docs(slice-2c): attempt #5 WASM_BUILD_STD=0 finding registered (alloc resuelto, std leak surface)

Charon sesión 2 continuation 2026-05-24 — empirical test Slice 2c attempt #5:
re-enable substrate-wasm-builder + set WASM_BUILD_STD=0 explicit override.

Findings canonical:
- ✅ alloc/exchange_malloc issue (Slice 2b attempts 1-4 blocker) RESUELTO canonical
- 🎯 NEW canonical layer: panic_impl duplicate via serde/std leakage transitive
- Error canonical: sp-io 40.0.1 panic_impl vs libstd-loaded panic_impl
- Diagnosis: serde pulled con std feature transitively → libstd linked en wasm32

Status canonical:
- Reverted canonical to safe state (no-op build.rs + substrate-wasm-builder dep
  commented). Slice 3 v0.0.13 mock-WASM fallback canonical sigue siendo path
  canonical estable canonical.
- Slice 2d canonical future requires deeper investigation canonical (inverted
  feature tree + serde patch o WASM_BUILD_RUSTFLAGS override o stable2512-4+ fix).

Documentation canonical filed:
- build.rs canonical: 5 attempts registered + Slice 2d path forward canonical
- Cargo.toml [build-deps]: comments canonical updated canonical
- CHANGELOG canonical: Unreleased section canonical Slice 2c attempt #5 entry

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,39 @@ by [Keep a Changelog](https://keepachangelog.com/en/1.1.0/). Versions follow
 
 ## [Unreleased]
 
+### Slice 2c attempt #5 finding canonical (2026-05-24 sesión 2 cont)
+
+**Empirical test canonical WASM_BUILD_STD=0 explicit override**:
+Re-enabled substrate-wasm-builder + set WASM_BUILD_STD=0 env explicit. Upstream
+docs confirman default = disabled para Rust >= 1.84 (mi pin 1.88.0).
+
+**Resultado canonical**:
+- ✅ `exchange_malloc/alloc` issue (Slice 2b attempts 1-4 blocker) **RESUELTO canonical**
+- 🎯 NEW canonical layer surface: `panic_impl` duplicate canonical via std leakage
+- Error canonical:
+  ```
+  error[E0152]: found duplicate lang item `panic_impl`
+    --> sp-io-40.0.1/src/lib.rs:1774:1
+    = note: the lang item is first defined in crate `std` (which `serde` depends on)
+    = note: first definition in `std` loaded from libstd-*.rlib
+    = note: second definition in the local crate (`sp_io`)
+  ```
+
+**Diagnosis canonical**: `serde` está siendo pulled con `std` feature canonical
+transitively desde algún dep (parity-scale-codec o frame-*) → libstd canonical
+linked en wasm32 → conflict canonical con `sp_io::panic` handler canonical (que
+define panic_impl para no_std runtime).
+
+**Path canonical Slice 2d future canonical**:
+- Inverted feature tree exact culprit identification canonical
+- Override canonical `[patch.crates-io] serde = {...}` con strict no-std
+- O explicit `WASM_BUILD_RUSTFLAGS` canonical override
+- O wait stable2512-4+ upstream canonical fix
+
+**Status canonical actual**: Reverted canonical to stable canonical state (no-op
+build.rs + substrate-wasm-builder dep canonical commented). Slice 3 v0.0.13
+mock-WASM fallback canonical sigue siendo el canonical path canonical estable.
+
 ## [0.0.13] — 2026-05-22 — Phase 1.6+ Slice 3 "ChainSpec builder canonical (mock-WASM fallback)"
 
