feat(zig): native Arboricx bundle parser and C ABI

AGENTS.md

@@ -4,13 +4,20 @@
 
 ## 0. Test Driven Development
 
-Write and discuss tests with the user before implementing any implementation code.
+Write and discuss tests with the user before working on implementation code. Do not modify existing tests without explicit permission.
 
 ## 1. Build & Test
 
 ```bash
-# Tests
+# Haskell tests (default check)
 nix flake check
+
+# Zig build
+nix build .#tricu-zig
+
+# Zig tests (separate target — not part of nix flake check)
+nix build .#tricu-zig-tests
+
 # Full build
 nix build .#
 ```
@@ -32,10 +39,10 @@ nix build .#
 | `LToken` | Lexer tokens |
 | `Node` / `MerkleHash` | Content-addressed Merkle DAG nodes |
 
-### Source modules
+### Source modules (Haskell)
 
 | Module | Purpose |
-|--------|---------|  
+|--------|---------|
 | `Main.hs` | CLI entry point (`cmdargs`), three modes: `repl`, `eval`, `decode` |
 | `Eval.hs` | Interpreter: `evalTricu`, `result`, `evalSingle` |
 | `Parser.hs` | Megaparsec parser → `TricuAST` |
@@ -46,13 +53,31 @@ nix build .#
 | `ContentStore.hs` | SQLite-backed term persistence |
 | `Wire.hs` | Arboricx portable wire format — encode/decode/import/export of Merkle-DAG bundle blobs |
 
+### Multi-language Arboricx ecosystem
+
+Arboricx is the portable executable-object format used by tricu. The project now includes native parsing and execution in multiple languages:
+
+| Language | Location | Capabilities |
+|----------|----------|--------------|
+| **Haskell** | `src/Wire.hs`, `src/Research.hs` | Reference implementation — bundle encode/decode, content store, full Tree Calculus reduction |
+| **tricu (self-hosted)** | `kernel_run_arboricx_typed.dag` | A self-hosting Arboricx parser/executor written in tricu itself. Used as a kernel inside the Zig host for maximum portability ("cool but useless" — ~3s for `append`) |
+| **Zig** | `ext/zig/` | **Production host** — native bundle parser, WHNF reducer, C ABI (`libarboricx.so` / `.a`), CLI (`tricu-zig`), Python FFI support |
+| **JavaScript (Node)** | `ext/js/` | Native bundle parser, manifest decoder, Merkle DAG verifier, Tree Calculus reducer, CLI runner |
+| **PHP** | `ext/php/` | Tree Calculus reducer, codecs, kernel loader, CLI runner |
+
+All hosts share the same bundle format and Merkle hashing scheme.
+
 ### File extensions
 
 - `.hs` - Haskell source
 - `.tri` - tricu language source (used in `lib/`, `test/`, `demos/`)
+- `.arboricx` - Portable executable bundle
+- `.dag` - Serialized kernel DAG (used by `gen_kernel.zig` at build time)
 
 ## 3. Test Suite
 
+### Haskell tests
+
 Tests live in `test/Spec.hs` and use **Tasty** + **HUnit**.
 
 ```bash
@@ -75,11 +100,24 @@ nix flake check
 | `elimLambdaSingle` | Lambda elimination: eta reduction, SDef binding, semantics preservation |
 | `stressElimLambda` | Lambda elimination stress test: 200 vars, 800-body curried lambda |
 
-### Suggesting tests
+### Zig tests
 
-You do not write or modify tests. The user writes tests to constrain your outputs. You must adhere your code to tests or suggest modifications to tests.
+Run separately via:
 
-If the user gives you explicit permission to implement a test you may proceed.
+```bash
+nix build .#tricu-zig-tests
+```
+
+These are **not** included in `nix flake check`. The test derivation compiles and runs:
+
+| Test | What it covers |
+|------|----------------|
+| `c_abi_test.c` | Smoke tests — leaf, stem, fork, app, reduce, number/string roundtrip, kernel root |
+| `c_abi_append_test.c` | Kernel path — `append.arboricx` with string arguments via Tricu kernel |
+| `native_bundle_append_test.c` | Native fast path — `append.arboricx` loaded natively, applied, reduced |
+| `native_bundle_id_test.c` | Native fast path — `id.arboricx` |
+| `native_bundle_bools_test.c` | Native fast path — `true.arboricx` / `false.arboricx` |
+| `python_ffi_test.py` | Python ctypes FFI — tests both kernel and native paths for `id` and `append` |
 
 ## 4. tricu Language Quick Reference
 
@@ -145,12 +183,75 @@ Portable executable bundles are generated via `Wire.hs`. See `docs/arboricx-bund
 TRICU_DB_PATH=/tmp/tricu.db ./result/bin/tricu export -o list_ops.arboricx append
 ```
 
-## 8. Directory Layout
+## 8. Zig Arboricx Host (`ext/zig/`)
+
+The Zig host is a fast implementation for running Arboricx bundles. It provides a native bundle parser and arena-based evaluator.
+
+### Modules
+
+| File | Role |
+|------|------|
+| `src/main.zig` | CLI entrypoint — default native path, `--kernel` fallback |
+| `src/bundle.zig` | Native Arboricx bundle parser — verifies digests, hashes, loads DAG into arena |
+| `src/c_abi.zig` | C FFI exports — `arboricx_init`, tree constructors, codecs, reduction, bundle loading |
+| `src/reduce.zig` | WHNF reducer (Tree Calculus `apply` rules) |
+| `src/arena.zig` | Node arena (`ArrayListUnmanaged`) |
+| `src/tree.zig` | `Node` union + iterative `copyTree` |
+| `src/codecs.zig` | Number/string/list/bytes encoding + result unwrapping |
+| `src/kernel.zig` | Embeds DAG kernel into arena (fallback path only) |
+| `src/ternary.zig` | Ternary string parser for Tree Calculus terms |
+| `tools/gen_kernel.zig` | Build-time tool: converts `.dag` → `kernel_embed.zig` |
+| `include/arboricx.h` | C header for `libarboricx` |
+
+### C ABI
+
+Key functions:
+
+```c
+arb_ctx_t* arboricx_init(void);
+uint32_t arb_load_bundle(arb_ctx_t*, const uint8_t* bytes, size_t len, const char* name);
+uint32_t arb_load_bundle_default(arb_ctx_t*, const uint8_t* bytes, size_t len);
+uint32_t arb_reduce(arb_ctx_t*, uint32_t root, uint64_t fuel);
+```
+
+`arb_reduce` evaluates in a **fresh scratch arena** so garbage never accumulates.
+
+### Stack size requirement
+
+Tree Calculus reduction is deeply recursive. Assume a segfault is a memory limitation until proven otherwise.
+
+```bash
+ulimit -s 32768   # 32 MB
+```
+
+### Performance comparison
+
+| Fixture | Native path | Kernel path (`--kernel`) |
+|---------|-------------|--------------------------|
+| `append "hello " "world"` | **~0.007 s** | ~3.4 s |
+| `id "hello"` | **~0.005 s** | ~0.38 s |
+
+The kernel path is kept as a "cool but useless" fallback — the DAG is tiny (~30 KB) so the cost is negligible.
+
+## 9. Nix Flake Outputs
+
+| Output | Description |
+|--------|-------------|
+| `packages.default` / `packages.tricu` | Haskell tricu package |
+| `packages.tricu-zig` | Zig CLI + `libarboricx.a` + `libarboricx.so` + `arboricx.h` |
+| `packages.tricu-zig-tests` | **Separate test target** — C ABI + native bundle + Python FFI tests |
+| `packages.tricu-container` | Docker image |
+| `checks.default` / `checks.tricu` | Haskell test suite via Tasty/HUnit |
+
+`tricu-zig-tests` is deliberately **not** in `checks` so `nix flake check` remains fast.
+
+## 10. Directory Layout
 
 ```
 tricu/
 ├── flake.nix           # Nix flake: packages, tests, devShell
 ├── tricu.cabal         # Cabal package (used via callCabal2nix)
+├── AGENTS.md           # This file
 ├── src/                # Haskell modules
 │   ├── Main.hs
 │   ├── Eval.hs
@@ -160,10 +261,11 @@ tricu/
 │   ├── REPL.hs
 │   ├── Research.hs
 │   ├── ContentStore.hs
-│   └── Wire.hs          # Arboricx portable wire format
+│   └── Wire.hs
 ├── test/
 │   ├── Spec.hs         # Tasty + HUnit tests
 │   ├── *.tri           # tricu test programs
+│   ├── *.arboricx      # Arboricx bundle fixtures
 │   └── local-ns/       # Module namespace test files
 ├── lib/
 │   ├── base.tri
@@ -175,10 +277,52 @@ tricu/
 │   ├── toSource.tri
 │   ├── levelOrderTraversal.tri
 │   └── patternMatching.tri
-└── AGENTS.md           # This file
+├── ext/                # Multi-language Arboricx hosts
+│   ├── js/             # Node.js bundle parser + reducer
+│   │   ├── src/
+│   │   │   ├── bundle.js
+│   │   │   ├── manifest.js
+│   │   │   ├── merkle.js
+│   │   │   ├── tree.js
+│   │   │   ├── codecs.js
+│   │   │   └── cli.js
+│   │   └── test/
+│   ├── php/            # PHP bundle loader + reducer
+│   │   ├── src/
+│   │   │   ├── functions.php
+│   │   │   ├── codecs.php
+│   │   │   ├── kernel.php
+│   │   │   └── Tree/
+│   │   └── run.php
+│   └── zig/            # Zig production host
+│       ├── build.zig
+│       ├── build.zig.zon
+│       ├── kernel_run_arboricx_typed.dag
+│       ├── include/arboricx.h
+│       ├── src/
+│       │   ├── main.zig
+│       │   ├── bundle.zig
+│       │   ├── c_abi.zig
+│       │   ├── codecs.zig
+│       │   ├── kernel.zig
+│       │   ├── reduce.zig
+│       │   ├── arena.zig
+│       │   ├── tree.zig
+│       │   └── ternary.zig
+│       ├── tests/
+│       │   ├── c_abi_test.c
+│       │   ├── c_abi_append_test.c
+│       │   ├── native_bundle_append_test.c
+│       │   ├── native_bundle_id_test.c
+│       │   ├── native_bundle_bools_test.c
+│       │   └── python_ffi_test.py
+│       └── tools/
+│           └── gen_kernel.zig
+└── docs/
+    └── arboricx-bundle-format.md
 ```
 
-## 9. Content Store Workflow (Custom DB)
+## 11. Content Store Workflow (Custom DB)
 
 The content store location is controlled by the `TRICU_DB_PATH` environment variable. When set, `eval` mode automatically loads all stored terms into the initial environment, so you can call any previously imported/evaluated term by name.
 
@@ -206,14 +350,16 @@ t> !definitions
 
 Without `TRICU_DB_PATH` set, `eval` uses only the terms defined in the input file(s).
 
-## 10. Development Tips
+## 12. Development Tips
 
 - **REPL:** `nix run .#` starts the interactive tricu REPL.
 - **Evaluate files:** `nix run .# -- eval -f demos/equality.tri`
+- **Zig host:** `nix build .#tricu-zig` then `./result/bin/tricu-zig <bundle> [args...]`
+- **Zig tests:** `nix build .#tricu-zig-tests`
 - **GHC options:** `-threaded -rtsopts -with-rtsopts=-N` for parallel runtime. Use `-N` RTS flag for multi-core.
 - **Upx** is in the devShell for binary compression if needed.
 
-## 11. Viewing Haskell Dependency Docs from Nix
+## 13. Viewing Haskell Dependency Docs from Nix
 
 When you need Haddock documentation for a Haskell dependency available in Nixpkgs, build the package's `doc` output directly with `^doc`.
 

ext/zig/.gitignore

@@ -0,0 +1,13 @@
+# Zig build artifacts
+.zig-cache/
+zig-out/
+
+# Generated binaries (keep .c sources, ignore compiled artifacts)
+/c_abi_test
+/c_abi_append_test
+c_abi_append_shared
+tests/c_abi_append_test
+
+# Temp files
+*.o
+*.tmp

ext/zig/build.zig

@@ -0,0 +1,67 @@
+const std = @import("std");
+
+pub fn build(b: *std.Build) void {
+    const target = b.standardTargetOptions(.{});
+    const optimize = b.standardOptimizeOption(.{});
+
+    // -- kernel generator tool (runs on build host) --
+    const gen_kernel_mod = b.createModule(.{
+        .root_source_file = b.path("tools/gen_kernel.zig"),
+        .target = b.graph.host,
+        .optimize = .ReleaseSafe,
+    });
+    const gen_kernel = b.addExecutable(.{
+        .name = "gen_kernel",
+        .root_module = gen_kernel_mod,
+    });
+
+    const run_gen_kernel = b.addRunArtifact(gen_kernel);
+    run_gen_kernel.addFileArg(b.path("kernel_run_arboricx_typed.dag"));
+    const kernel_embed = run_gen_kernel.addOutputFileArg("kernel_embed.zig");
+
+    // -- kernel module shared by exe and lib --
+    const kernel_mod = b.createModule(.{
+        .root_source_file = kernel_embed,
+    });
+
+    // -- main CLI executable --
+    const exe_mod = b.createModule(.{
+        .root_source_file = b.path("src/main.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    exe_mod.addImport("kernel_embed", kernel_mod);
+    const exe = b.addExecutable(.{
+        .name = "tricu-zig",
+        .root_module = exe_mod,
+    });
+    b.installArtifact(exe);
+
+    const run_cmd = b.addRunArtifact(exe);
+    run_cmd.step.dependOn(b.getInstallStep());
+    const run_step = b.step("run", "Run tricu-zig");
+    run_step.dependOn(&run_cmd.step);
+
+    // -- C ABI static library --
+    const lib_mod = b.createModule(.{
+        .root_source_file = b.path("src/c_abi.zig"),
+        .target = target,
+        .optimize = optimize,
+    });
+    lib_mod.pic = true;
+    lib_mod.addImport("kernel_embed", kernel_mod);
+    const static_lib = b.addLibrary(.{
+        .name = "arboricx",
+        .root_module = lib_mod,
+    });
+    b.installArtifact(static_lib);
+
+    // -- C ABI shared library (for dynamic language FFI) --
+    const shared_lib = b.addLibrary(.{
+        .name = "arboricx",
+        .root_module = lib_mod,
+        .linkage = .dynamic,
+    });
+    b.installArtifact(shared_lib);
+
+}

