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Fly.io vs Heroku

Heroku scores higher on the AgentReady, 63/100 against 53/100. They differ on 11 of the 41 signals. Which ones decides whether an agent can adopt them without a person watching.

What each one is

Fly.io. Fly.io provides real hardware-isolated Linux computers (called Sprites and Machines) for agents, evals, and tools, with a pay-as-you-go model where billing goes to zero when not in use.

Heroku. Heroku is a fully managed cloud application platform (PaaS) for building, deploying, and scaling apps.

Where Fly.io is ahead

Fly.io passes pricing understandable, and Heroku does not. That is understand, whether an agent can read the docs and work out how the API behaves before calling it.

It also holds adopt: self-service signup. Heroku misses it.

And on operate, agent compatibility verified. Heroku misses it.

Where Heroku is ahead

Heroku passes clear product positioning and llms-full.txt / full agent docs, and Fly.io does not. That is discover, whether an agent can find the product at all without being told it exists.

It also holds understand: structured api reference and limits / constraints documented. Fly.io misses those.

And on adopt, no mandatory sales call, agent-compatible signup flow and copyable quickstart. Fly.io misses those.

Finally, on operate, structured, predictable output. Fly.io misses it.

What neither does

Both fail openapi / spec quality, authentication documented, request examples provided, response examples provided, errors and status codes documented, programmatic credential creation, free trial or free allowance, fast time to first request, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable. If your agent needs any of those, you will be building it yourself either way.

Score, pillar by pillar

The AgentReady splits into four pillars, scored separately, because a product can be easy to find and still impossible to adopt.

Discover is whether an agent can find the product at all without being told it exists. Heroku leads 100 to 80. Fly.io misses clear product positioning, llms-full.txt / full agent docs; Heroku misses nothing.

Understand. Heroku leads 38 to 23. Fly.io misses structured api reference, openapi / spec quality, authentication documented, request examples provided, response examples provided, errors and status codes documented, limits / constraints documented; Heroku misses openapi / spec quality, authentication documented, pricing understandable, request examples provided, response examples provided, errors and status codes documented.

Adopt. Heroku leads 65 to 55. Fly.io misses no mandatory sales call, agent-compatible signup flow, programmatic credential creation, free trial or free allowance, fast time to first request, copyable quickstart; Heroku misses self-service signup, programmatic credential creation, free trial or free allowance, fast time to first request.

Operate. Fly.io leads 53 to 47. Fly.io misses structured, predictable output, machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable; Heroku misses machine-readable errors, retry behavior documented, idempotency support, rate-limit behavior predictable, agent compatibility verified.

Pricing

Fly.io starts at $29/mo. Heroku does not publish one.

Signal by signal

Which to pick

Heroku clears more of the signals an agent needs, so it is the safer default for unattended use. Full profiles: Fly.io and Heroku. Alternatives to each: Fly.io, Heroku.

An agent can fetch this as data: POST /v1/compare {"slugs": ["fly", "heroku"]}