diff --git a/.gencode_hash.txt b/.gencode_hash.txt
index 7421e14711..2d6b53e5d9 100644
--- a/.gencode_hash.txt
+++ b/.gencode_hash.txt
@@ -23,7 +23,7 @@ eeafb6e89a6c43816cfcb26244a95615a4ee75966e1c015cae5a13b6cfcb0078  gencode/docs/r
 741b880216be3743f6747800a042f2dbd89f3b0344c6b0a965f4bc010f03a930  gencode/docs/schema_doc.css
 878ea88206c974f40643c3cc430875f9c4e8c5e3fd6bcd6358bd3eb6d48699a9  gencode/docs/schema_doc.min.js
 7ed934930aee763e0beebc349725ba3909115e8d346bb762f28bcbe745bb163a  gencode/docs/schema_extras.js
-0f16008af7116a182322736046b05c2718ac8b1f2cd755a60d28c9cfaeb6a8a9  gencode/docs/site_metadata.html
+0da2fca987af8f37f82e93b8b3fd8b954e4fe185bfe1e1f55adee5fe7f8024a9  gencode/docs/site_metadata.html
 1bbcbf2d1ec1bf4554846b1daf09fa09c08dd967fa1f91ebec93027662529a31  gencode/docs/state.html
 b2398e7f9e352c47867e38f97168f3eb88e23280c7dd576f13e038c8c3f714c9  gencode/docs/state_mapping.html
 b8ff4cdb4b79449166b1c6e09ac0e58273ae62865b47bf943fdd365739c62a4c  gencode/docs/state_validation.html
@@ -121,7 +121,7 @@ fadf083200e73d46cfdec2f710d40e3d2bc4dbf05196e4d0900186e72b62d95e  gencode/java/u
 ad70168de2e1801e26f2c1a8c33a6169e236682de59fd3f6038a77ac264aca14  gencode/java/udmi/schema/SequenceValidationState.java
 72e3a07ce890c73fccd3d0cf757d073746b60b722c94edd5425dc066951a048f  gencode/java/udmi/schema/SetupUdmiConfig.java
 e5ce202bcf889287faa7d2d262d2f53f2241a10c659a83687de478803bdab127  gencode/java/udmi/schema/SetupUdmiState.java
-8fcb31df1070010da6d3ae61d741a77d2ce8b3757226bbe35ff9218a0581b1ec  gencode/java/udmi/schema/SiteLinks.java
+2f802c738dd4c19211af8b6dec71b7659c51177c2774cfd34fc07e617bbe5b3e  gencode/java/udmi/schema/SiteLinks.java
 a3dc7f14d4270ea370db2015785ad12d4bd61825213ab7ac4ee03dda21dde4f2  gencode/java/udmi/schema/SiteLocation.java
 4e51c21fcdb25e729258c428f55be4ac4909f526fdc3384734b6f5a87f1ef5cf  gencode/java/udmi/schema/SiteMetadata.java
 dc2fd582fffefbdeaf3bf7724ca34e94475c3cc820891ea4cc829847eb9ba79d  gencode/java/udmi/schema/State.java
@@ -213,7 +213,7 @@ d59671d0bc2ac184e820b70c277cdf91af0a936a60cdffd9b3af0ea314f08adc  gencode/python
 6c5f3dd1c5ca9d821e3c48298af118fc7eafd97af9265dfd34b2ed8642efca77  gencode/python/udmi/schema/persistent_device.py
 a58f8c98e837a5b56126ca0f410e02f1e9cfcd80a8cb429e0ef522defab1f690  gencode/python/udmi/schema/properties.py
 a84e00db471b2038a473c2c83d72ea59b02c3d2bab56d38bc22435309f01e763  gencode/python/udmi/schema/query_cloud.py
-d42bae60bd667cda893d3670896ed087f20df629635949cf418ee9be2e975347  gencode/python/udmi/schema/site_metadata.py
+77bcd0622552871b9b1543f26c4fe961955813f64a8702f4efe894fba91ce116  gencode/python/udmi/schema/site_metadata.py
 e604cf0280fe772de5f4e5ecf10dc6c564b6177eeff9cd9fb8b385af8fe10a95  gencode/python/udmi/schema/state.py
 4a908cee3fb8afb559bcbfa594e57dbc515a35e4468e02600751b2fcce05a238  gencode/python/udmi/schema/state_blobset.py
 182e07b534403dcc121d980672e41b0fa2ee55c4da1f5c56f0dad5d599450c80  gencode/python/udmi/schema/state_blobset_blob.py
diff --git a/bin/toolrun b/bin/toolrun
index 3c257664f4..2af47c18a7 100755
--- a/bin/toolrun
+++ b/bin/toolrun
@@ -28,4 +28,22 @@ fi
 
 cmd="java -cp $UDMI_JAR $JDWP $JAVA_CLASS $util_name $@"
 echo $cmd
-$cmd 2>&1 | tee $OUT_DIR/$util_name.log
+
+site_path=$(realpath "$1")
+if [[ ! -d $site_path ]]; then
+  site_path=$(dirname "$site_path")
+fi
+
+if [[ -e "$site_path/site_metadata.json" ]]; then
+  spreadsheet=$(jq -r '.sheet' "$site_path/site_metadata.json")
+else
+  spreadsheet=
+fi
+
+if [[ $spreadsheet != "null" && -n "$spreadsheet" ]]; then
+  spreadsheet_id=$(echo "$spreadsheet" | grep -oP '(?<=/d/)[^/]+')
+  echo "Streaming logs to gsheet id $spreadsheet_id"
+  $cmd 2>&1 | tee $OUT_DIR/$util_name.log | stream_to_gsheets "$util_name" "$spreadsheet_id"
+else
+  $cmd 2>&1 | tee $OUT_DIR/$util_name.log
+fi
diff --git a/etc/shell_common.sh b/etc/shell_common.sh
index e8074e9a36..dcd22131d5 100644
--- a/etc/shell_common.sh
+++ b/etc/shell_common.sh
@@ -104,3 +104,11 @@ export UDMI_VERSION=$udmi_version
