[V1][BugFix] Fix EAGLE3 encoder cache miss with disable_chunked_mm_input (#34220)

Signed-off-by: KrxGu <krishom70@gmail.com>

tests/v1/core/test_scheduler.py

@@ -3675,3 +3675,72 @@ def test_abort_request_finished_recving():
     # verify request is deleted
     assert request.request_id not in scheduler.requests
     assert not scheduler.finished_recving_kv_req_ids
+
+
+def test_eagle3_mm_encoder_cache_with_shift():
+    """Test EAGLE3 encoder scheduling accounts for shift_computed_tokens.
+
+    Regression test for issue #32469: When EAGLE3 is enabled with
+    disable_chunked_mm_input=True, ensure encoder inputs are scheduled
+    when tokens overlap the MM range, properly accounting for
+    shift_computed_tokens in the boundary calculation.
+
+    Without the fix, the scheduler would fail to schedule encoder inputs
+    at the boundary, causing "Encoder cache miss" errors.
+    """
+    scheduler = create_scheduler(
+        model="llava-hf/llava-1.5-7b-hf",
+        max_num_batched_tokens=1024,
+        disable_chunked_mm_input=True,
+        max_model_len=2048,
+        num_speculative_tokens=4,  # This enables EAGLE with shift=1
+    )
+
+    mm_start_pos = 100
+    mm_length = 576
+
+    mm_positions = [
+        [PlaceholderRange(offset=mm_start_pos, length=mm_length)],
+    ]
+
+    requests = create_requests(
+        num_requests=1,
+        num_tokens=mm_start_pos + mm_length + 100,
+        mm_positions=mm_positions,
+    )
+
+    # Start with some tokens already computed to simulate decoding
+    request = requests[0]
+    request.num_computed_tokens = 0
+
+    scheduler.add_request(request)
+    output = scheduler.schedule()
+
+    assert output is not None
+    shift_computed_tokens = 1
+    req_id = request.request_id
+
+    assert req_id in output.num_scheduled_tokens
+    num_scheduled = output.num_scheduled_tokens[req_id]
+
+    mm_feature = request.mm_features[0]
+    start_pos = mm_feature.mm_position.offset
+    tokens_end = request.num_computed_tokens + num_scheduled
+    scheduled_end_with_shift = tokens_end + shift_computed_tokens
+
+    # Assert that we scheduled into the MM range (test setup verification)
+    assert scheduled_end_with_shift > start_pos, (
+        f"Test setup error: expected to schedule into MM range. "
+        f"scheduled_end_with_shift={scheduled_end_with_shift}, "
+        f"start_pos={start_pos}"
+    )
+
+    # The key assertion: when scheduled tokens overlap MM range
+    # (accounting for EAGLE's shift), encoder MUST be scheduled.
+    # Without the fix, this would fail at the boundary case.
+    assert req_id in output.scheduled_encoder_inputs, (
+        f"Encoder input missing: scheduled {num_scheduled} tokens "
+        f"(computed={request.num_computed_tokens}, end={tokens_end}, "
+        f"shifted_end={scheduled_end_with_shift}) overlapping MM at "
+        f"{start_pos}. The fix must schedule encoder inputs."
+    )

vllm/v1/core/sched/scheduler.py

@@ -1155,7 +1155,12 @@ class Scheduler(SchedulerInterface):
                 and (num_computed_tokens + num_new_tokens)
                 < (start_pos + num_encoder_tokens)
             ):
-                num_new_tokens = start_pos - num_computed_tokens
+                # Account for EAGLE shift when rolling back to avoid
+                # encoder cache miss. This ensures the scheduled range
+                # stops before start_pos even with the shift.
+                num_new_tokens = max(
+                    0, start_pos - (num_computed_tokens + shift_computed_tokens)
+                )
                 break
             if not self.encoder_cache_manager.can_allocate(
                 request, i, encoder_compute_budget, num_embeds_to_schedule