test(ai): cover copilot claude messages routing + headers

packages/ai/test/transform-messages-copilot-openai-to-anthropic.test.ts

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+import { describe, expect, it } from "vitest";
+import { transformMessages } from "../src/providers/transform-messages.js";
+import type { AssistantMessage, Message, Model, ToolCall } from "../src/types.js";
+
+// Normalize function matching what anthropic.ts uses
+function anthropicNormalizeToolCallId(id: string): string {
+	return id.replace(/[^a-zA-Z0-9_-]/g, "_").slice(0, 64);
+}
+
+function makeCopilotClaudeModel(): Model<"anthropic-messages"> {
+	return {
+		id: "claude-sonnet-4",
+		name: "Claude Sonnet 4",
+		api: "anthropic-messages",
+		provider: "github-copilot",
+		baseUrl: "https://api.individual.githubcopilot.com",
+		reasoning: true,
+		input: ["text", "image"],
+		cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0 },
+		contextWindow: 128000,
+		maxTokens: 16000,
+	};
+}
+
+describe("OpenAI to Anthropic session migration for Copilot Claude", () => {
+	it("converts thinking blocks to plain text when source model differs", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			{ role: "user", content: "hello", timestamp: Date.now() },
+			{
+				role: "assistant",
+				content: [
+					{
+						type: "thinking",
+						thinking: "Let me think about this...",
+						thinkingSignature: "reasoning_content",
+					},
+					{ type: "text", text: "Hi there!" },
+				],
+				api: "openai-completions",
+				provider: "github-copilot",
+				model: "gpt-4o",
+				usage: {
+					input: 0,
+					output: 0,
+					cacheRead: 0,
+					cacheWrite: 0,
+					totalTokens: 0,
+					cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+				},
+				stopReason: "stop",
+				timestamp: Date.now(),
+			},
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+		const assistantMsg = result.find((m) => m.role === "assistant") as AssistantMessage;
+
+		// Thinking block should be converted to text since models differ
+		const textBlocks = assistantMsg.content.filter((b) => b.type === "text");
+		const thinkingBlocks = assistantMsg.content.filter((b) => b.type === "thinking");
+		expect(thinkingBlocks).toHaveLength(0);
+		expect(textBlocks.length).toBeGreaterThanOrEqual(2);
+	});
+
+	it("normalizes tool call IDs with disallowed characters", () => {
+		const model = makeCopilotClaudeModel();
+		const toolCallId = "call_abc+123/def=456|some_very_long_id_that_exceeds_limits";
+		const messages: Message[] = [
+			{ role: "user", content: "run a command", timestamp: Date.now() },
+			{
+				role: "assistant",
+				content: [
+					{
+						type: "toolCall",
+						id: toolCallId,
+						name: "bash",
+						arguments: { command: "ls" },
+					},
+				],
+				api: "openai-completions",
+				provider: "github-copilot",
+				model: "gpt-4o",
+				usage: {
+					input: 0,
+					output: 0,
+					cacheRead: 0,
+					cacheWrite: 0,
+					totalTokens: 0,
+					cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+				},
+				stopReason: "toolUse",
+				timestamp: Date.now(),
+			},
+			{
+				role: "toolResult",
+				toolCallId,
+				toolName: "bash",
+				content: [{ type: "text", text: "file1.txt\nfile2.txt" }],
+				isError: false,
+				timestamp: Date.now(),
+			},
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+
+		// Get the normalized tool call ID
+		const assistantMsg = result.find((m) => m.role === "assistant") as AssistantMessage;
+		const toolCall = assistantMsg.content.find((b) => b.type === "toolCall") as ToolCall;
+		const normalizedId = toolCall.id;
+
+		// Verify it only has allowed characters and is <= 64 chars
+		expect(normalizedId).toMatch(/^[a-zA-Z0-9_-]+$/);
+		expect(normalizedId.length).toBeLessThanOrEqual(64);
+
+		// Verify tool result references the normalized ID
+		const toolResultMsg = result.find((m) => m.role === "toolResult");
+		expect(toolResultMsg).toBeDefined();
+		if (toolResultMsg && toolResultMsg.role === "toolResult") {
+			expect(toolResultMsg.toolCallId).toBe(normalizedId);
+		}
+	});
+
+	it("removes thoughtSignature from tool calls when migrating between models", () => {
+		const model = makeCopilotClaudeModel();
+		const messages: Message[] = [
+			{ role: "user", content: "run a command", timestamp: Date.now() },
+			{
+				role: "assistant",
+				content: [
+					{
+						type: "toolCall",
+						id: "call_123",
+						name: "bash",
+						arguments: { command: "ls" },
+						thoughtSignature: JSON.stringify({ type: "reasoning.encrypted", id: "call_123", data: "encrypted" }),
+					},
+				],
+				api: "openai-responses",
+				provider: "github-copilot",
+				model: "gpt-5",
+				usage: {
+					input: 0,
+					output: 0,
+					cacheRead: 0,
+					cacheWrite: 0,
+					totalTokens: 0,
+					cost: { input: 0, output: 0, cacheRead: 0, cacheWrite: 0, total: 0 },
+				},
+				stopReason: "toolUse",
+				timestamp: Date.now(),
+			},
+			{
+				role: "toolResult",
+				toolCallId: "call_123",
+				toolName: "bash",
+				content: [{ type: "text", text: "output" }],
+				isError: false,
+				timestamp: Date.now(),
+			},
+		];
+
+		const result = transformMessages(messages, model, anthropicNormalizeToolCallId);
+		const assistantMsg = result.find((m) => m.role === "assistant") as AssistantMessage;
+		const toolCall = assistantMsg.content.find((b) => b.type === "toolCall") as ToolCall;
+
+		expect(toolCall.thoughtSignature).toBeUndefined();
+	});
+});