identity: identity->acl delegation boundary — 401 gates before 403 (+8 tests)

delegation.sx makes the loop's central rule concrete: check() introspects
the token first — inactive → {error, unauthenticated} (401), acl never
consulted — and only an authenticated subject's request is delegated to
acl, which returns permit/deny ({error, forbidden} = 403). 401 strictly
precedes 403. acl-on-sx (Datalog) is a different SX guest wired at the
integration layer, so the decider here is a labelled stub (permits when
Action in Scope); swap the pid and the boundary is unchanged. New
tests/delegation.sx. 185/185 — extensions backlog clear.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

lib/identity/tests/delegation.sx

@@ -0,0 +1,102 @@
+;; identity/tests/delegation.sx — the identity -> acl boundary.
+;; Authentication (identity) gates BEFORE authorization (acl): an inactive
+;; token is unauthenticated (401) and acl is never consulted; only an
+;; authenticated subject's request is delegated to acl for permit/deny.
+
+(define id-deleg-test-count 0)
+(define id-deleg-test-pass 0)
+(define id-deleg-test-fails (list))
+
+(define
+  id-deleg-test
+  (fn
+    (name actual expected)
+    (set! id-deleg-test-count (+ id-deleg-test-count 1))
+    (if
+      (= actual expected)
+      (set! id-deleg-test-pass (+ id-deleg-test-pass 1))
+      (append! id-deleg-test-fails {:name name :expected expected :actual actual}))))
+
+(define idl-ev erlang-eval-ast)
+(define idlnm (fn (v) (get v :name)))
+
+(identity-load-delegation!)
+
+;; Shared prelude: a token registry, a stub acl, and a token granting
+;; [read, write] to alice, all bound.
+(define
+  idl-setup
+  "R = identity_tokens:start(),\n   A = identity_delegation:stub_acl(),\n   {ok, T} = identity_tokens:issue(R, alice, web, [read, write])")
+
+;; ── authenticated + acl permits ──────────────────────────────────
+
+(id-deleg-test
+  "an authenticated, permitted request returns the subject"
+  (idlnm
+    (idl-ev
+      (str
+        idl-setup
+        ", case identity_delegation:check(R, A, T, read, doc1) of\n             {ok, S} -> S;\n             {error, W} -> W\n           end")))
+  "alice")
+
+;; ── authenticated + acl denies → 403 ─────────────────────────────
+
+(id-deleg-test
+  "an authenticated but unpermitted request is forbidden"
+  (idlnm
+    (idl-ev
+      "R = identity_tokens:start(),\n       A = identity_delegation:stub_acl(),\n       {ok, T} = identity_tokens:issue(R, alice, web, [read]),\n       case identity_delegation:check(R, A, T, write, doc1) of\n         {ok, _} -> permitted;\n         {error, W} -> W\n       end"))
+  "forbidden")
+
+;; ── unauthenticated → 401, acl never consulted ───────────────────
+
+(id-deleg-test
+  "a revoked token is unauthenticated, not forbidden"
+  (idlnm
+    (idl-ev
+      (str
+        idl-setup
+        ", identity_tokens:revoke(R, T),\n           case identity_delegation:check(R, A, T, read, doc1) of\n             {ok, _} -> permitted;\n             {error, W} -> W\n           end")))
+  "unauthenticated")
+
+(id-deleg-test
+  "an unknown token is unauthenticated"
+  (idlnm
+    (idl-ev
+      "R = identity_tokens:start(),\n       A = identity_delegation:stub_acl(),\n       Bogus = make_ref(),\n       case identity_delegation:check(R, A, Bogus, read, doc1) of\n         {ok, _} -> permitted;\n         {error, W} -> W\n       end"))
+  "unauthenticated")
+
+(id-deleg-test
+  "an expired token is unauthenticated"
+  (idlnm
+    (idl-ev
+      "R = identity_tokens:start(),\n       A = identity_delegation:stub_acl(),\n       {ok, T} = identity_tokens:issue(R, alice, web, [read], 100),\n       identity_tokens:advance(R, 100),\n       case identity_delegation:check(R, A, T, read, doc1) of\n         {ok, _} -> permitted;\n         {error, W} -> W\n       end"))
+  "unauthenticated")
+
+;; ── 401 takes precedence over 403 (identity gates first) ─────────
+
+(id-deleg-test
+  "a revoked token with no matching scope is still unauthenticated"
+  (idlnm
+    (idl-ev
+      "R = identity_tokens:start(),\n       A = identity_delegation:stub_acl(),\n       {ok, T} = identity_tokens:issue(R, alice, web, [admin]),\n       identity_tokens:revoke(R, T),\n       case identity_delegation:check(R, A, T, read, doc1) of\n         {ok, _} -> permitted;\n         {error, W} -> W\n       end"))
+  "unauthenticated")
+
+;; ── acl is what decides for an authenticated subject ─────────────
+
+(id-deleg-test
+  "the same subject is permitted one action and denied another"
+  (idl-ev
+    "R = identity_tokens:start(),\n     A = identity_delegation:stub_acl(),\n     {ok, T} = identity_tokens:issue(R, alice, web, [read]),\n     Allowed = case identity_delegation:check(R, A, T, read, doc1) of\n       {ok, _} -> 1; {error, _} -> 0 end,\n     Denied = case identity_delegation:check(R, A, T, write, doc1) of\n       {ok, _} -> 1; {error, _} -> 0 end,\n     Allowed - Denied")
+  1)
+
+(id-deleg-test
+  "identity does not widen permission beyond the token scope"
+  (idlnm
+    (idl-ev
+      "R = identity_tokens:start(),\n       A = identity_delegation:stub_acl(),\n       {ok, T} = identity_tokens:issue(R, alice, web, [read, write]),\n       case identity_delegation:check(R, A, T, delete, doc1) of\n         {ok, _} -> permitted;\n         {error, W} -> W\n       end"))
+  "forbidden")
+
+(define
+  id-deleg-test-summary
+  (str "delegation " id-deleg-test-pass "/" id-deleg-test-count))