diff --git a/next/genesis/audience/direct.sx b/next/genesis/audience/direct.sx
new file mode 100644
index 00000000..58b99fe4
--- /dev/null
+++ b/next/genesis/audience/direct.sx
@@ -0,0 +1,14 @@
+;; next/genesis/audience/direct.sx
+;;
+;; Direct audience: an actor is a member iff they are
+;; explicitly named in the activity's :to or :cc lists. No
+;; group expansion — true direct addressing only.
+
+(DefineAudience
+  :name "Direct"
+  :doc "Direct-addressing predicate. Tests literal membership\n        in the activity's :to or :cc."
+  :member-of (fn
+    (actor audience)
+    (or
+      (member? actor (-> audience :to))
+      (member? actor (-> audience :cc)))))
diff --git a/next/genesis/audience/followers.sx b/next/genesis/audience/followers.sx
new file mode 100644
index 00000000..e171d47b
--- /dev/null
+++ b/next/genesis/audience/followers.sx
@@ -0,0 +1,14 @@
+;; next/genesis/audience/followers.sx
+;;
+;; Followers audience: an actor is a member iff they appear in
+;; the audience-owner's :followers set in the audience-graph
+;; projection. Federation (m2) wires this to peer delivery.
+
+(DefineAudience
+  :name "Followers"
+  :doc "Followers-of-owner predicate. Looks up the\n        audience-graph projection's :followers list for the\n        audience owner and tests membership."
+  :member-of (fn
+    (actor audience)
+    (member?
+      actor
+      (-> (get-projection :audience-graph) (-> audience :owner) :followers))))
diff --git a/next/genesis/audience/public.sx b/next/genesis/audience/public.sx
new file mode 100644
index 00000000..c6aa01ce
--- /dev/null
+++ b/next/genesis/audience/public.sx
@@ -0,0 +1,9 @@
+;; next/genesis/audience/public.sx
+;;
+;; Public audience: every actor is a member. Maps to the AP
+;; magic id `https://www.w3.org/ns/activitystreams#Public`.
+
+(DefineAudience
+  :name "Public"
+  :doc "Public audience predicate. Always returns true — every\n        actor on the network is considered a member."
+  :member-of (fn (actor audience) true))
diff --git a/next/genesis/codecs/dag-cbor.sx b/next/genesis/codecs/dag-cbor.sx
new file mode 100644
index 00000000..58d03dcc
--- /dev/null
+++ b/next/genesis/codecs/dag-cbor.sx
@@ -0,0 +1,13 @@
+;; next/genesis/codecs/dag-cbor.sx
+;;
+;; Canonical CBOR encoding per IPLD dag-cbor. Used to compute
+;; envelope canonical bytes for signature coverage and to serialise
+;; the genesis bundle itself. In Erlang-on-SX mode the kernel
+;; dispatches to the host cid:to_string substrate (Step 1b) when
+;; this codec is requested.
+
+(DefineCodec
+  :name "dag-cbor"
+  :doc "Deterministic CBOR with dag-cbor restrictions: sorted\n        map keys, no floats unless required, no indefinite-length\n        items. The canonical wire format for fed-sx artifacts."
+  :encode (fn (term) (host-codec :dag-cbor :encode term))
+  :decode (fn (bytes) (host-codec :dag-cbor :decode bytes)))
diff --git a/next/genesis/codecs/dag-json.sx b/next/genesis/codecs/dag-json.sx
new file mode 100644
index 00000000..982d05e8
--- /dev/null
+++ b/next/genesis/codecs/dag-json.sx
@@ -0,0 +1,12 @@
+;; next/genesis/codecs/dag-json.sx
+;;
+;; JSON encoding with dag-json restrictions per IPLD: sorted map
+;; keys, no NaN / Infinity, no comments, CIDs as `{"/": "..."}`.
+;; Used as the human-readable wire format for ActivityPub interop
+;; (JSON-LD over dag-json).
