diff --git a/NEWS.md b/NEWS.md
index a0c917bd3..f39db63b9 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,4 +1,4 @@
-# User visible changes in `mruby3.5` from `mruby3.4`
+# User visible changes in `mruby4.0` from `mruby3.4`
 
 "**_NOTE_**:" are changes to be aware of.
 
@@ -19,21 +19,56 @@ mruby now supports pattern matching (case/in) syntax:
 
 ## Other Language Changes
 
+- `&nil` in formal parameters to explicitly opt out of block arguments ([b07518e](https://github.com/mruby/mruby/commit/b07518e))
+- Trailing comma in method definition parameters: `def foo(a, b,)` ([f78334b](https://github.com/mruby/mruby/commit/f78334b))
 - Array/Hash/String subclasses can now override `[]` and `[]=` methods ([#6675](https://github.com/mruby/mruby/pull/6675))
 - `OP_SETIDX` optimization for Array and Hash ([ddd8fe1](https://github.com/mruby/mruby/commit/ddd8fe1))
 
 # Changes in C API
 
+- **_NOTE_**: `mrb_alloca()` renamed to `mrb_temp_alloc()` ([7fe5c2e](https://github.com/mruby/mruby/commit/7fe5c2e))
 - **_NOTE_**: `mruby/ext/io.h` renamed to `mruby/io.h` ([2813f79](https://github.com/mruby/mruby/commit/2813f79))
-- `mrb_time_get_tm()` API for accessing struct tm ([daaaafe](https://github.com/mruby/mruby/commit/daaaafe))
+- `mrb_gc_add_region()` for contiguous heap region support ([072855a](https://github.com/mruby/mruby/commit/072855a))
+- `mrb_class_outer()` to get the outer class/module ([3a1b771](https://github.com/mruby/mruby/commit/3a1b771))
+- `MRB_ENSURE()` macro for exception-safe cleanup ([3ac682b](https://github.com/mruby/mruby/commit/3ac682b))
+- `mrb_time_get_tm()` for accessing struct tm ([daaaafe](https://github.com/mruby/mruby/commit/daaaafe))
 - `MRB_OPEN_FAILURE()` macro for checking mrb_open result ([40b0cb9](https://github.com/mruby/mruby/commit/40b0cb9))
 - `mrb_print_error()` now handles NULL gracefully ([8e50a45](https://github.com/mruby/mruby/commit/8e50a45))
 - `mrb_open()` returns mrb_state with exc set on init failure ([05ffe0c](https://github.com/mruby/mruby/commit/05ffe0c))
 - `mrb_utf8_to_buf()` for UTF-8 encoding consolidation ([7e28e68](https://github.com/mruby/mruby/commit/7e28e68))
 - `kh_is_end()` macro for safe khash iteration ([893cc75](https://github.com/mruby/mruby/commit/893cc75))
 
