diff --git a/ci/test-quality-policy.json b/ci/test-quality-policy.json
index 7984660..c5a1f4d 100644
--- a/ci/test-quality-policy.json
+++ b/ci/test-quality-policy.json
@@ -12,6 +12,7 @@
   "critical_cpu_paths": [
     "obliteratus/runtime_contracts.py",
     "obliteratus/persistence_contracts.py",
+    "obliteratus/remote_contracts.py",
     "obliteratus/device.py",
     "obliteratus/models/loader.py",
     "obliteratus/architecture_profiles.py",
diff --git a/ci/test-risk-map.json b/ci/test-risk-map.json
index 06f6949..027df86 100644
--- a/ci/test-risk-map.json
+++ b/ci/test-risk-map.json
@@ -98,6 +98,7 @@
         "obliteratus/local_ui.py",
         "obliteratus/models_client.py",
         "obliteratus/remote.py",
+        "obliteratus/remote_contracts.py",
         "obliteratus/ui_watchtower.py",
         "obliteratus/watchtower.py"
       ],
@@ -105,6 +106,7 @@
         "tests/test_cli.py",
         "tests/test_cli_boundaries.py",
         "tests/test_remote_boundaries.py",
+        "tests/test_remote_contracts.py",
         "tests/conditional/test_network_services.py",
         "tests/conditional/test_operator_ui.py",
         "tests/conditional/test_remote_runtime.py"
@@ -461,6 +463,13 @@
       "risk": "SSH discovery, quoting, execution, cancellation, and result synchronization",
       "required_tests": ["tests/test_remote_boundaries.py", "tests/conditional/test_remote_runtime.py"],
       "conditional_gates": ["remote-execution"]
+    },
+    {
+      "path": "obliteratus/remote_contracts.py",
+      "risk_class": "cpu-contract",
+      "risk": "remote target validation, GPU selection normalization, and shell-safe command construction",
+      "required_tests": ["tests/test_remote_contracts.py", "tests/test_remote_boundaries.py"],
+      "conditional_gates": []
     }
   ]
 }
diff --git a/obliteratus/cli.py b/obliteratus/cli.py
index 8b33af6..2c5ad85 100644
--- a/obliteratus/cli.py
+++ b/obliteratus/cli.py
@@ -35,6 +35,17 @@ def _positive_int(value: str) -> int:
     return parsed
 
 
+def _ssh_port(value: str) -> int:
+    """Parse the public SSH port boundary."""
+    try:
+        parsed = int(value)
+    except ValueError as exc:
+        raise argparse.ArgumentTypeError("must be an integer from 1 through 65535") from exc
+    if not 1 <= parsed <= 65535:
+        raise argparse.ArgumentTypeError("must be an integer from 1 through 65535")
+    return parsed
+
+
 def _add_gpu_args(parser):
     """Add --gpus flag for multi-GPU control."""
     gpu_group = parser.add_argument_group("GPU selection")
@@ -60,7 +71,7 @@ def _add_remote_args(parser):
         help="Path to SSH private key (default: use SSH agent or ~/.ssh/id_rsa)",
     )
     remote_group.add_argument(
-        "--ssh-port", type=int, default=22,
+        "--ssh-port", type=_ssh_port, default=22,
         help="SSH port on remote host (default: 22)",
     )
     remote_group.add_argument(
@@ -707,10 +718,13 @@ def _cmd_run(args):
             user=config.remote.user,
             port=config.remote.port,
             ssh_key=config.remote.ssh_key,
+            known_hosts_file=config.remote.known_hosts_file,
             remote_dir=config.remote.remote_dir,
+            install_timeout=config.remote.install_timeout,
             python=config.remote.python,
             sync_results=config.remote.sync_results,
             gpus=config.remote.gpus,
+            install_source=config.remote.install_source,
         )
         runner = RemoteRunner(rc)
         result_path = runner.run_config(
diff --git a/obliteratus/config.py b/obliteratus/config.py
index 96214e1..1c5ad95 100644
--- a/obliteratus/config.py
+++ b/obliteratus/config.py
@@ -44,10 +44,32 @@ class RemoteConfig:
     user: str = "root"
     port: int = 22
     ssh_key: str | None = None
+    known_hosts_file: str | None = None
     remote_dir: str = "/tmp/obliteratus_run"
+    install_timeout: int = 600
     python: str = "python3"
     sync_results: bool = True
     gpus: str | None = None  # comma-separated GPU IDs or "all"
+    install_source: str = "git+https://github.com/elder-plinius/OBLITERATUS.git"
+
+    def __post_init__(self) -> None:
+        from obliteratus.remote_contracts import validate_remote_settings
+
+        self.gpus = validate_remote_settings(
+            host=self.host,
+            user=self.user,
+            port=self.port,
+            remote_dir=self.remote_dir,
+            python=self.python,
+            gpus=self.gpus,
+            install_source=self.install_source,
+        )
+        if (
+            isinstance(self.install_timeout, bool)
+            or not isinstance(self.install_timeout, int)
+            or self.install_timeout <= 0
+        ):
+            raise ValueError("remote install timeout must be a positive integer")
 
 
 @dataclass
@@ -114,7 +136,7 @@ class StudyConfig:
         )
 
     def to_dict(self) -> dict:
-        return {
+        result = {
             "model": {
                 "name": self.model.name,
                 "task": self.model.task,
@@ -138,3 +160,18 @@ class StudyConfig:
             "max_length": self.max_length,
             "output_dir": self.output_dir,
         }
+        if self.remote is not None:
+            result["remote"] = {
+                "host": self.remote.host,
+                "user": self.remote.user,
+                "port": self.remote.port,
+                "ssh_key": self.remote.ssh_key,
+                "known_hosts_file": self.remote.known_hosts_file,
+                "remote_dir": self.remote.remote_dir,
+                "install_timeout": self.remote.install_timeout,
+                "python": self.remote.python,
+                "sync_results": self.remote.sync_results,
+                "gpus": self.remote.gpus,
+                "install_source": self.remote.install_source,
+            }
+        return result
diff --git a/obliteratus/remote.py b/obliteratus/remote.py
index 5dd8c5f..55a0d4f 100644
--- a/obliteratus/remote.py
+++ b/obliteratus/remote.py
@@ -20,13 +20,26 @@ Usage (YAML config):
 from __future__ import annotations
 
 import os
+import queue
 import shlex
 import subprocess
+import tempfile
+import threading
+import time
 from dataclasses import dataclass
 from pathlib import Path
 from typing import Callable
 
 from rich.console import Console
+import yaml
+
+from obliteratus import __version__
+from obliteratus.remote_contracts import (
+    parse_remote_target,
+    remote_python_command,
+    remote_scp_spec,
+    validate_remote_settings,
+)
 
 console = Console()
 
