diff --git a/mod/completion/function/analysis.zsh b/mod/completion/function/analysis.zsh
index 973dcea..969ab6d 100644
--- a/mod/completion/function/analysis.zsh
+++ b/mod/completion/function/analysis.zsh
@@ -10,8 +10,6 @@ z.completion.function._candidates() {
   local prefix=$1
   local function_names=("${z_completion_function_names[@]}")
 
-  z.int.is.zero ${#function_names[@]} && return 1
-
   local candidates=()
   for function_name in $function_names; do
     if z.str.start_with "$function_name" "z." &&
diff --git a/mod/completion/process.zsh b/mod/completion/process.zsh
index f684214..1c34f49 100644
--- a/mod/completion/process.zsh
+++ b/mod/completion/process.zsh
@@ -15,10 +15,10 @@ z.completion.enable() {
   z.completion.is._interactive || return 0
 
   z.completion.cache.build._names
-  z.completion.compdef._ignore_private || return 1
+  z.completion.compdef._ignore_private
   z.completion.compdef._register || return 1
   autoload -Uz add-zsh-hook
-  add-zsh-hook zshexit z.completion.cache._cancel || return 1
+  add-zsh-hook zshexit z.completion.cache._cancel
   z.completion.cache._cancel
 
   z.job.run \
diff --git a/mod/job/analysis.zsh b/mod/job/analysis.zsh
index b613c89..9276718 100644
--- a/mod/job/analysis.zsh
+++ b/mod/job/analysis.zsh
@@ -11,7 +11,7 @@ z.job.status() {
   z.arg.named id "$@" && local id=$REPLY
   z.is.null "$id" && return 1
 
-  z.job.file._path id=$id name=status || return 1
+  z.job.file._path id=$id name=status
   local status_file=$REPLY
   z.file.exists "$status_file" || return 1
 
diff --git a/mod/job/file/analysis.zsh b/mod/job/file/analysis.zsh
index 61eaedb..03c9c83 100644
--- a/mod/job/file/analysis.zsh
+++ b/mod/job/file/analysis.zsh
@@ -53,6 +53,6 @@ z.job.file._path() {
   z.is.null "$id" && return 1
   z.is.null "$name" && return 1
 
-  z.job.file._dir id=$id || return 1
+  z.job.file._dir id=$id
   z.return "$REPLY/$name"
 }
diff --git a/mod/job/process.zsh b/mod/job/process.zsh
index 3e9f4e2..98f0e30 100644
--- a/mod/job/process.zsh
+++ b/mod/job/process.zsh
@@ -25,7 +25,7 @@ z.job.run() {
     name="$name" \
     command="$command" \
     on_success="$on_success" \
-    on_failure="$on_failure" || return 1
+    on_failure="$on_failure"
   local -a prepared=("${REPLY[@]}")
   local id=$prepared[1]
   local dir=$prepared[2]
diff --git a/mod/job/run/process.zsh b/mod/job/run/process.zsh
index 2be558f..478d87e 100644
--- a/mod/job/run/process.zsh
+++ b/mod/job/run/process.zsh
@@ -1,11 +1,11 @@
-# prepare a job directory
+# prepare a job directory after argument validation
 #
 # $name: job name
 # $command: child function name
 # $on_success?: parent success callback function name
 # $on_failure?: parent failure callback function name
 # REPLY: job id and job directory
-# return: 0|1
+# return: null
 #
 # example:
 #  z.job.run._prepare name=example command=z.example.build
@@ -15,9 +15,6 @@ z.job.run._prepare() {
   z.arg.named on_success "$@" && local on_success=$REPLY
   z.arg.named on_failure "$@" && local on_failure=$REPLY
 
-  z.is.null "$name" && return 1
-  z.is.null "$command" && return 1
-
   z.job.file._jobs && local jobs_dir=$REPLY
   z.dir.exists "$jobs_dir" || z.dir.make path="$jobs_dir"
 
diff --git a/mod/wtproxy/config/analysis.zsh b/mod/wtproxy/config/analysis.zsh
index 65f8048..f053545 100644
--- a/mod/wtproxy/config/analysis.zsh
+++ b/mod/wtproxy/config/analysis.zsh
@@ -6,7 +6,7 @@
 # example:
 #  z.wtproxy._config
 z.wtproxy._config() {
-  z.wtproxy._config.values || return 1
+  z.wtproxy._config.values
   local -A config=("${(@)REPLY}")
 
   z.wtproxy._config.file.default_project || {
diff --git a/mod/wtproxy/port/analysis.zsh b/mod/wtproxy/port/analysis.zsh
index 69312f7..aafee38 100644
--- a/mod/wtproxy/port/analysis.zsh
+++ b/mod/wtproxy/port/analysis.zsh
@@ -26,7 +26,7 @@ z.wtproxy._port.proxies() {
 
