diff --git a/packages/hoppscotch-common/assets/themes/tippy-themes.scss b/packages/hoppscotch-common/assets/themes/tippy-themes.scss
index 7fe6ae22..30adb241 100644
--- a/packages/hoppscotch-common/assets/themes/tippy-themes.scss
+++ b/packages/hoppscotch-common/assets/themes/tippy-themes.scss
@@ -16,6 +16,25 @@
       @apply flex-col;
     }
 
+    // Constrained tooltip styles to prevent overflow beyond the viewport
+    // when environment variable values are very long (fixes #5876)
+    .env-tooltip-constrained {
+      @apply flex-col;
+      @apply w-full;
+      @apply box-border;
+      @apply overflow-hidden;
+
+      .env-tooltip-value {
+        @apply break-words;
+        @apply break-all;
+        @apply whitespace-pre-wrap;
+        @apply overflow-hidden;
+        @apply inline-block;
+        @apply max-w-full;
+        @apply align-top;
+      }
+    }
+
     .tippy-content {
       @apply flex;
       @apply text-tiny;
diff --git a/packages/hoppscotch-common/src/helpers/editor/extensions/HoppEnvironment.ts b/packages/hoppscotch-common/src/helpers/editor/extensions/HoppEnvironment.ts
index 61d20a5a..4b3e1df2 100644
--- a/packages/hoppscotch-common/src/helpers/editor/extensions/HoppEnvironment.ts
+++ b/packages/hoppscotch-common/src/helpers/editor/extensions/HoppEnvironment.ts
@@ -41,6 +41,10 @@ import {
   ENV_VAR_NAME_REGEX,
   HOPP_ENVIRONMENT_REGEX,
 } from "~/helpers/environment-regex"
+import {
+  constrainTooltipToViewport,
+  createTooltipValueRow,
+} from "~/helpers/utils/tooltip"
 
 const HOPP_ENV_HIGHLIGHT =
   "cursor-help transition rounded px-1 focus:outline-none mx-0.5 env-highlight"
@@ -49,6 +53,8 @@ const HOPP_COLLECTION_ENVIRONMENT_HIGHLIGHT = "collection-variable-highlight"
 const HOPP_ENVIRONMENT_HIGHLIGHT = "environment-variable-highlight"
 const HOPP_GLOBAL_ENVIRONMENT_HIGHLIGHT = "global-variable-highlight"
 const HOPP_ENV_HIGHLIGHT_NOT_FOUND = "environment-not-found-highlight"
+// Keep value rows above overlapping CodeMirror decoration layers inside tooltip content.
+const TOOLTIP_ENV_CONTAINER_Z_INDEX_CLASS = "!z-[1002]"
 
 const secretEnvironmentService = getService(SecretEnvironmentService)
 const currentEnvironmentValueService = getService(CurrentValueService)
@@ -282,36 +288,31 @@ const cursorTooltipField = (aggregateEnvs: AggregateEnvironment[]) =>
 
           const envContainer = document.createElement("div")
           tooltipContainer.appendChild(envContainer)
-          envContainer.className =
-            "flex flex-col items-start space-y-1 flex-1 w-full mt-2 !z-[1002]"
+          envContainer.className = `flex flex-col items-start space-y-1 flex-1 w-full mt-2 ${TOOLTIP_ENV_CONTAINER_Z_INDEX_CLASS}`
+          envContainer.style.overflow = "hidden"
 
-          const initialValueBlock = document.createElement("div")
-          initialValueBlock.className = "flex items-center space-x-2"
-          const initialValueTitle = document.createElement("div")
-          initialValueTitle.textContent = "Initial"
-          initialValueTitle.className = "font-bold mr-4 "
-          const initialValue = document.createElement("span")
-          initialValue.textContent = envInitialValue || ""
-          initialValueBlock.appendChild(initialValueTitle)
-          initialValueBlock.appendChild(initialValue)
+          // Use createTooltipValueRow for overflow-safe value display
+          const initialValueRow = createTooltipValueRow(
+            "Initial",
+            envInitialValue
+          )
+          const currentValueRow = createTooltipValueRow(
+            "Current",
+            envCurrentValue
+          )
 
