feat(context): implement Redis-based caching layer (#84)

Phase 6 of Context Management Engine - Caching Layer:

- Add ContextCache with Redis integration
- Support fingerprint-based assembled context caching
- Support token count caching (model-specific)
- Support score caching (scorer + context + query)
- Add in-memory fallback with LRU eviction
- Add cache invalidation with pattern matching
- Add cache statistics reporting

Key features:
- Hierarchical cache key structure (ctx:type:hash)
- Automatic TTL expiration
- Memory cache for fast repeated access
- Graceful degradation when Redis unavailable

Tests: 29 new tests, 285 total context tests passing

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

backend/app/services/context/__init__.py

@@ -85,6 +85,9 @@ from .adapters import (
     OpenAIAdapter,
 )
 
+# Cache
+from .cache import ContextCache
+
 # Prioritization
 from .prioritization import (
     ContextRanker,
@@ -132,6 +135,8 @@ __all__ = [
     "BudgetAllocator",
     "TokenBudget",
     "TokenCalculator",
+    # Cache
+    "ContextCache",
     # Compression
     "ContextCompressor",
     "TruncationResult",

backend/app/services/context/cache/__init__.py

@@ -3,3 +3,9 @@ Context Cache Module.
 
 Provides Redis-based caching for assembled contexts.
 """
+
+from .context_cache import ContextCache
+
+__all__ = [
+    "ContextCache",
+]

