diff --git a/lib/erlang/runtime.sx b/lib/erlang/runtime.sx
index b4043b1e..17a5ad99 100644
--- a/lib/erlang/runtime.sx
+++ b/lib/erlang/runtime.sx
@@ -1468,9 +1468,26 @@
 ;; entry is keyed by "Module/Name/Arity"; multi-arity BIFs register
 ;; once per arity. Called eagerly at the end of runtime.sx so the
 ;; registry is ready before any erlang-eval-ast call.
-(define er-register-builtin-bifs!
-  (fn ()
-    ;; erlang module — type predicates (all pure)
+(define
+  er-bif-http-listen
+  (fn
+    (vs)
+    (let
+      ((port (nth vs 0)) (handler (nth vs 1)))
+      (cond
+        (not (= (type-of port) "number"))
+        (raise (er-mk-error-marker (er-mk-atom "badarg")))
+        (not (er-fun? handler))
+        (raise (er-mk-error-marker (er-mk-atom "badarg")))
+        :else (let
+          ((sx-handler (fn (req-dict) (let ((er-req (er-of-sx req-dict))) (er-to-sx (er-apply-fun handler (list er-req)))))))
+          (http-listen port sx-handler))))))
+
+;; Register everything at load time.
+(define
+  er-register-builtin-bifs!
+  (fn
+    ()
     (er-register-pure-bif! "erlang" "is_integer" 1 er-bif-is-integer)
     (er-register-pure-bif! "erlang" "is_atom" 1 er-bif-is-atom)
     (er-register-pure-bif! "erlang" "is_list" 1 er-bif-is-list)
@@ -1479,27 +1496,61 @@
     (er-register-pure-bif! "erlang" "is_float" 1 er-bif-is-float)
     (er-register-pure-bif! "erlang" "is_boolean" 1 er-bif-is-boolean)
     (er-register-pure-bif! "erlang" "is_pid" 1 er-bif-is-pid)
-    (er-register-pure-bif! "erlang" "is_reference" 1 er-bif-is-reference)
+    (er-register-pure-bif!
+      "erlang"
+      "is_reference"
+      1
+      er-bif-is-reference)
     (er-register-pure-bif! "erlang" "is_binary" 1 er-bif-is-binary)
-    (er-register-pure-bif! "erlang" "is_function" 1 er-bif-is-function)
-    (er-register-pure-bif! "erlang" "is_function" 2 er-bif-is-function)
-    ;; erlang module — pure data ops
+    (er-register-pure-bif!
+      "erlang"
+      "is_function"
+      1
+      er-bif-is-function)
+    (er-register-pure-bif!
+      "erlang"
+      "is_function"
+      2
+      er-bif-is-function)
     (er-register-pure-bif! "erlang" "length" 1 er-bif-length)
     (er-register-pure-bif! "erlang" "hd" 1 er-bif-hd)
     (er-register-pure-bif! "erlang" "tl" 1 er-bif-tl)
     (er-register-pure-bif! "erlang" "element" 2 er-bif-element)
     (er-register-pure-bif! "erlang" "tuple_size" 1 er-bif-tuple-size)
     (er-register-pure-bif! "erlang" "byte_size" 1 er-bif-byte-size)
-    (er-register-pure-bif! "erlang" "atom_to_list" 1 er-bif-atom-to-list)
-    (er-register-pure-bif! "erlang" "list_to_atom" 1 er-bif-list-to-atom)
+    (er-register-pure-bif!
+      "erlang"
+      "atom_to_list"
+      1
+      er-bif-atom-to-list)
+    (er-register-pure-bif!
+      "erlang"
+      "list_to_atom"
+      1
+      er-bif-list-to-atom)
     (er-register-pure-bif! "erlang" "abs" 1 er-bif-abs)
     (er-register-pure-bif! "erlang" "min" 2 er-bif-min)
     (er-register-pure-bif! "erlang" "max" 2 er-bif-max)
-    (er-register-pure-bif! "erlang" "tuple_to_list" 1 er-bif-tuple-to-list)
-    (er-register-pure-bif! "erlang" "list_to_tuple" 1 er-bif-list-to-tuple)
-    (er-register-pure-bif! "erlang" "integer_to_list" 1 er-bif-integer-to-list)
-    (er-register-pure-bif! "erlang" "list_to_integer" 1 er-bif-list-to-integer)
-    ;; erlang module — process / runtime (side-effecting)
+    (er-register-pure-bif!
+      "erlang"
+      "tuple_to_list"
+      1
+      er-bif-tuple-to-list)
+    (er-register-pure-bif!