-          const currentValueBlock = document.createElement("div")
-          currentValueBlock.className = "flex items-center space-x-2"
-          const currentValueTitle = document.createElement("div")
-          currentValueTitle.textContent = "Current"
-          currentValueTitle.className = "font-bold mr-1.5"
-          const currentValue = document.createElement("span")
-          currentValue.textContent = envCurrentValue || ""
-          currentValueBlock.appendChild(currentValueTitle)
-          currentValueBlock.appendChild(currentValue)
+          envContainer.appendChild(initialValueRow)
+          envContainer.appendChild(currentValueRow)
 
-          envContainer.appendChild(initialValueBlock)
-          envContainer.appendChild(currentValueBlock)
-
-          tooltipContainer.className = "tippy-content env-tooltip-content"
+          tooltipContainer.className =
+            "tippy-content env-tooltip-content env-tooltip-constrained"
           dom.className = "tippy-box"
           dom.dataset.theme = "tooltip"
           dom.appendChild(tooltipContainer)
+
+          // Apply viewport-aware overflow constraints to the tooltip
+          constrainTooltipToViewport(dom, tooltipContainer)
+
           return { dom }
         },
       }
diff --git a/packages/hoppscotch-common/src/helpers/editor/extensions/HoppPredefinedVariables.ts b/packages/hoppscotch-common/src/helpers/editor/extensions/HoppPredefinedVariables.ts
index bd201f4d..dc3c0048 100644
--- a/packages/hoppscotch-common/src/helpers/editor/extensions/HoppPredefinedVariables.ts
+++ b/packages/hoppscotch-common/src/helpers/editor/extensions/HoppPredefinedVariables.ts
@@ -9,6 +9,10 @@ import { HOPP_SUPPORTED_PREDEFINED_VARIABLES } from "@hoppscotch/data"
 
 import IconSquareAsterisk from "~icons/lucide/square-asterisk?raw"
 import { isComment } from "./helpers"
+import {
+  constrainTooltipToViewport,
+  truncateText,
+} from "~/helpers/utils/tooltip"
 
 const HOPP_PREDEFINED_VARIABLES_REGEX = /(<<\$[a-zA-Z0-9-_]+>>)/g
 
@@ -76,7 +80,7 @@ const cursorTooltipField = () =>
       const variableIcon = `<span class="inline-flex items-center justify-center my-1">${IconSquareAsterisk}</span>`
       const variableDescription =
         variable !== undefined
-          ? `${variableName} - ${variable.description}`
+          ? `${variableName} - ${truncateText(variable.description)}`
           : `${variableName} is not a valid predefined variable.`
 
       return {
@@ -114,14 +118,18 @@ const cursorTooltipField = () =>
           tooltipContainer.appendChild(envContainer)
           envContainer.className =
             "flex flex-col items-start space-y-1 flex-1 w-full mt-2"
+          envContainer.style.overflow = "hidden"
 
           const valueBlock = document.createElement("div")
-          valueBlock.className = "flex items-center space-x-2"
+          valueBlock.className = "flex items-start space-x-2"
+          valueBlock.style.width = "100%"
           const valueTitle = document.createElement("div")
           const value = document.createElement("span")
-          value.textContent = variableDescription || ""
+          value.className = "env-tooltip-value"
+          value.textContent = variableDescription
           valueTitle.textContent = "Value"
-          valueTitle.className = "font-bold mr-4 "
+          valueTitle.className = "font-bold mr-4"
+          valueTitle.style.flexShrink = "0"
           valueBlock.appendChild(valueTitle)
           valueBlock.appendChild(value)
 
@@ -130,9 +138,14 @@ const cursorTooltipField = () =>
           dom.className = "tippy-box"
           dom.dataset.theme = "tooltip"
 
