diff --git a/.github/workflows/fetch_georelays.yml b/.github/workflows/fetch_georelays.yml
index 6aaf6693..ad5f0bb4 100644
--- a/.github/workflows/fetch_georelays.yml
+++ b/.github/workflows/fetch_georelays.yml
@@ -1,42 +1,228 @@
-name: Fetch GeoRelays Data
+name: Propose GeoRelay Data Update
 
 on:
   schedule:
-    - cron: '0 6 * * 0'
+    - cron: "0 6 * * 0"
   workflow_dispatch:
 
+# Default to read-only. The publishing job receives only the scopes required
+# to push its branch and publish either a PR or a tracking issue.
 permissions:
-  contents: write
-  pull-requests: write
+  contents: read
+
+concurrency:
+  group: georelay-data-update
+  cancel-in-progress: false
+
+env:
+  SOURCE_REPOSITORY: https://github.com/permissionlesstech/georelays.git
+  UPDATE_BRANCH: automation/georelay-data
+  TRACKING_ISSUE_TITLE: GeoRelay update awaiting pull request
 
 jobs:
-  update-relay-data:
+  propose-relay-data:
+    name: Validate and propose relay data
     runs-on: ubuntu-latest
+    timeout-minutes: 10
+    permissions:
+      contents: write
+      pull-requests: write
+      issues: write
 
     steps:
-      - name: Checkout repository
-        uses: actions/checkout@v4
+      - name: Checkout reviewed base
+        # Pinned actions/checkout v5 so a mutable action tag cannot change the
+        # code that receives this job's write-capable token.
+        uses: actions/checkout@93cb6efe18208431cddfb8368fd83d5badbf9bfd
         with:
-          token: ${{ secrets.GITHUB_TOKEN }}
+          ref: main
           fetch-depth: 0
+          # Do not expose the write token to fetch/validation subprocesses.
+          persist-credentials: false
 
-      - name: Fetch GeoRelays
+      - name: Test GeoRelay validator
         run: |
-          wget -q https://raw.githubusercontent.com/permissionlesstech/georelays/refs/heads/main/nostr_relays.csv
-          mv nostr_relays.csv ./relays/online_relays_gps.csv
+          set -euo pipefail
+          python3 -m unittest discover -s scripts/tests -p "test_*.py" -v
 
