diff --git a/nix-js/runtime-ts/src/builtins/conversion.ts b/nix-js/runtime-ts/src/builtins/conversion.ts
index a5efd81..0806b1e 100644
--- a/nix-js/runtime-ts/src/builtins/conversion.ts
+++ b/nix-js/runtime-ts/src/builtins/conversion.ts
@@ -32,8 +32,12 @@ export const toJSON = (e: NixValue): NixString => {
   return mkStringWithContext(string, context);
 };
 
-export const toXML = (_e: NixValue): never => {
-  throw new Error("Not implemented: toXML");
+export const toXML = (e: NixValue): NixString => {
+  const [xml, context] = Deno.core.ops.op_to_xml(force(e));
+  if (context.length === 0) {
+    return xml;
+  }
+  return mkStringWithContext(xml, new Set(context));
 };
 
 /**
diff --git a/nix-js/runtime-ts/src/types/global.d.ts b/nix-js/runtime-ts/src/types/global.d.ts
index 2015aad..7ba3c0d 100644
--- a/nix-js/runtime-ts/src/types/global.d.ts
+++ b/nix-js/runtime-ts/src/types/global.d.ts
@@ -60,6 +60,7 @@ declare global {
 
         function op_from_json(json: string): unknown;
         function op_from_toml(toml: string): unknown;
+        function op_to_xml(e: NixValue): [string, string[]];
 
         function op_finalize_derivation(input: {
           name: string;
diff --git a/nix-js/src/context.rs b/nix-js/src/context.rs
index 3ced860..2597051 100644
--- a/nix-js/src/context.rs
+++ b/nix-js/src/context.rs
@@ -119,8 +119,14 @@ impl Context {
             DERIVATION_NIX.to_string(),
         );
         let code = self.ctx.compile(source, None)?;
-        self.runtime
-            .eval(format!("Nix.builtins.derivation = {};Nix.builtins.storeDir=\"{}\"", code, self.get_store_dir()), &mut self.ctx)?;
+        self.runtime.eval(
+            format!(
+                "Nix.builtins.derivation = {};Nix.builtins.storeDir=\"{}\"",
+                code,
+                self.get_store_dir()
+            ),
+            &mut self.ctx,
+        )?;
         Ok(())
     }
 
diff --git a/nix-js/src/runtime.rs b/nix-js/src/runtime.rs
index 493b36e..e5bd710 100644
--- a/nix-js/src/runtime.rs
+++ b/nix-js/src/runtime.rs
@@ -73,6 +73,7 @@ fn runtime_extension<Ctx: RuntimeContext>() -> Extension {
         op_from_json(),
         op_from_toml(),
         op_finalize_derivation::<Ctx>(),
+        op_to_xml(),
     ];
     ops.extend(crate::fetcher::register_ops::<Ctx>());
 
@@ -193,7 +194,8 @@ impl<Ctx: RuntimeContext> Runtime<Ctx> {
 
     #[cfg(feature = "inspector")]
     pub(crate) fn wait_for_inspector_disconnect(&mut self) {
-        let _ = self.rt
+        let _ = self
+            .rt
             .block_on(self.js_runtime.run_event_loop(PollEventLoopOptions {
                 wait_for_inspector: true,
                 ..Default::default()
diff --git a/nix-js/src/runtime/ops.rs b/nix-js/src/runtime/ops.rs
index 34bc11c..b265e17 100644
--- a/nix-js/src/runtime/ops.rs
+++ b/nix-js/src/runtime/ops.rs
@@ -3,8 +3,7 @@ use std::str::FromStr;
 
 use hashbrown::hash_map::{Entry, HashMap};
 
-use deno_core::OpState;
-use deno_core::v8;
+use deno_core::{FromV8, OpState, v8};
 use regex::Regex;
 use rust_embed::Embed;
 
@@ -12,6 +11,8 @@ use super::{NixRuntimeError, OpStateExt, RuntimeContext};
 use crate::error::Source;
 use crate::store::Store as _;
 
+type Result<T> = std::result::Result<T, NixRuntimeError>;
+
 #[derive(Debug, Default)]
 pub(super) struct RegexCache {
     cache: HashMap<String, Regex>,
@@ -24,7 +25,7 @@ impl RegexCache {
         }
     }
 
-    fn get_regex(&mut self, pattern: &str) -> Result<Regex, regex::Error> {
+    fn get_regex(&mut self, pattern: &str) -> std::result::Result<Regex, regex::Error> {
         Ok(match self.cache.entry(pattern.to_string()) {
             Entry::Occupied(occupied) => occupied.get().clone(),
             Entry::Vacant(vacant) => {
@@ -44,7 +45,7 @@ pub(crate) struct CorePkgs;
 pub(super) fn op_import<Ctx: RuntimeContext>(
     state: &mut OpState,
     #[string] path: String,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     let _span = tracing::info_span!("op_import", path = %path).entered();
     let ctx: &mut Ctx = state.get_ctx_mut();
 
