diff --git a/src/agents/subagent-registry-announce-read.ts b/src/agents/subagent-registry-announce-read.ts
index da1908aa005..147cb4113cb 100644
--- a/src/agents/subagent-registry-announce-read.ts
+++ b/src/agents/subagent-registry-announce-read.ts
@@ -3,7 +3,7 @@ import { subagentRuns } from "./subagent-registry-memory.js";
 import {
   countPendingDescendantRunsExcludingRunFromRuns,
   countPendingDescendantRunsFromRuns,
-  findRunIdsByChildSessionKeyFromRuns,
+  isSubagentSessionRunActiveFromRuns,
   listRunsForRequesterFromRuns,
   resolveRequesterForChildSessionFromRuns,
   shouldIgnorePostCompletionAnnounceForSessionFromRuns,
@@ -29,18 +29,7 @@ export function resolveRequesterForChildSession(childSessionKey: string): {
 }
 
 export function isSubagentSessionRunActive(childSessionKey: string): boolean {
-  const runIds = findRunIdsByChildSessionKeyFromRuns(subagentRuns, childSessionKey);
-  let latest: SubagentRunRecord | undefined;
-  for (const runId of runIds) {
-    const entry = subagentRuns.get(runId);
-    if (!entry) {
-      continue;
-    }
-    if (!latest || entry.createdAt > latest.createdAt) {
-      latest = entry;
-    }
-  }
-  return Boolean(latest && typeof latest.endedAt !== "number");
+  return isSubagentSessionRunActiveFromRuns(subagentRuns, childSessionKey);
 }
 
 export function shouldIgnorePostCompletionAnnounceForSession(childSessionKey: string): boolean {
diff --git a/src/agents/subagent-registry-queries.ts b/src/agents/subagent-registry-queries.ts
index f6af4e81615..3e7b8ee373c 100644
--- a/src/agents/subagent-registry-queries.ts
+++ b/src/agents/subagent-registry-queries.ts
@@ -86,6 +86,43 @@ function findLatestRunForChildSession(
   return latest;
 }
 
+export function isSubagentSessionRunActiveFromRuns(
+  runs: Map<string, SubagentRunRecord>,
+  childSessionKey: string,
+): boolean {
+  const latest = findLatestRunForChildSession(runs, childSessionKey);
+  return Boolean(latest && typeof latest.endedAt !== "number");
+}
+
+export function getSubagentRunByChildSessionKeyFromRuns(
+  runs: Map<string, SubagentRunRecord>,
+  childSessionKey: string,
+): SubagentRunRecord | null {
+  const key = childSessionKey.trim();
+  if (!key) {
+    return null;
+  }
+
+  let latestActive: SubagentRunRecord | null = null;
+  let latestEnded: SubagentRunRecord | null = null;
+  for (const entry of runs.values()) {
+    if (entry.childSessionKey !== key) {
+      continue;
+    }
+    if (typeof entry.endedAt !== "number") {
+      if (!latestActive || entry.createdAt > latestActive.createdAt) {
+        latestActive = entry;
+      }
+      continue;
+    }
+    if (!latestEnded || entry.createdAt > latestEnded.createdAt) {
+      latestEnded = entry;
+    }
+  }
+
+  return latestActive ?? latestEnded;
+}
+
 export function resolveRequesterForChildSessionFromRuns(
   runs: Map<string, SubagentRunRecord>,
   childSessionKey: string,
diff --git a/src/agents/subagent-registry-read.ts b/src/agents/subagent-registry-read.ts
index c3f1defd81d..95f16c1d283 100644
--- a/src/agents/subagent-registry-read.ts
+++ b/src/agents/subagent-registry-read.ts
@@ -1,6 +1,7 @@
 import { subagentRuns } from "./subagent-registry-memory.js";
 import {
   countActiveDescendantRunsFromRuns,
+  getSubagentRunByChildSessionKeyFromRuns,
   listDescendantRunsForRequesterFromRuns,
   listRunsForControllerFromRuns,
 } from "./subagent-registry-queries.js";
@@ -40,29 +41,10 @@ export function listDescendantRunsForRequester(rootSessionKey: string): Subagent
 }
 
