refactor(egress): split DLP detector-config parsing into its own module

`egress_addon_core.py` mixed the per-route `dlp:` block parser
(`_parse_detectors` plus the detector-name and `outbound_on_match`
constants) in with the request-time scan/decision flow. Move that
config-parsing layer into a new stdlib-only `egress_dlp_config.py` as
`parse_dlp_block`, so the decision path in the core module reads
top-to-bottom without scrolling past config plumbing.

The constants and parser are re-exported from `egress_addon_core`
(and listed in `__all__`) so existing `from egress_addon_core import
ON_MATCH_*` / `OUTBOUND_DETECTOR_NAMES` callers are unchanged. The new
module ships flat into the sidecar bundle (Dockerfile.sidecars) and
uses the same flat/package import shim as its siblings. Pure refactor;
behavior and wire format unchanged.

Closes #287

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01NkwFXLFff9PYPy4wgVBJp9

Dockerfile.sidecars

@@ -62,6 +62,7 @@ COPY --from=gitleaks-src /usr/bin/gitleaks /usr/bin/gitleaks
 # top-level siblings (absolute imports), matching the prior
 # Dockerfile.egress / Dockerfile.supervise layout.
 COPY bot_bottle/egress_addon_core.py /app/egress_addon_core.py
+COPY bot_bottle/egress_dlp_config.py /app/egress_dlp_config.py
 COPY bot_bottle/egress_addon.py      /app/egress_addon.py
 COPY bot_bottle/dlp_detectors.py     /app/dlp_detectors.py
 COPY bot_bottle/yaml_subset.py       /app/yaml_subset.py

bot_bottle/egress_addon_core.py

@@ -21,6 +21,32 @@ try:
 except ImportError:  # pragma: no cover - host-side path
     from .yaml_subset import YamlSubsetError, parse_yaml_subset
 
+# DLP detector-config parsing lives in a sibling module (also flat-bundled
+# into the sidecar — see Dockerfile.sidecars). Re-exported below so existing
+# `from egress_addon_core import ON_MATCH_*` callers keep working.
+try:
+    from egress_dlp_config import (  # type: ignore[import-not-found]
+        DEFAULT_OUTBOUND_ON_MATCH,
+        INBOUND_DETECTOR_NAMES,
+        ON_MATCH_BLOCK,
+        ON_MATCH_REDACT,
+        ON_MATCH_SUPERVISE,
+        OUTBOUND_DETECTOR_NAMES,
+        OUTBOUND_ON_MATCH_VALUES,
+        parse_dlp_block,
+    )
+except ImportError:  # pragma: no cover - host-side path
+    from .egress_dlp_config import (
+        DEFAULT_OUTBOUND_ON_MATCH,
+        INBOUND_DETECTOR_NAMES,
+        ON_MATCH_BLOCK,
+        ON_MATCH_REDACT,
+        ON_MATCH_SUPERVISE,
+        OUTBOUND_DETECTOR_NAMES,
+        OUTBOUND_ON_MATCH_VALUES,
+        parse_dlp_block,
+    )
+
 
 # ---------------------------------------------------------------------------
 # Match types (Gateway API HTTPRoute vocabulary, PRD 0053)
@@ -34,18 +60,6 @@ VALID_METHODS = frozenset({
     "CONNECT",
 })
 
-OUTBOUND_DETECTOR_NAMES = frozenset({"token_patterns", "known_secrets", "entropy"})
-INBOUND_DETECTOR_NAMES = frozenset({"naive_injection_detection"})
-
-# Per-route policy for what the proxy does when an outbound DLP detector
-# matches a token (PRD 0062).
-ON_MATCH_BLOCK = "block"          # hard 403, never overridable
-ON_MATCH_REDACT = "redact"        # scrub the matched value, forward the request
-ON_MATCH_SUPERVISE = "supervise"  # queue for operator approval, hold the request
-OUTBOUND_ON_MATCH_VALUES = (ON_MATCH_BLOCK, ON_MATCH_REDACT, ON_MATCH_SUPERVISE)
-# Unset resolves to supervise (fall back to block when supervise is not wired).
-DEFAULT_OUTBOUND_ON_MATCH = ON_MATCH_SUPERVISE
-
 
