W5

src/lib/compiler.cpp

@@ -860,13 +860,25 @@ void compile_shared_unit(Request* context, SharedUnit* su)
 		));
 
 	if(su->compiler_messages.length() == 0 && !su->opt_so_optional && compiler_wasm_unit_compile_enabled(context))
-		su->compiler_messages = trim(shell_exec(shell_escape(compiler_wasm_compile_script(context))+" "+
+	{
+		// The wasm side-module build is best-effort: a unit that cannot compile
+		// to wasm (e.g. try/catch) still works via the native .so and falls back
+		// to native at request time. Record the failure, never fail the unit on
+		// it. On failure, remove any stale .wasm so the backend won't serve it.
+		String wasm_messages = trim(shell_exec(shell_escape(compiler_wasm_compile_script(context))+" "+
 			shell_escape(su->src_path)+" "+
 			shell_escape(su->bin_path)+" "+
 			shell_escape(su->file_name)+" "+
 			shell_escape(su->pre_file_name)+" "+
 			shell_escape(su->wasm_file_name)
 		));
+		if(wasm_messages.length() > 0)
+		{
+			file_put_contents(su->wasm_check_file_name, wasm_messages + "\n");
+			file_unlink(su->wasm_name);
+			printf("(i) wasm side-module unavailable for %s (native .so serves it)\n", su->file_name.c_str());
+		}
+	}
 
 	if(su->compiler_messages.length() > 0)
 	{

src/lib/functionlib.cpp

@@ -642,41 +642,69 @@ StringList regex_split(String pattern, String subject, String flags)
 
 #else
 
+// PCRE2 is not compiled into the wasm core; regex runs host-side (the host
+// already links libpcre2). One UCEB1-marshalled hostcall carries the request
+// {op,pattern,subject,flags,replacement} in and the result tree out — the host
+// runs the real regex_* and packs the answer. See uce_host_regex in
+// src/wasm/worker.cpp.
+extern "C" size_t uce_host_regex(const char* in, size_t in_len, char* out, size_t cap);
+
+static DValue wasm_regex_call(String op, String pattern, String subject, String flags, String replacement = "")
+{
+	DValue request;
+	request["op"] = op;
+	request["pattern"] = pattern;
+	request["subject"] = subject;
+	request["flags"] = flags;
+	request["replacement"] = replacement;
+	String encoded = ucb_encode(request);
+	size_t need = uce_host_regex(encoded.data(), encoded.size(), 0, 0);
+	if(need == 0)
+		return(DValue());
+	String buffer(need, 0);
+	size_t got = uce_host_regex(encoded.data(), encoded.size(), &buffer[0], need);
+	if(got == 0 || got > need)
+		return(DValue());
+	DValue response;
+	String error;
+	ucb_decode(String(buffer.data(), got), response, &error);
+	return(response);
+}
+
 bool regex_match(String pattern, String subject, String flags)
 {
-	(void)pattern; (void)subject; (void)flags;
-	return(false);
+	return(wasm_regex_call("match", pattern, subject, flags)["bool"].to_bool());
 }
 
 DValue regex_search(String pattern, String subject, String flags)
 {
-	DValue result;
-	result["matched"].set_bool(false);
-	result["pattern"] = pattern;
-	result["flags"] = flags == "" ? "default" : flags;
-	return(result);
+	DValue response = wasm_regex_call("search", pattern, subject, flags);
+	DValue* tree = response.key("tree");
+	return(tree ? *tree : DValue());
 }
 
 DValue regex_search_all(String pattern, String subject, String flags)
 {
-	DValue result;
-	result["matched"].set_bool(false);
-	result["pattern"] = pattern;
-	result["flags"] = flags == "" ? "default" : flags;
-	result["count"] = (f64)0;
-	return(result);
+	DValue response = wasm_regex_call("search_all", pattern, subject, flags);
+	DValue* tree = response.key("tree");
+	return(tree ? *tree : DValue());
 }
 
 String regex_replace(String pattern, String replacement, String subject, String flags)
 {
-	(void)pattern; (void)replacement; (void)flags;
-	return(subject);
+	return(wasm_regex_call("replace", pattern, subject, flags, replacement)["text"].to_string());
 }
 
