diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f4e67b..2fe4e33 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,7 @@ Full release notes with details on each version: [GitHub Releases](https://githu
 ## Unreleased
 
 - Fix: `--update`-style section writes to `CLAUDE.md`/`AGENTS.md` no longer corrupt or drop content (#1688, thanks @bdfinst). `_replace_or_append_section` located its managed block by substring (`marker in content`) and `next(... if marker in line)`, so a heading that appeared as a substring of another line (or duplicate headings) matched the wrong offset and the rewrite could truncate the file. It now matches the section heading exactly (`line.strip() == marker`), appends when absent, and prefers the last exact match when several exist, so unrelated content is preserved.
+- Fix: token estimation no longer crashes on files containing tiktoken special-token text like `<|endoftext|>` (#1685, thanks @Kyzcreig). `_TOKENIZER.encode(content)` raises `ValueError` by default when the text contains a special token, which aborted packing on docs/corpora that merely mention these strings. Both `encode` sites now pass `disallowed_special=()` so such text is tokenized as ordinary bytes.
 
 ## 0.9.7 (2026-07-06)
 
diff --git a/graphify/llm.py b/graphify/llm.py
index 16644e6..62dd4b6 100644
--- a/graphify/llm.py
+++ b/graphify/llm.py
@@ -1507,7 +1507,7 @@ def _estimate_file_tokens(unit: "Path | FileSlice") -> int:
             content = read_slice_text(unit)[:_FILE_CHAR_CAP]
         except OSError:
             return 0
-        return len(_TOKENIZER.encode(content)) + (_PER_FILE_OVERHEAD_CHARS // _CHARS_PER_TOKEN)
+        return len(_TOKENIZER.encode(content, disallowed_special=())) + (_PER_FILE_OVERHEAD_CHARS // _CHARS_PER_TOKEN)
 
     path = unit
     # Raster images are not read as text; a vision model bills them at a roughly
@@ -1526,7 +1526,7 @@ def _estimate_file_tokens(unit: "Path | FileSlice") -> int:
         content = path.read_text(encoding="utf-8", errors="replace")[:_FILE_CHAR_CAP]
     except OSError:
         return 0
-    return len(_TOKENIZER.encode(content)) + (_PER_FILE_OVERHEAD_CHARS // _CHARS_PER_TOKEN)
+    return len(_TOKENIZER.encode(content, disallowed_special=())) + (_PER_FILE_OVERHEAD_CHARS // _CHARS_PER_TOKEN)
 
 
 def _pack_chunks_by_tokens(
diff --git a/tests/test_chunking.py b/tests/test_chunking.py
index 21b28ee..2706dfd 100644
--- a/tests/test_chunking.py
+++ b/tests/test_chunking.py
@@ -118,7 +118,9 @@ def test_estimate_file_tokens_uses_tiktoken_when_available(tmp_path):
 
     # Force the tokenizer to be a mock that records calls and returns a known
     # token list, so we can assert the tiktoken path is taken.
-    fake_encoder = type("E", (), {"encode": staticmethod(lambda s: [0] * 999)})()
+    # Match tiktoken's real signature: encode(text, *, disallowed_special=...)
+    # so the #1685 hardening call (disallowed_special=()) reaches the mock.
+    fake_encoder = type("E", (), {"encode": staticmethod(lambda s, **kw: [0] * 999)})()
     with patch.object(llm, "_TOKENIZER", fake_encoder):
         n = llm._estimate_file_tokens(f)
     assert n == 999 + (llm._PER_FILE_OVERHEAD_CHARS // llm._CHARS_PER_TOKEN)
@@ -497,3 +499,30 @@ def test_corpus_parallel_uses_adaptive_retry(tmp_path):
     assert len(chunk_done_args) == 1
     assert chunk_done_args[0] == (0, 1, 4)
     assert len(result["nodes"]) == 4
+
+
+# ---- #1685: special-token strings in docs must not crash token estimation ----
+
+def test_estimate_file_tokens_handles_tiktoken_special_token(tmp_path):
+    """A doc containing a literal tiktoken special token (e.g. <|endoftext|>)
+    must not crash token estimation. tiktoken's default encode() raises on such
+    strings appearing as ordinary text; we pass disallowed_special=() since this
+    is only an estimate (#1685)."""
+    import graphify.llm as llm
+    if llm._TOKENIZER is None:
+        import pytest
+        pytest.skip("tiktoken not installed; estimation uses the char heuristic")
+    f = tmp_path / "tokenizer-notes.md"
+    f.write_text("The GPT end-of-text token is <|endoftext|> in the vocab.\n")
+    n = llm._estimate_file_tokens(f)  # must not raise
+    assert isinstance(n, int) and n > 0
+
+
+def test_pack_chunks_with_special_token_doc_does_not_crash(tmp_path):
+    """End to end: packing a corpus that includes a special-token doc must not
+    raise (the crash in #1685 happened during token-budget packing)."""
+    from graphify.llm import _pack_chunks_by_tokens
+    doc = tmp_path / "doc.md"; doc.write_text("see <|endoftext|> and <|im_start|> tokens\n")
+    code = tmp_path / "code.py"; code.write_text("def f():\n    return 1\n")
+    chunks = _pack_chunks_by_tokens([doc, code], token_budget=60_000)
+    assert chunks  # produced at least one chunk, no exception