Function resolveModelName

src/node/utils/main/tokenizer.ts:78–119

* Resolves a model string to a ModelName, falling back to a similar model if unknown. * Optionally logs a warning when falling back.

(modelString: string)

 * Optionally logs a warning when falling back.
 */
function resolveModelName(modelString: string): ModelName {
  const normalized = normalizeToCanonical(modelString);
  let modelName = normalizeModelKey(normalized);

  if (!modelName) {
    const provider = normalized.split(":")[0] || "anthropic";

    // GitHub Copilot hosts models from multiple providers.
    // Infer the tokenizer family from the model name prefix.
    let effectiveProvider = provider;
    if (provider === "github-copilot") {
      const modelId = normalized.split(":")[1] || "";
      if (modelId.startsWith("claude-")) {
        effectiveProvider = "anthropic";
      } else if (modelId.startsWith("gemini-")) {
        effectiveProvider = "google";
      } else {
        // gpt-*, grok-*, and unknown models use OpenAI tokenizer
        effectiveProvider = "openai";
      }
    }

    const fallbackModel =
      effectiveProvider === "anthropic"
        ? "anthropic/claude-sonnet-4.5"
        : effectiveProvider === "google"
          ? "google/gemini-2.5-pro"
          : "openai/gpt-5";

    // Only warn once per unknown model to avoid log spam
    if (!warnedModels.has(modelString)) {
      warnedModels.add(modelString);
      log.warn(
        `Unknown model '${modelString}', using ${fallbackModel} tokenizer for approximate token counting`
      );
    }

    modelName = fallbackModel as ModelName;
  }

  return modelName;
}

function resolveEncoding(modelName: ModelName): Promise<string> {
  let promise = encodingPromises.get(modelName);