diff --git a/pkgs/oizys/src/oizys.nim b/pkgs/oizys/src/oizys.nim
index e3f51d4..05704d1 100644
--- a/pkgs/oizys/src/oizys.nim
+++ b/pkgs/oizys/src/oizys.nim
@@ -1,7 +1,7 @@
 ## nix begat oizys
 import std/[os, osproc, sequtils, strformat, strutils, tables]
 import hwylterm, hwylterm/[hwylcli]
-import oizys/[context, github, nix, logging]
+import oizys/[context, github, nix, logging, utils]
 
 proc checkExes() =
   if findExe("nix") == "":
@@ -37,6 +37,7 @@ hwylCli:
       - m
   preSub:
     setupLoggers()
+    echo "ORIGINAL UPDATE CONTEXT"
     updateContext(host, flake, verbose, resetCache)
 
   subcommands:
@@ -74,11 +75,6 @@ hwylCli:
 
     [ci]
     ... "builtin ci"
-    # BUG: current behavior adds this block twice...
-    # when really I want it to only happen in the lowest "subcommand"
-    # needs to be fixed in hwylterm
-    preSub:
-      updateContext(host, flake, verbose, resetCache)
     subcommands:
       [update]
       ... "build current and updated hosts"
@@ -162,3 +158,32 @@ hwylCli:
         updateRepo()
         nixosRebuild(NixosRebuildSubcmd.switch)
 
+    [utils]
+    ... """
+    less common utils operations
+
+    some snippets I've reimplemented in nim so that nix isn't as annoying
+    """
+    subcommands:
+      [hash]
+      ... "collect build hash from failure"
+      positionals:
+        installable string
+      run:
+        stdout.write getBuildHash(installable)
+
+      [narinfo]
+      ... """
+      check active caches for nix derivation
+
+      by default will use [yellow]nix config show[/] to determine
+      the binary cache urls
+      """
+      positionals:
+        installables seq[string]
+      flags:
+        cache:
+          ? "url of nix binary cache, can be repeated"
+          T seq[string]
+      run:
+        checkForCache(installables, cache)
diff --git a/pkgs/oizys/src/oizys/exec.nim b/pkgs/oizys/src/oizys/exec.nim
index de0500b..3854606 100644
--- a/pkgs/oizys/src/oizys/exec.nim
+++ b/pkgs/oizys/src/oizys/exec.nim
@@ -7,8 +7,14 @@ import hwylterm
 import hwylterm/spin/spinners # todo: remove after hwylterm update
 
 
-func addArgs*(cmd: var string, args: varargs[string]) =
+func addArgs*(cmd: string, args: varargs[string]): string =
+  ## append to string for command
+  result = cmd & " " & args.join(" ")
+
+func addArgs*(cmd: var string, args: varargs[string]): string {.discardable.} =
+  ## append to string for command
   cmd &= " " & args.join(" ")
+  result = cmd
 
 # deprecate in favor of above?
 func addArg*(cmd: var string, arg: string ) =
@@ -50,32 +56,39 @@ proc runCmdCapt*(
         result.stderr.add line & '\n'
     result.exitCode = peekExitCode(p)
     if result.exitCode != -1:
-      result.stdout.add outstrm.readAll()
-      result.stderr.add errstrm.readAll()
+      if CaptStdout in capture:
+        result.stdout.add outstrm.readAll()
+      if CaptStderr in capture:
+        result.stderr.add errstrm.readAll()
       break
 
   close p
 
-proc formatStdoutStderr(stdout: string, stderr: string): BbString =
+proc formatSubprocessError*(s: string): BbString =
+  for line in s.splitLines():
+    result.add bb("[red]->[/] " & line & "\n")
+
+proc formatStdoutStderr*(stdout: string, stderr: string): BbString =
   template add(stream: string) =
     if stream.strip() != "":
       result.add astToStr(stream).bb("bold") & ":\n"
-      for line in stream.splitlines():
-        result.add bb("[red]->[/] " & line & "\n")
+      result.add formatSubprocessError(stream)
   add(stdout)
   add(stderr)
 
