diff --git a/packages/shared/src/agent-eligibility.test.ts b/packages/shared/src/agent-eligibility.test.ts
new file mode 100644
index 00000000000..20b3fff500c
--- /dev/null
+++ b/packages/shared/src/agent-eligibility.test.ts
@@ -0,0 +1,145 @@
+import { describe, expect, it } from "vitest";
+import {
+  getAgentOrgChainHealth,
+  getAgentWorkEligibility,
+  isAgentAssignableToWork,
+  isAgentInvokable,
+  type AgentEligibilityAgent,
+} from "./agent-eligibility.js";
+
+const companyId = "company-1";
+
+function agent(overrides: Partial<AgentEligibilityAgent> = {}): AgentEligibilityAgent {
+  return {
+    id: "agent-1",
+    companyId,
+    name: "Coder",
+    status: "active",
+    reportsTo: "manager-1",
+    ...overrides,
+  };
+}
+
+describe("agent work eligibility", () => {
+  it("allows healthy active agents to accept work and be invoked", () => {
+    const agents = [
+      agent(),
+      agent({ id: "manager-1", name: "CTO", status: "active", reportsTo: null }),
+    ];
+
+    expect(isAgentAssignableToWork({ agent: agents[0]!, agents })).toBe(true);
+    expect(isAgentInvokable({ agent: agents[0]!, agents })).toBe(true);
+    expect(getAgentWorkEligibility({ agent: agents[0]!, agents })).toMatchObject({
+      assignable: true,
+      invokable: true,
+      assignabilityReason: "eligible",
+      invokabilityReason: "eligible",
+      orgChainHealth: { status: "healthy" },
+    });
+  });
+
+  it("blocks terminated and pending approval agents from assignment and invocation", () => {
+    const manager = agent({ id: "manager-1", name: "CTO", status: "active", reportsTo: null });
+
+    for (const status of ["terminated", "pending_approval"]) {
+      const target = agent({ status });
+      const eligibility = getAgentWorkEligibility({ agent: target, agents: [target, manager] });
+
+      expect(eligibility.assignable).toBe(false);
+      expect(eligibility.invokable).toBe(false);
+      expect(eligibility.assignabilityReason).toBe(status);
+      expect(eligibility.invokabilityReason).toBe(status);
+    }
+  });
+
+  it("allows paused agents to keep assignments but blocks invocation", () => {
+    const target = agent({ status: "paused" });
+    const manager = agent({ id: "manager-1", name: "CTO", status: "active", reportsTo: null });
+
+    expect(getAgentWorkEligibility({ agent: target, agents: [target, manager] })).toMatchObject({
+      assignable: true,
+      invokable: false,
+      assignabilityReason: "eligible",
+      invokabilityReason: "paused",
+    });
+  });
+
+  it("blocks active descendants of terminated ancestors and reports repair details", () => {
+    const target = agent({ id: "qa-2", name: "QA 2", status: "active", reportsTo: "cto-2" });
+    const terminatedManager = agent({
+      id: "cto-2",
+      name: "CTO 2",
+      status: "terminated",
+      reportsTo: "ceo-2",
+    });
+    const terminatedRoot = agent({
+      id: "ceo-2",
+      name: "CEO 2",
+      status: "terminated",
+      reportsTo: null,
+    });
+    const agents = [target, terminatedManager, terminatedRoot];
+
+    const health = getAgentOrgChainHealth({ agent: target, agents });
+    expect(health.status).toBe("invalid_org_chain");
+    expect(health.reason).toBe("terminated_ancestor");
+    expect(health.fullChain).toEqual([
+      expect.objectContaining({ id: "qa-2", name: "QA 2", relation: "self", depth: 0 }),
+      expect.objectContaining({ id: "cto-2", name: "CTO 2", status: "terminated", relation: "ancestor", depth: 1 }),
+      expect.objectContaining({ id: "ceo-2", name: "CEO 2", status: "terminated", relation: "ancestor", depth: 2 }),
+    ]);
+    expect(health.firstInvalidAncestor).toEqual({ id: "cto-2", name: "CTO 2", status: "terminated" });
+    expect(health.invalidAncestors).toEqual([
+      { id: "cto-2", name: "CTO 2", status: "terminated" },
+      { id: "ceo-2", name: "CEO 2", status: "terminated" },
+    ]);
+    expect(health.repairGuidance).toContain("QA 2 reports through terminated ancestor CTO 2");
+
+    const eligibility = getAgentWorkEligibility({ agent: target, agents });
+    expect(eligibility.assignable).toBe(false);
+    expect(eligibility.invokable).toBe(false);
+    expect(eligibility.assignabilityReason).toBe("invalid_org_chain");
+    expect(eligibility.invokabilityReason).toBe("invalid_org_chain");
+  });
+
+  it("blocks agents whose manager is missing from the company org", () => {
+    const target = agent({ id: "qa-3", name: "QA 3", status: "active", reportsTo: "missing-manager" });
+
+    const health = getAgentOrgChainHealth({ agent: target, agents: [target] });
+    expect(health.status).toBe("invalid_org_chain");
+    expect(health.reason).toBe("missing_manager");
+    expect(health.fullChain).toEqual([
+      expect.objectContaining({ id: "qa-3", relation: "self", depth: 0 }),
+      expect.objectContaining({ id: "missing-manager", status: "missing", relation: "ancestor", depth: 1 }),
+    ]);
+    expect(health.repairGuidance).toContain("QA 3 reports to missing manager missing-manager");
