v0.0.1 release

CHANGELOG.md

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+# Changelog
+
+All notable changes to this project are documented here. The format
+follows [Keep a Changelog](https://keepachangelog.com/en/1.1.0/) and
+this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
+
+## [v0.0.1] — 2026-05-15
+
+Initial public release.
+
+### Added
+
+- **Quorum-based uptime monitoring.** Multiple cooperating nodes run
+  the same probes (HTTP, TCP, ICMP) and vote on the cluster-wide
+  truth. A check flips state only after two consecutive aggregate
+  evaluations agree (hysteresis), so single-node flake doesn't page
+  anyone.
+- **Deterministic master election.** Among the live members of the
+  quorum the lexicographically smallest NodeID wins — no negotiation
+  step, no split-brain window.
+- **mTLS inter-node transport** with TLS 1.3 minimum, SSH-style
+  fingerprint pinning, and a pre-shared `cluster_secret` gating the
+  Join RPC.
+- **Replicated `cluster.yaml`** carrying peers, checks, and alerts.
+  Master is the only writer; followers receive monotonic-versioned
+  snapshots and converge on the latest. Hand-edits to the file on any
+  node are picked up by the manual-edit watcher and forwarded through
+  the master.
+- **HTTP, TCP, and ICMP probes** with configurable interval,
+  timeout, expected status, and optional body-substring match. ICMP
+  defaults to unprivileged UDP-mode pings so the daemon can run as a
+  non-root user.
+- **SMTP and Discord alerts** with optional Go `text/template`
+  subject/body overrides per alert, default-attach mode (`default:
+  true`), and per-check opt-outs via `suppress_alert_ids`.
+- **Docker-friendly env-var configuration.** Every field in
+  `node.yaml` can also be supplied via a `QUPTIME_*` environment
+  variable; `qu serve` auto-initialises a fresh data volume from
+  these on first start, so `docker compose up` is enough to launch a
+  node.
+- **Interactive TUI** (`qu tui`) for peers, checks, and alerts with
+  live refresh.
+- **Hardened systemd unit** shipped via `install.sh`: dedicated
+  `quptime` user, `ProtectSystem=strict`, all capabilities dropped by
+  default.
+- **Multi-arch Docker images** (`linux/amd64`, `linux/arm64`)
+  published to `git.cer.sh/axodouble/quptime`.
+- **Static Linux binaries** (`amd64`, `arm64`) published per tag with
+  a `SHA256SUMS` file; the official installer verifies the checksum
+  before placing the binary on disk.
+
+### Security
+
+- Cluster secret is compared in constant time
+  (`crypto/subtle.ConstantTimeCompare`).
+- Self-signed RSA certs minted at `qu init`; SPKI SHA-256
+  fingerprints are what's pinned, matching the canonical OpenSSL
+  representation.
+- Private keys are written with mode `0600`; data and runtime
+  directories with `0700`/`0750`.
+- All `cluster.yaml` writes go through an atomic `tmpfile + rename`.
+- `install.sh` downloads the published `SHA256SUMS` and refuses to
+  install if the downloaded binary doesn't match.
+
+### Known limitations
+
+- **Cluster-wide secret distribution.** SMTP passwords and Discord
+  webhook URLs configured via `qu alert add …` are stored in
+  `cluster.yaml`, which is replicated to every node. Treat every node
+  as having read access to every alert credential. Restrict who can
+  reach the data directory accordingly. See
+  [docs/security.md](docs/security.md) for the threat model.
+- **No automatic key rotation.** Rolling a node's identity means
+  wiping its data directory, running `qu init` again, and re-adding
+  it from another node.
+- **No historical metrics.** Only the current aggregate state is kept
+  in memory. There is no built-in graph store, SLA calculator, or
+  audit log.
+- **Master-flap state.** Aggregator hysteresis state lives in
+  memory on the current master. When leadership changes the new
+  master starts from `StateUnknown` and re-accumulates hysteresis —
+  expect a few seconds of delayed alerting after a master switch.
+- **No release signing beyond SHA256SUMS** (no cosign / GPG).
+  Planned for a future release.
+
+[v0.0.1]: https://git.cer.sh/axodouble/quptime/releases/tag/v0.0.1