 export UDMI_COMMIT=$udmi_commit
 export UDMI_TIMEVER=$udmi_timever
 export UDMI_REV=$udmi_rev
+
+function stream_to_gsheets {
+    local tool_name=$1
+    local sheet_id=$2
+    timestamp=$(date +%Y%m%d_%H%M%S)
+    java -cp "$UDMI_JAR" "com.google.udmi.util.SheetsOutputStream" "$tool_name" \
+        "$sheet_id" "$tool_name.$timestamp.log"
+}
\ No newline at end of file
diff --git a/gencode/docs/site_metadata.html b/gencode/docs/site_metadata.html
index b209dd3b51..b08db5ebbe 100644
--- a/gencode/docs/site_metadata.html
+++ b/gencode/docs/site_metadata.html
@@ -684,6 +684,51 @@ <h2 class="mb-0">
 </pre></div>
 </div><div id="links_repo_ex2" class="jumbotron examples"><div class="highlight"><pre><span></span><span class="s2">&quot;git@github.com:faucetsdn/udmi_site_model.git&quot;</span>
 </pre></div>
+</div>
+            </div>
+        </div>
+    </div>
+</div>
+<div class="accordion" id="accordionlinks_sheet">
+    <div class="card">
+        <div class="card-header" id="headinglinks_sheet">
+            <h2 class="mb-0">
+                <button class="btn btn-link property-name-button" type="button" data-toggle="collapse" data-target="#links_sheet"
+                        aria-expanded="" aria-controls="links_sheet" onclick="setAnchor('#links_sheet')"><span class="property-name">sheet</span></button>
+            </h2>
+        </div>
+
+        <div id="links_sheet"
+             class="collapse property-definition-div" aria-labelledby="headinglinks_sheet"
+             data-parent="#accordionlinks_sheet">
+            <div class="card-body pl-5">
+
+    <div class="breadcrumbs">root
+        <svg width="1em" height="1em" viewBox="0 0 16 16" class="bi bi-arrow-right-short" fill="currentColor" xmlns="http://www.w3.org/2000/svg">
+            <path
+                fill-rule="evenodd"
+                d="M4 8a.5.5 0 0 1 .5-.5h5.793L8.146 5.354a.5.5 0 1 1 .708-.708l3 3a.5.5 0 0 1 0 .708l-3 3a.5.5 0 0 1-.708-.708L10.293 8.5H4.5A.5.5 0 0 1 4 8z"
+            />
+        </svg>
+    <a href="#links" onclick="anchorLink('links')">links</a>
+        <svg width="1em" height="1em" viewBox="0 0 16 16" class="bi bi-arrow-right-short" fill="currentColor" xmlns="http://www.w3.org/2000/svg">
+            <path
+                fill-rule="evenodd"
+                d="M4 8a.5.5 0 0 1 .5-.5h5.793L8.146 5.354a.5.5 0 1 1 .708-.708l3 3a.5.5 0 0 1 0 .708l-3 3a.5.5 0 0 1-.708-.708L10.293 8.5H4.5A.5.5 0 0 1 4 8z"
+            />
+        </svg>
+    <a href="#links_sheet" onclick="anchorLink('links_sheet')">sheet</a></div><span class="badge badge-dark value-type">Type: string</span><br/>
+<span class="description"><p>Link to a spreadsheet to observe real-time output from any tool</p>
+</span>
+            
+
+            
+            
+
+            <br/>
+<div class="badge badge-secondary">Example:</div>
+<br/><div id="links_sheet_ex1" class="jumbotron examples"><div class="highlight"><pre><span></span><span class="s2">&quot;https://docs.google.com/spreadsheets/d/&lt;spreadsheet_id&gt;&quot;</span>
+</pre></div>
 </div>
             </div>
         </div>
diff --git a/gencode/java/udmi/schema/SiteLinks.java b/gencode/java/udmi/schema/SiteLinks.java
index 899cdf62e9..41fc94ca6c 100644
--- a/gencode/java/udmi/schema/SiteLinks.java
+++ b/gencode/java/udmi/schema/SiteLinks.java
@@ -19,7 +19,8 @@
     "docs",
     "folder",
     "image",
-    "repo"
+    "repo",
+    "sheet"
 })
 public class SiteLinks {
 
@@ -58,6 +59,13 @@ public class SiteLinks {
     @JsonProperty("repo")
     @JsonPropertyDescription("Source repository where the UDMI site model is stored")
     public String repo;
+    /**
+     * Link to a spreadsheet to observe real-time output from any tool
+     * 
+     */
+    @JsonProperty("sheet")
+    @JsonPropertyDescription("Link to a spreadsheet to observe real-time output from any tool")
+    public String sheet;
 
     @Override
     public int hashCode() {
@@ -65,8 +73,9 @@ public int hashCode() {