-          tooltipContainer.className = "tippy-content env-tooltip-content"
+          tooltipContainer.className =
+            "tippy-content env-tooltip-content env-tooltip-constrained"
 
           dom.appendChild(tooltipContainer)
+
+          // Apply viewport-aware overflow constraints
+          constrainTooltipToViewport(dom, tooltipContainer)
+
           return { dom }
         },
       }
diff --git a/packages/hoppscotch-common/src/helpers/utils/__tests__/tooltip.spec.ts b/packages/hoppscotch-common/src/helpers/utils/__tests__/tooltip.spec.ts
new file mode 100644
index 00000000..6e3b0179
--- /dev/null
+++ b/packages/hoppscotch-common/src/helpers/utils/__tests__/tooltip.spec.ts
@@ -0,0 +1,399 @@
+import { describe, expect, test, beforeEach, afterEach } from "vitest"
+import {
+  truncateText,
+  formatTooltipValue,
+  calculateTooltipDimensions,
+  applyTooltipOverflowStyles,
+  createTooltipValueRow,
+  constrainTooltipToViewport,
+  TOOLTIP_MAX_VALUE_LENGTH,
+  TOOLTIP_MAX_HEIGHT_PX,
+  TOOLTIP_MAX_WIDTH_PX,
+  TOOLTIP_MIN_WIDTH_PX,
+  TOOLTIP_VIEWPORT_MARGIN_PX,
+} from "../tooltip"
+
+// ─── truncateText ────────────────────────────────────────────────
+
+describe("truncateText", () => {
+  test("returns original string when within default max length", () => {
+    const short = "hello world"
+    expect(truncateText(short)).toBe(short)
+  })
+
+  test("returns original string when exactly at max length", () => {
+    const exact = "a".repeat(TOOLTIP_MAX_VALUE_LENGTH)
+    expect(truncateText(exact)).toBe(exact)
+  })
+
+  test("truncates string exceeding default max length and appends char count", () => {
+    const long = "x".repeat(TOOLTIP_MAX_VALUE_LENGTH + 50)
+    const result = truncateText(long)
+    expect(result.length).toBeLessThan(long.length)
+    expect(result).toContain("\u2026")
+    expect(result).toContain(`${long.length} chars)`)
+  })
+
+  test("truncates string with custom max length", () => {
+    const text = "abcdefghij"
+    const result = truncateText(text, 5)
+    expect(result).toBe("abcde\u2026 (truncated, 10 chars)")
+  })
+
+  test("returns empty string for null input", () => {
+    expect(truncateText(null as unknown as string)).toBe("")
+  })
+
+  test("returns empty string for undefined input", () => {
+    expect(truncateText(undefined as unknown as string)).toBe("")
+  })
+
+  test("returns empty string for empty string input", () => {
+    expect(truncateText("")).toBe("")
+  })
+
+  test("handles maxLength of 0 by truncating everything", () => {
+    const result = truncateText("abc", 0)
+    expect(result).toContain("\u2026")
+    expect(result).toContain("3 chars)")
+  })
+
+  test("handles maxLength of 1", () => {
+    const result = truncateText("abc", 1)
+    expect(result).toBe("a\u2026 (truncated, 3 chars)")
+  })
+
+  test("preserves unicode characters during truncation", () => {
+    const emoji = "\u{1F600}".repeat(10)
+    const result = truncateText(emoji, 3)
+    expect(result).toContain("\u2026")
+  })
+
+  test("handles very long strings (10000+ chars) without error", () => {
+    const veryLong = "z".repeat(10000)
+    const result = truncateText(veryLong, 100)
+    expect(result.startsWith("z".repeat(100))).toBe(true)
+    expect(result).toContain("10000 chars)")
+  })
+})
+
+// ─── formatTooltipValue ──────────────────────────────────────────
+
+describe("formatTooltipValue", () => {
+  test("returns empty string for undefined", () => {
