Monitors production deployments by comparing live app state against pre-deploy baselines.

Install

mkdir -p .claude/skills/canary && curl -L -o skill.zip "https://agentskills.codes/api/skills/download/18872" && unzip -o skill.zip -d .claude/skills/canary && rm skill.zip

Installs to .claude/skills/canary

Activation

This is the description your AI agent reads to decide when to run this skill — the better it matches your request, the more reliably it fires.

Post-deploy canary monitoring. Watches the live app for console errors, performance regressions, and page failures using the browse daemon. Takes periodic screenshots, compares against pre-deploy baselines, and alerts on anomalies. Use when: "monitor deploy", "canary", "post-deploy check", "watch production", "verify deploy". (gstack)
336 chars✓ has a “when” triggerlonger than Claude Code's old 250-char listing cap (fine on current versions)
Intermediate

Key capabilities

  • Monitor live web applications for errors
  • Detect performance regressions in web apps
  • Take periodic screenshots of web pages
  • Compare current app state against pre-deploy baselines
  • Alert on anomalies in web application behavior

How it works

The skill uses a browser daemon to watch a live web app, capturing screenshots and monitoring for console errors and performance shifts, then compares these against a baseline to identify anomalies.

Inputs & outputs

You give it
live web application URL
You get back
canary report with status, errors, performance, and screenshots

When to use canary

  • Check site after deploy
  • Monitor production errors
  • Verify UI performance
  • Post-deployment validation

About this skill

<!-- AUTO-GENERATED from SKILL.md.tmpl — do not edit directly --> <!-- Regenerate: bun run gen:skill-docs -->

Preamble (run first)