 StringList regex_split(String pattern, String subject, String flags)
 {
-	(void)pattern; (void)flags;
-	return(StringList{ subject });
+	DValue response = wasm_regex_call("split", pattern, subject, flags);
+	StringList result;
+	DValue* list = response.key("list");
+	if(list)
+		list->each([&](const DValue& part, String) {
+			result.push_back(part.to_string());
+		});
+	return(result);
 }
 
 #endif

src/lib/sys.cpp

@@ -14,6 +14,8 @@ void uce_host_log(int level, const char* buf, size_t len);
 // cwd convention); file_read uses the length-query convention
 int uce_host_file_exists(const char* path, size_t path_len, const char* current, size_t current_len);
 size_t uce_host_file_read(const char* path, size_t path_len, const char* current, size_t current_len, char* buf, size_t cap);
+int uce_host_file_write(const char* path, size_t path_len, const char* current, size_t current_len, const char* content, size_t content_len, int append);
+void uce_host_file_unlink(const char* path, size_t path_len, const char* current, size_t current_len);
 }
 
 static String wasm_current_unit_file()
@@ -50,13 +52,25 @@ String file_get_contents(String file_name)
 	content.resize(got <= required ? got : 0);
 	return(content);
 }
-bool file_put_contents(String file_name, String content) { (void)file_name; (void)content; return(false); }
-bool file_append_contents(String file_name, String content) { (void)file_name; (void)content; return(false); }
+bool file_put_contents(String file_name, String content)
+{
+	String current = wasm_current_unit_file();
+	return(uce_host_file_write(file_name.data(), file_name.size(), current.data(), current.size(), content.data(), content.size(), 0) != 0);
+}
+bool file_append_contents(String file_name, String content)
+{
+	String current = wasm_current_unit_file();
+	return(uce_host_file_write(file_name.data(), file_name.size(), current.data(), current.size(), content.data(), content.size(), 1) != 0);
+}
 String cwd_get() { return("/"); }
 void cwd_set(String path) { (void)path; }
 String process_start_directory() { return("/"); }
 time_t file_mtime(String file_name) { (void)file_name; return(0); }
-void file_unlink(String file_name) { (void)file_name; }
+void file_unlink(String file_name)
+{
+	String current = wasm_current_unit_file();
+	uce_host_file_unlink(file_name.data(), file_name.size(), current.data(), current.size());
+}
 String expand_path(String path, String relative_to_path) { return(path_join(relative_to_path, path)); }
 StringList ls(String dir) { (void)dir; return(StringList()); }
 u64 config_map_u64(StringMap& cfg, String key, u64 fallback) { String raw = first(cfg[key], std::to_string(fallback)); char* end = 0; unsigned long long v = strtoull(raw.c_str(), &end, 10); return(end && *end == 0 ? (u64)v : fallback); }

src/lib/uce_lib.cpp

@@ -12,6 +12,16 @@
 #include "uri.cpp"
 #include "cli.cpp"
 
+#ifdef __UCE_WASM_CORE__
+// markdown is pure compute (no PCRE/syscalls/regex) — it belongs in the wasm
+// core so markdown_to_html/markdown_to_ast render in-workspace. compiler.cpp
+// (which declares component() ahead of markdown in the native build) is carved
+// out here, and the wasm core defines component() later in src/wasm/core.cpp,
+// so markdown just needs the forward declaration.
+String component(String name, DValue props, Request& context);
+#include "markdown.cpp"
+#endif
+
 #ifndef __UCE_WASM_CORE__
 #include "compiler-parser.cpp"
 #include "compiler.cpp"

src/lib/wasm_trace.h

@@ -15,7 +15,11 @@
 #include <string>
 #include <vector>
 
-#if defined(__GNUG__)
+// The demangler is a host-side nicety for trap traces. wasi-libc++ does not
+// provide __cxa_demangle, and a wasm unit that merely includes uce_lib.h must
+// not pull it in as an unresolvable import — so it is host-only.
+#if defined(__GNUG__) && !defined(__wasm__)
+#define UCE_WASM_TRACE_HAVE_DEMANGLE 1
 #include <cxxabi.h>
 #endif
 
@@ -30,7 +34,7 @@ struct WasmTraceSummary
 
 inline std::string wasm_trace_demangle(const std::string& name)
 {
-#if defined(__GNUG__)
+#if defined(UCE_WASM_TRACE_HAVE_DEMANGLE)
 	// frame names look like "module!symbol"; demangle the symbol part
 	auto bang = name.find('!');
 	std::string prefix = bang == std::string::npos ? "" : name.substr(0, bang + 1);

src/wasm/backend.cpp

@@ -10,6 +10,10 @@
 // handle_complete() changes. CLI, serve_http, and websocket stay native.
 
