adr-backfill

name

adr-backfill

description

This skill should be used to retroactively record an architectural decision that was made in the past but never written up as an ADR — typically surfaced by a doc audit or by a user realising a long-ago shipped change should have been documented. PROACTIVELY activate on "backfill ADR", "retroactive ADR", "post-hoc ADR", "reconstruct an ADR from history", "write up a past decision", "we never documented this decision", "decision was made but no ADR exists", "we decided years ago", "back when", "before my time", or "the audit surfaced a backfill candidate." Tense rule: `adr-drafting` claims "we decided / we're deciding"; `adr-backfill` claims "we decided years ago / back when / before my time / never wrote it down." Refuses when reconstruction confidence is `low` -- routes to `open-questions.md`. Requires evidence in two independent locations and a verbatim honesty clause in the record. Provides: backfill ADR template, confidence rubric, evidence corroboration, honesty-clause boilerplate.

adr-backfill

Retroactively records a past architectural decision that was made but never documented. Surfaces typically come from /doc-audit BACKFILL-ADR rows or from a user who realises a past change should have been an ADR. Operates with relaxed gates relative to adr-drafting (the decider may be unrecoverable, alternatives may not be reconstructible) but enforces stricter honesty: a backfill ADR must visibly mark itself as a backfill so future readers do not mistake it for a contemporaneous record.

When to use this skill

• /doc-audit surfaced a BACKFILL-ADR candidate row and the user wants to record it.
• The user describes a decision in past tense — "we decided years ago," "back when," "before my time," "we never wrote it down" — about a change whose effects are visible in the codebase today.
• A code-archaeology session uncovered a migration, vendor removal, or subsystem retirement with no corresponding decision record.

When NOT to use this skill

• The decision is current or in-flight — use adr-drafting instead.
• The decision is already recorded in any form — use adr-critique to tighten the existing record.
• reconstruction-confidence is low (only the what is recoverable, not the why) — refuse to draft and route to open-questions.md.
• The change is not architecturally significant — see _shared/adr-is-backfillable.md § 2. Route via the alternatives catalog in doc-diagnostic.

Inputs

• Required: at least two independent evidence locators (see _shared/adr-is-backfillable.md § 3). Examples: commit SHA + migration file, migration file + removed manifest entry, removed module + retired feature-flag commit.
• Required: a measurable signal for the architectural characteristic affected (see _shared/adr-is-backfillable.md § 4).
• Optional: a BACKFILL-ADR row from /doc-audit containing the proposed decision, evidence-locator, ASR-test-result, reconstruction-confidence, and suggested-status fields. If present, use it as the starting brief.

Refusal behaviors

The skill refuses to draft when:

• The eligibility self-check in _shared/adr-is-backfillable.md fails any of items 1-3 or 5 (no evidence, no ASR significance, single-locator evidence, or already recorded).
• reconstruction-confidence is low — the why would have to be fabricated. Route to open-questions.md.
• No measurable signal can be named for the architectural characteristic affected.
• The user wants the backfill ADR to look like a contemporaneous record (no honesty clause). The clause is non-negotiable.

Core operating rule

Never emit more than one question or one step per message. Inherits the one-question-per-turn discipline from adr-drafting. Backfill is at least as easy to over-stuff as forward drafting; tighter discipline, not looser.

The four phases

Phase 1 — Eligibility and evidence

Run the seven-item eligibility self-check from _shared/adr-is-backfillable.md against the candidate. Walk it one item at a time. If any item fails, stop:

• Items 1-3 or 5 failing → refuse to draft, explain which evidence is missing.
• Item 4 failing (no measurable signal) → drop to open-questions.md.
• Item 6 failing (confidence low) → drop to open-questions.md with the evidence that would upgrade it.
• Item 7 failing (decider not nameable and not yet marked unrecoverable) → ask once whether to use the unrecoverable marker or to keep digging.

Confirm the two-locator evidence in dialogue — quote the locators back to the user so they can correct a mistaken artifact. Do not proceed to Phase 2 until the user agrees the evidence is right.

Phase 2 — Historical context reconstruction (best effort)

For each section of the ADR, gather what can be reconstructed and mark gaps explicitly rather than papering over them.

Section	Reconstruction approach
Context (the forces)	Read commit messages, PR descriptions, ticket links, removed README content, retired runbooks. Cite each source. If the forces cannot be reconstructed, write "Forces at the time of the decision could not be reconstructed from available evidence." — do not invent.
Decision	The what — almost always reconstructible from the shipped change. Stated in present-tense active voice, same as a forward ADR.
Alternatives	Often the hardest to recover. If the original alternatives are visible in PR review comments, commit history, or contemporary RFCs, cite them. If not, the honesty clause covers the gap.
Consequences (Good / Bad)	Reconstruct from observable effects in the codebase today. "Removed 14k LOC" is observable; "Improved developer morale" is not.
Decider	Named human(s) from commit author / PR reviewer / explicit attribution, OR the literal token unrecoverable. Never fabricate.

