A loop that cannot be stopped is not an engine — it is a runaway cart. Before your serpent grows teeth (golems, fix lanes, self-merges), it must learn the Wardens’ first law: everything autonomous is OFF until a named switch turns it on, and it stops the instant that switch is unset. Today you build the gate itself — and then you meet the failure that killed the real engine three mornings straight without producing a single log line.

The real-world skills: opt-in automation via repository variables, go/no-go gate jobs, least-privilege permissions, and the GitHub Actions rule that a caller job’s permissions cap every job in a workflow it calls — validated at trigger time, where no linter can save you.

🧭 Campaign note: Level 0101 is the Factory — CI/CD & DevOps — exactly where a gate belongs. The campaign’s chapters climb its difficulty ladder, not the level order.

📖 The Legend Behind This Quest

When the quest-perfection engine first shipped, its conductor never played a note: three scheduled mornings in a row ended in startup_failure — zero jobs, zero logs, only a single sentence on the run’s page. The fix was two lines. The lesson was permanent: some laws are enforced by the realm itself, at the gate, before any of your code runs — and your loop must be designed so that “off” is a clean, silent, zero-cost state, not an error.

🎯 Quest Objectives

By the end of this quest you will:

• Add a kill switch — a LOOP_ENABLED repository variable your workflow checks before doing anything
• Build a gate job — one cheap job that outputs go=true/false; every other job needs it
• Apply least privilege — workflow-level permissions: contents: read, elevated only where written proof requires it
• Trigger and read a startup_failure — and learn why gh run view --log-failed returns nothing for it
• Grant caller permissions to a called workflow — the two-line fix for the whole class

🗺️ Quest Prerequisites

• 📋 Chapter I’s potion-book repo with a green First Turn run
• 📋 15 minutes of patience for GitHub’s scheduler (or use workflow_dispatch levers)

🧙‍♂️ Chapter 1: The Kill Switch and the Gate Job

The gate pattern is one cheap job that decides go or no-go — and a workflow whose every other job refuses to start without it. Add this to your First Turn workflow:

# .github/workflows/first-turn.yml  (additions)
permissions:
  contents: read          # the workflow-wide floor: read-only

jobs:
  gate:
    runs-on: ubuntu-latest
    outputs:
      go: ${{ steps.check.outputs.go }}
    steps:
      - id: check
        env:
          ENABLED: ${{ vars.LOOP_ENABLED }}
        run: |
          set -euo pipefail
          go=false
          if [ "$ENABLED" = "true" ]; then
            go=true
          else
            echo "loop idle (LOOP_ENABLED=$ENABLED) — flip the variable to arm."
          fi
          echo "go=$go" >> "$GITHUB_OUTPUT"

  turn:
    needs: gate
    if: ${{ needs.gate.outputs.go == 'true' }}
    permissions:
      contents: write     # elevated ONLY here — this job commits the ledger
    runs-on: ubuntu-latest
    steps:
      # … your Chapter I steps unchanged …

Arm and disarm it like a warden, and watch both behaviors:

gh variable set LOOP_ENABLED --body true    # armed
gh workflow run first-turn.yml && gh run watch

gh variable delete LOOP_ENABLED             # disarmed
gh workflow run first-turn.yml && gh run watch   # gate: success, turn: skipped

The disarmed run is the important one: green, silent, zero side effects. An automation that errors when disabled trains humans to ignore red — the Sentinel’s Horn fatigue rule applies to CI too.

⚔️ Skills You’ll Forge

• The vars.* context (repository variables) vs secrets.* — switches are variables, credentials are secrets
• Job outputs → needs.<job>.outputs.<name> — how gate verdicts travel
• Per-job permissions elevation over a read-only floor

🔍 Knowledge Check

• Why check the switch in a job instead of skipping the whole workflow with a repository setting?
• When you later add auth (Chapter III), the gate should require the switch and the secret. Why both?