@@ -45,6 +58,24 @@ class RemoteConfig:
     python: str = "python3"  # remote python binary
     sync_results: bool = True
     gpus: str | None = None  # comma-separated GPU IDs or "all"
+    install_source: str = "git+https://github.com/elder-plinius/OBLITERATUS.git"
+
+    def __post_init__(self) -> None:
+        self.gpus = validate_remote_settings(
+            host=self.host,
+            user=self.user,
+            port=self.port,
+            remote_dir=self.remote_dir,
+            python=self.python,
+            gpus=self.gpus,
+            install_source=self.install_source,
+        )
+        if (
+            isinstance(self.install_timeout, bool)
+            or not isinstance(self.install_timeout, int)
+            or self.install_timeout <= 0
+        ):
+            raise ValueError("remote install timeout must be a positive integer")
 
     @property
     def ssh_target(self) -> str:
@@ -53,11 +84,7 @@ class RemoteConfig:
     @classmethod
     def from_cli_args(cls, remote_str: str, **kwargs) -> RemoteConfig:
         """Parse 'user@host' or just 'host' from CLI --remote flag."""
-        if "@" in remote_str:
-            user, host = remote_str.rsplit("@", 1)
-        else:
-            user = "root"
-            host = remote_str
+        user, host = parse_remote_target(remote_str)
         return cls(host=host, user=user, **kwargs)
 
     @classmethod
@@ -127,15 +154,51 @@ class RemoteRunner:
                 text=True,
                 bufsize=1,
             )
+            if proc.stdout is None:
+                proc.kill()
+                proc.wait()
+                raise RuntimeError("remote process did not expose a stdout stream")
+
+            output: queue.Queue[object] = queue.Queue()
+            finished = object()
+
+            def read_output() -> None:
+                try:
+                    for line in proc.stdout:
+                        if not isinstance(line, str):
+                            raise RuntimeError("remote process emitted non-text output")
+                        output.put(line.rstrip("\n"))
+                except BaseException as exc:
+                    output.put(exc)
+                finally:
+                    output.put(finished)
+
+            threading.Thread(target=read_output, daemon=True).start()
+            deadline = time.monotonic() + timeout if timeout is not None else None
             try:
-                for line in proc.stdout:
-                    line = line.rstrip("\n")
-                    self.on_log(line)
-                proc.wait(timeout=timeout)
+                while True:
+                    remaining = None if deadline is None else max(0, deadline - time.monotonic())
+                    try:
+                        item = output.get(timeout=remaining)
+                    except queue.Empty as exc:
+                        raise subprocess.TimeoutExpired(cmd, timeout) from exc
+                    if item is finished:
+                        break
+                    if isinstance(item, BaseException):
+                        raise item
+                    self.on_log(item)
+                remaining = None if deadline is None else max(0, deadline - time.monotonic())
+                proc.wait(timeout=remaining)
             except subprocess.TimeoutExpired:
                 proc.kill()
+                proc.wait()
                 self.on_log("[red]Remote command timed out[/]")
-                return 1
+                return 124
+            except KeyboardInterrupt:
+                proc.kill()
+                proc.wait()
+                self.on_log("[yellow]Remote command cancelled[/]")
+                raise
             return proc.returncode
         else:
             return subprocess.run(
@@ -175,37 +238,43 @@ class RemoteRunner:
         self.on_log("[yellow]No GPUs detected on remote (nvidia-smi failed)[/]")
         return None
 
-    def _env_prefix(self) -> str:
-        """Build environment variable prefix for remote commands (e.g. CUDA_VISIBLE_DEVICES)."""
-        parts = []
-        if self.config.gpus and self.config.gpus.lower() != "all":
-            parts.append(f"CUDA_VISIBLE_DEVICES={self.config.gpus}")
-        return " ".join(parts) + " " if parts else ""
-
     def ensure_obliteratus(self) -> bool:
         """Install or update obliteratus on the remote if needed."""
-        # Check if already installed
+        version_command = remote_python_command(
+            self.config.python,
+            ["-c", "import obliteratus; print(obliteratus.__version__)"],
+        )
         check = self.run_ssh(
-            f"{self.config.python} -c \"import obliteratus; print(obliteratus.__version__)\"",
+            version_command,
             timeout=30,
         )
-        if isinstance(check, subprocess.CompletedProcess) and check.returncode == 0:
-            version = check.stdout.strip()
-            self.on_log(f"Obliteratus {version} already installed on remote")
+        if (
+            isinstance(check, subprocess.CompletedProcess)
+            and check.returncode == 0
+            and check.stdout.strip() == __version__
+        ):
+            self.on_log(f"Obliteratus {__version__} already installed on remote")
             return True
 
-        # Install from PyPI or git
-        self.on_log("Installing obliteratus on remote...")
-        install_cmd = (
-            f"{self.config.python} -m pip install --quiet "
-            f"git+https://github.com/StellaAthena/OBLITERATUS.git"
+        self.on_log(f"Installing Obliteratus {__version__} on remote...")
+        install_cmd = remote_python_command(
+            self.config.python,
+            ["-m", "pip", "install", "--quiet", "--upgrade", self.config.install_source],
         )
         rc = self.run_ssh(install_cmd, stream=True, timeout=self.config.install_timeout)
         if rc != 0:
             self.on_log("[red]Failed to install obliteratus on remote[/]")
             return False
 
-        self.on_log("Obliteratus installed successfully")
+        verify = self.run_ssh(version_command, timeout=30)
+        if not (
+            isinstance(verify, subprocess.CompletedProcess)
+            and verify.returncode == 0
+            and verify.stdout.strip() == __version__
+        ):
+            self.on_log("[red]Installed Obliteratus version could not be verified[/]")
+            return False
+        self.on_log(f"Obliteratus {__version__} installed successfully")
         return True
 
     def sync_results_back(self, remote_output_dir: str, local_output_dir: str) -> bool:
@@ -216,7 +285,7 @@ class RemoteRunner:
         self.on_log(f"Syncing results: {self.config.ssh_target}:{remote_output_dir} -> {local_output_dir}")
 
         cmd = self._scp_base_cmd() + [
-            f"{self.config.ssh_target}:{remote_output_dir}/",
+            remote_scp_spec(self.config.ssh_target, remote_output_dir, directory=True),
             str(local_path),
         ]
 
