diff --git a/packages/eve/src/execution/subagent-auth-proxy.integration.test.ts b/packages/eve/src/execution/subagent-auth-proxy.integration.test.ts
index f806e5101..e13b530b6 100644
--- a/packages/eve/src/execution/subagent-auth-proxy.integration.test.ts
+++ b/packages/eve/src/execution/subagent-auth-proxy.integration.test.ts
@@ -147,6 +147,7 @@ describe("subagent authorization proxy", () => {
         candidateId: "candidate-1",
         outcome: "pending",
         requestId: "approval-1",
+        responderPrincipalId: "slack:T1:U1",
         sequence: 0,
         stepIndex: 1,
         turnId: "child-turn",
diff --git a/packages/eve/src/harness/authorization.test.ts b/packages/eve/src/harness/authorization.test.ts
new file mode 100644
index 000000000..d6e456f81
--- /dev/null
+++ b/packages/eve/src/harness/authorization.test.ts
@@ -0,0 +1,50 @@
+import { describe, expect, it } from "vitest";
+
+import {
+  getPendingAuthorization,
+  setPendingAuthorization,
+  type AuthorizationChallenge,
+} from "#harness/authorization.js";
+
+function challenge(name: string, candidateId: string): AuthorizationChallenge {
+  return {
+    candidateId,
+    challenge: { url: `https://example.com/${name}` },
+    hookUrl: `https://eve.example/${name}`,
+    name,
+  };
+}
+
+describe("pending authorization state", () => {
+  it("merges concurrent candidate challenges by authorization name", () => {
+    const first = setPendingAuthorization(undefined, {
+      challenges: [challenge("candidate-1:github", "candidate-1")],
+    });
+    const second = setPendingAuthorization(first, {
+      challenges: [challenge("candidate-2:github", "candidate-2")],
+    });
+
+    expect(getPendingAuthorization(second)?.challenges).toEqual([
+      expect.objectContaining({ candidateId: "candidate-1", name: "candidate-1:github" }),
+      expect.objectContaining({ candidateId: "candidate-2", name: "candidate-2:github" }),
+    ]);
+  });
+
+  it("replaces a repeated challenge without duplicating it", () => {
+    const first = setPendingAuthorization(undefined, {
+      challenges: [challenge("candidate-1:github", "candidate-1")],
+    });
+    const second = setPendingAuthorization(first, {
+      challenges: [
+        {
+          ...challenge("candidate-1:github", "candidate-1"),
+          hookUrl: "https://eve.example/refreshed",
+        },
+      ],
+    });
+
+    expect(getPendingAuthorization(second)?.challenges).toEqual([
+      expect.objectContaining({ hookUrl: "https://eve.example/refreshed" }),
+    ]);
+  });
+});
diff --git a/packages/eve/src/harness/authorization.ts b/packages/eve/src/harness/authorization.ts
index f5d4ccd74..b7d9316c6 100644
--- a/packages/eve/src/harness/authorization.ts
+++ b/packages/eve/src/harness/authorization.ts
@@ -242,7 +242,13 @@ export function setPendingAuthorization(
   sessionState: Record<string, unknown> | undefined,
   value: PendingAuthorizationState,
 ): Record<string, unknown> {
-  return { ...sessionState, [PENDING_AUTHORIZATION_KEY]: value };
+  const existing = getPendingAuthorization(sessionState)?.challenges ?? [];
+  const byName = new Map(existing.map((challenge) => [challenge.name, challenge]));
+  for (const challenge of value.challenges) byName.set(challenge.name, challenge);
+  return {
+    ...sessionState,
+    [PENDING_AUTHORIZATION_KEY]: { challenges: [...byName.values()] },
+  };
 }
 