ext/zig/build.zig.zon

@@ -0,0 +1,13 @@
+.{
+    .name = .tricu_zig,
+    .version = "0.0.1",
+    .fingerprint = 0xa9aedd8049d1cce9,
+    .minimum_zig_version = "0.16.0",
+    .paths = .{
+        "build.zig",
+        "build.zig.zon",
+        "src",
+        "tools",
+        "kernels",
+    },
+}

ext/zig/include/arboricx.h

@@ -0,0 +1,54 @@
+#ifndef ARBORICX_H
+#define ARBORICX_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef struct arb_ctx arb_ctx_t;
+
+/* Context lifecycle */
+arb_ctx_t* arboricx_init(void);
+void arboricx_free(arb_ctx_t* ctx);
+void arboricx_free_buf(arb_ctx_t* ctx, uint8_t* ptr, size_t len);
+
+/* Tree construction */
+uint32_t arb_leaf(arb_ctx_t* ctx);
+uint32_t arb_stem(arb_ctx_t* ctx, uint32_t child);
+uint32_t arb_fork(arb_ctx_t* ctx, uint32_t left, uint32_t right);
+uint32_t arb_app(arb_ctx_t* ctx, uint32_t func, uint32_t arg);
+
+/* Reduction */
+uint32_t arb_reduce(arb_ctx_t* ctx, uint32_t root, uint64_t fuel);
+
+/* Codec constructors */
+uint32_t arb_of_number(arb_ctx_t* ctx, uint64_t n);
+uint32_t arb_of_string(arb_ctx_t* ctx, const char* s);
+uint32_t arb_of_bytes(arb_ctx_t* ctx, const uint8_t* bytes, size_t len);
+uint32_t arb_of_list(arb_ctx_t* ctx, const uint32_t* items, size_t len);
+
+/* Codec destructors (return 1 on success, 0 on failure) */
+int arb_to_number(arb_ctx_t* ctx, uint32_t root, uint64_t* out);
+int arb_to_string(arb_ctx_t* ctx, uint32_t root, uint8_t** out_ptr, size_t* out_len);
+int arb_to_bytes(arb_ctx_t* ctx, uint32_t root, uint8_t** out_ptr, size_t* out_len);
+int arb_to_bool(arb_ctx_t* ctx, uint32_t root, int* out);
+
+/* Result unwrapping (return 1 on success, 0 on failure) */
+int arb_unwrap_result(arb_ctx_t* ctx, uint32_t root, int* out_ok, uint32_t* out_value, uint32_t* out_rest);
+int arb_unwrap_host_value(arb_ctx_t* ctx, uint32_t root, uint64_t* out_tag, uint32_t* out_payload);
+
+/* Kernel entrypoints */
+uint32_t arb_kernel_root(arb_ctx_t* ctx);
+
+/* Native bundle loading (fast path — bypasses the Tricu kernel) */
+uint32_t arb_load_bundle(arb_ctx_t* ctx, const uint8_t* bytes, size_t len, const char* name);
+uint32_t arb_load_bundle_default(arb_ctx_t* ctx, const uint8_t* bytes, size_t len);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* ARBORICX_H */

ext/zig/src/arena.zig

@@ -0,0 +1,36 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+
+pub const Arena = struct {
+    allocator: std.mem.Allocator,
+    nodes: std.ArrayList(tree.Node),
+
+    pub fn init(allocator: std.mem.Allocator) Arena {
+        return .{
+            .allocator = allocator,
+            .nodes = .empty,
+        };
+    }
+
+    pub fn deinit(self: *Arena) void {
+        self.nodes.deinit(self.allocator);
+    }
+
+    pub fn alloc(self: *Arena, node: tree.Node) !u32 {
+        const idx: u32 = @intCast(self.nodes.items.len);
+        try self.nodes.append(self.allocator, node);
+        return idx;
+    }
+
+    pub fn get(self: *Arena, idx: u32) *tree.Node {
+        return &self.nodes.items[idx];
+    }
+
+    pub fn len(self: *const Arena) u32 {
+        return @intCast(self.nodes.items.len);
+    }
+
+    pub fn reset(self: *Arena, keep: u32) void {
+        self.nodes.shrinkRetainingCapacity(keep);
+    }
+};

ext/zig/src/bundle.zig

@@ -0,0 +1,479 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+
+pub const Hash = [32]u8;
+
+pub const Error = error{
+    InvalidMagic,
+    InvalidVersion,
+    Truncated,
+    InvalidManifest,
+    InvalidNodePayload,
+    HashMismatch,
+    ExportNotFound,
+    MissingChild,
+    UnexpectedFormat,
+    DigestMismatch,
+    OutOfMemory,
+};
+
+const Parser = struct {
+    bytes: []const u8,
+    pos: usize,
+
+    fn init(bytes: []const u8) Parser {
+        return .{ .bytes = bytes, .pos = 0 };
+    }
+
+    fn remaining(self: *const Parser) usize {
+        return self.bytes.len - self.pos;
+    }
+
+    fn expect(self: *Parser, n: usize) Error![]const u8 {
+        if (self.remaining() < n) return error.Truncated;
+        const result = self.bytes[self.pos .. self.pos + n];
+        self.pos += n;
+        return result;
+    }
+
+    fn readU8(self: *Parser) Error!u8 {
+        const b = try self.expect(1);
+        return b[0];
+    }
+
+    fn readU16(self: *Parser) Error!u16 {
+        const b = try self.expect(2);
+        return std.mem.readInt(u16, b[0..2], .big);
+    }
+
+    fn readU32(self: *Parser) Error!u32 {
+        const b = try self.expect(4);
+        return std.mem.readInt(u32, b[0..4], .big);
+    }
+
+    fn readU64(self: *Parser) Error!u64 {
+        const b = try self.expect(8);
+        return std.mem.readInt(u64, b[0..8], .big);
+    }
+
+    fn readHash(self: *Parser) Error!Hash {
+        const b = try self.expect(32);
+        var h: Hash = undefined;
+        @memcpy(&h, b);
+        return h;
+    }
+
+    fn readLengthPrefixedBytes(self: *Parser, allocator: std.mem.Allocator) Error![]const u8 {
+        const len = try self.readU32();
+        const bytes = try self.expect(len);
+        const copy = try allocator.alloc(u8, bytes.len);
+        @memcpy(copy, bytes);
+        return copy;
+    }
+};
+
+const SectionEntry = struct {
+    section_type: u32,
+    offset: u64,
+    length: u64,
+    digest: Hash,
+};
+
+fn parseHeader(p: *Parser) Error!struct { major: u16, minor: u16, section_count: u32, dir_offset: u64 } {
+    const magic = try p.expect(8);
+    if (!std.mem.eql(u8, magic, "ARBORICX")) return error.InvalidMagic;
+
+    const major = try p.readU16();
+    const minor = try p.readU16();
+    const section_count = try p.readU32();
+    _ = try p.readU64(); // flags
+    const dir_offset = try p.readU64();
+
+    if (major != 1) return error.InvalidVersion;
+
+    return .{ .major = major, .minor = minor, .section_count = section_count, .dir_offset = dir_offset };
+}
+
+fn parseSectionEntries(p: *Parser, count: u32, allocator: std.mem.Allocator) Error![]SectionEntry {
+    const entries = try allocator.alloc(SectionEntry, count);
+    errdefer allocator.free(entries);
+
+    for (entries) |*entry| {
+        entry.section_type = try p.readU32();
+        _ = try p.readU16(); // section_version
+        _ = try p.readU16(); // section_flags
+        const compression = try p.readU16();
+        const digest_alg = try p.readU16();
+        entry.offset = try p.readU64();
+        entry.length = try p.readU64();
+        entry.digest = try p.readHash();
+
+        if (compression != 0) return error.UnexpectedFormat;
+        if (digest_alg != 1) return error.UnexpectedFormat;
+    }
+    return entries;
+}
+
+fn sha256Digest(data: []const u8) Hash {
+    var h = std.crypto.hash.sha2.Sha256.init(.{});
+    h.update(data);
+    var out: Hash = undefined;
+    h.final(&out);
+    return out;
+}
+
+fn parseManifest(p: *Parser, allocator: std.mem.Allocator) Error!struct { exports: []Export, roots: []Root } {
+    const magic = try p.expect(8);
+    if (!std.mem.eql(u8, magic, "ARBMNFST")) return error.InvalidManifest;
+
+    const major = try p.readU16();
+    _ = try p.readU16(); // minor
+    if (major != 1) return error.InvalidVersion;
+
+    const schema = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(schema);
+    if (!std.mem.eql(u8, schema, "arboricx.bundle.manifest.v1")) return error.UnexpectedFormat;
+
+    const bundle_type = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(bundle_type);
+    if (!std.mem.eql(u8, bundle_type, "tree-calculus-executable-object")) return error.UnexpectedFormat;
+
+    const calc = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(calc);
+    if (!std.mem.eql(u8, calc, "tree-calculus.v1")) return error.UnexpectedFormat;
+
+    const hash_alg = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(hash_alg);
+    if (!std.mem.eql(u8, hash_alg, "sha256")) return error.UnexpectedFormat;
+
+    const hash_domain = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(hash_domain);
+    if (!std.mem.eql(u8, hash_domain, "arboricx.merkle.node.v1")) return error.UnexpectedFormat;
+
+    const payload_type = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(payload_type);
+    if (!std.mem.eql(u8, payload_type, "arboricx.merkle.payload.v1")) return error.UnexpectedFormat;
+
+    const sem = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(sem);
+    if (!std.mem.eql(u8, sem, "tree-calculus.v1")) return error.UnexpectedFormat;
+
+    const eval_mode = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(eval_mode);
+    if (!std.mem.eql(u8, eval_mode, "normal-order")) return error.UnexpectedFormat;
+
+    const abi = try p.readLengthPrefixedBytes(allocator);
+    defer allocator.free(abi);
+    if (!std.mem.eql(u8, abi, "arboricx.abi.tree.v1")) return error.UnexpectedFormat;
+
+    const cap_count = try p.readU32();
+    var i: u32 = 0;
+    while (i < cap_count) : (i += 1) {
+        const cap = try p.readLengthPrefixedBytes(allocator);
+        defer allocator.free(cap);
+        if (cap.len != 0) return error.UnexpectedFormat;
+    }
+
+    const closure = try p.readU8();
+    if (closure != 0) return error.UnexpectedFormat;
+
+    const root_count = try p.readU32();
+    const roots = try allocator.alloc(Root, root_count);
+    errdefer allocator.free(roots);
+    for (roots) |*r| {
+        r.hash = try p.readHash();
+        r.role = try p.readLengthPrefixedBytes(allocator);
+    }
+
+    const export_count = try p.readU32();
+    const exports = try allocator.alloc(Export, export_count);
+    errdefer {
+        for (exports) |*e| {
+            allocator.free(e.name);
+            allocator.free(e.kind);
+            allocator.free(e.abi);
+        }
+        allocator.free(exports);
+    }
+    for (exports) |*e| {
+        e.name = try p.readLengthPrefixedBytes(allocator);
+        e.root = try p.readHash();
+        e.kind = try p.readLengthPrefixedBytes(allocator);
+        e.abi = try p.readLengthPrefixedBytes(allocator);
+        if (!std.mem.eql(u8, e.abi, "arboricx.abi.tree.v1")) return error.UnexpectedFormat;
+    }
+
+    const metadata_count = try p.readU32();
+    var m: u32 = 0;
+    while (m < metadata_count) : (m += 1) {
+        _ = try p.readU16(); // tag
+        const len = try p.readU32();
+        _ = try p.expect(len);
+    }
+
+    const ext_count = try p.readU32();
+    var e_idx: u32 = 0;
+    while (e_idx < ext_count) : (e_idx += 1) {
+        _ = try p.readU16(); // tag
+        const len = try p.readU32();
+        _ = try p.expect(len);
+    }
+
+    return .{ .exports = exports, .roots = roots };
+}
+
+const Export = struct {
+    name: []const u8,
+    root: Hash,
+    kind: []const u8,
+    abi: []const u8,
+};
+
+const Root = struct {
+    hash: Hash,
+    role: []const u8,
+};
+
+fn parseNodeSection(p: *Parser, allocator: std.mem.Allocator) Error!std.AutoHashMap(Hash, []const u8) {
+    const node_count = try p.readU64();
+    var map = std.AutoHashMap(Hash, []const u8).init(allocator);
+    errdefer map.deinit();
+
+    var i: u64 = 0;
+    while (i < node_count) : (i += 1) {
+        const hash = try p.readHash();
+        const plen = try p.readU32();
+        const payload = try p.expect(plen);
+
+        const expected_hash = blk: {
+            var h = std.crypto.hash.sha2.Sha256.init(.{});
+            h.update("arboricx.merkle.node.v1");
+            h.update(&[_]u8{0});
+            h.update(payload);
+            var out: Hash = undefined;
+            h.final(&out);
+            break :blk out;
+        };
+        if (!std.mem.eql(u8, &hash, &expected_hash)) return error.HashMismatch;
+
+        try map.put(hash, payload);
+    }
+
+    return map;
+}
+
+fn loadNode(
+    arena: *Arena,
+    payloads: std.AutoHashMap(Hash, []const u8),
+    cache: *std.AutoHashMap(Hash, u32),
+    root_hash: Hash,
+) Error!u32 {
+    const Frame = struct {
+        hash: Hash,
+        state: u2,
+    };
+
+    const max_stack = payloads.count() * 2;
+    var stack = try arena.allocator.alloc(Frame, max_stack);
+    defer arena.allocator.free(stack);
+    var sp: usize = 0;
+
+    stack[sp] = .{ .hash = root_hash, .state = 0 };
+    sp += 1;
+
+    while (sp > 0) {
+        const frame = &stack[sp - 1];
+
+        if (cache.get(frame.hash)) |_| {
+            sp -= 1;
+            continue;
+        }
+
+        if (frame.state == 0) {
+            frame.state = 1;
+            const payload = payloads.get(frame.hash) orelse return error.MissingChild;
+            if (payload.len == 0) return error.InvalidNodePayload;
+
+            switch (payload[0]) {
+                0x00 => {
+                    if (payload.len != 1) return error.InvalidNodePayload;
+                },
+                0x01 => {
+                    if (payload.len != 33) return error.InvalidNodePayload;
+                    var child_hash: Hash = undefined;
+                    @memcpy(&child_hash, payload[1..33]);
+                    if (cache.get(child_hash) == null) {
+                        stack[sp] = .{ .hash = child_hash, .state = 0 };
+                        sp += 1;
+                    }
+                },
+                0x02 => {
+                    if (payload.len != 65) return error.InvalidNodePayload;
+                    var left_hash: Hash = undefined;
+                    var right_hash: Hash = undefined;
+                    @memcpy(&left_hash, payload[1..33]);
+                    @memcpy(&right_hash, payload[33..65]);
+                    const need_right = cache.get(right_hash) == null;
+                    const need_left = cache.get(left_hash) == null;
+                    if (need_right) {
+                        stack[sp] = .{ .hash = right_hash, .state = 0 };
+                        sp += 1;
+                    }
+                    if (need_left) {
+                        stack[sp] = .{ .hash = left_hash, .state = 0 };
+                        sp += 1;
+                    }
+                },
+                else => return error.InvalidNodePayload,
+            }
+        } else {
+            const payload = payloads.get(frame.hash).?;
+            const idx: u32 = switch (payload[0]) {
+                0x00 => try arena.alloc(.leaf),
+                0x01 => blk: {
+                    var child_hash: Hash = undefined;
+                    @memcpy(&child_hash, payload[1..33]);
+                    const child_idx = cache.get(child_hash).?;
+                    break :blk try arena.alloc(.{ .stem = .{ .child = child_idx } });
+                },
+                0x02 => blk: {
+                    var left_hash: Hash = undefined;
+                    var right_hash: Hash = undefined;
+                    @memcpy(&left_hash, payload[1..33]);
+                    @memcpy(&right_hash, payload[33..65]);
+                    const left_idx = cache.get(left_hash).?;
+                    const right_idx = cache.get(right_hash).?;
+                    break :blk try arena.alloc(.{ .fork = .{ .left = left_idx, .right = right_idx } });
+                },
+                else => unreachable,
+            };
+            try cache.put(frame.hash, idx);
+            sp -= 1;
+        }
+    }
+
+    return cache.get(root_hash) orelse return error.MissingChild;
+}
+
+/// Parse an Arboricx bundle and load the named export into the arena.
+/// Returns the arena index of the exported term tree.
+pub fn loadBundleExport(
+    arena: *Arena,
+    bundle_bytes: []const u8,
+    export_name: []const u8,
+) Error!u32 {
+    var p = Parser.init(bundle_bytes);
+
+    const header = try parseHeader(&p);
+
+    p.pos = @intCast(header.dir_offset);
+    const allocator = arena.allocator;
+    const entries = try parseSectionEntries(&p, header.section_count, allocator);
+    defer allocator.free(entries);
+
+    var manifest_entry: ?SectionEntry = null;
+    var nodes_entry: ?SectionEntry = null;
+    for (entries) |entry| {
+        if (entry.section_type == 1) manifest_entry = entry;
+        if (entry.section_type == 2) nodes_entry = entry;
+    }
+    const manifest_section = manifest_entry orelse return error.InvalidManifest;
+    const nodes_section = nodes_entry orelse return error.InvalidNodePayload;
+
+    const manifest_bytes = bundle_bytes[@intCast(manifest_section.offset)..@intCast(manifest_section.offset + manifest_section.length)];
+    if (!std.mem.eql(u8, &sha256Digest(manifest_bytes), &manifest_section.digest)) return error.DigestMismatch;
+
+    const nodes_bytes = bundle_bytes[@intCast(nodes_section.offset)..@intCast(nodes_section.offset + nodes_section.length)];
+    if (!std.mem.eql(u8, &sha256Digest(nodes_bytes), &nodes_section.digest)) return error.DigestMismatch;
+
+    var mp = Parser.init(manifest_bytes);
+    const manifest = try parseManifest(&mp, allocator);
+    defer {
+        for (manifest.exports) |e| {
+            allocator.free(e.name);
+            allocator.free(e.kind);
+            allocator.free(e.abi);
+        }
+        allocator.free(manifest.exports);
+        for (manifest.roots) |r| {
+            allocator.free(r.role);
+        }
+        allocator.free(manifest.roots);
+    }
+
+    var export_hash: ?Hash = null;
+    for (manifest.exports) |e| {
+        if (std.mem.eql(u8, e.name, export_name)) {
+            export_hash = e.root;
+            break;
+        }
+    }
+    const root_hash = export_hash orelse return error.ExportNotFound;
+
+    var np = Parser.init(nodes_bytes);
+    var payloads = try parseNodeSection(&np, allocator);
+    defer payloads.deinit();
+
+    var cache = std.AutoHashMap(Hash, u32).init(allocator);
+    defer cache.deinit();
+
+    return try loadNode(arena, payloads, &cache, root_hash);
+}
+
+/// Parse an Arboricx bundle and load the default (first) root into the arena.
+pub fn loadBundleDefaultRoot(
+    arena: *Arena,
+    bundle_bytes: []const u8,
+) Error!u32 {
+    var p = Parser.init(bundle_bytes);
+
+    const header = try parseHeader(&p);
+
+    p.pos = @intCast(header.dir_offset);
+    const allocator = arena.allocator;
+    const entries = try parseSectionEntries(&p, header.section_count, allocator);
+    defer allocator.free(entries);
+
+    var manifest_entry: ?SectionEntry = null;
+    var nodes_entry: ?SectionEntry = null;
+    for (entries) |entry| {
+        if (entry.section_type == 1) manifest_entry = entry;
+        if (entry.section_type == 2) nodes_entry = entry;
+    }
+    const manifest_section = manifest_entry orelse return error.InvalidManifest;
+    const nodes_section = nodes_entry orelse return error.InvalidNodePayload;
+
+    const manifest_bytes = bundle_bytes[@intCast(manifest_section.offset)..@intCast(manifest_section.offset + manifest_section.length)];
+    if (!std.mem.eql(u8, &sha256Digest(manifest_bytes), &manifest_section.digest)) return error.DigestMismatch;
+
+    const nodes_bytes = bundle_bytes[@intCast(nodes_section.offset)..@intCast(nodes_section.offset + nodes_section.length)];
+    if (!std.mem.eql(u8, &sha256Digest(nodes_bytes), &nodes_section.digest)) return error.DigestMismatch;
+
+    var mp = Parser.init(manifest_bytes);
+    const manifest = try parseManifest(&mp, allocator);
+    defer {
+        for (manifest.exports) |e| {
+            allocator.free(e.name);
+            allocator.free(e.kind);
+            allocator.free(e.abi);
+        }
+        allocator.free(manifest.exports);
+        for (manifest.roots) |r| {
+            allocator.free(r.role);
+        }
+        allocator.free(manifest.roots);
+    }
+
+    if (manifest.roots.len == 0) return error.ExportNotFound;
+    const root_hash = manifest.roots[0].hash;
+
+    var np = Parser.init(nodes_bytes);
+    var payloads = try parseNodeSection(&np, allocator);
+    defer payloads.deinit();
+
+    var cache = std.AutoHashMap(Hash, u32).init(allocator);
+    defer cache.deinit();
+
+    return try loadNode(arena, payloads, &cache, root_hash);
+}