+    expect(formatTooltipValue(undefined)).toBe("")
+  })
+
+  test("returns empty string for null", () => {
+    expect(formatTooltipValue(null)).toBe("")
+  })
+
+  test("returns 'Empty' for empty string", () => {
+    expect(formatTooltipValue("")).toBe("Empty")
+  })
+
+  test("returns original value for short strings", () => {
+    expect(formatTooltipValue("my-value")).toBe("my-value")
+  })
+
+  test("truncates long values", () => {
+    const longValue = "v".repeat(600)
+    const result = formatTooltipValue(longValue)
+    expect(result).toContain("\u2026")
+    expect(result).toContain("600 chars)")
+  })
+
+  test("respects custom maxLength parameter", () => {
+    const result = formatTooltipValue("abcdef", 3)
+    expect(result).toBe("abc\u2026 (truncated, 6 chars)")
+  })
+
+  test("does not truncate when value equals maxLength", () => {
+    const result = formatTooltipValue("abc", 3)
+    expect(result).toBe("abc")
+  })
+})
+
+// ─── calculateTooltipDimensions ──────────────────────────────────
+
+describe("calculateTooltipDimensions", () => {
+  test("returns max width capped at TOOLTIP_MAX_WIDTH_PX for large viewports", () => {
+    const { maxWidth } = calculateTooltipDimensions(1920, 1080)
+    expect(maxWidth).toBe(TOOLTIP_MAX_WIDTH_PX)
+  })
+
+  test("returns viewport-based width for small viewports", () => {
+    const viewportWidth = 300
+    const margin = TOOLTIP_VIEWPORT_MARGIN_PX
+    const { maxWidth } = calculateTooltipDimensions(viewportWidth, 600)
+    // effectiveWidth = 300 - 16*2 = 268, which is between MIN and MAX
+    expect(maxWidth).toBe(viewportWidth - margin * 2)
+  })
+
+  test("ensures minimum width for very small viewports", () => {
+    const { maxWidth } = calculateTooltipDimensions(100, 100)
+    expect(maxWidth).toBe(68)
+  })
+
+  test("respects custom margin", () => {
+    const customMargin = 50
+    const { maxWidth } = calculateTooltipDimensions(400, 600, customMargin)
+    // effectiveWidth = 400 - 100 = 300
+    expect(maxWidth).toBe(300)
+  })
+
+  test("caps maxHeight at TOOLTIP_MAX_HEIGHT_PX", () => {
+    const { maxHeight } = calculateTooltipDimensions(1920, 1080)
+    expect(maxHeight).toBe(TOOLTIP_MAX_HEIGHT_PX)
+  })
+
+  test("uses available height when viewport is small", () => {
+    const { maxHeight } = calculateTooltipDimensions(1920, 200)
+    // effectiveHeight = 200 - 32 = 168
+    expect(maxHeight).toBe(168)
+  })
+
+  test("handles zero dimensions gracefully", () => {
+    const dims = calculateTooltipDimensions(0, 0)
+    expect(dims.maxWidth).toBe(0)
+    expect(dims.maxHeight).toBeLessThanOrEqual(300)
+  })
+})
+
+// ─── applyTooltipOverflowStyles ──────────────────────────────────
+
+describe("applyTooltipOverflowStyles", () => {
+  let element: HTMLElement
+
+  beforeEach(() => {
+    element = document.createElement("div")
+  })
+
+  test("sets maxWidth to default TOOLTIP_MAX_WIDTH_PX when not specified", () => {
+    applyTooltipOverflowStyles(element)
+    expect(element.style.maxWidth).toBe(`${TOOLTIP_MAX_WIDTH_PX}px`)
+  })
+
+  test("sets maxWidth to custom value", () => {
+    applyTooltipOverflowStyles(element, 300)
+    expect(element.style.maxWidth).toBe("300px")
+  })
+
+  test("sets minWidth to TOOLTIP_MIN_WIDTH_PX when maxWidth allows", () => {
+    applyTooltipOverflowStyles(element)
+    expect(element.style.minWidth).toBe(`${TOOLTIP_MIN_WIDTH_PX}px`)
+  })
+
+  test("clamps minWidth to maxWidth on narrow viewports", () => {