 #include "../lib/wasm_trace.h"
+// The native server TU has the real connectors (sqlite/mysql) compiled in, so
+// the worker's host-side connector hostcalls are available here. The W3 CLI
+// driver does not define this and gets a named-trap stub for those imports.
+#define UCE_WASM_HOST_CONNECTORS 1
 #include "worker.cpp"
 
 #include <atomic>
@@ -44,6 +48,12 @@ static String wasm_backend_ensure_started(Request* context)
 		path_join(cfg["COMPILER_SYS_PATH"], "bin/wasm/core.wasm"));
 	wc.site_root = path_join(cfg["COMPILER_SYS_PATH"], cfg["SITE_DIRECTORY"]);
 	wc.cache_root = cfg["BIN_DIRECTORY"];
+	// write membrane allowlist: the site tree plus the runtime scratch dirs
+	// pages legitimately write to (matches native reachable write targets).
+	wc.write_roots = { wc.site_root, "/tmp" };
+	for(const char* key : { "BIN_DIRECTORY", "SESSION_PATH", "TMP_UPLOAD_PATH" })
+		if(cfg[key] != "")
+			wc.write_roots.push_back(cfg[key]);
 	wc.memory_limit = (int64_t)config_u64("WASM_MEMORY_LIMIT_BYTES", 512ull * 1024 * 1024);
 	wc.epoch_deadline_ticks = config_u64("WASM_EPOCH_DEADLINE_TICKS", 200);
 	wc.verbose = config_bool("WASM_BACKEND_VERBOSE", false);
@@ -75,31 +85,68 @@ static bool wasm_artifact_exists(Request* context, const String& entry_unit)
 	if(entry_unit == "")
 		return(false);
 	String wasm_path = context->server->config["BIN_DIRECTORY"] + entry_unit + ".wasm";
-	struct stat st;
-	return(stat(wasm_path.c_str(), &st) == 0 && S_ISREG(st.st_mode));
+	struct stat wasm_st;
+	if(stat(wasm_path.c_str(), &wasm_st) != 0 || !S_ISREG(wasm_st.st_mode))
+		return(false);
+	// The wasm path bypasses the native JIT recompile, so a source edit would
+	// otherwise be served from a stale .wasm. Require the artifact to be newer
+	// than the source; if it is stale, fall back to native — which JIT-rebuilds
+	// both .so and .wasm — so the next request gets a fresh artifact.
+	struct stat src_st;
+	if(stat(entry_unit.c_str(), &src_st) == 0 && wasm_st.st_mtime < src_st.st_mtime)
+		return(false);
+	return(true);
+}
+
+// Decide, by source inspection, whether a page must stay on the native
+// backend for now (W5 surfaces not yet behind the membrane).
+//
+// Caveats this deliberately accepts:
+//  - ENTRY-UNIT ONLY: a clean entry page that component()s into a native-only
+//    unit is still served by wasm. With signals_based_traps off (see
+//    make_engine) the worst case is a clean wasm error or a stubbed-empty
+//    result, never a worker crash — so this is a best-effort routing hint,
+//    not a guarantee. Full coverage is a W5 concern (un-stub the APIs).
+//  - SUBSTRING match, intentionally conservative: a token like "xml_" also
+//    matches an identifier or doc string containing it. That only ever
+//    over-routes to native (always correct), never the reverse.
+static bool wasm_backend_native_fallback_uncached(Request* context, const String& entry_unit)
+{
+	String source = file_get_contents(entry_unit);
+	// Supported by the wasm core, intentionally NOT in this list:
+	//  - regex_* (host PCRE2 hostcall), xml_*/yaml_*/markdown_* (compiled in),
+	//  - unit_render()/component() (host resolver).
+	// What remains is genuinely host-owned / native-only for now:
+	//  - zip, sqlite, background tasks, filesystem writes, sleeps;
+	//  - unit_call + compiler/unit introspection (need the native toolchain).
+	StringList native_only_tokens = {
+		"zip_", "task(", "task_repeat(",
+		"task_pid(", "task_kill(", "unit_call(",
+		"unit_compile(", "unit_info(", "units_list(", "compiler_load_shared_unit(",
+		"usleep(", "sleep("
+	};
+	for(auto& token : native_only_tokens)
+		if(source.find(token) != String::npos)
+			return(true);
+	return(false);
 }
 
