diff --git a/lib/__tests__/csv-parser.test.ts b/lib/__tests__/csv-parser.test.ts
new file mode 100644
index 0000000..81d34d3
--- /dev/null
+++ b/lib/__tests__/csv-parser.test.ts
@@ -0,0 +1,78 @@
+import { describe, it, expect } from 'vitest'
+import { parseCsvBatch } from '../csv-parser'
+
+// FlowwStar/FlowStar#340 — add unit tests for parseCsvLine via the public
+// parseCsvBatch entry point. Each test exercises one parseCsvLine branch
+// through a representative input the caller actually relies on.
+
+describe('parseCsvBatch / parseCsvLine edge cases', () => {
+  it('parses a plain comma-separated row', () => {
+    const csv = [
+      'recipient,amount,start_time,end_time',
+      'GA,1000,2026-01-01T00:00:00Z,2026-12-31T23:59:59Z',
+    ].join('\n')
+
+    const result = parseCsvBatch(csv)
+    expect(result.rows).toHaveLength(1)
+    expect(result.errors).toEqual([])
+    expect(result.rows[0]).toMatchObject({
+      recipient: 'GA',
+      amount: '1000',
+      start_time: '2026-01-01T00:00:00Z',
+      end_time: '2026-12-31T23:59:59Z',
+    })
+  })
+
+  it('preserves commas inside quoted fields', () => {
+    const csv = [
+      'recipient,amount,start_time,end_time',
+      '"GA,Attr-1",1000,2026-01-01T00:00:00Z,2026-12-31T23:59:59Z',
+    ].join('\n')
+
+    const result = parseCsvBatch(csv)
+    expect(result.rows).toHaveLength(1)
+    expect(result.errors).toEqual([])
+    expect(result.rows[0].recipient).toBe('GA,Attr-1')
+  })
+
+  it('un-escapes an embedded double-quote pair inside a quoted field', () => {
+    const csv = [
+      'recipient,amount,start_time,end_time',
+      '"GA""Spec",1000,2026-01-01T00:00:00Z,2026-12-31T23:59:59Z',
+    ].join('\n')
+
+    const result = parseCsvBatch(csv)
+    expect(result.rows).toHaveLength(1)
+    expect(result.errors).toEqual([])
+    expect(result.rows[0].recipient).toBe('GA"Spec')
+  })
+
+  it('parses empty trailing cells as empty strings', () => {
+    const csv = [
+      'recipient,amount,start_time,end_time,cliff_time',
+      'GA,1000,2026-01-01T00:00:00Z,2026-12-31T23:59:59Z,',
+    ].join('\n')
+
+    const result = parseCsvBatch(csv)
+    expect(result.rows).toHaveLength(1)
+    expect(result.rows[0].recipient).toBe('GA')
+    expect(result.rows[0].cliff_time).toBe('')
+  })
+
+  it('parses the optional duration row shape with quoted commas', () => {
+    const csv = [
+      'recipient,amount,start_time,cliff_time,cliff_amount,cliff_duration',
+      '"GA,Wallet-One",500000,1700000000,1700003600,250000,30d',
+    ].join('\n')
+
+    const result = parseCsvBatch(csv)
+    expect(result.rows).toHaveLength(1)
+    expect(result.errors).toEqual([])
+    expect(result.rows[0]).toMatchObject({
+      recipient: 'GA,Wallet-One',
+      amount: '500000',
+      cliff_amount: '250000',
+      cliff_duration: '30d',
+    })
+  })
+})