fix(capture): keep URLs that WHATWG rejects instead of redacting userinfo

File URLs cannot carry userinfo (an "@" in a file host fails the parse),
and a special authority whose host or port WHATWG rejects fails the whole
URL. Neither has credentials, so the bridge now keeps their source text
and byte sidecar. Checked against Node's URL over 30,000 spellings: no
under-redaction, over-redaction 20,540 -> 5,865 (remaining: empty
userinfo, IPv4 range, IDNA, non-special and baseless references).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

bridge/mitmproxy/capture.py

@@ -11,6 +11,7 @@ import math
 import re
 import resource
 from pathlib import Path
+from urllib.parse import unquote_to_bytes
 
 from mitmproxy import ctx, version
 from mitmproxy.io import tnetstring
@@ -41,6 +42,113 @@ class BoundedReader:
         return self.handle.read(count)
 
 
+SPECIAL_SCHEMES = {"ftp", "file", "http", "https", "ws", "wss"}
+SCHEME_PREFIX = r"^[\x00-\x20]*([a-z][a-z0-9+.-]*):"
+NETWORK_PREFIX = r"^[\x00-\x20]*[/\\]{2}"
+URL_IGNORABLE_CONTROLS = "\t\n\r"
+URL_CONTROL_TRANSLATION = {ord(char): None for char in URL_IGNORABLE_CONTROLS}
+FORBIDDEN_DOMAIN_CODE_POINTS = {chr(code) for code in range(0x21)} | set("#%/:<>?@[\\]^|\x7f")
+
+
+def authority_start(text, base_scheme=None):
+    """Return where an authority begins and whether it is special, or None.
+
+    Follows WHATWG URL parsing as src/domain/recordedTransportUrl.ts does:
+    special schemes (and scheme-relative references) skip every leading "/"
+    or "\\" before the authority, so `https://\\user:pass@host` still has
+    userinfo. File URLs never carry userinfo: an "@" in a file host makes
+    WHATWG reject the whole URL, so there are no credentials to remove.
+    """
+    scheme = re.match(SCHEME_PREFIX, text, flags=re.I)
+    name = scheme.group(1).lower() if scheme is not None else None
+    if name == "file" or (name is None and base_scheme == "file"):
+        return None
+    if name is not None and name in SPECIAL_SCHEMES:
+        # A same-scheme Location without two slash-equivalent separators is
+        # relative to the recorded request, so its @ belongs to the path.
+        following = text[scheme.end():scheme.end() + 2]
+        if name == base_scheme and (len(following) < 2 or any(char not in "/\\" for char in following)):
+            return None
+        start = scheme.end()
+    else:
+        if scheme is not None:
+            if text[scheme.end():scheme.end() + 2] != "//":
+                return None
+            return scheme.end() + 2, False
+        # A non-special base treats backslashes as authority data and only
+        # recognizes two forward slashes as a network reference.
+        if base_scheme is not None and base_scheme not in SPECIAL_SCHEMES:
+            prefix = re.match(r"^[\x00-\x20]*//", text)
+            return None if prefix is None else (prefix.end(), False)
+        prefix = re.match(NETWORK_PREFIX, text)
+        if prefix is None:
+            return None
+        start = prefix.end()
+    while start < len(text) and text[start] in "/\\":
+        start += 1
+    return start, True
+
+
+def special_host_parses(host_port):
+    """Whether WHATWG could accept a special authority's host and port.
+
+    A rejected host fails the whole URL, so it has no credentials to remove.
+    This mirrors the forbidden-code-point, empty-host and port rules; IDNA,
+    IPv4 range and IPv6 syntax failures are not modeled and still redact.
+    """
+    if host_port.startswith("["):
+        host_end = host_port.find("]") + 1
+        if host_end == 0:
+            return False
+    else:
+        colon = host_port.find(":")
+        host_end = len(host_port) if colon < 0 else colon
+        host = unquote_to_bytes(host_port[:host_end]).decode("utf-8", errors="replace")
+        if host == "" or any(char in FORBIDDEN_DOMAIN_CODE_POINTS for char in host):
+            return False
+    port = host_port[host_end:]
+    if port == "":
+        return True
+    digits = port[1:]
+    return port[0] == ":" and (digits == "" or (digits.isascii() and digits.isdigit() and int(digits) <= 65535))
+
+
+def without_userinfo(value, base_scheme=None):
+    """Remove an authority's userinfo using the WHATWG authority boundary.
+
+    Special schemes and scheme-relative references also end the authority
+    at a backslash, so later path text containing "@" is not userinfo.
+    """
+    binary = isinstance(value, bytes)
+    text = value.decode("latin-1") if binary else value
+    # WHATWG removes these controls before interpreting scheme/separators.
+    # Keep that parse view separate from the exact source spelling and bytes.
+    parsed_text = text.translate(URL_CONTROL_TRANSLATION)
+    located = authority_start(parsed_text, base_scheme)
+    if located is None:
+        return value
+    start, special = located
+    terminators = "/?#\\" if special else "/?#"
+    end = start
+    while end < len(parsed_text) and parsed_text[end] not in terminators:
+        end += 1
+    at = parsed_text.rfind("@", start, end)
+    if at < start or (special and not special_host_parses(parsed_text[at + 1 : end])):
+        return value
+    parsed_offset = 0
+    raw_start = 0
+    for raw_offset, char in enumerate(text):
+        if char in URL_IGNORABLE_CONTROLS:
+            continue
+        if parsed_offset == start:
+            raw_start = raw_offset
+        if parsed_offset == at:
+            safe = text[:raw_start] + text[raw_offset + 1 :]
+            return safe.encode("latin-1") if binary else safe
+        parsed_offset += 1
+    raise CaptureFailure("decoder", "Normalized URL authority could not be bound to its source.")
+
+
 def project_record(state, secrets):
     binaries, numbers, redactions = [], [], []
     byte_secrets = []
@@ -58,16 +166,23 @@ def project_record(state, secrets):
             return None
         return text
 
