Semantic Cache MCP
Semantic Cache MCP is a Model Context Protocol server that reduces AI model token usage by 80%+ through intelligent file caching, semantic search, and efficient file operations.
Token-Efficient File Reading:
read— Automatic three-state responses: full content (first read), unchanged marker (~0 tokens on cache hit), or unified diff (modified, 80-95% savings)batch_read— Read multiple files under a token budget with glob expansion, priority ordering, unchanged suppression, and batch embedding
File Modifications:
write— Create or replace files with cache refresh, overwrite diffs, append support, and optional auto-formattingedit— Targeted edits via three modes: find/replace, scoped (line-range bounded), or line-range replacementbatch_edit— Apply multiple edits to a single file in one call with partial success reportingdelete— Delete a file/symlink with cache eviction and dry-run preview
Search & Discovery:
search— Semantic (meaning-based) hybrid BM25 + HNSW vector search across cached files (no API keys, works offline)similar— Find semantically related files via nearest-neighbor lookupgrep— Exact regex or literal string search with line numbers and contextglob— Discover files by pattern with cache coverage indicatorsdiff— Compare two files with a unified diff and semantic similarity score
Cache Management & Diagnostics:
stats— View token savings, hit rates, tool call counts, embedding model performance, and memory usageclear— Reset all cache entries to force cold re-seeding
Key Technical Features:
BLAKE3 content hashing detects unchanged files even when timestamps change
Local ONNX embeddings (default: BAAI/bge-small-en-v1.5); supports custom HuggingFace models
LRU-K cache eviction with up to 10,000 entries
Optional GPU acceleration (NVIDIA CUDA)
DoS protection via configurable write/edit size limits and match count caps
Can block native file tools to force all I/O through semantic-cache for maximum savings
Click on "Install Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@Semantic Cache MCPSearch for code semantically related to the user authentication flow"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
Cut your MCP client's token usage by 98% on cached reads. Respond in milliseconds.
Semantic Cache MCP is a Model Context Protocol server that replaces redundant full-file reads with marker hits, unified diffs, and semantic summaries. Thirteen tools (read, read_image, batch_read, write, edit, edit_preview, batch_edit, search, grep, glob, delete, clear, stats) route every file operation through one cache-aware layer, so an MCP-capable agent skips files it has already seen.
Why this exists
In order of impact:
1. Reads stop costing tokens. The first read seeds the cache. Re-reads of unchanged files return a 5-token marker (mtime match, no disk I/O). Modified files return a unified diff. Files larger than the budget collapse to a semantic skeleton that preserves structure rather than slicing at a byte offset.
2. Search and grep run on the cache, not the disk. Semantic search (hybrid BM25 + HNSW), glob, and grep all read from the same indexed corpus that read/batch_read populate. An in-session result LRU collapses repeated queries to sub-millisecond hits.
3. Mutations are bounded by default. write, edit, and batch_edit enforce size and match limits, support dry_run, can run formatters, and refresh the cache atomically. Local FastEmbed is the default embedding provider; OpenAI-compatible endpoints are opt-in.
Installation
Add to Claude Code settings (~/.claude.json):
Option 1 — uvx (always runs latest version):
{
"mcpServers": {
"semantic-cache": {
"command": "uvx",
"args": ["semantic-cache-mcp"]
}
}
}Option 2 — uv tool install:
uv tool install semantic-cache-mcp{
"mcpServers": {
"semantic-cache": {
"command": "semantic-cache-mcp"
}
}
}Restart Claude Code.
GPU Acceleration (Optional)
For NVIDIA GPU acceleration, install with the gpu extra:
uv tool install "semantic-cache-mcp[gpu]"
# or with uvx: uvx "semantic-cache-mcp[gpu]"Then set EMBEDDING_DEVICE=gpu in your MCP config env block. Falls back to CPU automatically if CUDA is unavailable.
Custom Embedding Models
Any HuggingFace model with an ONNX export works — set EMBEDDING_MODEL in your env config:
"env": {
"EMBEDDING_MODEL": "Snowflake/snowflake-arctic-embed-m-v2.0"
}If the model isn't in fastembed's built-in list, it's automatically downloaded and registered from HuggingFace Hub on first startup (ONNX file integrity is verified via SHA256). See env_variables.md for model recommendations.
OpenAI-Compatible Embeddings
Local FastEmbed remains the default. To route embeddings through an OpenAI-compatible provider instead, enable it in the MCP env block. Defaults target Ollama:
"env": {
"OPENAI_EMBEDDINGS_ENABLED": "true",
"OPENAI_BASE_URL": "http://localhost:11434/v1",
"OPENAI_API_KEY": "ollama",
"OPENAI_EMBEDDING_MODEL": "nomic-embed-text"
}Run ollama pull nomic-embed-text first if the model is not installed. For hosted OpenAI, set OPENAI_BASE_URL=https://api.openai.com/v1, use a real OPENAI_API_KEY, and choose an embedding model such as text-embedding-3-small. OPENAI_EMBEDDING_DIMENSIONS is optional; leave it unset to infer the returned vector size.
Block Native File Tools (Recommended)
Disable the client's built-in file tools so all file I/O routes through semantic-cache.
Claude Code — add to ~/.claude/settings.json:
{
"permissions": {
"deny": ["Read", "Edit", "Write"]
}
}OpenCode — add to ~/.config/opencode/opencode.json:
{
"$schema": "https://opencode.ai/config.json",
"permission": {
"read": "deny",
"edit": "deny",
"write": "deny"
}
}CLAUDE.md Configuration
Add to ~/.claude/CLAUDE.md to enforce semantic-cache globally:
## Tools
- MUST use `semantic-cache-mcp` instead of native I/O tools (98% token savings on cached reads)Tools
Core
Tool | Description |
| Single-file cache-aware read. Returns full content on first read, unchanged markers on cache hits, diffs on modifications, and supports |
| Pass-through for image files. Returns an MCP image content block (base64 + mime) so vision models can see the pixels; sidecar metadata holds size and mime. Format verified by magic bytes (PNG, JPEG, GIF, TIFF, BMP, WebP) — not by extension. Bypasses the semantic cache. Capped at 5 MiB ( |
| Single-path delete for one file or symlink, with cache eviction and |
| Full-file create or replace with cache refresh. Returns creation status or an overwrite diff, supports |
| Single-file exact edit using cached content. Supports scoped and line-range replacement plus |
| Multiple exact edits in one file with partial success reporting. Preferred over repeated |
| Read-only probe that returns match count, line numbers, and small context snippets for a candidate |
Discovery
Tool | Description |
| Cache-only semantic search — find code by meaning when you don't know the exact symbol to grep for. Seed likely files first with |
| File discovery plus cache coverage. Use it to find candidates, then pass those paths into |
| Multi-file cache-aware read for seeding and retrieval. Handles globs, priorities, token budgets, unchanged suppression, and diff/full routing. |
| Cache-only exact search with regex or literal matching, line numbers, and optional context. Best for symbols and exact strings. |
Management
Tool | Description |
| Cache metrics, session usage (tokens saved, tool calls), and lifetime aggregates. |
| Reset all cache entries. |
Tool Reference
The table above is the authoritative tool map. This section only shows the common call shapes.
read path="/src/app.py" # automatic: full, unchanged, or diff
read path="/src/app.py" offset=120 limit=80 # lines 120–199 onlyAutomatic three states:
State | Response | Token cost |
First read | Full content + cached | Normal |
Unchanged |
| ~5 tokens |
Modified | Unified diff only | 5–20% of original |
write path="/src/new.py" content="..."