+# ROM Method Tables
+
+All built-in classes and most extension gems now use read-only method
+tables stored in `.rodata` instead of heap-allocated hash tables. Method
+definitions no longer consume heap memory, significantly reducing memory
+footprint for embedded use.
+
+Core classes converted: BasicObject, Object, Module, Class, Kernel,
+String, Array, Hash, Numeric, Integer, Float, NilClass, TrueClass,
+FalseClass, Range, Symbol, Exception, Proc.
+
+Extension gems converted: mruby-string-ext, mruby-array-ext, mruby-set,
+mruby-struct, mruby-class-ext, mruby-numeric-ext, mruby-random,
+mruby-kernel-ext, mruby-complex, mruby-rational, mruby-io, mruby-socket,
+mruby-method, mruby-metaprog, mruby-time, mruby-hash-ext, mruby-proc-ext,
+mruby-symbol-ext, mruby-range-ext, mruby-object-ext.
+
+# GC and Memory
+
+- **_NOTE_**: `MRB_NO_PRESYM` removed; presym is now always enabled ([81689045](https://github.com/mruby/mruby/commit/81689045))
+- Replace `gcnext` gray linked list with fixed-size gray stack, reducing per-object overhead ([31fea170](https://github.com/mruby/mruby/commit/31fea170))
+- `mrb_gc_add_region()` for providing contiguous memory buffers as GC heap pages ([072855a](https://github.com/mruby/mruby/commit/072855a))
+- Chunk-based pool for symbol string allocation ([e05bd8f](https://github.com/mruby/mruby/commit/e05bd8f))
+- Reduce `IV_INITIAL_SIZE` from 4 to 2 ([6bd1f51](https://github.com/mruby/mruby/commit/6bd1f51))
+- Lossless float encoding using rotation in word boxing ([b6148c8](https://github.com/mruby/mruby/commit/b6148c8))
+- Lossless rotation encoding for 32-bit float32 word boxing ([14a5cfb](https://github.com/mruby/mruby/commit/14a5cfb))
+- Consolidated irep allocation for .mrb loading ([74fb045](https://github.com/mruby/mruby/commit/74fb045))
+
 # Build & Configuration
 
+- Amalgamation support via `rake amalgam` task ([d995ca2](https://github.com/mruby/mruby/commit/d995ca2))
 - New Platform: Cosmopolitan Libc ([#6681](https://github.com/mruby/mruby/pull/6681))
 - Emscripten: use native WASM exception handling ([ca364e3](https://github.com/mruby/mruby/commit/ca364e3))
 - HAL (Hardware Abstraction Layer) for platform abstraction in mruby-io, mruby-socket, mruby-dir, mruby-task ([74ca22f](https://github.com/mruby/mruby/commit/74ca22f))
@@ -51,22 +86,34 @@ mruby now supports pattern matching (case/in) syntax:
 ## mruby-bin-mirb Improvements
 
 - Custom multi-line editor replacing readline ([527018c](https://github.com/mruby/mruby/commit/527018c))
+- Syntax highlighting for keywords, strings, result values, hash key symbols ([624272b](https://github.com/mruby/mruby/commit/624272b), [1713d4a](https://github.com/mruby/mruby/commit/1713d4a))
+- Automatic light/dark theme detection via OSC 11 ([db4c8d9](https://github.com/mruby/mruby/commit/db4c8d9))
 - Tab completion support ([2f15282](https://github.com/mruby/mruby/commit/2f15282))
 - Colored output for prompts and errors ([b36e0b4](https://github.com/mruby/mruby/commit/b36e0b4))
-- Auto-indentation for continuation lines ([d52f318](https://github.com/mruby/mruby/commit/d52f318))
-- TAB auto-indentation ([fa74186](https://github.com/mruby/mruby/commit/fa74186))
-- Auto-dedent for `else`, `elsif`, `when`, `rescue`, `ensure`, `in` ([e901b6d](https://github.com/mruby/mruby/commit/e901b6d), [814b0cc](https://github.com/mruby/mruby/commit/814b0cc))
+- Auto-indentation and auto-dedent ([d52f318](https://github.com/mruby/mruby/commit/d52f318), [e901b6d](https://github.com/mruby/mruby/commit/e901b6d))
 - Command history with Up/Down navigation ([5f85c1b](https://github.com/mruby/mruby/commit/5f85c1b))
 - Line numbers in multi-line prompts ([5a3f0e2](https://github.com/mruby/mruby/commit/5a3f0e2))
-- Enhanced syntax error display ([ac39b7d](https://github.com/mruby/mruby/commit/ac39b7d))
+- UTF-8 multibyte character support ([4a97da3](https://github.com/mruby/mruby/commit/4a97da3))
+
+## mruby-bigint Improvements
+
+- Toom-3 multiplication for large numbers ([99620804](https://github.com/mruby/mruby/commit/99620804))
+- Karatsuba multiplication for medium-sized numbers ([85e81072](https://github.com/mruby/mruby/commit/85e81072))
+- Balance multiplication for asymmetric operands ([0220ec2b](https://github.com/mruby/mruby/commit/0220ec2b))
+- Divide-and-conquer optimization for `to_s` ([990ff90f](https://github.com/mruby/mruby/commit/990ff90f))
+- Consolidated mpn layer for low-level limb operations ([9ef3362f](https://github.com/mruby/mruby/commit/9ef3362f))
+- Always use 32-bit limbs by default ([c747c77f](https://github.com/mruby/mruby/commit/c747c77f))
 
