feat(sdk): add skills.define + chat.skills runtime wiring

skills.define({ id, path }) registers a skill with the resource
catalog and returns a SkillHandle. SkillHandle.local() reads the
bundled SKILL.md from ./.trigger/skills/{id}/ at runtime, parses
frontmatter, and returns a ResolvedSkill ready for chat.skills.set().

chat.skills.set([...]) stores resolved skills for the current run.
chat.toStreamTextOptions() auto-injects the skills preamble into the
system prompt and merges three tools — loadSkill, readFile, bash —
scoped per-skill with path-traversal guards and output caps (64 KB
stdout/stderr, 1 MB readFile). Bash executes in the worker container
with the turn's abort signal, no sandbox — skills are developer code.

Shared packages/build/src/internal/copyFiles.ts extracted from the
additionalFiles extension so the CLI's built-in skill bundler and the
existing extension share one glob + copy implementation.

Part 2/3 of Phase 1 for the new ai.skills primitive.

Author: ericallam

packages/build/src/internal.ts

@@ -1 +1,2 @@
 export * from "./internal/additionalFiles.js";
+export * from "./internal/copyFiles.js";

packages/build/src/internal/additionalFiles.ts

@@ -1,8 +1,10 @@
 import { BuildManifest } from "@trigger.dev/core/v3";
 import { BuildContext } from "@trigger.dev/core/v3/build";
-import { copyFile, mkdir } from "node:fs/promises";
-import { dirname, join, posix, relative } from "node:path";
-import { glob } from "tinyglobby";
+import {
+  copyMatcherResults,
+  findFilesByMatchers,
+  type MatcherResult,
+} from "./copyFiles.js";
 
 export type AdditionalFilesOptions = {
   files: string[];
@@ -14,93 +16,21 @@ export async function addAdditionalFilesToBuild(
   context: BuildContext,
   manifest: BuildManifest
 ) {
-  // Copy any static assets to the destination
-  const staticAssets = await findStaticAssetFiles(options.files ?? [], manifest.outputPath, {
-    cwd: context.workingDir,
-  });
+  const matcherResults: MatcherResult[] = await findFilesByMatchers(
+    options.files ?? [],
+    manifest.outputPath,
+    { cwd: context.workingDir }
+  );
 
-  for (const { assets, matcher } of staticAssets) {
+  for (const { assets, matcher } of matcherResults) {
     if (assets.length === 0) {
       context.logger.warn(`[${source}] No files found for matcher`, matcher);
     } else {
       context.logger.debug(`[${source}] Found ${assets.length} files for matcher`, matcher);
     }
   }
 
-  await copyStaticAssets(staticAssets, source, context);
-}
-
-type MatchedStaticAssets = { source: string; destination: string }[];
-
-type FoundStaticAssetFiles = Array<{
-  matcher: string;
-  assets: MatchedStaticAssets;
-}>;
-
-async function findStaticAssetFiles(
-  matchers: string[],
-  destinationPath: string,
-  options?: { cwd?: string; ignore?: string[] }
-): Promise<FoundStaticAssetFiles> {
-  const result: FoundStaticAssetFiles = [];
-
-  for (const matcher of matchers) {
-    const assets = await findStaticAssetsForMatcher(matcher, destinationPath, options);
-
-    result.push({ matcher, assets });
-  }
-
-  return result;
-}
-
-async function findStaticAssetsForMatcher(
-  matcher: string,
-  destinationPath: string,
-  options?: { cwd?: string; ignore?: string[] }
-): Promise<MatchedStaticAssets> {
-  const result: MatchedStaticAssets = [];
-
-  const files = await glob({
-    patterns: [matcher],
-    cwd: options?.cwd,
-    ignore: options?.ignore ?? [],
-    onlyFiles: true,
-    absolute: true,
+  await copyMatcherResults(matcherResults, (pair) => {
+    context.logger.debug(`[${source}] Copying ${pair.source} to ${pair.destination}`);
   });
-
-  let matches = 0;
-
-  for (const file of files) {
-    matches++;
-
-    const pathInsideDestinationDir = relative(options?.cwd ?? process.cwd(), file)
-      .split(posix.sep)
-      .filter((p) => p !== "..")
-      .join(posix.sep);
-
-    const relativeDestinationPath = join(destinationPath, pathInsideDestinationDir);
-
-    result.push({
-      source: file,
-      destination: relativeDestinationPath,
-    });
-  }
-
-  return result;
-}
-
-async function copyStaticAssets(
-  staticAssetFiles: FoundStaticAssetFiles,
-  sourceName: string,
-  context: BuildContext
-): Promise<void> {
-  for (const { assets } of staticAssetFiles) {
-    for (const { source, destination } of assets) {
-      await mkdir(dirname(destination), { recursive: true });
-
-      context.logger.debug(`[${sourceName}] Copying ${source} to ${destination}`);
-
-      await copyFile(source, destination);
-    }
-  }
 }