-      - name: Check for changes
-        id: git-check
+      - name: Fetch candidate over pinned HTTPS policy
+        id: upstream
         run: |
-          git diff --exit-code || echo "changes=true" >> $GITHUB_OUTPUT
-    
-      - name: Commit and push changes
-        if: steps.git-check.outputs.changes == 'true'
+          set -euo pipefail
+          source_commit=$(git ls-remote --refs "$SOURCE_REPOSITORY" refs/heads/main | awk 'NR == 1 { print $1 }')
+          if [[ ! "$source_commit" =~ ^[0-9a-f]{40}$ ]]; then
+            echo "::error::Could not resolve an immutable upstream commit"
+            exit 1
+          fi
+          source_url="https://raw.githubusercontent.com/permissionlesstech/georelays/$source_commit/nostr_relays.csv"
+          effective_url=$(curl --fail --show-error --silent --location --proto "=https" --proto-redir "=https" --tlsv1.2 --max-time 60 --retry 3 --retry-all-errors --output "$RUNNER_TEMP/georelays-candidate.csv" --write-out "%{url_effective}" "$source_url")
+          if [[ "$effective_url" != "$source_url" ]]; then
+            echo "::error::Unexpected GeoRelay redirect target: $effective_url"
+            exit 1
+          fi
+          echo "source_commit=$source_commit" >> "$GITHUB_OUTPUT"
+          echo "source_url=$source_url" >> "$GITHUB_OUTPUT"
+
+      - name: Validate candidate against reviewed baseline
+        id: validation
         run: |
-          git config --local user.email "action@github.com"
-          git config --local user.name "GitHub Action"
-          git add relays/online_relays_gps.csv
-          git commit -m "Automated update of relay data - $(date -u)"
-          git push
+          set -euo pipefail
+          python3 scripts/validate_georelays.py --input "$RUNNER_TEMP/georelays-candidate.csv" --baseline relays/online_relays_gps.csv --output relays/online_relays_gps.csv --github-output "$GITHUB_OUTPUT"
+
+      - name: Check for a reviewed-file change
+        id: changes
+        run: |
+          set -euo pipefail
+          if git diff --quiet -- relays/online_relays_gps.csv; then
+            echo "changed=false" >> "$GITHUB_OUTPUT"
+            echo "Upstream GeoRelay data already matches main." >> "$GITHUB_STEP_SUMMARY"
+          else
+            echo "changed=true" >> "$GITHUB_OUTPUT"
+            git diff --stat -- relays/online_relays_gps.csv
+          fi
+
+      - name: Push automation branch and publish review request
+        if: steps.changes.outputs.changed == 'true'
         env:
-          GITHUB_TOKEN: ${{ secrets.GITHUB_TOKEN }}
\ No newline at end of file
+          GH_TOKEN: ${{ github.token }}
+          SOURCE_COMMIT: ${{ steps.upstream.outputs.source_commit }}
+          SOURCE_URL: ${{ steps.upstream.outputs.source_url }}
+          DATA_ROWS: ${{ steps.validation.outputs.data_rows }}
+          UNIQUE_RELAYS: ${{ steps.validation.outputs.unique_relays }}
+          DATA_SHA256: ${{ steps.validation.outputs.sha256 }}
+        run: |
+          set -euo pipefail
+
+          # Scope credential exposure to this final publishing step.
+          gh auth setup-git
+          git config user.name "github-actions[bot]"
+          git config user.email "41898282+github-actions[bot]@users.noreply.github.com"
+
+          git switch -C "$UPDATE_BRANCH"
+          git add -- relays/online_relays_gps.csv
+          git diff --cached --quiet && {
+            echo "::error::Expected a staged GeoRelay data change"
+            exit 1
+          }
+          git commit -m "Update reviewed georelay directory" -m "Upstream-commit: $SOURCE_COMMIT"
+
+          remote_ref="refs/remotes/origin/$UPDATE_BRANCH"
+          if git fetch --no-tags origin "+refs/heads/$UPDATE_BRANCH:$remote_ref" 2>/dev/null; then
+            remote_sha=$(git rev-parse "$remote_ref")
+            git push --force-with-lease="refs/heads/$UPDATE_BRANCH:$remote_sha" origin "HEAD:refs/heads/$UPDATE_BRANCH"
+          else
+            git push origin "HEAD:refs/heads/$UPDATE_BRANCH"
+          fi
+
+          body_file="$RUNNER_TEMP/georelay-pr-body.md"
+          {
+            echo "## Automated GeoRelay data proposal"
+            echo
+            echo "- Source: $SOURCE_URL"
+            echo "- Upstream commit: $SOURCE_COMMIT"
+            echo "- Data rows: $DATA_ROWS"
+            echo "- Unique normalized relays: $UNIQUE_RELAYS"
+            echo "- SHA-256: $DATA_SHA256"
+            echo
+            echo "The candidate passed strict UTF-8, schema, size, row-count, secure-host, coordinate, duplicate-conflict, and baseline-delta validation."
+            echo
+            echo "This PR is intentionally not auto-merged. Review the relay additions/removals before merging."
+          } > "$body_file"
+
+          existing_pr=$(gh pr list --repo "$GITHUB_REPOSITORY" --state open --base main --head "$UPDATE_BRANCH" --json number --jq '.[0].number // empty')
+          pr_error="$RUNNER_TEMP/georelay-pr-error.txt"
+          pr_url=""
+          if [[ -n "$existing_pr" ]]; then
+            if gh pr edit "$existing_pr" --repo "$GITHUB_REPOSITORY" --title "Update reviewed GeoRelay directory" --body-file "$body_file" 2> "$pr_error"; then
+              pr_url=$(gh pr view "$existing_pr" --repo "$GITHUB_REPOSITORY" --json url --jq .url)
+            fi
+          else
+            if created_pr_url=$(gh pr create --repo "$GITHUB_REPOSITORY" --base main --head "$UPDATE_BRANCH" --title "Update reviewed GeoRelay directory" --body-file "$body_file" 2> "$pr_error"); then
+              pr_url="$created_pr_url"
+            fi
+          fi
+
+          tracking_issue_numbers=$(gh issue list --repo "$GITHUB_REPOSITORY" --state open --search "\"$TRACKING_ISSUE_TITLE\" in:title" --limit 100 --json number,title --jq ".[] | select(.title == \"$TRACKING_ISSUE_TITLE\") | .number")
+          tracking_issues=()
+          if [[ -n "$tracking_issue_numbers" ]]; then
+            mapfile -t tracking_issues <<< "$tracking_issue_numbers"
+          fi
+
+          if [[ -n "$pr_url" ]]; then
+            for issue_number in "${tracking_issues[@]}"; do
+              gh issue close "$issue_number" --repo "$GITHUB_REPOSITORY" --comment "A pull request is now available at $pr_url; closing this fallback tracking issue."
+            done
+            echo "Published GeoRelay review PR: $pr_url" >> "$GITHUB_STEP_SUMMARY"
+            exit 0
+          fi
+
+          echo "::warning::GITHUB_TOKEN could not create or update the GeoRelay pull request; publishing the issues-write fallback."
+          if [[ -s "$pr_error" ]]; then
+            cat "$pr_error" >&2
+          fi
+
+          compare_url="https://github.com/${GITHUB_REPOSITORY}/compare/main...${UPDATE_BRANCH}?expand=1"
+          issue_body_file="$RUNNER_TEMP/georelay-tracking-issue-body.md"
+          {
+            echo "## Validated GeoRelay update awaiting review"
+            echo
+            echo "The automation branch was updated, but this workflow token could not create or update the pull request. Use the compare link below to create it manually."
+            echo
+            echo "- Compare and create PR: $compare_url"
+            echo "- Automation branch: $UPDATE_BRANCH"
+            echo "- Source: $SOURCE_URL"
+            echo "- Upstream commit: $SOURCE_COMMIT"
+            echo "- Data rows: $DATA_ROWS"
+            echo "- Unique normalized relays: $UNIQUE_RELAYS"
+            echo "- SHA-256: $DATA_SHA256"
+            echo
+            echo "The snapshot passed the repository's strict validator before the branch was pushed."
+          } > "$issue_body_file"
+
+          if (( ${#tracking_issues[@]} > 0 )); then
+            primary_issue="${tracking_issues[0]}"
+            gh issue edit "$primary_issue" --repo "$GITHUB_REPOSITORY" --title "$TRACKING_ISSUE_TITLE" --body-file "$issue_body_file"
+            issue_url=$(gh issue view "$primary_issue" --repo "$GITHUB_REPOSITORY" --json url --jq .url)
+            for duplicate_issue in "${tracking_issues[@]:1}"; do
+              gh issue close "$duplicate_issue" --repo "$GITHUB_REPOSITORY" --comment "Closing duplicate GeoRelay automation tracking issue; #$primary_issue is canonical."
+            done
+          else
+            issue_url=$(gh issue create --repo "$GITHUB_REPOSITORY" --title "$TRACKING_ISSUE_TITLE" --body-file "$issue_body_file")
+          fi
+
+          # Do not claim success until the fallback issue was confirmed.
+          [[ -n "$issue_url" ]]
+          echo "Published GeoRelay tracking issue fallback: $issue_url" >> "$GITHUB_STEP_SUMMARY"
+
+      - name: Clean obsolete automation review state
+        if: steps.changes.outputs.changed == 'false'
+        env:
+          GH_TOKEN: ${{ github.token }}
+        run: |
+          set -euo pipefail
+          gh auth setup-git
+
+          existing_pr=$(gh pr list --repo "$GITHUB_REPOSITORY" --state open --base main --head "$UPDATE_BRANCH" --json number --jq '.[0].number // empty')
+          if [[ -n "$existing_pr" ]]; then
+            gh pr close "$existing_pr" --repo "$GITHUB_REPOSITORY" --comment "Upstream now matches the reviewed file on main; closing this obsolete automation proposal."
+            echo "Closed obsolete PR #$existing_pr." >> "$GITHUB_STEP_SUMMARY"
+          fi
+
+          tracking_issue_numbers=$(gh issue list --repo "$GITHUB_REPOSITORY" --state open --search "\"$TRACKING_ISSUE_TITLE\" in:title" --limit 100 --json number,title --jq ".[] | select(.title == \"$TRACKING_ISSUE_TITLE\") | .number")
+          if [[ -n "$tracking_issue_numbers" ]]; then
+            while IFS= read -r issue_number; do
+              gh issue close "$issue_number" --repo "$GITHUB_REPOSITORY" --comment "Upstream now matches the reviewed file on main; closing this obsolete automation tracker."
+              echo "Closed obsolete tracking issue #$issue_number." >> "$GITHUB_STEP_SUMMARY"
+            done <<< "$tracking_issue_numbers"
+          fi
+
+          if git ls-remote --exit-code --heads origin "refs/heads/$UPDATE_BRANCH" > /dev/null; then
+            git push origin --delete "$UPDATE_BRANCH"
+            echo "Deleted obsolete automation branch $UPDATE_BRANCH." >> "$GITHUB_STEP_SUMMARY"
+          else
+            ls_remote_status=$?
+            if (( ls_remote_status != 2 )); then
+              echo "::error::Could not inspect the obsolete automation branch"
+              exit "$ls_remote_status"
+            fi
+          fi
diff --git a/bitchat/Nostr/GeoRelayDirectory.swift b/bitchat/Nostr/GeoRelayDirectory.swift
index 55a25e4d..2f4b20c2 100644
--- a/bitchat/Nostr/GeoRelayDirectory.swift
+++ b/bitchat/Nostr/GeoRelayDirectory.swift
@@ -32,6 +32,23 @@ struct GeoRelayDirectoryDependencies {
     var retrySleep: (TimeInterval) async -> Void
     var activeNotificationName: Notification.Name?
     var autoStart: Bool
+    var validationPolicy: GeoRelayDirectoryValidationPolicy
+}
+
+struct GeoRelayDirectoryValidationPolicy: Sendable {
+    let maximumBytes: Int
+    let maximumRows: Int
+    let maximumEntries: Int
+    let minimumRemoteEntries: Int
+    let minimumRetainedFraction: Double
+
+    static let live = GeoRelayDirectoryValidationPolicy(
+        maximumBytes: 512 * 1024,
+        maximumRows: 5_000,
+        maximumEntries: 5_000,
+        minimumRemoteEntries: 50,
+        minimumRetainedFraction: 0.5
+    )
 }
 
 private extension GeoRelayDirectoryDependencies {
@@ -44,12 +61,16 @@ private extension GeoRelayDirectoryDependencies {
 #else
         let activeNotificationName: Notification.Name? = nil
 #endif
+        let validationPolicy = GeoRelayDirectoryValidationPolicy.live
 
