Decision Journal Skill for Claude

Decision Journal Contract

When To Use

• A workflow has just made a decision and needs to record the tradeoff:

what was chosen, what was rejected, what was sacrificed.

• A workflow has hit a failed approach, rework, or blocker and needs to

record the lesson.

• Building or validating a consumer hook that writes to the journal.

When NOT To Use

• Scaffolding the files at project init (that is attune:project-init).
• Recording a full architecture decision that warrants a numbered ADR in

docs/adr/; reference its number from a journal entry instead of

duplicating it.

This is a convention and a helper rather than a hard runtime

dependency. Consumers degrade gracefully when leyline is absent

(see Fallback).

What This Captures, And Why

AI-assisted work tends to narrate tool output ("the agent built X") and lose

the human reasoning: the decision, the road not taken, and the honest rework

nobody mentions. Two append-only logs, co-located with the code, fix that:

• docs/tradeoffs.md records decisions and the alternatives sacrificed.
• docs/lessons-learned.md records insights, failed approaches, and rework,

framed blamelessly.

Files And Discipline

Both files live in docs/ (co-location is the strongest anti-staleness

lever). Each is a single append-only running log with a scannable

## Active index at the top and an ## Archive section at the bottom.

• Append-only. An accepted entry is never edited or deleted; only its

Status changes.

• Supersede, do not overwrite. A reversal adds a new entry, flips the old

entry's status to superseded-by: <new-id>, and links both ways.

• Stable IDs (TR-001, LL-001) so links from PRs, commits, and code

never break.

• Every entry links back to its PR, commit, or issue.

Status vocabularies:

• Tradeoffs: proposed -> accepted -> (superseded-by: TR-NNN | deprecated)
• Lessons: open -> actioned -> closed

Capture UX: Draft And Confirm

When a workflow reaches a decision or lesson point:

• Draft the entry from the live context of the phase (the options weighed,

what was given up, the failure and its root cause).

• Show the draft to the human and let them confirm or edit.
• Append it. Tradeoffs start proposed; lessons start open.

Do not auto-write without the confirm step. The point is to capture the

human reasoning, not to generate noise.

CLI Interface

Run the helper from leyline:

python3 ${LEYLINE}/scripts/journal_append.py <tradeoffs|lessons> \

--project-root <repo-root> \

--title "<short title>" \

[--phase <phase>] [--status <status>] \

[--field key=value ...] \

[--json '<full field object>'] \

[--supersedes TR-NNN] \

[--dry-run]

The helper assigns the next ID, renders the template, inserts the entry above

the ## Archive marker, updates the active index, and (with --supersedes)

flips the prior entry's status and adds backlinks. It is idempotent: appending

an entry whose substantive fields already appear is a no-op.

Tradeoff fields

title (required), context, drivers (list), options (list of

{name, pros, cons, chosen}), decision, ystatement,

consequences_positive, consequences_negative, phase, deciders,

links. Prefer --json for the list-valued fields. status and date

are auto-set (proposed / today) but can be overridden.

Lesson fields

title (required), what_happened, what_went_well, what_didnt_work,

root_cause, action, category, owner, phase, links. status

and date are auto-set (open / today) but can be overridden.

Fallback (leyline Absent)

The entry template ships inside each scaffolded file as an HTML-comment footer

(<!-- ENTRY TEMPLATE ... -->). When the helper is unavailable, a consumer (or

a human) copies that block into the section above ## Archive, assigns the

next sequential ID, fills it in, and adds an index row by hand. The fallback

template covers the same core sections as the canonical one so entries stay

consistent across the two paths.

Consumer Hook Shape

Each workflow adds one block at its natural endpoint:

Record to the decision journal (draft + confirm):

• If leyline is installed: run journal_append.py for a {tradeoff|lesson},

drafting fields from this phase's context; show the draft; append on

confirm.

• Fallback (leyline absent): append to docs/{tradeoffs|lessons-learned}.md

using the footer ENTRY TEMPLATE; assign the next sequential ID.

Compliance Test

python3 ${LEYLINE}/scripts/journal_append.py tradeoffs \

--title "Compliance check" --field context="verify" --dry-run

Must print a rendered entry containing ## TR-001: and write nothing.

Exit Criteria

• [ ] docs/tradeoffs.md and docs/lessons-learned.md exist with a

## Active index and an ## Archive section.

• [ ] A new entry has a unique TR-NNN/LL-NNN id and an index row.
• [ ] Superseding an entry flips the old status to superseded-by: <id> and

adds bidirectional links; the old entry is not deleted.

• [ ] Re-running the same append is a no-op (idempotency holds).
• [ ] A consumer with leyline absent still produces a correctly shaped entry

from the in-file ENTRY TEMPLATE.