diff --git a/__tests__/components/batch-create-page.test.tsx b/__tests__/components/batch-create-page.test.tsx
index 664f29d..2b89bbd 100644
--- a/__tests__/components/batch-create-page.test.tsx
+++ b/__tests__/components/batch-create-page.test.tsx
@@ -234,6 +234,25 @@ describe('BatchCreatePage — page-level composition', () => {
       })
     })
 
+    it('shows a checksum-specific error for a near-miss recipient address (issue #143)', async () => {
+      // Same length/prefix/alphabet as a real G-address, but not
+      // checksum-valid — e.g. a single mistyped character.
+      const nearMissAddress = 'G' + 'A'.repeat(55)
+      const checksumCsv = [
+        'recipient,amount,start_time,end_time',
+        `${nearMissAddress},100,${START_TS},${END_TS}`,
+      ].join('\n')
+
+      render(<BatchCreatePage />)
+      await uploadCsv(checksumCsv)
+
+      await waitFor(() => {
+        expect(
+          screen.getByText('Invalid recipient address checksum — check for a mistyped character'),
+        ).toBeInTheDocument()
+      })
+    })
+
     it('shows an upload error for non-CSV files', async () => {
       render(<BatchCreatePage />)
 
diff --git a/__tests__/components/create-form.test.tsx b/__tests__/components/create-form.test.tsx
index c07363e..569a33a 100644
--- a/__tests__/components/create-form.test.tsx
+++ b/__tests__/components/create-form.test.tsx
@@ -32,11 +32,25 @@ vi.mock('@/hooks/use-form-draft', () => ({
 }))
 
 // ─── Stellar / contract lib ───────────────────────────────────────────────────
-vi.mock('@/lib/stellar', () => ({
-  getAllTokens: () => [{ address: 'CNATIVE', symbol: 'XLM', decimals: 7 }],
-  saveCustomToken: vi.fn(),
-  checkAccountInfo: vi.fn().mockResolvedValue({ exists: true, funded: true, transactionCount: 1 }),
-}))
+vi.mock('@/lib/stellar', async () => {
+  const { StrKey } = await import('@stellar/stellar-sdk')
+  const ED25519_SHAPE_RE = /^G[A-Z2-7]{55}$/
+  return {
+    getAllTokens: () => [{ address: 'CNATIVE', symbol: 'XLM', decimals: 7 }],
+    saveCustomToken: vi.fn(),
+    checkAccountInfo: vi
+      .fn()
+      .mockResolvedValue({ exists: true, funded: true, transactionCount: 1 }),
+    // Mirrors the real lib/stellar.ts implementation (issue #143) so tests
+    // exercise the same valid/format/checksum classification.
+    validateStellarAddress: (address: string) => {
+      const trimmed = address.trim()
+      if (StrKey.isValidEd25519PublicKey(trimmed)) return { valid: true }
+      if (ED25519_SHAPE_RE.test(trimmed)) return { valid: false, reason: 'checksum' }
+      return { valid: false, reason: 'format' }
+    },
+  }
+})
 
 vi.mock('@/lib/contract', () => ({
   getTokenMetadata: vi.fn(),
@@ -133,6 +147,27 @@ describe('CreateForm — validation', () => {
       // No amount error should be present
       expect(screen.queryByText('Enter a valid amount greater than 0')).not.toBeInTheDocument()
     })
+
+    it('shows a checksum-specific error for a near-miss recipient (issue #143)', async () => {
+      render(<CreateForm />)
+
+      // Same length/prefix/alphabet as a real G-address, but not
+      // checksum-valid — e.g. a single mistyped character.
+      fireEvent.change(screen.getByPlaceholderText(/GABC/i), {
+        target: { value: 'G' + 'A'.repeat(55) },
+      })
+      fireEvent.change(screen.getByLabelText(/total amount/i), {
+        target: { value: '100' },
+      })
+
+      submitForm()
+
+      await waitFor(() => {
+        expect(
+          screen.getByText('Invalid checksum — double-check this address for a mistyped character'),
+        ).toBeInTheDocument()
+      })
+    })
   })
 
