feat: add new-sep scaffolding command (#272)

* feat: add new-sep scaffolding command

Related #243.

This commit adds the new-sep <NNNN> subcommand, which writes the file src/scenarios/<target>/sep-<NNNN>.yaml. This file contains the "sep", "spec_url", and "requirements" rows in the same style as sep-2164.yaml, with single quotes and two spaces. The spec source resolves in order: --spec-url → --spec-path → GitHub API against modelcontextprotocol/modelcontextprotocol (explicit --pr or title search for "SEP-NNNN").
The target directory is inferred from the spec path (`server/`, `client/`, or `basic/authorization*`); the --target flag overrides this. It refuses to overwrite without the --force flag.
Token resolution reuses the "gh auth token" fallback pattern from tier-check.

It also ships the .claude/skills/new-sep directory, which drives the CLI. It fetches the spec diff via "gh api" and extracts RFC 2119 sentences. There is a warning against regex-only matching. Bullets inherit keywords from their lead-in sentence. It rewrites the placeholder rows per the severity rules in AGENTS.md. MUST/SHALL/REQUIRED are checked for FAILURE. SHOULD is checked for WARNING. MAY/OPTIONAL are excluded.

Signed-off-by: Satoshi Ito <satoshi.ito.tf@hitachi.com>

* dropped --pr arg, list changed files, support multi-file seps w url override

* Consolidate SEP yamls into src/seps/ and tighten yaml ordering

- All sep-NNNN.yaml files now live in src/seps/ regardless of which
  scenario suite their checks run in
- Drop --target / inferTarget; output dir is fixed
- renderYaml: check rows emit `check:` first, excluded rows grouped at
  bottom with a blank-line separator
- SKILL.md: document key/row ordering, expand exclusion-confirmation step
- Move src/scenarios/server/sep-2164.yaml -> src/seps/

---------

Signed-off-by: Satoshi Ito <satoshi.ito.tf@hitachi.com>
Co-authored-by: Paul Carleton <paulc@anthropic.com>

src/index.ts

@@ -45,6 +45,7 @@ import {
   printBaselineResults
 } from './expected-failures';
 import { createTierCheckCommand } from './tier-check';
+import { createNewSepCommand } from './new-sep';
 import packageJson from '../package.json';
 
 // Note on naming: `command` refers to which CLI command is calling this.
@@ -540,6 +541,9 @@ program
 // Tier check command
 program.addCommand(createTierCheckCommand());
 
+// New SEP scaffolding command
+program.addCommand(createNewSepCommand());
+
 // List scenarios command
 program
   .command('list')

