docker mode: allow username override

README.md

@@ -107,6 +107,15 @@ When a container starts with either label, it automatically appears in the dashb
 
 Containers that only specify `webterm-theme` are still included and use the default auto command.
 
+**Environment Variables:**
+- `WEBTERM_DOCKER_USERNAME` - Set to run Docker exec sessions as a specific user (default: root)
+- `WEBTERM_DOCKER_AUTO_COMMAND` - Override the default `auto` command (default: `tmux new-session -As webterm`)
+
+Example: Start containers and exec into them as `developer` user:
+```bash
+WEBTERM_DOCKER_USERNAME=developer webterm --docker-watch
+```
+
 Example docker-compose.yaml:
 
 ```yaml

src/webterm/docker_exec_session.py

@@ -43,6 +43,7 @@ DA_PARTIAL_PATTERN = re.compile(rb"\x1b(?:\[(?:\?[\d;]*)?)?$")
 class DockerExecSpec:
     container: str
     command: list[str]
+    user: str | None = None
 
 
 class DockerExecSession(Session):
@@ -162,6 +163,8 @@ class DockerExecSession(Session):
             "Tty": True,
             "Cmd": self.exec_spec.command,
         }
+        if self.exec_spec.user:
+            payload["User"] = self.exec_spec.user
         response = self._request_json(
             "POST", f"/containers/{self.exec_spec.container}/exec", payload
         )

src/webterm/session_manager.py

@@ -2,6 +2,7 @@ from __future__ import annotations
 
 import asyncio
 import logging
+import os
 import shlex
 import sys
 from typing import TYPE_CHECKING
@@ -137,9 +138,11 @@ class SessionManager:
             log.warning("Sorry, webterm does not currently support terminals on Windows")
             return None
         if app.command == AUTO_COMMAND_SENTINEL:
+            docker_user = os.environ.get("WEBTERM_DOCKER_USERNAME")
             exec_spec = DockerExecSpec(
                 container=app.name,
                 command=shlex.split(_get_auto_command()),
+                user=docker_user,
             )
             session_process = DockerExecSession(self.poller, session_id, exec_spec)
         else:

tests/test_session_manager.py

@@ -214,6 +214,32 @@ class TestSessionManager:
 
             assert result is not None
             assert isinstance(result, DockerExecSession)
+            assert result.exec_spec.user is None
+
+    async def test_new_docker_exec_session_with_user(self, mock_poller, mock_path, monkeypatch):
+        from webterm.docker_exec_session import DockerExecSession
+
+        monkeypatch.setenv("WEBTERM_DOCKER_USERNAME", "testuser")
+
+        app = App(
+            name="my-container",
+            slug="my-container",
+            path="./",
+            command=AUTO_COMMAND_SENTINEL,
+            terminal=True,
+        )
+        manager = SessionManager(mock_poller, mock_path, [app])
+
+        with patch.object(DockerExecSession, "open", new_callable=AsyncMock):
+            result = await manager.new_session(
+                "my-container",
+                SessionID("test-session"),
+                RouteKey("test-route"),
+            )
+
+            assert result is not None
+            assert isinstance(result, DockerExecSession)
+            assert result.exec_spec.user == "testuser"
 
 
 class TestSessionManagerRoutes: