Support long-running agent turns

src/agent.rs

@@ -988,6 +988,37 @@ pub(crate) fn system_prompt(model: ModelChoice, extra: &str) -> String {
     }
 }
 
+pub(crate) fn system_prompt_reminder(model: ModelChoice, extra: &str) -> String {
+    format!(
+        "[System prompt reminder follows.]\n{}\n[End system prompt reminder.]",
+        system_prompt(model, extra)
+    )
+}
+
+pub(crate) fn prompt_reminder_due(used: u32, last: u32) -> bool {
+    used.saturating_sub(last) >= 50_000
+}
+
+pub(crate) fn datetime_context() -> String {
+    let when = Command::new("/bin/date")
+        .arg("+%Y-%m-%d %H:%M:%S %Z")
+        .output()
+        .ok()
+        .filter(|output| output.status.success())
+        .map(|output| String::from_utf8_lossy(&output.stdout).trim().to_owned())
+        .filter(|output| !output.is_empty())
+        .unwrap_or_else(|| {
+            SystemTime::now()
+                .duration_since(UNIX_EPOCH)
+                .unwrap_or_default()
+                .as_secs()
+                .to_string()
+        });
+    format!(
+        "Current local date and time at session start: {when}. Use this only when date or time matters."
+    )
+}
+
 pub(crate) fn try_tool_result(active: &ActiveTools) -> Result<Option<String>, String> {
     match active.results.try_recv() {
         Ok(result) => Ok(Some(result)),
@@ -1224,6 +1255,14 @@ mod tests {
             assert!(prompt.contains(&format!("\"name\":\"{name}\"")));
         }
         assert!(prompt.ends_with("extra"));
+        assert!(
+            system_prompt_reminder(ModelChoice::DeepSeekV4Flash, "extra")
+                .contains("[System prompt reminder follows.]")
+        );
+        assert!(datetime_context().starts_with("Current local date and time at session start:"));
+        assert!(!prompt_reminder_due(49_999, 0));
+        assert!(prompt_reminder_due(50_000, 0));
+        assert!(!prompt_reminder_due(80_000, 50_000));
 
         let text = "done<tool_call>read<arg_key>path</arg_key><arg_value>src/main.rs</arg_value></tool_call>";
         let (visible, calls) = parse_tool_calls(ModelChoice::Glm52, text).unwrap();