diff --git a/nix-js/runtime-ts/src/builtins/derivation.ts b/nix-js/runtime-ts/src/builtins/derivation.ts
index 5f9220e..944c3d9 100644
--- a/nix-js/runtime-ts/src/builtins/derivation.ts
+++ b/nix-js/runtime-ts/src/builtins/derivation.ts
@@ -107,6 +107,13 @@ const extractArgs = (attrs: NixAttrs, outContext: NixStringContext): string[] =>
   return argsList.map((a) => coerceToString(a, StringCoercionMode.ToString, true, outContext));
 };
 
+const outputPathName = (drvName: string, output: string) => {
+  if (output === "out") {
+    return drvName
+  }
+  return `${drvName}-${output}`
+}
+
 const structuredAttrsExcludedKeys = new Set([
   "__structuredAttrs",
   "__ignoreNulls",
@@ -296,7 +303,7 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
   let drvPath: string;
 
   if (fixedOutputInfo) {
-    const pathName = Deno.core.ops.op_output_path_name(drvName, "out");
+    const pathName = outputPathName(drvName, "out");
     const outPath = Deno.core.ops.op_make_fixed_output_path(
       fixedOutputInfo.hashAlgo,
       fixedOutputInfo.hash,
@@ -374,7 +381,7 @@ export const derivationStrict = (args: NixValue): NixAttrs => {
 
     outputInfos = new Map<string, OutputInfo>();
     for (const outputName of outputs) {
-      const pathName = Deno.core.ops.op_output_path_name(drvName, outputName);
+      const pathName = outputPathName(drvName, outputName);
       const outPath = Deno.core.ops.op_make_store_path(`output:${outputName}`, drvModuloHash, pathName);
       outputInfos.set(outputName, {
         path: outPath,
diff --git a/nix-js/runtime-ts/src/builtins/io.ts b/nix-js/runtime-ts/src/builtins/io.ts
index ca2433c..5a3bc20 100644
--- a/nix-js/runtime-ts/src/builtins/io.ts
+++ b/nix-js/runtime-ts/src/builtins/io.ts
@@ -19,6 +19,7 @@ import { getPathValue } from "../path";
 import type { NixStringContext, StringWithContext } from "../string-context";
 import { mkStringWithContext } from "../string-context";
 import { isAttrs, isPath } from "./type-check";
+import { baseNameOf } from "./path";
 
 const importCache = new Map<string, NixValue>();
 
@@ -108,14 +109,6 @@ export interface FetchGitResult {
   nar_hash: string | null;
 }
 
-export interface FetchHgResult {
-  out_path: string;
-  branch: string;
-  rev: string;
-  short_rev: string;
-  rev_count: number;
-}
-
 const normalizeUrlInput = (
   args: NixValue,
 ): { url: string; hash?: string; name?: string; executable?: boolean } => {
@@ -139,15 +132,25 @@ const normalizeUrlInput = (
 const normalizeTarballInput = (args: NixValue): { url: string; sha256?: string; name?: string } => {
   const forced = force(args);
   if (isAttrs(forced)) {
-    const url = forceStringNoCtx(forced.url);
+    const url = resolvePseudoUrl(forceStringNoCtx(forced.url));
     const sha256 = "sha256" in forced ? forceStringNoCtx(forced.sha256) : undefined;
-    const name = "name" in forced ? forceStringNoCtx(forced.name) : undefined;
+    const nameRaw = "name" in forced ? forceStringNoCtx(forced.name) : undefined;
+    // FIXME: extract baseNameOfRaw
+    const name = nameRaw === "" ? baseNameOf(nameRaw) as string : nameRaw;
     return { url, sha256, name };
   } else {
     return { url: forceStringNoCtx(forced) };
   }
 };
 
+const resolvePseudoUrl = (url: string) => {
+  if (url.startsWith("channel:")) {
+    return `https://channels.nixos.org/${url.substring(8)}/nixexprs.tar.xz`
+  } else {
+    return url
+  }
+}
+
 export const fetchurl = (args: NixValue): string => {
   const { url, hash, name, executable } = normalizeUrlInput(args);
   const result: FetchUrlResult = Deno.core.ops.op_fetch_url(
@@ -212,21 +215,8 @@ export const fetchGit = (args: NixValue): NixAttrs => {
   };
 };
 