@@ -242,14 +311,24 @@ class RemoteRunner:
         refinement_passes: int | None = None,
         large_model: bool = False,
         verify_sample_size: int | None = None,
+        min_layer_fraction: float | None = None,
+        max_layer_fraction: float | None = None,
+        harmless_pc_count: int | None = None,
+        shield_concept_count: int | None = None,
+        shield_ridge: float | None = None,
+        shield_residualize: bool | None = None,
+        shield_layer_penalty: float | None = None,
+        projection_target: str | None = None,
+        projection_row_fraction: float | None = None,
+        refusal_max_tokens: int | None = None,
     ) -> str:
         """Build the remote obliteratus CLI command."""
         remote_output = output_dir or f"{self.config.remote_dir}/output/{model.replace('/', '_')}"
 
         parts = [
-            self._env_prefix() + self.config.python, "-m", "obliteratus",
-            "obliterate", shlex.quote(model),
-            "--output-dir", shlex.quote(remote_output),
+            "-m", "obliteratus",
+            "obliterate", model,
+            "--output-dir", remote_output,
             "--method", method,
             "--device", device,
             "--dtype", dtype,
@@ -268,20 +347,36 @@ class RemoteRunner:
             parts.append("--large-model")
         if verify_sample_size is not None:
             parts.extend(["--verify-sample-size", str(verify_sample_size)])
+        optional_values = (
+            ("--min-layer-fraction", min_layer_fraction),
+            ("--max-layer-fraction", max_layer_fraction),
+            ("--harmless-pc-count", harmless_pc_count),
+            ("--shield-concept-count", shield_concept_count),
+            ("--shield-ridge", shield_ridge),
+            ("--shield-layer-penalty", shield_layer_penalty),
+            ("--projection-target", projection_target),
+            ("--projection-row-fraction", projection_row_fraction),
+            ("--refusal-max-tokens", refusal_max_tokens),
+        )
+        for flag, value in optional_values:
+            if value is not None:
+                parts.extend([flag, str(value)])
+        if shield_residualize:
+            parts.append("--shield-residualize")
 
-        return " ".join(parts)
+        return remote_python_command(self.config.python, parts, gpus=self.config.gpus)
 
     def build_run_command(self, remote_config_path: str, output_dir: str | None = None, preset: str | None = None) -> str:
         """Build remote 'obliteratus run' command."""
         parts = [
-            self._env_prefix() + self.config.python, "-m", "obliteratus",
-            "run", shlex.quote(remote_config_path),
+            "-m", "obliteratus",
+            "run", remote_config_path,
         ]
         if output_dir:
-            parts.extend(["--output-dir", shlex.quote(output_dir)])
+            parts.extend(["--output-dir", output_dir])
         if preset:
             parts.extend(["--preset", preset])
-        return " ".join(parts)
+        return remote_python_command(self.config.python, parts, gpus=self.config.gpus)
 
     def build_tourney_command(
         self,
@@ -299,9 +394,9 @@ class RemoteRunner:
         remote_output = output_dir or f"{self.config.remote_dir}/tourney/{model.replace('/', '_')}"
 
         parts = [
-            self._env_prefix() + self.config.python, "-m", "obliteratus",
-            "tourney", shlex.quote(model),
-            "--output-dir", shlex.quote(remote_output),
+            "-m", "obliteratus",
+            "tourney", model,
+            "--output-dir", remote_output,
             "--device", device,
             "--dtype", dtype,
             "--dataset", dataset,
@@ -314,18 +409,26 @@ class RemoteRunner:
             parts.extend(["--hub-repo", hub_repo])
         if methods:
             parts.extend(["--methods"] + methods)
-        return " ".join(parts)
+        return remote_python_command(self.config.python, parts, gpus=self.config.gpus)
 
     def upload_config(self, local_config_path: str) -> str:
-        """Upload a YAML config file to the remote."""
+        """Upload a YAML config without recursively redispatching remotely."""
         remote_path = f"{self.config.remote_dir}/config.yaml"
-        self.run_ssh(f"mkdir -p {shlex.quote(self.config.remote_dir)}")
+        self.run_ssh(shlex.join(["mkdir", "-p", self.config.remote_dir]))
 
-        cmd = self._scp_base_cmd()
-        # scp uses -P not -p, already handled in _scp_base_cmd
-        cmd += [local_config_path, f"{self.config.ssh_target}:{remote_path}"]
+        source = Path(local_config_path)
+        payload = yaml.safe_load(source.read_text(encoding="utf-8"))
+        if not isinstance(payload, dict):
+            raise ValueError("remote study config must contain a YAML mapping")
+        payload.pop("remote", None)
 
-        result = subprocess.run(cmd, capture_output=True, text=True, timeout=60)
+        with tempfile.TemporaryDirectory(prefix="obliteratus-remote-config-") as temp_dir:
+            upload_path = Path(temp_dir) / "config.yaml"
+            upload_path.write_text(yaml.safe_dump(payload, sort_keys=False), encoding="utf-8")
+            cmd = self._scp_base_cmd()
+            # scp uses -P not -p, already handled in _scp_base_cmd
+            cmd += [str(upload_path), remote_scp_spec(self.config.ssh_target, remote_path)]
+            result = subprocess.run(cmd, capture_output=True, text=True, timeout=60)
         if result.returncode != 0:
             raise RuntimeError(f"Failed to upload config: {result.stderr}")
         self.on_log(f"Config uploaded to {remote_path}")
@@ -353,7 +456,7 @@ class RemoteRunner:
             return None
 
         # 4. Create remote working directory
-        self.run_ssh(f"mkdir -p {shlex.quote(self.config.remote_dir)}")
+        self.run_ssh(shlex.join(["mkdir", "-p", self.config.remote_dir]))
 