         result = ((result* 31)+((this.image == null)? 0 :this.image.hashCode()));
         result = ((result* 31)+((this.folder == null)? 0 :this.folder.hashCode()));
         result = ((result* 31)+((this.docs == null)? 0 :this.docs.hashCode()));
-        result = ((result* 31)+((this.dashboard == null)? 0 :this.dashboard.hashCode()));
         result = ((result* 31)+((this.repo == null)? 0 :this.repo.hashCode()));
+        result = ((result* 31)+((this.sheet == null)? 0 :this.sheet.hashCode()));
+        result = ((result* 31)+((this.dashboard == null)? 0 :this.dashboard.hashCode()));
         return result;
     }
 
@@ -79,7 +88,7 @@ public boolean equals(Object other) {
             return false;
         }
         SiteLinks rhs = ((SiteLinks) other);
-        return ((((((this.image == rhs.image)||((this.image!= null)&&this.image.equals(rhs.image)))&&((this.folder == rhs.folder)||((this.folder!= null)&&this.folder.equals(rhs.folder))))&&((this.docs == rhs.docs)||((this.docs!= null)&&this.docs.equals(rhs.docs))))&&((this.dashboard == rhs.dashboard)||((this.dashboard!= null)&&this.dashboard.equals(rhs.dashboard))))&&((this.repo == rhs.repo)||((this.repo!= null)&&this.repo.equals(rhs.repo))));
+        return (((((((this.image == rhs.image)||((this.image!= null)&&this.image.equals(rhs.image)))&&((this.folder == rhs.folder)||((this.folder!= null)&&this.folder.equals(rhs.folder))))&&((this.docs == rhs.docs)||((this.docs!= null)&&this.docs.equals(rhs.docs))))&&((this.repo == rhs.repo)||((this.repo!= null)&&this.repo.equals(rhs.repo))))&&((this.sheet == rhs.sheet)||((this.sheet!= null)&&this.sheet.equals(rhs.sheet))))&&((this.dashboard == rhs.dashboard)||((this.dashboard!= null)&&this.dashboard.equals(rhs.dashboard))));
     }
 
 }
diff --git a/gencode/python/udmi/schema/site_metadata.py b/gencode/python/udmi/schema/site_metadata.py
index ed3d248ff7..73d1c9d2db 100644
--- a/gencode/python/udmi/schema/site_metadata.py
+++ b/gencode/python/udmi/schema/site_metadata.py
@@ -55,6 +55,7 @@ def __init__(self):
     self.folder = None
     self.image = None
     self.repo = None
+    self.sheet = None
 
   @staticmethod
   def from_dict(source):
@@ -66,6 +67,7 @@ def from_dict(source):
     result.folder = source.get('folder')
     result.image = source.get('image')
     result.repo = source.get('repo')
+    result.sheet = source.get('sheet')
     return result
 
   @staticmethod
@@ -96,6 +98,8 @@ def to_dict(self):
       result['image'] = self.image # 5
     if self.repo:
       result['repo'] = self.repo # 5
+    if self.sheet:
+      result['sheet'] = self.sheet # 5
     return result
 from .dimension import Dimension
 from .dimension import Dimension
diff --git a/schema/site_metadata.json b/schema/site_metadata.json
index bbab8c27e3..9ec087a69f 100644
--- a/schema/site_metadata.json
+++ b/schema/site_metadata.json
@@ -92,6 +92,11 @@
           "description": "Source repository where the UDMI site model is stored",
           "type": "string",
           "examples": ["https://github.com/faucetsdn/udmi_site_model", "git@github.com:faucetsdn/udmi_site_model.git"]
+        },
+        "sheet": {
+          "description": "Link to a spreadsheet to observe real-time output from any tool",
+          "type": "string",
+          "examples": ["https://docs.google.com/spreadsheets/d/<spreadsheet_id>"]
         }
       }
     },
diff --git a/udmis/build.gradle b/udmis/build.gradle
index ce88919556..d11a1aaadd 100644
--- a/udmis/build.gradle
+++ b/udmis/build.gradle
@@ -111,4 +111,7 @@ dependencies {
     testImplementation 'org.junit.jupiter:junit-jupiter-api:5.9.2'
     testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.2'
     testImplementation 'org.mockito:mockito-core:5.3.1'
+
+    implementation 'com.google.oauth-client:google-oauth-client-jetty:1.20.0'
+    implementation 'com.google.apis:google-api-services-sheets:v4-rev484-1.20.0'
 }
diff --git a/validator/build.gradle b/validator/build.gradle
index d89cb1c159..c242f2c388 100644
