Normalize skill context snapshots (#1269)

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: stephentoub

test/harness/replayingCapiProxy.test.ts

@@ -370,6 +370,45 @@ describe("ReplayingCapiProxy", () => {
     expect(result.conversations[0].messages[0].content).toBe("Say hello.");
   });
 
+  test("strips skill metadata frontmatter from skill-context user messages", async () => {
+    const skillDir = path.join(workDir, ".test_skills", "test-skill");
+    const requestBody = JSON.stringify({
+      messages: [
+        {
+          role: "user",
+          content: `<skill-context name="test-skill">
+Base directory for this skill: ${skillDir}
+
+---
+name: test-skill
+description: A test skill that adds a marker to responses
+---
+
+# Test Skill Instructions
+
+Always include PINEAPPLE_COCONUT_42.
+</skill-context>`,
+        },
+      ],
+    });
+    const responseBody = JSON.stringify({
+      choices: [{ message: { role: "assistant", content: "OK!" } }],
+    });
+
+    const outputPath = await createProxy([
+      { url: "/chat/completions", requestBody, responseBody },
+    ]);
+
+    const result = await readYamlOutput(outputPath);
+    expect(result.conversations[0].messages[0].content).toBe(`<skill-context name="test-skill">
+Base directory for this skill: ${workingDirPlaceholder}/.test_skills/test-skill
+
+# Test Skill Instructions
+
+Always include PINEAPPLE_COCONUT_42.
+</skill-context>`);
+  });
+
   test("applies tool result normalizers to tool response content", async () => {
     const requestBody = JSON.stringify({
       messages: [

test/harness/replayingCapiProxy.ts

@@ -1032,7 +1032,7 @@ function transformOpenAIRequestMessage(
 }
 
 function normalizeUserMessage(content: string): string {
-  return content
+  return normalizeSkillContextFrontmatter(content)
     .replace(/<current_datetime>.*?<\/current_datetime>/g, "")
     .replace(/<reminder>[\s\S]*?<\/reminder>/g, "")
     .replace(/<system_reminder>[\s\S]*?<\/system_reminder>/g, "")
@@ -1044,6 +1044,14 @@ function normalizeUserMessage(content: string): string {
     .trim();
 }
 
+function normalizeSkillContextFrontmatter(content: string): string {
+  // Runtime versions may include or omit SKILL.md metadata in the prompt context.
+  return content.replace(
+    /(<skill-context\b[^>]*>\s*Base directory for this skill:[^\r\n]*(?:\r?\n)+)---\r?\n(?:(?!<\/skill-context>)[\s\S])*?\r?\n---(?:\r?\n)+/g,
+    "$1",
+  );
+}
+
 function normalizeLargeOutputFilepaths(result: string): string {
   // Replaces filenames like 1774637043987-copilot-tool-output-tk7puw.txt with PLACEHOLDER-copilot-tool-output-PLACEHOLDER
   return result

test/snapshots/skills/should_load_and_apply_skill_from_skilldirectories.yaml

@@ -23,15 +23,6 @@ conversations:
           Base directory for this skill: ${workdir}/.test_skills/test-skill
 
 
-          ---
-
-          name: test-skill
-
-          description: A test skill that adds a marker to responses
-
-          ---
-
-
           # Test Skill Instructions