
+    cwd_flag = "--bind" if policy.fs == "rw" else "--ro-bind"
+    args += [cwd_flag, str(cwd), str(cwd)]
+    for name in _PASSTHROUGH_ENV:
+        value = os.environ.get(name)
+        if value is not None:
+            args += ["--setenv", name, value]
+    args.append("--")
+    args += command
+    return args
diff --git a/src/hqt/sessions/service.py b/src/hqt/sessions/service.py
index 1f4579c..83ee26c 100644
--- a/src/hqt/sessions/service.py
+++ b/src/hqt/sessions/service.py
@@ -1,8 +1,9 @@
 import asyncio
 import contextlib
+import json
 import logging
 import time
-from collections.abc import Mapping
+from collections.abc import Mapping, Sequence
 from dataclasses import dataclass
 from datetime import UTC, datetime
 from pathlib import Path
@@ -10,11 +11,13 @@ from pathlib import Path
 from sqlalchemy.orm import Session as DBSession
 from sqlalchemy.orm import selectinload, sessionmaker
 
+from hqt import sandbox
 from hqt.db.models import Harness, Project, ScheduledPrompt, Session
 from hqt.errors import ServiceError
 from hqt.git import worktree
 from hqt.git.worktree import WorktreeState
 from hqt.harnesses.base import HarnessConfigurator, SpawnConfig
+from hqt.sandbox import Bind, SandboxPolicy
 from hqt.status import window_label
 from hqt.tmux.manager import SpawnRequest, TmuxManager
 from hqt.tmux.runner import WindowInfo
@@ -164,6 +167,51 @@ class SessionService:
             return created_at.timestamp()
         return 0.0
 
+    def _sandbox_policy(self, sess: Session) -> SandboxPolicy | None:
+        """Decode the persisted sandbox policy, or None if the session is plain."""
+        if not sess.sandbox_json:
+            return None
+        data = json.loads(sess.sandbox_json)
+        return SandboxPolicy(fs=data["fs"], net=data["net"])
+
+    def _worktree_git_binds(self, db: DBSession, sess: Session) -> list[Bind]:
+        """Extra binds a sandboxed worktree session needs for git to work.
+
+        A linked worktree's `.git` is a file pointing at the real gitdir under
+        the repo's common `.git` directory (`<repo>/.git/worktrees/<branch>`),
+        which lives OUTSIDE the bound cwd. Bind the repo's `.git` writable so
+        git operations (status, commit) resolve inside the jail. Plain sessions
+        need nothing extra.
+        """
+        if not sess.worktree_path or sess.worktree_branch is None:
+            return []
+        repo = self._repo_path_for_worktree(
+            db, sess.project_id, sess.worktree_path, sess.worktree_branch
+        )
+        return [Bind(repo / ".git", writable=True)]
+
+    def _wrap_command(
+        self,
+        configurator: HarnessConfigurator,
+        command: list[str],
+        cwd: Path,
+        policy: SandboxPolicy | None,
+        extra_binds: Sequence[Bind] = (),
+    ) -> list[str]:
+        """Wrap a harness command in bwrap when a policy is set.
+
+        Raises ServiceError if a sandbox is required but bwrap is unavailable —
+        a backstop; the dialog already disables the toggle in that case.
+        """
+        if policy is None:
+            return command
+        if not sandbox.is_available():
+            raise ServiceError(
+                "bubblewrap (bwrap) is not available; cannot start a sandboxed session"
+            )
+        binds = [*configurator.sandbox_binds(), *extra_binds]
+        return sandbox.wrap(command, cwd, policy, binds)
+
     def _maybe_capture_missing_session_id(self, db: DBSession, sess: Session) -> None:
         configurator = self.harnesses.get(sess.harness.name)
         if configurator is None or not configurator.captures_session_id:
@@ -197,6 +245,7 @@ class SessionService:
         nickname: str | None = None,
         model: str | None = None,
         worktree_branch: str | None = None,
+        sandbox: SandboxPolicy | None = None,
     ) -> "CreateSessionResult":
         """Create a new session row, spawn the harness window, and return a
         CreateSessionResult with the Session row and spawn outcome.
@@ -243,13 +292,25 @@ class SessionService:
             sess.tmux_session_name = f"hqt-{sess.id}"
             harness_session_id = configurator.generate_session_id(sess.id)
             sess.harness_session_id = harness_session_id
+            sess.sandbox_json = (
+                json.dumps({"fs": sandbox.fs, "net": sandbox.net})
+                if sandbox is not None
+                else None
+            )
             spawn_cfg = configurator.build_spawn_config(
-                run_path, harness_session_id, model
+                run_path, harness_session_id, model, sandboxed=sandbox is not None
+            )
+            command = self._wrap_command(
+                configurator,
+                spawn_cfg.command,
+                spawn_cfg.cwd,
+                sandbox,
+                self._worktree_git_binds(db, sess),
             )
             log.info(
                 "Spawning window %s: cmd=%s cwd=%s",
                 sess.tmux_session_name,
-                spawn_cfg.command,
+                command,
                 spawn_cfg.cwd,
             )
             async with self._maybe_capture_lock(configurator.captures_session_id):
@@ -257,7 +318,7 @@ class SessionService:
                 spawn_result = await self.tmux.spawn(
                     SpawnRequest(
                         window_name=sess.tmux_session_name,
-                        command=spawn_cfg.command,
+                        command=command,
                         cwd=str(spawn_cfg.cwd),
                         env=spawn_cfg.env,
                     )
@@ -358,13 +419,21 @@ class SessionService:
         harness_session_id = (
             sess.harness_session_id or configurator.generate_session_id(sess.id)
         )
+        policy = self._sandbox_policy(sess)
         spawn_cfg = configurator.build_spawn_config(
-            run_path, harness_session_id, sess.model
+            run_path, harness_session_id, sess.model, sandboxed=policy is not None
+        )
+        command = self._wrap_command(
+            configurator,
+            spawn_cfg.command,
+            spawn_cfg.cwd,
+            policy,
+            self._worktree_git_binds(db, sess),
         )
         async with self._maybe_capture_lock(configurator.captures_session_id):
             since = time.time()
             result = await self.tmux.respawn_verified(
-                window_name, spawn_cfg.command, str(spawn_cfg.cwd), env=spawn_cfg.env
+                window_name, command, str(spawn_cfg.cwd), env=spawn_cfg.env
             )
             if not result.ok:
                 log.error(
@@ -643,6 +712,14 @@ class SessionService:
         harness_session_id = (
             sess.harness_session_id or configurator.generate_session_id(sess.id)
         )
-        return configurator.build_resume_config(
-            self._session_path(db, sess), harness_session_id, sess.model
+        policy = self._sandbox_policy(sess)
+        cfg = configurator.build_resume_config(
+            self._session_path(db, sess),
+            harness_session_id,
+            sess.model,
+            sandboxed=policy is not None,
         )
+        command = self._wrap_command(
+            configurator, cfg.command, cfg.cwd, policy, self._worktree_git_binds(db, sess)
+        )
+        return SpawnConfig(command=command, env=cfg.env, cwd=cfg.cwd)
diff --git a/src/hqt/tui/app.py b/src/hqt/tui/app.py
index 82a1de1..2726734 100644
--- a/src/hqt/tui/app.py
+++ b/src/hqt/tui/app.py
@@ -10,6 +10,7 @@ from textual.screen import ModalScreen
 from textual.theme import Theme
 from textual.widgets import Footer
 