@@ -93,7 +94,7 @@ pub(super) fn op_scoped_import<Ctx: RuntimeContext>(
     state: &mut OpState,
     #[string] path: String,
     #[serde] scope: Vec<String>,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     let _span = tracing::info_span!("op_scoped_import", path = %path).entered();
     let ctx: &mut Ctx = state.get_ctx_mut();
 
@@ -119,7 +120,7 @@ pub(super) fn op_scoped_import<Ctx: RuntimeContext>(
 
 #[deno_core::op2]
 #[string]
-pub(super) fn op_read_file(#[string] path: String) -> std::result::Result<String, NixRuntimeError> {
+pub(super) fn op_read_file(#[string] path: String) -> Result<String> {
     Ok(std::fs::read_to_string(&path).map_err(|e| format!("Failed to read {}: {}", path, e))?)
 }
 
@@ -140,9 +141,7 @@ pub(super) fn op_path_exists(#[string] path: String) -> bool {
 
 #[deno_core::op2]
 #[string]
-pub(super) fn op_read_file_type(
-    #[string] path: String,
-) -> std::result::Result<String, NixRuntimeError> {
+pub(super) fn op_read_file_type(#[string] path: String) -> Result<String> {
     let path = Path::new(&path);
     let metadata = std::fs::symlink_metadata(path)
         .map_err(|e| format!("Failed to read file type for {}: {}", path.display(), e))?;
@@ -165,7 +164,7 @@ pub(super) fn op_read_file_type(
 #[serde]
 pub(super) fn op_read_dir(
     #[string] path: String,
-) -> std::result::Result<std::collections::HashMap<String, String>, NixRuntimeError> {
+) -> Result<std::collections::HashMap<String, String>> {
     let path = Path::new(&path);
 
     if !path.is_dir() {
@@ -210,7 +209,7 @@ pub(super) fn op_read_dir(
 pub(super) fn op_resolve_path(
     #[string] current_dir: String,
     #[string] path: String,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     let _span = tracing::debug_span!("op_resolve_path").entered();
     tracing::debug!(current_dir, path);
 
@@ -261,7 +260,7 @@ pub(super) fn op_make_placeholder(#[string] output: String) -> String {
 pub(super) fn op_decode_span<Ctx: RuntimeContext>(
     state: &mut OpState,
     #[string] span_str: String,
-) -> std::result::Result<serde_json::Value, NixRuntimeError> {
+) -> Result<serde_json::Value> {
     let parts: Vec<&str> = span_str.split(':').collect();
     if parts.len() != 3 {
         return Ok(serde_json::json!({
@@ -317,7 +316,7 @@ pub(super) struct ParsedHash {
 pub(super) fn op_parse_hash(
     #[string] hash_str: String,
     #[string] algo: Option<String>,
-) -> std::result::Result<ParsedHash, NixRuntimeError> {
+) -> Result<ParsedHash> {
     use nix_compat::nixhash::{HashAlgo, NixHash};
 
     let hash_algo = algo
@@ -347,7 +346,7 @@ pub(super) fn op_add_path<Ctx: RuntimeContext>(
     #[string] name: Option<String>,
     recursive: bool,
     #[string] sha256: Option<String>,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     use nix_compat::nixhash::{HashAlgo, NixHash};
     use sha2::{Digest, Sha256};
     use std::fs;
@@ -423,7 +422,7 @@ pub(super) fn op_add_path<Ctx: RuntimeContext>(
 pub(super) fn op_store_path<Ctx: RuntimeContext>(
     state: &mut OpState,
     #[string] path: String,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     use crate::store::validate_store_path;
 
     let ctx: &Ctx = state.get_ctx();
@@ -446,7 +445,7 @@ pub(super) fn op_to_file<Ctx: RuntimeContext>(
     #[string] name: String,
     #[string] contents: String,
     #[serde] references: Vec<String>,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     let ctx: &Ctx = state.get_ctx();
     let store = ctx.get_store();
     let store_path = store
@@ -461,7 +460,7 @@ pub(super) fn op_to_file<Ctx: RuntimeContext>(
 pub(super) fn op_copy_path_to_store<Ctx: RuntimeContext>(
     state: &mut OpState,
     #[string] path: String,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     use std::path::Path;
 
     let path_obj = Path::new(&path);
@@ -490,7 +489,7 @@ pub(super) fn op_copy_path_to_store<Ctx: RuntimeContext>(
 