 export function getSubagentRunByChildSessionKey(childSessionKey: string): SubagentRunRecord | null {
-  const key = childSessionKey.trim();
-  if (!key) {
-    return null;
-  }
-
-  let latestActive: SubagentRunRecord | null = null;
-  let latestEnded: SubagentRunRecord | null = null;
-  for (const entry of getSubagentRunsSnapshotForRead(subagentRuns).values()) {
-    if (entry.childSessionKey !== key) {
-      continue;
-    }
-    if (typeof entry.endedAt !== "number") {
-      if (!latestActive || entry.createdAt > latestActive.createdAt) {
-        latestActive = entry;
-      }
-      continue;
-    }
-    if (!latestEnded || entry.createdAt > latestEnded.createdAt) {
-      latestEnded = entry;
-    }
-  }
-
-  return latestActive ?? latestEnded;
+  return getSubagentRunByChildSessionKeyFromRuns(
+    getSubagentRunsSnapshotForRead(subagentRuns),
+    childSessionKey,
+  );
 }
 
 export function getSessionDisplaySubagentRunByChildSessionKey(
diff --git a/src/agents/subagent-registry-run-manager.ts b/src/agents/subagent-registry-run-manager.ts
index 71573306643..63c3cac401f 100644
--- a/src/agents/subagent-registry-run-manager.ts
+++ b/src/agents/subagent-registry-run-manager.ts
@@ -31,6 +31,26 @@ function shouldDeleteAttachments(entry: SubagentRunRecord) {
   return entry.cleanup === "delete" || !entry.retainAttachmentsOnKeep;
 }
 
+export type RegisterSubagentRunParams = {
+  runId: string;
+  childSessionKey: string;
+  controllerSessionKey?: string;
+  requesterSessionKey: string;
+  requesterOrigin?: DeliveryContext;
+  requesterDisplayKey: string;
+  task: string;
+  cleanup: "delete" | "keep";
+  label?: string;
+  model?: string;
+  workspaceDir?: string;
+  runTimeoutSeconds?: number;
+  expectsCompletionMessage?: boolean;
+  spawnMode?: "run" | "session";
+  attachmentsDir?: string;
+  attachmentsRootDir?: string;
+  retainAttachmentsOnKeep?: boolean;
+};
+
 export function createSubagentRunManager(params: {
   runs: Map<string, SubagentRunRecord>;
   resumedRuns: Set<string>;
@@ -261,25 +281,7 @@ export function createSubagentRunManager(params: {
     return true;
   };
 
-  const registerSubagentRun = (registerParams: {
-    runId: string;
-    childSessionKey: string;
-    controllerSessionKey?: string;
-    requesterSessionKey: string;
-    requesterOrigin?: DeliveryContext;
-    requesterDisplayKey: string;
-    task: string;
-    cleanup: "delete" | "keep";
-    label?: string;
-    model?: string;
-    workspaceDir?: string;
-    runTimeoutSeconds?: number;
-    expectsCompletionMessage?: boolean;
-    spawnMode?: "run" | "session";
-    attachmentsDir?: string;
-    attachmentsRootDir?: string;
-    retainAttachmentsOnKeep?: boolean;
-  }) => {
+  const registerSubagentRun = (registerParams: RegisterSubagentRunParams) => {
     const runId = registerParams.runId.trim();
     const childSessionKey = registerParams.childSessionKey.trim();
     const requesterSessionKey = registerParams.requesterSessionKey.trim();
diff --git a/src/agents/subagent-registry.ts b/src/agents/subagent-registry.ts
index 21ed36cc093..2eac8e8c97c 100644
--- a/src/agents/subagent-registry.ts
+++ b/src/agents/subagent-registry.ts
@@ -38,14 +38,18 @@ import {
   countActiveRunsForSessionFromRuns,
   countPendingDescendantRunsExcludingRunFromRuns,
   countPendingDescendantRunsFromRuns,
-  findRunIdsByChildSessionKeyFromRuns,
+  getSubagentRunByChildSessionKeyFromRuns,
+  isSubagentSessionRunActiveFromRuns,
   listRunsForControllerFromRuns,
   listDescendantRunsForRequesterFromRuns,
   listRunsForRequesterFromRuns,
   resolveRequesterForChildSessionFromRuns,
   shouldIgnorePostCompletionAnnounceForSessionFromRuns,
 } from "./subagent-registry-queries.js";
-import { createSubagentRunManager } from "./subagent-registry-run-manager.js";
+import {
+  createSubagentRunManager,
+  type RegisterSubagentRunParams,
+} from "./subagent-registry-run-manager.js";
 import {
   getSubagentRunsSnapshotForRead,
   persistSubagentRunsToDisk,
@@ -723,25 +727,7 @@ export function replaceSubagentRunAfterSteer(params: {
   return subagentRunManager.replaceSubagentRunAfterSteer(params);
 }
 