+from hqt import sandbox
 from hqt.config import get_settings
 from hqt.git import worktree
 from hqt.db.engine import ensure_db, get_engine, get_session_factory
@@ -255,10 +256,10 @@ class HqtApp(App):
         project_path = project.path
 
         def on_dismiss(
-            result: tuple[str, str, str | None, str | None] | None,
+            result: tuple[str, str, str | None, str | None, object] | None,
         ) -> None:
             if result:
-                harness_name, nickname, model, worktree_branch = result
+                harness_name, nickname, model, worktree_branch, sandbox_policy = result
 
                 async def _do() -> None:
                     create_result = await self._sessions().create_session(
@@ -267,6 +268,7 @@ class HqtApp(App):
                         nickname,
                         model,
                         worktree_branch=worktree_branch,
+                        sandbox=sandbox_policy,
                     )
                     if not create_result.spawn_ok:
                         first_line = next(
@@ -296,7 +298,14 @@ class HqtApp(App):
             except Exception as exc:  # noqa: BLE001 - keep the worker from crashing the TUI
                 log.warning("is_git_repo check failed for %s: %s", project_path, exc)
                 is_git_repo = False
-            self.push_screen(NewSessionScreen(harness_names, is_git_repo), on_dismiss)
+            self.push_screen(
+                NewSessionScreen(
+                    harness_names,
+                    is_git_repo,
+                    sandbox_available=sandbox.is_available(),
+                ),
+                on_dismiss,
+            )
 
         self.run_worker(_open())
 
diff --git a/src/hqt/tui/screens/new_session.py b/src/hqt/tui/screens/new_session.py
index 4933cf9..2b43fd6 100644
--- a/src/hqt/tui/screens/new_session.py
+++ b/src/hqt/tui/screens/new_session.py
@@ -1,15 +1,24 @@
 from textual.app import ComposeResult
 from textual.containers import Horizontal, Vertical
 from textual.screen import ModalScreen
-from textual.widgets import Button, Checkbox, Input, Label, Select
+from textual.widgets import Button, Checkbox, Input, Label, Select, Switch
 
 from hqt.git import worktree
+from hqt.sandbox import SandboxPolicy
 
 
-class NewSessionScreen(ModalScreen[tuple[str, str, str | None, str | None] | None]):
-    def __init__(self, harness_names: list[str], is_git_repo: bool) -> None:
+class NewSessionScreen(
+    ModalScreen[tuple[str, str, str | None, str | None, SandboxPolicy | None] | None]
+):
+    def __init__(
+        self,
+        harness_names: list[str],
+        is_git_repo: bool = False,
+        sandbox_available: bool = False,
+    ) -> None:
         self.harness_names = harness_names
         self._is_git_repo = is_git_repo
+        self.sandbox_available = sandbox_available
         super().__init__()
 
