diff --git a/apps/agent/agent/middleware/open_pr.py b/apps/agent/agent/middleware/open_pr.py
index 158b7671..af19bf70 100644
--- a/apps/agent/agent/middleware/open_pr.py
+++ b/apps/agent/agent/middleware/open_pr.py
@@ -32,7 +32,7 @@ from ..utils.github import (
     git_push,
 )
 from ..utils.linear import comment_on_linear_issue
-from ..utils.sandbox_state import SANDBOX_BACKENDS
+from ..utils.sandbox_state import get_sandbox_backend
 
 logger = logging.getLogger(__name__)
 
@@ -147,7 +147,7 @@ I've {action} pull request to address this issue:
         repo_owner = repo_config.get("owner")
         repo_name = repo_config.get("name")
 
-        sandbox_backend = SANDBOX_BACKENDS.get(thread_id)
+        sandbox_backend = await get_sandbox_backend(thread_id) if thread_id else None
 
         repo_dir = f"/workspace/{repo_name}"
 
diff --git a/apps/agent/agent/server.py b/apps/agent/agent/server.py
index c44c76b4..b3d92cb7 100644
--- a/apps/agent/agent/server.py
+++ b/apps/agent/agent/server.py
@@ -223,13 +223,29 @@ async def get_agent(config: RunnableConfig) -> Pregel:  # noqa: PLR0915
             tools=[],
         ).with_config(config)
 
+    sandbox_backend = SANDBOX_BACKENDS.get(thread_id)
     sandbox_id = await _get_sandbox_id_from_metadata(thread_id)
 
-    if sandbox_id == SANDBOX_CREATING:
+    if sandbox_id == SANDBOX_CREATING and not sandbox_backend:
         logger.info("Sandbox creation in progress, waiting...")
         sandbox_id = await _wait_for_sandbox_id(thread_id)
 
-    if sandbox_id is None:
+    if sandbox_backend:
+        logger.info("Using cached sandbox backend for thread %s", thread_id)
+        thread = await client.threads.get(thread_id=thread_id)
+        repo_dir = thread.get("metadata", {}).get("repo_dir")
+
+        if repo_owner and repo_name:
+            logger.info("Pulling latest changes for repo %s/%s", repo_owner, repo_name)
+            try:
+                repo_dir = await _clone_or_pull_repo_in_sandbox(
+                    sandbox_backend, repo_owner, repo_name, github_token
+                )
+            except Exception:
+                logger.exception("Failed to pull repo in cached sandbox")
+                raise
+
+    elif sandbox_id is None:
         logger.info("Creating new sandbox for thread %s", thread_id)
         await client.threads.update(thread_id=thread_id, metadata={"sandbox_id": SANDBOX_CREATING})
 
diff --git a/apps/agent/agent/tools/commit_and_open_pr.py b/apps/agent/agent/tools/commit_and_open_pr.py
index 6a40ac73..2afc3615 100644
--- a/apps/agent/agent/tools/commit_and_open_pr.py
+++ b/apps/agent/agent/tools/commit_and_open_pr.py
@@ -5,7 +5,6 @@ from typing import Any
 from langgraph.config import get_config
 
 from ..encryption import decrypt_token
-from ..integrations.langsmith import _create_langsmith_sandbox
 from ..utils.github import (
     create_github_pr,
     get_github_default_branch,
@@ -19,7 +18,7 @@ from ..utils.github import (
     git_has_unpushed_commits,
     git_push,
 )
-from ..utils.sandbox_state import SANDBOX_BACKENDS
+from ..utils.sandbox_state import get_sandbox_backend_sync
 
 logger = logging.getLogger(__name__)
 
@@ -128,15 +127,9 @@ def commit_and_open_pr(
                 "pr_url": None,
             }
 
-        sandbox_backend = SANDBOX_BACKENDS.get(thread_id)
+        sandbox_backend = get_sandbox_backend_sync(thread_id)
         if not sandbox_backend:
-            sandbox_id = configurable.get("sandbox_id")
-
-            if not sandbox_id:
-                return {"success": False, "error": "No sandbox found for thread", "pr_url": None}
-
-            sandbox_backend = _create_langsmith_sandbox(sandbox_id)
-            SANDBOX_BACKENDS[thread_id] = sandbox_backend
+            return {"success": False, "error": "No sandbox found for thread", "pr_url": None}
 
         repo_dir = f"/workspace/{repo_name}"
 
diff --git a/apps/agent/agent/utils/sandbox_state.py b/apps/agent/agent/utils/sandbox_state.py
index 5d8d2b9c..46adc855 100644
--- a/apps/agent/agent/utils/sandbox_state.py
+++ b/apps/agent/agent/utils/sandbox_state.py
@@ -2,7 +2,46 @@
 
 from __future__ import annotations
 
+import asyncio
+import logging
 from typing import Any
 
+from langgraph_sdk import get_client
+
+from ..integrations.langsmith import _create_langsmith_sandbox
+
+logger = logging.getLogger(__name__)
+client = get_client()
+
 # Thread ID -> SandboxBackend mapping, shared between server.py and middleware
 SANDBOX_BACKENDS: dict[str, Any] = {}
+
+
+async def _get_sandbox_id_from_metadata(thread_id: str) -> str | None:
+    """Fetch sandbox_id from thread metadata."""
+    try:
+        thread = await client.threads.get(thread_id=thread_id)
+    except Exception:
+        logger.exception("Failed to fetch thread metadata for sandbox")
+        return None
+    return thread.get("metadata", {}).get("sandbox_id")
+
+
+async def get_sandbox_backend(thread_id: str) -> Any | None:
+    """Get sandbox backend from cache, or connect using thread metadata."""
+    sandbox_backend = SANDBOX_BACKENDS.get(thread_id)
+    if sandbox_backend:
+        return sandbox_backend
+
+    sandbox_id = await _get_sandbox_id_from_metadata(thread_id)
+    if not sandbox_id:
+        return None
+
+    sandbox_backend = await asyncio.to_thread(_create_langsmith_sandbox, sandbox_id)
+    SANDBOX_BACKENDS[thread_id] = sandbox_backend
+    return sandbox_backend
+
+
+def get_sandbox_backend_sync(thread_id: str) -> Any | None:
+    """Sync wrapper for get_sandbox_backend."""
+    return asyncio.run(get_sandbox_backend(thread_id))