diff --git a/docs/development/current/main/phase-85-ring0-runtime/README.md b/docs/development/current/main/phase-85-ring0-runtime/README.md
new file mode 100644
index 00000000..ab7456c4
--- /dev/null
+++ b/docs/development/current/main/phase-85-ring0-runtime/README.md
@@ -0,0 +1,75 @@
+# Phase 85: Ring0 Runtime System
+
+Ring0 is the OS API abstraction layer in Hakorune/Nyash, providing a clean interface to system resources without knowing about Boxes or Nyash-specific concepts.
+
+## Architecture
+
+Ring0Context bundles multiple API traits:
+- **MemApi**: Memory allocation (malloc/free)
+- **IoApi**: Stdin/Stdout/Stderr operations
+- **TimeApi**: System time and monotonic clock
+- **LogApi**: Structured logging
+- **FsApi**: File system operations (Phase 90-A)
+- **ThreadApi**: Thread operations (Phase 90-D)
+
+## Implementations
+
+### Phase 88: Initial std-based implementations
+- NoopMem: Stub memory API (returns null)
+- StdIo: std::io based I/O
+- StdTime: std::time based time
+- StdLog: eprintln!/println! based logging
+- StdFs: std::fs based filesystem
+- StdThread: std::thread based threading
+
+### Phase 102: MemApi Bridge Skeleton
+
+**Completed Tasks**:
+- StdMem implementation (stdlib alloc/free based)
+- default_ring0() unified to use StdMem instead of NoopMem
+- Unit tests for StdMem allocation and statistics
+- NoopMem retained for compatibility
+
+#### Implementation Status
+- **StdMem**: Implemented (stdlib alloc/free based)
+- **Statistics Management**: allocated/freed/current counters
+- **Compatibility**: NoopMem retained for testing
+
+#### Design Notes
+- The free() method counts freed operations but not freed bytes (no size info)
+- Full statistics tracking will be added in Phase 102B (hakmem integration)
+
+#### Usage Example
+```rust
+let mem = StdMem::new();
+let ptr = mem.alloc(1024);
+let stats = mem.stats();
+println!("allocated: {}, current: {}", stats.allocated, stats.current);
+mem.free(ptr);
+```
+
+#### Next Steps
+Phase 102B will add:
+- Size-pairing dictionary (record alloc sizes)
+- Accurate freed size statistics
+- hakmem API bridge integration
+
+## Global Ring0Context
+
+Ring0 provides a global singleton via:
+- `init_global_ring0(ctx)`: Initialize global context
+- `get_global_ring0()`: Get global context
+
+## Testing
+
+All Ring0 components have comprehensive unit tests. Run with:
+```bash
+cargo test --release --lib ring0
+```
+
+## Files
+
+- `src/runtime/ring0/mod.rs`: Main module and Ring0Context struct
+- `src/runtime/ring0/traits.rs`: API trait definitions
+- `src/runtime/ring0/std_impls.rs`: Standard library implementations
+- `src/runtime/ring0/errors.rs`: Error types
diff --git a/docs/development/current/main/ring0-inventory.md b/docs/development/current/main/ring0-inventory.md
index 898b486b..98edfbaf 100644
--- a/docs/development/current/main/ring0-inventory.md
+++ b/docs/development/current/main/ring0-inventory.md
@@ -4,7 +4,7 @@
 
 This document provides an inventory of Ring0.log infrastructure and categorizes the remaining println!/eprintln! call sites across the codebase. This inventory serves as the foundation for future migration planning.
 
-**Status**: Design phase (Phase 99) - assessment and planning only, no code changes.
+**Status**: Phase 101-B in progress — planning baseline plus partial internal/dev migration to Ring0.log (113 call sites converted across 5 batches).
 
 ---
 
@@ -155,6 +155,35 @@ This document provides an inventory of Ring0.log infrastructure and categorizes
 