   describe('cliff amount exceeds total amount', () => {
diff --git a/__tests__/hooks/use-streams.test.ts b/__tests__/hooks/use-streams.test.ts
index 0598839..d0452de 100644
--- a/__tests__/hooks/use-streams.test.ts
+++ b/__tests__/hooks/use-streams.test.ts
@@ -1,5 +1,5 @@
-import { describe, it, expect, vi, beforeEach } from 'vitest'
-import { renderHook, waitFor } from '@testing-library/react'
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest'
+import { renderHook, waitFor, act } from '@testing-library/react'
 import type { StreamData } from '@/types/stream'
 
 // ── Mocks ──────────────────────────────────────────────────────────────────
@@ -83,6 +83,76 @@ describe('useStreams', () => {
   })
 })
 
+// Issue #142: polling intervals must be created exactly once per mount and
+// fully cleared on unmount — no orphaned `setInterval` continuing to fire
+// (and make RPC calls) after the component is gone.
+describe('useStreams polling lifecycle', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+    vi.mocked(fetchStreamsForAddress).mockResolvedValue([mockStream])
+    vi.useFakeTimers()
+  })
+
+  afterEach(() => {
+    vi.useRealTimers()
+  })
+
+  it('polls on the configured interval while mounted', async () => {
+    const { result } = renderHook(() => useStreams({ enablePolling: true, pollInterval: 1000 }))
+
+    await act(async () => {
+      await vi.advanceTimersByTimeAsync(0)
+    })
+    await waitFor(() => expect(result.current.loading).toBe(false))
+
+    const callsAfterMount = vi.mocked(fetchStreamsForAddress).mock.calls.length
+
+    await act(async () => {
+      await vi.advanceTimersByTimeAsync(3000)
+    })
+
+    // 3 ticks at 1000ms each.
+    expect(vi.mocked(fetchStreamsForAddress).mock.calls.length).toBe(callsAfterMount + 3)
+  })
+
+  it('clears the polling interval on unmount — no orphaned fetches afterward', async () => {
+    const { result, unmount } = renderHook(() =>
+      useStreams({ enablePolling: true, pollInterval: 1000 }),
+    )
+
+    await act(async () => {
+      await vi.advanceTimersByTimeAsync(0)
+    })
+    await waitFor(() => expect(result.current.loading).toBe(false))
+
+    unmount()
+    const callsAtUnmount = vi.mocked(fetchStreamsForAddress).mock.calls.length
+
+    await act(async () => {
+      await vi.advanceTimersByTimeAsync(10000)
+    })
+
+    // No further polling ticks should have fired after unmount.
+    expect(vi.mocked(fetchStreamsForAddress).mock.calls.length).toBe(callsAtUnmount)
+  })
+
+  it('clears exactly one interval per mount on unmount (no leaked timer handle)', async () => {
+    const clearIntervalSpy = vi.spyOn(global, 'clearInterval')
+
+    const { unmount } = renderHook(() => useStreams({ enablePolling: true, pollInterval: 1000 }))
+    await act(async () => {
+      await vi.advanceTimersByTimeAsync(0)
+    })
+
+    unmount()
+
+    // The polling-interval cleanup should run exactly once for this mount.
+    expect(clearIntervalSpy).toHaveBeenCalledTimes(1)
+
+    clearIntervalSpy.mockRestore()
+  })
+})
+
 describe('invalidateStreams', () => {
   it('triggers refetch in subscribed hooks', async () => {
     vi.mocked(fetchStreamsForAddress).mockResolvedValue([mockStream])
diff --git a/__tests__/lib/stellar-address-validation.test.ts b/__tests__/lib/stellar-address-validation.test.ts
new file mode 100644
