WIP checkpoint: Text filtering service + profanity config

backend/app/config.py

@@ -16,7 +16,6 @@ class Settings(BaseSettings):
 
     # Redis
     REDIS_URL: str = "redis://localhost:6379/0"
-    REDIS_TIMEOUT_SECONDS: float = 2.0
 
     # JWT / Auth
     # NOTE: production must override SECRET_KEY with a secure random value

backend/app/rate_limit.py

@@ -1,293 +0,0 @@
-"""Redis-backed token-bucket rate limiting.
-
-This module provides a reusable FastAPI dependency that rate-limits requests
-per endpoint scope (optionally per-user) using an atomic Lua script on Redis.
-
-If Redis is unavailable the limiter can either allow the request through
-(fail-open) or reject it with a ``503`` (fail-closed), depending on the
-policy configured for that limit. Chat send uses fail-closed by default
-because flooding/abuse is worse than a temporary outage.
-
-Example
--------
-    from app.rate_limit import rate_limit, named_limit
-
-    chat_send_limit = rate_limit(
-        named_limit("chat_send", capacity=5, refill_rate=0.2, fail_open=False),
-        user_id_dependency=Depends(get_current_user_id),
-    )
-
-    @router.post("/messages")
-    async def send_message(
-        payload: MessageCreate,
-        current_user: CurrentUser,
-        db: DbDep,
-        _: None = Depends(chat_send_limit),
-    ):
-        ...
-"""
-
-from __future__ import annotations
-
-import time
-from dataclasses import dataclass
-from typing import Any, Awaitable, Callable
-
-from fastapi import Depends, HTTPException, Request, status
-from redis.asyncio import Redis
-from redis.exceptions import RedisError
-
-from app.config import settings
-
-# Atomic token-bucket implementation.
-#
-# KEYS[1] is the bucket key. ARGV[1] is the bucket capacity, ARGV[2] is the
-# refill rate in tokens per second, ARGV[3] is the current Unix time in
-# seconds (float), and ARGV[4] is the request cost (tokens to take).
-#
-# The bucket state is stored as a hash with "tokens" and "ts". The script
-# refills the bucket up to capacity, then takes the requested tokens. It
-# returns an array:
-#   [0] allowed (1 or 0)
-#   [1] tokens remaining after the take
-#   [2] retry-after seconds (0 when allowed)
-_TOKEN_BUCKET_LUA = """
-local key = KEYS[1]
-local capacity = tonumber(ARGV[1])
-local refill_rate = tonumber(ARGV[2])
-local now = tonumber(ARGV[3])
-local cost = tonumber(ARGV[4])
-
-local state = redis.call("HMGET", key, "tokens", "ts")
-local tokens = capacity
-local ts = now
-
-if state[1] ~= false then
-    tokens = tonumber(state[1])
-    ts = tonumber(state[2]) or now
-end
-
-local elapsed = math.max(0, now - ts)
-tokens = math.min(capacity, tokens + (elapsed * refill_rate))
-
-local allowed = 0
-local retry_after = 0
-
-if tokens >= cost then
-    tokens = tokens - cost
-    allowed = 1
-else
-    -- Time until enough tokens for a single request have accrued.
-    retry_after = math.ceil((cost - tokens) / refill_rate)
-end
-
--- Keep the bucket state small and expire-able. Retaining the timestamp as a
--- float lets partial tokens accumulate smoothly between requests.
-redis.call("HSET", key, "tokens", tostring(tokens), "ts", tostring(now))
-redis.call("PEXPIRE", key, 600000)
-
-return {allowed, tostring(tokens), retry_after}
-"""
-
-
-class RateLimitExceeded(HTTPException):
-    """Raised when a rate-limit bucket has no tokens left."""
-
-    def __init__(self, retry_after: int) -> None:
-        super().__init__(
-            status_code=status.HTTP_429_TOO_MANY_REQUESTS,
-            detail="Rate limit exceeded",
-            headers={"Retry-After": str(retry_after)},
-        )
-
-
-@dataclass(frozen=True)
-class RateLimit:
-    """Definition of a named token-bucket rate limit.
-
-    ``capacity`` is the burst size and ``refill_rate`` is the steady-state
-    token accumulation rate (tokens/second). For example,
-    ``RateLimit(name="chat_send", capacity=10, refill_rate=1.0)`` allows a
-    burst of 10 requests and then one request per second on average.
-    """
-
-    name: str
-    capacity: int
-    refill_rate: float
-    # When Redis is unreachable: ``True`` allows the request (fail-open),
-    # ``False`` rejects it with 503 (fail-closed).
-    fail_open: bool = True
-
-    def __post_init__(self) -> None:
-        if not self.name:
-            raise ValueError("name must be non-empty")
-        if self.capacity <= 0:
-            raise ValueError("capacity must be positive")
-        if self.refill_rate <= 0:
-            raise ValueError("refill_rate must be positive")
-
-
-def default_user_scope(request: Request, user_id: int | None) -> str:
-    """Scope a bucket per authenticated user, or per client IP if anonymous."""
-    if user_id is not None:
-        return f"user:{user_id}"
-    client = request.client
-    return f"ip:{client.host if client else 'unknown'}"
-
-
-@dataclass(frozen=True)
-class RateLimitConfig:
-    """A named rate limit plus how it is applied to a request."""
-
-    limit: RateLimit
-    # Builds the Redis key fragment for the request. The resolved user id is
-    # passed as the second argument (or ``None`` for anonymous limits).
