sk-pipeline-patterns

name	sk-pipeline-patterns
description	Defines the six canonical pipeline topologies (Sequential, Parallel Fan-Out, Iterative Loop, Human-Gated, Spec-Driven, 4D Wrapper) and their capability requirements. Use when an orchestrator is selecting an execution pattern for a new pipeline, matching a task's information flow to a topology, or checking Q7 capability gates before pattern traversal.
disable-model-invocation	true
user-invocable	false

Pipeline Patterns — Selection Reference

Distills Patterns 1–6 for pipeline topology selection. Load via agent skills: frontmatter; not user-invocable.

A fix/heal cycle bounded by max iterations and an escalation protocol. A multi-phase workflow where a specification acts as a formal contract for parallel implementation. A per-invocation processing framework that runs inside all other patterns.

Pattern Selection Matrix

<pattern_matrix>

Pattern	Information Flow	Worktree	Capability Requirements (Q7)	Best Applied To
1. Sequential	Linear (A → B → C)	Optional	none	Strictly dependent sequential phases.
2. Parallel	Fan-Out / Merge	Conditional	parallel_subagents: true; worktrees: true only for tracked-source writers	Independent analyses or reviews.
3. Iterative	Loop (Test → Fix)	Conditional	worktrees: true only for tracked-source writers	Fix/heal cycles with defined exit criteria.
4. Gated	Phase → GATE → User	Selective	none	Destructive or irreversible operations.
5. Spec-Driven	Spec → Plan → Implement	Conditional	parallel_subagents: true; worktrees: true only for tracked-source writers	Large feature work or complex migrations.
6. 4D Method	Wrapper (Internal)	N/A	none	Every agent turn within any other pattern.
</pattern_matrix>

Q7 capability gating: A worktree requirement is about tracked-source writer isolation, not topology alone. "Degrades to sequential" hides this — degrading scope is fine; degrading tracked-source isolation is not. Pattern 2, 3, or 5 on a platform with worktrees: false is valid for artifact-only data pipelines, but invalid when any step edits tracked source across parallel, iterative, or spec-driven branches. The worktree requirement binds code-writer steps only: data-retrieval/generation steps within a worktree pattern still OMIT isolation (a no-tracked-change worktree is auto-cleaned, losing gitignored artifacts — issue #31).

Pattern 3 — Iterative Loop Protocol

### 1. LOOP EXECUTION - **Cycle**: Tester (identifies failures) → Analyzer (diagnoses RCA) → Fixer (applies fix) → Restart. - **Iteration Cap**: Maximum 3 iterations by default.

2. ESCALATION (HARD-GATE)

**STOP** immediately and escalate to the user if: - Iteration count ≥ 3. - Failure count does not decrease for 2 consecutive cycles. - A fix reveals a new failure in a different architectural location (regression).

3. EARLY TERMINATION SIGNALS

• "One more fix should do it" (after 2+ failures).
• "The fix is almost working" (indicates lack of convergence).

Pattern 5 — Spec-Driven Development (SDD)

<sdd_workflow>

1. Specify: Generate spec.md (WHAT + WHY).
2. Plan: Generate plan.md (HOW).
3. Tasks: Decompose into tasks.md.
4. Gate: Mandatory human review of spec and tasks.
5. Implement: Parallel execution of tasks with two-stage review. </sdd_workflow>

Decision Tree

<decision_tree> Q7 capability preflight (consult before traversal):

• IF workflow_requires_tracked_source_isolation == true AND platform_profile.capabilities.worktrees == false: available patterns = {1, 4, 6}. Skip the Pattern 2 / 3 / 5 branches below and emit advisory: "This workflow requires tracked-source writer isolation, but this platform has worktrees:false. Limited to Patterns 1 and 4."
• IF platform_profile.capabilities.parallel_subagents == false: Patterns 2 and 5 are unavailable (their parallel fan-out cannot execute safely). Allow Pattern 3 when either worktrees: true OR workflow_requires_tracked_source_isolation == false.

Is the task multi-step with dependencies?

• NO: Apply 4D Method and execute directly.
• YES:
  • Independent/Mergeable tasks? → Pattern 2 (requires worktrees + parallel_subagents).
  • Fix/Heal cycle? → Pattern 3 (requires worktrees).
  • Irreversible action? → Pattern 4 (Human Gate).
  • Feature work? → Pattern 5 (SDD; requires worktrees + parallel_subagents).
  • Linear dependency? → Pattern 1. </decision_tree>

- Disk-based handoffs (file paths) must be used instead of pasting content between agents. - Pattern 6 (4D) must execute within every agent turn across all patterns. - Escalation state must be explicitly written to `pipeline-state.json` on failure.

Reference Files

• sk-4d-method/SKILL.md — Per-invocation wrapper.
• sk-spec-driven-development/SKILL.md — SDD implementation details.
• sk-write-review-isolation/SKILL.md — Review loop protocol.
• sk-worktree-safety/SKILL.md — Parallel isolation rules.
• references/ai-pipelines-trimmed.md — Full conventions trimmed for runtime.