diff --git a/.github/workflows/windows.yml b/.github/workflows/windows.yml
index a7a444e..eb7d859 100644
--- a/.github/workflows/windows.yml
+++ b/.github/workflows/windows.yml
@@ -1,15 +1,11 @@
 name: Windows Build
 
-# Phase 0 Windows de-risk spike. The point of this job is information, not a
-# shippable artifact: it proves (or kills) the make-or-break dependency — gpui
-# at our pinned zed rev, plus the guise component library on top of it —
-# compiling on Windows, and confirms the platform-independent crates build
-# cleanly. A final informational step compiles the whole workspace to log the
-# remaining Windows porting surface (pty/terminal/app are still Unix-only)
-# without failing the gate.
+# Windows build gate. The whole workspace compiles on Windows: the terminal
+# app (ConPTY backend) and the relay sidecar included. The gpui/guise probes
+# run first as distinct steps so a failure in the make-or-break UI dependency
+# is obvious at a glance, then the full workspace build gates every crate.
 #
-# Every probe carries `if: always()` so one failure never hides the others: a
-# single run collects gpui, guise, and full-workspace logs together.
+# Each step carries `if: always()` so one failure never hides the others.
 on:
   workflow_dispatch: {}
   pull_request:
@@ -45,25 +41,8 @@ jobs:
         if: always()
         run: cargo build -p guise-ui
 
-      # Platform-independent crates: pure logic, no OS calls. These must build.
-      - name: Build portable crates
+      # The whole workspace now builds on Windows — the terminal app (ConPTY
+      # backend) and the relay sidecar included. This gates every crate.
+      - name: Build workspace
         if: always()
-        run: >
-          cargo build
-          -p vt -p input -p workspace -p theme -p config
-          -p macros -p mcp -p cast -p plugin
-
-      # The terminal application and its backend: pty (ConPTY), terminal, notes,
-      # and app itself all build on Windows.
-      - name: Build terminal app
-        if: always()
-        run: cargo build -p pty -p terminal -p notes -p app
-
-      # Informational only: compile the whole workspace so the log captures the
-      # remaining Windows surface. `relay` (the standalone sidecar) is still
-      # Unix-only; `--keep-going` enumerates every failing crate in one run.
-      # Expected to fail on relay today; never gates.
-      - name: Full workspace surface (informational)
-        if: always()
-        continue-on-error: true
-        run: cargo build --workspace --keep-going
+        run: cargo build --workspace
diff --git a/Cargo.lock b/Cargo.lock
index 9626ab1..f3e263b 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6903,6 +6903,7 @@ dependencies = [
  "tracing",
  "tracing-subscriber",
  "uuid",
+ "windows 0.58.0",
 ]
 
 [[package]]
diff --git a/crates/relay/Cargo.toml b/crates/relay/Cargo.toml
index fbcc3b2..77b1e58 100644
--- a/crates/relay/Cargo.toml
+++ b/crates/relay/Cargo.toml
@@ -22,4 +22,12 @@ tracing = "0.1"
 tracing-subscriber = { version = "0.3", features = ["env-filter"] }
 anyhow = "1"
 clap = { version = "4", features = ["derive"] }
+
+[target.'cfg(unix)'.dependencies]
 libc = "0.2"
+
+[target.'cfg(windows)'.dependencies]
+windows = { version = "0.58", features = [
+    "Win32_Foundation",
+    "Win32_System_Threading",
+] }
diff --git a/crates/relay/src/cli/launch.rs b/crates/relay/src/cli/launch.rs
index 338e2c0..a7a15fe 100644
--- a/crates/relay/src/cli/launch.rs
+++ b/crates/relay/src/cli/launch.rs
@@ -1,7 +1,6 @@
 use super::{agent, http, paths, role, LaunchArgs};
 use anyhow::{anyhow, Result};
 use std::io::Write;
-use std::os::unix::process::CommandExt;
 use std::process::Command;
 
 /// Launch an agent wired to the bus. Foreground takes over this terminal;
@@ -101,11 +100,26 @@ pub async fn launch(a: LaunchArgs) -> Result<()> {
     } else {
         let label = if a.cmd.is_some() { "custom" } else { agent_name.as_str() };
         println!("launching {label} as '{name}' on {endpoint} …");
-        let err = Command::new(&built.program)
-            .args(&built.args)
-            .current_dir(&cwd)
-            .exec();
-        Err(anyhow!("failed to exec {}: {err}", built.program))
+        // Foreground: replace this process on Unix; on Windows, run it to
+        // completion and exit with its status (there is no exec()).
+        #[cfg(unix)]
+        {
+            use std::os::unix::process::CommandExt;
+            let err = Command::new(&built.program)
+                .args(&built.args)
+                .current_dir(&cwd)
+                .exec();
+            Err(anyhow!("failed to exec {}: {err}", built.program))
+        }
+        #[cfg(windows)]
+        {
+            let status = Command::new(&built.program)
+                .args(&built.args)
+                .current_dir(&cwd)
+                .status()
+                .map_err(|e| anyhow!("failed to run {}: {e}", built.program))?;
+            std::process::exit(status.code().unwrap_or(1));
+        }
     }
 }
 
