diff --git a/.github/workflows/container.yml b/.github/workflows/container.yml
index 40d6603..4821fb3 100644
--- a/.github/workflows/container.yml
+++ b/.github/workflows/container.yml
@@ -9,7 +9,8 @@ name: Container
 #   a prerelease is not tagged :latest.
 # - Actions -> Container -> Run workflow builds and pushes any released version.
 # - A pull request that changes the Dockerfile or this workflow builds and
-#   smoke-tests the current pyproject version, and never pushes.
+#   smoke-tests the newest version already on PyPI (a version-bump PR's own
+#   version is not released yet), and never pushes.
 #
 # The image's org.opencontainers.image.source label links the package to this
 # repository. Only GITHUB_TOKEN is used (no PAT, no stored secret). Every action
@@ -73,7 +74,10 @@ jobs:
               latest="$INPUT_LATEST"
               push=true ;;
             *)
-              version=$(python3 -c "import tomllib; print(tomllib.load(open('pyproject.toml','rb'))['project']['version'])")
+              # Test the Dockerfile and workflow against the newest release on PyPI;
+              # the PR's own pyproject version may not be published yet.
+              version=$(curl --silent --fail https://pypi.org/pypi/flashspec/json \
+                | python3 -c "import json, sys; print(json.load(sys.stdin)['info']['version'])")
               latest=false
               push=false ;;
           esac
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 43dcfff..5591c30 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,33 @@ Versioning follows [Semantic Versioning 2.0.0](https://semver.org/).
 
 ## [Unreleased]
 
+## [0.3.1] — 2026-10-26 — Optional selector, simpler quickstart, container image
+
+Development status stays Alpha. No measurement in this release: 0.3.1 does
+not change the decoding path (an omitted selector is the same one-arm UCB1
+that one-drafter users already passed), so the README tables remain the
+0.3.0 release run (bundle `3c43e08`).
+
+### Highlights
+- `SpeculativeEngine(config, [drafter], target)`: with one arm, the bandit
+  selector argument is optional. The README quickstart no longer needs
+  `BanditConfig` or a selector, and it prints which drafter strategy ran.
+- A GPU-oriented server image on GitHub Container Registry,
+  `ghcr.io/mattral/flashspec:<version>`, built from the PyPI release and
+  smoke-tested on every publish (first published for 0.3.0).
+- Engineering notes in the docs (`docs/lessons.md`), with figures drawn from
+  the result JSONs by `scripts/article/`.
+
+### Upgrade notes
+- Nothing to change: every 0.3.0 call works as before. Passing a selector
+  with one arm is still allowed; omitting it with several arms raises a
+  `ValueError` that says which selector to pass.
+
+### Known issues
+- Unchanged from 0.3.0 (first call compiles; fp16 greedy exact ties; batch
+  > 1 and other GPUs or model pairs not measured; bandit experimental; the
+  CUDA-graph "distinct sizes" warning).
+
 ### Added
 - `SpeculativeEngine`'s `bandit` argument is optional (default `None`). When the resolved strategy has one arm (the default
   `drafter_strategy="auto"` with one model drafter, an explicit `"bandit"` strategy with one drafter, or a single explicit
diff --git a/CITATION.cff b/CITATION.cff
index 13df915..185772a 100644
--- a/CITATION.cff
+++ b/CITATION.cff
@@ -35,7 +35,7 @@ abstract: >-
   UCB1/Thompson draft selector is experimental: measured once over seven
   arms, it did not beat the best fixed arm. The Triton and assembly
   kernels are experimental and not on the generation critical path.
-version: 0.3.0
+version: 0.3.1
 date-released: "2026-10-26"
 license: Apache-2.0
 repository-code: "https://github.com/Mattral/FlashSpec"
diff --git a/README.md b/README.md
index fd97a8d..56f9546 100644
--- a/README.md
+++ b/README.md
@@ -45,8 +45,8 @@ You need Python 3.11 or later, PyTorch 2.2 or later and transformers 4.40 or lat
 **Container image (GPU-oriented).** Each release is also published as a server image on GitHub Container Registry. It is built from the PyPI release on CUDA 13.0, with the torch build the GPU results were measured with, and it runs as a non-root user. It needs an NVIDIA GPU and the NVIDIA Container Toolkit; it starts on CPU too, but CPU is not where FlashSpec is faster. The default command serves the measured pair in fp16 on port 8000.
 
 ```bash
-docker pull ghcr.io/mattral/flashspec:0.3.0
-docker run --gpus all -p 8000:8000 ghcr.io/mattral/flashspec:0.3.0
+docker pull ghcr.io/mattral/flashspec:0.3.1
+docker run --gpus all -p 8000:8000 ghcr.io/mattral/flashspec:0.3.1
 ```
 
 ## Quickstart
@@ -153,7 +153,7 @@ python -m flashspec.serve --target Qwen/Qwen2.5-1.5B-Instruct --drafter Qwen/Qwe
 Or with the container image. Arguments replace its default command, so pass `--host 0.0.0.0`. The volume keeps downloaded checkpoints between runs:
 
 ```bash
-docker run --gpus all -p 8000:8000 -v flashspec-hf:/home/flashspec/.cache/huggingface ghcr.io/mattral/flashspec:0.3.0 \
+docker run --gpus all -p 8000:8000 -v flashspec-hf:/home/flashspec/.cache/huggingface ghcr.io/mattral/flashspec:0.3.1 \
     --target Qwen/Qwen2.5-1.5B-Instruct --drafter Qwen/Qwen2.5-0.5B-Instruct \
     --device cuda:0 --dtype float16 --temperature 0 --host 0.0.0.0
 ```
@@ -328,7 +328,7 @@ With `compile` on, both models run on static KV caches and the fixed-shape decod
 
 ## Status and limitations
 
-FlashSpec is alpha, version 0.3.0.
+FlashSpec is alpha, version 0.3.1.
 