         return Self(
             userDefaults: .standard,
             notificationCenter: .default,
             now: Date.init,
-            remoteURL: URL(string: "https://raw.githubusercontent.com/permissionlesstech/georelays/refs/heads/main/nostr_relays.csv")!,
+            // Runtime refreshes only from bitchat's reviewed copy. Upstream
+            // georelays/main is imported by a validator-backed pull request,
+            // so an upstream mutation cannot immediately retarget clients.
+            remoteURL: URL(string: "https://raw.githubusercontent.com/permissionlesstech/bitchat/refs/heads/main/relays/online_relays_gps.csv")!,
             fetchInterval: TransportConfig.geoRelayFetchIntervalSeconds,
             refreshCheckInterval: TransportConfig.geoRelayRefreshCheckIntervalSeconds,
             retryInitialSeconds: TransportConfig.geoRelayRetryInitialSeconds,
@@ -58,7 +79,27 @@ private extension GeoRelayDirectoryDependencies {
             makeFetchData: {
                 let session = TorURLSession.shared.session
                 return { request in
-                    let (data, _) = try await session.data(for: request)
+                    let (bytes, response) = try await session.bytes(for: request)
+                    guard let response = response as? HTTPURLResponse,
+                          (200...299).contains(response.statusCode),
+                          response.url == request.url else {
+                        throw URLError(.badServerResponse)
+                    }
+
+                    let maximumBytes = validationPolicy.maximumBytes
+                    guard response.expectedContentLength <= Int64(maximumBytes) else {
+                        throw URLError(.dataLengthExceedsMaximum)
+                    }
+                    var data = Data()
+                    if response.expectedContentLength > 0 {
+                        data.reserveCapacity(Int(response.expectedContentLength))
+                    }
+                    for try await byte in bytes {
+                        guard data.count < maximumBytes else {
+                            throw URLError(.dataLengthExceedsMaximum)
+                        }
+                        data.append(byte)
+                    }
                     return data
                 }
             },
@@ -76,7 +117,11 @@ private extension GeoRelayDirectoryDependencies {
                     )
                     let dir = base.appendingPathComponent("bitchat", isDirectory: true)
                     try? FileManager.default.createDirectory(at: dir, withIntermediateDirectories: true)
-                    return dir.appendingPathComponent("georelays_cache.csv")
+                    // v2 ignores caches populated from the old direct-upstream
+                    // trust path and subjects every load to strict validation.
+                    let legacyCache = dir.appendingPathComponent("georelays_cache.csv")
+                    try? FileManager.default.removeItem(at: legacyCache)
+                    return dir.appendingPathComponent("georelays_cache_v2.csv")
                 } catch {
                     return nil
                 }
@@ -94,7 +139,8 @@ private extension GeoRelayDirectoryDependencies {
                 try? await Task.sleep(nanoseconds: nanoseconds)
             },
             activeNotificationName: activeNotificationName,
-            autoStart: true
+            autoStart: true,
+            validationPolicy: validationPolicy
         )
     }
 }
@@ -125,7 +171,7 @@ final class GeoRelayDirectory {
     }
 
     private enum DetachedFetchOutcome: Sendable {
-        case success(entries: [Entry], csv: String)
+        case success(entries: [Entry], csv: Data)
         case torNotReady
         case invalidData
         case network(String)
@@ -212,6 +258,8 @@ final class GeoRelayDirectory {
         )
         let awaitTorReady = dependencies.awaitTorReady
         let fetchData = dependencies.makeFetchData()
+        let validationPolicy = dependencies.validationPolicy
+        let baselineEntries = Set(entries)
 
         Task { [weak self] in
             guard let self else { return }
@@ -219,7 +267,9 @@ final class GeoRelayDirectory {
             let outcome = await Self.fetchRemoteOutcome(
                 request: request,
                 awaitTorReady: awaitTorReady,
-                fetchData: fetchData
+                fetchData: fetchData,
+                validationPolicy: validationPolicy,
+                baselineEntries: baselineEntries
             )
 
             switch outcome {
@@ -238,7 +288,9 @@ final class GeoRelayDirectory {
     nonisolated private static func fetchRemoteOutcome(
         request: URLRequest,
         awaitTorReady: @escaping @Sendable () async -> Bool,
-        fetchData: @escaping @Sendable (URLRequest) async throws -> Data
+        fetchData: @escaping @Sendable (URLRequest) async throws -> Data,
+        validationPolicy: GeoRelayDirectoryValidationPolicy,
+        baselineEntries: Set<Entry>
     ) async -> DetachedFetchOutcome {
         await Task.detached(priority: .utility) {
             let ready = await awaitTorReady()
@@ -246,16 +298,16 @@ final class GeoRelayDirectory {
 
             do {
                 let data = try await fetchData(request)
-                guard let text = String(data: data, encoding: .utf8) else {
+                guard let parsed = Self.validatedEntries(
+                    from: data,
+                    policy: validationPolicy,
+                    minimumEntries: validationPolicy.minimumRemoteEntries,
+                    baselineEntries: baselineEntries
+                ) else {
                     return .invalidData
                 }
 
-                let parsed = Self.parseCSV(text)
-                guard !parsed.isEmpty else {
-                    return .invalidData
-                }
-
-                return .success(entries: parsed, csv: text)
+                return .success(entries: parsed, csv: data)
             } catch {
                 return .network(error.localizedDescription)
             }
@@ -269,7 +321,7 @@ final class GeoRelayDirectory {
     }
 
     @MainActor
-    private func handleFetchSuccess(entries parsed: [Entry], csv: String) {
+    private func handleFetchSuccess(entries parsed: [Entry], csv: Data) {
         entries = parsed
         persistCache(csv)
         dependencies.userDefaults.set(dependencies.now(), forKey: lastFetchKey)
@@ -321,9 +373,8 @@ final class GeoRelayDirectory {
         cleanupState.retryTask = nil
     }
 
-    private func persistCache(_ text: String) {
+    private func persistCache(_ data: Data) {
         guard let url = dependencies.cacheURL() else { return }
-        guard let data = text.data(using: .utf8) else { return }
         do {
             try dependencies.writeData(data, url)
         } catch {
@@ -336,9 +387,12 @@ final class GeoRelayDirectory {
         // Prefer cached file if present
         if let cache = dependencies.cacheURL(),
            let data = dependencies.readData(cache),
-           let text = String(data: data, encoding: .utf8) {
-            let arr = Self.parseCSV(text)
-            if !arr.isEmpty { return arr }
+           let entries = Self.validatedEntries(
+               from: data,
+               policy: dependencies.validationPolicy,
+               minimumEntries: 1
+           ) {
+            return entries
         }
 
         // Try bundled resource(s)
@@ -346,36 +400,157 @@ final class GeoRelayDirectory {
 
         for url in bundleCandidates {
             if let data = dependencies.readData(url),
-               let text = String(data: data, encoding: .utf8) {
-                let arr = Self.parseCSV(text)
-                if !arr.isEmpty { return arr }
+               let entries = Self.validatedEntries(
+                   from: data,
+                   policy: dependencies.validationPolicy,
+                   minimumEntries: 1
+               ) {
+                return entries
             }
         }
 
         // Try filesystem path (development/test)
         if let cwd = dependencies.currentDirectoryPath(),
            let data = dependencies.readData(URL(fileURLWithPath: cwd).appendingPathComponent("relays/online_relays_gps.csv")),
-           let text = String(data: data, encoding: .utf8) {
-            return Self.parseCSV(text)
+           let entries = Self.validatedEntries(
+               from: data,
+               policy: dependencies.validationPolicy,
+               minimumEntries: 1
+           ) {
+            return entries
         }
 
         SecureLogger.warning("GeoRelayDirectory: no local CSV found; entries empty", category: .session)
         return []
     }
 
