diff --git a/browse/src/server.ts b/browse/src/server.ts
index 042616e75b..e63a87e949 100644
--- a/browse/src/server.ts
+++ b/browse/src/server.ts
@@ -324,6 +324,7 @@ const DIALOG_LOG_PATH = config.dialogLog;
 // terminal-agent.ts; chat queue + per-tab agent multiplexing are no
 // longer needed.
 
+let lastConsoleFlushed = 0;
 let lastNetworkFlushed = 0;
 let lastDialogFlushed = 0;
 let flushInProgress = false;
diff --git a/browse/test/server-flush-trackers.test.ts b/browse/test/server-flush-trackers.test.ts
new file mode 100644
index 0000000000..306729af4e
--- /dev/null
+++ b/browse/test/server-flush-trackers.test.ts
@@ -0,0 +1,73 @@
+/**
+ * Regression: flushBuffers state-tracker declaration audit.
+ *
+ * `flushBuffers()` (server.ts) maintains per-buffer cursors so it only
+ * appends *new* entries to each on-disk log on every interval tick:
+ *
+ *   const newConsoleCount  = consoleBuffer.totalAdded  - lastConsoleFlushed;
+ *   const newNetworkCount  = networkBuffer.totalAdded  - lastNetworkFlushed;
+ *   const newDialogCount   = dialogBuffer.totalAdded   - lastDialogFlushed;
+ *
+ * The trackers must be declared with `let X = 0;` at module scope so the
+ * subtraction returns a real number on the first tick. If a tracker is
+ * referenced inside flushBuffers but never declared at module scope, the
+ * interval throws `ReferenceError: X is not defined` every second — the
+ * throw is swallowed by the catch at the bottom of flushBuffers (logged
+ * as `[browse] Buffer flush failed: <name> is not defined`), the
+ * corresponding on-disk log file is *never written*, and the regression
+ * is silent in production.
+ *
+ * This source-level guard catches that exact class of regression — a
+ * future flush-perf refactor that adds a fourth buffer cursor (or a
+ * future contributor that copy-pastes the `last*Flushed` pattern without
+ * the matching declaration) will fail this test before it ships.
+ *
+ * Pattern matches `terminal-agent.test.ts` and `dual-listener.test.ts`:
+ * read source as text, assert an invariant, no daemon required.
+ */
+
+import { describe, test, expect } from 'bun:test';
+import { readFileSync } from 'fs';
+import * as path from 'path';
+
+const SERVER_TS = readFileSync(
+  path.resolve(import.meta.dir, '../src/server.ts'),
+  'utf-8',
+);
+
+describe('server.ts — flushBuffers tracker declarations', () => {
+  test('every `last*Flushed` tracker referenced inside flushBuffers is declared at module scope', () => {
+    // Locate the flushBuffers function body. The function is `async function
+    // flushBuffers() { ... }` — match through the closing brace at the start
+    // of a line (one-level-deep function in the file).
+    const fnMatch = SERVER_TS.match(
+      /async function flushBuffers\([^)]*\)[^{]*\{([\s\S]*?)\n\}/,
+    );
+    expect(fnMatch, 'flushBuffers function not found in server.ts').not.toBeNull();
+    const body = fnMatch![1]!;
+
+    // Pull every identifier matching the `lastXxxFlushed` cursor pattern.
+    const trackerMatches = [...body.matchAll(/\blast([A-Z]\w+)Flushed\b/g)];
+    const trackers = Array.from(new Set(trackerMatches.map((m) => `last${m[1]}Flushed`)));
+
+    expect(
+      trackers.length,
+      'flushBuffers should reference at least one last*Flushed tracker',
+    ).toBeGreaterThan(0);
+
+    for (const tracker of trackers) {
+      // Module-level `let X = 0;` declaration (not inside a function body).
+      // Anchored start-of-line to avoid matching nested re-declarations or
+      // string literals.
+      const declared = new RegExp(
+        `(?:^|\\n)let\\s+${tracker}\\s*=\\s*0\\s*;`,
+      ).test(SERVER_TS);
+      expect(
+        declared,
+        `\`${tracker}\` is referenced inside flushBuffers but never declared at module scope ` +
+          `with \`let ${tracker} = 0;\` — the interval will throw ReferenceError every tick ` +
+          `and the corresponding on-disk log will never be written`,
+      ).toBe(true);
+    }
+  });
+});