diff --git a/src/aegis_gitea_mcp/tools/arguments.py b/src/aegis_gitea_mcp/tools/arguments.py
index f201b8d..b5f3f29 100644
--- a/src/aegis_gitea_mcp/tools/arguments.py
+++ b/src/aegis_gitea_mcp/tools/arguments.py
@@ -468,6 +468,67 @@ _RAW_CROSS_REPO_OWNERS = frozenset({"search", "issues"})
 # Resources whose trailing segments form a file path target for policy checks.
 _RAW_FILE_RESOURCES = frozenset({"contents", "raw", "media"})
 
+# Known top-level segments of the Gitea ``/api/v1`` surface. A raw request whose
+# first path segment is not in this set is rejected (fail closed): we never pass
+# an unrecognized path straight through to Gitea.
+KNOWN_API_PREFIXES = frozenset(
+    {
+        "activitypub",
+        "admin",
+        "gitignore",
+        "issues",
+        "label",
+        "licenses",
+        "markdown",
+        "markup",
+        "miscellaneous",
+        "nodeinfo",
+        "notifications",
+        "org",
+        "orgs",
+        "packages",
+        "repos",
+        "repositories",
+        "settings",
+        "signing-key.gpg",
+        "teams",
+        "topics",
+        "user",
+        "users",
+        "version",
+    }
+)
+
+# Override table: provably side-effect-free POSTs that may be treated as reads so
+# they do not needlessly require WRITE_MODE. This table may ONLY ever DOWNGRADE a
+# write to a read for endpoints that render content and mutate nothing — never
+# the reverse. Keyed by the final path segment of the endpoint.
+_RAW_READ_ONLY_POST_LEAVES = frozenset({"markdown", "markup", "raw"})
+
+
+def raw_is_known_api_path(endpoint: str) -> bool:
+    """Return whether the endpoint's top segment is a known Gitea API prefix."""
+    return raw_top_segment(endpoint) in KNOWN_API_PREFIXES
+
+
+def raw_request_is_write(method: str, endpoint: str) -> bool:
+    """Classify a raw request as read or write from its method and path.
+
+    ``GET``/``HEAD`` are reads; every other method is a write — except for the
+    small, explicit override table of render-only POSTs (e.g. markdown/markup),
+    which are reads. The override can only make a request *more* permissive for
+    provably side-effect-free endpoints; it never reclassifies a mutating call as
+    a read, so a misclassified write cannot slip past the write-mode gate.
+    """
+    upper = method.upper()
+    if upper in {"GET", "HEAD"}:
+        return False
+    if upper == "POST":
+        rel = _raw_relative_segments(endpoint)
+        if rel and rel[-1] in _RAW_READ_ONLY_POST_LEAVES:
+            return False
+    return True
+
 
 def normalize_raw_endpoint(path: str) -> str:
     """Normalize a raw API path into an ``/api/v1``-prefixed endpoint.
@@ -501,6 +562,11 @@ def _raw_relative_segments(endpoint: str) -> list[str]:
     return segments[2:] if segments[:2] == ["api", "v1"] else segments
 
 
+def raw_relative_segments(endpoint: str) -> list[str]:
+    """Return the endpoint path segments after the ``/api/v1`` prefix (public)."""
+    return _raw_relative_segments(endpoint)
+
+
 def raw_top_segment(endpoint: str) -> str:
     """Return the first path segment after ``/api/v1`` for coarse policy grouping."""
     rel = _raw_relative_segments(endpoint)
diff --git a/src/aegis_gitea_mcp/tools/raw_tools.py b/src/aegis_gitea_mcp/tools/raw_tools.py
index 3c0caaa..94c7fbd 100644
--- a/src/aegis_gitea_mcp/tools/raw_tools.py
+++ b/src/aegis_gitea_mcp/tools/raw_tools.py
@@ -38,8 +38,9 @@ from aegis_gitea_mcp.tools.arguments import (
     normalize_raw_endpoint,
     parse_raw_repository,
     parse_raw_target_path,
+    raw_is_known_api_path,
     raw_is_sensitive,
-    raw_method_is_write,
+    raw_request_is_write,
     raw_top_segment,
 )
 
@@ -75,7 +76,21 @@ async def raw_api_request_tool(gitea: GiteaClient, arguments: dict[str, Any]) ->
     parsed = RawApiRequestArgs.model_validate(arguments)
     method = parsed.method
     endpoint = normalize_raw_endpoint(parsed.path)
-    is_write = raw_method_is_write(method)
+
+    # Fail closed on paths that do not match a known Gitea API prefix: an
+    # unrecognized path is never passed straight through to the backend.
+    if not raw_is_known_api_path(endpoint):
+        audit.log_access_denied(tool_name="gitea_request", reason="raw_unknown_path_denied")
+        raise ToolError(
+            "Endpoint does not match a known Gitea API route prefix.",
+            status_code=403,
+        )
+
+    # Deterministic read/write classification (override-aware): a non-GET/HEAD
+    # method is a write unless it is in the explicit render-only override table,
+    # so a mutating call can never be misclassified as a read and slip past the
+    # write-mode gate.
+    is_write = raw_request_is_write(method, endpoint)
 