diff --git a/crates/relay/src/cli/paths.rs b/crates/relay/src/cli/paths.rs
index ba17c3f..9ee9fb2 100644
--- a/crates/relay/src/cli/paths.rs
+++ b/crates/relay/src/cli/paths.rs
@@ -44,15 +44,21 @@ pub fn abs_dir() -> PathBuf {
 pub fn ensure_dir() -> Result<()> {
     let d = dir();
     std::fs::create_dir_all(&d)?;
-    use std::os::unix::fs::PermissionsExt;
-    let _ = std::fs::set_permissions(&d, std::fs::Permissions::from_mode(0o700));
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let _ = std::fs::set_permissions(&d, std::fs::Permissions::from_mode(0o700));
+    }
     Ok(())
 }
 
 /// Restrict a freshly written file in the state dir to owner read/write.
-pub fn lock_file(path: &std::path::Path) {
-    use std::os::unix::fs::PermissionsExt;
-    let _ = std::fs::set_permissions(path, std::fs::Permissions::from_mode(0o600));
+pub fn lock_file(_path: &std::path::Path) {
+    #[cfg(unix)]
+    {
+        use std::os::unix::fs::PermissionsExt;
+        let _ = std::fs::set_permissions(_path, std::fs::Permissions::from_mode(0o600));
+    }
 }
 
 pub fn info_path() -> PathBuf {
@@ -108,7 +114,7 @@ pub fn endpoint(addr: &str) -> String {
 
 /// True if a process with this pid is alive.
 pub fn alive(pid: u32) -> bool {
-    unsafe { libc::kill(pid as i32, 0) == 0 }
+    crate::proc::alive(pid)
 }
 
 /// Pids of spawned workers, persisted so a fresh daemon can reap children left
@@ -169,9 +175,7 @@ pub fn reap_stray_workers() {
     let me = std::process::id();
     for pid in read_pids() {
         if pid != 0 && pid != me && alive(pid) {
-            unsafe {
-                libc::kill(pid as i32, libc::SIGKILL);
-            }
+            crate::proc::kill(pid);
         }
     }
     let _ = std::fs::remove_file(workers_pids_path());
diff --git a/crates/relay/src/cli/server.rs b/crates/relay/src/cli/server.rs
index 00a1622..9a9e497 100644
--- a/crates/relay/src/cli/server.rs
+++ b/crates/relay/src/cli/server.rs
@@ -11,7 +11,6 @@ use axum::http::{header::AUTHORIZATION, StatusCode};
 use axum::response::{IntoResponse, Response};
 use axum::routing::{get, post};
 use axum::Router;
-use std::os::unix::process::CommandExt;
 use std::process::{Command, Stdio};
 use std::time::Duration;
 
@@ -145,11 +144,19 @@ fn constant_time_eq(a: &str, b: &str) -> bool {
 }
 
 async fn shutdown(app: App) {
-    use tokio::signal::unix::{signal, SignalKind};
-    let mut term = signal(SignalKind::terminate()).expect("sigterm");
-    tokio::select! {
-        _ = tokio::signal::ctrl_c() => {}
-        _ = term.recv() => {}
+    #[cfg(unix)]
+    {
+        use tokio::signal::unix::{signal, SignalKind};
+        let mut term = signal(SignalKind::terminate()).expect("sigterm");
+        tokio::select! {
+            _ = tokio::signal::ctrl_c() => {}
+            _ = term.recv() => {}
+        }
+    }
+    #[cfg(windows)]
+    {
+        // No SIGTERM on Windows; Ctrl-C (or a hard terminate) ends the daemon.
+        let _ = tokio::signal::ctrl_c().await;
     }
     tracing::info!("shutting down; stopping workers");
     spawn::stop_all(&app).await;
@@ -183,12 +190,25 @@ pub fn start(args: ServeArgs) -> Result<()> {
         .stdin(Stdio::null())
         .stdout(Stdio::from(log))
         .stderr(Stdio::from(errlog));
+    // Detach into a new session/group so the daemon survives the launching
+    // shell exiting.
+    #[cfg(unix)]
     unsafe {
+        use std::os::unix::process::CommandExt;
         cmd.pre_exec(|| {
             libc::setsid();
             Ok(())
         });
     }
+    #[cfg(windows)]
+    {
+        use std::os::windows::process::CommandExt;
+        // DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP | CREATE_NO_WINDOW.
+        const DETACHED_PROCESS: u32 = 0x0000_0008;
+        const CREATE_NEW_PROCESS_GROUP: u32 = 0x0000_0200;
+        const CREATE_NO_WINDOW: u32 = 0x0800_0000;
+        cmd.creation_flags(DETACHED_PROCESS | CREATE_NEW_PROCESS_GROUP | CREATE_NO_WINDOW);
+    }
     cmd.spawn()?;
 
