diff --git a/crates/genie-core/src/lib.rs b/crates/genie-core/src/lib.rs
index 2192cca2..f97d25d5 100644
--- a/crates/genie-core/src/lib.rs
+++ b/crates/genie-core/src/lib.rs
@@ -52,6 +52,7 @@ pub mod prompt;
 pub mod reasoning;
 pub mod repl;
 pub mod runtime_contract;
+pub mod runtime_mode;
 pub mod security;
 pub mod server;
 pub mod skills;
diff --git a/crates/genie-core/src/main.rs b/crates/genie-core/src/main.rs
index 99bd1c6d..69aef1b8 100644
--- a/crates/genie-core/src/main.rs
+++ b/crates/genie-core/src/main.rs
@@ -170,13 +170,25 @@ async fn main() -> Result<()> {
     let voice_requested = std::env::args().any(|a| a == "--voice")
         || std::env::var("GENIEPOD_VOICE").unwrap_or_default() == "1"
         || config.core.voice_enabled;
+    let wakeword_available =
+        !config.core.wakeword_script.as_os_str().is_empty() && config.core.wakeword_script.exists();
+    let startup_decision =
+        runtime_mode::decide_startup_mode(voice_requested, interactive, wakeword_available);
 
     // Whether the running binary actually has the voice subsystem compiled in.
     // When voice was requested but the binary is chat-only (issue #41 feature
     // gate), emit one warning and fall through to the chat path so an existing
     // voice-tagged `geniepod.toml` still deploys cleanly on a chat-only build.
     #[cfg(feature = "voice")]
-    let voice_mode = voice_requested;
+    let voice_mode = {
+        if startup_decision.blocked_push_to_talk() {
+            tracing::warn!(
+                "push-to-talk voice mode requested without an interactive terminal and no wakeword script is available; \
+                 running HTTP API only"
+            );
+        }
+        startup_decision.enters_voice()
+    };
     #[cfg(not(feature = "voice"))]
     let voice_mode = {
         if voice_requested {
@@ -187,6 +199,7 @@ async fn main() -> Result<()> {
                  enable the voice loop."
             );
         }
+        let _ = startup_decision;
         false
     };
 
diff --git a/crates/genie-core/src/runtime_mode.rs b/crates/genie-core/src/runtime_mode.rs
new file mode 100644
index 00000000..8db2f27a
--- /dev/null
+++ b/crates/genie-core/src/runtime_mode.rs
@@ -0,0 +1,108 @@
+//! Startup-mode selection for genie-core.
+
+/// High-level interface selected at process startup.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum StartupMode {
+    /// Run the voice loop.
+    Voice,
+    /// Run the HTTP API / daemon path.
+    HttpOnly,
+}
+
+/// Why startup selected a mode.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub enum StartupReason {
+    VoiceNotRequested,
+    InteractivePushToTalk,
+    WakewordDaemon,
+    PushToTalkNeedsTerminal,
+}
+
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+pub struct StartupDecision {
+    pub mode: StartupMode,
+    pub reason: StartupReason,
+}
+
+impl StartupDecision {
+    pub fn enters_voice(self) -> bool {
+        self.mode == StartupMode::Voice
+    }
+
+    pub fn blocked_push_to_talk(self) -> bool {
+        self.reason == StartupReason::PushToTalkNeedsTerminal
+    }
+}
+
+/// Decide whether startup may enter voice mode.
+///
+/// Push-to-talk consumes stdin, so it is only valid with an interactive
+/// terminal. Wake-word mode owns its own listener process and can run as a
+/// daemon under systemd.
+pub fn decide_startup_mode(
+    voice_requested: bool,
+    stdin_interactive: bool,
+    wakeword_available: bool,
+) -> StartupDecision {
+    if !voice_requested {
+        return StartupDecision {
+            mode: StartupMode::HttpOnly,
+            reason: StartupReason::VoiceNotRequested,
+        };
+    }
+
+    if wakeword_available {
+        return StartupDecision {
+            mode: StartupMode::Voice,
+            reason: StartupReason::WakewordDaemon,
+        };
+    }
+
+    if stdin_interactive {
+        return StartupDecision {
+            mode: StartupMode::Voice,
+            reason: StartupReason::InteractivePushToTalk,
+        };
+    }
+
+    StartupDecision {
+        mode: StartupMode::HttpOnly,
+        reason: StartupReason::PushToTalkNeedsTerminal,
+    }
+}
+
+#[cfg(test)]
+mod tests {
+    use super::{StartupMode, StartupReason, decide_startup_mode};
+
+    #[test]
+    fn systemd_push_to_talk_falls_back_to_http() {
+        let decision = decide_startup_mode(true, false, false);
+        assert_eq!(decision.mode, StartupMode::HttpOnly);
+        assert_eq!(decision.reason, StartupReason::PushToTalkNeedsTerminal);
+        assert!(decision.blocked_push_to_talk());
+    }
+
+    #[test]
+    fn terminal_push_to_talk_still_runs() {
+        let decision = decide_startup_mode(true, true, false);
+        assert_eq!(decision.mode, StartupMode::Voice);
+        assert_eq!(decision.reason, StartupReason::InteractivePushToTalk);
+        assert!(decision.enters_voice());
+    }
+
+    #[test]
+    fn wakeword_voice_can_run_without_terminal() {
+        let decision = decide_startup_mode(true, false, true);
+        assert_eq!(decision.mode, StartupMode::Voice);
+        assert_eq!(decision.reason, StartupReason::WakewordDaemon);
+        assert!(decision.enters_voice());
+    }
+
+    #[test]
+    fn voice_disabled_stays_http_only() {
+        let decision = decide_startup_mode(false, true, true);
+        assert_eq!(decision.mode, StartupMode::HttpOnly);
+        assert_eq!(decision.reason, StartupReason::VoiceNotRequested);
+    }
+}