diff --git a/.env.example b/.env.example
index edb147aaf..f1b396a47 100644
--- a/.env.example
+++ b/.env.example
@@ -101,9 +101,9 @@ SEARXNG_INSTANCE=http://localhost:8080
 # Skip the external-context exact-approval pause for unattended local agents.
 # Keep false for shared or internet-exposed deployments.
 
-# Optional post-external-context tool approval gate. Off by default because it
-# can block normal agent work; enable only for deployments that want this fence.
-# ODYSSEUS_TOOL_APPROVAL_GATE=0
+# Post-external-context tool approval gate. On by default; set to 0 only for
+# trusted single-user setups that accept injected content reaching side-effect tools.
+# ODYSSEUS_TOOL_APPROVAL_GATE=1
 
 # Mark session cookies Secure. Left unset, this follows the request scheme:
 # an HTTPS login gets a Secure cookie, a plain-HTTP one does not. Set true to
diff --git a/THREAT_MODEL.md b/THREAT_MODEL.md
index d63d1335b..ba4999157 100644
--- a/THREAT_MODEL.md
+++ b/THREAT_MODEL.md
@@ -60,13 +60,11 @@ External content that reaches the LLM is treated as untrusted via `src/prompt_se
 
 **Untrusted surfaces that must go through this wrapper:** web search results, fetched URLs, emails (read), saved memories, skill text, notes, and any tool output sourced from outside the server. Injecting untrusted content directly into the system role is a security bug.
 
-### Post-external-context tool approval gate — off by default
+### Post-external-context tool approval gate — on by default
 
 `src/tool_capabilities.py` carries a second layer: once untrusted content has entered a run, `ToolRunSecurityContext.decision_for()` blocks tools that execute code, mutate state, or cause external side effects until the user authorises the action separately.
 
-**It is disabled unless `ODYSSEUS_TOOL_APPROVAL_GATE` is set** (`1`/`true`/`yes`/`on`). The default is off because the gate is conservative enough to interrupt ordinary agent work. That is a deliberate usability trade, and it means a default deployment relies on the wrapper above — not on the gate — to contain injected instructions.
-
-Operators who run the agent against untrusted web or email content with side-effecting tools enabled should turn it on. With the gate off, a successful injection can reach `bash`, `host_shell`, `send_email` and `delete_email` without a separate confirmation; with it on, each of those is refused until approved.
+It is on unless `ODYSSEUS_TOOL_APPROVAL_GATE` is set to a falsy value (`0`/`false`/`no`/`off`). Request authority narrows which tool families a turn may use, but within an admitted family it does not bind the exact action: a request to read email admits `send_email` and `delete_email`, and agent processes inherit the host network. Until those are covered by their own boundaries, this gate is what stops an injected instruction from reaching them. Turning it off lets a successful injection reach `bash`, `host_shell`, `send_email` and `delete_email` without a separate confirmation.
 
 Two exemptions apply even when the gate is on, both deliberate:
 
@@ -85,7 +83,7 @@ Two exemptions apply even when the gate is on, both deliberate:
 
 These are open, acknowledged, and contributor help is welcome:
 
-1. **No shell/filesystem sandbox.** The agent `bash` and `read_file`/`write_file` tools run as the app process user with no network egress filtering or filesystem confinement. A successful prompt-injection reaching a shell-enabled admin session can make outbound requests to internal services. See #1058 for the sandbox proposal. The tool approval gate above is the compensating control, and it is off by default — so on a default deployment this gap is unmitigated beyond the untrusted-context wrapper.
+1. **No shell/filesystem sandbox.** The agent `bash` and `read_file`/`write_file` tools run as the app process user with no network egress filtering or filesystem confinement. A successful prompt-injection reaching a shell-enabled admin session can make outbound requests to internal services. See #1058 for the sandbox proposal. The tool approval gate above is the compensating control and is on by default; turning it off leaves this gap unmitigated beyond the untrusted-context wrapper.
 
