refactor(gateway): replace flat-file import shims with installed package

Install bot_bottle via pip in Dockerfile.gateway instead of COPYing
individual .py files flat under /app/. This eliminates the try/except
import shims in egress_addon_core, dlp_detectors, egress_addon,
supervise, supervise_server, and git_http_backend that existed only
to support the flat-bundle layout.

Adds bot_bottle/constants.py as a single source of truth for
IDENTITY_HEADER and GIT_GATE_TIMEOUT_SECS, removing the duplicated
literal definitions in egress_addon.py, supervise_server.py,
git_http_backend.py, and git_gate_render.py.

Test files updated to match: test_supervise_server.py drops the
sys.path.insert hack in favour of direct package imports; the
egress_addon test shims no longer pre-populate sys.modules with a
bare egress_addon_core alias.

Dockerfile.gateway

@@ -16,10 +16,12 @@
 # Layout:
 #
 #   /usr/bin/gitleaks                    gitleaks binary
-#   /app/egress_addon.py + siblings      mitmproxy addon (egress)
+#   /app/egress_addon.py                 mitmproxy addon entry point
 #   /app/egress-entrypoint.sh            mitmdump launcher
-#   /app/supervise_server.py + .py       supervise MCP server
+#   /app/supervise_server.py             supervise MCP server entry point
-#   /app/gateway_init.py                 PID 1 supervisor
+#   /app/gateway_init.py                 PID 1 supervisor entry point
+#   /app/git_http_backend.py             git-http entry point
+#   /usr/local/lib/python*/bot_bottle/   installed package (all shared modules)
 #   /etc/egress/routes.yaml              bind-mounted at run time
 #   /etc/git-gate/pre-receive            docker-cp'd at start time
 #   /git-gate-entrypoint.sh              docker-cp'd at start time
@@ -74,24 +76,18 @@ RUN url="https://github.com/gitleaks/gitleaks/releases/download/v${GITLEAKS_VERS
  && tar -xzf /tmp/gitleaks.tar.gz -C /usr/bin gitleaks \
  && rm /tmp/gitleaks.tar.gz
 
-# Project Python: addon + server modules + the init supervisor.
+# Install bot_bottle as a proper package so entry-point scripts can use
-# Kept flat under /app/ so mitmdump's loader resolves them as
+# `from bot_bottle.X import Y` absolute imports. A rename or a missing
-# top-level siblings (absolute imports), matching the prior
+# module is caught at pip-install time — not at container runtime.
-# Dockerfile.egress / Dockerfile.supervise layout.
+COPY pyproject.toml /src/
-COPY bot_bottle/egress_addon_core.py /app/egress_addon_core.py
+COPY bot_bottle/    /src/bot_bottle/
-COPY bot_bottle/egress_dlp_config.py /app/egress_dlp_config.py
+RUN pip install --no-cache-dir /src/
+
+# Entry-point scripts invoked by gateway_init.py. These live at /app/
+# so the supervisor, shell entrypoint, and ENTRYPOINT all reach them at
+# known fixed paths. Their sibling imports all go through bot_bottle.*
+# (the installed package above), not flat /app/ neighbours.
 COPY bot_bottle/egress_addon.py      /app/egress_addon.py
-COPY bot_bottle/policy_resolver.py   /app/policy_resolver.py
-COPY bot_bottle/dlp_detectors.py     /app/dlp_detectors.py
-COPY bot_bottle/yaml_subset.py       /app/yaml_subset.py
-COPY bot_bottle/paths.py             /app/paths.py
-COPY bot_bottle/migrations.py        /app/migrations.py
-COPY bot_bottle/db_store.py          /app/db_store.py
-COPY bot_bottle/supervise_types.py   /app/supervise_types.py
-COPY bot_bottle/queue_store.py       /app/queue_store.py
-COPY bot_bottle/audit_store.py       /app/audit_store.py
-COPY bot_bottle/store_manager.py     /app/store_manager.py
-COPY bot_bottle/supervise.py         /app/supervise.py
 COPY bot_bottle/supervise_server.py  /app/supervise_server.py
 COPY bot_bottle/gateway_init.py      /app/gateway_init.py
 COPY bot_bottle/git_http_backend.py  /app/git_http_backend.py
@@ -113,8 +109,6 @@ RUN mkdir -p \
 # subset the bottle uses.
 EXPOSE 8888 9099 9418 9420 9100
 