 #[deno_core::op2]
 #[string]
-pub(super) fn op_get_env(#[string] key: String) -> std::result::Result<String, NixRuntimeError> {
+pub(super) fn op_get_env(#[string] key: String) -> Result<String> {
     match std::env::var(key) {
         Ok(val) => Ok(val),
         Err(std::env::VarError::NotPresent) => Ok("".into()),
@@ -500,14 +499,12 @@ pub(super) fn op_get_env(#[string] key: String) -> std::result::Result<String, N
 
 #[deno_core::op2]
 #[serde]
-pub(super) fn op_walk_dir(
-    #[string] path: String,
-) -> std::result::Result<Vec<(String, String)>, NixRuntimeError> {
+pub(super) fn op_walk_dir(#[string] path: String) -> Result<Vec<(String, String)>> {
     fn walk_recursive(
         base: &Path,
         current: &Path,
         results: &mut Vec<(String, String)>,
-    ) -> std::result::Result<(), NixRuntimeError> {
+    ) -> Result<()> {
         let entries = std::fs::read_dir(current)
             .map_err(|e| NixRuntimeError::from(format!("failed to read directory: {}", e)))?;
 
@@ -564,7 +561,7 @@ pub(super) fn op_add_filtered_path<Ctx: RuntimeContext>(
     recursive: bool,
     #[string] sha256: Option<String>,
     #[serde] include_paths: Vec<String>,
-) -> std::result::Result<String, NixRuntimeError> {
+) -> Result<String> {
     use nix_compat::nixhash::{HashAlgo, NixHash};
     use sha2::{Digest, Sha256};
     use std::fs;
@@ -667,7 +664,7 @@ pub(super) fn op_match(
     state: &mut OpState,
     #[string] regex: String,
     #[string] text: String,
-) -> std::result::Result<Option<Vec<Option<String>>>, NixRuntimeError> {
+) -> Result<Option<Vec<Option<String>>>> {
     let cache = state.borrow_mut::<RegexCache>();
     let re = cache
         .get_regex(&format!("^{}$", regex))
@@ -692,7 +689,7 @@ pub(super) fn op_split(
     state: &mut OpState,
     #[string] regex: String,
     #[string] text: String,
-) -> std::result::Result<Vec<SplitResult>, NixRuntimeError> {
+) -> Result<Vec<SplitResult>> {
     let cache = state.borrow_mut::<RegexCache>();
     let re = cache
         .get_regex(&regex)
@@ -741,41 +738,39 @@ pub(super) enum NixJsonValue {
 }
 
 impl<'a> deno_core::convert::ToV8<'a> for NixJsonValue {
-    type Error = deno_error::JsErrorBox;
+    type Error = NixRuntimeError;
 
     fn to_v8<'i>(
         self,
         scope: &mut v8::PinScope<'a, 'i>,
     ) -> std::result::Result<v8::Local<'a, v8::Value>, Self::Error> {
-        match self {
-            Self::Null => Ok(v8::null(scope).into()),
-            Self::Bool(b) => Ok(v8::Boolean::new(scope, b).into()),
-            Self::Int(i) => Ok(v8::BigInt::new_from_i64(scope, i).into()),
-            Self::Float(f) => Ok(v8::Number::new(scope, f).into()),
+        Ok(match self {
+            Self::Null => v8::null(scope).into() ,
+            Self::Bool(b) => v8::Boolean::new(scope, b).into() ,
+            Self::Int(i) => v8::BigInt::new_from_i64(scope, i).into() ,
+            Self::Float(f) => v8::Number::new(scope, f).into() ,
             Self::Str(s) => v8::String::new(scope, &s)
                 .map(|s| s.into())
-                .ok_or_else(|| deno_error::JsErrorBox::type_error("failed to create v8 string")),
+                .ok_or("failed to create v8 string")?,
             Self::Arr(arr) => {
                 let elements = arr
                     .into_iter()
                     .map(|v| v.to_v8(scope))
                     .collect::<std::result::Result<Vec<_>, _>>()?;
-                Ok(v8::Array::new_with_elements(scope, &elements).into())
+                v8::Array::new_with_elements(scope, &elements).into() 
             }
             Self::Obj(entries) => {
                 let obj = v8::Object::new(scope);
                 for (k, v) in entries {
                     let key: v8::Local<v8::Value> = v8::String::new(scope, &k)
-                        .ok_or_else(|| {
-                            deno_error::JsErrorBox::type_error("failed to create v8 string")
-                        })?
+                        .ok_or("failed to create v8 string")?
                         .into();
                     let val = v.to_v8(scope)?;
                     obj.set(scope, key, val);
                 }
-                Ok(obj.into())
+                obj.into() 
             }
-        }
+        })
     }
 }
 
