# Bounded 2D implementation and validation scope

This inventory uses dev `8403956a9afc0b0bb89265cec374392013d89016` as its
production source checkpoint. The accompanying tests add coverage; their presence
is not a passing GPU receipt. Historical campaigns retain their original source
identities and acceptance gates.

## Implementation boundaries

- Uniform D2Q9 supports SRT, TRT and MRT. An available collision selector does not
  qualify every wall, inlet/outlet, forcing, storage or LES combination.
- Fixed refinement supports SRT/MRT, FP32 and double-buffer streaming; TRT and LES
  are rejected. Shifted refinement requires all-blocked storage. Refined channel
  boundaries have narrower configuration guards than uniform boundaries.
- Uniform checkpoints support compatible same-method continuation. Changing
  collision or LES parameters is a different evolution, not exact continuation.
  Jet checkpoints and refined checkpoints are unsupported; synchronized remapping
  is not persistent restart.
- Keep these conclusions 2D. Local D3Q19 operator tests do not establish a supported
  3D Simulation runtime.

## Evidence and remaining gaps

| Area | Available evidence | Boundary of the conclusion |
|---|---|---|
| MRT cylinder flow and observation windows | Full matched uniform/refined MRT DFG and the window-ledger campaign passed their frozen periodicity, reference and matched-comparison gates. The window campaign used `185a919`; dev adds only a docstring correction. | This does not qualify other collision/boundary combinations or every refinement interface. Timing improvements are not additional accuracy evidence. |
| Uniform forced channel | Six Poiseuille GPU cases on `8403956`: SRT/TRT/MRT at wall-normal resolutions H16/H32 passed. | This is the tested analytic channel configuration, not open-boundary or all-layout qualification. |
| Uniform restart | Ten SRT/MRT checkpoint GPU tests passed on `8403956`. | The new representative TRT same-method double-buffer continuation test still requires its own GPU receipt; no LES, Jet or refined checkpoint claim follows. |
| Taylor–Green refinement | Independent topology checks for the exact TG setup are available. The companion phase regression checks the actual lattice-rate configuration. | The physical interface-accuracy gate remains open. Topology and phase setup checks do not establish convergence or close that gate. |
| Porous Couette and annulus | Prior campaign evidence exists and must remain associated with its original setup and source. | The reconstructed annulus is a validation helper, not qualification of a public boundary-condition API. Do not infer absence of evidence from a missing current rerun. |
| LES and other combinations | Separate scalar and uniform-flow normalization evidence exists for the reviewed temporary correction. | That correction is not integrated into this source checkpoint. Do not transfer its acceptance to unchanged production, or to TRT/MRT LES, forcing, EsoPull, objects or refinement. |

Historical uniform SRT cylinder-startup and inlet-rounding findings remain separate
from the passed MRT DFG result. Raw exchange/window consistency is a measurement
contract, not a general stress or force-accuracy certification. Existing source-pinned
runners may intentionally reject a newer checkout; never silently repin old receipts.

## Small next batch

1. Cross-review the added TRT checkpoint and actual-rate TG phase tests, then run
   their applicable checks with exact checkout/import receipts. Preserve the
   existing SRT checkpoint cases and numerical criteria.
2. Run the single added TRT checkpoint GPU case with the same method on both sides
   of save/load. Record its result separately from the ten existing SRT/MRT passes.
3. Continue the existing TG accuracy investigation using its actual fine-level
   rates and the established analytic convention. Keep the accuracy gate open
   until the relevant physical comparison passes.

No repeat of the accepted full MRT DFG or Cartesian expansion across unsupported
combinations is required by this document. Main integration remains a separate
review of complete, bounded feature scope.