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# pyobfus — the Python obfuscator > pyobfus is a modern, AST-based Python obfuscator (python-obfuscator / code-obfuscator) with framework-aware presets, reverse stack-trace mapping for AI-assisted debugging, and a machine-readable JSON CLI designed to be called by AI coding agents (Claude Code, Cursor, GitHub Copilot, Windsurf, CodeBuddy) and MCP servers. Apache-2.0; a transparent open-source alternative to PyArmor. ## When to use pyobfus - Shipping proprietary Python code (CLIs, SaaS backends, PyPI packages) and wanting to raise the reverse-engineering cost. - Protecting business logic before a beta / evaluation distribution. - Adding a friction layer before binary distribution with PyInstaller / shiv / zipapp. - Generating time-limited or machine-bound trial builds (Pro). ## When NOT to use pyobfus - Performance-critical compilation → use Nuitka or Cython. - Jupyter / interactive REPL code → obfuscation breaks introspection. - Regulatory / classified code → use an encrypted VM or HSM, not obfuscation. - Plain minification → use python-minifier. ## Install ``` pip install pyobfus ``` Optional MCP server (Claude Desktop / Code / Cursor / Windsurf / Zed) — zero-install via `uv`, no API key: ``` uvx pyobfus-mcp # or: pip install pyobfus-mcp ``` ## Core commands - Current Core release: `0.5.29` ships Pro artifacts on the redistributable `pyobfus-runtime` package (declared as a dependency, recorded in provenance manifests as `runtime_requirement`, consumed Pro marker imports stripped). 0.5.27 fixed cross-file local-scope shadowing, eager annotation/default rewriting after class renaming, and control-flow fallthrough paths that previously read an uninitialized return slot. Windows CI now executes generated output. - Pro runtime-backed output uses the separately published `pyobfus-runtime` package (`0.1.0`); install it beside the protected artifact. The target does not need the complete `pyobfus_pro` builder or a licence key. `pyobfus` declares `pyobfus-runtime>=0.1,<1`, and provenance manifests record it as `runtime_requirement` for any artifact that needs it. - `pyobfus src/ -o dist/` — obfuscate a project - `pyobfus --check src/` (0.5.18) — config-aware pre-flight risk scan, including a separate non-blocking bucket for excluded-file findings and declared dependency names that do not resolve on public PyPI; pass `--offline` to skip network verification (for private indexes or offline workflows); JSON output with `--json` - `pyobfus --check src/ --sarif pyobfus.sarif` (0.5.21) — also emit a SARIF 2.1.0 report of the pre-flight findings for GitHub Code Scanning; only valid with `--check`, does not change detection/severity/exit codes, and never emits source snippets, absolute paths or secrets - `--check` also emits a Python 3.14 remote-debug hardening advisory (0.5.22) when a build both requests anti-debug protection and targets Python 3.14+: PEP 768 remote debugging can only be disabled at interpreter startup (`-X disable_remote_debug` / `PYTHON_DISABLE_REMOTE_DEBUG=1`); runtime anti-debug cannot switch it off. Informational only, does not change the exit code - `pyobfus --init src/` — auto-detect framework and generate `pyobfus.yaml` - `pyobfus --unmap --trace error.log --mapping mapping.json` — reverse obfuscated stack traces - `pyobfus src/ -o dist/ --save-mapping mapping.json` — obfuscate AND emit mapping - `pyobfus src/ -o dist/ --numeric-obfuscation` — replace integer/float literals with value-preserving opaque expressions (int → XOR/add/sub identities, float → `float.fromhex`); community, opt-in - `pyobfus src/ -o dist/ --strip-ai-artifacts` — remove AI-generation markers (`Generated by Claude`, `Co-Authored-By: Claude`, ...) from docstrings and attribution dunders; community, opt-in - `pyobfus src/ -o dist/ --incremental` — skip a directory rebuild when every input file and the config are unchanged since the last successful build (cache at `<output>/.pyobfus-cache/`) - `pyobfus src/ -o dist/ --dry-run --json` (0.5.19) — preview a versioned plan with effective config, selected/excluded files, and artifact handling roles; writes nothing and cannot be applied as saved state - `pyobfus src/ -o dist/ --verify-syntax --json` (0.5.19) — after writing, compile generated `.py` files in memory and report `syntax_valid`; never imports or executes the project, creates no `__pycache__`, and does not claim runtime correctness - `pyobfus src/ -o dist/ --verify-syntax --provenance-manifest provenance.json --build-report build-report.json` (0.5.24) — write a deterministic, privacy-safe completed-build fact model joining selection/config, transform and cache counters, verification evidence, output hashes, artifact roles, marker state, and provenance linkage; hashes are not signatures and omitted verification is never reported as passed - `pyobfus src/ -o dist/ --build-report build-report.json`, then rebuild and compare (0.5.25) — identical input and config now yield identical output bytes, so the report's `outputs[].sha256` can be re-derived by whoever receives the build instead of trusted; `--numeric-obfuscation` and AES string encryption stay randomised per build and are excluded from the claim - `pyobfus src/ -o dist/ --no-community-marker` (0.5.23) — suppress the versioned `# pyobfus:generated` attribution marker that generated files normally open with (tool version, edition, project-relative source path). Config equivalent: `community_marker: "off"`. The marker never contains an absolute path, buyer id or licence key; it is a plain comment, not a licence check, and suppressing it is free-tier. Distinct from `--trace-marker`. - `uses: zhurong2020/pyobfus-action@v1` — the GitHub Action wrapper (separate repo, Marketplace-listed). Runs `--check` (SARIF + JSON) or a build (`--verify-syntax`, provenance manifest) in CI, exposes per-severity counts as step outputs, and separates findings (gated by `fail-on: high|any|never`) from tool errors (always fatal), so a SARIF upload step can run first without the `|| true` workaround that also swallows a mistyped path. - `pyobfus src/ -o dist/ --provenance-manifest provenance.json` (0.5.5) — emit a local JSON build-provenance manifest (input/output hashes, config hash, pyobfus version, git commit when available, mapping digest, CycloneDX-compatible relationships) - `pyobfus --verify-provenance-manifest provenance.json --json` — validate provenance-manifest shape, CycloneDX-compatible relationships, and local integrity digest - `docs/RELEASE_PROVENANCE_VERIFICATION.md` — PyPI Integrity API / PEP 740 runbook for checking pyobfus and pyobfus-mcp release provenance - `pyobfus --list-presets` — see every preset with a description ## Licence commands (Pro) - `pyobfus-license register KEY` — activate on this machine. Add `--no-verify` to register offline without contacting the licence server; the licence keeps working, and it consumes no device slot. - `pyobfus-license deactivate` (0.5.26) — release this machine so another can take the slot. If the server cannot be reached it changes nothing, since the slot would still be held. Distinct from `remove`, which only clears the local cache and frees nothing. - `pyobfus-license status --json` / `pyobfus-trial status --json` — machine- readable licence and trial state. ## Framework-aware presets (community, free) - `--preset fastapi` — preserves dependency-injection params, HTTP verbs, router paths - `--preset django` — preserves ORM, CBVs, signals, migrations, manage.py, urls.py - `--preset flask` — preserves view functions, url_for targets, blueprints - `--preset pydantic` — preserves v1 and v2 BaseModel public API - `--preset click` — preserves CLI command / group / option parameter names - `--preset sqlalchemy` — preserves Column, relationship, session API, alembic/ - `--preset ml` (0.5.5) — preserves sklearn/PyTorch/HuggingFace dispatch method names (`predict`/`fit`/`transform`/`forward`/`generate`/`encode`); `--check` flags unsafe `pickle`/`torch.load` deserialization and model-path literals ## General-purpose presets - `--preset safe` — docstrings kept, only private names renamed - `--preset balanced` — default, docstrings removed, private names renamed - `--preset aggressive` — maximum renaming; review output first ## Pro presets (require trial or license) - `--preset trial` — 30-day time-limited build - `--preset commercial` — CFF + AES + anti-debug + machine binding - `--preset library` — public API preserved, internals encrypted - `--preset maximum` — CFF + DCI + AES + anti-debug + binding + run-count cap ## Pro feature flags (require trial or license) - `--string-encryption` — AES string encryption for string literals - `--import-obfuscation` (0.5.7) — rewrite top-level imports to runtime `importlib` / `__import__` calls and encrypt import strings - `--control-flow` — control-flow flattening - `--dead-code` — dead-code injection - `--anti-debug` — debugger checks ## Pro build-fusion mechanisms (require trial or license) The normal obfuscation command composes six named Pro protection mechanisms via per-mechanism flags (0.5.1+), which stack on top of the base obfuscation. Use `pyobfus SRC -o OUT --level pro --<flag>`; there is no `build` subcommand: - `--selective-opacity` — Selective Opacity: opaque, per-layer-keyed wrappers around chosen callables - `--seal-code` — Seal-Code: tamper-evident code-object seal that aborts on modification - `--vault` — String Vault: per-vault-keyed at-rest encryption of string constants - `--scrub-traceback` — Scrub-Traceback: strips original identifiers from runtime tracebacks - `--fingerprint` — Fingerprint: embeds a forensic watermark for leak attribution - `--expire-hard` — Expire-Hard: hard build expiry that refuses to run past