The math on building your own agent monitor

A weekend of agent time looks like enough to build your own. AgentPeek is what that idea looks like finished: over a thousand Swift files and more than a hundred thousand lines of native macOS code covering twenty-six agents, each with its own session format, ingestion channel, and integration-specific regression coverage, plus a usage reader wherever an agent keeps local records.

A personal watcher can be much smaller. If one agent, one log format, and one terminal solve your problem, building that may be the right trade. Matching AgentPeek means reproducing the integrations, response channels, usage readers, native windows, release pipeline, and regression coverage those files represent.

There is no honest universal token estimate. API cost depends on the model, input and output mix, cache behavior, retries, and how much work you do yourself; subscription plans use limits rather than a direct per-token bill. The fixed comparison is the license: $19.99 for one Mac. Your build cost is your time plus whatever provider usage your implementation consumes.

Maintenance remains part of the scope. Coding agents change: CLIs rename, session logs move, and hook APIs gain and lose fields. AgentPeek has shipped 118 releases across 60 separate days since launch, each one in the public release log. That cadence is what it takes to keep twenty-six integrations honest.

A homemade clone also makes you the maintainer when a CLI, hook schema, or session store changes. The $19.99 license buys the current app and future updates; a personal build keeps its own maintenance queue. The size of that queue depends on how many agents and surfaces you choose to support.

AgentPeek is a one-time purchase: $19.99 for one Mac, with 2-Mac and 3-Mac licenses alongside. Future updates are included and there is no subscription. A free 3-day trial runs first, so the decision is made with the app on your notch, not from screenshots.

Compare your implementation and maintenance hours with the fixed license price. The result depends on how narrow your personal watcher is and how long you intend to maintain it.

If the project is the point, build it: writing a session watcher is a great way to learn how these agents work under the hood. Good free tools cover slices of this too, and the honest comparisons are on their own pages: ccusage for CLI usage reports and Claude block monitoring, and CodexBar for broad provider usage plus summary-level Claude and Codex session presence. If you want AgentPeek's operational scope without owning its maintenance, the license is the fixed-price option.