_GSTACK_PROJECT_DIR="${CLAUDE_PROJECT_DIR:-$(git rev-parse --show-toplevel 2>/dev/null || pwd)}"
if [ -x "$_GSTACK_PROJECT_DIR/.codex/skills/gstack/bin/gstack-config" ]; then
  GSTACK_SKILLS_ROOT="$_GSTACK_PROJECT_DIR/.codex/skills/gstack"
elif [ -x "$HOME/.codex/skills/gstack/bin/gstack-config" ]; then
  GSTACK_SKILLS_ROOT="$HOME/.codex/skills/gstack"
else
  GSTACK_SKILLS_ROOT="$_GSTACK_PROJECT_DIR/.codex/skills/gstack"
fi
GSTACK_BIN="$GSTACK_SKILLS_ROOT/bin"
_UPD=$($GSTACK_BIN/gstack-update-check 2>/dev/null || $GSTACK_BIN/gstack-update-check 2>/dev/null || true)
[ -n "$_UPD" ] && echo "$_UPD" || true
mkdir -p ~/.gstack/sessions
touch ~/.gstack/sessions/"$PPID"
_SESSIONS=$(find ~/.gstack/sessions -mmin -120 -type f 2>/dev/null | wc -l | tr -d ' ')
find ~/.gstack/sessions -mmin +120 -type f -exec rm {} + 2>/dev/null || true
_PROACTIVE=$($GSTACK_BIN/gstack-config get proactive 2>/dev/null || echo "true")
_PROACTIVE_PROMPTED=$([ -f ~/.gstack/.proactive-prompted ] && echo "yes" || echo "no")
_BRANCH=$(git branch --show-current 2>/dev/null || echo "unknown")
echo "BRANCH: $_BRANCH"
_SKILL_PREFIX=$($GSTACK_BIN/gstack-config get skill_prefix 2>/dev/null || echo "false")
echo "PROACTIVE: $_PROACTIVE"
echo "PROACTIVE_PROMPTED: $_PROACTIVE_PROMPTED"
echo "SKILL_PREFIX: $_SKILL_PREFIX"
source <($GSTACK_BIN/gstack-repo-mode 2>/dev/null) || true
REPO_MODE=${REPO_MODE:-unknown}
echo "REPO_MODE: $REPO_MODE"
_LAKE_SEEN=$([ -f ~/.gstack/.completeness-intro-seen ] && echo "yes" || echo "no")
echo "LAKE_INTRO: $_LAKE_SEEN"
_TEL=$($GSTACK_BIN/gstack-config get telemetry 2>/dev/null || true)
_TEL_PROMPTED=$([ -f ~/.gstack/.telemetry-prompted ] && echo "yes" || echo "no")
_TEL_START=$(date +%s)
_SESSION_ID="$$-$(date +%s)"
echo "TELEMETRY: ${_TEL:-off}"
echo "TEL_PROMPTED: $_TEL_PROMPTED"
_EXPLAIN_LEVEL=$($GSTACK_BIN/gstack-config get explain_level 2>/dev/null || echo "default")
if [ "$_EXPLAIN_LEVEL" != "default" ] && [ "$_EXPLAIN_LEVEL" != "terse" ]; then _EXPLAIN_LEVEL="default"; fi
echo "EXPLAIN_LEVEL: $_EXPLAIN_LEVEL"
_QUESTION_TUNING=$($GSTACK_BIN/gstack-config get question_tuning 2>/dev/null || echo "false")
echo "QUESTION_TUNING: $_QUESTION_TUNING"
mkdir -p ~/.gstack/analytics
if [ "$_TEL" != "off" ]; then
echo '{"skill":"canary","ts":"'$(date -u +%Y-%m-%dT%H:%M:%SZ)'","repo":"'$(basename "$(git rev-parse --show-toplevel 2>/dev/null)" 2>/dev/null || echo "unknown")'"}'  >> ~/.gstack/analytics/skill-usage.jsonl 2>/dev/null || true
fi
for _PF in $(find ~/.gstack/analytics -maxdepth 1 -name '.pending-*' 2>/dev/null); do
  if [ -f "$_PF" ]; then
    if [ "$_TEL" != "off" ] && [ -x "$GSTACK_BIN/gstack-telemetry-log" ]; then
      $GSTACK_BIN/gstack-telemetry-log --event-type skill_run --skill _pending_finalize --outcome unknown --session-id "$_SESSION_ID" 2>/dev/null || true
    fi
    rm -f "$_PF" 2>/dev/null || true
  fi
  break
done
eval "$($GSTACK_BIN/gstack-slug 2>/dev/null)" 2>/dev/null || true
_LEARN_FILE="${GSTACK_HOME:-$HOME/.gstack}/projects/${SLUG:-unknown}/learnings.jsonl"
if [ -f "$_LEARN_FILE" ]; then
  _LEARN_COUNT=$(wc -l < "$_LEARN_FILE" 2>/dev/null | tr -d ' ')
  echo "LEARNINGS: $_LEARN_COUNT entries loaded"
  if [ "$_LEARN_COUNT" -gt 5 ] 2>/dev/null; then
    $GSTACK_BIN/gstack-learnings-search --limit 3 2>/dev/null || true
  fi
else
  echo "LEARNINGS: 0"
fi
$GSTACK_BIN/gstack-timeline-log '{"skill":"canary","event":"started","branch":"'"$_BRANCH"'","session":"'"$_SESSION_ID"'"}' 2>/dev/null &
_HAS_ROUTING="no"
if [ -f CLAUDE.md ] && grep -q "## Skill routing" CLAUDE.md 2>/dev/null; then
  _HAS_ROUTING="yes"
fi
_ROUTING_DECLINED=$($GSTACK_BIN/gstack-config get routing_declined 2>/dev/null || echo "false")
echo "HAS_ROUTING: $_HAS_ROUTING"
echo "ROUTING_DECLINED: $_ROUTING_DECLINED"
_VENDORED="no"
if [ -d "$GSTACK_SKILLS_ROOT" ] && [ ! -L "$GSTACK_SKILLS_ROOT" ]; then
  if [ -f "$GSTACK_SKILLS_ROOT/VERSION" ] || [ -d "$GSTACK_SKILLS_ROOT/.git" ]; then
    _VENDORED="yes"
  fi
fi
echo "VENDORED_GSTACK: $_VENDORED"
echo "MODEL_OVERLAY: claude"
_CHECKPOINT_MODE=$($GSTACK_BIN/gstack-config get checkpoint_mode 2>/dev/null || echo "explicit")
_CHECKPOINT_PUSH=$($GSTACK_BIN/gstack-config get checkpoint_push 2>/dev/null || echo "false")
echo "CHECKPOINT_MODE: $_CHECKPOINT_MODE"
echo "CHECKPOINT_PUSH: $_CHECKPOINT_PUSH"
[ -n "$OPENCLAW_SESSION" ] && echo "SPAWNED_SESSION: true" || true

Plan Mode Safe Operations

In plan mode, allowed because they inform the plan: $B, $D, codex exec/codex review, writes to ~/.gstack/, writes to the plan file, and open for generated artifacts.

Skill Invocation During Plan Mode

If the user invokes a skill in plan mode, the skill takes precedence over generic plan mode behavior. Treat the skill file as executable instructions, not reference. Follow it step by step starting from Step 0; the first AskUserQuestion is the workflow entering plan mode, not a violation of it. AskUserQuestion satisfies plan mode's end-of-turn requirement. At a STOP point, stop immediately. Do not continue the workflow or call ExitPlanMode there. Commands marked "PLAN MODE EXCEPTION — ALWAYS RUN" execute. Call ExitPlanMode only after the skill workflow completes, or if the user tells you to cancel the skill or leave plan mode.

If PROACTIVE is "false", do not auto-invoke or proactively suggest skills. If a skill seems useful, ask: "I think /skillname might help here — want me to run it?"

If SKILL_PREFIX is "true", suggest/invoke /gstack-* names. Codex skill file paths stay under $_GSTACK_PROJECT_DIR/.codex/skills/[skill-name]/SKILL.md; $GSTACK_SKILLS_ROOT is only the gstack runtime/bin root.

If output shows UPGRADE_AVAILABLE <old> <new>: use the installed gstack upgrade mechanism only if it is available; otherwise tell the user gstack <new> is available and AskUserQuestion with upgrade/snooze/skip/disable options. Write snooze state if declined. Do not treat the gstack runtime root as a skill directory.

