diff --git a/src/services/analytics.healthMetrics.test.js b/src/services/analytics.healthMetrics.test.js
index 3fdf4f6..f459c9d 100644
--- a/src/services/analytics.healthMetrics.test.js
+++ b/src/services/analytics.healthMetrics.test.js
@@ -114,3 +114,59 @@ describe('computeBusFactor', () => {
     expect(computeBusFactor(contributors)).toEqual({ factor: 2, risk: 'high' })
   })
 })
+
+describe('computeHealthScore with invalid inputs', () => {
+  // Regression guards for this PR. Two NaN sources in computeHealthScore:
+  //  - open_issues_count: the issueHealth line used a bare repo.open_issues_count,
+  //    so a missing or non-numeric value produced NaN (#211).
+  //  - pushed_at: an unguarded new Date(repo.pushed_at) made daysSince NaN for a
+  //    missing/invalid timestamp. Both are now guarded; these fail on the
+  //    unguarded code and pass with the fix.
+
+  it('returns a finite score when open_issues_count is missing but pushed_at is valid', () => {
+    const score = computeHealthScore({ pushed_at: new Date().toISOString() }, 2)
+    expect(Number.isFinite(score)).toBe(true)
+  })
+
+  it('returns a finite score for an empty repo object', () => {
+    expect(Number.isFinite(computeHealthScore({}, 3))).toBe(true)
+  })
+
+  it('treats a missing open_issues_count the same as zero open issues', () => {
+    const missing = computeHealthScore({ pushed_at: daysAgoISO(10) }, 2)
+    const zero    = computeHealthScore({ pushed_at: daysAgoISO(10), open_issues_count: 0 }, 2)
+    expect(missing).toBe(zero)
+  })
+
+  it('returns a finite score when open_issues_count is a non-numeric value', () => {
+    const score = computeHealthScore({ pushed_at: new Date().toISOString(), open_issues_count: 'oops' }, 2)
+    expect(Number.isFinite(score)).toBe(true)
+  })
+
+  it('returns a finite score when pushed_at is null', () => {
+    expect(Number.isFinite(computeHealthScore({ pushed_at: null, open_issues_count: 0 }, 2))).toBe(true)
+  })
+
+  it('returns a finite score when pushed_at is an unparseable string', () => {
+    expect(Number.isFinite(computeHealthScore({ pushed_at: 'not-a-date', open_issues_count: 0 }, 2))).toBe(true)
+  })
+})
+
+describe('computeActivityClassification with missing or invalid pushed_at', () => {
+  // Regression guard: computeActivityClassification parses pushed_at with
+  // Date.parse + Number.isFinite; an invalid or missing value is treated as
+  // maximally stale and classified as Hibernating rather than throwing or
+  // mislabelling.
+
+  it('classifies a null pushed_at as Hibernating', () => {
+    expect(computeActivityClassification({ pushed_at: null })).toBe('Hibernating')
+  })
+
+  it('classifies a missing pushed_at as Hibernating', () => {
+    expect(computeActivityClassification({})).toBe('Hibernating')
+  })
+
+  it('classifies an unparseable pushed_at string as Hibernating', () => {
+    expect(computeActivityClassification({ pushed_at: 'not-a-date' })).toBe('Hibernating')
+  })
+})
\ No newline at end of file
diff --git a/src/services/analytics.js b/src/services/analytics.js
index 2ca5969..3ffedfd 100644
--- a/src/services/analytics.js
+++ b/src/services/analytics.js
@@ -1,19 +1,21 @@
 //  Repo Health Indicator
 // Activity (40%) + Issue Health (30%) + Diversity (30%)
 export function computeHealthScore(repo, contributorCount = 0) {
-  const daysSince   = (Date.now() - new Date(repo.pushed_at)) / 86_400_000
-  const activity    = Math.max(0, 100 - daysSince)
-  const total       = (repo.open_issues_count || 0) + 10
-  const issueHealth = Math.max(0, 100 - (repo.open_issues_count / total) * 100)
-  const diversity   = Math.min(100, contributorCount * 10)
+  const pushedAtMs = Date.parse(repo.pushed_at)
+  const daysSince = Number.isFinite(pushedAtMs) ? (Date.now() - pushedAtMs) / 86_400_000 : Infinity
+  const activity = Math.max(0, 100 - daysSince)
+  const total = (Number(repo.open_issues_count) || 0) + 10
+  const issueHealth = Math.max(0, 100 - ((Number(repo.open_issues_count) || 0) / total) * 100)
+  const diversity = Math.min(100, contributorCount * 10)
   return Math.round(activity * 0.4 + issueHealth * 0.3 + diversity * 0.3)
 }
 
 // Repo Lifecycle — Thriving, Active, Dormant, Hibernating based on recency of last push
 export function computeActivityClassification(repo) {
-  const days = (Date.now() - new Date(repo.pushed_at)) / 86_400_000
-  if (days <= 30)  return 'Thriving'
-  if (days <= 90)  return 'Active'
+  const pushedAtMs = Date.parse(repo.pushed_at)
+  const days = Number.isFinite(pushedAtMs) ? (Date.now() - pushedAtMs) / 86_400_000 : Infinity
+  if (days <= 30) return 'Thriving'
+  if (days <= 90) return 'Active'
   if (days <= 180) return 'Dormant'
   return 'Hibernating'
 }
@@ -38,7 +40,7 @@ export function computeBusFactor(contributors = []) {
 // Merges multiple orgs into one normalized graph:
 // Organization → Repositories → Contributors → Issues/PRs
 export function buildAnalyticalModel(orgs, reposPerOrg, contribsPerRepo, totalReposPerOrg) {
-  const allRepos      = []
+  const allRepos = []
   const contributorMap = {}
   const totalRepos = [];
 