 ## Other Gem Changes
 
+- **_NOTE_**: `Hash#deconstruct_keys` removed for CRuby compatibility ([34b9412](https://github.com/mruby/mruby/commit/34b9412))
 - **mruby-array-ext**: Add `Array#find` and `Array#rfind` methods
 - **mruby-io**: Add `IO#putc` and `Kernel#putc` ([baff6e6](https://github.com/mruby/mruby/commit/baff6e6))
 - **mruby-random**: Replace xoshiro with PCG for better memory efficiency ([f1bab01](https://github.com/mruby/mruby/commit/f1bab01))
 - **mruby-compiler**: Variable-sized AST nodes for reduced memory usage
 - **mruby-compiler**: `no_return_value` context flag for script optimization ([613b03a](https://github.com/mruby/mruby/commit/613b03a))
+- `initialize_copy` and `respond_to_missing?` defined as private ([#6708](https://github.com/mruby/mruby/pull/6708))
+- Struct keyword argument initialization ([#6574](https://github.com/mruby/mruby/pull/6574))
 
 # Compiler Improvements
 
@@ -74,52 +121,67 @@ mruby now supports pattern matching (case/in) syntax:
 - Pattern matching bytecode optimizations ([21d4135](https://github.com/mruby/mruby/commit/21d4135))
 - Optimized masgn to generate literals directly into target registers ([fb5d966](https://github.com/mruby/mruby/commit/fb5d966))
 - Optimized splat of literal arrays in args/literals ([1cb8d73](https://github.com/mruby/mruby/commit/1cb8d73))
+- Early termination after too many parse errors ([510ebd7](https://github.com/mruby/mruby/commit/510ebd7))
 
 # VM Optimizations
 
 New super-instructions that fuse common opcode sequences to reduce bytecode size and improve performance:
 
+- `OP_SEND0`/`OP_SSEND0`: Zero-argument method call, avoiding argument count setup ([9123ef4](https://github.com/mruby/mruby/commit/9123ef4))
 - `OP_TDEF`/`OP_SDEF`: Fused method definition combining TCLASS/SCLASS+METHOD+DEF into single instruction, saving 4 bytes per method ([8d4f47e](https://github.com/mruby/mruby/commit/8d4f47e))
 - `OP_GETIDX0`: Fast path for `array[0]` and `Array#first` access ([680f7ec](https://github.com/mruby/mruby/commit/680f7ec))
 - `OP_ADDILV`/`OP_SUBILV`: Local variable increment/decrement fusion for `i += n` patterns ([43f64b9](https://github.com/mruby/mruby/commit/43f64b9))
 - `OP_RETSELF`: Single-byte instruction for `return self` pattern ([a71db8c](https://github.com/mruby/mruby/commit/a71db8c))
-- `OP_MATCHERR`: Pattern matching error with conditional execution for `in` patterns ([944168a](https://github.com/mruby/mruby/commit/944168a), [e9a9ba4](https://github.com/mruby/mruby/commit/e9a9ba4))
-- `OP_BLKCALL`: Direct block call for `yield`, bypassing method dispatch (13-17% faster) ([3aa2872](https://github.com/mruby/mruby/commit/3aa2872))
 - `OP_RETNIL`: Single-byte instruction for `return nil` pattern ([64e30bf](https://github.com/mruby/mruby/commit/64e30bf))
 - `OP_RETTRUE`/`OP_RETFALSE`: Single-byte instructions for `return true`/`return false` patterns ([0b15727](https://github.com/mruby/mruby/commit/0b15727))
+- `OP_MATCHERR`: Pattern matching error with conditional execution ([944168a](https://github.com/mruby/mruby/commit/944168a))
+- `OP_BLKCALL`: Direct block call for `yield`, bypassing method dispatch (13-17% faster) ([3aa2872](https://github.com/mruby/mruby/commit/3aa2872))
+
+Other optimizations:
+
+- 1.5x stack growth instead of linear growth for reduced reallocations ([f7988c93](https://github.com/mruby/mruby/commit/f7988c93))
+- Skip keyword argument hash duplication ([5970e350](https://github.com/mruby/mruby/commit/5970e350))
 