-    nonisolated static func parseCSV(_ text: String) -> [Entry] {
-        var result: Set<Entry> = []
-        let lines = text.split(whereSeparator: { $0.isNewline })
-        for (idx, raw) in lines.enumerated() {
-            guard let line = raw.trimmedOrNilIfEmpty else { continue }
-            if idx == 0 && line.lowercased().contains("relay url") { continue }
-            let parts = line.split(separator: ",").map { $0.trimmed }
-            guard parts.count >= 3 else { continue }
-            guard let host = NostrRelayURL.directoryAddress(parts[0]) else { continue }
-            guard let lat = Double(parts[1]), let lon = Double(parts[2]) else { continue }
-            result.insert(Entry(host: host, lat: lat, lon: lon))
+    /// Parses the fixed three-column format as an all-or-nothing trust unit.
+    /// One malformed or conflicting row rejects the complete dataset rather
+    /// than silently shrinking or partially replacing the current directory.
+    nonisolated static func validatedEntries(
+        from data: Data,
+        policy: GeoRelayDirectoryValidationPolicy,
+        minimumEntries: Int,
+        baselineEntries: Set<Entry>? = nil
+    ) -> [Entry]? {
+        guard !data.isEmpty, data.count <= policy.maximumBytes,
+              let text = String(data: data, encoding: .utf8),
+              !text.hasPrefix("\u{feff}") else {
+            return nil
         }
-        return Array(result)
+
+        let lines = text.split(whereSeparator: { $0.isNewline })
+            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+            .filter { !$0.isEmpty }
+        guard let header = lines.first,
+              lines.count - 1 <= policy.maximumRows else {
+            return nil
+        }
+
+        let headerParts = header
+            .split(separator: ",", omittingEmptySubsequences: false)
+            .map { $0.trimmingCharacters(in: .whitespacesAndNewlines).lowercased() }
+        let supportedHeaders = [
+            ["relay url", "latitude", "longitude"],
+            ["relay url", "lat", "lon"]
+        ]
+        guard supportedHeaders.contains(headerParts) else {
+            return nil
+        }
+
+        var entriesByHost: [String: Entry] = [:]
+        for line in lines.dropFirst() {
+            let parts = line
+                .split(separator: ",", omittingEmptySubsequences: false)
+                .map { $0.trimmingCharacters(in: .whitespacesAndNewlines) }
+            guard parts.count == 3,
+                  let host = validatedDirectoryAddress(parts[0]),
+                  let latitude = Double(parts[1]), latitude.isFinite,
+                  (-90.0...90.0).contains(latitude),
+                  let longitude = Double(parts[2]), longitude.isFinite,
+                  (-180.0...180.0).contains(longitude) else {
+                return nil
+            }
+
+            let entry = Entry(host: host, lat: latitude, lon: longitude)
+            if let existing = entriesByHost[host], existing != entry {
+                // One endpoint cannot truthfully occupy two coordinates. Do
+                // not let row ordering choose which location clients trust.
+                return nil
+            }
+            entriesByHost[host] = entry
+            guard entriesByHost.count <= policy.maximumEntries else { return nil }
+        }
+
+        let parsedEntries = Set(entriesByHost.values)
+        guard parsedEntries.count >= minimumEntries else { return nil }
+
+        if let baselineEntries {
+            guard (0...1).contains(policy.minimumRetainedFraction) else { return nil }
+            let requiredOverlap = Int(
+                ceil(Double(baselineEntries.count) * policy.minimumRetainedFraction)
+            )
+            guard parsedEntries.intersection(baselineEntries).count >= requiredOverlap else {
+                return nil
+            }
+        }
+
+        return parsedEntries.sorted {
+            ($0.host, $0.lat, $0.lon) < ($1.host, $1.lat, $1.lon)
+        }
+    }
+
+    nonisolated private static func validatedDirectoryAddress(_ rawValue: String) -> String? {
+        let value = rawValue.trimmingCharacters(in: .whitespacesAndNewlines)
+        guard !value.isEmpty,
+              value.unicodeScalars.allSatisfy({
+                  $0.isASCII && !CharacterSet.controlCharacters.contains($0)
+              }) else {
+            return nil
+        }
+
+        let candidate = value.contains("://") ? value : "wss://\(value)"
+        guard let components = URLComponents(string: candidate),
+              let scheme = components.scheme?.lowercased(),
+              scheme == "wss" || scheme == "https",
+              components.user == nil,
+              components.password == nil,
+              components.query == nil,
+              components.fragment == nil,
+              components.path.isEmpty || components.path == "/",
+              let rawHost = components.host else {
+            return nil
+        }
+
+        let host = rawHost.lowercased()
+        guard !host.isEmpty, host.count <= 253,
+              host.unicodeScalars.allSatisfy({ $0.isASCII }),
+              !host.hasSuffix("."),
+              host != "localhost",
+              !host.hasSuffix(".localhost"),
+              !host.hasSuffix(".local"),
+              !host.hasSuffix(".internal") else {
+            return nil
+        }
+
+        let labels = host.split(separator: ".", omittingEmptySubsequences: false)
+        let allowed = CharacterSet(charactersIn: "abcdefghijklmnopqrstuvwxyz0123456789-")
+        guard labels.count >= 2,
+              !labels.allSatisfy({ $0.allSatisfy(\.isNumber) }),
+              labels.allSatisfy({ label in
+                  (1...63).contains(label.count) &&
+                  label.first != "-" &&
+                  label.last != "-" &&
+                  label.unicodeScalars.allSatisfy { allowed.contains($0) }
+              }) else {
+            return nil
+        }
+
+        if let port = components.port {
+            guard (1...65_535).contains(port) else { return nil }
+            if port != 443 { return "\(host):\(port)" }
+        }
+        return host
     }
 
     // MARK: - Observers & Timers
diff --git a/bitchat/Nostr/NostrRelayURL.swift b/bitchat/Nostr/NostrRelayURL.swift
index be9a6fb6..eb2e2afc 100644
--- a/bitchat/Nostr/NostrRelayURL.swift
+++ b/bitchat/Nostr/NostrRelayURL.swift
@@ -39,13 +39,4 @@ enum NostrRelayURL {
 
         return components.string
     }
-
-    static func directoryAddress(_ rawValue: String) -> String? {
-        guard var normalized = normalized(rawValue, defaultScheme: "wss") else { return nil }
-        for prefix in ["wss://", "ws://"] where normalized.hasPrefix(prefix) {
-            normalized.removeFirst(prefix.count)
-            break
-        }
-        return normalized
-    }
 }
diff --git a/bitchatTests/Nostr/GeoRelayDirectoryTests.swift b/bitchatTests/Nostr/GeoRelayDirectoryTests.swift
index 516f4a1d..bbcccc42 100644
--- a/bitchatTests/Nostr/GeoRelayDirectoryTests.swift
+++ b/bitchatTests/Nostr/GeoRelayDirectoryTests.swift
@@ -5,19 +5,25 @@ import XCTest
 
 @MainActor
 final class GeoRelayDirectoryTests: XCTestCase {
-    func test_parseCSV_normalizesRelaySchemesAndDeduplicatesEntries() {
+    private func parse(_ csv: String) -> [GeoRelayDirectory.Entry] {
+        GeoRelayDirectory.validatedEntries(
+            from: Data(csv.utf8),
+            policy: .live,
+            minimumEntries: 1
+        ) ?? []
+    }
+
+    func test_parseCSV_normalizesSecureRelaySchemesAndDeduplicatesEntries() {
         let csv = """
         relay url,lat,lon
         wss://one.example/,10,20
         https://one.example,10,20
         wss://one.example:443/,10,20
-        http://two.example/,11,21
+        two.example,11,21
         wss://two.example:443,11,21
-        invalid row
-        ws://three.example,not-a-lat,22
         """
 
