diff --git a/scripts/__tests__/generate-cncf-missions.description-branches.test.mjs b/scripts/__tests__/generate-cncf-missions.description-branches.test.mjs
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+// Coverage extension for generate-cncf-missions.mjs.
+//
+// Targets branches in buildDescription (bug-arm error-pattern extraction) and
+// buildResolutionSummary (all three source-URL fallback arms) that are not
+// exercised by generate-cncf-missions.format-branches.test.mjs. Also covers
+// the generateMission end-to-end orchestrator so that regressions in the
+// buildMissionJson wiring — including the linkedPR presence/absence branch
+// and the non-K8s-native prerequisites arm — are caught.
+//
+// All pure formatting; no fs, no network, no LLM.
+
+import { describe, it, expect } from 'vitest'
+import {
+  buildDescription,
+  buildResolutionSummary,
+  generateMission,
+} from '../generate-cncf-missions.mjs'
+
+function mockIssue(overrides = {}) {
+  return {
+    title: overrides.title || 'Test issue',
+    body: overrides.body || 'Some issue body text',
+    labels: overrides.labels || [],
+    comments: overrides.comments ?? 0,
+    reactions: overrides.reactions || { total_count: 0 },
+    html_url: overrides.html_url || 'https://github.com/test/repo/issues/1',
+    number: overrides.number ?? 1,
+    ...overrides,
+  }
+}
+
+// ─── buildDescription — bug-arm errorMatch branch ─────────────────────
+
+describe('buildDescription — bug arm error extraction', () => {
+  it('extracts "error: <message>" from the body and surfaces it as "Users encounter"', () => {
+    // No feature-request signals → bug arm. The error pattern must be
+    // 10-100 chars after the colon to match.
+    const issue = mockIssue({
+      title: 'Pod fails on startup',
+      body: 'On boot we see error: failed to bind socket on port 8080 already in use',
+    })
+    const desc = buildDescription(issue, {})
+    expect(desc).toContain('Users encounter:')
+    expect(desc).toContain('failed to bind socket')
+    // The community-reported / N+ users suffix is skipped when the error
+    // match is used.
+    expect(desc).not.toContain('Community-reported issue')
+    expect(desc).not.toContain('+ users')
+  })
+
+  it('extracts "panic: <message>" from the body', () => {
+    const issue = mockIssue({
+      title: 'Crash on shutdown',
+      body: 'stacktrace shows panic: runtime error: index out of range on shutdown',
+    })
+    const desc = buildDescription(issue, {})
+    expect(desc).toContain('Users encounter:')
+    expect(desc).toContain('runtime error: index out of range')
+  })
+
+  it('extracts "fatal: <message>" case-insensitively', () => {
+    const issue = mockIssue({
+      title: 'Startup fails to complete',
+      body: 'log tail: FATAL: unable to load config file from /etc/app/config.yaml missing',
+    })
+    const desc = buildDescription(issue, {})
+    expect(desc).toContain('Users encounter:')
+    expect(desc).toContain('unable to load config')
+  })
+
+  it('extracts "failed to <message>" pattern', () => {
+    const issue = mockIssue({
+      title: 'Rollout broken on push',
+      body: 'reports: failed to: connect to registry within 30s and rollout stalls',
+    })
+    const desc = buildDescription(issue, {})
+    expect(desc).toContain('Users encounter:')
+    expect(desc).toContain('connect to registry')
+  })
+
+  it('falls back to community-reported when no error/panic/failed-to pattern matches', () => {
+    // Reactions < 5, no error pattern → "Community-reported issue." suffix.
+    const issue = mockIssue({
+      title: 'Widget cannot render on Safari',
+      body: 'The widget renders on Chrome and Firefox but not on Safari.',
+      reactions: { total_count: 2 },
+    })
+    const desc = buildDescription(issue, {})
+    expect(desc).toContain('Community-reported issue')
+    expect(desc).not.toContain('Users encounter:')
+  })
+
+  it('uses "affects N+ users" suffix when reactions >= 5 and no error pattern', () => {
+    const issue = mockIssue({
+      title: 'Queries broken under heavy load',
+      body: 'Queries stop returning results when many clients connect at once.',
+      reactions: { total_count: 42 },
+    })
+    const desc = buildDescription(issue, {})
+    expect(desc).toContain('affects 42+ users')
+  })
+})
+
+// ─── buildResolutionSummary — source-URL fallback arms ─────────────────
+
+describe('buildResolutionSummary — buildResolutionFallback branches', () => {
+  it('prefers the PR link when both pr and issue URLs are present', () => {
+    // Short cleanSolution triggers the fallback path.
+    const summary = buildResolutionSummary({}, '', 'bug', {
+      pr: 'https://github.com/o/r/pull/42',
+      issue: 'https://github.com/o/r/issues/41',
+    })
+    expect(summary).toContain('fix PR')
+    expect(summary).toContain('https://github.com/o/r/pull/42')
+    // The issue URL is NOT included when the PR arm fires.
+    expect(summary).not.toContain('issues/41')
+  })
+
+  it('falls back to the issue link when no PR URL is provided', () => {
+    const summary = buildResolutionSummary({}, '', 'bug', {
+      issue: 'https://github.com/o/r/issues/41',
+    })
+    expect(summary).toContain('source issue')
+    expect(summary).toContain('https://github.com/o/r/issues/41')
+  })
+
+  it('uses a generic fallback when neither pr nor issue URL is provided', () => {
+    const summary = buildResolutionSummary({}, '', 'bug', {})
+    expect(summary).toContain('See the linked issue and PR')
+  })
+
+  it('uses the generic fallback when sourceUrls is undefined', () => {
+    const summary = buildResolutionSummary({}, '', 'bug', undefined)
+    expect(summary).toContain('See the linked issue and PR')
+  })
+
+  it('takes the sentence-truncation happy path when cleanSolution is long enough', () => {
+    // >50 chars, and the truncation will exceed the 30-char minimum → the
+    // truncated summary is returned instead of the fallback.
