feat: add GET /system endpoint for LLM system prompt injection

- GET /system returns a structured system prompt grounding the LLM in
  the environment (OS, hostname, user, shell, Python version) with
  directives for tool usage
- Gated by OPEN_TERMINAL_ENABLE_SYSTEM_PROMPT env var (default: true)
- Advertised via features.system in GET /api/config for consumer discovery
- OPEN_TERMINAL_SYSTEM_PROMPT env var for full prompt override
- Endpoint excluded from OpenAPI schema, auth-protected

Author: tjbck

CHANGELOG.md

@@ -4,6 +4,14 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/).
 
+## [0.11.27] - 2026-03-22
+
+### Added
+
+- 🧠 **System prompt endpoint** (`GET /system`) — returns a structured system prompt for LLM integration, grounding the model in the environment (OS, hostname, user, shell, Python version) with directives for tool usage. Gated by `OPEN_TERMINAL_ENABLE_SYSTEM_PROMPT` (default `true`); advertised via `features.system` in `GET /api/config` so consumers can check support before fetching.
+- ⚙️ **`OPEN_TERMINAL_ENABLE_SYSTEM_PROMPT`** — environment variable (or `enable_system_prompt` in config.toml) to enable/disable the `/system` endpoint and feature flag. Defaults to `true`.
+- ⚙️ **`OPEN_TERMINAL_SYSTEM_PROMPT`** — environment variable (or `system_prompt` in config.toml) to fully override the generated system prompt with custom content.
+
 ## [0.11.26] - 2026-03-20
 
 ### Changed

open_terminal/env.py

@@ -131,6 +131,16 @@ def _resolve_file_env(var: str, default: str = "") -> str:
     str(config.get("enable_notebooks", True)),
 ).lower() not in ("false", "0", "no")
 
+ENABLE_SYSTEM_PROMPT = os.environ.get(
+    "OPEN_TERMINAL_ENABLE_SYSTEM_PROMPT",
+    str(config.get("enable_system_prompt", True)),
+).lower() not in ("false", "0", "no")
+
+SYSTEM_PROMPT = os.environ.get(
+    "OPEN_TERMINAL_SYSTEM_PROMPT",
+    config.get("system_prompt", ""),
+)
+
 MULTI_USER = os.environ.get(
     "OPEN_TERMINAL_MULTI_USER",
     str(config.get("multi_user", False)),

open_terminal/main.py

@@ -23,7 +23,7 @@
 from fastapi.security import HTTPAuthorizationCredentials, HTTPBearer
 from pydantic import BaseModel, Field
 
-from open_terminal.env import API_KEY, BINARY_FILE_MIME_PREFIXES, CORS_ALLOWED_ORIGINS, ENABLE_NOTEBOOKS, ENABLE_TERMINAL, EXECUTE_DESCRIPTION, EXECUTE_TIMEOUT, LOG_DIR, MAX_TERMINAL_SESSIONS, MULTI_USER, OPEN_TERMINAL_INFO, PROCESS_LOG_RETENTION, TERMINAL_TERM
+from open_terminal.env import API_KEY, BINARY_FILE_MIME_PREFIXES, CORS_ALLOWED_ORIGINS, ENABLE_NOTEBOOKS, ENABLE_SYSTEM_PROMPT, ENABLE_TERMINAL, EXECUTE_DESCRIPTION, EXECUTE_TIMEOUT, LOG_DIR, MAX_TERMINAL_SESSIONS, MULTI_USER, OPEN_TERMINAL_INFO, PROCESS_LOG_RETENTION, SYSTEM_PROMPT, TERMINAL_TERM
 from open_terminal.utils.runner import PipeRunner, ProcessRunner, create_runner
 from open_terminal.utils.fs import UserFS
 
@@ -54,6 +54,31 @@ def get_system_info() -> str:
     )
 
 
+def get_system_prompt() -> str:
+    """Build a default system prompt for LLM integration."""
+    if SYSTEM_PROMPT:
+        return SYSTEM_PROMPT
+
+    shell = os.environ.get("SHELL", "/bin/sh")
+    user_part = f" as user '{os.getenv('USER', 'unknown')}'" if not MULTI_USER else ""
+
+    prompt = (
+        f"You have access to a computer running {platform.system()} {platform.release()} ({platform.machine()}) "
+        f'on host "{socket.gethostname()}"{user_part} with {shell}. '
+        f"Python {sys.version.split()[0]} is available.\n\n"
+        "Use your tools to directly interact with the system \u2014 run commands, read and write files, "
+        "and search the filesystem. "
+        "Prefer verifying the current state before making changes. "
+        "When running commands, check the output to confirm success. "
+        "If a command produces no output, that typically means it succeeded."
+    )
+
+    if OPEN_TERMINAL_INFO:
+        prompt += f"\n\n{OPEN_TERMINAL_INFO}"
+
+    return prompt
+
+
 _EXECUTE_DESCRIPTION = (
     "Run a shell command in the background and return a command ID.\n\n"
     + get_system_info()
@@ -304,10 +329,23 @@ async def get_config():
         "features": {
             "terminal": ENABLE_TERMINAL,
             "notebooks": ENABLE_NOTEBOOKS,
+            "system": ENABLE_SYSTEM_PROMPT,
         },
     }
 
 
+if ENABLE_SYSTEM_PROMPT:
+
+    @app.get(
+        "/system",
+        include_in_schema=False,
+        dependencies=[Depends(verify_api_key)],
+    )
+    async def get_system():
+        """Return a system prompt for LLM integration."""
+        return {"prompt": get_system_prompt()}
+
+
 if OPEN_TERMINAL_INFO:
 
     @app.get(

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "open-terminal"
-version = "0.11.26"
+version = "0.11.27"
 description = "A remote terminal API."
 readme = "README.md"
 authors = [