     def compose(self) -> ComposeResult:
@@ -43,6 +52,26 @@ class NewSessionScreen(ModalScreen[tuple[str, str, str | None, str | None] | Non
             branch_input = Input(placeholder="branch name", id="branch-input")
             branch_input.display = False
             yield branch_input
+            yield Label("Sandboxed (bubblewrap):")
+            yield Switch(
+                id="sandbox-switch",
+                value=False,
+                disabled=not self.sandbox_available,
+            )
+            if not self.sandbox_available:
+                yield Label(
+                    "bubblewrap not found — run `hqt doctor`",
+                    id="sandbox-warning",
+                )
+            yield Label("Filesystem access:")
+            yield Select(
+                [("Read-write", "rw"), ("Read-only", "ro")],
+                id="fs-select",
+                value="rw",
+                allow_blank=False,
+            )
+            yield Label("Network:")
+            yield Switch(id="net-switch", value=True)
             with Horizontal(classes="dialog-actions"):
                 yield Button("OK", variant="primary", id="ok-btn")
                 yield Button("Cancel", id="cancel-btn")
@@ -71,6 +100,13 @@ class NewSessionScreen(ModalScreen[tuple[str, str, str | None, str | None] | Non
         # can be completed from the keyboard without reaching for the mouse.
         self._submit()
 
+    @staticmethod
+    def _policy_from(enabled: bool, fs: str, net: bool) -> SandboxPolicy | None:
+        """Pure mapping from widget values to a policy (None when disabled)."""
+        if not enabled:
+            return None
+        return SandboxPolicy(fs=fs, net=net)
+
     def _submit(self) -> None:
         harness = self.query_one("#harness-select", Select).value
         nickname = self.query_one("#nickname-input", Input).value
@@ -86,7 +122,12 @@ class NewSessionScreen(ModalScreen[tuple[str, str, str | None, str | None] | Non
                 branch_input.focus()
                 return
 
+        enabled = self.query_one("#sandbox-switch", Switch).value
+        fs = self.query_one("#fs-select", Select).value
+        net = self.query_one("#net-switch", Switch).value
+        policy = self._policy_from(bool(enabled), str(fs), bool(net))
+
         if harness and harness != Select.BLANK:
-            self.dismiss((str(harness), nickname, model, worktree_branch))
+            self.dismiss((str(harness), nickname, model, worktree_branch, policy))
         else:
             self.dismiss(None)
diff --git a/tests/test_cli.py b/tests/test_cli.py
new file mode 100644
index 0000000..377c809
--- /dev/null
+++ b/tests/test_cli.py
@@ -0,0 +1,35 @@
+from unittest.mock import patch
+
+from click.testing import CliRunner
+
+from hqt import cli as cli_module
+from hqt import sandbox
+from hqt.cli import main
+
+
+def _which(found: set[str]):
+    return lambda name: f"/usr/bin/{name}" if name in found else None
+
+
+def test_doctor_reports_bwrap_present():
+    """Test that doctor reports bubblewrap when present."""
+    # tmux is discovered via cli.shutil.which; bwrap availability comes from the
+    # shared sandbox.is_available() helper (the single source of truth).
+    with (
+        patch.object(cli_module.shutil, "which", side_effect=_which({"tmux", "bwrap"})),
+        patch.object(sandbox, "is_available", return_value=True),
+    ):
+        result = CliRunner().invoke(main, ["doctor"])
+    assert result.exit_code == 0
+    assert "bubblewrap: ✓" in result.output
+
+
+def test_doctor_reports_bwrap_missing():
+    """Test that doctor reports bubblewrap as missing when not present."""
+    with (
+        patch.object(cli_module.shutil, "which", side_effect=_which({"tmux"})),
+        patch.object(sandbox, "is_available", return_value=False),
+    ):
+        result = CliRunner().invoke(main, ["doctor"])
+    assert result.exit_code == 0
+    assert "bubblewrap: ✗" in result.output
diff --git a/tests/test_db.py b/tests/test_db.py
index 10c1671..cabeb6d 100644
--- a/tests/test_db.py
+++ b/tests/test_db.py
@@ -98,6 +98,7 @@ def test_unversioned_existing_db_stamped_latest(tmp_path):
         conn.exec_driver_sql("DROP TABLE scheduled_prompts")
         conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN worktree_path")
         conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN worktree_branch")
+        conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN sandbox_json")
     migrate(engine)
     assert _user_version(engine) == migrations.LATEST_VERSION
 