-# WORKDIR matches Dockerfile.supervise's prior layout so the
-# in-app same-dir import in supervise_server.py stays deterministic.
 WORKDIR /app
 
 # PID 1 is the supervisor. It owns signal handling and exit-code

bot_bottle/backend/docker/gateway_provision.py

@@ -94,6 +94,12 @@ def provision_git_gate(
     transport.exec(["mkdir", "-p", "/etc/git-gate"])
     transport.cp_into(str(plan.hook_script), "/etc/git-gate/pre-receive")
     transport.cp_into(str(plan.access_hook_script), "/etc/git-gate/access-hook")
+    # The access-hook is exec'd directly (not via `sh`), so it needs the x bit.
+    # Set it here rather than trusting the copy to carry the staged 0o700:
+    # `docker cp` preserves source mode, but the Apple `container cp` does not,
+    # landing the hook 0o644 → EACCES when the git-http handler tries to exec it.
+    # chmod on the gateway side is backend-neutral and fixes every transport.
+    transport.exec(["chmod", "+x", "/etc/git-gate/access-hook"])
     creds = _creds_dir(bottle_id)
     transport.exec(["mkdir", "-p", creds])
     for u in plan.upstreams:

bot_bottle/constants.py

@@ -0,0 +1,17 @@
+"""Shared wire-protocol constants for gateway-bundled modules.
+
+Single source of truth for values that appear across the egress addon,
+git-http backend, supervise server, and git-gate renderer. Importing
+from this module instead of duplicating the literals means a rename is
+a one-line change and is caught by the type checker at the import site."""
+
+# App-layer identity token header. Delivered as proxy credentials
+# (HTTPS_PROXY=http://<bottle_id>:<token>@gw) by launch; the egress
+# addon reads and strips it, the supervise server and git-http backend
+# read it for attribution, and none of them forward it upstream.
+IDENTITY_HEADER = "x-bot-bottle-identity"
+
+# Shared timeout (seconds) for all git-gate subprocess and CGI calls:
+# git daemon (--timeout/--init-timeout), the access-hook subprocess in
+# git_http_backend, and the git http-backend CGI subprocess.
+GIT_GATE_TIMEOUT_SECS = 15

bot_bottle/dlp_detectors.py

@@ -3,9 +3,8 @@
 Pure Python, no mitmproxy dependency. Each detector is a module-level
 function returning `ScanResult | None`.
 
-Ships flat into the gateway image alongside
+Available in the gateway via the installed `bot_bottle` package
-`egress_addon_core.py` — both this file and the package source use
+(see `Dockerfile.gateway`).
-the same try/except import shim pattern.
 """
 
 from __future__ import annotations
@@ -20,10 +19,7 @@ from math import log2
 from collections import Counter
 from urllib.parse import quote as url_quote
 
-try:
+from .egress_addon_core import ScanResult
-    from egress_addon_core import ScanResult  # type: ignore[import-not-found]
-except ImportError:  # pragma: no cover - host-side path
-    from .egress_addon_core import ScanResult
 
 
 # ---------------------------------------------------------------------------

bot_bottle/egress_addon.py

@@ -17,7 +17,9 @@ from pathlib import Path
 
 from mitmproxy import http  # type: ignore[import-not-found]  # pylint: disable=import-error
 
