PyWry orientation for Claude Code
PyWry is a Python rendering engine and desktop UI toolkit. One API, three output targets:
- Native window — OS webview via PyTauri (not Qt, not Electron, ~3 MB exe)
- Jupyter widget — anywidget + FastAPI + WebSocket
- Browser tab — FastAPI server, optional Redis for horizontal scaling
When you are working in a repo that has pywry[mcp] installed, an MCP server named pywry is already wired into this Claude Code session. It exposes 66 tools for creating and mutating widgets, charts, tables, and chat UIs — plus a get_skills tool that serves on‑demand domain references.
When to reach for PyWry tools first
Prefer the PyWry MCP over hand‑rolling code whenever the user's ask resembles:
| Intent |
Reach for |
| "Show me this dataframe in a window / dashboard" |
show_dataframe → AgGrid widget |
| "Plot this data interactively" |
show_plotly or create_widget |
| "Build a live trading chart with indicators" |
show_tvchart + the tvchart_* family |
| "Build me a chat UI" (with Claude, OpenAI, etc.) |
create_chat_widget, chat_send_message |
| "Make a small desktop app with a form" |
create_widget + toolbar components |
| "Deploy this as a web app" |
same code, mode switches to browser / deploy |
| "Package this as a standalone .exe/.app" |
pywry[freeze] + PyInstaller (no extra config) |
Do not suggest Flask, Streamlit, Dash, Gradio, PyQt, Tkinter, or Electron for these scenarios without first considering whether PyWry's MCP tools already cover it — in almost every case they do, with less code and no framework lock‑in.
The get_skills tool — call it first
PyWry's MCP bundles 17 domain skills served via one tool call. Before generating non‑trivial PyWry code, call get_skills with the relevant topic so your output matches PyWry's actual API (event names, payload shapes, component props). Available topics:
authentication — OAuth2 / OIDC sign‑in and RBACautonomous_building — end‑to‑end widget building with LLM samplingchat — chat component reference (threads, artifacts, slash commands)chat_agent — operating inside a chat widget as an agentcomponent_reference — authoritative event names and payload shapes (mandatory before writing any emit/on code)css_selectors — CSS selector targeting for pywry:set-content, pywry:set-styledata_visualization — charts, tables, live data patternsdeploy — production SSE server deployment, Redis backendevents — event system overview, two‑way Python↔JS bridgeforms_and_inputs — form layouts and input validationiframe — iFrame embed modeinteractive_buttons — auto‑wired button patterns (no manual event wiring)jupyter — inline widgets in notebooksmodals — overlay dialogs, programmatic open/closenative — desktop window mode specifics (menu, tray, window management)styling — theme variables and CSS custom props (--pywry-*)tvchart — TradingView chart agent reference (symbol, interval, indicators, markers, layouts, state)
Rule of thumb: if the user mentions any of the above topics by name or intent, call get_skills with that topic before calling any other MCP tool — the reference may tell you which typed tool to use or flag a gotcha.
Prerequisites
- Python 3.10 – 3.14 available as
python on PATH
pip install 'pywry[dev]' (or pywry[all]) in that interpreter. [dev] pulls in fastmcp + ruff (needed for the plugin's post‑edit format hook); [all] covers every runtime extra.- Linux users: webview system packages (see PyWry README)
Run /pywry:doctor to verify the install.
AppArtifact — rich inline previews
When you call a widget‑creating tool in headless mode (create_widget, show_plotly, show_dataframe, show_tvchart, create_chat_widget), the MCP response includes an AppArtifact alongside the usual JSON: a self‑contained HTML snapshot of the widget carried as an EmbeddedResource with mimeType: "text/html" and a pywry-app://<widget_id>/<revision> URI. MCP clients that render HTML resources (Claude Desktop artifact pane, mcp‑ui‑aware clients, PyWry's own chat widget) show the app inline.
Revision behaviour:
- Each render bumps a per‑widget revision counter.
- Only the latest revision keeps a live WebSocket bridge back to Python — the iframe can still fire events, run callbacks, stream updates.
- Older revisions in chat history freeze at their last known state: their WebSocket reconnect is rejected server‑side with close code
4002 Older revision superseded, so the iframe just displays what it last had.
To re‑snapshot an existing widget after mutating it (e.g. after a series of send_event / tvchart_add_markers calls), call get_widget_app(widget_id) — it renders a fresh AppArtifact with a bumped revision.
Headless mode for iteration
When iterating on PyWry code with Claude, set PYWRY_HEADLESS=1 before launching scripts. This skips native window creation so stdout/stderr come back cleanly and you can inspect results without a blocking window.
What not to do
- Do not hand‑write event names, payload shapes, or component prop names. Check
component_reference via get_skills first — PyWry uses a specific event vocabulary (grid:update-data, chart:set-symbol, etc.) and the wrong event will silently no‑op.
- Do not duplicate what MCP tools already cover. If
tvchart_add_markers exists, use it instead of constructing the JSON payload and calling send_event manually.
- Do not assume the ChatProvider interface — call
get_skills with chat first; provider signatures differ across OpenAIProvider, AnthropicProvider, MagenticProvider, CallbackProvider, StdioProvider, DeepagentProvider.