+      "erlang"
+      "list_to_tuple"
+      1
+      er-bif-list-to-tuple)
+    (er-register-pure-bif!
+      "erlang"
+      "integer_to_list"
+      1
+      er-bif-integer-to-list)
+    (er-register-pure-bif!
+      "erlang"
+      "list_to_integer"
+      1
+      er-bif-list-to-integer)
     (er-register-bif! "erlang" "self" 0 er-bif-self)
     (er-register-bif! "erlang" "spawn" 1 er-bif-spawn)
     (er-register-bif! "erlang" "spawn" 3 er-bif-spawn)
@@ -1515,12 +1566,16 @@
     (er-register-bif! "erlang" "unregister" 1 er-bif-unregister)
     (er-register-bif! "erlang" "whereis" 1 er-bif-whereis)
     (er-register-bif! "erlang" "registered" 0 er-bif-registered)
-    ;; erlang module — exception raising (modelled as side-effecting)
-    (er-register-bif! "erlang" "throw" 1
+    (er-register-bif!
+      "erlang"
+      "throw"
+      1
       (fn (vs) (raise (er-mk-throw-marker (er-bif-arg1 vs "throw")))))
-    (er-register-bif! "erlang" "error" 1
+    (er-register-bif!
+      "erlang"
+      "error"
+      1
       (fn (vs) (raise (er-mk-error-marker (er-bif-arg1 vs "error")))))
-    ;; lists module — all pure
     (er-register-pure-bif! "lists" "reverse" 1 er-bif-lists-reverse)
     (er-register-pure-bif! "lists" "map" 2 er-bif-lists-map)
     (er-register-pure-bif! "lists" "foldl" 3 er-bif-lists-foldl)
@@ -1534,11 +1589,13 @@
     (er-register-pure-bif! "lists" "filter" 2 er-bif-lists-filter)
     (er-register-pure-bif! "lists" "any" 2 er-bif-lists-any)
     (er-register-pure-bif! "lists" "all" 2 er-bif-lists-all)
-    (er-register-pure-bif! "lists" "duplicate" 2 er-bif-lists-duplicate)
-    ;; io module — side-effecting (writes to io buffer)
+    (er-register-pure-bif!
+      "lists"
+      "duplicate"
+      2
+      er-bif-lists-duplicate)
     (er-register-bif! "io" "format" 1 er-bif-io-format)
     (er-register-bif! "io" "format" 2 er-bif-io-format)
-    ;; ets module — side-effecting (mutates table state)
     (er-register-bif! "ets" "new" 2 er-bif-ets-new)
     (er-register-bif! "ets" "insert" 2 er-bif-ets-insert)
     (er-register-bif! "ets" "lookup" 2 er-bif-ets-lookup)
@@ -1546,23 +1603,21 @@
     (er-register-bif! "ets" "delete" 2 er-bif-ets-delete)
     (er-register-bif! "ets" "tab2list" 1 er-bif-ets-tab2list)
     (er-register-bif! "ets" "info" 2 er-bif-ets-info)
-    ;; code module — side-effecting (mutates module registry, kills procs)
     (er-register-bif! "code" "load_binary" 3 er-bif-code-load-binary)
     (er-register-bif! "code" "purge" 1 er-bif-code-purge)
     (er-register-bif! "code" "soft_purge" 1 er-bif-code-soft-purge)
     (er-register-bif! "code" "which" 1 er-bif-code-which)
     (er-register-bif! "code" "is_loaded" 1 er-bif-code-is-loaded)
     (er-register-bif! "code" "all_loaded" 0 er-bif-code-all-loaded)
-    ;; file module
     (er-register-bif! "file" "read_file" 1 er-bif-file-read-file)
     (er-register-bif! "file" "write_file" 2 er-bif-file-write-file)
     (er-register-bif! "file" "delete" 1 er-bif-file-delete)
-    ;; Phase 8 FFI — host-primitive BIFs (loops/fed-prims)
     (er-register-pure-bif! "crypto" "hash" 2 er-bif-crypto-hash)
     (er-register-pure-bif! "cid" "from_bytes" 1 er-bif-cid-from-bytes)
     (er-register-pure-bif! "cid" "to_string" 1 er-bif-cid-to-string)
     (er-register-bif! "file" "list_dir" 1 er-bif-file-list-dir)
     (er-mk-atom "ok")))
 
-;; Register everything at load time.
