diff --git a/CHANGELOG.md b/CHANGELOG.md
new file mode 100644
index 0000000..e74288c
--- /dev/null
+++ b/CHANGELOG.md
@@ -0,0 +1,119 @@
+# Changelog
+
+All notable changes to this crate are documented here. The format is
+based on [Keep a Changelog](https://keepachangelog.com/en/1.1.0/), and
+this crate adheres to [Semantic Versioning](https://semver.org/).
+
+## [0.2.0] - 2026-08-17
+
+A breaking release that replaces the v0.1.0 `AlkType:*` custom-keyword
+JSON Schema format with BAST (Binary Abstract Syntax Tree) — a JSON
+document that describes binary layouts using a `kind`-based vocabulary
+with `$defs`/`$ref` for composition. BAST is itself a valid JSON Schema
+instance (it has a meta-schema), making it self-validating,
+editor-friendly, and trivially consumable from any language with a JSON
+parser. The engine works the same way as before: compile a document
+once into an `AlkTypeEngine`, then read/write fields at computed offsets
+and validate bytes/JSON. The pivot was made now because v0.1.0 has no
+real consumers (≈15 crates.io downloads, mostly bots/scanners), so the
+custom-keyword wart could be removed cleanly.
+
+### Breaking changes
+
+- **Schema format.** The v0.1.0 `AlkType:*` custom-keyword JSON Schema
+  format (`{ "AlkType:Struct": true, "fields": [...] }`) is removed.
+  Schemas are now BAST documents:
+  `{ "$defs": { "<TypeName>": { "kind": "struct", "fields": [...] } } }`.
+  The `kind`-based vocabulary covers 18 binary kinds (integers, floats,
+  bytes, string, struct, union, enum, array, etc.).
+- **`AlkTypeEngine::compile` signature.** Now takes
+  `(bast_doc: &Value, root_name: &str, mode: LayoutMode, json_schema: Option<&Value>)`.
+  The root type name is a required parameter — it selects which `$defs`
+  entry is the top-level type (previously the root was implicit from the
+  single top-level schema object).
+- **Builder API output.** `Definitions`/`Schema`/`Discriminator` now
+  produce BAST JSON via `Definitions::build_doc(name, schema)`. The
+  builder method names are unchanged; only the emitted JSON shape
+  changed. `Schema::struct_()` produces a BAST struct;
+  `Schema::object()` produces a standard JSON Schema (for the
+  `validate_json` path).
+- **Validation split.** v0.1.0 used a single `jsonschema` validator
+  with 19 custom `AlkType:*` keywords for both bytes and JSON
+  validation. 0.2.0 splits this into two independent paths:
+  - `validate_bytes` uses a new BAST-native validator
+    (`bast_validation`) — a recursive walker over the BAST type tree.
+  - `validate_json` / `is_valid_json` use a standard
+    `jsonschema::Validator` built from a consumer-provided JSON Schema
+    (passed to `compile` as the `json_schema` parameter). No custom
+    keywords; BAST is not involved — BAST describes bytes, not JSON
+    shape.
+  Both paths return `AlkTypeError::Validation` with a uniform
+  `jsonschema::ValidationError<'static>` payload.
+- **Removed.** The v0.1.0 custom-keyword accessor layer
+  (`AlkTypeKind::FromStr`, `parse_*`, `resolve_ref*`,
+  `DiscriminatorKind`) is removed. The BAST parser (`bast` module)
+  exposes a cleaner typed surface (`BastDoc`/`BastDef`/`BastStruct`/
+  `BastField`/`BastType`/etc.) that borrows from the source
+  `serde_json::Value` without cloning field data.
+- **Public module surface.** New public modules: `bast`, `bast_meta`,
+  `bast_validation`, `builder`, `materialize`. The `schema` module is
+  retained but now holds only `Endian`/`AlkTypeKind`/`VariableEncoding`
+  (the binary-kind vocabulary); the v0.1.0 custom-keyword machinery is
+  gone.