src/new-sep/index.test.ts

@@ -0,0 +1,115 @@
+import { describe, it, expect } from 'vitest';
+import { specPathToUrl, renderYaml } from './index';
+
+describe('specPathToUrl', () => {
+  it('strips the docs/specification/draft/ prefix and .mdx suffix', () => {
+    expect(specPathToUrl('docs/specification/draft/server/resources.mdx')).toBe(
+      'https://modelcontextprotocol.io/specification/draft/server/resources'
+    );
+  });
+
+  it('handles nested paths', () => {
+    expect(specPathToUrl('docs/specification/draft/basic/lifecycle.mdx')).toBe(
+      'https://modelcontextprotocol.io/specification/draft/basic/lifecycle'
+    );
+  });
+
+  it('rejects paths outside docs/specification/draft/', () => {
+    expect(() =>
+      specPathToUrl('docs/specification/2025-11-25/server/x.mdx')
+    ).toThrow(/must start with/);
+  });
+});
+
+describe('renderYaml', () => {
+  it('emits placeholder yaml in the sep-2164.yaml style', () => {
+    const out = renderYaml({
+      sep: 9999,
+      specUrl:
+        'https://modelcontextprotocol.io/specification/draft/server/resources'
+    });
+    expect(out).toBe(
+      `sep: 9999
+spec_url: https://modelcontextprotocol.io/specification/draft/server/resources
+requirements:
+  - check: sep-9999-todo
+    text: 'TODO: quote the normative sentence from the spec diff'
+
+  - text: 'TODO: requirement that cannot be tested'
+    excluded: 'TODO: reason'
+    issue: https://github.com/modelcontextprotocol/conformance/issues/<NNNN>
+`
+    );
+  });
+
+  it('matches the byte-shape of the real sep-2164.yaml when given its rows', () => {
+    const out = renderYaml({
+      sep: 2164,
+      specUrl:
+        'https://modelcontextprotocol.io/specification/draft/server/resources#error-handling',
+      requirements: [
+        {
+          text: 'Servers MUST NOT return an empty contents array for a non-existent resource',
+          check: 'sep-2164-no-empty-contents'
+        },
+        {
+          text: 'Servers SHOULD return standard JSON-RPC errors for common failure cases: Resource not found: -32602 (Invalid Params)',
+          check: 'sep-2164-error-code'
+        },
+        {
+          text: 'clients SHOULD also accept -32002 as a resource not found error',
+          excluded:
+            'Client-side error handling is implementation-defined; not protocol-observable'
+        }
+      ]
+    });
+    expect(out).toBe(
+      `sep: 2164
+spec_url: https://modelcontextprotocol.io/specification/draft/server/resources#error-handling
+requirements:
+  - check: sep-2164-no-empty-contents
+    text: 'Servers MUST NOT return an empty contents array for a non-existent resource'
+  - check: sep-2164-error-code
+    text: 'Servers SHOULD return standard JSON-RPC errors for common failure cases: Resource not found: -32602 (Invalid Params)'
+
+  - text: 'clients SHOULD also accept -32002 as a resource not found error'
+    excluded: 'Client-side error handling is implementation-defined; not protocol-observable'
+`
+    );
+  });
+
+  it('emits per-row url: overrides', () => {
+    const out = renderYaml({
+      sep: 1234,
+      specUrl: 'https://modelcontextprotocol.io/specification/draft/server/a',
+      requirements: [
+        { text: 'from primary file', check: 'sep-1234-a' },
+        {
+          text: 'from secondary file',
+          check: 'sep-1234-b',
+          url: 'https://modelcontextprotocol.io/specification/draft/server/b#x'
+        }
+      ]
+    });
+    expect(out).toBe(
+      `sep: 1234
+spec_url: https://modelcontextprotocol.io/specification/draft/server/a
+requirements:
+  - check: sep-1234-a
+    text: 'from primary file'
+  - check: sep-1234-b
+    text: 'from secondary file'
+    url: https://modelcontextprotocol.io/specification/draft/server/b#x
+`
+    );
+  });
+
+  it('escapes single quotes by doubling them', () => {
+    const out = renderYaml({
+      sep: 1,
+      specUrl: 'https://example.com/x',
+      requirements: [{ text: "can't happen", check: 'sep-1-x' }]
+    });
+    expect(out).toContain("text: 'can''t happen'");
+  });
+});