write path="/src/new.py" content="..." auto_format=true
write path="/src/large.py" content="...chunk1..." append=false # first chunk
write path="/src/large.py" content="...chunk2..." append=true # subsequent chunks# Mode A — find/replace: searches entire file
edit path="/src/app.py" old_string="def foo():" new_string="def foo(x: int):"
edit path="/src/app.py" old_string="..." new_string="..." replace_all=true auto_format=true
# Mode B — scoped find/replace: search only within line range (shorter old_string suffices)
edit path="/src/app.py" old_string="pass" new_string="return x" start_line=42 end_line=42
# Mode C — line replace: replace entire range, no old_string needed (maximum token savings)
edit path="/src/app.py" new_string=" return result\n" start_line=80 end_line=83Mode selection:
Mode | Parameters | Best for |
Find/replace |
| Unique strings, no line numbers known |
Scoped |
| Shorter context when |
Line replace |
| Maximum token savings when line numbers are known |
# Mode A — find/replace: [old, new]
batch_edit path="/src/app.py" edits='[["old1","new1"],["old2","new2"]]'
# Mode B — scoped: [old, new, start_line, end_line]
batch_edit path="/src/app.py" edits='[["pass","return x",42,42]]'
# Mode C — line replace: [null, new, start_line, end_line]
batch_edit path="/src/app.py" edits='[[null," return result\n",80,83]]'
# Mixed modes in one call (object syntax also supported)
batch_edit path="/src/app.py" edits='[
["old1", "new1"],
{"old": "pass", "new": "return x", "start_line": 42, "end_line": 42},
{"old": null, "new": " return result\n", "start_line": 80, "end_line": 83}
]' auto_format=truebatch_read paths="/src/a.py,/src/b.py" max_total_tokens=50000
batch_read paths='["/src/a.py","/src/b.py"]' priority="/src/main.py"
batch_read paths="/src/*.py" max_total_tokens=30000Expands simple globs, honors
priority, enforcesmax_total_tokens, and reports skipped paths with recovery hints.Unchanged files are collapsed into the summary instead of repeating content.
search query="authentication middleware logic" k=5
glob pattern="**/*.py" directory="./src" cached_only=true
grep pattern="class Cache" path="src/**/*.py"Configuration
Environment Variables
Variable | Default | Description |
|
| Logging verbosity ( |
|
| Response detail ( |
|
| Global response token cap ( |
|
| Seconds before tool call times out (auto-resets executor) |
|
| Max bytes returned by read operations |
|
| Max cache entries before LRU-K eviction |
|
| Embedding hardware: |
|
| FastEmbed model for search/similarity (options) |
|
| Use OpenAI-compatible remote embeddings instead of local FastEmbed |
|
| OpenAI-compatible base URL; default targets Ollama |
|
| API key for the remote embedding provider |
|
| Remote embedding model name |
| (inferred) | Optional requested/expected remote embedding dimension |
| (platform) | Override cache/database directory path |
See docs/env_variables.md for detailed descriptions, model selection guidance, and examples.
Safety Limits
Limit | Value | Protects Against |
| 10 MB | Memory exhaustion via large writes |
| 10 MB | Memory exhaustion via large file edits |
| 10,000 | CPU exhaustion via unbounded |
MCP Server Config
{
"mcpServers": {
"semantic-cache": {
"command": "uvx",
"args": ["semantic-cache-mcp"],
"env": {
"LOG_LEVEL": "INFO",
"TOOL_OUTPUT_MODE": "compact",
"MAX_CONTENT_SIZE": "100000",
"EMBEDDING_DEVICE": "cpu",
"EMBEDDING_MODEL": "BAAI/bge-small-en-v1.5"
}
}
}
}Cache location: ~/.cache/semantic-cache-mcp/ (Linux), ~/Library/Caches/semantic-cache-mcp/ (macOS), %LOCALAPPDATA%\semantic-cache-mcp\ (Windows). Override with SEMANTIC_CACHE_DIR.
