Story Splitting (Vertical Slicing Patterns) Skill

Story Splitting (Vertical Slicing Patterns)

Overview

A pattern catalog for splitting epics and large stories into smaller, shippable, end-to-end slices that still deliver user value. Built on Richard Lawrence's canonical story-splitting flowchart (the 9 patterns most product teams converge on) with worked before/after examples and a quick-reference decision tree.

The single most common reason teams fail to deliver predictably is that stories are too large. Large stories balloon in cycle time (see cycle-time-analyzer/), create coordination overhead, and resist incremental release. The remedy is not to estimate more carefully; it is to split smaller — vertically, so each slice (1) delivers value the end user can perceive, (2) fits in a single sprint, (3) is independently shippable, and (4) passes INVEST quality gates (see wwas/). The skill is pattern-based — no Python tool is needed; the value is the recipes and the worked examples.

Core Capabilities

9 canonical Lawrence patterns — workflow steps, business-rule variations, happy/unhappy path, input/output variations, data variations, data-entry methods, deferred performance/quality, CRUD operations, and break-out-a-spike (plus optional "Major Effort First").
Vertical-slicing decision tree — a top-down tree that names the first applicable pattern for any oversized story.
Vertical-vs-horizontal discipline — keeps every slice end-to-end and demoable instead of layer-by-layer.
Ordering & INVEST gating — sequences slices smallest-value-first and verifies each against I-N-V-E-S-T.

When to Use

Sprint refinement -- A story exceeds the team's 85th-percentile cycle time or fails the INVEST-S (Small) test.
Epic decomposition -- An epic from create-prd/ or story-mapping/ needs to be broken into a release backlog.
Stuck story -- A story has been "almost done" for two sprints; usually a sign it should have been split.
New team onboarding -- A team's stories are routinely too large; introduce the patterns explicitly.
Release planning -- Need to find a thin slice that ships in 2 weeks instead of 8.

When NOT to Use

The work is a true atomic operation that genuinely cannot be split (rare; usually a sign of incomplete analysis).
The team is splitting horizontally by layer (DB, API, UI) -- that produces non-shippable slices and defeats the point.
The work is a spike (timeboxed investigation); spikes are intentionally not user-facing.

Clarify First

Before splitting, confirm these inputs. If any is unknown or vague, ASK — do not assume:

[ ] The original story's user value in one sentence — no clear value means reframe the problem (create-prd/), not split (gates the whole procedure, Step 1)
[ ] What ships next — beta cohort vs general availability (changes which pattern applies: happy-path-only vs full business rules)
[ ] Why it's too big — exceeds cycle time, fails INVEST-S, or has been "almost done" for sprints (points to the first applicable pattern in the decision tree)

Stop rule: ask only the 2-3 that most change the output. If the user says "just draft it," proceed and list your assumptions at the top of the artifact.

Quick Start

State the user value of the original story in one sentence. (No clear value? Reframe the problem via create-prd/, don't split.)
Walk the decision tree (in references/story-splitting-procedure.md); stop at the first pattern that applies.
Draft slices in wwas/ or job-stories/ format; verify each is vertical (crosses all layers, independently demoable).
Order slices smallest-value-first, run the INVEST check, and replace the original story in the backlog.

References

Load the reference that matches the task — keep this file lean and pull detail on demand:

references/story-splitting-procedure.md — vertical-vs-horizontal slicing, all 9 patterns with before/after examples, the full decision tree, the optional tenth pattern, the 8-step workflow, an end-to-end worked example, troubleshooting, and success criteria. Read when splitting a specific story.
references/splitting-patterns-guide.md — the deepest pattern catalog: each pattern with cues, recipes, multiple worked examples, pattern-selection order, anti-patterns, and the post-split INVEST check. Read for the full theory or when a pattern is ambiguous.
references/red-flags.md — common ways splits go wrong, each with bad/good examples. Read before split tickets enter a sprint.
assets/before-after-examples.md — 15+ before/after splits across SaaS, mobile, B2B, and platform scenarios. Use as a copy-from library.

Scope & Limitations

In Scope:

The 9 canonical Lawrence patterns plus optional "Major Effort First"
Vertical-slicing decision tree
Worked examples for SaaS, mobile, and B2B scenarios
Integration with INVEST (via wwas/) and story mapping (via story-mapping/)

Out of Scope:

User story format itself (use wwas/, job-stories/)
Sprint capacity calculation (use scrum-master/sprint_capacity_calculator.py)
Backlog prioritization (use prioritization-frameworks/)
Story mapping at the release level (use story-mapping/)

Important Caveats:

Splitting cannot rescue a poorly defined problem. If the story has no clear user value, the answer is problem framing (create-prd/), not slicing.
Slicing has limits. A story may be at the smallest useful size and still feel large because the team has not done the work before. Treat the first few of any new kind of story as a learning tax.
The "right" split depends on what ships next. The same epic can be split differently for a beta cohort (Pattern 3: happy path only) vs general availability (Pattern 2: full business rules). Choose based on the next release context, not in the abstract.

Integration Points

| Integration | Direction | What Flows | |-------------|-----------|------------| | wwas/ | Output format | Split slices are written as WWAS items | | job-stories/ | Output format | Alternative format for situation-driven slices | | create-prd/ | Receives from | Epic-level scope from PRD feeds splitting | | story-mapping/ | Complementary | Story map identifies the slices that need splitting | | prioritization-frameworks/ | Feeds into | Split slices get individually scored (RICE/ICE) for ordering | | cycle-time-analyzer/ | Diagnostic for | Long cycle times indicate stories that should have been split | | backlog-refinement/ | Used in | Splitting is the core activity in refinement sessions | | scrum-master/ | Improves | Predictability improves dramatically when stories are uniformly small |

Agent Skills: Story Splitting (Vertical Slicing Patterns)

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