+
+    const eligibility = getAgentWorkEligibility({ agent: target, agents: [target] });
+    expect(eligibility.assignable).toBe(false);
+    expect(eligibility.invokable).toBe(false);
+    expect(eligibility.assignabilityReason).toBe("invalid_org_chain");
+    expect(eligibility.invokabilityReason).toBe("invalid_org_chain");
+  });
+
+  it("blocks agents with reporting cycles", () => {
+    const target = agent({ id: "qa-4", name: "QA 4", status: "active", reportsTo: "cto-4" });
+    const manager = agent({ id: "cto-4", name: "CTO 4", status: "active", reportsTo: "qa-4" });
+    const agents = [target, manager];
+
+    const health = getAgentOrgChainHealth({ agent: target, agents });
+    expect(health.status).toBe("invalid_org_chain");
+    expect(health.reason).toBe("cycle");
+    expect(health.fullChain).toEqual([
+      expect.objectContaining({ id: "qa-4", relation: "self", depth: 0 }),
+      expect.objectContaining({ id: "cto-4", relation: "ancestor", depth: 1 }),
+      expect.objectContaining({ id: "qa-4", status: "cycle", relation: "ancestor", depth: 2 }),
+    ]);
+    expect(health.repairGuidance).toContain("QA 4 has a cycle in its reporting chain");
+
+    const eligibility = getAgentWorkEligibility({ agent: target, agents });
+    expect(eligibility.assignable).toBe(false);
+    expect(eligibility.invokable).toBe(false);
+    expect(eligibility.assignabilityReason).toBe("invalid_org_chain");
+    expect(eligibility.invokabilityReason).toBe("invalid_org_chain");
+  });
+});
diff --git a/packages/shared/src/agent-eligibility.ts b/packages/shared/src/agent-eligibility.ts
new file mode 100644
index 00000000000..d1e9c266a81
--- /dev/null
+++ b/packages/shared/src/agent-eligibility.ts
@@ -0,0 +1,240 @@
+import type { AgentStatus } from "./constants.js";
+
+export type AgentEligibilityLifecycleReason =
+  | "eligible"
+  | "terminated"
+  | "pending_approval"
+  | "paused"
+  | "invalid_org_chain";
+
+export interface AgentEligibilityAgent {
+  id: string;
+  companyId: string;
+  name: string;
+  status: AgentStatus | string;
+  reportsTo?: string | null;
+}
+
+export interface AgentOrgChainEntry {
+  id: string;
+  companyId: string;
+  name: string;
+  status: AgentStatus | string;
+  reportsTo: string | null;
+  depth: number;
+  relation: "self" | "ancestor";
+}
+
+export interface AgentInvalidOrgChainAncestor {
+  id: string;
+  name: string;
+  status: AgentStatus | string;
+}
+
+export type AgentOrgChainInvalidReason =
+  | "healthy"
+  | "terminated_ancestor"
+  | "missing_manager"
+  | "cycle";
+
+export interface AgentOrgChainHealth {
+  status: "healthy" | "invalid_org_chain";
+  reason: AgentOrgChainInvalidReason;
+  fullChain: AgentOrgChainEntry[];
+  firstInvalidAncestor: AgentInvalidOrgChainAncestor | null;
+  invalidAncestors: AgentInvalidOrgChainAncestor[];
+  repairGuidance: string | null;
+}
+
+export interface AgentWorkEligibility {
+  assignable: boolean;
+  invokable: boolean;
+  assignabilityReason: AgentEligibilityLifecycleReason;
+  invokabilityReason: AgentEligibilityLifecycleReason;
+  orgChainHealth: AgentOrgChainHealth;
+}
+
+const NON_ASSIGNABLE_AGENT_STATUSES = new Set<string>(["terminated", "pending_approval"]);
+const NON_INVOKABLE_AGENT_STATUSES = new Set<string>(["terminated", "pending_approval", "paused"]);
+const ASSIGNABLE_AGENT_STATUSES = new Set<string>(["active", "paused", "idle", "running", "error"]);
+const INVOKABLE_AGENT_STATUSES = new Set<string>(["active", "idle", "running", "error"]);
+
+export function isAgentStatusAssignableToWork(status: AgentStatus | string): boolean {
+  return ASSIGNABLE_AGENT_STATUSES.has(status) && !NON_ASSIGNABLE_AGENT_STATUSES.has(status);
+}
+
+export function isAgentStatusInvokable(status: AgentStatus | string): boolean {
+  return INVOKABLE_AGENT_STATUSES.has(status) && !NON_INVOKABLE_AGENT_STATUSES.has(status);
+}
+
+function chainEntry(
+  agent: AgentEligibilityAgent,
+  depth: number,
+  relation: AgentOrgChainEntry["relation"],
+): AgentOrgChainEntry {
+  return {
+    id: agent.id,
+    companyId: agent.companyId,
+    name: agent.name,
+    status: agent.status,
+    reportsTo: agent.reportsTo ?? null,
+    depth,
+    relation,
+  };
+}
+
+function invalidAncestor(agent: AgentEligibilityAgent): AgentInvalidOrgChainAncestor {
+  return {
+    id: agent.id,
+    name: agent.name,
+    status: agent.status,
+  };
+}
+
+function buildRepairGuidance(
+  agent: AgentEligibilityAgent,
+  firstInvalidAncestor: AgentInvalidOrgChainAncestor,
+): string {
+  if (firstInvalidAncestor.status === "missing") {
+    return [
+      `${agent.name} reports to missing manager ${firstInvalidAncestor.id}.`,
+      `Reassign ${agent.name} or the nearest affected ancestor under an active manager/root, or explicitly pause or terminate the invalid subtree before assigning work or starting runs.`,
+    ].join(" ");
+  }
+  if (firstInvalidAncestor.status === "cycle") {
+    return [