         # 5. Build and run the command
         remote_output = f"{self.config.remote_dir}/output/{model.replace('/', '_')}"
diff --git a/obliteratus/remote_contracts.py b/obliteratus/remote_contracts.py
new file mode 100644
index 0000000..7b7a3b7
--- /dev/null
+++ b/obliteratus/remote_contracts.py
@@ -0,0 +1,99 @@
+"""Pure validation and command contracts for remote execution."""
+
+from __future__ import annotations
+
+import re
+import shlex
+
+
+_REMOTE_USER = re.compile(r"[A-Za-z0-9_.-]+")
+
+
+def _require_text(value: object, label: str) -> str:
+    if not isinstance(value, str) or not value:
+        raise ValueError(f"{label} must be a non-empty string")
+    if any(ord(character) < 32 or ord(character) == 127 for character in value):
+        raise ValueError(f"{label} may not contain control characters")
+    return value
+
+
+def normalize_gpu_selection(value: str | None) -> str | None:
+    """Return a canonical CUDA device selection or reject malformed input."""
+    if value is None:
+        return None
+    value = _require_text(value, "remote gpus").strip()
+    if value.lower() == "all":
+        return "all"
+    parts = value.split(",")
+    if any(not part.strip().isdigit() for part in parts):
+        raise ValueError("remote gpus must be 'all' or comma-separated non-negative integers")
+    return ",".join(str(int(part.strip())) for part in parts)
+
+
+def _validate_remote_identity(host: str, user: str) -> None:
+    """Validate the host and user portions shared by CLI and YAML inputs."""
+    host = _require_text(host, "remote host")
+    user = _require_text(user, "remote user")
+    if host.startswith("-") or "@" in host or any(character.isspace() for character in host):
+        raise ValueError("remote host must be a host name or address without user or options")
+    if user.startswith("-") or _REMOTE_USER.fullmatch(user) is None:
+        raise ValueError("remote user contains unsupported characters")
+
+
+def validate_remote_settings(
+    *,
+    host: str,
+    user: str,
+    port: int,
+    remote_dir: str,
+    python: str,
+    gpus: str | None,
+    install_source: str,
+) -> str | None:
+    """Validate public remote settings and return canonical GPU selection."""
+    _validate_remote_identity(host, user)
+    remote_dir = _require_text(remote_dir, "remote directory")
+    _require_text(python, "remote Python")
+    _require_text(install_source, "remote install source")
+
+    if isinstance(port, bool) or not isinstance(port, int) or not 1 <= port <= 65535:
+        raise ValueError("remote port must be an integer from 1 through 65535")
+    if not remote_dir.startswith("/"):
+        raise ValueError("remote directory must be an absolute POSIX path")
+    return normalize_gpu_selection(gpus)
+
+
+def parse_remote_target(remote: str) -> tuple[str, str]:
+    """Parse and validate ``[USER@]HOST`` without accepting SSH options."""
+    remote = _require_text(remote, "remote target").strip()
+    if remote.count("@") > 1:
+        raise ValueError("remote target may contain at most one user separator")
+    user, separator, host = remote.partition("@")
+    if not separator:
+        user, host = "root", user
+    _validate_remote_identity(host, user)
+    return user, host
+
+
+def remote_python_command(
+    python: str,
+    arguments: list[str],
+    *,
+    gpus: str | None = None,
+) -> str:
+    """Build one shell-safe command for the remote SSH shell."""
+    tokens: list[str] = []
+    normalized_gpus = normalize_gpu_selection(gpus)
+    if normalized_gpus not in (None, "all"):
+        tokens.extend(["env", f"CUDA_VISIBLE_DEVICES={normalized_gpus}"])
+    tokens.extend([_require_text(python, "remote Python"), *arguments])
+    return shlex.join(tokens)
+
+
+def remote_scp_spec(target: str, path: str, *, directory: bool = False) -> str:
+    """Quote a remote SCP path while preserving the host/path separator."""
+    target = _require_text(target, "SSH target")
+    path = _require_text(path, "remote SCP path")
+    if directory:
+        path = f"{path.rstrip('/')}/"
+    return f"{target}:{shlex.quote(path)}"
diff --git a/pyproject.toml b/pyproject.toml
index 073ef90..5a158d2 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -120,6 +120,7 @@ only_mutate = [
     "obliteratus/analysis/numerical_contracts.py",
     "obliteratus/runtime_contracts.py",
     "obliteratus/persistence_contracts.py",
+    "obliteratus/remote_contracts.py",
     "scripts/check_coverage_thresholds.py",
 ]
 pytest_add_cli_args = ["--no-cov", "-q"]
@@ -129,6 +130,7 @@ pytest_add_cli_args_test_selection = [
     "tests/test_coverage_thresholds.py",
     "tests/test_numerical_contracts.py",
     "tests/test_persistence_contracts.py",
+    "tests/test_remote_contracts.py",
     "tests/test_runtime_contracts.py",
 ]
 mutate_only_covered_lines = true
diff --git a/scripts/run_repeat_gate.py b/scripts/run_repeat_gate.py
index dfe77f0..c2d53c4 100644
--- a/scripts/run_repeat_gate.py
+++ b/scripts/run_repeat_gate.py
@@ -18,9 +18,13 @@ DEFAULT_TESTS = (
     "tests/test_config.py",
     "tests/test_config_properties.py",
     "tests/test_coverage_thresholds.py",
+    "tests/test_numerical_contracts.py",
+    "tests/test_persistence_contracts.py",
     "tests/test_property_contracts.py",
     "tests/test_advanced_metrics.py",
     "tests/test_metrics.py",
+    "tests/test_remote_contracts.py",
+    "tests/test_runtime_contracts.py",
 )
 HASH_SEEDS = ("0", "1", "8675309")
 
diff --git a/tests/test_cli_boundaries.py b/tests/test_cli_boundaries.py
index 406c1f2..811d936 100644
--- a/tests/test_cli_boundaries.py
+++ b/tests/test_cli_boundaries.py
@@ -168,7 +168,8 @@ def test_run_local_overrides_and_remote_config(monkeypatch, tmp_path):
 
     config.remote = ns(
         host="host", user="user", port=2200, ssh_key="key", remote_dir="/work",
-        python="python", sync_results=True, gpus="0",
+        known_hosts_file="known_hosts", install_timeout=120, python="python",
+        sync_results=True, gpus="0", install_source="obliteratus==0.1.2",
     )
     runner = MagicMock()
     runner.run_config.return_value = "/local/results"
@@ -347,6 +348,15 @@ def test_remote_runner_factory_and_commands(monkeypatch):
     monkeypatch.setattr(obliteratus.remote, "RemoteRunner", Mock(return_value=runner))
     args = _remote_args()
     assert cli._make_remote_runner(args) is runner
+    obliteratus.remote.RemoteConfig.from_cli_args.assert_called_once_with(
+        "user@host",
+        port=22,
+        ssh_key=None,
+        remote_dir="/work",
+        python="python3",
+        sync_results=True,
+        gpus="0",
+    )
 
     monkeypatch.setattr(cli, "_make_remote_runner", lambda _args: runner)
     runner.run_obliterate.return_value = "results"
@@ -359,6 +369,25 @@ def test_remote_runner_factory_and_commands(monkeypatch):
     cli._cmd_remote_abliterate(args)
     assert "refusal_max_tokens" not in runner.run_obliterate.call_args.kwargs
 
+    for name in (
+        "quantization", "n_directions", "direction_method", "regularization",
+        "refinement_passes", "min_layer_fraction", "max_layer_fraction",
+        "harmless_pc_count", "shield_concept_count", "shield_ridge",
+        "shield_residualize", "shield_layer_penalty", "projection_target",
+        "projection_row_fraction", "verify_sample_size", "refusal_max_tokens",
+    ):
+        setattr(args, name, None)
+    args.large_model = False
+    runner.run_obliterate.reset_mock()
+    cli._cmd_remote_abliterate(args)
+    assert runner.run_obliterate.call_args.kwargs == {
+        "model": "model",
+        "local_output_dir": "out",
+        "method": "advanced",
+        "device": "cuda",
+        "dtype": "float16",
+    }
+
     runner.run_config.return_value = "results"
     cli._cmd_remote_run(args)
     runner.run_tourney.return_value = "results"
@@ -375,6 +404,20 @@ def test_remote_runner_factory_and_commands(monkeypatch):
         cli._cmd_remote_tourney(args)
 
