diff --git a/src/tests/session-memory-leaks.test.ts b/src/tests/session-memory-leaks.test.ts
new file mode 100644
index 000000000..17a3590bb
--- /dev/null
+++ b/src/tests/session-memory-leaks.test.ts
@@ -0,0 +1,144 @@
+/**
+ * Regression tests for CPU/memory leak fixes in long-running sessions.
+ *
+ * Structural tests that verify the fix patterns are present in source —
+ * NOT runtime integration tests. This approach is chosen because:
+ * - The leaks manifest over hours of real usage, not in unit test timescales
+ * - The fixes are defensive guards (caps, disposal, handler cleanup)
+ * - Structural verification catches regressions when code is refactored
+ */
+import test from "node:test";
+import assert from "node:assert/strict";
+import { readFileSync } from "node:fs";
+import { join } from "node:path";
+
+// ── Helpers ──────────────────────────────────────────────────────────
+
+function readSource(relativePath: string): string {
+  return readFileSync(join(import.meta.dirname, "..", "..", relativePath), "utf-8");
+}
+
+function extractFunctionBody(src: string, name: string): string {
+  const fnStart = src.indexOf(name);
+  assert.ok(fnStart > -1, `${name} must exist in source`);
+  let depth = 0;
+  let fnEnd = -1;
+  for (let i = src.indexOf("{", fnStart); i < src.length; i++) {
+    if (src[i] === "{") depth++;
+    if (src[i] === "}") depth--;
+    if (depth === 0) { fnEnd = i; break; }
+  }
+  return src.slice(fnStart, fnEnd + 1);
+}
+
+// ── TUI render-skip ─────────────────────────────────────────────────
+
+test("Container caches render output for stable-reference comparison", () => {
+  const src = readSource("packages/pi-tui/src/tui.ts");
+  assert.ok(
+    src.includes("_prevRender"),
+    "Container must have _prevRender cache for render-skip optimization",
+  );
+});
+
+test("TUI skips post-processing when component output is unchanged", () => {
+  const src = readSource("packages/pi-tui/src/tui.ts");
+  assert.ok(
+    src.includes("_lastRenderedComponents"),
+    "TUI must track _lastRenderedComponents for reference-equality skip",
+  );
+});
+
+// ── Loader frame isolation ──────────────────────────────────────────
+
+test("Loader does not call setText on every spinner tick", () => {
+  const src = readSource("packages/pi-tui/src/components/loader.ts");
+  // The old pattern was: setText(`${frame} ${message}`) inside the interval
+  // The new pattern: only update Text when message changes, prepend frame in render()
+  assert.ok(
+    src.includes("_lastMessage"),
+    "Loader must track _lastMessage to avoid setText on every tick",
+  );
+  // Verify the interval does NOT call setText or updateDisplay
+  const intervalMatch = src.match(/setInterval\s*\(\s*\(\)\s*=>\s*\{([^}]+)\}/s);
+  assert.ok(intervalMatch, "Loader must have a setInterval callback");
+  const intervalBody = intervalMatch[1];
+  assert.ok(
+    !intervalBody.includes("setText") && !intervalBody.includes("updateDisplay"),
+    "Loader interval must NOT call setText or updateDisplay — " +
+    "frame rotation should only trigger requestRender()",
+  );
+});
+
+// ── Text cache guard ────────────────────────────────────────────────
+
+test("Text.setText returns early when text is unchanged", () => {
+  const src = readSource("packages/pi-tui/src/components/text.ts");
+  const setTextBody = extractFunctionBody(src, "setText(");
+  assert.ok(
+    setTextBody.includes("if (this.text === text) return"),
+    "setText must early-return when text is identical to prevent cache invalidation",
+  );
+});
+
+// ── Chat component cap ──────────────────────────────────────────────
+
+test("InteractiveMode caps rendered chat components", () => {
+  const src = readSource("packages/pi-coding-agent/src/modes/interactive/interactive-mode.ts");
+  assert.ok(
+    src.includes("MAX_CHAT_COMPONENTS"),
+    "InteractiveMode must define MAX_CHAT_COMPONENTS to prevent unbounded growth",
+  );
+  assert.ok(
+    src.includes("trimChatHistory"),
+    "InteractiveMode must call trimChatHistory to enforce the cap",
+  );
+});
+
+// ── ToolExecution dispose ───────────────────────────────────────────
+
+test("ToolExecutionComponent has dispose() to clear heavy references", () => {
+  const src = readSource("packages/pi-coding-agent/src/modes/interactive/components/tool-execution.ts");
+  assert.ok(
+    src.includes("dispose()"),
+    "ToolExecutionComponent must have dispose() for GC of image maps, diff previews, etc.",
+  );
+});
+
+// ── Orphan process prevention ───────────────────────────────────────
+
+test("InteractiveMode kills descendant processes on shutdown", () => {
+  const src = readSource("packages/pi-coding-agent/src/modes/interactive/interactive-mode.ts");
+  assert.ok(
+    src.includes("listDescendants"),
+    "Shutdown must use listDescendants to find orphan child processes",
+  );
+  assert.ok(
+    src.includes("SIGTERM") && src.includes("SIGKILL"),
+    "Shutdown must send SIGTERM then SIGKILL to descendants",
+  );
+});
+
+// ── Signal handler accumulation ─────────────────────────────────────
+
+test("bg-shell removes signal handlers on session_shutdown", () => {
+  const src = readSource("src/resources/extensions/bg-shell/bg-shell-lifecycle.ts");
+  assert.ok(
+    src.includes('process.off("SIGTERM"') || src.includes("process.off('SIGTERM'"),
+    "session_shutdown must remove SIGTERM handler to prevent accumulation",
+  );
+  assert.ok(
+    src.includes('process.off("SIGINT"') || src.includes("process.off('SIGINT'"),
+    "session_shutdown must remove SIGINT handler to prevent accumulation",
+  );
+});
+
+// ── Alert queue cap ─────────────────────────────────────────────────
+
+test("pendingAlerts has a maximum size cap", () => {
+  const src = readSource("src/resources/extensions/bg-shell/process-manager.ts");
+  assert.ok(
+    src.includes("MAX_PENDING_ALERTS"),
+    "process-manager must cap pendingAlerts to prevent unbounded growth",
+  );
+});