diff --git a/Cargo.toml b/Cargo.toml
index aaadbf9..6e797ca 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "echoircd"
-version = "0.1.0"
+version = "5.0.0"
 edition = "2021"
 description = "A small, dependency-light IRC daemon in Rust with a modular command/mode/module API."
 license = "MIT"
diff --git a/build.rs b/build.rs
new file mode 100644
index 0000000..cc3a3ce
--- /dev/null
+++ b/build.rs
@@ -0,0 +1,42 @@
+use std::process::Command;
+
+// Capture build provenance (git rev/date, toolchain, target) into env vars the
+// crate reads via env! for the VERSION reply. Always emits every var, with an
+// "unknown" fallback, so a non-git build (e.g. a source tarball) still compiles.
+fn main() {
+    println!("cargo:rerun-if-changed=.git/HEAD");
+    println!("cargo:rerun-if-changed=.git/index");
+
+    let git = |args: &[&str]| {
+        Command::new("git")
+            .args(args)
+            .output()
+            .ok()
+            .filter(|o| o.status.success())
+            .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_string())
+            .filter(|s| !s.is_empty())
+    };
+
+    let hash = git(&["rev-parse", "--short=7", "HEAD"]).unwrap_or_else(|| "unknown".into());
+    let dirty = match git(&["status", "--porcelain", "--untracked-files=no"]) {
+        Some(s) if !s.is_empty() => "-dirty",
+        _ => "",
+    };
+    let date = git(&["log", "-1", "--format=%cd", "--date=short"]).unwrap_or_else(|| "unknown".into());
+
+    let rustc = Command::new(std::env::var("RUSTC").unwrap_or_else(|_| "rustc".into()))
+        .arg("--version")
+        .output()
+        .ok()
+        .map(|o| String::from_utf8_lossy(&o.stdout).trim().to_string())
+        .and_then(|s| s.split_whitespace().nth(1).map(str::to_string))
+        .unwrap_or_else(|| "unknown".into());
+
+    let target = std::env::var("TARGET").unwrap_or_else(|_| "unknown".into());
+
+    println!("cargo:rustc-env=ECHOIRCD_GIT_HASH={hash}");
+    println!("cargo:rustc-env=ECHOIRCD_GIT_DIRTY={dirty}");
+    println!("cargo:rustc-env=ECHOIRCD_COMMIT_DATE={date}");
+    println!("cargo:rustc-env=ECHOIRCD_RUSTC={rustc}");
+    println!("cargo:rustc-env=ECHOIRCD_TARGET={target}");
+}
diff --git a/src/coremods/core_info.rs b/src/coremods/core_info.rs
index 3b3afc6..07325e0 100644
--- a/src/coremods/core_info.rs
+++ b/src/coremods/core_info.rs
@@ -2,7 +2,7 @@
 
 use crate::command::{CmdResult, Command};
 use crate::numeric::*;
-use crate::server::{Server, VERSION};
+use crate::server::{version_comment, Server, RELEASE};
 use crate::users::User;
 use crate::Uid;
 
@@ -677,10 +677,8 @@ impl Command for VersionCmd {
         true
     }
     fn handle(&self, s: &mut Server, uid: Uid, _params: &[String]) -> CmdResult {
-        s.send(
-            uid,
-            format!(":{} 351 * echoircd-{VERSION} {} :", s.name, s.name),
-        );
+        let line = format!("echoircd-{RELEASE} {} :{}", s.name, version_comment());
+        s.numeric(uid, RPL_VERSION, &line);
         CmdResult::Ok
     }
 }
diff --git a/src/numeric.rs b/src/numeric.rs
index 38eb2eb..d81ca43 100644
--- a/src/numeric.rs
+++ b/src/numeric.rs
@@ -78,6 +78,7 @@ pub const RPL_WELCOME: u16 = 1;
 pub const RPL_YOURHOST: u16 = 2;
 pub const RPL_CREATED: u16 = 3;
 pub const RPL_MYINFO: u16 = 4;
+pub const RPL_VERSION: u16 = 351;
 pub const RPL_ISUPPORT: u16 = 5;
 
 pub const RPL_UMODEIS: u16 = 221;
diff --git a/src/server.rs b/src/server.rs
index b02c4b3..7bd5810 100644
--- a/src/server.rs
+++ b/src/server.rs
@@ -28,6 +28,19 @@ use crate::xline::XLine;
 use crate::Uid;
 
 pub const VERSION: &str = env!("CARGO_PKG_VERSION");
+/// The wire version token, major only (e.g. `echoircd-5`), for 002/004/351.
+pub const RELEASE: &str = env!("CARGO_PKG_VERSION_MAJOR");
+// Build provenance, captured by build.rs.
+pub const GIT_HASH: &str = env!("ECHOIRCD_GIT_HASH");
+pub const GIT_DIRTY: &str = env!("ECHOIRCD_GIT_DIRTY");
+pub const COMMIT_DATE: &str = env!("ECHOIRCD_COMMIT_DATE");
+pub const RUSTC: &str = env!("ECHOIRCD_RUSTC");
+pub const TARGET: &str = env!("ECHOIRCD_TARGET");
+
+/// The `RPL_VERSION` (351) comment: full version, build, and toolchain.
+pub fn version_comment() -> String {
+    format!("echoircd {VERSION} · {GIT_HASH}{GIT_DIRTY} · built {COMMIT_DATE} · rustc {RUSTC} · {TARGET}")
+}
 
 /// Background timer cadence + idle/ping timeouts, in seconds.
 pub const TICK_SECS: u64 = 15;
@@ -1507,6 +1520,14 @@ mod tests {
     use crate::users::{valid_nick, User, UserFlags};
     use std::sync::mpsc::{self, Receiver};
 
+    #[test]
+    fn version_token_and_comment() {
+        assert_eq!(RELEASE, "5");
+        let c = version_comment();
+        assert!(c.starts_with("echoircd 5.0.0 \u{b7}"), "unexpected: {c}");
+        assert!(c.contains("rustc ") && c.contains("built "));
+    }
+
     /// Insert a registered user with an output channel readable in the test.
     fn add_user(s: &mut Server, uid: Uid, nick: &str) -> Receiver<String> {
         let (tx, rx) = mpsc::channel();
diff --git a/src/users.rs b/src/users.rs
index ae95865..3a6f092 100644
--- a/src/users.rs
+++ b/src/users.rs
@@ -7,7 +7,7 @@ use std::net::{SocketAddr, TcpStream};
 use crate::extensible::Extensible;
 use crate::module::Hook;
 use crate::numeric::*;
-use crate::server::{Server, VERSION};
+use crate::server::{Server, RELEASE};
 use crate::socketengine::OutSink;
 use crate::Uid;
 
@@ -464,7 +464,7 @@ impl Server {
         self.numeric(
             uid,
             RPL_YOURHOST,
-            &format!(":Your host is {}, running echoircd-{VERSION}", self.name),
+            &format!(":Your host is {}, running echoircd-{RELEASE}", self.name),
         );
         self.numeric(
             uid,
@@ -475,7 +475,7 @@ impl Server {
             uid,
             RPL_MYINFO,
             &format!(
-                "{} echoircd-{VERSION} iowxsgBkDIHrRzWhc qaohvbeIklimnpstzCTcSNORMfjFLgGuBQAPJUdKXwD",
+                "{} echoircd-{RELEASE} iowxsgBkDIHrRzWhc qaohvbeIklimnpstzCTcSNORMfjFLgGuBQAPJUdKXwD",
                 self.name
             ),
         );