-from egress_addon_core import (  # type: ignore[import-not-found]  # pylint: disable=import-error
+from bot_bottle.constants import IDENTITY_HEADER
+from bot_bottle.dlp_detectors import redact_tokens, strip_crlf
+from bot_bottle.egress_addon_core import (
     LOG_BLOCKS,
     LOG_FULL,
     DEFAULT_OUTBOUND_ON_MATCH,
@@ -41,24 +43,8 @@ from egress_addon_core import (  # type: ignore[import-not-found]  # pylint: dis
     scan_inbound,
     scan_outbound,
 )
-
+from bot_bottle import supervise as _sv
-try:
+from bot_bottle.policy_resolver import PolicyResolver
-    from dlp_detectors import redact_tokens, strip_crlf  # type: ignore[import-not-found]
-except ImportError:  # pragma: no cover - host-side path
-    from bot_bottle.dlp_detectors import (  # type: ignore[import-not-found]
-        redact_tokens,
-        strip_crlf,
-    )
-
-try:
-    import supervise as _sv  # type: ignore[import-not-found]
-except ImportError:  # pragma: no cover - host-side path
-    from bot_bottle import supervise as _sv  # type: ignore[import-not-found]
-
-try:
-    from policy_resolver import PolicyResolver  # type: ignore[import-not-found]
-except ImportError:  # pragma: no cover - host-side path
-    from bot_bottle.policy_resolver import PolicyResolver
 
 
 DEFAULT_ROUTES_PATH = "/etc/egress/routes.yaml"
@@ -71,13 +57,6 @@ INTROSPECT_HOST = "_egress.local"
 # → legacy per-bottle single-tenant mode (unchanged).
 ORCHESTRATOR_URL_ENV = "BOT_BOTTLE_ORCHESTRATOR_URL"
 
-# App-layer identity token. Delivered as proxy credentials
-# (`HTTPS_PROXY=http://<bottle_id>:<token>@gw`): clients honor it as part of
-# the proxy protocol without app changes, and the addon reads + strips it so
-# it never leaks upstream. The legacy `x-bot-bottle-identity` request header
-# is still stripped defensively (git-http uses that header on its own port).
-IDENTITY_HEADER = "x-bot-bottle-identity"
-
 # Per-flow key under which `request()` stashes the resolved (Config, supervise
 # slug, env) so the later `response()` and `websocket_message()` hooks scan
 # against the *calling bottle's* policy. In the consolidated (multi-tenant)

bot_bottle/egress_addon_core.py

@@ -6,9 +6,9 @@ exercise the parse + decision functions without depending on the
 `mitmproxy.http.HTTPFlow` API and is loaded inside the gateway
 container.
 
-Imports: stdlib + `yaml_subset` (which is itself stdlib-only and
+Imports: stdlib + sibling package modules (`yaml_subset`,
-ships flat into the gateway image alongside this file —
+`egress_dlp_config`). Available in the gateway via the installed
-see `Dockerfile.gateway`)."""
+`bot_bottle` package (see `Dockerfile.gateway`)."""
 
 from __future__ import annotations
 
@@ -16,36 +16,20 @@ import re
 import typing
 from dataclasses import dataclass
 
-try:
+from .yaml_subset import YamlSubsetError, parse_yaml_subset
-    from yaml_subset import YamlSubsetError, parse_yaml_subset  # type: ignore[import-not-found]
-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
+# DLP detector-config parsing lives in a sibling module. Re-exported below
-# into the gateway — see Dockerfile.gateway). Re-exported below so existing
+# so existing `from egress_addon_core import ON_MATCH_*` callers keep working.
-# `from egress_addon_core import ON_MATCH_*` callers keep working.
+from .egress_dlp_config import (
-try:
+    DEFAULT_OUTBOUND_ON_MATCH,
-    from egress_dlp_config import (  # type: ignore[import-not-found]
+    INBOUND_DETECTOR_NAMES,
-        DEFAULT_OUTBOUND_ON_MATCH,
+    ON_MATCH_BLOCK,
-        INBOUND_DETECTOR_NAMES,
+    ON_MATCH_REDACT,
-        ON_MATCH_BLOCK,
+    ON_MATCH_SUPERVISE,
-        ON_MATCH_REDACT,
+    OUTBOUND_DETECTOR_NAMES,
-        ON_MATCH_SUPERVISE,
+    OUTBOUND_ON_MATCH_VALUES,
-        OUTBOUND_DETECTOR_NAMES,
+    parse_dlp_block,
-        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,
-    )
 