src/new-sep/index.ts

@@ -0,0 +1,256 @@
+import { Command } from 'commander';
+import { Octokit } from '@octokit/rest';
+import { promises as fs } from 'fs';
+import path from 'path';
+
+export interface RequirementRow {
+  text: string;
+  check?: string;
+  excluded?: string;
+  issue?: string;
+  /** Full spec URL for this requirement; overrides the file-level spec_url. */
+  url?: string;
+}
+
+const OUT_DIR = 'src/seps';
+const SPEC_PATH_PREFIX = 'docs/specification/draft/';
+const DEFAULT_SPEC_REPO = 'modelcontextprotocol/modelcontextprotocol';
+
+export function specPathToUrl(specPath: string): string {
+  if (!specPath.startsWith(SPEC_PATH_PREFIX)) {
+    throw new Error(
+      `spec path must start with "${SPEC_PATH_PREFIX}"; got: ${specPath}`
+    );
+  }
+  const rest = specPath.slice(SPEC_PATH_PREFIX.length).replace(/\.mdx$/, '');
+  return `https://modelcontextprotocol.io/specification/draft/${rest}`;
+}
+
+function escapeSingleQuoted(s: string): string {
+  return s.replace(/'/g, "''");
+}
+
+function defaultPlaceholderRequirements(sep: number): RequirementRow[] {
+  return [
+    {
+      text: 'TODO: quote the normative sentence from the spec diff',
+      check: `sep-${sep}-todo`
+    },
+    {
+      text: 'TODO: requirement that cannot be tested',
+      excluded: 'TODO: reason',
+      issue: 'https://github.com/modelcontextprotocol/conformance/issues/<NNNN>'
+    }
+  ];
+}
+
+export function renderYaml(input: {
+  sep: number;
+  specUrl: string;
+  requirements?: RequirementRow[];
+}): string {
+  const reqs = input.requirements ?? defaultPlaceholderRequirements(input.sep);
+  const checkRows = reqs.filter((r) => r.check);
+  const excludedRows = reqs.filter((r) => !r.check);
+
+  const lines: string[] = [];
+  lines.push(`sep: ${input.sep}`);
+  lines.push(`spec_url: ${input.specUrl}`);
+  lines.push('requirements:');
+
+  for (const r of checkRows) {
+    lines.push(`  - check: ${r.check}`);
+    lines.push(`    text: '${escapeSingleQuoted(r.text)}'`);
+    if (r.url) lines.push(`    url: ${r.url}`);
+  }
+
+  if (checkRows.length > 0 && excludedRows.length > 0) {
+    lines.push('');
+  }
+
+  for (const r of excludedRows) {
+    lines.push(`  - text: '${escapeSingleQuoted(r.text)}'`);
+    if (r.excluded) {
+      lines.push(`    excluded: '${escapeSingleQuoted(r.excluded)}'`);
+    }
+    if (r.issue) lines.push(`    issue: ${r.issue}`);
+  }
+
+  return lines.join('\n') + '\n';
+}
+
+async function resolveToken(explicit?: string): Promise<string | undefined> {
+  let token = explicit || process.env.GITHUB_TOKEN;
+  if (!token) {
+    try {
+      const { execSync } = await import('child_process');
+      token = execSync('gh auth token', { encoding: 'utf-8' }).trim();
+    } catch {
+      // gh not installed or not authenticated
+    }
+  }
+  return token;
+}
+
+interface SpecCandidate {
+  filename: string;
+  additions: number;
+}
+
+async function lookupSpecPath(args: {
+  sep: number;
+  repo: string;
+  token: string;
+}): Promise<string[]> {
+  const [owner, repoName] = args.repo.split('/');
+  if (!owner || !repoName) {
+    throw new Error(`Invalid --repo: ${args.repo} (expected owner/repo)`);
+  }
+  const octokit = new Octokit({ auth: args.token });
+
+  // SEP numbers are PR numbers in the spec repo by convention.
+  const prNumber = args.sep;
+
+  const files = await octokit.paginate(octokit.pulls.listFiles, {
+    owner,
+    repo: repoName,
+    pull_number: prNumber,
+    per_page: 100
+  });
+
+  const candidates: SpecCandidate[] = files
+    .filter(
+      (f) =>
+        f.filename.startsWith(SPEC_PATH_PREFIX) && f.filename.endsWith('.mdx')
+    )
+    .map((f) => ({ filename: f.filename, additions: f.additions }));
+
+  if (candidates.length === 0) {
+    throw new Error(
+      `PR #${prNumber} in ${args.repo} does not change any ` +
+        `${SPEC_PATH_PREFIX}*.mdx file. Pass --spec-path <path> to override.`
+    );
+  }
+  candidates.sort((a, b) => b.additions - a.additions);
+  return candidates.map((c) => c.filename);
+}
+
+export function createNewSepCommand(): Command {
+  return new Command('new-sep')
+    .description(
+      'Scaffold a sep-NNNN.yaml requirement-traceability file for a new SEP'
+    )
+    .argument('<number>', 'SEP number, e.g. 2164')