+    applyTooltipOverflowStyles(element, 68)
+    expect(element.style.minWidth).toBe("68px")
+  })
+
+  test("sets boxSizing to border-box", () => {
+    applyTooltipOverflowStyles(element)
+    expect(element.style.boxSizing).toBe("border-box")
+  })
+
+  test("sets maxHeight when provided", () => {
+    applyTooltipOverflowStyles(element, undefined, 250)
+    expect(element.style.maxHeight).toBe("250px")
+  })
+
+  test("does not set maxHeight when undefined", () => {
+    applyTooltipOverflowStyles(element)
+    expect(element.style.maxHeight).toBe("")
+  })
+})
+
+// ─── createTooltipValueRow ───────────────────────────────────────
+
+describe("createTooltipValueRow", () => {
+  test("creates a div element", () => {
+    const row = createTooltipValueRow("Initial", "test-value")
+    expect(row.tagName).toBe("DIV")
+  })
+
+  test("contains a label element with correct text", () => {
+    const row = createTooltipValueRow("Initial", "test-value")
+    const label = row.querySelector("div")
+    expect(label).not.toBeNull()
+    expect(label!.textContent).toBe("Initial")
+  })
+
+  test("contains a value element with correct text", () => {
+    const row = createTooltipValueRow("Current", "my-value")
+    const value = row.querySelector("span")
+    expect(value).not.toBeNull()
+    expect(value!.textContent).toBe("my-value")
+  })
+
+  test("truncates long values", () => {
+    const longValue = "a".repeat(600)
+    const row = createTooltipValueRow("Initial", longValue)
+    const value = row.querySelector("span")
+    expect(value!.textContent).toContain("\u2026")
+    expect(value!.textContent).toContain("600 chars)")
+  })
+
+  test("shows 'Empty' for empty string value", () => {
+    const row = createTooltipValueRow("Current", "")
+    const value = row.querySelector("span")
+    expect(value!.textContent).toBe("Empty")
+  })
+
+  test("shows empty string for undefined value", () => {
+    const row = createTooltipValueRow("Initial", undefined)
+    const value = row.querySelector("span")
+    expect(value!.textContent).toBe("")
+  })
+
+  test("shows empty string for null value", () => {
+    const row = createTooltipValueRow("Current", null)
+    const value = row.querySelector("span")
+    expect(value!.textContent).toBe("")
+  })
+
+  test("applies env-tooltip-value class to the value element", () => {
+    const row = createTooltipValueRow("Initial", "test")
+    const value = row.querySelector(".env-tooltip-value")
+    expect(value).not.toBeNull()
+  })
+
+  test("sets title attribute when value is truncated", () => {
+    const longValue = "b".repeat(600)
+    const row = createTooltipValueRow("Initial", longValue, 100)
+    const value = row.querySelector("span")
+    expect(value!.title).toContain("600 characters")
+  })
+
+  test("does not set title attribute when value is not truncated", () => {
+    const row = createTooltipValueRow("Initial", "short")
+    const value = row.querySelector("span")
+    expect(value!.title).toBe("")
+  })
+
+  test("label has flexShrink 0 so it does not compress", () => {
+    const row = createTooltipValueRow("Initial", "value")
+    const label = row.querySelector("div")
+    expect(label!.style.flexShrink).toBe("0")
+  })
+
+  test("row has width 100%", () => {
+    const row = createTooltipValueRow("Current", "value")
+    expect(row.style.width).toBe("100%")
+  })
+
+  test("respects custom maxValueLength parameter", () => {
+    const result = createTooltipValueRow("Initial", "abcdefghij", 5)
