name	derrick-decision-log
description	Record a new architectural decision in DESIGN.md §12. Use when locking in a choice that has been open, when superseding an existing decision, or when promoting an open question to a resolved decision. Triggers include "record a decision", "lock this in", "add D entry", "decision log", or natural-language equivalents.

Derrick Decision Log

Append a new D# entry to DESIGN.md §12 (Decisions taken) without breaking the format. Update or remove the corresponding open question if there was one.

When to use

A choice that has been an open question is now resolved.
A new constraint emerges mid-implementation that future PRs need to respect.
An existing D entry is being superseded.

Format

Each entry is one row in the existing table:

| D## | **Title**: one or two sentences describing the decision. | §section |

D## is the next integer (D27, D28, …). Never reuse a number even if a decision is superseded.
Title is bold, ≤8 words, captures the essence.
Body is one or two sentences. Reference the chosen approach, not the alternatives.
§section points at the load-bearing locus in DESIGN.md.
A superseding decision body begins "Supersedes D##." and explains the shift.

Process

Read DESIGN.md §12 to find the next free D number.
Locate the affected section in DESIGN.md. If it doesn't reflect the decision yet, update it first (the prose, not the table).
Add the new row to the §12 decisions table.
If the decision resolves an open question, remove the question from the "Remaining open questions" subsection.
Commit with a message in the form design: D## — <title> so the decision is greppable in git history.

What this skill does NOT do

Edit existing D entries. They are immutable except for typo fixes (handled by direct edit, not this skill).
Add code. Pure documentation skill.
Add open questions. New open questions are added directly to §12 by design-keeper without using this skill.

Reference

DESIGN.md §12 — Decisions taken & remaining open questions.
AGENTS.md — house rule 7 (DESIGN.md is the rulebook).
.claude/agents/design-keeper.md — the agent that uses this skill most often.

Derrick Decision Log

Append a new D# entry to DESIGN.md §12 (Decisions taken) without breaking the format. Update or remove the corresponding open question if there was one.

When to use

A choice that has been an open question is now resolved.

A new constraint emerges mid-implementation that future PRs need to respect.

An existing D entry is being superseded.

Format

Each entry is one row in the existing table:

| D## | **Title**: one or two sentences describing the decision. | §section |

D## is the next integer (D27, D28, …). Never reuse a number even if a decision is superseded.

Title is bold, ≤8 words, captures the essence.

Body is one or two sentences. Reference the chosen approach, not the alternatives.

§section points at the load-bearing locus in DESIGN.md.

A superseding decision body begins "Supersedes D##." and explains the shift.

Process

Read DESIGN.md §12 to find the next free D number.

Locate the affected section in DESIGN.md. If it doesn't reflect the decision yet, update it first (the prose, not the table).

Add the new row to the §12 decisions table.

If the decision resolves an open question, remove the question from the "Remaining open questions" subsection.

Commit with a message in the form design: D## — <title> so the decision is greppable in git history.

What this skill does NOT do

Edit existing D entries. They are immutable except for typo fixes (handled by direct edit, not this skill).

Add code. Pure documentation skill.

Add open questions. New open questions are added directly to §12 by design-keeper without using this skill.

Reference

DESIGN.md §12 — Decisions taken & remaining open questions.

AGENTS.md — house rule 7 (DESIGN.md is the rulebook).

.claude/agents/design-keeper.md — the agent that uses this skill most often.

derrick-decision-log