@@ -815,7 +810,7 @@ impl DrvHashCache {
     }
 }
 
-fn toml_to_nix(value: toml::Value) -> std::result::Result<NixJsonValue, NixRuntimeError> {
+fn toml_to_nix(value: toml::Value) -> Result<NixJsonValue> {
     match value {
         toml::Value::String(s) => Ok(NixJsonValue::Str(s)),
         toml::Value::Integer(i) => Ok(NixJsonValue::Int(i)),
@@ -839,18 +834,14 @@ fn toml_to_nix(value: toml::Value) -> std::result::Result<NixJsonValue, NixRunti
 }
 
 #[deno_core::op2]
-pub(super) fn op_from_json(
-    #[string] json_str: String,
-) -> std::result::Result<NixJsonValue, NixRuntimeError> {
+pub(super) fn op_from_json(#[string] json_str: String) -> Result<NixJsonValue> {
     let parsed: serde_json::Value = serde_json::from_str(&json_str)
         .map_err(|e| NixRuntimeError::from(format!("builtins.fromJSON: {e}")))?;
     Ok(json_to_nix(parsed))
 }
 
 #[deno_core::op2]
-pub(super) fn op_from_toml(
-    #[string] toml_str: String,
-) -> std::result::Result<NixJsonValue, NixRuntimeError> {
+pub(super) fn op_from_toml(#[string] toml_str: String) -> Result<NixJsonValue> {
     let parsed: toml::Value = toml::from_str(&toml_str)
         .map_err(|e| NixRuntimeError::from(format!("while parsing TOML: {e}")))?;
     toml_to_nix(parsed)
@@ -898,7 +889,7 @@ fn output_path_name(drv_name: &str, output: &str) -> String {
 pub(super) fn op_finalize_derivation<Ctx: RuntimeContext>(
     state: &mut OpState,
     #[serde] input: FinalizeDerivationInput,
-) -> std::result::Result<FinalizeDerivationOutput, NixRuntimeError> {
+) -> Result<FinalizeDerivationOutput> {
     use crate::derivation::{DerivationData, OutputInfo};
     use crate::string_context::extract_input_drvs_and_srcs;
 
@@ -1104,10 +1095,7 @@ fn op_make_fixed_output_path_impl(
 
 #[deno_core::op2]
 #[string]
-pub(super) fn op_hash_string(
-    #[string] algo: String,
-    #[string] data: String,
-) -> std::result::Result<String, NixRuntimeError> {
+pub(super) fn op_hash_string(#[string] algo: String, #[string] data: String) -> Result<String> {
     use sha2::{Digest, Sha256, Sha512};
 
     let hash_bytes: Vec<u8> = match algo.as_str() {
@@ -1144,10 +1132,7 @@ pub(super) fn op_hash_string(
 
 #[deno_core::op2]
 #[string]
-pub(super) fn op_hash_file(
-    #[string] algo: String,
-    #[string] path: String,
-) -> std::result::Result<String, NixRuntimeError> {
+pub(super) fn op_hash_file(#[string] algo: String, #[string] path: String) -> Result<String> {
     let data = std::fs::read(&path)
         .map_err(|e| NixRuntimeError::from(format!("cannot read '{}': {}", path, e)))?;
 
@@ -1187,9 +1172,7 @@ pub(super) fn op_hash_file(
 
 #[deno_core::op2]
 #[string]
-pub(super) fn op_convert_hash(
-    #[serde] input: ConvertHashInput,
-) -> std::result::Result<String, NixRuntimeError> {
+pub(super) fn op_convert_hash(#[serde] input: ConvertHashInput) -> Result<String> {
     use nix_compat::nixhash::{HashAlgo, NixHash};
 
