diff --git a/include/rcp/version.hpp b/include/rcp/version.hpp
index c454f76..92a75aa 100644
--- a/include/rcp/version.hpp
+++ b/include/rcp/version.hpp
@@ -6,6 +6,6 @@
 namespace rcp {
 
 // Semantic version of the cpp-RCP implementation (matches the latest git tag).
-constexpr std::string_view kVersion = "0.3.0";
+constexpr std::string_view kVersion = "1.0.0";
 
 } // namespace rcp
diff --git a/include/relay/relay.hpp b/include/relay/relay.hpp
index 487b7e8..8ada4e8 100644
--- a/include/relay/relay.hpp
+++ b/include/relay/relay.hpp
@@ -24,11 +24,11 @@ namespace relay {
 
 // ── Spec version (§19.4) ─────────────────────────────────────────────────────
 
-constexpr std::string_view kRelaySpecVersion = "0.3";
+constexpr std::string_view kRelaySpecVersion = "1.0";
 
-// NOTE: keep in sync with RELAY spec/version.json. The v0.3 breaking change
-// (§15.7.6 — SOME/IP numeric msg_type) does NOT affect RCP; RCP's
-// ToMessage()/FromMessage() mappings are unchanged from v0.2.
+// NOTE: keep in sync with RELAY spec/version.json. RELAY v1.0 (stable) carries
+// no normative changes from v0.3 — it promotes the spec and freezes §5/§10/§12/
+// §15. RCP's ToMessage()/FromMessage() mappings are unchanged.
 
 // ── Protocol identifiers (§3) ────────────────────────────────────────────────
 
diff --git a/tests/test_cli.cpp b/tests/test_cli.cpp
index bc0e5e9..d1261c3 100644
--- a/tests/test_cli.cpp
+++ b/tests/test_cli.cpp
@@ -75,7 +75,7 @@ TEST_CASE("cli: version --format json has all required fields", "[cli][conforman
         REQUIRE(has_key(s, k));
     }
     REQUIRE(s.find("\"language\":\"cpp\"") != std::string::npos);
-    REQUIRE(s.find("\"spec_version\":\"0.3\"") != std::string::npos);
+    REQUIRE(s.find("\"spec_version\":\"1.0\"") != std::string::npos);
     REQUIRE(s.find("\"protocol_int\":5") != std::string::npos);
 }
 
diff --git a/tests/test_relay.cpp b/tests/test_relay.cpp
index 10384dd..6d18ded 100644
--- a/tests/test_relay.cpp
+++ b/tests/test_relay.cpp
@@ -21,8 +21,8 @@ using namespace std::chrono_literals;
 
 // ── §19.4: SpecVersion constant ───────────────────────────────────────────────
 
-TEST_CASE("relay: kRelaySpecVersion is 0.3", "[relay][conformance]") {
-    REQUIRE(relay::kRelaySpecVersion == "0.3");
+TEST_CASE("relay: kRelaySpecVersion is 1.0", "[relay][conformance]") {
+    REQUIRE(relay::kRelaySpecVersion == "1.0");
 }
 
 // ── §3: Protocol enum ─────────────────────────────────────────────────────────