Instead of lines changed, sem tells you what entities changed: functions, methods, classes.

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 

brew install sem-cli

Or build from source (requires Rust):

git clone https://github.com/Ataraxy-Labs/sem cd sem/crates cargo install --path sem-cli

Or grab a binary from GitHub Releases.

Or run via Docker:

docker build -t sem . docker run --rm -it -u "$(id -u):$(id -g)" -v "$(pwd):/repo" sem diff

Works in any Git repo. No setup required. Also works outside Git for arbitrary file comparison.

# 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 # Plain text output (git status style) sem diff --format plain # JSON output (for AI agents, CI pipelines) sem diff --format json # Compare any two files (no git repo needed) sem diff file1.ts file2.ts # 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.ts

Replace git diff output with entity-level diffs. Agents and humans get sem output automatically without changing any commands.

# Set sem as your git diff tool git config --global diff.external sem-diff-wrapper # Create the wrapper script echo '#!/bin/sh sem diff "$2" "$5"' > ~/.local/bin/sem-diff-wrapper chmod +x ~/.local/bin/sem-diff-wrapper

Now git diff shows entity-level changes instead of line-level. No prompts, no agent configuration needed. Everything that calls git diff gets sem output automatically.

To disable and go back to normal git diff:

git config --global --unset diff.external

21 programming languages with full entity extraction via tree-sitter:

Plus structured data formats:

Everything else falls back to chunk-based diffing.

Three-phase entity matching:

1. Exact ID match — same entity in before/after = modified or unchanged
2. Structural hash match — same AST structure, different name = renamed or moved (ignores whitespace/comments)
3. 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.

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" } ] }

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

Want to add a new language? See CONTRIBUTING.md for a step-by-step guide.

MIT OR Apache-2.0