Merge branch 'main' into claude/slowest-test-analysis-8t0pny

_REDACT_AUTH_HEADER matched the value's opening as `\s*["\']?\s*`: two
`\s*` separated only by an optional quote. With no quote, a whitespace
run could be split between them in every possible way, and when no
credential followed (end of text, or `,` `"` `<` ...) the engine tried
them all before giving up: quadratic, 8s for `authorization:` and 20k
spaces, 17s with `Proxy-Authorization:` (tried again at the inner
`authorization`). Same stall as the URL pattern: re.sub holds the GIL,
and the display service redacts everything it publishes.

The quote and the whitespace after it are now one optional unit,
`\s*(?:["\']\s*)?`, which matches the same strings with only one way to
split them. Output is identical to the old pattern on 300k fuzzed
inputs; 20k spaces now take ~1.6ms. A scan of all three redaction
patterns over prefix/run/suffix shapes finds none left that scales
superlinearly.

test/test_redaction.py pins exact output for quoted, tabbed, multi-line
and credential-less headers, and bounds header + 20k whitespace at 1s;
against the previous pattern those fail at 8-17s each.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KMXdS2S4NXTJ8ET96GymhK

CHANGELOG.md

@@ -120,6 +120,13 @@ floor on the release that ships them):
   when the count is only known to the display service.
 - The Logs tab has a **Plugin errors** panel: per-plugin counts, repeating
   errors and a Clear button.
+- Credential redaction in exception text (`src/redaction.py`) takes time
+  proportional to the text, not its square. Two patterns were quadratic: URL
+  `user:password@`, on a long unbroken run of letters or digits (a hex digest,
+  an ID), and `Authorization:` followed by a long run of whitespace. Either
+  used to stall every thread of the display service for up to seconds each
+  time the snapshot was published: about 0.5s for 20k characters of hex, 8s
+  for 20k spaces. What gets redacted is unchanged.
 
 ### Removed
 

src/redaction.py

@@ -24,8 +24,13 @@ _REDACT_CREDENTIAL = re.compile(
 # silently leak the ones nobody thought of. Not covered by the generic pattern
 # above, whose value part stops at whitespace and so would keep the credential
 # once a space follows the scheme.
+#
+# The opening quote and the whitespace after it are one optional unit. Written
+# `\s*["\']?\s*`, a whitespace run with no quote in it could be split between
+# the two `\s*` in every possible way, and a header with no credential after
+# it tried them all: quadratic, 8s for 20k spaces.
 _REDACT_AUTH_HEADER = re.compile(
-    r'((?:proxy-)?authorization["\']?\s*[=:]\s*["\']?\s*'
+    r'((?:proxy-)?authorization["\']?\s*[=:]\s*(?:["\']\s*)?'
     r'(?:[A-Za-z][\w.+-]*[ \t]+)?)'          # optional scheme name, kept
     r'([^\s,"\'<>}]+)',                       # the credential, redacted
     re.IGNORECASE,
@@ -34,8 +39,16 @@ _REDACT_AUTH_HEADER = re.compile(
 # Credentials embedded in a URL: https://user:password@host. requests quotes
 # the full URL in its exceptions, so this is a realistic leak. The username is
 # kept -- it identifies which account failed without being the secret.
-_REDACT_URL_USERINFO = re.compile(r'([a-z][a-z0-9+.-]*://[^/\s:@]+:)([^/\s@]+)(@)',
-                                  re.IGNORECASE)
+#
+# A match may only start where a run of scheme characters starts. Unanchored,
+# `[a-z][a-z0-9+.-]*://` was tried from every letter of a long run (a hex
+# digest, an ID, a blob of response body), each attempt reading to the end of
+# the run: quadratic, 1.6s for 20k characters, all of it holding the GIL.
+# Leading digits and `+.-` sit inside group 1 so the substitution puts them
+# back; the scheme proper still has to start with a letter.
+_REDACT_URL_USERINFO = re.compile(
+    r'((?<![a-z0-9+.-])[0-9+.-]*[a-z][a-z0-9+.-]*://[^/\s:@]+:)([^/\s@]+)(@)',
+    re.IGNORECASE)
 
 
 def redact_credentials(text: str) -> str:

