fix(cli): prevent /rewind from dropping conversation history after /compress-fast

packages/cli/src/acp-integration/session/Session.test.ts

@@ -3137,6 +3137,23 @@ describe('Session', () => {
       expect(session.getRewindableUserTurnCount()).toBe(1);
     });
 
+    it('counts cleared media placeholders as rewindable prompts (twin divergence)', () => {
+      // The TUI twin (isUserTextContent in ui/utils/historyMapping.ts)
+      // excludes microcompaction media-clear placeholders from its rewind
+      // prompt count. The ACP twin must keep counting them: ACP rewind
+      // maps against per-prompt file-history snapshots, which ARE created
+      // for media-only prompts.
+      const history: Content[] = [
+        {
+          role: 'user',
+          parts: [{ text: '[Old inline media cleared: image/png]' }],
+        },
+      ];
+      vi.mocked(mockChat.getHistoryShallow).mockReturnValue(history);
+
+      expect(session.getRewindableUserTurnCount()).toBe(1);
+    });
+
     it('rejects unreachable user turns', () => {
       const history: Content[] = [{ role: 'user', parts: [{ text: 'first' }] }];
       vi.mocked(mockChat.getHistory).mockReturnValue(history);

packages/cli/src/acp-integration/session/Session.ts

@@ -3579,6 +3579,13 @@ export class Session implements SessionContext {
       return false;
     }
 
+    // Deliberate twin divergence: the TUI twin (isUserTextContent in
+    // packages/cli/src/ui/utils/historyMapping.ts) excludes microcompaction
+    // media-clear placeholders ('[Old inline media cleared: ...]') from the
+    // rewind prompt count because a cleared media-only entry never produced
+    // a TUI user turn. Here the placeholders MUST stay counted: ACP rewind
+    // maps against per-prompt file-history snapshots, which ARE created for
+    // media-only prompts. Do not mirror that exclusion into this twin.
     return content.parts.some((part) => 'text' in part && part.text);
   }
 

packages/cli/src/ui/commands/compressCommand.test.ts

@@ -89,6 +89,7 @@ describe('compressCommand', () => {
           compressionStatus: CompressionStatus.COMPRESSED,
           originalTokenCount: 200,
           newTokenCount: 100,
+          compressionKind: 'summarize',
         },
       },
       expect.any(Number),

packages/cli/src/ui/commands/compressCommand.ts

@@ -170,6 +170,7 @@ export const compressCommand: SlashCommand = {
               originalTokenCount: compressed.originalTokenCount,
               newTokenCount: compressed.newTokenCount,
               compressionStatus: compressed.compressionStatus,
+              compressionKind: 'summarize',
             },
           } as HistoryItemCompression,
           Date.now(),

packages/cli/src/ui/commands/compressFastCommand.test.ts

@@ -155,6 +155,7 @@ describe('compressFastCommand', () => {
           originalTokenCount: 200,
           newTokenCount: 100,
           compressionStatus: CompressionStatus.COMPRESSED,
+          compressionKind: 'fast',
         },
       },
       expect.any(Number),

packages/cli/src/ui/commands/compressFastCommand.ts

@@ -138,6 +138,7 @@ export const compressFastCommand: SlashCommand = {
               originalTokenCount: compressed.originalTokenCount,
               newTokenCount: compressed.newTokenCount,
               compressionStatus: compressed.compressionStatus,
+              compressionKind: 'fast',
             },
           } as HistoryItemCompression,
           Date.now(),

packages/cli/src/ui/types.ts

@@ -102,6 +102,14 @@ export interface CompressionProps {
   originalTokenCount: number | null;
   newTokenCount: number | null;
   compressionStatus: CompressionStatus | null;
+  /**
+   * Which compression path produced this item. 'summarize' replaces the
+   * pre-marker history with a synthetic summary prefix; 'fast' (rule-based,
+   * no LLM summary) removes no user prompts from the API history, so its
+   * marker must not be treated as a rewind boundary. Absent on items from
+   * older sessions, which are treated as 'summarize'.
+   */
+  compressionKind?: 'summarize' | 'fast';
 }
 
 export interface SummaryProps {