@@ -117,22 +118,23 @@ def test_pending_migrations_applied_in_order_once(tmp_path, monkeypatch):
     ensure_db(settings)  # stamps migrations.LATEST_VERSION
     applied: list[int] = []
     # Use versions above current LATEST_VERSION so none have been applied yet.
+    next_version = migrations.LATEST_VERSION + 1
     monkeypatch.setattr(
         migrations,
         "MIGRATIONS",
         [
             *migrations.MIGRATIONS,
-            (4, lambda conn: applied.append(4)),
-            (5, lambda conn: applied.append(5)),
+            (next_version, lambda conn: applied.append(next_version)),
+            (next_version + 1, lambda conn: applied.append(next_version + 1)),
         ],
     )
-    monkeypatch.setattr(migrations, "LATEST_VERSION", 5)
+    monkeypatch.setattr(migrations, "LATEST_VERSION", next_version + 1)
     engine = get_engine(settings)
     migrate(engine)
-    assert applied == [4, 5]
-    assert _user_version(engine) == 5
+    assert applied == [next_version, next_version + 1]
+    assert _user_version(engine) == next_version + 1
     migrate(engine)  # re-run is a no-op
-    assert applied == [4, 5]
+    assert applied == [next_version, next_version + 1]
 
 
 def _session_column_names(engine) -> list[str]:
@@ -154,11 +156,12 @@ def test_fresh_db_has_worktree_columns(tmp_path):
     cols = _session_column_names(engine)
     assert "worktree_path" in cols
     assert "worktree_branch" in cols
+    assert "sandbox_json" in cols
     assert _user_version(engine) == migrations.LATEST_VERSION
 
 
-def test_v1_db_upgraded_to_v2(tmp_path):
-    # Build a v1 database: create all tables, drop the two new columns, stamp v1.
+def test_v1_db_upgraded_to_latest(tmp_path):
+    # Build a v1 database: create all tables, drop v2+ objects, stamp v1.
     settings = _tmp_settings(tmp_path)
     settings.db_path.parent.mkdir(parents=True, exist_ok=True)
     engine = get_engine(settings)
@@ -167,6 +170,7 @@ def test_v1_db_upgraded_to_v2(tmp_path):
         conn.exec_driver_sql("DROP TABLE scheduled_prompts")
         conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN worktree_path")
         conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN worktree_branch")
+        conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN sandbox_json")
         conn.exec_driver_sql("PRAGMA user_version = 1")
 
     migrate(engine)
@@ -174,6 +178,8 @@ def test_v1_db_upgraded_to_v2(tmp_path):
     cols = _session_column_names(engine)
     assert "worktree_path" in cols
     assert "worktree_branch" in cols
+    assert "sandbox_json" in cols
+    assert "scheduled_prompts" in inspect(engine).get_table_names()
     assert _user_version(engine) == migrations.LATEST_VERSION
 
 
@@ -195,22 +201,24 @@ def test_fresh_db_has_scheduled_prompts_table(tmp_path):
         "created_at",
         "sent_at",
     ]
-    assert _user_version(engine) == 3
+    assert _user_version(engine) == migrations.LATEST_VERSION
 
 
-def test_v2_db_upgraded_to_v3_adds_scheduled_prompts(tmp_path):
+def test_v2_db_upgraded_to_latest_adds_scheduled_prompts_and_sandbox(tmp_path):
     settings = _tmp_settings(tmp_path)
     settings.db_path.parent.mkdir(parents=True, exist_ok=True)
     engine = get_engine(settings)
     Base.metadata.create_all(engine)
     with engine.begin() as conn:
         conn.exec_driver_sql("DROP TABLE scheduled_prompts")
+        conn.exec_driver_sql("ALTER TABLE sessions DROP COLUMN sandbox_json")
         conn.exec_driver_sql("PRAGMA user_version = 2")
 
     migrate(engine)
 
     assert "scheduled_prompts" in inspect(engine).get_table_names()
-    assert _user_version(engine) == 3
+    assert "sandbox_json" in _session_column_names(engine)
+    assert _user_version(engine) == migrations.LATEST_VERSION
 
 
 def test_scheduled_prompt_one_row_per_session(tmp_path):
@@ -291,3 +299,45 @@ def test_rows_stay_readable_after_session_closes(tmp_path):
         session.add(p)
         session.commit()
     assert p.name == "x"  # would raise DetachedInstanceError without the flag
+
+
+def test_latest_version_is_four():
+    assert migrations.LATEST_VERSION == 4
+
+
+def test_migration_adds_sandbox_json_column(tmp_path):
+    # Simulate a v3 DB whose sessions table predates the sandbox column.
+    settings = _tmp_settings(tmp_path)
+    settings.db_path.parent.mkdir(parents=True, exist_ok=True)
+    engine = get_engine(settings)
+    with engine.begin() as conn:
+        conn.exec_driver_sql(
+            "CREATE TABLE sessions ("
+            "id INTEGER PRIMARY KEY, project_id INTEGER, harness_id INTEGER, "
+            "tmux_session_name TEXT)"
+        )
+        conn.exec_driver_sql("PRAGMA user_version = 3")
+    migrate(engine)
+    cols = [c["name"] for c in inspect(engine).get_columns("sessions")]
+    assert "sandbox_json" in cols
+    assert _user_version(engine) == migrations.LATEST_VERSION
+
+
+def test_session_round_trips_sandbox_json(tmp_path):
+    settings = _tmp_settings(tmp_path)
+    ensure_db(settings)
+    factory = get_session_factory(get_engine(settings))
+    with factory() as session:
+        p = Project(name="proj", path="/tmp/proj-sandbox")
+        h = Harness(name="claude-sandbox")
+        session.add_all([p, h])
+        session.commit()
+        s = Session(
+            project_id=p.id,
+            harness_id=h.id,
+            tmux_session_name="hqt-9",
+            sandbox_json='{"fs": "rw", "net": true}',
+        )
+        session.add(s)
+        session.commit()
+        assert session.get(Session, s.id).sandbox_json == '{"fs": "rw", "net": true}'
diff --git a/tests/test_harnesses.py b/tests/test_harnesses.py
index 2e164a6..eae807e 100644
--- a/tests/test_harnesses.py
+++ b/tests/test_harnesses.py
@@ -4,8 +4,11 @@ import time
 from pathlib import Path
 from unittest.mock import patch
 