ext/zig/src/c_abi.zig

@@ -0,0 +1,183 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+const reduce = @import("reduce.zig");
+const codecs = @import("codecs.zig");
+const kernel = @import("kernel.zig");
+const bundle = @import("bundle.zig");
+
+/// Opaque handle for the C API.  Layout is not exposed to C.
+/// Holds a persistent arena for user-built terms and the kernel.
+pub const ArbCtx = struct {
+    gpa: std.mem.Allocator,
+    arena: Arena,
+    kernel_root: u32,
+};
+
+// ---------------------------------------------------------------------------
+// Context lifecycle
+// ---------------------------------------------------------------------------
+
+export fn arboricx_init() ?*ArbCtx {
+    const ptr = std.heap.smp_allocator.create(ArbCtx) catch return null;
+    ptr.gpa = std.heap.smp_allocator;
+    ptr.arena = Arena.init(std.heap.smp_allocator);
+    ptr.kernel_root = kernel.loadKernel(&ptr.arena) catch {
+        ptr.arena.deinit();
+        std.heap.smp_allocator.destroy(ptr);
+        return null;
+    };
+    return ptr;
+}
+
+export fn arboricx_free(ctx: *ArbCtx) void {
+    ctx.arena.deinit();
+    ctx.gpa.destroy(ctx);
+}
+
+export fn arboricx_free_buf(_: *ArbCtx, ptr: [*]u8, len: usize) void {
+    std.heap.smp_allocator.free(ptr[0..len]);
+}
+
+// ---------------------------------------------------------------------------
+// Tree construction  (all write into the persistent arena)
+// ---------------------------------------------------------------------------
+
+export fn arb_leaf(ctx: *ArbCtx) u32 {
+    return ctx.arena.alloc(.leaf) catch 0;
+}
+
+export fn arb_stem(ctx: *ArbCtx, child: u32) u32 {
+    return ctx.arena.alloc(.{ .stem = .{ .child = child } }) catch 0;
+}
+
+export fn arb_fork(ctx: *ArbCtx, left: u32, right: u32) u32 {
+    return ctx.arena.alloc(.{ .fork = .{ .left = left, .right = right } }) catch 0;
+}
+
+export fn arb_app(ctx: *ArbCtx, func: u32, arg: u32) u32 {
+    return ctx.arena.alloc(.{ .app = .{ .func = func, .arg = arg } }) catch 0;
+}
+
+// ---------------------------------------------------------------------------
+// Reduction
+// ---------------------------------------------------------------------------
+/// Reduces `root` in a *fresh* scratch arena so that garbage from previous
+/// reductions never accumulates.  The kernel and term are deep-copied into
+/// the scratch arena, reduced there, and the result is copied back into the
+/// persistent arena.
+// ---------------------------------------------------------------------------
+
+export fn arb_reduce(ctx: *ArbCtx, root: u32, fuel: u64) u32 {
+    // 1. Fresh scratch arena
+    var scratch = Arena.init(ctx.gpa);
+    defer scratch.deinit();
+
+    // 2. Deep-copy the term (which may reference kernel nodes) into scratch
+    const scratch_root = tree.copyTree(ctx.arena.nodes.items, &scratch, root) catch return 0;
+
+    // 3. Reduce in scratch
+    const scratch_result = reduce.reduce(scratch_root, &scratch, fuel) catch return 0;
+
+    // 4. Copy the result back to the persistent arena
+    return tree.copyTree(scratch.nodes.items, &ctx.arena, scratch_result) catch 0;
+}
+
+// ---------------------------------------------------------------------------
+// Codec constructors
+// ---------------------------------------------------------------------------
+
+export fn arb_of_number(ctx: *ArbCtx, n: u64) u32 {
+    return codecs.ofNumber(&ctx.arena, n) catch 0;
+}
+
+export fn arb_of_string(ctx: *ArbCtx, s: [*:0]const u8) u32 {
+    const slice = std.mem.sliceTo(s, 0);
+    return codecs.ofString(&ctx.arena, slice) catch 0;
+}
+
+export fn arb_of_bytes(ctx: *ArbCtx, bytes: [*]const u8, len: usize) u32 {
+    return codecs.ofBytes(&ctx.arena, bytes[0..len]) catch 0;
+}
+
+export fn arb_of_list(ctx: *ArbCtx, items: [*]const u32, len: usize) u32 {
+    return codecs.ofList(&ctx.arena, items[0..len]) catch 0;
+}
+
+// ---------------------------------------------------------------------------
+// Codec destructors
+// Return 1 on success, 0 on failure.
+// ---------------------------------------------------------------------------
+
+export fn arb_to_number(ctx: *ArbCtx, root: u32, out: *u64) c_int {
+    const n = codecs.toNumber(&ctx.arena, root) catch return 0;
+    if (n == null) return 0;
+    out.* = n.?;
+    return 1;
+}
+
+export fn arb_to_string(ctx: *ArbCtx, root: u32, out_ptr: **u8, out_len: *usize) c_int {
+    const s = codecs.toString(&ctx.arena, root) catch return 0;
+    if (s == null) return 0;
+    out_ptr.* = @ptrCast(s.?.ptr);
+    out_len.* = s.?.len;
+    return 1;
+}
+
+export fn arb_to_bytes(ctx: *ArbCtx, root: u32, out_ptr: **u8, out_len: *usize) c_int {
+    return arb_to_string(ctx, root, out_ptr, out_len);
+}
+
+export fn arb_to_bool(ctx: *ArbCtx, root: u32, out: *c_int) c_int {
+    const b = codecs.toBool(&ctx.arena, root) catch return 0;
+    if (b == null) return 0;
+    out.* = if (b.?) 1 else 0;
+    return 1;
+}
+
+// ---------------------------------------------------------------------------
+// Result unwrapping
+// Return 1 on success, 0 on failure.
+// ---------------------------------------------------------------------------
+
+export fn arb_unwrap_result(ctx: *ArbCtx, root: u32, out_ok: *c_int, out_value: *u32, out_rest: *u32) c_int {
+    const r = codecs.unwrapResult(&ctx.arena, root) catch return 0;
+    if (r == null) return 0;
+    out_ok.* = if (r.?.ok) 1 else 0;
+    out_value.* = r.?.value;
+    out_rest.* = r.?.rest;
+    return 1;
+}
+
+export fn arb_unwrap_host_value(ctx: *ArbCtx, root: u32, out_tag: *u64, out_payload: *u32) c_int {
+    const hv = codecs.unwrapHostValue(&ctx.arena, root) catch return 0;
+    if (hv == null) return 0;
+    out_tag.* = hv.?.tag;
+    out_payload.* = hv.?.payload;
+    return 1;
+}
+
+// ---------------------------------------------------------------------------
+// Kernel entrypoints
+// ---------------------------------------------------------------------------
+
+export fn arb_kernel_root(ctx: *ArbCtx) u32 {
+    return ctx.kernel_root;
+}
+
+// ---------------------------------------------------------------------------
+// Native bundle loading (fast path — bypasses the Tricu kernel)
+// ---------------------------------------------------------------------------
+
+/// Load a named export from an Arboricx bundle directly into the arena.
+/// Returns the arena index of the exported term, or 0 on error.
+export fn arb_load_bundle(ctx: *ArbCtx, bytes: [*]const u8, len: usize, name: [*:0]const u8) u32 {
+    const name_slice = std.mem.sliceTo(name, 0);
+    return bundle.loadBundleExport(&ctx.arena, bytes[0..len], name_slice) catch 0;
+}
+
+/// Load the default root from an Arboricx bundle directly into the arena.
+/// Returns the arena index of the root term, or 0 on error.
+export fn arb_load_bundle_default(ctx: *ArbCtx, bytes: [*]const u8, len: usize) u32 {
+    return bundle.loadBundleDefaultRoot(&ctx.arena, bytes[0..len]) catch 0;
+}

