diff --git a/CHANGELOG.md b/CHANGELOG.md
index b7d81603..0a736c4f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,6 +1,10 @@
 # Changelog
 ## [Unreleased]
 
+### Fixed
+
+- **Citation formatting**: Replace raw UUIDs (`[doc_id:chunk_id]`) with human-readable identifiers (`[index] title`) in `format_citations()` output, preventing LLMs from hallucinating opaque ID markers in answers
+
 ## [0.36.2] - 2026-03-28
 
 ### Fixed
diff --git a/haiku_rag_slim/haiku/rag/utils.py b/haiku_rag_slim/haiku/rag/utils.py
index 43f82f05..c7d554ec 100644
--- a/haiku_rag_slim/haiku/rag/utils.py
+++ b/haiku_rag_slim/haiku/rag/utils.py
@@ -338,9 +338,10 @@ def format_citations(citations: "list[Citation]") -> str:
 
     lines = ["## Citations\n"]
 
-    for c in citations:
-        # Header line
-        header = f"[{c.document_id}:{c.chunk_id}]"
+    for i, c in enumerate(citations):
+        idx = c.index if c.index is not None else (i + 1)
+        title = c.document_title or c.document_uri
+        header = f"[{idx}] {title}"
 
         # Location info
         location_parts = []
@@ -353,8 +354,6 @@ def format_citations(citations: "list[Citation]") -> str:
             location_parts.append(f"Section: {c.headings[-1]}")
 
         source = c.document_uri
-        if c.document_title:
-            source = f"{c.document_title} ({c.document_uri})"
         if location_parts:
             source += f" - {', '.join(location_parts)}"
 
diff --git a/tests/test_utils.py b/tests/test_utils.py
index fc9d52d9..f598163a 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -475,8 +475,10 @@ def test_format_citations_with_citation():
         headings=["Intro"],
     )
     result = format_citations([citation])
-    assert "[doc1:chunk1]" in result
-    assert "Test Doc" in result
+    assert "[1] Test Doc" in result
+    assert "doc1" not in result
+    assert "chunk1" not in result
+    assert "test://doc" in result
     assert "p. 1" in result
     assert "Section: Intro" in result
     assert "Some content" in result
@@ -494,6 +496,7 @@ def test_format_citations_multiple_pages():
         page_numbers=[1, 2, 3],
     )
     result = format_citations([citation])
+    assert "[1] test://doc" in result
     assert "pp. 1-3" in result
 
 
@@ -508,7 +511,49 @@ def test_format_citations_no_title():
         content="Content",
     )
     result = format_citations([citation])
-    assert "test://doc" in result
+    assert "[1] test://doc" in result
+    assert "doc1" not in result
+
+
+def test_format_citations_with_index():
+    from haiku.rag.agents.research.models import Citation
+    from haiku.rag.utils import format_citations
+
+    citation = Citation(
+        index=5,
+        document_id="doc1",
+        chunk_id="chunk1",
+        document_uri="test://doc",
+        document_title="Test Doc",
+        content="Content",
+    )
+    result = format_citations([citation])
+    assert "[5] Test Doc" in result
+
+
+def test_format_citations_sequential_indices():
+    from haiku.rag.agents.research.models import Citation
+    from haiku.rag.utils import format_citations
+
+    citations = [
+        Citation(
+            document_id="doc1",
+            chunk_id="chunk1",
+            document_uri="test://doc1",
+            document_title="First",
+            content="Content 1",
+        ),
+        Citation(
+            document_id="doc2",
+            chunk_id="chunk2",
+            document_uri="test://doc2",
+            document_title="Second",
+            content="Content 2",
+        ),
+    ]
+    result = format_citations(citations)
+    assert "[1] First" in result
+    assert "[2] Second" in result
 
 
 # --- format_citations_rich tests ---