-from hqt.harnesses.configurators.codex import CodexConfigurator
+from hqt.harnesses.base import HarnessConfigurator
 from hqt.harnesses.configurators.claude import ClaudeConfigurator
+from hqt.harnesses.configurators.codex import CodexConfigurator
+from hqt.harnesses.configurators.generic import GenericConfigurator
+from hqt.harnesses.configurators.kiro import KiroConfigurator
 from hqt.harnesses.registry import discover_harnesses
 
 
@@ -129,8 +132,6 @@ def test_codex_captures_session_id_flag():
 
 def test_base_captures_session_id_flag_false():
     """HarnessConfigurator base class default must be False."""
-    from hqt.harnesses.base import HarnessConfigurator
-
     assert HarnessConfigurator.captures_session_id is False
 
 
@@ -287,8 +288,6 @@ CODEX_IDLE_SCREEN = """\
 
 def test_base_parse_status_returns_none():
     """Base HarnessConfigurator.parse_status always returns None."""
-    from hqt.harnesses.configurators.kiro import KiroConfigurator
-
     k = KiroConfigurator()
     assert k.parse_status("anything") is None
     assert k.parse_status("") is None
@@ -346,3 +345,56 @@ def test_codex_parse_status_none_for_empty():
     """CodexConfigurator: empty text → None."""
     c = CodexConfigurator()
     assert c.parse_status("") is None
+
+
+# ---------------------------------------------------------------------------
+# Task 3: sandbox skip-permission flags and binds
+# ---------------------------------------------------------------------------
+
+
+def test_base_skip_flags_default_empty():
+    assert HarnessConfigurator.sandbox_skip_permission_flags == []
+
+
+def test_base_sandbox_binds_default_empty():
+    # GenericConfigurator does not override sandbox_binds; verifies the base default.
+    assert GenericConfigurator(["mytool"]).sandbox_binds() == []
+
+
+def test_claude_skip_flag_added_when_sandboxed():
+    c = ClaudeConfigurator()
+    sid = c.generate_session_id(1)
+    cfg = c.build_spawn_config(Path("/tmp"), sid, sandboxed=True)
+    assert "--dangerously-skip-permissions" in cfg.command
+
+
+def test_claude_skip_flag_absent_when_not_sandboxed():
+    c = ClaudeConfigurator()
+    sid = c.generate_session_id(1)
+    cfg = c.build_spawn_config(Path("/tmp"), sid, sandboxed=False)
+    assert "--dangerously-skip-permissions" not in cfg.command
+
+
+def test_claude_resume_skip_flag_when_sandboxed():
+    c = ClaudeConfigurator()
+    sid = c.generate_session_id(1)
+    cfg = c.build_resume_config(Path("/tmp"), sid, sandboxed=True)
+    assert "--dangerously-skip-permissions" in cfg.command
+
+
+def test_claude_sandbox_binds_includes_dot_claude():
+    c = ClaudeConfigurator()
+    binds = c.sandbox_binds()
+    assert any(b.src == Path.home() / ".claude" and b.writable for b in binds)
+
+
+def test_codex_skip_flag_added_when_sandboxed():
+    c = CodexConfigurator()
+    cfg = c.build_spawn_config(Path("/tmp"), "1", sandboxed=True)
+    assert "--dangerously-bypass-approvals-and-sandbox" in cfg.command
+
+
+def test_generic_sandboxed_is_noop_flagwise():
+    g = GenericConfigurator(["mytool"])
+    cfg = g.build_spawn_config(Path("/tmp"), "1", sandboxed=True)
+    assert cfg.command == ["mytool"]
diff --git a/tests/test_sandbox.py b/tests/test_sandbox.py
new file mode 100644
index 0000000..d3c9143
--- /dev/null
+++ b/tests/test_sandbox.py
@@ -0,0 +1,123 @@
+from pathlib import Path
+
+from hqt import sandbox
+from hqt.sandbox import Bind, SandboxPolicy
+
+
+def test_bind_defaults_readonly():
+    b = Bind(Path("/home/u/.claude"))
+    assert b.src == Path("/home/u/.claude")
+    assert b.writable is False
+
+
+def test_sandbox_policy_fields():
+    p = SandboxPolicy(fs="rw", net=True)
+    assert p.fs == "rw"
+    assert p.net is True
+
+
+def test_is_available_true_on_linux_with_bwrap(monkeypatch):
+    monkeypatch.setattr(sandbox.sys, "platform", "linux")
+    monkeypatch.setattr(sandbox.shutil, "which", lambda name: "/usr/bin/bwrap")
+    assert sandbox.is_available() is True
+
+
