diff --git a/contracts/streaming/src/lib.rs b/contracts/streaming/src/lib.rs
index 723100b..a7ea5c5 100644
--- a/contracts/streaming/src/lib.rs
+++ b/contracts/streaming/src/lib.rs
@@ -242,6 +242,9 @@ pub enum StreamError {
     RateIsZero = 19,
     /// Stream is not yet cancelled or fully drained; cleanup is not allowed.
     StreamNotEligibleForCleanup = 20,
+    /// The start_time is in the past (before the current ledger timestamp);
+    /// backdating a stream would unlock funds immediately on creation.
+    PastStartTime = 21,
 }
 
 // ─── Events ───────────────────────────────────────────────────────────────────
@@ -515,6 +518,13 @@ impl StreamingContract {
         if duration > MAX_STREAM_DURATION {
             return Err(StreamError::DurationExceedsMaximum);
         }
+        // Security: reject backdated start times. A stream whose start_time is
+        // in the past would have a large chunk of its deposit already unlocked
+        // (and withdrawable) the moment it is created, bypassing the vesting UX
+        // entirely and misleading the recipient about the schedule.
+        if params.start_time < env.ledger().timestamp() {
+            return Err(StreamError::PastStartTime);
+        }
         if params.cliff_time < params.start_time || params.cliff_time > params.end_time {
             return Err(StreamError::InvalidCliff);
         }
@@ -638,6 +648,12 @@ impl StreamingContract {
             if duration > MAX_STREAM_DURATION {
                 return Err(StreamError::DurationExceedsMaximum);
             }
+            // Security: reject backdated start times — same rule as
+            // create_stream, applied per-input before any funds move so the
+            // whole batch is rejected atomically.
+            if input.start_time < env.ledger().timestamp() {
+                return Err(StreamError::PastStartTime);
+            }
             if input.cliff_time < input.start_time || input.cliff_time > input.end_time {
                 return Err(StreamError::InvalidCliff);
             }
diff --git a/contracts/streaming/src/test.rs b/contracts/streaming/src/test.rs
index 327474f..ef7037f 100644
--- a/contracts/streaming/src/test.rs
+++ b/contracts/streaming/src/test.rs
@@ -216,6 +216,86 @@ fn test_create_stream_zero_amount() {
     assert_eq!(result, Err(Ok(StreamError::InvalidAmount)));
 }
 
+// ─── create_stream: backdated start/cliff times ───────────────────────────────
+
+#[test]
+fn test_create_stream_rejects_past_start_time() {
+    let t = TestEnv::setup();
+    let now = 1_000_000u64;
+    t.set_time(now);
+    let client = t.client();
+    let mut params = t.default_params(now);
+    // Backdate the start (and cliff) into the past — must be rejected so a
+    // large chunk of the deposit cannot unlock immediately on creation.
+    params.start_time = now - 1000;
+    params.cliff_time = now - 1000;
+    t.token().approve(
+        &t.sender,
+        &t.contract_id,
+        &params.total_amount,
+        &(t.env.ledger().sequence() + 500),
+    );
+    let result = client.try_create_stream(&t.sender, &params);
+    assert_eq!(result, Err(Ok(StreamError::PastStartTime)));
+
+    // No funds should have moved.
+    assert_eq!(t.token().balance(&t.contract_id), 0);
+}
+
+#[test]
+fn test_create_stream_rejects_backdated_cliff() {
+    let t = TestEnv::setup();
+    let now = 1_000_000u64;
+    t.set_time(now);
+    let client = t.client();
+    let mut params = t.default_params(now);
+    params.cliff_time = params.start_time - 1; // cliff before start
+    t.token().approve(
+        &t.sender,
+        &t.contract_id,
+        &params.total_amount,
+        &(t.env.ledger().sequence() + 500),
+    );
+    let result = client.try_create_stream(&t.sender, &params);
+    assert_eq!(result, Err(Ok(StreamError::InvalidCliff)));
+}
+
+// ─── pagination: large offset/limit must clamp, not abort ────────────────────
+
+#[test]
+fn test_pagination_clamps_large_offset_limit() {
+    let t = TestEnv::setup();
+    let now = 1_000_000u64;
+    t.set_time(now);
+    let client = t.client();
+
+    // Create 5 streams from the same sender so the index has 5 entries.
+    let per_stream = 1_000_0000000i128;
+    t.token().approve(
+        &t.sender,
+        &t.contract_id,
+        &(per_stream * 5),
+        &(t.env.ledger().sequence() + 500),
+    );
+    for _ in 0..5 {
+        client.create_stream(&t.sender, &t.default_params(now));
+    }
+
+    // offset=2 + limit=u32::MAX overflows u32 — must clamp to the tail of the
+    // index (streams 3..5) instead of aborting the call.
+    let tail = client.get_sent_streams(&t.sender, &2u32, &u32::MAX);
+    assert_eq!(tail.len(), 3);
+    assert_eq!(tail.get(0).unwrap(), 3u64);
+
+    // Huge offset beyond the list → empty page, still no abort.
+    let empty = client.get_sent_streams(&t.sender, &u32::MAX, &u32::MAX);
+    assert_eq!(empty.len(), 0);
+
+    // A plain full-page read still returns everything.
+    let all = client.get_sent_streams(&t.sender, &0u32, &u32::MAX);
+    assert_eq!(all.len(), 5);
+}
+
 // ─── withdraw ──────────────────────────────────────────────────────────────────
 
 #[test]
diff --git a/contracts/streaming/src/test_batch.rs b/contracts/streaming/src/test_batch.rs
index 561f8ff..2b9ef7f 100644
--- a/contracts/streaming/src/test_batch.rs
+++ b/contracts/streaming/src/test_batch.rs
@@ -389,6 +389,35 @@ fn test_batch_self_stream_fails() {
     assert_eq!(result, Err(Ok(StreamError::SelfStream)));
 }
 
+#[test]
+fn test_batch_rejects_past_start_time() {
+    let t = TestEnv::setup();
+    let now = 1_000_000u64;
+    t.set_time(now);
+
+    let r1 = Address::generate(&t.env);
+    let r2 = Address::generate(&t.env);
+    let per_stream = 1_000_0000000i128;
+    t.approve(per_stream * 2);
+
+    let mut inputs: Vec<CreateStreamInput> = Vec::new(&t.env);
+    inputs.push_back(t.make_input(&r1, now));
+    // Second stream backdates its start_time into the past.
+    let mut bad = t.make_input(&r2, now);
+    bad.start_time = now - 1000;
+    bad.end_time = now + 1000;
+    bad.cliff_time = now - 1000;
+    inputs.push_back(bad);
+
+    let result = t.client().try_create_streams_batch(&t.sender, &inputs);
+    assert_eq!(result, Err(Ok(StreamError::PastStartTime)));
+
+    // Atomicity: the valid first stream must not have been created and no
+    // funds may have moved.
+    assert_eq!(t.client().get_sent_streams(&t.sender, &0u32, &100u32).len(), 0);
+    assert_eq!(t.token().balance(&t.contract_id), 0);
+}
+
 // ─── Batch size limits ────────────────────────────────────────────────────────
 
 #[test]