diff --git a/.changeset/bumpy-llamas-allow.md b/.changeset/bumpy-llamas-allow.md
new file mode 100644
index 00000000..7753be0c
--- /dev/null
+++ b/.changeset/bumpy-llamas-allow.md
@@ -0,0 +1,98 @@
+---
+"@offload-project/rrule": patch
+---
+
+Refactored the core recurrence-rule implementation to share query/caching logic across RRule and RRuleSet, while also fixing a few correctness/performance issues in iteration and caching behavior.
+
+## Bug Fixes
+
+- Fixed removeFilteredDays accumulation bug
+    - Was overwriting filtered on each iteration instead of accumulating. Only the last day's filter status was returned, causing sub-daily frequencies to   
+      potentially skip the wrong number of days when earlier days in the set were filtered out.
+
+- Fixed RRuleSet.clone() inverted noCache
+    - Changed new RRuleSet(!!this._cache) to new RRuleSet(!this._cache). The constructor param is noCache, so the old code was enabling cache on uncached
+      sets and vice versa.
+
+- Removed dead lno1wkst = 0 assignment
+    - The value was assigned inside an if block but never read afterward. Changed declaration from let to const.
+
+## Architecture
+
+- Extracted RRuleBase abstract class
+    - Moved shared query methods (all, between, before, after, count) and caching logic into RRuleBase.
+    - RRule extends RRuleBase — keeps options, _iter, toString, toText, NLP methods.
+    - RRuleSet extends RRuleBase — no longer extends RRule or calls super({}, noCache) with fake empty options.
+    - Exported RRuleBase from src/index.ts so consumers can use instanceof RRuleBase for any rule-like object.
+    - Updated test utilities to use RRuleBase for shared type checking.
+
+## Performance
+
+- rrules()/exrules() — eliminated serialize+reparse
+    - Was: this._rrule.map((e) => rrulestr(e.toString())) — serializes to RFC string then re-parses.
+    - Now: this._rrule.map((e) => e.clone()) — direct clone, removed the rrulestr import entirely.
+
+- _addRule/_addDate — eliminated O(n) array allocation
+    - Was: collection.map(String).includes(String(rrule)) — allocates a new array on every call.
+    - Now: collection.some((r) => String(r) === str) — short-circuits without allocating.
+    - Same pattern for _addDate: .some((d) => d.getTime() === time) instead of .map(Number).includes(Number(date)).
+
+- Added cache size bounds (src/cache.ts)
+    - Added MAX_CACHE_SIZE = 64 constant.
+    - before/after/between caches now evict the oldest entry (FIFO) when the limit is reached, preventing unbounded memory growth on long-lived instances.
+
+## Type Safety
+
+- Narrowed bynweekday to tuple type (src/types.ts)
+    - Changed bynweekday: number[][] | null to bynweekday: [number, number][] | null in ParsedOptions, enabling safe destructuring without ! assertions in
+      monthinfo.ts and parseoptions.ts.
+
+- Narrowed toText options to ParsedOptions (src/nlp/totext.ts)
+    - Changed private options: Partial<Options> to private options: ParsedOptions, removing ~40 ! assertions on this.options.freq, this.options.interval,
+      this.options.bymonthday, etc.
+
+- Added explicit return types to dateutil helpers (src/dateutil.ts)
+    - getWeekday(): number, getMonthDays(): number, monthRange(): [number, number].
+    - Eliminated downstream ! assertions in datetime.ts and yearinfo.ts where these return values were used.
+
+- Added explicit return type to extractName (src/rrulestr.ts)
+    - Typed as { name: string; value: string } with default destructuring values, removing ! assertions on name and value.
+
+- Added default destructuring values in parseString (src/parsestring.ts)
+    - const [key = '', value = ''] = attr.split('=') and similar patterns, eliminating undefined-possibility assertions.
+
+- Fixed Cache.all type (src/cache.ts)
+    - Was: Date[] | Partial<IterArgs> | false — Partial<IterArgs> was never stored as all.
+    - Now: Date[] | false.
+
+- Clarified cache miss check (src/cache.ts)
+    - Changed if (!cached && this.all) to if (cached === false && this.all) — makes intent explicit for "not in cache" vs "cached as null".
+
+## Code Cleanup
+
+Converted C-style loops to for...of across 7 files
+- monthinfo.ts, optionstostring.ts, parseoptions.ts, yearinfo.ts, iterset.ts, iter/index.ts, iter/poslist.ts — eliminates uncertain array-index !
+  assertions.
+
+Removed dead code (src/iter/index.ts)
+- Deleted redundant interval === 0 check (already checked at function entry).
+
+Removed redundant instanceof runtime guards (src/rruleset.ts)
+- _addRule had if (!(rrule instanceof RRule)) and _addDate had if (!(date instanceof Date)) — parameters are already typed, so these were always true.
+  Removed guards and corresponding tests.
+
+Fixed test parse() null safety (test/lib/utils.ts)
+- Added null guard for regex match result before destructuring. Simplified with Number() instead of intermediate variables.
+
+## Features
+
+- toText() now includes start date (src/nlp/totext.ts)
+    - When dtstart is explicitly set in rule options, toText() appends , starting [formatted date] to the output.
+    - Example: "every 2 months on the 15th, starting February 18, 2026".
+    - Rules without an explicit dtstart are unaffected.
+
+## Tooling
+
+- Updated README (README.md)
+    - Fixed stale badges, broken code examples, byeaster docs, wkst typo, LICENCE/LICENSE link, dev tooling (Biome), and documented new toText() starting
+      date behavior.
diff --git a/.github/workflows/release.yml b/.github/workflows/release.yml
index c7f8af3c..d3b8b552 100644
--- a/.github/workflows/release.yml
+++ b/.github/workflows/release.yml
@@ -28,6 +28,9 @@ jobs:
         shell: bash
         run: bun install
 
+      - name: Build
+        run: bun run build
+
       - name: Capture New Release Version
         run: |
           bun changeset status --output=release.json
diff --git a/package.json b/package.json
index 12c43dc9..5b64b562 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@offload-project/rrule",
-  "version": "2.8.1",
+  "version": "2.8.0",
   "description": "JavaScript library for working with recurrence rules for calendar dates.",
   "homepage": "http://offload-project.github.io/rrule/",
   "license": "BSD-3-Clause",
@@ -44,6 +44,7 @@
     "preview": "vite preview",
     "test": "jest **/*.test.ts",
     "change": "changeset",
+    "prepack": "bun run build",
     "publish-package": "changeset version && changeset publish"
   },
   "publishConfig": {