Semantic version control. 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
Build from source (requires Rust):
git clone https://github.com/Ataraxy-Labs/sem
cd sem/crates
cargo install --path sem-cliOr grab a binary from GitHub Releases.
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
# Read file changes from stdin (no git repo needed)
echo '[{"filePath":"src/main.rs","status":"modified","beforeContent":"...","afterContent":"..."}]' \
| sem diff --stdin --format json
# Only specific file types
sem diff --file-exts .py .rs
# Entity dependency graph
sem graph
# Impact analysis (what breaks if this entity changes?)
sem impact validateToken
# Entity-level blame
sem blame src/auth.ts13 programming languages with full entity extraction via tree-sitter:
| Language | Extensions | Entities |
|---|---|---|
| TypeScript | .ts .tsx |
functions, classes, interfaces, types, enums, exports |
| JavaScript | .js .jsx .mjs .cjs |
functions, classes, variables, exports |
| Python | .py |
functions, classes, decorated definitions |
| Go | .go |
functions, methods, types, vars, consts |
| Rust | .rs |
functions, structs, enums, impls, traits, mods, consts |
| Java | .java |
classes, methods, interfaces, enums, fields, constructors |
| C | .c .h |
functions, structs, enums, unions, typedefs |
| C++ | .cpp .cc .hpp |
functions, classes, structs, enums, namespaces, templates |
| C# | .cs |
classes, methods, interfaces, enums, structs, properties |
| Ruby | .rb |
methods, classes, modules |
| PHP | .php |
functions, classes, methods, interfaces, traits, enums |
| Fortran | .f90 .f95 .f |
functions, subroutines, modules, programs |
Plus structured data formats:
| Format | Extensions | Entities |
|---|---|---|
| JSON | .json |
properties, objects (RFC 6901 paths) |
| YAML | .yml .yaml |
sections, properties (dot paths) |
| TOML | .toml |
sections, properties |
| CSV | .csv .tsv |
rows (first column as identity) |
| Markdown | .md .mdx |
heading-based sections |
Everything else falls back to chunk-based diffing.
Three-phase entity matching:
- Exact ID match — same entity in before/after = modified or unchanged
- Structural hash match — same AST structure, different name = renamed or moved (ignores whitespace/comments)
- Fuzzy similarity — >80% token overlap = probable rename
This means sem detects renames and moves, not just additions and deletions. Structural hashing also distinguishes cosmetic changes (whitespace, formatting) from real logic changes.
{
"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"
}
]
}sem-core can be used as a Rust library dependency:
[dependencies]
sem-core = { git = "https://github.com/Ataraxy-Labs/sem", version = "0.3" }Used by weave (semantic merge driver) and inspect (entity-level code review).
- tree-sitter for code parsing (native Rust, not WASM)
- git2 for Git operations
- rayon for parallel file processing
- xxhash for structural hashing
- Plugin system for adding new languages and formats
MIT OR Apache-2.0