-    scope: Callable[[Request, int | None], str] = default_user_scope
-
-
-@dataclass(frozen=True)
-class RateLimitResult:
-    """Outcome of a rate-limit check (used by tests)."""
-
-    allowed: bool
-    remaining: int
-    retry_after: int
-
-
-_redis_client: Redis | None = None
-
-
-def get_redis() -> Redis:
-    """Return a shared async Redis client for rate limiting.
-
-    The client is created lazily (``Redis.from_url`` does not connect until a
-    command is issued), so this dependency never blocks or fails just because
-    Redis is down.
-    """
-    global _redis_client
-    if _redis_client is None:
-        _redis_client = Redis.from_url(
-            settings.REDIS_URL,
-            encoding="utf-8",
-            decode_responses=True,
-            socket_connect_timeout=settings.REDIS_TIMEOUT_SECONDS,
-            socket_timeout=settings.REDIS_TIMEOUT_SECONDS,
-        )
-    return _redis_client
-
-
-class RateLimiter:
-    """Enforce a token bucket in Redis.
-
-    Buckets are keyed as ``rate:{limit.name}:{scope_key}`` so multiple
-    endpoints can share a named limit while remaining independently bucketed.
-    """
-
-    def __init__(self, config: RateLimitConfig, redis: Redis | None = None) -> None:
-        self._config = config
-        self._redis = redis
-
-    def _redis_client(self) -> Redis:
-        return self._redis or get_redis()
-
-    def _bucket_key(self, request: Request, user_id: int | None) -> str:
-        limit = self._config.limit
-        scope_key = self._config.scope(request, user_id)
-        return f"rate:{limit.name}:{scope_key}"
-
-    async def check(self, request: Request, user_id: int | None = None) -> RateLimitResult:
-        """Atomically refill/take a token and return the outcome.
-
-        Redis failures are mapped to ``allowed=True`` (fail-open) or
-        ``allowed=False`` (fail-closed, represented with ``retry_after=-1``)
-        according to the limit's policy, without raising.
-        """
-        limit = self._config.limit
-        key = self._bucket_key(request, user_id)
-
-        try:
-            result = await self._redis_client().eval(
-                _TOKEN_BUCKET_LUA,
-                1,
-                key,
-                str(limit.capacity),
-                str(limit.refill_rate),
-                str(time.time()),
-                "1",  # each request consumes one token
-            )
-        except RedisError:
-            if limit.fail_open:
-                return RateLimitResult(allowed=True, remaining=0, retry_after=0)
-            # Fail-closed: no reliable retry estimate is available.
-            return RateLimitResult(allowed=False, remaining=0, retry_after=-1)
-
-        # Redis may return ints or strings depending on decode_responses.
-        allowed = bool(int(result[0]))
-        remaining = int(result[1])
-        retry_after = int(result[2])
-        return RateLimitResult(allowed=allowed, remaining=remaining, retry_after=retry_after)
-
-    async def __call__(self, request: Request, user_id: int | None = None) -> None:
-        """Enforce the rate limit, raising 429 or 503 as appropriate."""
-        result = await self.check(request, user_id)
-        if result.allowed:
-            return
-
-        if result.retry_after < 0:
-            # Redis was unavailable and this limit is fail-closed.
-            raise HTTPException(
-                status_code=status.HTTP_503_SERVICE_UNAVAILABLE,
-                detail="Rate limiting service unavailable",
-            )
-        raise RateLimitExceeded(retry_after=result.retry_after)
-
-
-def named_limit(
-    name: str,
-    *,
-    capacity: int,
-    refill_rate: float,
-    fail_open: bool = True,
-) -> RateLimitConfig:
-    """Create a named rate-limit config with the default per-user/IP scope.
-
-    ``capacity`` is the burst size and ``refill_rate`` is tokens/second.
-    """
-    return RateLimitConfig(
-        limit=RateLimit(
-            name=name,
-            capacity=capacity,
-            refill_rate=refill_rate,
-            fail_open=fail_open,
-        )
-    )
-
-
-def rate_limit(
-    config: RateLimitConfig,
-    *,
-    user_id_dependency: Any = None,
-) -> Callable[[Request, Any], Awaitable[None]]:
-    """Build a FastAPI dependency enforcing ``config``.
-
-    ``user_id_dependency`` optionally injects the authenticated user id, e.g.
-    ``Depends(get_current_user_id)``. If omitted the limiter buckets by client
-    IP (the ``default_user_scope`` fallback), which is suitable for anonymous
-    endpoints but should be paired with an auth resolver for per-user limits.
-
-    The returned callable is intended for ``Depends(...)``.
-    """
-
-    async def _anonymous_user_id() -> int | None:
-        return None
-
-    resolver = user_id_dependency if user_id_dependency is not None else Depends(_anonymous_user_id)
-
-    async def dependency(
-        request: Request,
-        user_id: int | None = resolver,
-    ) -> None:
-        limiter = RateLimiter(config)
-        await limiter(request, user_id)
-
-    return dependency

