{"record":{"id":"f2919346d4941872","repo":"dotnet/machinelearning","slug":"could-not-find-the-merges-file-mergesfile","errorCode":null,"errorMessage":"Could not find the merges file '{mergesFile}'.","messagePattern":"Could not find the merges file '(.+?)'\\.","errorType":"exception","errorClass":"ArgumentException","httpStatus":null,"severity":"error","filePath":"src/Microsoft.ML.Tokenizers/Model/BpeOptions.cs","lineNumber":63,"sourceCode":"            {\n                throw new ArgumentException($\"Could not find the vocabulary file '{vocabFile}'.\");\n            }\n\n            using Stream vocabStream = File.OpenRead(vocabFile);\n            Dictionary<string, int>? dictionary = JsonSerializer.Deserialize<Dictionary<string, int>>(vocabStream);\n\n            if (dictionary is null)\n            {\n                throw new InvalidOperationException($\"The content of the vocabulary file '{vocabFile}' is not valid.\");\n            }\n\n            Vocabulary = dictionary;\n\n            if (mergesFile is not null)\n            {\n                if (!File.Exists(mergesFile))\n                {\n                    throw new ArgumentException($\"Could not find the merges file '{mergesFile}'.\");\n                }\n\n                using Stream mergesStream = File.OpenRead(mergesFile);\n                using StreamReader reader = new(mergesStream);\n\n                List<string> merges = new();\n\n                int lineNumber = 0;\n                string? line;\n\n                while ((line = reader.ReadLine()) is not null)\n                {\n                    lineNumber++;\n                    if (line.StartsWith(\"#version\", StringComparison.Ordinal) || line.Length == 0)\n                    {\n                        continue;\n                    }\n","sourceCodeStart":45,"sourceCodeEnd":81,"githubUrl":"https://github.com/dotnet/machinelearning/blob/7b76e69cf964daeca3f1377af6bc5543284d56c6/src/Microsoft.ML.Tokenizers/Model/BpeOptions.cs#L45-L81","documentation":"When a mergesFile path is supplied (it is optional), BpeOptions verifies it exists and throws ArgumentException if not. The merges file contains the BPE token-pair merge rules and is required for correct BPE encoding, so a supplied-but-missing file is rejected immediately.","triggerScenarios":"new BpeOptions(\"vocab.json\", \"merges.txt\") where merges.txt is missing; passing a merges path from config where the file was never deployed; confusing the merges file name (some models ship merges.txt, others merges-model.txt).","commonSituations":"Only the vocab was downloaded from the model repo but the merges file was skipped; wrong relative path when app runs from a different working directory; renaming of asset files during deployment.","solutions":["Verify merges.txt exists at the exact path with File.Exists before constructing BpeOptions.","Download both vocab.json and merges.txt from the same model release so they are consistent.","Use an absolute or AppContext.BaseDirectory-relative path for the merges file.","If you truly do not need merges, pass null (the default) rather than a path to a missing file."],"exampleFix":"// before\nvar options = new BpeOptions(vocabPath, \"merges.txt\");\n// after\nstring mergesPath = Path.Combine(AppContext.BaseDirectory, \"models\", \"merges.txt\");\nif (!File.Exists(mergesPath)) throw new FileNotFoundException(\"BPE merges file missing\", mergesPath);\nvar options = new BpeOptions(vocabPath, mergesPath);","handlingStrategy":"validation","validationCode":"if (!File.Exists(mergesPath)) throw new FileNotFoundException(\"BPE merges file not found\", mergesPath);","typeGuard":null,"tryCatchPattern":"try { var options = new BpeOptions(vocabPath, mergesPath); } catch (ArgumentException ex) { logger.LogError(ex, \"Merges file missing at {Path}\", mergesPath); }","preventionTips":["Download vocab and merges together from the same model release","Keep model asset paths in one config section validated at startup","Pass null explicitly when merges are intentionally omitted"],"tags":["csharp","file-path","tokenizer"],"backgroundTag":"file-not-found","analyzedSha":"7b76e69cf964daeca3f1377af6bc5543284d56c6","analyzedAt":"2026-09-11T12:35:38.930Z","contentChangedAt":"2026-09-11T12:35:38.930Z","schemaVersion":2},"datasetVersion":"2026-09-23T08:17:48.524Z"}