-export const fetchMercurial = (args: NixValue): NixAttrs => {
-  const attrs = forceAttrs(args);
-  const url = forceStringValue(attrs.url);
-  const rev = "rev" in attrs ? forceStringValue(attrs.rev) : null;
-  const name = "name" in attrs ? forceStringValue(attrs.name) : null;
-
-  const result: FetchHgResult = Deno.core.ops.op_fetch_hg(url, rev, name);
-
-  return {
-    outPath: result.out_path,
-    branch: result.branch,
-    rev: result.rev,
-    shortRev: result.short_rev,
-    revCount: BigInt(result.rev_count),
-  };
+export const fetchMercurial = (_args: NixValue): NixAttrs => {
+  throw new Error("Not implemented: fetchMercurial")
 };
 
 export const fetchTree = (args: NixValue): NixAttrs => {
diff --git a/nix-js/runtime-ts/src/builtins/misc.ts b/nix-js/runtime-ts/src/builtins/misc.ts
index 2896712..de2bdff 100644
--- a/nix-js/runtime-ts/src/builtins/misc.ts
+++ b/nix-js/runtime-ts/src/builtins/misc.ts
@@ -41,6 +41,7 @@ export const hasContext = context.hasContext;
 export const hashFile =
   (type: NixValue) =>
   (p: NixValue): never => {
+    const ty = forceStringNoCtx(type);
     throw new Error("Not implemented: hashFile");
   };
 
diff --git a/nix-js/runtime-ts/src/builtins/path.ts b/nix-js/runtime-ts/src/builtins/path.ts
index 965601d..f46db90 100644
--- a/nix-js/runtime-ts/src/builtins/path.ts
+++ b/nix-js/runtime-ts/src/builtins/path.ts
@@ -25,36 +25,6 @@ import { mkStringWithContext, type NixStringContext } from "../string-context";
  * - baseNameOf "foo" → "foo"
  */
 export const baseNameOf = (s: NixValue): NixString => {
-  const forced = force(s);
-
-  // Path input → string output (no context)
-  if (isNixPath(forced)) {
-    const pathStr = forced.value;
-
-    if (pathStr.length === 0) {
-      return "";
-    }
-
-    let last = pathStr.length - 1;
-    if (pathStr[last] === "/" && last > 0) {
-      last -= 1;
-    }
-
-    let pos = last;
-    while (pos >= 0 && pathStr[pos] !== "/") {
-      pos -= 1;
-    }
-
-    if (pos === -1) {
-      pos = 0;
-    } else {
-      pos += 1;
-    }
-
-    return pathStr.substring(pos, last + 1);
-  }
-
-  // String input → string output (preserve context)
   const context: NixStringContext = new Set();
   const pathStr = coerceToString(s, StringCoercionMode.Base, false, context);
 
diff --git a/nix-js/runtime-ts/src/types/global.d.ts b/nix-js/runtime-ts/src/types/global.d.ts
index 72fb844..fce683b 100644
--- a/nix-js/runtime-ts/src/types/global.d.ts
+++ b/nix-js/runtime-ts/src/types/global.d.ts
@@ -21,7 +21,6 @@ declare global {
           column: number | null;
         };
         function op_make_store_path(ty: string, hash_hex: string, name: string): string;
-        function op_output_path_name(drv_name: string, output_name: string): string;
         function op_parse_hash(hash_str: string, algo: string | null): { hex: string; algo: string };
         function op_make_fixed_output_path(
           hash_algo: string,
@@ -49,7 +48,6 @@ declare global {
           all_refs: boolean,
           name: string | null,
         ): FetchGitResult;
-        function op_fetch_hg(url: string, rev: string | null, name: string | null): FetchHgResult;
         function op_add_path(
           path: string,
           name: string | null,
diff --git a/nix-js/src/fetcher.rs b/nix-js/src/fetcher.rs
index 5d2cded..5ed3a9b 100644
--- a/nix-js/src/fetcher.rs
+++ b/nix-js/src/fetcher.rs
@@ -13,7 +13,6 @@ mod archive;
 pub(crate) mod cache;
 mod download;
 mod git;
-mod hg;
 mod metadata_cache;
 
 pub use cache::FetcherCache;
@@ -47,15 +46,6 @@ pub struct FetchGitResult {
     pub nar_hash: Option<String>,
 }
 