+      `${agent.name} has a cycle in its reporting chain at ${firstInvalidAncestor.name}.`,
+      `Break the cycle by assigning one affected agent to an active manager/root, or explicitly pause or terminate the invalid subtree before assigning work or starting runs.`,
+    ].join(" ");
+  }
+  return [
+    `${agent.name} reports through terminated ancestor ${firstInvalidAncestor.name}.`,
+    `Reassign ${agent.name} or the nearest affected ancestor under an active manager/root, or explicitly pause or terminate the invalid subtree before assigning work or starting runs.`,
+  ].join(" ");
+}
+
+export function getAgentOrgChainHealth(input: {
+  agent: AgentEligibilityAgent;
+  agents: AgentEligibilityAgent[];
+}): AgentOrgChainHealth {
+  const byId = new Map(input.agents.map((agent) => [agent.id, agent]));
+  const fullChain: AgentOrgChainEntry[] = [chainEntry(input.agent, 0, "self")];
+  const invalidAncestors: AgentInvalidOrgChainAncestor[] = [];
+  const seen = new Set<string>([input.agent.id]);
+
+  let current = input.agent;
+  let depth = 1;
+  while (current.reportsTo) {
+    if (seen.has(current.reportsTo)) {
+      const cycleAgent = byId.get(current.reportsTo);
+      const invalid = {
+        id: current.reportsTo,
+        name: cycleAgent?.name ?? current.reportsTo,
+        status: "cycle",
+      };
+      fullChain.push({
+        id: invalid.id,
+        companyId: input.agent.companyId,
+        name: invalid.name,
+        status: invalid.status,
+        reportsTo: cycleAgent?.reportsTo ?? null,
+        depth,
+        relation: "ancestor",
+      });
+      invalidAncestors.push(invalid);
+      break;
+    }
+    seen.add(current.reportsTo);
+
+    const parent = byId.get(current.reportsTo);
+    if (!parent || parent.companyId !== input.agent.companyId) {
+      const invalid = {
+        id: current.reportsTo,
+        name: current.reportsTo,
+        status: "missing",
+      };
+      fullChain.push({
+        id: invalid.id,
+        companyId: input.agent.companyId,
+        name: invalid.name,
+        status: invalid.status,
+        reportsTo: null,
+        depth,
+        relation: "ancestor",
+      });
+      invalidAncestors.push(invalid);
+      break;
+    }
+
+    fullChain.push(chainEntry(parent, depth, "ancestor"));
+    if (parent.status === "terminated") {
+      invalidAncestors.push(invalidAncestor(parent));
+    }
+
+    current = parent;
+    depth += 1;
+  }
+
+  const firstInvalidAncestor = invalidAncestors[0] ?? null;
+  return {
+    status: firstInvalidAncestor ? "invalid_org_chain" : "healthy",
+    reason: firstInvalidAncestor
+      ? firstInvalidAncestor.status === "missing"
+        ? "missing_manager"
+        : firstInvalidAncestor.status === "cycle"
+          ? "cycle"
+          : "terminated_ancestor"
+      : "healthy",
+    fullChain,
+    firstInvalidAncestor,
+    invalidAncestors,
+    repairGuidance: firstInvalidAncestor
+      ? buildRepairGuidance(input.agent, firstInvalidAncestor)
+      : null,
+  };
+}
+
+export function getAgentWorkEligibility(input: {
+  agent: AgentEligibilityAgent;
+  agents: AgentEligibilityAgent[];
+}): AgentWorkEligibility {
+  const orgChainHealth = getAgentOrgChainHealth(input);
+  const assignabilityReason: AgentEligibilityLifecycleReason = !isAgentStatusAssignableToWork(input.agent.status)
+    ? input.agent.status === "terminated"
+      ? "terminated"
+      : "pending_approval"
+    : orgChainHealth.status === "invalid_org_chain"
+      ? "invalid_org_chain"
+      : "eligible";
+  const invokabilityReason: AgentEligibilityLifecycleReason = !isAgentStatusInvokable(input.agent.status)
+    ? input.agent.status === "terminated"
+      ? "terminated"
+      : input.agent.status === "pending_approval"
+        ? "pending_approval"
+        : "paused"
+    : orgChainHealth.status === "invalid_org_chain"
+      ? "invalid_org_chain"
+      : "eligible";
+
+  return {
+    assignable: assignabilityReason === "eligible",
+    invokable: invokabilityReason === "eligible",
+    assignabilityReason,
+    invokabilityReason,
+    orgChainHealth,
+  };
+}
+
+export function isAgentAssignableToWork(input: {
+  agent: AgentEligibilityAgent;
+  agents: AgentEligibilityAgent[];
+}): boolean {
+  return getAgentWorkEligibility(input).assignable;
+}
+
+export function isAgentInvokable(input: {
+  agent: AgentEligibilityAgent;
+  agents: AgentEligibilityAgent[];
+}): boolean {
+  return getAgentWorkEligibility(input).invokable;
+}
diff --git a/packages/shared/src/index.ts b/packages/shared/src/index.ts
index 559e5ddd8c6..7744af39364 100644
--- a/packages/shared/src/index.ts
+++ b/packages/shared/src/index.ts
@@ -1,4 +1,19 @@
 export { agentAdapterTypeSchema, optionalAgentAdapterTypeSchema } from "./adapter-type.js";
+export {
+  getAgentOrgChainHealth,
+  getAgentWorkEligibility,
+  isAgentAssignableToWork,
+  isAgentInvokable,
+  isAgentStatusAssignableToWork,
+  isAgentStatusInvokable,
+  type AgentEligibilityAgent,