 
 # ---------------------------------------------------------------------------

bot_bottle/git_gate.py

@@ -112,8 +112,10 @@ class GitGate(ABC):
         access_hook = stage_dir / "git_gate_access_hook.sh"
         access_hook.write_text(git_gate_render_access_hook())
         # 0o700 (not 0o600): git daemon execs --access-hook directly,
-        # not via `sh`, so the script needs the x bit. docker cp
+        # not via `sh`, so the script needs the x bit. The gateway copy
-        # preserves source mode into the container.
+        # does not necessarily preserve this mode (`docker cp` does, the
+        # Apple `container cp` does not), so provision_git_gate re-applies
+        # +x on the gateway side — see backend/docker/gateway_provision.py.
         access_hook.chmod(0o700)
         upstreams_with_files: list[GitGateUpstream] = []
         for u in upstreams:

bot_bottle/git_gate_render.py

@@ -14,18 +14,12 @@ import shlex
 from dataclasses import dataclass
 from pathlib import Path
 
+from .constants import GIT_GATE_TIMEOUT_SECS, IDENTITY_HEADER
 from .manifest import ManifestBottle, ManifestGitEntry
 
 # Short network alias for git-gate inside the gateway. The
 # agent's `.gitconfig` insteadOf rewrites resolve through this name.
 GIT_GATE_HOSTNAME = "git-gate"
-# App-layer identity token header the agent's git sends to git-http and the
-# gateway validates (mirrors egress_addon / git_http_backend IDENTITY_HEADER).
-IDENTITY_HEADER = "x-bot-bottle-identity"
-# Shared timeout (seconds) for all git-gate subprocess and CGI calls:
-# git daemon (--timeout/--init-timeout), the access-hook subprocess in
-# git_http_backend, and the git http-backend CGI subprocess.
-GIT_GATE_TIMEOUT_SECS = 15
 
 
 @dataclass(frozen=True)

bot_bottle/git_http_backend.py

@@ -27,16 +27,8 @@ from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer
 from pathlib import Path
 from urllib.parse import urlsplit
 
-# policy_resolver ships flat alongside this file in the gateway
+from bot_bottle.constants import GIT_GATE_TIMEOUT_SECS, IDENTITY_HEADER
-# image (see Dockerfile.gateway); the bot_bottle.* fallback is the
+from bot_bottle.policy_resolver import PolicyResolveError, PolicyResolver
-# host-side / test path. Mirrors egress_addon's import shape.
-try:
-    from policy_resolver import (  # type: ignore[import-not-found]
-        PolicyResolveError,
-        PolicyResolver,
-    )
-except ImportError:  # pragma: no cover - host-side path
-    from bot_bottle.policy_resolver import PolicyResolveError, PolicyResolver
 
 
 DEFAULT_PORT = 9420
@@ -49,12 +41,6 @@ DEFAULT_PORT = 9420
 # flips the whole shared gateway multi-tenant.
 ORCHESTRATOR_URL_ENV = "BOT_BOTTLE_ORCHESTRATOR_URL"
 
-# App-layer identity token (defense-in-depth over the source-IP invariant);
-# the agent injects it, the backend reads it for attribution and never
-# forwards it to `git http-backend`. Mirrors egress_addon.IDENTITY_HEADER
-# (duplicated, not imported: egress_addon pulls in mitmproxy).
-IDENTITY_HEADER = "x-bot-bottle-identity"
-
 # Default flat repo root (single-tenant, and the base under which
 # consolidated mode nests each sandbox's namespace).
 DEFAULT_REPO_ROOT = "/git"
@@ -102,13 +88,6 @@ def resolve_sandbox_root(
         return None  # bottle_id tried to escape the root → deny
     return namespace
 
-# Mirrors git_gate_render.GIT_GATE_TIMEOUT_SECS. Duplicated rather than
-# imported: this module ships as a flat top-level sibling in the gateway
-# bundle image (see Dockerfile.gateway), not as part of the bot_bottle
-# package, so `bot_bottle.git_gate` and its dependency chain aren't
-# available at runtime.
-GIT_GATE_TIMEOUT_SECS = 15
-
 # Bound memory use while still allowing ordinary git push packfiles.
 MAX_BODY_BYTES = 100 * 1024 * 1024
 
