diff --git a/docker/scripts/bash-guard-hook.sh b/docker/scripts/bash-guard-hook.sh
index eca8ea6b..6b634a64 100755
--- a/docker/scripts/bash-guard-hook.sh
+++ b/docker/scripts/bash-guard-hook.sh
@@ -321,4 +321,21 @@ if echo "$low" | grep -qE '(^|[[:space:];&|])rm[[:space:]]+[^|;&]*-[[:alpha:]]*[
     fi
 fi
 
+# --- package-environment mutations targeting /app (ALL providers) -------------
+# /app holds the orchestrator code and the MCP-gateway venv (/app/.venv). An
+# agent that `uv sync` / `pip install`s into /app rebuilds that venv and breaks
+# its OWN gateway tools (every roboco-flow / -do / -git verb) — stranding the
+# agent and getting its task reaped. Agents manage dependencies in their
+# workspace clone under /data/workspaces, never in /app. Two-step: a
+# package-mutation verb AND a target that resolves to /app's environment
+# (cd /app, --project/--directory /app, /app/.venv, UV_PROJECT_ENVIRONMENT=/app).
+# Reads of /app (cat/ls/grep) and workspace installs are untouched. Deliberately
+# NOT gated by ROBOCO_GUARD_SKIP_GIT, so it fires for every provider — the Claude
+# PreToolUse hook AND the grok exfil hook (and future provider hooks).
+if echo "$low" | grep -qE '(^|[[:space:];&|])(uv[[:space:]]+(sync|lock|add|remove)|uv[[:space:]]+pip[[:space:]]+(install|uninstall)|pip3?[[:space:]]+(install|uninstall))' && \
+   echo "$low" | grep -qE '(/app/\.venv|--project[[:space:]=]+"?/app([^a-z]|$)|--directory[[:space:]=]+"?/app([^a-z]|$)|uv_project_environment="?/app([^a-z]|$)|(^|[[:space:];&|])cd[[:space:]]+"?/app([^a-z]|$))'; then
+    echo "Denied: installing or syncing packages into /app rebuilds the orchestrator / MCP-gateway venv (/app/.venv) and breaks your own gateway tools. Manage dependencies in your workspace clone under /data/workspaces, never /app. If /app's environment looks broken, report it via your blocked / escalation verb — don't try to repair it." >&2
+    exit 2
+fi
+
 exit 0
diff --git a/tests/unit/scripts/test_bash_guard.py b/tests/unit/scripts/test_bash_guard.py
index 4a92661b..3322dd8d 100644
--- a/tests/unit/scripts/test_bash_guard.py
+++ b/tests/unit/scripts/test_bash_guard.py
@@ -381,3 +381,71 @@ def test_allows_pytest_even_if_suite_uses_requests() -> None:
     """The command string is just the runner — no http-client token and
     no internal host literal — so it must pass."""
     assert _run("uv run python -m pytest tests/unit/ -q") == _ALLOWED
+
+
+# ---------------------------------------------------------------------------
+# Package-environment mutations targeting /app (the orchestrator + MCP-gateway
+# venv). Must be blocked for EVERY provider so an agent can't corrupt its own
+# gateway by `uv sync` / `pip install`ing into /app.
+# ---------------------------------------------------------------------------
+
+
+def test_blocks_uv_sync_cd_app() -> None:
+    assert _run("cd /app && uv sync") == _DENIED
+
+
+def test_blocks_pip_install_cd_app() -> None:
+    assert _run("cd /app && pip install httpcore httpx") == _DENIED
+
+
+def test_blocks_uv_sync_project_app() -> None:
+    assert _run("uv sync --project /app") == _DENIED
+
+
+def test_blocks_uv_pip_install_app_venv() -> None:
+    assert _run("uv pip install --python /app/.venv/bin/python httpx") == _DENIED
+
+
+def test_blocks_uv_project_environment_app() -> None:
+    assert _run("UV_PROJECT_ENVIRONMENT=/app/.venv uv sync --no-dev") == _DENIED
+
+
+def test_blocks_app_mutation_even_in_grok_mode() -> None:
+    """Grok runs the hook with ROBOCO_GUARD_SKIP_GIT=1; the /app rule is NOT a
+    git rule, so it must STILL fire — every provider is protected."""
+    payload = json.dumps(
+        {"tool_name": "Bash", "tool_input": {"command": "cd /app && uv sync"}}
+    )
+    result = subprocess.run(
+        [str(GUARD)],
+        input=payload,
+        capture_output=True,
+        text=True,
+        check=False,
+        env={**os.environ, "ROBOCO_GUARD_SKIP_GIT": "1"},
+    )
+    assert result.returncode == _DENIED
+
+
+def test_allows_uv_sync_in_workspace() -> None:
+    """Legit dependency sync in the agent's own workspace clone must pass."""
+    assert (
+        _run("cd /data/workspaces/roboco/backend/be-dev-1 && uv sync --extra dev")
+        == _ALLOWED
+    )
+
+
+def test_allows_pip_install_in_workspace() -> None:
+    assert _run("pip install -r requirements.txt") == _ALLOWED
+
+
+def test_allows_reading_files_under_app() -> None:
+    """Reads of /app (not env mutations) are untouched."""
+    assert _run("cat /app/pyproject.toml") == _ALLOWED
+    assert _run("ls -la /app/.venv/bin") == _ALLOWED
+
+
+def test_allows_uv_sync_for_app_named_workspace_project() -> None:
+    """A workspace path that merely contains 'app' (e.g. .../myapp/...) must not
+    trip the rule — the boundary requires /app to be its own path segment."""
+    assert _run("cd /data/workspaces/myapp/backend/be-dev-1 && uv sync") == _ALLOWED