[paul-nechifor]

Problem

We need a light-er weight simulator.

Closes DIM-xxx

Solution

• Add the DimSim simulator.
• Add tests which use it.

Breaking Changes

The --simulation flag now takes a parameter: either mujoco or dimsim.

How to Test

Run the apt scene:

uv run dimos --simulation=dimsim run unitree-go2-agentic

Run the empty scene:

uv run dimos --dimsim-scene=empty --simulation=dimsim run unitree-go2-agentic

Run the dimsim tests:

uv run pytest -m dimsim

Contributor License Agreement

• I have read and approved the CLA.

[greptile-apps]

Greptile Summary

This PR introduces DimSim as a second simulation backend (alongside MuJoCo), adds a Python SDK (scene_client.py) for WebSocket-based scene control, wires up new e2e tests, and changes the --simulation flag from a boolean to a string parameter.

• Core addition: DimSimConnection, DimSimProcess, and SceneClient provide the new simulator backend with Deno/Playwright-based process management and a rich scene-manipulation API over WebSocket.
• Breaking change: --simulation now takes a value (mujoco or dimsim) instead of acting as a boolean flag; users with SIMULATION=true in .env will silently get a broken routing path instead of an error message.
• Test infrastructure: New dim_sim fixture, DimSimClient wrapper, spawn_wall_on_pose fixture, and three new @pytest.mark.dimsim e2e tests; dimsim mark is correctly excluded from CI.

Confidence Score: 2/5

The DimSim backend is not functional as written: the robot cannot move, odometry is never forwarded to consumers, and the test assertions against robot position will always fail.

The core connection class (DimSimConnection) has multiple unresolved gaps from previous review rounds: move() returns True without publishing to /cmd_vel, odom_stream()/lidar_stream()/video_stream() are permanently silent Subject instances that no code ever pushes to, and _handle_odom only publishes TF without notifying the odom Subject. Together these make every e2e test that asserts on robot position structurally unable to pass. The scene client has an unresolved JS injection path and a recv-thread crash race. DimSimClient.stop() still unconditionally creates and connects a fresh SceneClient during teardown, and the client always binds to hard-coded port 8090.

dimos/robot/unitree/dimsim_connection.py needs the most attention — move(), odom_stream(), lidar_stream(), and video_stream() all need real implementations before any e2e test can pass. dimos/e2e_tests/dim_sim_client.py needs the lazy-init guard in stop() and the configurable port. dimos/simulation/dimsim/scene_client.py needs the JS injection fix in add_collider/remove_collider and the recv-thread KeyError guard.

Important Files Changed

Filename	Overview
dimos/robot/unitree/dimsim_connection.py	New DimSim connection class with multiple unresolved issues: odom/lidar/video streams are permanently silent Subjects, move() never publishes cmd_vel, functools.cache on instance methods leaks memory, and stderr race with log-reader thread.
dimos/simulation/dimsim/scene_client.py	Large new WebSocket SDK for scene manipulation; has JS injection via unencoded name in error strings, a KeyError race in _recv_loop when exec() times out, and unsynchronised _ws.send() calls that race with stop().
dimos/simulation/dimsim/dimsim_process.py	Manages the DimSim subprocess; repo URL points to a personal fork, partial clones leave the directory in a broken state, stderr is closed while the log-reader thread is still iterating it, and playwright install runs unconditionally on every start().
dimos/e2e_tests/dim_sim_client.py	Test fixture wrapper for DimSim; stop() unconditionally triggers lazy SceneClient creation (blocking WebSocket connect) even when no client method was ever called, and always hard-codes port 8090 ignoring dimsim_port config.
dimos/core/global_config.py	Changes simulation from bool to str; a silent breaking change for users with SIMULATION=true/false in .env — the string is accepted by Pydantic but routes to an unrecognised connection type with no helpful error message.
dimos/experimental/security_demo/security_module.py	Defers depth estimator start to start_security_patrol(); _create_visual_servo still uses a plain truthiness check so SIMULATION=dimsim silently uses MuJoCo camera intrinsics instead of DimSim ones.
dimos/simulation/dimsim/deno_utils.py	New utility that auto-installs Deno from GitHub and ensures Playwright Chromium; download is atomic via a temp dir so partial failures clean up correctly. Unsupported platform raises a clear RuntimeError.
dimos/msgs/sensor_msgs/CameraInfo.py	Adds from_intrinsics() and from_fov() factory methods; math is correct for both vertical and horizontal FOV axes, and from_intrinsics sets standard zero-distortion/identity-rectification matrices consistently.
dimos/e2e_tests/conftest.py	Adds dim_sim fixture, spawn_wall_on_pose, explore_house, and refactors start_blueprint to accept simulator kwarg; mcp_port is now injected via fixture rather than passed to the inner function.
dimos/e2e_tests/lcm_spy.py	Refactors listener tracking from index-based to identity-based removal; the change is correct and removes the fragility of index invalidation when listeners are removed out of order.
dimos/robot/unitree/go2/connection.py	Adds dimsim branch in make_connection() and refactors GO2 camera info to use CameraInfo.from_intrinsics(); intrinsics are numerically identical to the previous hand-written K/P matrices.
dimos/robot/unitree/mujoco_connection.py	Replaces manual camera-info computation with CameraInfo.from_fov(axis=vertical), which produces numerically identical results to the old formula.

_{Reviews (22): Last reviewed commit: "feat(sim): add dimsim" | Re-trigger Greptile}

[codecov]

Codecov Report

❌ Patch coverage is 25.78125% with 285 lines in your changes missing coverage. Please review.
✅ All tests successful. No failed tests found.

Files with missing lines	Patch %	Lines
dimos/simulation/dimsim/scene_client.py	15.57%	168 Missing ⚠️
dimos/e2e_tests/conftest.py	14.54%	47 Missing ⚠️
dimos/e2e_tests/test_dimsim_path_replaning.py	16.66%	15 Missing ⚠️
dimos/e2e_tests/dim_sim_client.py	52.00%	12 Missing ⚠️
dimos/e2e_tests/test_dimsim_walk_forward.py	30.00%	7 Missing ⚠️
dimos/e2e_tests/test_dimsim_spatial_memory.py	33.33%	6 Missing ⚠️
dimos/agents/skills/person_follow.py	0.00%	5 Missing ⚠️
dimos/conftest.py	44.44%	4 Missing and 1 partial ⚠️
dimos/e2e_tests/lcm_spy.py	33.33%	4 Missing ⚠️
...imos/experimental/security_demo/security_module.py	20.00%	4 Missing ⚠️
... and 6 more

📢 Thoughts on this report? Let us know!

[leshy]

I have no notes on this apart from LCM, can fix in the followup, amazing!