 - **Measured scope.** One model pair (`Qwen/Qwen2.5-1.5B-Instruct` verified by `Qwen/Qwen2.5-0.5B-Instruct`), one Tesla T4, fp16, batch 1, 10 MT-Bench and 10 HumanEval prompts, run from `main` at git `3c43e08` with the defaults `compile="auto"` and `drafter_strategy="auto"` (which ran `composite-g6-f2`). No other GPU, model pair or batch size has been measured. Every H100 number in the docs is a design target.
 - **The first call compiles.** On CUDA the first `generate` compiles the forwards and captures CUDA graphs, which can take minutes; later calls reuse them. The tables exclude that call.
diff --git a/deploy/Dockerfile b/deploy/Dockerfile
index 4f906b7..7d6c08b 100644
--- a/deploy/Dockerfile
+++ b/deploy/Dockerfile
@@ -1,6 +1,6 @@
 # FlashSpec server image: the released PyPI package on a CUDA 13.0 base.
 #
-#   docker build -f deploy/Dockerfile --build-arg FLASHSPEC_VERSION=0.3.0 -t flashspec deploy/
+#   docker build -f deploy/Dockerfile --build-arg FLASHSPEC_VERSION=0.3.1 -t flashspec deploy/
 #   docker run --gpus all -p 8000:8000 flashspec
 #
 # GPU-oriented: torch is the CUDA 13.0 build FlashSpec's GPU results were
diff --git a/deploy/docker-compose.yml b/deploy/docker-compose.yml
index f578408..f6213e8 100644
--- a/deploy/docker-compose.yml
+++ b/deploy/docker-compose.yml
@@ -7,7 +7,7 @@
 
 services:
   flashspec:
-    image: ghcr.io/mattral/flashspec:0.3.0
+    image: ghcr.io/mattral/flashspec:0.3.1
     ports:
       - "8000:8000"
     volumes:
diff --git a/deploy/k8s/flashspec-deployment.yaml b/deploy/k8s/flashspec-deployment.yaml
index 5db8069..3a40a83 100644
--- a/deploy/k8s/flashspec-deployment.yaml
+++ b/deploy/k8s/flashspec-deployment.yaml
@@ -4,7 +4,7 @@ metadata:
   name: flashspec
   labels:
     app: flashspec
-    version: "0.3.0"
+    version: "0.3.1"
 spec:
   replicas: 1
   selector:
@@ -19,7 +19,7 @@ spec:
         - name: flashspec
           # GPU-oriented image; the default command serves Qwen2.5-1.5B-Instruct
           # verified by Qwen2.5-0.5B-Instruct in fp16 on port 8000.
-          image: ghcr.io/mattral/flashspec:0.3.0
+          image: ghcr.io/mattral/flashspec:0.3.1
           imagePullPolicy: IfNotPresent
           ports:
             - containerPort: 8000
diff --git a/docs/install.md b/docs/install.md
index c625e31..738288e 100644
--- a/docs/install.md
+++ b/docs/install.md
@@ -26,8 +26,8 @@ git clone https://github.com/Mattral/FlashSpec && cd FlashSpec
 pip install -e ".[dev,gpu]"   # omit ",gpu" on Windows/macOS
 
 # Container image (Linux + NVIDIA GPU), published for each release:
-docker pull ghcr.io/mattral/flashspec:0.3.0
-docker run --gpus all -p 8000:8000 ghcr.io/mattral/flashspec:0.3.0
+docker pull ghcr.io/mattral/flashspec:0.3.1
+docker run --gpus all -p 8000:8000 ghcr.io/mattral/flashspec:0.3.1
 ```
 
 **The container image** (`ghcr.io/mattral/flashspec:<version>` and `:latest`) is
@@ -48,7 +48,7 @@ built by `.github/workflows/container.yml` when a release is published:
 To build it yourself from a released version:
 
 ```bash
-docker build -f deploy/Dockerfile --build-arg FLASHSPEC_VERSION=0.3.0 -t flashspec deploy/
+docker build -f deploy/Dockerfile --build-arg FLASHSPEC_VERSION=0.3.1 -t flashspec deploy/
 ```
 
 A development checkout, by platform:
diff --git a/flashspec/__init__.py b/flashspec/__init__.py
index 4fa855e..f681a26 100644
--- a/flashspec/__init__.py
+++ b/flashspec/__init__.py
@@ -42,5 +42,5 @@
     "register",
 ]
 
-__version__ = "0.3.0"
+__version__ = "0.3.1"
 __author__ = "Min Htet Myet (Mattral)"
diff --git a/pyproject.toml b/pyproject.toml
index 3d8c639..f0a30a6 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "flashspec"
-version = "0.3.0"
+version = "0.3.1"
 description = "Lossless speculative decoding for HuggingFace causal LMs, with a static-cache CUDA-graph fast path; bandit draft selection and Triton kernels are experimental"
 readme = {file = "README.md", content-type = "text/markdown"}
 license = { file = "LICENSE" }