+def test_is_available_false_without_bwrap(monkeypatch):
+    monkeypatch.setattr(sandbox.sys, "platform", "linux")
+    monkeypatch.setattr(sandbox.shutil, "which", lambda name: None)
+    assert sandbox.is_available() is False
+
+
+def test_is_available_false_off_linux(monkeypatch):
+    monkeypatch.setattr(sandbox.sys, "platform", "darwin")
+    monkeypatch.setattr(sandbox.shutil, "which", lambda name: "/usr/bin/bwrap")
+    assert sandbox.is_available() is False
+
+
+def _split(args, flag):
+    """Return list of (src, dst) pairs that follow each occurrence of flag."""
+    out = []
+    for i, a in enumerate(args):
+        if a == flag:
+            out.append((args[i + 1], args[i + 2]))
+    return out
+
+
+def test_wrap_command_after_double_dash(tmp_path):
+    cmd = ["claude", "--session-id", "x"]
+    args = sandbox.wrap(cmd, tmp_path, SandboxPolicy(fs="rw", net=True), [])
+    assert args[0] == "bwrap"
+    assert "--" in args
+    assert args[args.index("--") + 1 :] == cmd
+
+
+def test_wrap_base_flags(tmp_path):
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [])
+    assert "--die-with-parent" in args
+    assert "--unshare-all" in args
+    assert "--proc" in args and "--dev" in args
+
+
+def test_wrap_net_on_shares_net(tmp_path):
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [])
+    assert "--share-net" in args
+
+
+def test_wrap_net_off_does_not_share(tmp_path):
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="rw", net=False), [])
+    assert "--share-net" not in args
+
+
+def test_wrap_cwd_rw_is_bind(tmp_path):
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [])
+    assert (str(tmp_path), str(tmp_path)) in _split(args, "--bind")
+
+
+def test_wrap_cwd_ro_is_ro_bind(tmp_path):
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="ro", net=True), [])
+    assert (str(tmp_path), str(tmp_path)) in _split(args, "--ro-bind")
+
+
+def test_wrap_writable_bind_spliced(tmp_path):
+    cred = tmp_path / "cred"
+    cred.mkdir()
+    args = sandbox.wrap(
+        ["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [Bind(cred, writable=True)]
+    )
+    assert (str(cred), str(cred)) in _split(args, "--bind")
+
+
+def test_wrap_readonly_bind_spliced(tmp_path):
+    cred = tmp_path / "cred"
+    cred.mkdir()
+    args = sandbox.wrap(
+        ["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [Bind(cred)]
+    )
+    assert (str(cred), str(cred)) in _split(args, "--ro-bind")
+
+
+def test_wrap_skips_missing_binds(tmp_path):
+    missing = tmp_path / "nope"
+    args = sandbox.wrap(
+        ["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [Bind(missing)]
+    )
+    assert str(missing) not in args
+
+
+def test_wrap_binds_gitconfig_readonly_when_present(tmp_path, monkeypatch):
+    """~/.gitconfig is bound read-only so `git commit` works inside the jail."""
+    home = tmp_path / "home"
+    home.mkdir()
+    gitconfig = home / ".gitconfig"
+    gitconfig.write_text("[user]\n\tname = Test\n")
+    monkeypatch.setattr(sandbox.Path, "home", classmethod(lambda cls: home))
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [])
+    assert (str(gitconfig), str(gitconfig)) in _split(args, "--ro-bind")
+
+
+def test_wrap_skips_gitconfig_when_absent(tmp_path, monkeypatch):
+    home = tmp_path / "home"
+    home.mkdir()
+    monkeypatch.setattr(sandbox.Path, "home", classmethod(lambda cls: home))
+    args = sandbox.wrap(["sh"], tmp_path, SandboxPolicy(fs="rw", net=True), [])
+    assert str(home / ".gitconfig") not in args
diff --git a/tests/test_sessions.py b/tests/test_sessions.py
index d645222..cf3544f 100644
--- a/tests/test_sessions.py
+++ b/tests/test_sessions.py
@@ -9,6 +9,7 @@ from sqlalchemy.pool import StaticPool
 
 from hqt.db.models import Base, Harness, Project, ScheduledPrompt, Session
 from hqt.errors import ServiceError
+from hqt.sandbox import SandboxPolicy
 from hqt.sessions.service import SessionInfo, SessionService
 from hqt.tmux.manager import SpawnResult, TmuxManager
 