-        let parsed = Set(GeoRelayDirectory.parseCSV(csv))
+        let parsed = Set(parse(csv))
 
         XCTAssertEqual(
             parsed,
@@ -28,6 +34,136 @@ final class GeoRelayDirectoryTests: XCTestCase {
         )
     }
 
+    func test_parseCSV_rejectsWholeDatasetWhenAnyRowOrHeaderIsUnsafe() {
+        let invalidCSVs = [
+            "relay,lat,lon\nrelay.example,1,2\n",
+            "relay url,lat,lon\nrelay.example,1\n",
+            "relay url,lat,lon\nhttp://relay.example,1,2\n",
+            "relay url,lat,lon\nwss://user@relay.example,1,2\n",
+            "relay url,lat,lon\nwss://relay.example/path,1,2\n",
+            "relay url,lat,lon\nwss://relay.example?,1,2\n",
+            "relay url,lat,lon\nwss://relay.example#,1,2\n",
+            "relay url,lat,lon\nrelay.example:0,1,2\n",
+            "relay url,lat,lon\nrelay.example:99999,1,2\n",
+            "relay url,lat,lon\nlocalhost,1,2\n",
+            "relay url,lat,lon\nr\u{00e9}lay.example,1,2\n",
+            "relay url,lat,lon\nrelay\u{202e}.example,1,2\n",
+            "relay url,lat,lon\nrelay.example,NaN,2\n",
+            "relay url,lat,lon\nrelay.example,1_0,2\n",
+            "relay url,lat,lon\nrelay.example,\u{0661}\u{0660},2\n",
+            "relay url,lat,lon\nrelay.example,\u{ff11}\u{ff10},2\n",
+            "relay url,lat,lon\nrelay.example,91,2\n",
+            "relay url,lat,lon\nrelay.example,1,181\n",
+            "relay url,lat,lon\nrelay.example,1,2\nrelay.example,3,4\n"
+        ]
+
+        for csv in invalidCSVs {
+            XCTAssertTrue(parse(csv).isEmpty, csv)
+        }
+    }
+
+    func test_validatedEntries_enforcesByteRowEntryAndRetentionLimits() {
+        let restrictive = GeoRelayDirectoryValidationPolicy(
+            maximumBytes: 100,
+            maximumRows: 2,
+            maximumEntries: 2,
+            minimumRemoteEntries: 1,
+            minimumRetainedFraction: 0.5
+        )
+        let one = Data("relay url,lat,lon\none.example,1,2\n".utf8)
+        let three = Data("relay url,lat,lon\none.example,1,2\ntwo.example,3,4\nthree.example,5,6\n".utf8)
+
+        XCTAssertNil(GeoRelayDirectory.validatedEntries(
+            from: one,
+            policy: restrictive,
+            minimumEntries: 2
+        ))
+        XCTAssertNil(GeoRelayDirectory.validatedEntries(
+            from: Data(repeating: 0x41, count: 101),
+            policy: restrictive,
+            minimumEntries: 1
+        ))
+        XCTAssertNil(GeoRelayDirectory.validatedEntries(
+            from: three,
+            policy: restrictive,
+            minimumEntries: 1
+        ))
+    }
+
+    func test_validatedEntries_requiresExactBaselineEntryOverlap() throws {
+        let policy = GeoRelayDirectoryValidationPolicy(
+            maximumBytes: 1_000,
+            maximumRows: 10,
+            maximumEntries: 10,
+            minimumRemoteEntries: 1,
+            minimumRetainedFraction: 0.5
+        )
+        let baseline = Set(try XCTUnwrap(GeoRelayDirectory.validatedEntries(
+            from: Data("""
+            relay url,lat,lon
+            one.example,1,1
+            two.example,2,2
+            three.example,3,3
+            """.utf8),
+            policy: policy,
+            minimumEntries: 1
+        )))
+        let disjoint = Data("""
+        relay url,lat,lon
+        four.example,1,1
+        five.example,2,2
+        six.example,3,3
+        """.utf8)
+        let rewrittenCoordinates = Data("""
+        relay url,lat,lon
+        one.example,11,11
+        two.example,12,12
+        three.example,13,13
+        """.utf8)
+        let halfRetained = Data("""
+        relay url,lat,lon
+        wss://one.example:443/,1,1
+        https://two.example/,2,2
+        replacement.example,4,4
+        """.utf8)
+
+        XCTAssertNil(GeoRelayDirectory.validatedEntries(
+            from: disjoint,
+            policy: policy,
+            minimumEntries: 1,
+            baselineEntries: baseline
+        ))
+        XCTAssertNil(GeoRelayDirectory.validatedEntries(
+            from: rewrittenCoordinates,
+            policy: policy,
+            minimumEntries: 1,
+            baselineEntries: baseline
+        ))
+        XCTAssertNotNil(GeoRelayDirectory.validatedEntries(
+            from: halfRetained,
+            policy: policy,
+            minimumEntries: 1,
+            baselineEntries: baseline
+        ))
+    }
+
+    func test_bundledReviewedCSV_passesStrictProductionValidation() throws {
+        let repositoryRoot = URL(fileURLWithPath: #filePath)
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+            .deletingLastPathComponent()
+        let data = try Data(
+            contentsOf: repositoryRoot.appendingPathComponent("relays/online_relays_gps.csv")
+        )
+
+        let entries = try XCTUnwrap(GeoRelayDirectory.validatedEntries(
+            from: data,
+            policy: .live,
+            minimumEntries: GeoRelayDirectoryValidationPolicy.live.minimumRemoteEntries
+        ))
+        XCTAssertGreaterThan(entries.count, 250)
+    }
+
     func test_closestRelays_sortsByDistanceForLatLonAndGeohash() {
         let harness = makeHarness(
             cacheCSV: """
@@ -243,6 +379,53 @@ final class GeoRelayDirectoryTests: XCTestCase {
         XCTAssertFalse(directory.debugHasRetryTask)
     }
 