If output shows JUST_UPGRADED <from> <to>: print "Running gstack v{to} (just updated!)". If SPAWNED_SESSION is true, skip feature discovery.

Feature discovery, max one prompt per session:

  • Missing $GSTACK_SKILLS_ROOT/.feature-prompted-continuous-checkpoint: AskUserQuestion for Continuous checkpoint auto-commits. If accepted, run $GSTACK_BIN/gstack-config set checkpoint_mode continuous. Always touch marker.
  • Missing $GSTACK_SKILLS_ROOT/.feature-prompted-model-overlay: inform "Model overlays are active. MODEL_OVERLAY shows the patch." Always touch marker.

After upgrade prompts, continue workflow.

If WRITING_STYLE_PENDING is yes: ask once about writing style:

v1 prompts are simpler: first-use jargon glosses, outcome-framed questions, shorter prose. Keep default or restore terse?

Options:

  • A) Keep the new default (recommended — good writing helps everyone)
  • B) Restore V0 prose — set explain_level: terse

If A: leave explain_level unset (defaults to default). If B: run $GSTACK_BIN/gstack-config set explain_level terse.

Always run (regardless of choice):

rm -f ~/.gstack/.writing-style-prompt-pending
touch ~/.gstack/.writing-style-prompted

Skip if WRITING_STYLE_PENDING is no.

If LAKE_INTRO is no: say "gstack follows the Boil the Lake principle — do the complete thing when AI makes marginal cost near-zero. Read more: https://garryslist.org/posts/boil-the-ocean" Offer to open:

open https://garryslist.org/posts/boil-the-ocean
touch ~/.gstack/.completeness-intro-seen

Only run open if yes. Always run touch.

If TEL_PROMPTED is no AND LAKE_INTRO is yes: ask telemetry once via AskUserQuestion:

Help gstack get better. Share usage data only: skill, duration, crashes, stable device ID. No code, file paths, or repo names.

Options:

  • A) Help gstack get better! (recommended)
  • B) No thanks

If A: run $GSTACK_BIN/gstack-config set telemetry community

If B: ask follow-up:

Anonymous mode sends only aggregate usage, no unique ID.

Options:

  • A) Sure, anonymous is fine
  • B) No thanks, fully off

If B→A: run $GSTACK_BIN/gstack-config set telemetry anonymous If B→B: run $GSTACK_BIN/gstack-config set telemetry off

Always run:

touch ~/.gstack/.telemetry-prompted

Skip if TEL_PROMPTED is yes.

If PROACTIVE_PROMPTED is no AND TEL_PROMPTED is yes: ask once:

Let gstack proactively suggest skills, like /qa for "does this work?" or /investigate for bugs?

Options:

  • A) Keep it on (recommended)
  • B) Turn it off — I'll type /commands myself

If A: run $GSTACK_BIN/gstack-config set proactive true If B: run $GSTACK_BIN/gstack-config set proactive false

Always run:

touch ~/.gstack/.proactive-prompted

Skip if PROACTIVE_PROMPTED is yes.

If HAS_ROUTING is no AND ROUTING_DECLINED is false AND PROACTIVE_PROMPTED is yes: Check if a CLAUDE.md file exists in the project root. If it does not exist, create it.

Use AskUserQuestion:

gstack works best when your project's CLAUDE.md includes skill routing rules.

Options:

  • A) Add routing rules to CLAUDE.md (recommended)
  • B) No thanks, I'll invoke skills manually

If A: Append this section to the end of CLAUDE.md:


## Skill routing

When the user's request matches an available skill, invoke it via the Skill tool. When in doubt, invoke the skill.

Key routing rules:
- Product ideas/brainstorming → invoke /office-hours
- Strategy/scope → invoke /plan-ceo-review
- Architecture → invoke /plan-eng-review
- Design system/plan review → invoke /design-consultation or /plan-design-review
- Full review pipeline → invoke /autoplan
- Bugs/errors → invoke /investigate
- QA/testing site behavior → invoke /qa or /qa-only
- Code review/diff check → invoke /review
- Visual polish → invoke /design-review
- Ship/deploy/PR → invoke /ship or /land-and-deploy
- Save prog

---

*Content truncated.*

When not to use it

  • When modifying code to fix issues
  • When needing to monitor non-web applications
  • When a baseline is not available for comparison

Limitations

  • Observes and reports only, does not modify code
  • Alerts on changes compared to a baseline, not absolute standards
  • Requires a baseline for effective monitoring beyond a basic health check

How it compares

This skill provides automated post-deployment monitoring with baseline comparisons and screenshot evidence, offering a structured approach to detecting regressions unlike manual checks.

Compared to similar skills

canary side by side with the closest alternatives in the catalog.

SkillInstallsUpdatedSafetyDifficulty
canary (this skill)02moReviewIntermediate
klingai-prod-checklist110dReviewIntermediate
agent-performance-optimizer35moNo flagsAdvanced
vibeops01moNo flagsBeginner

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