     for _ in 0..40 {
@@ -211,9 +231,7 @@ pub fn stop() -> Result<()> {
         println!("relay was not running (cleaned stale record)");
         return Ok(());
     }
-    unsafe {
-        libc::kill(info.pid as i32, libc::SIGTERM);
-    }
+    crate::proc::terminate(info.pid);
     for _ in 0..40 {
         if !paths::alive(info.pid) {
             paths::clear_info();
diff --git a/crates/relay/src/main.rs b/crates/relay/src/main.rs
index f10e28e..f6d6c5e 100644
--- a/crates/relay/src/main.rs
+++ b/crates/relay/src/main.rs
@@ -3,6 +3,7 @@ mod cli;
 mod control;
 mod db;
 mod mcp;
+mod proc;
 mod protocol;
 mod spawn;
 mod state;
diff --git a/crates/relay/src/proc.rs b/crates/relay/src/proc.rs
new file mode 100644
index 0000000..cae915d
--- /dev/null
+++ b/crates/relay/src/proc.rs
@@ -0,0 +1,65 @@
+//! Cross-platform process control for the daemon manager: liveness checks and
+//! termination by pid. Unix uses signals; Windows uses the process APIs — there
+//! is no SIGTERM for a detached console daemon, so `terminate` is a hard
+//! `TerminateProcess` there, same as `kill`.
+
+/// True if a process with this pid exists.
+#[cfg(unix)]
+pub fn alive(pid: u32) -> bool {
+    unsafe { libc::kill(pid as i32, 0) == 0 }
+}
+
+/// Ask the process to stop (SIGTERM).
+#[cfg(unix)]
+pub fn terminate(pid: u32) {
+    unsafe {
+        libc::kill(pid as i32, libc::SIGTERM);
+    }
+}
+
+/// Force-kill the process (SIGKILL).
+#[cfg(unix)]
+pub fn kill(pid: u32) {
+    unsafe {
+        libc::kill(pid as i32, libc::SIGKILL);
+    }
+}
+
+#[cfg(windows)]
+use windows::Win32::Foundation::CloseHandle;
+#[cfg(windows)]
+use windows::Win32::System::Threading::{
+    OpenProcess, TerminateProcess, PROCESS_QUERY_LIMITED_INFORMATION, PROCESS_TERMINATE,
+};
+
+/// True if a handle can be opened for this pid (the process exists).
+#[cfg(windows)]
+pub fn alive(pid: u32) -> bool {
+    unsafe {
+        match OpenProcess(PROCESS_QUERY_LIMITED_INFORMATION, false, pid) {
+            Ok(h) => {
+                let _ = CloseHandle(h);
+                true
+            }
+            Err(_) => false,
+        }
+    }
+}
+
+/// Terminate the process. No SIGTERM equivalent for a detached console daemon,
+/// so this hard-terminates (same as [`kill`]).
+#[cfg(windows)]
+pub fn terminate(pid: u32) {
+    kill(pid);
+}
+
+/// Force-kill the process.
+#[cfg(windows)]
+pub fn kill(pid: u32) {
+    unsafe {
+        if let Ok(h) = OpenProcess(PROCESS_TERMINATE, false, pid) {
+            let _ = TerminateProcess(h, 1);
+            let _ = CloseHandle(h);
+        }
+    }
+}
diff --git a/crates/relay/src/spawn/mod.rs b/crates/relay/src/spawn/mod.rs
index dceaef3..dccac28 100644
--- a/crates/relay/src/spawn/mod.rs
+++ b/crates/relay/src/spawn/mod.rs
@@ -211,9 +211,7 @@ pub async fn stop(app: &App, name: &str) -> bool {
     w.stop.store(true, Ordering::SeqCst);
     let pid = w.pid.load(Ordering::SeqCst);
     if pid != 0 {
-        unsafe {
-            libc::kill(pid as i32, libc::SIGTERM);
-        }
+        crate::proc::terminate(pid);
     }
     true
 }