diff --git a/src/servers/api/chat/websocket.ts b/src/servers/api/chat/websocket.ts
index 908fa75b..7c24224d 100644
--- a/src/servers/api/chat/websocket.ts
+++ b/src/servers/api/chat/websocket.ts
@@ -34,7 +34,6 @@ import { resolveHomeDir } from '@@/user-home';
 import { renameClaudeSession, type ChatIdentity } from './claude-sessions';
 import { chatIdentity } from './chat';
 import { commanderBlock } from '../command-hq/commander-block';
-import { getClaudeSession } from '../../sidecar/claude/state';
 import { claudeLoginState } from '@@/os-user-claude';
 import { mkdirSync } from 'node:fs';
 import { logger } from './logger';
@@ -561,6 +560,8 @@ function createMessageHandler(
     // written on its very first turn rather than on its second.
     if (msg.type === 'session:claude' && msg.claudeSessionId) {
       transcriptId = msg.claudeSessionId;
+      // The platform's own copy of the mapping — see `transcriptIdBySessionKey`.
+      transcriptIdBySessionKey.set(sessionId, msg.claudeSessionId);
       record();
       fileAsCommander();
     }
@@ -904,6 +905,24 @@ export type ClaudeTurnOutcome = { ok: true; transcriptId: string } | { ok: false
  * generic timeout: the reasons below (member not signed in, Claude not installed, spawn failure) are the
  * same reasons a websocket caller already sees via `sendToClient`, just mirrored to a second listener.
  */
+/**
+ * Officer's session key → Claude's transcript id, for the platform's own use.
+ *
+ * The sidecar keeps this mapping and the platform cannot read it: `state.ts` holds it in the sidecar's
+ * memory, and re-loading its file from here does not find a live session. So the platform keeps its own,
+ * filled from the `session:claude` message it already handles.
+ *
+ * This is the third distinct place the two ids have caused a bug today. The mapping is not derivable — it is
+ * announced, once, mid-turn — so anything needing it either records it when it passes or does without.
+ */
+const transcriptIdBySessionKey = new Map<string, string>();
+
+/** The mapping read backwards, for callers holding a transcript id — the delete route, mainly. */
+export function sessionKeyForTranscript(transcriptId: string): string | undefined {
+  for (const [key, id] of transcriptIdBySessionKey) if (id === transcriptId) return key;
+  return undefined;
+}
+
 /**
  * Sessions already told what they are and where to record it.
  *
@@ -960,7 +979,7 @@ export async function startClaudeTurn(params: {
   if (!briefedSessions.has(sessionId)) {
     const block = await commanderBlock({
       userId,
-      sessionId: getClaudeSession(sessionId, userId) ?? msg.resumeSessionId ?? null,
+      sessionId: transcriptIdBySessionKey.get(sessionId) ?? msg.resumeSessionId ?? null,
     });
     if (block) {
       briefedSessions.add(sessionId);
diff --git a/src/servers/api/command-hq/router.ts b/src/servers/api/command-hq/router.ts
index 42246ecf..a5943c55 100644
--- a/src/servers/api/command-hq/router.ts
+++ b/src/servers/api/command-hq/router.ts
@@ -8,6 +8,7 @@ import { getCommandersDir, toShellUsername } from '@@/data-path';
 import { forgetChatSessions, getChatEventsSince, ingestSpawnedChildren } from 'officerdb';
 import { killClaudeSession } from '@@/sidecar/claude/claude-manager';
 import { findSessionKeyByClaudeSession } from '@@/sidecar/claude/state';
+import { sessionKeyForTranscript } from '../chat/websocket';
 import {
   clearSpawnedRecord,
   listSpawnedSessions,
@@ -556,7 +557,9 @@ commandHqRouter.delete('/commanders/:sessionId', async (ctx) => {
     holds only the uuid. Ending the session takes its children with it, and the pid-based stop below then
     catches anything that outlived its parent.
   */
-  const sessionKey = findSessionKeyByClaudeSession(sessionId, user.id);
+  // Same mapping problem as the briefing: the sidecar's map is not visible from here, so the platform's own
+  // is asked first and the sidecar's is kept as a fallback for a session that predates this process.
+  const sessionKey = sessionKeyForTranscript(sessionId) ?? findSessionKeyByClaudeSession(sessionId, user.id);
   const sessionKilled = sessionKey ? killClaudeSession(sessionKey, user.id) : false;
   const stopped = stopCommanderProcesses(who.email, sessionId);