     let hash_algo = input
@@ -1229,3 +1212,540 @@ pub(super) struct ConvertHashInput {
     #[serde(rename = "toHashFormat")]
     to_format: String,
 }
+
+struct XmlCtx<'s> {
+    force_fn: v8::Local<'s, v8::Function>,
+    is_thunk: v8::Local<'s, v8::Symbol>,
+    has_context: v8::Local<'s, v8::Symbol>,
+    is_path: v8::Local<'s, v8::Symbol>,
+    primop_meta: v8::Local<'s, v8::Symbol>,
+}
+
+impl<'s> XmlCtx<'s> {
+    fn new<'i>(
+        scope: &mut v8::PinScope<'s, 'i>,
+        nix_obj: v8::Local<'s, v8::Object>,
+    ) -> Result<Self> {
+        let get_fn = |scope: &v8::PinScope<'s, 'i>, name: &str| {
+            let key = v8::String::new(scope, name).ok_or("v8 string" )?;
+            let val = nix_obj
+                .get(scope, key.into())
+                .ok_or_else(|| format!("no {name}") )?;
+            v8::Local::<v8::Function>::try_from(val)
+                .map_err(|e| format!("{name} not function: {e}") )
+        };
+        let get_sym = |scope: &v8::PinScope<'s, 'i>, name: &str| {
+            let key = v8::String::new(scope, name).ok_or("v8 string" )?;
+            let val = nix_obj
+                .get(scope, key.into())
+                .ok_or_else(|| format!("no {name}") )?;
+            v8::Local::<v8::Symbol>::try_from(val).map_err(|e| format!("{name} not symbol: {e}") )
+        };
+        Ok(Self {
+            force_fn: get_fn(scope, "force")?,
+            is_thunk: get_sym(scope, "IS_THUNK")?,
+            has_context: get_sym(scope, "HAS_CONTEXT")?,
+            is_path: get_sym(scope, "IS_PATH")?,
+            primop_meta: get_sym(scope, "PRIMOP_METADATA")?,
+        })
+    }
+}
+
+struct XmlWriter {
+    buf: String,
+    context: Vec<String>,
+    drvs_seen: hashbrown::HashSet<String>,
+}
+
+impl XmlWriter {
+    fn new() -> Self {
+        Self {
+            buf: String::with_capacity(4096),
+            context: Vec::new(),
+            drvs_seen: hashbrown::HashSet::new(),
+        }
+    }
+
+    fn indent(&mut self, depth: usize) {
+        for _ in 0..depth {
+            self.buf.push_str("  ");
+        }
+    }
+
+    fn escape_attr(&mut self, s: &str) {
+        for ch in s.chars() {
+            match ch {
+                '"' => self.buf.push_str("&quot;"),
+                '<' => self.buf.push_str("&lt;"),
+                '>' => self.buf.push_str("&gt;"),
+                '&' => self.buf.push_str("&amp;"),
+                '\n' => self.buf.push_str("&#xA;"),
+                '\r' => self.buf.push_str("&#xD;"),
+                '\t' => self.buf.push_str("&#x9;"),
+                c => self.buf.push(c),
+            }
+        }
+    }
+
+    fn force<'s>(
+        &self,
+        val: v8::Local<'s, v8::Value>,
+        scope: &mut v8::PinScope<'s, '_>,
+        ctx: &XmlCtx<'s>,
+    ) -> Result<v8::Local<'s, v8::Value>> {
+        let undef = v8::undefined(scope);
+        ctx.force_fn
+            .call(scope, undef.into(), &[val])
+            .ok_or_else(|| ("force() threw an exception").into())
+    }
+
+    fn has_sym<'s>(
+        obj: v8::Local<'s, v8::Object>,
+        scope: &mut v8::PinScope<'s, '_>,
+        sym: v8::Local<'s, v8::Symbol>,
+    ) -> bool {
+        matches!(obj.get(scope, sym.into()), Some(v) if v.is_true())
+    }
+
+    fn extract_str<'s>(
+        &self,
+        val: v8::Local<'s, v8::Value>,
+        scope: &mut v8::PinScope<'s, '_>,
+        ctx: &XmlCtx<'s>,
+    ) -> Option<String> {
+        if val.is_string() {
+            return Some(val.to_rust_string_lossy(scope));
+        }
+        if val.is_object() {
+            let obj = val.to_object(scope)?;
+            if Self::has_sym(obj, scope, ctx.has_context) {
+                let key = v8::String::new(scope, "value")?;
+                let s = obj.get(scope, key.into())?;
+                return Some(s.to_rust_string_lossy(scope));
+            }
+        }
+        None
+    }
+
+    fn collect_context<'s>(
+        &mut self,
+        obj: v8::Local<'s, v8::Object>,
+        scope: &mut v8::PinScope<'s, '_>,
+    ) {
+        let context_key = match v8::String::new(scope, "context") {
+            Some(k) => k,
+            None => return,
+        };
+        let ctx_val = match obj.get(scope, context_key.into()) {
+            Some(v) => v,
+            None => return,
+        };
+        let global = scope.get_current_context().global(scope);
+        let array_key = match v8::String::new(scope, "Array") {
+            Some(k) => k,
+            None => return,
+        };
+        let array_obj = match global
+            .get(scope, array_key.into())
+            .and_then(|v| v.to_object(scope))
+        {
+            Some(o) => o,
+            None => return,
+        };
+        let from_key = match v8::String::new(scope, "from") {
+            Some(k) => k,
+            None => return,
+        };
