feat(FN-3706): gate research tools behind experimental feature

The merge introduces a research tool surface gating mechanism: shared availability helpers in core and engine, applied to the executor and triage agent so research prompts and tool exposure are gated behind experimental-feature flags, with tests covering the new logic.

Fusion-Task-Id: FN-3706

packages/engine/src/__tests__/agent-tools.test.ts

@@ -19,6 +19,7 @@ import {
 } from "../agent-tools.js";
 import * as core from "@fusion/core";
 import type { MessageStore, Message } from "@fusion/core";
+import { getEnabledPluginTools, getResearchToolSurfaceStatus } from "../tool-availability.js";
 
 const loggerSpies = vi.hoisted(() => ({
   log: vi.fn(),
@@ -60,6 +61,30 @@ vi.mock("node:child_process", async () => {
   };
 });
 
+describe("tool availability helpers", () => {
+  it("treats research surface as disabled when researchView experimental flag is off", () => {
+    expect(getResearchToolSurfaceStatus({ experimentalFeatures: { researchView: false } } as any)).toEqual({
+      enabled: false,
+      reason: "experimental-disabled",
+    });
+  });
+
+  it("treats research surface as enabled when researchView experimental flag is on", () => {
+    expect(getResearchToolSurfaceStatus({ experimentalFeatures: { researchView: true } } as any)).toEqual({
+      enabled: true,
+      reason: "enabled",
+    });
+  });
+
+  it("resolves legacy experimental feature aliases through core helper", () => {
+    expect(core.isExperimentalFeatureEnabled({ experimentalFeatures: { devServer: true } } as any, "devServerView")).toBe(true);
+  });
+
+  it("returns no plugin tools when plugin runner is absent", () => {
+    expect(getEnabledPluginTools(undefined)).toEqual([]);
+  });
+});
+
 describe("createTaskCreateTool", () => {
   it("returns details.taskId and keeps Created <id> response text", async () => {
     const store = {

packages/engine/src/__tests__/executor.test.ts

@@ -4938,6 +4938,72 @@ describe("Code review verdict enforcement - fn_task_update blocking", () => {
     expect(result.content[0].text).toContain('type="code"');
   });
 
+  it("omits research prompt guidance when researchView experimental flag is disabled", async () => {
+    let capturedSystemPrompt = "";
+    mockedCreateFnAgent.mockImplementation(async (opts: any) => {
+      capturedSystemPrompt = opts.systemPrompt || "";
+      return {
+        session: {
+          prompt: vi.fn().mockResolvedValue(undefined),
+          dispose: vi.fn(),
+          sessionManager: { getLeafId: vi.fn(), branchWithSummary: vi.fn() },
+          navigateTree: vi.fn(),
+        },
+      } as any;
+    });
+
+    const store = createMockStore();
+    store.getSettings.mockResolvedValue({ ...(await store.getSettings()), experimentalFeatures: { researchView: false } });
+    const executor = new TaskExecutor(store, "/tmp/test");
+    await executor.execute({
+      id: "FN-SYS-NO-RESEARCH",
+      title: "Test",
+      description: "Test",
+      column: "in-progress",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    });
+
+    expect(capturedSystemPrompt).not.toContain("fn_research_run");
+  });
+
+  it("includes research prompt guidance when researchView experimental flag is enabled", async () => {
+    let capturedSystemPrompt = "";
+    mockedCreateFnAgent.mockImplementation(async (opts: any) => {
+      capturedSystemPrompt = opts.systemPrompt || "";
+      return {
+        session: {
+          prompt: vi.fn().mockResolvedValue(undefined),
+          dispose: vi.fn(),
+          sessionManager: { getLeafId: vi.fn(), branchWithSummary: vi.fn() },
+          navigateTree: vi.fn(),
+        },
+      } as any;
+    });
+
+    const store = createMockStore();
+    store.getSettings.mockResolvedValue({ ...(await store.getSettings()), experimentalFeatures: { researchView: true } });
+    const executor = new TaskExecutor(store, "/tmp/test");
+    await executor.execute({
+      id: "FN-SYS-RESEARCH",
+      title: "Test",
+      description: "Test",
+      column: "in-progress",
+      dependencies: [],
+      steps: [],
+      currentStep: 0,
+      log: [],
+      createdAt: new Date().toISOString(),
+      updatedAt: new Date().toISOString(),
+    });
+
+    expect(capturedSystemPrompt).toContain("fn_research_run");
+  });
+
   it("EXECUTOR_SYSTEM_PROMPT contains code review enforcement language", async () => {
     // Capture the system prompt passed to createFnAgent
     let capturedSystemPrompt = "";