+    func test_prefetchIfNeeded_rejectsSharpValidLookingTruncationBeforeCaching() async {
+        let cached = """
+        relay url,lat,lon
+        old-one.example,1,1
+        old-two.example,2,2
+        old-three.example,3,3
+        """
+        let truncated = """
+        relay url,lat,lon
+        attacker.example,9,9
+        """
+        let recovered = """
+        relay url,lat,lon
+        old-one.example,1,1
+        old-two.example,2,2
+        new-three.example,6,6
+        """
+        let harness = makeHarness(
+            cacheCSV: cached,
+            fetchResults: [
+                .success(Data(truncated.utf8)),
+                .success(Data(recovered.utf8))
+            ],
+            validationPolicy: GeoRelayDirectoryValidationPolicy(
+                maximumBytes: 64 * 1024,
+                maximumRows: 1_000,
+                maximumEntries: 1_000,
+                minimumRemoteEntries: 1,
+                minimumRetainedFraction: 0.5
+            )
+        )
+        let directory = GeoRelayDirectory(dependencies: harness.dependencies)
+
+        directory.prefetchIfNeeded()
+
+        let refreshed = await waitUntil {
+            directory.entries.contains(where: { $0.host == "new-three.example" })
+        }
+        XCTAssertTrue(refreshed)
+        XCTAssertFalse(directory.entries.contains(where: { $0.host == "attacker.example" }))
+        let requestCount = await harness.fetcher.recordedRequestCount()
+        let retryDelays = await harness.retryRecorder.recordedDelays()
+        XCTAssertEqual(requestCount, 2)
+        XCTAssertEqual(retryDelays, [5])
+        XCTAssertEqual(harness.fileStore.dataByURL[harness.cacheURL], Data(recovered.utf8))
+    }
+
     func test_observers_triggerPrefetchesForTorReadyAndAppActivation() async {
         let activeNotification = Notification.Name("GeoRelayDirectoryTests.didBecomeActive")
         let harness = makeHarness(
@@ -289,7 +472,14 @@ final class GeoRelayDirectoryTests: XCTestCase {
         fetchFactoryObserver: (@MainActor @Sendable () -> Void)? = nil,
         fetchObserver: (@Sendable () async -> Void)? = nil,
         autoStart: Bool = false,
-        activeNotificationName: Notification.Name? = nil
+        activeNotificationName: Notification.Name? = nil,
+        validationPolicy: GeoRelayDirectoryValidationPolicy = GeoRelayDirectoryValidationPolicy(
+            maximumBytes: 64 * 1024,
+            maximumRows: 1_000,
+            maximumEntries: 1_000,
+            minimumRemoteEntries: 1,
+            minimumRetainedFraction: 0
+        )
     ) -> GeoRelayHarness {
         let userDefaultsSuite = "GeoRelayDirectoryTests.\(UUID().uuidString)"
         let userDefaults = UserDefaults(suiteName: userDefaultsSuite)!
@@ -347,7 +537,8 @@ final class GeoRelayDirectoryTests: XCTestCase {
                 await retryRecorder.record(delay)
             },
             activeNotificationName: activeNotificationName,
-            autoStart: autoStart
+            autoStart: autoStart,
+            validationPolicy: validationPolicy
         )
 