+    const value = result.querySelector("span")
+    expect(value!.textContent).toContain("\u2026")
+  })
+
+  test("applies env-tooltip-value class for overflow styles", () => {
+    const row = createTooltipValueRow("Initial", "test")
+    const value = row.querySelector("span")
+    expect(value!.classList.contains("env-tooltip-value")).toBe(true)
+  })
+})
+
+// ─── constrainTooltipToViewport ──────────────────────────────────
+
+describe("constrainTooltipToViewport", () => {
+  let tooltipBox: HTMLElement
+  let tooltipContent: HTMLElement
+  let originalInnerWidth: number
+  let originalInnerHeight: number
+
+  beforeEach(() => {
+    tooltipBox = document.createElement("div")
+    tooltipContent = document.createElement("div")
+
+    originalInnerWidth = window.innerWidth
+    originalInnerHeight = window.innerHeight
+
+    // jsdom has window.innerWidth and innerHeight set to 0 by default
+    // We mock them for consistent test results
+    Object.defineProperty(window, "innerWidth", {
+      writable: true,
+      configurable: true,
+      value: 1024,
+    })
+    Object.defineProperty(window, "innerHeight", {
+      writable: true,
+      configurable: true,
+      value: 768,
+    })
+  })
+
+  afterEach(() => {
+    Object.defineProperty(window, "innerWidth", {
+      writable: true,
+      configurable: true,
+      value: originalInnerWidth,
+    })
+    Object.defineProperty(window, "innerHeight", {
+      writable: true,
+      configurable: true,
+      value: originalInnerHeight,
+    })
+  })
+
+  test("sets maxWidth on tooltipBox", () => {
+    constrainTooltipToViewport(tooltipBox, tooltipContent)
+    expect(tooltipBox.style.maxWidth).not.toBe("")
+  })
+
+  test("sets minWidth on tooltipBox", () => {
+    constrainTooltipToViewport(tooltipBox, tooltipContent)
+    expect(tooltipBox.style.minWidth).toBe(`${TOOLTIP_MIN_WIDTH_PX}px`)
+  })
+
+  test("sets maxWidth 100% on tooltipContent", () => {
+    constrainTooltipToViewport(tooltipBox, tooltipContent)
+    expect(tooltipContent.style.maxWidth).toBe("100%")
+  })
+
+  test("sets overflow hidden on tooltipContent", () => {
+    constrainTooltipToViewport(tooltipBox, tooltipContent)
+    expect(tooltipContent.style.overflow).toBe("hidden")
+  })
+
+  test("sets boxSizing on tooltipContent", () => {
+    constrainTooltipToViewport(tooltipBox, tooltipContent)
+    expect(tooltipContent.style.boxSizing).toBe("border-box")
+  })
+
+  test("works with small viewport", () => {
+    Object.defineProperty(window, "innerWidth", { value: 250 })
+    Object.defineProperty(window, "innerHeight", { value: 200 })
+    constrainTooltipToViewport(tooltipBox, tooltipContent)
+    // Should use minimum width since viewport is too small
+    expect(parseInt(tooltipBox.style.maxWidth)).toBeLessThanOrEqual(
+      TOOLTIP_MAX_WIDTH_PX
+    )
+  })
+})
+
+// ─── Constants ───────────────────────────────────────────────────
+
+describe("Tooltip Constants", () => {
+  test("TOOLTIP_MAX_VALUE_LENGTH is a positive number", () => {
+    expect(TOOLTIP_MAX_VALUE_LENGTH).toBeGreaterThan(0)
+  })
+
+  test("TOOLTIP_MAX_WIDTH_PX is a positive number", () => {
+    expect(TOOLTIP_MAX_WIDTH_PX).toBeGreaterThan(0)
+  })
+
+  test("TOOLTIP_MIN_WIDTH_PX is less than TOOLTIP_MAX_WIDTH_PX", () => {
+    expect(TOOLTIP_MIN_WIDTH_PX).toBeLessThan(TOOLTIP_MAX_WIDTH_PX)
+  })
+
+  test("TOOLTIP_MIN_WIDTH_PX is a positive number", () => {