     # Admin/credential denylist applies to every method and cannot be re-opened
     # from policy.yaml — only RAW_API_ALLOW_SENSITIVE overrides it.
diff --git a/tests/test_classifier.py b/tests/test_classifier.py
new file mode 100644
index 0000000..1470817
--- /dev/null
+++ b/tests/test_classifier.py
@@ -0,0 +1,128 @@
+"""Tests for the gitea_request read/write classifier and known-path gate."""
+
+from __future__ import annotations
+
+from pathlib import Path
+from typing import Any
+
+import pytest
+
+from aegis_gitea_mcp.config import reset_settings
+from aegis_gitea_mcp.errors import ToolError
+from aegis_gitea_mcp.tools.arguments import (
+    normalize_raw_endpoint,
+    raw_is_known_api_path,
+    raw_request_is_write,
+)
+from aegis_gitea_mcp.tools.raw_tools import raw_api_request_tool
+
+
+@pytest.fixture
+def raw_env(monkeypatch: pytest.MonkeyPatch, tmp_path: Path) -> None:
+    """API-key-mode settings with default policy (read allow, write deny)."""
+    reset_settings()
+    monkeypatch.setenv("GITEA_URL", "https://gitea.example.com")
+    monkeypatch.setenv("GITEA_TOKEN", "test-token")
+    monkeypatch.setenv("MCP_API_KEYS", "a" * 64)
+    monkeypatch.setenv("ENVIRONMENT", "test")
+    monkeypatch.setenv("POLICY_FILE_PATH", str(tmp_path / "missing-policy.yaml"))
+
+
+class StubRawGitea:
+    """Stub Gitea client capturing raw_request calls."""
+
+    def __init__(self, response: Any = None) -> None:
+        self._response: Any = {"ok": True} if response is None else response
+        self.calls: list[dict[str, Any]] = []
+
+    async def raw_request(
+        self,
+        method: str,
+        endpoint: str,
+        *,
+        params: dict[str, Any] | None = None,
+        json_body: dict[str, Any] | None = None,
+    ) -> Any:
+        self.calls.append({"method": method, "endpoint": endpoint})
+        return self._response
+
+
+# --- Pure classifier --------------------------------------------------------
+
+
+@pytest.mark.parametrize(
+    ("method", "path", "expected_write"),
+    [
+        ("GET", "/repos/o/r/issues", False),
+        ("HEAD", "/repos/o/r", False),
+        ("POST", "/repos/o/r/issues", True),
+        ("PUT", "/repos/o/r/pulls/1/merge", True),
+        ("PATCH", "/repos/o/r/issues/1", True),
+        ("DELETE", "/repos/o/r/issues/1", True),
+        # Render-only overrides are reads even though they are POSTs.
+        ("POST", "/markdown", False),
+        ("POST", "/markdown/raw", False),
+        ("POST", "/repos/o/r/markup", False),
+    ],
+)
+def test_raw_request_is_write(method: str, path: str, expected_write: bool) -> None:
+    endpoint = normalize_raw_endpoint(path)
+    assert raw_request_is_write(method, endpoint) is expected_write
+
+
+def test_override_never_upgrades_a_mutating_post() -> None:
+    """A normal mutating POST is never reclassified as a read."""
+    endpoint = normalize_raw_endpoint("/repos/o/r/issues")
+    assert raw_request_is_write("POST", endpoint) is True
+
+
+@pytest.mark.parametrize(
+    ("path", "known"),
+    [
+        ("/repos/o/r", True),
+        ("/orgs/acme/repos", True),
+        ("/admin/users", True),
+        ("/user/repos", True),
+        ("/markdown", True),
+        ("/version", True),
+        ("/definitely/not/a/real/prefix", False),
+        ("/wibble", False),
+    ],
+)
+def test_raw_is_known_api_path(path: str, known: bool) -> None:
+    assert raw_is_known_api_path(normalize_raw_endpoint(path)) is known
+
+
+# --- Handler: unknown path is denied before any network call ----------------
+
+
+async def test_unknown_prefix_denied_before_network(raw_env: None) -> None:
+    stub = StubRawGitea()
+    with pytest.raises(ToolError) as exc_info:
+        await raw_api_request_tool(stub, {"method": "GET", "path": "/wibble/wobble"})
+    assert exc_info.value.status_code == 403
+    assert "known Gitea API route prefix" in str(exc_info.value.detail)
+    assert stub.calls == []
+
+
+# --- Write-mode bypass: a write that "looks like a read" is still a write ----
+
+
+async def test_write_method_denied_with_write_mode_off_even_on_readish_path(
+    raw_env: None,
+) -> None:
+    """A POST to a known repo path is a write and is denied while write-mode is off."""
+    stub = StubRawGitea()
+    with pytest.raises(ToolError) as exc_info:
+        await raw_api_request_tool(stub, {"method": "POST", "path": "/repos/acme/app/issues"})
+    assert exc_info.value.status_code == 403
+    assert "write mode is disabled" in str(exc_info.value.detail)
+    assert stub.calls == []
+
+
+async def test_render_only_post_allowed_as_read_without_write_mode(raw_env: None) -> None:
+    """A markdown-render POST is classified read and proceeds with write-mode off."""
+    stub = StubRawGitea({"rendered": "<p>hi</p>"})
+    result = await raw_api_request_tool(stub, {"method": "POST", "path": "/markdown"})
+    assert result["write"] is False
+    assert stub.calls and stub.calls[0]["endpoint"] == "/api/v1/markdown"