backend/app/services/context/cache/context_cache.py

@@ -0,0 +1,417 @@
+"""
+Context Cache Implementation.
+
+Provides Redis-based caching for context operations including
+assembled contexts, token counts, and scoring results.
+"""
+
+import hashlib
+import json
+import logging
+from typing import TYPE_CHECKING, Any
+
+from ..config import ContextSettings, get_context_settings
+from ..exceptions import CacheError
+from ..types import AssembledContext, BaseContext
+
+if TYPE_CHECKING:
+    from redis.asyncio import Redis
+
+logger = logging.getLogger(__name__)
+
+
+class ContextCache:
+    """
+    Redis-based caching for context operations.
+
+    Provides caching for:
+    - Assembled contexts (fingerprint-based)
+    - Token counts (content hash-based)
+    - Scoring results (context + query hash-based)
+
+    Cache keys use a hierarchical structure:
+    - ctx:assembled:{fingerprint}
+    - ctx:tokens:{model}:{content_hash}
+    - ctx:score:{scorer}:{context_hash}:{query_hash}
+    """
+
+    def __init__(
+        self,
+        redis: "Redis | None" = None,
+        settings: ContextSettings | None = None,
+    ) -> None:
+        """
+        Initialize the context cache.
+
+        Args:
+            redis: Redis connection (optional for testing)
+            settings: Cache settings
+        """
+        self._redis = redis
+        self._settings = settings or get_context_settings()
+        self._prefix = self._settings.cache_prefix
+        self._ttl = self._settings.cache_ttl_seconds
+
+        # In-memory fallback cache when Redis unavailable
+        self._memory_cache: dict[str, tuple[str, float]] = {}
+        self._max_memory_items = 1000
+
+    def set_redis(self, redis: "Redis") -> None:
+        """Set Redis connection."""
+        self._redis = redis
+
+    @property
+    def is_enabled(self) -> bool:
+        """Check if caching is enabled and available."""
+        return self._settings.cache_enabled and self._redis is not None
+
+    def _cache_key(self, *parts: str) -> str:
+        """
+        Build a cache key from parts.
+
+        Args:
+            *parts: Key components
+
+        Returns:
+            Colon-separated cache key
+        """
+        return f"{self._prefix}:{':'.join(parts)}"
+
+    @staticmethod
+    def _hash_content(content: str) -> str:
+        """
+        Compute hash of content for cache key.
+
+        Args:
+            content: Content to hash
+
+        Returns:
+            32-character hex hash
+        """
+        return hashlib.sha256(content.encode()).hexdigest()[:32]
+
+    def compute_fingerprint(
+        self,
+        contexts: list[BaseContext],
+        query: str,
+        model: str,
+    ) -> str:
+        """
+        Compute a fingerprint for a context assembly request.
+
+        The fingerprint is based on:
+        - Context content and metadata
+        - Query string
+        - Target model
+
+        Args:
+            contexts: List of contexts
+            query: Query string
+            model: Model name
+
+        Returns:
+            32-character hex fingerprint
+        """
+        # Build a deterministic representation
+        context_data = []
+        for ctx in contexts:
+            context_data.append({
+                "type": ctx.get_type().value,
+                "content": ctx.content,
+                "source": ctx.source,
+                "priority": ctx.priority,  # Already an int
+            })
+
+        data = {
+            "contexts": context_data,
+            "query": query,
+            "model": model,
+        }
+
+        content = json.dumps(data, sort_keys=True)
+        return self._hash_content(content)
+
+    async def get_assembled(
+        self,
+        fingerprint: str,
+    ) -> AssembledContext | None:
+        """
+        Get cached assembled context by fingerprint.
+
+        Args:
+            fingerprint: Assembly fingerprint
+
+        Returns:
+            Cached AssembledContext or None if not found
+        """
+        if not self.is_enabled:
+            return None
+
+        key = self._cache_key("assembled", fingerprint)
+
+        try:
+            data = await self._redis.get(key)  # type: ignore
+            if data:
+                logger.debug(f"Cache hit for assembled context: {fingerprint}")
+                result = AssembledContext.from_json(data)
+                result.cache_hit = True
+                result.cache_key = fingerprint
+                return result
+        except Exception as e:
+            logger.warning(f"Cache get error: {e}")
+            raise CacheError(f"Failed to get assembled context: {e}") from e
+
+        return None
+
+    async def set_assembled(
+        self,
+        fingerprint: str,
+        context: AssembledContext,
+        ttl: int | None = None,
+    ) -> None:
+        """
+        Cache an assembled context.
+
+        Args:
+            fingerprint: Assembly fingerprint
+            context: Assembled context to cache
+            ttl: Optional TTL override in seconds
+        """
+        if not self.is_enabled:
+            return
+
+        key = self._cache_key("assembled", fingerprint)
+        expire = ttl or self._ttl
+
+        try:
+            await self._redis.setex(key, expire, context.to_json())  # type: ignore
+            logger.debug(f"Cached assembled context: {fingerprint}")
+        except Exception as e:
+            logger.warning(f"Cache set error: {e}")
+            raise CacheError(f"Failed to cache assembled context: {e}") from e
+
+    async def get_token_count(
+        self,
+        content: str,
+        model: str | None = None,
+    ) -> int | None:
+        """
+        Get cached token count.
+
+        Args:
+            content: Content to look up
+            model: Model name for model-specific tokenization
+
+        Returns:
+            Cached token count or None if not found
+        """
+        model_key = model or "default"
+        content_hash = self._hash_content(content)
+        key = self._cache_key("tokens", model_key, content_hash)