-export function registerSubagentRun(params: {
-  runId: string;
-  childSessionKey: string;
-  controllerSessionKey?: string;
-  requesterSessionKey: string;
-  requesterOrigin?: DeliveryContext;
-  requesterDisplayKey: string;
-  task: string;
-  cleanup: "delete" | "keep";
-  label?: string;
-  model?: string;
-  workspaceDir?: string;
-  runTimeoutSeconds?: number;
-  expectsCompletionMessage?: boolean;
-  spawnMode?: "run" | "session";
-  attachmentsDir?: string;
-  attachmentsRootDir?: string;
-  retainAttachmentsOnKeep?: boolean;
-}) {
+export function registerSubagentRun(params: RegisterSubagentRunParams) {
   subagentRunManager.registerSubagentRun(params);
 }
 
@@ -791,10 +777,6 @@ export function releaseSubagentRun(runId: string) {
   subagentRunManager.releaseSubagentRun(runId);
 }
 
-function findRunIdsByChildSessionKey(childSessionKey: string): string[] {
-  return findRunIdsByChildSessionKeyFromRuns(subagentRuns, childSessionKey);
-}
-
 export function resolveRequesterForChildSession(childSessionKey: string): {
   requesterSessionKey: string;
   requesterOrigin?: DeliveryContext;
@@ -813,18 +795,7 @@ export function resolveRequesterForChildSession(childSessionKey: string): {
 }
 
 export function isSubagentSessionRunActive(childSessionKey: string): boolean {
-  const runIds = findRunIdsByChildSessionKey(childSessionKey);
-  let latest: SubagentRunRecord | undefined;
-  for (const runId of runIds) {
-    const entry = subagentRuns.get(runId);
-    if (!entry) {
-      continue;
-    }
-    if (!latest || entry.createdAt > latest.createdAt) {
-      latest = entry;
-    }
-  }
-  return Boolean(latest && typeof latest.endedAt !== "number");
+  return isSubagentSessionRunActiveFromRuns(subagentRuns, childSessionKey);
 }
 
 export function shouldIgnorePostCompletionAnnounceForSession(childSessionKey: string): boolean {
@@ -896,29 +867,10 @@ export function listDescendantRunsForRequester(rootSessionKey: string): Subagent
 }
 
 export function getSubagentRunByChildSessionKey(childSessionKey: string): SubagentRunRecord | null {
-  const key = childSessionKey.trim();
-  if (!key) {
-    return null;
-  }
-
-  let latestActive: SubagentRunRecord | null = null;
-  let latestEnded: SubagentRunRecord | null = null;
-  for (const entry of subagentRegistryDeps.getSubagentRunsSnapshotForRead(subagentRuns).values()) {
-    if (entry.childSessionKey !== key) {
-      continue;
-    }
-    if (typeof entry.endedAt !== "number") {
-      if (!latestActive || entry.createdAt > latestActive.createdAt) {
-        latestActive = entry;
-      }
-      continue;
-    }
-    if (!latestEnded || entry.createdAt > latestEnded.createdAt) {
-      latestEnded = entry;
-    }
-  }
-
-  return latestActive ?? latestEnded;
+  return getSubagentRunByChildSessionKeyFromRuns(
+    subagentRegistryDeps.getSubagentRunsSnapshotForRead(subagentRuns),
+    childSessionKey,
+  );
 }
 
 export function getLatestSubagentRunByChildSessionKey(