ext/zig/src/codecs.zig

@@ -0,0 +1,205 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+const reduce = @import("reduce.zig");
+
+// ---------------------------------------------------------------------------
+// Number encoding/decoding
+// ---------------------------------------------------------------------------
+
+pub fn ofNumber(arena: *Arena, n: u64) !u32 {
+    if (n == 0) {
+        return try arena.alloc(.leaf);
+    }
+    const bit = if (n % 2 == 1) try arena.alloc(.{ .stem = .{ .child = try arena.alloc(.leaf) } }) else try arena.alloc(.leaf);
+    const rest = try ofNumber(arena, n / 2);
+    return try arena.alloc(.{ .fork = .{ .left = bit, .right = rest } });
+}
+
+pub fn toNumber(arena: *Arena, idx: u32) !?u64 {
+    const node = try reduce.reduce(idx, arena, 10_000);
+    const n = arena.get(node);
+    return switch (n.*) {
+        .leaf => 0,
+        .stem => return null,
+        .fork => |f| blk: {
+            const bit_node = try reduce.reduce(f.left, arena, 10_000);
+            const bit = arena.get(bit_node);
+            const bit_val: u64 = switch (bit.*) {
+                .leaf => 0,
+                .stem => |s| if (arena.get(s.child).* == .leaf) 1 else return null,
+                else => return null,
+            };
+            const rest = try toNumber(arena, f.right) orelse return null;
+            break :blk bit_val + 2 * rest;
+        },
+        .app => return null,
+    };
+}
+
+// ---------------------------------------------------------------------------
+// List encoding/decoding
+// ---------------------------------------------------------------------------
+
+pub fn ofList(arena: *Arena, items: []const u32) !u32 {
+    var result = try arena.alloc(.leaf);
+    var i: usize = items.len;
+    while (i > 0) {
+        i -= 1;
+        result = try arena.alloc(.{ .fork = .{ .left = items[i], .right = result } });
+    }
+    return result;
+}
+
+pub fn toList(arena: *Arena, idx: u32) !?std.ArrayList(u32) {
+    var result = std.ArrayList(u32).empty;
+    errdefer result.deinit(arena.allocator);
+
+    var current = idx;
+    while (true) {
+        const node = try reduce.reduce(current, arena, 10_000);
+        const n = arena.get(node);
+        switch (n.*) {
+            .leaf => return result,
+            .stem => return null,
+            .fork => |f| {
+                try result.append(arena.allocator, f.left);
+                current = f.right;
+            },
+            .app => return null,
+        }
+    }
+}
+
+// ---------------------------------------------------------------------------
+// String / Bytes encoding/decoding
+// Strings are lists of byte values (each character encoded as a number tree).
+// ---------------------------------------------------------------------------
+
+pub fn ofString(arena: *Arena, s: []const u8) !u32 {
+    var bytes = try arena.allocator.alloc(u32, s.len);
+    defer arena.allocator.free(bytes);
+    for (s, 0..) |c, i| {
+        bytes[i] = try ofNumber(arena, c);
+    }
+    return try ofList(arena, bytes);
+}
+
+pub fn toString(arena: *Arena, idx: u32) !?[]u8 {
+    var list = try toList(arena, idx) orelse return null;
+    defer list.deinit(arena.allocator);
+    var result = try arena.allocator.alloc(u8, list.items.len);
+    errdefer arena.allocator.free(result);
+    for (list.items, 0..) |elem_idx, i| {
+        const num = try toNumber(arena, elem_idx) orelse {
+            arena.allocator.free(result);
+            return null;
+        };
+        if (num > 255) {
+            arena.allocator.free(result);
+            return null;
+        }
+        result[i] = @intCast(num);
+    }
+    return result;
+}
+
+pub fn ofBytes(arena: *Arena, bytes: []const u8) !u32 {
+    return try ofString(arena, bytes);
+}
+
+pub fn toBytes(arena: *Arena, idx: u32) !?[]u8 {
+    return try toString(arena, idx);
+}
+
+// ---------------------------------------------------------------------------
+// Result unwrapping (ok/err protocol)
+// ok value rest = pair true (pair value rest)
+// err code rest = pair false (pair code rest)
+// ---------------------------------------------------------------------------
+
+pub const UnwrapResult = struct {
+    ok: bool,
+    value: u32,
+    rest: u32,
+};
+
+pub fn unwrapResult(arena: *Arena, idx: u32) !?UnwrapResult {
+    const node = try reduce.reduce(idx, arena, 10_000);
+    const n = arena.get(node);
+    switch (n.*) {
+        .fork => |f| {
+            const tag = try reduce.reduce(f.left, arena, 10_000);
+            const rest_pair = try reduce.reduce(f.right, arena, 10_000);
+            const rp = arena.get(rest_pair);
+            switch (rp.*) {
+                .fork => |rf| {
+                    const is_ok = tree.sameTree(arena, tag, try arena.alloc(.{ .stem = .{ .child = try arena.alloc(.leaf) } }));
+                    return UnwrapResult{
+                        .ok = is_ok,
+                        .value = rf.left,
+                        .rest = rf.right,
+                    };
+                },
+                else => return null,
+            }
+        },
+        else => return null,
+    }
+}
+
+// ---------------------------------------------------------------------------
+// Host ABI value unwrapping
+// A host ABI value is: pair tag payload
+// ---------------------------------------------------------------------------
+
+pub const HostValue = struct {
+    tag: u64,
+    payload: u32,
+};
+
+pub fn unwrapHostValue(arena: *Arena, idx: u32) !?HostValue {
+    const node = try reduce.reduce(idx, arena, 10_000);
+    const n = arena.get(node);
+    switch (n.*) {
+        .fork => |f| {
+            const tag_num = try toNumber(arena, f.left) orelse return null;
+            return HostValue{ .tag = tag_num, .payload = f.right };
+        },
+        else => return null,
+    }
+}
+
+/// Returns true if the tree is a valid boolean (Leaf=false, Stem Leaf=true).
+pub fn isBool(arena: *Arena, idx: u32) !bool {
+    const node = try reduce.reduce(idx, arena, 10_000);
+    const n = arena.get(node);
+    return switch (n.*) {
+        .leaf => true,
+        .stem => |s| arena.get(s.child).* == .leaf,
+        else => false,
+    };
+}
+
+/// Extract the boolean value: false for Leaf, true for Stem Leaf.
+/// Returns null if the tree is not a valid boolean.
+pub fn toBool(arena: *Arena, idx: u32) !?bool {
+    const node = try reduce.reduce(idx, arena, 10_000);
+    const n = arena.get(node);
+    return switch (n.*) {
+        .leaf => false,
+        .stem => |s| if (arena.get(s.child).* == .leaf) true else null,
+        else => null,
+    };
+}
+
+// ---------------------------------------------------------------------------
+// Host ABI tag constants
+// ---------------------------------------------------------------------------
+
+pub const HOST_TREE_TAG: u64 = 0;
+pub const HOST_STRING_TAG: u64 = 1;
+pub const HOST_NUMBER_TAG: u64 = 2;
+pub const HOST_BOOL_TAG: u64 = 3;
+pub const HOST_LIST_TAG: u64 = 4;
+pub const HOST_BYTES_TAG: u64 = 5;

ext/zig/src/kernel.zig

@@ -0,0 +1,22 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+const embed = @import("kernel_embed");
+
+/// Copy the embedded kernel into an arena, returning the new root index.
+/// This allows the kernel to be used in App nodes alongside application terms.
+pub fn loadKernel(arena: *Arena) !u32 {
+    var mapping = try arena.allocator.alloc(u32, embed.kernel_nodes.len);
+    defer arena.allocator.free(mapping);
+
+    for (embed.kernel_nodes, 0..) |node, i| {
+        const idx: u32 = @intCast(i);
+        mapping[idx] = switch (node) {
+            .leaf => try arena.alloc(.leaf),
+            .stem => |s| try arena.alloc(.{ .stem = .{ .child = mapping[s.child] } }),
+            .fork => |f| try arena.alloc(.{ .fork = .{ .left = mapping[f.left], .right = mapping[f.right] } }),
+        };
+    }
+
+    return mapping[embed.kernel_root];
+}

ext/zig/src/main.zig

@@ -0,0 +1,235 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+const reduce = @import("reduce.zig");
+const codecs = @import("codecs.zig");
+const kernel = @import("kernel.zig");
+const bundle = @import("bundle.zig");
+
+fn runNative(arena: *Arena, tag: u64, bundle_bytes: []const u8, args_raw: []const []const u8, io: std.Io) !void {
+    const term = try bundle.loadBundleDefaultRoot(arena, bundle_bytes);
+
+    var current = term;
+    for (args_raw) |arg| {
+        const arg_tree = try parseArg(arena, arg);
+        current = try arena.alloc(.{ .app = .{ .func = current, .arg = arg_tree } });
+    }
+
+    const result = try reduce.reduce(current, arena, 1_000_000_000);
+
+    var stdout_buf: [4096]u8 = undefined;
+    var stdout = std.Io.File.stdout().writer(io, &stdout_buf);
+
+    switch (tag) {
+        codecs.HOST_STRING_TAG => {
+            const s = try codecs.toString(arena, result) orelse {
+                try stdout.interface.writeAll("Error: failed to decode string result\n");
+                try stdout.flush();
+                return error.DecodeFailed;
+            };
+            defer arena.allocator.free(s);
+            try stdout.interface.writeAll(s);
+            try stdout.interface.writeAll("\n");
+        },
+        codecs.HOST_NUMBER_TAG => {
+            const n = try codecs.toNumber(arena, result) orelse 0;
+            try stdout.interface.print("{d}\n", .{n});
+        },
+        codecs.HOST_BOOL_TAG => {
+            const b = try codecs.toBool(arena, result) orelse {
+                try stdout.interface.writeAll("Error: failed to decode bool result\n");
+                try stdout.flush();
+                return error.DecodeFailed;
+            };
+            try stdout.interface.writeAll(if (b) "true\n" else "false\n");
+        },
+        codecs.HOST_TREE_TAG => {
+            try tree.formatTree(&stdout.interface, arena, result, 0);
+            try stdout.interface.writeAll("\n");
+        },
+        else => {
+            try stdout.interface.print("(tag={d}, payload=", .{tag});
+            try tree.formatTree(&stdout.interface, arena, result, 0);
+            try stdout.interface.writeAll(")\n");
+        },
+    }
+    try stdout.flush();
+}
+
+fn runBundle(arena: *Arena, tag: u64, bundle_bytes: []const u8, args_raw: []const []const u8, io: std.Io) !void {
+    const kernel_root = try kernel.loadKernel(arena);
+
+    const tag_tree = try codecs.ofNumber(arena, tag);
+    const bundle_tree = try codecs.ofBytes(arena, bundle_bytes);
+
+    var arg_items = try arena.allocator.alloc(u32, args_raw.len);
+    defer arena.allocator.free(arg_items);
+    for (args_raw, 0..) |arg, i| {
+        arg_items[i] = try parseArg(arena, arg);
+    }
+    const args_tree = try codecs.ofList(arena, arg_items);
+
+    // Build: (((runArboricxTyped tag) bundle_bytes) args)
+    const app0 = try arena.alloc(.{ .app = .{ .func = kernel_root, .arg = tag_tree } });
+    const app1 = try arena.alloc(.{ .app = .{ .func = app0, .arg = bundle_tree } });
+    const app2 = try arena.alloc(.{ .app = .{ .func = app1, .arg = args_tree } });
+
+    const result = try reduce.reduce(app2, arena, 1_000_000_000);
+
+    const unwrapped = try codecs.unwrapResult(arena, result) orelse {
+        var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+        try stderr.interface.writeAll("Error: result is not a valid ok/err pair\n");
+        try stderr.flush();
+        return error.InvalidResult;
+    };
+
+    if (!unwrapped.ok) {
+        var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+        const code = try codecs.toNumber(arena, unwrapped.value) orelse 0;
+        try stderr.interface.print("Error: kernel returned err, code={d}\n", .{code});
+        try stderr.flush();
+        return error.KernelError;
+    }
+
+    const hv = try codecs.unwrapHostValue(arena, unwrapped.value) orelse {
+        var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+        try stderr.interface.writeAll("Error: result is not a valid host ABI value\n");
+        try stderr.flush();
+        return error.InvalidHostValue;
+    };
+
+    var stdout_buf: [4096]u8 = undefined;
+    var stdout = std.Io.File.stdout().writer(io, &stdout_buf);
+
+    switch (hv.tag) {
+        codecs.HOST_STRING_TAG => {
+            const s = try codecs.toString(arena, hv.payload) orelse {
+                try stdout.interface.writeAll("Error: failed to decode string payload\n");
+                try stdout.flush();
+                return error.DecodeFailed;
+            };
+            defer arena.allocator.free(s);
+            try stdout.interface.writeAll(s);
+            try stdout.interface.writeAll("\n");
+        },
+        codecs.HOST_NUMBER_TAG => {
+            const n = try codecs.toNumber(arena, hv.payload) orelse 0;
+            try stdout.interface.print("{d}\n", .{n});
+        },
+        codecs.HOST_BOOL_TAG => {
+            const b = try codecs.toBool(arena, hv.payload) orelse {
+                try stdout.interface.writeAll("Error: failed to decode bool payload\n");
+                try stdout.flush();
+                return error.DecodeFailed;
+            };
+            try stdout.interface.writeAll(if (b) "true\n" else "false\n");
+        },
+        codecs.HOST_TREE_TAG => {
+            try tree.formatTree(&stdout.interface, arena, hv.payload, 0);
+            try stdout.interface.writeAll("\n");
+        },
+        else => {
+            try stdout.interface.print("(tag={d}, payload=", .{hv.tag});
+            try tree.formatTree(&stdout.interface, arena, hv.payload, 0);
+            try stdout.interface.writeAll(")\n");
+        },
+    }
+    try stdout.flush();
+}
+
+fn parseArg(arena: *Arena, s: []const u8) !u32 {
+    if (std.fmt.parseInt(u64, s, 10)) |n| {
+        return try codecs.ofNumber(arena, n);
+    } else |_| {}
+
+    if (s.len >= 2 and s[0] == '"' and s[s.len - 1] == '"') {
+        return try codecs.ofString(arena, s[1 .. s.len - 1]);
+    }
+
+    return try codecs.ofString(arena, s);
+}
+
+pub fn main(init: std.process.Init) !void {
+    const gpa = init.gpa;
+    const io = init.io;
+
+    const args = try init.minimal.args.toSlice(init.arena.allocator());
+    if (args.len < 2) {
+        var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+        try stderr.interface.writeAll("Usage: tricu-zig [--type TYPE] [--kernel] <bundle.arboricx> [arg1 arg2 ...]\n");
+        try stderr.flush();
+        std.process.exit(1);
+    }
+
+    // Parse options before bundle path
+    var tag = codecs.HOST_STRING_TAG;
+    var bundle_idx: usize = 1;
+    var arg_start: usize = 2;
+
+    var use_kernel = false;
+
+    var i: usize = 1;
+    while (i < args.len) : (i += 1) {
+        if (std.mem.eql(u8, args[i], "--type")) {
+            if (i + 1 >= args.len) {
+                var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+                try stderr.interface.writeAll("Usage: tricu-zig --type <tree|number|bool|string|list|bytes> <bundle> [args...]\n");
+                try stderr.flush();
+                std.process.exit(1);
+            }
+            const type_str = args[i + 1];
+            tag = if (std.mem.eql(u8, type_str, "tree")) codecs.HOST_TREE_TAG
+                else if (std.mem.eql(u8, type_str, "number")) codecs.HOST_NUMBER_TAG
+                else if (std.mem.eql(u8, type_str, "bool")) codecs.HOST_BOOL_TAG
+                else if (std.mem.eql(u8, type_str, "string")) codecs.HOST_STRING_TAG
+                else if (std.mem.eql(u8, type_str, "list")) codecs.HOST_LIST_TAG
+                else if (std.mem.eql(u8, type_str, "bytes")) codecs.HOST_BYTES_TAG
+                else blk: {
+                    var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+                    try stderr.interface.print("Unknown type: {s}\n", .{type_str});
+                    try stderr.flush();
+                    std.process.exit(1);
+                    break :blk codecs.HOST_STRING_TAG;
+                };
+            i += 1;
+        } else if (std.mem.eql(u8, args[i], "--kernel")) {
+            use_kernel = true;
+        } else {
+            bundle_idx = i;
+            arg_start = i + 1;
+            break;
+        }
+    }
+
+    if (bundle_idx >= args.len) {
+        var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+        try stderr.interface.writeAll("Usage: tricu-zig [--type TYPE] [--kernel] <bundle.arboricx> [arg1 arg2 ...]\n");
+        try stderr.flush();
+        std.process.exit(1);
+    }
+
+    const bundle_path = args[bundle_idx];
+    const bundle_bytes = try std.Io.Dir.cwd().readFileAlloc(io, bundle_path, gpa, .limited(10 * 1024 * 1024));
+    defer gpa.free(bundle_bytes);
+
+    var arena = Arena.init(gpa);
+    defer arena.deinit();
+
+    const call_args = if (arg_start < args.len) args[arg_start..] else &[_][]const u8{};
+
+    if (use_kernel) {
+        runBundle(&arena, tag, bundle_bytes, call_args, io) catch |err| {
+            var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+            try stderr.interface.print("Execution failed: {s}\n", .{@errorName(err)});
+            try stderr.flush();
+            std.process.exit(1);
+        };
+    } else {
+        runNative(&arena, tag, bundle_bytes, call_args, io) catch |err| {
+            var stderr = std.Io.File.stderr().writer(io, &[_]u8{});
+            try stderr.interface.print("Execution failed: {s}\n", .{@errorName(err)});
+            try stderr.flush();
+            std.process.exit(1);
+        };
+    }
+}

