dotnet/orleans · error · ArgumentException

Input is not in a valid format: Encountered unsupported esca

Error message

Input is not in a valid format: Encountered unsupported escape sequence

What it means

Thrown by CosmosIdSanitizer when decoding a previously-sanitized identifier: an escape character is followed by a replacement character that is not in the known ReplacementCharacters set. This means the input is not a string produced by this sanitizer.

Source

Thrown at src/Azure/Shared/Cosmos/CosmosIdSanitizer.cs:85

        }

        if (count == 0)
        {
            return input;
        }

        return string.Create(input.Length - count, input, static (output, input) =>
        {
            var i = 0;
            var isEscaped = false;
            foreach (var c in input)
            {
                if (isEscaped)
                {
                    var charId = ReplacementCharacters.IndexOf(c);
                    if (charId < 0)
                    {
                        throw new ArgumentException($"Input is not in a valid format: Encountered unsupported escape sequence");
                    }

                    output[i++] = SanitizedCharacters[charId];
                    isEscaped = false;
                }
                else if (c == EscapeChar)
                {
                    isEscaped = true;
                }
                else
                {
                    output[i++] = c;
                }
            }
        });
    }
}

View on GitHub (pinned to fca799fa70)

Solutions

1. Only pass ids that were produced by the sanitizer's encode path to the decode path.
2. If the id is user-supplied, run it through the encode (sanitize) direction first.
3. Avoid constructing ids containing the escape character manually.

Example fix

// before
var raw = "grain|weird"; // contains sanitizer escape-like sequence
sanitizer.Decode(raw);

// after
var encoded = sanitizer.Encode(userInput); // round-trip safe
sanitizer.Decode(encoded);

var encoded = sanitizer.Encode(input); // only ever decode encoded output
var decoded = sanitizer.Decode(encoded);

static bool LooksSanitized(string? s) => s is not null && s.IndexOf(EscapeChar) >= 0;

When it happens

Trigger: Calling the sanitizer's decode path on a hand-authored or externally-produced id that contains the escape char followed by an unexpected character.

Common situations: Manually constructing grain ids or Cosmos partition keys that resemble sanitized ids but were never actually sanitized; mixing sanitized and raw ids; a schema change in the sanitizer's escape set across versions.

Related errors

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• Configuration for AzureBlobStorageOptions {name} is invalid.

AI-assisted analysis of dotnet/orleans@fca799fa70 (2026-08-13). Data as JSON: /api/errors/ee16a4de50ea5282. Report an issue: GitHub.