 export function clearPendingAuthorization(
diff --git a/packages/eve/src/harness/tool-loop.ts b/packages/eve/src/harness/tool-loop.ts
index 673484492..3694874a6 100644
--- a/packages/eve/src/harness/tool-loop.ts
+++ b/packages/eve/src/harness/tool-loop.ts
@@ -580,6 +580,10 @@ export function createToolLoopHarness(config: ToolLoopHarnessConfig): StepFn {
           candidateId: authorized.candidateId ?? `stale:${authorized.requestId}`,
           outcome: authorized.kind === "authorization-required" ? "pending" : authorized.kind,
           requestId: authorized.requestId,
+          responderPrincipalId:
+            getApprovalAuditState(session.state).activeCandidates.find(
+              (candidate) => candidate.candidateId === authorized.candidateId,
+            )?.responder.principalId ?? "unknown",
           safeReason: "safeReason" in authorized ? authorized.safeReason : undefined,
           sequence: emissionState.sequence,
           stepIndex: emissionState.stepIndex,
diff --git a/packages/eve/src/protocol/message.ts b/packages/eve/src/protocol/message.ts
index 4762eab1a..5dc9bb5c0 100644
--- a/packages/eve/src/protocol/message.ts
+++ b/packages/eve/src/protocol/message.ts
@@ -221,6 +221,7 @@ export interface ApprovalCandidateStreamEvent {
     candidateId: string;
     outcome: ApprovalCandidateOutcome;
     requestId: string;
+    responderPrincipalId: string;
     safeReason?: string;
     sequence: number;
     stepIndex: number;
diff --git a/packages/eve/src/public/channels/slack/defaults.test.ts b/packages/eve/src/public/channels/slack/defaults.test.ts
index 8c9b62402..6399db72d 100644
--- a/packages/eve/src/public/channels/slack/defaults.test.ts
+++ b/packages/eve/src/public/channels/slack/defaults.test.ts
@@ -66,6 +66,7 @@ describe("defaultEvents approval lifecycle", () => {
         candidateId: "candidate-1",
         outcome: "pending",
         requestId: "approval-1",
+        responderPrincipalId: "slack:T1:U777",
         sequence: 1,
         stepIndex: 0,
         turnId: "turn-1",
diff --git a/packages/eve/src/public/channels/slack/defaults.ts b/packages/eve/src/public/channels/slack/defaults.ts
index 6ad851bf0..156bb7a0f 100644
--- a/packages/eve/src/public/channels/slack/defaults.ts
+++ b/packages/eve/src/public/channels/slack/defaults.ts
@@ -163,17 +163,28 @@ function buildInputRequestPosts(
  */
 export const defaultEvents: SlackChannelInternalEvents = {
   async "approval.candidate"(event, channel, ctx) {
-    const userId = slackUserIdFromAuthContext(ctx.session.auth.current);
-    if (userId === undefined) return;
-    if (event.outcome === "pending") {
-      await channel.thread.postEphemeral(userId, "Checking whether you can approve this action…");
+    const currentUserId = slackUserIdFromAuthContext(ctx.session.auth.current);
+    if (event.outcome === "pending" && currentUserId !== undefined) {
+      channel.state.pendingApprovalCandidateUsers = {
+        ...channel.state.pendingApprovalCandidateUsers,
+        [event.candidateId]: currentUserId,
+      };
+      await channel.thread.postEphemeral(
+        currentUserId,
+        "Checking whether you can approve this action…",
+      );
       return;
     }
+    const userId = channel.state.pendingApprovalCandidateUsers?.[event.candidateId];
+    if (userId === undefined) return;
     if (event.outcome === "rejected" || event.outcome === "failed") {
       await channel.thread.postEphemeral(
         userId,
         event.safeReason ?? "We couldn’t verify your approval. Please try again.",
       );
+      const next = { ...channel.state.pendingApprovalCandidateUsers };
+      delete next[event.candidateId];
+      channel.state.pendingApprovalCandidateUsers = next;
     }
   },
 
diff --git a/packages/eve/src/public/channels/slack/slackChannel.ts b/packages/eve/src/public/channels/slack/slackChannel.ts
index 873140c4c..aa6a8e932 100644
--- a/packages/eve/src/public/channels/slack/slackChannel.ts
+++ b/packages/eve/src/public/channels/slack/slackChannel.ts
@@ -213,6 +213,7 @@ export interface SlackChannelState {
    */
   pendingAuthMessageTs?: Record<string, string>;
   pendingApprovalCards?: Record<string, SlackPendingApprovalCard>;
+  pendingApprovalCandidateUsers?: Record<string, string>;
 }
 
 /**
@@ -698,6 +699,7 @@ export function slackChannel(config: SlackChannelConfig = {}): SlackChannel {
       lastReasoningTypingStatus: null,
       pendingAuthMessageTs: {},
       pendingApprovalCards: {},
+      pendingApprovalCandidateUsers: {},
     },
     fetchFile: slackFetchFile,
     metadata(state): SlackInstrumentationMetadata {