Analysis: Never call a constant an identity once the map travels

[marcoroth]

This pull request fixes a slot dependency map that told a client it could write a value the client has never been given.

SlotDependencies classifies each slot by where its next value comes from. identity means the slot's expression is the state itself, so a client writes it by copying what it already holds. Everything computed is derived, and only the server can answer it.

A constant is a dependency and not something a page can set, so it can never be an identity. for had that right and across did not, and across is the one whose answer is delivered:

subject.for(path)      #=> { 0 => { state: ["Post.count"], mode: :derived } }
subject.across(path)   #=> { "Post.count" => [{ …, mode: :identity }] }
subject.payload(path)  #=> { "state" => { "Post.count" => [{ "mode" => "identity" }] } }

A partial's incoming locals are not among the names it declares, so #2281 treats the names the trace carries as settable, which is what lets a partial answer in its caller's terms. Constants arrive through the same door and are settable by nothing, so the exclusion for applies was lost on the way.

The map already leaves constants out of the request names it publishes, so payload["params"] is empty for a template whose only state is Post.count, and nothing resolves to it by the name a request would use. Reaching it takes calling state.set("Post.count", …) by the state's own name, through the escape hatch meant for state whose request name could not be derived.

[nx-cloud]

View your CI Pipeline Execution ↗ for commit faea43e

Command	Status	Duration	Result
nx run-many -t test --all --parallel --exclude=...	✅ Succeeded	2m 55s	View ↗
nx run-many -t build --all --exclude=herb-langu...	✅ Succeeded	33s	View ↗
nx build @herb-tools/tailwind-class-sorter	✅ Succeeded	1s	View ↗

💡 Verify your cache is correct by running tasks in a sandbox. Read docs ↗

---

☁️ Nx Cloud last updated this comment at 2026-08-19 00:58:11 UTC

[github-actions]

🌿 Interactive Playground and Documentation Preview

A preview deployment has been built for this pull request. Try out the changes live in the interactive playground:

• Playground Preview
• Documentation Preview
• Website Preview

---

_{🌱 Grown from commit faea43e}

---

✅ Preview deployment has been cleaned up.

[pkg-pr-new]

npx https://pkg.pr.new/@herb-tools/formatter@2290

npx https://pkg.pr.new/@herb-tools/language-server@2290

npx https://pkg.pr.new/@herb-tools/linter@2290

commit: faea43e