Osprey Agent: a Coding Agent on the pydantic-ai Port
The pydantic-ai agent engine is ported to Osprey's Python flavor, and a desktop coding agent runs on it with real file and command tools.
Osprey Blog
Language design and implementation notes.
An Accessibility Tree AI Agents Can Drive: Automated UI Testing by Label
Computer-use agents squint at screenshots; browser agents read the page's accessibility tree. Osprey's UI machines give every native control a role and a label, so tests and agents find the Play button by name and press it with real pointer events, with no window, browser or device.
How to Chromecast From a Mac to a TV: A Native Player Written in Osprey
Chrome only casts a tab, and macOS has no Cast button. This native Mac player finds your Chromecast or Google TV, plays an MP3 on it with full controls, and puts a moving spectrum on the TV instead of a still picture.
A Rust UI Framework Without Writing Rust: GPUI Apps as State Machines
GPUI is the GPU-rendered Rust UI framework behind the Zed editor. Osprey's UI machines put a whole GPUI app's interface in one data file: parallel state machines, a view, and skins drawn from an image atlas. The only code left is a small adapter.
Static Typing for Python-Style Code, Without Writing Type Hints
Static typing catches the wrong value before the program runs; dynamic typing finds out when that line executes. Osprey's Python flavor keeps def, lambda and f-strings, and infers every type and checks it at compile time. Here it is on a real 1,262-line port of a Chromecast sender.
Desktop Apps on GPUI, Written in Osprey
Osprey Native now has a GPUI host: the application is Osprey, Zed's Rust UI framework draws it with the GPU. A boids game holds 120 fps on an M4 Max, and a port of GPUI's painting example matches the Rust original pixel for pixel.
Python Packages in Osprey: NumPy, PyTorch-Style Code, and uv
Osprey's Python-flavor ports compile as Osprey packages. Real Python dependencies use uv. Here is how effects, scoped package names and verified locks connect the two.
Automated Testing with Osprey Hunt: Find the Input That Crashes
Give Osprey Hunt a program and an input bound. It explores branches with KLEE, records a failing input, and checks whether a native build reproduces the crash.
GPT-2 Runs on Osprey’s GPU Backend, in the Python Flavor Too
GPT-2 generation in Osprey’s Default and Python syntax flavors, with CPU and GPU handlers. Recorded Apple M4 Max measurements include a 3.3× training-step speedup on Metal.
Effect Handlers You Can Call
Osprey handlers are now ordinary values, operations declare whether they can be abandoned, and integer overflow is an effect the compiler makes you handle.
Exceptions and Panics Were a Mistake: Better Error Handling
Exceptions and panics turn ordinary control flow into hidden exits. Osprey makes expected failure explicit with Result types and algebraic effect handlers.
SemVer Is All Lies. Please Stop
Semantic versioning records maintainer intent, not compatibility proof. Osprey's package plan proposes exact identity, compatibility epochs, and downstream testing.
Perceus ARC in Osprey: Functional Memory Management
Osprey ships opt-in Perceus automatic reference counting. The compiler inserts ownership operations, and the runtime reclaims values as owner counts reach zero.
Osprey Flavors: Any Syntax, One Language
Every Osprey flavor lowers its concrete syntax tree into one canonical AST.
Persistent Collections in Osprey: Immutable List and Map with Structural Sharing
Osprey now ships persistent List<T> and Map<K,V> backed by a 32-way bitmapped vector trie and a HAMT — the same data structures that power Clojure and Scala. Append, set and remove are O(log32 n); old versions of a collection stay valid in O(1) extra space.
Memory Safety and Osprey's Runtime Boundary
Osprey-managed values are memory-safe; C calls cross that boundary.
Modeling Web API Results with Pattern Matching
Use union variants to represent API outcomes and match each case explicitly.