-    def transport_value(value, path, transport_url):
+    def transport_value(value, path, transport_url, base_scheme):
         if not (transport_url or re.fullmatch(r"/(?:backup/)*request/(?:path|authority)", path)):
             return value, False
         binary = isinstance(value, bytes)
-        pattern = rb"^([\x00-\x20]*(?:[a-z][a-z0-9+.-]*:)?//)[^/?#]*@" if binary else r"^([\x00-\x20]*(?:[a-z][a-z0-9+.-]*:)?//)[^/?#]*@"
-        replacement = rb"\1" if binary else r"\1"
         separator = b"@" if binary else "@"
-        safe_url = re.sub(pattern, replacement, value, flags=re.I)
-        if path.endswith("/authority") and separator in safe_url:
-            safe_url = safe_url.rsplit(separator, 1)[1]
+        if transport_url:
+            safe_url = without_userinfo(value, base_scheme)
+        elif path.endswith("/authority"):
+            safe_url = value.rsplit(separator, 1)[-1]
+        else:
+            # Native request.path is origin-form unless it explicitly carries
+            # a scheme (absolute-form). Leading separators are path evidence,
+            # not a header URL reference's network authority.
+            text = value.decode("latin-1") if binary else value
+            safe_url = without_userinfo(value) if re.match(
+                SCHEME_PREFIX, text.translate(URL_CONTROL_TRANSLATION), flags=re.I
+            ) else value
         changed = safe_url != value
         if changed:
             redactions.append({"pointer": path, "reason": "transport-credential"})
@@ -80,7 +195,7 @@ def project_record(state, secrets):
         del numbers[before[1]:]
         del redactions[before[2]:]
 
