diff --git a/apps/desktop/src/app/session/hooks/use-message-stream/index.ts b/apps/desktop/src/app/session/hooks/use-message-stream/index.ts
index a73852f6e923f..979bbc1e2f5e2 100644
--- a/apps/desktop/src/app/session/hooks/use-message-stream/index.ts
+++ b/apps/desktop/src/app/session/hooks/use-message-stream/index.ts
@@ -656,12 +656,21 @@ export function useMessageStream({
         const hasInlineError = nextMessages.some(m => m.role === 'assistant' && m.error && !m.hidden)
         const lastVisible = [...nextMessages].reverse().find(m => !m.hidden)
         const unresolvedUserTail = lastVisible?.role === 'user'
+        // Having streamed the reply normally means this window owns the whole
+        // turn and re-reading stored history would be wasted work. That only
+        // holds for a turn it STARTED: an adopted one (resumed onto a session
+        // already running elsewhere) arrives reply-first, with no prompt row,
+        // so it has to hydrate or the user's own message never shows up.
         shouldHydrate =
-          !completionError && !hasInlineError && !unresolvedUserTail && (!state.sawAssistantPayload || !finalText)
+          !completionError &&
+          !hasInlineError &&
+          !unresolvedUserTail &&
+          (state.adoptedRunningTurn || !state.sawAssistantPayload || !finalText)
 
         return {
           ...state,
           messages: nextMessages,
+          adoptedRunningTurn: false,
           streamId: null,
           pendingBranchGroup: null,
           awaitingResponse: false,
diff --git a/apps/desktop/src/app/session/hooks/use-session-actions.test.tsx b/apps/desktop/src/app/session/hooks/use-session-actions.test.tsx
index 1bdb521efabcb..cb3f6df916d2b 100644
--- a/apps/desktop/src/app/session/hooks/use-session-actions.test.tsx
+++ b/apps/desktop/src/app/session/hooks/use-session-actions.test.tsx
@@ -937,6 +937,7 @@ describe('resumeSession failure recovery', () => {
             interimBoundaryPending: false,
             interrupted: false,
             messages: [],
+            adoptedRunningTurn: false,
             model: '',
             needsInput: false,
             pendingBranchGroup: null,
diff --git a/apps/desktop/src/app/session/hooks/use-session-actions/index.ts b/apps/desktop/src/app/session/hooks/use-session-actions/index.ts
index 0f13a375c0837..b09db251ccae7 100644
--- a/apps/desktop/src/app/session/hooks/use-session-actions/index.ts
+++ b/apps/desktop/src/app/session/hooks/use-session-actions/index.ts
@@ -735,8 +735,17 @@ export function useSessionActions({
             } else {
               const runtimeInfo = applyRuntimeInfo(activated.info)
 
-              let activatedMessages =
-                activated.messages.length || activated.inflight || activated.queued
+              // `omit_messages` means the response carries NO transcript, not
+              // an empty one — the cache is the base and the live projection is
+              // a tail to graft onto it. Reconciling against the empty list
+              // instead rebuilds the thread out of the projection alone, so
+              // activating a session that is mid-turn somewhere else (leaving
+              // HUD mode is exactly that) collapsed the whole conversation down
+              // to the in-flight prompt until the turn finished and the
+              // post-turn hydrate restored it.
+              let activatedMessages = activated.messages_omitted
+                ? appendLiveSessionProjection(cachedViewState.messages, activated)
+                : activated.messages.length || activated.inflight || activated.queued
                   ? reconcileAuthoritativeMessages(activated.messages, cachedViewState.messages, activated)
                   : cachedViewState.messages
 
@@ -773,7 +782,11 @@ export function useSessionActions({
                   ...(runtimeInfo ?? {}),
                   messages: activatedMessages,
                   busy: running,
-                  awaitingResponse: running
+                  awaitingResponse: running,
+                  // Adopting someone else's turn: we'll stream its reply
+                  // without ever having received its prompt, so the settle
+                  // path must not take the "I saw it all" shortcut.
+                  adoptedRunningTurn: state.adoptedRunningTurn || running
                 }),
                 storedSessionId
               )
@@ -933,7 +946,15 @@ export function useSessionActions({
                   ? preserveLocalPendingTurnMessages(currentMessages, resumeStartMessages)
                   : currentMessages
 
-                const resumedMessages = reconcileAuthoritativeMessages(resumed.messages, previousMessages, resumed)
+                // Omitted, not empty — same trap as the activate path above.
+                // The REST prefetch IS the transcript here; the resume payload
+                // only contributes the live tail, so graft rather than rebuild.
+                // (Without a usable prefetch there is nothing better to stand
+                // on, so the projection alone remains the degraded fallback.)
+                const resumedMessages =
+                  resumed.messages_omitted && prefetchApplied && prefetchMatchesResumedSession
+                    ? appendLiveSessionProjection(localSnapshot, resumed)
+                    : reconcileAuthoritativeMessages(resumed.messages, previousMessages, resumed)
 
                 return chatMessageArraysEquivalent(currentMessages, resumedMessages) ? currentMessages : resumedMessages
               })()
@@ -990,6 +1011,7 @@ export function useSessionActions({
             messages: messagesForView,
             busy: resumedRunning,
             awaitingResponse: resumedRunning && !recoveredInFlightTail,
+            adoptedRunningTurn: state.adoptedRunningTurn || resumedRunning,
             ...(inFlightRecovery.applied
               ? {
                   sawAssistantPayload: true,
diff --git a/apps/desktop/src/app/types.ts b/apps/desktop/src/app/types.ts
index f7452607f7c83..743c2b95be019 100644
--- a/apps/desktop/src/app/types.ts
+++ b/apps/desktop/src/app/types.ts
@@ -187,6 +187,12 @@ export interface ClientSessionState {
   awaitingResponse: boolean
   streamId: string | null
   sawAssistantPayload: boolean
+  /** This window picked up a turn it did not start — it resumed onto a session
+   *  that was already running somewhere else (leaving HUD mode, opening a
+   *  pop-out mid-turn). It therefore holds the reply but never received the
+   *  prompt, so the usual "I streamed it, my transcript is complete" shortcut
+   *  is false and the turn must hydrate from stored history when it settles. */
+  adoptedRunningTurn: boolean
   pendingBranchGroup: string | null
   interrupted: boolean
   /** True after message.interim finalized a bubble in the still-running turn. */
diff --git a/apps/desktop/src/lib/chat-runtime.ts b/apps/desktop/src/lib/chat-runtime.ts
index 99585a3c7642f..c581daaea9c7e 100644
--- a/apps/desktop/src/lib/chat-runtime.ts
+++ b/apps/desktop/src/lib/chat-runtime.ts
@@ -52,6 +52,7 @@ export function createClientSessionState(
     awaitingResponse: false,
     streamId: null,
     sawAssistantPayload: false,
+    adoptedRunningTurn: false,
     pendingBranchGroup: null,
     interrupted: false,
     interimBoundaryPending: false,