   z.wtproxy._port.keys.from_config config
   for port_key in ${(@)REPLY}; do
-    z.wtproxy._port.worktree.index $port_key || return 1
+    z.wtproxy._port.worktree.index $port_key
     local port_index=$REPLY
     z.wtproxy._port.proxy.key $port_index
     local config_key=$REPLY
diff --git a/mod/wtproxy/proxy/is/operator.zsh b/mod/wtproxy/proxy/is/operator.zsh
index 0490ea3..bb7da2f 100644
--- a/mod/wtproxy/proxy/is/operator.zsh
+++ b/mod/wtproxy/proxy/is/operator.zsh
@@ -31,7 +31,6 @@ z.wtproxy._proxy.is.pid() {
   z.is.null "$pid" && return 1
   z.io.null kill -0 "$pid" || return 1
 
-  local command_line
-  command_line=$(ps -p "$pid" -o command= 2>/dev/null) || return 1
+  local command_line=$(ps -p "$pid" -o command= 2>/dev/null)
   z.str.includes "$command_line" "z.wtproxy.start._serve"
 }
diff --git a/test/mod/completion/cache/process_test.zsh b/test/mod/completion/cache/process_test.zsh
index 99759c9..36a6221 100644
--- a/test/mod/completion/cache/process_test.zsh
+++ b/test/mod/completion/cache/process_test.zsh
@@ -81,6 +81,21 @@ z.t.describe "z.completion.cache._cancel"; {
     }
   }
 
+  z.t.context "jobの取消に失敗した場合"; {
+    z.t.it "補完側のIDを破棄して成功する"; {
+      local z_completion_cache_job_id=cache-job
+      z.t.mock name="z.job.status" behavior="z.return running"
+      z.t.mock name="z.job.cancel" behavior="return 1"
+
+      z.completion.cache._cancel
+      local result_code=$?
+      local remaining_id=$z_completion_cache_job_id
+
+      z.t.expect "$result_code" 0
+      z.t.expect.is.null "$remaining_id"
+    }
+  }
+
   z.t.context "補完jobがない場合"; {
     z.t.it "他のjobに触れず成功する"; {
       local z_completion_cache_job_id=""
diff --git a/test/mod/completion/process_test.zsh b/test/mod/completion/process_test.zsh
index 1e65e8e..8d47b8c 100644
--- a/test/mod/completion/process_test.zsh
+++ b/test/mod/completion/process_test.zsh
@@ -58,17 +58,23 @@ z.t.describe "z.completion.enable"; {
   }
 
   z.t.context "private除外設定に失敗した場合"; {
-    z.t.it "jobを起動しない"; {
+    z.t.it "補完登録とcache jobの起動を続ける"; {
+      local z_completion_cache_job_id=""
+      local -a zshexit_functions=()
+      local -a completion_calls=()
       z.t.mock name="z.completion.is._interactive" behavior="return 0"
       z.t.mock name="z.completion.compdef._ignore_private" behavior="return 1"
-      z.t.mock name="z.completion.compdef._register" behavior="return 0"
-      z.t.mock name="z.job.run" behavior="z.return job-id"
+      z.t.mock name="z.completion.compdef._register" behavior='completion_calls+=(register); return 0'
+      z.t.mock name="z.job.run" behavior='completion_calls+=(job); z.return job-id'
 
       z.completion.enable
+      local result_code=$?
+      local result_reply=$REPLY
 
-      z.t.expect.status.is.false skip_unmock=true
-      z.t.mock.result name="z.job.run"
-      z.t.expect.reply ""
+      z.t.expect "$result_code" 0 skip_unmock=true
+      z.t.expect "$result_reply" job-id skip_unmock=true
+      z.t.expect "$completion_calls" "register job" skip_unmock=true
+      z.t.expect "$zshexit_functions" z.completion.cache._cancel
     }
   }
 
diff --git a/test/mod/wtproxy/proxy/is/operator_test.zsh b/test/mod/wtproxy/proxy/is/operator_test.zsh
index f43260e..8b0816a 100644
--- a/test/mod/wtproxy/proxy/is/operator_test.zsh
+++ b/test/mod/wtproxy/proxy/is/operator_test.zsh
@@ -38,4 +38,15 @@ z.t.describe "z.wtproxy._proxy.is.pid"; {
       z.t.expect.status.is.false
     }
   }
+
+  z.t.context "pid確認後にprocessが終了した場合"; {
+    z.t.it "commandを取得できないためfalseを返す"; {
+      z.t.mock name="kill" behavior="return 0"
+      z.t.mock name="ps" behavior="return 1"
+
+      z.wtproxy._proxy.is.pid 12345
+
+      z.t.expect.status.is.false
+    }
+  }
 }