fix: prevent agents from duplicating delegated subagent work

Addresses user reports where Sisyphus/Hephaestus would delegate tasks
to explore/librarian subagents but then immediately perform the same
search/work themselves, wasting context and defeating the purpose of
delegation.

Changes:
- Add Anti-Duplication section to dynamic-agent-prompt-builder with
  clear rules: once you delegate, do NOT manually re-do the same search
- Update all agent prompts (sisyphus, hephaestus, sis-junior gemini/gpt)
  to use 'non-overlapping work' instead of 'keep working' after delegation
- Add buildAntiDuplicationSection() with explicit examples of forbidden
  vs allowed behavior after delegation
- Add 'Delegation Trust Rule' to explore section
- Add 'Delegation Duplication' to anti-patterns list

Atlas fixes:
- Add AUTO-CONTINUE POLICY to all Atlas variants (default, gemini, gpt)
  preventing the 'should I continue?' confirmation loop between plan steps
- Fix plan file path in default atlas (.sisyphus/tasks/ -> .sisyphus/plans/)
- Update GPT atlas uncertainty section to only ask questions during initial
  plan analysis, not during execution

Fixes: subagent delegation duplication, Atlas continuation prompting

src/agents/anti-duplication.test.ts

@@ -0,0 +1,92 @@
+/// <reference types="bun-types" />
+
+import { describe, it, expect } from "bun:test"
+import { buildAntiDuplicationSection } from "./dynamic-agent-prompt-builder"
+
+describe("buildAntiDuplicationSection", () => {
+  it("#given no arguments #when building anti-duplication section #then returns comprehensive rule section", () => {
+    //#given: no special configuration needed
+
+    //#when: building the anti-duplication section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should contain the anti-duplication rule with all key concepts
+    expect(result).toContain("Anti-Duplication Rule")
+    expect(result).toContain("CRITICAL")
+    expect(result).toContain("DO NOT perform the same search yourself")
+  })
+
+  it("#given no arguments #when building #then explicitly forbids manual re-search after delegation", () => {
+    //#given: no special configuration
+
+    //#when: building the section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should explicitly list forbidden behaviors
+    expect(result).toContain("FORBIDDEN")
+    expect(result).toContain("manually grep/search for the same information")
+    expect(result).toContain("Re-doing the research")
+  })
+
+  it("#given no arguments #when building #then allows non-overlapping work", () => {
+    //#given: no special configuration
+
+    //#when: building the section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should explicitly allow non-overlapping work
+    expect(result).toContain("ALLOWED")
+    expect(result).toContain("non-overlapping work")
+    expect(result).toContain("work that doesn't depend on the delegated research")
+  })
+
+  it("#given no arguments #when building #then includes wait-for-results instructions", () => {
+    //#given: no special configuration
+
+    //#when: building the section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should include instructions for waiting properly
+    expect(result).toContain("Wait for Results Properly")
+    expect(result).toContain("End your response")
+    expect(result).toContain("Wait for the completion notification")
+    expect(result).toContain("background_output")
+  })
+
+  it("#given no arguments #when building #then explains why this matters", () => {
+    //#given: no special configuration
+
+    //#when: building the section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should explain the purpose
+    expect(result).toContain("Why This Matters")
+    expect(result).toContain("Wasted tokens")
+    expect(result).toContain("Confusion")
+    expect(result).toContain("Efficiency")
+  })
+
+  it("#given no arguments #when building #then provides code examples", () => {
+    //#given: no special configuration
+
+    //#when: building the section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should include examples
+    expect(result).toContain("Example")
+    expect(result).toContain("WRONG")
+    expect(result).toContain("CORRECT")
+    expect(result).toContain("task(subagent_type=")
+  })
+
+  it("#given no arguments #when building #then uses proper markdown formatting", () => {
+    //#given: no special configuration
+
+    //#when: building the section
+    const result = buildAntiDuplicationSection()
+
+    //#then: should be wrapped in Anti_Duplication tag
+    expect(result).toContain("<Anti_Duplication>")
+    expect(result).toContain("</Anti_Duplication>")
+  })
+})