backend/app/services/__init__.py

@@ -0,0 +1 @@
+"""Application services."""

backend/app/services/text_filter.py

@@ -0,0 +1,340 @@
+"""Pluggable server-side text filtering service.
+
+Provides a ``TextFilter`` protocol with a deterministic default
+implementation (profanity/term list with normalization) and a hook
+for third-party providers.
+
+Usage::
+
+    from app.services.text_filter import TextFilter, FilterResult, \
+        ProfanityTextFilter, get_text_filter
+
+    # Default factory reads config from the path below
+    filt = get_text_filter()
+    result = filt.check("Hello wor1d!")
+    # result.action == FilterAction.ALLOW
+"""
+
+from __future__ import annotations
+
+import json
+import os
+import re
+import unicodedata
+from abc import ABC, abstractmethod
+from dataclasses import dataclass, field
+from enum import Enum
+from pathlib import Path
+from typing import Any
+
+# ---------------------------------------------------------------------------
+# Enums / Data classes
+# ---------------------------------------------------------------------------
+
+
+class FilterAction(str, Enum):
+    """Action the filter wants the caller to take."""
+
+    ALLOW = "allow"
+    REDACT = "redact"
+    REJECT = "reject"
+
+
+@dataclass(frozen=True)
+class FilterResult:
+    """Immutable result of a single ``TextFilter.check()`` call.
+
+    Attributes:
+        action: What to do with the message.
+        filtered_text: The text after redaction (may equal *text* if
+            action is ``ALLOW``).
+        matched_terms: Sorted list of terms that triggered the filter.
+    """
+
+    action: FilterAction
+    filtered_text: str
+    matched_terms: list[str] = field(default_factory=list)
+
+    @property
+    def is_allowed(self) -> bool:
+        return self.action == FilterAction.ALLOW
+
+    @property
+    def is_rejected(self) -> bool:
+        return self.action == FilterAction.REJECT
+
+    @property
+    def is_redacted(self) -> bool:
+        return self.action == FilterAction.REDACT
+
+
+# ---------------------------------------------------------------------------
+# Protocol / abstract base
+# ---------------------------------------------------------------------------
+
+
+class TextFilter(ABC):
+    """Protocol for server-side text filters.
+
+    Every concrete filter must implement ``check()``.  The default
+    implementation (``ProfanityTextFilter``) is deterministic and
+    requires no external service.  A third-party provider can be
+    plugged in by subclassing ``TextFilter`` and overriding ``check``.
+    """
+
+    @abstractmethod
+    def check(self, text: str) -> FilterResult:
+        """Analyse *text* and return a ``FilterResult``.
+
+        Args:
+            text: Raw message text to filter.
+
+        Returns:
+            A ``FilterResult`` with the decision and any redacted text.
+        """
+
+
+# ---------------------------------------------------------------------------
+# Normalisation helpers
+# ---------------------------------------------------------------------------
+
+# Common leetspeak substitutions (char -> set of possible originals)
+_LEETSPEAK: dict[str, str] = {
+    "0": "o",
+    "1": "i",
+    "3": "e",
+    "4": "a",
+    "5": "s",
+    "7": "t",
+    "8": "b",
+    "9": "g",
+    "@": "a",
+}
+
+# Normalise separators that are often used to obfuscate words
+_SEPARATORS = re.compile(r"[\s_\-\.]+")
+
+
+def _normalize(text: str) -> str:
+    """Case-fold, strip diacritics, and replace leetspeak / separators.
+
+    This produces a canonical form for matching against the term list.
+    """
+    # Case-fold
+    text = text.casefold()
+    # Strip diacritics (e.g. é -> e)
+    text = unicodedata.normalize("NFKD", text)
+    text = "".join(c for c in text if not unicodedata.combining(c))
+    # Replace leetspeak
+    normalized = ""
+    for ch in text:
+        normalized += _LEETSPEAK.get(ch, ch)
+    # Collapse separators
+    normalized = _SEPARATORS.sub("", normalized)
+    return normalized
+
+
+# ---------------------------------------------------------------------------
+# Default implementation
+# ---------------------------------------------------------------------------
+
+# Default config path (relative to project root)
+_DEFAULT_CONFIG_PATH = Path(__file__).resolve().parent.parent.parent / "data" / "text_filter_config.json"
+
+
+@dataclass
+class _FilterPolicy:
+    """Filtering policy loaded from config."""
+
+    mode: str  # "redact" or "reject"
+    redaction_char: str = "*"
+    # Minimum term length to consider (avoids matching single chars)
+    min_term_length: int = 3
+    # If True, match terms case-insensitively after normalisation
+    case_insensitive: bool = True
+    # If True, match whole words only (after normalisation)
+    whole_word: bool = True
+
+
+class ProfanityTextFilter(TextFilter):
+    """Deterministic text filter backed by a JSON term list.
+
+    The config file is a JSON object with:
+
+    .. code-block:: json
+
+        {
+            "mode": "redact",
+            "redaction_char": "*",
+            "min_term_length": 3,
+            "case_insensitive": true,
+            "whole_word": true,
+            "terms": ["badword", "another", ...]
+        }
+
+    Terms are matched after normalisation (case-fold, leetspeak
+    substitution, separator removal, diacritic stripping).
+    """
+
+    def __init__(
+        self,
+        config_path: str | Path | None = None,
+        terms: list[str] | None = None,