--- a/validator/build.gradle
+++ b/validator/build.gradle
@@ -104,4 +104,12 @@ dependencies {
     implementation 'com.google.cloud:google-cloud-firestore:0.84.0-beta'
     implementation group: 'junit', name: 'junit', version: '4.13.2'
     implementation 'org.jetbrains:annotations:20.1.0'
+
+    implementation 'com.google.oauth-client:google-oauth-client-jetty:1.20.0'
+    implementation 'com.google.apis:google-api-services-sheets:v4-rev484-1.20.0'
+
+    testImplementation 'org.junit.jupiter:junit-jupiter-api:5.9.2'
+    testRuntimeOnly 'org.junit.jupiter:junit-jupiter-engine:5.9.2'
+    testImplementation 'org.mockito:mockito-core:5.3.1'
+    testImplementation 'org.mockito:mockito-junit-jupiter:5.6.0'
 }
diff --git a/validator/src/main/java/com/google/udmi/util/DualOutputStream.java b/validator/src/main/java/com/google/udmi/util/DualOutputStream.java
new file mode 100644
index 0000000000..8b157c6954
--- /dev/null
+++ b/validator/src/main/java/com/google/udmi/util/DualOutputStream.java
@@ -0,0 +1,50 @@
+package com.google.udmi.util;
+
+import java.io.IOException;
+import java.io.OutputStream;
+import org.jetbrains.annotations.NotNull;
+
+/**
+ * An OutputStream that duplicates output to two output streams, useful for scenarios such as
+ * logging to two destinations simultaneously.
+ */
+public class DualOutputStream extends OutputStream {
+
+  private final OutputStream primary;
+  private final OutputStream secondary;
+
+  public DualOutputStream(OutputStream primary, OutputStream secondary) {
+    this.primary = primary;
+    this.secondary = secondary;
+  }
+
+  @Override
+  public void write(int i) throws IOException {
+    primary.write(i);
+    secondary.write(i);
+  }
+
+  @Override
+  public void write(byte @NotNull [] b) throws IOException {
+    primary.write(b);
+    secondary.write(b);
+  }
+
+  @Override
+  public void write(byte @NotNull [] b, int off, int len) throws IOException {
+    primary.write(b, off, len);
+    secondary.write(b, off, len);
+  }
+
+  @Override
+  public void flush() throws IOException {
+    primary.flush();
+    secondary.flush();
+  }
+
+  @Override
+  public void close() throws IOException {
+    primary.close();
+    secondary.close();
+  }
+}
diff --git a/validator/src/main/java/com/google/udmi/util/SheetsOutputStream.java b/validator/src/main/java/com/google/udmi/util/SheetsOutputStream.java
new file mode 100644
index 0000000000..344bf59588
--- /dev/null
+++ b/validator/src/main/java/com/google/udmi/util/SheetsOutputStream.java
@@ -0,0 +1,256 @@
+package com.google.udmi.util;
+
+import com.google.api.client.googleapis.javanet.GoogleNetHttpTransport;
+import com.google.api.client.http.javanet.NetHttpTransport;
+import com.google.api.client.json.JsonFactory;
+import com.google.api.client.json.gson.GsonFactory;
+import com.google.api.services.sheets.v4.Sheets;
+import com.google.api.services.sheets.v4.SheetsScopes;
+import com.google.api.services.sheets.v4.model.AddSheetRequest;
+import com.google.api.services.sheets.v4.model.BatchUpdateSpreadsheetRequest;
+import com.google.api.services.sheets.v4.model.Request;
+import com.google.api.services.sheets.v4.model.SheetProperties;
+import com.google.api.services.sheets.v4.model.Spreadsheet;
+import com.google.api.services.sheets.v4.model.ValueRange;
+import com.google.auth.http.HttpCredentialsAdapter;
+import com.google.auth.oauth2.GoogleCredentials;
+import java.io.BufferedReader;
+import java.io.IOException;
+import java.io.InputStreamReader;
+import java.io.OutputStream;
+import java.io.PrintStream;
+import java.security.GeneralSecurityException;
+import java.time.Instant;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.stream.Collectors;
+import org.jetbrains.annotations.NotNull;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+
+/**
+ * Generic utility to log messages to Google Sheets. This class extends {@link OutputStream} and
+ * redirects output to a specified sheet in a Google Spreadsheet.