 static bool wasm_backend_native_fallback_needed(Request* context, const String& entry_unit)
 {
 	if(!context || !context->server || entry_unit == "")
 		return(true);
-	String site_root = path_join(context->server->config["COMPILER_SYS_PATH"], context->server->config["SITE_DIRECTORY"]);
-	// W5 keeps native as the reference backend for compiler/docs pages and the
-	// host-owned service surfaces that are not membrane APIs yet. This makes the
-	// default backend safe while W6 decides which fallbacks to retire vs keep.
-	if(entry_unit.rfind(path_join(site_root, "doc") + "/", 0) == 0)
-		return(true);
-	String source = file_get_contents(entry_unit);
-	StringList native_only_tokens = {
-		"markdown_to_", "zip_", "sqlite_", "regex_", "xml_", "yaml_", "task(", "task_repeat(",
-		"task_pid(", "task_kill(", "unit_call(", "unit_render(",
-		"unit_compile(", "unit_info(", "units_list(", "compiler_load_shared_unit(",
-		"file_put_contents(", "file_append(", "usleep(", "sleep("
-	};
-	for(auto& token : native_only_tokens)
-		if(source.find(token) != String::npos)
-			return(true);
-	return(false);
+	// Cache the verdict per process, keyed on path + mtime: the source scan is
+	// otherwise a file read + 20 substring searches on every page request.
+	struct CachedVerdict { time_t mtime; bool fallback; };
+	static std::map<String, CachedVerdict> cache;
+	struct stat st;
+	time_t mtime = (stat(entry_unit.c_str(), &st) == 0) ? st.st_mtime : 0;
+	auto it = cache.find(entry_unit);
+	if(it != cache.end() && it->second.mtime == mtime)
+		return(it->second.fallback);
+	bool fallback = wasm_backend_native_fallback_uncached(context, entry_unit);
+	cache[entry_unit] = { mtime, fallback };
+	return(fallback);
 }
 
 // True if this request should be served by the wasm backend. Falls through to
@@ -142,12 +189,17 @@ String wasm_backend_serve(Request& request, const String& entry_unit)
 	if(!response.ok)
 		return(response.error == "" ? String("wasm workspace failed") : response.error);
 
-	request.header["X-UCE-Backend"] = "wasm";
-	request.header["X-UCE-Wasm-Workspace-Birth-Us"] = std::to_string(response.workspace_birth_us);
-	request.header["X-UCE-Wasm-Component-Resolve-Count"] = std::to_string(response.component_resolve_count);
-	request.header["X-UCE-Wasm-Component-Resolve-Total-Us"] = std::to_string(response.component_resolve_total_us);
-	request.header["X-UCE-Wasm-Component-Resolve-Avg-Us"] = std::to_string(
-		response.component_resolve_count ? response.component_resolve_total_us / response.component_resolve_count : 0);
+	// Diagnostic timing headers are opt-in: they leak workspace internals and
+	// belong to the W5 benchmark harness, not public responses.
+	if(config_bool("WASM_BACKEND_VERBOSE", false))
+	{
+		request.header["X-UCE-Backend"] = "wasm";
+		request.header["X-UCE-Wasm-Workspace-Birth-Us"] = std::to_string(response.workspace_birth_us);
+		request.header["X-UCE-Wasm-Component-Resolve-Count"] = std::to_string(response.component_resolve_count);
+		request.header["X-UCE-Wasm-Component-Resolve-Total-Us"] = std::to_string(response.component_resolve_total_us);
+		request.header["X-UCE-Wasm-Component-Resolve-Avg-Us"] = std::to_string(
+			response.component_resolve_count ? response.component_resolve_total_us / response.component_resolve_count : 0);
+	}
 