src/agents/atlas/atlas-prompt.test.ts

@@ -0,0 +1,118 @@
+import { describe, test, expect } from "bun:test"
+import { ATLAS_SYSTEM_PROMPT } from "./default"
+import { ATLAS_GPT_SYSTEM_PROMPT } from "./gpt"
+import { ATLAS_GEMINI_SYSTEM_PROMPT } from "./gemini"
+
+describe("Atlas prompts auto-continue policy", () => {
+  test("default variant should forbid asking user for continuation confirmation", () => {
+    // given
+    const prompt = ATLAS_SYSTEM_PROMPT
+
+    // when
+    const lowerPrompt = prompt.toLowerCase()
+
+    // then
+    expect(lowerPrompt).toContain("auto-continue policy")
+    expect(lowerPrompt).toContain("never ask the user")
+    expect(lowerPrompt).toContain("should i continue")
+    expect(lowerPrompt).toContain("proceed to next task")
+    expect(lowerPrompt).toContain("approval-style")
+    expect(lowerPrompt).toContain("auto-continue immediately")
+  })
+
+  test("gpt variant should forbid asking user for continuation confirmation", () => {
+    // given
+    const prompt = ATLAS_GPT_SYSTEM_PROMPT
+
+    // when
+    const lowerPrompt = prompt.toLowerCase()
+
+    // then
+    expect(lowerPrompt).toContain("auto-continue policy")
+    expect(lowerPrompt).toContain("never ask the user")
+    expect(lowerPrompt).toContain("should i continue")
+    expect(lowerPrompt).toContain("proceed to next task")
+    expect(lowerPrompt).toContain("approval-style")
+    expect(lowerPrompt).toContain("auto-continue immediately")
+  })
+
+  test("gemini variant should forbid asking user for continuation confirmation", () => {
+    // given
+    const prompt = ATLAS_GEMINI_SYSTEM_PROMPT
+
+    // when
+    const lowerPrompt = prompt.toLowerCase()
+
+    // then
+    expect(lowerPrompt).toContain("auto-continue policy")
+    expect(lowerPrompt).toContain("never ask the user")
+    expect(lowerPrompt).toContain("should i continue")
+    expect(lowerPrompt).toContain("proceed to next task")
+    expect(lowerPrompt).toContain("approval-style")
+    expect(lowerPrompt).toContain("auto-continue immediately")
+  })
+
+  test("all variants should require immediate continuation after verification passes", () => {
+    // given
+    const prompts = [ATLAS_SYSTEM_PROMPT, ATLAS_GPT_SYSTEM_PROMPT, ATLAS_GEMINI_SYSTEM_PROMPT]
+
+    // when / then
+    for (const prompt of prompts) {
+      const lowerPrompt = prompt.toLowerCase()
+      expect(lowerPrompt).toMatch(/auto-continue immediately after verification/)
+      expect(lowerPrompt).toMatch(/immediately delegate next task/)
+    }
+  })
+
+  test("all variants should define when user interaction is actually needed", () => {
+    // given
+    const prompts = [ATLAS_SYSTEM_PROMPT, ATLAS_GPT_SYSTEM_PROMPT, ATLAS_GEMINI_SYSTEM_PROMPT]
+
+    // when / then
+    for (const prompt of prompts) {
+      const lowerPrompt = prompt.toLowerCase()
+      expect(lowerPrompt).toMatch(/only pause.*truly blocked/)
+      expect(lowerPrompt).toMatch(/plan needs clarification|blocked by external/)
+    }
+  })
+})
+
+describe("Atlas prompts plan path consistency", () => {
+  test("default variant should use .sisyphus/plans/{plan-name}.md path", () => {
+    // given
+    const prompt = ATLAS_SYSTEM_PROMPT
+
+    // when / then
+    expect(prompt).toContain(".sisyphus/plans/{plan-name}.md")
+    expect(prompt).not.toContain(".sisyphus/tasks/{plan-name}.yaml")
+    expect(prompt).not.toContain(".sisyphus/tasks/")
+  })
+
+  test("gpt variant should use .sisyphus/plans/{plan-name}.md path", () => {
+    // given
+    const prompt = ATLAS_GPT_SYSTEM_PROMPT
+
+    // when / then
+    expect(prompt).toContain(".sisyphus/plans/{plan-name}.md")
+    expect(prompt).not.toContain(".sisyphus/tasks/")
+  })
+
+  test("gemini variant should use .sisyphus/plans/{plan-name}.md path", () => {
+    // given
+    const prompt = ATLAS_GEMINI_SYSTEM_PROMPT
+
+    // when / then
+    expect(prompt).toContain(".sisyphus/plans/{plan-name}.md")
+    expect(prompt).not.toContain(".sisyphus/tasks/")
+  })
+
+  test("all variants should read plan file after verification", () => {
+    // given
+    const prompts = [ATLAS_SYSTEM_PROMPT, ATLAS_GPT_SYSTEM_PROMPT, ATLAS_GEMINI_SYSTEM_PROMPT]
+
+    // when / then
+    for (const prompt of prompts) {
+      expect(prompt).toMatch(/read[\s\S]*?\.sisyphus\/plans\//)
+    }
+  })
+})