+        let from_fn = match array_obj
+            .get(scope, from_key.into())
+            .and_then(|v| v8::Local::<v8::Function>::try_from(v).ok())
+        {
+            Some(f) => f,
+            None => return,
+        };
+        let arr_val = match from_fn.call(scope, array_obj.into(), &[ctx_val]) {
+            Some(v) => v,
+            None => return,
+        };
+        let arr = match v8::Local::<v8::Array>::try_from(arr_val) {
+            Ok(a) => a,
+            Err(_) => return,
+        };
+        for i in 0..arr.length() {
+            if let Some(elem) = arr.get_index(scope, i) {
+                self.context.push(elem.to_rust_string_lossy(scope));
+            }
+        }
+    }
+
+    fn is_derivation<'s>(obj: v8::Local<'s, v8::Object>, scope: &mut v8::PinScope<'s, '_>) -> bool {
+        let key = match v8::String::new(scope, "type") {
+            Some(k) => k,
+            None => return false,
+        };
+        match obj.get(scope, key.into()) {
+            Some(v) if v.is_string() => v.to_rust_string_lossy(scope) == "derivation",
+            _ => false,
+        }
+    }
+
+    fn write_value<'s>(
+        &mut self,
+        val: v8::Local<'s, v8::Value>,
+        scope: &mut v8::PinScope<'s, '_>,
+        ctx: &XmlCtx<'s>,
+        depth: usize,
+    ) -> Result<()> {
+        let val = self.force(val, scope, ctx)?;
+
+        if val.is_null() {
+            self.indent(depth);
+            self.buf.push_str("<null />\n");
+            return Ok(());
+        }
+        if val.is_true() {
+            self.indent(depth);
+            self.buf.push_str("<bool value=\"true\" />\n");
+            return Ok(());
+        }
+        if val.is_false() {
+            self.indent(depth);
+            self.buf.push_str("<bool value=\"false\" />\n");
+            return Ok(());
+        }
+        if val.is_big_int() {
+            let bi = val.to_big_int(scope).ok_or("bigint" )?;
+            let (i, _) = bi.i64_value();
+            self.indent(depth);
+            self.buf.push_str("<int value=\"");
+            self.buf.push_str(&i.to_string());
+            self.buf.push_str("\" />\n");
+            return Ok(());
+        }
+        if val.is_number() {
+            let n = val.number_value(scope).ok_or("number" )?;
+            self.indent(depth);
+            self.buf.push_str("<float value=\"");
+            self.buf.push_str(&format!("{}", n));
+            self.buf.push_str("\" />\n");
+            return Ok(());
+        }
+        if val.is_string() {
+            let s = val.to_rust_string_lossy(scope);
+            self.indent(depth);
+            self.buf.push_str("<string value=\"");
+            self.escape_attr(&s);
+            self.buf.push_str("\" />\n");
+            return Ok(());
+        }
+        if val.is_array() {
+            let arr = v8::Local::<v8::Array>::try_from(val).map_err(|e| e.to_string() )?;
+            self.indent(depth);
+            self.buf.push_str("<list>\n");
+            for i in 0..arr.length() {
+                let elem = arr.get_index(scope, i).ok_or("array elem" )?;
+                self.write_value(elem, scope, ctx, depth + 1)?;
+            }
+            self.indent(depth);
+            self.buf.push_str("</list>\n");
+            return Ok(());
+        }
+        if val.is_function() {
+            return self.write_function(val, scope, ctx, depth);
+        }
+        if val.is_object() {
+            let obj = val.to_object(scope).ok_or("to_object" )?;
+
+            if Self::has_sym(obj, scope, ctx.has_context) {
+                let key = v8::String::new(scope, "value").ok_or("v8 str" )?;
+                let s = obj
+                    .get(scope, key.into())
+                    .ok_or("value" )?
+                    .to_rust_string_lossy(scope);
+                self.collect_context(obj, scope);
+                self.indent(depth);
+                self.buf.push_str("<string value=\"");
+                self.escape_attr(&s);
+                self.buf.push_str("\" />\n");
+                return Ok(());
+            }
+            if Self::has_sym(obj, scope, ctx.is_path) {
+                let key = v8::String::new(scope, "value").ok_or("v8 str" )?;
+                let s = obj
+                    .get(scope, key.into())
+                    .ok_or("value" )?
+                    .to_rust_string_lossy(scope);
+                self.indent(depth);
+                self.buf.push_str("<path value=\"");
+                self.escape_attr(&s);
+                self.buf.push_str("\" />\n");
+                return Ok(());
+            }
+            if Self::has_sym(obj, scope, ctx.is_thunk) {
+                self.indent(depth);
+                self.buf.push_str("<unevaluated />\n");
+                return Ok(());
+            }
+
+            return self.write_attrs(obj, scope, ctx, depth);
