supabase · seanoliver · Aug 25, 2026 · Aug 25, 2026 · Aug 25, 2026 · Aug 31, 2026
diff --git a/README.md b/README.md
@@ -163,7 +163,7 @@ To use a skill in an experiment, reference its directory name in the experiment'
 
 Both runtimes load skills lazily ([progressive disclosure](https://ai-sdk.dev/cookbook/guides/agent-skills)): only each skill's name+description is in the system prompt, and the agent pulls a skill's full instructions on demand. They differ only in how the body is fetched, because the tools-mode agent has no filesystem:
 
-- **Local-stack (sandbox) mode:** skills are installed into the workspace with [Vercel's `skills` CLI](https://github.com/vercel-labs/skills) (baked into the sandbox image, sourced from the local `skills/` directory — never the network) under `.claude/skills/`. When a task matches, the agent reads `.claude/skills/<name>/SKILL.md` (and any files it references) with its file tools.
+- **Local-stack (sandbox) mode:** skills are installed into the workspace with [Vercel's `skills` CLI](https://github.com/vercel-labs/skills) (baked into the sandbox image, sourced from the local `skills/` directory — never the network), into every project scope the CLI harnesses discover natively: `.claude/skills/` for Claude Code, `.agents/skills/` for Codex and OpenCode. Each CLI discovers the scope it reads and surfaces those skills to the model itself. The framework also still injects a listing naming them, so a CLI harness hears about them twice; removing that is a separate change.
 - **Tools mode:** no filesystem, so a `load_skill` tool returns a skill's full instructions when the agent calls it with the skill's name.
 
 ## Framework Checks

diff --git a/apps/framework/harness/run-eval.ts b/apps/framework/harness/run-eval.ts
@@ -420,6 +420,7 @@ async function runOne(
       : undefined;
     await using session = disposable(
       await exp.localStack.startSession({
+        agent: exp.agent.id,
         cliVersion: ev.metadata.cliVersion,
         localDir: ev.localDir,
         includeServices: ev.metadata.services,
@@ -494,6 +495,7 @@ async function runOne(
   await using cliSandbox = agentRunsInSandbox
     ? disposable(
         await createBareSandbox({
+          agent: exp.agent.id,
           skills: skillSources,
           mounts: supabaseMcpServerMounts(),
         })

diff --git a/packages/core/src/index.ts b/packages/core/src/index.ts
@@ -430,6 +430,11 @@ export type SandboxMount = {
 };
 
 export type LocalStackSessionArgs = {
+  /**
+   * The agent harness this session serves. The prompt addendum builders take it
+   * but do not branch on it yet; a follow-up change gates their output on it.
+   */
+  agent: AgentHarnessId;
   /** Supabase CLI version this scenario requires, overriding the runtime default. */
   cliVersion?: string;
   /**

diff --git a/packages/sandbox/src/agent-environment.ts b/packages/sandbox/src/agent-environment.ts
@@ -38,7 +38,7 @@ export interface AgentEnvironmentOptions {
   cliVersion?: string;
   /** Host directory whose contents seed the workspace. */
   localDir?: string;
-  /** Skills to install into the sandbox (the agent reads them with its file tools). */
+  /** Skills to install into the sandbox (in every CLI harness's project scope). */
   skills?: readonly SkillSource[];
   /**
    * Run the Supabase local stack. Present → local-stack mode; omitted → tools
@@ -92,7 +92,8 @@ export async function createAgentEnvironment(
     } else if (options.localDir) {
       await sandbox.copyToContainer(options.localDir, sandbox.workdir);
     }
-    // Skills are installed in both modes; the agent reads SKILL.md with its file tools.
+    // Skills are installed in both modes, into every CLI harness's native
+    // project scope (see installSkills) so each agent discovers them itself.
     const skills = await installSkills(sandbox, options.skills ?? []);
     return { sandbox, skills, close: () => sandbox.stop() };
   } catch (err) {

diff --git a/packages/sandbox/src/bare-sandbox.ts b/packages/sandbox/src/bare-sandbox.ts
@@ -1,4 +1,5 @@
 import type {
+  AgentHarnessId,
   AgentSandbox,
   SandboxMount,
   SkillSource,
@@ -14,6 +15,21 @@ export interface BareSandboxHandle {
   close(): Promise<void>;
 }
 
