diff --git a/.changeset/fn-8545-mission-admission.md b/.changeset/fn-8545-mission-admission.md
new file mode 100644
index 0000000000..c91c1d9a8b
--- /dev/null
+++ b/.changeset/fn-8545-mission-admission.md
@@ -0,0 +1,7 @@
+---
+"@runfusion/fusion": patch
+---
+
+summary: Fix supervised task creation and defined-feature mission bootstrap admission.
+category: fix
+dev: No-task heartbeat creates still require approved lineage; first defined-feature tasks link and triage safely.
diff --git a/docs/agents.md b/docs/agents.md
index 573c2d836c..0f423184a3 100644
--- a/docs/agents.md
+++ b/docs/agents.md
@@ -83,6 +83,12 @@ printf "deploy report" | fn chat agent-abc123 --once --non-interactive
 
 > Replies require a running engine for the same project (for example `fn` dashboard or `fn serve`).
 
+## Mission lineage and task creation
+
+`fn_task_create` and `fn_delegate_task` use two distinct controls. In an autonomous no-task heartbeat, the caller must provide approved `mission_lineage` (mission, slice, and feature); a rejection states that approved mission lineage is required, and no permission grant overrides it. In interactive/user-supervised and task-scoped sessions, lineage is optional and `task_agent_mutation` category rules and exact-tool overrides decide whether creation is allowed, requires approval, or is blocked.
+
+A valid active lineage can bootstrap the first task for a hand-authored `defined` feature. The feature is linked to that exact task and promoted to `triaged`; later autonomous scheduler work still requires a `triaged` or `in-progress` feature.
+
 ## Agent configuration updates from agents
 
 The `fn_agent_update` extension tool lets chat/extension callers update existing non-ephemeral agents in place instead of deleting and recreating them. It accepts `agent_id` plus any editable subset of:
diff --git a/docs/missions.md b/docs/missions.md
index dd50e20f58..4b327b4ef1 100644
--- a/docs/missions.md
+++ b/docs/missions.md
@@ -23,6 +23,14 @@ Mission: Improve Reliability
         Task: FN-214
 ```
 
+## Agent task-creation admission
+
+Mission lineage is an admission requirement only for **autonomous no-task heartbeat** creates and delegations. Those idle patrol calls must supply a valid active Mission → Milestone → Slice → Feature chain; an allow rule for `task_agent_mutation` cannot bypass this requirement. Missing or invalid lineage is rejected before a task is persisted with an explicit mission-lineage remedy.
+
+Interactive/user-supervised, task-scoped heartbeat, executor, triage, and workflow-step calls may create or delegate freeform tasks without lineage. They remain governed by the normal `task_agent_mutation` permission policy, including category and exact-tool allow, approval, and block rules.
+
+A valid active lineage may name a hand-authored `defined` feature only for its first task. Fusion atomically claims the feature, links that exact task, and promotes the feature to `triaged`; an already-linked feature rejects rather than overwriting its canonical task. This bootstrap exception does not make `defined` executable: later scheduler and symbol-lock admission still uses the stricter contract below.
+
 ## Canonical lineage approval for autonomous symbol locks
 
 Before autonomous scheduler work may acquire a symbol lock, it resolves the task's Mission → Milestone → Slice → Feature lineage and evaluates the single `@fusion/core` contract: `evaluateMissionLineageApproval`. Resolution and lock acquisition remain scheduler responsibilities; downstream schedulers must not redefine the approval rule.
@@ -32,7 +40,7 @@ Approval requires every one of these statuses:
 - Mission: `active`
 - Milestone: `active`
 - Slice: `active`
-- Feature: `triaged` or `in-progress`
+- Feature: `triaged` or `in-progress` (never `defined`; defined is only allowed at the first-task bootstrap boundary)
 
 When the scheduler passes `planApprovalRequired: true`, the linked task must also have an `approvedPlanFingerprint` that is a non-empty string after trimming whitespace. The predicate does not recompute the fingerprint; `plan-approval.ts` owns its generation and validation. When plan approval is not required, the fingerprint is ignored.
 
@@ -722,4 +730,4 @@ A completed cited research finding may become a normal Mission Feature. Its feat
 
 ### Autonomous mission admission
 
-Heartbeat agents may create or delegate implementation work only with an approved Feature → Slice → Milestone → Mission lineage. The created task stores that lineage as task metadata; it does not replace the canonical feature `taskId` link. Missing or invalid lineage is rejected before a task is persisted. Roadmap reconciliation marks done tasks done, returns cancelled/requeued tasks to triaged, keeps failed work non-complete, and treats archives as non-promoting no-ops.
+Autonomous no-task heartbeat agents may create or delegate implementation work only with an approved Feature → Slice → Milestone → Mission lineage. Interactive and task-scoped calls remain governed by `task_agent_mutation` policy as described in [Agent task-creation admission](#agent-task-creation-admission). The created task stores that lineage as task metadata; it does not replace the canonical feature `taskId` link except at the documented `defined`-feature first-task bootstrap. Missing or invalid autonomous lineage is rejected before a task is persisted. Roadmap reconciliation marks done tasks done, returns cancelled/requeued tasks to triaged, keeps failed work non-complete, and treats archives as non-promoting no-ops.
diff --git a/packages/core/src/__tests__/postgres/mission-store.pg.test.ts b/packages/core/src/__tests__/postgres/mission-store.pg.test.ts
index 8e704945d8..0593653c0e 100644
--- a/packages/core/src/__tests__/postgres/mission-store.pg.test.ts
+++ b/packages/core/src/__tests__/postgres/mission-store.pg.test.ts
@@ -15,6 +15,9 @@
 
 import { describe, it, expect, beforeAll, beforeEach, afterEach, afterAll, vi } from "vitest";
 import { eq, sql } from "drizzle-orm";
+import { readFile } from "node:fs/promises";
+import type { DbTransaction } from "../../postgres/data-layer.js";
+import type { TaskCreateInput } from "../../types/task-core.js";
 
 import {
   pgDescribe,
@@ -244,6 +247,122 @@ pgTest("MissionStore (PostgreSQL backend mode)", () => {
     expect(unlinked.status).toBe("defined");
   });
 
+  it("does not overwrite an existing task directory on a creation collision", async () => {
+    const taskStore = h.store();
+    const existing = await taskStore.createTask({ description: "the existing task must keep its prompt" });
+    const existingDir = taskStore.taskDir(existing.id);
+    const originalPrompt = await readFile(`${existingDir}/PROMPT.md`, "utf8");
+    const allocator = {
+      reserveDistributedTaskId: vi.fn().mockResolvedValue({ taskId: existing.id, reservationId: "duplicate-id-reservation" }),
+      commitDistributedTaskIdReservation: vi.fn().mockResolvedValue(undefined),
+      abortDistributedTaskIdReservation: vi.fn().mockResolvedValue(undefined),
+    };
+    const allocatorSpy = vi.spyOn(taskStore, "getDistributedTaskIdAllocator").mockReturnValue(allocator as ReturnType<typeof taskStore.getDistributedTaskIdAllocator>);
+    try {
+      await expect(taskStore.createTask({ description: "a competing task must not overwrite files" }))
+        .rejects.toThrow(`Task ID already exists: ${existing.id}`);
+
+      /* FNXC:MissionAdmission 2026-07-23-19:00: a task-row collision leaves the winner's final artifacts untouched because the loser wrote only its staging directory. */
+      await expect(readFile(`${existingDir}/PROMPT.md`, "utf8")).resolves.toBe(originalPrompt);
+    } finally {
+      allocatorSpy.mockRestore();
+    }
+  });
+
+  it("does not claim a defined feature when task-file materialization fails", async () => {
+    const m = missions();
+    const mission = await m.createMission({ title: "Bootstrap file failure" });
+    const milestone = await m.addMilestone(mission.id, { title: "MS" });
+    const slice = await m.addSlice(milestone.id, { title: "SL" });
+    const feature = await m.addFeature(slice.id, { title: "Target feature" });
+    const taskStore = h.store();
+    const claim = vi.fn(async (tx: DbTransaction, taskId: string) =>
+      m.claimDefinedFeatureTaskInTransaction(tx, {
+        featureId: feature.id,
+        taskId,
+        missionId: mission.id,
+        sliceId: slice.id,
+      }),
+    );
+    const writeTaskJson = vi.spyOn(taskStore, "writeTaskJsonFile").mockRejectedValueOnce(new Error("injected task-file failure"));
+
+    try {
+      await expect(taskStore.createTask({
+        description: "must not become a partial feature bootstrap",
+        missionId: mission.id,
+        sliceId: slice.id,
+        afterTaskInsert: (tx: DbTransaction, task: { id: string }) => claim(tx, task.id),
+      } as TaskCreateInput & { afterTaskInsert: (tx: DbTransaction, task: { id: string }) => Promise<void> })).rejects.toThrow("injected task-file failure");
+    } finally {
+      writeTaskJson.mockRestore();
+    }
+
+    /* FNXC:MissionAdmission 2026-07-23-17:10: filesystem failure precedes the insert-and-claim transaction, so no feature promotion can survive a failed task create. */
+    expect(claim).not.toHaveBeenCalled();
+    expect(await m.getFeature(feature.id)).toMatchObject({ status: "defined", taskId: undefined });
+    expect((await taskStore.listTasks()).some((task) => task.description === "must not become a partial feature bootstrap")).toBe(false);
+  });
+
+  it("rejects an unlinked duplicate canonical even when its mission and slice match", async () => {
+    const m = missions();
+    const mission = await m.createMission({ title: "Bootstrap duplicate guard" });
+    const milestone = await m.addMilestone(mission.id, { title: "MS" });
+    const slice = await m.addSlice(milestone.id, { title: "SL" });
+    const feature = await m.addFeature(slice.id, { title: "Target feature" });
+    const task = await h.store().createTask({
+      description: "existing work for another feature",
+      missionId: mission.id,
+      sliceId: slice.id,
+    });
+
+    /*
+    FNXC:MissionAdmission 2026-07-23-17:20:
+    A duplicate canonical does not inherit a feature merely because it shares a
+    slice. Only the insert transaction may claim a defined feature for a new
+    task; retry reconciliation requires an existing bidirectional link.
