diff --git a/bin/gstack-developer-profile b/bin/gstack-developer-profile
index a5721a9c5b..803b65317f 100755
--- a/bin/gstack-developer-profile
+++ b/bin/gstack-developer-profile
@@ -55,7 +55,7 @@ do_migrate() {
 
   # Run migration in a temp file, then atomic rename.
   local TMPOUT
-  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.XXXXXX.tmp")
+  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
   trap 'rm -f "$TMPOUT"' EXIT
 
   cat "$LEGACY_FILE" | bun -e "
@@ -182,7 +182,7 @@ do_log_session() {
   ensure_profile
 
   local TMPOUT
-  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.XXXXXX.tmp")
+  TMPOUT=$(mktemp "$GSTACK_HOME/developer-profile.json.tmp.XXXXXX")
   trap 'rm -f "$TMPOUT"' EXIT
 
   PROFILE_FILE_PATH="$PROFILE_FILE" RECORD_INPUT="$INPUT" TMPOUT_PATH="$TMPOUT" bun -e "
diff --git a/claude/SKILL.md.tmpl b/claude/SKILL.md.tmpl
index 94552cbe4e..e109f21f74 100644
--- a/claude/SKILL.md.tmpl
+++ b/claude/SKILL.md.tmpl
@@ -95,8 +95,8 @@ Create temp files:
 
 ```bash
 PROMPT_FILE=$(mktemp /tmp/gstack-claude-prompt-XXXXXX)
-RESP_FILE=$(mktemp /tmp/gstack-claude-response-XXXXXX.json)
-ERR_FILE=$(mktemp /tmp/gstack-claude-error-XXXXXX.txt)
+RESP_FILE=$(mktemp /tmp/gstack-claude-response-XXXXXX)
+ERR_FILE=$(mktemp /tmp/gstack-claude-error-XXXXXX)
 ```
 
 Cleanup at the end of every mode:
@@ -151,7 +151,7 @@ Review the current branch diff with nested Claude in tool-less mode.
 ```bash
 _REPO_ROOT=$(git rev-parse --show-toplevel) || { echo "ERROR: not in a git repo" >&2; exit 1; }
 cd "$_REPO_ROOT"
-DIFF_FILE=$(mktemp /tmp/gstack-claude-diff-XXXXXX.patch)
+DIFF_FILE=$(mktemp /tmp/gstack-claude-diff-XXXXXX)
 git fetch origin <base> --quiet 2>/dev/null || true
 git diff "origin/<base>" > "$DIFF_FILE" 2>/dev/null || git diff "<base>" > "$DIFF_FILE"
 ```
diff --git a/codex/SKILL.md b/codex/SKILL.md
index 33228ff9b8..d5617335de 100644
--- a/codex/SKILL.md
+++ b/codex/SKILL.md
@@ -967,7 +967,7 @@ Run Codex code review against the current branch diff.
 
 1. Create temp files for output capture:
 ```bash
-TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX.txt")
+TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX")
 ```
 
 2. Run the review (5-minute timeout). **Codex CLI ≥ 0.130.0 rejects passing a
@@ -1015,7 +1015,7 @@ when the diff content is adversarial:
 _REPO_ROOT=$(git rev-parse --show-toplevel) || { echo "ERROR: not in a git repo" >&2; exit 1; }
 cd "$_REPO_ROOT"
 _USER_INSTRUCTIONS="<everything after '/codex review ' in user input>"
-_PROMPT_FILE=$(mktemp "$TMP_ROOT/codex-prompt-XXXXXX.txt")
+_PROMPT_FILE=$(mktemp "$TMP_ROOT/codex-prompt-XXXXXX")
 {
   printf '%s\n' "IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. Do NOT modify agents/openai.yaml. Stay focused on repository code only."
   printf '\nCustom focus: %s\n\n' "$_USER_INSTRUCTIONS"
@@ -1266,7 +1266,7 @@ if [ -z "$PYTHON_CMD" ]; then
 fi
 # Fix 1+2: wrap with timeout (gtimeout/timeout fallback chain via probe helper),
 # capture stderr to $TMPERR for auth error detection (was: 2>/dev/null).
-TMPERR=${TMPERR:-$(mktemp "$TMP_ROOT/codex-err-XXXXXX.txt")}
+TMPERR=${TMPERR:-$(mktemp "$TMP_ROOT/codex-err-XXXXXX")}
 _gstack_codex_timeout_wrapper 600 codex exec "<prompt>" -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="high"' --enable web_search_cached --json < /dev/null 2>"$TMPERR" | PYTHONUNBUFFERED=1 "$PYTHON_CMD" -u -c "
 import sys, json
 turn_completed_count = 0
@@ -1365,8 +1365,8 @@ B) Start a new conversation
 
 2. Create temp files:
 ```bash
-TMPRESP=$(mktemp "$TMP_ROOT/codex-resp-XXXXXX.txt")
-TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX.txt")
+TMPRESP=$(mktemp "$TMP_ROOT/codex-resp-XXXXXX")
+TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX")
 ```
 
 3. **Plan review auto-detection:** If the user's prompt is about reviewing a plan,
diff --git a/codex/SKILL.md.tmpl b/codex/SKILL.md.tmpl
index 333de7d8d5..afb8b38a7e 100644
--- a/codex/SKILL.md.tmpl
+++ b/codex/SKILL.md.tmpl
@@ -158,7 +158,7 @@ Run Codex code review against the current branch diff.
 