src/agents/atlas/default.ts

@@ -99,6 +99,29 @@ Every \`task()\` prompt MUST include ALL 6 sections:
 **If your prompt is under 30 lines, it's TOO SHORT.**
 </delegation_system>
 
+<auto_continue>
+## AUTO-CONTINUE POLICY (STRICT)
+
+**CRITICAL: NEVER ask the user "should I continue", "proceed to next task", or any approval-style questions between plan steps.**
+
+**You MUST auto-continue immediately after verification passes:**
+- After any delegation completes and passes verification → Immediately delegate next task
+- Do NOT wait for user input, do NOT ask "should I continue"
+- Only pause or ask if you are truly blocked by missing information, an external dependency, or a critical failure
+
+**The only time you ask the user:**
+- Plan needs clarification or modification before execution
+- Blocked by an external dependency beyond your control
+- Critical failure prevents any further progress
+
+**Auto-continue examples:**
+- Task A done → Verify → Pass → Immediately start Task B
+- Task fails → Retry 3x → Still fails → Document → Move to next independent task
+- NEVER: "Should I continue to the next task?"
+
+**This is NOT optional. This is core to your role as orchestrator.**
+</auto_continue>
+
 <workflow>
 ## Step 0: Register Tracking
 
@@ -214,7 +237,7 @@ After EVERY delegation, complete ALL of these steps — no shortcuts:
 
 After verification, READ the plan file directly — every time, no exceptions:
 \`\`\`
-Read(".sisyphus/tasks/{plan-name}.yaml")
+Read(".sisyphus/plans/{plan-name}.md")
 \`\`\`
 Count remaining \`- [ ]\` tasks. This is your ground truth for what comes next.
 

src/agents/atlas/gemini.ts

@@ -116,6 +116,29 @@ Every \`task()\` prompt MUST include ALL 6 sections:
 **Minimum 30 lines per delegation prompt. Under 30 lines = the subagent WILL fail.**
 </delegation_system>
 
+<auto_continue>
+## AUTO-CONTINUE POLICY (STRICT)
+
+**CRITICAL: NEVER ask the user "should I continue", "proceed to next task", or any approval-style questions between plan steps.**
+
+**You MUST auto-continue immediately after verification passes:**
+- After any delegation completes and passes verification → Immediately delegate next task
+- Do NOT wait for user input, do NOT ask "should I continue"
+- Only pause or ask if you are truly blocked by missing information, an external dependency, or a critical failure
+
+**The only time you ask the user:**
+- Plan needs clarification or modification before execution
+- Blocked by an external dependency beyond your control
+- Critical failure prevents any further progress
+
+**Auto-continue examples:**
+- Task A done → Verify → Pass → Immediately start Task B
+- Task fails → Retry 3x → Still fails → Document → Move to next independent task
+- NEVER: "Should I continue to the next task?"
+
+**This is NOT optional. This is core to your role as orchestrator.**
+</auto_continue>
+
 <workflow>
 ## Step 0: Register Tracking
 

src/agents/atlas/gpt.ts

@@ -48,9 +48,10 @@ Complete ALL tasks in a work plan via \`task()\` until fully done.
 </scope_and_design_constraints>
 