packages/build/src/internal/copyFiles.ts

@@ -0,0 +1,99 @@
+import { cp, copyFile, mkdir } from "node:fs/promises";
+import { dirname, join, posix, relative } from "node:path";
+import { glob } from "tinyglobby";
+
+/**
+ * A single matched asset — source file and its destination inside the
+ * build output directory.
+ */
+export type CopyPair = { source: string; destination: string };
+
+/**
+ * Result of a single matcher's glob, grouped with the matcher that
+ * produced it so callers can warn on empty matches.
+ */
+export type MatcherResult = {
+  matcher: string;
+  assets: CopyPair[];
+};
+
+/**
+ * Glob a set of matchers relative to `cwd` and return pairs describing
+ * where each matched file should be copied to under `destinationDir`.
+ *
+ * Relative paths are preserved under `destinationDir`. Leading `..`
+ * segments (from `../shared/file.txt` style patterns) are stripped so
+ * files always land inside the destination.
+ */
+export async function findFilesByMatchers(
+  matchers: string[],
+  destinationDir: string,
+  options?: { cwd?: string; ignore?: string[] }
+): Promise<MatcherResult[]> {
+  const result: MatcherResult[] = [];
+  const cwd = options?.cwd ?? process.cwd();
+
+  for (const matcher of matchers) {
+    const files = await glob({
+      patterns: [matcher],
+      cwd,
+      ignore: options?.ignore ?? [],
+      onlyFiles: true,
+      absolute: true,
+    });
+
+    const assets: CopyPair[] = files.map((file) => {
+      const pathInsideDestinationDir = relative(cwd, file)
+        .split(posix.sep)
+        .filter((p) => p !== "..")
+        .join(posix.sep);
+      return {
+        source: file,
+        destination: join(destinationDir, pathInsideDestinationDir),
+      };
+    });
+
+    result.push({ matcher, assets });
+  }
+
+  return result;
+}
+
+/**
+ * Copy a single file, creating parent directories as needed.
+ */
+export async function copyFileEnsuringDir(source: string, destination: string): Promise<void> {
+  await mkdir(dirname(destination), { recursive: true });
+  await copyFile(source, destination);
+}
+
+/**
+ * Copy every pair in the given matcher results. Parent directories are
+ * created automatically. Returns the total number of files copied.
+ */
+export async function copyMatcherResults(
+  matcherResults: MatcherResult[],
+  onCopy?: (pair: CopyPair) => void
+): Promise<number> {
+  let count = 0;
+  for (const { assets } of matcherResults) {
+    for (const pair of assets) {
+      onCopy?.(pair);
+      await copyFileEnsuringDir(pair.source, pair.destination);
+      count++;
+    }
+  }
+  return count;
+}
+
+/**
+ * Recursively copy a directory to another location. Preserves structure;
+ * overwrites existing files at the destination.
+ *
+ * Used by the built-in skill bundler — we copy entire skill folders as a
+ * unit, not file-by-file.
+ */
+export async function copyDirectoryRecursive(source: string, destination: string): Promise<void> {
+  await mkdir(destination, { recursive: true });
+  await cp(source, destination, { recursive: true, force: true });
+}