 # Fixed GitHub Issues
 
-- [#6675](https://github.com/mruby/mruby/issues/6675) Allow Hash#[] to be aliased again
-- [#6674](https://github.com/mruby/mruby/issues/6674) Document pattern matching limitations
-- [#6671](https://github.com/mruby/mruby/issues/6671) Separate inter-gem headers from external API headers
-- [#6668](https://github.com/mruby/mruby/issues/6668) Method#== for aliased methods and comparison bug
-- [#6666](https://github.com/mruby/mruby/issues/6666) Regexp literal with encoding
-- [#6664](https://github.com/mruby/mruby/issues/6664) Set#flatten memory leak
-- [#6662](https://github.com/mruby/mruby/issues/6662) Array set operations use-after-free
-- [#6660](https://github.com/mruby/mruby/issues/6660) Regression on struct/array/hash == override with super
-- [#6659](https://github.com/mruby/mruby/issues/6659) Super with keyword arguments
-- [#6657](https://github.com/mruby/mruby/issues/6657) Exception handling for ||= on class variables
-- [#6652](https://github.com/mruby/mruby/issues/6652) Array comparison use-after-realloc
-- [#6650](https://github.com/mruby/mruby/issues/6650) Array#fill validation
-- [#6649](https://github.com/mruby/mruby/issues/6649) Array#sort! use-after-realloc
-- [#6648](https://github.com/mruby/mruby/issues/6648) sprintf buffer overread
-- [#6647](https://github.com/mruby/mruby/issues/6647) IO#ungetc buffer overflow
-- [#6646](https://github.com/mruby/mruby/issues/6646) IO#gets negative length
-- [#6645](https://github.com/mruby/mruby/issues/6645) Set memory leak from double initialization
-- [#6642](https://github.com/mruby/mruby/issues/6642) Task segfault when sleep called from C
-- [#6637](https://github.com/mruby/mruby/issues/6637) arm64 mingw64 builtin setjmp/longjmp
-- [#6635](https://github.com/mruby/mruby/issues/6635), [#6636](https://github.com/mruby/mruby/issues/6636) Colon3 constant lookup
-- [#6613](https://github.com/mruby/mruby/issues/6613) const_added hook during bootstrapping
-- [#6570](https://github.com/mruby/mruby/issues/6570) instance_eval crash
-- [#6554](https://github.com/mruby/mruby/issues/6554) Socket private #initialize
-- [#6516](https://github.com/mruby/mruby/issues/6516) Private backquote
-- [#6515](https://github.com/mruby/mruby/issues/6515) y.tab.c in repository
-- [#6509](https://github.com/mruby/mruby/issues/6509) scope_new nregs initialization
-- [#6508](https://github.com/mruby/mruby/issues/6508) Enumerable#sum index
-- [#6507](https://github.com/mruby/mruby/issues/6507) tally multi-values
-- [#6506](https://github.com/mruby/mruby/issues/6506) Constant lookup in singleton class
 - [#5531](https://github.com/mruby/mruby/issues/5531) Hash recursion detection
+- [#6506](https://github.com/mruby/mruby/issues/6506) Constant lookup in singleton class
+- [#6507](https://github.com/mruby/mruby/issues/6507) tally multi-values
+- [#6508](https://github.com/mruby/mruby/issues/6508) Enumerable#sum index
+- [#6509](https://github.com/mruby/mruby/issues/6509) scope_new nregs initialization
+- [#6515](https://github.com/mruby/mruby/issues/6515) y.tab.c in repository
