Method copilotFetchFn

src/node/services/providerModelFactory.ts:1809–1872

(
          input: Parameters<typeof fetch>[0],
          init?: Parameters<typeof fetch>[1]
        )

        const baseFetch = getProviderFetch(providerConfig);
        const copilotFetchFn = async (
          input: Parameters<typeof fetch>[0],
          init?: Parameters<typeof fetch>[1]
        ) => {
          const headers = new Headers(input instanceof Request ? input.headers : undefined);
          if (init?.headers) {
            for (const [key, value] of new Headers(init.headers).entries()) {
              headers.set(key, value);
            }
          }
          headers.set("Authorization", `Bearer ${resolvedApiKey ?? ""}`);
          headers.set("Openai-Intent", "conversation-edits");

          const urlString = getFetchInputUrl(input);

          const method = (
            init?.method ?? (input instanceof Request ? input.method : "GET")
          ).toUpperCase();
          // normalizeCodexResponsesBody() applies only to the stock OpenAI provider's
          // /v1/responses path (used by Codex OAuth). The custom CopilotResponsesLanguageModel
          // posts directly to /responses, intentionally bypassing this normalization.
          const isResponsesRequest = /\/v1\/responses(\?|$)/.test(urlString);

          let nextInit: Parameters<typeof fetch>[1] = { ...init, headers };

          // Resolve request body text for billing classification.
          // Standard AI SDK path: init.body is a JSON string.
          // Request object path: clone + read body text so the original stream
          // remains intact for the real network request.
          let originalBodyText: string | undefined;
          if (typeof init?.body === "string") {
            originalBodyText = init.body;
          } else if (input instanceof Request) {
            try {
              originalBodyText = await input.clone().text();
            } catch {
              // Fall back to undefined so classifyCopilotInitiator defaults to "user".
            }
          }

          if (typeof originalBodyText === "string" && method === "POST" && isResponsesRequest) {
            try {
              const normalizedBody = normalizeCodexResponsesBody(originalBodyText);
              headers.delete("content-length");
              nextInit = {
                ...nextInit,
                headers,
                body: normalizedBody,
              };
            } catch {
              // If body isn't JSON, keep the original request body for Copilot.
            }
          }

          // GitHub Copilot uses X-Initiator to determine premium request billing.
          // "user" = consumes a premium request; "agent" = free (tool/agent work).
          // If the caller explicitly marked this as agent-initiated (e.g., sub-agent,
          // compaction, internal utility), skip the heuristic and always use "agent".