fix(core): present the project dir to the model as the App Data Dir in the default system prompt (#61)

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>

packages/server/src/http/routes/agent-config.ts

@@ -1,6 +1,8 @@
 /**
  * Agent config routes (reads/writes system_config.yaml and AGENTS.md):
- * GET|PUT /api/projects/:p/agents/:a/config. Members can read and write (unrestricted).
+ * GET|PUT /api/projects/:p/agents/:a/config, plus POST …/config/reset to adopt the
+ * current default config (keeps only name/description/version — the config-side
+ * analogue of a skill update). Members can read and write (unrestricted).
  */
 import { Hono } from "hono";
 import type { AgentConfigResponse, AgentConfigUpdateRequest } from "../../api/types.js";
@@ -46,5 +48,20 @@ export function agentConfigRoutes(deps: AppDeps): Hono<AppEnv> {
     } satisfies AgentConfigResponse);
   });
 
+  // Overwrite system_config.yaml with the current defaults (see AgentConfigService.resetConfig
+  // for the exact semantics); same authorization as PUT, and responds like GET/PUT with the
+  // fresh config so the client can refresh in place.
+  app.post("/reset", async (c) => {
+    const projectId = requireValidId(c, "projectId");
+    const agentId = requireValidId(c, "agentId");
+    deps.projectService.requireProjectAccess(c.var.user.userId, projectId);
+    await deps.agentConfigService.resetConfig(projectId, agentId);
+    const view = await deps.agentConfigService.getConfig(projectId, agentId);
+    return c.json({
+      ...view,
+      activeSessionCount: deps.manager.activeCountForAgent(projectId, agentId),
+    } satisfies AgentConfigResponse);
+  });
+
   return app;
 }

packages/server/src/services/agent-config-service.ts

@@ -16,6 +16,7 @@ import {
   VAULT_VALUE_MAX_LENGTH,
   isValidVaultKey,
   loadAgentVault,
+  resetSystemConfigToDefaults,
   saveAgentVault,
   systemConfigPath,
 } from "@prismshadow/penguin-core";
@@ -173,6 +174,19 @@ export class AgentConfigService {
     }
   }
 
+  /**
+   * Overwrites system_config.yaml with the current code defaults (core's
+   * resetSystemConfigToDefaults) — same semantics as updating an installed skill:
+   * only the identity fields (name / description / version) survive; the system
+   * prompt, max_turns, model/compaction settings and the tool list (incl. MCP
+   * servers) become the current defaults. AGENTS.md, skills and the vault are
+   * untouched.
+   */
+  async resetConfig(projectId: string, agentId: string): Promise<void> {
+    await this.requireExists(projectId, agentId);
+    await resetSystemConfigToDefaults(this.root, projectId, agentId);
+  }
+
   private async applyConfigUpdate(
     projectId: string,
     agentId: string,

packages/server/test/agent-config-reset.test.ts

@@ -0,0 +1,89 @@
+/**
+ * POST /api/projects/:projectId/agents/:agentId/config/reset — overwrites
+ * system_config.yaml with the current code defaults, keeping only the identity fields
+ * (name / description / version); the config-side analogue of a skill update. Same
+ * member-level authorization as PUT config; a non-member gets 404 without a write.
+ */
+import { afterEach, beforeEach, describe, expect, it } from "vitest";
+import { defaultSystemConfig } from "@prismshadow/penguin-core";
+import type { AgentConfigResponse, ProjectCreateResponse } from "../src/api/types.js";
+import { apiClient, createTestApp, provisionUser } from "./helpers.js";
+import type { TestApp } from "./helpers.js";
+
+describe("POST agent config reset", () => {
+  let t: TestApp;
+  let alice: ReturnType<typeof apiClient>;
+  let projectId: string;
+  const configUrl = () => `/api/projects/${projectId}/agents/default_agent/config`;
+
+  beforeEach(async () => {
+    t = await createTestApp();
+    const a = await provisionUser(t.app, "alice");
+    alice = apiClient(t.app, a.cookie);
+    // Project ids are username-prefixed (`alice-…`), same as the other route tests.
+    const created = (await (
+      await alice.post("/api/projects", { projectId: "alice-reset", name: "Reset project" })
+    ).json()) as ProjectCreateResponse;
+    projectId = created.project.projectId;
+  });
+  afterEach(async () => {
+    await t.cleanup();
+  });
+
+  it("restores the defaults while preserving name / description / version", async () => {
+    // Customize everything the reset is supposed to overwrite, plus the kept fields.
+    const put = await alice.put(configUrl(), {
+      config: {
+        name: "Custom Name",
+        description: "Custom description",
+        systemPrompt: "CUSTOM PROMPT",
+        maxTurns: 3,
+        model: { maxTokens: 1234 },
+        compaction: { mode: "discard" },
+        toolsBuiltin: [],
+        mcpServers: [{ name: "custom-mcp", config: {} }],
+      },
+    });
+    expect(put.status).toBe(200);
+
+    const res = await alice.post(`${configUrl()}/reset`);
+    expect(res.status).toBe(200);
+    const body = (await res.json()) as AgentConfigResponse;
+    const defaults = defaultSystemConfig();
+
+    // Identity fields survive.
+    expect(body.config.name).toBe("Custom Name");
+    expect(body.config.description).toBe("Custom description");
+    expect(body.config.version).toBe(1);
+    // Everything else is back to the current defaults.
+    expect(body.config.systemPrompt).toBe(defaults.system_prompt);
+    expect(body.config.systemPrompt).toContain("App Data Dir: {{PROJECT_DIR}}");
+    expect(body.config.maxTurns).toBe(defaults.max_turns);
+    expect(body.config.model?.maxTokens).toBe(defaults.model?.max_tokens);
+    expect(body.config.compaction?.mode).toBe("summarize");
+    expect(body.config.toolsBuiltin.map((tool) => tool.name)).toEqual(
+      (defaults.tools?.builtin ?? []).map((tool) => tool.name),
+    );
+    expect(body.config.mcpServers).toEqual([]);
+
+    // A later GET sees the same reset state (it was persisted, not just echoed).
+    const got = (await (await alice.get(configUrl())).json()) as AgentConfigResponse;
+    expect(got.config.systemPrompt).toBe(defaults.system_prompt);
+    expect(got.config.name).toBe("Custom Name");
+  });
+
+  it("404 for a nonexistent agent (no initialization side effect)", async () => {
+    const res = await alice.post(`/api/projects/${projectId}/agents/ghost/config/reset`);
+    expect(res.status).toBe(404);
+  });
+
+  it("404 for a non-member; the config is not modified", async () => {
+    const before = (await (await alice.get(configUrl())).json()) as AgentConfigResponse;
+    const m = await provisionUser(t.app, "mallory");
+    const mallory = apiClient(t.app, m.cookie);
+    const res = await mallory.post(`${configUrl()}/reset`);
+    expect(res.status).toBe(404);
+    const after = (await (await alice.get(configUrl())).json()) as AgentConfigResponse;
+    expect(after.systemConfigYaml).toBe(before.systemConfigYaml);
+  });
+});