fix(pty-connection): correct sequencing and state bugs in spawn and reat

- Fix terminal tail slice to take prefix instead of suffix, preserving escape
  sequence markers needed by next scan
- Clear pending pane serializer when direct SSH retry PTY is unclaimed
- Initialize interrupt status baseline to undefined so first input advances
  sequence counter
- Bump reattach generation only after confirming current attempt owns the stream,
  preventing superseded results from canceling in-flight prepaint

src/renderer/src/components/terminal-pane/pty-connection/fresh-spawn-follow-reset.ts

@@ -85,7 +85,9 @@ export function bindFreshSpawnFollowReset(session: ConnectPanePtySession): void
         return ''
       }
     }
-    return tail.slice(-TERMINAL_RENDERER_RISK_SCAN_TAIL_CHARS)
+    // Why: keep the head — a suffix slice of an oversized parameter run drops
+    // the `\x1b[` the next scan needs to recognize the carried sequence.
+    return tail.slice(0, TERMINAL_RENDERER_RISK_SCAN_TAIL_CHARS)
   }
 
   session.foregroundRendererRiskOutputPrefersRenderRefresh = function (data: string): boolean {

src/renderer/src/components/terminal-pane/pty-connection/fresh-spawn-start.ts

@@ -114,6 +114,12 @@ export function bindStartFreshSpawn(session: ConnectPanePtySession): void {
               : session.transport.getPtyId()
         if (resolvedPtyId && !session.claimCapturedDirectSshRetryPty(resolvedPtyId)) {
           session.finishReattachLiveDataDeferral(false, outputCallbacks.generation)
+          // Why: an outstanding declare keeps main's cooperation gate suppressing
+          // this paneKey's daemon-snapshot seed until something releases it.
+          const gen = await preSignalPromise
+          if (typeof gen === 'number') {
+            void window.api.pty.clearPendingPaneSerializer(session.cacheKey, gen).catch(() => {})
+          }
           return null
         }
         const connectResult =
@@ -193,7 +199,9 @@ export function bindStartFreshSpawn(session: ConnectPanePtySession): void {
           session.reconcilePtySizeAfterSpawn(resolvedPtyId, session.cols, session.rows)
         }
         const gen = await preSignalPromise
-        if (resolvedPtyId && (typeof gen === 'number' || isRemoteRuntimePtyId(resolvedPtyId))) {
+        // Why: a bound PTY owns the renderer serializer even when the declare was
+        // rejected; the gen token only settles or clears the pending declaration.
+        if (resolvedPtyId) {
           if (!isRemoteRuntimePtyId(resolvedPtyId) || !hasPtySerializer(resolvedPtyId)) {
             session.registerPaneSerializerFor(resolvedPtyId)
           }

src/renderer/src/components/terminal-pane/pty-connection/interrupt-input-intent.ts

@@ -162,7 +162,10 @@ export function installInterruptInputIntent(session: ConnectPanePtySession): voi
     session.questionAnsweredInference.observeSentTerminalInput(data)
   }
   session.pendingTerminalInputWrite = null
-  session.sequencedInterruptStatusBaseline = 0
+  // Why: an unset baseline must differ from the first `?? null` snapshot so the
+  // first acknowledged input still advances the sequence.
+  session.sequencedInterruptStatusBaseline = undefined
+  session.interruptStatusBaselineSequence = 0
   session.setPendingTerminalInputWrite = (promise: Promise<boolean | null>): void => {
     session.pendingTerminalInputWrite = promise
     void promise.finally(() => {

src/renderer/src/components/terminal-pane/pty-connection/reattach-result-handler.ts

@@ -57,13 +57,15 @@ export function bindHandleReattachResult(sessionBag: ConnectPanePtySession): voi
     coldRestoreStartup?: ColdRestoreAgentResumeStartup | null,
     attemptGeneration = session.transportStreamGeneration
   ): Promise<boolean> => {
-    session.authoritativeReattachGeneration += 1
     if (session.disposed) {
       return false
     }
     if (attemptGeneration !== session.transportStreamGeneration) {
       return false
     }
+    // Why: bump only once this attempt owns the stream, or a superseded result
+    // would cancel the current attempt's in-flight snapshot prepaint.
+    session.authoritativeReattachGeneration += 1
     const connectResult =
       result && typeof result === 'object' && 'id' in result ? (result as PtyConnectResult) : null