 
+@pytest.mark.parametrize("port", ["0", "65536", "not-a-port"])
+def test_remote_cli_rejects_invalid_ssh_ports_before_dispatch(port):
+    with pytest.raises(SystemExit) as exc:
+        cli.main(["run", "config.yml", "--remote", "host", "--ssh-port", port])
+    assert exc.value.code == 2
+
+
+def test_remote_cli_accepts_valid_ssh_port_and_dispatches(monkeypatch):
+    dispatch = Mock()
+    monkeypatch.setattr(cli, "_cmd_remote_run", dispatch)
+    cli.main(["run", "config.yml", "--remote", "host", "--ssh-port", "2222"])
+    assert dispatch.call_args.args[0].ssh_port == 2222
+
+
 def test_abliterate_pipeline_callbacks_residue_and_contribution(monkeypatch, tmp_path):
     import obliteratus.abliterate
     import obliteratus.community
diff --git a/tests/test_config.py b/tests/test_config.py
index ef982f6..db38f25 100644
--- a/tests/test_config.py
+++ b/tests/test_config.py
@@ -4,6 +4,7 @@ from __future__ import annotations
 
 
 import yaml
+import pytest
 
 from obliteratus.config import StudyConfig
 
@@ -71,3 +72,39 @@ class TestStudyConfig:
         assert config.model.quantization == "4bit"
         assert config.model.num_labels == 7
         assert StudyConfig.from_dict(config.to_dict()).model == config.model
+
+    def test_remote_config_roundtrip_preserves_security_and_execution_settings(self):
+        raw = {
+            **SAMPLE_CONFIG,
+            "remote": {
+                "host": "compute.example",
+                "user": "runner",
+                "port": 2222,
+                "ssh_key": "/keys/id",
+                "known_hosts_file": "/keys/known_hosts",
+                "remote_dir": "/srv/obliteratus",
+                "install_timeout": 120,
+                "python": "/opt/python",
+                "sync_results": False,
+                "gpus": "02, 0",
+                "install_source": "obliteratus==0.1.2",
+            },
+        }
+        config = StudyConfig.from_dict(raw)
+        assert config.remote is not None
+        assert config.remote.gpus == "2,0"
+        assert StudyConfig.from_dict(config.to_dict()) == config
+
+    @pytest.mark.parametrize(
+        "remote",
+        [
+            {"host": ""},
+            {"host": "host", "port": 0},
+            {"host": "host", "remote_dir": "relative"},
+            {"host": "host", "gpus": "0; injected"},
+            {"host": "host", "install_timeout": 0},
+        ],
+    )
+    def test_remote_config_rejects_invalid_public_values(self, remote):
+        with pytest.raises(ValueError):
+            StudyConfig.from_dict({**SAMPLE_CONFIG, "remote": remote})
diff --git a/tests/test_remote_boundaries.py b/tests/test_remote_boundaries.py
index 8ad20d1..1026170 100644
--- a/tests/test_remote_boundaries.py
+++ b/tests/test_remote_boundaries.py
@@ -2,6 +2,15 @@
 
 from __future__ import annotations
 
+import shlex
+import subprocess
+from pathlib import Path
+from unittest.mock import Mock
+
+import pytest
+import yaml
+
+from obliteratus import __version__
 from obliteratus.remote import RemoteConfig, RemoteRunner
 