+export interface BareSandboxOptions {
+  /** Harness driving this sandbox. */
+  agent: AgentHarnessId;
+  /** Supabase CLI version baked into the sandbox image. */
+  cliVersion?: string;
+  /** Skills to install into the sandbox. */
+  skills?: readonly SkillSource[];
+  /**
+   * Extra host directories bind-mounted into the sandbox (read-only by
+   * default) — e.g. a local MCP server build the in-container agent must be
+   * able to launch. See `supabaseMcpServerMounts`.
+   */
+  mounts?: readonly SandboxMount[];
+}
+
 /**
  * The agent's execution environment for tools mode: the shared agent
  * environment (image, tooling, skills) **without** the Supabase local stack.
@@ -24,11 +40,7 @@ export interface BareSandboxHandle {
  * platform-lite via `host.docker.internal` on the default bridge).
  */
 export async function createBareSandbox(
-  options: {
-    cliVersion?: string;
-    skills?: readonly SkillSource[];
-    mounts?: readonly SandboxMount[];
-  } = {}
+  options: BareSandboxOptions
 ): Promise<BareSandboxHandle> {
   const env = await createAgentEnvironment({
     cliVersion: options.cliVersion,
@@ -37,7 +49,7 @@ export async function createBareSandbox(
   });
   return {
     sandbox: toAgentSandbox(env.sandbox),
-    promptAddendum: buildSkillsPrompt(env.skills),
+    promptAddendum: buildSkillsPrompt(options.agent, env.skills),
     close: env.close,
   };
 }
diff --git a/packages/sandbox/src/index.ts b/packages/sandbox/src/index.ts
@@ -19,21 +19,25 @@ export type { SetupSupabaseSandboxOptions } from './supabase.js';
 export {
   buildLocalStackScoringContext,
   buildLocalStackTools,
+  buildToolSurfaceAddendum,
   localStackRuntime,
   toAgentSandbox,
 } from './local-stack-runtime.js';
 export type { LocalStackRuntimeOptions } from './local-stack-runtime.js';
 export {
   SKILLS_CLI_VERSION,
+  SKILLS_INSTALL_AGENTS,
   SKILLS_INSTALL_DIR,
+  SKILLS_INSTALL_DIRS,
+  buildSkillsAddCommand,
   buildSkillsPrompt,
   frontmatterDescription,
   installSkills,
   stripFrontmatter,
 } from './skills.js';
 export type { SkillEntry } from './skills.js';
 export { createBareSandbox } from './bare-sandbox.js';
-export type { BareSandboxHandle } from './bare-sandbox.js';
+export type { BareSandboxHandle, BareSandboxOptions } from './bare-sandbox.js';
 export { createAgentEnvironment } from './agent-environment.js';
 export type {
   AgentEnvironment,

diff --git a/packages/sandbox/src/local-stack-runtime.ts b/packages/sandbox/src/local-stack-runtime.ts
@@ -3,6 +3,7 @@ import { jsonSchema, tool, type ToolSet } from 'ai';
 import { createClient } from '@supabase/supabase-js';
 import {
   supabaseMcpServer,
+  type AgentHarnessId,
   type AgentSandbox,
   type HostedLink,
   type LocalStackRuntime,
@@ -73,6 +74,7 @@ export function localStackRuntime(
   return {
     id: 'local-stack',
     async startSession({
+      agent,
       cliVersion,
       localDir,
       includeServices,
@@ -105,22 +107,14 @@ export function localStackRuntime(
 
       const mcpServers = await resolveMcpServers(options, hosted);
 
-      let baseAddendum =
-        'docker, psql, git, and curl are installed in the workspace. ' +
-        'Use the bash tool to run commands (the working directory is always the workspace root) ' +
-        'and the files tools to inspect and modify files.';
-
-      if (!skipCliInstall) {
-        baseAddendum = 'The Supabase CLI (`supabase`), ' + baseAddendum;
-        baseAddendum +=
-          ' Services started with `supabase start` are reachable on their default 127.0.0.1 ports.';
-      }
-
       return {
         tools: buildLocalStackTools(sandbox),
         sandbox: toAgentSandbox(sandbox),
         mcpServers,
-        promptAddendum: [baseAddendum, buildSkillsPrompt(env.skills)]
+        promptAddendum: [
+          buildToolSurfaceAddendum(agent, { skipCliInstall }),
+          buildSkillsPrompt(agent, env.skills),
+        ]
           .filter(Boolean)
           .join('\n\n'),
         scoringContext: buildLocalStackScoringContext(sandbox, hosted),
@@ -135,6 +129,27 @@ export function localStackRuntime(
   };
 }
 
+/**
+ * Describes the session's tool surface: the binaries installed in the workspace
+ * and the in-process `bash`/`files_*` tools from `buildLocalStackTools`.
+ */
+export function buildToolSurfaceAddendum(
+  agent: AgentHarnessId,
+  options: { skipCliInstall?: boolean } = {}
+): string {
+  let addendum =
+    'docker, psql, git, and curl are installed in the workspace. ' +
+    'Use the bash tool to run commands (the working directory is always the workspace root) ' +
+    'and the files tools to inspect and modify files.';
+
+  if (!options.skipCliInstall) {
+    addendum = 'The Supabase CLI (`supabase`), ' + addendum;
+    addendum +=
+      ' Services started with `supabase start` are reachable on their default 127.0.0.1 ports.';
+  }
+  return addendum;
+}
+
 /**
  * Build the MCP server map for a session. An explicit `options.mcpServers`
  * wins. Otherwise, when the eval links to a hosted project, expose a Supabase