+
+(DefineCodec
+  :name "dag-json"
+  :doc "Deterministic JSON with dag-json restrictions. Sorted\n        keys, CIDs as the {\"/\": \"...\"} object. Used by the\n        HTTP server (Step 8) for application/json responses."
+  :encode (fn (term) (host-codec :dag-json :encode term))
+  :decode (fn (bytes) (host-codec :dag-json :decode bytes)))
diff --git a/next/genesis/codecs/raw.sx b/next/genesis/codecs/raw.sx
new file mode 100644
index 00000000..e4a27301
--- /dev/null
+++ b/next/genesis/codecs/raw.sx
@@ -0,0 +1,12 @@
+;; next/genesis/codecs/raw.sx
+;;
+;; Identity codec — input bytes pass through unchanged in both
+;; directions. Used for already-encoded payloads and for binary
+;; artifacts (images, archives) whose CID is computed over the
+;; raw bytes directly.
+
+(DefineCodec
+  :name "raw"
+  :doc "Identity codec. The CID's multicodec byte is 0x55.\n        :encode and :decode return their input unchanged."
+  :encode (fn (bytes) bytes)
+  :decode (fn (bytes) bytes))
diff --git a/next/genesis/manifest.sx b/next/genesis/manifest.sx
index cba82f45..4dbeb568 100644
--- a/next/genesis/manifest.sx
+++ b/next/genesis/manifest.sx
@@ -41,6 +41,6 @@
   :validators ("validators/envelope-shape.sx"
     "validators/signature.sx"
     "validators/type-schema.sx")
-  :codecs ()
-  :sig-suites ()
-  :audience ())
+  :codecs ("codecs/dag-cbor.sx" "codecs/raw.sx" "codecs/dag-json.sx")
+  :sig-suites ("sig-suites/rsa-sha256-2018.sx" "sig-suites/ed25519-2020.sx")
+  :audience ("audience/public.sx" "audience/followers.sx" "audience/direct.sx"))
diff --git a/next/genesis/sig-suites/ed25519-2020.sx b/next/genesis/sig-suites/ed25519-2020.sx
new file mode 100644
index 00000000..eb07cc8d
--- /dev/null
+++ b/next/genesis/sig-suites/ed25519-2020.sx
@@ -0,0 +1,11 @@
+;; next/genesis/sig-suites/ed25519-2020.sx
+;;
+;; W3C Verifiable Credential signature suite — Ed25519 over
+;; canonical bytes, key material in multibase. Default suite
+;; for fed-sx actors per design §9.
+
+(DefineSigSuite
+  :name "ed25519-2020"
+  :doc "Ed25519 verification. Key carries publicKeyMultibase.\n        :verify takes canonical-bytes + signature + key and\n        returns bool. Real verification deferred to m2 once\n        crypto:verify_ed25519/3 BIF lands; v1 stand-in returns\n        false to defer all Ed25519-signed activities."
+  :verify (fn (canonical-bytes signature key) false)
+  :key-format (fn (key-doc) (string? (-> key-doc :publicKeyMultibase))))
diff --git a/next/genesis/sig-suites/rsa-sha256-2018.sx b/next/genesis/sig-suites/rsa-sha256-2018.sx
new file mode 100644
index 00000000..c778f4cb
--- /dev/null
+++ b/next/genesis/sig-suites/rsa-sha256-2018.sx
@@ -0,0 +1,11 @@
+;; next/genesis/sig-suites/rsa-sha256-2018.sx
+;;
+;; W3C Verifiable Credential signature suite — RSA-SHA256 over
+;; canonical bytes, key material in PEM. Compatible with
+;; Mastodon's HTTP-Signatures / Linked-Data-Signatures-2017.
+
+(DefineSigSuite
+  :name "rsa-sha256-2018"
+  :doc "RSA-SHA256 verification. Key carries publicKeyPem.\n        :verify takes canonical-bytes + signature + key and\n        returns bool. Real verification deferred to m2 once\n        crypto:verify_rsa/3 BIF lands; v1 stand-in returns\n        false to defer all RSA-signed activities."
