architectural-decision-record

# Create ADR

## Operating Principles

- **YAGNI applies to ADRs themselves.** Apply the evidence-based YAGNI rule from [../../references/yagni-rule.md](../../references/yagni-rule.md). An ADR is worth recording only when there is a concrete forcing function today — a real decision the team is actively making, an existing code path or architectural choice that will be locked in by this record, an applicable regulation, a customer commitment, or a documented incident that drove the choice. ADRs about decisions that don't have to be made yet, "for future flexibility", "best practice says we should pick X", or symmetry with other ADRs ("we have one for auth, so we should have one for billing") are YAGNI candidates and the ADR should not be written. When proposed, recommend deferral with the trigger that would justify writing the ADR (a real decision arising, a real incident, a real regulation taking effect). The user always wins; the rule's job is to make the cost of writing speculative architectural records visible — every ADR is a future-reader's load and a pattern future agents will treat as committed.
- **The companion evidence rule applies to the ADR's supporting evidence.** Apply the evidence rule from [../../references/evidence-rule.md](../../references/evidence-rule.md) to the citations that justify the ADR's decision and rejected alternatives. Name the trust class of each citation (codebase, web, provided); mark single-source web claims that drive the chosen option; and when no evidence at any tier supports a claimed trade-off, label it rather than presenting it as a weak preference.

## Project Context

- CLAUDE.md: !`find . -maxdepth 1 -name "CLAUDE.md" -type f`
- project-discovery.md: !`find . -maxdepth 3 -name "project-discovery.md" -type f`

## Step 1: Determine Mode

Determine which mode to operate in based on the user's request:

| Mode | When | Initial Status | Then |
|------|------|----------------|------|
| Creating new | Building an ADR from scratch for a new or recent decision | `proposed` | → Step 2 |
| Converting existing | User provides an existing document to convert into an ADR | `accepted` | → Step 2 |
| Updating existing | Modifying an existing ADR (status change, superseding, adding notes) | — | Read the existing ADR, → Step 3 |

## Step 2: Discover Project Structure

1. **Retrieve project config:** Resolve project config: read CLAUDE.md's `## Project Discovery` section for docs and ADR directories; fall back to project-discovery.md; fall back to Glob defaults (`docs/`, `docs/adr/`). Continue without any keys that remain unfound.

2. **Determine the ADR directory:** Use the ADR directory if found; otherwise use `{docs-dir}/adr/` if a docs directory was found; otherwise use `docs/adr/`. Run `mkdir -p` on the resolved directory to ensure it exists.

3. **Enumerate existing ADRs:** Use Glob to find existing `.md` files in the ADR directory.

4. **Check existing ADR format:** If existing ADRs were found, read one to understand the project's format. If it differs from [template.md](./references/template.md), ask the user whether to match the existing format or use this skill's template.

5. **Discover the filename hierarchy taxonomy:** ADRs are organized by a one- or two-level hierarchy encoded in the filename so related decisions sort together in a directory listing. Discover the taxonomy that applies to *this* project — never hardcode it.
   - **From existing filenames:** If existing ADRs were enumerated, parse their filenames to extract the leading hierarchy segments already in use (e.g., `auth-session-storage.md` → top-level `auth`; `auth-tokens-rotation.md` → top-level `auth`, second-level `tokens`). Build a list of top-level prefixes and known second-level prefixes per top-level.
   - **From project context:** Read CLAUDE.md and project-discovery.md (paths from project context above) to identify the project's languages, frameworks, runtimes, subsystems, and bounded contexts. Each is a candidate top-level hierarchy (e.g., `auth`, `billing`, `api`, `worker`, `postgres`, `terraform`).
   - **Carry forward to Step 4:** the discovered top-level prefixes (existing + candidate) and any second-level prefixes already in use under each.

## Step 3: Gather Context

1. From the arguments and conversation, determine:
   - **Topic/title** — What is the ADR about?
   - **Decision** — What was decided and why?
   - **Alternatives** — What other options were considered?
   - **Forcing function** — What concrete trigger requires this decision *now*? Per [../../references/yagni-rule.md](../../references/yagni-rule.md), an ADR requires evidence that the decision must be made today: an active engineering choice, a code path locking in, a regulation taking effect, a customer commitment, a documented incident driving the choice. If no forcing function exists, recommend deferring the ADR rather than writing it; surface the recommendation to the user with the trigger that would justify revisiting.
2. If any of these are unclear or missing, use `AskUserQuestion` to clarify before writing. If the forcing function is the unclear one, surface that explicitly — "I don't see a current trigger forcing this decision; recommend deferring the ADR until {trigger}. Override?"

### Explore the Codebase

Skip agent exploration if the user has already provided full context (converting or updating). When creating a new ADR with sparse context, launch 1-2 `han.core:codebase-explorer` agents to discover evidence. Use 1 agent for narrow decisions, 2 when the decision crosses multiple system areas. Explorer 1 focuses on code affected by the decision topic (current patterns, entry points, core logic). Explorer 2 focuses on existing ADRs, coding standards, and project docs (starting from the docs directory found in Step 2).

### Compile Evidence

After agents complete (or if skipped), merge findings with user-provided context. Agent discovery items map to Context (current state of the codebase), Decision (