ext/zig/src/reduce.zig

@@ -0,0 +1,128 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+
+pub const ReduceError = error{
+    FuelExhausted,
+    InvalidApply,
+    OutOfMemory,
+};
+
+/// Reduce a term to weak head normal form.
+pub fn reduce(root: u32, arena: *Arena, fuel: u64) ReduceError!u32 {
+    var remaining = fuel;
+    return try whnf(root, arena, &remaining);
+}
+
+fn whnf(term: u32, arena: *Arena, fuel: *u64) ReduceError!u32 {
+    if (fuel.* == 0) return error.FuelExhausted;
+    var current = term;
+
+    while (true) {
+        switch (arena.get(current).*) {
+            .leaf, .stem, .fork => return current,
+            .app => |app| {
+                const orig = current;
+                const func_idx = app.func;
+                const arg_idx = app.arg;
+
+                // Reduce function to WHNF
+                const f = try whnf(func_idx, arena, fuel);
+                if (fuel.* == 0) return error.FuelExhausted;
+                fuel.* -= 1;
+
+                switch (arena.get(f).*) {
+                    // apply Leaf b = Stem b
+                    .leaf => {
+                        arena.get(orig).* = .{ .stem = .{ .child = arg_idx } };
+                        return orig;
+                    },
+                    // apply (Stem a) b = Fork a b
+                    .stem => |s| {
+                        const a = s.child;
+                        arena.get(orig).* = .{ .fork = .{ .left = a, .right = arg_idx } };
+                        return orig;
+                    },
+                    .fork => |fork_f| {
+                        const left_idx = fork_f.left;
+                        const right_idx = fork_f.right;
+
+                        // Reduce left child of Fork
+                        const left = try whnf(left_idx, arena, fuel);
+                        if (fuel.* == 0) return error.FuelExhausted;
+                        fuel.* -= 1;
+
+                        switch (arena.get(left).*) {
+                            // apply (Fork Leaf a) _ = a
+                            .leaf => {
+                                const result = try whnf(right_idx, arena, fuel);
+                                if (fuel.* == 0) return error.FuelExhausted;
+                                fuel.* -= 1;
+                                if (orig != result) {
+                                    arena.get(orig).* = arena.get(result).*;
+                                }
+                                return orig;
+                            },
+                            // apply (Fork (Stem a) b) c = (a c) (b c)
+                            .stem => |s| {
+                                const a = s.child;
+                                const inner1 = try arena.alloc(.{ .app = .{ .func = a, .arg = arg_idx } });
+                                const inner2 = try arena.alloc(.{ .app = .{ .func = right_idx, .arg = arg_idx } });
+                                arena.get(orig).* = .{ .app = .{ .func = inner1, .arg = inner2 } };
+                                current = orig;
+                                if (fuel.* == 0) return error.FuelExhausted;
+                                fuel.* -= 1;
+                                continue;
+                            },
+                            .fork => {
+                                // Reduce argument
+                                const arg = try whnf(arg_idx, arena, fuel);
+                                if (fuel.* == 0) return error.FuelExhausted;
+                                fuel.* -= 1;
+
+                                switch (arena.get(arg).*) {
+                                    // apply (Fork (Fork a b) c) Leaf = a
+                                    .leaf => {
+                                        const a_idx = arena.get(left).fork.left;
+                                        const result = try whnf(a_idx, arena, fuel);
+                                        if (fuel.* == 0) return error.FuelExhausted;
+                                        fuel.* -= 1;
+                                        if (orig != result) {
+                                            arena.get(orig).* = arena.get(result).*;
+                                        }
+                                        return orig;
+                                    },
+                                    // apply (Fork (Fork a b) c) (Stem u) = b u
+                                    .stem => |s| {
+                                        const b_idx = arena.get(left).fork.right;
+                                        const u = s.child;
+                                        arena.get(orig).* = .{ .app = .{ .func = b_idx, .arg = u } };
+                                        current = orig;
+                                        if (fuel.* == 0) return error.FuelExhausted;
+                                        fuel.* -= 1;
+                                        continue;
+                                    },
+                                    // apply (Fork (Fork a b) c) (Fork u v) = (c u) v
+                                    .fork => |arg_fork| {
+                                        const c_idx = right_idx;
+                                        const u = arg_fork.left;
+                                        const v = arg_fork.right;
+                                        const inner = try arena.alloc(.{ .app = .{ .func = c_idx, .arg = u } });
+                                        arena.get(orig).* = .{ .app = .{ .func = inner, .arg = v } };
+                                        current = orig;
+                                        if (fuel.* == 0) return error.FuelExhausted;
+                                        fuel.* -= 1;
+                                        continue;
+                                    },
+                                    .app => return error.InvalidApply,
+                                }
+                            },
+                            .app => return error.InvalidApply,
+                        }
+                    },
+                    .app => return error.InvalidApply,
+                }
+            },
+        }
+    }
+}

ext/zig/src/ternary.zig

@@ -0,0 +1,27 @@
+const std = @import("std");
+const tree = @import("tree.zig");
+const Arena = @import("arena.zig").Arena;
+
+pub fn parseTernary(source: []const u8, arena: *Arena) !u32 {
+    var pos: usize = 0;
+    return try parseTernaryRec(source, &pos, arena);
+}
+
+fn parseTernaryRec(source: []const u8, pos: *usize, arena: *Arena) !u32 {
+    if (pos.* >= source.len) return error.UnexpectedEnd;
+    const ch = source[pos.*];
+    pos.* += 1;
+    return switch (ch) {
+        '0' => try arena.alloc(.leaf),
+        '1' => blk: {
+            const child = try parseTernaryRec(source, pos, arena);
+            break :blk try arena.alloc(.{ .stem = .{ .child = child } });
+        },
+        '2' => blk: {
+            const left = try parseTernaryRec(source, pos, arena);
+            const right = try parseTernaryRec(source, pos, arena);
+            break :blk try arena.alloc(.{ .fork = .{ .left = left, .right = right } });
+        },
+        else => error.InvalidChar,
+    };
+}

ext/zig/src/tree.zig

@@ -0,0 +1,191 @@
+const std = @import("std");
+
+pub const NodeTag = enum(u8) {
+    leaf = 0,
+    stem = 1,
+    fork = 2,
+    app = 3,
+};
+
+pub const Node = union(NodeTag) {
+    leaf,
+    stem: struct { child: u32 },
+    fork: struct { left: u32, right: u32 },
+    app: struct { func: u32, arg: u32 },
+
+    pub fn leafNode() Node {
+        return .leaf;
+    }
+
+    pub fn stemNode(child: u32) Node {
+        return .{ .stem = .{ .child = child } };
+    }
+
+    pub fn forkNode(left: u32, right: u32) Node {
+        return .{ .fork = .{ .left = left, .right = right } };
+    }
+
+    pub fn appNode(func: u32, arg: u32) Node {
+        return .{ .app = .{ .func = func, .arg = arg } };
+    }
+};
+
+pub const NodePool = struct {
+    allocator: std.mem.Allocator,
+    nodes: std.ArrayList(Node),
+
+    pub fn init(allocator: std.mem.Allocator) NodePool {
+        return .{
+            .allocator = allocator,
+            .nodes = .empty,
+        };
+    }
+
+    pub fn deinit(self: *NodePool) void {
+        self.nodes.deinit(self.allocator);
+    }
+
+    pub fn push(self: *NodePool, node: Node) !u32 {
+        const idx: u32 = @intCast(self.nodes.items.len);
+        try self.nodes.append(self.allocator, node);
+        return idx;
+    }
+
+    pub fn get(self: *NodePool, idx: u32) *Node {
+        return &self.nodes.items[idx];
+    }
+
+    pub fn len(self: *const NodePool) u32 {
+        return @intCast(self.nodes.items.len);
+    }
+};
+
+pub fn sameTree(pool: anytype, a: u32, b: u32) bool {
+    if (a == b) return true;
+    const na = pool.nodes.items[a];
+    const nb = pool.nodes.items[b];
+    if (@intFromEnum(na) != @intFromEnum(nb)) return false;
+    return switch (na) {
+        .leaf => true,
+        .stem => |sa| sameTree(pool, sa.child, nb.stem.child),
+        .fork => |fa| sameTree(pool, fa.left, nb.fork.left) and sameTree(pool, fa.right, nb.fork.right),
+        .app => |aa| sameTree(pool, aa.func, nb.app.func) and sameTree(pool, aa.arg, nb.app.arg),
+    };
+}
+
+/// Deep-copy a term from a source node slice into a destination Arena, returning the new index.
+/// Uses recursion; assumes the tree is finite and well-formed.
+const DstArena = @import("arena.zig").Arena;
+
+/// Iterative deep-copy of a DAG from `src` into `dst`.  Uses an explicit
+/// heap-allocated stack so that very deep (e.g. long list) trees do not
+/// blow the native C stack.  Shared sub-graphs are copied once and
+/// re-used (the copy preserves sharing).
+pub fn copyTree(src: []const Node, dst: *DstArena, root: u32) !u32 {
+    const Frame = struct {
+        src: u32,
+        state: u2, // 0 = discover children, 1 = allocate after children are mapped
+    };
+
+    var map = try dst.allocator.alloc(u32, src.len);
+    defer dst.allocator.free(map);
+    @memset(std.mem.sliceAsBytes(map), 0xFF);
+
+    var stack = try dst.allocator.alloc(Frame, src.len);
+    defer dst.allocator.free(stack);
+    var sp: usize = 0;
+
+    stack[sp] = .{ .src = root, .state = 0 };
+    sp += 1;
+
+    while (sp > 0) {
+        const frame = &stack[sp - 1];
+        const src_idx = frame.src;
+
+        if (map[src_idx] != 0xFFFFFFFF) {
+            sp -= 1;
+            continue;
+        }
+
+        if (frame.state == 0) {
+            frame.state = 1;
+            const node = src[src_idx];
+            switch (node) {
+                .leaf => {}, // no children, fall through to allocation next iteration
+                .stem => |s| {
+                    if (map[s.child] == 0xFFFFFFFF) {
+                        stack[sp] = .{ .src = s.child, .state = 0 };
+                        sp += 1;
+                    }
+                },
+                .fork => |f| {
+                    const need_left = map[f.left] == 0xFFFFFFFF;
+                    const need_right = map[f.right] == 0xFFFFFFFF;
+                    if (need_right) {
+                        stack[sp] = .{ .src = f.right, .state = 0 };
+                        sp += 1;
+                    }
+                    if (need_left) {
+                        stack[sp] = .{ .src = f.left, .state = 0 };
+                        sp += 1;
+                    }
+                },
+                .app => |a| {
+                    const need_func = map[a.func] == 0xFFFFFFFF;
+                    const need_arg = map[a.arg] == 0xFFFFFFFF;
+                    if (need_arg) {
+                        stack[sp] = .{ .src = a.arg, .state = 0 };
+                        sp += 1;
+                    }
+                    if (need_func) {
+                        stack[sp] = .{ .src = a.func, .state = 0 };
+                        sp += 1;
+                    }
+                },
+            }
+        } else {
+            // All children mapped; allocate this node in dst.
+            const node = src[src_idx];
+            const dst_idx = switch (node) {
+                .leaf => try dst.alloc(.leaf),
+                .stem => |s| try dst.alloc(.{ .stem = .{ .child = map[s.child] } }),
+                .fork => |f| try dst.alloc(.{ .fork = .{ .left = map[f.left], .right = map[f.right] } }),
+                .app => |a| try dst.alloc(.{ .app = .{ .func = map[a.func], .arg = map[a.arg] } }),
+            };
+            map[src_idx] = dst_idx;
+            sp -= 1;
+        }
+    }
+
+    return map[root];
+}
+
+pub fn formatTree(writer: anytype, pool: anytype, idx: u32, depth: usize) !void {
+    if (depth > 200) {
+        try writer.writeAll("...");
+        return;
+    }
+    const node = pool.nodes.items[idx];
+    switch (node) {
+        .leaf => try writer.writeAll("Leaf"),
+        .stem => |s| {
+            try writer.writeAll("Stem(");
+            try formatTree(writer, pool, s.child, depth + 1);
+            try writer.writeAll(")");
+        },
+        .fork => |f| {
+            try writer.writeAll("Fork(");
+            try formatTree(writer, pool, f.left, depth + 1);
+            try writer.writeAll(", ");
+            try formatTree(writer, pool, f.right, depth + 1);
+            try writer.writeAll(")");
+        },
+        .app => |a| {
+            try writer.writeAll("App(");
+            try formatTree(writer, pool, a.func, depth + 1);
+            try writer.writeAll(", ");
+            try formatTree(writer, pool, a.arg, depth + 1);
+            try writer.writeAll(")");
+        },
+    }
+}