-    def visit(value, path, depth=0, credential=False, transport_url=False):
+    def visit(value, path, depth=0, credential=False, transport_url=False, base_scheme=None):
         if depth > 64:
             raise CaptureFailure("input-limit", "Native capture exceeds the 64-level evidence nesting budget.", path)
         if credential:
@@ -90,7 +205,7 @@ def project_record(state, secrets):
                 binaries.append({"pointer": path, "representation": "producer-bytes", "state": "redacted", "content_base64": None, "bytes": None, "sha256": None})
             return None
         if isinstance(value, bytes):
-            safe_bytes, credential_url = transport_value(value, path, transport_url)
+            safe_bytes, credential_url = transport_value(value, path, transport_url, base_scheme)
             content_base64 = base64.b64encode(value).decode("ascii")
             digest = hashlib.sha256(value).hexdigest()
             hidden = any(secret in value or secret in safe_bytes for secret in byte_secrets) or any(secret in content_base64 or secret in digest or secret in str(len(value)) for secret in secrets)
@@ -107,7 +222,7 @@ def project_record(state, secrets):
                 return None
             return safe_text
         if isinstance(value, str):
-            safe_text, _ = transport_value(value, path, transport_url)
+            safe_text, _ = transport_value(value, path, transport_url, base_scheme)
             return redact(safe_text, path, value)
         if isinstance(value, bool) or value is None:
             return value
@@ -125,10 +240,16 @@ def project_record(state, secrets):
                 for index, field in enumerate(value):
                     if not isinstance(field, (list, tuple)) or len(field) != 2 or not isinstance(field[0], bytes):
                         raise CaptureFailure("format", "Native header/trailer is not an ordered byte pair.", pointer(path, index))
-                    result.append([visit(field[0], pointer(pointer(path, index), 0), depth + 2), visit(field[1], pointer(pointer(path, index), 1), depth + 2, field[0].lower() in CREDENTIALS, field[0].lower() in {b"location", b"referer", b"origin"})])
+                    result.append([visit(field[0], pointer(pointer(path, index), 0), depth + 2), visit(field[1], pointer(pointer(path, index), 1), depth + 2, field[0].lower() in CREDENTIALS, field[0].lower() in {b"location", b"referer", b"origin"}, base_scheme if field[0].lower() == b"location" else None)])
                 return result
-            return [visit(item, pointer(path, index), depth + 1) for index, item in enumerate(value)]
+            return [visit(item, pointer(path, index), depth + 1, base_scheme=base_scheme) for index, item in enumerate(value)]
         if isinstance(value, dict):
+            if path == "" or re.fullmatch(r"/backup(?:/backup)*", path):
+                request = value.get("request")
+                scheme = request.get("scheme") if isinstance(request, dict) else None
+                if isinstance(scheme, bytes):
+                    scheme = scheme.decode("latin-1")
+                base_scheme = scheme.lower() if isinstance(scheme, str) and re.fullmatch(r"[a-z][a-z0-9+.-]*", scheme, flags=re.I) else None
             result = {}
             for key, item in value.items():
                 if not isinstance(key, str):
@@ -139,7 +260,7 @@ def project_record(state, secrets):
                     validate_omitted(item, pointer(path, key), depth + 1)
                     redactions.append({"pointer": path, "reason": "explicit-sensitive-value", "scope": "property-name"})
                     continue
-                result[key] = visit(item, pointer(path, key), depth + 1)
+                result[key] = visit(item, pointer(path, key), depth + 1, base_scheme=base_scheme)
             return result
         raise CaptureFailure("decoder", "Native parser returned an unexpected value type: " + type(value).__name__ + ".", path)
 