+
 proc runCmdCaptWithSpinner*(
   cmd: string,
   msg: BbString | string = bb"",
-  capture: set[CaptureGrp] = {CaptStdout}
+  capture: set[CaptureGrp] = {CaptStdout},
+  check: bool = true
 ): tuple[output, err: string] =
   var
     output, err: string
     code: int
   with(Dots2, msg):
     (output, err, code) = runCmdCapt(cmd, capture)
-  if code != 0:
+  if check and code != 0:
     stderr.write($formatStdoutStderr(output,err))
     error fmt"{cmd} had non zero exit"
     quit code
diff --git a/pkgs/oizys/src/oizys/nix.nim b/pkgs/oizys/src/oizys/nix.nim
index 6fdbaea..10f5380 100644
--- a/pkgs/oizys/src/oizys/nix.nim
+++ b/pkgs/oizys/src/oizys/nix.nim
@@ -3,11 +3,12 @@ import std/[
   enumerate, os, sequtils, sets, strformat,
   strutils, sugar, logging, tables, times
 ]
+export tables
 import hwylterm, hwylterm/logging, jsony
 
 import ./[context, exec]
 
-proc nixCommand(cmd: string, nom: bool = false): string =
+proc nixCommand*(cmd: string, nom: bool = false): string =
   if nom:
     if findExe("nom") == "":
       fatalQuit "--nom requires nix-output-monitor is installed"
@@ -53,13 +54,13 @@ proc nixosRebuild*(subcmd: NixosRebuildSubcmd, args: openArray[string] = [], rem
 
 type
   Derivation = object
-    storePath, hash, name: string
+    storePath*, hash*, name*: string
 
   DryRunOutput = object
     toBuild: seq[Derivation]
     toFetch: seq[Derivation]
 
-func toDerivation(pkg: string): Derivation =
+func toDerivation*(pkg: string): Derivation =
   let path = pkg.strip()
   let s = path.split("-", 1)
   result.storePath = path
@@ -108,7 +109,7 @@ proc parseDryRunOutput(err: string): DryRunOutput =
   result.toBuild.sort(cmpDrv)
   result.toFetch.sort(cmpDrv)
 
-proc trunc(s: string, limit: int): string =
+proc trunc*(s: string, limit: int): string =
   if s.len <= limit:
     s
   else:
@@ -143,22 +144,30 @@ proc toBuildNixosConfiguration(): seq[string] =
 
 type
   DerivationOutput = object
-    path: string
+    path*: string
     # hashAlgo: string
     # hash: string
   NixDerivation = object
-    inputDrvs: Table[string, JsonNode]
-    name: string
-    outputs: Table[string, DerivationOutput]
+    inputDrvs*: Table[string, JsonNode]
+    name*: string
+    outputs*: Table[string, DerivationOutput]
 
-proc evaluateDerivations(drvs: seq[string]): Table[string, NixDerivation] =
+# here a results var would be nice...
+proc narHash*(s: string): string =
+  ## get hash from nix store path
+  if not s.startsWith("/nix/store/") and s.len >= 44:
+    fatalQuit "failed to extract narHash from: " &  s
+  let ss = s.split("-")
+  result = ss[0].split("/")[^1]
+
+proc evaluateDerivations(drvs: openArray[string]): Table[string, NixDerivation] =
   var cmd = "nix derivation show -r"
   cmd.addArgs drvs
   let (output, _) =
     runCmdCaptWithSpinner(cmd, "evaluating derivations")
   fromJson(output, Table[string, NixDerivation])
 
