diff --git a/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/FormatValueBase.js b/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/FormatValueBase.js
index 35bc4c2664..139d773f60 100644
--- a/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/FormatValueBase.js
+++ b/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/FormatValueBase.js
@@ -16,29 +16,59 @@
 */
 
 import 'sprintf-js'
+// Match any whitespace control character we want to make visible in
+// single-line displays. Kept as a module-level constant so the regex is
+// compiled once and reused across every formatValueBase call.
+const WHITESPACE_CONTROL_REGEX = /[\n\r\t]/
+const WHITESPACE_CONTROL_REGEX_G = /[\n\r\t]/g
 export default {
   methods: {
-    formatValueBase(value, formatString) {
+    formatValueBase(value, formatString, options) {
       if (this.isJsonString(value)) {
         return this.formatJsonString(value)
       }
+      const preserveWhitespace = options?.preserveWhitespace === true
       if (Array.isArray(value)) {
-        return JSON.stringify(value).replace(/\\n/g, '')
+        return this.escapeWhitespace(JSON.stringify(value), preserveWhitespace)
       }
       if (this.isObject(value)) {
-        return JSON.stringify(value).replace(/\\n/g, '')
+        return this.escapeWhitespace(JSON.stringify(value), preserveWhitespace)
       }
       if (formatString && value) {
         if (typeof value === 'bigint') {
           return this.formatBigInt(value, formatString)
         }
-        return sprintf(formatString, value)
+        return this.escapeWhitespace(
+          sprintf(formatString, value),
+          preserveWhitespace,
+        )
       }
       if (value === null || value === undefined) {
         return 'null'
       }
+      if (typeof value === 'string') {
+        return this.escapeWhitespace(value, preserveWhitespace)
+      }
       return String(value)
     },
+    // Make embedded newlines, carriage returns, and tabs visible in
+    // single-line displays (e.g. Packet Viewer) by replacing them with their
+    // escape sequences. Pass preserveWhitespace=true to return the value
+    // unchanged for multi-line displays such as the TEXTBOX widget.
+    escapeWhitespace(value, preserveWhitespace) {
+      if (preserveWhitespace || typeof value !== 'string') {
+        return value
+      }
+      // Cheap test first so we only allocate a new string when needed.
+      if (!WHITESPACE_CONTROL_REGEX.test(value)) {
+        return value
+      }
+      return value.replace(WHITESPACE_CONTROL_REGEX_G, (m) => {
+        if (m === '\n') return String.raw`\n`
+        if (m === '\r') return String.raw`\r`
+        return String.raw`\t`
+      })
+    },
     // sprintf-js doesn't support BigInt values so we handle common
     // integer format specifiers manually to preserve full precision
     formatBigInt(value, formatString) {
diff --git a/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/TextboxWidget.vue b/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/TextboxWidget.vue
index a9d02a3153..895246aafe 100644
--- a/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/TextboxWidget.vue
+++ b/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/TextboxWidget.vue
@@ -66,6 +66,9 @@ export default {
     return {
       width: 200,
       height: 200,
+      // Let v-textarea render embedded newlines as actual line breaks
+      // rather than the escaped "\n" sequence used by single-line displays.
+      preserveWhitespace: true,
     }
   },
   computed: {
diff --git a/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/VWidget.js b/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/VWidget.js
index 02b6248ae1..ac1c65f1c6 100644
--- a/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/VWidget.js
+++ b/openc3-cosmos-init/plugins/packages/openc3-vue-common/src/widgets/VWidget.js
@@ -43,6 +43,9 @@ export default {
   emits: ['addItem', 'deleteItem', 'open'],
   data() {
     return {
+      // Subclasses (e.g. TextboxWidget) set this true to let embedded
+      // newlines / tabs pass through to multi-line displays unchanged.
+      preserveWhitespace: false,
       appliedTimeZone: 'local',
       curValue: null,
       prevValue: null,
@@ -214,7 +217,9 @@ export default {
             this.appliedTimeZone,
           )
         }
-        return this.formatValueBase(value, this.formatString)
+        return this.formatValueBase(value, this.formatString, {
+          preserveWhitespace: this.preserveWhitespace,
+        })
       } catch (e) {
         // eslint-disable-next-line no-console
         console.log(
diff --git a/playwright/tests/packet-viewer.p.spec.ts b/playwright/tests/packet-viewer.p.spec.ts
index 9019502a50..eca508519c 100644
--- a/playwright/tests/packet-viewer.p.spec.ts
+++ b/playwright/tests/packet-viewer.p.spec.ts
@@ -150,6 +150,58 @@ test('gets details with right click', async ({ page, utils }) => {
   )
 })
 
+// Regression for openc3#154: newlines embedded in a string telemetry value
+// must be visible in the single-line Packet Viewer cell (escaped as \n) and
+// not silently truncate everything after the first newline.
+test('displays embedded newlines in string telemetry values', async ({
+  page,
+  utils,
+}) => {
+  // 1) Override INST HEALTH_STATUS ASCIICMD with a multi-line string. We do
+  //    this via Script Runner because the cmd-tlm API does not expose
+  //    override_tlm directly over HTTP.
+  await page.goto('/tools/scriptrunner')
+  await expect(page.locator('.v-app-bar')).toContainText('Script Runner')
+  await page.locator('[data-test=script-runner-file]').click()
+  await page.locator('text=New File').click()
+  await expect(page.locator('textarea')).toHaveText('')
+  await page
+    .locator('textarea')
+    .fill(
+      String.raw`override_tlm("INST HEALTH_STATUS ASCIICMD = \"line1\nline2\nline3\"")`,
+    )
+  await page.locator('[data-test=start-button]').click()
+  await expect(page.locator('[data-test=state] input')).toHaveValue(
+    'completed',
+    { timeout: 30000 },
+  )
+
+  // 2) Verify the Packet Viewer renders the embedded newlines as a literal
+  //    `\n` sequence rather than chopping at the first newline.
+  await page.goto('/tools/packetviewer/INST/HEALTH_STATUS/')
+  await expect(page.locator('.v-app-bar')).toContainText('Packet Viewer')
+  await expect
+    .poll(
+      async () =>
+        await page.inputValue('tr:has(td div:text-is("ASCIICMD")) input'),
+      { timeout: 10000 },
+    )
+    .toBe(String.raw`line1\nline2\nline3`)
+
+  // 3) Clear the override so we don't leak state into other tests.
+  await page.goto('/tools/scriptrunner')
+  await page.locator('[data-test=script-runner-file]').click()
+  await page.locator('text=New File').click()
+  await page
+    .locator('textarea')
+    .fill(`normalize_tlm("INST HEALTH_STATUS ASCIICMD")`)
+  await page.locator('[data-test=start-button]').click()
+  await expect(page.locator('[data-test=state] input')).toHaveValue(
+    'completed',
+    { timeout: 30000 },
+  )
+})
+
 test('stops posting to the api after closing', async ({ page, utils }) => {
   await page.goto('/tools/packetviewer/INST/ADCS/')
   let requestCount = 0