+  type AgentEligibilityLifecycleReason,
+  type AgentInvalidOrgChainAncestor,
+  type AgentOrgChainEntry,
+  type AgentOrgChainHealth,
+  type AgentOrgChainInvalidReason,
+  type AgentWorkEligibility,
+} from "./agent-eligibility.js";
 export {
   asBoolean,
   asString,
diff --git a/packages/shared/src/types/index.ts b/packages/shared/src/types/index.ts
index 6b72c752643..b1ea7661f26 100644
--- a/packages/shared/src/types/index.ts
+++ b/packages/shared/src/types/index.ts
@@ -142,6 +142,15 @@ export type {
   AdapterEnvironmentCheck,
   AdapterEnvironmentTestResult,
 } from "./agent.js";
+export type {
+  AgentEligibilityAgent,
+  AgentEligibilityLifecycleReason,
+  AgentInvalidOrgChainAncestor,
+  AgentOrgChainEntry,
+  AgentOrgChainHealth,
+  AgentOrgChainInvalidReason,
+  AgentWorkEligibility,
+} from "../agent-eligibility.js";
 export type { AssetImage } from "./asset.js";
 export type {
   CreateDocumentAnnotationCommentRequest,
diff --git a/server/src/__tests__/issues-service.test.ts b/server/src/__tests__/issues-service.test.ts
index 1fdae88939d..a74b438c0f6 100644
--- a/server/src/__tests__/issues-service.test.ts
+++ b/server/src/__tests__/issues-service.test.ts
@@ -168,6 +168,183 @@ describeEmbeddedPostgres("issueService.list participantAgentId", () => {
     await tempDb?.cleanup();
   });
 
+  async function seedAssignableAgentCompany() {
+    const companyId = randomUUID();
+    await db.insert(companies).values({
+      id: companyId,
+      name: "Paperclip",
+      issuePrefix: `T${companyId.replace(/-/g, "").slice(0, 6).toUpperCase()}`,
+      requireBoardApprovalForNewAgents: false,
+    });
+    return companyId;
+  }
+
+  function agentRow(companyId: string, input: {
+    id: string;
+    name: string;
+    status?: string;
+    reportsTo?: string | null;
+  }) {
+    return {
+      id: input.id,
+      companyId,
+      name: input.name,
+      role: "engineer",
+      status: input.status ?? "active",
+      reportsTo: input.reportsTo ?? null,
+      adapterType: "codex_local",
+      adapterConfig: {},
+      runtimeConfig: {},
+      permissions: {},
+    };
+  }
+
+  it("rejects direct terminated assignees with structured conflict details", async () => {
+    const companyId = await seedAssignableAgentCompany();
+    const terminatedAgentId = randomUUID();
+    await db.insert(agents).values(agentRow(companyId, {
+      id: terminatedAgentId,
+      name: "TerminatedCoder",
+      status: "terminated",
+    }));
+
+    await expect(svc.create(companyId, {
+      title: "Do not assign this",
+      description: null,
+      status: "todo",
+      priority: "medium",
+      assigneeAgentId: terminatedAgentId,
+    })).rejects.toMatchObject({
+      status: 409,
+      details: {
+        code: "agent_not_assignable",
+        reason: "assignee_terminated",
+        assigneeAgentId: terminatedAgentId,
+      },
+    });
+  });
+
+  it("rejects invalid ancestor-chain assignees and preserves the existing assignment", async () => {
+    const companyId = await seedAssignableAgentCompany();
+    const activeAgentId = randomUUID();
+    const terminatedManagerId = randomUUID();
+    const blockedAgentId = randomUUID();
+    await db.insert(agents).values([
+      agentRow(companyId, { id: activeAgentId, name: "ActiveCoder" }),
+      agentRow(companyId, {
+        id: terminatedManagerId,
+        name: "TerminatedManager",
+        status: "terminated",
+      }),
+      agentRow(companyId, {
+        id: blockedAgentId,
+        name: "BlockedCoder",
+        reportsTo: terminatedManagerId,
+      }),
+    ]);
+    const issue = await svc.create(companyId, {
+      title: "Keep current assignment",
+      description: null,
+      status: "todo",
+      priority: "medium",
+      assigneeAgentId: activeAgentId,
+    });
+
+    await expect(svc.update(issue.id, {
+      assigneeAgentId: blockedAgentId,
+    })).rejects.toMatchObject({
+      status: 409,
+      details: {
+        code: "agent_not_assignable",
+        reason: "ancestor_terminated",
+        assigneeAgentId: blockedAgentId,
+        invalidAncestorAgentId: terminatedManagerId,
+      },
+    });
+
+    const persisted = await db
+      .select({ assigneeAgentId: issues.assigneeAgentId })
+      .from(issues)
+      .where(eq(issues.id, issue.id))
+      .then((rows) => rows[0] ?? null);
+    expect(persisted?.assigneeAgentId).toBe(activeAgentId);
+  });
+
+  it("rejects checkout by a terminated agent before assigning the issue", async () => {
+    const companyId = await seedAssignableAgentCompany();
+    const terminatedAgentId = randomUUID();
+    await db.insert(agents).values(agentRow(companyId, {
+      id: terminatedAgentId,
+      name: "TerminatedCheckoutCoder",
+      status: "terminated",
+    }));
+    const issue = await svc.create(companyId, {
+      title: "Checkout must stay unassigned",
+      description: null,
+      status: "todo",
+      priority: "medium",
+      assigneeAgentId: null,
+    });
+