 
@@ -34,3 +43,375 @@ def test_remote_config_accepts_versioned_known_hosts_setting():
     )
     assert config.known_hosts_file == "/secure/known_hosts"
     assert config.ssh_target == "runner@compute.example"
+
+
+def _completed(returncode=0, stdout="", stderr=""):
+    return subprocess.CompletedProcess([], returncode, stdout=stdout, stderr=stderr)
+
+
+def test_remote_config_cli_defaults_and_optional_command_flags_are_shell_safe():
+    config = RemoteConfig.from_cli_args(
+        "runner@compute.example",
+        python="/opt/python builds/python",
+        remote_dir="/srv/remote work",
+        gpus="02, 0",
+    )
+    runner = RemoteRunner(config, on_log=lambda _message: None)
+    command = runner.build_obliterate_command(
+        "org/model; touch /tmp/injected",
+        method="advanced",
+        device="cuda",
+        dtype="float16",
+        quantization="4bit",
+        n_directions=3,
+        direction_method="svd",
+        regularization=0.2,
+        refinement_passes=2,
+        large_model=True,
+        verify_sample_size=7,
+        min_layer_fraction=0.1,
+        max_layer_fraction=0.9,
+        harmless_pc_count=4,
+        shield_concept_count=5,
+        shield_ridge=0.05,
+        shield_residualize=True,
+        shield_layer_penalty=0.3,
+        projection_target="attention",
+        projection_row_fraction=0.25,
+        refusal_max_tokens=256,
+    )
+    tokens = shlex.split(command)
+    assert tokens[:4] == ["env", "CUDA_VISIBLE_DEVICES=2,0", "/opt/python builds/python", "-m"]
+    assert tokens[4:7] == ["obliteratus", "obliterate", "org/model; touch /tmp/injected"]
+    expected = {
+        "--quantization": "4bit",
+        "--n-directions": "3",
+        "--direction-method": "svd",
+        "--regularization": "0.2",
+        "--refinement-passes": "2",
+        "--verify-sample-size": "7",
+        "--min-layer-fraction": "0.1",
+        "--max-layer-fraction": "0.9",
+        "--harmless-pc-count": "4",
+        "--shield-concept-count": "5",
+        "--shield-ridge": "0.05",
+        "--shield-layer-penalty": "0.3",
+        "--projection-target": "attention",
+        "--projection-row-fraction": "0.25",
+        "--refusal-max-tokens": "256",
+    }
+    for flag, value in expected.items():
+        assert tokens[tokens.index(flag) + 1] == value
+    assert "--large-model" in tokens
+    assert "--shield-residualize" in tokens
+
+
+def test_remote_config_rejects_invalid_install_timeout():
+    with pytest.raises(ValueError, match="install timeout"):
+        RemoteConfig(host="host", install_timeout=0)
+
+
+def test_run_and_tourney_commands_quote_all_public_values():
+    runner = RemoteRunner(
+        RemoteConfig(host="host", user="runner", gpus="all"),
+        on_log=lambda _message: None,
+    )
+    assert shlex.split(
+        runner.build_run_command("/tmp/a config.yml", output_dir="/tmp/out dir", preset="x; echo bad")
+    ) == [
+        "python3", "-m", "obliteratus", "run", "/tmp/a config.yml",
+        "--output-dir", "/tmp/out dir", "--preset", "x; echo bad",
+    ]
+    tokens = shlex.split(
+        runner.build_tourney_command(
+            "org/model", output_dir="/tmp/out dir", quantization="8bit",
+            hub_org="org; bad", hub_repo="org/repo bad", methods=["basic", "advanced"],
+            dataset="data; bad",
+        )
+    )
+    assert tokens[tokens.index("--hub-org") + 1] == "org; bad"
+    assert tokens[tokens.index("--hub-repo") + 1] == "org/repo bad"
+    assert tokens[tokens.index("--dataset") + 1] == "data; bad"
+    assert tokens[-3:] == ["--methods", "basic", "advanced"]
+    assert shlex.split(runner.build_run_command("config.yml", preset="quick")) == [
+        "python3", "-m", "obliteratus", "run", "config.yml", "--preset", "quick",
+    ]
+
+
+def test_run_ssh_non_stream_uses_argv_and_propagates_timeout(monkeypatch):
+    observed = {}
+
+    def fake_run(command, **kwargs):
+        observed.update(command=command, kwargs=kwargs)
+        return _completed(stdout="ok\n")
+
+    monkeypatch.setattr(subprocess, "run", fake_run)
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=lambda _message: None)
+    result = runner.run_ssh("printf '%s' 'safe value'", timeout=9)
+    assert result.stdout == "ok\n"
+    assert observed["command"][-1] == "printf '%s' 'safe value'"
+    assert observed["kwargs"] == {"capture_output": True, "text": True, "timeout": 9}
+
+
+class _StreamProcess:
+    def __init__(self, stdout):
+        self.stdout = stdout
+        self.returncode = 0
+        self.killed = False
+        self.wait_calls = 0
+
+    def wait(self, timeout=None):
+        self.wait_calls += 1
+        return self.returncode
+
+    def kill(self):
+        self.killed = True
+
+
+def test_run_ssh_streams_lines_and_returns_exit_status(monkeypatch):
+    process = _StreamProcess(["first\n", "second\n"])
+    monkeypatch.setattr(subprocess, "Popen", lambda *_args, **_kwargs: process)
+    logs = []
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=logs.append)
+    assert runner.run_ssh("command", stream=True, timeout=4) == 0
+    assert logs == ["first", "second"]
+    assert process.wait_calls == 1
+
+
+def test_run_ssh_timeout_kills_and_reaps_process(monkeypatch):
+    process = _StreamProcess([])
+
+    def wait(timeout=None):
+        process.wait_calls += 1
+        if process.wait_calls == 1:
+            raise subprocess.TimeoutExpired("ssh", timeout)
+        return 0
+
+    process.wait = wait
+    monkeypatch.setattr(subprocess, "Popen", lambda *_args, **_kwargs: process)
+    logs = []
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=logs.append)
+    assert runner.run_ssh("command", stream=True, timeout=4) == 124
+    assert process.killed is True
+    assert process.wait_calls == 2
+    assert any("timed out" in line for line in logs)
+
+
+class _CancelledOutput:
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        raise KeyboardInterrupt
+
+
+def test_run_ssh_cancellation_kills_reaps_and_reraises(monkeypatch):
+    process = _StreamProcess(_CancelledOutput())
+    monkeypatch.setattr(subprocess, "Popen", lambda *_args, **_kwargs: process)
+    logs = []
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=logs.append)
+    with pytest.raises(KeyboardInterrupt):
+        runner.run_ssh("command", stream=True)
+    assert process.killed is True
+    assert process.wait_calls == 1
+    assert any("cancelled" in line for line in logs)
+
+
+def test_run_ssh_rejects_malformed_process_without_stdout(monkeypatch):
+    process = _StreamProcess(None)
+    monkeypatch.setattr(subprocess, "Popen", lambda *_args, **_kwargs: process)
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=lambda _message: None)
+    with pytest.raises(RuntimeError, match="stdout"):
+        runner.run_ssh("command", stream=True)
+    assert process.killed is True
+    assert process.wait_calls == 1
+
+
+def test_connection_and_gpu_probes_cover_success_and_malformed_responses():
+    logs = []
+    runner = RemoteRunner(RemoteConfig(host="host", gpus="1"), on_log=logs.append)
+    runner.run_ssh = Mock(return_value=_completed(stdout="ok\n"))
+    assert runner.check_connection() is True
+    runner.run_ssh.return_value = 0
+    assert runner.check_connection() is False
+
+    runner.run_ssh.return_value = _completed(stdout="0, A100, 80 GiB, 70 GiB\n1, A100, 80 GiB, 60 GiB\n")
+    assert runner.check_gpu().splitlines() == [