-#[derive(Serialize)]
-pub struct FetchHgResult {
-    pub out_path: String,
-    pub branch: String,
-    pub rev: String,
-    pub short_rev: String,
-    pub rev_count: u64,
-}
-
 #[op2]
 #[serde]
 pub fn op_fetch_url<Ctx: RuntimeContext>(
@@ -119,7 +109,7 @@ pub fn op_fetch_url<Ctx: RuntimeContext>(
 
     info!(bytes = data.len(), "Download complete");
 
-    let hash = crate::nix_utils::sha256_hex(&String::from_utf8_lossy(&data));
+    let hash = crate::nix_utils::sha256_hex(&data);
 
     if let Some(ref expected) = expected_hash {
         let normalized_expected = normalize_hash(expected);
@@ -228,9 +218,7 @@ pub fn op_fetch_tarball<Ctx: RuntimeContext>(
     info!(bytes = data.len(), "Download complete");
 
     info!("Extracting tarball");
-    let cache = FetcherCache::new().map_err(|e| NixRuntimeError::from(e.to_string()))?;
-    let (extracted_path, _temp_dir) = cache
-        .extract_tarball_to_temp(&data)
+    let (extracted_path, _temp_dir) = archive::extract_tarball_to_temp(&data)
         .map_err(|e| NixRuntimeError::from(e.to_string()))?;
 
     info!("Computing NAR hash");
@@ -311,20 +299,6 @@ pub fn op_fetch_git<Ctx: RuntimeContext>(
     .map_err(|e| NixRuntimeError::from(e.to_string()))
 }
 
-#[op2]
-#[serde]
-pub fn op_fetch_hg(
-    #[string] url: String,
-    #[string] rev: Option<String>,
-    #[string] name: Option<String>,
-) -> Result<FetchHgResult, NixRuntimeError> {
-    let cache = FetcherCache::new().map_err(|e| NixRuntimeError::from(e.to_string()))?;
-    let dir_name = name.unwrap_or_else(|| "source".to_string());
-
-    hg::fetch_hg(&cache, &url, rev.as_deref(), &dir_name)
-        .map_err(|e| NixRuntimeError::from(e.to_string()))
-}
-
 fn normalize_hash(hash: &str) -> String {
     use base64::prelude::*;
     if hash.starts_with("sha256-")
@@ -341,6 +315,5 @@ pub fn register_ops<Ctx: RuntimeContext>() -> Vec<deno_core::OpDecl> {
         op_fetch_url::<Ctx>(),
         op_fetch_tarball::<Ctx>(),
         op_fetch_git::<Ctx>(),
-        op_fetch_hg(),
     ]
 }
diff --git a/nix-js/src/fetcher/archive.rs b/nix-js/src/fetcher/archive.rs
index 58f3e03..5ee9fc2 100644
--- a/nix-js/src/fetcher/archive.rs
+++ b/nix-js/src/fetcher/archive.rs
@@ -1,5 +1,6 @@
 use std::fs::{self, File};
 use std::io::Cursor;
+use std::os::unix::ffi::OsStrExt;
 use std::path::{Path, PathBuf};
 
 use flate2::read::GzDecoder;
@@ -125,7 +126,7 @@ fn extract_zip(data: &[u8], dest: &Path) -> Result<(), ArchiveError> {
 fn strip_single_toplevel(temp_dir: &Path, dest: &Path) -> Result<PathBuf, ArchiveError> {
     let entries: Vec<_> = fs::read_dir(temp_dir)?
         .filter_map(|e| e.ok())
-        .filter(|e| !e.file_name().to_string_lossy().starts_with('.'))
+        .filter(|e| e.file_name().as_os_str().as_bytes()[0] != b'.')
         .collect();
 
     let source_dir = if entries.len() == 1 && entries[0].file_type()?.is_dir() {
@@ -182,6 +183,14 @@ fn copy_dir_recursive(src: &Path, dst: &Path) -> Result<(), std::io::Error> {
     Ok(())
 }
 