@@ -148,12 +127,24 @@ class GitHttpHandler(BaseHTTPRequestHandler):
                 "GIT_GATE_ACCESS_HOOK", "/etc/git-gate/access-hook",
             )
             peer = self.client_address[0]
-            hook = subprocess.run(
+            try:
-                [hook_path, "upload-pack", str(repo_dir), peer, peer],
+                hook = subprocess.run(
-                capture_output=True,
+                    [hook_path, "upload-pack", str(repo_dir), peer, peer],
-                check=False,
+                    capture_output=True,
-                timeout=GIT_GATE_TIMEOUT_SECS,
+                    check=False,
-            )
+                    timeout=GIT_GATE_TIMEOUT_SECS,
+                )
+            except (OSError, subprocess.SubprocessError) as exc:
+                # The access-hook couldn't be run (missing, not executable,
+                # timed out, …). Fail closed with a real HTTP error rather
+                # than letting the exception kill the handler thread — an
+                # unhandled exception closes the socket with no response, which
+                # the client sees as an opaque "empty reply from server".
+                self.log_message(
+                    "access-hook could not run for %s: %s", parsed.path, exc,
+                )
+                self.send_error(503, "git-gate access-hook unavailable")
+                return
             if hook.returncode != 0:
                 detail = (hook.stderr or hook.stdout).decode(
                     "utf-8", errors="replace",

bot_bottle/policy_resolver.py

@@ -22,8 +22,7 @@ closed too rather than silently serving stale or empty policy.
 
 The resolved value is the policy blob the orchestrator stores verbatim; the
 consumer parses it (e.g. the egress addon's `load_config`). This module is
-stdlib-only and free of bot-bottle imports so it can be COPYed flat into
+stdlib-only and free of bot-bottle imports.
-the gateway.
 """
 
 from __future__ import annotations

bot_bottle/supervise.py

@@ -37,40 +37,22 @@ from abc import ABC
 from dataclasses import dataclass
 from pathlib import Path
 
-try:
+from .supervise_types import (
-    from .supervise_types import (
+    ACTION_OPERATOR_EDIT,
-        ACTION_OPERATOR_EDIT,
+    AuditEntry,
-        AuditEntry,
+    Proposal,
-        Proposal,
+    Response,
-        Response,
+    STATUSES,
-        STATUSES,
+    STATUS_APPROVED,
-        STATUS_APPROVED,
+    STATUS_MODIFIED,
-        STATUS_MODIFIED,
+    STATUS_REJECTED,
-        STATUS_REJECTED,
+    TOOLS,
-        TOOLS,
+    TOOL_EGRESS_ALLOW,
-        TOOL_EGRESS_ALLOW,
+    TOOL_EGRESS_BLOCK,
-        TOOL_EGRESS_BLOCK,
+    TOOL_EGRESS_TOKEN_ALLOW,
-        TOOL_EGRESS_TOKEN_ALLOW,
+    TOOL_GITLEAKS_ALLOW,
-        TOOL_GITLEAKS_ALLOW,
+    TOOL_LIST_EGRESS_ROUTES,
-        TOOL_LIST_EGRESS_ROUTES,
+)
-    )
-except ImportError:
-    from supervise_types import (  # type: ignore[import-not-found,no-redef]  # pylint: disable=import-error,no-name-in-module
-        ACTION_OPERATOR_EDIT,
-        AuditEntry,
-        Proposal,
-        Response,
-        STATUSES,
-        STATUS_APPROVED,
-        STATUS_MODIFIED,
-        STATUS_REJECTED,
-        TOOLS,
-        TOOL_EGRESS_ALLOW,
-        TOOL_EGRESS_BLOCK,
-        TOOL_EGRESS_TOKEN_ALLOW,
-        TOOL_GITLEAKS_ALLOW,
-        TOOL_LIST_EGRESS_ROUTES,
-    )
 
 
 try:

bot_bottle/supervise_server.py

@@ -30,9 +30,8 @@ Speaks MCP over HTTP+JSON-RPC. Methods handled:
 
 Everything else returns JSON-RPC error -32601 (method not found).
 
