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I originally was just messing with pi-autoresearch. Gave it a sample task to build the most portable coding agent.First cut was 6 KB of shell. Great for one-shots, unusable interactively. I was shocked it actually worked.Started building up -- adding features — but with a self-imposed rule: no new dependencies, and sub 500 LOC. This thing had to be truly portable. Just sh, curl, awk. System primitives only.Which means I did some genuinely disgusting things in awk, including JSON parsing and the OpenAI
Responses tool loop with reasoning items carried across turns.It's now ~400 lines. In the box: Anthropic + OpenAI, 7 tools (bash, read, write, edit, grep, find, ls),
REPL, auto-compaction, checkpoint/resume, pipe mode, 90 no-API tests. Not in the box: TUI, streaming,
images, OAuth, Windows, dignity.Two honest things:1. I stole/modified the system prompt and the architecture. Pi/Claude/Codex wrote the awk. I cannot read most of this code. This wasn't possible for me a year ago.2. Heavily inspired by Pi (pi.dev) — same 7-tool surface, same exact-text edit model. Credit where it's
due. Pi is awesome -- you should probably use them.The agent loop itself is tiny. Almost everything else in a "real" agent CLI is DX and hardening. You can
probably build your own harness exactly how you like it. Mario Zechner's AI Engineer talk on taking back control of
your tools nudged me here.The name is because it's a .sh file. The other thing it sounds like is, regrettably, also accurate.
Show HN: Pu.sh – a full coding-agent harness in 400 lines of shell
A highly portable, dependency-free coding agent harness built with system primitives (sh, curl, awk), offering Anthropic/OpenAI integration and a suite of 7 tools for interactive and automated coding tasks.
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AI Executive Synthesis
A highly portable, dependency-free coding agent harness built with system primitives (sh, curl, awk), offering Anthropic/OpenAI integration and a suite of 7 tools for interactive and automated coding tasks.
Pu.sh demonstrates a radical approach to AI agent development, prioritizing extreme portability and minimal dependencies by leveraging core shell utilities. This project highlights a counter-trend to complex, framework-heavy AI solutions, proving that powerful agent capabilities can be achieved with a lean footprint. The ability to integrate with major AI models (Anthropic, OpenAI) and provide essential tools (bash, read, write, edit) within 400 lines of shell script is a significant technical feat. This addresses a developer pain point of bloated environments and complex setups, offering a "build your own harness" philosophy. The market implication is the potential for highly embeddable, resource-efficient AI agents, suitable for constrained environments or as foundational components in larger systems where overhead must be minimized.
Related Ecosystem & Alternatives
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Deep-Dive FAQs
What is Pu.sh – a full coding-agent harness in 400 lines of shell?
Pu.sh – a full coding-agent harness in 400 lines of shell is analyzed by our AI as: A highly portable, dependency-free coding agent harness built with system primitives (sh, curl, awk), offering Anthropic/OpenAI integration and a suite of 7 tools for interactive and automated coding tasks.. It focuses on Pu.sh demonstrates a radical approach to AI agent development, prioritizing extreme portability and minimal dependencies by leveraging core shell u...
Where did Pu.sh – a full coding-agent harness in 400 lines of shell originate?
Data for Pu.sh – a full coding-agent harness in 400 lines of shell was aggregated directly from the Hacker News community ecosystem, representing raw developer and early-adopter sentiment.
When was Pu.sh – a full coding-agent harness in 400 lines of shell publicly launched?
The initial public indexing or launch date for Pu.sh – a full coding-agent harness in 400 lines of shell within our tracked developer communities was recorded on May 1, 2026.
How popular is Pu.sh – a full coding-agent harness in 400 lines of shell?
Pu.sh – a full coding-agent harness in 400 lines of shell has achieved measurable traction, logging over 71 traction score and facilitating 21 recorded discussions or engagements.
Which technical categories define Pu.sh – a full coding-agent harness in 400 lines of shell?
Based on metadata extraction, Pu.sh – a full coding-agent harness in 400 lines of shell is categorized under topics such as: coding-agent harness, shell script, portable, no new dependencies.
Are there open-source alternatives related to Pu.sh – a full coding-agent harness in 400 lines of shell?
Yes, the GitHub ecosystem contains correlated projects. For example, a repository named tanweai/pua shares highly similar architectural descriptions and topics.
How does the creator describe Pu.sh – a full coding-agent harness in 400 lines of shell?
The original author or development team describes the product as follows: "I originally was just messing with pi-autoresearch. Gave it a sample task to build the most portable coding agent.First cut was 6 KB of shell. Great for one-shots, unusable interactively. I was sho..."
Community Voice & Feedback
I like the small-surface-area approach. The question I’d use to evaluate this is how well the harness records/replays tool calls and failure modes, since that is where debugging agent behavior usually gets messy.
if you are looking for a customizable agent harness that provides everything except a tui (cli, acp, embeddable python package) i built and use this for a handful of projects where i needed a vendor-agnostic replacement for claude agent sdk: https://github.com/zackham/aloop
why the LOC limit? just because?
Could you post the initial 6KB version? I'd love to have a version that I can actually read and understand. I don't care if it's 2K LOC.
Does it work in just-bash?https://github.com/vercel-labs/just-bash/blob/main/packages/...
Kudos. I set on this exact journey a couple of days back and Pi is what I started reading for inspiration as well. I really can't stand the text boxes and the animations of the mainstream harnesses.
I love this. This is the grown-up brother of my one-liner bash+python athttps://github.com/kkovacs/kkrc/blob/ecff1f65d5ccfa24d5f6695...:)
I'd love to learn how to build something like this, but unfortunately the code is unreadable.If author could write a heavily commented version that would be amazing.
Really like the looks of it, but minifying the code to achieve the “400 lines” marketing gimmick is a huge turn-off.It’s also a security nightmare, and ensures it remains 100% vibe coded. Would rather have a readable source with an honest line count.
your 500 LOC requirement has made this thing completely and unnecessarily inscrutable and unreadable.Pass.
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