bridge/mitmproxy/test_capture.py

@@ -0,0 +1,214 @@
+"""Source-owned tests for the mitmproxy adapter's record projection."""
+
+import importlib.util
+import os
+import sys
+import types
+import unittest
+from unittest import mock
+
+
+def load_capture():
+    """Load the adapter with fresh mitmproxy stand-ins scoped to its import."""
+    fake_mitmproxy = types.ModuleType("mitmproxy")
+    fake_mitmproxy.ctx = types.SimpleNamespace()
+    fake_mitmproxy.version = types.SimpleNamespace(VERSION="12.2.3")
+    fake_io = types.ModuleType("mitmproxy.io")
+    fake_io.tnetstring = types.ModuleType("mitmproxy.io.tnetstring")
+    stand_ins = {
+        "mitmproxy": fake_mitmproxy,
+        "mitmproxy.io": fake_io,
+        "mitmproxy.io.tnetstring": fake_io.tnetstring,
+    }
+    spec = importlib.util.spec_from_file_location(
+        "rea_mitmproxy_capture", os.path.join(os.path.dirname(__file__), "capture.py")
+    )
+    module = importlib.util.module_from_spec(spec)
+    with mock.patch.dict(sys.modules, stand_ins):
+        spec.loader.exec_module(module)
+    return module
+
+
+capture = load_capture()
+
+
+def location(value, scheme=None):
+    state = {"response": {"headers": [[b"Location", value]]}}
+    if scheme is not None:
+        state["request"] = {"scheme": scheme}
+    record = capture.project_record(state, [])
+    sidecar = next(
+        field for field in record["binary_fields"] if field["pointer"] == "/response/headers/0/1"
+    )
+    return record["reported"]["response"]["headers"][0][1], sidecar, record["redactions"]
+
+
+class TransportUserinfoTests(unittest.TestCase):
+    def test_ignorable_controls_cannot_hide_authority_credentials(self):
+        for control in [b"\t", b"\n", b"\r"]:
+            for value in [b"https://" + control + b"/user:pass@host/path", b"ht" + control + b"tps://user:" + control + b"pass@host/path"]:
+                with self.subTest(value=value):
+                    text, sidecar, redactions = location(value, b"https")
+                    self.assertNotIn("user", text)
+                    self.assertNotIn("pass", text)
+                    self.assertEqual(sidecar["state"], "redacted")
+                    self.assertEqual(len(redactions), 1)
+
+    def test_mixed_network_separators_remove_credentials(self):
+        for prefix in [b"\\\\", b"/\\", b"\\/"]:
+            with self.subTest(prefix=prefix):
+                text, sidecar, redactions = location(prefix + b"user:pass@host/path", b"https")
+                self.assertEqual(text, prefix.decode("ascii") + "host/path")
+                self.assertEqual(sidecar["state"], "redacted")
+                self.assertEqual(len(redactions), 1)
+
+    def test_non_special_base_keeps_backslashes_inside_network_authorities(self):
+        text, sidecar, redactions = location(b"//user\\name:pass@host/x", b"foo")
+        self.assertEqual(text, "//host/x")
+        self.assertEqual(sidecar["state"], "redacted")
+        self.assertEqual(len(redactions), 1)
+        text, sidecar, redactions = location(b"/\\invoice@customer", b"foo")
+        self.assertEqual(text, "/\\invoice@customer")
+        self.assertEqual(sidecar["state"], "retained")
+        self.assertEqual(redactions, [])
+
+    def test_native_request_paths_preserve_origin_form_and_redact_absolute_form(self):
+        for value in [b"/\\invoice@customer", b"//invoice@customer", b"\\\\invoice@customer"]:
+            with self.subTest(value=value):
+                record = capture.project_record({"request": {"path": value}}, [])
+                self.assertEqual(record["reported"]["request"]["path"], value.decode("ascii"))
+                self.assertEqual(record["binary_fields"][0]["state"], "retained")
+                self.assertEqual(record["redactions"], [])
+        record = capture.project_record({"request": {"path": b"https://user:pass@host/x"}}, [])
+        self.assertEqual(record["reported"]["request"]["path"], "https://host/x")
+        self.assertEqual(record["binary_fields"][0]["state"], "redacted")
+
+    def test_same_scheme_locations_preserve_relative_path_text_and_bytes(self):
+        for value in [b"https:invoice@customer", b"https:/invoice@customer", b"https:\\invoice@customer"]:
+            with self.subTest(value=value):
+                text, sidecar, redactions = location(value, b"https")
+                self.assertEqual(text, value.decode("ascii"))
+                self.assertEqual(sidecar["state"], "retained")
+                self.assertEqual(redactions, [])
+
+    def test_location_authorities_still_remove_credentials_with_a_base_scheme(self):
+        for value, scheme, expected in [
+            (b"https://user:pass@host/path", b"https", "https://host/path"),
+            (b"https:\\\\user:pass@host/path", b"https", "https:\\\\host/path"),
+            (b"https:user:pass@host/path", b"http", "https:host/path"),
+        ]:
+            with self.subTest(value=value, scheme=scheme):
+                text, sidecar, redactions = location(value, scheme)
+                self.assertEqual(text, expected)
+                self.assertEqual(sidecar["state"], "redacted")
+                self.assertEqual(len(redactions), 1)
+