+        "0, A100, 80 GiB, 70 GiB",
+        "1, A100, 80 GiB, 60 GiB",
+    ]
+    assert any("Selected GPUs: 1" in line for line in logs)
+    runner.run_ssh.return_value = _completed(returncode=1, stderr="missing")
+    assert runner.check_gpu() is None
+
+
+def test_gpu_probe_reports_all_devices_when_unrestricted():
+    logs = []
+    runner = RemoteRunner(RemoteConfig(host="host", gpus="all"), on_log=logs.append)
+    runner.run_ssh = Mock(return_value=_completed(stdout="0, A100\n"))
+    assert runner.check_gpu() == "0, A100"
+    assert any("Using: all 1 GPUs" in line for line in logs)
+
+
+def test_ensure_obliteratus_accepts_exact_version_or_installs_and_verifies():
+    logs = []
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=logs.append)
+    runner.run_ssh = Mock(return_value=_completed(stdout=f"{__version__}\n"))
+    assert runner.ensure_obliteratus() is True
+    assert runner.run_ssh.call_count == 1
+
+    runner.run_ssh = Mock(side_effect=[_completed(stdout="0.0.1\n"), 0, _completed(stdout=f"{__version__}\n")])
+    assert runner.ensure_obliteratus() is True
+    install_command = runner.run_ssh.call_args_list[1].args[0]
+    assert shlex.split(install_command)[-1] == "git+https://github.com/elder-plinius/OBLITERATUS.git"
+
+
+def test_ensure_obliteratus_reports_install_and_verification_failures():
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=lambda _message: None)
+    runner.run_ssh = Mock(side_effect=[_completed(returncode=1), 1])
+    assert runner.ensure_obliteratus() is False
+    runner.run_ssh = Mock(side_effect=[_completed(stdout="old\n"), 0, _completed(stdout="still-old\n")])
+    assert runner.ensure_obliteratus() is False
+
+
+def test_result_sync_creates_local_directory_and_quotes_remote_path(monkeypatch, tmp_path):
+    responses = iter([_completed(), _completed(returncode=1, stderr="denied")])
+    observed = []
+
+    def fake_run(command, **_kwargs):
+        observed.append(command)
+        return next(responses)
+
+    monkeypatch.setattr(subprocess, "run", fake_run)
+    runner = RemoteRunner(RemoteConfig(host="host", user="runner"), on_log=lambda _message: None)
+    local = tmp_path / "local results"
+    assert runner.sync_results_back("/tmp/remote results", str(local)) is True
+    assert local.is_dir()
+    assert observed[0][-2] == "runner@host:'/tmp/remote results/'"
+    assert runner.sync_results_back("/tmp/remote results", str(local)) is False
+
+
+def test_upload_config_returns_remote_path_or_raises(monkeypatch, tmp_path):
+    config_path = tmp_path / "study config.yml"
+    config_path.write_text("model: fixture\nremote:\n  host: compute.example\n")
+    responses = iter([_completed(), _completed(returncode=1, stderr="denied")])
+    observed = []
+    uploaded_payloads = []
+
+    def fake_run(command, **_kwargs):
+        observed.append(command)
+        uploaded_payloads.append(yaml.safe_load(Path(command[-2]).read_text()))
+        return next(responses)
+
+    monkeypatch.setattr(subprocess, "run", fake_run)
+    runner = RemoteRunner(
+        RemoteConfig(host="host", user="runner", remote_dir="/srv/remote work"),
+        on_log=lambda _message: None,
+    )
+    runner.run_ssh = Mock()
+    assert runner.upload_config(str(config_path)) == "/srv/remote work/config.yaml"
+    assert observed[0][-1] == "runner@host:'/srv/remote work/config.yaml'"
+    assert uploaded_payloads[0] == {"model": "fixture"}
+    with pytest.raises(RuntimeError, match="denied"):
+        runner.upload_config(str(config_path))
+
+
+def test_upload_config_requires_yaml_mapping(monkeypatch, tmp_path):
+    config_path = tmp_path / "study.yml"
+    config_path.write_text("- not\n- a\n- mapping\n")
+    runner = RemoteRunner(RemoteConfig(host="host"), on_log=lambda _message: None)
+    runner.run_ssh = Mock()
+    monkeypatch.setattr(subprocess, "run", Mock())
+    with pytest.raises(ValueError, match="must contain a YAML mapping"):
+        runner.upload_config(str(config_path))
+    subprocess.run.assert_not_called()
+
+
+def _prepared_runner(*, sync_results=True):
+    runner = RemoteRunner(
+        RemoteConfig(host="host", remote_dir="/srv/run", sync_results=sync_results),
+        on_log=lambda _message: None,
+    )
+    runner.check_connection = Mock(return_value=True)
+    runner.check_gpu = Mock(return_value="gpu")
+    runner.ensure_obliteratus = Mock(return_value=True)
+    return runner
+
+
+def test_remote_obliterate_orchestration_success_failure_and_sync_paths():
+    runner = _prepared_runner(sync_results=False)
+    runner.run_ssh = Mock(side_effect=[_completed(), 0])
+    assert runner.run_obliterate("org/model") == "/srv/run/output/org_model"
+
+    runner = _prepared_runner()
+    runner.run_ssh = Mock(side_effect=[_completed(), 9])
+    assert runner.run_obliterate("org/model") is None
+
+    runner = _prepared_runner()
+    runner.run_ssh = Mock(side_effect=[_completed(), 0])
+    runner.sync_results_back = Mock(return_value=True)
+    assert runner.run_obliterate("org/model", local_output_dir="local") == "local"
+    runner.run_ssh = Mock(side_effect=[_completed(), 0])
+    runner.sync_results_back.return_value = False
+    assert runner.run_obliterate("org/model") is None
+
+
+def test_remote_obliterate_stops_at_connection_or_install_failure():
+    runner = _prepared_runner()
+    runner.check_connection.return_value = False
+    assert runner.run_obliterate("model") is None
+    runner.check_connection.return_value = True
+    runner.ensure_obliteratus.return_value = False
+    assert runner.run_obliterate("model") is None
+
+
+def test_remote_config_orchestration_success_failure_and_sync_paths():
+    runner = _prepared_runner(sync_results=False)
+    runner.upload_config = Mock(return_value="/srv/run/config.yaml")
+    runner.run_ssh = Mock(return_value=0)
+    assert runner.run_config("local.yml", preset="quick") == "/srv/run/results"
+
+    runner = _prepared_runner()
+    runner.upload_config = Mock(return_value="/srv/run/config.yaml")
+    runner.run_ssh = Mock(return_value=2)
+    assert runner.run_config("local.yml") is None
+
+    runner.run_ssh.return_value = 0
+    runner.sync_results_back = Mock(return_value=True)
+    assert runner.run_config("local.yml", local_output_dir="local") == "local"
+    runner.sync_results_back.return_value = False
+    assert runner.run_config("local.yml") is None
+
+
+def test_remote_config_stops_at_connection_or_install_failure():
+    runner = _prepared_runner()
+    runner.check_connection.return_value = False
+    assert runner.run_config("local.yml") is None
+    runner.check_connection.return_value = True
+    runner.ensure_obliteratus.return_value = False
+    assert runner.run_config("local.yml") is None
+
+
+def test_remote_tourney_orchestration_success_failure_and_sync_paths():
+    runner = _prepared_runner(sync_results=False)
+    runner.run_ssh = Mock(return_value=0)
+    assert runner.run_tourney("org/model") == "/srv/run/tourney/org_model"
+
+    runner = _prepared_runner()
+    runner.run_ssh = Mock(return_value=3)
+    assert runner.run_tourney("org/model") is None
+
+    runner.run_ssh.return_value = 0
+    runner.sync_results_back = Mock(return_value=True)
+    assert runner.run_tourney("org/model", local_output_dir="local") == "local"
+    runner.sync_results_back.return_value = False
+    assert runner.run_tourney("org/model") is None
+
+
+def test_remote_tourney_stops_at_connection_or_install_failure():
