[eichhorl]

What

One wrapper:

/// The number of nodes on the subnet this canister runs on.
public let subnetSelfNodeCount : () -> Nat32 = Prim.subnetSelfNodeCount;

InternetComputer already wraps Prim.call_raw, Prim.isReplicatedExecution and Prim.performanceCounter. ic0.subnet_self_node_count was the one left out, so a canister that needs the subnet's node count has to import Prim "mo:⛔" itself.

Why now

Flexible HTTPS outcalls need it. flexible_http_request takes ReplicationCounts, and total_requests must not exceed the number of nodes on the subnet, so asking a committee smaller than the subnet means sizing it against the count:

let totalRequests = Nat32.min(InternetComputer.subnetSelfNodeCount(), 5);

A smaller committee is the point of the feature: fewer requests cost less and are gentler on the endpoint's rate limits. Hardcoding a number instead breaks on a subnet smaller than that number.

Rust has this as ordinary public API, ic_cdk::api::subnet_self_node_count(), so Motoko is the only side reaching into a module named "no entry" for it. That is now visible in published material: the Motoko flexible outcall example in dfinity/examples#1490 and the https-outcalls agent skill both import mo:⛔ and carry a comment explaining why.

Why CI will be red, and what you have to decide

Prim.subnetSelfNodeCount exists from moc 2.1.0. This repo pins [toolchain] moc = "1.16.0" and runs a second CI leg on moc 2.0.0. Verified with check:orphans on this branch:

moc 2.1.0    ✓ src/InternetComputer.mo
moc 1.16.0   src/InternetComputer.mo:49.55-49.74: type error [M0072],
             field subnetSelfNodeCount does not exist in module.

So this cannot merge as-is, and the change that makes it mergeable is not mine to make. core is foundational: anything that stops type-checking below moc 2.1.0 raises the floor for every consumer, not just callers of the new function. Projects on moc 1.x would fail mops check the way a moc 2.x project does today against base and its ExperimentalStableMemory.

I am opening it as a one-line proposal so the cost is visible rather than described, and I have deliberately not bundled the pin bump, the CI leg change, validation/api/api.lock.json, or a [requirements] raise. Happy to do any of that, split it differently, or close this if the floor should not move yet.

The Changelog.md entry under ## Next carries a #TBD that wants this PR number.

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