+    */
+    await expect(m.claimDefinedFeatureTask({
+      featureId: feature.id,
+      taskId: task.id,
+      missionId: mission.id,
+      sliceId: slice.id,
+    })).rejects.toThrow("is not linked to this feature");
+    expect(await m.getFeature(feature.id)).toMatchObject({ status: "defined", taskId: undefined });
+  });
+
+  it("preserves a late bootstrap duplicate already linked to another feature", async () => {
+    const m = missions();
+    const mission = await m.createMission({ title: "Bootstrap sibling ownership" });
+    const milestone = await m.addMilestone(mission.id, { title: "MS" });
+    const slice = await m.addSlice(milestone.id, { title: "SL" });
+    const firstFeature = await m.addFeature(slice.id, { title: "First feature" });
+    const siblingFeature = await m.addFeature(slice.id, { title: "Sibling feature" });
+    const taskStore = h.store();
+    const claimedTask = await taskStore.createTask({
+      description: "same fingerprint work",
+      missionId: mission.id,
+      sliceId: slice.id,
+    });
+    await m.linkFeatureToTask(firstFeature.id, claimedTask.id);
+    const siblingTask = await taskStore.createTask({
+      description: "same fingerprint work",
+      missionId: mission.id,
+      sliceId: slice.id,
+    });
+    await m.linkFeatureToTask(siblingFeature.id, siblingTask.id);
+
+    await m.archiveDefinedFeatureBootstrapDuplicate({
+      featureId: firstFeature.id,
+      taskId: claimedTask.id,
+      duplicateTaskId: siblingTask.id,
+    });
+
+    /* FNXC:MissionAdmission 2026-07-23-21:10: a late same-fingerprint task claimed by another feature is not a duplicate eligible for archival. */
+    expect(await taskStore.getTask(siblingTask.id)).toMatchObject({ id: siblingTask.id, column: "triage" });
+    expect(await m.getFeature(siblingFeature.id)).toMatchObject({ taskId: siblingTask.id, status: "triaged" });
+    expect(await m.getFeature(firstFeature.id)).toMatchObject({ taskId: claimedTask.id, status: "triaged" });
+  });
+
   /*
   FNXC:MissionReconciliation 2026-07-20-08:34:
   Regression coverage exercises every terminal-evidence representation through the real PostgreSQL store. Reconciliation must never route through ordinary triage linking, mutate loop attempts or mission controls, or partially commit when the transaction fails.
diff --git a/packages/core/src/async-mission-store.ts b/packages/core/src/async-mission-store.ts
index 43e82e7405..01f72a5e6c 100644
--- a/packages/core/src/async-mission-store.ts
+++ b/packages/core/src/async-mission-store.ts
@@ -1022,27 +1022,198 @@ export class AsyncMissionStore extends EventEmitter<MissionStoreEvents> {
     return outcome.feature;
   }
 
-  async linkFeatureToTask(featureId: string, taskId: string): Promise<MissionFeature> {
-    const feature = await getFeature(this.db, featureId);
-    if (!feature) throw new Error(`Feature ${featureId} not found`);
-    const liveTask = await getLiveTaskById(this.db, taskId);
-    if (!liveTask) {
-      throw new Error(
-        `Cannot link feature ${featureId} to task ${taskId}: task is not on the active board (it may be archived, deleted, or never existed). Only active tasks can be linked to features.`,
-      );
+  /**
+   * Atomically claim a hand-authored defined feature for a task already inserted
+   * in the caller's transaction. This is intentionally narrower than
+   * linkFeatureToTask(): existing manual links may establish task lineage,
+   * whereas a duplicate bootstrap canonical must already prove this lineage.
+   */
+  async claimDefinedFeatureTaskInTransaction(
+    tx: import("./postgres/data-layer.js").DbTransaction,
+    input: { featureId: string; taskId: string; missionId: string; sliceId: string; requireExistingFeatureLink?: boolean },
+  ): Promise<MissionFeature> {
+    /*
+    FNXC:MissionAdmission 2026-07-23-15:30:
+    Defined is creation-admissible only at the first-task claim boundary. Check
+    the project-scoped task's existing lineage before updating either record so
+    a deterministic duplicate from another mission can never be repurposed.
+    */
+    /*
+    FNXC:MissionAdmission 2026-08-10-00:00:
+    Concurrent bootstrap requests must serialize on the defined Feature before
+    either inserts its task. READ COMMITTED alone permits both readers to claim
+    it; this row lock makes the second request re-read the committed taskId and
+    reject, preserving one exclusive first-task claim.
+    */
+    const lockedFeatures = await tx
+      .select({ id: schema.project.missionFeatures.id })
+      .from(schema.project.missionFeatures)
+      .where(eq(schema.project.missionFeatures.id, input.featureId))
+      .for("update");
+    if (lockedFeatures.length === 0) throw new Error(`Feature ${input.featureId} not found`);
+    const feature = await getFeature(tx, input.featureId);
+    if (!feature) throw new Error(`Feature ${input.featureId} not found`);
+    if (feature.sliceId !== input.sliceId) throw new Error(`Feature ${input.featureId} does not belong to slice ${input.sliceId}`);
+    if (feature.taskId && feature.taskId !== input.taskId) {
+      throw new Error(`Feature ${input.featureId} is already linked to task ${feature.taskId}`);
     }
-    const linkage = await this.resolveTaskLinkage(feature.sliceId);
+    if (feature.status !== "defined" && feature.taskId !== input.taskId) {
+      throw new Error(`Feature ${input.featureId} is not available for first-task bootstrap`);
+    }
+    /*
+    FNXC:MissionAdmission 2026-07-23-17:20:
+    A duplicate canonical was not inserted in this transaction. It may be
+    reused only after this feature already owns it; allowing an arbitrary
+    unlinked task from the same slice would silently assign another feature's
+    work to this bootstrap request.
