Flutter Slipstream

Flutter Slipstream is an agentic plugin that makes AI coding agents more effective for Dart and Flutter projects. It enables live app introspection for Flutter apps: screenshots, widget-tree inspection, tap/type/scroll interaction, and error capture, as well as Dart package API summarization for agents.

This addresses two structural problems that agents face:

• a lack of runtime visibility into a running Flutter app — agents can't see screenshots, inspect the widget tree, or verify that a state change took effect
• training cutoffs that leads to stale package choices and subtly wrong API signatures

Features

• Live app inspection — launch a Flutter app, take screenshots, inspect the widget tree, evaluate Dart expressions, and observe runtime errors, all from agent tool calls.
• Tap, type, and scroll — interact with the running app via semantics or widget finders; no test harness required.
• Accurate package APIs — retrieve any package's public API directly from the local pub cache as a compact Dart stub, version-matched and free of implementation noise.
• Package safety guidance — the bundled skill instructs agents to read pub command output for discontinued packages and outdated major versions, and take corrective action before bad dependencies land.

Installation

Coding Agent	Installing Slipstream
Claude Code *	claude plugin marketplace add devoncarew/slipstream claude plugin install flutter-slipstream@slipstream
GitHub Copilot	copilot plugin marketplace add devoncarew/slipstream copilot plugin install flutter-slipstream@slipstream
Gemini CLI	gemini extensions install https://github.com/devoncarew/flutter-slipstream

Note

If you see a "Failed to install plugin ... No ED25519 host key is known for github.com ... Host key verification failed" error, see anthropics/claude-code/issues/26588 / anthropics/claude-code/issues/50725 for possible workarounds.

Getting Started / Using Slipstream

Install the plugin, then work on Flutter projects as you normally would. No special prompting is required — Slipstream works in the background.

UI development workflow: When building or debugging UI, ask the agent to run the app. It will launch on a desktop device automatically, then iterate using hot reload after each source edit. Because the agent can take screenshots and inspect the widget tree, it catches overflow errors, layout surprises, and rendering regressions on its own — without you having to describe what went wrong.

Package hygiene: When an agent adds a package, the bundled skill guides it to read flutter pub add output for discontinued-package and outdated-version warnings, and to take corrective action (switching to the replacement package, or updating the version constraint) before the bad dependency lands.

Optional: richer instrumentation. Add package:slipstream_agent as a dependency for finder-based interactions (tap by key, type, or text), scroll support, and router-aware navigation. Without it, Slipstream still works well via semantics and the Flutter inspector protocol.

Tools

Flutter UI agent (inspector)

MCP commands for launching, inspecting, and interacting with a running Flutter app. Gives agents a Playwright-style interface to the running app: take screenshots, inspect the widget tree, evaluate arbitrary Dart expressions, and observe runtime errors with widget IDs.

Command	Description
run_app	Builds and launches the Flutter app.
reload	Applies source file changes to a running Flutter app.
get_output	Returns buffered app output and runtime events since the last call (or the last reload/restart).
take_screenshot	Captures a PNG screenshot of the running Flutter app.
inspect_layout	Use when debugging layout issues, overflow errors, or unexpected widget sizing.
evaluate	Evaluates a Dart expression on the running app's main isolate and returns the result as a string.
get_route	Returns the current navigator route stack with screen widget names and source locations.
navigate	Navigates the app to a route path.
perform_tap	Taps a widget located by a finder.
perform_set_text	Sets the text content of a text field located by a finder.
perform_scroll	Scrolls a Scrollable widget by a fixed number of logical pixels.
perform_scroll_until_visible	Scrolls a Scrollable until a target widget is visible in the viewport.
get_semantics	Returns a flat list of visible semantics nodes from the running Flutter app.
perform_semantic_action	Dispatches a semantics action on a widget by semantics node ID or label.
close_app	Stops the running Flutter app and releases its session.

Package API retrieval (packages)

Retrieves a package's public API surface directly from the local pub cache and returns it as a compact Dart stub — signatures only, no bodies, no private members. Agents get accurate, version-matched API information without reading raw source files or relying on training-data summaries.

Command	Description
package_summary	Returns API summaries for Dart or Flutter packages; start here to orient on an unfamiliar package.
library_stub	Returns the full public API for one library as a Dart stub (signatures only, no bodies).
class_stub	Returns the public API for a single named class, mixin, or extension as a Dart stub (signatures only, no bodies).

Package safety skill

The add-package skill fires automatically when an agent is about to add a Dart or Flutter package dependency. It instructs the agent to:

• Use flutter pub add rather than editing pubspec.yaml directly, so pub output is always visible.
• Read pub add output for (discontinued replaced by X) annotations and switch to the replacement package.
• Read pub add output for (X.Y.Z available) annotations on newly added direct dependencies, and run flutter pub outdated to confirm a major-version gap before proceeding.

Contributing

See CONTRIBUTING.md.