joinery-designer

name	joinery-designer
description	Determines joinery type per connection based on structural model bounds and user preferences. Explains load transfer behavior and outputs joinery maps.
allowed-tools	Read, Write

Expected Inputs

context/staging/structure.json (members section) generated by structural-engine. User preference for joinery (mechanical fasteners vs traditional timber framing).

Core Responsibilities

1. Evaluate all post-to-beam, beam-to-rafter connections.
2. If traditional timber framing chosen: assign half-laps, mortise and tenons, or housing depths.
3. If mechanical chosen: assign specific bolt patterns and Simpson Strong-Tie brackets.
4. Output specifics to context/staging/joinery-model.json.

Gotchas

• Mortise-and-tenon requires minimum beam depth. Traditional joinery is only valid when the beam actual depth is ≥ 7.25" (nominal 6×8). For smaller beams, default to mechanical hardware and note the constraint in joinery-model.json.
• Bolt count scales with span. The minimum two-bolt pattern (2 × 1/2" through-bolts per connection) is valid for spans ≤ 10ft. Spans > 10ft require three bolts minimum. Do not apply the two-bolt default universally.
• Do NOT lock joinery-model.json. The bracing-system-designer writes brace joinery into this file; locking it prematurely blocks that step.
• User preference must be captured before this skill runs. If joinery-type preference is missing from the transcript, the skill must prompt the orchestrator for clarification rather than defaulting silently.
• Hardware schedule must reference specific product numbers. Vague references like "Simpson bracket" are not sufficient — include the full product code (e.g. BC6) to make the lumber-purchase-list actionable.

Smoke Test

1. Traditional preference, qualifying beam: Given structure.json with 6×8 beams and user preference for timber framing: outputs joinery-model.json with mortise-and-tenon entries, no error. ✓
2. Mechanical preference, standard span: Given structure.json with span=10ft and preference=mechanical: outputs bolt pattern with 2 bolts per connection, named Simpson product codes. ✓
3. Long span mechanical: Given span=12ft and preference=mechanical: outputs 3-bolt pattern per connection. ✓

Completion: HANDOFF_BLOCK

On successful completion emit this block so the design-orchestrator can gate Stage 2:

{
  "stage": "joinery-designer",
  "status": "COMPLETE",
  "outputs": ["context/staging/joinery-model.json"],
  "joinery_type": "<mechanical|timber>",
  "locked": false,
  "next_stage": "bracing-system-designer"
}

If preference was missing and a clarification is needed, set "status": "NEEDS_CLARIFICATION" and specify the missing field.