+    */
+    if (input.requireExistingFeatureLink === true && feature.taskId !== input.taskId) {
+      throw new Error(`Cannot bootstrap feature ${input.featureId}: pre-existing task ${input.taskId} is not linked to this feature`);
+    }
+
+    const projectId = this.layer.projectId;
+    if (!projectId) throw new Error("Defined-feature bootstrap requires a project-scoped data layer");
+    const taskRows = await tx
+      .select({ id: schema.project.tasks.id, missionId: schema.project.tasks.missionId, sliceId: schema.project.tasks.sliceId, column: schema.project.tasks.column })
+      .from(schema.project.tasks)
+      .where(and(
+        eq(schema.project.tasks.projectId, projectId),
+        eq(schema.project.tasks.id, input.taskId),
+        sql`${schema.project.tasks.deletedAt} is null`,
+      ));
+    const task = taskRows[0];
+    if (!task || task.column === "archived") {
+      throw new Error(`Cannot bootstrap feature ${input.featureId}: task ${input.taskId} is not active in this project`);
+    }
+    if (task.missionId !== input.missionId || task.sliceId !== input.sliceId) {
+      throw new Error(`Cannot bootstrap feature ${input.featureId}: task ${input.taskId} has unrelated mission lineage`);
+    }
+    const conflict = await getConflictingFeatureByTaskId(tx, input.taskId, input.featureId);
+    if (conflict) throw new Error(`Task ${input.taskId} is already linked to feature ${conflict.id}`);
+
+    const now = new Date().toISOString();
     const shouldTransitionLoop = !feature.loopState || feature.loopState === "idle";
-    const loopStateUpdates: Partial<MissionFeature> = shouldTransitionLoop
-      ? { loopState: "implementing", implementationAttemptCount: 1 }
-      : {};
-    const updated = await this.updateFeature(featureId, { taskId, status: "triaged", ...loopStateUpdates });
-    await setTaskMissionLinkage(this.db, taskId, linkage.missionId, linkage.sliceId);
-    await this.recomputeSliceStatus(updated.sliceId);
-    this.emit("feature:linked", { feature: updated, taskId });
+    const updated: MissionFeature = {
+      ...feature,
+      taskId: input.taskId,
+      status: "triaged",
+      ...(shouldTransitionLoop ? { loopState: "implementing", implementationAttemptCount: 1 } : {}),
+      updatedAt: now,
+    };
+    await updateFeature(tx, updated);
+    // The inserted task already carries this verified linkage; retain this write
+    // for retry parity when the same canonical is claimed again.
+    await setTaskMissionLinkage(tx, input.taskId, input.missionId, input.sliceId);
     return updated;
   }
 
+  async claimDefinedFeatureTask(input: { featureId: string; taskId: string; missionId: string; sliceId: string }): Promise<MissionFeature> {
+    const feature = await this.layer.transactionImmediate((tx) => this.claimDefinedFeatureTaskInTransaction(tx, { ...input, requireExistingFeatureLink: true }));
+    this.emit("feature:updated", feature);
+    this.emit("feature:linked", { feature, taskId: input.taskId });
+    await this.recomputeSliceStatus(feature.sliceId);
+    return feature;
+  }
+
+  /**
+   * Keep the task that atomically claimed a defined Feature as the sole live
+   * deterministic-duplicate canonical. This compensates for a duplicate that
+   * became visible only after the create preflight, without ever allowing the
+   * generic intake path to archive feature.taskId.
+   */
+  async archiveDefinedFeatureBootstrapDuplicate(input: { featureId: string; taskId: string; duplicateTaskId: string }): Promise<void> {
+    /*
+    FNXC:MissionAdmission 2026-07-23-21:10:
+    Project-agnostic legacy stores remain scoped to their reserved RLS
+    partition, so reconciliation never falls back to an unscoped task ID.
+    */
+    const projectId = this.layer.projectId || "__legacy_unscoped__";
+    await this.layer.transactionImmediate(async (tx) => {
+      /*
+      FNXC:MissionAdmission 2026-07-23-20:00:
+      A late deterministic duplicate must not reverse the first-task claim and
+      archive feature.taskId. Verify that the feature still owns the claimed,
+      project-scoped live task, then archive only the competing live task in
+      this transaction. `defined` remains scheduler-ineligible throughout.
+      */
+      const feature = await getFeature(tx, input.featureId);
+      if (!feature || feature.taskId !== input.taskId || feature.status !== "triaged") {
+        throw new Error(`Cannot reconcile defined-feature bootstrap duplicate for ${input.featureId}`);
+      }
+      const claimed = await tx.select({ id: schema.project.tasks.id })
+        .from(schema.project.tasks)
+        .where(and(
+          eq(schema.project.tasks.projectId, projectId),
+          eq(schema.project.tasks.id, input.taskId),
+          sql`${schema.project.tasks.deletedAt} is null`,
+          sql`${schema.project.tasks.column} <> 'archived'`,
+        ));
+      if (!claimed[0]) throw new Error(`Cannot reconcile defined-feature bootstrap duplicate: claimed task ${input.taskId} is not live`);
+      /*
+      FNXC:MissionAdmission 2026-07-23-21:10:
+      Fingerprint equality does not make work interchangeable across Features.
+      A late sibling already claimed by another Feature remains live; archiving
+      it here would corrupt that Feature's canonical task. Keep both tasks and
+      let each feature retain its own transactional bootstrap claim.
+      */
+      const duplicateFeature = await getConflictingFeatureByTaskId(tx, input.duplicateTaskId, input.featureId);
+      if (duplicateFeature) return;
+      await tx.update(schema.project.tasks)
+        .set({ column: "archived", updatedAt: new Date().toISOString() })
+        .where(and(
+          eq(schema.project.tasks.projectId, projectId),
+          eq(schema.project.tasks.id, input.duplicateTaskId),
+          sql`${schema.project.tasks.deletedAt} is null`,
+          sql`${schema.project.tasks.column} <> 'archived'`,
+        ));
+    });
+  }
+
+  async linkFeatureToTask(featureId: string, taskId: string): Promise<MissionFeature> {
+    /*
+    FNXC:MissionAdmission 2026-07-23-12:00:
+    First-task bootstrap must claim the feature, promote it, and backlink the
+    exact project-scoped task as one transaction. Never overwrite a feature's
+    existing taskId: retries may reuse only that same canonical task.
+    */
+    const outcome = await this.layer.transactionImmediate(async (tx) => {
+      const feature = await getFeature(tx, featureId);
+      if (!feature) throw new Error(`Feature ${featureId} not found`);
+      if (feature.taskId && feature.taskId !== taskId) {
+        throw new Error(`Feature ${featureId} is already linked to task ${feature.taskId}`);
+      }
+      const liveTask = await getLiveTaskById(tx, taskId);
+      if (!liveTask) {
+        throw new Error(
+          `Cannot link feature ${featureId} to task ${taskId}: task is not on the active board (it may be archived, deleted, or never existed). Only active tasks can be linked to features.`,
+        );
+      }
+      const conflictingFeature = await getConflictingFeatureByTaskId(tx, taskId, featureId);
+      if (conflictingFeature) {
+        throw new Error(`Task ${taskId} is already linked to feature ${conflictingFeature.id}`);
+      }
+      const slice = await getSlice(tx, feature.sliceId);
+      const milestone = slice ? await getMilestone(tx, slice.milestoneId) : undefined;
+      if (!slice || !milestone) throw new Error(`Feature ${featureId} has incomplete mission hierarchy`);
+      const shouldTransitionLoop = !feature.loopState || feature.loopState === "idle";
+      const now = new Date().toISOString();
+      const updated: MissionFeature = {
+        ...feature,
+        taskId,
+        status: "triaged",
+        ...(shouldTransitionLoop ? { loopState: "implementing", implementationAttemptCount: 1 } : {}),
+        updatedAt: now,
+      };
+      await updateFeature(tx, updated);
+      await setTaskMissionLinkage(tx, taskId, milestone.missionId, slice.id);
+      return updated;
+    });
+    this.emit("feature:updated", outcome);
+    this.emit("feature:linked", { feature: outcome, taskId });
+    await this.recomputeSliceStatus(outcome.sliceId);
+    return outcome;
+  }
+
   async unlinkFeatureFromTask(featureId: string): Promise<MissionFeature> {
     const feature = await getFeature(this.db, featureId);
     if (!feature) throw new Error(`Feature ${featureId} not found`);
diff --git a/packages/core/src/duplicate-guard.ts b/packages/core/src/duplicate-guard.ts
index 1422eed293..48eb996bc6 100644
--- a/packages/core/src/duplicate-guard.ts
+++ b/packages/core/src/duplicate-guard.ts
@@ -139,8 +139,10 @@ export async function reconcileDeterministicDuplicate(
     windowMs?: number;
     sourceParentTaskId?: string | null;
     logger?: { warn(msg: string, data?: Record<string, unknown>): void };
+    /** Handle a duplicate without archiving `createdTask` (e.g. claimed feature bootstrap). */
+    onDuplicate?: (canonical: Task) => Promise<"keep-created" | "archive-created">;
   },
-): Promise<{ outcome: "kept" | "archived"; canonical: Task }> {
+): Promise<{ outcome: "kept" | "archived" | "kept-duplicate"; canonical: Task }> {
   if (!args.fingerprint) {
     return { outcome: "kept", canonical: args.createdTask };
   }
@@ -160,6 +162,16 @@ export async function reconcileDeterministicDuplicate(
       return { outcome: "kept", canonical: args.createdTask };
     }
 
+    /*
+    FNXC:MissionAdmission 2026-07-23-20:00:
+    A defined-feature bootstrap has already transactionally made its inserted
+    task feature.taskId. Let that caller reconcile the older sibling without
+    routing the generic duplicate path through an archive of the claimed row.