 <uncertainty_and_ambiguity>
-- If a task is ambiguous or underspecified:
+- During initial plan analysis, if a task is ambiguous or underspecified:
   - Ask 1-3 precise clarifying questions, OR
   - State your interpretation explicitly and proceed with the simplest approach.
+- Once execution has started, do NOT stop to ask for continuation or approval between steps.
 - Never fabricate task details, file paths, or requirements.
 - Prefer language like "Based on the plan..." instead of absolute claims.
 - When unsure about parallelization, default to sequential execution.
@@ -134,6 +135,29 @@ Every \`task()\` prompt MUST include ALL 6 sections:
 **Minimum 30 lines per delegation prompt.**
 </delegation_system>
 
+<auto_continue>
+## AUTO-CONTINUE POLICY (STRICT)
+
+**CRITICAL: NEVER ask the user "should I continue", "proceed to next task", or any approval-style questions between plan steps.**
+
+**You MUST auto-continue immediately after verification passes:**
+- After any delegation completes and passes verification → Immediately delegate next task
+- Do NOT wait for user input, do NOT ask "should I continue"
+- Only pause or ask if you are truly blocked by missing information, an external dependency, or a critical failure
+
+**The only time you ask the user:**
+- Plan needs clarification or modification before execution
+- Blocked by an external dependency beyond your control
+- Critical failure prevents any further progress
+
+**Auto-continue examples:**
+- Task A done → Verify → Pass → Immediately start Task B
+- Task fails → Retry 3x → Still fails → Document → Move to next independent task
+- NEVER: "Should I continue to the next task?"
+
+**This is NOT optional. This is core to your role as orchestrator.**
+</auto_continue>
+
 <workflow>
 ## Step 0: Register Tracking
 

src/agents/delegation-trust-prompt.test.ts

@@ -0,0 +1,88 @@
+import { describe, expect, test } from "bun:test"
+import { createSisyphusAgent } from "./sisyphus"
+import { createHephaestusAgent } from "./hephaestus"
+import { buildSisyphusJuniorPrompt } from "./sisyphus-junior/agent"
+import {
+  buildAntiDuplicationSection,
+  buildExploreSection,
+  type AvailableAgent,
+} from "./dynamic-agent-prompt-builder"
+
+const exploreAgent = {
+  name: "explore",
+  description: "Contextual grep specialist",
+  metadata: {
+    category: "advisor",
+    cost: "FREE",
+    promptAlias: "Explore",
+    triggers: [],
+    useWhen: ["Multiple search angles needed"],
+    avoidWhen: ["Single keyword search is enough"],
+  },
+} satisfies AvailableAgent
+
+describe("delegation trust prompt rules", () => {
+  test("buildAntiDuplicationSection explains overlap is forbidden", () => {
+    // given
+    const section = buildAntiDuplicationSection()
+
+    // when / then
+    expect(section).toContain("DO NOT perform the same search yourself")
+    expect(section).toContain("non-overlapping work")
+    expect(section).toContain("End your response")
+  })
+
+  test("buildExploreSection includes delegation trust rule", () => {
+    // given
+    const agents = [exploreAgent]
+
+    // when
+    const section = buildExploreSection(agents)
+
+    // then
+    expect(section).toContain("Delegation Trust Rule")
+    expect(section).toContain("do **not** manually perform that same search yourself")
+  })
+
+  test("Sisyphus prompt forbids duplicate delegated exploration", () => {
+    // given
+    const agent = createSisyphusAgent("anthropic/claude-sonnet-4-6", [exploreAgent])
+
+    // when
+    const prompt = agent.prompt
+
+    // then
+    expect(prompt).toContain("Continue only with non-overlapping work")
+    expect(prompt).toContain("DO NOT perform the same search yourself")
+  })
+
+  test("Hephaestus prompt forbids duplicate delegated exploration", () => {
+    // given
+    const agent = createHephaestusAgent("openai/gpt-5.2", [exploreAgent])
+
+    // when
+    const prompt = agent.prompt
+
+    // then
+    expect(prompt).toContain("Continue only with non-overlapping work after launching background agents")
+    expect(prompt).toContain("DO NOT perform the same search yourself")
+  })
+
+  test("Sisyphus-Junior GPT prompt forbids duplicate delegated exploration", () => {
+    // given
+    const prompt = buildSisyphusJuniorPrompt("openai/gpt-5.2", false)
+
+    // when / then
+    expect(prompt).toContain("continue only with non-overlapping work while they search")
+    expect(prompt).toContain("DO NOT perform the same search yourself")
+  })
+
+  test("Sisyphus-Junior Gemini prompt forbids duplicate delegated exploration", () => {
+    // given
+    const prompt = buildSisyphusJuniorPrompt("google/gemini-3.1-pro", false)
+
+    // when / then
+    expect(prompt).toContain("continue only with non-overlapping work while they search")
+    expect(prompt).toContain("DO NOT perform the same search yourself")
+  })
+})

