I Hated Every Coding Agent, So I Built My Own — Mario Zechner (Pi)

Source URL: https://www.youtube.com/watch?v=Dli5slNaJu0 Type: Video / Talk Date: 2026 (approx) Speaker: Mario Zechner (creator of Pi coding agent, also known as badlogic — libGDX author)

Why Pi was created

Mario was frustrated by existing coding agents (Claude Code, OpenCode, Codex CLI, AMP) for several reasons:

Feature bloat — agents pile on features (built-in to-dos, complex tool suites) that aren't needed and add hidden context injection
Hidden behaviors — vendors change things under the hood (system prompts, context injection) that make LLMs behave unpredictably with existing workflows
Poor observability — hard to see what the agent is actually doing, what context it's using, how much it costs
Lack of extensibility — no way for power users to add custom tools or modify behavior without forking
Approval fatigue — agents offer either full autonomy or approval for every action; both are bad UX
Poor context management — agents like OpenCode rely on session compaction but lose important context

Key quote: "So obviously they're doing things right, but not for me."

Pi's design philosophy

Minimal core — only 4 tools: read file, write file, edit file, bash. That's all you need.
Tiny system prompt — frontier RL-trained models don't need massive system prompts
Tree-structured sessions — not linear chat history; sub-agents can branch and read files independently while preserving context/lineage
Full cost tracking — built-in, not an afterthought
Hot-reloadable TypeScript extensions — users can define custom tools, UIs, multi-agent setups without modifying core
No hidden context injection — what you see is what the model gets

Community extensions

pi-annotate — visual feedback on live websites
pi-messenger — multi-agent chatroom with custom UI
Custom UIs, tool integrations — all as hot-reloadable TS modules

Performance

On TerminalBench, Pi (with Claude Opus 4.5) scored close to Terminus even before advanced optimizations like compaction.

Key insight

"We are in the messing around and finding out stage, and nobody has any idea what the perfect coding agent should look like." — simplification can lead to effective performance without unnecessary complexity.

Pi website: https://pi.dev/
Pi GitHub: https://github.com/earendil-works/pi
Pi is part of OpenClaw ecosystem
Mario Zechner is also the author of libGDX (Java game dev framework)

2.6 KiB Raw Blame History