+    */
+    if (await args.onDuplicate?.(olderSibling) === "keep-created") {
+      return { outcome: "kept-duplicate", canonical: args.createdTask };
+    }
+
     await store.updateTask(args.createdTask.id, {
       sourceMetadataPatch: {
         contentFingerprint: args.fingerprint,
diff --git a/packages/core/src/mission-store.ts b/packages/core/src/mission-store.ts
index 8b5640e010..f8efd5134a 100644
--- a/packages/core/src/mission-store.ts
+++ b/packages/core/src/mission-store.ts
@@ -2461,6 +2461,21 @@ export class MissionStore extends EventEmitter<MissionStoreEvents> {
       );
     }
 
+    if (feature.taskId && feature.taskId !== taskId) {
+      throw new Error(`Feature ${featureId} is already linked to task ${feature.taskId}`);
+    }
+    const conflictingFeature = this.db
+      .prepare(`SELECT id FROM mission_features WHERE taskId = ? AND id != ? LIMIT 1`)
+      .get(taskId, featureId) as { id: string } | undefined;
+    if (conflictingFeature) {
+      throw new Error(`Task ${taskId} is already linked to feature ${conflictingFeature.id}`);
+    }
+
+    /*
+    FNXC:MissionAdmission 2026-07-23-12:00:
+    Keep sync test-contract parity with PostgreSQL: a defined feature's first
+    task claim is exclusive and must never overwrite another feature backlink.
+    */
     const linkage = this.resolveTaskLinkage(feature.sliceId);
 
     // When first linking (loopState is idle or falsy), transition to implementing
diff --git a/packages/core/src/task-store/task-creation.ts b/packages/core/src/task-store/task-creation.ts
index 123dd45fb7..394bdedd70 100644
--- a/packages/core/src/task-store/task-creation.ts
+++ b/packages/core/src/task-store/task-creation.ts
@@ -8,9 +8,10 @@
  */
 import {TaskStore, storeLog} from "../store.js";
 import {InvalidFileScopeError, SelfDefeatingDependencyError, detectSelfDefeatingDependency, TombstonedTaskResurrectionError} from "./errors.js";
-import {mkdir, rm, writeFile} from "node:fs/promises";
+import {mkdir, rename, rm, writeFile} from "node:fs/promises";
 import {join} from "node:path";
 import {existsSync} from "node:fs";
+import {randomUUID} from "node:crypto";
 import type {Task, TaskCreateInput, Settings} from "../types.js";
 import "../builtin-traits.js";
 import {applyReviewLevelPreset} from "../review-level-preset.js";
@@ -29,6 +30,17 @@ import {withTaskBranchContextInSourceMetadata} from "../task-store/branch-contex
 import {resolveCreateDeclaredSymbols} from "../task-symbol-resolution.js";
 import {softDeleteTaskRow as softDeleteTaskRowAsync, insertTaskRowInTransaction, isTaskIdConflictError} from "../task-store/async-persistence.js";
 import {recordRunAuditEvent as recordRunAuditEventAsync} from "../task-store/async-audit.js";
+import type {DbTransaction} from "../postgres/data-layer.js";
+
+type CreateTaskWithAfterInsert = TaskCreateInput & {
+  /** Internal transaction hook; never persisted in task source metadata. */
+  afterTaskInsert?: (tx: DbTransaction, task: Task) => Promise<void>;
+  /**
+   * Internal bootstrap escape hatch. The caller supplies an equivalent
+   * transactionally-safe duplicate reconciliation after the feature claim.
+   */
+  skipSameAgentDuplicateIntake?: boolean;
+};
 
 function ensureSqliteProposalClaimUniqueness(store: TaskStore): void {
   /*
@@ -371,49 +383,44 @@ export async function _createTaskInternalBackendImpl(store: TaskStore, input: Ta
     }
 
     const dir = store.taskDir(id);
+    const stagingDir = `${dir}.creating-${randomUUID()}`;
+    let ownsStagingDirectory = false;
+    let ownsPromotedTaskDirectory = false;
+    const cleanupPreparedTaskFiles = async () => {
+      if (store.isWatching) store.taskCache.delete(id);
+      if (ownsStagingDirectory && existsSync(stagingDir)) {
+        await rm(stagingDir, { recursive: true, force: true });
+      }
+      // A rollback after promotion removes only this create's final directory.
+      // A conflicting existing row never reaches promotion, so its files survive.
+      if (ownsPromotedTaskDirectory && existsSync(dir)) {
+        await rm(dir, { recursive: true, force: true });
+      }
+    };
 
-    // FNXC:RuntimeTaskOrchestrationAsync 2026-06-24-13:30:
-    // Insert the task row via async Drizzle insert inside a transaction.
-    // A duplicate-ID collision raises a unique_violation (23505) which we
-    // catch and surface as "Task ID already exists" (matching the SQLite path).
-    const context = store.createTaskPersistSerializationContext(task);
+    /*
+    FNXC:MissionAdmission 2026-07-23-17:10:
+    Materialize task files before the transaction that inserts and claims a
+    defined feature. Filesystem writes cannot join PostgreSQL; this ordering
+    means a write failure cannot commit a triaged feature pointing at a deleted
+    task, while the database transaction still makes task insert + feature claim
+    indivisible.
+    */
     try {
-      await layer.transactionImmediate(async (tx) => {
-        // FNXC:MultiProjectIsolation 2026-07-10: stamp the bound projectId so the
-        // new task row is attributed to (and later filtered under) this project.
-        await insertTaskRowInTransaction(tx, task as unknown as Record<string, unknown>, context, layer.projectId);
-      });
-    } catch (error) {
       /*
-      FNXC:EphemeralAgentTaskCreation 2026-07-30-18:30:
-      Proposal creation retries can race after a creation lease is released while
-      the original creator is still inserting. Both attempts deliberately use the
-      same stable proposalClaimId, so the partial unique index is the at-most-once
-      authority. A 23505 for that key returns the committed winner instead of
-      treating it as an ID collision; no loser may continue into task-file or
-      workflow materialization. Other unique violations remain task-ID errors.
+      FNXC:MissionAdmission 2026-07-23-19:00:
+      PostgreSQL ID/proposal collisions are discovered at row insert, while a
+      defined-feature bootstrap needs all task artifacts to be writable before
+      its transaction can commit. Materialize into a unique staging directory;
+      only the successful insert atomically promotes it to the task directory.
+      A losing proposal therefore cannot overwrite its winner's task files.
       */
-      if (input.proposalClaimId && isTaskIdConflictError(error)) {
-        const existing = (await store.listTasks()).find((candidate) => candidate.proposalClaimId === input.proposalClaimId);
-        if (existing) {
-          options?.onProposalClaimConflict?.(existing);
-          return existing;
-        }
-      }
-      if (isTaskIdConflictError(error)) {
-        throw new Error(`Task ID already exists: ${task.id}`);
-      }
-      throw error;
-    }
+      await mkdir(stagingDir, { recursive: true });
+      ownsStagingDirectory = true;
 
-    // FNXC:ReservationAtomicity 2026-07-12-00:00:
-    // Wrap post-insert filesystem/prompt work so any failure rolls back the
-    // inserted row. Without this, a writeTaskJsonFile or prompt-validation throw
-    // leaves a live row paired with an aborted reservation (FN-7074 invariant).
