fix(ui): neutralize Usage CSV text cells [AI] (#111653)

* fix(ui): neutralize usage csv text cells

* test(ui): align usage csv fixture types

* fix(ui): preserve benign usage csv whitespace

ui/src/pages/usage/query.test.ts

@@ -16,4 +16,92 @@ describe("usage query CSV export", () => {
 
     expect(csv).toContain("session-1,Session 1,,,,,,,,,,,,,,,");
   });
+
+  it.each([
+    ["equals", "=1+1", "'=1+1"],
+    ["plus", "+1+1", "'+1+1"],
+    ["minus", "-1+1", "'-1+1"],
+    ["at", "@SUM(A1:A2)", "'@SUM(A1:A2)"],
+    ["leading whitespace", " \t=1+1", "' \t=1+1"],
+    ["fullwidth equals", "\uFF1D1+1", "'\uFF1D1+1"],
+    ["fullwidth plus", "\uFF0B1+1", "'\uFF0B1+1"],
+    ["fullwidth minus", "\uFF0D1+1", "'\uFF0D1+1"],
+    ["fullwidth at", "\uFF20SUM(A1:A2)", "'\uFF20SUM(A1:A2)"],
+  ])("neutralizes spreadsheet formula labels with %s prefix", (_name, label, expected) => {
+    const csv = buildSessionsCsv([
+      {
+        key: "session-1",
+        label,
+        updatedAt: 0,
+        usage: null,
+      } satisfies UsageSessionEntry,
+    ]);
+
+    expect(csv).toContain(`session-1,${expected},`);
+  });
+
+  it("quotes carriage returns in formula-neutralized labels", () => {
+    const csv = buildSessionsCsv([
+      {
+        key: "session-1",
+        label: "\r=1+1",
+        updatedAt: 0,
+        usage: null,
+      } satisfies UsageSessionEntry,
+    ]);
+
+    expect(csv).toContain('session-1,"\'\r=1+1",');
+  });
+
+  it.each([
+    ["tab", "\tplain", "\tplain"],
+    ["carriage return", "\rplain", '"\rplain"'],
+    ["newline", "\nplain", '"\nplain"'],
+  ])("preserves benign labels with leading %s", (_name, label, expected) => {
+    const csv = buildSessionsCsv([
+      {
+        key: "session-1",
+        label,
+        updatedAt: 0,
+        usage: null,
+      } satisfies UsageSessionEntry,
+    ]);
+
+    expect(csv).toContain(`session-1,${expected},`);
+  });
+
+  it("keeps numeric cells numeric while neutralizing string labels", () => {
+    const csv = buildSessionsCsv([
+      {
+        key: "session-1",
+        label: "-remote-label",
+        updatedAt: 0,
+        usage: {
+          durationMs: -1,
+          messageCounts: {
+            total: -2,
+            user: -3,
+            assistant: -4,
+            toolCalls: -5,
+            toolResults: -6,
+            errors: -7,
+          },
+          input: -5,
+          output: -6,
+          cacheRead: -7,
+          cacheWrite: -8,
+          totalTokens: -9,
+          totalCost: -10,
+          inputCost: -11,
+          outputCost: -12,
+          cacheReadCost: -13,
+          cacheWriteCost: -14,
+          missingCostEntries: -15,
+        },
+      } satisfies UsageSessionEntry,
+    ]);
+
+    expect(csv).toContain("session-1,'-remote-label,,,");
+    expect(csv).toContain(",-1,-2,-7,-5,-5,-6,-7,-8,-9,-10");
+  });
 });

ui/src/pages/usage/query.ts

@@ -14,11 +14,16 @@ function downloadTextFile(filename: string, content: string, type = "text/plain"
   URL.revokeObjectURL(url);
 }
 
-function csvEscape(value: string): string {
-  if (/[",\n]/.test(value)) {
-    return `"${value.replaceAll('"', '""')}"`;
+function neutralizeSpreadsheetFormulaCell(value: string): string {
+  return /^[ \t\r\n]*[=+\-@\uFF0B\uFF0D\uFF1D\uFF20]/u.test(value) ? `'${value}` : value;
+}
+
+function csvEscape(value: string, neutralizeFormulas = true): string {
+  const safeValue = neutralizeFormulas ? neutralizeSpreadsheetFormulaCell(value) : value;
+  if (/[",\r\n]/.test(safeValue)) {
+    return `"${safeValue.replaceAll('"', '""')}"`;
   }
-  return value;
+  return safeValue;
 }
 
 function toCsvRow(values: Array<string | number | undefined | null>): string {
@@ -27,7 +32,7 @@ function toCsvRow(values: Array<string | number | undefined | null>): string {
       if (value === undefined || value === null) {
         return "";
       }
-      return csvEscape(String(value));
+      return csvEscape(String(value), typeof value === "string");
     })
     .join(",");
 }