         return GeoRelayHarness(
diff --git a/scripts/tests/test_fetch_georelays_workflow.py b/scripts/tests/test_fetch_georelays_workflow.py
new file mode 100644
index 00000000..57c5d81d
--- /dev/null
+++ b/scripts/tests/test_fetch_georelays_workflow.py
@@ -0,0 +1,61 @@
+import re
+from pathlib import Path
+import unittest
+
+
+REPOSITORY_ROOT = Path(__file__).resolve().parents[2]
+WORKFLOW_PATH = REPOSITORY_ROOT / ".github/workflows/fetch_georelays.yml"
+
+
+class FetchGeoRelaysWorkflowTests(unittest.TestCase):
+    @classmethod
+    def setUpClass(cls) -> None:
+        cls.workflow = WORKFLOW_PATH.read_text(encoding="utf-8")
+
+    def test_write_capable_checkout_action_is_immutable(self) -> None:
+        checkout = re.search(r"uses: actions/checkout@([0-9a-f]+)", self.workflow)
+        self.assertIsNotNone(checkout)
+        self.assertRegex(checkout.group(1), r"^[0-9a-f]{40}$")
+        self.assertIn("persist-credentials: false", self.workflow)
+
+    def test_pr_failure_has_single_issue_fallback_with_review_metadata(self) -> None:
+        required_fragments = [
+            "issues: write",
+            "TRACKING_ISSUE_TITLE: GeoRelay update awaiting pull request",
+            "gh pr create",
+            "gh issue create",
+            "gh issue edit",
+            "compare/main...${UPDATE_BRANCH}?expand=1",
+            "Upstream commit: $SOURCE_COMMIT",
+            "Data rows: $DATA_ROWS",
+            "Unique normalized relays: $UNIQUE_RELAYS",
+            "SHA-256: $DATA_SHA256",
+            '[[ -n "$issue_url" ]]',
+        ]
+        for fragment in required_fragments:
+            with self.subTest(fragment=fragment):
+                self.assertIn(fragment, self.workflow)
+
+        confirmed = self.workflow.index('[[ -n "$issue_url" ]]')
+        success_summary = self.workflow.index(
+            "Published GeoRelay tracking issue fallback: $issue_url"
+        )
+        self.assertLess(confirmed, success_summary)
+
+    def test_obsolete_review_state_is_cleaned_without_pushing_main(self) -> None:
+        self.assertIn("gh pr close", self.workflow)
+        self.assertIn("gh issue close", self.workflow)
+        self.assertIn('git push origin --delete "$UPDATE_BRANCH"', self.workflow)
+        self.assertIn('git switch -C "$UPDATE_BRANCH"', self.workflow)
+        self.assertNotIn("git push origin main", self.workflow)
+        self.assertNotIn("git push --force origin main", self.workflow)
+
+    def test_workflow_runs_all_validator_tests(self) -> None:
+        self.assertIn(
+            'python3 -m unittest discover -s scripts/tests -p "test_*.py" -v',
+            self.workflow,
+        )
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/scripts/tests/test_validate_georelays.py b/scripts/tests/test_validate_georelays.py
new file mode 100644
index 00000000..faf63834
--- /dev/null
+++ b/scripts/tests/test_validate_georelays.py
@@ -0,0 +1,186 @@
+import tempfile
+from pathlib import Path
+import sys
+import unittest
+
+sys.path.insert(0, str(Path(__file__).resolve().parents[1]))
+import validate_georelays as validator
+
+
+def csv_bytes(rows: list[str]) -> bytes:
+    return ("Relay URL,Latitude,Longitude\n" + "\n".join(rows) + "\n").encode()
+
+
+class ValidateGeoRelaysTests(unittest.TestCase):
+    def test_validates_and_deduplicates_secure_relay_addresses(self) -> None:
+        data = csv_bytes(
+            [
+                "relay.example.com,10,20",
+                "wss://relay.example.com:443/,10,20",
+                "https://second.example.org,11,21",
+            ]
+        )
+
+        summary = validator.validate_bytes(data, minimum_unique_relays=2)
+
+        self.assertEqual(summary.data_rows, 3)
+        self.assertEqual(summary.unique_relays, 2)
+
+    def test_rejects_insecure_or_non_host_relay_urls(self) -> None:
+        bad_addresses = [
+            "http://relay.example.com",
+            "ws://relay.example.com",
+            "wss://user@relay.example.com",
+            "wss://relay.example.com/path",
+            "wss://relay.example.com?",
+            "wss://relay.example.com#",
+            "relay.example.com:0",
+            "relay.example.com:99999",
+            "localhost",
+            "127.0.0.1",
+            "relay_example.com",
+            "relay\u202e.example.com",
+        ]
+
+        for address in bad_addresses:
+            with self.subTest(address=address):
+                with self.assertRaises(validator.ValidationError):
+                    validator.validate_bytes(
+                        csv_bytes([f"{address},10,20"]),
+                        minimum_unique_relays=1,
+                    )
+
+    def test_rejects_malformed_rows_and_unsafe_coordinates(self) -> None:
+        bad_rows = [
+            "relay.example.com,10",
+            "relay.example.com,NaN,20",
+            "relay.example.com,1_0,20",
+            "relay.example.com,\u0661\u0660,20",
+            "relay.example.com,\uff11\uff10,20",
+            "relay.example.com,91,20",
+            "relay.example.com,10,-181",
+            "relay.example.com,10,20,extra",
+            '"relay.example.com",10,20',
+        ]
+
+        for row in bad_rows:
+            with self.subTest(row=row):
+                with self.assertRaises(validator.ValidationError):
+                    validator.validate_bytes(csv_bytes([row]), minimum_unique_relays=1)
+
+    def test_accepts_ascii_coordinate_forms_supported_by_swift_double(self) -> None:
+        summary = validator.validate_bytes(
+            csv_bytes(
+                [
+                    "one.example.com,+1,-.5",
+                    "two.example.com,1.e1,2E+1",
+                    "three.example.com,01,20.",
+                ]
+            ),
+            minimum_unique_relays=3,
+        )
+
+        self.assertEqual(summary.unique_relays, 3)
+
+    def test_rejects_conflicts_limits_and_large_baseline_deltas(self) -> None:
+        with self.assertRaises(validator.ValidationError):
+            validator.validate_bytes(
+                csv_bytes(["relay.example.com,10,20", "relay.example.com,11,21"]),
+                minimum_unique_relays=1,
+            )
+        with self.assertRaises(validator.ValidationError):
+            validator.validate_bytes(b"x" * 20, maximum_bytes=10, minimum_unique_relays=1)
+        with self.assertRaises(validator.ValidationError):
+            validator.validate_bytes(
+                csv_bytes(["one.example.com,1,1", "two.example.com,2,2"]),
+                minimum_unique_relays=3,
+            )
+
+        baseline = csv_bytes(
+            [f"relay-{index}.example.com,{index % 80},{index % 170}" for index in range(120)]
+        )
+        shrunken = csv_bytes(
+            [f"relay-{index}.example.com,{index % 80},{index % 170}" for index in range(59)]
+        )
+        with self.assertRaises(validator.ValidationError):
+            validator.validate_update(shrunken, baseline)
+
+        smaller_baseline = csv_bytes(
+            [f"relay-{index}.example.com,{index % 80},{index % 170}" for index in range(60)]
+        )
+        expanded = csv_bytes(
+            [f"relay-{index}.example.com,{index % 80},{index % 170}" for index in range(121)]
+        )
+        with self.assertRaises(validator.ValidationError):
+            validator.validate_update(expanded, smaller_baseline)
+
+    def test_update_requires_exact_normalized_baseline_entry_overlap(self) -> None:
+        baseline_rows = [
+            f"relay-{index}.example.com,{index % 80},{index % 170}"
+            for index in range(60)
+        ]
+        baseline = csv_bytes(baseline_rows)
+        disjoint = csv_bytes(
+            [
+                f"attacker-{index}.example.com,{index % 80},{index % 170}"
+                for index in range(60)
+            ]
+        )
+        rewritten_coordinates = csv_bytes(
+            [
+                f"relay-{index}.example.com,{(index % 80) + 0.5},{index % 170}"
+                for index in range(60)
+            ]
+        )
+
+        for candidate in (disjoint, rewritten_coordinates):
+            with self.subTest(candidate=candidate[:80]):
+                with self.assertRaisesRegex(
+                    validator.ValidationError,
+                    "exact relay-coordinate entries",
+                ):
+                    validator.validate_update(candidate, baseline)
+
+        half_retained = csv_bytes(
+            [
+                f"wss://relay-{index}.example.com:443/,{index % 80},{index % 170}"
+                for index in range(30)
+            ]
+            + [
+                f"replacement-{index}.example.com,{index % 80},{index % 170}"
+                for index in range(30)
+            ]
+        )
+        summary = validator.validate_update(half_retained, baseline)
+        self.assertEqual(summary.unique_relays, 60)
+
+    def test_cli_copies_only_validated_data_and_emits_review_metadata(self) -> None:
+        rows = [f"relay-{index}.example.com,{index % 80},{index % 170}" for index in range(60)]
+        data = csv_bytes(rows)
+        with tempfile.TemporaryDirectory() as directory:
+            root = Path(directory)
+            candidate = root / "candidate.csv"
+            baseline = root / "baseline.csv"
+            output = root / "output.csv"
+            github_output = root / "github-output.txt"
+            candidate.write_bytes(data)
+            baseline.write_bytes(data)
+
+            result = validator.main(
+                [
+                    "--input", str(candidate),
+                    "--baseline", str(baseline),
+                    "--output", str(output),
+                    "--github-output", str(github_output),
+                ]
+            )
+
+            self.assertEqual(result, 0)
+            self.assertEqual(output.read_bytes(), data)
+            metadata = github_output.read_text()
+            self.assertIn("unique_relays=60", metadata)
+            self.assertIn("sha256=", metadata)
+
+
+if __name__ == "__main__":
+    unittest.main()
diff --git a/scripts/validate_georelays.py b/scripts/validate_georelays.py
new file mode 100644
index 00000000..513a4dc0
--- /dev/null
+++ b/scripts/validate_georelays.py
@@ -0,0 +1,271 @@
+#!/usr/bin/env python3
+"""Strict validator for the reviewed georelay CSV update workflow."""
+
+from __future__ import annotations
+
+import argparse
+import csv
+import hashlib
+import io
+import math
+import re
+from dataclasses import dataclass