+- [#6516](https://github.com/mruby/mruby/issues/6516) Private backquote
+- [#6554](https://github.com/mruby/mruby/issues/6554) Socket private #initialize
+- [#6570](https://github.com/mruby/mruby/issues/6570) instance_eval crash
+- [#6613](https://github.com/mruby/mruby/issues/6613) const_added hook during bootstrapping
+- [#6635](https://github.com/mruby/mruby/issues/6635), [#6636](https://github.com/mruby/mruby/issues/6636) Colon3 constant lookup
+- [#6637](https://github.com/mruby/mruby/issues/6637) arm64 mingw64 builtin setjmp/longjmp
+- [#6642](https://github.com/mruby/mruby/issues/6642) Task segfault when sleep called from C
+- [#6645](https://github.com/mruby/mruby/issues/6645) Set memory leak from double initialization
+- [#6646](https://github.com/mruby/mruby/issues/6646) IO#gets negative length
+- [#6647](https://github.com/mruby/mruby/issues/6647) IO#ungetc buffer overflow
+- [#6648](https://github.com/mruby/mruby/issues/6648) sprintf buffer overread
+- [#6649](https://github.com/mruby/mruby/issues/6649) Array#sort! use-after-realloc
+- [#6650](https://github.com/mruby/mruby/issues/6650) Array#fill validation
+- [#6652](https://github.com/mruby/mruby/issues/6652) Array comparison use-after-realloc
+- [#6657](https://github.com/mruby/mruby/issues/6657) Exception handling for ||= on class variables
+- [#6659](https://github.com/mruby/mruby/issues/6659) Super with keyword arguments
+- [#6660](https://github.com/mruby/mruby/issues/6660) Regression on struct/array/hash == override with super
+- [#6662](https://github.com/mruby/mruby/issues/6662) Array set operations use-after-free
+- [#6664](https://github.com/mruby/mruby/issues/6664) Set#flatten memory leak
+- [#6666](https://github.com/mruby/mruby/issues/6666) Regexp literal with encoding
+- [#6668](https://github.com/mruby/mruby/issues/6668) Method#== for aliased methods and comparison bug
+- [#6671](https://github.com/mruby/mruby/issues/6671) Separate inter-gem headers from external API headers
+- [#6674](https://github.com/mruby/mruby/issues/6674) Document pattern matching limitations
+- [#6675](https://github.com/mruby/mruby/issues/6675) Allow Hash#[] to be aliased again
+- [#6687](https://github.com/mruby/mruby/issues/6687) Expand MRB_SYM/MRB_GVSYM support for symbols with special characters
+- [#6698](https://github.com/mruby/mruby/issues/6698) Bigint tests fail on architectures other than x86_64 and i386
+- [#6701](https://github.com/mruby/mruby/issues/6701) Heap-use-after-free in mrb_vm_exec involving mruby-rational / mruby-bigint
+- [#6702](https://github.com/mruby/mruby/issues/6702) mruby-bigint doesn't compile in C++ project
+- [#6704](https://github.com/mruby/mruby/issues/6704) Heap-buffer-overflow in mrb_vm_exec via malformed source code
+- [#6705](https://github.com/mruby/mruby/issues/6705) Can't get outer class of an object in C
+- [#6713](https://github.com/mruby/mruby/issues/6713) mruby-polarssl not work
+- [#6720](https://github.com/mruby/mruby/issues/6720) Random float range: different behavior from CRuby
 