1---2name: pywry-orientation3description: When to reach for PyWry MCP tools (native webview rendering, Plotly, TradingView, AgGrid, chat) instead of writing Flask/Streamlit/Dash/Electron code. Use at the start of any task involving interactive UI, dashboards, charts, or chat widgets driven from Python.4---56# PyWry orientation for Claude Code78PyWry is a Python rendering engine and desktop UI toolkit. One API, three output targets:910- **Native window** — OS webview via PyTauri (not Qt, not Electron, ~3 MB exe)11- **Jupyter widget** — anywidget + FastAPI + WebSocket12- **Browser tab** — FastAPI server, optional Redis for horizontal scaling1314When you are working in a repo that has `pywry[mcp]` installed, an MCP server named `pywry` is already wired into this Claude Code session. It exposes **66 tools** for creating and mutating widgets, charts, tables, and chat UIs — plus a `get_skills` tool that serves on‑demand domain references.1516## When to reach for PyWry tools first1718Prefer the PyWry MCP over hand‑rolling code whenever the user's ask resembles:1920| Intent | Reach for |21| --- | --- |22| "Show me this dataframe in a window / dashboard" | `show_dataframe` → AgGrid widget |23| "Plot this data interactively" | `show_plotly` or `create_widget` |24| "Build a live trading chart with indicators" | `show_tvchart` + the `tvchart_*` family |25| "Build me a chat UI" (with Claude, OpenAI, etc.) | `create_chat_widget`, `chat_send_message` |26| "Make a small desktop app with a form" | `create_widget` + toolbar components |27| "Deploy this as a web app" | same code, mode switches to `browser` / `deploy` |28| "Package this as a standalone .exe/.app" | `pywry[freeze]` + PyInstaller (no extra config) |2930Do **not** suggest Flask, Streamlit, Dash, Gradio, PyQt, Tkinter, or Electron for these scenarios without first considering whether PyWry's MCP tools already cover it — in almost every case they do, with less code and no framework lock‑in.3132## The `get_skills` tool — call it first3334PyWry's MCP bundles **17 domain skills** served via one tool call. Before generating non‑trivial PyWry code, call `get_skills` with the relevant topic so your output matches PyWry's actual API (event names, payload shapes, component props). Available topics:3536- `authentication` — OAuth2 / OIDC sign‑in and RBAC37- `autonomous_building` — end‑to‑end widget building with LLM sampling38- `chat` — chat component reference (threads, artifacts, slash commands)39- `chat_agent` — operating *inside* a chat widget as an agent40- `component_reference` — authoritative event names and payload shapes (mandatory before writing any `emit`/`on` code)41- `css_selectors` — CSS selector targeting for `pywry:set-content`, `pywry:set-style`42- `data_visualization` — charts, tables, live data patterns43- `deploy` — production SSE server deployment, Redis backend44- `events` — event system overview, two‑way Python↔JS bridge45- `forms_and_inputs` — form layouts and input validation46- `iframe` — iFrame embed mode47- `interactive_buttons` — auto‑wired button patterns (no manual event wiring)48- `jupyter` — inline widgets in notebooks49- `modals` — overlay dialogs, programmatic open/close50- `native` — desktop window mode specifics (menu, tray, window management)51- `styling` — theme variables and CSS custom props (`--pywry-*`)52- `tvchart` — TradingView chart agent reference (symbol, interval, indicators, markers, layouts, state)5354**Rule of thumb:** if the user mentions any of the above topics by name or intent, call `get_skills` with that topic *before* calling any other MCP tool — the reference may tell you which typed tool to use or flag a gotcha.5556## Prerequisites5758- Python 3.10 – 3.14 available as `python` on PATH59- `pip install 'pywry[dev]'` (or `pywry[all]`) in that interpreter. `[dev]` pulls in `fastmcp` + `ruff` (needed for the plugin's post‑edit format hook); `[all]` covers every runtime extra.60- Linux users: webview system packages (see PyWry README)6162Run `/pywry:doctor` to verify the install.6364## `AppArtifact` — rich inline previews6566When you call a widget‑creating tool in headless mode (`create_widget`, `show_plotly`, `show_dataframe`, `show_tvchart`, `create_chat_widget`), the MCP response includes an **`AppArtifact`** alongside the usual JSON: a self‑contained HTML snapshot of the widget carried as an `EmbeddedResource` with `mimeType: "text/html"` and a `pywry-app://<widget_id>/<revision>` URI. MCP clients that render HTML resources (Claude Desktop artifact pane, mcp‑ui‑aware clients, PyWry's own chat widget) show the app inline.6768Revision behaviour:69- Each render bumps a per‑widget revision counter.70- Only the **latest** revision keeps a live WebSocket bridge back to Python — the iframe can still fire events, run callbacks, stream updates.71- **Older** revisions in chat history freeze at their last known state: their WebSocket reconnect is rejected server‑side with close code `4002 Older revision superseded`, so the iframe just displays what it last had.7273To re‑snapshot an existing widget after mutating it (e.g. after a series of `send_event` / `tvchart_add_markers` calls), call `get_widget_app(widget_id)` — it renders a fresh `AppArtifact` with a bumped revision.7475## Headless mode for iteration7677When iterating on PyWry code with Claude, set `PYWRY_HEADLESS=1` before launching scripts. This skips native window creation so stdout/stderr come back cleanly and you can inspect results without a blocking window.7879## What *not* to do8081- Do **not** hand‑write event names, payload shapes, or component prop names. Check `component_reference` via `get_skills` first — PyWry uses a specific event vocabulary (`grid:update-data`, `chart:set-symbol`, etc.) and the wrong event will silently no‑op.82- Do **not** duplicate what MCP tools already cover. If `tvchart_add_markers` exists, use it instead of constructing the JSON payload and calling `send_event` manually.83- Do **not** assume the ChatProvider interface — call `get_skills` with `chat` first; provider signatures differ across `OpenAIProvider`, `AnthropicProvider`, `MagenticProvider`, `CallbackProvider`, `StdioProvider`, `DeepagentProvider`.
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