 	// status line: keep the native default unless the unit set one
 	String status = response.meta["status"].to_string();

src/wasm/core.cpp

@@ -37,14 +37,81 @@ DValue MySQL::get_pending_result() { return(DValue()); }
 
 String mysql_escape(String raw, char quote_char) { (void)quote_char; return(raw); }
 
-bool SQLite::connect(String path) { this->path = path; connection = 0; set_error(1, WASM_DB_UNAVAILABLE); return(false); }
-void SQLite::disconnect() { connection = 0; }
-String SQLite::error() { return(error_code ? String(WASM_DB_UNAVAILABLE) : String("")); }
-DValue SQLite::query(String q) { (void)q; set_error(1, WASM_DB_UNAVAILABLE); return(DValue()); }
-DValue SQLite::query(String q, const StringMap& params) { (void)q; (void)params; set_error(1, WASM_DB_UNAVAILABLE); return(DValue()); }
+// sqlite runs host-side (the host links libsqlite and owns the connections in
+// a per-workspace handle table). One UCEB1-marshalled hostcall carries
+// {op,handle,path,query,params} in and {handle,result,insert_id,affected,
+// error_code,statement_info} out. `connection` holds the host handle (>0).
+extern "C" size_t uce_host_sqlite(const char* in, size_t in_len, char* out, size_t cap);
+
+static DValue wasm_sqlite_call(DValue request)
+{
+	String encoded = ucb_encode(request);
+	size_t need = uce_host_sqlite(encoded.data(), encoded.size(), 0, 0);
+	if(need == 0)
+		return(DValue());
+	String buffer(need, 0);
+	size_t got = uce_host_sqlite(encoded.data(), encoded.size(), &buffer[0], need);
+	if(got == 0 || got > need)
+		return(DValue());
+	DValue response;
+	String error;
+	ucb_decode(String(buffer.data(), got), response, &error);
+	return(response);
+}
+
 void SQLite::set_error(s32 code, String info) { error_code = code; statement_info = info; }
-bool SQLite::apply_default_pragmas() { return(false); }
-bool SQLite::bind_params(void* statement, const StringMap& params) { (void)statement; (void)params; return(false); }
+
+bool SQLite::connect(String path)
+{
+	this->path = path;
+	DValue request;
+	request["op"] = "connect";
+	request["path"] = path;
+	DValue response = wasm_sqlite_call(request);
+	u64 handle = response["handle"].to_u64();
+	connection = (void*)(uintptr_t)handle;
+	error_code = (s32)response["error_code"].to_s64();
+	statement_info = response["statement_info"].to_string();
+	return(handle != 0 && error_code == 0);
+}
+
+void SQLite::disconnect()
+{
+	if(connection)
+	{
+		DValue request;
+		request["op"] = "disconnect";
+		request["handle"] = (f64)(uintptr_t)connection;
+		wasm_sqlite_call(request);
+		connection = 0;
+	}
+}
+
+String SQLite::error()
+{
+	return(statement_info);
+}
+
+DValue SQLite::query(String q, const StringMap& params)
+{
+	DValue request;
+	request["op"] = "query";
+	request["handle"] = (f64)(uintptr_t)connection;
+	request["query"] = q;
+	for(auto& entry : params)
+		request["params"][entry.first] = entry.second;
+	DValue response = wasm_sqlite_call(request);
+	insert_id = response["insert_id"].to_u64();
+	affected_rows = (u32)response["affected"].to_u64();
+	error_code = (s32)response["error_code"].to_s64();
+	statement_info = response["statement_info"].to_string();
+	DValue* result = response.key("result");
+	return(result ? *result : DValue());
+}
+
+DValue SQLite::query(String q) { return(query(q, StringMap())); }
+bool SQLite::apply_default_pragmas() { return(true); }
+bool SQLite::bind_params(void* statement, const StringMap& params) { (void)statement; (void)params; return(true); }
 DValue SQLite::collect_rows(void* statement) { (void)statement; return(DValue()); }
 