+        }
+
+        self.indent(depth);
+        self.buf.push_str("<unevaluated />\n");
+        Ok(())
+    }
+
+    fn write_attrs<'s>(
+        &mut self,
+        obj: v8::Local<'s, v8::Object>,
+        scope: &mut v8::PinScope<'s, '_>,
+        ctx: &XmlCtx<'s>,
+        depth: usize,
+    ) -> Result<()> {
+        if Self::is_derivation(obj, scope) {
+            self.indent(depth);
+            self.buf.push_str("<derivation");
+
+            let drv_path_key = v8::String::new(scope, "drvPath").ok_or("v8 str" )?;
+            let drv_str = if let Some(drv_val) = obj.get(scope, drv_path_key.into()) {
+                let forced = self.force(drv_val, scope, ctx)?;
+                let s = self.extract_str(forced, scope, ctx);
+                if let Some(ref s) = s {
+                    self.buf.push_str(" drvPath=\"");
+                    self.escape_attr(s);
+                    self.buf.push('"');
+                }
+                s
+            } else {
+                None
+            };
+
+            let out_path_key = v8::String::new(scope, "outPath").ok_or("v8 str" )?;
+            if let Some(out_val) = obj.get(scope, out_path_key.into()) {
+                let forced = self.force(out_val, scope, ctx)?;
+                if let Some(ref s) = self.extract_str(forced, scope, ctx) {
+                    self.buf.push_str(" outPath=\"");
+                    self.escape_attr(s);
+                    self.buf.push('"');
+                }
+            }
+
+            self.buf.push_str(">\n");
+
+            let is_repeated = if let Some(ref dp) = drv_str {
+                !self.drvs_seen.insert(dp.clone())
+            } else {
+                false
+            };
+
+            if is_repeated {
+                self.indent(depth + 1);
+                self.buf.push_str("<repeated />\n");
+            } else {
+                self.write_attrs_sorted(obj, scope, ctx, depth + 1)?;
+            }
+
+            self.indent(depth);
+            self.buf.push_str("</derivation>\n");
+        } else {
+            self.indent(depth);
+            self.buf.push_str("<attrs>\n");
+            self.write_attrs_sorted(obj, scope, ctx, depth + 1)?;
+            self.indent(depth);
+            self.buf.push_str("</attrs>\n");
+        }
+        Ok(())
+    }
+
+    fn write_attrs_sorted<'s>(
+        &mut self,
+        obj: v8::Local<'s, v8::Object>,
+        scope: &mut v8::PinScope<'s, '_>,
+        ctx: &XmlCtx<'s>,
+        depth: usize,
+    ) -> Result<()> {
+        let keys = obj
+            .get_own_property_names(scope, v8::GetPropertyNamesArgsBuilder::new().build())
+            .ok_or("property names" )?;
+
+        let mut key_strings: Vec<String> = Vec::with_capacity(keys.length() as usize);
+        for i in 0..keys.length() {
+            let key = keys.get_index(scope, i).ok_or("key index" )?;
+            key_strings.push(key.to_rust_string_lossy(scope));
+        }
+        key_strings.sort();
+
+        for key_str in &key_strings {
+            let v8_key = v8::String::new(scope, key_str).ok_or("v8 str" )?;
+            let val = obj
+                .get(scope, v8_key.into())
+                .ok_or("attr value" )?;
+
+            self.indent(depth);
+            self.buf.push_str("<attr name=\"");
+            self.escape_attr(key_str);
+            self.buf.push_str("\">\n");
+
+            self.write_value(val, scope, ctx, depth + 1)?;
+
+            self.indent(depth);
+            self.buf.push_str("</attr>\n");
+        }
+        Ok(())
+    }
+
+    fn write_function<'s>(
+        &mut self,
+        val: v8::Local<'s, v8::Value>,
+        scope: &mut v8::PinScope<'s, '_>,
+        ctx: &XmlCtx<'s>,
+        depth: usize,
+    ) -> Result<()> {
+        let obj = val.to_object(scope).ok_or("fn to_object" )?;
+
+        if let Some(meta) = obj.get(scope, ctx.primop_meta.into())
+            && meta.is_object()
+            && !meta.is_null_or_undefined()
+        {
+            self.indent(depth);
+            self.buf.push_str("<unevaluated />\n");
+            return Ok(());
+        }
+
+        let args_key = v8::String::new(scope, "args").ok_or("v8 str" )?;
+        let args_val = obj.get(scope, args_key.into());
+
+        match args_val {
+            Some(args) if args.is_object() && !args.is_null_or_undefined() => {
+                let args_obj = args.to_object(scope).ok_or("args to_object" )?;
+
+                let req_key = v8::String::new(scope, "required").ok_or("v8 str" )?;
+                let opt_key = v8::String::new(scope, "optional").ok_or("v8 str" )?;
+                let ellipsis_key = v8::String::new(scope, "ellipsis").ok_or("v8 str" )?;
+
+                let mut all_formals: Vec<String> = Vec::new();
+                if let Some(req) = args_obj.get(scope, req_key.into())
