32 lines
1.7 KiB
Markdown
32 lines
1.7 KiB
Markdown
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---
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type: ADR
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id: "0017"
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title: "Canary release channel and local feature flags"
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status: active
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date: 2026-03-25
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---
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## Context
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Shipping new features directly to all users is risky. A mechanism was needed to let early adopters test pre-release builds and to gate experimental features behind flags that can be toggled without a new release.
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[[Keyboard-first design principle]]
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## Decision
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**Add a canary release channel alongside stable, with builds from the **`canary`** branch. Feature flags are localStorage-based (**`ff_<name>`**) with compile-time defaults, checked via **`useFeatureFlag(flag)`** hook. The update channel is configurable in Settings.**
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## Options considered
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* **Option A** (chosen): Canary branch + localStorage feature flags — simple, no server infrastructure, users opt in via Settings. Downside: no remote flag management, no gradual rollout percentages.
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* **Option B**: Server-side feature flags (LaunchDarkly, Unleash) — gradual rollouts, A/B testing. Downside: external dependency, requires server infrastructure, adds latency.
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* **Option C**: Single release channel with only feature flags — simpler CI. Downside: no way to test full pre-release builds.
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## Consequences
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* `release.yml` builds stable from `main`; `release-canary.yml` builds canary from `canary` branch.
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* Canary releases produce `latest-canary.json` on GitHub Pages, marked as prerelease.
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* `useUpdater(channel)` checks the appropriate update manifest.
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* `useFeatureFlag(flag)` checks localStorage override, then compile-time default. Type-safe via `FeatureFlagName` union.
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* `update_channel` stored in Settings as `"stable"` or `"canary"`.
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* Re-evaluation trigger: if user base grows enough to warrant server-side gradual rollouts.
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