diff --git a/tools/terminal_tool.py b/tools/terminal_tool.py
index 8d091705fc1..3e17d2c865e 100644
--- a/tools/terminal_tool.py
+++ b/tools/terminal_tool.py
@@ -972,9 +972,14 @@ def register_task_env_overrides(task_id: str, overrides: Dict[str, Any]):
     # while letting an explicit ACP cwd change win, as the client expects.
     new_cwd = overrides.get("cwd")
     if isinstance(new_cwd, str) and new_cwd.strip():
+        # The live env is cached under the raw task_id for per-session surfaces
+        # (ACP/gateway/dashboard) and under the collapsed container id for
+        # isolation-keyed rollouts. Try the raw id first, then the container id,
+        # so a CWD-only override (which collapses to "default") still finds and
+        # updates the originating session's env.
         container_id = _resolve_container_task_id(task_id)
         with _env_lock:
-            env = _active_environments.get(container_id)
+            env = _active_environments.get(task_id) or _active_environments.get(container_id)
         if env is not None and getattr(env, "cwd", None) is not None:
             env.cwd = new_cwd
 
@@ -1848,8 +1853,20 @@ def terminal_tool(
         effective_task_id = _resolve_container_task_id(task_id)
 
         # Check per-task overrides (set by environments like TerminalBench2Env)
-        # before falling back to global env var config
-        overrides = _task_env_overrides.get(effective_task_id, {})
+        # before falling back to global env var config.
+        #
+        # Overrides are keyed by the *raw* task_id (that's the key
+        # ``register_task_env_overrides`` writes under), NOT by the collapsed
+        # container id. A CWD-only override collapses ``effective_task_id`` to
+        # ``"default"`` for container sharing, but its cwd must still be read
+        # back here under the originating task_id, or the override is silently
+        # dropped. Fall back to the collapsed id so isolation-keyed RL/benchmark
+        # overrides (registered under an id that equals their container id) keep
+        # resolving as before.
+        overrides = (
+            (_task_env_overrides.get(task_id) if task_id else None)
+            or _task_env_overrides.get(effective_task_id, {})
+        )
         
         # Select image based on env type, with per-task override support
         if env_type == "docker":
@@ -1898,9 +1915,18 @@ def terminal_tool(
         # task_id wait for the first one to finish creating the sandbox,
         # instead of each creating their own (wasting Modal resources).
         with _env_lock:
-            if effective_task_id in _active_environments:
-                _last_activity[effective_task_id] = time.time()
-                env = _active_environments[effective_task_id]
+            # Prefer the collapsed container id, but fall back to an env cached
+            # under the raw task_id. Per-session surfaces (ACP/gateway/dashboard)
+            # with a CWD-only override collapse to "default" for container
+            # sharing, yet an env may already be cached under the originating
+            # task_id; honor it instead of spawning a duplicate.
+            _existing_key = (
+                effective_task_id if effective_task_id in _active_environments
+                else (task_id if task_id and task_id in _active_environments else None)
+            )
+            if _existing_key is not None:
+                _last_activity[_existing_key] = time.time()
+                env = _active_environments[_existing_key]
                 needs_creation = False
             else:
                 needs_creation = True
@@ -1915,9 +1941,13 @@ def terminal_tool(
             with task_lock:
                 # Double-check after acquiring the per-task lock
                 with _env_lock:
-                    if effective_task_id in _active_environments:
-                        _last_activity[effective_task_id] = time.time()
-                        env = _active_environments[effective_task_id]
+                    _existing_key = (
+                        effective_task_id if effective_task_id in _active_environments
+                        else (task_id if task_id and task_id in _active_environments else None)
+                    )
+                    if _existing_key is not None:
+                        _last_activity[_existing_key] = time.time()
+                        env = _active_environments[_existing_key]
                         needs_creation = False
 
                 if needs_creation: