diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..99b7341
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,16 @@
+# Changelog
+
+## v0.4.0
+
+### Breaking changes
+
+- If you're running agentapi behind a reverse proxy, you'll now likely need to set the `--allowed-hosts` flag. See the [README](./README.md) for more details.
+
+### New features
+
+- Sourcegraph Amp support
+- Added a new `--allowed-hosts` flag to the `server` command.
+
+### Fixes
+
+- Updated Codex support after its TUI has been updated in a recent version.
diff --git a/chat/package.json b/chat/package.json
index c37fcb9..cd780d1 100644
--- a/chat/package.json
+++ b/chat/package.json
@@ -1,6 +1,6 @@
 {
   "name": "chat",
-  "version": "0.3.3",
+  "version": "0.4.0",
   "private": true,
   "scripts": {
     "dev": "next dev --turbopack",
diff --git a/cmd/root.go b/cmd/root.go
index dbeb9c4..4ece80e 100644
--- a/cmd/root.go
+++ b/cmd/root.go
@@ -13,7 +13,7 @@ var rootCmd = &cobra.Command{
 	Use:     "agentapi",
 	Short:   "AgentAPI CLI",
 	Long:    `AgentAPI - HTTP API for Claude Code, Goose, Aider, Gemini and Codex`,
-	Version: "0.3.3",
+	Version: "0.4.0",
 }
 
 func Execute() {
diff --git a/lib/httpapi/server.go b/lib/httpapi/server.go
index 4f1bb14..34b11f5 100644
--- a/lib/httpapi/server.go
+++ b/lib/httpapi/server.go
@@ -188,7 +188,7 @@ func NewServer(ctx context.Context, config ServerConfig) (*Server, error) {
 	})
 	router.Use(corsMiddleware.Handler)
 
-	humaConfig := huma.DefaultConfig("AgentAPI", "0.3.3")
+	humaConfig := huma.DefaultConfig("AgentAPI", "0.4.0")
 	humaConfig.Info.Description = "HTTP API for Claude Code, Goose, and Aider.\n\nhttps://github.com/coder/agentapi"
 	api := humachi.New(router, humaConfig)
 	formatMessage := func(message string, userInput string) string {
diff --git a/openapi.json b/openapi.json
index 639e180..c77c5b6 100644
--- a/openapi.json
+++ b/openapi.json
@@ -307,7 +307,7 @@
   "info": {
     "description": "HTTP API for Claude Code, Goose, and Aider.\n\nhttps://github.com/coder/agentapi",
     "title": "AgentAPI",
-    "version": "0.3.3"
+    "version": "0.4.0"
   },
   "openapi": "3.1.0",
   "paths": {