packages/engine/src/__tests__/triage.test.ts

@@ -587,9 +587,9 @@ describe("buildSpecificationPrompt", () => {
 });
 
 describe("TRIAGE_SYSTEM_PROMPT", () => {
-  it("includes bounded research guidance", () => {
-    expect(TRIAGE_SYSTEM_PROMPT).toContain("fn_research_run");
-    expect(TRIAGE_SYSTEM_PROMPT).toContain("Keep research bounded");
+  it("does not include unconditional research guidance", () => {
+    expect(TRIAGE_SYSTEM_PROMPT).not.toContain("fn_research_run");
+    expect(TRIAGE_SYSTEM_PROMPT).not.toContain("Keep research bounded");
   });
 
   it("requires specs to keep lint, tests, build, and typecheck green even outside initial file scope", () => {
@@ -889,7 +889,7 @@ describe("fast-mode triage", () => {
     }
   });
 
-  it("omits research tools when researchView experimental flag is disabled", async () => {
+  it("omits research tools and prompt guidance when researchView experimental flag is disabled", async () => {
     const task = createTriageTask({ id: "FN-FAST-005", executionMode: "fast" });
     const store = createMockStore({
       getSettings: vi.fn().mockResolvedValue({
@@ -904,8 +904,10 @@ describe("fast-mode triage", () => {
     });
 
     let capturedTools: any[] = [];
+    let capturedSystemPrompt = "";
     mockCreateFnAgent.mockImplementationOnce(async (opts: any) => {
       capturedTools = opts.customTools;
+      capturedSystemPrompt = opts.systemPrompt;
       return {
         session: {
           state: {},
@@ -924,6 +926,42 @@ describe("fast-mode triage", () => {
     expect(capturedTools.some((tool: any) => tool.name === "fn_research_list")).toBe(false);
     expect(capturedTools.some((tool: any) => tool.name === "fn_research_get")).toBe(false);
     expect(capturedTools.some((tool: any) => tool.name === "fn_research_cancel")).toBe(false);
+    expect(capturedSystemPrompt).not.toContain("fn_research_run");
+  });
+
+  it("includes research prompt guidance when researchView experimental flag is enabled", async () => {
+    const task = createTriageTask({ id: "FN-FAST-006", executionMode: "fast" });
+    const store = createMockStore({
+      getSettings: vi.fn().mockResolvedValue({
+        maxConcurrent: 2,
+        maxWorktrees: 4,
+        pollIntervalMs: 10000,
+        groupOverlappingFiles: false,
+        autoMerge: true,
+        experimentalFeatures: { researchView: true },
+      } as Settings),
+      getTask: vi.fn().mockResolvedValue({ ...mockTaskDetail, id: task.id, attachments: [], comments: [] }),
+    });
+
+    let capturedSystemPrompt = "";
+    mockCreateFnAgent.mockImplementationOnce(async (opts: any) => {
+      capturedSystemPrompt = opts.systemPrompt;
+      return {
+        session: {
+          state: {},
+          sessionManager: { getLeafId: vi.fn().mockReturnValue(null) },
+          prompt: vi.fn().mockResolvedValue(undefined),
+          dispose: vi.fn(),
+          navigateTree: vi.fn(),
+        },
+      };
+    });
+
+    const processor = new TriageProcessor(store, "/tmp/root");
+    await processor.specifyTask(task);
+
+    expect(capturedSystemPrompt).toContain("fn_research_run");
+    expect(capturedSystemPrompt).toContain("Keep research bounded");
   });
 });
 