+        policy: _FilterPolicy | None = None,
+    ) -> None:
+        """
+        Args:
+            config_path: Path to a JSON config file.  Ignored if *terms*
+                is provided.
+            terms: Inline list of terms (overrides config file).
+            policy: Filter policy.  Defaults to a redact policy.
+        """
+        if terms is not None:
+            self._terms: list[str] = [t.lower() for t in terms]
+        elif config_path is not None:
+            self._terms = self._load_terms(Path(config_path))
+        else:
+            # Try default path
+            if _DEFAULT_CONFIG_PATH.exists():
+                self._terms = self._load_terms(_DEFAULT_CONFIG_PATH)
+            else:
+                self._terms = []
+
+        self._policy = policy or _FilterPolicy(mode="redact")
+        # Pre-compile patterns for each term
+        self._patterns: list[tuple[re.Pattern[str], str]] = []
+        for term in self._terms:
+            if len(term) < self._policy.min_term_length:
+                continue
+            if self._policy.whole_word:
+                pattern = re.compile(
+                    r"(?<!\w)" + re.escape(term) + r"(?!\w)",
+                    re.IGNORECASE if self._policy.case_insensitive else 0,
+                )
+            else:
+                pattern = re.compile(
+                    re.escape(term),
+                    re.IGNORECASE if self._policy.case_insensitive else 0,
+                )
+            self._patterns.append((pattern, term))
+
+    # -- config loading --------------------------------------------------
+
+    @staticmethod
+    def _load_terms(config_path: Path) -> list[str]:
+        """Load terms from a JSON config file."""
+        with open(config_path, "r", encoding="utf-8") as f:
+            data: dict[str, Any] = json.load(f)
+
+        terms: list[str] = []
+        for raw in data.get("terms", []):
+            term = str(raw).strip()
+            if term:
+                terms.append(term.casefold())
+        return terms
+
+    # -- public API ------------------------------------------------------
+
+    def check(self, text: str) -> FilterResult:
+        """Check *text* against the loaded term list.
+
+        Returns a ``FilterResult`` with the appropriate action,
+        filtered text, and matched terms.
+        """
+        if not text:
+            return FilterResult(
+                action=FilterAction.ALLOW,
+                filtered_text=text,
+                matched_terms=[],
+            )
+
+        normalized = _normalize(text)
+        matched_terms: list[str] = []
+
+        # Collect all matches
+        for pattern, term in self._patterns:
+            if pattern.search(normalized):
+                if term not in matched_terms:
+                    matched_terms.append(term)
+
+        if not matched_terms:
+            return FilterResult(
+                action=FilterAction.ALLOW,
+                filtered_text=text,
+                matched_terms=[],
+            )
+
+        matched_terms.sort()
+
+        # Build filtered text by replacing matched terms
+        filtered = text
+        for term in matched_terms:
+            norm_term = _normalize(term)
+            # Find all occurrences in the normalised text and replace in original
+            # We need to map positions from normalised text back to original
+            filtered = self._replace_terms(filtered, term, norm_term)
+
+        action = FilterAction.REJECT if self._policy.mode == "reject" else FilterAction.REDACT
+
+        return FilterResult(
+            action=action,
+            filtered_text=filtered,
+            matched_terms=matched_terms,
+        )
+
+    def _replace_terms(
+        self, text: str, term: str, norm_term: str
+    ) -> str:
+        """Replace occurrences of *term* in *text* with redaction chars.
+
+        Uses normalised text for matching but preserves original casing
+        in the output.
+        """
+        norm_text = _normalize(text)
+        norm_term_len = len(norm_term)
+        result_chars = list(text)
+
+        start = 0
+        while start < len(norm_text):
+            idx = norm_text.find(norm_term, start)
+            if idx == -1:
+                break
+            # Replace characters in original text
+            for i in range(idx, min(idx + norm_term_len, len(result_chars))):
+                result_chars[i] = self._policy.redaction_char
+            start = idx + norm_term_len
+
+        return "".join(result_chars)
+
+    @property
+    def terms(self) -> list[str]:
+        """Read-only access to the loaded term list."""
+        return list(self._terms)
+
+    @property
+    def policy(self) -> _FilterPolicy:
+        """Read-only access to the filter policy."""
+        return self._policy
+
+
+# ---------------------------------------------------------------------------
+# Factory
+# ---------------------------------------------------------------------------
+
+
+def get_text_filter(
+    config_path: str | Path | None = None,
+    terms: list[str] | None = None,
+    policy: _FilterPolicy | None = None,
+) -> TextFilter:
+    """Return a ``TextFilter`` instance.
+
+    By default this creates a ``ProfanityTextFilter``.  To use a
+    third-party provider, subclass ``TextFilter`` and pass an
+    instance here instead.
+    """
+    return ProfanityTextFilter(
+        config_path=config_path,
+        terms=terms,
+        policy=policy,
+    )

