Mitchell Hashimoto builds a non-trivial Ghostty feature with Amp
Ghostty's creator walked through the agent sessions he used to build in-window, non-intrusive update notifications for the macOS app, including the planning, the dead ends and the cleanup.
The problem
Most AI coding demos are toy projects. This one shows an experienced maintainer shipping a real feature in a large production codebase with an agent, and where human judgment still mattered.
How they did it
- Start by writing a full plan interactively with the agent before any code.
- Hand the agent well-scoped fill-in-the-blank tasks, steering and reviewing as it goes.
- Finish with cleanup sessions, especially of the view model between UI and logic.
Results
- The work took a total of 16 separate sessions totalling $15.98 in token spend on Amp.
- The author warns never to ship AI-written code without a thorough manual review.
As reported by the source (Mitchell Hashimoto's blog); AgentGid did not measure these figures.
This suits an experienced developer who already knows their codebase well enough to write a plan, scope tasks and catch bad output, since the human judgment is what keeps the sessions cheap. Watch the $15.98 figure: it's one author's spend on Amp, and Amp ranks 21st in its category with a Gid Score of 31, so expect different results elsewhere. Pi (Free, OSS) is a no-cost alternative, with only model provider costs.
The agent used here
Similar use cases
JustHTML: a Python HTML5 parser built with coding agents that passes html5lib tests
A developer spent his off-hours using Copilot agent mode with several models to build a dependency-free HTML5 parser, and wrote up every stage, including a full restart.
JustHTML is about 3,000 lines of Python with 8,500+ tests passing.
Turn a Figma frame into code by connecting the Figma MCP server
Figma's hosted MCP server gives a coding agent the variables, components and layout data of a frame you link to, so the code it writes matches the design.
The agent gets design context such as variables, components and layout for the selected frame.
How Thomson Reuters modernized legacy .NET applications with AWS Transform
Thomson Reuters used AWS Transform's agents to port old .NET Framework applications to cross-platform .NET and Linux. AWS reports faster upgrades and lower running costs.
As reported by AWS: Thomson Reuters modernizes '1.5 million lines of code every month — a 4x boost in velocity'.