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/core/test/state.test.ts

@@ -26,6 +26,8 @@ import {
   buildToolConfig,
   selectBuiltinToolsForModel,
   defaultProjectConfig,
+  defaultSystemConfig,
+  resetSystemConfigToDefaults,
   getModel,
   isValidVaultKey,
   loadOrInitAgentState,
@@ -313,6 +315,12 @@ describe("assembleSystemPrompt", () => {
     expect(prompt).not.toContain(PLATFORM_PLACEHOLDER);
     expect(prompt).not.toContain(OS_VERSION_PLACEHOLDER);
     expect(prompt).not.toContain(DATE_PLACEHOLDER);
+    expect(prompt).not.toContain(PROJECT_DIR_PLACEHOLDER);
+    // The project dir is labeled "App Data Dir" (the app data root, not the task's
+    // directory) — the raw "Project Dir" label must never reach the model.
+    expect(prompt).toContain("App Data Dir: /tmp/proj");
+    expect(prompt).not.toContain("Project Dir:");
+    expect(prompt).not.toContain("<project_dir>");
   });
 
   it("default prompt carries the port and API-key guardrails", async () => {
@@ -498,7 +506,7 @@ describe("assembleSystemPrompt", () => {
     expect(prompt).toContain("Session ID: session-test-1");
     expect(prompt).toContain("CWD: /tmp/penguin-ws");
     expect(prompt).toContain("Agent ID: agent-x");
-    expect(prompt).toContain("Project Dir: /tmp/proj");
+    expect(prompt).toContain("App Data Dir: /tmp/proj");
     expect(prompt).toContain("Provider: openai");
     expect(prompt).toContain("Model ID: gpt-5.5");
     expect(prompt).toContain("Platform:");
@@ -506,8 +514,8 @@ describe("assembleSystemPrompt", () => {
     expect(prompt).toContain("Date: 2026-06-30");
     expect(prompt.indexOf("Platform:")).toBeLessThan(prompt.indexOf("OS Version:"));
     expect(prompt.indexOf("OS Version:")).toBeLessThan(prompt.indexOf("Date:"));
-    expect(prompt.indexOf("Date:")).toBeLessThan(prompt.indexOf("Project Dir:"));
-    expect(prompt.indexOf("Project Dir:")).toBeLessThan(prompt.indexOf("Agent ID:"));
+    expect(prompt.indexOf("Date:")).toBeLessThan(prompt.indexOf("App Data Dir:"));
+    expect(prompt.indexOf("App Data Dir:")).toBeLessThan(prompt.indexOf("Agent ID:"));
     expect(prompt.indexOf("Agent ID:")).toBeLessThan(prompt.indexOf("CWD:"));
     expect(prompt.indexOf("CWD:")).toBeLessThan(prompt.indexOf("Provider:"));
     expect(prompt.indexOf("Provider:")).toBeLessThan(prompt.indexOf("Model ID:"));
@@ -515,6 +523,81 @@ describe("assembleSystemPrompt", () => {
   });
 });
 
+describe("resetSystemConfigToDefaults", () => {
+  it("replaces everything with the current defaults, keeping only name/description/version", async () => {
+    await loadOrInitAgentState();
+    const configPath = systemConfigPath(tmpRoot, DEFAULT_PROJECT_ID, DEFAULT_AGENT_ID);
+    // An old on-disk config: custom prompt/runtime/tools plus a key outside the schema.
+    await fs.writeFile(
+      configPath,
+      [
+        "name: Custom Name",
+        "description: Custom description",
+        "version: 7",
+        "system_prompt: Custom prompt with {{PROJECT_DIR}}",
+        "max_turns: 5",
+        "model:",
+        "  max_tokens: 1234",
+        "compaction:",
+        "  mode: discard",
+        "tools:",
+        "  builtin: []",
+        "  mcpServers:",
+        "    - name: custom-mcp",
+        "      config: {}",
+        "custom_extra_key: should-be-dropped",
+      ].join("\n"),
+      "utf8",
+    );
+
+    const written = await resetSystemConfigToDefaults(
+      tmpRoot,
+      DEFAULT_PROJECT_ID,
+      DEFAULT_AGENT_ID,
+    );
+    // Identity fields survive; everything else is the current default.
+    expect(written.name).toBe("Custom Name");
+    expect(written.description).toBe("Custom description");
+    expect(written.version).toBe(7);
+    const defaults = defaultSystemConfig();
+    expect(written.system_prompt).toBe(defaults.system_prompt);
+    expect(written.max_turns).toBe(defaults.max_turns);
+    expect(written.model).toEqual(defaults.model);
+    expect(written.compaction).toEqual(defaults.compaction);
+    expect(written.tools).toEqual(defaults.tools);
+
+    // The file on disk round-trips to the same object; out-of-schema keys are gone.
+    const reloaded = await loadOrInitAgentState();
+    expect(reloaded.systemConfig).toEqual(written);
+    expect("custom_extra_key" in reloaded.systemConfig).toBe(false);
+    expect(reloaded.systemConfig.system_prompt).toContain("App Data Dir: {{PROJECT_DIR}}");
+  });
+
+  it("normalizes an invalid version to 1 and keeps a missing name/description absent", async () => {
+    await loadOrInitAgentState();
+    const configPath = systemConfigPath(tmpRoot, DEFAULT_PROJECT_ID, DEFAULT_AGENT_ID);
+    await fs.writeFile(configPath, "system_prompt: old\nversion: nonsense\n", "utf8");
+    const written = await resetSystemConfigToDefaults(
+      tmpRoot,
+      DEFAULT_PROJECT_ID,
+      DEFAULT_AGENT_ID,
+    );
+    expect(written.version).toBe(1);
+    expect("name" in written).toBe(false);
+    expect("description" in written).toBe(false);
+  });
+
+  it("throws for a nonexistent Agent instead of initializing one", async () => {
+    await expect(
+      resetSystemConfigToDefaults(tmpRoot, DEFAULT_PROJECT_ID, "ghost_agent"),
+    ).rejects.toThrow(/not found/);
+    // No directory is created as a side effect.
+    await expect(
+      fs.access(agentStateDir(tmpRoot, DEFAULT_PROJECT_ID, "ghost_agent")),
+    ).rejects.toThrow();
+  });
+});
+
 describe("project-config round trip", () => {
   it("returns default config when file is absent (without writing)", async () => {
     const cfg = await loadProjectConfig(tmpRoot, DEFAULT_PROJECT_ID);