+
+        # Try in-memory first
+        if key in self._memory_cache:
+            return int(self._memory_cache[key][0])
+
+        if not self.is_enabled:
+            return None
+
+        try:
+            data = await self._redis.get(key)  # type: ignore
+            if data:
+                count = int(data)
+                # Store in memory for faster subsequent access
+                self._set_memory(key, str(count))
+                return count
+        except Exception as e:
+            logger.warning(f"Cache get error for tokens: {e}")
+
+        return None
+
+    async def set_token_count(
+        self,
+        content: str,
+        count: int,
+        model: str | None = None,
+        ttl: int | None = None,
+    ) -> None:
+        """
+        Cache a token count.
+
+        Args:
+            content: Content that was counted
+            count: Token count
+            model: Model name
+            ttl: Optional TTL override in seconds
+        """
+        model_key = model or "default"
+        content_hash = self._hash_content(content)
+        key = self._cache_key("tokens", model_key, content_hash)
+        expire = ttl or self._ttl
+
+        # Always store in memory
+        self._set_memory(key, str(count))
+
+        if not self.is_enabled:
+            return
+
+        try:
+            await self._redis.setex(key, expire, str(count))  # type: ignore
+        except Exception as e:
+            logger.warning(f"Cache set error for tokens: {e}")
+
+    async def get_score(
+        self,
+        scorer_name: str,
+        context_id: str,
+        query: str,
+    ) -> float | None:
+        """
+        Get cached score.
+
+        Args:
+            scorer_name: Name of the scorer
+            context_id: Context identifier
+            query: Query string
+
+        Returns:
+            Cached score or None if not found
+        """
+        query_hash = self._hash_content(query)[:16]
+        key = self._cache_key("score", scorer_name, context_id, query_hash)
+
+        # Try in-memory first
+        if key in self._memory_cache:
+            return float(self._memory_cache[key][0])
+
+        if not self.is_enabled:
+            return None
+
+        try:
+            data = await self._redis.get(key)  # type: ignore
+            if data:
+                score = float(data)
+                self._set_memory(key, str(score))
+                return score
+        except Exception as e:
+            logger.warning(f"Cache get error for score: {e}")
+
+        return None
+
+    async def set_score(
+        self,
+        scorer_name: str,
+        context_id: str,
+        query: str,
+        score: float,
+        ttl: int | None = None,
+    ) -> None:
+        """
+        Cache a score.
+
+        Args:
+            scorer_name: Name of the scorer
+            context_id: Context identifier
+            query: Query string
+            score: Score value
+            ttl: Optional TTL override in seconds
+        """
+        query_hash = self._hash_content(query)[:16]
+        key = self._cache_key("score", scorer_name, context_id, query_hash)
+        expire = ttl or self._ttl
+
+        # Always store in memory
+        self._set_memory(key, str(score))
+
+        if not self.is_enabled:
+            return
+
+        try:
+            await self._redis.setex(key, expire, str(score))  # type: ignore
+        except Exception as e:
+            logger.warning(f"Cache set error for score: {e}")
+
+    async def invalidate(self, pattern: str) -> int:
+        """
+        Invalidate cache entries matching a pattern.
+
+        Args:
+            pattern: Key pattern (supports * wildcard)
+
+        Returns:
+            Number of keys deleted
+        """
+        if not self.is_enabled:
+            return 0
+
+        full_pattern = self._cache_key(pattern)
+        deleted = 0
+
+        try:
+            async for key in self._redis.scan_iter(match=full_pattern):  # type: ignore
+                await self._redis.delete(key)  # type: ignore
+                deleted += 1
+
+            logger.info(f"Invalidated {deleted} cache entries matching {pattern}")
+        except Exception as e:
+            logger.warning(f"Cache invalidation error: {e}")
+            raise CacheError(f"Failed to invalidate cache: {e}") from e
+
+        return deleted
+
+    async def clear_all(self) -> int:
+        """
+        Clear all context cache entries.
+
+        Returns:
+            Number of keys deleted
+        """
+        self._memory_cache.clear()
+        return await self.invalidate("*")
+
+    def _set_memory(self, key: str, value: str) -> None:
+        """
+        Set a value in the memory cache.
+
+        Uses LRU-style eviction when max items reached.
+
+        Args:
+            key: Cache key
+            value: Value to store
+        """
+        import time
+
+        if len(self._memory_cache) >= self._max_memory_items:
+            # Evict oldest entries
+            sorted_keys = sorted(
+                self._memory_cache.keys(),
+                key=lambda k: self._memory_cache[k][1],
+            )
+            for k in sorted_keys[: len(sorted_keys) // 2]:
+                del self._memory_cache[k]
+
+        self._memory_cache[key] = (value, time.time())
+
+    async def get_stats(self) -> dict[str, Any]:
+        """
+        Get cache statistics.
+
+        Returns:
+            Dictionary with cache stats
+        """
+        stats = {
+            "enabled": self._settings.cache_enabled,
+            "redis_available": self._redis is not None,
+            "memory_items": len(self._memory_cache),
+            "ttl_seconds": self._ttl,
+        }
+
+        if self.is_enabled:
+            try:
+                # Get Redis info
+                info = await self._redis.info("memory")  # type: ignore
+                stats["redis_memory_used"] = info.get("used_memory_human", "unknown")
+            except Exception:
+                pass
+
+        return stats