-    try {
       // Write task.json for backward compatibility and debugging.
       if (store.isWatching) store.taskCache.set(id, { ...task });
-      await store.writeTaskJsonFile(dir, task);
+      await store.writeTaskJsonFile(stagingDir, task);
 
       // Write PROMPT.md (same logic as SQLite path).
       /*
@@ -443,20 +450,73 @@ export async function _createTaskInternalBackendImpl(store: TaskStore, input: Ta
           throw new InvalidFileScopeError(id, validation.invalid);
         }
       }
-      await mkdir(dir, { recursive: true });
-      await writeFile(join(dir, "PROMPT.md"), prompt);
+      await writeFile(join(stagingDir, "PROMPT.md"), prompt);
     } catch (error) {
-      // Rollback: soft-delete the inserted row and remove the directory.
-      await softDeleteTaskRowAsync(layer, id, new Date().toISOString());
-      if (store.isWatching) store.taskCache.delete(id);
-      if (existsSync(dir)) {
-        await rm(dir, { recursive: true, force: true });
+      await cleanupPreparedTaskFiles();
+      if ((error as NodeJS.ErrnoException).code === "EEXIST") {
+        throw new Error(`Task ID already exists: ${task.id}`);
       }
       throw error;
     }
 
-    // Auto-archive dedup (best-effort, same as SQLite path but using async reads).
-    await store._maybeAutoArchiveSameAgentDuplicateBackend(task, input);
+    // FNXC:RuntimeTaskOrchestrationAsync 2026-06-24-13:30:
+    // Insert the task row via async Drizzle insert inside a transaction.
+    // A duplicate-ID collision raises a unique_violation (23505) which we
+    // catch and surface as "Task ID already exists" (matching the SQLite path).
+    const context = store.createTaskPersistSerializationContext(task);
+    try {
+      await layer.transactionImmediate(async (tx) => {
+        // FNXC:MultiProjectIsolation 2026-07-10: stamp the bound projectId so the
+        // new task row is attributed to (and later filtered under) this project.
+        await insertTaskRowInTransaction(tx, task as unknown as Record<string, unknown>, context, layer.projectId);
+        /*
+        FNXC:MissionAdmission 2026-07-23-19:00:
+        The row insert establishes this task as the sole winner before its staged
+        artifacts replace any stale directory. Promotion remains inside the same
+        transaction as the defined-feature claim, so a filesystem or claim
+        failure rolls back the row and cleans only this attempt's files.
+        */
+        if (existsSync(dir)) await rm(dir, { recursive: true, force: true });
+        await rename(stagingDir, dir);
+        ownsStagingDirectory = false;
+        ownsPromotedTaskDirectory = true;
+        await (input as CreateTaskWithAfterInsert).afterTaskInsert?.(tx, task);
+      });
+    } catch (error) {
+      await cleanupPreparedTaskFiles();
+      /*
+      FNXC:EphemeralAgentTaskCreation 2026-07-30-18:30:
+      Proposal creation retries can race after a creation lease is released while
+      the original creator is still inserting. Both attempts deliberately use the
+      same stable proposalClaimId, so the partial unique index is the at-most-once
+      authority. A 23505 for that key returns the committed winner instead of
+      treating it as an ID collision; no loser may continue into task-file or
+      workflow materialization. Other unique violations remain task-ID errors.
+      */
+      if (input.proposalClaimId && isTaskIdConflictError(error)) {
+        const existing = (await store.listTasks()).find((candidate) => candidate.proposalClaimId === input.proposalClaimId);
+        if (existing) {
+          options?.onProposalClaimConflict?.(existing);
+          return existing;
+        }
+      }
+      if (isTaskIdConflictError(error)) {
+        throw new Error(`Task ID already exists: ${task.id}`);
+      }
+      throw error;
+    }
+
+    /*
+    FNXC:MissionAdmission 2026-07-23-20:00:
+    A defined-feature first task has already claimed feature.taskId in the insert
+    transaction. The ordinary same-agent intake may archive that claimed row
+    after commit, so this narrow internal opt-out delegates duplicate resolution
+    to the bootstrap caller, which preserves the claimed canonical atomically.
+    */
+    if (!(input as CreateTaskWithAfterInsert).skipSameAgentDuplicateIntake) {
+      // Auto-archive dedup (best-effort, same as SQLite path but using async reads).
+      await store._maybeAutoArchiveSameAgentDuplicateBackend(task, input);
+    }
 
     store.emitTaskLifecycleEventSafely("task:created", [task]);
     if (options?.invokeTaskCreatedHook !== false) {
diff --git a/packages/engine/src/__tests__/agent-tools-delegation.test.ts b/packages/engine/src/__tests__/agent-tools-delegation.test.ts
index e9d5ce9a3c..8e4a20f67b 100644
--- a/packages/engine/src/__tests__/agent-tools-delegation.test.ts
+++ b/packages/engine/src/__tests__/agent-tools-delegation.test.ts
@@ -1,5 +1,5 @@
 import { describe, it, expect, vi, beforeEach } from "vitest";
-import type { Agent, AgentStore, TaskStore, Task } from "@fusion/core";
+import type { Agent, AgentStore, TaskStore, Task, TaskCreateInput } from "@fusion/core";
 import { createAgentTask, createListAgentsTool, createDelegateTaskTool, createTaskCreateTool } from "../agent-tools.js";
 
 function createMockAgentStore(overrides: Partial<AgentStore> = {}): AgentStore {
@@ -553,6 +553,142 @@ describe("createDelegateTaskTool", () => {
     expect(createInput.sliceId).toBeUndefined();
   });
 
+  it("bootstraps a defined feature by linking and promoting its first created task", async () => {
+    const missionStore = {
+      getFeature: vi.fn().mockResolvedValue({ id: "F-001", sliceId: "SL-001", status: "defined" }),
+      getSlice: vi.fn().mockResolvedValue({ id: "SL-001", milestoneId: "MS-001", status: "active" }),
+      getMilestone: vi.fn().mockResolvedValue({ id: "MS-001", missionId: "M-001", status: "active" }),
+      getMission: vi.fn().mockResolvedValue({ id: "M-001", status: "active" }),
+      claimDefinedFeatureTaskInTransaction: vi.fn().mockResolvedValue({ id: "F-001", taskId: "FN-001", status: "triaged" }),
+      claimDefinedFeatureTask: vi.fn().mockResolvedValue({ id: "F-001", taskId: "FN-001", status: "triaged" }),
+      archiveDefinedFeatureBootstrapDuplicate: vi.fn().mockResolvedValue(undefined),
+    };
+    const store = createMockTaskStore({
+      getMissionStore: vi.fn().mockReturnValue(missionStore),
+      createTask: vi.fn().mockImplementation(async (input) => {
+        const task = { id: "FN-001", dependencies: [], column: "triage", steps: [], currentStep: 0, log: [], createdAt: "", updatedAt: "" } as Task;
+        await (input as { afterTaskInsert?: (tx: object, created: Task) => Promise<void> }).afterTaskInsert?.({}, task);
+        return task;
+      }),
+    });
+    const result = await createTaskCreateTool(store).execute(
+      "call-1", { description: "Bootstrap the hand-authored feature", mission_lineage: APPROVED_LINEAGE },
+      undefined as any, undefined as any, undefined as any,
+    );
+
+    expect(result).not.toMatchObject({ isError: true });
+    expect(missionStore.claimDefinedFeatureTaskInTransaction).toHaveBeenCalledWith({}, { featureId: "F-001", taskId: "FN-001", missionId: "M-001", sliceId: "SL-001" });
+    expect(store.createTask).toHaveBeenCalledWith(expect.objectContaining({ missionId: "M-001", sliceId: "SL-001" }), expect.anything());
+  });
+
+  it("keeps a claimed defined-feature task canonical when a late duplicate appears", async () => {
