[Bug]: try_parse_json_object turns backslash escapes into spaces when valid JSON comes in a code fence or after a sentence

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Evaluación

Dificultad
2/5
Tiempo estimado
1-3 horas
Aptitud para principiantes
74/100
Tipo de issue
Error
Claridad
Bien especificado
Estado de actividad
Activo
Stack tecnológico
python
Área
ai

Línea de trabajo

Empieza en packages/graphrag/graphrag/query/llm/text_utils.py en try_parse_json_object, donde el fragmento desde el primer { hasta el último } pasa por la limpieza de barras invertidas con .replace antes de cualquier comprobación de validez. Ejecuta el script de reproducción del issue para confirmar que line1\nline2 devuelve line1 nline2, y comprueba que GlobalSearch._parse_search_response en el search.py de la búsqueda global muestra el mismo daño. Está terminado cuando el JSON válido recortado conserva sus escapes, la entrada inválida sigue pasando por la limpieza antigua y por json_repair, y una prueba de regresión cubre respuestas con cercas de código y con prefijos.

Escrito por el modelo de indexación a partir del texto del issue.

Descripción

Do you need to file an issue?
  • I have searched the existing issues and this bug is not already filed.
  • My model is hosted on OpenAI or Azure. If not, please look at the "model providers" issue and don't file a new one here.
  • I believe this is a legitimate bug, not just a question. If this is a question, please use the Discussions area.
Describe the bug

try_parse_json_object in packages/graphrag/graphrag/query/llm/text_utils.py first calls json.loads on the whole response. If the model wraps valid JSON in a markdown fence or puts a sentence before it, that call fails. The function then cuts out the text from the first { to the last } and runs a cleanup chain on it. One step of that chain is .replace("\\", " "). It runs before anything checks whether the cut-out text is already valid JSON.

So every escape inside a string value is broken, even though the cut-out text was valid:

  • \n becomes a space and the letter n. line1\nline2 comes back as line1 nline2.
  • \" becomes a space and a quote. He said \"hi\" today comes back as He said "hi " today.
  • \\ becomes two spaces. C:\\data\\x.txt comes back as C: data x.txt.
  • \t, \r and \u00e9 are broken the same way.

The same JSON without the fence parses correctly, because the first json.loads succeeds.

This function parses model output in three query paths:

  • the global search map step, GlobalSearch._parse_search_response (the description text of each key point)
  • rate_relevancy in dynamic community selection
  • DRIFT, DriftAction.search (the response text and follow_up_queries)

Map and DRIFT answers are markdown, so they often contain \n. A fenced map response is a real case: #1173 shows gemma2 on ollama returning the map response inside a ```json fence. Also, #2625 shows that response_format_json_object=True does not reach the model on main, and it reports that Qwen and Mistral on vLLM sometimes answer with prose around the JSON. I did not find a trace from OpenAI or Azure, so this mostly affects local and other non-JSON-mode providers.

Back in #801 a maintainer review asked for a json.loads check first, so valid JSON would skip the string cleanup (done in #834). That check only covers the whole response. It does not cover the object cut out of a fenced or prefixed response.

Steps to reproduce

No model is needed. With graphrag installed from main:

import json

from graphrag.query.llm.text_utils import try_parse_json_object
from graphrag.query.structured_search.global_search.search import GlobalSearch

BS = "\\"
raw = "```json\n" + '{"d": "line1' + BS + 'nline2"}' + "\n```"
expected = json.loads(raw[raw.index("{") : raw.rindex("}") + 1])
_, got = try_parse_json_object(raw, verbose=False)
print("expected:", repr(expected))
print("got:     ", repr(got))

map_raw = (
    "```json\n"
    + '{"points": [{"description": "first line' + BS + 'nsecond line, said '
    + BS + '"ok' + BS + '"", "score": 80}]}'
    + "\n```"
)
print(GlobalSearch._parse_search_response(None, map_raw))
Expected Behavior

When the cut-out object is already valid JSON, it should be returned as parsed. The cleanup and json_repair should only run when it is not valid.

Expected output:

expected: {'d': 'line1\nline2'}
got:      {'d': 'line1\nline2'}
[{'answer': 'first line\nsecond line, said "ok"', 'score': 80}]
GraphRAG Config Used
# Not needed. The reproduction calls the parser directly and uses no settings file.
Logs and screenshots

Output on main:

expected: {'d': 'line1\nline2'}
got:      {'d': 'line1 nline2'}
[{'answer': 'first line nsecond line, said  "ok "', 'score': 80}]
Additional Information
  • GraphRAG Version: 3.3.0 (main at 34b2b67)
  • Operating System: Windows 11
  • Python Version: 3.13
  • Related Issues: #1173 (fenced map response from gemma2 on ollama, fixed the regex then). #2625 (JSON mode is not sent to the model). Point 2 of #2625 also shows the backslash cleanup splitting single-quoted follow-up queries at \'. That input is not valid JSON, so the fix below does not change it.
  • I have a small fix with a regression test. After the cut-out step it tries json.loads and returns the result when it is a non-empty dict. Everything else still goes through the old cleanup path. I will open a PR that references this issue.

Validated with Claude Opus 5.5.

Lenguaje dominante
Python
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Forks
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Merge medio
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PR fusionados (30 d)
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