How It Works
┌──────────┐ ┌────────────┐ ┌──────────────────────────┐
│ Claude │────▶│ smart_read │────▶│ stat() + cache lookup │
│ Code │ │ │ │ (BEFORE any disk read) │
└──────────┘ └────────────┘ └──────────────────────────┘
│
┌────────────────┼─────────────────┬──────────────────┐
▼ ▼ ▼ ▼
┌──────────┐ ┌──────────┐ ┌──────────┐ ┌────────────┐
│ mtime │ │ mtime │ │ Changed │ │ New / │
│ match │ │ drift, │ │ content │ │ Large │
│ FAST │ │ hash │ │ → diff │ │ → summary │
│ PATH │ │ match │ │ (80-95%) │ │ or full │
│ ~5 tok │ │ ~5 tok │ └──────────┘ └────────────┘
│ (99%) │ │ (99%) │
│ ~1 ms │ │ ~1 ms │
│ no I/O │ │ +update │
└──────────┘ └──────────┘search works the same way. An in-session LRU keyed on (query, k, directory)
returns warm hits in ~10 µs; misses fall through to embed + BM25 + HNSW. Every
cache mutation (put, clear, delete_path, update_mtime) bumps the LRU, so
callers never see a result that predates a write.
Performance
Measured on this project's 43 source files (168,614 tokens), CPU embeddings, i9-13900K, commit 5cd7100. Reproducible via --json output for CI diffing.
Token savings — 98.5% overall (phases 2–6)
Phase | Scenario | Savings |
Overall (cached, phases 2–6) | Aggregate token reduction | 98.5% |
Unchanged re-read | mtime match — fast path skips disk I/O | 98.9% |
Content hash | mtime drifted, BLAKE3 still matches | 98.9% |
Batch read | All files via | 98.9% |
Search previews | 5 queries × k=5, previews vs full reads | 98.3% |
Small edits | Real ~5% line changes in 30% of files | 97.3% |
Cold read | First read, no cache (baseline) | 0% |
Latency — unchanged reads ~1 ms; repeat searches ~10 µs
Operation | p50 | Notes |
Single unchanged read (fast path) | 1.1 ms | mtime + cache hit; no disk I/O |
Single diff read (changed file) | 1.0 ms | hash check + unified diff |
Search k=5 (cache hit) | < 0.01 ms | in-session LRU; 2,000×+ vs cold |
Search k=5 (cache miss) | 5.6 ms | embed query + hybrid BM25/HNSW |
Edit (scoped find/replace) | 3.3 ms | uses cached content |
Grep (literal | 1.4 ms | FTS5 over cached corpus |
Grep (regex) | 2.1 ms | regex compiled once |
Batch read (43 files, diff mode) | 40.2 ms | one ONNX inference for all new/changed files |
Unchanged re-read (43 files) | 26.9 ms | whole-corpus pass |
Cold read (43 files, total) | 1,990 ms | includes disk I/O, tokenisation, embedding |
Write (200-line file) | 49.1 ms | creates + caches + embeds |
Single embedding (largest file) | 47 ms | ONNX, single thread |
Model warmup (one-time) | 195 ms | startup only |
Run benchmarks yourself:
uv run python benchmarks/benchmark_token_savings.py # token savings
uv run python benchmarks/benchmark_performance.py # operation latencySee docs/performance.md for full benchmarks and methodology.
Documentation
Guide | Description |
Component design, algorithms, data flow | |
Optimization techniques, benchmarks | |
Threat model, input validation, size limits | |
Programmatic API, custom storage backends | |
Common issues, debug logging | |
All configurable env vars with defaults and examples |
Contributing
git clone https://github.com/CoderDayton/semantic-cache-mcp.git
cd semantic-cache-mcp
uv sync
uv run pytestSee CONTRIBUTING.md for commit conventions, pre-commit hooks, and code standards.
License
MIT License — use freely in personal and commercial projects.
Credits
Built with FastMCP 3.0 and:
FastEmbed — local ONNX embeddings (configurable, default BAAI/bge-small-en-v1.5)
SimpleVecDB ≥ 2.6.0 — HNSW vector storage with FTS5 keyword search, atomic
delete_collection, and opt-in embedding persistence (store_embeddings=True)Semantic summarization based on TCRA-LLM (arXiv:2310.15556)
BLAKE3 cryptographic hashing for content freshness
LRU-K frequency-aware cache eviction
Maintenance
Appeared in Searches
Latest Blog Posts
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