 SQLite* sqlite_connect(String path)

src/wasm/core_hostcalls.syms

@@ -6,3 +6,7 @@ uce_host_random
 uce_host_component_resolve
 uce_host_file_exists
 uce_host_file_read
+uce_host_file_write
+uce_host_file_unlink
+uce_host_regex
+uce_host_sqlite

src/wasm/worker.cpp

@@ -35,6 +35,7 @@
 #include <optional>
 #include <string>
 #include <sys/stat.h>
+#include <unistd.h>
 #include <sys/time.h>
 #include <vector>
 
@@ -69,6 +70,7 @@ struct WasmWorkerConfig
 	String core_wasm_path = "bin/wasm/core.wasm";
 	String site_root;                  // absolute
 	String cache_root = "/tmp/uce/work";
+	std::vector<String> write_roots;   // absolute prefixes the write membrane allows
 	int64_t memory_limit = 512ll * 1024 * 1024;
 	u32 table_headroom = 4096;
 	u64 epoch_deadline_ticks = 200;    // ticker period × ticks = CPU budget
@@ -308,6 +310,15 @@ private:
 	{
 		wasmtime::Config config;
 		config.epoch_interruption(true);
+		// CRITICAL: the host (linux_fastcgi.cpp) installs its own SIGSEGV/SIGILL/
+		// SIGBUS handlers per request (install_request_fault_handlers) with plain
+		// signal(), which clobbers Wasmtime's trap-handling handlers. With
+		// signals_based_traps on, a guest `unreachable`/OOB surfaces as a host
+		// signal that the native on_segfault catches and abort()s the worker —
+		// a 502 instead of a clean wasm trap. Disabling it makes Cranelift emit
+		// explicit trap checks: guest traps stay pure wasm traps returned as
+		// Result errors, never a host signal, so the two never collide.
+		config.signals_based_traps(false);
 		return(wasmtime::Engine(std::move(config)));
 	}
 
@@ -329,6 +340,18 @@ public:
 	{
 	}
 
+#ifdef UCE_WASM_HOST_CONNECTORS
+	// Host-owned resource handle table (§3.1): connections opened by the guest
+	// live here and are closed when the workspace drops at request end.
+	std::vector<SQLite*> sqlite_handles;
+	~WasmWorkspace()
+	{
+		for(auto* db : sqlite_handles)
+			if(db)
+				delete db;   // ~SQLite disconnects
+	}
+#endif
+
 	// resolve-kind values shared with the guest core (src/wasm/core.cpp)
 	// must match WasmResolveKind in src/wasm/core.cpp
 	enum ResolveKind { RESOLVE_COMPONENT = 0, RESOLVE_RENDER = 1, RESOLVE_EXISTS = 2, RESOLVE_ONCE = 3 };
@@ -794,6 +817,13 @@ private:
 		if(worker.cfg.verbose)
 			fprintf(stderr, "[wasm] loaded %s (mem_base=%u table_base=%u)\n",
 				source_path.c_str(), memory_base, table_base);
+		// The epoch budget is a guest-CPU watchdog, but the ticker is wall-clock
+		// and host-side module compilation here (lazy, mid-render, possibly many
+		// units) burns it without the guest running. Reset the deadline after a
+		// load so the budget measures guest execution between membrane crossings,
+		// not our compile time. A genuine runaway loop makes no loads, so it
+		// still trips the deadline.
+		ctx().set_epoch_deadline(worker.cfg.epoch_deadline_ticks);
 		return("");
 	}
 