+    await expect(svc.checkout(issue.id, terminatedAgentId, ["todo"], randomUUID()))
+      .rejects.toMatchObject({
+        status: 409,
+        details: {
+          code: "agent_not_assignable",
+          reason: "assignee_terminated",
+          assigneeAgentId: terminatedAgentId,
+        },
+      });
+
+    const persisted = await db
+      .select({ assigneeAgentId: issues.assigneeAgentId, status: issues.status })
+      .from(issues)
+      .where(eq(issues.id, issue.id))
+      .then((rows) => rows[0] ?? null);
+    expect(persisted).toMatchObject({
+      assigneeAgentId: null,
+      status: "todo",
+    });
+  });
+
+  it("rejects moving an existing terminated assignment into progress without clearing it", async () => {
+    const companyId = await seedAssignableAgentCompany();
+    const assigneeAgentId = randomUUID();
+    await db.insert(agents).values(agentRow(companyId, {
+      id: assigneeAgentId,
+      name: "SoonTerminatedCoder",
+    }));
+    const issue = await svc.create(companyId, {
+      title: "Do not restart after termination",
+      description: null,
+      status: "todo",
+      priority: "medium",
+      assigneeAgentId,
+    });
+    await db.update(agents).set({ status: "terminated" }).where(eq(agents.id, assigneeAgentId));
+
+    await expect(svc.update(issue.id, {
+      status: "in_progress",
+    })).rejects.toMatchObject({
+      status: 409,
+      details: {
+        code: "agent_not_assignable",
+        reason: "assignee_terminated",
+        assigneeAgentId,
+      },
+    });
+
+    const persisted = await db
+      .select({ assigneeAgentId: issues.assigneeAgentId, status: issues.status })
+      .from(issues)
+      .where(eq(issues.id, issue.id))
+      .then((rows) => rows[0] ?? null);
+    expect(persisted).toMatchObject({
+      assigneeAgentId,
+      status: "todo",
+    });
+  });
+
   it("returns issues an agent participated in across the supported signals", async () => {
     const companyId = randomUUID();
     const agentId = randomUUID();
diff --git a/server/src/__tests__/routines-service.test.ts b/server/src/__tests__/routines-service.test.ts
index f78ab907c13..22756ff9727 100644
--- a/server/src/__tests__/routines-service.test.ts
+++ b/server/src/__tests__/routines-service.test.ts
@@ -539,6 +539,11 @@ describeEmbeddedPostgres("routine service live-execution coalescing", () => {
     ).rejects.toMatchObject({
       status: 409,
       message: "Cannot assign routines to terminated agents",
+      details: {
+        code: "agent_not_assignable",
+        reason: "assignee_terminated",
+        assigneeAgentId: agentId,
+      },
     });
     await expect(svc.get(routine.id)).resolves.toMatchObject({
       description: "revision 2",
@@ -546,6 +551,74 @@ describeEmbeddedPostgres("routine service live-execution coalescing", () => {
     });
   });
 
+  it("blocks routine reassignment to agents under terminated managers", async () => {
+    const { agentId, companyId, routine, svc } = await seedFixture();
+    const terminatedManagerId = randomUUID();
+    const blockedAgentId = randomUUID();
+    await db.insert(agents).values([
+      {
+        id: terminatedManagerId,
+        companyId,
+        name: "TerminatedManager",
+        role: "manager",
+        status: "terminated",
+        adapterType: "codex_local",
+        adapterConfig: {},
+        runtimeConfig: {},
+        permissions: {},
+      },
+      {
+        id: blockedAgentId,
+        companyId,
+        name: "BlockedRoutineCoder",
+        role: "engineer",
+        status: "active",
+        reportsTo: terminatedManagerId,
+        adapterType: "codex_local",
+        adapterConfig: {},
+        runtimeConfig: {},
+        permissions: {},
+      },
+    ]);
+
+    await expect(svc.update(routine.id, {
+      assigneeAgentId: blockedAgentId,
+    }, { userId: "board-user" })).rejects.toMatchObject({
+      status: 409,
+      details: {
+        code: "agent_not_assignable",
+        reason: "ancestor_terminated",
+        assigneeAgentId: blockedAgentId,
+        invalidAncestorAgentId: terminatedManagerId,
+      },
+    });
+
+    await expect(svc.get(routine.id)).resolves.toMatchObject({
+      assigneeAgentId: agentId,
+    });
+  });
+
+  it("blocks manual routine runs when the persisted assignee is no longer assignable", async () => {
+    const { agentId, routine, svc } = await seedFixture();
+    await db
+      .update(agents)
+      .set({ status: "terminated" })
+      .where(eq(agents.id, agentId));
+
+    await expect(svc.runRoutine(routine.id, {
+      source: "manual",
+      payload: null,
+      variables: null,
+    }, { userId: "board-user" })).rejects.toMatchObject({
+      status: 409,
+      details: {
+        code: "agent_not_assignable",
+        reason: "assignee_terminated",
+        assigneeAgentId: agentId,
+      },
+    });
+  });
+
   it("appends safe trigger metadata revisions without leaking webhook secrets", async () => {