packages/engine/src/executor.ts

@@ -11,7 +11,6 @@ import {
   buildExecutionMemoryInstructions,
   getTaskMergeBlocker,
   isEphemeralAgent,
-  isResearchExperimentalEnabled,
   resolveAgentPrompt,
   resolveEffectiveAgentPermissionPolicy,
   resolveProjectDefaultModel,
@@ -73,6 +72,11 @@ import {
   createTaskLogTool as sharedCreateTaskLogTool,
 } from "./agent-tools.js";
 import { getTaskCompletionBlockerForStore } from "./task-completion.js";
+import {
+  getEnabledPluginTools,
+  getResearchGuidanceForSurface,
+  isResearchToolSurfaceEnabled,
+} from "./tool-availability.js";
 import { createFusionAuthStorage, getModelRegistryModelsPath } from "./auth-storage.js";
 import { createRunVerificationTool } from "./run-verification-tool.js";
 import { createFallbackModelObserver } from "./fallback-model-observer.js";
@@ -381,12 +385,6 @@ You can save and retrieve named documents for this task. Use these to store plan
 
 Documents are versioned — each write creates a new revision. Use meaningful keys like "plan", "notes", "research", "architecture".
 
-## Research tools
-When implementation needs external context, you may use research tools (
-\`fn_research_run\`, \`fn_research_list\`, \`fn_research_get\`, \`fn_research_cancel\`) to run bounded research.
-Keep runs focused and short, and persist durable conclusions into task documents (for example key="research").
-If research is disabled or providers are not configured, use the actionable tool response and continue with available local context.
-
 **IMPORTANT — Save your deliverables as documents:** When your task produces written output (documentation, specifications, reports, API references, README updates, guides, or any other content), you MUST save that content as a task document using \`fn_task_document_write\`. Use a key that describes the deliverable (e.g., key="readme", key="api-docs", key="changelog"). Do this in addition to writing the file to disk — the document persists in the task for review even after the worktree is cleaned up.
 
 If the task's PROMPT.md includes a "Documentation Requirements" section listing files to update, save each updated file's final content as a task document with a matching key.
@@ -503,7 +501,12 @@ The tool prevents your session from being killed by the inactivity watchdog duri
 /** Resolve the executor system prompt from settings, falling back to the hardcoded constant. */
 function getExecutorSystemPrompt(settings: Settings): string {
   const customPrompt = resolveAgentPrompt("executor", settings.agentPrompts);
-  return customPrompt || EXECUTOR_SYSTEM_PROMPT;
+  const basePrompt = customPrompt || EXECUTOR_SYSTEM_PROMPT;
+  const sections = [
+    basePrompt,
+    isResearchToolSurfaceEnabled(settings) ? getResearchGuidanceForSurface("executor") : "",
+  ].filter((section) => section.trim());
+  return sections.join("\n\n");
 }
 
 
@@ -2880,7 +2883,7 @@ export class TaskExecutor {
         this.createSpawnAgentTool(task.id, worktreePath, settings),
         this.createTaskDocumentWriteTool(task.id),
         this.createTaskDocumentReadTool(task.id),
-        ...(isResearchExperimentalEnabled(settings)
+        ...(isResearchToolSurfaceEnabled(settings)
           ? createResearchTools({
             store: this.store,
             rootDir: this.rootDir,
@@ -2911,7 +2914,7 @@ export class TaskExecutor {
           createReadMessagesTool(this.options.messageStore, assignedAgentId),
         ] : []),
         // Add plugin tools from PluginRunner
-        ...(this.options.pluginRunner?.getPluginTools() ?? []),
+        ...getEnabledPluginTools(this.options.pluginRunner),
       ];
 
       // Accumulates the full assistant text output for the most recent session.

