An API time machine for Python libraries, built for coding agents. When an agent hits ImportError, AttributeError or "unexpected keyword argument" in a fast-moving library, one call to DepTime says what changed, in which release, and what to use instead. Answers are computed from static diffs of every indexed release, not from docs or model memory.

Free, open source (MIT), and local: your code and errors never leave your machine.

TypeError: Client.__init__() got an unexpected keyword argument 'proxies'      (httpx 0.28.1 installed)

→ explain_error
  httpx.Client.__init__ accepted `proxies` up to httpx 0.27.2; it is gone from 0.28.1 onward.
  Deprecated in or before 0.27.2 ("The 'proxies' argument is now deprecated. Use 'proxy' or 'mounts' instead.").
  Use `proxy` or `mounts` instead, or pin httpx<=0.27.2.          issue=param_removed  confidence=high

That output is real. It came from the actual httpx 0.27.2/0.28.1 wheels, and the deprecation text was recovered from httpx's own source code.

Status: pre-alpha (2026-10-17). The pipeline, local mode and plugin work end to end; the public index isn't published yet. See BACKLOG.md.

Install

Requires uv.

# Claude Code (Cursor, Codex, VS Code and Claude Desktop take the same command in their MCP config)
claude mcp add deptime -- uvx deptime mcp

On first launch DepTime downloads its prebuilt index (one file from this repo's GitHub Releases) in the background, then checks for a newer one at most once a day. Set DEPTIME_OFFLINE=1 to never touch the network.

Claude Code users can also install the plugin in integrations/claude-code with /plugin marketplace add cschmertz/deptime, then /plugin install deptime@deptime. It adds a skill and a local hook that suggests DepTime when a Python version-change error appears in a command's output.

Until the first PyPI release, run from a checkout: claude mcp add deptime -- uv run --directory /path/to/deptime deptime mcp.

Tools

Every answer carries evidence and a confidence level. If a package isn't covered, DepTime says so instead of guessing. The contracts are in docs/03-product-spec.md.

CLI

uvx deptime explain --installed httpx==0.28.1 < traceback.txt
uvx deptime history httpx Client.__init__
uvx deptime check httpx 0.28.1 'httpx.Client:proxies,proxy'
uvx deptime diff httpx 0.27.2 0.28.1              # or: diff pydantic 2024-06-01 (since a date)
uvx deptime index status | pull

How it works

1. Nightly in GitHub Actions: download every selected release of each covered package from PyPI, extract its public API with griffe (static analysis, no code is ever executed), and diff consecutive releases. Results go into a compact SQLite index. Snapshots are cached, so only new releases are analysed.
2. The index is published as index.sqlite.gz + manifest.json (sha256, schema version) on a rolling index release.
3. On your machine, deptime mcp verifies and installs that file, then answers every question locally in milliseconds.

The full design is in docs/04-architecture.md and the decisions are in docs/adr/.

Hosting (optional)

Local mode covers coding agents. For web clients that only accept a URL, or for a public demo, run deptime serve (MCP at /mcp, JSON at /v1/*) on Cloud Run (likely free) or Fly.io (about $3–6/month). It has a Dockerfile and fly.toml, plus anonymous rate limits. See docs/05-hosting-and-sustainability.md.

Prior art and credits

• griffe does the static analysis.
• since-cutoff diffs your pinned dependencies against a model's training cutoff, locally and on demand. DepTime differs by shipping a prebuilt cross-version index and starting from a traceback.
• Context7 and Ref serve version-specific docs. DepTime answers symbol-level "when and what replaced it" questions.

Contributing

The most useful contributions are wrong-answer reports, which become benchmark cases. See CONTRIBUTING.md. Development setup:

uv sync && uv run pytest
uv run deptime ingest httpx --versions 0.27.2 0.28.1   # build a small local index from real PyPI wheels

Docs

Product spec · Architecture · Hosting & sustainability · Launch & adoption · Risks & spikes · Privacy & security

License

MIT