+pub fn extract_tarball_to_temp(
+    data: &[u8],
+) -> Result<(PathBuf, tempfile::TempDir), ArchiveError> {
+    let temp_dir = tempfile::tempdir()?;
+    let extracted_path = extract_archive(data, temp_dir.path())?;
+    Ok((extracted_path, temp_dir))
+}
+
 #[derive(Debug)]
 pub enum ArchiveError {
     IoError(std::io::Error),
diff --git a/nix-js/src/fetcher/cache.rs b/nix-js/src/fetcher/cache.rs
index 30567d6..4a41d97 100644
--- a/nix-js/src/fetcher/cache.rs
+++ b/nix-js/src/fetcher/cache.rs
@@ -1,37 +1,6 @@
 use std::fs;
 use std::path::PathBuf;
 
-use super::archive::ArchiveError;
-
-#[derive(Debug)]
-pub enum CacheError {
-    Io(std::io::Error),
-    Archive(ArchiveError),
-}
-
-impl std::fmt::Display for CacheError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            CacheError::Io(e) => write!(f, "I/O error: {}", e),
-            CacheError::Archive(e) => write!(f, "Archive error: {}", e),
-        }
-    }
-}
-
-impl std::error::Error for CacheError {}
-
-impl From<std::io::Error> for CacheError {
-    fn from(e: std::io::Error) -> Self {
-        CacheError::Io(e)
-    }
-}
-
-impl From<ArchiveError> for CacheError {
-    fn from(e: ArchiveError) -> Self {
-        CacheError::Archive(e)
-    }
-}
-
 #[derive(Debug)]
 pub struct FetcherCache {
     base_dir: PathBuf,
@@ -49,41 +18,12 @@ impl FetcherCache {
         Ok(Self { base_dir })
     }
 
-    pub fn make_store_path(&self, hash: &str, name: &str) -> PathBuf {
-        let short_hash = &hash[..32.min(hash.len())];
-        self.base_dir
-            .join("store")
-            .join(format!("{}-{}", short_hash, name))
-    }
-
     fn git_cache_dir(&self) -> PathBuf {
-        self.base_dir.join("gitv3")
-    }
-
-    fn hg_cache_dir(&self) -> PathBuf {
-        self.base_dir.join("hg")
-    }
-
-    fn hash_key(url: &str) -> String {
-        crate::nix_utils::sha256_hex(url)
+        self.base_dir.join("git")
     }
 