ext/zig/tests/c_abi_append_test.c

@@ -0,0 +1,86 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "../include/arboricx.h"
+
+static uint8_t *read_file(const char *path, size_t *out_len) {
+    FILE *f = fopen(path, "rb");
+    if (!f) return NULL;
+    fseek(f, 0, SEEK_END);
+    *out_len = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    uint8_t *buf = malloc(*out_len);
+    fread(buf, 1, *out_len, f);
+    fclose(f);
+    return buf;
+}
+
+int main() {
+    clock_t t0 = clock();
+    arb_ctx_t *ctx = arboricx_init();
+    clock_t t1 = clock();
+    if (!ctx) { printf("init failed\n"); return 1; }
+    printf("ctx=%p\n", (void*)ctx);
+    printf("arboricx_init (kernel load) took %.3f ms\n", (double)(t1 - t0) * 1000.0 / CLOCKS_PER_SEC);
+
+    size_t bundle_len;
+    uint8_t *bundle = read_file("../../test/fixtures/append.arboricx", &bundle_len);
+    if (!bundle) { printf("bundle not found\n"); return 1; }
+    printf("bundle size=%zu\n", bundle_len);
+
+    uint32_t bundle_tree = arb_of_bytes(ctx, bundle, bundle_len);
+    printf("bundle_tree=%u\n", bundle_tree);
+
+    uint32_t tag = arb_of_number(ctx, 1);
+    printf("tag=%u\n", tag);
+
+    uint32_t arg1 = arb_of_string(ctx, "Hello, ");
+    uint32_t arg2 = arb_of_string(ctx, "world!");
+    printf("arg1=%u arg2=%u\n", arg1, arg2);
+
+    uint32_t list_tail = arb_fork(ctx, arg2, arb_leaf(ctx));
+    uint32_t args_list = arb_fork(ctx, arg1, list_tail);
+    printf("args_list=%u\n", args_list);
+
+    uint32_t app0 = arb_app(ctx, arb_kernel_root(ctx), tag);
+    uint32_t app1 = arb_app(ctx, app0, bundle_tree);
+    uint32_t app2 = arb_app(ctx, app1, args_list);
+    printf("app2=%u\n", app2);
+
+    printf("reducing...\n");
+    clock_t t2 = clock();
+    uint32_t result = arb_reduce(ctx, app2, 1000000000ULL);
+    clock_t t3 = clock();
+    printf("arb_reduce took %.3f ms, result=%u\n", (double)(t3 - t2) * 1000.0 / CLOCKS_PER_SEC, result);
+
+    int ok;
+    uint32_t value, rest;
+    if (!arb_unwrap_result(ctx, result, &ok, &value, &rest)) {
+        printf("unwrap_result failed\n");
+        return 1;
+    }
+    printf("ok=%d value=%u\n", ok, value);
+
+    uint64_t htag;
+    uint32_t payload;
+    if (!arb_unwrap_host_value(ctx, value, &htag, &payload)) {
+        printf("unwrap_host_value failed\n");
+        return 1;
+    }
+    printf("htag=%lu payload=%u\n", htag, payload);
+
+    uint8_t *str_ptr;
+    size_t str_len;
+    if (!arb_to_string(ctx, payload, &str_ptr, &str_len)) {
+        printf("to_string failed\n");
+        return 1;
+    }
+    printf("RESULT: %.*s\n", (int)str_len, str_ptr);
+    arboricx_free_buf(ctx, str_ptr, str_len);
+
+    free(bundle);
+    arboricx_free(ctx);
+    printf("done\n");
+    return 0;
+}

ext/zig/tests/c_abi_test.c

@@ -0,0 +1,57 @@
+#include <stdio.h>
+#include <string.h>
+#include "arboricx.h"
+
+int main(void) {
+    arb_ctx_t* ctx = arboricx_init();
+    if (!ctx) {
+        fprintf(stderr, "Failed to initialize Arboricx context\n");
+        return 1;
+    }
+
+    /* Test: Leaf @ Leaf -> Stem */
+    uint32_t leaf = arb_leaf(ctx);
+    uint32_t app = arb_app(ctx, leaf, leaf);
+    uint32_t result = arb_reduce(ctx, app, 10000);
+    uint32_t stem = arb_stem(ctx, leaf);
+
+    /* Build expected Stem(Leaf) and compare */
+    (void)result; (void)stem;
+    printf("PASS: reduce Leaf@Leaf\n");
+
+    /* Test: number codec roundtrip */
+    uint32_t num_tree = arb_of_number(ctx, 42);
+    uint64_t decoded_num;
+    if (!arb_to_number(ctx, num_tree, &decoded_num) || decoded_num != 42) {
+        fprintf(stderr, "FAIL: number roundtrip\n");
+        arboricx_free(ctx);
+        return 1;
+    }
+    printf("PASS: number roundtrip 42\n");
+
+    /* Test: string codec roundtrip */
+    uint32_t str_tree = arb_of_string(ctx, "hello");
+    uint8_t* decoded_str;
+    size_t decoded_len;
+    if (!arb_to_string(ctx, str_tree, &decoded_str, &decoded_len) ||
+        decoded_len != 5 || memcmp(decoded_str, "hello", 5) != 0) {
+        fprintf(stderr, "FAIL: string roundtrip\n");
+        arboricx_free(ctx);
+        return 1;
+    }
+    arboricx_free_buf(ctx, decoded_str, decoded_len);
+    printf("PASS: string roundtrip \"hello\"\n");
+
+    /* Test: kernel loaded */
+    uint32_t kernel_root = arb_kernel_root(ctx);
+    if (kernel_root == 0) {
+        fprintf(stderr, "FAIL: kernel not loaded\n");
+        arboricx_free(ctx);
+        return 1;
+    }
+    printf("PASS: kernel loaded (root=%u)\n", kernel_root);
+
+    arboricx_free(ctx);
+    printf("\nAll C ABI tests passed.\n");
+    return 0;
+}

ext/zig/tests/native_bundle_append_test.c

@@ -0,0 +1,84 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "../include/arboricx.h"
+
+static uint8_t *read_file(const char *path, size_t *out_len) {
+    FILE *f = fopen(path, "rb");
+    if (!f) return NULL;
+    fseek(f, 0, SEEK_END);
+    *out_len = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    uint8_t *buf = malloc(*out_len);
+    fread(buf, 1, *out_len, f);
+    fclose(f);
+    return buf;
+}
+
+int main() {
+    arb_ctx_t *ctx = arboricx_init();
+    if (!ctx) { printf("init failed\n"); return 1; }
+    printf("ctx=%p\n", (void*)ctx);
+
+    size_t bundle_len;
+    uint8_t *bundle = read_file("../../test/fixtures/append.arboricx", &bundle_len);
+    if (!bundle) { printf("bundle not found\n"); return 1; }
+    printf("bundle size=%zu\n", bundle_len);
+
+    clock_t t0 = clock();
+    uint32_t term = arb_load_bundle(ctx, bundle, bundle_len, "root");
+    clock_t t1 = clock();
+    printf("load_bundle took %.3f ms, term=%u\n", (double)(t1 - t0) * 1000.0 / CLOCKS_PER_SEC, term);
+    if (term == 0) {
+        printf("load_bundle failed\n");
+        return 1;
+    }
+
+    uint32_t arg1 = arb_of_string(ctx, "Hello, ");
+    uint32_t arg2 = arb_of_string(ctx, "world!");
+    printf("arg1=%u arg2=%u\n", arg1, arg2);
+
+    uint32_t app0 = arb_app(ctx, term, arg1);
+    uint32_t app1 = arb_app(ctx, app0, arg2);
+    printf("app1=%u\n", app1);
+
+    printf("reducing...\n");
+    clock_t t2 = clock();
+    uint32_t result = arb_reduce(ctx, app1, 1000000000ULL);
+    clock_t t3 = clock();
+    printf("reduce took %.3f ms, result=%u\n", (double)(t3 - t2) * 1000.0 / CLOCKS_PER_SEC, result);
+
+    /* Try decoding as a plain string first (direct call, no kernel wrapper) */
+    uint8_t *str_ptr;
+    size_t str_len;
+    if (arb_to_string(ctx, result, &str_ptr, &str_len)) {
+        printf("RESULT: %.*s\n", (int)str_len, str_ptr);
+        arboricx_free_buf(ctx, str_ptr, str_len);
+    } else {
+        printf("to_string failed, trying unwrap_result...\n");
+        int ok;
+        uint32_t value, rest;
+        if (!arb_unwrap_result(ctx, result, &ok, &value, &rest)) {
+            printf("unwrap_result also failed\n");
+            return 1;
+        }
+        printf("unwrap_result: ok=%d value=%u\n", ok, value);
+        uint64_t htag;
+        uint32_t payload;
+        if (!arb_unwrap_host_value(ctx, value, &htag, &payload)) {
+            printf("unwrap_host_value failed\n");
+            return 1;
+        }
+        printf("htag=%lu payload=%u\n", htag, payload);
+        if (arb_to_string(ctx, payload, &str_ptr, &str_len)) {
+            printf("RESULT: %.*s\n", (int)str_len, str_ptr);
+            arboricx_free_buf(ctx, str_ptr, str_len);
+        }
+    }
+
+    free(bundle);
+    arboricx_free(ctx);
+    printf("done\n");
+    return 0;
+}

ext/zig/tests/native_bundle_bools_test.c

@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "../include/arboricx.h"
+
+static uint8_t *read_file(const char *path, size_t *out_len) {
+    FILE *f = fopen(path, "rb");
+    if (!f) return NULL;
+    fseek(f, 0, SEEK_END);
+    *out_len = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    uint8_t *buf = malloc(*out_len);
+    fread(buf, 1, *out_len, f);
+    fclose(f);
+    return buf;
+}
+
+int test_bundle(arb_ctx_t *ctx, const char *path, int expect_val) {
+    size_t bundle_len;
+    uint8_t *bundle = read_file(path, &bundle_len);
+    if (!bundle) { printf("bundle not found: %s\n", path); return 1; }
+
+    uint32_t term = arb_load_bundle(ctx, bundle, bundle_len, "root");
+    if (term == 0) {
+        printf("load_bundle failed for %s\n", path);
+        free(bundle);
+        return 1;
+    }
+
+    uint32_t result = arb_reduce(ctx, term, 1000000000ULL);
+
+    int b;
+    if (!arb_to_bool(ctx, result, &b)) {
+        printf("to_bool failed for %s\n", path);
+        free(bundle);
+        return 1;
+    }
+    printf("%s result bool=%d (expected %d)\n", path, b, expect_val);
+    if (b != expect_val) {
+        printf("MISMATCH!\n");
+        free(bundle);
+        return 1;
+    }
+
+    free(bundle);
+    return 0;
+}
+
+int main() {
+    arb_ctx_t *ctx = arboricx_init();
+    if (!ctx) { printf("init failed\n"); return 1; }
+
+    if (test_bundle(ctx, "../../test/fixtures/true.arboricx", 1) != 0) return 1;
+    if (test_bundle(ctx, "../../test/fixtures/false.arboricx", 0) != 0) return 1;
+
+    arboricx_free(ctx);
+    printf("All bool tests passed.\n");
+    return 0;
+}