@@ -864,17 +894,33 @@ private:
 				candidates.push_back(entry_dir + "/" + raw);
 			candidates.push_back(worker.cfg.site_root + "/" + raw);
 		}
-		char site_real[4096];
-		if(!realpath(worker.cfg.site_root.c_str(), site_real))
-			return("");
-		String site_prefix = String(site_real) + "/";
+		// readable roots = the site tree plus the writable scratch dirs (a page
+		// can read back what it is allowed to write, e.g. /tmp), canonicalized.
+		std::vector<String> read_roots;
+		read_roots.push_back(worker.cfg.site_root);
+		for(auto& root : worker.cfg.write_roots)
+			read_roots.push_back(root);
+		std::vector<String> root_prefixes;
+		for(auto& root : read_roots)
+		{
+			char root_real[4096];
+			if(root != "" && realpath(root.c_str(), root_real))
+				root_prefixes.push_back(String(root_real) + "/");
+		}
 		for(auto& candidate : candidates)
 		{
 			char resolved[4096];
 			if(!realpath(candidate.c_str(), resolved))
 				continue;
 			String path(resolved);
-			if(path.rfind(site_prefix, 0) != 0)
+			bool allowed = false;
+			for(auto& prefix : root_prefixes)
+				if(path.rfind(prefix, 0) == 0)
+				{
+					allowed = true;
+					break;
+				}
+			if(!allowed)
 				continue;
 			if(file_exists_host(path))
 				return(path);
@@ -882,6 +928,42 @@ private:
 		return("");
 	}
 