+ */
+public class SheetsOutputStream extends OutputStream {
+
+  private static final Logger LOGGER = LoggerFactory.getLogger(SheetsOutputStream.class);
+  private static final JsonFactory JSON_FACTORY = GsonFactory.getDefaultInstance();
+  static final List<String> SCOPES = Collections.singletonList(SheetsScopes.SPREADSHEETS);
+  private static final long DEFAULT_SYNC_TIME = 2000;
+  private static final NetHttpTransport HTTP_TRANSPORT;
+
+  static {
+    try {
+      HTTP_TRANSPORT = GoogleNetHttpTransport.newTrustedTransport();
+    } catch (GeneralSecurityException | IOException e) {
+      throw new ExceptionInInitializerError("Error initializing HTTP Transport: " + e.getMessage());
+    }
+  }
+
+  final long syncTime;
+  private long lastWriteMillis = 0;
+  private final String applicationName;
+  private final String spreadsheetId;
+  private final String outputSheetTitle;
+  private final Sheets sheetsService;
+  final StringBuilder buffer = new StringBuilder();
+  private PrintStream originalSystemOut;
+  private PrintStream originalSystemErr;
+
+  /**
+   * Constructs a new `GSheetsOutputStream` with default sync time.
+   *
+   * @param applicationName The name of the application using the Google Sheets API.
+   * @param spreadsheetId The ID of the Google Spreadsheet.
+   * @param outputSheetTitle The title of the sheet where the output will be written.
+   * @throws IOException If there's an error creating the Google Sheets service or adding the sheet.
+   */
+  public SheetsOutputStream(String applicationName, String spreadsheetId, String outputSheetTitle)
+      throws IOException {
+    this(applicationName, spreadsheetId, outputSheetTitle, DEFAULT_SYNC_TIME);
+  }
+
+  /**
+   * Constructs a new `GSheetsOutputStream`.
+   *
+   * @param applicationName The name of the application using the Google Sheets API.
+   * @param spreadsheetId The ID of the Google Spreadsheet.
+   * @param outputSheetTitle The title of the sheet where the output will be written.
+   * @param syncTime The time in milliseconds to wait before syncing the buffer to the sheet.
+   * @throws IOException If there's an error creating the Google Sheets service or adding the sheet.
+   */
+  public SheetsOutputStream(String applicationName, String spreadsheetId, String outputSheetTitle,
+      long syncTime)
+      throws IOException {
+    this.applicationName = applicationName;
+    this.spreadsheetId = spreadsheetId;
+    this.outputSheetTitle = outputSheetTitle;
+    this.sheetsService = createSheetsService();
+    this.syncTime = syncTime;
+    addOutputSheet();
+  }
+
+  @Override
+  public void write(int i) {
+    buffer.append((char) i);
+    syncIfNeeded();
+  }
+
+  @Override
+  public void write(byte @NotNull [] b, int off, int len) {
+    buffer.append(new String(b, off, len));
+    syncIfNeeded();
+  }
+
+  private void syncIfNeeded() {
+    long currentTimeMillis = Instant.now().toEpochMilli();
+    if (buffer.indexOf("\n") != -1 && currentTimeMillis - lastWriteMillis >= syncTime) {
+      lastWriteMillis = currentTimeMillis;
+      appendToSheet();
+    }
+  }
+
+  void appendToSheet() {
+    String content = buffer.toString();
+    if (content.trim().isEmpty()) {
+      buffer.setLength(0); // Clear buffer even if nothing to write
+      return;
+    }
+    try {
+      List<List<Object>> values = Arrays.stream(content.split("\\n"))
+          .filter(line -> !line.trim().isEmpty()) // Filter out empty lines
+          .map(line -> Collections.singletonList((Object) line))
+          .collect(Collectors.toList());
+
+      if (!values.isEmpty()) {
+        ValueRange appendBody = new ValueRange().setValues(values);
+        sheetsService.spreadsheets().values()
+            .append(spreadsheetId, outputSheetTitle, appendBody)
+            .setValueInputOption("RAW").execute();
+      }
+      buffer.setLength(0);
+    } catch (IOException e) {
+      LOGGER.error("Error appending to sheet", e);
+    }
+  }
+
+  Sheets createSheetsService() throws IOException {
+    GoogleCredentials credential =
+        GoogleCredentials.getApplicationDefault().createScoped(SCOPES);
+    return new Sheets.Builder(HTTP_TRANSPORT, JSON_FACTORY, new HttpCredentialsAdapter(credential))
+        .setApplicationName(this.applicationName)
+        .build();
+  }
+
+
+  private boolean outputSheetExists() throws IOException {
+    Spreadsheet spreadsheet = sheetsService.spreadsheets().get(spreadsheetId).execute();
+    return spreadsheet.getSheets().stream()
+        .anyMatch(sheet -> sheet.getProperties().getTitle().equalsIgnoreCase(outputSheetTitle));
+  }
+
+  private void addOutputSheet() throws IOException {
+    if (!outputSheetExists()) {
+      BatchUpdateSpreadsheetRequest body = new BatchUpdateSpreadsheetRequest()
+          .setRequests(List.of(new Request().setAddSheet(new AddSheetRequest()
+              .setProperties(new SheetProperties().setTitle(outputSheetTitle)))));
+      try {
+        sheetsService.spreadsheets().batchUpdate(spreadsheetId, body).execute();
+      } catch (IOException e) {
+        throw new IOException("Failed to add output sheet: " + outputSheetTitle, e);
+      }
+    }
+  }
+
+  /**
+   * Redirects `System.out` and `System.err` to google sheets.