+    const missionStore = {
+      getFeature: vi.fn().mockResolvedValue({ id: "F-001", sliceId: "SL-001", status: "defined" }),
+      getSlice: vi.fn().mockResolvedValue({ id: "SL-001", milestoneId: "MS-001", status: "active" }),
+      getMilestone: vi.fn().mockResolvedValue({ id: "MS-001", missionId: "M-001", status: "active" }),
+      getMission: vi.fn().mockResolvedValue({ id: "M-001", status: "active" }),
+      claimDefinedFeatureTaskInTransaction: vi.fn().mockResolvedValue({ id: "F-001", taskId: "FN-new", status: "triaged" }),
+      claimDefinedFeatureTask: vi.fn(),
+      archiveDefinedFeatureBootstrapDuplicate: vi.fn().mockResolvedValue(undefined),
+    };
+    const created = { id: "FN-new", description: "Bootstrap feature", dependencies: [], column: "triage" as const, steps: [], currentStep: 0, log: [], createdAt: "2026-01-02T00:00:00.000Z", updatedAt: "2026-01-02T00:00:00.000Z" } as Task;
+    const older = { ...created, id: "FN-old", createdAt: "2026-01-01T00:00:00.000Z" };
+    const store = createMockTaskStore({
+      getMissionStore: vi.fn().mockReturnValue(missionStore),
+      createTask: vi.fn().mockImplementation(async (input) => {
+        await (input as { afterTaskInsert?: (tx: object, created: Task) => Promise<void> }).afterTaskInsert?.({}, created);
+        return created;
+      }),
+      findRecentTasksByContentFingerprint: vi.fn().mockResolvedValueOnce([]).mockResolvedValueOnce([older, created]),
+    });
+
+    const result = await createTaskCreateTool(store).execute(
+      "call-1", { description: "Bootstrap feature", mission_lineage: APPROVED_LINEAGE },
+      undefined as any, undefined as any, undefined as any,
+    );
+
+    expect(result).not.toMatchObject({ isError: true });
+    expect((result.details as { taskId: string }).taskId).toBe("FN-new");
+    expect(missionStore.claimDefinedFeatureTaskInTransaction).toHaveBeenCalledOnce();
+    /* FNXC:MissionAdmission 2026-07-23-19:00: a task that atomically claimed feature.taskId must never be archived by post-create duplicate reconciliation. */
+    expect(store.findRecentTasksByContentFingerprint).toHaveBeenCalledTimes(2);
+    expect(missionStore.archiveDefinedFeatureBootstrapDuplicate).toHaveBeenCalledWith({
+      featureId: "F-001", taskId: "FN-new", duplicateTaskId: "FN-old",
+    });
+    expect(store.moveTask).not.toHaveBeenCalledWith("FN-new", "archived");
+  });
+
+  it("rolls back a newly-created task when defined-feature bootstrap cannot link", async () => {
+    const missionStore = {
+      getFeature: vi.fn().mockResolvedValue({ id: "F-001", sliceId: "SL-001", status: "defined" }),
+      getSlice: vi.fn().mockResolvedValue({ id: "SL-001", milestoneId: "MS-001", status: "active" }),
+      getMilestone: vi.fn().mockResolvedValue({ id: "MS-001", missionId: "M-001", status: "active" }),
+      getMission: vi.fn().mockResolvedValue({ id: "M-001", status: "active" }),
+      claimDefinedFeatureTaskInTransaction: vi.fn().mockRejectedValue(new Error("Feature F-001 is already linked to task FN-OTHER")),
+      claimDefinedFeatureTask: vi.fn(),
+      archiveDefinedFeatureBootstrapDuplicate: vi.fn().mockResolvedValue(undefined),
+    };
+    const store = createMockTaskStore({
+      getMissionStore: vi.fn().mockReturnValue(missionStore),
+      createTask: vi.fn().mockImplementation(async (input) => {
+        await (input as { afterTaskInsert?: (tx: object, created: Task) => Promise<void> }).afterTaskInsert?.({}, { id: "FN-001" } as Task);
+        throw new Error("bootstrap hook unexpectedly succeeded");
+      }),
+    });
+    const result = createTaskCreateTool(store).execute(
+      "call-1", { description: "Bootstrap conflicting feature", mission_lineage: APPROVED_LINEAGE },
+      undefined as any, undefined as any, undefined as any,
+    );
+
+    await expect(result).rejects.toThrow("Feature F-001 is already linked to task FN-OTHER");
+    expect(missionStore.claimDefinedFeatureTaskInTransaction).toHaveBeenCalledOnce();
+  });
+
+  it("rejects a pre-existing same-agent bootstrap duplicate before claiming or creating", async () => {
+    const canonical = {
+      id: "FN-existing", title: "Bootstrap feature", description: "Bootstrap the hand-authored feature",
+      sourceAgentId: "agent-001", dependencies: [], column: "triage" as const, steps: [], currentStep: 0,
+      log: [], createdAt: new Date().toISOString(), updatedAt: new Date().toISOString(),
+    } as Task;
+    const store = createMockTaskStore({ listTasks: vi.fn().mockResolvedValue([canonical]) });
+    const validate = vi.fn().mockRejectedValue(new Error("pre-existing task is not linked to this feature"));
+
+    await expect(createAgentTask(store, {
+      title: "Bootstrap feature",
+      description: "Bootstrap the hand-authored feature",
+      source: { sourceType: "api", sourceAgentId: "agent-001" },
+      preflightSameAgentDuplicate: true,
+      validateDuplicateCanonical: validate,
+    } as TaskCreateInput & { preflightSameAgentDuplicate: boolean; validateDuplicateCanonical: (task: Task) => Promise<void> }))
+      .rejects.toThrow("pre-existing task is not linked to this feature");
+
+    expect(validate).toHaveBeenCalledWith(canonical);
+    expect(store.createTask).not.toHaveBeenCalled();
+  });
+
+  it("does not select an archived same-agent task as a defined-feature bootstrap canonical", async () => {
+    const archived = {
+      id: "FN-archived", title: "Bootstrap feature", description: "Bootstrap the hand-authored feature",
+      sourceAgentId: "agent-001", dependencies: [], column: "archived" as const, steps: [], currentStep: 0,
+      log: [], createdAt: new Date().toISOString(), updatedAt: new Date().toISOString(),
+    } as Task;
+    const store = createMockTaskStore({ listTasks: vi.fn().mockResolvedValue([archived]) });
+    const validate = vi.fn().mockResolvedValue(undefined);
+
+    const result = await createAgentTask(store, {
+      title: "Bootstrap feature",
+      description: "Bootstrap the hand-authored feature",
+      source: { sourceType: "api", sourceAgentId: "agent-001" },
+      preflightSameAgentDuplicate: true,
+      validateDuplicateCanonical: validate,
+    } as TaskCreateInput & { preflightSameAgentDuplicate: boolean; validateDuplicateCanonical: (task: Task) => Promise<void> });
+
+    /* FNXC:MissionAdmission 2026-07-23-21:10: archived tasks are not live bootstrap canonicals and must not block a valid first task. */
+    expect(result.wasDuplicate).toBe(false);
+    expect(validate).not.toHaveBeenCalled();
+    expect(store.createTask).toHaveBeenCalledOnce();
+  });
+
   it("serializes three concurrent paraphrased creates from one parent", async () => {
     const tasks: Task[] = [];
     vi.mocked(taskStore.findRecentTasksBySourceParentTaskId).mockImplementation(async () => tasks);
@@ -592,7 +728,11 @@ describe("createDelegateTaskTool", () => {
       return canonical;
     });
 
-    const result = await createAgentTask(taskStore, { description: "Add new support" }, { sourceTaskId: "fn-parent" });
+    const validateDuplicateCanonical = vi.fn().mockResolvedValue(undefined);
+    const result = await createAgentTask(taskStore, {
+      description: "Add new support",
+      validateDuplicateCanonical,
+    } as TaskCreateInput & { validateDuplicateCanonical: (task: Task) => Promise<void> }, { sourceTaskId: "fn-parent" });
 
     expect(taskStore.findRecentTasksBySourceParentTaskId).toHaveBeenCalledWith("FN-PARENT");
     expect(taskStore.createTask).toHaveBeenCalledWith(expect.objectContaining({
