From 2d5da34b3d3412f35c228a551e0ed6b2720d4327 Mon Sep 17 00:00:00 2001
From: aran-yogesh <yogesh.mahendran@langchain.dev>
Date: Sun, 22 Feb 2026 22:01:21 -0800
Subject: [PATCH] feat: inject AGENTS.md into system prompt

---
 apps/agent/agent/prompt.py          | 12 ++++++++++++
 apps/agent/agent/server.py          |  9 +++++++--
 apps/agent/agent/utils/agents_md.py | 30 +++++++++++++++++++++++++++++
 3 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 apps/agent/agent/utils/agents_md.py

diff --git a/apps/agent/agent/prompt.py b/apps/agent/agent/prompt.py
index 0e356ebd..ad94bfbf 100644
--- a/apps/agent/agent/prompt.py
+++ b/apps/agent/agent/prompt.py
@@ -4,6 +4,7 @@ You are operating in a **remote Linux sandbox** at `{working_dir}`.
 
 All code execution and file operations happen in this sandbox environment.
 
+{agents_md_section}
 
 **Important:**
 - Use `{working_dir}` as your working directory for all operations
@@ -72,9 +73,20 @@ def construct_system_prompt(
     working_dir: str,
     linear_project_id: str = "",
     linear_issue_number: str = "",
+    agents_md: str | None = None,
 ) -> str:
+    agents_md_section = ""
+    if agents_md:
+        agents_md_section = (
+            "\nThe following text is pulled from the repository's AGENTS.md file. "
+            "It may contain specific instructions and guidelines for the agent.\n"
+            "<agents_md>\n"
+            f"{agents_md}\n"
+            "</agents_md>\n"
+        )
     return SYSTEM_PROMPT.format(
         working_dir=working_dir,
         linear_project_id=linear_project_id or "<PROJECT_ID>",
         linear_issue_number=linear_issue_number or "<ISSUE_NUMBER>",
+        agents_md_section=agents_md_section,
     )
diff --git a/apps/agent/agent/server.py b/apps/agent/agent/server.py
index c5c97898..37007cc8 100644
--- a/apps/agent/agent/server.py
+++ b/apps/agent/agent/server.py
@@ -42,6 +42,7 @@ SANDBOX_CREATING = "__creating__"
 SANDBOX_CREATION_TIMEOUT = 180
 SANDBOX_POLL_INTERVAL = 1.0
 
+from .utils.agents_md import read_agents_md_in_sandbox
 from .utils.github import (
     git_has_uncommitted_changes,
     is_valid_git_repo,
@@ -136,8 +137,10 @@ async def _clone_or_pull_repo_in_sandbox(  # noqa: PLR0915
                 logger.exception("Failed to restore clean remote URL")
                 raise
 
-        logger.info("Repo updated at %s", repo_dir)
-        return repo_dir
+    logger.info("Repo updated at %s", repo_dir)
+    return repo_dir
+
+
 
     logger.info("Cloning repo %s/%s to %s", owner, repo, repo_dir)
     try:
@@ -327,6 +330,7 @@ async def get_agent(config: RunnableConfig) -> Pregel:  # noqa: PLR0915
     linear_issue = config["configurable"].get("linear_issue", {})
     linear_project_id = linear_issue.get("linear_project_id", "")
     linear_issue_number = linear_issue.get("linear_issue_number", "")
+    agents_md = await read_agents_md_in_sandbox(sandbox_backend, repo_dir)
 
     logger.info("Returning agent with sandbox for thread %s", thread_id)
     return create_deep_agent(
@@ -335,6 +339,7 @@ async def get_agent(config: RunnableConfig) -> Pregel:  # noqa: PLR0915
             repo_dir,
             linear_project_id=linear_project_id,
             linear_issue_number=linear_issue_number,
+            agents_md=agents_md,
         ),
         tools=[http_request, fetch_url, commit_and_open_pr],
         backend=sandbox_backend,
diff --git a/apps/agent/agent/utils/agents_md.py b/apps/agent/agent/utils/agents_md.py
new file mode 100644
index 00000000..3d7ef45b
--- /dev/null
+++ b/apps/agent/agent/utils/agents_md.py
@@ -0,0 +1,30 @@
+"""Helpers for reading agent instructions from AGENTS.md."""
+
+from __future__ import annotations
+
+import asyncio
+import shlex
+
+from deepagents.backends.protocol import SandboxBackendProtocol
+
+
+async def read_agents_md_in_sandbox(
+    sandbox_backend: SandboxBackendProtocol,
+    repo_dir: str | None,
+) -> str | None:
+    """Read AGENTS.md from the repo root if it exists."""
+    if not repo_dir:
+        return None
+
+    safe_agents_path = shlex.quote(f"{repo_dir}/AGENTS.md")
+    loop = asyncio.get_event_loop()
+    result = await loop.run_in_executor(
+        None,
+        sandbox_backend.execute,
+        f"test -f {safe_agents_path} && cat {safe_agents_path}",
+    )
+    if result.exit_code != 0:
+        return None
+    content = result.output or ""
+    content = content.strip()
+    return content or None