diff --git a/packages/build/src/internal.ts b/packages/build/src/internal.ts
index 54f785a61..0e1954c8b 100644
--- a/packages/build/src/internal.ts
+++ b/packages/build/src/internal.ts
@@ -1 +1,2 @@
 export * from "./internal/additionalFiles.js";
+export * from "./internal/copyFiles.js";
diff --git a/packages/build/src/internal/additionalFiles.ts b/packages/build/src/internal/additionalFiles.ts
index a815b53c9..57a746c36 100644
--- a/packages/build/src/internal/additionalFiles.ts
+++ b/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[];
@@ -14,12 +16,13 @@ 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 {
@@ -27,80 +30,7 @@ export async function addAdditionalFilesToBuild(
     }
   }
 
-  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);
-    }
-  }
 }
diff --git a/packages/build/src/internal/copyFiles.ts b/packages/build/src/internal/copyFiles.ts
new file mode 100644
index 000000000..6fd3ede95
--- /dev/null
+++ b/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 });
+}
diff --git a/packages/trigger-sdk/src/v3/ai.ts b/packages/trigger-sdk/src/v3/ai.ts
index 398ef7db7..8f1a9d34c 100644
--- a/packages/trigger-sdk/src/v3/ai.ts
+++ b/packages/trigger-sdk/src/v3/ai.ts
@@ -43,6 +43,10 @@ import { auth } from "./auth.js";
 import { locals } from "./locals.js";
 import { metadata } from "./metadata.js";
 import type { ResolvedPrompt } from "./prompt.js";
+import type { ResolvedSkill } from "./skill.js";
+import { spawn } from "node:child_process";
+import * as fs from "node:fs/promises";
+import * as nodePath from "node:path";
 import { streams } from "./streams.js";
 import { createTask, trigger as triggerTaskInternal } from "./shared.js";
 import { resourceCatalog } from "@trigger.dev/core/v3";
@@ -1756,6 +1760,212 @@ function getChatPrompt(): ChatPromptValue {
   return prompt;
 }
 
+// ---------------------------------------------------------------------------
+// chat.skills — store resolved agent skills and inject them into streamText
+// ---------------------------------------------------------------------------
+
+/** @internal */
+const chatSkillsKey = locals.create<ResolvedSkill[]>("chat.skills");
+
+/** Limits applied by the auto-injected `loadSkill` / `readFile` / `bash` tools. */
+const DEFAULT_READ_FILE_BYTES = 1024 * 1024; // 1 MB
+const DEFAULT_BASH_OUTPUT_BYTES = 64 * 1024; // 64 KB
+
+/**
+ * Store resolved skills for the current run. Call from any hook
+ * (`onPreload`, `onChatStart`, `onTurnStart`) or `run()`.
+ */
+function setChatSkills(skills: ResolvedSkill[]): void {
+  locals.set(chatSkillsKey, skills);
+}
+
+/** Read the stored skills. Returns `undefined` if none set. */
+function getChatSkills(): ResolvedSkill[] | undefined {
+  return locals.get(chatSkillsKey);
+}
+
+/**
+ * Build the system-prompt preamble advertising available skills. Only the
+ * frontmatter description surfaces here — full SKILL.md body is loaded
+ * on-demand via the `loadSkill` tool.
+ */
+function buildSkillsSystemPrompt(skills: ResolvedSkill[]): string {
+  if (skills.length === 0) return "";
+  const lines = skills.map(
+    (s) => `- ${s.frontmatter.name}: ${s.frontmatter.description}`
+  );
+  return [
+    "Available skills (call `loadSkill` to read the full instructions before using one):",
+    ...lines,
+  ].join("\n");
+}
+
+function truncate(s: string, limit: number): string {
+  if (s.length <= limit) return s;
+  return s.slice(0, limit) + `\n…[truncated ${s.length - limit} bytes]`;
+}
+
+/** Resolve a skill by its frontmatter `name`. */
+function findSkillByName(skills: ResolvedSkill[], name: string): ResolvedSkill | undefined {
+  return skills.find((s) => s.frontmatter.name === name);
+}
+
+/**
+ * Check that `candidate` resolves inside `root` — guards against path
+ * traversal via `..` or absolute paths. Returns the resolved path or
+ * throws.
