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 about 98% on cached reads, and get answers back in milliseconds.
Semantic Cache MCP is a Model Context Protocol server that puts every file operation behind one cache. The first read of a file seeds the cache and returns a content hash. After that, an unchanged file comes back as a short unchanged reply instead of the whole file, a changed file comes back as a unified diff, and a file that is too large is summarized down to its structure. Search and grep run over the same cached files, so the agent searches what it already read instead of going back to disk. Thirteen tools (read, read_image, batch_read, write, edit, edit_preview, batch_edit, search, grep, glob, delete, clear, stats) share that one cache-aware layer.
Why this exists
1. Reads stop costing tokens. The first read seeds the cache and hands back a content_hash. Send that hash back on the next read (as known_hash) and the server replies unchanged without resending the file. A modified file returns a unified diff with the changed line numbers. A file larger than the budget collapses to a structure-preserving summary instead of a blind cut at a byte offset.
2. Search and grep run on the cache, not the disk. Keyword search (BM25), 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.
Related MCP server: Ambiance MCP Server
Installation
Add to Claude Code settings (~/.claude.json):
Option 1: uvx (always runs the 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.
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 plus a |
| 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 BM25 keyword search that ranks cached files by relevance to a query. 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 to 199 onlyThree states, picked for you:
State | Response | Token cost |
First read | Full content plus a | Normal |
Unchanged |
| A few tokens |
Modified | Unified diff only | 5 to 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 the 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, searches only within the line range (a shorter old_string works)
edit path="/src/app.py" old_string="pass" new_string="return x" start_line=42 end_line=42
# Mode C: line replace, swaps the whole range with no old_string needed (most 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 W-TinyLFU eviction |
| (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"
}
}
}
}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 │
└──────────┘ └──────────┘Every read also returns a content_hash. Hand it back as known_hash on your
next read and the server answers unchanged from that fact alone, with no guess
about what it already sent you.
search works the same way. An in-session LRU keyed on (query, k, directory)
returns warm hits in ~10 µs; misses fall through to BM25 keyword search. 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 40 source files (177,509 tokens), i9-13900K, with the corpus held fixed across all phases. Reproducible via --json output for CI diffing.
Token savings: 98.9% overall (phases 2 to 6)
Phase | Scenario | Savings |
Overall (cached, phases 2 to 6) | Aggregate token reduction | 98.9% |
Unchanged re-read | mtime match, fast path skips disk I/O | 99.1% |
Content hash | mtime drifted, BLAKE3 still matches | 99.1% |
Batch read | All files via | 99.1% |
Search previews | 5 queries × k=5, previews vs full reads | 99.7% |
Small edits | Real ~5% line changes in 30% of files | 97.8% |
Cold read | First read, no cache (baseline) | 0% |
Latency: unchanged reads ~0.9 ms; repeat searches < 0.01 ms
Operation | p50 | Notes |
Single unchanged read (fast path) | 0.9 ms | mtime + cache hit; no disk I/O |
Single diff read (changed file) | 0.7 ms | hash check + unified diff |
Search k=5 (cache hit) | < 0.01 ms | in-session LRU; hundreds× vs cold |
Search k=5 (cache miss) | 1.5 ms | BM25 keyword search |
Edit (scoped find/replace) | 2.4 ms | uses cached content |
Grep (literal | 1.3 ms | FTS5 over cached corpus |
Grep (regex) | 3.7 ms | regex compiled once |
Batch read (40 files, diff mode) | 26.0 ms | chunk + tokenize new/changed files |
Unchanged re-read (40 files) | 18 ms | whole-corpus pass |
Cold read (40 files, total) | 125 ms | no embedding model, pure disk I/O plus tokenisation |
Write (200-line file) | 1.8 ms | creates + caches (no embed) |
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 it freely in personal and commercial projects.
Credits
Built with FastMCP 3.2+ and:
SQLite with FTS5 for keyword (BM25) full-text search, vendored as a small built-in store
Semantic summarization based on TCRA-LLM (arXiv:2310.15556)
BLAKE3 cryptographic hashing for content freshness
W-TinyLFU frequency-aware cache eviction
Maintenance
Appeared in Searches
Latest Blog Posts
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