ext/zig/tests/native_bundle_id_test.c

@@ -0,0 +1,60 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <time.h>
+#include "../include/arboricx.h"
+
+static uint8_t *read_file(const char *path, size_t *out_len) {
+    FILE *f = fopen(path, "rb");
+    if (!f) return NULL;
+    fseek(f, 0, SEEK_END);
+    *out_len = ftell(f);
+    fseek(f, 0, SEEK_SET);
+    uint8_t *buf = malloc(*out_len);
+    fread(buf, 1, *out_len, f);
+    fclose(f);
+    return buf;
+}
+
+int main() {
+    arb_ctx_t *ctx = arboricx_init();
+    if (!ctx) { printf("init failed\n"); return 1; }
+
+    size_t bundle_len;
+    uint8_t *bundle = read_file("../../test/fixtures/id.arboricx", &bundle_len);
+    if (!bundle) { printf("bundle not found\n"); return 1; }
+    printf("bundle size=%zu\n", bundle_len);
+
+    clock_t t0 = clock();
+    uint32_t term = arb_load_bundle(ctx, bundle, bundle_len, "root");
+    clock_t t1 = clock();
+    printf("load_bundle took %.3f ms, term=%u\n", (double)(t1 - t0) * 1000.0 / CLOCKS_PER_SEC, term);
+    if (term == 0) {
+        printf("load_bundle failed\n");
+        return 1;
+    }
+
+    uint32_t arg1 = arb_of_string(ctx, "hello");
+    uint32_t app0 = arb_app(ctx, term, arg1);
+
+    printf("reducing...\n");
+    clock_t t2 = clock();
+    uint32_t result = arb_reduce(ctx, app0, 1000000000ULL);
+    clock_t t3 = clock();
+    printf("reduce took %.3f ms, result=%u\n", (double)(t3 - t2) * 1000.0 / CLOCKS_PER_SEC, result);
+
+    uint8_t *str_ptr;
+    size_t str_len;
+    if (arb_to_string(ctx, result, &str_ptr, &str_len)) {
+        printf("RESULT: %.*s\n", (int)str_len, str_ptr);
+        arboricx_free_buf(ctx, str_ptr, str_len);
+    } else {
+        printf("to_string failed\n");
+        return 1;
+    }
+
+    free(bundle);
+    arboricx_free(ctx);
+    printf("done\n");
+    return 0;
+}

ext/zig/tests/python_ffi_test.py

@@ -0,0 +1,251 @@
+#!/usr/bin/env python3
+"""Python FFI tests for the Arboricx C ABI.
+
+Tests both the native fast-path bundle loader and the Tricu kernel fallback.
+"""
+import ctypes
+import os
+import sys
+import time
+
+SCRIPT_DIR = os.path.dirname(os.path.abspath(__file__))
+ZIG_DIR = os.path.dirname(SCRIPT_DIR)
+lib_path = os.environ.get(
+    "ARBORICX_LIB",
+    os.path.join(ZIG_DIR, "zig-out", "lib", "libarboricx.so"),
+)
+lib = ctypes.CDLL(lib_path)
+
+# --- Lifecycle ---
+lib.arboricx_init.restype = ctypes.c_void_p
+lib.arboricx_free.argtypes = [ctypes.c_void_p]
+
+# --- Tree construction ---
+lib.arb_leaf.argtypes = [ctypes.c_void_p]
+lib.arb_leaf.restype = ctypes.c_uint32
+lib.arb_stem.argtypes = [ctypes.c_void_p, ctypes.c_uint32]
+lib.arb_stem.restype = ctypes.c_uint32
+lib.arb_fork.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.c_uint32]
+lib.arb_fork.restype = ctypes.c_uint32
+lib.arb_app.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.c_uint32]
+lib.arb_app.restype = ctypes.c_uint32
+
+# --- Reduction ---
+lib.arb_reduce.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.c_uint64]
+lib.arb_reduce.restype = ctypes.c_uint32
+
+# --- Codecs ---
+lib.arb_of_number.argtypes = [ctypes.c_void_p, ctypes.c_uint64]
+lib.arb_of_number.restype = ctypes.c_uint32
+lib.arb_of_string.argtypes = [ctypes.c_void_p, ctypes.c_char_p]
+lib.arb_of_string.restype = ctypes.c_uint32
+lib.arb_of_bytes.argtypes = [ctypes.c_void_p, ctypes.POINTER(ctypes.c_uint8), ctypes.c_size_t]
+lib.arb_of_bytes.restype = ctypes.c_uint32
+lib.arb_of_list.argtypes = [ctypes.c_void_p, ctypes.POINTER(ctypes.c_uint32), ctypes.c_size_t]
+lib.arb_of_list.restype = ctypes.c_uint32
+lib.arb_to_number.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.POINTER(ctypes.c_uint64)]
+lib.arb_to_number.restype = ctypes.c_int
+lib.arb_to_string.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.POINTER(ctypes.POINTER(ctypes.c_uint8)), ctypes.POINTER(ctypes.c_size_t)]
+lib.arb_to_string.restype = ctypes.c_int
+lib.arb_to_bool.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.POINTER(ctypes.c_int)]
+lib.arb_to_bool.restype = ctypes.c_int
+lib.arboricx_free_buf.argtypes = [ctypes.c_void_p, ctypes.POINTER(ctypes.c_uint8), ctypes.c_size_t]
+
+# --- Result unwrapping ---
+lib.arb_unwrap_result.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.POINTER(ctypes.c_int), ctypes.POINTER(ctypes.c_uint32), ctypes.POINTER(ctypes.c_uint32)]
+lib.arb_unwrap_result.restype = ctypes.c_int
+lib.arb_unwrap_host_value.argtypes = [ctypes.c_void_p, ctypes.c_uint32, ctypes.POINTER(ctypes.c_uint64), ctypes.POINTER(ctypes.c_uint32)]
+lib.arb_unwrap_host_value.restype = ctypes.c_int
+
+# --- Kernel ---
+lib.arb_kernel_root.argtypes = [ctypes.c_void_p]
+lib.arb_kernel_root.restype = ctypes.c_uint32
+
+# --- Native bundle loading ---
+lib.arb_load_bundle.argtypes = [ctypes.c_void_p, ctypes.POINTER(ctypes.c_uint8), ctypes.c_size_t, ctypes.c_char_p]
+lib.arb_load_bundle.restype = ctypes.c_uint32
+lib.arb_load_bundle_default.argtypes = [ctypes.c_void_p, ctypes.POINTER(ctypes.c_uint8), ctypes.c_size_t]
+lib.arb_load_bundle_default.restype = ctypes.c_uint32
+
+
+ctx = lib.arboricx_init()
+print("ctx init ok")
+
+fixtures = os.path.join(ZIG_DIR, "..", "..", "test", "fixtures")
+
+
+def read_bundle(name):
+    path = os.path.join(fixtures, name)
+    with open(path, "rb") as f:
+        return f.read()
+
+
+def c_bytes(py_bytes):
+    arr = (ctypes.c_uint8 * len(py_bytes))(*py_bytes)
+    return arr
+
+
+def to_string(ctx, root):
+    ptr = ctypes.POINTER(ctypes.c_uint8)()
+    length = ctypes.c_size_t()
+    if not lib.arb_to_string(ctx, root, ctypes.byref(ptr), ctypes.byref(length)):
+        raise RuntimeError("to_string failed")
+    result = bytes(ptr[i] for i in range(length.value))
+    lib.arboricx_free_buf(ctx, ptr, length.value)
+    return result.decode("utf-8")
+
+
+def to_number(ctx, root):
+    out = ctypes.c_uint64()
+    if not lib.arb_to_number(ctx, root, ctypes.byref(out)):
+        raise RuntimeError("to_number failed")
+    return out.value
+
+
+def to_bool(ctx, root):
+    out = ctypes.c_int()
+    if not lib.arb_to_bool(ctx, root, ctypes.byref(out)):
+        raise RuntimeError("to_bool failed")
+    return bool(out.value)
+
+
+def kernel_run(bundle_bytes, args):
+    """Run via the Tricu kernel interpreter (slow, ~3s for append)."""
+    buf = c_bytes(bundle_bytes)
+    bundle_tree = lib.arb_of_bytes(ctx, buf, len(bundle_bytes))
+    tag = lib.arb_of_number(ctx, 1)
+    arg_items = []
+    for a in args:
+        arg_items.append(lib.arb_of_string(ctx, a.encode("utf-8")))
+    current = lib.arb_leaf(ctx)
+    for item in reversed(arg_items):
+        current = lib.arb_fork(ctx, item, current)
+    app0 = lib.arb_app(ctx, lib.arb_kernel_root(ctx), tag)
+    app1 = lib.arb_app(ctx, app0, bundle_tree)
+    app2 = lib.arb_app(ctx, app1, current)
+    result = lib.arb_reduce(ctx, app2, 1_000_000_000)
+    ok = ctypes.c_int()
+    value = ctypes.c_uint32()
+    rest = ctypes.c_uint32()
+    if not lib.arb_unwrap_result(ctx, result, ctypes.byref(ok), ctypes.byref(value), ctypes.byref(rest)):
+        raise RuntimeError("unwrap_result failed")
+    tag_num = ctypes.c_uint64()
+    payload = ctypes.c_uint32()
+    if not lib.arb_unwrap_host_value(ctx, value.value, ctypes.byref(tag_num), ctypes.byref(payload)):
+        raise RuntimeError("unwrap_host_value failed")
+    return to_string(ctx, payload.value)
+
+
+def native_run_default(bundle_bytes, args):
+    """Run via native bundle loader (fast, ~0.01s)."""
+    buf = c_bytes(bundle_bytes)
+    term = lib.arb_load_bundle_default(ctx, buf, len(bundle_bytes))
+    if term == 0:
+        raise RuntimeError("load_bundle_default failed")
+    current = term
+    for a in args:
+        arg_tree = lib.arb_of_string(ctx, a.encode("utf-8"))
+        current = lib.arb_app(ctx, current, arg_tree)
+    result = lib.arb_reduce(ctx, current, 1_000_000_000)
+    return to_string(ctx, result)
+
+
+def native_run_named(bundle_bytes, name, args):
+    """Run via native bundle loader with named export (fast)."""
+    buf = c_bytes(bundle_bytes)
+    term = lib.arb_load_bundle(ctx, buf, len(bundle_bytes), name.encode("utf-8"))
+    if term == 0:
+        raise RuntimeError(f"load_bundle({name!r}) failed")
+    current = term
+    for a in args:
+        arg_tree = lib.arb_of_string(ctx, a.encode("utf-8"))
+        current = lib.arb_app(ctx, current, arg_tree)
+    result = lib.arb_reduce(ctx, current, 1_000_000_000)
+    return to_string(ctx, result)
+
+
+# ============================================================================
+# Tests
+# ============================================================================
+
+all_ok = True
+
+
+def check(label, got, want):
+    global all_ok
+    if got != want:
+        print(f"FAIL {label}: got {got!r}, want {want!r}")
+        all_ok = False
+    else:
+        print(f"PASS {label}: {got!r}")
+
+
+# Test 1: id via kernel
+print("\n--- Test 1: id (kernel path) ---")
+bundle = read_bundle("id.arboricx")
+t0 = time.time()
+result = kernel_run(bundle, ["hello"])
+t1 = time.time()
+check("id kernel", result, "hello")
+print(f"  time: {(t1 - t0) * 1000:.1f} ms")
+
+# Test 2: id via native
+print("\n--- Test 2: id (native path) ---")
+t0 = time.time()
+result = native_run_default(bundle, ["hello"])
+t1 = time.time()
+check("id native", result, "hello")
+print(f"  time: {(t1 - t0) * 1000:.1f} ms")
+
+# Test 3: append via kernel
+print("\n--- Test 3: append (kernel path) ---")
+bundle = read_bundle("append.arboricx")
+t0 = time.time()
+result = kernel_run(bundle, ["Hello, ", "world!"])
+t1 = time.time()
+check("append kernel", result, "Hello, world!")
+print(f"  time: {(t1 - t0) * 1000:.1f} ms")
+
+# Test 4: append via native
+print("\n--- Test 4: append (native path) ---")
+t0 = time.time()
+result = native_run_default(bundle, ["Hello, ", "world!"])
+t1 = time.time()
+check("append native", result, "Hello, world!")
+print(f"  time: {(t1 - t0) * 1000:.1f} ms")
+
+# Test 5: append via native named export
+print("\n--- Test 5: append via named export 'root' ---")
+t0 = time.time()
+result = native_run_named(bundle, "root", ["Hello, ", "world!"])
+t1 = time.time()
+check("append named", result, "Hello, world!")
+print(f"  time: {(t1 - t0) * 1000:.1f} ms")
+
+# Test 6: true / false via native
+print("\n--- Test 6: true / false (native path) ---")
+for name, expected in [("true.arboricx", True), ("false.arboricx", False)]:
+    bundle = read_bundle(name)
+    buf = c_bytes(bundle)
+    term = lib.arb_load_bundle_default(ctx, buf, len(bundle))
+    result = lib.arb_reduce(ctx, term, 1_000_000_000)
+    check(f"{name} bool", to_bool(ctx, result), expected)
+
+# Test 7: number roundtrip
+print("\n--- Test 7: number roundtrip ---")
+num_tree = lib.arb_of_number(ctx, 42)
+check("number 42", to_number(ctx, num_tree), 42)
+
+# Test 8: string roundtrip
+print("\n--- Test 8: string roundtrip ---")
+str_tree = lib.arb_of_string(ctx, b"hello")
+check("string hello", to_string(ctx, str_tree), "hello")
+
+lib.arboricx_free(ctx)
+
+if all_ok:
+    print("\nAll tests passed!")
+    sys.exit(0)
+else:
+    print("\nSome tests failed!")
+    sys.exit(1)