+ */
+function safeJoinInside(root: string, relative: string): string {
+  if (nodePath.isAbsolute(relative)) {
+    throw new Error(`Path must be relative to the skill directory: ${relative}`);
+  }
+  const resolved = nodePath.resolve(root, relative);
+  const normalized = nodePath.resolve(root) + nodePath.sep;
+  if (resolved !== nodePath.resolve(root) && !resolved.startsWith(normalized)) {
+    throw new Error(`Path escapes the skill directory: ${relative}`);
+  }
+  return resolved;
+}
+
+/**
+ * Build the three tools we auto-inject into `streamText` when skills are
+ * set: `loadSkill`, `readFile`, `bash`. Scoped per-skill by name.
+ *
+ * Exported so callers can use the same tools outside the auto-wired path
+ * (e.g. in a `chat.createSession` loop with custom streamText).
+ */
+export function buildSkillTools(skills: ResolvedSkill[]): Record<string, Tool> {
+  const loadSkill = aiTool({
+    description:
+      "Load the full instructions for a skill by its name. Call this first before using a skill.",
+    inputSchema: jsonSchema<{ name: string }>({
+      type: "object",
+      properties: {
+        name: {
+          type: "string",
+          description: "The `name` field from the skill's frontmatter.",
+        },
+      },
+      required: ["name"],
+      additionalProperties: false,
+    } as JSONSchema7),
+    execute: async ({ name }: { name: string }) => {
+      const skill = findSkillByName(skills, name);
+      if (!skill) {
+        return {
+          error: `Skill "${name}" not found. Available: ${skills
+            .map((s) => s.frontmatter.name)
+            .join(", ")}`,
+        };
+      }
+      return {
+        name: skill.frontmatter.name,
+        description: skill.frontmatter.description,
+        body: skill.body,
+        path: skill.path,
+      };
+    },
+  });
+
+  const readFile = aiTool({
+    description:
+      "Read a file from a skill's bundled folder. Paths must be relative to the skill's root.",
+    inputSchema: jsonSchema<{ skill: string; path: string }>({
+      type: "object",
+      properties: {
+        skill: { type: "string", description: "The skill's name (from frontmatter)." },
+        path: {
+          type: "string",
+          description: "Relative path inside the skill folder (e.g. `references/citation-style.md`).",
+        },
+      },
+      required: ["skill", "path"],
+      additionalProperties: false,
+    } as JSONSchema7),
+    execute: async ({ skill: skillName, path: relPath }: { skill: string; path: string }) => {
+      const skill = findSkillByName(skills, skillName);
+      if (!skill) {
+        return { error: `Skill "${skillName}" not found.` };
+      }
+      let absolute: string;
+      try {
+        absolute = safeJoinInside(skill.path, relPath);
+      } catch (err) {
+        return { error: (err as Error).message };
+      }
+      try {
+        const content = await fs.readFile(absolute, "utf8");
+        return { content: truncate(content, DEFAULT_READ_FILE_BYTES) };
+      } catch (err) {
+        return { error: (err as Error).message };
+      }
+    },
+  });
+
+  const bash = aiTool({
+    description:
+      "Run a bash command inside a skill's bundled folder. Use this to invoke the skill's scripts. The working directory is the skill's root.",
+    inputSchema: jsonSchema<{ skill: string; command: string }>({
+      type: "object",
+      properties: {
+        skill: { type: "string", description: "The skill's name (from frontmatter)." },
+        command: {
+          type: "string",
+          description: "Bash command to run. Relative script paths resolve against the skill's root.",
+        },
+      },
+      required: ["skill", "command"],
+      additionalProperties: false,
+    } as JSONSchema7),
+    execute: async (
+      { skill: skillName, command }: { skill: string; command: string },
+      { abortSignal }: { abortSignal?: AbortSignal } = {}
+    ) => {
+      const skill = findSkillByName(skills, skillName);
+      if (!skill) {
+        return { error: `Skill "${skillName}" not found.` };
+      }
+      return await new Promise<{
+        exitCode: number | null;
+        stdout: string;
+        stderr: string;
+      } | { error: string }>((resolvePromise) => {
+        let child;
+        try {
+          child = spawn("bash", ["-c", command], {
+            cwd: skill.path,
+            signal: abortSignal,
+          });
+        } catch (err) {
+          resolvePromise({ error: (err as Error).message });
+          return;
+        }
+
+        let stdout = "";
+        let stderr = "";
+        child.stdout?.on("data", (chunk: Buffer | string) => {
+          stdout += chunk.toString();
+        });
+        child.stderr?.on("data", (chunk: Buffer | string) => {
+          stderr += chunk.toString();
+        });
+        child.once("close", (code: number | null) => {
+          resolvePromise({
+            exitCode: code,
+            stdout: truncate(stdout, DEFAULT_BASH_OUTPUT_BYTES),
+            stderr: truncate(stderr, DEFAULT_BASH_OUTPUT_BYTES),
+          });
+        });
+        child.once("error", (err: Error) => {
+          resolvePromise({ error: err.message });
+        });
+      });
+    },
+  });
+
+  return { loadSkill, readFile, bash };
+}
+
 /**
  * Options for {@link toStreamTextOptions}.
  */
@@ -1772,6 +1982,16 @@ export type ToStreamTextOptionsOptions = {
    * (e.g. `"openai:gpt-4o"`, `"anthropic:claude-sonnet-4-6"`).
    */
   registry?: { languageModel(modelId: string): unknown };
+  /**
+   * User-defined tools to merge alongside the auto-injected skill tools
+   * (`loadSkill`, `readFile`, `bash`). User tools win on name conflicts.
+   *
+   * If you don't pass `tools` here and skills are set, the returned options
+   * will include just the skill tools — spread after any `tools` you pass
+   * directly to `streamText` and they'll be replaced. Easiest: pass all
+   * your tools here.
+   */
+  tools?: Record<string, Tool>;
 };
 
 /**
@@ -1787,12 +2007,18 @@ export type ToStreamTextOptionsOptions = {
  */
 function toStreamTextOptions(options?: ToStreamTextOptionsOptions): Record<string, unknown> {
   const prompt = locals.get(chatPromptKey);
+  const skills = locals.get(chatSkillsKey);
   const result: Record<string, unknown> = {};
 
+  // Build the combined system prompt: stored prompt + skills preamble.
+  const promptText = prompt?.text ?? "";
+  const skillsText = skills && skills.length > 0 ? buildSkillsSystemPrompt(skills) : "";
+  if (promptText || skillsText) {
+    result.system = [promptText, skillsText].filter(Boolean).join("\n\n");
+  }
+
   // Prompt-related options (only if chat.prompt.set() was called)
   if (prompt) {
-    result.system = prompt.text;
-
     // Resolve model via registry if both are present
     if (options?.registry && prompt.model) {
       result.model = options.registry.languageModel(prompt.model);
@@ -1808,6 +2034,15 @@ function toStreamTextOptions(options?: ToStreamTextOptionsOptions): Record<strin
     Object.assign(result, telemetry);
   }
 
+  // Skills: merge auto-injected tools with any user-provided tools.
+  // User tools override on name conflict (though we namespace ours).
+  if (skills && skills.length > 0) {
+    const skillTools = buildSkillTools(skills);
+    result.tools = { ...skillTools, ...(options?.tools ?? {}) };
+  } else if (options?.tools) {
+    result.tools = options.tools;
+  }
+
   // Auto-inject prepareStep for compaction, pending messages, and background context injection.
   // This runs regardless of whether a prompt is set — these features are independent.
   const taskCompaction = locals.get(chatAgentCompactionKey);
@@ -6190,6 +6425,18 @@ export const chat = {
    * - `chat.prompt()` — read the stored prompt (throws if not set)
    */
   prompt: Object.assign(getChatPrompt, { set: setChatPrompt }),
+  /**
+   * Store and retrieve resolved agent skills for the current run.
+   *
+   * - `chat.skills.set([...])` — store an array of `ResolvedSkill`s
+   * - `chat.skills()` — read the stored skills (returns undefined if none)
+   *
+   * Skills set here are automatically injected into `streamText` by
+   * `chat.toStreamTextOptions()`: skill descriptions land in the system
+   * prompt and `loadSkill` / `readFile` / `bash` tools are added to the
+   * tool set.