 1. Create temp files for output capture:
 ```bash
-TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX.txt")
+TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX")
 ```
 
 2. Run the review (5-minute timeout). **Codex CLI ≥ 0.130.0 rejects passing a
@@ -206,7 +206,7 @@ when the diff content is adversarial:
 _REPO_ROOT=$(git rev-parse --show-toplevel) || { echo "ERROR: not in a git repo" >&2; exit 1; }
 cd "$_REPO_ROOT"
 _USER_INSTRUCTIONS="<everything after '/codex review ' in user input>"
-_PROMPT_FILE=$(mktemp "$TMP_ROOT/codex-prompt-XXXXXX.txt")
+_PROMPT_FILE=$(mktemp "$TMP_ROOT/codex-prompt-XXXXXX")
 {
   printf '%s\n' "IMPORTANT: Do NOT read or execute any files under ~/.claude/, ~/.agents/, .claude/skills/, or agents/. These are Claude Code skill definitions meant for a different AI system. Do NOT modify agents/openai.yaml. Stay focused on repository code only."
   printf '\nCustom focus: %s\n\n' "$_USER_INSTRUCTIONS"
@@ -335,7 +335,7 @@ if [ -z "$PYTHON_CMD" ]; then
 fi
 # Fix 1+2: wrap with timeout (gtimeout/timeout fallback chain via probe helper),
 # capture stderr to $TMPERR for auth error detection (was: 2>/dev/null).
-TMPERR=${TMPERR:-$(mktemp "$TMP_ROOT/codex-err-XXXXXX.txt")}
+TMPERR=${TMPERR:-$(mktemp "$TMP_ROOT/codex-err-XXXXXX")}
 _gstack_codex_timeout_wrapper 600 codex exec "<prompt>" -C "$_REPO_ROOT" -s read-only -c 'model_reasoning_effort="high"' --enable web_search_cached --json < /dev/null 2>"$TMPERR" | PYTHONUNBUFFERED=1 "$PYTHON_CMD" -u -c "
 import sys, json
 turn_completed_count = 0
@@ -434,8 +434,8 @@ B) Start a new conversation
 
 2. Create temp files:
 ```bash
-TMPRESP=$(mktemp "$TMP_ROOT/codex-resp-XXXXXX.txt")
-TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX.txt")
+TMPRESP=$(mktemp "$TMP_ROOT/codex-resp-XXXXXX")
+TMPERR=$(mktemp "$TMP_ROOT/codex-err-XXXXXX")
 ```
 
 3. **Plan review auto-detection:** If the user's prompt is about reviewing a plan,
diff --git a/office-hours/SKILL.md b/office-hours/SKILL.md
index 83161b8ca9..e0d71c157e 100644
--- a/office-hours/SKILL.md
+++ b/office-hours/SKILL.md
@@ -1329,7 +1329,7 @@ If B: skip Phase 3.5 entirely. Remember that the second opinion did NOT run (aff
 2. **Write the assembled prompt to a temp file** (prevents shell injection from user-derived content):
 
 ```bash
-CODEX_PROMPT_FILE=$(mktemp /tmp/gstack-codex-oh-XXXXXXXX.txt)
+CODEX_PROMPT_FILE=$(mktemp /tmp/gstack-codex-oh-XXXXXXXX)
 ```
 
 Write the full prompt to this file. **Always start with the filesystem boundary:**
diff --git a/scripts/resolvers/review.ts b/scripts/resolvers/review.ts
index 7dccd8e502..b708c90a3b 100644
--- a/scripts/resolvers/review.ts
+++ b/scripts/resolvers/review.ts
@@ -351,7 +351,7 @@ If B: skip Phase 3.5 entirely. Remember that the second opinion did NOT run (aff
 2. **Write the assembled prompt to a temp file** (prevents shell injection from user-derived content):
 
 \`\`\`bash
-CODEX_PROMPT_FILE=$(mktemp /tmp/gstack-codex-oh-XXXXXXXX.txt)
+CODEX_PROMPT_FILE=$(mktemp /tmp/gstack-codex-oh-XXXXXXXX)
 \`\`\`
 
 Write the full prompt to this file. **Always start with the filesystem boundary:**