 2. **SSRF via `/api/v1/chat` `base_url` parameter.** A chat-scoped API token can supply an arbitrary `base_url`; the server forwards the LLM request to that host without validating the scheme or address. PR #1039 fixes this.
 
diff --git a/scripts/generate_env_reference.py b/scripts/generate_env_reference.py
index b6edad2a6..d3372fbc7 100644
--- a/scripts/generate_env_reference.py
+++ b/scripts/generate_env_reference.py
@@ -488,8 +488,9 @@ VARIABLE_NOTES: dict[str, tuple[str, str, str]] = {
     # -- Agent loop and tool execution -------------------------------------
     "ODYSSEUS_TOOL_APPROVAL_GATE": (
         "Agent loop and tool execution", USER,
-        "Security-relevant. Truthy makes tool calls pass through the approval gate. "
-        "Off by default.",
+        "Security-relevant. On by default: after external content enters a run, "
+        "tools that execute code, mutate state or cause external side effects need "
+        "a separate approval. Set to 0 to opt out.",
     ),
     "ODYSSEUS_MCP_ALLOWED_COMMANDS": (
         "Agent loop and tool execution", USER,
diff --git a/src/tool_capabilities.py b/src/tool_capabilities.py
index 89bba9596..f0ba4b3b1 100644
--- a/src/tool_capabilities.py
+++ b/src/tool_capabilities.py
@@ -678,9 +678,13 @@ POST_EXTERNAL_BLOCKED_EFFECTS = frozenset(
 )
 
 
+# On by default: until agent processes run without network and side-effecting
+# non-process tools have their own exact-approval boundary, this gate is the
+# only check between injected external content and those tools. Set it to a
+# falsy value to opt out.
 TOOL_APPROVAL_GATE_ENABLED = (
-    str(os.getenv("ODYSSEUS_TOOL_APPROVAL_GATE", "0")).strip().lower()
-    in {"1", "true", "yes", "on"}
+    str(os.getenv("ODYSSEUS_TOOL_APPROVAL_GATE", "1")).strip().lower()
+    not in {"0", "false", "no", "off"}
 )
 
 
diff --git a/tests/test_agent_runtime_context.py b/tests/test_agent_runtime_context.py
index 403835231..ebb793f9f 100644
--- a/tests/test_agent_runtime_context.py
+++ b/tests/test_agent_runtime_context.py
@@ -1109,6 +1109,9 @@ def test_tui_local_workspace_turn_hides_backend_file_tools(monkeypatch):
 
 
 def test_native_host_shell_call_runs_through_bridge_and_threads_result(monkeypatch):
+    # Routing test written for the opt-out posture; the gate default is pinned in
+    # tests/test_tool_approval_gate_default.py.
+    monkeypatch.setattr("src.tool_capabilities.TOOL_APPROVAL_GATE_ENABLED", False)
     monkeypatch.setattr(al, "get_setting", lambda key, default=None: default, raising=False)
     monkeypatch.setattr(al, "get_mcp_manager", lambda: None, raising=False)
     monkeypatch.setattr(al, "estimate_tokens", lambda *args, **kwargs: 10, raising=False)
diff --git a/tests/test_tool_approval_gate_default.py b/tests/test_tool_approval_gate_default.py
new file mode 100644
index 000000000..372b56ed7
--- /dev/null
+++ b/tests/test_tool_approval_gate_default.py
@@ -0,0 +1,52 @@
+"""Pin the production default of the post-external-context approval gate.
+
+Every other gate test sets ``TOOL_APPROVAL_GATE_ENABLED`` explicitly, so none of
+them notices if the default flips. The flag is read once at import, so each
+case imports the module in a fresh interpreter with a controlled environment.
+"""
+import json
+import os
+import subprocess
+import sys
+from pathlib import Path
+
+import pytest
+
+REPO = Path(__file__).resolve().parents[1]
+
+_PROBE = """
+import json
+from src.tool_capabilities import TOOL_APPROVAL_GATE_ENABLED, ToolRunSecurityContext
+context = ToolRunSecurityContext(external_untrusted_context_seen=True, external_sources=["read_email"])
+print(json.dumps({
+    "enabled": TOOL_APPROVAL_GATE_ENABLED,
+    "allowed": {tool: context.decision_for(tool, "{}").allowed
+                for tool in ("bash", "send_email", "delete_email", "read_file")},
+}))
+"""
+
+
+def _probe(gate_value):
+    env = {key: value for key, value in os.environ.items() if key != "ODYSSEUS_TOOL_APPROVAL_GATE"}
+    if gate_value is not None:
+        env["ODYSSEUS_TOOL_APPROVAL_GATE"] = gate_value
+    out = subprocess.run(
+        [sys.executable, "-c", _PROBE], cwd=REPO, env=env,
+        capture_output=True, text=True, timeout=60, check=True,
+    )
+    return json.loads(out.stdout.strip().splitlines()[-1])
+
+
+def test_gate_is_on_when_the_variable_is_unset():
+    result = _probe(None)
+    assert result["enabled"] is True
+    assert result["allowed"] == {
+        "bash": False, "send_email": False, "delete_email": False, "read_file": True,
+    }
+
+
+@pytest.mark.parametrize("value", ["0", "false", "no", "off", " OFF "])
+def test_gate_can_be_turned_off_explicitly(value):
+    result = _probe(value)
+    assert result["enabled"] is False
+    assert all(result["allowed"].values())
diff --git a/tests/test_tool_policy.py b/tests/test_tool_policy.py
index 40d875cb2..d9e9c75f8 100644
--- a/tests/test_tool_policy.py
+++ b/tests/test_tool_policy.py
@@ -1613,6 +1613,9 @@ def test_agent_loop_synthesizes_web_answer_after_tool_preamble(monkeypatch):
 