-Stdlib-only. The Dockerfile copies this file + bot_bottle/supervise.py
+The Dockerfile copies this script to /app/supervise_server.py and installs
-into the image; the server imports `supervise` for the queue / Proposal
+the bot_bottle package so its `from bot_bottle.*` imports resolve.
-plumbing.
 """
 
 from __future__ import annotations
@@ -48,29 +47,18 @@ import urllib.error
 import urllib.request
 from dataclasses import dataclass, replace
 
-try:
+from bot_bottle.constants import IDENTITY_HEADER
-    # Same-directory imports inside the bundle container; these files are
+from bot_bottle.egress_addon_core import (
-    # COPYed flat under /app by Dockerfile.gateway.
+    LOG_OFF, load_config, resolve_client_context, route_to_yaml_dict,
-    from egress_addon_core import (
+)
-        LOG_OFF, load_config, resolve_client_context, route_to_yaml_dict,
+from bot_bottle.policy_resolver import PolicyResolveError, PolicyResolver
-    )
+from bot_bottle import supervise as _sv
-    from policy_resolver import PolicyResolveError, PolicyResolver
-    import supervise as _sv
-except ModuleNotFoundError:
-    # Package imports for host-side tests and tooling.
-    from .egress_addon_core import (
-        LOG_OFF, load_config, resolve_client_context, route_to_yaml_dict,
-    )
-    from .policy_resolver import PolicyResolveError, PolicyResolver
-    from . import supervise as _sv
 
 
 # --- JSON-RPC / MCP plumbing ----------------------------------------------
 
 
 MCP_PROTOCOL_VERSION = "2024-11-05"
-# App-layer identity token header (mirrors egress_addon / git_http_backend).
-IDENTITY_HEADER = "x-bot-bottle-identity"
 SERVER_NAME = "bot-bottle-supervise"
 SERVER_VERSION = "0.1.0"
 

pyproject.toml

@@ -0,0 +1,8 @@
+[build-system]
+requires = ["setuptools>=68"]
+build-backend = "setuptools.backends.legacy:build"
+
+[project]
+name = "bot-bottle"
+version = "0.0.0"
+requires-python = ">=3.11"

tests/unit/test_egress_addon_log_redaction.py

@@ -18,7 +18,7 @@ from unittest.mock import patch
 
 
 # ---------------------------------------------------------------------------
-# Gateway-import shims — must run before importing egress_addon
+# mitmproxy stub — must run before importing egress_addon
 # ---------------------------------------------------------------------------
 
 def _ensure_shims() -> None:
@@ -28,9 +28,6 @@ def _ensure_shims() -> None:
         setattr(_mm, "http", _mh)
         sys.modules["mitmproxy"] = _mm
         sys.modules["mitmproxy.http"] = _mh
-    if "egress_addon_core" not in sys.modules:
-        import bot_bottle.egress_addon_core as _core
-        sys.modules["egress_addon_core"] = _core
 
 
 _ensure_shims()

tests/unit/test_egress_addon_request_flow.py

@@ -182,9 +182,6 @@ def _ensure_shims() -> None:
         setattr(mh, "Response", _Response)
     if not hasattr(mh, "HTTPFlow"):
         setattr(mh, "HTTPFlow", object)
-    if "egress_addon_core" not in sys.modules:
-        import bot_bottle.egress_addon_core as _core
-        sys.modules["egress_addon_core"] = _core
 
 
 _ensure_shims()

tests/unit/test_gateway_provision.py

@@ -69,6 +69,18 @@ class TestProvisionGitGate(unittest.TestCase):
         self.assertEqual(1, len(exec_scripts))
         self.assertIn("repo=/git/bottle1/${name}.git", exec_scripts[0][-1])
 