backend/tests/services/context/test_cache.py

@@ -0,0 +1,479 @@
+"""Tests for context cache module."""
+
+from unittest.mock import AsyncMock, MagicMock
+
+import pytest
+
+from app.services.context.cache import ContextCache
+from app.services.context.config import ContextSettings
+from app.services.context.exceptions import CacheError
+from app.services.context.types import (
+    AssembledContext,
+    ContextPriority,
+    KnowledgeContext,
+    SystemContext,
+    TaskContext,
+)
+
+
+class TestContextCacheBasics:
+    """Basic tests for ContextCache."""
+
+    def test_creation(self) -> None:
+        """Test cache creation without Redis."""
+        cache = ContextCache()
+        assert cache._redis is None
+        assert not cache.is_enabled
+
+    def test_creation_with_settings(self) -> None:
+        """Test cache creation with custom settings."""
+        settings = ContextSettings(
+            cache_prefix="test",
+            cache_ttl_seconds=60,
+        )
+        cache = ContextCache(settings=settings)
+        assert cache._prefix == "test"
+        assert cache._ttl == 60
+
+    def test_set_redis(self) -> None:
+        """Test setting Redis connection."""
+        cache = ContextCache()
+        mock_redis = MagicMock()
+        cache.set_redis(mock_redis)
+        assert cache._redis is mock_redis
+
+    def test_is_enabled(self) -> None:
+        """Test is_enabled property."""
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(settings=settings)
+        assert not cache.is_enabled  # No Redis
+
+        cache.set_redis(MagicMock())
+        assert cache.is_enabled
+
+        # Disabled in settings
+        settings2 = ContextSettings(cache_enabled=False)
+        cache2 = ContextCache(redis=MagicMock(), settings=settings2)
+        assert not cache2.is_enabled
+
+    def test_cache_key(self) -> None:
+        """Test cache key generation."""
+        cache = ContextCache()
+        key = cache._cache_key("assembled", "abc123")
+        assert key == "ctx:assembled:abc123"
+
+    def test_hash_content(self) -> None:
+        """Test content hashing."""
+        hash1 = ContextCache._hash_content("hello world")
+        hash2 = ContextCache._hash_content("hello world")
+        hash3 = ContextCache._hash_content("different")
+
+        assert hash1 == hash2
+        assert hash1 != hash3
+        assert len(hash1) == 32
+
+
+class TestFingerprintComputation:
+    """Tests for fingerprint computation."""
+
+    def test_compute_fingerprint(self) -> None:
+        """Test fingerprint computation."""
+        cache = ContextCache()
+
+        contexts = [
+            SystemContext(content="System", source="system"),
+            TaskContext(content="Task", source="task"),
+        ]
+
+        fp1 = cache.compute_fingerprint(contexts, "query", "claude-3")
+        fp2 = cache.compute_fingerprint(contexts, "query", "claude-3")
+        fp3 = cache.compute_fingerprint(contexts, "different", "claude-3")
+
+        assert fp1 == fp2  # Same inputs = same fingerprint
+        assert fp1 != fp3  # Different query = different fingerprint
+        assert len(fp1) == 32
+
+    def test_fingerprint_includes_priority(self) -> None:
+        """Test that fingerprint changes with priority."""
+        cache = ContextCache()
+
+        # Use KnowledgeContext since SystemContext has __post_init__ that may override
+        ctx1 = [
+            KnowledgeContext(
+                content="Knowledge",
+                source="docs",
+                priority=ContextPriority.NORMAL.value,
+            )
+        ]
+        ctx2 = [
+            KnowledgeContext(
+                content="Knowledge",
+                source="docs",
+                priority=ContextPriority.HIGH.value,
+            )
+        ]
+
+        fp1 = cache.compute_fingerprint(ctx1, "query", "claude-3")
+        fp2 = cache.compute_fingerprint(ctx2, "query", "claude-3")
+
+        assert fp1 != fp2
+
+    def test_fingerprint_includes_model(self) -> None:
+        """Test that fingerprint changes with model."""
+        cache = ContextCache()
+        contexts = [SystemContext(content="System", source="system")]
+
+        fp1 = cache.compute_fingerprint(contexts, "query", "claude-3")
+        fp2 = cache.compute_fingerprint(contexts, "query", "gpt-4")
+
+        assert fp1 != fp2
+
+
+class TestMemoryCache:
+    """Tests for in-memory caching."""
+
+    def test_memory_cache_fallback(self) -> None:
+        """Test memory cache when Redis unavailable."""
+        cache = ContextCache()
+
+        # Should use memory cache
+        cache._set_memory("test-key", "42")
+        assert "test-key" in cache._memory_cache
+        assert cache._memory_cache["test-key"][0] == "42"
+
+    def test_memory_cache_eviction(self) -> None:
+        """Test memory cache eviction."""
+        cache = ContextCache()
+        cache._max_memory_items = 10
+
+        # Fill cache
+        for i in range(15):
+            cache._set_memory(f"key-{i}", f"value-{i}")
