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 {

hive-ag3nt/src/web_ui.rs

@@ -357,6 +357,12 @@ struct StateSnapshot {
     /// the operator can see what they just switched to (and what's
     /// in flight). Mutable at runtime via `POST /api/model`.
     model: String,
+    /// Effective context-window token budget for the current model.
+    /// Derived from `events::context_window_tokens(&model)` — respects
+    /// per-model and global `HIVE_CONTEXT_WINDOW_TOKENS_*` overrides then
+    /// falls back to model-family heuristic. Consumers (e.g. dashboard
+    /// badge) use this to render the ctx-usage percentage.
+    context_window_tokens: u64,
     /// Last-inference token usage from the most recent completed
     /// turn — represents the current context-window size at turn-end.
     /// `null` until the first turn finishes.
@@ -451,6 +457,7 @@ async fn api_state(State(state): State<AppState>) -> axum::Json<StateSnapshot> {
     let inbox = recent_inbox(&state.socket, state.flavor()).await;
     let (turn_state, turn_state_since) = state.bus.state_snapshot();
     let model = state.bus.model();
+    let context_window_tokens = crate::events::context_window_tokens(&model);
     let ctx_usage = state.bus.last_ctx_usage();
     let cost_usage = state.bus.last_cost_usage();
     axum::Json(StateSnapshot {
@@ -463,6 +470,7 @@ async fn api_state(State(state): State<AppState>) -> axum::Json<StateSnapshot> {
         turn_state,
         turn_state_since,
         model,
+        context_window_tokens,
         ctx_usage,
         cost_usage,
         gui_enabled: state.gui_vnc_port.is_some(),

nix/templates/harness-base.nix

@@ -37,20 +37,28 @@
   };
 
   options.hyperhive.contextWindowTokens = lib.mkOption {
-    type = lib.types.int;
+    type = lib.types.attrsOf lib.types.int;
-    default = 0;
+    default = { };
-    example = 1000000;
+    example = {
+      haiku = 150000;
+      sonnet = 900000;
+    };
     description = ''
-      Context-window size in tokens for this agent's model. `0` (the
+      Per-model context-window overrides. Each attribute name is a
-      default) means "auto-derive from the model name": haiku → 200 000,
+      model-family short name (e.g. `"haiku"`, `"sonnet"`) matched as a
-      sonnet / opus → 1 000 000. Set an explicit value here when you are
+      case-insensitive substring of the active model name at runtime, so
-      using a model the harness does not recognise, or when Anthropic
+      `"sonnet"` matches `"claude-sonnet-4-5"` and any future variant.
-      changes the window for an existing model family.
+      Empty map (the default) means auto-derive: haiku → 200 000,
+      sonnet / opus → 1 000 000.
 
-      Sets the `HIVE_CONTEXT_WINDOW_TOKENS` environment variable; the
+      Each entry is rendered as
-      harness reads it at runtime and uses it to compute the default
+      `HIVE_CONTEXT_WINDOW_TOKENS_<KEY_UPPER>` (e.g.
-      compaction and auto-reset watermarks (75% and 50% of the window
+      `HIVE_CONTEXT_WINDOW_TOKENS_SONNET = "900000"`). The harness checks
-      respectively).
+      these per-model vars first, then the global
+      `HIVE_CONTEXT_WINDOW_TOKENS`, then the model-family heuristic.
+      At runtime, the effective window drives compaction (75%) and
+      auto-reset (50%) watermarks, and is exposed via `/api/state` as
+      `context_window_tokens`.
     '';
   };
 
@@ -249,13 +257,23 @@
 
     # Model + context-window env vars consumed by the harness at boot.
     # HIVE_DEFAULT_MODEL seeds the initial model selection when no persisted
-    # model choice exists in the state dir. HIVE_CONTEXT_WINDOW_TOKENS
+    # model choice exists in the state dir.
-    # overrides the auto-derived window size (only set when the NixOS option
+    # HIVE_CONTEXT_WINDOW_TOKENS_<KEY_UPPER> provides per-model overrides
-    # is non-zero so an unset env var lets the harness use its own heuristic).
+    # (e.g. HIVE_CONTEXT_WINDOW_TOKENS_SONNET) from contextWindowTokens attrset.
-    environment.variables.HIVE_DEFAULT_MODEL = config.hyperhive.model;
+    # SHELL must be set so claude's Bash tool finds a POSIX shell.
-    environment.variables = lib.mkIf (config.hyperhive.contextWindowTokens != 0) {
+    environment.variables = lib.mkMerge (
-      HIVE_CONTEXT_WINDOW_TOKENS = toString config.hyperhive.contextWindowTokens;
+      [
-    };
+        {
+          HIVE_DEFAULT_MODEL = config.hyperhive.model;
+          SHELL = "${pkgs.bashInteractive}/bin/bash";
+        }
+      ]
+      ++ lib.mapAttrsToList
+        (model: tokens: {
+          "HIVE_CONTEXT_WINDOW_TOKENS_${lib.toUpper model}" = toString tokens;
+        })
+        config.hyperhive.contextWindowTokens
+    );
 
     boot.isNspawnContainer = true;
 
@@ -356,9 +374,6 @@
       };
     };
 
-    # claude's Bash tool refuses to run without a POSIX shell + $SHELL set.
-    environment.variables.SHELL = "${pkgs.bashInteractive}/bin/bash";
-
     system.stateVersion = "25.11";
   };
 }