fail fast on dimsim lfs pointers

[paul-nechifor]

Problem

If you use GIT_LFS_SKIP_SMUDGE=1 in your environment, git leaves LFS files as pointers. This gives a hard to see 90s timeout error when running dimos --simulation dimsim --dimsim-scene=apartment run unitree-go2-agentic.

Solution

Error faster if the files are LFS pointers.

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ All tests successful. No failed tests found.

@@            Coverage Diff             @@
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+ Coverage   75.73%   76.76%   +1.03%     
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  Files        1264     1237      -27     
  Lines      122029   119026    -3003     
  Branches    10894    10590     -304     
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- Hits        92416    91368    -1048     
+ Misses      26545    24598    -1947     
+ Partials     3068     3060       -8     

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[greptile-apps]

Greptile Summary

This change adds a startup check for Git LFS pointer files in DimSim assets so users receive an actionable fetch command before the simulator starts.

The scene check does not follow the same external-scene precedence as the bridge. A selected scene from DIMSIM_SCENES_DIR can contain an LFS pointer and pass the check, while an unrelated same-named built-in pointer can prevent a valid external scene from starting. The scene directory selected for validation should match the directory that the bridge will serve.

Confidence Score: 4/5

Not safe to merge until the preflight resolves the active scene source using the bridge's external-directory-first behavior.

A focused runtime harness exercised both external and built-in scene shadowing directions through the production preflight helper and the actual bridge resolver. It showed that the two components select different asset sources.

Files Needing Attention: dimos/simulation/dimsim/dimsim_process.py needs to select the effective scene directory consistently with misc/DimSim/cli/bridge/server.ts.

T-Rex Logs

What T-Rex did

• T-Rex produced proofs for two posted P1 findings and linked them to the corresponding review comments.
• Executed the Focused DimSim scene preflight validation harness and captured its execution output.
• Reviewed the general-contract-validation-proof describing preflight guard resolution and noted potential bypass risk for externally resolved scenes and stale built-ins.

_{Ran code and verified through T-Rex}

Comments Outside Diff (1)

1. General comment

   DimSim LFS preflight checks a different scene source than the frontend resolves

   • Bug
     • With a same-named external scene containing an LFS-pointer model.glb and a real built-in model.glb, the preflight returned ALLOWED while the actual bridge served the external pointer. Reversing the assets made preflight BLOCKED even though the bridge served the external real asset.
   • Cause
     • _check_lfs_stubs(scene) scans _DIMSIM_DIR/scenes/<scene> only, while startBridgeServer checks DIMSIM_SCENES_DIR before built-in scene directories.
   • Fix
     • Resolve the effective scene directory using the same precedence as startBridgeServer, then scan that selected scene's GLB/GLTF assets. Preserve the embodiment scan as appropriate.

   _{Ran code and verified through T-Rex}

_{Reviews (1): Last reviewed commit: "fail fast on dimsim lfs pointers" | Re-trigger Greptile}

[greptile-apps]

Scene preflight scans the wrong asset source

DIMSIM_SCENES_DIR takes precedence when the bridge resolves /scenes/, but this check always scans the same-named built-in scene directory. An external scene containing a Git LFS pointer can therefore pass preflight and then be served to DimSim, restoring the delayed asset-loading failure this change is intended to avoid. Conversely, a pointer in a shadowed built-in scene prevents startup even when the selected external scene has valid assets. Resolve the effective scene directory with the bridge's DIMSIM_SCENES_DIR-first precedence before scanning it.

Artifacts

Focused DimSim scene preflight validation harness

• This authored Python harness creates same-named built-in and external scene fixtures, invokes the PR helper body, and requests the actual bridge scene asset, proving whether preflight and resolution agree.

Focused DimSim scene preflight execution output

• This captured successful harness run shows the external LFS pointer was allowed and served, while a built-in pointer falsely blocked a real external override.

_{Ran code and verified through T-Rex}