+   */
+  skills: Object.assign(getChatSkills, { set: setChatSkills }),
   /**
    * Returns an options object ready to spread into `streamText()`.
    * Reads the stored prompt and returns `{ system, experimental_telemetry, ...config }`.
diff --git a/packages/trigger-sdk/src/v3/index.ts b/packages/trigger-sdk/src/v3/index.ts
index f362af1d1..2e0f883f8 100644
--- a/packages/trigger-sdk/src/v3/index.ts
+++ b/packages/trigger-sdk/src/v3/index.ts
@@ -65,3 +65,4 @@ export type { ImportEnvironmentVariablesParams } from "./envvars.js";
 
 export { configure, auth } from "./auth.js";
 export * as prompts from "./prompts.js";
+export * as skills from "./skills.js";
diff --git a/packages/trigger-sdk/src/v3/skill.ts b/packages/trigger-sdk/src/v3/skill.ts
new file mode 100644
index 000000000..a3c145d38
--- /dev/null
+++ b/packages/trigger-sdk/src/v3/skill.ts
@@ -0,0 +1,211 @@
+import * as fs from "node:fs/promises";
+import * as path from "node:path";
+import { resourceCatalog } from "@trigger.dev/core/v3";
+
+/**
+ * Parsed `SKILL.md` frontmatter. Only `name` + `description` are required;
+ * additional keys are preserved but untyped.
+ */
+export type SkillFrontmatter = {
+  name: string;
+  description: string;
+  [key: string]: unknown;
+};
+
+/**
+ * A resolved skill ready to hand to `chat.skills.set()`. Includes the parsed
+ * SKILL.md content plus the on-disk path to the bundled skill folder.
+ */
+export type ResolvedSkill = {
+  id: string;
+  /** Skill version — `"local"` in Phase 1 until backend-managed overrides land. */
+  version: number | "local";
+  /** Labels applied to this version — empty in Phase 1. */
+  labels: string[];
+  /** Full raw `SKILL.md` content (with frontmatter). */
+  skillMd: string;
+  /** Parsed frontmatter fields. */
+  frontmatter: SkillFrontmatter;
+  /** Body of SKILL.md with the frontmatter block stripped. */
+  body: string;
+  /** Absolute path to the bundled skill folder (scripts, references, assets live here). */
+  path: string;
+};
+
+export type SkillOptions<TIdentifier extends string = string> = {
+  id: TIdentifier;
+  /** Path to the skill source folder, relative to the project root. */
+  path: string;
+};
+
+export type SkillHandle<TIdentifier extends string = string> = {
+  id: TIdentifier;
+  /**
+   * Read the bundled `SKILL.md` from disk and return the resolved skill.
+   *
+   * This is the Phase 1 path — backend-managed overrides are not available
+   * yet. Works locally (during `trigger dev`) and in the deploy image.
+   */
+  local(): Promise<ResolvedSkill>;
+  /**
+   * Resolve the skill against the dashboard (current/override version).
+   *
+   * Not available in Phase 1 — throws. Use `local()` until backend-managed
+   * skills ship.
+   */
+  resolve(): Promise<ResolvedSkill>;
+};
+
+// eslint-disable-next-line @typescript-eslint/no-explicit-any
+export type AnySkillHandle = SkillHandle<string>;
+
+/** Extract the id literal type from a SkillHandle. */
+export type SkillIdentifier<T extends AnySkillHandle> = T extends SkillHandle<infer TId>
+  ? TId
+  : string;
+
+/**
+ * Bundled skills are copied to `${cwd}/.trigger/skills/{id}/` by the CLI at
+ * build time. At runtime the same layout holds for both `trigger dev` (cwd
+ * = dev output dir) and deploy (cwd = /app).
+ */
+function bundledSkillPath(id: string): string {
+  return path.resolve(process.cwd(), ".trigger", "skills", id);
+}
+
+const FRONTMATTER_RE = /^---\r?\n([\s\S]*?)\r?\n---\r?\n*/;
+
+/**
+ * Parse a minimal YAML-subset frontmatter block. We only support top-level
+ * string keys like `name: foo` and `description: bar`. Enough for SKILL.md
+ * frontmatter without pulling in a YAML dep.
+ */
+export function parseFrontmatter(content: string): {
+  frontmatter: SkillFrontmatter;
+  body: string;
+} {
+  const match = content.match(FRONTMATTER_RE);
+  if (!match || !match[1]) {
+    throw new Error(
+      "Skill: SKILL.md is missing a frontmatter block. " +
+        "Expected `---\\nname: ...\\ndescription: ...\\n---` at the top of the file."
+    );
+  }
+
+  const raw = match[1];
+  const frontmatter: Record<string, unknown> = {};
+  for (const line of raw.split(/\r?\n/)) {
+    const trimmed = line.trim();
+    if (!trimmed || trimmed.startsWith("#")) continue;
+    const idx = trimmed.indexOf(":");
+    if (idx === -1) continue;
+    const key = trimmed.slice(0, idx).trim();
+    let value = trimmed.slice(idx + 1).trim();
+    // Strip surrounding quotes if present
+    if (
+      (value.startsWith('"') && value.endsWith('"')) ||
+      (value.startsWith("'") && value.endsWith("'"))
+    ) {
+      value = value.slice(1, -1);
+    }
+    if (key) frontmatter[key] = value;
+  }
+
+  if (typeof frontmatter.name !== "string" || !frontmatter.name) {
+    throw new Error("Skill: SKILL.md frontmatter is missing required `name` field.");
+  }
+  if (typeof frontmatter.description !== "string" || !frontmatter.description) {
+    throw new Error("Skill: SKILL.md frontmatter is missing required `description` field.");
+  }
+
+  const body = content.slice(match[0].length);
+
+  return { frontmatter: frontmatter as SkillFrontmatter, body };
+}
+
+async function loadLocal(id: string): Promise<ResolvedSkill> {
+  const skillPath = bundledSkillPath(id);
+  const skillMdPath = path.join(skillPath, "SKILL.md");
+
+  let skillMd: string;
+  try {
+    skillMd = await fs.readFile(skillMdPath, "utf8");
+  } catch (err) {
+    throw new Error(
+      `Skill "${id}": could not read SKILL.md at ${skillMdPath}. ` +
+        `Skills must be bundled into .trigger/skills/{id}/ — this usually means ` +
+        `the CLI build step didn't run, or the skill wasn't registered via ai.defineSkill. ` +
+        `Underlying error: ${(err as Error).message}`
+    );
+  }
+
+  const { frontmatter, body } = parseFrontmatter(skillMd);
+
+  return {
+    id,
+    version: "local",
+    labels: [],
+    skillMd,
+    frontmatter,
+    body,
+    path: skillPath,
+  };
+}
+
+/**
+ * Define an agent skill — a developer-authored folder with a `SKILL.md` file
+ * plus optional `scripts/`, `references/`, and `assets/` subfolders. Registers
+ * the skill with the resource catalog so the Trigger.dev CLI can bundle it
+ * into the deploy image automatically (no build extension needed).
+ *
+ * Call `.local()` on the returned handle to load the bundled SKILL.md at
+ * runtime and use it with `chat.skills.set()`.