 
 def test_open_calendar_request_uses_ui_control_panel_not_event_dump(monkeypatch):
+    # Routing test written for the opt-out posture; the gate default is pinned in
+    # tests/test_tool_approval_gate_default.py.
+    monkeypatch.setattr("src.tool_capabilities.TOOL_APPROVAL_GATE_ENABLED", False)
     _patch_loop_basics(monkeypatch)
     src = Path(__file__).resolve().parent.parent.joinpath("src", "agent_loop.py").read_text(encoding="utf-8")
     assert 'if isinstance(_ev, dict) and _ev.get("context_only"):' in src
@@ -1679,6 +1682,9 @@ def test_open_calendar_request_uses_ui_control_panel_not_event_dump(monkeypatch)
 
 
 def test_calendar_create_response_includes_persistent_event_link(monkeypatch):
+    # Routing test written for the opt-out posture; the gate default is pinned in
+    # tests/test_tool_approval_gate_default.py.
+    monkeypatch.setattr("src.tool_capabilities.TOOL_APPROVAL_GATE_ENABLED", False)
     _patch_loop_basics(monkeypatch)
     from src.user_time import clear_user_time_context, set_user_timezone
 
@@ -3505,6 +3511,9 @@ def test_notes_about_calendar_context_still_route_to_notes():
 
 
 def test_notes_panel_open_plus_create_keeps_both_tool_calls(monkeypatch):
+    # Routing test written for the opt-out posture; the gate default is pinned in
+    # tests/test_tool_approval_gate_default.py.
+    monkeypatch.setattr("src.tool_capabilities.TOOL_APPROVAL_GATE_ENABLED", False)
     _patch_loop_basics(monkeypatch)
     seen_blocks = []
 
diff --git a/website/configuration-reference.md b/website/configuration-reference.md
index f94dd2e66..98ff1f6b4 100644
--- a/website/configuration-reference.md
+++ b/website/configuration-reference.md
@@ -77,7 +77,7 @@ The source tree reads **117** `ODYSSEUS_*` variables: 81 an operator may want to
 | `ODYSSEUS_MCP_ALLOWED_COMMANDS` | `''` | `src/agent_tools/admin_tools.py:140` | Security-relevant. Comma-separated allowlist of MCP launcher basenames the agent may start. Empty by default, and the deny list still wins. |
 | `ODYSSEUS_PYTHON_TOOL_SITE_PACKAGES` | `''` | `src/agent_runtime/process_resources.py:59` (+2 more) | Security-relevant. Absolute package roots, separated by the platform path separator, exposed to the sandboxed Python tool. Empty exposes none. |
 | `ODYSSEUS_SCRIPT_HOST` | `'localhost'` | `src/builtin_actions.py:925` | Default host for the run-script action. `localhost`, `127.0.0.1`, `local` and empty run locally; any other value runs over SSH. |
-| `ODYSSEUS_TOOL_APPROVAL_GATE` | `'0'` | `src/tool_capabilities.py:682` | Security-relevant. Truthy makes tool calls pass through the approval gate. Off by default. |
+| `ODYSSEUS_TOOL_APPROVAL_GATE` | `'1'` | `src/tool_capabilities.py:686` | Security-relevant. On by default: after external content enters a run, tools that execute code, mutate state or cause external side effects need a separate approval. Set to 0 to opt out. |
 
 ### Browser automation