 @dataclass(frozen=True)
 class PathMatch:
@@ -230,72 +244,6 @@ def _parse_match_entry(idx: int, k: int, raw: object) -> MatchEntry:
     return MatchEntry(paths=paths, methods=methods, headers=headers)
 
 
-def _parse_detectors(
-    idx: int,
-    host: str,
-    raw_dict: dict[str, object],
-) -> tuple[tuple[str, ...] | None, tuple[str, ...] | None, str]:
-    """Parse the optional `dlp` block on a route, returning
-    (outbound_detectors, inbound_detectors, outbound_on_match)."""
-    dlp_raw = raw_dict.get("dlp")
-    if dlp_raw is None:
-        return None, None, ""
-    label = f"route[{idx}] ({host})"
-    if not isinstance(dlp_raw, dict):
-        raise ValueError(f"{label}: 'dlp' must be an object")
-    dlp = typing.cast(dict[str, object], dlp_raw)
-
-    def _parse_detector_field(
-        field: str,
-        valid_names: frozenset[str],
-    ) -> tuple[str, ...] | None:
-        val = dlp.get(field)
-        if val is None:
-            return None
-        if val is False:
-            return ()
-        if not isinstance(val, list):
-            raise ValueError(
-                f"{label}: dlp.{field} must be false, a list, or omitted"
-            )
-        items = typing.cast(list[object], val)
-        names: list[str] = []
-        for j, item in enumerate(items):
-            if not isinstance(item, str):
-                raise ValueError(
-                    f"{label}: dlp.{field}[{j}] must be a string"
-                )
-            if item not in valid_names:
-                raise ValueError(
-                    f"{label}: dlp.{field}[{j}] {item!r} is not a valid "
-                    f"detector name; valid names: {', '.join(sorted(valid_names))}"
-                )
-            names.append(item)
-        return tuple(names)
-
-    outbound = _parse_detector_field("outbound_detectors", OUTBOUND_DETECTOR_NAMES)
-    inbound = _parse_detector_field("inbound_detectors", INBOUND_DETECTOR_NAMES)
-
-    on_match = ""
-    on_match_raw = dlp.get("outbound_on_match")
-    if on_match_raw is not None:
-        if not isinstance(on_match_raw, str) or on_match_raw not in OUTBOUND_ON_MATCH_VALUES:
-            raise ValueError(
-                f"{label}: dlp.outbound_on_match must be one of "
-                f"{', '.join(OUTBOUND_ON_MATCH_VALUES)} (got {on_match_raw!r})"
-            )
-        on_match = on_match_raw
-
-    for k in dlp:
-        if k not in ("outbound_detectors", "inbound_detectors", "outbound_on_match"):
-            raise ValueError(
-                f"{label}: dlp has unknown key {k!r}; accepted keys "
-                f"are 'outbound_detectors', 'inbound_detectors', "
-                f"'outbound_on_match'"
-            )
-    return outbound, inbound, on_match
-
-
 def parse_routes(payload: object) -> tuple[Route, ...]:
     if not isinstance(payload, dict):
         raise ValueError("routes payload: top-level must be an object")
@@ -364,7 +312,7 @@ def _parse_one(idx: int, raw: object) -> Route:
                 )
 
     # dlp detectors
-    outbound_detectors, inbound_detectors, outbound_on_match = _parse_detectors(
+    outbound_detectors, inbound_detectors, outbound_on_match = parse_dlp_block(
         idx, host, raw_dict,
     )
 