index 0000000..4d16578
--- /dev/null
+++ b/__tests__/lib/stellar-address-validation.test.ts
@@ -0,0 +1,63 @@
+import { describe, it, expect } from 'vitest'
+import { validateStellarAddress } from '@/lib/stellar'
+
+// A real, checksum-valid ed25519 public key.
+const VALID = 'GBZXN7PIRZGNMHGA7MUUUF4GWPY5AYPV6LY4UV2GL6VJGIQRXFDNMADI'
+
+describe('validateStellarAddress', () => {
+  it('accepts a valid ed25519 public key', () => {
+    expect(validateStellarAddress(VALID)).toEqual({ valid: true })
+  })
+
+  it('trims surrounding whitespace before validating', () => {
+    expect(validateStellarAddress(`  ${VALID}  `)).toEqual({ valid: true })
+  })
+
+  it('flags a near-miss (right shape, mistyped character) as a checksum error', () => {
+    // Same length (56) and 'G' + base32 shape as a real key, but not a
+    // real checksum-valid key — this is the "one mistyped character"
+    // scenario issue #143 is about.
+    const nearMiss = 'G' + 'A'.repeat(55)
+    expect(nearMiss).toHaveLength(56)
+    expect(validateStellarAddress(nearMiss)).toEqual({ valid: false, reason: 'checksum' })
+  })
+
+  it('flags a single-character mutation of a valid address as a checksum error', () => {
+    const mutated = VALID.slice(0, -1) + (VALID.at(-1) === 'A' ? 'B' : 'A')
+    expect(validateStellarAddress(mutated)).toEqual({ valid: false, reason: 'checksum' })
+  })
+
+  it('flags an address that is too short as a format error', () => {
+    expect(validateStellarAddress(VALID.slice(0, -1))).toEqual({ valid: false, reason: 'format' })
+  })
+
+  it('flags an address that is too long as a format error', () => {
+    expect(validateStellarAddress(VALID + 'A')).toEqual({ valid: false, reason: 'format' })
+  })
+
+  it('flags an address with the wrong prefix as a format error', () => {
+    // Contract addresses start with 'C', not 'G'.
+    expect(
+      validateStellarAddress('CDLZFC3SYJYDZT7K67VZ75HPJVIEUVNIXF47ZG2FB2RMQQVU2HHGCYSC'),
+    ).toEqual({ valid: false, reason: 'format' })
+  })
+
+  it('flags an address with invalid base32 characters as a format error', () => {
+    // '0', '1', '8', '9' are not in the base32 alphabet used by StrKey.
+    expect(validateStellarAddress('G' + '0'.repeat(55))).toEqual({
+      valid: false,
+      reason: 'format',
+    })
+  })
+
+  it('flags an empty string as a format error', () => {
+    expect(validateStellarAddress('')).toEqual({ valid: false, reason: 'format' })
+  })
+
+  it('flags an arbitrary non-address string as a format error', () => {
+    expect(validateStellarAddress('not-a-stellar-address')).toEqual({
+      valid: false,
+      reason: 'format',
+    })
+  })
+})
diff --git a/app/app/create/batch/page.tsx b/app/app/create/batch/page.tsx
index 04137e2..9e32eed 100644
--- a/app/app/create/batch/page.tsx
+++ b/app/app/create/batch/page.tsx
@@ -20,7 +20,7 @@ import { useNetwork } from '@/components/providers/network-provider'
 import { parseTokenAmount, formatDateTime } from '@/lib/stream-utils'
 import { parseCsvBatch, parseDuration, resolveCliffTime, type CsvBatchRow } from '@/lib/csv-parser'
 import { downloadCSV } from '@/lib/export'
-import { isValidStellarAddress } from '@/lib/stellar'
+import { validateStellarAddress } from '@/lib/stellar'
 import { batchCreateCopy } from '@/lib/copy/batch-create'
 import type { TokenInfo } from '@/types/stream'
 