+  :verify (fn (canonical-bytes signature key) false)
+  :key-format (fn (key-doc) (string? (-> key-doc :publicKeyPem))))
diff --git a/next/tests/genesis_parse.sh b/next/tests/genesis_parse.sh
index 913a68ee..2cb3eba7 100755
--- a/next/tests/genesis_parse.sh
+++ b/next/tests/genesis_parse.sh
@@ -3,7 +3,7 @@
 #
 # Confirms the seed genesis SX files parse cleanly and have the
 # expected top-level head form. The bundler (Step 4c+) consumes
-# these forms directly as data. 36 cases.
+# these forms directly as data. 50 cases.
 
 set -uo pipefail
 cd "$(git rev-parse --show-toplevel)"
@@ -94,6 +94,34 @@ cat > "$TMPFILE" <<'EPOCHS'
 (eval "(get (apply dict (rest (parse (file-read \"next/genesis/validators/type-schema.sx\")))) :name)")
 (epoch 64)
 (eval "(len (get (apply dict (rest (parse (file-read \"next/genesis/manifest.sx\")))) :validators))")
+(epoch 70)
+(eval "(first (parse (file-read \"next/genesis/codecs/dag-cbor.sx\")))")
+(epoch 71)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/codecs/dag-cbor.sx\")))) :name)")
+(epoch 72)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/codecs/raw.sx\")))) :name)")
+(epoch 73)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/codecs/dag-json.sx\")))) :name)")
+(epoch 74)
+(eval "(len (get (apply dict (rest (parse (file-read \"next/genesis/manifest.sx\")))) :codecs))")
+(epoch 80)
+(eval "(first (parse (file-read \"next/genesis/sig-suites/rsa-sha256-2018.sx\")))")
+(epoch 81)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/sig-suites/rsa-sha256-2018.sx\")))) :name)")
+(epoch 82)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/sig-suites/ed25519-2020.sx\")))) :name)")
+(epoch 83)
+(eval "(len (get (apply dict (rest (parse (file-read \"next/genesis/manifest.sx\")))) :sig-suites))")
+(epoch 90)
+(eval "(first (parse (file-read \"next/genesis/audience/public.sx\")))")
+(epoch 91)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/audience/public.sx\")))) :name)")
+(epoch 92)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/audience/followers.sx\")))) :name)")
+(epoch 93)
+(eval "(get (apply dict (rest (parse (file-read \"next/genesis/audience/direct.sx\")))) :name)")
+(epoch 94)
+(eval "(len (get (apply dict (rest (parse (file-read \"next/genesis/manifest.sx\")))) :audience))")
 EPOCHS
 
 OUTPUT=$(timeout 30 "$SX_SERVER" < "$TMPFILE" 2>/dev/null)
@@ -153,6 +181,20 @@ check 61 "envelope-shape.sx name"       "envelope-shape"
 check 62 "signature.sx name"            "signature"
 check 63 "type-schema.sx name"          "type-schema"
 check 64 "manifest has 3 validators"    "3"
+check 70 "dag-cbor.sx head form"        "DefineCodec"
+check 71 "dag-cbor.sx name"             "dag-cbor"
+check 72 "raw.sx name"                  "raw"
+check 73 "dag-json.sx name"             "dag-json"
+check 74 "manifest has 3 codecs"        "3"
+check 80 "rsa-sha256-2018.sx head form" "DefineSigSuite"
+check 81 "rsa-sha256-2018.sx name"      "rsa-sha256-2018"
+check 82 "ed25519-2020.sx name"         "ed25519-2020"
+check 83 "manifest has 2 sig-suites"    "2"
+check 90 "public.sx head form"          "DefineAudience"
+check 91 "public.sx name"               "Public"
+check 92 "followers.sx name"            "Followers"
+check 93 "direct.sx name"               "Direct"
+check 94 "manifest has 3 audience"      "3"
 
 TOTAL=$((PASS+FAIL))
 if [ $FAIL -eq 0 ]; then
diff --git a/plans/fed-sx-milestone-1.md b/plans/fed-sx-milestone-1.md
index 3da23403..ec5de1d3 100644
--- a/plans/fed-sx-milestone-1.md
+++ b/plans/fed-sx-milestone-1.md
@@ -249,7 +249,7 @@ replay(LogState, InitAcc, Fun) -> ...