 Charon sesión 2. **Phase 1.6+ Slice 3 canonical shipped** — real ChainSpec JSON

crates/origin-chain-runtime/Cargo.toml

@@ -64,18 +64,17 @@ log.workspace = true
 serde_json.workspace = true
 
 [build-dependencies]
-# Slice 2b investigation registered canonical 2026-05-21: 4 fix attempts canonical:
-#   1. Remove direct serde dep (transitive from FRAME) — NO solved
-#   2. Pin serde =1.0.219 + =1.0.217 — NO solved
-#   3. Remove profile.release lto/codegen-units customization — NO solved
-#   4. WasmBuilder::build_using_defaults() (upstream pattern) — NO solved
+# Slice 2c canonical multi-attempt findings registered (build.rs doc canonical):
+#   1-4 (Slice 2b 2026-05-21): direct serde / pin / profile / build_using_defaults
+#      — ALL NO solved alloc/exchange_malloc conflict canonical
+#   5 (Slice 2c attempt #5 2026-05-24 sesión 2 cont): WASM_BUILD_STD=0 explicit
+#      → alloc issue RESUELTO canonical. NEW canonical layer canonical surface:
+#      panic_impl duplicate canonical via serde/std leakage canonical.
 #
-# Root cause empírico: wbuild compila su propio alloc canonical con panic=abort
-# pero la precompiled rustup alloc canonical para wasm32 también está linked.
-# Conflict canonical es duplicate exchange_malloc lang item canonical.
-#
-# Slice 2c canonical requires Larihana Substrate-adjacent expertise canonical
-# (Plan C Rust ports + WASM workspace canonical experience) — diary filed.
+# Slice 2d canonical future requires deeper canonical: inverted feature tree
+# identify exact dep canonical activating serde/std + override canonical OR
+# stable2512-4+ upstream fix canonical. Mientras canonical Slice 3 v0.0.13
+# mock-WASM canonical path canonical estable canonical.
 # substrate-wasm-builder = { workspace = true, optional = true }
 
 [features]

crates/origin-chain-runtime/build.rs

@@ -1,9 +1,47 @@
-//! # Build script canonical (Slice 2b investigation registered, Slice 2c deferred)
+//! # Build script — Slice 2c canonical multi-attempt findings registered
 //!
-//! `substrate-wasm-builder` integration canonical bloqueado por structural Cargo
-//! + WASM stdlib alloc conflict canonical. Slice 2c canonical requires Larihana
-//! Substrate-adjacent expertise canonical — diary filed 2026-05-21.
+//! Slice 2b investigation registered (sesión 1, 2026-05-21) — 4 fix attempts
+//! NO solved canonical:
+//!   1. Remove direct serde dep (transitive from FRAME) — NO solved
+//!   2. Pin serde =1.0.219 + =1.0.217 — NO solved
+//!   3. Remove profile.release lto/codegen-units customization — NO solved
+//!   4. WasmBuilder::build_using_defaults() upstream pattern — NO solved
+//!
+//! Slice 2c attempt #5 (Charon sesión 2 cont. 2026-05-24) — empirical test
+//! WASM_BUILD_STD=0 explicit override canonical. Upstream docs confirman:
+//! "WASM_BUILD_STD is disabled by default for WASM target and Rust >= 1.84".
+//!
+//! ## Attempt #5 finding canonical (BIG progress)
+//!
+//! `WASM_BUILD_STD=0` explicit + WasmBuilder re-enabled → **alloc/exchange_malloc
+//! issue RESUELTO canonical**. Pero canonical surface NEW error canonical:
+//!
+//! ```
+//! error[E0152]: found duplicate lang item `panic_impl`
+//!   --> sp-io-40.0.1/src/lib.rs:1774:1
+//!   = note: the lang item is first defined in crate `std` (which `serde` depends on)
+//!   = note: first definition in `std` loaded from libstd-*.rlib
+//!   = note: second definition in the local crate (`sp_io`)
+//! ```
+//!
+//! Diagnosis canonical: serde está siendo pulled con `std` feature canonical
+//! transitively desde algún dep canonical (parity-scale-codec o frame-*) →
+//! libstd canonical linked en wasm32 → conflict canonical con sp_io::panic
+//! handler canonical (que define panic_impl para no_std runtime).
+//!
+//! ## Path canonical resolución pending (Slice 2d canonical future)
+//!
+//! Requires deeper investigation canonical:
+//! - Inverted feature tree exact culprit identification canonical
+//! - Override canonical: `[patch.crates-io] serde = { ... }` con strict no-std
+//! - O explicit `WASM_BUILD_RUSTFLAGS` canonical override
+//! - O wait stable2512-4+ upstream canonical fix
+//!
+//! Mientras Slice 2d land canonical, build script canonical mantain no-op +
+//! Slice 3 (v0.0.13) mock-WASM fallback canonical path estable canonical.
 
 fn main() {
-    // No-op canonical — Slice 2c land WASM_BINARY post Larihana expertise canonical.
+    // No-op canonical — Slice 2d canonical land WASM_BINARY post serde/std
+    // leakage canonical resolution canonical. Slice 3 mock-WASM (chain_spec
+    // builder JSON canonical) sigue siendo el path canonical estable canonical.
 }