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Earendil has released Pi 1.0, a hardened, minimal agent harness with new support for Codemode, extensions for virtual models, deferred tool loading and other features. The company also released Pi Durable as an experimental package for building long-running agentic applications. Both offerings are MIT licensed.
Earendil has released Pi 1.0, a stable version of its minimal agent harness, adding features including Codemode, virtual-model extensions and deferred tool loading. The company also made Pi Durable, an experimental package for building longer-running agentic applications, available alongside the release.
Earendil describes Pi 1.0 as a hardened and extensible agent harness shaped by months of development and user feedback. The company says hundreds of thousands of people use Pi each week, and that users have submitted issues and pull requests during the work toward the release. That usage figure comes from Earendil; the announcement does not provide an independent measure or a definition of weekly use.
The update adds Codemode, which Earendil says brings native support for MCP and non-LLM models, including Jev and image models. Other additions include extensions for virtual models, deferred tool loading, cache warming for Anthropic models, and the ability to change system messages mid-conversation while accounting for the transcript. Pi 1.0 also has a new terminal user interface theme and opens in full-screen mode by default.
Earendil says Pi 1.0 is available now through its installation instructions, with documentation at pi.dev and source code on GitHub. Pi and Pi Durable are MIT licensed. Pi Durable is distributed as a separate experimental package, with dependencies listed by Earendil for installation through npm.
Pi Adds Tools Without Expanding Its Scope
The release gives developers new ways to build and adapt agents while preserving Pi’s stated emphasis on minimalism and extensibility. Features such as virtual-model extensions and Codemode are intended to let users combine models or connect tools without making every capability part of the core harness. That approach may appeal to teams that want to customize agent behavior, though the announcement does not include independent performance tests or comparative evaluations.
Pi Durable addresses a different use case: applications that need to support longer-running conversations and tasks, and reach users beyond a coding agent in a terminal. Earendil presents it as a separate substrate rather than changing Pi itself to serve that role. Its experimental status means prospective users should distinguish the new package from Pi 1.0’s stable-release positioning.
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Why Earendil Kept Pi Minimal
Earendil says Pi already supported the latest models from major providers and had become a daily coding agent for users, as well as a base for building agentic applications. The company says it adopts additions only after they have proved useful, weighing their functionality against the complexity they add. It describes the 1.0 feature set as the result of that process, with other potential changes left out.
The announcement also points to a separate discussion about Codemode and MCP published earlier in the week. Earendil says it began developing Pi Durable after recognizing that some users wanted Pi’s approach outside coding and terminal environments, including for longer-running work. Rather than broaden the main product, it released that effort as an experimental package.
“We wait until something has proven itself, and only then do we consider adopting it; weighing its true functionality against its inherent added complexity.”
— Earendil, in its Pi 1.0 announcement
Pi Durable’s Readiness and Limits
The announcement does not specify how long Pi Durable will remain experimental, what stability guarantees it offers, or when it might reach a stable release. It also does not give benchmarks, detailed compatibility information, or a fuller account of how the new features perform in production. Earendil’s statement that hundreds of thousands use Pi weekly is not accompanied by a measurement method.
It is also not clear from the announcement which capabilities will be maintained as core Pi features over time, or how much additional setup Codemode and the new extension options require for particular applications. The company describes the release and its intended design, but independent testing and user experience after launch are not yet included in the source material.
User Feedback Will Shape Pi
Earendil says it wants feedback on the releases and plans to continue developing its tools openly. Users can access Pi 1.0 through the installation instructions on pi.dev, while developers can obtain the code from the company’s GitHub repository. Pi Durable is available as an experimental npm package, so its development and status may change as the company gathers feedback.
The announcement gives no dates for further Pi releases or for changes to Pi Durable’s experimental status. The next confirmed step is therefore user adoption and feedback, rather than a specified roadmap milestone.
Key Questions
What is Pi 1.0?
Pi 1.0 is a stable release of Earendil’s minimal, extensible agent harness, with new tools for model and tool integration and changes to its terminal interface.
What features are new in Pi 1.0?
The release adds Codemode, virtual-model extensions, deferred tool loading and Anthropic cache warming. It also supports mid-conversation system-message changes, introduces a new TUI theme and makes full-screen mode the default.
What is Pi Durable?
Pi Durable is a separate experimental package for building agentic applications intended to support longer-running conversations and tasks. Earendil says it extends Pi’s principles but does not present it as a stable Pi 1.0 feature.
How can developers get Pi?
Earendil directs users to pi.dev for installation instructions and documentation, and to its GitHub repository for the source code. Pi and Pi Durable are MIT licensed.
Source: hn
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