src/agents/dynamic-agent-prompt-builder.ts

@@ -118,6 +118,8 @@ export function buildExploreSection(agents: AvailableAgent[]): string {
 
 Use it as a **peer tool**, not a fallback. Fire liberally.
 
+**Delegation Trust Rule:** Once you fire an explore agent for a search, do **not** manually perform that same search yourself. Use direct tools only for non-overlapping work or when you intentionally skipped delegation.
+
 **Use Direct Tools when:**
 ${avoidWhen.map((w) => `- ${w}`).join("\n")}
 
@@ -308,6 +310,7 @@ export function buildAntiPatternsSection(): string {
     "- **Search**: Firing agents for single-line typos or obvious syntax errors",
     "- **Debugging**: Shotgun debugging, random changes",
     "- **Background Tasks**: Polling `background_output` on running tasks — end response and wait for notification",
+    "- **Delegation Duplication**: Delegating exploration to explore/librarian and then manually doing the same search yourself",
     "- **Oracle**: Delivering answer without collecting Oracle results",
   ]
 
@@ -409,3 +412,52 @@ export function buildUltraworkSection(
 
   return lines.join("\n")
 }
+
+// Anti-duplication section for agent prompts
+export function buildAntiDuplicationSection(): string {
+  return `<Anti_Duplication>
+## Anti-Duplication Rule (CRITICAL)
+
+Once you delegate exploration to explore/librarian agents, **DO NOT perform the same search yourself**.
+
+### What this means:
+
+**FORBIDDEN:**
+- After firing explore/librarian, manually grep/search for the same information
+- Re-doing the research the agents were just tasked with
+- "Just quickly checking" the same files the background agents are checking
+
+**ALLOWED:**
+- Continue with **non-overlapping work** — work that doesn't depend on the delegated research
+- Work on unrelated parts of the codebase
+- Preparation work (e.g., setting up files, configs) that can proceed independently
+
+### Wait for Results Properly:
+
+When you need the delegated results but they're not ready:
+
+1. **End your response** — do NOT continue with work that depends on those results
+2. **Wait for the completion notification** — the system will trigger your next turn
+3. **Then** collect results via \`background_output(task_id="...")\`
+4. **Do NOT** impatiently re-search the same topics while waiting
+
+### Why This Matters:
+
+- **Wasted tokens**: Duplicate exploration wastes your context budget
+- **Confusion**: You might contradict the agent's findings
+- **Efficiency**: The whole point of delegation is parallel throughput
+
+### Example:
+
+\`\`\`typescript
+// WRONG: After delegating, re-doing the search
+task(subagent_type="explore", run_in_background=true, ...)
+// Then immediately grep for the same thing yourself — FORBIDDEN
+
+// CORRECT: Continue non-overlapping work
+task(subagent_type="explore", run_in_background=true, ...)
+// Work on a different, unrelated file while they search
+// End your response and wait for the notification
+\`\`\`
+</Anti_Duplication>`
+}