     const { routine, svc } = await seedFixture();
     const created = await svc.createTrigger(routine.id, {
diff --git a/server/src/services/access.ts b/server/src/services/access.ts
index ad58db87df4..1aaa53713cb 100644
--- a/server/src/services/access.ts
+++ b/server/src/services/access.ts
@@ -1,7 +1,6 @@
 import { and, eq, inArray, ne, sql } from "drizzle-orm";
 import type { Db } from "@paperclipai/db";
 import {
-  agents,
   companyMemberships,
   instanceUserRoles,
   issues,
@@ -9,6 +8,7 @@ import {
 } from "@paperclipai/db";
 import type { PermissionKey, PrincipalType } from "@paperclipai/shared";
 import { conflict } from "../errors.js";
+import { assertAssignableAgent } from "./agent-assignability.js";
 import { authorizationService, type AuthorizationActor, type AuthorizationResource } from "./authorization.js";
 import { ensureHumanRoleDefaultGrants } from "./principal-access-compatibility.js";
 
@@ -315,21 +315,7 @@ export function accessService(db: Db) {
       return;
     }
 
-    const agent = await tx
-      .select({
-        id: agents.id,
-        companyId: agents.companyId,
-        status: agents.status,
-      })
-      .from(agents)
-      .where(eq(agents.id, input.assigneeAgentId!))
-      .then((rows) => rows[0] ?? null);
-    if (!agent || agent.companyId !== companyId) {
-      throw conflict("Replacement agent must belong to the same company");
-    }
-    if (agent.status === "pending_approval" || agent.status === "terminated") {
-      throw conflict("Replacement agent must be assignable");
-    }
+    await assertAssignableAgent(tx as Db, companyId, input.assigneeAgentId, { kind: "work" });
   }
 
   async function archiveMember(companyId: string, memberId: string, input: MemberArchiveInput = {}) {
diff --git a/server/src/services/agent-assignability.ts b/server/src/services/agent-assignability.ts
new file mode 100644
index 00000000000..f3b48e3a1a0
--- /dev/null
+++ b/server/src/services/agent-assignability.ts
@@ -0,0 +1,157 @@
+import { eq } from "drizzle-orm";
+import type { Db } from "@paperclipai/db";
+import { agents } from "@paperclipai/db";
+import {
+  getAgentWorkEligibility,
+  type AgentEligibilityAgent,
+  type AgentOrgChainHealth,
+} from "@paperclipai/shared";
+import { conflict, notFound, unprocessable } from "../errors.js";
+
+type AgentAssignmentKind = "work" | "routine";
+
+type AssignabilityAgent = AgentEligibilityAgent;
+
+type AgentAssignmentConflictReason =
+  | "pending_approval"
+  | "assignee_terminated"
+  | "ancestor_terminated"
+  | "ancestor_missing"
+  | "ancestor_cross_company"
+  | "ancestor_cycle"
+  | "ancestor_depth_exceeded";
+
+function assignmentMessage(kind: AgentAssignmentKind, reason: AgentAssignmentConflictReason) {
+  if (reason === "pending_approval") {
+    return kind === "routine"
+      ? "Cannot assign routines to pending approval agents"
+      : "Cannot assign work to pending approval agents";
+  }
+  if (reason === "assignee_terminated") {
+    return kind === "routine"
+      ? "Cannot assign routines to terminated agents"
+      : "Cannot assign work to terminated agents";
+  }
+  return kind === "routine"
+    ? "Cannot assign routines to agents with an invalid org chain"
+    : "Cannot assign work to agents with an invalid org chain";
+}
+
+function conflictDetails(input: {
+  companyId: string;
+  assigneeAgentId: string;
+  reason: AgentAssignmentConflictReason;
+  chain: AssignabilityAgent[];
+  invalidAncestorAgentId?: string | null;
+  missingAncestorAgentId?: string | null;
+}) {
+  return {
+    code: "agent_not_assignable",
+    reason: input.reason,
+    companyId: input.companyId,
+    assigneeAgentId: input.assigneeAgentId,
+    invalidAncestorAgentId: input.invalidAncestorAgentId ?? null,
+    missingAncestorAgentId: input.missingAncestorAgentId ?? null,
+    ancestorChain: input.chain.map((agent) => ({
+      id: agent.id,
+      companyId: agent.companyId,
+      status: agent.status,
+      reportsTo: agent.reportsTo,
+    })),
+  };
+}
+
+async function getAgent(db: Db, agentId: string): Promise<AssignabilityAgent | null> {
+  return db
+    .select({
+      id: agents.id,
+      companyId: agents.companyId,
+      name: agents.name,
+      status: agents.status,
+      reportsTo: agents.reportsTo,
+    })
+    .from(agents)
+    .where(eq(agents.id, agentId))
+    .then((rows) => rows[0] ?? null);
+}
+
+async function listCompanyAgents(db: Db, companyId: string): Promise<AssignabilityAgent[]> {
+  return db
+    .select({
+      id: agents.id,
+      companyId: agents.companyId,
+      name: agents.name,
+      status: agents.status,
+      reportsTo: agents.reportsTo,
+    })
+    .from(agents)
+    .where(eq(agents.companyId, companyId));
+}
+
+function assignmentReasonFromHealth(health: AgentOrgChainHealth): AgentAssignmentConflictReason {
+  if (health.reason === "terminated_ancestor") return "ancestor_terminated";
+  if (health.reason === "missing_manager") return "ancestor_missing";
