fix: preserve conversation context in /clear-screen

The previous implementation replaced the messages array with a single
empty-content assistant message to preserve prompt cache. This caused
two problems:

1. Claude lost all conversation context and treated the next message
   as the start of a new session ("This is the first message...")
2. The prompt cache was not actually preserved — cache breakpoints
   are set via cache_control in the API request, and the usage field
   in the saved assistant message is a response from the previous
   call, not an instruction for the next one.

The new implementation hides messages from the UI without removing
them from the messages array:

- On /clear-screen, all current message UUIDs (first 24 chars) are
  collected into a globalThis.__tweakccHiddenUUIDs Set.
- The render filter function (g97) is patched to check this Set and
  skip messages whose UUID prefix matches.
- Messages remain in the array and are sent to the API as usual,
  preserving full conversation context.

UUID prefix (24 chars) is used because the render pipeline function
lP() splits multi-content assistant messages into separate objects
with modified UUIDs (original.slice(0,24) + hex index). Matching on
the prefix ensures both original and split messages are hidden.

The approach with a per-message flag (__tweakccHiddenFromUI) was
tried first but failed: lP() creates new objects for assistant
messages with a fixed set of fields, dropping custom properties.
User messages worked because lP() uses object spread for string
content, preserving extra fields — but assistant messages did not.

After session resume, globalThis is empty, so previously hidden
messages become visible again (acceptable trade-off).

Author: VitalyOstanin

src/patches/clearScreen.test.ts

@@ -1,12 +1,16 @@
 import { describe, expect, it } from 'vitest';
 
-import { writeClearScreen } from './clearScreen';
+import { writeClearScreen, patchRenderFilter } from './clearScreen';
 
 const cmds = Array.from({ length: 31 }, (_, i) => `c${i}`).join(',');
 const slashCommandArray = `=>[${cmds}]`;
 
+const renderFilter =
+  'function g97(H,$){if(H.type!=="user")return!0;if(H.isMeta){if(H.origin?.kind==="channel")return!0;return!1}if(H.isVisibleInTranscriptOnly&&!$)return!1;return!0}';
+
 const makeInput = (delimiter = ';') =>
   'const x=1' +
+  renderFilter +
   slashCommandArray +
   `${delimiter}let Z=G_H.useCallback(()=>{Nw.get(process.stdout)?.forceRedraw()})`;
 
@@ -19,10 +23,30 @@ describe('clearScreen', () => {
       'globalThis.__tweakccForceRedraw=()=>Nw.get(process.stdout)?.forceRedraw()'
     );
     expect(result).toContain('name:"clear-screen"');
-    expect(result).toContain('$.setMessages(');
+    expect(result).toContain('__tweakccHiddenUUIDs');
     expect(result).toContain('globalThis.__tweakccForceRedraw?.()');
   });
 
+  it('preserves all messages for API context (hides via UUID set, does not remove)', () => {
+    const result = writeClearScreen(makeInput());
+
+    expect(result).not.toBeNull();
+    expect(result).toContain('__tweakccHiddenUUIDs=new Set(');
+    expect(result).toContain('return[...m]');
+    expect(result).not.toContain('content:[]');
+    expect(result).not.toContain('return k?[');
+    expect(result).not.toContain('return[]');
+  });
+
+  it('patches render filter to check __tweakccHiddenUUIDs', () => {
+    const result = writeClearScreen(makeInput());
+
+    expect(result).not.toBeNull();
+    expect(result).toContain(
+      'globalThis.__tweakccHiddenUUIDs?.has(H.uuid?.slice(0,24)))return!1;if(H.type!=="user")'
+    );
+  });
+
   it('preserves original app:redraw callback', () => {
     const result = writeClearScreen(makeInput());
 
@@ -45,11 +69,14 @@ describe('clearScreen', () => {
     expect(result).toBeNull();
   });
 
-  it('preserves fallback for assistant messages without usage', () => {
-    const result = writeClearScreen(makeInput());
+  it('returns null when render filter not found', () => {
+    const input =
+      'const x=1' +
+      slashCommandArray +
+      ';let Z=G_H.useCallback(()=>{Nw.get(process.stdout)?.forceRedraw()})';
+    const result = writeClearScreen(input);
 