src/agents/hephaestus.ts

@@ -16,6 +16,7 @@ import {
   buildOracleSection,
   buildHardBlocksSection,
   buildAntiPatternsSection,
+  buildAntiDuplicationSection,
   categorizeTools,
 } from "./dynamic-agent-prompt-builder";
 
@@ -290,11 +291,13 @@ Prompt structure for each agent:
 - Fire 2-5 explore agents in parallel for any non-trivial codebase question
 - Parallelize independent file reads — don't read files one at a time
 - NEVER use \`run_in_background=false\` for explore/librarian
-- Continue your work immediately after launching background agents
+- Continue only with non-overlapping work after launching background agents
 - Collect results with \`background_output(task_id="...")\` when needed
 - BEFORE final answer, cancel DISPOSABLE tasks individually: \`background_cancel(taskId="bg_explore_xxx")\`, \`background_cancel(taskId="bg_librarian_xxx")\`
 - **NEVER use \`background_cancel(all=true)\`** — it kills tasks whose results you haven't collected yet
 
+${buildAntiDuplicationSection()}
+
 ### Search Stop Conditions
 
 STOP searching when:

src/agents/sisyphus-junior/gemini.ts

@@ -9,6 +9,7 @@
  */
 
 import { resolvePromptAppend } from "../builtin-agents/resolve-file-uri"
+import { buildAntiDuplicationSection } from "../dynamic-agent-prompt-builder"
 
 export function buildGeminiSisyphusJuniorPrompt(
   useTaskSystem: boolean,
@@ -58,7 +59,7 @@ Before responding, ask yourself: What tools do I need to call? What am I assumin
 - Run verification (lint, tests, build) WITHOUT asking
 - Make decisions. Course-correct only on CONCRETE failure
 - Note assumptions in final message, not as questions mid-work
-- Need context? Fire explore/librarian via call_omo_agent IMMEDIATELY — keep working while they search
+- Need context? Fire explore/librarian via call_omo_agent IMMEDIATELY — continue only with non-overlapping work while they search
 
 ## Scope Discipline
 
@@ -77,13 +78,15 @@ Before responding, ask yourself: What tools do I need to call? What am I assumin
 
 <tool_usage_rules>
 - Parallelize independent tool calls: multiple file reads, grep searches, agent fires — all at once
-- Explore/Librarian via call_omo_agent = background research. Fire them and keep working
+- Explore/Librarian via call_omo_agent = background research. Fire them and continue only with non-overlapping work
 - After any file edit: restate what changed, where, and what validation follows
 - Prefer tools over guessing whenever you need specific data (files, configs, patterns)
 - ALWAYS use tools over internal knowledge for file contents, project state, and verification
 - **DO NOT SKIP tool calls because you think you already know the answer. You DON'T.**
 </tool_usage_rules>
 
+${buildAntiDuplicationSection()}
+
 ${taskDiscipline}
 
 ## Progress Updates

src/agents/sisyphus-junior/gpt.ts

@@ -7,6 +7,7 @@
  */
 
 import { resolvePromptAppend } from "../builtin-agents/resolve-file-uri"
+import { buildAntiDuplicationSection } from "../dynamic-agent-prompt-builder"
 
 export function buildGptSisyphusJuniorPrompt(
   useTaskSystem: boolean,
@@ -40,7 +41,7 @@ When blocked: try a different approach → decompose the problem → challenge a
 - Run verification (lint, tests, build) WITHOUT asking
 - Make decisions. Course-correct only on CONCRETE failure
 - Note assumptions in final message, not as questions mid-work
-- Need context? Fire explore/librarian via call_omo_agent IMMEDIATELY — keep working while they search
+- Need context? Fire explore/librarian via call_omo_agent IMMEDIATELY — continue only with non-overlapping work while they search
 