@@ -931,7 +932,7 @@ async def test_attach_late_capture_updates_id_before_resume(
 
     assert ok is True
     harness.build_resume_config.assert_called_with(
-        Path("/tmp/myproj"), "late-codex-id", result.session.model
+        Path("/tmp/myproj"), "late-codex-id", result.session.model, sandboxed=False
     )
     from hqt.db.models import Session as DBSession
 
@@ -1646,3 +1647,96 @@ async def test_create_session_no_lock_for_non_capturing_harness(service, db, tmu
     # The `service` fixture's harness has captures_session_id = False, so the
     # spawn must NOT be serialized under the capture lock.
     assert observed["locked_during_spawn"] is False
+
+
+# ---------------------------------------------------------------------------
+# Task 5: sandbox wrapping on spawn and resume
+# ---------------------------------------------------------------------------
+
+
+@pytest.fixture
+def sandbox_harness():
+    h = MagicMock()
+    h.captures_session_id = False
+    h.generate_session_id.return_value = "sess-1"
+    h.build_spawn_config.return_value = MagicMock(
+        command=["claude", "--dangerously-skip-permissions"],
+        env={},
+        cwd=Path("/tmp/myproj"),
+    )
+    h.sandbox_binds.return_value = []
+    h.parse_status = MagicMock(return_value=None)
+    return {"claude-code": h}
+
+
+@pytest.fixture
+def sandbox_service(factory, db, tmux, sandbox_harness):
+    return SessionService(factory=factory, tmux=tmux, harnesses=sandbox_harness)
+
+
+@pytest.mark.asyncio
+async def test_sandboxed_create_wraps_command(
+    sandbox_service, db, tmux, sandbox_harness
+):
+    with (
+        patch("hqt.sessions.service.sandbox.is_available", return_value=True),
+        patch(
+            "hqt.sessions.service.sandbox.wrap", return_value=["bwrap", "--", "claude"]
+        ) as mock_wrap,
+    ):
+        result = await sandbox_service.create_session(
+            project_id=1,
+            harness_name="claude-code",
+            sandbox=SandboxPolicy(fs="rw", net=True),
+        )
+    mock_wrap.assert_called_once()
+    sandbox_harness["claude-code"].build_spawn_config.assert_called_once()
+    assert (
+        sandbox_harness["claude-code"].build_spawn_config.call_args.kwargs["sandboxed"]
+        is True
+    )
+    assert tmux.spawn.call_args.args[0].command == ["bwrap", "--", "claude"]
+    assert result.session.sandbox_json == '{"fs": "rw", "net": true}'
+
+
+@pytest.mark.asyncio
+async def test_unsandboxed_create_does_not_wrap(service, db, tmux, harnesses):
+    with patch("hqt.sessions.service.sandbox.wrap") as mock_wrap:
+        result = await service.create_session(project_id=1, harness_name="claude-code")
+    mock_wrap.assert_not_called()
+    assert result.session.sandbox_json is None
+
+
+@pytest.mark.asyncio
+async def test_sandboxed_create_raises_when_bwrap_missing(sandbox_service, db):
+    with patch("hqt.sessions.service.sandbox.is_available", return_value=False):
+        with pytest.raises(ServiceError, match="bubblewrap"):
+            await sandbox_service.create_session(
+                project_id=1,
+                harness_name="claude-code",
+                sandbox=SandboxPolicy(fs="rw", net=True),
+            )
+
+
+@pytest.mark.asyncio
+async def test_sandboxed_worktree_binds_repo_git_dir(
+    sandbox_service, db, tmux, sandbox_harness, fake_worktree
+):
+    """A sandboxed worktree session binds the repo's common .git writable so
+    git works inside the jail (the worktree's gitdir lives under <repo>/.git)."""
+    from hqt.sandbox import Bind
+
+    with (
+        patch("hqt.sessions.service.sandbox.is_available", return_value=True),
+        patch(
+            "hqt.sessions.service.sandbox.wrap", return_value=["bwrap", "--", "claude"]
+        ) as mock_wrap,
+    ):
+        await sandbox_service.create_session(
+            project_id=1,
+            harness_name="claude-code",
+            worktree_branch="feature-x",
+            sandbox=SandboxPolicy(fs="rw", net=True),
+        )
+    binds = mock_wrap.call_args.args[3]
+    assert Bind(Path("/tmp/myproj/.git"), writable=True) in binds
diff --git a/tests/test_tui.py b/tests/test_tui.py
index d5ad978..5ee64a4 100644
--- a/tests/test_tui.py
+++ b/tests/test_tui.py
@@ -292,7 +292,12 @@ async def test_new_session_on_dismiss_sequential_create_then_refresh():
         call_order: list[str] = []
 
         async def fake_create(
-            project_id, harness_name, nickname, model, worktree_branch=None
+            project_id,
+            harness_name,
+            nickname,
+            model,
+            worktree_branch=None,
+            sandbox=None,
         ):
             # Brief yield so that, if two separate workers were used, the list
             # worker would be able to start and record "list" before this
@@ -324,7 +329,7 @@ async def test_new_session_on_dismiss_sequential_create_then_refresh():
             await pilot.pause()
 