+    runner = _prepared_runner()
+    runner.check_connection.return_value = False
+    assert runner.run_tourney("model") is None
+    runner.check_connection.return_value = True
+    runner.ensure_obliteratus.return_value = False
+    assert runner.run_tourney("model") is None
diff --git a/tests/test_remote_contracts.py b/tests/test_remote_contracts.py
new file mode 100644
index 0000000..20565d8
--- /dev/null
+++ b/tests/test_remote_contracts.py
@@ -0,0 +1,180 @@
+"""Mutation-safe contracts for remote input and shell construction."""
+
+from __future__ import annotations
+
+import shlex
+
+import pytest
+
+from obliteratus.remote_contracts import (
+    normalize_gpu_selection,
+    parse_remote_target,
+    remote_python_command,
+    remote_scp_spec,
+    validate_remote_settings,
+)
+
+
+VALID_REMOTE_SETTINGS = {
+    "host": "compute.example",
+    "user": "runner",
+    "port": 22,
+    "remote_dir": "/tmp/obliteratus",
+    "python": "python3",
+    "gpus": None,
+    "install_source": "obliteratus",
+}
+
+
+@pytest.mark.parametrize(
+    ("raw", "expected"),
+    [(None, None), ("all", "all"), ("ALL", "all"), ("0", "0"), (" 02, 0,11 ", "2,0,11")],
+)
+def test_gpu_selection_normalizes_public_values(raw, expected):
+    assert normalize_gpu_selection(raw) == expected
+
+
+@pytest.mark.parametrize(
+    ("raw", "message"),
+    [
+        ("", "remote gpus must be a non-empty string"),
+        ("\x7f", "remote gpus may not contain control characters"),
+        ("0,,1", "remote gpus must be 'all' or comma-separated non-negative integers"),
+        ("-1", "remote gpus must be 'all' or comma-separated non-negative integers"),
+        (
+            "0; touch /tmp/pwned",
+            "remote gpus must be 'all' or comma-separated non-negative integers",
+        ),
+        ("gpu0", "remote gpus must be 'all' or comma-separated non-negative integers"),
+        ("0\n1", "remote gpus may not contain control characters"),
+    ],
+)
+def test_gpu_selection_rejects_non_device_input(raw, message):
+    with pytest.raises(ValueError) as error:
+        normalize_gpu_selection(raw)
+    assert str(error.value) == message
+
+
+def test_remote_target_defaults_user_and_parses_single_at_sign():
+    assert parse_remote_target("compute.example") == ("root", "compute.example")
+    assert parse_remote_target("runner@compute.example") == ("runner", "compute.example")
+    assert parse_remote_target(" runner@compute.example ") == ("runner", "compute.example")
+
+
+@pytest.mark.parametrize(
+    ("target", "message"),
+    [
+        ("", "remote target must be a non-empty string"),
+        ("\x7f", "remote target may not contain control characters"),
+        ("runner@", "remote host must be a non-empty string"),
+        ("@host", "remote user must be a non-empty string"),
+        ("bad user@host", "remote user contains unsupported characters"),
+        (
+            "runner@-oProxyCommand=evil",
+            "remote host must be a host name or address without user or options",
+        ),
+        ("runner@host name", "remote host must be a host name or address without user or options"),
+        ("a@b@host", "remote target may contain at most one user separator"),
+    ],
+)
+def test_remote_target_rejects_empty_or_option_like_components(target, message):
+    with pytest.raises(ValueError) as error:
+        parse_remote_target(target)
+    assert str(error.value) == message
+
+
+@pytest.mark.parametrize(
+    ("override", "message"),
+    [
+        ({"host": ""}, "remote host must be a non-empty string"),
+        (
+            {"host": "bad@host"},
+            "remote host must be a host name or address without user or options",
+        ),
+        (
+            {"host": "bad host"},
+            "remote host must be a host name or address without user or options",
+        ),
+        ({"user": ""}, "remote user must be a non-empty string"),
+        ({"user": "-oProxy"}, "remote user contains unsupported characters"),
+        ({"user": "bad user"}, "remote user contains unsupported characters"),
+        ({"port": 0}, "remote port must be an integer from 1 through 65535"),
+        ({"port": 65536}, "remote port must be an integer from 1 through 65535"),
+        ({"port": True}, "remote port must be an integer from 1 through 65535"),
+        ({"port": "22"}, "remote port must be an integer from 1 through 65535"),
+        ({"remote_dir": ""}, "remote directory must be a non-empty string"),
+        ({"remote_dir": "relative"}, "remote directory must be an absolute POSIX path"),
+        ({"python": ""}, "remote Python must be a non-empty string"),
+        ({"install_source": ""}, "remote install source must be a non-empty string"),
+        (
+            {"install_source": "bad\nsource"},
+            "remote install source may not contain control characters",
+        ),
+    ],
+)
+def test_remote_settings_reject_invalid_boundaries(override, message):
+    values = dict(VALID_REMOTE_SETTINGS)
+    values.update(override)
+    with pytest.raises(ValueError) as error:
+        validate_remote_settings(**values)
+    assert str(error.value) == message
+
+
+@pytest.mark.parametrize("port", [1, 65535])
+def test_remote_settings_accept_port_boundaries(port):
+    values = dict(VALID_REMOTE_SETTINGS, port=port, gpus=" 02,0 ")
+    assert validate_remote_settings(**values) == "2,0"
+
+
+def test_remote_python_command_preserves_each_untrusted_value_as_one_argument():
+    command = remote_python_command(
+        "/opt/python builds/current/python",
+        ["-m", "obliteratus", "run", "/tmp/a config.yml", "--preset", "x; echo injected"],
+        gpus="02,0",
+    )
+    assert shlex.split(command) == [
+        "env",
+        "CUDA_VISIBLE_DEVICES=2,0",
+        "/opt/python builds/current/python",
+        "-m",
+        "obliteratus",
+        "run",
+        "/tmp/a config.yml",
+        "--preset",
+        "x; echo injected",
+    ]
+
+
+def test_remote_python_command_omits_environment_for_all_devices():
+    assert shlex.split(remote_python_command("python3", ["-V"], gpus="all")) == ["python3", "-V"]
+    assert shlex.split(remote_python_command("python3", ["-V"])) == ["python3", "-V"]
+
+
+def test_remote_python_command_reports_invalid_python_contract():
+    with pytest.raises(ValueError) as error:
+        remote_python_command("", ["-V"])
+    assert str(error.value) == "remote Python must be a non-empty string"
+
+
+def test_remote_scp_spec_quotes_remote_paths_and_directory_suffix():
+    assert remote_scp_spec("runner@host", "/tmp/result file", directory=True) == (
+        "runner@host:'/tmp/result file/'"
+    )
+    assert remote_scp_spec("runner@host", "/tmp/results/", directory=True) == (
+        "runner@host:/tmp/results/"
+    )
+    assert remote_scp_spec("runner@host", "/tmp/config.yml") == "runner@host:/tmp/config.yml"
+
+
+@pytest.mark.parametrize(
+    ("target", "path", "message"),
+    [
+        ("", "/tmp/config.yml", "SSH target must be a non-empty string"),
+        ("runner@host", "", "remote SCP path must be a non-empty string"),
+        ("runner@host", "/tmp/bad\x7fpath", "remote SCP path may not contain control characters"),
+    ],
+)
+def test_remote_scp_spec_reports_invalid_input_contract(target, path, message):
+    with pytest.raises(ValueError) as error:
+        remote_scp_spec(target, path)
+    assert str(error.value) == message