 ## Scope Discipline
 
@@ -58,12 +59,14 @@ When blocked: try a different approach → decompose the problem → challenge a
 
 <tool_usage_rules>
 - Parallelize independent tool calls: multiple file reads, grep searches, agent fires — all at once
-- Explore/Librarian via call_omo_agent = background research. Fire them and keep working
+- Explore/Librarian via call_omo_agent = background research. Fire them and continue only with non-overlapping work
 - After any file edit: restate what changed, where, and what validation follows
 - Prefer tools over guessing whenever you need specific data (files, configs, patterns)
 - ALWAYS use tools over internal knowledge for file contents, project state, and verification
 </tool_usage_rules>
 
+${buildAntiDuplicationSection()}
+
 ${taskDiscipline}
 
 ## Progress Updates

src/agents/sisyphus.ts

@@ -35,6 +35,7 @@ import {
   buildAntiPatternsSection,
   buildDeepParallelSection,
   buildNonClaudePlannerSection,
+  buildAntiDuplicationSection,
   categorizeTools,
 } from "./dynamic-agent-prompt-builder";
 
@@ -333,7 +334,7 @@ task(subagent_type="explore", run_in_background=true, load_skills=[], descriptio
 // Reference Grep (external)
 task(subagent_type="librarian", run_in_background=true, load_skills=[], description="Find JWT security docs", prompt="I'm implementing JWT auth and need current security best practices to choose token storage (httpOnly cookies vs localStorage) and set expiration policy. Find: OWASP auth guidelines, recommended token lifetimes, refresh token rotation strategies, common JWT vulnerabilities. Skip 'what is JWT' tutorials — production security guidance only.")
 task(subagent_type="librarian", run_in_background=true, load_skills=[], description="Find Express auth patterns", prompt="I'm building Express auth middleware and need production-quality patterns to structure my middleware chain. Find how established Express apps (1000+ stars) handle: middleware ordering, token refresh, role-based access control, auth error propagation. Skip basic tutorials — I need battle-tested patterns with proper error handling.")
-// Continue working immediately. System notifies on completion — collect with background_output then.
+// Continue only with non-overlapping work. System notifies on completion — collect with background_output then.
 
 // WRONG: Sequential or blocking
 result = task(..., run_in_background=false)  // Never wait synchronously for explore/librarian
@@ -341,11 +342,13 @@ result = task(..., run_in_background=false)  // Never wait synchronously for exp
 
 ### Background Result Collection:
 1. Launch parallel agents \u2192 receive task_ids
-2. Continue immediate work
+2. Continue only with non-overlapping work
 3. System sends \`<system-reminder>\` on each task completion — then call \`background_output(task_id="...")\`
 4. Need results not yet ready? **End your response.** The notification will trigger your next turn.
 5. Cleanup: Cancel disposable tasks individually via \`background_cancel(taskId="...")\`
 
+${buildAntiDuplicationSection()}
+
 ### Search Stop Conditions
 
 STOP searching when:

src/tools/background-task/create-background-output.ts

@@ -87,7 +87,6 @@ export function createBackgroundOutput(manager: BackgroundOutputManager, client:
 
         const shouldBlock = args.block === true
         const timeoutMs = Math.min(args.timeout ?? 60000, 600000)
-        const fullSession = args.full_session ?? true
 
         let resolvedTask = task
 
@@ -123,6 +122,10 @@ export function createBackgroundOutput(manager: BackgroundOutputManager, client:
         }
 
         const isActive = isTaskActiveStatus(resolvedTask.status)
+        const fullSessionProvided = args.full_session !== undefined
+        const fullSession = fullSessionProvided
+          ? (args.full_session ?? true)
+          : !isActive
         const includeThinking = isActive || (args.include_thinking ?? false)
         const includeToolResults = isActive || (args.include_tool_results ?? false)