         # The NewSessionScreen is now on top; dismiss it with a valid result tuple.
-        app.screen.dismiss(("claude", "mynick", None, None))
+        app.screen.dismiss(("claude", "mynick", None, None, None))
         await pilot.pause()
 
         # Wait for the worker spawned by on_dismiss to finish deterministically.
@@ -396,7 +401,7 @@ async def test_new_session_on_dismiss_notifies_on_spawn_failure():
                 await app.workers.wait_for_complete()
                 await pilot.pause()
 
-                app.screen.dismiss(("claude", "mynick", None, None))
+                app.screen.dismiss(("claude", "mynick", None, None, None))
                 await pilot.pause()
                 await app.workers.wait_for_complete()
                 await pilot.pause()
@@ -467,7 +472,7 @@ async def test_new_session_on_dismiss_no_notify_on_success():
                 await app.workers.wait_for_complete()
                 await pilot.pause()
 
-                app.screen.dismiss(("claude", "mynick", None, None))
+                app.screen.dismiss(("claude", "mynick", None, None, None))
                 await pilot.pause()
                 await app.workers.wait_for_complete()
                 await pilot.pause()
@@ -582,7 +587,7 @@ async def test_new_session_enter_in_input_submits_dialog():
         await pilot.press("enter")
         await pilot.pause()
 
-        assert results == [("claude", "mywork", None, None)], f"got {results}"
+        assert results == [("claude", "mywork", None, None, None)], f"got {results}"
 
 
 # ---------------------------------------------------------------------------
@@ -1291,7 +1296,7 @@ async def test_new_session_worktree_unchecked_returns_none_branch():
         app.screen.query_one("#nickname-input", Input).value = "mywork"
         app.screen.query_one("#ok-btn", Button).press()
         await pilot.pause()
-        assert results == [("claude", "mywork", None, None)], f"got {results}"
+        assert results == [("claude", "mywork", None, None, None)], f"got {results}"
 
 
 @pytest.mark.asyncio
@@ -1316,7 +1321,9 @@ async def test_new_session_worktree_checked_uses_typed_branch():
         branch.value = "feature-x"
         app.screen.query_one("#ok-btn", Button).press()
         await pilot.pause()
-        assert results == [("claude", "My Work", None, "feature-x")], f"got {results}"
+        assert results == [("claude", "My Work", None, "feature-x", None)], (
+            f"got {results}"
+        )
 
 
 @pytest.mark.asyncio
@@ -1338,7 +1345,7 @@ async def test_new_session_worktree_checked_blank_branch_slugifies_nickname():
         app.screen.query_one("#branch-input", Input).value = ""
         app.screen.query_one("#ok-btn", Button).press()
         await pilot.pause()
-        assert results == [("claude", "Cool Feature!", None, "cool-feature")], (
+        assert results == [("claude", "Cool Feature!", None, "cool-feature", None)], (
             f"got {results}"
         )
 
@@ -1504,3 +1511,50 @@ async def test_delete_non_worktree_session_does_not_push_modal():
         verify_db = app._db_factory()
         assert verify_db.get(Session, sess_id) is None
         verify_db.close()
+
+
+# ---------------------------------------------------------------------------
+# Task 6: Sandbox controls in NewSessionScreen
+# ---------------------------------------------------------------------------
+
+
+def test_policy_from_disabled_returns_none():
+    from hqt.tui.screens.new_session import NewSessionScreen
+
+    assert NewSessionScreen._policy_from(False, "rw", True) is None
+
+
+def test_policy_from_enabled_builds_policy():
+    from hqt.sandbox import SandboxPolicy
+    from hqt.tui.screens.new_session import NewSessionScreen
+
+    p = NewSessionScreen._policy_from(True, "ro", False)
+    assert p == SandboxPolicy(fs="ro", net=False)
+
+
+@pytest.mark.asyncio
+async def test_sandbox_switch_disabled_when_unavailable():
+    from hqt.tui.screens.new_session import NewSessionScreen
+    from textual.widgets import Switch
+
+    app = HqtApp()
+    async with app.run_test(size=(120, 40)) as pilot:
+        app.push_screen(
+            NewSessionScreen(["claude"], is_git_repo=False, sandbox_available=False)
+        )
+        await pilot.pause()
+        assert app.screen.query_one("#sandbox-switch", Switch).disabled is True
+
+
+@pytest.mark.asyncio
+async def test_sandbox_switch_enabled_when_available():
+    from hqt.tui.screens.new_session import NewSessionScreen
+    from textual.widgets import Switch
+
+    app = HqtApp()
+    async with app.run_test(size=(120, 40)) as pilot:
+        app.push_screen(
+            NewSessionScreen(["claude"], is_git_repo=False, sandbox_available=True)
+        )
+        await pilot.pause()
+        assert app.screen.query_one("#sandbox-switch", Switch).disabled is False