🧙‍♂️ Chapter 2: The Error With No Logs — startup_failure

Some failures happen before any job exists. GitHub validates the whole workflow graph at trigger time; if the graph itself is illegal, the run is stamped startup_failure — no jobs, no logs, and gh run view --log-failed shrugs. The real engine hit exactly this, three days straight, with this shape:

# The trap: a workflow-level read-only floor…
permissions:
  contents: read

jobs:
  fix:
    uses: ./.github/workflows/quest-fix.yml   # …calling a workflow whose jobs
    secrets: inherit                          # request contents:write — DENIED

The realm’s law: a caller job’s permissions cap every job in the workflow it calls. The called workflow requested contents: write, pull-requests: write; the caller granted contents: read. Verdict, rendered at the gate, before the gate job itself could even run:

Invalid workflow file …
The nested job 'fix' is requesting 'contents: write, pull-requests: write',
but is only allowed 'contents: read, pull-requests: none'.

The two-line cure — grant on the caller job exactly what the called jobs request:

  fix:
    permissions:
      contents: write
      pull-requests: write
    uses: ./.github/workflows/quest-fix.yml
    secrets: inherit

Two survival notes from the same battle:

• actionlint cannot catch this. The rule is validated server-side. Lint locally, but smoke-test the graph by dispatching with inputs that make the expensive jobs no-op (the real engine uses a max_slices: 0 dispatch input for exactly this).
• The error lives only on the run’s web page. When a scheduled run shows startup_failure with zero jobs, open it in the browser — the one-sentence verdict is printed there and nowhere else.

🔍 Knowledge Check

• Why does GitHub validate called-workflow permissions at trigger time instead of when the job starts?
• Your gate job never ran during the startup failures. What does that tell you about where in the lifecycle graph validation sits?

🔁 Reproduce It

Study the real two-line fix and its battle report:

• PR #422 — bamr87/it-journey@cfeb5e3aa (+24/−2): the caller-permissions grant, the artifact-name fix, and the max_slices=0 smoke-test pattern, written up after three silent startup_failure mornings
• The gate pattern at full scale: gate: jobs in .github/workflows/quest-perfection.yml, quest-fix.yml, and quest-walkthrough.yml — every lane carries its own *_ENABLED switch (QUEST_PERFECTION_ENABLED, QUEST_FIX_ENABLED, …), so a human can kill one arm without silencing the others

🎮 Mastery Challenge

Objective: stage-gate your potion book like a real fleet.

Success Criteria:

• Split your loop into two lanes — first-turn.yml (check + ledger) and a stub potion-fix.yml reusable workflow with its own FIX_ENABLED gate — and call the stub from the first lane
• Deliberately reproduce the startup_failure (call the stub while its jobs request contents: write under a read-only caller), read the error on the run page, then fix it with the caller grant
• Prove both kill switches work independently: walk-only mode (LOOP_ENABLED=true, FIX_ENABLED unset) runs the check and skips the fix lane cleanly

🎁 Rewards & Progression

• 🚦 Warden of the Gate — earned when your disarmed loop runs green, silent, and free
• ⚡ Skills unlocked: gate jobs · kill switches · least privilege · startup-failure forensics
• 📊 +75 XP

🗺️ Quest Network

graph LR
    Prev[🔁 I · The First Turn] --> Cur[🚦 II · The Warden's Gate]
    Cur --> Next[🤖 III · Summon the Golem]
    click Prev "/quests/0000/ouroboros-loop-01-the-first-turn/"
    click Next "/quests/0011/ouroboros-loop-03-summon-the-golem/"

🔮 Next Adventures

• 🤖 Chapter III — Summon the Golem: a Claude Code agent joins the loop, under oath
• 👑 Campaign hub: Epic Quest: The Ouroboros Loop

📚 Resource Codex

• GitHub Actions: workflow permissions
• GitHub Actions: reusing workflows — the caller/called permission rules
• actionlint — catches much, but not server-side graph law

🕸️ Knowledge Graph

Structured wiki-links connect this quest to the IT-Journey knowledge graph.

Campaign hub: [[Epic Quest: The Ouroboros Loop]] Previous: [[The First Turn]] · Next: [[Summon the Golem]] Level home: [[Level 0101 - CI/CD & DevOps]]