+    .option(
+      '--spec-url <url>',
+      'Use this spec URL verbatim (skips GitHub lookup)'
+    )
+    .option(
+      '--spec-path <path>',
+      `${SPEC_PATH_PREFIX}... path to derive spec_url from (skips GitHub lookup)`
+    )
+    .option(
+      '--repo <owner/repo>',
+      'Spec repo to query for the SEP PR',
+      DEFAULT_SPEC_REPO
+    )
+    .option(
+      '--token <token>',
+      'GitHub token (defaults to GITHUB_TOKEN env or `gh auth token`)'
+    )
+    .option('--force', 'Overwrite existing sep-NNNN.yaml')
+    .action(async (sepArg: string, options) => {
+      const sep = parseInt(sepArg, 10);
+      if (!Number.isFinite(sep) || sep <= 0 || String(sep) !== sepArg.trim()) {
+        console.error(`Invalid SEP number: ${sepArg}`);
+        process.exit(1);
+      }
+
+      let specUrl: string | undefined = options.specUrl;
+      let specPath: string | undefined = options.specPath;
+      let otherSpecPaths: string[] = [];
+
+      if (!specUrl && !specPath) {
+        const token = await resolveToken(options.token);
+        if (!token) {
+          console.error(
+            'GitHub token required to look up the SEP PR. Either:\n' +
+              '  gh auth login\n' +
+              '  export GITHUB_TOKEN=$(gh auth token)\n' +
+              '  or pass --token <token>\n' +
+              '  or pass --spec-url / --spec-path to skip the lookup'
+          );
+          process.exit(1);
+        }
+        try {
+          const specPaths = await lookupSpecPath({
+            sep,
+            repo: options.repo,
+            token
+          });
+          specPath = specPaths[0];
+          otherSpecPaths = specPaths.slice(1);
+          console.error(`Resolved spec path: ${specPath}`);
+        } catch (err) {
+          console.error((err as Error).message);
+          process.exit(1);
+        }
+      }
+
+      if (specPath && !specUrl) {
+        try {
+          specUrl = specPathToUrl(specPath);
+        } catch (err) {
+          console.error((err as Error).message);
+          process.exit(1);
+        }
+      }
+      if (!specUrl) {
+        console.error('Could not resolve spec_url. Internal error.');
+        process.exit(1);
+      }
+
+      const outPath = path.join(OUT_DIR, `sep-${sep}.yaml`);
+
+      await fs.mkdir(OUT_DIR, { recursive: true });
+
+      if (!options.force) {
+        try {
+          await fs.access(outPath);
+          console.error(
+            `${outPath} already exists. Pass --force to overwrite.`
+          );
+          process.exit(1);
+        } catch {
+          // does not exist, OK
+        }
+      }
+
+      const yaml = renderYaml({ sep, specUrl });
+      await fs.writeFile(outPath, yaml, 'utf-8');
+
+      console.error(`Wrote ${outPath}`);
+      if (otherSpecPaths.length > 0) {
+        console.error(
+          `Note: PR also changes ${otherSpecPaths.length} other spec file(s):`
+        );
+        for (const p of otherSpecPaths) {
+          console.error(`  ${specPathToUrl(p)}`);
+        }
+        console.error(
+          `  Use a per-row "url:" for requirements from those files.`
+        );
+      }
+      console.error('Next steps:');
+      console.error(
+        '  1. Edit the file to quote real normative sentences from the spec diff'
+      );
+      console.error(
+        '     (and add a "#anchor" to spec_url if the requirement lives in a subsection)'
+      );
+      console.error('  2. Implement the TypeScript scenario');
+      console.error(
+        '  3. Register it in the appropriate suite list in src/scenarios/index.ts'
+      );
+    });
+}

src/seps/sep-2164.yaml

@@ -0,0 +1,10 @@
+sep: 2164
+spec_url: https://modelcontextprotocol.io/specification/draft/server/resources#error-handling
+requirements:
+  - check: sep-2164-no-empty-contents
+    text: 'Servers MUST NOT return an empty contents array for a non-existent resource'
+  - check: sep-2164-error-code
+    text: 'Servers SHOULD return standard JSON-RPC errors for common failure cases: Resource not found: -32602 (Invalid Params)'
+
+  - text: 'clients SHOULD also accept -32002 as a resource not found error'
+    excluded: 'Client-side error handling is implementation-defined; not protocol-observable'