---
base_model: Qwen/Qwen3.5-4B
library_name: transformers
tags:
- vision-language-navigation
- r2r
- simplememvln
---
# SimpleMemVLN R2R fullcontext — option B

**Not yet evaluated in Habitat.** Training loss is not a navigation success metric.
The observation-before-action alignment is declared but not independently verified
from collector source or Habitat replay.

## Recipe
Independently initialized from Qwen/Qwen3.5-4B revision
`851bf6e806efd8d0a36b00ddf55e13ccb7b8cd0a`, not from the other variant.
Code commit: `d50174daf1fda692849cfaa3e69286a504339fb2`.
Serializer: `vln_append_only_chat_v1`. Native LLM text-action head (option B),
gold action history, per-action mean token CE including assistant terminator.
Frozen vision/merger; trainable text backbone and LLM head. BF16, ZeRO-2,
nonreentrant full-episode gradient checkpointing, no truncation or TBPTT.
Four H100 GPUs, one episode/rank, GAS 2: global batch 8 episodes.
R2R train: 10,819 unique episodes, 631,244 actions; distributed repetition
adds one episode per epoch. Three epochs, 4,059 updates, 122 warmup updates.
Peak LR 5e-6, cosine decay to 10% of peak, weight decay 0.01, seed 429.
Memory mode: `fullcontext`. Window8 keeps prefix plus eight complete steps
for full-attention KV; persistent GDN state and gradients are not reset.

## Snapshots
`epoch-1`, `epoch-2`, `epoch-3` correspond to updates 1353, 2706, 4059.
**Epochs 1–2 are mid-schedule snapshots of one 3-epoch cosine run**, not
independently trained one-/two-epoch models. All optimizer states remain local.

## Loading and integrity
These weights use the SimpleMemVLN navigation wrapper, not an unmodified
`AutoModel` state dictionary. Download an epoch directory and load it with
`qwen_vl.train.vln_runtime.load_checkpoint(path, model_path)` using the pinned
base snapshot and the recorded environment. Navigation metadata contains the
complete serializer and memory contract.
`SHA256SUMS.json` records model/configuration/metric hashes. The uploader
downloads every uploaded file at the immutable commit revision and verifies
SHA256 before marking publication complete locally. Dataset images, credentials
and optimizer states are not published.