@@ -837,6 +785,9 @@ __all__ = [
     "ON_MATCH_SUPERVISE",
     "OUTBOUND_ON_MATCH_VALUES",
     "DEFAULT_OUTBOUND_ON_MATCH",
+    "OUTBOUND_DETECTOR_NAMES",
+    "INBOUND_DETECTOR_NAMES",
+    "parse_dlp_block",
     "Config",
     "Decision",
     "HeaderMatch",

bot_bottle/egress_dlp_config.py

@@ -0,0 +1,92 @@
+"""DLP detector-config parsing for egress routes (PRD 0053, PRD 0062).
+
+A route's optional `dlp:` block names which outbound/inbound detectors run
+and what the proxy does when an outbound detector matches a token
+(`outbound_on_match`). This module owns parsing and validating that block,
+kept apart from the request-time scan/decision flow in `egress_addon_core`
+so each half reads top-to-bottom without scrolling past the other.
+
+Stdlib-only; ships flat into the sidecar bundle image alongside
+`egress_addon_core.py` — see `Dockerfile.sidecars`."""
+
+from __future__ import annotations
+
+import typing
+
+OUTBOUND_DETECTOR_NAMES = frozenset({"token_patterns", "known_secrets", "entropy"})
+INBOUND_DETECTOR_NAMES = frozenset({"naive_injection_detection"})
+
+# Per-route policy for what the proxy does when an outbound DLP detector
+# matches a token (PRD 0062).
+ON_MATCH_BLOCK = "block"          # hard 403, never overridable
+ON_MATCH_REDACT = "redact"        # scrub the matched value, forward the request
+ON_MATCH_SUPERVISE = "supervise"  # queue for operator approval, hold the request
+OUTBOUND_ON_MATCH_VALUES = (ON_MATCH_BLOCK, ON_MATCH_REDACT, ON_MATCH_SUPERVISE)
+# Unset resolves to supervise (fall back to block when supervise is not wired).
+DEFAULT_OUTBOUND_ON_MATCH = ON_MATCH_SUPERVISE
+
+
+def parse_dlp_block(
+    idx: int,
+    host: str,
+    raw_dict: dict[str, object],
+) -> tuple[tuple[str, ...] | None, tuple[str, ...] | None, str]:
+    """Parse the optional `dlp` block on a route, returning
+    (outbound_detectors, inbound_detectors, outbound_on_match)."""
+    dlp_raw = raw_dict.get("dlp")
+    if dlp_raw is None:
+        return None, None, ""
+    label = f"route[{idx}] ({host})"
+    if not isinstance(dlp_raw, dict):
+        raise ValueError(f"{label}: 'dlp' must be an object")
+    dlp = typing.cast(dict[str, object], dlp_raw)
+
+    def _parse_detector_field(
+        field: str,
+        valid_names: frozenset[str],
+    ) -> tuple[str, ...] | None:
+        val = dlp.get(field)
+        if val is None:
+            return None
+        if val is False:
+            return ()
+        if not isinstance(val, list):
+            raise ValueError(
+                f"{label}: dlp.{field} must be false, a list, or omitted"
+            )
+        items = typing.cast(list[object], val)
+        names: list[str] = []
+        for j, item in enumerate(items):
+            if not isinstance(item, str):
+                raise ValueError(
+                    f"{label}: dlp.{field}[{j}] must be a string"
+                )
+            if item not in valid_names:
+                raise ValueError(
+                    f"{label}: dlp.{field}[{j}] {item!r} is not a valid "
+                    f"detector name; valid names: {', '.join(sorted(valid_names))}"
+                )
+            names.append(item)
+        return tuple(names)
+
+    outbound = _parse_detector_field("outbound_detectors", OUTBOUND_DETECTOR_NAMES)
+    inbound = _parse_detector_field("inbound_detectors", INBOUND_DETECTOR_NAMES)
+
+    on_match = ""
+    on_match_raw = dlp.get("outbound_on_match")
+    if on_match_raw is not None:
+        if not isinstance(on_match_raw, str) or on_match_raw not in OUTBOUND_ON_MATCH_VALUES:
+            raise ValueError(
+                f"{label}: dlp.outbound_on_match must be one of "
+                f"{', '.join(OUTBOUND_ON_MATCH_VALUES)} (got {on_match_raw!r})"
+            )
+        on_match = on_match_raw
+
+    for k in dlp:
+        if k not in ("outbound_detectors", "inbound_detectors", "outbound_on_match"):
+            raise ValueError(
+                f"{label}: dlp has unknown key {k!r}; accepted keys "
+                f"are 'outbound_detectors', 'inbound_detectors', "
+                f"'outbound_on_match'"
+            )
+    return outbound, inbound, on_match