+
+### Additions
+
+- **BAST meta-schema.** Embedded in the crate as
+  `BAST_META_SCHEMA` (re-exported from the crate root) and published at
+  `https://alk.dev/bast/v1/schema`. BAST documents are validated against
+  it at compile time (`AlkTypeEngine::compile` calls
+  `validate_bast_doc` before parsing).
+- **`materialize` module.** Materializes a `serde_json::Value` tree from
+  a binary buffer by walking the BAST typed tree. Used by
+  `AlkTypeEngine::validate_bytes` (ADR-010).
+- **Builder for JSON Schemas.** `Schema::object()` produces a standard
+  JSON Schema object (for the `validate_json` path), complementing
+  `Schema::struct_()` which produces a BAST struct (for the bytes path).
+  One builder, two output shapes — the method name selects which.
+
+### Bug fixes vs v0.1.0
+
+- **Enum index bounds are now checked.** The v0.1.0 validator had a
+  dead constraint: enum variant indices were never bounds-checked
+  against `values.len()`. The BAST-native validator enforces it
+  (`validate_enum` checks `idx < values.len()`).
+- **Offset-indirect, field-level endian, and aligned materialization**
+  bugs found during review #003 are fixed.
+
+### Non-breaking improvements
+
+- `$ref` is restricted to `#/$defs/<name>` — one hash lookup, no
+  `normalize_refs` pass (the v0.1.0 engine needed one).
+- Schemas remain untrusted input: every engine path that walks a BAST
+  document returns `Err` on a malformed document, never `panic!`/
+  `unreachable!`. Overflow-safe arithmetic (`checked_add`,
+  `usize::try_from`) on all offset/count casts.
+- Still two dependencies (`jsonschema` with `default-features = false`,
+  `serde_json` with `preserve_order`), no `async`, no `unsafe`, no
+  platform deps, no feature flags. Compiles to
+  `wasm32-unknown-unknown`.
+
+### Upgrade notes
+
+There is no migration path from v0.1.0 `AlkType:*` schemas — the format
+is incompatible. Rewrite schemas as BAST documents (the `builder` API
+produces them; see the README usage example) and update `compile` calls
+to pass the root type name and the optional JSON Schema. The
+read/write/validate API surface (`read_field`, `write_field`,
+`sequential_reader`, `validate_bytes`, `validate_json`,
+`is_valid_json`) is unchanged.
+
+## [0.1.0] - 2025-11-10
+
+Initial crates.io release. Custom-keyword JSON Schema format
+(`AlkType:*`), single `jsonschema` validator for both bytes and JSON,
+`AlkTypeEngine` with packed/aligned layout modes, builder API producing
+`serde_json::Value`.
+
+[0.2.0]: https://git.alk.dev/alkdev/alktype/releases/tag/v0.2.0
+[0.1.0]: https://git.alk.dev/alkdev/alktype/releases/tag/v0.1.0
\ No newline at end of file
diff --git a/Cargo.lock b/Cargo.lock
index 69f3a1c..85d78be 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -27,7 +27,7 @@ dependencies = [
 
 [[package]]
 name = "alktype"
-version = "0.1.0"
+version = "0.2.0"
 dependencies = [
  "jsonschema",
  "serde_json",
diff --git a/Cargo.toml b/Cargo.toml
index dfdfb8f..d794a25 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -1,6 +1,6 @@
 [package]
 name = "alktype"
-version = "0.1.0"
+version = "0.2.0"
 edition = "2021"
 rust-version = "1.85"
 license = "MIT OR Apache-2.0"
@@ -9,7 +9,7 @@ repository = "https://git.alk.dev/alkdev/alktype"
 readme = "README.md"
 keywords = ["binary", "jsonschema", "wire-format", "serialization", "layout"]
 categories = ["encoding", "data-structures", "parsing"]
-exclude = [".opencode/", "docs/reviews/", "docs/research/", "docs/sdd_process.md", "Cargo.lock"]
+exclude = [".opencode/", "docs/reviews/", "docs/research/", "docs/sdd_process.md", "Cargo.lock", "AGENTS.md"]
 
 [lib]
 name = "alktype"