+from pathlib import Path
+import sys
+import unicodedata
+from urllib.parse import urlsplit
+
+
+MAX_BYTES = 512 * 1024
+MAX_ROWS = 5_000
+MAX_UNIQUE_RELAYS = 5_000
+MIN_UNIQUE_RELAYS = 50
+MIN_BASELINE_FRACTION = 0.5
+MAX_BASELINE_MULTIPLIER = 2.0
+EXPECTED_HEADER = ("relay url", "latitude", "longitude")
+ASCII_DECIMAL_PATTERN = re.compile(
+    r"[+-]?(?:[0-9]+(?:\.[0-9]*)?|\.[0-9]+)(?:[eE][+-]?[0-9]+)?\Z"
+)
+
+
+class ValidationError(ValueError):
+    pass
+
+
+@dataclass(frozen=True)
+class ValidationSummary:
+    data_rows: int
+    unique_relays: int
+    sha256: str
+
+
+@dataclass(frozen=True)
+class _ValidatedDataset:
+    summary: ValidationSummary
+    entries: frozenset[tuple[str, float, float]]
+
+
+def _has_disallowed_control(value: str) -> bool:
+    return any(
+        unicodedata.category(character) in {"Cc", "Cf"}
+        and character not in {"\r", "\n", "\t"}
+        for character in value
+    )
+
+
+def normalize_relay_address(raw_value: str) -> str:
+    value = raw_value.strip()
+    if not value or _has_disallowed_control(value):
+        raise ValidationError("relay address is empty or contains control characters")
+    # urlsplit cannot distinguish an absent query/fragment from an explicitly
+    # empty one. Reject the delimiters themselves so this validator matches
+    # URLComponents in the client and reviewed data cannot fail closed there.
+    if "?" in value or "#" in value:
+        raise ValidationError(f"relay query or fragment is not allowed: {value}")
+
+    candidate = value if "://" in value else f"wss://{value}"
+    try:
+        parsed = urlsplit(candidate)
+        port = parsed.port
+    except ValueError as error:
+        raise ValidationError(f"invalid relay URL: {value}") from error
+
+    if parsed.scheme.lower() not in {"wss", "https"}:
+        raise ValidationError(f"relay must use wss/https or a bare hostname: {value}")
+    if parsed.username is not None or parsed.password is not None:
+        raise ValidationError(f"relay credentials are not allowed: {value}")
+    if parsed.path not in {"", "/"} or parsed.query or parsed.fragment:
+        raise ValidationError(f"relay path, query, or fragment is not allowed: {value}")
+
+    host = (parsed.hostname or "").lower()
+    if not host or len(host) > 253 or not host.isascii():
+        raise ValidationError(f"relay hostname is missing or non-ASCII: {value}")
+    if host.endswith(".") or host == "localhost" or host.endswith((".localhost", ".local", ".internal")):
+        raise ValidationError(f"local or absolute relay hostname is not allowed: {value}")
+
+    labels = host.split(".")
+    if len(labels) < 2 or all(label.isdigit() for label in labels):
+        raise ValidationError(f"relay must use a public DNS hostname: {value}")
+    for label in labels:
+        if not 1 <= len(label) <= 63:
+            raise ValidationError(f"invalid DNS label length: {value}")
+        if label[0] == "-" or label[-1] == "-":
+            raise ValidationError(f"DNS labels cannot start or end with '-': {value}")
+        if any(character not in "abcdefghijklmnopqrstuvwxyz0123456789-" for character in label):
+            raise ValidationError(f"invalid DNS hostname character: {value}")
+
+    if port is not None and not 1 <= port <= 65_535:
+        raise ValidationError(f"invalid relay port: {value}")
+    if port in {None, 443}:
+        return host
+    return f"{host}:{port}"
+
+
+def _validated_dataset(
+    data: bytes,
+    *,
+    minimum_unique_relays: int = MIN_UNIQUE_RELAYS,
+    maximum_bytes: int = MAX_BYTES,
+    maximum_rows: int = MAX_ROWS,
+    maximum_unique_relays: int = MAX_UNIQUE_RELAYS,
+) -> _ValidatedDataset:
+    if not data or len(data) > maximum_bytes:
+        raise ValidationError(f"CSV must contain 1..{maximum_bytes} bytes")
+
+    try:
+        text = data.decode("utf-8")
+    except UnicodeDecodeError as error:
+        raise ValidationError("CSV is not valid UTF-8") from error
+    if text.startswith("\ufeff"):
+        raise ValidationError("UTF-8 BOM is not allowed")
+    if _has_disallowed_control(text):
+        raise ValidationError("CSV contains disallowed control characters")
+    # Runtime intentionally implements the fixed three-field schema without
+    # general CSV quoting. Reject quoted variants here so reviewed workflow
+    # output and client-side validation cannot disagree.
+    if '"' in text:
+        raise ValidationError("quoted CSV fields are not allowed")
+
+    reader = csv.reader(io.StringIO(text, newline=""), strict=True)
+    try:
+        header = next(reader)
+    except (StopIteration, csv.Error) as error:
+        raise ValidationError("CSV header is missing") from error
+    normalized_header = tuple(field.strip().lower() for field in header)
+    if normalized_header != EXPECTED_HEADER:
+        raise ValidationError(f"unexpected CSV header: {header!r}")
+
+    data_rows = 0
+    relays: dict[str, tuple[float, float]] = {}
+    try:
+        for row in reader:
+            if not row or all(not field.strip() for field in row):
+                continue
+            data_rows += 1
+            if data_rows > maximum_rows:
+                raise ValidationError(f"CSV exceeds {maximum_rows} data rows")
+            if len(row) != 3:
+                raise ValidationError(f"row {reader.line_num} must contain exactly 3 columns")
+
+            address = normalize_relay_address(row[0])
+            latitude_text = row[1].strip()
+            longitude_text = row[2].strip()
+            if not ASCII_DECIMAL_PATTERN.fullmatch(latitude_text) or not ASCII_DECIMAL_PATTERN.fullmatch(longitude_text):
+                raise ValidationError(
+                    f"row {reader.line_num} coordinates must be ASCII decimal numbers"
+                )
+            latitude = float(latitude_text)
+            longitude = float(longitude_text)
+            if not math.isfinite(latitude) or not -90 <= latitude <= 90:
+                raise ValidationError(f"row {reader.line_num} latitude is out of range")
+            if not math.isfinite(longitude) or not -180 <= longitude <= 180:
+                raise ValidationError(f"row {reader.line_num} longitude is out of range")
+
+            coordinates = (latitude, longitude)
+            previous = relays.get(address)
+            if previous is not None and previous != coordinates:
+                raise ValidationError(f"relay {address} has conflicting coordinates")
+            relays[address] = coordinates
+            if len(relays) > maximum_unique_relays:
+                raise ValidationError(f"CSV exceeds {maximum_unique_relays} unique relays")
+    except csv.Error as error:
+        raise ValidationError(f"malformed CSV near line {reader.line_num}") from error
+
+    if len(relays) < minimum_unique_relays:
+        raise ValidationError(
+            f"CSV has {len(relays)} unique relays; minimum is {minimum_unique_relays}"
+        )
+
+    return _ValidatedDataset(
+        summary=ValidationSummary(
+            data_rows=data_rows,
+            unique_relays=len(relays),
+            sha256=hashlib.sha256(data).hexdigest(),
+        ),
+        entries=frozenset(
+            (address, coordinates[0], coordinates[1])
+            for address, coordinates in relays.items()
+        ),
+    )
+
+
+def validate_bytes(
+    data: bytes,
+    *,
+    minimum_unique_relays: int = MIN_UNIQUE_RELAYS,
+    maximum_bytes: int = MAX_BYTES,
+    maximum_rows: int = MAX_ROWS,
+    maximum_unique_relays: int = MAX_UNIQUE_RELAYS,
+) -> ValidationSummary:
+    return _validated_dataset(
+        data,
+        minimum_unique_relays=minimum_unique_relays,
+        maximum_bytes=maximum_bytes,
+        maximum_rows=maximum_rows,
+        maximum_unique_relays=maximum_unique_relays,
+    ).summary
+
+
+def validate_update(candidate: bytes, baseline: bytes) -> ValidationSummary:
+    baseline_dataset = _validated_dataset(baseline, minimum_unique_relays=1)
+    candidate_dataset = _validated_dataset(candidate)
+    baseline_summary = baseline_dataset.summary
+    candidate_summary = candidate_dataset.summary
+
+    minimum_from_baseline = math.ceil(
+        baseline_summary.unique_relays * MIN_BASELINE_FRACTION
+    )
+    maximum_from_baseline = math.floor(
+        baseline_summary.unique_relays * MAX_BASELINE_MULTIPLIER
+    )
+    if candidate_summary.unique_relays < minimum_from_baseline:
+        raise ValidationError(
+            "candidate loses more than half of the baseline's unique relays "
+            f"({candidate_summary.unique_relays} < {minimum_from_baseline})"
+        )
+    if candidate_summary.unique_relays > maximum_from_baseline:
+        raise ValidationError(
+            "candidate more than doubles the baseline's unique relays "
+            f"({candidate_summary.unique_relays} > {maximum_from_baseline})"
+        )
+
+    retained_entries = len(baseline_dataset.entries & candidate_dataset.entries)
+    if retained_entries < minimum_from_baseline:
+        raise ValidationError(
+            "candidate retains fewer than half of the baseline's exact relay-coordinate entries "
+            f"({retained_entries} < {minimum_from_baseline})"
+        )
+    return candidate_summary
+
+
+def main(argv: list[str] | None = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument("--input", required=True, type=Path)
+    parser.add_argument("--baseline", required=True, type=Path)
+    parser.add_argument("--output", required=True, type=Path)
+    parser.add_argument("--github-output", type=Path)
+    args = parser.parse_args(argv)
+
+    try:
+        candidate = args.input.read_bytes()
+        baseline = args.baseline.read_bytes()
+        summary = validate_update(candidate, baseline)
+        args.output.write_bytes(candidate)
+        if args.github_output is not None:
+            with args.github_output.open("a", encoding="utf-8") as output:
+                output.write(f"data_rows={summary.data_rows}\n")
+                output.write(f"unique_relays={summary.unique_relays}\n")
+                output.write(f"sha256={summary.sha256}\n")
+    except (OSError, ValidationError) as error:
+        print(f"georelay validation failed: {error}", file=sys.stderr)
+        return 1
+
+    print(
+        f"validated {summary.unique_relays} unique relays across "
+        f"{summary.data_rows} rows (sha256 {summary.sha256})"
+    )
+    return 0
+
+
+if __name__ == "__main__":
+    raise SystemExit(main())