-proc nixDerivationShow(drvs: seq[string]): Table[string, NixDerivation] =
+proc nixDerivationShow*(drvs: openArray[string]): Table[string, NixDerivation] =
   var cmd = "nix derivation show"
   cmd.addArgs drvs
   let (output, _ ) =
diff --git a/pkgs/oizys/src/oizys/utils.nim b/pkgs/oizys/src/oizys/utils.nim
new file mode 100644
index 0000000..66c6360
--- /dev/null
+++ b/pkgs/oizys/src/oizys/utils.nim
@@ -0,0 +1,89 @@
+import std/[strformat, strutils, osproc, sugar, httpclient]
+import hwylterm
+import ./[nix, exec,logging]
+
+
+# TODO: refactor runCmdCaptWithSpinner so it works in getBuildHash
+proc checkBuild(installable: string): tuple[stdout: string, stderr: string] =
+  var
+    output, err: string
+    code: int
+  let cmd = nixCommand("build").addArgs(installable)
+  with(Dots2, bbfmt"attempt to build: [b]{installable}"):
+    (output, err, code) = runCmdCapt(cmd, capture = {CaptStdout, CaptStderr})
+  if code == 0:
+    fatalQuit fmt"{cmd} had zero exit"
+  result = (output, err)
+
+proc getBuildHash*(installable: string): string =
+  let (output, err) = checkBuild(installable)
+  for line in err.splitLines():
+    if line.strip().startsWith("got: "):
+      let s = line.split("got:")
+      result = s[1].strip()
+  if result == "":
+    stderr.write formatStdoutStderr(output, err) & "\n"
+    fatalQuit "failed to find update hash from above output"
+
+proc getCaches(): seq[string] =
+  ## use nix to get the current cache urls
+  debug "determing caches to check"
+  let (output, code) = execCmdEx("nix config show")
+  if code != 0:
+    echo formatSubprocessError(output)
+    fatalQuit "error running `nix config show`"
+
+  for line in output.splitLines():
+    if line.startsWith("substituters ="):
+      let s = line.split("=")[1].strip()
+      for u in s.split():
+        result.add u
+
+  if result.len == 0:
+    echo formatSubprocessError(output)
+    fatalQuit "error running `nix config show`"
+
+
+
+
+proc hasNarinfo*(cache: string, path: string): bool =
+  debug fmt"checking {cache} for {path}"
+  let
+    hash = narHash(path)
+    url = cache & "/" & hash & ".narinfo"
+  try:
+    let client = newHttpClient()
+    result = client.head(url).code == Http200
+  except:
+    result = false
+
+proc prettyDerivation(path: string): BbString =
+  let drv = path.toDerivation()
+  const maxLen = 40
+  result.add drv.name.trunc(maxLen).alignLeft(maxLen)
+  result.add " "
+  result.add drv.hash.bb("faint")
+
+proc checkForCache*(installables: seq[string], caches: seq[string]) =
+  let caches =
+    if caches.len > 0: caches
+    else: getCaches()
+  let drvs = nixDerivationShow(installables)
+  # outputs['outs'] might blow up
+  let outs = collect:
+    for name, drv in drvs:
+      {name: drv.outputs["out"].path}
+
+  for name, path in outs:
+    var found = false
+    for cache in caches:
+      if hasNarinfo(cache, path):
+        found = true
+        info prettyDerivation(path)
+        info fmt"exists in {cache}"
+        break
+
+    if not found:
+      info fmt"failed to find:"
+      info prettyDerivation(path)
+
diff --git a/todo.md b/todo.md
index 8072c0a..ef13fce 100644
--- a/todo.md
+++ b/todo.md
@@ -4,7 +4,6 @@
 
 Could make an `oizys check` command:
 
-- `utils hash` given some flake-url or path attempt to build and extract "got:   <hash>" string
 - `check lock` could encapsulate any diagnostic code I want to run that does things like check for too many "inputs".
   essentially getting the same output as this `jq < flake.lock '.nodes | keys[] | select(contains("_"))`
 - `utils cache <path>` check for the narinfo in my cache given some nix store path