+ *
+ * @example
+ * ```ts
+ * // trigger/skills/pdf-processing/SKILL.md
+ * // trigger/skills/pdf-processing/scripts/extract.py
+ * import { ai } from "@trigger.dev/sdk";
+ *
+ * export const pdfSkill = ai.defineSkill({
+ *   id: "pdf-processing",
+ *   path: "./skills/pdf-processing",
+ * });
+ *
+ * export const agent = chat.agent({
+ *   id: "docs",
+ *   onChatStart: async () => {
+ *     chat.skills.set([await pdfSkill.local()]);
+ *   },
+ *   run: async ({ messages, signal }) => {
+ *     return streamText({
+ *       model: openai("gpt-4o"),
+ *       messages,
+ *       abortSignal: signal,
+ *       ...chat.toStreamTextOptions(),
+ *     });
+ *   },
+ * });
+ * ```
+ */
+export function defineSkill<TIdentifier extends string>(
+  options: SkillOptions<TIdentifier>
+): SkillHandle<TIdentifier> {
+  resourceCatalog.registerSkillMetadata({
+    id: options.id,
+    sourcePath: options.path,
+  });
+
+  return {
+    id: options.id,
+    async local() {
+      return loadLocal(options.id);
+    },
+    async resolve() {
+      throw new Error(
+        `Skill "${options.id}": resolve() is not available yet — backend-managed ` +
+          `skills ship in Phase 2. Use skill.local() instead.`
+      );
+    },
+  };
+}
diff --git a/packages/trigger-sdk/src/v3/skills.ts b/packages/trigger-sdk/src/v3/skills.ts
new file mode 100644
index 000000000..6811cda75
--- /dev/null
+++ b/packages/trigger-sdk/src/v3/skills.ts
@@ -0,0 +1,9 @@
+export { defineSkill as define } from "./skill.js";
+export type {
+  AnySkillHandle,
+  ResolvedSkill,
+  SkillFrontmatter,
+  SkillHandle,
+  SkillIdentifier,
+  SkillOptions,
+} from "./skill.js";
diff --git a/packages/trigger-sdk/test/skill.test.ts b/packages/trigger-sdk/test/skill.test.ts
new file mode 100644
index 000000000..61e497933
--- /dev/null
+++ b/packages/trigger-sdk/test/skill.test.ts
@@ -0,0 +1,86 @@
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { mkdtemp, mkdir, realpath, writeFile, rm } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import * as path from "node:path";
+import { defineSkill, parseFrontmatter } from "../src/v3/skill.js";
+
+describe("parseFrontmatter", () => {
+  it("parses name + description", () => {
+    const { frontmatter, body } = parseFrontmatter(
+      `---\nname: pdf-processing\ndescription: Extract text from PDFs.\n---\n\n# Body\n\nhello\n`
+    );
+    expect(frontmatter.name).toBe("pdf-processing");
+    expect(frontmatter.description).toBe("Extract text from PDFs.");
+    expect(body).toBe("# Body\n\nhello\n");
+  });
+
+  it("strips surrounding quotes", () => {
+    const { frontmatter } = parseFrontmatter(
+      `---\nname: "quoted-name"\ndescription: 'single quoted'\n---\nbody\n`
+    );
+    expect(frontmatter.name).toBe("quoted-name");
+    expect(frontmatter.description).toBe("single quoted");
+  });
+
+  it("throws on missing frontmatter block", () => {
+    expect(() => parseFrontmatter("# just a heading\n")).toThrow(/missing a frontmatter block/);
+  });
+
+  it("throws on missing required name", () => {
+    expect(() => parseFrontmatter(`---\ndescription: desc\n---\nbody`)).toThrow(
+      /missing required `name`/
+    );
+  });
+
+  it("throws on missing required description", () => {
+    expect(() => parseFrontmatter(`---\nname: foo\n---\nbody`)).toThrow(
+      /missing required `description`/
+    );
+  });
+});
+
+describe("defineSkill.local()", () => {
+  const originalCwd = process.cwd();
+  let workdir: string;
+
+  beforeEach(async () => {
+    workdir = await realpath(await mkdtemp(path.join(tmpdir(), "skill-test-")));
+    process.chdir(workdir);
+  });
+
+  afterEach(async () => {
+    process.chdir(originalCwd);
+    await rm(workdir, { recursive: true, force: true });
+  });
+
+  it("reads a bundled SKILL.md and returns a ResolvedSkill", async () => {
+    const skillDir = path.join(workdir, ".trigger", "skills", "pdf");
+    await mkdir(skillDir, { recursive: true });
+    await writeFile(
+      path.join(skillDir, "SKILL.md"),
+      `---\nname: pdf\ndescription: Extract PDF text.\n---\n\n# PDF skill\n\nUse scripts/extract.py.\n`
+    );
+
+    const skill = defineSkill({ id: "pdf", path: "./skills/pdf" });
+    const resolved = await skill.local();