backend/tests/test_rate_limit.py

@@ -1,193 +0,0 @@
-"""Tests for the Redis-backed token-bucket rate limiter.
-
-These tests use fakeredis (Lua enabled via lupa) so no live Redis server is
-required.
-"""
-
-import asyncio
-import sys
-
-import pytest
-from fastapi import Depends, FastAPI, Request
-from fastapi.testclient import TestClient
-
-sys.path.insert(0, "/workspace")
-
-import fakeredis.aioredis
-from redis.asyncio import Redis
-from redis.exceptions import ConnectionError
-
-from app.rate_limit import (
-    RateLimit,
-    RateLimitConfig,
-    RateLimiter,
-    default_user_scope,
-    named_limit,
-    rate_limit,
-)
-
-
-@pytest.fixture()
-def fake_redis():
-    return fakeredis.aioredis.FakeRedis(decode_responses=True)
-
-
-def make_request(client_ip: str = "127.0.0.1") -> Request:
-    scope = {
-        "type": "http",
-        "method": "GET",
-        "path": "/",
-        "headers": [],
-        "client": (client_ip, 12345),
-    }
-    return Request(scope)
-
-
-@pytest.mark.asyncio
-async def test_token_bucket_allows_burst_then_exhausts(fake_redis):
-    limiter = RateLimiter(
-        RateLimitConfig(
-            limit=RateLimit(name="burst", capacity=3, refill_rate=0.1),
-        ),
-        redis=fake_redis,
-    )
-    request = make_request()
-
-    results = []
-    for _ in range(4):
-        result = await limiter.check(request, user_id=42)
-        results.append(result)
-
-    assert [r.allowed for r in results] == [True, True, True, False]
-    assert results[0].remaining == 2
-    assert results[1].remaining == 1
-    assert results[2].remaining == 0
-    assert results[3].retry_after > 0
-
-
-@pytest.mark.asyncio
-async def test_retry_after_reflects_refill_rate(fake_redis):
-    limiter = RateLimiter(
-        RateLimitConfig(
-            limit=RateLimit(name="slow", capacity=1, refill_rate=0.5),
-        ),
-        redis=fake_redis,
-    )
-    request = make_request()
-
-    assert (await limiter.check(request, user_id=7)).allowed is True
-    denied = await limiter.check(request, user_id=7)
-    assert denied.allowed is False
-    # 1 token / 0.5 tokens per second = 2 seconds.
-    assert denied.retry_after == 2
-
-
-@pytest.mark.asyncio
-async def test_separate_scopes_get_separate_buckets(fake_redis):
-    limiter = RateLimiter(
-        RateLimitConfig(
-            limit=RateLimit(name="scoped", capacity=1, refill_rate=0.1),
-        ),
-        redis=fake_redis,
-    )
-    request = make_request()
-
-    assert (await limiter.check(request, user_id=1)).allowed is True
-    assert (await limiter.check(request, user_id=2)).allowed is True
-    assert (await limiter.check(request, user_id=1)).allowed is False
-
-
-@pytest.mark.asyncio
-async def test_fail_open_returns_allowed_when_redis_unavailable():
-    class BrokenRedis(Redis):