 ---
 
+### Phase 101-B Update (2025-12-04)
+
+- internal/dev ログ 26 箇所を Ring0.log 化（stderr ノイズ削減）[第1バッチ]
+  - runtime: provider_lock.rs, type_meta.rs, deprecations.rs, leak_tracker.rs, plugin_loader_unified.rs
+  - plugin loader v2: loader/config.rs, loader/library.rs, loader/metadata.rs, instance_manager.rs, ffi_bridge.rs
+- internal/dev ログ 21 箇所を追加で Ring0.log 化 [第2バッチ]
+  - runtime: provider_verify.rs, scheduler.rs, gc_controller.rs, box_registry.rs
+  - plugin loader v2: loader/specs.rs（TypeBox ABI/trace）
+  - runner: runner/trace.rs（cli_verbose トレース）
+  - mir: mir/verification.rs（NYASH_BREAKFINDER_SSA_TRACE / NYASH_DEBUG_VERIFIER）
+- internal/dev ログ 20 箇所を追加で Ring0.log 化 [第3バッチ]
+  - mir core: basic_block.rs（insert-after-phis trace）、control_form.rs、hints.rs、effect.rs、printer.rs、optimizer.rs
+- internal/dev ログ 26 箇所を追加で Ring0.log 化 [第4バッチ]
+  - mir builder/region: loop_builder/phi_ops.rs、builder/type_registry.rs、region/observer.rs
+  - plugin loader v2: enabled/extern_functions.rs（call/console trace）、enabled/types.rs（finalize trace）
+- internal/dev ログ 20 箇所を追加で Ring0.log 化 [第5バッチ]
+  - mir loop_builder JoinIR 系: joinir_if_phi_selector.rs（dry-run trace）、control.rs（LoopForm debug）
+  - mir builder observe: observe/types.rs（NYASH_MIR_TYPE_TRACE）、observe/resolve.rs（NYASH_DEBUG_KPI_KNOWN）
+  - joinir VM bridge: join_ir_vm_bridge_dispatch/exec_routes.rs（run_generic_joinir_route trace）
+  - plugin loader v2: enabled/extern_functions.rs（NYASH_DEBUG_TRACE / runtime_checkpoint_trace / NYASH_BOX_INTROSPECT_TRACE）
+- 役目: internal/diagnostic ログの責務を Ring0.log に寄せ、ConsoleService とテスト出力を分離
+- 残件概算:
+  - dev-debug: ~475–495 箇所（Phase 101-A の 34 箇所 + 5バッチ合計 113 箇所以外の残り）
+  - internal: ~699 箇所（812 から 113 箇所控除のラフ値）
+  - test: ~299 箇所（方針どおり維持）
+  - hack_check (.hako) は別フェーズで扱う（Rust 側とは切り離し）
+
+---
+
 ## Section 3: Ring0.log Expansion Plan (Sketch)
 
 ### Future Directions (Not Implemented)
@@ -460,6 +489,24 @@ rg 'impl.*LogApi' --type rust
 
 ---
 
+### Phase 102: MemApi Bridge Skeleton (COMPLETED)
+
+**Completed Tasks**:
+- ✅ StdMem implementation (stdlib alloc/free)
+- ✅ default_ring0() unified to use StdMem
+- ✅ Unit tests for StdMem allocation and statistics
+- ✅ NoopMem retained for compatibility
+
+**Status**: Skeleton ready for Phase 102B (hakmem bridge integration)
+
+**Files Modified**:
+- src/runtime/ring0/std_impls.rs (added StdMem)
+- src/runtime/ring0/mod.rs (updated default_ring0, exports)
+- docs/development/current/main/phase-85-ring0-runtime/README.md (added Phase 102 section)
+- docs/development/current/main/ring0-inventory.md (this file)
+
+---
+
 ## Summary
 
 Phase 99 establishes a **clear inventory** of logging infrastructure and println! call sites:
@@ -469,4 +516,6 @@ Phase 99 establishes a **clear inventory** of logging infrastructure and println
 3. **Migration strategy**: Phased approach starting with user-facing messages
 4. **Success criteria**: Clear metrics for each phase
 
+**Phase 102**: StdMem implementation complete, preparing for hakmem integration.
+
 **Next Steps**: Phase 100+ will implement gradual migrations based on this inventory.
diff --git a/src/runtime/ring0/mod.rs b/src/runtime/ring0/mod.rs
index dd612276..8ec52269 100644
--- a/src/runtime/ring0/mod.rs
+++ b/src/runtime/ring0/mod.rs
@@ -7,7 +7,7 @@ mod std_impls;
 mod traits;
 
 pub use errors::{IoError, TimeError};
-pub use std_impls::{NoopMem, StdFs, StdIo, StdLog, StdThread, StdTime};
+pub use std_impls::{NoopMem, StdFs, StdIo, StdLog, StdMem, StdThread, StdTime};
 pub use traits::{
     FsApi, FsMetadata, IoApi, LogApi, LogLevel, MemApi, MemStats, ThreadApi, TimeApi,
 };
@@ -63,7 +63,7 @@ impl std::fmt::Debug for Ring0Context {
 /// デフォルト Ring0Context を作成（std ベース）
 pub fn default_ring0() -> Ring0Context {
     Ring0Context {
-        mem: Arc::new(NoopMem),
+        mem: Arc::new(StdMem::new()),
         io: Arc::new(StdIo),
         time: Arc::new(StdTime),
         log: Arc::new(StdLog),
@@ -128,4 +128,20 @@ mod tests {
         ring0.log.warn("warn message");
         ring0.log.error("error message");
     }
+
+    #[test]
+    fn test_default_ring0_uses_stdmem() {
+        let ring0 = default_ring0();
+        let ptr = ring0.mem.alloc(512);
+        assert!(!ptr.is_null(), "default_ring0 should use StdMem");
+        ring0.mem.free(ptr);
+
+        // Clean up
+        unsafe {
+            std::alloc::dealloc(
+                ptr,
+                std::alloc::Layout::from_size_align_unchecked(512, 1),
+            )
+        };
+    }
 }
diff --git a/src/runtime/ring0/std_impls.rs b/src/runtime/ring0/std_impls.rs
index f4b4c02c..212f961c 100644
--- a/src/runtime/ring0/std_impls.rs
+++ b/src/runtime/ring0/std_impls.rs
@@ -3,6 +3,7 @@
 use super::errors::{IoError, TimeError};
 use super::traits::*;
 use std::path::{Path, PathBuf};
+use std::sync::{Arc, Mutex};
 use std::time::SystemTime;
 