+   */
+  public void startStream() {
+    if (originalSystemOut == null) {
+      originalSystemOut = System.out;
+      originalSystemErr = System.err;
+      DualOutputStream tee = new DualOutputStream(originalSystemOut, this);
+      PrintStream printStream = new PrintStream(tee);
+      System.setOut(printStream);
+      System.setErr(printStream);
+    }
+  }
+
+  /**
+   * Restores `System.out` and `System.err` to their original streams.
+   */
+  public void stopStream() {
+    if (originalSystemOut != null) {
+      System.setOut(originalSystemOut);
+      System.setErr(originalSystemErr);
+      originalSystemOut = null;
+      originalSystemErr = null;
+
+      // flush out
+      appendToSheet();
+    }
+  }
+
+  /**
+   * Redirects standard input to Google Sheet output.
+   */
+  public void startStreamFromInput() {
+    try (
+        DualOutputStream tee = new DualOutputStream(System.out, this);
+        PrintStream printStream = new PrintStream(tee);
+        BufferedReader reader = new BufferedReader(new InputStreamReader(System.in))
+    ) {
+      String line;
+      while ((line = reader.readLine()) != null) {
+        printStream.println(line);
+      }
+    } catch (IOException e) {
+      throw new RuntimeException("Exception while reading input", e);
+    } finally {
+      // added to ensure last batch is always appended & to prevent loss in case of exceptions
+      appendToSheet();
+    }
+  }
+
+  /**
+   * Main method for the class. Can be used to start the logger from command line.
+   *
+   * @param args Command line arguments. Required: applicationName, spreadsheetId, sheetTitle.
+   *     Optional: syncTime.
+   */
+  public static void main(String[] args) {
+    if (args.length < 3 || args.length > 4) {
+      System.err.println(
+          "Usage: GSheetsOutputStream <applicationName> <spreadsheetId> <sheetTitle> [<syncTime>]");
+      System.exit(1);
+    }
+
+    String applicationName = args[0];
+    String spreadsheetId = args[1];
+    String sheetTitle = args[2];
+    long syncTime = DEFAULT_SYNC_TIME;
+
+    if (args.length == 4) {
+      try {
+        syncTime = Long.parseLong(args[3]);
+        if (syncTime <= 0) {
+          System.err.println("Sync time should be greater than zero");
+          System.exit(1);
+        }
+      } catch (NumberFormatException e) {
+        System.err.println("Invalid sync time format: " + args[3]);
+        System.exit(1);
+      }
+    }
+
+    try (SheetsOutputStream sheetsOutputStream =
+        new SheetsOutputStream(applicationName, spreadsheetId, sheetTitle, syncTime)) {
+      sheetsOutputStream.startStreamFromInput();
+    } catch (Exception e) {
+      e.printStackTrace();
+    }
+  }
+}
\ No newline at end of file
diff --git a/validator/src/test/java/com/google/udmi/util/SheetsOutputStreamTest.java b/validator/src/test/java/com/google/udmi/util/SheetsOutputStreamTest.java
new file mode 100644
index 0000000000..6d45e0a5aa
--- /dev/null
+++ b/validator/src/test/java/com/google/udmi/util/SheetsOutputStreamTest.java
@@ -0,0 +1,238 @@
+package com.google.udmi.util;
+
+import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.junit.jupiter.api.Assertions.assertNotEquals;
+import static org.junit.jupiter.api.Assertions.assertNotNull;
+import static org.junit.jupiter.api.Assertions.assertThrows;
+import static org.mockito.ArgumentMatchers.any;
+import static org.mockito.ArgumentMatchers.eq;
+import static org.mockito.Mockito.anyString;
+import static org.mockito.Mockito.mock;
+import static org.mockito.Mockito.never;
+import static org.mockito.Mockito.times;
+import static org.mockito.Mockito.verify;
+import static org.mockito.Mockito.when;
+
+import com.google.api.services.sheets.v4.Sheets;
+import com.google.api.services.sheets.v4.Sheets.Spreadsheets;
+import com.google.api.services.sheets.v4.Sheets.Spreadsheets.BatchUpdate;
+import com.google.api.services.sheets.v4.Sheets.Spreadsheets.Get;
+import com.google.api.services.sheets.v4.Sheets.Spreadsheets.Values;
+import com.google.api.services.sheets.v4.Sheets.Spreadsheets.Values.Append;
+import com.google.api.services.sheets.v4.model.AppendValuesResponse;
