sem

Entity-level diffs on top of Git. Instead of line 43 changed, sem tells you function validateToken was added in src/auth.ts.

sem diff

┌─ src/auth/login.ts ──────────────────────────────────
│
│  ⊕ function  validateToken          [added]
│  ∆ function  authenticateUser       [modified]
│  ⊖ function  legacyAuth             [deleted]
│
└──────────────────────────────────────────────────────

┌─ config/database.yml ─────────────────────────────────
│
│  ∆ property  production.pool_size   [modified]
│    - 5
│    + 20
│
└──────────────────────────────────────────────────────

Summary: 1 added, 1 modified, 1 deleted across 2 files

Install

npm install -g @ataraxy-labs/sem

Or run directly:

npx @ataraxy-labs/sem diff

Usage

Works in any Git repo. No setup required.

# Semantic diff of working changes
sem diff

# Staged changes only
sem diff --staged

# Specific commit
sem diff --commit abc1234

# Commit range
sem diff --from HEAD~5 --to HEAD

# JSON output (for AI agents, CI pipelines)
sem diff --format json

# Semantic commit history
sem log -n 5

# SQL queries against stored changes
sem init
sem diff --store
sem query "SELECT entity_type, entity_name, change_type FROM changes"

What It Parses

Everything else falls back to chunk-based diffing.

How Matching Works

Three-phase entity matching:

1. Exact ID match: same entity in before/after → modified or unchanged
2. Content hash match: same content, different name → renamed or moved
3. Fuzzy similarity: >80% token overlap → probable rename

This means sem detects renames and moves in addition to adds and deletes.

JSON Output

sem diff --format json

{
  "summary": {
    "fileCount": 2,
    "added": 1,
    "modified": 1,
    "deleted": 1,
    "total": 3
  },
  "changes": [
    {
      "entityId": "src/auth.ts::function::validateToken",
      "changeType": "added",
      "entityType": "function",
      "entityName": "validateToken",
      "filePath": "src/auth.ts"
    }
  ]
}

SQL Queries

sem init
sem log --store
sem query "SELECT change_type, count(*) as n FROM changes GROUP BY change_type"

change_type          │ n
─────────────────────────────────
added                │ 29
deleted              │ 2
modified             │ 7

Architecture

• tree-sitter (native) for code parsing. Not WASM.
• better-sqlite3 for storage. WAL mode, fast transactions.
• simple-git for Git operations
• Plugin system. Add your own parsers.

View on GitHub · Read the technical deep dive · MIT License