packages/engine/src/tool-availability.ts

@@ -0,0 +1,38 @@
+import type { Settings } from "@fusion/core";
+import { isResearchExperimentalEnabled } from "@fusion/core";
+import type { PluginRunner } from "./plugin-runner.js";
+import type { ToolDefinition } from "@mariozechner/pi-coding-agent";
+
+export function isResearchToolSurfaceEnabled(settings: Partial<Settings> | undefined): boolean {
+  return isResearchExperimentalEnabled(settings);
+}
+
+export function getResearchToolSurfaceStatus(settings: Partial<Settings> | undefined): {
+  enabled: boolean;
+  reason: "experimental-disabled" | "enabled";
+} {
+  const enabled = isResearchToolSurfaceEnabled(settings);
+  return {
+    enabled,
+    reason: enabled ? "enabled" : "experimental-disabled",
+  };
+}
+
+const TRIAGE_RESEARCH_GUIDANCE = `## Research tools
+When spec work needs missing domain context, you may use research tools (\`fn_research_run\`, \`fn_research_list\`, \`fn_research_get\`, \`fn_research_cancel\`). Keep research bounded to the task at hand, prefer concise queries, and write durable findings into task documents when useful.
+If research is unavailable or unconfigured, continue planning with repository context and clearly note assumptions.`;
+
+const EXECUTOR_RESEARCH_GUIDANCE = `## Research tools
+When implementation needs external context, you may use research tools (
+\`fn_research_run\`, \`fn_research_list\`, \`fn_research_get\`, \`fn_research_cancel\`) to run bounded research.
+Keep runs focused and short, and persist durable conclusions into task documents (for example key="research").
+If research is disabled or providers are not configured, use the actionable tool response and continue with available local context.`;
+
+export function getResearchGuidanceForSurface(surface: "triage" | "executor"): string {
+  return surface === "triage" ? TRIAGE_RESEARCH_GUIDANCE : EXECUTOR_RESEARCH_GUIDANCE;
+}
+
+export function getEnabledPluginTools(pluginRunner: PluginRunner | undefined): ToolDefinition[] {
+  if (!pluginRunner) return [];
+  return pluginRunner.getPluginTools();
+}

packages/engine/src/triage.ts

@@ -8,7 +8,6 @@ import type {
 } from "@fusion/core";
 import {
   buildTriageMemoryInstructions,
-  isResearchExperimentalEnabled,
   resolveAgentPrompt,
   sortTasksByPriorityThenAgeAndId,
 } from "@fusion/core";
@@ -56,6 +55,10 @@ import {
   createTaskDocumentReadTool,
   createTaskDocumentWriteTool,
 } from "./agent-tools.js";
+import {
+  getResearchGuidanceForSurface,
+  isResearchToolSurfaceEnabled,
+} from "./tool-availability.js";
 
 export const TRIAGE_SYSTEM_PROMPT = `You are a task specification agent for "fn", an AI-orchestrated task board.
 
@@ -244,10 +247,6 @@ When the planning conversation produces a structured plan, save it as a document
 - Testing & Verification must run before Documentation & Delivery
 - Avoid giant catch-all steps; split outcomes so execution can be verified incrementally
 
-## Research tools
-When spec work needs missing domain context, you may use research tools (\`fn_research_run\`, \`fn_research_list\`, \`fn_research_get\`, \`fn_research_cancel\`). Keep research bounded to the task at hand, prefer concise queries, and write durable findings into task documents when useful.
-If research is unavailable or unconfigured, continue planning with repository context and clearly note assumptions.
-
 ## Guidelines
 - Read the project structure and relevant source files to understand context BEFORE writing
 - Check package.json/scripts and explicit project commands to align real lint/test/build/typecheck commands
@@ -951,7 +950,7 @@ export class TriageProcessor {
           }),
           createTaskDocumentWriteTool(this.store, task.id),
           createTaskDocumentReadTool(this.store, task.id),
-          ...(isResearchExperimentalEnabled(settings)
+          ...(isResearchToolSurfaceEnabled(settings)
             ? createResearchTools({
               store: this.store,
               rootDir: this.rootDir,
@@ -1016,7 +1015,13 @@ export class TriageProcessor {
         const triageSystemPrompt = buildSystemPromptWithInstructions(
           resolveAgentPrompt("triage", settings.agentPrompts)
             || (isFast ? FAST_TRIAGE_SYSTEM_PROMPT : TRIAGE_SYSTEM_PROMPT),
-          [triageIdentitySection, triageInstructions].filter((section) => section.trim()).join("\n\n"),
+          [
+            triageIdentitySection,
+            triageInstructions,
+            isResearchToolSurfaceEnabled(settings)
+              ? getResearchGuidanceForSurface("triage")
+              : "",
+          ].filter((section) => section.trim()).join("\n\n"),
         );
         const triageContributions = this.options.pluginRunner
           ?.getPromptContributionsForSurface("triage")