 # Merged Pull Requests
 
@@ -224,14 +286,35 @@ New super-instructions that fuse common opcode sequences to reduce bytecode size
 - [#6678](https://github.com/mruby/mruby/pull/6678) Put ls-lint and pre-commit in separate workflow files
 - [#6679](https://github.com/mruby/mruby/pull/6679) pre-commit autoupdate; update node and prettier
 - [#6681](https://github.com/mruby/mruby/pull/6681) Add Cosmopolitan Libc build configuration
+- [#6689](https://github.com/mruby/mruby/pull/6689) docs: fix pre-commit manual hooks; fix link
+- [#6694](https://github.com/mruby/mruby/pull/6694) Fix mirb build under Cosmopolitan
+- [#6695](https://github.com/mruby/mruby/pull/6695) Dependabot: add a cooldown period for new releases
+- [#6696](https://github.com/mruby/mruby/pull/6696) Fix parse error with required kwargs and omitted parens
+- [#6699](https://github.com/mruby/mruby/pull/6699) Fix mruby-task for PicoRuby Integration
+- [#6700](https://github.com/mruby/mruby/pull/6700) Fix float/double pack/unpack on s390x
+- [#6706](https://github.com/mruby/mruby/pull/6706) Refactor task class to use symbol IDs
+- [#6708](https://github.com/mruby/mruby/pull/6708) `initialize_copy` and `respond_to_missing?` defined as private
+- [#6709](https://github.com/mruby/mruby/pull/6709) Add the `MRB_ENSURE()` macro
+- [#6711](https://github.com/mruby/mruby/pull/6711) Fix out of bounds read and write in IO.select
+- [#6714](https://github.com/mruby/mruby/pull/6714) Fix OP_DEBUG operand type and add NULL check for debug_op_hook
+- [#6716](https://github.com/mruby/mruby/pull/6716) Fixes identity for proc object
+- [#6717](https://github.com/mruby/mruby/pull/6717) Fix mruby-task: wrapping by critical section and setting initial task receiver
+- [#6718](https://github.com/mruby/mruby/pull/6718) Add installation instructions for conda and Homebrew
 
 # Security Fixes
 
 - Buffer overflow in bigint uadd ([3f2611e](https://github.com/mruby/mruby/commit/3f2611e))
+- Stack buffer overflow in Montgomery reduction ([edce0a3](https://github.com/mruby/mruby/commit/edce0a3))
 - Buffer overflow in pack_uu encoding ([2993302](https://github.com/mruby/mruby/commit/2993302))
 - Buffer overflow in IO#ungetc ([01ab2ff](https://github.com/mruby/mruby/commit/01ab2ff))
+- Heap-buffer-overflow in pattern alternation codegen ([eea9e30](https://github.com/mruby/mruby/commit/eea9e30))
+- Out of bounds read and write in IO.select ([44831711](https://github.com/mruby/mruby/commit/44831711))
+- Off-by-one in bounds check for symbol names and pool strings in load.c ([b3b8c01](https://github.com/mruby/mruby/commit/b3b8c01))
 - Use-after-free in Set operations ([a6b55e7](https://github.com/mruby/mruby/commit/a6b55e7))
 - Use-after-free in Array set operations ([729b84c](https://github.com/mruby/mruby/commit/729b84c))
 - Use-after-free in Set#join ([0e653eb](https://github.com/mruby/mruby/commit/0e653eb))
 - Use-after-realloc in Array#sort! ([eb39897](https://github.com/mruby/mruby/commit/eb39897))
+- Heap-use-after-free in insertion_sort ([099d2c47](https://github.com/mruby/mruby/commit/099d2c47))
+- Integer overflow in str_check_length ([6afff1c3](https://github.com/mruby/mruby/commit/6afff1c3))
+- Integer overflow in Integer#lcm ([070bef24](https://github.com/mruby/mruby/commit/070bef24))
 - Multiple memory leak fixes in bigint, Set, Array, and Task gems