     pub fn get_git_bare(&self, url: &str) -> PathBuf {
-        let key = Self::hash_key(url);
+        let key = crate::nix_utils::sha256_hex(url.as_bytes());
         self.git_cache_dir().join(key)
     }
-
-    pub fn get_hg_bare(&self, url: &str) -> PathBuf {
-        let key = Self::hash_key(url);
-        self.hg_cache_dir().join(key)
-    }
-
-    pub fn extract_tarball_to_temp(
-        &self,
-        data: &[u8],
-    ) -> Result<(PathBuf, tempfile::TempDir), CacheError> {
-        let temp_dir = tempfile::tempdir()?;
-        let extracted_path = super::archive::extract_archive(data, temp_dir.path())?;
-        Ok((extracted_path, temp_dir))
-    }
 }
diff --git a/nix-js/src/fetcher/hg.rs b/nix-js/src/fetcher/hg.rs
deleted file mode 100644
index 711a401..0000000
--- a/nix-js/src/fetcher/hg.rs
+++ /dev/null
@@ -1,196 +0,0 @@
-use std::fs;
-use std::path::PathBuf;
-use std::process::Command;
-
-use super::FetchHgResult;
-use super::cache::FetcherCache;
-
-pub fn fetch_hg(
-    cache: &FetcherCache,
-    url: &str,
-    rev: Option<&str>,
-    name: &str,
-) -> Result<FetchHgResult, HgError> {
-    let bare_repo = cache.get_hg_bare(url);
-
-    if !bare_repo.exists() {
-        clone_repo(url, &bare_repo)?;
-    } else {
-        pull_repo(&bare_repo)?;
-    }
-
-    let target_rev = rev.unwrap_or("tip").to_string();
-    let resolved_rev = resolve_rev(&bare_repo, &target_rev)?;
-    let branch = get_branch(&bare_repo, &resolved_rev)?;
-
-    let checkout_dir = checkout_rev(&bare_repo, &resolved_rev, name, cache)?;
-
-    let rev_count = get_rev_count(&bare_repo, &resolved_rev)?;
-
-    let short_rev = if resolved_rev.len() >= 12 {
-        resolved_rev[..12].to_string()
-    } else {
-        resolved_rev.clone()
-    };
-
-    Ok(FetchHgResult {
-        out_path: checkout_dir.to_string_lossy().to_string(),
-        branch,
-        rev: resolved_rev,
-        short_rev,
-        rev_count,
-    })
-}
-
-fn clone_repo(url: &str, dest: &PathBuf) -> Result<(), HgError> {
-    fs::create_dir_all(dest.parent().unwrap_or(dest))?;
-
-    let output = Command::new("hg")
-        .args(["clone", "-U", url])
-        .arg(dest)
-        .env("HGPLAIN", "")
-        .output()?;
-
-    if !output.status.success() {
-        return Err(HgError::CommandFailed {
-            operation: "clone".to_string(),
-            message: String::from_utf8_lossy(&output.stderr).to_string(),
-        });
-    }
-
-    Ok(())
-}
-
-fn pull_repo(repo: &PathBuf) -> Result<(), HgError> {
-    let output = Command::new("hg")
-        .args(["pull"])
-        .current_dir(repo)
-        .env("HGPLAIN", "")
-        .output()?;
-
-    if !output.status.success() {
-        return Err(HgError::CommandFailed {
-            operation: "pull".to_string(),
-            message: String::from_utf8_lossy(&output.stderr).to_string(),
-        });
-    }
-
-    Ok(())
-}
-
-fn resolve_rev(repo: &PathBuf, rev: &str) -> Result<String, HgError> {
-    let output = Command::new("hg")
-        .args(["log", "-r", rev, "--template", "{node}"])
-        .current_dir(repo)
-        .env("HGPLAIN", "")
-        .output()?;
-
-    if !output.status.success() {
-        return Err(HgError::CommandFailed {
-            operation: "log".to_string(),
-            message: format!(
-                "Could not resolve rev '{}': {}",
-                rev,
-                String::from_utf8_lossy(&output.stderr)
-            ),
-        });
-    }
-
-    Ok(String::from_utf8_lossy(&output.stdout).trim().to_string())
-}
-
-fn get_branch(repo: &PathBuf, rev: &str) -> Result<String, HgError> {
-    let output = Command::new("hg")
-        .args(["log", "-r", rev, "--template", "{branch}"])
-        .current_dir(repo)
-        .env("HGPLAIN", "")
-        .output()?;
-
-    if !output.status.success() {
-        return Ok("default".to_string());
-    }
-
-    let branch = String::from_utf8_lossy(&output.stdout).trim().to_string();
-    if branch.is_empty() {
-        Ok("default".to_string())
-    } else {
-        Ok(branch)
-    }
-}
-
-fn checkout_rev(
-    bare_repo: &PathBuf,
-    rev: &str,
-    name: &str,
-    cache: &FetcherCache,
-) -> Result<PathBuf, HgError> {
-    let hash = crate::nix_utils::sha256_hex(&format!("{}:{}", bare_repo.display(), rev));
-    let checkout_dir = cache.make_store_path(&hash, name);
-
-    if checkout_dir.exists() {
-        return Ok(checkout_dir);
-    }
-
-    fs::create_dir_all(&checkout_dir)?;
-
-    let output = Command::new("hg")
-        .args(["archive", "-r", rev])
-        .arg(&checkout_dir)
-        .current_dir(bare_repo)
-        .env("HGPLAIN", "")
-        .output()?;
-
-    if !output.status.success() {
-        fs::remove_dir_all(&checkout_dir)?;
-        return Err(HgError::CommandFailed {
-            operation: "archive".to_string(),
-            message: String::from_utf8_lossy(&output.stderr).to_string(),
-        });
-    }
-
-    let hg_archival = checkout_dir.join(".hg_archival.txt");
-    if hg_archival.exists() {
-        fs::remove_file(&hg_archival)?;
-    }
-
-    Ok(checkout_dir)
-}
-
-fn get_rev_count(repo: &PathBuf, rev: &str) -> Result<u64, HgError> {
-    let output = Command::new("hg")
-        .args(["log", "-r", &format!("0::{}", rev), "--template", "x"])
-        .current_dir(repo)
-        .env("HGPLAIN", "")
-        .output()?;
-
-    if !output.status.success() {
-        return Ok(0);
-    }
-
-    Ok(output.stdout.len() as u64)
-}
-
-#[derive(Debug)]
-pub enum HgError {
-    IoError(std::io::Error),
-    CommandFailed { operation: String, message: String },
-}
-
-impl std::fmt::Display for HgError {
-    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
-        match self {
-            HgError::IoError(e) => write!(f, "I/O error: {}", e),
-            HgError::CommandFailed { operation, message } => {
-                write!(f, "Mercurial {} failed: {}", operation, message)
-            }
-        }
-    }
-}
-
-impl std::error::Error for HgError {}
-
-impl From<std::io::Error> for HgError {
-    fn from(e: std::io::Error) -> Self {
-        HgError::IoError(e)
-    }
-}
diff --git a/nix-js/src/nix_utils.rs b/nix-js/src/nix_utils.rs
index 64e544d..08c2b5c 100644
--- a/nix-js/src/nix_utils.rs
+++ b/nix-js/src/nix_utils.rs
@@ -1,9 +1,9 @@
 use nix_compat::store_path::compress_hash;
 use sha2::{Digest as _, Sha256};
 