-    expect(result).not.toBeNull();
-    expect(result).toContain('if(!k&&m[i]?.type==="assistant")k=m[i]');
+    expect(result).toBeNull();
   });
 
   it('works with different delimiters before useCallback', () => {
@@ -60,3 +87,39 @@ describe('clearScreen', () => {
     }
   });
 });
+
+describe('patchRenderFilter', () => {
+  it('adds __tweakccHiddenUUIDs check at the start of the function', () => {
+    const result = patchRenderFilter(renderFilter);
+
+    expect(result).not.toBeNull();
+    expect(result).toContain(
+      'function g97(H,$){if(globalThis.__tweakccHiddenUUIDs?.has(H.uuid?.slice(0,24)))return!1;if(H.type!=="user")'
+    );
+  });
+
+  it('preserves the rest of the function', () => {
+    const result = patchRenderFilter(renderFilter);
+
+    expect(result).not.toBeNull();
+    expect(result).toContain('if(H.isMeta)');
+    expect(result).toContain('if(H.isVisibleInTranscriptOnly&&!$)return!1');
+  });
+
+  it('returns null when pattern not found', () => {
+    const result = patchRenderFilter('const x=1;');
+
+    expect(result).toBeNull();
+  });
+
+  it('works with different function and argument names', () => {
+    const input =
+      'function abc(X$,Y$){if(X$.type!=="user")return!0;if(X$.isMeta){if(X$.origin?.kind==="channel")return!0;return!1}return!0}';
+    const result = patchRenderFilter(input);
+
+    expect(result).not.toBeNull();
+    expect(result).toContain(
+      'if(globalThis.__tweakccHiddenUUIDs?.has(X$.uuid?.slice(0,24)))return!1;'
+    );
+  });
+});

src/patches/clearScreen.ts

@@ -24,7 +24,7 @@ export const writeClearScreen = (oldFile: string): string | null => {
     `${delimiter}globalThis.__tweakccForceRedraw=()=>${mapVar}.get(process.stdout)?.forceRedraw();` +
     redrawMatch[0].slice(1);
 
-  const file =
+  let file =
     oldFile.slice(0, redrawMatch.index) +
     redrawReplacement +
     oldFile.slice(redrawMatch.index + redrawMatch[0].length);
@@ -37,18 +37,22 @@ export const writeClearScreen = (oldFile: string): string | null => {
     redrawMatch.index + redrawMatch[0].length
   );
 
+  const renderFilterResult = patchRenderFilter(file);
+  if (!renderFilterResult) {
+    debug('patch: clearScreen: failed to patch render filter g97');
+    return null;
+  }
+  file = renderFilterResult;
+
   const commandDef =
     ',{type:"local",name:"clear-screen",' +
     'description:"Clear screen without resetting conversation context",' +
     'supportsNonInteractive:!1,' +
     'load:()=>Promise.resolve().then(()=>({call:(H,$)=>{' +
     '$.setMessages(m=>{' +
-    'let k=null;' +
-    'for(let i=m.length-1;i>=0;i--){' +
-    'if(m[i]?.type==="assistant"&&m[i].message?.usage){k=m[i];break}' +
-    'if(!k&&m[i]?.type==="assistant")k=m[i]}' +
-    'return k?[{...k,message:{...k.message,content:[]}}]:[]});' +
-    'process.stdout.write("\\x1b[3J");' +
+    'globalThis.__tweakccHiddenUUIDs=new Set(m.map(x=>x.uuid?.slice(0,24)).filter(Boolean));' +
+    'return[...m]});' +
+    'process.stdout.write("\\x1b[2J\\x1b[H\\x1b[3J");' +
     'globalThis.__tweakccForceRedraw?.();' +
     'return{type:"skip"}}}))}';
 
@@ -60,3 +64,37 @@ export const writeClearScreen = (oldFile: string): string | null => {
 
   return result;
 };
+
+export const patchRenderFilter = (oldFile: string): string | null => {
+  const pattern =
+    /(function [$\w]+\([$\w]+,[$\w]+\)\{)if\([$\w]+\.type!=="user"\)return!0;if\([$\w]+\.isMeta\)/;
+  const match = oldFile.match(pattern);
+  if (!match || match.index === undefined) {
+    return null;
+  }
+
+  const funcPrefix = match[1];
+  const firstArg = match[0].match(/function ([$\w]+)\(([$\w]+),/)?.[2];
+  if (!firstArg) {
+    return null;
+  }
+
+  const replacement =
+    `${funcPrefix}if(globalThis.__tweakccHiddenUUIDs?.has(${firstArg}.uuid?.slice(0,24)))return!1;` +
+    match[0].slice(funcPrefix.length);
+
+  const result =
+    oldFile.slice(0, match.index) +
+    replacement +
+    oldFile.slice(match.index + match[0].length);
+
+  showDiff(
+    oldFile,
+    result,
+    replacement,
+    match.index,
+    match.index + match[0].length
+  );
+
+  return result;
+};