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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.

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

read

Single-file cache-aware read. Returns full content plus a content_hash on the first read, a short unchanged reply when you pass back a matching known_hash, and a diff when the file changed. Supports offset/limit for targeted line recovery.

read_image

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 (SCMCP_MAX_IMAGE_BYTES).

delete

Single-path delete for one file or symlink, with cache eviction and dry_run=true. Intentionally does not support globs, recursive delete, or real-directory delete.

write

Full-file create or replace with cache refresh. Returns creation status or an overwrite diff, supports append=true, and can run formatters.

edit

Single-file exact edit using cached content. Supports scoped and line-range replacement plus dry_run=true. For multiple edits to the same file, prefer batch_edit.

batch_edit

Multiple exact edits in one file with partial success reporting. Preferred over repeated edit calls on the same file: single response, atomic, faster on large files.

edit_preview

Read-only probe that returns match count, line numbers, and small context snippets for a candidate old_string. Use before a costly edit to confirm anchor uniqueness.

Discovery

Tool

Description

search

Cache-only BM25 keyword search that ranks cached files by relevance to a query. Seed likely files first with batch_read.

glob

File discovery plus cache coverage. Use it to find candidates, then pass those paths into batch_read.

batch_read

Multi-file cache-aware read for seeding and retrieval. Handles globs, priorities, token budgets, unchanged suppression, and diff/full routing.

grep

Cache-only exact search with regex or literal matching, line numbers, and optional context. Best for symbols and exact strings.

Management

Tool

Description

stats

Cache metrics, session usage (tokens saved, tool calls), and lifetime aggregates.

clear

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 only

Three states, picked for you:

State

Response

Token cost

First read

Full content plus a content_hash

Normal

Unchanged

unchanged: true, returned when you pass back a matching known_hash

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=83

Mode selection:

Mode

Parameters

Best for

Find/replace

old_string + new_string

Unique strings, no line numbers known

Scoped

old_string + new_string + start_line/end_line

Shorter context when read gave you line numbers

Line replace

new_string + start_line/end_line (no old_string)

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=true
batch_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=30000
  • Expands simple globs, honors priority, enforces max_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

LOG_LEVEL

INFO

Logging verbosity (DEBUG, INFO, WARNING, ERROR)

TOOL_OUTPUT_MODE

compact

Response detail (compact, normal, debug)

TOOL_MAX_RESPONSE_TOKENS

0

Global response token cap (0 = disabled)

TOOL_TIMEOUT

30

Seconds before tool call times out (auto-resets executor)

MAX_CONTENT_SIZE

100000

Max bytes returned by read operations

MAX_CACHE_ENTRIES

10000

Max cache entries before W-TinyLFU eviction

SEMANTIC_CACHE_DIR

(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

MAX_WRITE_SIZE

10 MB

Memory exhaustion via large writes

MAX_EDIT_SIZE

10 MB

Memory exhaustion via large file edits

MAX_MATCHES

10,000

CPU exhaustion via unbounded replace_all

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 batch_read, 200K budget

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 def )

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 latency

See docs/performance.md for full benchmarks and methodology.


Documentation

Guide

Description

Architecture

Component design, algorithms, data flow

Performance

Optimization techniques, benchmarks

Security

Threat model, input validation, size limits

Advanced Usage

Programmatic API, custom storage backends

Troubleshooting

Common issues, debug logging

Environment Variables

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 pytest

See 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

Install Server
A
license - permissive license
A
quality
A
maintenance

Maintenance

Maintainers
Response time
5dRelease cycle
20Releases (12mo)
Commit activity

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