diff --git a/playbooks/deploy-fish-s2.yaml b/playbooks/deploy-fish-s2.yaml
index a6f13f2..b4c4746 100644
--- a/playbooks/deploy-fish-s2.yaml
+++ b/playbooks/deploy-fish-s2.yaml
@@ -103,10 +103,20 @@ verify:
     shell: curl -sf -o /dev/null http://localhost:{{ host_port }}/v1/health
     changed_when: "false"
 
-  - name: /v1/audio/voices returns valid JSON
+  - name: /v1/tts returns a real WAV (POST with text body)
+    # Fish's API is NOT OpenAI-compatible — there's no /v1/audio/speech
+    # and no /v1/audio/voices. The single TTS endpoint is POST /v1/tts
+    # with at minimum {"text":"..."} returning audio/wav. Voice cloning
+    # is via reference= field in the body (paths under /app/references).
+    # Verify by POST + asserting the response is a real RIFF WAV.
     shell: |
-      curl -sf http://localhost:{{ host_port }}/v1/audio/voices \
-        | python3 -c "import json,sys; json.load(sys.stdin)"
+      out=$(mktemp --suffix=.wav)
+      curl -sf -X POST http://localhost:{{ host_port }}/v1/tts \
+        -H 'Content-Type: application/json' \
+        -d '{"text":"Verify."}' \
+        -o "$out" --max-time 30
+      file -b "$out" | grep -q '^RIFF.*WAVE'
+      rm -f "$out"
     changed_when: "false"
 
   - name: Container is running
diff --git a/stacks/fish-s2/README.md b/stacks/fish-s2/README.md
index 7965a65..3ef74bb 100644
--- a/stacks/fish-s2/README.md
+++ b/stacks/fish-s2/README.md
@@ -60,26 +60,37 @@ reinforcement-learning alignment. Win rates per upstream:
 
 ## API
 
-OpenAI-compat at `http://10.100.79.3:8195`:
+**Fish ships a custom API, NOT OpenAI-compatible.** The wrapper has
+exactly one TTS endpoint (`POST /v1/tts`) plus liveness probes — no
+`/v1/audio/speech`, no `/v1/audio/voices`, no `/v1/models`. Voice
+cloning happens via the `references` field in the request body
+(pointing at files under `/app/references`).
 
 ```bash
-# Single-shot synthesis with paralinguistic tags inline.
-curl -fsS -X POST http://10.100.79.3:8195/v1/audio/speech \
+# Minimal POST — text only, default voice.
+curl -fsS -X POST http://10.100.79.3:8195/v1/tts \
   -H 'Content-Type: application/json' \
-  -d '{"model":"fish-s2","input":"Oh wow [super happy] I cannot believe it. [laugh] What a day.","voice":"glados","response_format":"wav"}' \
+  -d '{"text":"Oh wow [super happy] I cannot believe it. [laugh] What a day."}' \
   > out.wav
 
-# Built-in voices.
-curl http://10.100.79.3:8195/v1/audio/voices
-
-# Streaming.
-curl -fsS -X POST http://10.100.79.3:8195/v1/audio/speech \
+# With voice cloning — point at a reference file (drop the .wav into
+# /worktank/fish-s2/references/ on the host first).
+curl -fsS -X POST http://10.100.79.3:8195/v1/tts \
   -H 'Content-Type: application/json' \
-  -d '{"model":"fish-s2","input":"long passage…","voice":"glados","stream":true}' \
-  | mpv --no-cache -
+  -d '{"text":"...", "references":[{"audio":"/app/references/glados.wav","text":"transcript of the reference"}]}' \
+  > out.wav
 ```
 
-WebUI at `/`. OpenAPI / docs at `/docs`. Healthcheck at `/v1/health`.
+Other endpoints:
+
+| path | purpose |
+|---|---|
+| `GET /v1/health` | liveness probe (used by our Docker healthcheck) |
+| `GET /heartbeat` | alternate liveness signal |
+| `GET /` | Swagger Editor UI for the OpenAPI spec |
+
+The 200-line OpenAPI spec is rendered through Swagger Editor at the
+root path; there's no `/openapi.json` endpoint exposed directly.
 
 ## Voice library
 
@@ -102,4 +113,29 @@ cache + warms torch.compile (adds ~60 s). Both are cached afterwards.
 - **VRAM**: ~17 GB practical, 24 GB recommended. Pinned to GPU 1
   (RTX A6000) by default — plenty of headroom for long contexts and
   large mmproj if a future checkpoint adds vision.
-- **Disk**: ~9 GB for the model checkpoint + HF cache.
+- **Disk**: ~11 GB for the s2-pro checkpoint
+  (codec.pth 1.9 GB + 2 safetensors shards 9 GB + tokenizer/config).
+
+## Lessons learned during deploy (2026-04-27)
+
+Took 5 iterations to land. Recording for next time:
+
+1. **`dockerfile`** (lowercase, root) — doesn't exist. Fish doesn't
+   ship a plain Dockerfile.
+2. **`dockerfile.dev`** — exists at root, but it's a 2-line wrapper
+   (`FROM ghcr.io/fishaudio/fish-speech:${VERSION}`) over a private
+   GHCR base image. Anonymous pulls 403.
+3. **`docker/Dockerfile`** — the real build path (referenced by
+   upstream's `compose.base.yml`).
+4. **Multi-stage default builds the wrong target.** Without
+   `target: server`, docker builds the last stage which is `webui`
+   (gradio only — no `start_server.sh`, container exits silently
+   rc=0 because the API entrypoint is missing).
+5. **Fish doesn't auto-download checkpoints.** `start_server.sh`
+   validates `/app/checkpoints/s2-pro/` exists and exits clean if
+   not. The playbook now pre-pulls `fishaudio/s2-pro` (~11 GB) via a
+   one-shot `huggingface_hub.snapshot_download` container before
+   starting the service.
+6. **API is NOT OpenAI-compatible.** Endpoint is `POST /v1/tts`, not
+   `/v1/audio/speech`. No `/v1/audio/voices` or `/v1/models`. Voice
+   cloning is via `references` field in the POST body.