ln-plan

name	ln-plan
description	Break a feature or project area into frontier items and update `memory/PLAN.md`. Re-run to retire completed work, reorder priorities, or add new items.
argument-hint	[feature or project area to plan]

Ln Plan

Plan the rolling frontier, not the whole historical timeline.

memory/PLAN.md is the canonical record of what's next. docs/archive/PLAN_HISTORY.md is the only sanctioned archive for retired plan history. memory/CARDS.md is the sanctioned derivative queue for multiple prepared scope cards inside one frontier item; it is not canonical planning state. Do not invent other sidecar plan docs, milestone ledgers, or alternate memory locations without explicit permission.

Frontier vs slice vocabulary

Use frontier item for a named canonical work item in memory/PLAN.md. Frontier items are the unit of Linear issue / Graphite branch work and should be vertical enough to establish or unlock a meaningful product or architecture step.

Use slice for the buildable scope card produced by ln-scope and implemented by ln-build. A slice is often a sub-unit of one frontier item. Several slices may land on the same frontier branch. Do not turn slices into separate PLAN entries unless the frontier itself changes shape, ownership, or dependency ordering.

The vertical-slicing instinct still applies at planning time: frontier items should cut through the relevant concerns of memory/SPEC.md instead of becoming layer-by-layer chores. The term "frontier" names their canonical/branch role; the term "slice" remains reserved for scoped execution.

Plan document shape

Prefer the conflict-resistant mature shape:

• Context — short rolling narrative for re-entry
• Sequencing — small, frequently edited ordering/status references by stable frontier id
• Frontier Definitions — relatively stable per-frontier definitions keyed by stable id
• Recently Completed — last 2-3 completed frontier items only
• Dependencies — active / next blocking relationships by stable id only

Within Sequencing, use:

• Active — ordered frontier items open now
• Next — near-horizon frontier items, loosely ordered
• Parallel / Low-conflict — useful work that can proceed without disturbing the main stack
• Horizon — future work, lightly shaped

Archive deeper history to docs/archive/PLAN_HISTORY.md instead of keeping it live in memory/PLAN.md.

Treat frontier items as branch-sized work, not commit-sized work. If one frontier item will unfold as several consecutive verified slices, keep that execution queue in memory/CARDS.md or in session context instead of fragmenting memory/PLAN.md into a commit ledger. memory/PLAN.md may carry at most a lightweight pointer such as current card queue: memory/CARDS.md; detailed discretionary sub-slicing belongs in memory/CARDS.md.

Input

The feature or project area: $ARGUMENTS

If context is thin, run a brief interview — not a full ln-grill.

If this is a fresh thread or the frontier rationale is unclear, read HANDOFF.md if present before planning.

Planning rules

Stable frontier ids

Every frontier definition should have a stable lowercase id / slug. Good ids are short and semantic, e.g. agent-fixture-substrate, intent-graph-semantics, changeset-ledger.

Rules:

• Sequencing references frontier ids; it does not duplicate definition blocks.
• Frontier Definitions are keyed by frontier id and should not move just because ordering changes.
• Rename a frontier id only when the identity of the work changed, not because the title improved.
• Linear issue ids belong in the definition metadata when known; they are not the only stable id.

Work-type awareness

Classify each frontier item before deciding how much planning weight it needs.

Work type	Planning weight
Structural	full frontier definition with memory/SPEC.md traceability
Bounded feature	objective + acceptance + verification; add memory/SPEC.md links only if durable boundaries change
Hardening	task-level objective + acceptance
Bugfix	usually do not add to memory/PLAN.md unless it changes frontier priority
Refactor	route through ln-refactor unless it is itself frontier work

Anti-fragmentation

Create a new frontier item only when it introduces at least one of:

1. a new lifecycle seam
2. a new transport or persistence seam
3. a new workflow entry / exit behavior
4. a meaningful unblocker for forward progress
5. a distinct dependency / branch boundary that should be tracked independently

Do not fragment the plan for minor action/status variants or ordinary follow-through inside a settled seam.

Do not split one frontier item into several new PLAN entries just because execution will require several scope cards or commits. Only split when the frontier itself changes shape, ownership, or dependency ordering.

Sequencing vs definition edits

When priorities change, edit Sequencing first. Do not move or rewrite frontier definitions merely to reorder work.

When the meaning, acceptance, verification, traceability, or design-doc references of a frontier changes, edit its Frontier Definitions entry.

When a frontier completes, remove it from Sequencing, add a terse Recently Completed entry, and archive older completion history if needed. Keep the definition only if it still carries live rationale for nearby work; otherwise archive/retire it.

Epistemic horizon

If live low-confidence assumptions block downstream work, stop the plan at that boundary. Plan spikes or thinner proving frontier items, not fantasy certainty.

Procedure

1. Read memory/PLAN.md if it exists. Identify existing frontier ids and retire/archive stale completed material into docs/archive/PLAN_HISTORY.md.
2. Read memory/SPEC.md if it exists. Pull only the live requirements, assumptions, decisions, and invariants that still constrain forward work.
3. Explore the codebase enough to understand real boundaries.
4. Draft or revise Sequencing (Active, Next, Parallel / Low-conflict, Horizon) by stable frontier id.
5. Draft or revise Frontier Definitions only for new or substantively changed frontier items.
6. Add Why now / unlocks in a frontier definition when ordering would otherwise be opaque to a fresh thread.
7. Keep Recently Completed to 2-3 terse items max. Move older history to docs/archive/PLAN_HISTORY.md, not to handoff files or ad hoc notes.
8. Update Dependencies to reflect only active / next items, by frontier id.
9. If several commit-sized execution steps are already obvious inside one frontier item, keep them out of memory/PLAN.md; they belong in memory/CARDS.md or in the active thread as derivative execution detail.

Traceability

Traceability is conditional on structural significance.

• Structural frontier items should name relevant requirements, assumptions, decisions, or invariants from memory/SPEC.md.
• Bounded features and hardening tasks only need SPEC links if they change durable boundaries or depend on a live assumption.
• Scope-card slices inherit traceability from their containing frontier unless ln-scope discovers a durable change that must promote back into SPEC/PLAN.

Output

Write or update memory/PLAN.md using the plan template.

Routing

After writing the plan, present these options to the user (use tool-ask-question):

#	Label	Target	Why
1	Scope next slice	ln-scope	The frontier is clear and ready to scope
2	Design oracles	ln-oracles	Verification design needs explicit work
3	Grill it more	ln-grill	Planning surfaced unresolved product questions
4	Back to triage	ln-consult	Direction needs reassessment

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