+    expect(TOOLTIP_MIN_WIDTH_PX).toBeGreaterThan(0)
+  })
+
+  test("TOOLTIP_VIEWPORT_MARGIN_PX is a positive number", () => {
+    expect(TOOLTIP_VIEWPORT_MARGIN_PX).toBeGreaterThan(0)
+  })
+})
diff --git a/packages/hoppscotch-common/src/helpers/utils/tooltip.ts b/packages/hoppscotch-common/src/helpers/utils/tooltip.ts
new file mode 100644
index 00000000..97698d88
--- /dev/null
+++ b/packages/hoppscotch-common/src/helpers/utils/tooltip.ts
@@ -0,0 +1,197 @@
+/**
+ * Utility functions for tooltip text truncation, formatting, and
+ * viewport-constrained positioning. These helpers ensure that long
+ * variable values displayed in editor hover tooltips stay within
+ * the visible viewport boundaries.
+ *
+ * @module tooltip
+ */
+
+/** Default maximum character length before a tooltip value is truncated. */
+export const TOOLTIP_MAX_VALUE_LENGTH = 500
+
+/** Default maximum pixel width for the tooltip container. */
+export const TOOLTIP_MAX_WIDTH_PX = 450
+
+/** Minimum pixel width for the tooltip container. */
+export const TOOLTIP_MIN_WIDTH_PX = 200
+
+/** Maximum pixel height for the tooltip container. */
+export const TOOLTIP_MAX_HEIGHT_PX = 300
+
+/** Viewport margin in pixels — the tooltip will stay this far from edges. */
+export const TOOLTIP_VIEWPORT_MARGIN_PX = 16
+
+/**
+ * Truncates a string to a maximum length and appends an ellipsis
+ * indicator when the text exceeds the limit.
+ *
+ * @param text - The input string to potentially truncate
+ * @param maxLength - The maximum number of characters to keep
+ *                    (defaults to TOOLTIP_MAX_VALUE_LENGTH)
+ * @returns The original string if within limits, or a truncated version
+ *          with a trailing ellipsis and character-count annotation
+ *
+ * @example
+ * ```ts
+ * truncateText("short")           // "short"
+ * truncateText("a".repeat(600))   // "aaa...aaa (600 chars)"
+ * truncateText("abc", 2)          // "ab... (3 chars)"
+ * ```
+ */
+export function truncateText(
+  text: string,
+  maxLength: number = TOOLTIP_MAX_VALUE_LENGTH
+): string {
+  if (!text) {
+    return text ?? ""
+  }
+
+  const codePoints = Array.from(text)
+  if (codePoints.length <= maxLength) return text
+
+  // Show the beginning of the text plus a count so the user knows
+  // the full length of the value.
+  const truncated = codePoints.slice(0, maxLength).join("")
+  return `${truncated}\u2026 (truncated, ${codePoints.length} chars)`
+}
+
+/**
+ * Formats a variable value for display inside a tooltip.
+ * Handles null/undefined/empty cases and applies truncation.
+ *
+ * @param value - The raw variable value
+ * @param maxLength - Optional max character length
+ * @returns A human-readable display string
+ */
+export function formatTooltipValue(
+  value: string | undefined | null,
+  maxLength: number = TOOLTIP_MAX_VALUE_LENGTH
+): string {
+  if (value === undefined || value === null) {
+    return ""
+  }
+
+  if (value === "") {
+    return "Empty"
+  }
+
+  return truncateText(value, maxLength)
+}
+
+/**
+ * Calculates appropriate tooltip dimensions so the tooltip stays
+ * within the visible viewport.
+ *
+ * @param viewportWidth - Current viewport width in pixels
+ * @param viewportHeight - Current viewport height in pixels
+ * @param margin - Margin from viewport edges (defaults to TOOLTIP_VIEWPORT_MARGIN_PX)
+ * @returns An object with maxWidth and maxHeight constraints in pixels
+ */
+export function calculateTooltipDimensions(
+  viewportWidth: number,
+  viewportHeight: number,
