swarm: a soft context limit per agent, as a percent of the window, applied at turn end

swarmctl/src/inference.rs

@@ -36,6 +36,7 @@ impl SetFlags {
             effort: effort.or(current.effort),
             subagent_models: self.subagent_models.or(current.subagent_models),
             max_subagents: current.max_subagents,
+            soft_context_percent: current.soft_context_percent,
         })
     }
 }
@@ -130,14 +131,18 @@ fn render_configured(s: Option<&InferenceSettings>) -> String {
 fn render(s: &InferenceSettings) -> String {
     const UNSET: &str = "(not set; the agent's own)";
     format!(
-        "model: {}\neffort: {}\nsubagent_models: {}\nmax_subagents: {}\n",
+        "model: {}\neffort: {}\nsubagent_models: {}\nmax_subagents: {}\nsoft_context_percent: {}\n",
         s.model.as_deref().unwrap_or(UNSET),
         s.effort.map_or(UNSET, Effort::as_str),
         s.subagent_models
             .as_ref()
             .map_or_else(|| UNSET.to_owned(), |m| m.join(", ")),
         s.max_subagents
-            .map_or_else(|| "(not set; no cap)".to_owned(), |n| n.to_string())
+            .map_or_else(|| "(not set; no cap)".to_owned(), |n| n.to_string()),
+        s.soft_context_percent.map_or_else(
+            || "(not set; the harness's own watermark)".to_owned(),
+            |n| format!("{n}%")
+        )
     )
 }
 
@@ -198,10 +203,12 @@ mod tests {
         assert_eq!(merged.effort, Some(Effort::High));
     }
 
-    /// `set` has no flag for the cap, and a stored one survives it.
+    /// `set` has no flag for the cap or the soft limit, and stored ones
+    /// survive it.
     #[test]
-    fn set_keeps_the_stored_max_subagents() {
-        let current: InferenceSettings = serde_json::from_str(r#"{"max_subagents":3}"#).unwrap();
+    fn set_keeps_the_stored_cap_and_soft_limit() {
+        let current: InferenceSettings =
+            serde_json::from_str(r#"{"max_subagents":3,"soft_context_percent":20}"#).unwrap();
         let merged = SetFlags {
             model: Some("opus".to_owned()),
             ..flags()
@@ -209,6 +216,7 @@ mod tests {
         .merge(current)
         .unwrap();
         assert_eq!(merged.max_subagents, Some(3));
+        assert_eq!(merged.soft_context_percent, Some(20));
     }
 
     /// An effort the controller would answer 422 for fails before the request.
@@ -259,15 +267,19 @@ mod tests {
             serde_json::from_str(r#"{"configured":{},"effective":null}"#).unwrap();
         assert_eq!(
             render_configured(empty.configured.as_ref()).lines().count(),
-            4
+            5
         );
     }
 
     #[test]
     fn an_empty_value_renders_every_field_as_unset() {
         let row = render(&serde_json::from_str("{}").unwrap());
-        assert_eq!(row.lines().count(), 4);
-        assert!(row.ends_with("max_subagents: (not set; no cap)\n"), "{row}");
+        assert_eq!(row.lines().count(), 5);
+        assert!(
+            row.ends_with("soft_context_percent: (not set; the harness's own watermark)\n"),
+            "{row}"
+        );
+        assert!(row.contains("max_subagents: (not set; no cap)\n"), "{row}");
         assert!(
             row.lines()
                 .take(3)

swarmctl/src/main.rs

@@ -386,11 +386,13 @@ enum AgentVerb {
     /// show what it last did. Fails when the swarm has never heard from the
     /// agent.
     Watch(AgentWatchArgs),
-    /// Show the model, effort, subagent models and subagent cap the swarm sets
-    /// for an agent, or change the model, effort and subagent models.
+    /// Show the model, effort, subagent models, subagent cap and soft context
+    /// limit the swarm sets for an agent, or change the model, effort and
+    /// subagent models.
     ///
-    /// `get` prints the subagent cap (`max_subagents`); `set` has no flag for
-    /// it and keeps a stored one. Only swarm-ui sets it.
+    /// `get` prints the subagent cap (`max_subagents`) and the soft context
+    /// limit (`soft_context_percent`); `set` has no flag for them and keeps
+    /// stored ones. Only swarm-ui sets them.
     ///
     /// A field the swarm sets wins over the agent's own value (its agent.nix
     /// or a `hyperhive-model`/`hyperhive-effort` file) from its next turn on;