+
+        # Should have evicted some items
+        assert len(cache._memory_cache) < 15
+
+
+class TestAssembledContextCache:
+    """Tests for assembled context caching."""
+
+    @pytest.mark.asyncio
+    async def test_get_assembled_no_redis(self) -> None:
+        """Test get_assembled without Redis returns None."""
+        cache = ContextCache()
+        result = await cache.get_assembled("fingerprint")
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_get_assembled_not_found(self) -> None:
+        """Test get_assembled when key not found."""
+        mock_redis = AsyncMock()
+        mock_redis.get.return_value = None
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        result = await cache.get_assembled("fingerprint")
+        assert result is None
+
+    @pytest.mark.asyncio
+    async def test_get_assembled_found(self) -> None:
+        """Test get_assembled when key found."""
+        # Create a context
+        ctx = AssembledContext(
+            content="Test content",
+            total_tokens=100,
+            context_count=2,
+        )
+
+        mock_redis = AsyncMock()
+        mock_redis.get.return_value = ctx.to_json()
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        result = await cache.get_assembled("fingerprint")
+
+        assert result is not None
+        assert result.content == "Test content"
+        assert result.total_tokens == 100
+        assert result.cache_hit is True
+        assert result.cache_key == "fingerprint"
+
+    @pytest.mark.asyncio
+    async def test_set_assembled(self) -> None:
+        """Test set_assembled."""
+        mock_redis = AsyncMock()
+
+        settings = ContextSettings(cache_enabled=True, cache_ttl_seconds=60)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        ctx = AssembledContext(
+            content="Test content",
+            total_tokens=100,
+            context_count=2,
+        )
+
+        await cache.set_assembled("fingerprint", ctx)
+
+        mock_redis.setex.assert_called_once()
+        call_args = mock_redis.setex.call_args
+        assert call_args[0][0] == "ctx:assembled:fingerprint"
+        assert call_args[0][1] == 60  # TTL
+
+    @pytest.mark.asyncio
+    async def test_set_assembled_custom_ttl(self) -> None:
+        """Test set_assembled with custom TTL."""
+        mock_redis = AsyncMock()
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        ctx = AssembledContext(
+            content="Test",
+            total_tokens=10,
+            context_count=1,
+        )
+
+        await cache.set_assembled("fp", ctx, ttl=120)
+
+        call_args = mock_redis.setex.call_args
+        assert call_args[0][1] == 120
+
+    @pytest.mark.asyncio
+    async def test_cache_error_on_get(self) -> None:
+        """Test CacheError raised on Redis error."""
+        mock_redis = AsyncMock()
+        mock_redis.get.side_effect = Exception("Redis error")
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        with pytest.raises(CacheError):
+            await cache.get_assembled("fingerprint")
+
+    @pytest.mark.asyncio
+    async def test_cache_error_on_set(self) -> None:
+        """Test CacheError raised on Redis error."""
+        mock_redis = AsyncMock()
+        mock_redis.setex.side_effect = Exception("Redis error")
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        ctx = AssembledContext(
+            content="Test",
+            total_tokens=10,
+            context_count=1,
+        )
+
+        with pytest.raises(CacheError):
+            await cache.set_assembled("fp", ctx)
+
+
+class TestTokenCountCache:
+    """Tests for token count caching."""
+
+    @pytest.mark.asyncio
+    async def test_get_token_count_memory_fallback(self) -> None:
+        """Test get_token_count uses memory cache."""
+        cache = ContextCache()
+
+        # Set in memory
+        key = cache._cache_key("tokens", "default", cache._hash_content("hello"))
+        cache._set_memory(key, "42")
+
+        result = await cache.get_token_count("hello")
+        assert result == 42
+
+    @pytest.mark.asyncio
+    async def test_set_token_count_memory(self) -> None:
+        """Test set_token_count stores in memory."""
+        cache = ContextCache()
+
+        await cache.set_token_count("hello", 42)
+
+        result = await cache.get_token_count("hello")
+        assert result == 42
+
+    @pytest.mark.asyncio
+    async def test_set_token_count_with_model(self) -> None:
+        """Test set_token_count with model-specific tokenization."""
+        mock_redis = AsyncMock()
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        await cache.set_token_count("hello", 42, model="claude-3")
+        await cache.set_token_count("hello", 50, model="gpt-4")
+
+        # Different models should have different keys
+        assert mock_redis.setex.call_count == 2
+        calls = mock_redis.setex.call_args_list
+
+        key1 = calls[0][0][0]
+        key2 = calls[1][0][0]
+        assert "claude-3" in key1