+    const long =
+      'Set the timeout to at least 30 seconds and increase the retry backoff. ' +
+      'This gives the upstream time to warm up before the health probe fires. ' +
+      'A shorter value causes flapping in busy clusters.'
+    const summary = buildResolutionSummary({}, long, 'bug', {
+      pr: 'https://github.com/o/r/pull/42',
+    })
+    expect(summary).toContain('Set the timeout')
+    // The PR-fallback text must NOT be emitted on the happy path.
+    expect(summary).not.toContain('fix PR')
+  })
+})
+
+// ─── generateMission — end-to-end wiring ──────────────────────────────
+
+describe('generateMission — full document assembly', () => {
+  const k8sProject = {
+    name: 'kubernetes',
+    repo: 'kubernetes/kubernetes',
+    maturity: 'graduated',
+    category: 'orchestration',
+  }
+
+  it('produces a kc-mission-v1 document with the expected top-level shape', async () => {
+    const issue = mockIssue({
+      title: 'kubelet crashloop on node',
+      body: 'error: connection refused when contacting apiserver',
+      number: 1234,
+      reactions: { total_count: 10 },
+      comments: 4,
+    })
+    const doc = await generateMission(k8sProject, issue, {
+      problem: 'kubelet keeps restarting',
+      solution: 'Restart the kubelet service and check /var/log/messages for details on the failure to reach the apiserver.',
+      yamlSnippets: [],
+      steps: ['a', 'b'],
+    })
+    expect(doc.version).toBe('kc-mission-v1')
+    expect(doc.missionClass).toBe('fixer')
+    expect(doc.name).toContain('kubernetes-1234')
+    expect(doc.mission.title).toBe('kubernetes: kubelet crashloop on node')
+    expect(doc.mission.type).toBe('troubleshoot')
+    expect(doc.mission.status).toBe('completed')
+    expect(doc.metadata.cncfProjects).toEqual(['kubernetes'])
+    expect(doc.metadata.maturity).toBe('graduated')
+    expect(doc.metadata.reactions).toBe(10)
+    expect(doc.metadata.comments).toBe(4)
+    // K8s-native project → prerequisites include kubectl.
+    expect(doc.prerequisites.tools).toContain('kubectl')
+    expect(doc.prerequisites.kubernetes).toBeDefined()
+    // No linkedPR → sourceUrls has no pr key.
+    expect(doc.metadata.sourceUrls.pr).toBeUndefined()
+    expect(doc.metadata.sourceUrls.issue).toBe(issue.html_url)
+    // security section is populated.
+    expect(doc.security.sanitized).toBe(true)
+    expect(doc.security.scannerVersion).toBe('cncf-gen-3.0.0')
+  })
+
+  it('includes the linkedPR URL when resolution._linkedPR is present', async () => {
+    const issue = mockIssue({
+      title: 'race condition in scheduler',
+      body: 'panic: concurrent map write when many pods land at once',
+      number: 5555,
+    })
+    const linkedPR = { html_url: 'https://github.com/kubernetes/kubernetes/pull/9999' }
+    const doc = await generateMission(k8sProject, issue, {
+      problem: 'concurrent map write',
+      solution: 'Guard the pod cache mutations with a per-scheduler mutex so parallel schedules cannot race.',
+      yamlSnippets: [],
+      steps: [],
+      _linkedPR: linkedPR,
+    })
+    expect(doc.metadata.sourceUrls.pr).toBe(linkedPR.html_url)
+    // "advanced" bucket via race-condition keyword (+3).
+    expect(doc.metadata.difficulty).toBe('advanced')
+  })
+
+  it('uses non-K8s prerequisites for a project not in the K8s-native set', async () => {
+    // "harbor" is in the NON_K8S_PROJECTS set → isKubernetesNative returns
+    // false → prerequisites take the PROJECT_CLI_MAP path.
+    const harborProject = {
+      name: 'harbor',
+      repo: 'goharbor/harbor',
+      maturity: 'graduated',
+      category: 'security-compliance',
+    }
+    const issue = mockIssue({ title: 'push fails', body: 'error: 500 from registry' })
+    const doc = await generateMission(harborProject, issue, {
+      problem: 'push fails',
+      solution: 'Check the docker-compose logs for the registry container — a 500 indicates the backing storage is unreachable.',
+      yamlSnippets: [],
+      steps: [],
+    })
+    // harbor is mapped to docker-compose+curl in PROJECT_CLI_MAP.
+    expect(doc.prerequisites.tools).toContain('docker-compose')
+    // No kubectl / kubernetes version pin for non-K8s projects.
+    expect(doc.prerequisites.kubernetes).toBeUndefined()
+    expect(doc.prerequisites.tools).not.toContain('kubectl')
+  })
+
+  it('caps codeSnippets at 3 entries from resolution.yamlSnippets', async () => {
+    const issue = mockIssue({ title: 'ingress not routing' })
+    const snippets = [
+      'apiVersion: v1\nkind: ConfigMap\n# one',
+      'apiVersion: v1\nkind: ConfigMap\n# two',
+      'apiVersion: v1\nkind: ConfigMap\n# three',
+      'apiVersion: v1\nkind: ConfigMap\n# four',
+    ]
+    const doc = await generateMission(k8sProject, issue, {
+      problem: 'ingress not routing',
+      solution: 'apply the corrected ingress rule and reload.',
+      yamlSnippets: snippets,
+      steps: [],
+    })
+    expect(doc.mission.resolution.codeSnippets).toHaveLength(3)
+  })
+})