@@ -86,10 +88,10 @@ export function buildAnalyticalModel(orgs, reposPerOrg, contribsPerRepo, totalRe
   // Finalize contributors: compute signals
   const contributors = Object.values(contributorMap).map(c => ({
     ...c,
-    orgs:        Array.from(c.orgs),
+    orgs: Array.from(c.orgs),
     isConnector: c.repos.length >= 3,
-    isCrossOrg:  c.orgs.size > 1,
-    freshness:   c.lastActive
+    isCrossOrg: c.orgs.size > 1,
+    freshness: c.lastActive
       ? Math.max(0, 100 - (Date.now() - new Date(c.lastActive)) / 86_400_000)
       : 0,
   })).sort((a, b) => b.totalContribs - a.totalContribs)
@@ -127,7 +129,7 @@ export function buildTimeSeries(issues = [], granularity = 'monthly') {
     if (ck) {
       ensure(ck)
       if (isPR) buckets[ck].prs_created++
-      else      buckets[ck].issues_created++
+      else buckets[ck].issues_created++
     }
 
     if (item.closed_at) {
@@ -135,7 +137,7 @@ export function buildTimeSeries(issues = [], granularity = 'monthly') {
       if (xk) {
         ensure(xk)
         if (isPR) buckets[xk].prs_closed++
-        else      buckets[xk].issues_closed++
+        else buckets[xk].issues_closed++
       }
     }
 
@@ -153,27 +155,27 @@ export function buildTimeSeries(issues = [], granularity = 'monthly') {
 // CSV Export
 function download(content, filename, type = 'text/csv') {
   const blob = new Blob([content], { type })
-  const url  = URL.createObjectURL(blob)
-  const a    = Object.assign(document.createElement('a'), { href: url, download: filename })
+  const url = URL.createObjectURL(blob)
+  const a = Object.assign(document.createElement('a'), { href: url, download: filename })
   a.click()
   URL.revokeObjectURL(url)
 }
 
 export function exportReposCSV(repos) {
-  const header = ['Repository','Org','Stars','Forks','Open Issues','Health Score','Activity Classification','Language','Last Active']
-  const rows   = repos.map(r => [r.name, r.orgLogin, r.stargazers_count, r.forks_count, r.open_issues_count, r.healthScore, r.activityClassification, r.language || 'N/A', r.pushed_at?.slice(0, 10)])
+  const header = ['Repository', 'Org', 'Stars', 'Forks', 'Open Issues', 'Health Score', 'Activity Classification', 'Language', 'Last Active']
+  const rows = repos.map(r => [r.name, r.orgLogin, r.stargazers_count, r.forks_count, r.open_issues_count, r.healthScore, r.activityClassification, r.language || 'N/A', r.pushed_at?.slice(0, 10)])
   download([header, ...rows].map(r => r.join(',')).join('\n'), 'orgexplorer-repos.csv')
 }
 
 export function exportContributorsCSV(contributors) {
-  const header = ['Login','Total Contributions','Repos','Orgs','Last Active','Connector','Cross-Org']
-  const rows   = contributors.map(c => [c.login, c.totalContribs, c.repos.length, c.orgs.length, c.lastActive?.slice(0, 10) || '', c.isConnector, c.isCrossOrg])
+  const header = ['Login', 'Total Contributions', 'Repos', 'Orgs', 'Last Active', 'Connector', 'Cross-Org']
+  const rows = contributors.map(c => [c.login, c.totalContribs, c.repos.length, c.orgs.length, c.lastActive?.slice(0, 10) || '', c.isConnector, c.isCrossOrg])
   download([header, ...rows].map(r => r.join(',')).join('\n'), 'orgexplorer-contributors.csv')
 }
 
 export function exportTrendsCSV(series) {
-  const header = ['Date','PRs Created','PRs Merged','PRs Closed','Issues Created','Issues Closed']
-  const rows   = series.map(s => [s.date, s.prs_created, s.prs_merged, s.prs_closed, s.issues_created, s.issues_closed])
+  const header = ['Date', 'PRs Created', 'PRs Merged', 'PRs Closed', 'Issues Created', 'Issues Closed']
+  const rows = series.map(s => [s.date, s.prs_created, s.prs_merged, s.prs_closed, s.issues_created, s.issues_closed])
   download([header, ...rows].map(r => r.join(',')).join('\n'), 'orgexplorer-trends.csv')
 }
 
@@ -182,16 +184,16 @@ export function getTopRepositories(repos, limit = 10) {
 
   return [...repos]
     .map(repo => {
-      const pushedAtMs = Date.parse(repo.pushed_at);  
+      const pushedAtMs = Date.parse(repo.pushed_at);
       const daysSinceLastPush = Number.isFinite(pushedAtMs) ? (Date.now() - pushedAtMs) / MS_PER_DAY : Infinity;
 
       const activityBonus = 0.5 * Math.max(0, 365 - daysSinceLastPush);
 
-      const score =  
-        (repo.stargazers_count ?? 0) +  
-        (repo.forks_count ?? 0) * 2 +  
-        (repo.watchers_count ?? 0) * 1.5 +  
-        activityBonus;  
+      const score =
+        (repo.stargazers_count ?? 0) +
+        (repo.forks_count ?? 0) * 2 +
+        (repo.watchers_count ?? 0) * 1.5 +
+        activityBonus;
 
       return {
         ...repo,