diagram-gen-spec

name	diagram-gen-spec
description	Generate a top-down structural diagram from a mache schema file. Shows intended architecture — what the PR proposes, not what the code does. Reviewer local context only, never posted to GitHub. Pair with diagram-gen-emergent to see spec vs reality drift.
allowed-tools	Bash,Read,Glob,Grep,mcp__mache__*
argument-hint	<schema-path-or-pr-number> [source-path]

diagram-gen-spec — Spec-Driven Structural Diagram

Generate a top-down diagram from a mache schema. Shows what the author intended to build. This is reviewer-local context only — never post this output to GitHub.

Arguments

$ARGUMENTS — <schema-path-or-pr-number> [source-path]

• First argument: path to a mache schema JSON file, OR a PR number (to find the schema in the PR's changed files)
• Second argument (optional): source directory to serve against the schema

What To Do

Step 1: Find the schema

If first argument looks like a PR number (all digits or owner/repo#N):

# Look for schema files changed in the PR
gh pr diff $ARG --name-only 2>/dev/null | grep -E "(schema\.json|mache\.json|\.schema\.json)"

If first argument is a file path: use it directly.

If no schema found from PR, look in the repo root:

ls examples/*.json 2>/dev/null | head -5
ls *.json 2>/dev/null | grep -i schema | head -3

If no schema found anywhere, return:

status: unavailable
type: spec-driven
reason: no mache schema found in PR changed files or repo root

Stop here.

Step 2: Determine source path

If a second argument was provided, use it as SOURCE. Otherwise, if argument was a PR number, derive source from the repo:

gh pr view $ARG --json headRepository --jq '.headRepository.nameWithOwner' 2>/dev/null

Fall back to current working directory if detection fails.

Step 3: Start mache with the schema on port 7534

MACHE_BIN=$(which mache 2>/dev/null || echo "$HOME/go/bin/mache")
if [ ! -x "$MACHE_BIN" ]; then
  echo "status: unavailable — mache binary not found"
  exit 0
fi

# Use port 7534 to avoid colliding with the emergent server on 7532
$MACHE_BIN serve "$SOURCE" --schema "$SCHEMA_PATH" --http localhost:7534 &
SPEC_PID=$!

for i in $(seq 1 10); do
  sleep 1
  curl -s --max-time 2 -X POST http://localhost:7534/mcp \
    -H "Content-Type: application/json" \
    -H "Accept: application/json, text/event-stream" \
    -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"check","version":"1"}}}' \
    | python3 -c "import sys,json; d=json.load(sys.stdin); exit(0) if 'result' in d else exit(1)" 2>/dev/null && break
  if [ $i -eq 10 ]; then
    kill $SPEC_PID 2>/dev/null
    echo "status: unavailable — mache serve with schema failed to start"
    exit 0
  fi
done

Initialize session:

SESSION=$(curl -s -X POST http://localhost:7534/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -d '{"jsonrpc":"2.0","id":1,"method":"initialize","params":{"protocolVersion":"2024-11-05","capabilities":{},"clientInfo":{"name":"diagram-gen-spec","version":"1"}}}' \
  -D - 2>/dev/null | grep -i "^mcp-session-id:" | tr -d '\r' | awk -F': ' '{print $2}' | tr -d ' ')
if [ -z "$SESSION" ]; then
  echo "status: unavailable — session initialization failed"
  exit 0
fi

Step 4: Get architecture narrative

NARRATIVE=$(curl -s -X POST http://localhost:7534/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "mcp-session-id: $SESSION" \
  -d '{"jsonrpc":"2.0","id":2,"method":"tools/call","params":{"name":"get_architecture","arguments":{}}}' \
  | python3 -c "import sys,json; d=json.load(sys.stdin); print(d['result']['content'][0]['text'])" 2>/dev/null)

Truncate to 200 words if longer.

Step 5: Get diagram

DIAGRAM=$(curl -s -X POST http://localhost:7534/mcp \
  -H "Content-Type: application/json" \
  -H "Accept: application/json, text/event-stream" \
  -H "mcp-session-id: $SESSION" \
  -d '{"jsonrpc":"2.0","id":3,"method":"tools/call","params":{"name":"get_diagram","arguments":{"compact":true,"layout":"LR","exclude_tests":true}}}' \
  | python3 -c "import sys,json; d=json.load(sys.stdin); print(d['result']['content'][0]['text'])" 2>/dev/null)

If $DIAGRAM contains "No cross-references" or is empty, set DIAGRAM_STATUS to "partial". Otherwise set DIAGRAM_STATUS to "available".

Step 6: Format and return

Output this structure exactly (downstream skills parse it):

status: available
type: spec-driven
label: Proposed structure (spec-driven)
schema: <SCHEMA_PATH>

narrative:
<NARRATIVE truncated to 200 words>

diagram:
```mermaid
<DIAGRAM truncated to 50 lines>

If DIAGRAM_STATUS is "partial":

status: partial type: spec-driven label: Proposed structure (spec-driven) schema: <SCHEMA_PATH> diagram: unavailable — schema defines structure but insufficient cross-references to cluster

narrative:

Step 7: Stop the spec server

kill $SPEC_PID 2>/dev/null