+(er-register-bif! "http" "listen" 2 er-bif-http-listen)
+
 (er-register-builtin-bifs!)
diff --git a/next/tests/http_listen_bif.sh b/next/tests/http_listen_bif.sh
new file mode 100755
index 00000000..5df39296
--- /dev/null
+++ b/next/tests/http_listen_bif.sh
@@ -0,0 +1,96 @@
+#!/usr/bin/env bash
+# next/tests/http_listen_bif.sh — Step 8a acceptance test.
+#
+# Verifies the http:listen/2 BIF wrapper is registered and
+# validates its arguments. We do NOT exercise the actual listen
+# loop — http-listen blocks forever, so production callers spawn
+# an Erlang process to host the call. The BIF wrapper itself is
+# tested for: registration, integer port enforcement, function
+# handler enforcement.
+#
+# This BIF is the briefing's allowed-exception scope addition
+# to lib/erlang/runtime.sx. 5 cases.
+
+set -uo pipefail
+cd "$(git rev-parse --show-toplevel)"
+
+SX_SERVER="${SX_SERVER:-hosts/ocaml/_build/default/bin/sx_server.exe}"
+if [ ! -x "$SX_SERVER" ]; then
+  SX_SERVER="/root/rose-ash/hosts/ocaml/_build/default/bin/sx_server.exe"
+fi
+if [ ! -x "$SX_SERVER" ]; then
+  echo "ERROR: sx_server.exe not found." >&2
+  exit 1
+fi
+
+VERBOSE="${1:-}"
+PASS=0; FAIL=0; ERRORS=""
+TMPFILE=$(mktemp); trap "rm -f $TMPFILE" EXIT
+
+cat > "$TMPFILE" <<'EPOCHS'
+(epoch 1)
+(load "lib/erlang/tokenizer.sx")
+(load "lib/erlang/parser.sx")
+(load "lib/erlang/parser-core.sx")
+(load "lib/erlang/parser-expr.sx")
+(load "lib/erlang/parser-module.sx")
+(load "lib/erlang/transpile.sx")
+(load "lib/erlang/runtime.sx")
+(load "lib/erlang/vm/dispatcher.sx")
+
+;; BIF registered under http/listen/2
+(epoch 10)
+(eval "(not (= (er-lookup-bif \"http\" \"listen\" 2) nil))")
+
+;; BIF is non-pure (side effect: opens a socket)
+(epoch 11)
+(eval "(get (er-lookup-bif \"http\" \"listen\" 2) :pure?)")
+
+;; Non-integer port -> badarg
+(epoch 12)
+(eval "(get (erlang-eval-ast \"try http:listen(not_a_number, fun () -> ok end) catch error:badarg -> ok end\") :name)")
+
+;; Non-fun handler -> badarg
+(epoch 13)
+(eval "(get (erlang-eval-ast \"try http:listen(8080, not_a_fun) catch error:badarg -> ok end\") :name)")
+
+;; Wrong arity not registered (http/listen/1 should be nil)
+(epoch 14)
+(eval "(= (er-lookup-bif \"http\" \"listen\" 1) nil)")
+EPOCHS
+
+OUTPUT=$(timeout 60 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
+
+check() {
+  local epoch="$1" desc="$2" expected="$3"
+  local actual
+  actual=$(echo "$OUTPUT" | awk -v e="$epoch" '
+    $0 ~ "^\\(ok-len " e " " { getline; print; exit }
+    $0 ~ "^\\(ok " e " "     { print; exit }
+    $0 ~ "^\\(error " e " "  { print; exit }
+  ')
+  [ -z "$actual" ] && actual="<no output for epoch $epoch>"
+  if echo "$actual" | grep -qF -- "$expected"; then
+    PASS=$((PASS+1))
+    [ "$VERBOSE" = "-v" ] && echo "  ok $desc"
+  else
+    FAIL=$((FAIL+1))
+    ERRORS+="  FAIL [$desc] (epoch $epoch) expected: $expected | actual: $actual
+"
+  fi
+}
+
+check 10  "BIF registered under http/listen/2" "true"
+check 11  "BIF marked non-pure"                "false"
+check 12  "non-integer port -> badarg"         "ok"
+check 13  "non-fun handler -> badarg"          "ok"
+check 14  "no /1 arity registered"             "true"
+
+TOTAL=$((PASS+FAIL))
+if [ $FAIL -eq 0 ]; then
+  echo "ok $PASS/$TOTAL next/tests/http_listen_bif.sh passed"
+else
+  echo "FAIL $PASS/$TOTAL passed, $FAIL failed:"
+  echo "$ERRORS"
+fi
+[ $FAIL -eq 0 ]
diff --git a/plans/fed-sx-milestone-1.md b/plans/fed-sx-milestone-1.md
index 93277443..427b3edf 100644
--- a/plans/fed-sx-milestone-1.md
+++ b/plans/fed-sx-milestone-1.md
@@ -505,6 +505,12 @@ publish(ActorId, ActivityRequest) ->
 
 ## Step 8 — HTTP server + endpoints
 
+**Sub-deliverables:**
+- [x] **8a** — `http:listen/2` BIF wrapper in `lib/erlang/runtime.sx` (the briefing's allowed exception). Validates args, bridges Erlang handler funs to SX-callable lambdas via `er-of-sx`/`er-to-sx`, delegates to the native `http-listen` primitive in `bin/sx_server.ml`. Tests verify registration + arg validation (not the blocking listen loop). `next/tests/http_listen_bif.sh` (5 cases).
