ZigBase 0.8.0

Breaking

• Feature flags are now declared-only. Flags must be declared in the App(.{ .flags = .{ … } }) literal; only declared flags resolve. The v0.7 runtime-string API ctx.flag("arbitrary") (KV-or-false) has been removed — use the typed App.flag(ctx, .name) for known flags, or ctx.flagByName("name") (returns ?bool, null when undeclared) for dynamic names.
• ctx.setFlag now writes a declared-flag override. It writes the flag:<name> override key for a DECLARED flag and errors error.UndeclaredFlag otherwise (the typed, compile-checked form is App.setFlag(ctx, .name, enabled)). Previously it set an arbitrary <name> KV value.

Features

• Comptime feature-flag + experiment registry (#128/#129/#130). Declare .flags (bare-bool default or .{ .default, .description }) and .experiments (.{ .variants, .weights, .sticky, .description }) in the App(cfg) literal. Malformed declarations (unknown sub-key, non-bool flag, variants/weights length mismatch, empty/duplicate variants, all-zero weights) are loud @compileErrors.
• Typed, compile-checked accessors. App.flag(ctx, .name) bool, App.setFlag(ctx, .name, enabled) !void, and App.experiment(ctx, .name, subject) ![]const u8 — a typo'd flag/experiment name is a compile error (generated App.Flag / App.Experiment enums).
• Runtime resolution. ctx.flagByName(name) ?bool (dynamic read), ctx.flags().resolveAll(subject) resolves every declared flag + experiment in a single batched _kv scan, and deterministic experiment bucketing (FNV1a-64(name ++ 0x00 ++ subject) over cumulative weights) gives a stable variant per (name, subject). Per-flag overrides live in _kv under flag:<name>; experiment weight overrides under exp:<name>:weights (JSON).
• Admin UI gains a Feature Flags & Experiments screen (/_/#/features) showing every declared flag (name, default, description, effective value) with a toggle to set/clear the flag:<name> override, and each declared experiment's variants with editable weight sliders that write the exp:<name>:weights override; a "Reset to declared" action clears the override. Superuser-only; backed by the new GET /api/features endpoint.
• New GET /api/features endpoint (superuser) returns the comptime-declared flag + experiment registry alongside each entry's current _kv override — useful for custom admin tooling.
• Feature exposure events: register .onFeatureExposure to receive an ExposureEvent ({ kind: .flag | .experiment, name, subject, value, variant }) each time a declared flag or experiment is resolved. The hook is notify-only and zero-cost when unregistered (the resolver never builds the event without a handler).
• Realtime feature signal: any flag/experiment override change (ctx.setFlag/App.setFlag or an admin PUT/DELETE of a flag:<name> / exp:<name>:weights setting) broadcasts a signal-only {"type":"features.changed"} frame on the public __features channel. Clients may subscribe anonymously and re-GET /api/state on receipt; no per-subject state or experiment assignment is ever pushed over the socket.
• Public feature-state endpoint (#130). GET /api/state?subject=<id> is an unauthenticated, read-only projection of resolved flags + experiments: { "flags": { "<name>": <bool>, … }, "experiments": { "<name>": "<variant>", … } }. It exposes resolved values ONLY — never the _kv keys, defaults, weights, timestamps, or any superuser settings verb (those stay behind requireSuperuser). A .sticky experiment returns its persisted assignment here too (agreeing with App.experiment), resolved reader-first so a caller-supplied subject can't storm the writer lock. Auto-mounts at /api/state; configure with .features = .{ .public_route = "/state" } to remap or .{ .public_route = .disabled } to turn off.
• Typed zb.flags.resolveAll(subject) in the TypeScript SDK. zig build gen-client now emits a fully-typed feature-state surface from your App(.{ .flags, .experiments }): flags as named booleans and each experiment as a string-literal union of its declared variants (FeatureState). await zb.flags.resolveAll("user-42") calls GET /api/state and returns { flags: { … }, experiments: { … } } with no any. Emitted only when flags/experiments are declared; the runtime-introspection tier omits it (no comptime metadata), matching typed routes and custom auth methods.
• Sticky experiment assignments (#129): declare an experiment .sticky = true to persist a subject's first variant in _experiment_assignments so it survives later weight changes (new subjects still follow the current weights; empty subjects are never persisted). A framework-internal _experiment_gc job — installed only when a .sticky experiment is declared — reaps assignments older than the new .experiment_assignment_ttl config (in days, default 90) hourly in bounded batches.