test/test_redaction.py

@@ -0,0 +1,110 @@
+"""redact_credentials must stay linear in the length of its input.
+
+Regressions under test, both quadratic regexes in src/redaction.py:
+
+- The URL-userinfo pattern (`scheme://user:password@`) could start a match at
+  every letter of a run of scheme characters, and each attempt read to the end
+  of the run looking for `://`: 1.6s for a 20k-character run.
+- The Authorization-header pattern had two `\\s*` separated only by an
+  optional quote, so a header followed by whitespace and no credential tried
+  every split of that whitespace between them: 8s for 20k spaces.
+
+The display service redacts every message, stack trace and context value it
+publishes in the error snapshot, and re.sub holds the GIL throughout, so an
+exception quoting a hex digest or a long ID stalled the render loop with it.
+test_error_snapshot_cross_process.py's snapshot-size test spent 140s here.
+
+The fixed patterns have to redact exactly what the old ones did.
+"""
+
+import time
+
+import pytest
+
+from src.redaction import redact_credentials
+
+# Each timed input took seconds before the fix and takes about a millisecond
+# after it; the bound leaves CI plenty of headroom while still failing on a
+# quadratic pattern.
+_TIME_LIMIT = 1.0
+
+
+def _timed(text):
+    start = time.perf_counter()
+    result = redact_credentials(text)
+    return result, time.perf_counter() - start
+
+
+class TestUrlUserinfo:
+    @pytest.mark.parametrize("text,expected", [
+        ("401 for https://user:hunter2@example.com/api",
+         "401 for https://user:<redacted>@example.com/api"),
+        ("HTTPS://USER:HUNTER2@EXAMPLE.COM",
+         "HTTPS://USER:<redacted>@EXAMPLE.COM"),
+        ("git+ssh://deploy:hunter2@host/repo",
+         "git+ssh://deploy:<redacted>@host/repo"),
+        # The scheme starts after digits or +.- in the same run. Those
+        # characters must survive, and the password must still go.
+        ("1http://user:hunter2@host", "1http://user:<redacted>@host"),
+        ("+.-http://user:hunter2@host", "+.-http://user:<redacted>@host"),
+        ("a1+http://user:hunter2@host", "a1+http://user:<redacted>@host"),
+        ("see a://u:first@b and c://v:second@d",
+         "see a://u:<redacted>@b and c://v:<redacted>@d"),
+    ])
+    def test_password_is_redacted_and_the_rest_kept(self, text, expected):
+        assert redact_credentials(text) == expected
+
+    def test_a_url_without_a_password_is_untouched(self):
+        text = "GET https://user@example.com/path failed"
+        assert redact_credentials(text) == text
+
+
+class TestAuthorizationHeader:
+    @pytest.mark.parametrize("text,expected", [
+        ("Authorization: Bearer eyJ.SECRET.sig", "Authorization: Bearer <redacted>"),
+        ("Proxy-Authorization: Basic dXNlcg==", "Proxy-Authorization: Basic <redacted>"),
+        ("authorization: barecredential", "authorization: <redacted>"),
+        # Whitespace and an opening quote around the value, in either order.
+        ('authorization="  Bearer  tok"', 'authorization="  Bearer  <redacted>"'),
+        ("authorization:  '  tok'", "authorization:  '  <redacted>'"),
+        ("authorization:\n\tBearer tok", "authorization:\n\tBearer <redacted>"),
+    ])
+    def test_credential_is_redacted_and_the_rest_kept(self, text, expected):
+        assert redact_credentials(text) == expected
+
+    @pytest.mark.parametrize("text", ["authorization:   ", "authorization:   , next"])
+    def test_a_header_without_a_credential_is_untouched(self, text):
+        assert redact_credentials(text) == text
+
+
+class TestLinearTime:
+    @pytest.mark.parametrize("unit", ["x", "0123456789abcdef", "1a", "a+", "1"])
+    def test_long_scheme_character_runs(self, unit):
+        text = (unit * 50_000)[:50_000]
+        result, elapsed = _timed(text)
+        assert result == text
+        assert elapsed < _TIME_LIMIT, f"{elapsed:.2f}s to redact {len(text)} chars of {unit!r}"
+
+    def test_a_credential_after_a_long_run_is_still_found(self):
+        run = "ab12" * 10_000
+        result, elapsed = _timed(f"{run} https://user:hunter2@example.com")
+        assert result == f"{run} https://user:<redacted>@example.com"
+        assert elapsed < _TIME_LIMIT
+
+    @pytest.mark.parametrize("header,whitespace", [
+        ("authorization:", " "),
+        ("Proxy-Authorization:", "\t"),
+        ("authorization=", "\n"),
+    ])
+    def test_a_header_followed_by_long_whitespace(self, header, whitespace):
+        text = header + whitespace * 20_000 + ","
+        result, elapsed = _timed(text)
+        assert result == text
+        assert elapsed < _TIME_LIMIT, (
+            f"{elapsed:.2f}s to redact {header!r} and {len(text) - len(header)} more chars")
+
+    def test_a_credential_after_long_whitespace_is_still_found(self):
+        gap = " " * 20_000
+        result, elapsed = _timed(f"authorization:{gap}Bearer tok")
+        assert result == f"authorization:{gap}Bearer <redacted>"
+        assert elapsed < _TIME_LIMIT