+                    && let Ok(arr) = v8::Local::<v8::Array>::try_from(req)
+                {
+                    for i in 0..arr.length() {
+                        if let Some(elem) = arr.get_index(scope, i) {
+                            all_formals.push(elem.to_rust_string_lossy(scope));
+                        }
+                    }
+                }
+                if let Some(opt) = args_obj.get(scope, opt_key.into())
+                    && let Ok(arr) = v8::Local::<v8::Array>::try_from(opt)
+                {
+                    for i in 0..arr.length() {
+                        if let Some(elem) = arr.get_index(scope, i) {
+                            all_formals.push(elem.to_rust_string_lossy(scope));
+                        }
+                    }
+                }
+                all_formals.sort();
+
+                let has_ellipsis = matches!(
+                    args_obj.get(scope, ellipsis_key.into()),
+                    Some(v) if v.is_true()
+                );
+
+                self.indent(depth);
+                self.buf.push_str("<function>\n");
+                self.indent(depth + 1);
+                if has_ellipsis {
+                    self.buf.push_str("<attrspat ellipsis=\"1\">\n");
+                } else {
+                    self.buf.push_str("<attrspat>\n");
+                }
+                for formal in &all_formals {
+                    self.indent(depth + 2);
+                    self.buf.push_str("<attr name=\"");
+                    self.escape_attr(formal);
+                    self.buf.push_str("\" />\n");
+                }
+                self.indent(depth + 1);
+                self.buf.push_str("</attrspat>\n");
+                self.indent(depth);
+                self.buf.push_str("</function>\n");
+            }
+            _ => {
+                let source = val
+                    .to_detail_string(scope)
+                    .map(|s| s.to_rust_string_lossy(scope));
+                let param = source.as_deref().and_then(extract_lambda_param);
+                self.indent(depth);
+                self.buf.push_str("<function>\n");
+                self.indent(depth + 1);
+                self.buf.push_str("<varpat name=\"");
+                self.buf.push_str(param.unwrap_or("x"));
+                self.buf.push_str("\" />\n");
+                self.indent(depth);
+                self.buf.push_str("</function>\n");
+            }
+        }
+        Ok(())
+    }
+}
+
+fn extract_lambda_param(source: &str) -> Option<&str> {
+    let s = source.trim();
+    let arrow_pos = s.find("=>")?;
+    let before = s[..arrow_pos].trim();
+    if before.starts_with('(') && before.ends_with(')') {
+        let inner = before[1..before.len() - 1].trim();
+        if !inner.is_empty() && !inner.contains(',') {
+            return Some(inner);
+        }
+    } else if !before.is_empty()
+        && !before.contains(' ')
+        && !before.contains('(')
+        && before
+            .chars()
+            .all(|c| c.is_alphanumeric() || c == '_' || c == '$')
+    {
+        return Some(before);
+    }
+    None
+}
+
+pub(super) struct ToXmlResult {
+    pub xml: String,
+    pub context: Vec<String>,
+}
+
+impl<'a> FromV8<'a> for ToXmlResult {
+    type Error = NixRuntimeError;
+
+    fn from_v8(
+        scope: &mut v8::PinScope<'a, '_>,
+        value: v8::Local<'a, v8::Value>,
+    ) -> std::result::Result<Self, Self::Error> {
+        let global = scope.get_current_context().global(scope);
+        let nix_key = v8::String::new(scope, "Nix").ok_or("v8 string" )?;
+        let nix_obj = global
+            .get(scope, nix_key.into())
+            .ok_or("no Nix global" )?
+            .to_object(scope)
+            .ok_or("Nix not object" )?;
+
+        let ctx = XmlCtx::new(scope, nix_obj)?;
+
+        let mut writer = XmlWriter::new();
+        writer
+            .buf
+            .push_str("<?xml version='1.0' encoding='utf-8'?>\n<expr>\n");
+        writer.write_value(value, scope, &ctx, 1)?;
+        writer.buf.push_str("</expr>\n");
+
+        Ok(ToXmlResult {
+            xml: writer.buf,
+            context: writer.context,
+        })
+    }
+}
+
+#[deno_core::op2]
+#[serde]
+pub(super) fn op_to_xml(#[scoped] value: ToXmlResult) -> (String, Vec<String>) {
+    (value.xml, value.context)
+}
diff --git a/nix-js/tests/lang.rs b/nix-js/tests/lang.rs
index 666784f..96ce500 100644
--- a/nix-js/tests/lang.rs
+++ b/nix-js/tests/lang.rs
@@ -241,14 +241,8 @@ eval_okay_test!(
     tail_call_1
 );
 eval_okay_test!(tojson);
-eval_okay_test!(
-    #[ignore = "not implemented: toXML"]
-    toxml
-);
-eval_okay_test!(
-    #[ignore = "not implemented: toXML"]
-    toxml2
-);
+eval_okay_test!(toxml);
+eval_okay_test!(toxml2);
 eval_okay_test!(tryeval);
 eval_okay_test!(types);
 eval_okay_test!(versions);