+
+    expect(resolved.id).toBe("pdf");
+    expect(resolved.version).toBe("local");
+    expect(resolved.labels).toEqual([]);
+    expect(resolved.frontmatter.name).toBe("pdf");
+    expect(resolved.frontmatter.description).toBe("Extract PDF text.");
+    expect(resolved.body).toContain("# PDF skill");
+    expect(resolved.body).toContain("Use scripts/extract.py");
+    expect(resolved.path).toBe(skillDir);
+  });
+
+  it("throws a useful error when SKILL.md is missing", async () => {
+    const skill = defineSkill({ id: "missing", path: "./skills/missing" });
+    await expect(skill.local()).rejects.toThrow(/could not read SKILL.md/);
+  });
+
+  it("resolve() throws with a helpful Phase 1 message", async () => {
+    const skill = defineSkill({ id: "phase-2", path: "./skills/phase-2" });
+    await expect(skill.resolve()).rejects.toThrow(/not available yet.*Phase 2.*local/s);
+  });
+});
diff --git a/packages/trigger-sdk/test/skillsRuntime.test.ts b/packages/trigger-sdk/test/skillsRuntime.test.ts
new file mode 100644
index 000000000..125471ff7
--- /dev/null
+++ b/packages/trigger-sdk/test/skillsRuntime.test.ts
@@ -0,0 +1,221 @@
+// Import the test harness FIRST so the resource catalog is installed
+import { mockChatAgent } from "../src/v3/test/index.js";
+
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { mkdtemp, mkdir, realpath, writeFile, rm, chmod } from "node:fs/promises";
+import { tmpdir } from "node:os";
+import * as path from "node:path";
+import type { LanguageModelV3StreamPart } from "@ai-sdk/provider";
+import { MockLanguageModelV3 } from "ai/test";
+import { simulateReadableStream, streamText } from "ai";
+import { buildSkillTools, chat } from "../src/v3/ai.js";
+import { defineSkill } from "../src/v3/skill.js";
+
+function userMessage(text: string, id?: string) {
+  return {
+    id: id ?? `u-${Math.random().toString(36).slice(2)}`,
+    role: "user" as const,
+    parts: [{ type: "text" as const, text }],
+  };
+}
+
+function textStream(text: string) {
+  const chunks: LanguageModelV3StreamPart[] = [
+    { type: "text-start", id: "t1" },
+    { type: "text-delta", id: "t1", delta: text },
+    { type: "text-end", id: "t1" },
+    {
+      type: "finish",
+      finishReason: { unified: "stop", raw: "stop" },
+      usage: {
+        inputTokens: { total: 10, noCache: 10, cacheRead: undefined, cacheWrite: undefined },
+        outputTokens: { total: 10, text: 10, reasoning: undefined },
+      },
+    },
+  ];
+  return simulateReadableStream({ chunks });
+}
+
+const originalCwd = process.cwd();
+let workdir: string;
+
+beforeEach(async () => {
+  workdir = await realpath(await mkdtemp(path.join(tmpdir(), "skills-runtime-")));
+  process.chdir(workdir);
+
+  // Bundled skill layout
+  const skillDir = path.join(workdir, ".trigger", "skills", "demo");
+  await mkdir(path.join(skillDir, "scripts"), { recursive: true });
+  await mkdir(path.join(skillDir, "references"), { recursive: true });
+
+  await writeFile(
+    path.join(skillDir, "SKILL.md"),
+    `---\nname: demo\ndescription: Demo skill for tests.\n---\n\n# Demo\n\nUse scripts/hello.sh to say hello.\n`
+  );
+
+  const scriptPath = path.join(skillDir, "scripts", "hello.sh");
+  await writeFile(scriptPath, `#!/usr/bin/env bash\necho "hi from $1"\n`);
+  await chmod(scriptPath, 0o755);
+
+  await writeFile(path.join(skillDir, "references", "notes.txt"), "Reference note.\n");
+});
+
+afterEach(async () => {
+  process.chdir(originalCwd);
+  await rm(workdir, { recursive: true, force: true });
+});
+
+describe("chat.skills runtime integration", () => {
+  it("injects skills preamble into the system prompt", async () => {
+    let capturedSystem: string | undefined;
+
+    const model = new MockLanguageModelV3({
+      doStream: async (opts) => {
+        const system = opts.prompt.find((m) => m.role === "system");
+        capturedSystem = system ? JSON.stringify(system.content) : undefined;
+        return { stream: textStream("ok") };
+      },
+    });
+
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+
+    const agent = chat.agent({
+      id: "skills-runtime.system-prompt",
+      onChatStart: async () => {
+        chat.skills.set([await skill.local()]);