@@ -600,6 +740,8 @@ describe("createDelegateTaskTool", () => {
       proposalClaimId: expect.stringMatching(/^agent-parent-intent:FN-PARENT:/),
     }), expect.anything());
     expect(result).toMatchObject({ task: canonical, wasDuplicate: true });
+    /* FNXC:MissionAdmission 2026-07-23-17:20: proposal-claim reuse must validate the final canonical, not only pre-create duplicate probes. */
+    expect(validateDuplicateCanonical).toHaveBeenCalledWith(canonical);
   });
 
   it("carries delegation routing onto the reconcile canonical task", async () => {
@@ -626,17 +768,21 @@ describe("createDelegateTaskTool", () => {
       id === "FN-old" ? moved : { ...created, id, column },
     );
 
+    const validateDuplicateCanonical = vi.fn().mockResolvedValue(undefined);
     const result = await createAgentTask(taskStore, {
       description: "Write tests",
       mission_lineage: APPROVED_LINEAGE,
       column: "todo",
       assignedAgentId: "agent-002",
-    });
+      validateDuplicateCanonical,
+    } as TaskCreateInput & { validateDuplicateCanonical: (task: Task) => Promise<void> });
 
     expect(result.wasDuplicate).toBe(true);
     expect(result.task).toBe(moved);
     expect(taskStore.updateTask).toHaveBeenCalledWith("FN-old", { assignedAgentId: "agent-002" });
     expect(taskStore.moveTask).toHaveBeenCalledWith("FN-old", "todo");
+    /* FNXC:MissionAdmission 2026-07-23-17:20: post-create archival reconciliation must validate its returned canonical before duplicate success. */
+    expect(validateDuplicateCanonical).toHaveBeenCalledWith(moved);
   });
 
   it("returns success message with task ID and agent name", async () => {
diff --git a/packages/engine/src/agent-tools.ts b/packages/engine/src/agent-tools.ts
index e47b942eb2..b523ad7e3f 100644
--- a/packages/engine/src/agent-tools.ts
+++ b/packages/engine/src/agent-tools.ts
@@ -13,7 +13,7 @@ import { createHash, randomUUID } from "node:crypto";
 import { tmpdir } from "node:os";
 import { extname, isAbsolute, join, relative, resolve, sep } from "node:path";
 import * as fusionCore from "@fusion/core";
-import type { AgentState, AgentCapability, AgentUpdateInput, AgentLogEntry, Artifact, ArtifactCreateInput, ArtifactWithTask, Task, TaskDocument, TaskDocumentCreateInput, TaskStore, RunMutationContext, MessageStore, Message, SourceType, Settings, ResearchRun, ResearchRunStatus, TaskCreateInput, ReflectionStore, ApprovalRequestStore, ProjectSettings, ChatStore, WorkflowSettingDefinition, GoalStatus, WorkflowIrNode, IdeationCandidate, MissionWithHierarchy } from "@fusion/core";
+import type { AgentState, AgentCapability, AgentUpdateInput, AgentLogEntry, Artifact, ArtifactCreateInput, ArtifactWithTask, Task, TaskDocument, TaskDocumentCreateInput, TaskStore, RunMutationContext, MessageStore, Message, SourceType, Settings, ResearchRun, ResearchRunStatus, TaskCreateInput, ReflectionStore, ApprovalRequestStore, ProjectSettings, ChatStore, WorkflowSettingDefinition, GoalStatus, WorkflowIrNode, IdeationCandidate, MissionWithHierarchy, DbTransaction } from "@fusion/core";
 import { listTraits, isBuiltinWorkflowId, AgentStore, validateColumnAgentBindings, ColumnAgentBindingError, stripApprovalBypassFlags, WorkflowSettingRejectionError, resolveEffectiveSettingsById, resolveWorkflowIrById, findOrphanedSettingValues, BUILTIN_WORKFLOW_SETTINGS, MAX_TASK_LIST_TEXT_CHARS, formatCurrentTaskLine, normalizeWorkflowIcon, parseWorkflowIr, WorkflowIrError, assertColumnTraitsValid, ColumnTraitValidationError } from "@fusion/core";
 import { promoteHeldTask } from "./hold-release.js";
 import { computeCrossParentDiagnosticClaim, computeCrossParentDiagnosticClaimId, computeParentIntentClaimId, DASHBOARD_USER_ID, dailyMemoryPath, ensureOpenClawMemoryFiles, evaluateImplementationTaskBind, extractAgentProvisioningRequest, findSameAgentDuplicates, getMemoryBackendCapabilities, getProjectMemory, isEphemeralAgent, memoryLongTermPath, normalizeMessageParticipant, reconcileDeterministicDuplicate, resolveAgentProvisioningPolicy, resolveMemoryBackend, resolveResearchSettings, resolveTaskGithubTracking, runDeterministicDuplicateGuard, scheduleQmdProjectMemoryRefresh, searchProjectMemory, shouldSkipBackgroundQmdRefresh } from "@fusion/core";
@@ -979,6 +979,8 @@ type MissionLineageReference = {
   missionId: string;
   sliceId: string;
   featureId: string;
+  /** Defined features are admitted only to atomically claim their first task. */
+  bootstrapDefinedFeature?: boolean;
 };
 
 /**
@@ -1040,14 +1042,108 @@ async function resolveApprovedMissionLineage(
   const approval = fusionCore.evaluateMissionLineageApproval({
     feature, slice, milestone, mission, task: {}, planApprovalRequired: false,
   });
-  if (!approval.approved) return { error: `Mission lineage is not approved (${approval.reason}); no task was created.` };
+  /*
+  FNXC:MissionAdmission 2026-07-23-12:00:
+  A hand-authored defined Feature has no first task to link, so scheduler-only
+  approval would dead-end task creation. Admit it solely as a bootstrap claim;
+  symbol-lock admission remains triaged/in-progress in the core predicate.
+  */
+  if (!approval.approved) {
+    if (approval.reason === "feature-not-implementable" && feature.status === "defined" && !feature.taskId) {
+      return { missionId: mission.id, sliceId: slice.id, featureId: feature.id, bootstrapDefinedFeature: true };
+    }
+    return { error: `Mission lineage is not approved (${approval.reason}); no task was created.` };
+  }
   return { missionId: mission.id, sliceId: slice.id, featureId: feature.id };
 }
 
+type DefinedFeatureBootstrapStore = {
+  claimDefinedFeatureTaskInTransaction: (tx: DbTransaction, input: { featureId: string; taskId: string; missionId: string; sliceId: string }) => Promise<unknown>;
+  claimDefinedFeatureTask: (input: { featureId: string; taskId: string; missionId: string; sliceId: string }) => Promise<unknown>;
+  archiveDefinedFeatureBootstrapDuplicate: (input: { featureId: string; taskId: string; duplicateTaskId: string }) => Promise<void>;
+};
+
+type AgentTaskInputWithBootstrap = TaskCreateInput & {
+  afterTaskInsert?: (tx: DbTransaction, task: Task) => Promise<void>;
+  validateDuplicateCanonical?: (task: Task) => Promise<void>;
+  skipSameAgentDuplicateIntake?: boolean;
+  preflightSameAgentDuplicate?: boolean;
+  reconcileCreatedDuplicate?: (duplicate: Task, created: Task) => Promise<void>;
+};
+
+function definedFeatureBootstrapInput(store: TaskStore, lineage: MissionLineageReference | null): Pick<AgentTaskInputWithBootstrap, "afterTaskInsert" | "validateDuplicateCanonical" | "skipSameAgentDuplicateIntake" | "preflightSameAgentDuplicate" | "reconcileCreatedDuplicate"> {
+  if (!lineage?.bootstrapDefinedFeature) return {};
+  const missionStore = store.getMissionStore() as Partial<DefinedFeatureBootstrapStore>;
+  if (!missionStore.claimDefinedFeatureTaskInTransaction || !missionStore.claimDefinedFeatureTask || !missionStore.archiveDefinedFeatureBootstrapDuplicate) {
+    throw new Error("Defined-feature bootstrap requires the PostgreSQL mission store; no task was created.");
+  }
+  const claim = (taskId: string) => ({ featureId: lineage.featureId, taskId, missionId: lineage.missionId, sliceId: lineage.sliceId });
+  return {
+    /*
+    FNXC:MissionAdmission 2026-07-23-15:30:
+    The first defined-feature task and feature promotion are one PostgreSQL
+    transaction. Do not replace this hook with create-then-link compensation:
+    a failed claim must roll back the task row before any task is observable.
