diff --git a/README.md b/README.md
index c7399bf..e334d21 100644
--- a/README.md
+++ b/README.md
@@ -58,7 +58,7 @@ Spindle uses three separate credentials:
 Generate an API key for your Spindle server and store it as a [Modal Secret](https://modal.com/docs/guide/secrets):
 
 ```bash
-export TINKER_API_KEY="$(openssl rand -hex 32)"
+export TINKER_API_KEY="tml-$(openssl rand -hex 32)"
 modal secret create spindle-api TINKER_API_KEY="$TINKER_API_KEY"
 ```
 
diff --git a/docs/lora_validation.md b/docs/lora_validation.md
index a09f54f..12cde6d 100644
--- a/docs/lora_validation.md
+++ b/docs/lora_validation.md
@@ -94,3 +94,36 @@ samples, lr 1e-4, PPO clip 0.8/1.28, no KL. Both runs use an 8×H200 trainer and
 
 The Spindle curve covers the steps completed at the time of writing; the native
 Miles curve is the full run.
+
+## DPO on HHH: Qwen3.5-9B-Base (2026-10-02)
+
+DPO runs on the stock `qwen35-9b-lora-16k` deployment with no extra config. The
+tinker-cookbook DPO recipe uses `forward_backward_custom` (a `forward` followed by
+`cross_entropy` with per-token weights) and gets reference logprobs from
+`compute_logprobs` on a sampler published from the step-0 weights. The run is the
+[cookbook DPO recipe](https://github.com/thinking-machines-lab/tinker-cookbook/blob/main/tinker_cookbook/recipes/preference/dpo/README.md)
+pointed at a Spindle server, with lr 1e-4 for 10 steps:
+
+```bash
+export TINKER_BASE_URL=https://your-modal-server-url
+export TINKER_API_KEY=...
+# dataset=hhh: https://huggingface.co/datasets/Anthropic/hh-rlhf
+python -m tinker_cookbook.recipes.preference.dpo.train \
+  base_url=$TINKER_BASE_URL model_name=Qwen/Qwen3.5-9B-Base dataset=hhh \
+  renderer_name=role_colon learning_rate=1e-4 dpo_beta=0.1 max_steps=10 \
+  log_path=/tmp/dpo-hhh-experiment
+```
+
+| Metric | Step 0 | Step 9 |
+| --- | --- | --- |
+| dpo_loss | 0.6939 | 0.6795 |
+| accuracy | 0.480 | 0.557 |
+| margin | −0.0011 | 0.0502 |
+| chosen reward | −0.0001 | 0.0855 |
+| rejected reward | 0.0011 | 0.0353 |
+
+- Margin and accuracy rise over the run, with chosen rewards pulling away from
+  rejected ones.
+- A warm step takes about 21 s, plus 9–14 s to compute reference logprobs on
+  the sampler pool.
+- [W&B run](https://wandb.ai/modal-labs/spindle-dpo-validation/runs/0z0obns5).
diff --git a/src/spindle/inference/sampling.py b/src/spindle/inference/sampling.py
index 74fc3fa..88c92aa 100644
--- a/src/spindle/inference/sampling.py
+++ b/src/spindle/inference/sampling.py
@@ -19,7 +19,12 @@
 RETRY_MAX_DELAY_SECONDS = 5.0
 TCP_KEEPALIVE_OPTIONS = (
     (socket.SOL_SOCKET, socket.SO_KEEPALIVE, 1),
-    (socket.IPPROTO_TCP, socket.TCP_KEEPIDLE, 60),
+    # TCP configs validated on MacOS and Linux.
+    (
+        socket.IPPROTO_TCP,
+        getattr(socket, "TCP_KEEPIDLE", None) or socket.TCP_KEEPALIVE,
+        60,
+    ),
     (socket.IPPROTO_TCP, socket.TCP_KEEPINTVL, 60),
     (socket.IPPROTO_TCP, socket.TCP_KEEPCNT, 5),
 )