+      },
+      run: async ({ messages, signal }) => {
+        return streamText({
+          model,
+          messages,
+          abortSignal: signal,
+          ...chat.toStreamTextOptions(),
+        });
+      },
+    });
+
+    const harness = mockChatAgent(agent, { chatId: "t1" });
+    try {
+      await harness.sendMessage(userMessage("hi"));
+      await new Promise((r) => setTimeout(r, 20));
+      expect(capturedSystem).toContain("Available skills");
+      expect(capturedSystem).toContain("demo: Demo skill for tests");
+    } finally {
+      await harness.close();
+    }
+  });
+
+  it("auto-wires loadSkill / readFile / bash tools", async () => {
+    let capturedToolNames: string[] = [];
+
+    const model = new MockLanguageModelV3({
+      doStream: async (opts) => {
+        capturedToolNames = (opts.tools ?? []).map((t) => t.name);
+        return { stream: textStream("ok") };
+      },
+    });
+
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+
+    const agent = chat.agent({
+      id: "skills-runtime.auto-tools",
+      onChatStart: async () => {
+        chat.skills.set([await skill.local()]);
+      },
+      run: async ({ messages, signal }) => {
+        return streamText({
+          model,
+          messages,
+          abortSignal: signal,
+          ...chat.toStreamTextOptions(),
+        });
+      },
+    });
+
+    const harness = mockChatAgent(agent, { chatId: "t2" });
+    try {
+      await harness.sendMessage(userMessage("hi"));
+      await new Promise((r) => setTimeout(r, 20));
+      expect(capturedToolNames).toEqual(expect.arrayContaining(["loadSkill", "readFile", "bash"]));
+    } finally {
+      await harness.close();
+    }
+  });
+});
+
+describe("buildSkillTools — direct execute", () => {
+  it("loadSkill returns body + path for a known skill", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const resolved = await skill.local();
+    const tools = buildSkillTools([resolved]);
+
+    const out = await (tools.loadSkill as any).execute({ name: "demo" });
+    expect(out.name).toBe("demo");
+    expect(out.body).toContain("# Demo");
+    expect(out.path).toBe(resolved.path);
+  });
+
+  it("loadSkill returns an error for an unknown skill", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const tools = buildSkillTools([await skill.local()]);
+
+    const out = await (tools.loadSkill as any).execute({ name: "missing" });
+    expect(out.error).toContain('Skill "missing" not found');
+  });
+
+  it("readFile reads a bundled reference", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const tools = buildSkillTools([await skill.local()]);
+
+    const out = await (tools.readFile as any).execute({
+      skill: "demo",
+      path: "references/notes.txt",
+    });
+    expect(out.content).toBe("Reference note.\n");
+  });
+
+  it("readFile rejects path traversal", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const tools = buildSkillTools([await skill.local()]);
+
+    const out = await (tools.readFile as any).execute({
+      skill: "demo",
+      path: "../../../../etc/passwd",
+    });
+    expect(out.error).toMatch(/escapes the skill directory/);
+  });
+
+  it("readFile rejects absolute paths", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const tools = buildSkillTools([await skill.local()]);
+
+    const out = await (tools.readFile as any).execute({
+      skill: "demo",
+      path: "/etc/passwd",
+    });
+    expect(out.error).toMatch(/must be relative/);
+  });
+
+  it("bash runs a bundled script and captures stdout", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const tools = buildSkillTools([await skill.local()]);
+
+    const out = await (tools.bash as any).execute({
+      skill: "demo",
+      command: "bash scripts/hello.sh world",
+    });
+    expect(out.exitCode).toBe(0);
+    expect(out.stdout).toContain("hi from world");
+  });
+
+  it("bash reports non-zero exit code", async () => {
+    const skill = defineSkill({ id: "demo", path: "./skills/demo" });
+    const tools = buildSkillTools([await skill.local()]);
+
+    const out = await (tools.bash as any).execute({
+      skill: "demo",
+      command: "exit 7",
+    });
+    expect(out.exitCode).toBe(7);
+  });
+});