+    def test_makes_access_hook_executable_on_the_gateway(self) -> None:
+        # Regression: the access-hook is exec'd directly, so it needs the x
+        # bit. The copy alone can't be trusted to carry the staged 0o700
+        # (`docker cp` preserves mode, the Apple `container cp` does not),
+        # so provisioning must re-apply +x on the gateway side.
+        calls: list[list[str]] = []
+        with patch(_RUN, side_effect=_recorder(calls)):
+            provision_git_gate(DockerGatewayTransport("gw"), "bottle1", _plan(_up("foo")))
+        self.assertIn(
+            ["docker", "exec", "gw", "chmod", "+x", "/etc/git-gate/access-hook"], calls,
+        )
+
     def test_omits_known_hosts_copy_when_absent(self) -> None:
         calls: list[list[str]] = []
         with patch(_RUN, side_effect=_recorder(calls)):

tests/unit/test_git_http_backend.py

@@ -364,6 +364,48 @@ class TestGitHttpBackend(unittest.TestCase):
                 self.assertIn("access-hook denied", logged)
                 self.assertIn("exit=2", logged)
 
+    def test_access_hook_that_cannot_run_fails_closed_503(self):
+        """Regression: when the access-hook can't be exec'd (missing / not
+        executable — a PermissionError from subprocess.run), the handler must
+        fail closed with a real HTTP status instead of letting the exception
+        kill the thread, which closes the socket with no response and the
+        client sees an opaque "empty reply from server"."""
+        from http.server import ThreadingHTTPServer
+        import io
+        import sys
+
+        with tempfile.TemporaryDirectory() as tmp:
+            root = Path(tmp)
+            (root / "repo.git").mkdir()
+            old_root = os.environ.get("GIT_PROJECT_ROOT")
+            os.environ["GIT_PROJECT_ROOT"] = str(root)
+            self.addCleanup(self._restore_env, old_root)
+
+            server = ThreadingHTTPServer(("127.0.0.1", 0), GitHttpHandler)
+            thread = threading.Thread(target=server.serve_forever, daemon=True)
+            thread.start()
+            self.addCleanup(server.shutdown)
+            self.addCleanup(server.server_close)
+
+            with mock.patch(
+                "bot_bottle.git_http_backend.subprocess.run",
+                side_effect=PermissionError(13, "Permission denied"),
+            ):
+                buf = io.StringIO()
+                with mock.patch.object(sys, "stdout", buf):
+                    req = urllib.request.Request(
+                        f"http://127.0.0.1:{server.server_port}"
+                        "/repo.git/info/refs?service=git-upload-pack",
+                        method="GET",
+                    )
+                    try:
+                        urllib.request.urlopen(req, timeout=5)
+                        self.fail("expected HTTPError 503")
+                    except urllib.error.HTTPError as e:  # type: ignore
+                        self.assertEqual(503, e.code)
+
+                self.assertIn("access-hook could not run", buf.getvalue())
+
     @staticmethod
     def _restore_env(value: str | None) -> None:
         if value is None:

tests/unit/test_supervise_server.py

@@ -2,7 +2,6 @@
 
 import http.client
 import json
-import sys
 import tempfile
 import threading
 import time
@@ -13,15 +12,9 @@ from unittest.mock import patch
 
 from tests.unit import use_bottle_root
 
-
+from bot_bottle import supervise as _sv
-# The server module loads `supervise` via same-directory import inside
+from bot_bottle import queue_store as _qs
-# the container (Dockerfile.supervise WORKDIRs into /app). For tests
+from bot_bottle import audit_store as _as
-# we mirror that by injecting bot_bottle/ onto sys.path under the
-# bare name `supervise`.
-sys.path.insert(0, str(Path(__file__).resolve().parent.parent.parent / "bot_bottle"))
-import supervise as _sv  # noqa: E402  # type: ignore
-import queue_store as _qs  # noqa: E402  # type: ignore
-import audit_store as _as  # noqa: E402  # type: ignore
 
 from bot_bottle import supervise_server  # noqa: E402
 from bot_bottle.supervise_server import (