+    */
+    afterTaskInsert: async (tx, task) => { await missionStore.claimDefinedFeatureTaskInTransaction!(tx, claim(task.id)); },
+    validateDuplicateCanonical: async (task) => { await missionStore.claimDefinedFeatureTask!(claim(task.id)); },
+    /*
+    FNXC:MissionAdmission 2026-07-23-20:00:
+    The ordinary same-agent intake runs after task-row commit and could archive
+    feature.taskId. Suppress only that path; deterministic reconciliation below
+    retains the claimed task and atomically archives a late competing duplicate.
+    */
+    skipSameAgentDuplicateIntake: true,
+    preflightSameAgentDuplicate: true,
+    reconcileCreatedDuplicate: async (duplicate, created) => {
+      await missionStore.archiveDefinedFeatureBootstrapDuplicate!({
+        featureId: lineage.featureId,
+        taskId: created.id,
+        duplicateTaskId: duplicate.id,
+      });
+    },
+  };
+}
+
 /*
 FNXC:AgentRouting 2026-07-29-00:00:
 FN-8207 requires deterministic-duplicate canonical tasks to honor an explicit delegate's owner and todo-column request. Carry both mutations in the engine task-creation seam so every canonical return path is truthful without changing the shared core duplicate-guard API.
 */
+async function findDefinedFeatureBootstrapDuplicate(
+  store: TaskStore,
+  input: TaskCreateInput,
+  sourceAgentId: string | undefined,
+  sourceParentTaskId: string | undefined,
+): Promise<Task | undefined> {
+  if (!sourceAgentId && !sourceParentTaskId) return undefined;
+  const candidates = await store.listTasks({ slim: true, includeArchived: true, includeDeleted: true });
+  const byId = new Map(candidates.map((task) => [task.id, task]));
+  const matches = findSameAgentDuplicates({
+    title: input.title,
+    description: input.description,
+    sourceParentTaskId,
+  }, candidates.flatMap((task) => {
+    const createdAt = Date.parse(task.createdAt);
+    /*
+    FNXC:MissionAdmission 2026-07-23-21:10:
+    Defined-feature retry preflight follows the normal duplicate guard's live
+    task boundary. An archived sibling cannot be a bootstrap canonical because
+    claimDefinedFeatureTask rejects non-live task rows.
+    */
+    if (Number.isNaN(createdAt) || task.deletedAt || task.column === "archived") return [];
+    return [{
+      id: task.id,
+      title: task.title ?? "",
+      description: task.description,
+      column: task.column,
+      createdAt,
+      sourceAgentId: task.sourceAgentId ?? null,
+      sourceParentTaskId: task.sourceParentTaskId ?? null,
+    }];
+  }), { sourceAgentId: sourceAgentId ?? null });
+  return matches[0] ? byId.get(matches[0].id) : undefined;
+}
+
 async function carryCanonicalTaskRouting(
   store: TaskStore,
   canonical: Task,
@@ -1071,6 +1167,7 @@ export async function createAgentTask(
   input: TaskCreateInput,
   options?: AgentTaskCreationOptions,
 ): Promise<{ task: Awaited<ReturnType<TaskStore["createTask"]>>; wasDuplicate: boolean }> {
+  const validateDuplicateCanonical = (input as AgentTaskInputWithBootstrap).validateDuplicateCanonical;
   const settings = typeof (store as { getSettings?: unknown }).getSettings === "function"
     ? await store.getSettings()
     : {} as Settings;
@@ -1106,6 +1203,7 @@ export async function createAgentTask(
 
   try {
     if (guard.action === "duplicate" && guard.existing) {
+      await validateDuplicateCanonical?.(guard.existing);
       return {
         task: await carryCanonicalTaskRouting(store, guard.existing, input),
         wasDuplicate: true,
@@ -1130,6 +1228,7 @@ export async function createAgentTask(
           .sort((left, right) => Date.parse(left.createdAt) - Date.parse(right.createdAt));
         const canonical = candidates[0];
         if (canonical) {
+          await validateDuplicateCanonical?.(canonical);
           return { task: await carryCanonicalTaskRouting(store, canonical, input), wasDuplicate: true };
         }
       } catch (error) {
@@ -1161,6 +1260,7 @@ export async function createAgentTask(
         const match = matches.find((candidate) => !acknowledged.has(candidate.id));
         const canonical = match ? candidates.find((candidate) => candidate.id === match.id) : undefined;
         if (canonical) {
+          await validateDuplicateCanonical?.(canonical);
           return { task: await carryCanonicalTaskRouting(store, canonical, input), wasDuplicate: true };
         }
       } catch (error) {
@@ -1172,6 +1272,21 @@ export async function createAgentTask(
       }
     }
 
+    /*
+    FNXC:MissionAdmission 2026-07-23-20:00:
+    Probe same-agent duplicates before a defined Feature is claimed. The generic
+    intake probe happens after commit and can archive feature.taskId; an existing
+    canonical must already belong to this feature or creation fails with no new
+    task, rather than silently repurposing unrelated work.
+    */
+    if ((input as AgentTaskInputWithBootstrap).preflightSameAgentDuplicate && validateDuplicateCanonical) {
+      const duplicate = await findDefinedFeatureBootstrapDuplicate(store, input, sourceAgentId, sourceParentTaskId);
+      if (duplicate) {
+        await validateDuplicateCanonical(duplicate);
+        return { task: await carryCanonicalTaskRouting(store, duplicate, input), wasDuplicate: true };
+      }
+    }
+
     const sourceMetadata = {
       ...(effectiveSource?.sourceMetadata ?? {}),
       ...(guard.fingerprint ? { contentFingerprint: guard.fingerprint } : {}),
@@ -1220,21 +1335,35 @@ export async function createAgentTask(
       onProposalClaimConflict: () => { proposalClaimConflict = true; },
     });
 
+    const reconcileCreatedDuplicate = (input as AgentTaskInputWithBootstrap).reconcileCreatedDuplicate;
     const reconcile = await reconcileDeterministicDuplicate(store, {
       createdTask,
       fingerprint: guard.fingerprint,
       sourceParentTaskId,
       logger: log,
+      onDuplicate: reconcileCreatedDuplicate
+        ? async (duplicate) => {
+          await reconcileCreatedDuplicate(duplicate, createdTask);
+          return "keep-created";
+        }
+        : undefined,
     });
 
-    return {
-      task: proposalClaimConflict
-        ? await carryCanonicalTaskRouting(store, createdTask, input)
-        : reconcile.outcome === "archived"
-        ? await carryCanonicalTaskRouting(store, reconcile.canonical, input)
-        : reconcile.canonical,
-      wasDuplicate: proposalClaimConflict || reconcile.outcome === "archived",
-    };
+    const wasDuplicate = proposalClaimConflict || reconcile.outcome === "archived" || reconcile.outcome === "kept-duplicate";
+    const canonical = proposalClaimConflict
+      ? await carryCanonicalTaskRouting(store, createdTask, input)
+      : reconcile.outcome === "archived"
+      ? await carryCanonicalTaskRouting(store, reconcile.canonical, input)
+      : reconcile.canonical;
+    /*
+    FNXC:MissionAdmission 2026-07-23-17:20:
+    A proposal-claim race and post-create reconciliation both select an existing
+    canonical after createTask returns. Revalidate that canonical before reporting
+    duplicate success so a defined feature cannot remain unlinked or claim an
+    archived/unrelated loser.
+    */
+    if (wasDuplicate) await validateDuplicateCanonical?.(canonical);
+    return { task: canonical, wasDuplicate };
   } finally {
     guard.releaseLock();
   }
@@ -1334,6 +1463,7 @@ export function createTaskCreateTool(
           priority: params.priority,
           ...(workflowId ? { workflowId } : {}),
           ...(lineage ? { missionId: lineage.missionId, sliceId: lineage.sliceId } : {}),
+          ...definedFeatureBootstrapInput(store, lineage),
           source: {
             sourceType: provenance?.sourceType ?? "api",
             sourceAgentId: provenance?.sourceAgentId,
@@ -4672,6 +4802,7 @@ export function createDelegateTaskTool(
           assignedAgentId: params.agent_id,
           ...(workflowId ? { workflowId } : {}),
           ...(lineage ? { missionId: lineage.missionId, sliceId: lineage.sliceId } : {}),
+          ...definedFeatureBootstrapInput(taskStore, lineage),
           source: {
             sourceType: "api",
             sourceParentTaskId: options?.sourceTaskId,