v0.4.3

## 🚀 Announcing Agent Sandbox v0.4.3!

We are excited to announce the release of **Agent Sandbox v0.4.3**!

This release expands documentation significantly, with new guides covering filesystems, volumes, lifecycle, snapshots, metrics, custom environments, and a Python SDK quickstart — plus a reorganized Use Cases section and Go sandbox client docs. It introduces new **lifecycle APIs**, including a `Finished` condition on Sandbox and SandboxClaim and a `ttlSecondsAfterFinished` field for automatic cleanup of finished claims, alongside volumeClaimTemplates support for persistent storage. **Warm pool correctness** improves with fixes for duplicate Sandbox adoption during informer cache lag, retain-policy deletion, and cross-namespace adoption protection. **Observability** gains a `--version` flag, an `agent_sandbox_build_info` Prometheus metric, and more accurate startup-latency tracking. Finally, the Python SDK adds a new `SandboxInClusterConnectionConfig` so in-cluster clients can bypass the router — using stable cluster DNS by default, with an opt-in low-latency pod-IP mode.

### Key Highlights

* **Documentation Expansion**: Comprehensive new docs covering filesystems, volumes, lifecycle/TTL, snapshots, metrics, custom environments, and use cases. Added a Python SDK quickstart, Go sandbox client docs, and a homepage Use Cases grid. The `docs/examples/` section has been reorganized under `docs/use-cases/`.
* **Lifecycle & Cleanup**: New `Finished` condition on `Sandbox` (mirrored to `SandboxClaim`) reporting `PodSucceeded` / `PodFailed`. New `ttlSecondsAfterFinished` field on `SandboxClaim.spec.lifecycle` for automatic cleanup of finished claims, honoring the existing `shutdownPolicy` (`Retain`, `Delete`, `DeleteForeground`).
* **Storage**: Added `volumeClaimTemplates` support to `SandboxTemplate`, propagated through `SandboxClaim` and `SandboxWarmPool` to the underlying `Sandbox`. PVC-backed volumes use StatefulSet-style merge semantics with the pod template.
* **Warm Pool Correctness**: Fixed duplicate Sandbox adoption during informer cache lag by recording the adopted Sandbox name on the claim via the `agents.x-k8s.io/sandbox-name` label. Fixed warm-pool sandbox deletion when `shutdownPolicy: Retain` is set. Added cross-namespace adoption protection.
* **Python SDK Enhancements**: New `SandboxInClusterConnectionConfig` for in-cluster clients to bypass the router — defaults to stable cluster DNS, with an opt-in `use_pod_ip=True` mode for low-latency direct pod connections (with cache invalidation on errors). `Sandbox.status.podIPs` is now exposed end-to-end.
* **Observability**: Added a `--version` flag and `agent_sandbox_build_info` Prometheus metric (with git version, SHA, build date, Go version, platform). Improved `ControllerStartupLatency` accuracy by keying observed-time entries on both name and UID, so recreated claims with the same name no longer reuse stale timestamps.
* **Stability**: SandboxClaim now requeues quietly (instead of erroring) when its template is missing and recovers automatically when the template is created. Sandbox controller now safely handles `AlreadyExists` on pod creation, refusing to adopt pods owned by other controllers.
* **Testing**: Go unit tests now run with `-race` enabled by default; new `make test-e2e-race` target. Added a kOps-on-GCP benchmark scenario and a `resourcectl` CLI for Boskos resource management.

### Installation

#### Core & Extensions

```bash
# To install only the core components:
kubectl apply -f https://github.com/kubernetes-sigs/agent-sandbox/releases/download/v0.4.3/manifest.yaml

# To install the extensions components:
kubectl apply -f https://github.com/kubernetes-sigs/agent-sandbox/releases/download/v0.4.3/extensions.yaml
```

#### Python SDK

```bash
pip install k8s-agent-sandbox==0.4.3
```

---

## Contributors

A huge thank you to all the contributors who made this release possible! 

@angristan, @noeljackson, @vgunapati, @igooch, @chw120, @yashasvimisra2798, @bittermandel, @Oneimu, @alimx07, @aleks-stefanovic, @justinsb, @janetkuo, @dongjiang1989, @rayowang, @vicentefb, @volatilemolotov

### 👋 New Contributors

@vgunapati made their first contribution in #489
@alimx07 made their first contribution in #645
@bittermandel made their first contribution in #583
@angristan made their first contribution in #240

**Full Changelog**: https://github.com/kubernetes-sigs/agent-sandbox/compare/v0.4.2...v0.4.3