+        assert "gpt-4" in key2
+
+
+class TestScoreCache:
+    """Tests for score caching."""
+
+    @pytest.mark.asyncio
+    async def test_get_score_memory_fallback(self) -> None:
+        """Test get_score uses memory cache."""
+        cache = ContextCache()
+
+        # Set in memory
+        query_hash = cache._hash_content("query")[:16]
+        key = cache._cache_key("score", "relevance", "ctx-123", query_hash)
+        cache._set_memory(key, "0.85")
+
+        result = await cache.get_score("relevance", "ctx-123", "query")
+        assert result == 0.85
+
+    @pytest.mark.asyncio
+    async def test_set_score_memory(self) -> None:
+        """Test set_score stores in memory."""
+        cache = ContextCache()
+
+        await cache.set_score("relevance", "ctx-123", "query", 0.85)
+
+        result = await cache.get_score("relevance", "ctx-123", "query")
+        assert result == 0.85
+
+    @pytest.mark.asyncio
+    async def test_set_score_with_redis(self) -> None:
+        """Test set_score with Redis."""
+        mock_redis = AsyncMock()
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        await cache.set_score("relevance", "ctx-123", "query", 0.85)
+
+        mock_redis.setex.assert_called_once()
+
+
+class TestCacheInvalidation:
+    """Tests for cache invalidation."""
+
+    @pytest.mark.asyncio
+    async def test_invalidate_pattern(self) -> None:
+        """Test invalidate with pattern."""
+        mock_redis = AsyncMock()
+
+        # Set up scan_iter to return matching keys
+        async def mock_scan_iter(match=None):
+            for key in ["ctx:assembled:1", "ctx:assembled:2"]:
+                yield key
+
+        mock_redis.scan_iter = mock_scan_iter
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        deleted = await cache.invalidate("assembled:*")
+
+        assert deleted == 2
+        assert mock_redis.delete.call_count == 2
+
+    @pytest.mark.asyncio
+    async def test_clear_all(self) -> None:
+        """Test clear_all."""
+        mock_redis = AsyncMock()
+
+        async def mock_scan_iter(match=None):
+            for key in ["ctx:1", "ctx:2", "ctx:3"]:
+                yield key
+
+        mock_redis.scan_iter = mock_scan_iter
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        # Add to memory cache
+        cache._set_memory("test", "value")
+        assert len(cache._memory_cache) > 0
+
+        deleted = await cache.clear_all()
+
+        assert deleted == 3
+        assert len(cache._memory_cache) == 0
+
+
+class TestCacheStats:
+    """Tests for cache statistics."""
+
+    @pytest.mark.asyncio
+    async def test_get_stats_no_redis(self) -> None:
+        """Test get_stats without Redis."""
+        cache = ContextCache()
+        cache._set_memory("key", "value")
+
+        stats = await cache.get_stats()
+
+        assert stats["enabled"] is True
+        assert stats["redis_available"] is False
+        assert stats["memory_items"] == 1
+
+    @pytest.mark.asyncio
+    async def test_get_stats_with_redis(self) -> None:
+        """Test get_stats with Redis."""
+        mock_redis = AsyncMock()
+        mock_redis.info.return_value = {"used_memory_human": "1.5M"}
+
+        settings = ContextSettings(cache_enabled=True, cache_ttl_seconds=300)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        stats = await cache.get_stats()
+
+        assert stats["enabled"] is True
+        assert stats["redis_available"] is True
+        assert stats["ttl_seconds"] == 300
+        assert stats["redis_memory_used"] == "1.5M"
+
+
+class TestCacheIntegration:
+    """Integration tests for cache."""
+
+    @pytest.mark.asyncio
+    async def test_full_workflow(self) -> None:
+        """Test complete cache workflow."""
+        mock_redis = AsyncMock()
+        mock_redis.get.return_value = None
+
+        settings = ContextSettings(cache_enabled=True)
+        cache = ContextCache(redis=mock_redis, settings=settings)
+
+        contexts = [
+            SystemContext(content="System", source="system"),
+            KnowledgeContext(content="Knowledge", source="docs"),
+        ]
+
+        # Compute fingerprint
+        fp = cache.compute_fingerprint(contexts, "query", "claude-3")
+        assert len(fp) == 32
+
+        # Check cache (miss)
+        result = await cache.get_assembled(fp)
+        assert result is None
+
+        # Create and cache assembled context
+        assembled = AssembledContext(
+            content="Assembled content",
+            total_tokens=100,
+            context_count=2,
+            model="claude-3",
+        )
+        await cache.set_assembled(fp, assembled)
+
+        # Verify setex was called
+        mock_redis.setex.assert_called_once()
+
+        # Mock cache hit
+        mock_redis.get.return_value = assembled.to_json()
+        result = await cache.get_assembled(fp)
+
+        assert result is not None
+        assert result.cache_hit is True
+        assert result.content == "Assembled content"