@@ -113,8 +113,17 @@ export default function BatchCreatePage() {
           : null
 
         const errors: string[] = []
-        if (!recipient || !isValidStellarAddress(recipient)) {
+        if (!recipient) {
           errors.push(batchCreateCopy.rowValidation.invalidRecipient)
+        } else {
+          const addressCheck = validateStellarAddress(recipient)
+          if (!addressCheck.valid) {
+            errors.push(
+              addressCheck.reason === 'checksum'
+                ? batchCreateCopy.rowValidation.invalidRecipientChecksum
+                : batchCreateCopy.rowValidation.invalidRecipient,
+            )
+          }
         }
         if (!amount || parseDecimalAmount(amount, selectedTokenInfo.decimals) === null) {
           errors.push(batchCreateCopy.rowValidation.invalidAmount)
diff --git a/app/app/create/create-form.tsx b/app/app/create/create-form.tsx
index 42f1b61..4381f49 100644
--- a/app/app/create/create-form.tsx
+++ b/app/app/create/create-form.tsx
@@ -29,7 +29,7 @@ import {
 } from '@/components/ui/select'
 import { useContract } from '@/hooks/use-contract'
 import { useWallet } from '@/hooks/use-wallet'
-import { getAllTokens, saveCustomToken, checkAccountInfo } from '@/lib/stellar'
+import { getAllTokens, saveCustomToken, checkAccountInfo, validateStellarAddress } from '@/lib/stellar'
 import { getTokenMetadata, getTokenBalance } from '@/lib/contract'
 import { parseTokenAmount, formatTokenAmount } from '@/lib/stream-utils'
 import { StreamPreview } from '@/components/streams/stream-preview'
@@ -442,14 +442,23 @@ export function CreateForm() {
       newErrors.recipient = copy.errors.federationResolving
     } else if (federationStatus === 'error') {
       newErrors.recipient = federationError ?? copy.errors.federationLookupFailed
-    } else if (
-      // Issue #28: use StrKey for proper Stellar address validation
-      !form.recipient.trim() ||
-      !StrKey.isValidEd25519PublicKey(form.recipient.trim())
-    ) {
+    } else if (!form.recipient.trim()) {
       newErrors.recipient = isFederationAddress(recipientInput.trim())
         ? copy.errors.federationDidNotResolve
         : copy.errors.invalidAddressFormat
+    } else {
+      // Issue #28/#143: use StrKey for proper Stellar address validation,
+      // and surface a checksum-specific message for near-miss typos.
+      const addressCheck = validateStellarAddress(form.recipient.trim())
+      if (!addressCheck.valid) {
+        if (isFederationAddress(recipientInput.trim())) {
+          newErrors.recipient = copy.errors.federationDidNotResolve
+        } else if (addressCheck.reason === 'checksum') {
+          newErrors.recipient = copy.errors.invalidAddressChecksum
+        } else {
+          newErrors.recipient = copy.errors.invalidAddressFormat
+        }
+      }
     }
     // Issue #103: require warning acknowledgment for unfunded accounts
     if (recipientAccountInfo && !recipientAccountInfo.exists && !recipientWarningAcknowledged) {
diff --git a/hooks/use-streams.ts b/hooks/use-streams.ts
index af6fb6e..229bb25 100644
--- a/hooks/use-streams.ts
+++ b/hooks/use-streams.ts
@@ -198,6 +198,17 @@ export function useStreams(options?: UseStreamsOptions): CategorizedStreams {
     fetch()
   }, [fetch])
 
+  // Issue #142: abort whatever request is still in flight when this hook
+  // instance unmounts (or `fetch` is about to be replaced because address/
+  // network changed), rather than only aborting on the *next* fetch call.
+  // Without this, a slow response can land after unmount and still call
+  // setState on a component that's gone.
+  useEffect(() => {
+    return () => {
+      abortCtrlRef.current?.abort()
+    }
+  }, [fetch])
+
   // Re-fetch when a write invalidates the cache
   useInvalidation(fetch)
 
@@ -358,6 +369,15 @@ export function useStream(id: string): {
     fetch()
   }, [fetch])
 
