model/context: per-model ctx window overrides + expose window size in /api/state

hive-ag3nt/src/events.rs

@@ -303,8 +303,30 @@ pub fn default_model() -> &'static str {
 /// Overridable at runtime via `HIVE_CONTEXT_WINDOW_TOKENS` (useful for
 /// future models or when the operator knows the exact limit). The env
 /// var takes precedence over the model-name heuristic.
+///
+/// Resolution order (first match wins):
+/// 1. `HIVE_CONTEXT_WINDOW_TOKENS_<KEY>` — per-model override where KEY
+///    (case-insensitive) is a substring of the active model name.
+///    Set by `hyperhive.contextWindowTokens.<key>` in `agent.nix`.
+/// 2. `HIVE_CONTEXT_WINDOW_TOKENS` — global override (any model).
+/// 3. Auto-derive: haiku → 200 000, sonnet / opus → 1 000 000.
 #[must_use]
 pub fn context_window_tokens(model: &str) -> u64 {
+    let m = model.to_ascii_lowercase();
+    // Per-model overrides: HIVE_CONTEXT_WINDOW_TOKENS_<KEY_UPPER> where
+    // KEY (lowercased) must be a non-empty substring of the model name.
+    for (key, val) in std::env::vars() {
+        if let Some(suffix) = key.strip_prefix("HIVE_CONTEXT_WINDOW_TOKENS_") {
+            if !suffix.is_empty() && m.contains(&suffix.to_ascii_lowercase()) {
+                if let Ok(v) = val.trim().parse::<u64>() {
+                    if v > 0 {
+                        return v;
+                    }
+                }
+            }
+        }
+    }
+    // Global override.
     if let Ok(s) = std::env::var("HIVE_CONTEXT_WINDOW_TOKENS") {
         if let Ok(v) = s.trim().parse::<u64>() {
             if v > 0 {
@@ -312,7 +334,7 @@ pub fn context_window_tokens(model: &str) -> u64 {
             }
         }
     }
-    let m = model.to_ascii_lowercase();
+    // Auto-derive from model family.
     if m.contains("sonnet") || m.contains("opus") {
         1_000_000
     } else {