Phase 3 — Draft with honesty clause (MANDATORY)

Every backfill ADR must contain a verbatim honesty clause near the top of the body (after the title, before Context). The verbatim form, required fields, terminal punctuation, and refusal conditions live in references/honesty-clause.md — read it before drafting.

The clause exists so a future reader cannot mistake the backfill for a contemporaneous record. Removing or softening it is a critique-flag (see adr-critique audit checklist).

Phase 4 — Save

Same save discipline as adr-drafting:

1. Glob ADR Explorer-friendly directories first (docs/adr/, docs/decisions/, docs/architecture/decisions/, **/adr/*.md); also check legacy architecture/decisions/ but warn it may need custom ADR Explorer root configuration. Use the first existing directory; if none, create docs/adr/.
2. Auto-number: read existing ADRs, take max+1, zero-pad to 4 digits. The backfill ADR takes the next available number, not a number from the past. Numbering reflects creation order, not decision order. The original decision date appears inside the file (see frontmatter); the number is just-now.
3. Filename: NNNN-kebab-imperative-title.md.
4. Write the file with the honesty clause and the backfill-specific frontmatter (see template below).
5. Update the decision-log README.md index, marking the row with (backfilled YYYY-MM-DD).

Backfill-specific frontmatter

---

title: "<imperative verb phrase>"
status: accepted                   # or deprecated if reversed; keep status ADR Explorer-compatible
date: <original decision date if known, else first-evidence date in ISO 8601>
backfilled-on: YYYY-MM-DD          # today
deciders:
  - <named human, or unrecoverable>
evidence:                          # at least two locators
  - <commit SHA / file path / manifest line>
  - <commit SHA / file path / manifest line>
reconstruction-confidence: high | medium
asr-characteristic: <latency | cost | availability | security | maintainability | operability | portability | ...>
asr-signal: "<measurable signal -- e.g., removed 14k LOC and one vendor dependency>"
tags: [backfill]
---

If the decision has since been reversed by a later shipped change, set status: deprecated and cite the reversing commit / migration in evidence: plus the honesty clause or notes. The backfill still gets recorded — the historical decision matters even after reversal — but the status remains ADR Explorer-compatible.

Status conventions

Status	Use when…
accepted	The decision is still in force today. Default.
deprecated	A later shipped change undid the original decision. Cite the reversing evidence.

Backfill ADRs never use proposed or rfc — a backfill is, by definition, a recording of a decision that was already shipped. Keep backfill identity in tags: [backfill], backfilled-on, evidence fields, and the mandatory honesty clause; do not encode it in status.

Refusal: when the user wants the honesty clause removed

The honesty clause is the single non-negotiable element of a backfill ADR. If the user asks to remove it, soften it, or hide it in a footnote, refuse. Explain that a backfill without the clause looks like a contemporaneous record and silently poisons the decision log — a future reader has no way to tell the rationale was reconstructed rather than recorded in the moment. The clause stays in the body.

adr-critique enforces this independently: a record with tags: [backfill] or backfilled-on whose body lacks the honesty clause is a flag in the audit checklist.

Hand-off

adr-backfill does not chain automatically to other skills. After the backfill record is saved, the user may choose to:

• Run adr-critique against the new record to tighten language (especially if reconstruction-confidence was medium).
• Run c4-model to add a Context / Container view that reflects the post-decision system shape (optional).
• Update open-questions.md to close out any locked questions the backfill resolved.

None of these are forced. Soft hand-off via skill triggers only.

References

• references/honesty-clause.md — the canonical spec for the Phase 3 honesty clause (form, required fields, terminal punctuation, refusal conditions). Single source of truth; adr-critique reads the same file.
• ../_shared/adr-is-backfillable.md — the seven-item eligibility self-check (used in Phase 1)
• ../_shared/adr-is-not.md — applies to backfill ADRs the same as forward ADRs (no tutorial, no implementation guide, no marketing, no hedging, no long-form padding)
• ../doc-diagnostic/references/audit-procedure.md — defines the BACKFILL-ADR row schema that feeds this skill
• adr-drafting skill — the forward-drafting counterpart for in-the-moment decisions
• adr-critique skill — for tightening the saved backfill record afterwards
• doc-diagnostic skill — for the ASR definition and the alternatives catalog