+  margin: number = TOOLTIP_VIEWPORT_MARGIN_PX
+): { maxWidth: number; maxHeight: number } {
+  const effectiveWidth = Math.max(viewportWidth - margin * 2, 0)
+  const effectiveHeight = Math.max(viewportHeight - margin * 2, 0)
+
+  const maxWidth = Math.min(effectiveWidth, TOOLTIP_MAX_WIDTH_PX)
+
+  const maxHeight = Math.min(effectiveHeight, TOOLTIP_MAX_HEIGHT_PX)
+
+  return { maxWidth, maxHeight }
+}
+
+/**
+ * Applies overflow-safe styles to a tooltip DOM element so that its
+ * content is constrained to the viewport. This mutates the element
+ * in-place by setting inline styles.
+ *
+ * @param element - The tooltip DOM element to constrain
+ * @param maxWidth - Maximum width in pixels (or undefined to use default)
+ * @param maxHeight - Maximum height in pixels (or undefined to skip)
+ */
+export function applyTooltipOverflowStyles(
+  element: HTMLElement,
+  maxWidth?: number,
+  maxHeight?: number
+): void {
+  const resolvedMaxWidth = maxWidth ?? TOOLTIP_MAX_WIDTH_PX
+  const resolvedMinWidth = Math.min(TOOLTIP_MIN_WIDTH_PX, resolvedMaxWidth)
+
+  element.style.maxWidth = `${resolvedMaxWidth}px`
+  element.style.minWidth = `${resolvedMinWidth}px`
+  element.style.boxSizing = "border-box"
+
+  if (maxHeight !== undefined) {
+    element.style.maxHeight = `${maxHeight}px`
+  }
+}
+
+/**
+ * Creates a fully styled value row for the tooltip, including
+ * a label (e.g., "Initial" or "Current") and a value element
+ * with proper overflow handling.
+ *
+ * @param label - The label text (e.g., "Initial", "Current", "Value")
+ * @param value - The raw value string to display
+ * @param maxValueLength - Maximum characters before truncation
+ * @returns The row container element
+ */
+export function createTooltipValueRow(
+  label: string,
+  value: string | undefined | null,
+  maxValueLength: number = TOOLTIP_MAX_VALUE_LENGTH
+): HTMLDivElement {
+  const row = document.createElement("div")
+  row.className = "flex items-start space-x-2"
+  row.style.width = "100%"
+
+  const labelEl = document.createElement("div")
+  labelEl.textContent = label
+  labelEl.className = "font-bold"
+  labelEl.style.flexShrink = "0"
+  labelEl.style.minWidth = "50px"
+  labelEl.style.marginRight = "0.5rem"
+
+  const valueEl = document.createElement("span")
+  valueEl.className = "env-tooltip-value"
+  const displayValue = formatTooltipValue(value, maxValueLength)
+  valueEl.textContent = displayValue
+
+  // Add a title attribute with the truncated indicator so users
+  // know the full length if it was truncated
+  if (value && value.length > maxValueLength) {
+    valueEl.title = `Full value: ${value.length} characters`
+  }
+
+  row.appendChild(labelEl)
+  row.appendChild(valueEl)
+
+  return row
+}
+
+/**
+ * Applies overflow constraints to the outer tooltip container element
+ * (the `.tippy-box` wrapper). This ensures the entire tooltip
+ * respects viewport boundaries.
+ *
+ * @param tooltipBox - The outer `.tippy-box` element
+ * @param tooltipContent - The inner `.tippy-content` element
+ */
+export function constrainTooltipToViewport(
+  tooltipBox: HTMLElement,
+  tooltipContent: HTMLElement
+): void {
+  const { maxWidth, maxHeight } = calculateTooltipDimensions(
+    window.innerWidth,
+    window.innerHeight
+  )
+
+  applyTooltipOverflowStyles(tooltipBox, maxWidth, maxHeight)
+
+  tooltipContent.style.maxWidth = "100%"
+  tooltipContent.style.overflow = "hidden"
+  tooltipContent.style.boxSizing = "border-box"
+}