+  // Issue #142: abort any in-flight request on unmount/id change instead of
+  // only on the next fetch call, so a late response can't update state after
+  // this hook instance is gone.
+  useEffect(() => {
+    return () => {
+      abortCtrlRef.current?.abort()
+    }
+  }, [fetch])
+
   useInvalidation(fetch)
 
   return { stream, loading, refetch: fetch }
diff --git a/lib/copy/batch-create.ts b/lib/copy/batch-create.ts
index ecb19be..9f6d7ef 100644
--- a/lib/copy/batch-create.ts
+++ b/lib/copy/batch-create.ts
@@ -71,6 +71,8 @@ export const batchCreateCopy = {
 
   rowValidation: {
     invalidRecipient: "Invalid recipient address",
+    invalidRecipientChecksum:
+      "Invalid recipient address checksum — check for a mistyped character",
     invalidAmount: "Invalid amount",
     invalidStartTime: "Invalid start_time",
     invalidEndTime: "Invalid end_time",
diff --git a/lib/copy/create-form.ts b/lib/copy/create-form.ts
index 8cb9b68..1d4e204 100644
--- a/lib/copy/create-form.ts
+++ b/lib/copy/create-form.ts
@@ -154,6 +154,8 @@ export const createFormCopy = {
     federationLookupFailed: 'Federation lookup failed',
     federationDidNotResolve: 'Federation address did not resolve to a valid Stellar account',
     invalidAddressFormat: 'Invalid Stellar address format',
+    invalidAddressChecksum:
+      'Invalid checksum — double-check this address for a mistyped character',
     acknowledgeRecipientWarning: 'Please acknowledge the warning about this recipient address',
     invalidAmount: 'Enter a valid amount greater than 0',
     amountExceedsBalance: (balance: string, symbol: string) =>
diff --git a/lib/stellar.ts b/lib/stellar.ts
index 6e6be22..9c5c404 100644
--- a/lib/stellar.ts
+++ b/lib/stellar.ts
@@ -37,6 +37,42 @@ export function isValidStellarAddress(address: string): boolean {
   return StrKey.isValidEd25519PublicKey(address.trim())
 }
 
+/**
+ * Matches the shape of a Stellar Ed25519 public key (`G` + 55 base32
+ * characters) without verifying the embedded CRC-16 checksum. Used by
+ * {@link validateStellarAddress} to tell a near-miss (right shape, wrong
+ * checksum — e.g. a single mistyped character) apart from a value that
+ * isn't even trying to be a G-address.
+ */
+const ED25519_SHAPE_RE = /^G[A-Z2-7]{55}$/
+
+/**
+ * Result of {@link validateStellarAddress}.
+ *
+ * - `reason: 'checksum'` — the value has the correct length, prefix, and
+ *   base32 alphabet of a Stellar Ed25519 address, but the CRC-16 checksum
+ *   encoded in its last two bytes doesn't match (a classic single-typo
+ *   near-miss).
+ * - `reason: 'format'` — the value doesn't even match the basic shape of a
+ *   Stellar G-address (wrong prefix, wrong length, or invalid characters).
+ */
+export type StellarAddressValidation =
+  | { valid: true }
+  | { valid: false; reason: 'checksum' | 'format' }
+
+/**
+ * Validates `address` as a Stellar Ed25519 public key and, when invalid,
+ * distinguishes a bad checksum (right shape, mistyped character) from a
+ * value that is the wrong shape entirely. This lets callers show a more
+ * actionable error than a single generic "invalid address" message.
+ */
+export function validateStellarAddress(address: string): StellarAddressValidation {
+  const trimmed = address.trim()
+  if (StrKey.isValidEd25519PublicKey(trimmed)) return { valid: true }
+  if (ED25519_SHAPE_RE.test(trimmed)) return { valid: false, reason: 'checksum' }
+  return { valid: false, reason: 'format' }
+}
+
 /**
  * Static per-network configuration map (RPC endpoints, Horizon URLs, network
  * passphrases, and built-in known tokens). Does **not** include the streaming