+	// write membrane policy: resolve the target (absolute, or relative to the
+	// current unit / site root) and allow it only if its parent directory
+	// canonicalizes under one of the configured write roots (site tree + the
+	// runtime scratch dirs). The file itself need not exist yet.
+	String resolve_guest_write(const String& raw, const String& current_unit)
+	{
+		if(raw == "" || raw.find('\0') != String::npos)
+			return("");
+		String target;
+		if(raw.rfind("/", 0) == 0)
+			target = raw;
+		else
+		{
+			String current_dir = current_unit != "" ? dir_of(current_unit) : String("");
+			target = (current_dir != "" ? current_dir : worker.cfg.site_root) + "/" + raw;
+		}
+		String parent = dir_of(target);
+		String base = parent.size() < target.size() ? target.substr(parent.size() + 1) : String("");
+		if(base == "" || base == "." || base == "..")
+			return("");
+		char parent_real[4096];
+		if(!realpath(parent.c_str(), parent_real))
+			return("");
+		String resolved_parent(parent_real);
+		for(auto& root : worker.cfg.write_roots)
+		{
+			char root_real[4096];
+			if(root == "" || !realpath(root.c_str(), root_real))
+				continue;
+			String root_prefix(root_real);
+			if(resolved_parent == root_prefix || resolved_parent.rfind(root_prefix + "/", 0) == 0)
+				return(resolved_parent + "/" + base);
+		}
+		return("");
+	}
+
 	static String sanitize_symbol_suffix(const String& raw)
 	{
 		// mirrors ascii_safe_name in functionlib.cpp
@@ -1062,6 +1144,133 @@ private:
 				results[0] = Val((int32_t)bytes.size());
 				return(std::monostate());
 			}));
+		if(mod == "env" && name == "uce_host_file_write")
+			return(add([self](Caller, Span<const Val> args, Span<Val> results) -> Result<std::monostate, Trap> {
+				String path, current, content;
+				self->hostcall_read(args[0].i32(), args[1].i32(), path);
+				self->hostcall_read(args[2].i32(), args[3].i32(), current);
+				self->hostcall_read(args[4].i32(), args[5].i32(), content);
+				bool append = args[6].i32() != 0;
+				String resolved = self->resolve_guest_write(path, current);
+				bool ok = false;
+				if(resolved != "")
+					ok = append ? file_append_contents(resolved, content) : file_put_contents(resolved, content);
+				else if(self->worker.cfg.verbose)
+					fprintf(stderr, "[wasm] file_write denied: %s\n", path.c_str());
+				results[0] = Val(ok ? (int32_t)1 : (int32_t)0);
+				return(std::monostate());
+			}));
+#ifdef UCE_WASM_HOST_CONNECTORS
+		if(mod == "env" && name == "uce_host_sqlite")
+			return(add([self](Caller, Span<const Val> args, Span<Val> results) -> Result<std::monostate, Trap> {
+				// {op,handle,path,query,params} in → result out. The real native
+				// connector runs host-side; connections live in the workspace
+				// handle table (handle = 1-based index).
+				String encoded;
+				self->hostcall_read(args[0].i32(), args[1].i32(), encoded);
+				DValue request, response, decode_err_unused;
+				String decode_error;
+				if(ucb_decode(encoded, request, &decode_error))
+				{
+					String op = request["op"].to_string();
+					if(op == "connect")
+					{
+						SQLite* db = new SQLite();
+						db->connect(request["path"].to_string());
+						u64 handle = 0;
+						if(db->connection)
+						{
+							self->sqlite_handles.push_back(db);
+							handle = self->sqlite_handles.size();
+						}
+						response["handle"] = (f64)handle;
+						response["error_code"] = (f64)db->error_code;
+						response["statement_info"] = db->error();
+						if(handle == 0)
+							delete db;
+					}
+					else
+					{
+						u64 handle = request["handle"].to_u64();
+						SQLite* db = (handle >= 1 && handle <= self->sqlite_handles.size())
+							? self->sqlite_handles[(size_t)handle - 1] : 0;
+						if(op == "query" && db)
+						{
+							StringMap params;
+							DValue* p = request.key("params");
+							if(p)
+								p->each([&](const DValue& value, String key) { params[key] = value.to_string(); });
+							response["result"] = db->query(request["query"].to_string(), params);
+							response["insert_id"] = (f64)db->insert_id;
+							response["affected"] = (f64)db->affected_rows;
+							response["error_code"] = (f64)db->error_code;
+							response["statement_info"] = db->error();
+						}
+						else if(op == "disconnect" && db)
+						{
+							delete db;
+							self->sqlite_handles[(size_t)handle - 1] = 0;
+						}
+					}
+				}
+				String out = ucb_encode(response);
+				u32 cap = (u32)args[3].i32();
+				int32_t buf = args[2].i32();
+				if(buf != 0 && cap >= out.size())
+					self->hostcall_write(buf, out);
+				results[0] = Val((int32_t)out.size());
+				return(std::monostate());
+			}));
+#endif
+		if(mod == "env" && name == "uce_host_file_unlink")
+			return(add([self](Caller, Span<const Val> args, Span<Val>) -> Result<std::monostate, Trap> {
+				String path, current;
+				self->hostcall_read(args[0].i32(), args[1].i32(), path);
+				self->hostcall_read(args[2].i32(), args[3].i32(), current);
+				String resolved = self->resolve_guest_write(path, current);
+				if(resolved != "")
+					::unlink(resolved.c_str());
+				return(std::monostate());
+			}));
+		if(mod == "env" && name == "uce_host_regex")
+			return(add([self](Caller, Span<const Val> args, Span<Val> results) -> Result<std::monostate, Trap> {
+				// {op,pattern,subject,flags,replacement} in (UCEB1) → result out.
+				// PCRE2 lives host-side; this runs the real native regex_*.
+				String encoded;
+				self->hostcall_read(args[0].i32(), args[1].i32(), encoded);
+				DValue request;
+				String decode_error;
+				DValue response;
+				if(ucb_decode(encoded, request, &decode_error))
+				{
+					String op = request["op"].to_string();
+					String pattern = request["pattern"].to_string();
+					String subject = request["subject"].to_string();
+					String flags = request["flags"].to_string();
+					if(op == "match")
+						response["bool"].set_bool(regex_match(pattern, subject, flags));
+					else if(op == "search")
+						response["tree"] = regex_search(pattern, subject, flags);
+					else if(op == "search_all")
+						response["tree"] = regex_search_all(pattern, subject, flags);
+					else if(op == "replace")
+						response["text"] = regex_replace(pattern, request["replacement"].to_string(), subject, flags);
+					else if(op == "split")
+						for(auto& part : regex_split(pattern, subject, flags))
+						{
+							DValue value;
+							value = part;
+							response["list"].push(value);
+						}
+				}
+				String out = ucb_encode(response);
+				u32 cap = (u32)args[3].i32();
+				int32_t buf = args[2].i32();
+				if(buf != 0 && cap >= out.size())
+					self->hostcall_write(buf, out);
+				results[0] = Val((int32_t)out.size());
+				return(std::monostate());
+			}));
 		if(mod == "env" && name == "uce_host_component_resolve")
 			return(add([self](Caller, Span<const Val> args, Span<Val> results) -> Result<std::monostate, Trap> {
 				String target, current, resolved;