+  if (health.reason === "cycle") return "ancestor_cycle";
+  return "ancestor_missing";
+}
+
+export async function assertAssignableAgent(
+  db: Db,
+  companyId: string,
+  agentId: string | null | undefined,
+  options: { kind?: AgentAssignmentKind } = {},
+) {
+  if (!agentId) return;
+  const kind = options.kind ?? "work";
+  const assignee = await getAgent(db, agentId);
+  if (!assignee) throw notFound("Assignee agent not found");
+  if (assignee.companyId !== companyId) {
+    throw unprocessable("Assignee must belong to same company");
+  }
+
+  const companyAgents = await listCompanyAgents(db, companyId);
+  const eligibility = getAgentWorkEligibility({ agent: assignee, agents: companyAgents });
+  const chain = eligibility.orgChainHealth.fullChain.map((entry) => ({
+    id: entry.id,
+    companyId: entry.companyId,
+    name: entry.name,
+    status: entry.status,
+    reportsTo: entry.reportsTo,
+  }));
+
+  if (eligibility.assignable) return;
+
+  if (eligibility.assignabilityReason === "pending_approval") {
+    throw conflict(assignmentMessage(kind, "pending_approval"), conflictDetails({
+      companyId,
+      assigneeAgentId: agentId,
+      reason: "pending_approval",
+      chain,
+    }));
+  }
+  if (eligibility.assignabilityReason === "terminated") {
+    throw conflict(assignmentMessage(kind, "assignee_terminated"), conflictDetails({
+      companyId,
+      assigneeAgentId: agentId,
+      reason: "assignee_terminated",
+      chain,
+    }));
+  }
+
+  const reason = assignmentReasonFromHealth(eligibility.orgChainHealth);
+  const firstInvalidAncestor = eligibility.orgChainHealth.firstInvalidAncestor;
+  throw conflict(assignmentMessage(kind, reason), conflictDetails({
+    companyId,
+    assigneeAgentId: agentId,
+    reason,
+    chain,
+    invalidAncestorAgentId:
+      firstInvalidAncestor && firstInvalidAncestor.status !== "missing"
+        ? firstInvalidAncestor.id
+        : null,
+    missingAncestorAgentId:
+      firstInvalidAncestor?.status === "missing"
+        ? firstInvalidAncestor.id
+        : null,
+  }));
+}
diff --git a/server/src/services/issues.ts b/server/src/services/issues.ts
index b7f91508a61..e4c01818ee7 100644
--- a/server/src/services/issues.ts
+++ b/server/src/services/issues.ts
@@ -75,6 +75,7 @@ import { redactSensitiveText } from "../redaction.js";
 import { resolveIssueGoalId, resolveNextIssueGoalId } from "./issue-goal-fallback.js";
 import { getRunLogStore } from "./run-log-store.js";
 import { getDefaultCompanyGoal } from "./goals.js";
+import { assertAssignableAgent } from "./agent-assignability.js";
 import {
   isVerifiedIssueTreeControlInteractionWake,
   issueTreeControlService,
@@ -3372,29 +3373,6 @@ export function issueService(db: Db) {
     });
   }
 
-  async function assertAssignableAgent(companyId: string, agentId: string) {
-    const assignee = await db
-      .select({
-        id: agents.id,
-        companyId: agents.companyId,
-        status: agents.status,
-      })
-      .from(agents)
-      .where(eq(agents.id, agentId))
-      .then((rows) => rows[0] ?? null);
-
-    if (!assignee) throw notFound("Assignee agent not found");
-    if (assignee.companyId !== companyId) {
-      throw unprocessable("Assignee must belong to same company");
-    }
-    if (assignee.status === "pending_approval") {
-      throw conflict("Cannot assign work to pending approval agents");
-    }
-    if (assignee.status === "terminated") {
-      throw conflict("Cannot assign work to terminated agents");
-    }
-  }
-
   async function isTreeHoldInteractionCheckoutAllowed(
     companyId: string,
     checkoutRunId: string | null,
@@ -4733,7 +4711,7 @@ export function issueService(db: Db) {
         throw unprocessable("Issue can only have one assignee");
       }
       if (data.assigneeAgentId) {
-        await assertAssignableAgent(companyId, data.assigneeAgentId);
+        await assertAssignableAgent(db, companyId, data.assigneeAgentId, { kind: "work" });
       }
       if (data.assigneeUserId) {
         await assertAssignableUser(companyId, data.assigneeUserId);
@@ -5021,8 +4999,11 @@ export function issueService(db: Db) {
           throw unprocessable("Issue is blocked by unresolved blockers", { unresolvedBlockerIssueIds });
         }
       }
-      if (issueData.assigneeAgentId) {
-        await assertAssignableAgent(existing.companyId, issueData.assigneeAgentId);
+      const shouldValidateNextAssignee =
+        Boolean(nextAssigneeAgentId) &&
+        (issueData.assigneeAgentId !== undefined || patch.status === "in_progress");
+      if (shouldValidateNextAssignee) {
+        await assertAssignableAgent(dbOrTx as Db, existing.companyId, nextAssigneeAgentId, { kind: "work" });
       }
       if (issueData.assigneeUserId) {
         await assertAssignableUser(existing.companyId, issueData.assigneeUserId);
@@ -5347,7 +5328,7 @@ export function issueService(db: Db) {
         .where(eq(issues.id, id))
         .then((rows) => rows[0] ?? null);