+    def test_backup_location_uses_its_own_request_scheme(self):
+        record = capture.project_record({
+            "request": {"scheme": b"http"},
+            "backup": {
+                "request": {"scheme": b"https"},
+                "response": {"headers": [[b"Location", b"https:invoice@customer"]]},
+            },
+        }, [])
+        self.assertEqual(record["reported"]["backup"]["response"]["headers"][0][1], "https:invoice@customer")
+        self.assertEqual(record["redactions"], [])
+
+    def test_backslash_ends_a_special_scheme_authority(self):
+        text, sidecar, redactions = location(b"https://example.test\\part@tail")
+        self.assertEqual(text, "https://example.test\\part@tail")
+        self.assertEqual(sidecar["state"], "retained")
+        self.assertIsNotNone(sidecar["content_base64"])
+        self.assertEqual(redactions, [])
+
+    def test_userinfo_before_a_backslash_is_still_removed(self):
+        text, sidecar, redactions = location(b"https://user:pw@example.test\\path")
+        self.assertEqual(text, "https://example.test\\path")
+        self.assertEqual(sidecar["state"], "redacted")
+        self.assertEqual(
+            redactions,
+            [{"pointer": "/response/headers/0/1", "reason": "transport-credential"}],
+        )
+
+    def test_ordinary_userinfo_is_removed(self):
+        text, _sidecar, _redactions = location(b"https://user:pw@example.test/a@b")
+        self.assertEqual(text, "https://example.test/a@b")
+
+    def test_empty_userinfo_marker_is_removed(self):
+        self.assertEqual(
+            capture.without_userinfo("https://@host"), "https://host"
+        )
+
+    def test_special_schemes_skip_leading_slashes_before_userinfo(self):
+        for value, expected in [
+            (b"https://\\user:pass@host/path", b"https://\\host/path"),
+            (b"https:\\\\user:pass@host/path", b"https:\\\\host/path"),
+            (b"https:user:pass@host", b"https:host"),
+            (b"//\\user:pass@host", b"//\\host"),
+        ]:
+            with self.subTest(value=value):
+                self.assertEqual(capture.without_userinfo(value), expected)
+        text, sidecar, redactions = location(b"https://\\user:pass@host/path")
+        self.assertEqual(text, "https://\\host/path")
+        self.assertEqual(sidecar["state"], "redacted")
+        self.assertEqual(len(redactions), 1)
+
+    def test_file_base_keeps_paths_after_the_fixed_network_boundary(self):
+        for value in [b"///u@h", b"////u@h"]:
+            with self.subTest(value=value):
+                text, sidecar, redactions = location(value, b"file")
+                self.assertEqual(text, value.decode("ascii"))
+                self.assertEqual(sidecar["state"], "retained")
+                self.assertIsNotNone(sidecar["content_base64"])
+                self.assertEqual(redactions, [])
+
+    def test_file_urls_keep_path_text(self):
+        self.assertEqual(capture.without_userinfo("file:///a@b"), "file:///a@b")
+
+    def test_file_urls_reject_userinfo_and_keep_their_source(self):
+        # WHATWG rejects an "@" in a file host, so nothing parses as credentials.
+        self.assertEqual(
+            capture.without_userinfo("file://user:pass@host/x"), "file://user:pass@host/x"
+        )
+        for value in [b"\\\\user:pass@host/x", b"/\\user:pass@host/x", b"//user:pass@host/x"]:
+            with self.subTest(value=value):
+                text, sidecar, redactions = location(value, b"file")
+                self.assertEqual(text, value.decode("ascii"))
+                self.assertEqual(sidecar["state"], "retained")
+                self.assertEqual(redactions, [])
+
+    def test_rejected_special_hosts_keep_their_source(self):
+        # A rejected host or port fails the whole URL, so it has no userinfo.
+        for value in [
+            "https:user@%",
+            "https://user@",
+            "https://user:pass@h^st/x",
+            "https://user@ho st/x",
+            "https://user@host:99999/x",
+            "https://user@host:12a",
+            "https://user@[::1",
+        ]:
+            with self.subTest(value=value):
+                self.assertEqual(capture.without_userinfo(value), value)
+        text, sidecar, redactions = location(b"https://user:pass@h^st/x", b"https")
+        self.assertEqual(text, "https://user:pass@h^st/x")
+        self.assertEqual(sidecar["state"], "retained")
+        self.assertEqual(redactions, [])
+
+    def test_accepted_special_hosts_still_remove_userinfo(self):
+        for value, expected in [
+            ("https:user@%41", "https:%41"),
+            ("https://user@[::1]:8443/x", "https://[::1]:8443/x"),
+            ("https://user@host:/x", "https://host:/x"),
+            ("wss://user:pass@host:65535", "wss://host:65535"),
+        ]:
+            with self.subTest(value=value):
+                self.assertEqual(capture.without_userinfo(value), expected)
+
+    def test_non_special_schemes_keep_backslashes_in_the_authority(self):
+        self.assertEqual(capture.without_userinfo("foo://a\\b@host/x"), "foo://host/x")
+        self.assertEqual(capture.without_userinfo(b"//a\\b@host"), b"//a\\b@host")
+
+
+if __name__ == "__main__":
+    unittest.main()