 - [x] **4b-obj** — Object-types: SXArtifact, Note, Tombstone, DefineActivity, DefineObject, DefineProjection, DefineValidator, DefineCodec, DefineSigSuite, Snapshot — 10 `DefineObject` files + manifest updated + 12 new parse tests
 - [x] **4b-proj** — Projections: activity-log, by-type, by-actor, by-object, actor-state, define-registry, audience-graph — 7 `DefineProjection` files + manifest updated + 9 new parse tests
 - [x] **4b-vld** — Validators: envelope-shape, signature, type-schema — 3 `DefineValidator` files + manifest updated + 5 new parse tests
-- [ ] **4b-cod** — Codecs + sig-suites + audience predicates
+- [x] **4b-cod** — Codecs (dag-cbor, raw, dag-json) + sig-suites (rsa-sha256-2018, ed25519-2020) + audience predicates (Public, Followers, Direct) — 8 SX files + manifest fully populated + 14 new parse tests
 - [ ] **4c** — `bootstrap:read_genesis/1` in Erlang: walk the manifest, file-read each referenced .sx, return parsed forms
 - [ ] **4d** — `bootstrap:build_genesis/1` + `bootstrap:verify_genesis/1`: compute bundle CID over the read forms via the host `cid:to_string` substrate; verify against a stored `bundle.cidhash`
 - [ ] **4e** — `bootstrap:load_genesis/1`: register parsed definitions into the in-memory registry (depends on Step 5)
@@ -955,6 +955,7 @@ 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.
 
+- **2026-05-27** — Step 4b-cod: bootstrap codecs + sig-suites + audience predicates complete. 3 `DefineCodec` files (dag-cbor + raw + dag-json, dag-cbor + dag-json deferring to host-codec primitive when wired), 2 `DefineSigSuite` files (rsa-sha256-2018 PEM-keyed, ed25519-2020 multibase-keyed, both :verify returning false as m2-deferred stand-in), 3 `DefineAudience` files (Public/Followers/Direct member-of predicates per design §16). Manifest now lists 26 bootstrap files across all eight sections; `next/tests/genesis_parse.sh` 50/50. Step 4b complete; remaining Step 4 is bundler code (4c–4e). Erlang conformance 729/729.
 - **2026-05-27** — Step 4b-vld: bootstrap validators complete — 3 `DefineValidator` SX files (envelope-shape mirroring Step 2a, signature stub delegating to envelope:verify_signature/2 per design §9.6, type-schema looking up the object-type schema from define-registry). Manifest `:validators` populated; `next/tests/genesis_parse.sh` 36/36. Erlang conformance 729/729.
 - **2026-05-27** — Step 4b-proj: bootstrap projections complete — 7 `DefineProjection` SX files authored (activity-log identity, by-type/by-actor/by-object indexes, actor-state with key history fold, define-registry meta-fold over Create{Define*}, audience-graph stub). Manifest `:projections` populated; `next/tests/genesis_parse.sh` 31/31. Erlang conformance 729/729.
 - **2026-05-27** — Step 4b-obj: bootstrap object-types complete — 10 `DefineObject` SX files authored (SXArtifact, Note, Tombstone, DefineActivity, DefineObject, DefineProjection, DefineValidator, DefineCodec, DefineSigSuite, Snapshot). Each carries an SX `:schema` predicate. Manifest `:object-types` populated; `next/tests/genesis_parse.sh` 22/22. Erlang conformance 729/729.