       if (!issueCompany) throw notFound("Issue not found");
-      await assertAssignableAgent(issueCompany.companyId, agentId);
+      await assertAssignableAgent(db, issueCompany.companyId, agentId, { kind: "work" });
 
       const now = new Date();
       const activePauseHold = await treeControlSvc.getActivePauseHoldGate(issueCompany.companyId, id);
diff --git a/server/src/services/routines.ts b/server/src/services/routines.ts
index 44197312a71..7081377c5e2 100644
--- a/server/src/services/routines.ts
+++ b/server/src/services/routines.ts
@@ -52,6 +52,7 @@ import { logger } from "../middleware/logger.js";
 import { getTelemetryClient } from "../telemetry.js";
 import { getConfiguredSecretProvider } from "../secrets/configured-provider.js";
 import { issueService } from "./issues.js";
+import { assertAssignableAgent } from "./agent-assignability.js";
 import { secretService } from "./secrets.js";
 import { getSecretProvider } from "../secrets/provider-registry.js";
 import { parseCron, validateCron } from "./cron.js";
@@ -610,25 +611,12 @@ export function routineService(
     return routine;
   }
 
-  async function assertAssignableAgent(companyId: string, agentId: string | null | undefined) {
-    if (!agentId) return;
-    const agent = await db
-      .select({ id: agents.id, companyId: agents.companyId, status: agents.status })
-      .from(agents)
-      .where(eq(agents.id, agentId))
-      .then((rows) => rows[0] ?? null);
-    if (!agent) throw notFound("Assignee agent not found");
-    if (agent.companyId !== companyId) throw unprocessable("Assignee must belong to same company");
-    if (agent.status === "pending_approval") throw conflict("Cannot assign routines to pending approval agents");
-    if (agent.status === "terminated") throw conflict("Cannot assign routines to terminated agents");
-  }
-
   async function assertRestorableAssignee(
     companyId: string,
     assigneeAgentId: string | null | undefined,
     actor: Actor,
   ) {
-    await assertAssignableAgent(companyId, assigneeAgentId);
+    await assertAssignableAgent(db, companyId, assigneeAgentId, { kind: "routine" });
     if (actor.agentId && assigneeAgentId !== actor.agentId) {
       throw forbidden("Agents can only restore routine revisions assigned to themselves");
     }
@@ -1170,6 +1158,7 @@ export function routineService(
     if (!assigneeAgentId) {
       throw unprocessable("Default agent required");
     }
+    await assertAssignableAgent(db, input.routine.companyId, assigneeAgentId, { kind: "routine" });
     const automaticVariables: Record<string, string | number | boolean> = {};
     if (input.executionWorkspaceId && routineUsesWorkspaceBranch(input.routine)) {
       const workspace = await db
@@ -1581,7 +1570,7 @@ export function routineService(
 
     create: async (companyId: string, input: CreateRoutine, actor: Actor): Promise<Routine> => {
       await assertProject(companyId, input.projectId ?? null);
-      await assertAssignableAgent(companyId, input.assigneeAgentId ?? null);
+      await assertAssignableAgent(db, companyId, input.assigneeAgentId ?? null, { kind: "routine" });
       if (input.goalId) await assertGoal(companyId, input.goalId);
       if (input.parentIssueId) await assertParentIssue(companyId, input.parentIssueId);
       const env = input.env === undefined || input.env === null
@@ -1663,7 +1652,9 @@ export function routineService(
         patch.variables === undefined ? existing.variables : sanitizeRoutineVariableInputs(patch.variables),
       );
       if (patch.projectId !== undefined) await assertProject(existing.companyId, nextProjectId);
-      if (patch.assigneeAgentId !== undefined) await assertAssignableAgent(existing.companyId, nextAssigneeAgentId);
+      if (patch.assigneeAgentId !== undefined || patch.status === "active") {
+        await assertAssignableAgent(db, existing.companyId, nextAssigneeAgentId, { kind: "routine" });
+      }
       if (patch.goalId) await assertGoal(existing.companyId, patch.goalId);
       if (patch.parentIssueId) await assertParentIssue(existing.companyId, patch.parentIssueId);
       assertRoutineVariableDefinitions(nextVariables);
@@ -2187,7 +2178,8 @@ export function routineService(
       if (!routine) throw notFound("Routine not found");
       if (routine.status === "archived") throw conflict("Routine is archived");
       await assertProject(routine.companyId, input.projectId ?? null);
-      await assertAssignableAgent(routine.companyId, input.assigneeAgentId ?? null);
+      const assigneeAgentId = input.assigneeAgentId ?? routine.assigneeAgentId ?? null;
+      await assertAssignableAgent(db, routine.companyId, assigneeAgentId, { kind: "routine" });
       const trigger = input.triggerId ? await getTriggerById(input.triggerId) : null;
       if (trigger && trigger.routineId !== routine.id) throw forbidden("Trigger does not belong to routine");
       if (trigger && !trigger.enabled) throw conflict("Routine trigger is not active");