+import com.google.api.services.sheets.v4.model.BatchUpdateSpreadsheetRequest;
+import com.google.api.services.sheets.v4.model.BatchUpdateSpreadsheetResponse;
+import com.google.api.services.sheets.v4.model.Sheet;
+import com.google.api.services.sheets.v4.model.SheetProperties;
+import com.google.api.services.sheets.v4.model.Spreadsheet;
+import com.google.api.services.sheets.v4.model.ValueRange;
+import java.io.IOException;
+import java.io.PrintStream;
+import java.util.ArrayList;
+import java.util.Collections;
+import java.util.List;
+import org.junit.Before;
+import org.junit.Test;
+import org.junit.jupiter.api.extension.ExtendWith;
+import org.mockito.ArgumentCaptor;
+import org.mockito.junit.jupiter.MockitoExtension;
+
+/**
+ * Unit tests for SheetsOutputStream.java
+ */
+@ExtendWith(MockitoExtension.class)
+public class SheetsOutputStreamTest {
+
+  private final Append mockAppend = mock(Append.class);
+  private final AppendValuesResponse mockAppendValuesResponse = mock(AppendValuesResponse.class);
+  private final BatchUpdate mockBatchUpdate = mock(BatchUpdate.class);
+  private final BatchUpdateSpreadsheetResponse mockBatchUpdateResponse = mock(
+      BatchUpdateSpreadsheetResponse.class);
+  private final Get mockSpreadsheetsGet = mock(Get.class);
+  private final Sheet mockSheet = new Sheet();
+  private final Sheets mockSheetsService = mock(Sheets.class);
+  private final Spreadsheet mockSpreadSheet = mock(Spreadsheet.class);
+  private final Spreadsheets mockSpreadsheets = mock(Spreadsheets.class);
+  private final Values mockValues = mock(Values.class);
+
+  private final String applicationName = "TestApp";
+  private final String spreadsheetId = "testSpreadsheetId";
+  private final String outputSheetTitle = "TestSheet";
+  private final long syncTime = 2000;
+  private SheetsOutputStream sheetsOutputStream;
+
+
+  /**
+   * Mock interactions with the gcloud API.
+   */
+  @Before
+  public void setup() throws IOException {
+    mockSheet.setProperties(
+        new SheetProperties().setTitle(outputSheetTitle)
+    );
+
+    when(mockSheetsService.spreadsheets()).thenReturn(mockSpreadsheets);
+    when(mockSpreadsheets.get(anyString())).thenReturn(mockSpreadsheetsGet);
+    when(mockSpreadsheetsGet.execute()).thenReturn(mockSpreadSheet);
+    when(mockSpreadSheet.getSheets()).thenReturn(new ArrayList<Sheet>(List.of(mockSheet)));
+    when(mockSpreadsheets.batchUpdate(anyString(),
+        any(BatchUpdateSpreadsheetRequest.class))).thenReturn(mockBatchUpdate);
+    when(mockBatchUpdate.execute()).thenReturn(mockBatchUpdateResponse);
+    when(mockSpreadsheets.values()).thenReturn(mockValues);
+    when(mockValues.append(any(), any(), any())).thenReturn(mockAppend);
+    when(mockAppend.setValueInputOption(anyString())).thenReturn(mockAppend);
+    when(mockAppend.execute()).thenReturn(mockAppendValuesResponse);
+    sheetsOutputStream = new SheetsOutputStream(applicationName, spreadsheetId, outputSheetTitle,
+        syncTime) {
+      @Override
+      Sheets createSheetsService() {
+        return mockSheetsService;
+      }
+    };
+  }
+
+  @Test
+  public void testConstructorWithDefaultSyncTime() throws IOException {
+    SheetsOutputStream stream = new SheetsOutputStream(applicationName, spreadsheetId,
+        outputSheetTitle) {
+      @Override
+      Sheets createSheetsService() {
+        return mockSheetsService;
+      }
+    };
+    assertNotNull(stream);
+  }
+
+  @Test
+  public void testConstructorWithCustomSyncTime() {
+    assertNotNull(sheetsOutputStream);
+    assertEquals(syncTime, sheetsOutputStream.syncTime);
+  }
+
+
+  @Test
+  public void testWriteSingleCharacter() throws IOException {
+    sheetsOutputStream.startStream();
+    sheetsOutputStream.write('A');
+    assertEquals(sheetsOutputStream.buffer.toString(), "A");
+    sheetsOutputStream.stopStream();
+
+    // verify stream was appended to the sheet
+    verify(mockValues, times(1)).append(any(), any(), any());
+  }
+
+
+  @Test
+  public void testWriteMultipleCharacters() throws IOException {
+    sheetsOutputStream.startStream();
+    String testString = "Hello World!";
+    sheetsOutputStream.write(testString.getBytes(), 0, testString.length());