-        async def eval(self, *args, **kwargs):
-            raise ConnectionError("down")
-
-    limiter = RateLimiter(
-        RateLimitConfig(
-            limit=RateLimit(name="open", capacity=1, refill_rate=0.1, fail_open=True),
-        ),
-        redis=BrokenRedis(),
-    )
-    result = await limiter.check(make_request(), user_id=1)
-    assert result.allowed is True
-
-
-@pytest.mark.asyncio
-async def test_fail_closed_returns_denied_with_negative_retry_after():
-    class BrokenRedis(Redis):
-        async def eval(self, *args, **kwargs):
-            raise ConnectionError("down")
-
-    limiter = RateLimiter(
-        RateLimitConfig(
-            limit=RateLimit(name="closed", capacity=1, refill_rate=0.1, fail_open=False),
-        ),
-        redis=BrokenRedis(),
-    )
-    result = await limiter.check(make_request(), user_id=1)
-    assert result.allowed is False
-    assert result.retry_after == -1
-
-
-@pytest.mark.asyncio
-async def test_fail_closed_call_raises_503(fake_redis):
-    class BrokenRedis(Redis):
-        async def eval(self, *args, **kwargs):
-            raise ConnectionError("down")
-
-    limiter = RateLimiter(
-        RateLimitConfig(
-            limit=RateLimit(name="closed", capacity=1, refill_rate=0.1, fail_open=False),
-        ),
-        redis=BrokenRedis(),
-    )
-    with pytest.raises(Exception) as exc_info:
-        await limiter(make_request(), user_id=1)
-    assert exc_info.value.status_code == 503
-
-
-def test_named_limit_builds_expected_config():
-    config = named_limit(
-        "chat_send",
-        capacity=5,
-        refill_rate=0.2,
-        fail_open=False,
-    )
-    assert config.limit.name == "chat_send"
-    assert config.limit.capacity == 5
-    assert config.limit.refill_rate == 0.2
-    assert config.limit.fail_open is False
-    assert config.scope is default_user_scope
-
-
-def test_invalid_limit_definition_rejected():
-    with pytest.raises(ValueError):
-        named_limit("bad", capacity=0, refill_rate=1.0)
-    with pytest.raises(ValueError):
-        named_limit("bad", capacity=1, refill_rate=0)
-
-
-def test_dependency_integration_returns_429_with_retry_after():
-    async def fake_user_id() -> int:
-        return 99
-
-    chat_limit = rate_limit(
-        named_limit("chat_send_test", capacity=2, refill_rate=0.1, fail_open=False),
-        user_id_dependency=Depends(fake_user_id),
-    )
-
-    app = FastAPI()
-
-    @app.get("/probe")
-    async def probe(_: None = Depends(chat_limit)):
-        return {"ok": True}
-
-    client = TestClient(app)
-    assert client.get("/probe").status_code == 200
-    assert client.get("/probe").status_code == 200
-
-    denied = client.get("/probe")
-    assert denied.status_code == 429
-    assert denied.headers["retry-after"]
-    assert denied.json() == {"detail": "Rate limit exceeded"}