-pub fn sha256_hex(data: &str) -> String {
+pub fn sha256_hex(data: &[u8]) -> String {
     let mut hasher = Sha256::new();
-    hasher.update(data.as_bytes());
+    hasher.update(data);
     hex::encode(hasher.finalize())
 }
 
@@ -19,11 +19,3 @@ pub fn make_store_path(store_dir: &str, ty: &str, hash_hex: &str, name: &str) ->
 
     format!("{}/{}-{}", store_dir, encoded, name)
 }
-
-pub fn output_path_name(drv_name: &str, output_name: &str) -> String {
-    if output_name == "out" {
-        drv_name.to_string()
-    } else {
-        format!("{}-{}", drv_name, output_name)
-    }
-}
diff --git a/nix-js/src/runtime.rs b/nix-js/src/runtime.rs
index c133227..a61544d 100644
--- a/nix-js/src/runtime.rs
+++ b/nix-js/src/runtime.rs
@@ -55,7 +55,6 @@ fn runtime_extension<Ctx: RuntimeContext>() -> Extension {
         op_make_placeholder(),
         op_decode_span::<Ctx>(),
         op_make_store_path::<Ctx>(),
-        op_output_path_name(),
         op_parse_hash(),
         op_make_fixed_output_path::<Ctx>(),
         op_add_path::<Ctx>(),
diff --git a/nix-js/src/runtime/ops.rs b/nix-js/src/runtime/ops.rs
index 507c00d..89e8483 100644
--- a/nix-js/src/runtime/ops.rs
+++ b/nix-js/src/runtime/ops.rs
@@ -246,7 +246,7 @@ pub(super) fn op_resolve_path(
 #[deno_core::op2]
 #[string]
 pub(super) fn op_sha256_hex(#[string] data: String) -> String {
-    crate::nix_utils::sha256_hex(&data)
+    crate::nix_utils::sha256_hex(data.as_bytes())
 }
 
 #[deno_core::op2]
@@ -325,15 +325,6 @@ pub(super) fn op_make_store_path<Ctx: RuntimeContext>(
     crate::nix_utils::make_store_path(store_dir, &ty, &hash_hex, &name)
 }
 
-#[deno_core::op2]
-#[string]
-pub(super) fn op_output_path_name(
-    #[string] drv_name: String,
-    #[string] output_name: String,
-) -> String {
-    crate::nix_utils::output_path_name(&drv_name, &output_name)
-}
-
 #[derive(serde::Serialize)]
 pub(super) struct ParsedHash {
     hex: String,