+    assertEquals(testString, sheetsOutputStream.buffer.toString());
+    sheetsOutputStream.stopStream();
+
+    // verify stream was appended to the sheet
+    verify(mockValues, times(1)).append(any(), any(), any());
+  }
+
+  @Test
+  public void testWriteMultiLineString() throws IOException {
+    sheetsOutputStream.startStream();
+    String testString = "First line.\nSecond line.\nThird line.";
+    sheetsOutputStream.write(testString.getBytes(), 0, testString.length());
+
+    // verify stream was appended to the sheet
+    ArgumentCaptor<ValueRange> argumentCaptor = ArgumentCaptor.forClass(ValueRange.class);
+    verify(mockValues, times(1)).append(eq(spreadsheetId), eq(outputSheetTitle),
+        argumentCaptor.capture());
+    ValueRange capturedValue = argumentCaptor.getValue();
+    assertEquals(3, capturedValue.getValues().size());
+    assertEquals("First line.", capturedValue.getValues().get(0).get(0));
+    assertEquals("Second line.", capturedValue.getValues().get(1).get(0));
+    assertEquals("Third line.", capturedValue.getValues().get(2).get(0));
+
+    // buffer is emptied after appending to the sheet
+    assertEquals("", sheetsOutputStream.buffer.toString());
+
+    sheetsOutputStream.stopStream();
+  }
+
+  @Test
+  public void testAppendToSheetEmptyContent() throws IOException {
+    sheetsOutputStream.buffer.append("  \n  \n"); // Whitespace and empty lines
+    sheetsOutputStream.appendToSheet();
+
+    // empty content is not appended to the sheet
+    verify(mockValues, never()).append(any(), any(), any());
+    assertEquals("", sheetsOutputStream.buffer.toString());
+  }
+
+  @Test
+  public void testAddSheetIfNotExist() throws IOException {
+    when(mockSpreadsheetsGet.execute()).thenReturn(
+        new Spreadsheet().setSheets(Collections.emptyList()));
+    SheetsOutputStream outputStream =
+        new SheetsOutputStream(applicationName, spreadsheetId, outputSheetTitle, syncTime) {
+          @Override
+          Sheets createSheetsService() {
+            return mockSheetsService;
+          }
+        };
+    verify(mockBatchUpdate, times(1)).execute();
+  }
+
+  @Test
+  public void testAddSheetFails() throws IOException {
+    when(mockSpreadsheetsGet.execute()).thenReturn(
+        new Spreadsheet().setSheets(Collections.emptyList()));
+    when(mockBatchUpdate.execute()).thenThrow(new IOException("Failed to add sheet"));
+    assertThrows(
+        IOException.class,
+        () -> new SheetsOutputStream(applicationName, spreadsheetId, outputSheetTitle,
+            syncTime) {
+          @Override
+          Sheets createSheetsService() {
+            return mockSheetsService;
+          }
+        });
+  }
+
+
+  @Test
+  public void testSheetExists() throws IOException {
+    SheetProperties sheetProperties = new SheetProperties().setTitle(outputSheetTitle);
+    Sheet sheet = new Sheet().setProperties(sheetProperties);
+    when(mockSpreadsheetsGet.execute()).thenReturn(
+        new Spreadsheet().setSheets(Collections.singletonList(sheet)));
+    SheetsOutputStream outputStream =
+        new SheetsOutputStream(applicationName, spreadsheetId, outputSheetTitle, syncTime) {
+          @Override
+          Sheets createSheetsService() {
+            return mockSheetsService;
+          }
+        };
+    verify(mockBatchUpdate, never()).execute();
+  }
+
+
+  @Test
+  public void testStartAndStopStream() throws IOException {
+    SheetsOutputStream outputStream =
+        new SheetsOutputStream(applicationName, spreadsheetId, outputSheetTitle, syncTime) {
+          @Override
+          Sheets createSheetsService() {
+            return mockSheetsService;
+          }
+        };
+    PrintStream originalOut = System.out;
+    PrintStream originalErr = System.err;
+    outputStream.startStream();
+    assertNotEquals(originalOut, System.out);
+    assertNotEquals(originalErr, System.err);
+    String testString = "Test output";
+    System.out.println(testString);
+    outputStream.stopStream();
+    assertEquals(originalOut, System.out);
+    assertEquals(originalErr, System.err);
+  }
+
+}
\ No newline at end of file