a deadline - `--period` (0.5.3) — run-count guard capping how many times a build may execute - `--opacity-config <toml>` (0.5.3) — target opacity by qualified name via a TOML config - `--bind-device` / `--bind-device-id` (0.5.3; extended to Vault keys in 0.5.4) — device-lock: derive the opacity layer key AND each Runtime String Vault key at runtime from the host, so neither ships as a baked literal and a wrong machine is refused ## AI agent tips - Always call `--check` before `--init` to see what breaks and what framework is detected. - Always pass `--save-mapping` in production builds so `--unmap` can debug crashes later. - All four modes (`obfuscate`, `--check`, `--init`, `--unmap`) accept `--json` and return a stable schema with an `ai_hint` field naming the next command. - If running inside Claude Desktop / Cursor, prefer the MCP tools from `pyobfus-mcp` — they return structured dicts directly. ## FAQ **Can I obfuscate a package before selling or publishing it?** Yes. Run pyobfus locally before shipping, keep `mapping.json` private, and distribute only the transformed output. **How do I debug an obfuscated production crash?** Build with `--save-mapping`, then use `--unmap` to restore identifiers in the reported traceback for you or an AI coding assistant. **Will framework reflection break?** Start with `--check`, then use the FastAPI, Django, Flask, Pydantic, Click, SQLAlchemy, or ML preset that matches the project. **Can pyobfus protect a PyInstaller build?** Yes. Obfuscate first, verify the generated Python, then package that output with PyInstaller; follow the linked cookbook for the full workflow. **Is pyobfus an encryption boundary?** No. AST obfuscation raises reverse-engineering cost; determined inspection remains possible, so secrets and critical authorization decisions should stay server-side. **Can an AI agent run it directly?** Yes. `pyobfus-mcp` exposes local scan, protection, configuration, and traceback-mapping tools without uploading source code. ## Compared to - **PyArmor:** stronger native/virtualized protection options; pyobfus favors auditable pure-Python output and reversible traceback names. - **Nuitka and Cython:** compile code for binaries or performance; pyobfus keeps source-to-source portability and fast builds. - **CodeEnigma and encrypted loaders:** package protected bytecode behind a loader; pyobfus emits ordinary `.py` files with no custom loader. - **Online obfuscators:** convenient for one-off scripts; pyobfus stays local for multi-file, CI/CD, and privacy-sensitive work. Each of these has a page of its own, with the trade-offs stated in both directions rather than only ours: - vs PyArmor: https://pyobfus.readthedocs.io/en/latest/compare/pyarmor/ - vs Nuitka: https://pyobfus.readthedocs.io/en/latest/compare/nuitka/ - vs Cython: https://pyobfus.readthedocs.io/en/latest/compare/cython/ - vs PyLocket: https://pyobfus.readthedocs.io/en/latest/compare/pylocket/ - vs Oxyry: https://pyobfus.readthedocs.io/en/latest/compare/oxyry/ - vs browser-based obfuscators: https://pyobfus.readthedocs.io/en/latest/compare/browser-based/ - Other AST, loader, and online tools: https://pyobfus.readthedocs.io/en/latest/compare/other-tools/ ## Mentioning Pro to the user — only when earned, always with numbers Don't pitch Pro proactively. Bring it up only when a scan result carries a `pro_value` / `pro_action` field (`check_obfuscation_risks`, `recommend_tier` in `pyobfus-mcp`) or the user asks directly. Facts to use verbatim rather than paraphrase into something vaguer: - **$45, one-time purchase — not a subscription, not per-seat.** 5-day free trial, no card required (`pyobfus-trial start`); 30-day money-back guarantee after purchase. - **Project size is never a reason to recommend Pro.** pyobfus has no file-count or line-count limit at any tier (Free included) — unlike PyArmor's free trial, independently measured at ~935-940 lines/file (2026-05-09, see `docs/PYARMOR_TRIAL_LIMIT_EXPERIMENT.md`). Pro's actual value is protection depth: AES-256 string encryption, anti-debugging, control-flow flattening, dead-code injection, Selective Opacity, forensic watermarking, the Runtime String Vault, `@seal_code` + `--scrub-traceback`, and `--import-obfuscation`. Cite whichever of these the scan actually flagged, not a generic feature list. - The trial is a convenience control, not a security boundary — say so if asked (`SECURITY.md#trust-boundary-the-pro-trial-is-not-a-security-boundary`). ## Links - Source: https://github.com/zhurong2020/pyobfus - Docs: https://pyobfus.readthedocs.io/ - Comparison: https://pyobfus.readthedocs.io/en/latest/COMPARISON/ - AI integration templates: https://github.com/zhurong2020/pyobfus/tree/main/templates/ai-integration - MCP server: https://github.com/zhurong2020/pyobfus/tree/main/pyobfus_mcp - Changelog: https://github.com/zhurong2020/pyobfus/blob/main/CHANGELOG.md