diff --git a/packages/mettagrid/cpp/include/mettagrid/core/grid_object.hpp b/packages/mettagrid/cpp/include/mettagrid/core/grid_object.hpp
index de8e1c538e2..109300f6446 100644
--- a/packages/mettagrid/cpp/include/mettagrid/core/grid_object.hpp
+++ b/packages/mettagrid/cpp/include/mettagrid/core/grid_object.hpp
@@ -1,6 +1,7 @@
 #ifndef PACKAGES_METTAGRID_CPP_INCLUDE_METTAGRID_CORE_GRID_OBJECT_HPP_
 #define PACKAGES_METTAGRID_CPP_INCLUDE_METTAGRID_CORE_GRID_OBJECT_HPP_
 
+#include <climits>
 #include <cstdint>
 #include <optional>
 #include <span>
@@ -153,8 +154,11 @@ class GridObject : public HasVibe {
     aoe.unregister_effects();
   }
 
-  virtual std::vector<PartialObservationToken> obs_features() const {
-    return {};  // Default: no observable features
+  // observer_agent_id: The agent observing this object (UINT_MAX means no specific observer)
+  // Used by Assembler to report agent-specific cooldowns
+  virtual std::vector<PartialObservationToken> obs_features(unsigned int observer_agent_id = UINT_MAX) const {
+    (void)observer_agent_id;  // Unused in base class
+    return {};                // Default: no observable features
   }
 
   // Commons support
diff --git a/packages/mettagrid/cpp/include/mettagrid/objects/agent.hpp b/packages/mettagrid/cpp/include/mettagrid/objects/agent.hpp
index fbb5d2986ae..74d4e463f80 100644
--- a/packages/mettagrid/cpp/include/mettagrid/objects/agent.hpp
+++ b/packages/mettagrid/cpp/include/mettagrid/objects/agent.hpp
@@ -65,7 +65,7 @@ class Agent : public GridObject, public HasInventory, public Usable {
   // Implementation of Usable interface
   bool onUse(Agent& actor, ActionArg arg) override;
 
-  std::vector<PartialObservationToken> obs_features() const override;
+  std::vector<PartialObservationToken> obs_features(unsigned int observer_agent_id = UINT_MAX) const override;
 
   // Set observation encoder for inventory feature ID lookup
   void set_obs_encoder(const ObservationEncoder* encoder) {
diff --git a/packages/mettagrid/cpp/include/mettagrid/objects/assembler.hpp b/packages/mettagrid/cpp/include/mettagrid/objects/assembler.hpp
index 37f73d93580..1960b6d9689 100644
--- a/packages/mettagrid/cpp/include/mettagrid/objects/assembler.hpp
+++ b/packages/mettagrid/cpp/include/mettagrid/objects/assembler.hpp
@@ -499,7 +499,8 @@ class Assembler : public GridObject, public Usable {
     return true;
   }
 
-  virtual std::vector<PartialObservationToken> obs_features() const override {
+  virtual std::vector<PartialObservationToken> obs_features(unsigned int observer_agent_id = UINT_MAX) const override {
+    (void)observer_agent_id;  // Unused for assemblers
     std::vector<PartialObservationToken> features;
 
     unsigned int remaining = std::min(cooldown_remaining(), 255u);
diff --git a/packages/mettagrid/cpp/include/mettagrid/objects/chest.hpp b/packages/mettagrid/cpp/include/mettagrid/objects/chest.hpp
index fc48bfe3748..d36854c59f5 100644
--- a/packages/mettagrid/cpp/include/mettagrid/objects/chest.hpp
+++ b/packages/mettagrid/cpp/include/mettagrid/objects/chest.hpp
@@ -125,7 +125,8 @@ class Chest : public GridObject, public Usable, public HasInventory {
     return false;
   }
 
-  virtual std::vector<PartialObservationToken> obs_features() const override {
+  virtual std::vector<PartialObservationToken> obs_features(unsigned int observer_agent_id = UINT_MAX) const override {
+    (void)observer_agent_id;  // Unused for chests
     if (!this->obs_encoder) {
       throw std::runtime_error("Observation encoder not set for chest");
     }
diff --git a/packages/mettagrid/cpp/include/mettagrid/objects/commons_chest.hpp b/packages/mettagrid/cpp/include/mettagrid/objects/commons_chest.hpp
index 50d02b02a5b..cf2422239b9 100644
--- a/packages/mettagrid/cpp/include/mettagrid/objects/commons_chest.hpp
+++ b/packages/mettagrid/cpp/include/mettagrid/objects/commons_chest.hpp
@@ -95,7 +95,8 @@ class CommonsChest : public Chest {
   }
 
   // Override obs_features to observe the commons inventory
-  virtual std::vector<PartialObservationToken> obs_features() const override {
+  virtual std::vector<PartialObservationToken> obs_features(unsigned int observer_agent_id = UINT_MAX) const override {
+    (void)observer_agent_id;  // Unused for commons_chests
     if (!this->obs_encoder) {
       throw std::runtime_error("Observation encoder not set for commons_chest");
     }
diff --git a/packages/mettagrid/cpp/include/mettagrid/objects/wall.hpp b/packages/mettagrid/cpp/include/mettagrid/objects/wall.hpp
index dc7bcdc09bb..5a20783f55b 100644
--- a/packages/mettagrid/cpp/include/mettagrid/objects/wall.hpp
+++ b/packages/mettagrid/cpp/include/mettagrid/objects/wall.hpp
@@ -23,7 +23,8 @@ class Wall : public GridObject {
     GridObject::init(cfg.type_id, cfg.type_name, GridLocation(r, c), cfg.tag_ids, cfg.initial_vibe, cfg.aoe);
   }
 
-  std::vector<PartialObservationToken> obs_features() const override {
+  std::vector<PartialObservationToken> obs_features(unsigned int observer_agent_id = UINT_MAX) const override {
+    (void)observer_agent_id;  // Unused for walls
     std::vector<PartialObservationToken> features;
     features.reserve(1 + tag_ids.size() + (this->vibe != 0 ? 1 : 0));
 
diff --git a/packages/mettagrid/cpp/src/mettagrid/objects/agent.cpp b/packages/mettagrid/cpp/src/mettagrid/objects/agent.cpp
index f92d007c84e..8ab7d6c041d 100644
--- a/packages/mettagrid/cpp/src/mettagrid/objects/agent.cpp
+++ b/packages/mettagrid/cpp/src/mettagrid/objects/agent.cpp
@@ -208,7 +208,8 @@ bool Agent::onUse(Agent& actor, ActionArg arg) {
   return false;
 }
 
-std::vector<PartialObservationToken> Agent::obs_features() const {
+std::vector<PartialObservationToken> Agent::obs_features(unsigned int observer_agent_id) const {
+  (void)observer_agent_id;  // Unused for agents
   if (!this->obs_encoder) {
     throw std::runtime_error("Observation encoder not set for agent");
   }