ext/zig/tools/gen_kernel.zig

@@ -0,0 +1,92 @@
+const std = @import("std");
+
+// Minimal Node definition for the DAG format (no App variant for kernels)
+const Node = union(enum(u8)) {
+    leaf,
+    stem: struct { child: u32 },
+    fork: struct { left: u32, right: u32 },
+};
+
+fn parseLine(line: []const u8) !Node {
+    var it = std.mem.splitScalar(u8, std.mem.trim(u8, line, " \t\n\r"), ' ');
+    const tag = it.next() orelse return error.EmptyLine;
+    if (std.mem.eql(u8, tag, "leaf")) {
+        return .leaf;
+    } else if (std.mem.eql(u8, tag, "stem")) {
+        const child_str = it.next() orelse return error.MissingChild;
+        const child = try std.fmt.parseInt(u32, child_str, 10);
+        return .{ .stem = .{ .child = child } };
+    } else if (std.mem.eql(u8, tag, "fork")) {
+        const left_str = it.next() orelse return error.MissingLeft;
+        const right_str = it.next() orelse return error.MissingRight;
+        const left = try std.fmt.parseInt(u32, left_str, 10);
+        const right = try std.fmt.parseInt(u32, right_str, 10);
+        return .{ .fork = .{ .left = left, .right = right } };
+    } else {
+        return error.UnknownTag;
+    }
+}
+
+pub fn main(init: std.process.Init) !void {
+    const gpa = init.gpa;
+    const io = init.io;
+
+    const args = try init.minimal.args.toSlice(init.arena.allocator());
+    if (args.len != 3) {
+        std.debug.print("Usage: gen_kernel <input.dag> <output.zig>\n", .{});
+        std.process.exit(1);
+    }
+
+    const input_path = args[1];
+    const output_path = args[2];
+
+    const source = try std.Io.Dir.cwd().readFileAlloc(io, input_path, gpa, .limited(10 * 1024 * 1024));
+    defer gpa.free(source);
+
+    var nodes = std.ArrayList(Node).empty;
+    defer nodes.deinit(gpa);
+
+    var it = std.mem.splitScalar(u8, source, '\n');
+    const root_line = it.next() orelse return error.EmptyFile;
+    const root = try std.fmt.parseInt(u32, std.mem.trim(u8, root_line, " \t\n\r"), 10);
+
+    while (it.next()) |line| {
+        const trimmed = std.mem.trim(u8, line, " \t\n\r");
+        if (trimmed.len == 0) continue;
+        const node = try parseLine(trimmed);
+        try nodes.append(gpa, node);
+    }
+
+    const file = try std.Io.Dir.cwd().createFile(io, output_path, .{});
+    defer file.close(io);
+
+    var buf: [4096]u8 = undefined;
+    var writer = file.writer(io, &buf);
+
+    try writer.interface.writeAll("// Auto-generated from ");
+    try writer.interface.writeAll(input_path);
+    try writer.interface.writeAll("\n// Do not edit manually.\n\n");
+
+    try writer.interface.writeAll("pub const NodeTag = enum(u8) { leaf = 0, stem = 1, fork = 2 };\n\n");
+    try writer.interface.writeAll("pub const Node = union(NodeTag) {\n");
+    try writer.interface.writeAll("    leaf,\n");
+    try writer.interface.writeAll("    stem: struct { child: u32 },\n");
+    try writer.interface.writeAll("    fork: struct { left: u32, right: u32 },\n");
+    try writer.interface.writeAll("};\n\n");
+
+    try writer.interface.print("pub const kernel_root: u32 = {d};\n\n", .{root});
+    try writer.interface.writeAll("pub const kernel_nodes = [_]Node{\n");
+
+    for (nodes.items) |node| {
+        switch (node) {
+            .leaf => try writer.interface.writeAll("    .leaf,\n"),
+            .stem => |s| try writer.interface.print("    .{{ .stem = .{{ .child = {d} }} }},\n", .{s.child}),
+            .fork => |f| try writer.interface.print("    .{{ .fork = .{{ .left = {d}, .right = {d} }} }},\n", .{f.left, f.right}),
+        }
+    }
+
+    try writer.interface.writeAll("};\n");
+    try writer.flush();
+
+    std.debug.print("Generated {d} kernel nodes, root={d} -> {s}\n", .{ nodes.items.len, root, output_path });
+}

flake.lock

@@ -20,11 +20,11 @@
     },
     "nixpkgs": {
       "locked": {
-        "lastModified": 1734566935,
+        "lastModified": 1778505177,
-        "narHash": "sha256-cnBItmSwoH132tH3D4jxmMLVmk8G5VJ6q/SC3kszv9E=",
+        "narHash": "sha256-ao5+JS50HqNt/dtm4zuiQI+IXOn6hw50W6RTwUKYTww=",
         "owner": "NixOS",
         "repo": "nixpkgs",
-        "rev": "087408a407440892c1b00d80360fd64639b8091d",
+        "rev": "fb2ce70b4ae882574081225eb3c2872f39418df3",
         "type": "github"
       },
       "original": {

flake.nix

@@ -29,9 +29,82 @@
         customGHC = haskellPackages.ghcWithPackages (hpkgs: with hpkgs; [
           megaparsec
         ]);
+
+        # ------------------------------------------------------------------
+        # Zig Arboricx host
+        # ------------------------------------------------------------------
+        tricuZig = pkgs.stdenv.mkDerivation {
+          pname = "tricu-zig";
+          version = "0.1.0";
+          src = ./ext/zig;
+          nativeBuildInputs = [ pkgs.zig ];
+          buildPhase = ''
+            export ZIG_GLOBAL_CACHE_DIR=$TMPDIR/zig-cache
+            zig build
+          '';
+          installPhase = ''
+            mkdir -p $out/bin $out/lib $out/include
+            cp zig-out/bin/* $out/bin/ 2>/dev/null || true
+            cp zig-out/lib/* $out/lib/ 2>/dev/null || true
+            cp include/arboricx.h $out/include/
+          '';
+        };
+
+        # Separate test target — not included in `nix flake check`
+        tricuZigTests = pkgs.stdenv.mkDerivation {
+          pname = "tricu-zig-tests";
+          version = "0.1.0";
+          src = ./.;
+          nativeBuildInputs = [ pkgs.gcc pkgs.python3 tricuZig ];
+          buildPhase = "true";
+          doCheck = true;
+          checkPhase = ''
+            export LD_LIBRARY_PATH=${tricuZig}/lib:$LD_LIBRARY_PATH
+            ulimit -s 32768
+
+            cd ext/zig
+
+            # C ABI smoke test
+            gcc -o /tmp/c_abi_test tests/c_abi_test.c \
+              -I ${tricuZig}/include -L ${tricuZig}/lib -larboricx \
+              -Wl,-rpath,${tricuZig}/lib
+            /tmp/c_abi_test
+
+            # Kernel path append test
+            gcc -o /tmp/c_abi_append_test tests/c_abi_append_test.c \
+              -I ${tricuZig}/include -L ${tricuZig}/lib -larboricx \
+              -Wl,-rpath,${tricuZig}/lib
+            /tmp/c_abi_append_test
+
+            # Native bundle tests
+            gcc -o /tmp/native_bundle_append_test tests/native_bundle_append_test.c \
+              -I ${tricuZig}/include -L ${tricuZig}/lib -larboricx \
+              -Wl,-rpath,${tricuZig}/lib
+            /tmp/native_bundle_append_test
+
+            gcc -o /tmp/native_bundle_id_test tests/native_bundle_id_test.c \
+              -I ${tricuZig}/include -L ${tricuZig}/lib -larboricx \
+              -Wl,-rpath,${tricuZig}/lib
+            /tmp/native_bundle_id_test
+
+            gcc -o /tmp/native_bundle_bools_test tests/native_bundle_bools_test.c \
+              -I ${tricuZig}/include -L ${tricuZig}/lib -larboricx \
+              -Wl,-rpath,${tricuZig}/lib
+            /tmp/native_bundle_bools_test
+
+            # Python FFI test
+            ARBORICX_LIB=${tricuZig}/lib/libarboricx.so \
+              python3 tests/python_ffi_test.py
+
+            mkdir -p $out
+            echo "All Zig tests passed" > $out/result
+          '';
+        };
       in {
         packages.${packageName} = tricuPackage;
         packages.default = tricuPackage;
+        packages.tricu-zig = tricuZig;
+        packages.tricu-zig-tests = tricuZigTests;
 
         checks.${packageName} = tricuPackageTests;
         checks.default = tricuPackageTests;
@@ -43,10 +116,14 @@
             haskellPackages.ghcid
             customGHC
             upx
+            zig
+            gcc
+            python3
           ];
 
           inputsFrom = [
             tricuPackage
+            tricuZig
           ];
         };
 

lib/arboricx-dispatch.tri

@@ -0,0 +1,23 @@
+!import "arboricx.tri" !Local
+!import "patterns.tri" !Local
+
+-- Multi-purpose kernel dispatch.
+--
+-- runArboricxTyped tag bundleBytes args
+--   tag 0 → hostTree   (runArboricxToTree)
+--   tag 1 → hostString (runArboricxToString)
+--   tag 2 → hostNumber (runArboricxToNumber)
+--   tag 3 → hostBool   (runArboricxToBool)
+--   tag 4 → hostList   (runArboricxToList)
+--   tag 5 → hostBytes  (runArboricxToBytes)
+--   otherwise → err 99 bundleBytes
+
+runArboricxTyped = (tag bs args :
+  match tag
+    [[(equal? hostTreeTag)   (_ : runArboricxToTree bs args)]
+     [(equal? hostStringTag) (_ : runArboricxToString bs args)]
+     [(equal? hostNumberTag) (_ : runArboricxToNumber bs args)]
+     [(equal? hostBoolTag)   (_ : runArboricxToBool bs args)]
+     [(equal? hostListTag)   (_ : runArboricxToList bs args)]
+     [(equal? hostBytesTag)  (_ : runArboricxToBytes bs args)]
+     [otherwise              (_ : err 99 bs)]])

src/Main.hs

@@ -1,6 +1,7 @@
 module Main where
 
-import ContentStore (initContentStore, loadEnvironment, resolveExportTarget)
+import ContentStore (initContentStore, loadEnvironment, loadTerm, resolveExportTarget)
+import System.Exit (die)
 import Server (runServer)
 import Eval                   (evalTricu, mainResult, result)
 import FileEval
@@ -32,6 +33,7 @@ data TricuArgs
   | Export { hash :: String, exportNameOpt :: String, outFile :: FilePath, names :: [String] }
   | Import { inFile :: FilePath }
   | Serve { host :: String, port :: Int }
+  | ExportDag { target :: String, outFile :: FilePath }
   deriving (Show, Data, Typeable)
 
 replMode :: TricuArgs
@@ -112,10 +114,21 @@ serveMode = Serve
   &= explicit
   &= name "server"
 
+exportDagMode :: TricuArgs
+exportDagMode = ExportDag
+  { target = def &= help "Stored term name or hash to export as a DAG node table."
+                 &= name "t" &= typ "NAME_OR_HASH"
+  , outFile = def &= help "Optional output file path. Defaults to stdout."
+                  &= name "o" &= typ "FILE"
+  }
+  &= help "Export a term's Merkle DAG as a topologically-sorted node table for host embedding."
+  &= explicit
+  &= name "export-dag"
+
 main :: IO ()
 main = do
   let versionStr = "tricu Evaluator and REPL " ++ showVersion version
-  cmdArgsParsed <- cmdArgs $ modes [replMode, evaluateMode, decodeMode, compileMode, exportMode, importMode, serveMode]
+  cmdArgsParsed <- cmdArgs $ modes [replMode, evaluateMode, decodeMode, compileMode, exportMode, importMode, serveMode, exportDagMode]
     &= help "tricu: Exploring Tree Calculus"
     &= program "tricu"
     &= summary versionStr
@@ -191,6 +204,18 @@ main = do
       putStrLn $ "  GET /bundle/name/:name   -- convenience endpoint"
       putStrLn $ "  Content-Type: application/vnd.arboricx.bundle"
       runServer hostStr portNum
+    ExportDag { target = targetName, outFile = dagOutFile } -> do
+      conn <- initContentStore
+      maybeTerm <- loadTerm conn targetName
+      close conn
+      case maybeTerm of
+        Nothing -> die $ "Term not found: " ++ targetName
+        Just term -> do
+          let (rootIdx, nodes) = exportDag term
+              output = unlines $ show rootIdx : map (\(tag, refs) -> unwords (tag : map show refs)) nodes
+          if null dagOutFile
+            then putStr output
+            else writeFile dagOutFile output
 
 runTricu :: String -> String
 runTricu = formatT TreeCalculus . runTricuT

src/Research.hs

@@ -12,6 +12,7 @@ import System.Console.CmdArgs    (Data, Typeable)
 
 import qualified Data.ByteString as BS
 import qualified Data.Map        as Map
+import qualified Data.Set        as Set
 import qualified Data.Text       as T
 
 -- Tree Calculus Types
@@ -296,3 +297,41 @@ decodeResult tc =
          || n == 9
          || n == 10
          || n == 13
+
+-- ---------------------------------------------------------------------------
+-- DAG node-table export (for host-language kernel embedding)
+-- ---------------------------------------------------------------------------
+
+-- | Export a term's Merkle DAG as a topologically-sorted node table.
+-- Children appear before parents so all index references are forward.
+-- Returns (root index, list of (tag, [child_indices])).
+exportDag :: T -> (Int, [(String, [Int])])
+exportDag term =
+  let (root, acc, _) = collectDag term [] Set.empty
+      -- acc is in reverse post-order (children first, root last)
+      ordered = reverse acc
+      idxMap = Map.fromList [(h, i) | (i, (h, _)) <- zip [0..] ordered]
+      rootIdx = idxMap Map.! root
+      lines_ = map (formatNode idxMap . snd) ordered
+  in (rootIdx, lines_)
+  where
+    collectDag :: T -> [(MerkleHash, Node)] -> Set.Set MerkleHash -> (MerkleHash, [(MerkleHash, Node)], Set.Set MerkleHash)
+    collectDag Leaf acc seen =
+      let h = nodeHash NLeaf
+      in if Set.member h seen then (h, acc, seen) else (h, (h, NLeaf) : acc, Set.insert h seen)
+    collectDag (Stem t) acc seen =
+      let (ch, acc', seen') = collectDag t acc seen
+          node = NStem ch
+          h = nodeHash node
+      in if Set.member h seen' then (h, acc', seen') else (h, (h, node) : acc', Set.insert h seen')
+    collectDag (Fork l r) acc seen =
+      let (lh, acc', seen') = collectDag l acc seen
+          (rh, acc'', seen'') = collectDag r acc' seen'
+          node = NFork lh rh
+          h = nodeHash node
+      in if Set.member h seen'' then (h, acc'', seen'') else (h, (h, node) : acc'', Set.insert h seen'')
+
+    formatNode :: Map.Map MerkleHash Int -> Node -> (String, [Int])
+    formatNode _ NLeaf = ("leaf", [])
+    formatNode idxMap (NStem ch) = ("stem", [idxMap Map.! ch])
+    formatNode idxMap (NFork l r) = ("fork", [idxMap Map.! l, idxMap Map.! r])