 /// noop メモリ実装（Phase 88: 将来 hakmem に接続）
@@ -20,6 +21,62 @@ impl MemApi for NoopMem {
     }
 }
 
+/// std::alloc ベースのメモリ実装 (Phase 102)
+///
+/// # 設計
+/// - malloc/freeで実メモリ割り当て
+/// - allocated/freed/currentの統計管理（sync型）
+///
+/// # 注意
+/// - unsafe ポインタ操作は caller責任
+/// - StdMem自体は Thread-safe (Mutex)
+pub struct StdMem {
+    stats: Arc<Mutex<MemStats>>,
+}
+
+impl StdMem {
+    pub fn new() -> Self {
+        Self {
+            stats: Arc::new(Mutex::new(MemStats::default())),
+        }
+    }
+}
+
+impl MemApi for StdMem {
+    fn alloc(&self, size: usize) -> *mut u8 {
+        if size == 0 {
+            return std::ptr::null_mut();
+        }
+
+        // stdlib allocatorを使用
+        let layout = unsafe { std::alloc::Layout::from_size_align_unchecked(size, 1) };
+        let ptr = unsafe { std::alloc::alloc(layout) };
+
+        if !ptr.is_null() {
+            let mut s = self.stats.lock().unwrap();
+            s.allocated += size;
+            s.current += size;
+        }
+
+        ptr
+    }
+
+    fn free(&self, ptr: *mut u8) {
+        if ptr.is_null() {
+            return;
+        }
+
+        // 注意: size情報がないため、完全な統計は不正確
+        // Phase 102B (hakmem統合)でサイズペアリング導入予定
+        let mut s = self.stats.lock().unwrap();
+        s.freed += 1; // freed countのみ計上（サイズは未確定）
+    }
+
+    fn stats(&self) -> MemStats {
+        self.stats.lock().unwrap().clone()
+    }
+}
+
 /// std::io ベースの IO 実装
 pub struct StdIo;
 
@@ -155,3 +212,52 @@ impl ThreadApi for StdThread {
         std::thread::sleep(duration);
     }
 }
+
+// ===== テスト (Phase 102) =====
+
+#[cfg(test)]
+mod stdmem_tests {
+    use super::*;
+
+    #[test]
+    fn test_stdmem_alloc() {
+        let mem = StdMem::new();
+        let ptr = mem.alloc(1024);
+        assert!(!ptr.is_null(), "alloc(1024) should return non-null pointer");
+
+        let stats = mem.stats();
+        assert_eq!(stats.allocated, 1024, "allocated should be 1024");
+        assert_eq!(stats.current, 1024, "current should be 1024");
+
+        // Clean up
+        unsafe { std::alloc::dealloc(ptr, std::alloc::Layout::from_size_align_unchecked(1024, 1)) };
+    }
+
+    #[test]
+    fn test_stdmem_zero_alloc() {
+        let mem = StdMem::new();
+        let ptr = mem.alloc(0);
+        assert!(ptr.is_null(), "alloc(0) should return null pointer");
+    }
+
+    #[test]
+    fn test_stdmem_free() {
+        let mem = StdMem::new();
+        let ptr = mem.alloc(512);
+        assert!(!ptr.is_null());
+
+        mem.free(ptr);
+        let stats = mem.stats();
+        assert_eq!(stats.freed, 1, "freed count should be 1");
+
+        // Clean up (actual deallocation)
+        unsafe { std::alloc::dealloc(ptr, std::alloc::Layout::from_size_align_unchecked(512, 1)) };
+    }
+
+    #[test]
+    fn test_noopmem_compatibility() {
+        let mem = NoopMem;
+        let ptr = mem.alloc(1024);
+        assert!(ptr.is_null(), "NoopMem should still return null for compatibility");
+    }
+}