[michielbdejong]

Piece 5 of #1700 (answer 5): wasip2 class extenders don't reach the integration proxy.

First of three stacked PRs:

1. this one: piece 5, base claude/atomic-proxy-scheme (atomic-proxy: URLs for plugins, resolved to the delegated connection on the configured proxy (#1700, answer 4) #1725);
2. piece 7, v2 required plus a replay cache, stacked on this one;
3. piece 8, fix(plugins): refuse to run an app whose key is not on this node #1644 sees installation identities, stacked on piece 7.

The three pieces don't depend on each other. They're stacked only so each diff stays small.

What changes

wasip2 class extenders were already refused at the proxy: their identity is the plugin agent in PluginMeta, so the host has no installation agent to sign as. But the error you got depended on which later check tripped first: an undeclared proxy platform, or "no app agent on this node".

• HostCore::fetch now refuses a class extender's proxy request before any other check, with CLASS_EXTENDER_PROXY_REFUSAL. It covers both atomic-proxy: URLs and the proxy's absolute URL, even when the manifest lists the proxy origin in network.origins. The message says the proxy only accepts an installation's agent on this node, and points to JS plugins instead.
• The docs get a new section, "Class extenders and the integration proxy", in docs/src/plugins/creating-plugins.md, and the proxy bullet links to it.

Tests

host_core::tests::a_class_extender_is_refused_at_the_proxy_and_told_why sets up a class-extender host whose manifest declares the proxy origin, on a node with a proxy configured. It checks that both URL forms are refused with exactly that message, before any connection is made.

cargo test -p atomic-server --lib and clippy -D warnings pass, and so did the pre-commit hook's workspace clippy.

🤖 Generated with Claude Code

[michielbdejong]

Merge-risk triage (2026-09-28). This is a read-only review of this PR's own diff. The rule it applies: nothing that works today may break for existing users or clients, and new behaviour is added alongside the old. The stack is being rebased onto develop as one chain before merging, so line references are against the current stacked base.

Verdict: SAFE

Adds an earlier, clearer refusal for class extenders calling the proxy; those requests already failed in sign_for_proxy. It only matters when a proxy is configured.

🤖 Generated with Claude Code

[michielbdejong]

Closing as part of the plugin-host stack cleanup (Q-101): not needed by atomic-plugins now. See the inventory at #1726 (comment). The branch is kept, and pin candidates are unaffected. Closed by Claude (VPS coordinator) on behalf of Michiel.