package.json

@@ -138,7 +138,7 @@
     "test": "npm run test:with-build",
     "test:with-build": "npm run test:prepare && vitest run",
     "test:run": "vitest run",
-    "test:python": "python3 -m unittest bridge/native/test_rea_lldb_tracer.py -v && python3 -m unittest discover -s experiments/analysis-efficiency -p 'test_*.py' -v",
+    "test:python": "python3 -m unittest bridge/native/test_rea_lldb_tracer.py bridge/mitmproxy/test_capture.py -v && python3 -m unittest discover -s experiments/analysis-efficiency -p 'test_*.py' -v",
     "test:local": "node scripts/run-development-tests.mjs local",
     "test:fast": "node scripts/ci/test-group.mjs source",
     "test:built": "node scripts/ci/test-group.mjs built",

scripts/lib/clean-linux-hopper-runtime.d.mts

@@ -1,4 +1,5 @@
 export function assertCleanLinuxHopperRuntime(
   launcherPaths?: readonly string[],
   procRoot?: string,
+  listProcesses?: () => Promise<{ stdout: string }>,
 ): Promise<void>;

scripts/lib/clean-linux-hopper-runtime.mjs

@@ -17,8 +17,9 @@ export const assertCleanLinuxHopperRuntime = async (
       : [process.env.HOPPER_LAUNCHER_PATH]),
   ],
   procRoot = "/proc",
+  listProcesses = () => execFileAsync("ps", ["-ax", "-o", "command="]),
 ) => {
-  const { stdout } = await execFileAsync("ps", ["-ax", "-o", "command="]);
+  const { stdout } = await listProcesses();
   if (/\/opt\/hopper\/bin\/Hopper|\bXvfb\b|hopper-demo-x11\.py/u.test(stdout))
     throw new Error("Clean Linux runner retained a Hopper demo process");
   const launchers = [];

src/domain/recordedTransportUrl.test.ts

@@ -0,0 +1,11 @@
+import { expect, it } from "vitest";
+
+import { parseRecordedTransportUrl } from "./recordedTransportUrl.js";
+
+it("recognizes an empty userinfo marker at the authority start", () => {
+  expect(parseRecordedTransportUrl("https://@host")).toMatchObject({
+    origin: "https://host",
+    path: "/",
+    credentials: { start: 8, end: 9 },
+  });
+});

tests/process-global/cleanLinuxHopperRuntime.test.ts

@@ -34,6 +34,10 @@ it
     const procRoot = join(directory, "proc");
     await mkdir(procRoot);
     const alternateMode = mode === "alternate launcher";
+    let orphanPid: number | undefined;
+    const isolatedProcessList = async () => ({
+      stdout: alternateMode || orphanPid === undefined ? "" : "Xvfb",
+    });
     if (alternateMode) {
       await copyFile("/usr/bin/sleep", launcher);
       await chmod(launcher, 0o700);
@@ -47,6 +51,7 @@ it
     await assertCleanLinuxHopperRuntime(
       alternateMode ? [launcher] : [],
       procRoot,
+      isolatedProcessList,
     );
     const command = alternateMode ? alternate : process.execPath;
     const arguments_ = alternateMode ? ["30"] : ["-e", childCode];
@@ -69,7 +74,6 @@ it
     const parentPid = parent.child.pid;
     if (parentPid === undefined)
       throw new Error("Fixture parent did not spawn");
-    let orphanPid: number | undefined;
     try {
       const { stdout } = await parent;
       const { pid } = JSON.parse(stdout) as { pid: number };
@@ -115,6 +119,7 @@ it
         assertCleanLinuxHopperRuntime(
           alternateMode ? [launcher] : [],
           procRoot,
+          isolatedProcessList,
         ),
       ).rejects.toThrow("Clean Linux runner retained a Hopper demo process");
       // Observation must not terminate the fixture, even though it resembles Xvfb.