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Earendil has released Pi 1.0, a stable, minimal agent harness with new features including Codemode, extension support for virtual models and deferred tool loading. The company also introduced Pi Durable, an experimental package for building longer-running agent applications. Both are available now under the MIT license.
Earendil has released Pi 1.0, a hardened and extensible agent harness that adds Codemode, virtual model support and several workflow features. The company also made Pi Durable, an experimental package for building longer-running agent applications, available alongside the release.
Earendil describes Pi 1.0 as the result of months of development and user feedback. The company says hundreds of thousands of people use Pi each week and that users have contributed issues and pull requests. The release is intended to make the software more stable while preserving its minimal design.
The new capabilities include Codemode, which Earendil says adds native support for MCP and for non-LLM models, including Jev and image models. Pi 1.0 also adds extensions for virtual models, deferred tool loading, cache warming for Anthropic models, and system messages that can be changed mid-conversation with awareness of the transcript. The release includes a new terminal interface theme and makes full-screen mode the default.
Earendil says Pi 1.0 is available through installation commands for macOS, Linux and Windows. The company also lists Pi Durable as available through npm, in an experimental package alongside Pi AI and Chord. Both offerings are MIT licensed, and documentation is available at pi.dev, with source code at the Earendil Works GitHub repository.
New Tools Expand Pi’s Agent Workflows
Pi 1.0 adds ways to connect tools and models while retaining an emphasis on keeping the agent harness small. Codemode and virtual models allow developers to build workflows involving different model types or route work among models, while deferred tool loading and cache warming address how tools and model interactions are handled. The announcement describes the features, but does not provide independent performance measurements.
The separate Pi Durable package addresses a different use case: long-running agent applications that may need to be accessed outside a coding agent or terminal. Earendil says it wants Pi’s approach to be usable across different surfaces and for longer tasks. Keeping that work in an experimental package lets the company explore those needs without changing Pi’s core product into something it says does not fit its minimal roots.
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From Coding Agent to Durable Apps
Earendil says Pi already runs current models from major providers and is used as a coding agent as well as a base for building agent applications. The company frames version 1.0 as a milestone after months of refining the software in response to use and community contributions, rather than as a change in Pi’s basic purpose.
The announcement also describes a deliberate approach to feature selection: Earendil says it waits for tools and approaches to prove their value before adding them, weighing their usefulness against added complexity. It says more proposed features were rejected than included. The report offers examples of Pi writing a script to summarize a week of commits and creating an extension that routes planning and implementation among models, but does not give independent test results for those demonstrations.
“We care about holding that line.”
— Earendil, in the Pi 1.0 announcement
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Durable Package Remains Experimental
Earendil has not specified in the announcement when Pi Durable might leave experimental status, what its future release schedule will be, or which features it will ultimately support. It also does not provide benchmarks, adoption figures for Pi 1.0, or independent evidence for the benefits of the new capabilities. The claim that hundreds of thousands of people use Pi each week is the company’s own figure; the announcement does not define how that usage is measured.
The announcement lists Pi 1.0’s features but does not detail compatibility requirements, migration steps for existing users, or the scope of support for each model and tool integration. Those practical details will depend on the product documentation and subsequent updates.
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Documentation and User Feedback
Pi 1.0 and Pi Durable are available now, and Earendil is asking users to share feedback. The company points developers to pi.dev for documentation and to its GitHub repository for the code. Further information about Pi Durable’s development and Pi’s feature decisions may clarify how the experimental package develops and which capabilities become part of established workflows.
For now, the immediate next step for users is to review the documentation and test the new release for their own use cases. Earendil has not announced a date for another Pi release or a timetable for Pi Durable’s development.
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Key Questions
What is Pi 1.0?
Pi 1.0 is a release of Earendil’s agent harness, which the company describes as hardened, minimal and extensible. It adds Codemode and other model, tool-loading and interface features.
What is new in Pi 1.0?
The release adds Codemode, extensions for virtual models, deferred tool loading and cache warming for Anthropic models. It also supports mid-conversation system messages, introduces a new terminal theme and sets full-screen mode as the default.
What is Pi Durable?
Pi Durable is a separate experimental package for building long-running agent applications. Earendil says it is intended to make agent applications usable across different surfaces and for longer-running conversations and tasks.
How can developers access Pi 1.0?
Earendil provides installation commands for Unix-like systems and Windows. Its announcement also directs users to pi.dev for documentation and the Earendil Works GitHub repository for source code. Pi 1.0 and the listed Pi Durable packages are MIT licensed.
Source: hn
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