+- [ ] **8b** — `next/kernel/http_server.erl`: `start/1(Port)` spawns an Erlang process hosting `http:listen/2`, routes requests via `route/1`. Returns the Pid for shutdown.
+- [ ] **8c** — `route/1`: dispatch table for GET /actors/{id}, /outbox, /artifacts/{cid}, /projections, POST /activity (Step 6e auth via bearer token), /.well-known/sx-capabilities, /.well-known/webfinger.
+- [ ] **8d** — Content negotiation by Accept header: application/activity+json (default), application/cbor, application/json, application/sx.
+
 **Deliverables:**
 
 Core endpoints (per design §16.1):
@@ -977,6 +983,7 @@ A few things still under-specified; resolve as work begins.
 Newest first. One line per sub-deliverable commit. Erlang conformance gate
 (`bash lib/erlang/conformance.sh`) must remain 729/729 on every entry.
 
+- **2026-05-28** — Step 8a: `http:listen/2` BIF wrapper added to `lib/erlang/runtime.sx` (the briefing's single allowed scope exception). The BIF takes `(Port, Handler)`, validates Port is an integer and Handler is an Erlang fun (else `badarg`), then builds an SX-callable bridge lambda that marshals request dict↔Erlang term via `er-of-sx`/`er-to-sx` and calls `er-apply-fun` on the handler. Delegates to the native `http-listen` primitive (registered in `bin/sx_server.ml`, native-only). Tests verify registration + arg validation paths (the blocking listen loop itself is not exercised — production callers spawn an Erlang process to host the call). `next/tests/http_listen_bif.sh` 5/5; Erlang conformance preserved at 729/729 despite the runtime.sx edit. Step 8 broken into 8a–8d on the plan.
 - **2026-05-28** — Step 7c: `outbox:publish` now broadcasts the signed activity to every projection process named in `Context`'s `:projections` entry — fired immediately after `log:append`, via `projection:async_fold`. Missing/nil/empty list is a no-op (preserves the Step 6d-publish contract). Stage halts (replay duplicate, sig failure) suppress the broadcast — projection state stays at zero while the activity is rejected. `next/tests/outbox_broadcast.sh` 14/14 covers single + multi projection fan-out, three-publish accumulation, replay-skip, sig-skip, and the projection receiving the post-sign Signed envelope (not the pre-sign skeleton). Erlang conformance 729/729.
 - **2026-05-28** — Step 7b: `projection.erl` extended with gen_server callbacks + per-projection named-process API. `start_link/3(Name, InitialState, FoldFn)` spawns and registers under the supplied atom; `async_fold/2(Name, Activity)` casts a fold message; `query/1(Name)` synchronously returns the current state. Same port quirks as registry gen_server (Step 5b): raw Pid return, no `?MODULE` macro, processes don't survive between separate `erlang-eval-ast` calls — tests inline start_link with operations. Two named projections are independent. Snapshot persistence deferred to a later sub-step (needs SX-source eval + on-disk state). `next/tests/projection_server.sh` 11/11. Erlang conformance 729/729.
 - **2026-05-28** — Step 7a: `next/kernel/projection.erl` — pure-functional projection driver. Record shape `[{name, _}, {state, _}, {fold, fun}]`; `fold_activity/2` advances state by one activity; `replay/2` folds a whole list (mirrors `log:entries/1` semantics); `new/2` defaults to the identity fold and `new/3` accepts a custom Erlang fun. Multiple projections share no state — independent record values. Step 7 split into 7a (done) + 7b (gen_server-per-projection) + 7c (broadcast hook from outbox) + 7d (sandbox eval, needs SX-source bridge). `next/tests/projection_pure.sh` 12/12. Erlang conformance 729/729.