fix(tools): preserve complete bounded presentations

packages/fs/tool-fs/src/read-render.ts

@@ -37,9 +37,9 @@ export interface FileTextLine {
 export interface WindowResult {
   /** Returned lines, already numbered. */
   lines: FileTextLine[]
-  /** Total line count in the file, unless `truncatedByBytes` stopped scanning early. */
+  /** Exact total line count in the file. */
   totalLines: number
-  /** Whether selected output hit the byte cap before EOF or the requested limit. */
+  /** Whether selected output hit the byte cap. */
   truncatedByBytes: boolean
 }
 
@@ -49,9 +49,9 @@ export interface FileReadOutcome {
   offset: number
   /** Returned lines, already numbered. */
   lines: FileTextLine[]
-  /** Total line count in the file, unless `truncatedByBytes` stopped scanning early. */
+  /** Exact total line count in the file. */
   totalLines: number
-  /** Whether selected output hit the byte cap before EOF or the requested limit. */
+  /** Whether selected output hit the byte cap. */
   truncatedByBytes?: true
 }
 
@@ -60,11 +60,10 @@ interface WindowAccumulator {
   totalLines: number
   outputBytes: number
   truncatedByBytes: boolean
-  done: boolean
 }
 
 function newAccumulator(): WindowAccumulator {
-  return { lines: [], totalLines: 0, outputBytes: 0, truncatedByBytes: false, done: false }
+  return { lines: [], totalLines: 0, outputBytes: 0, truncatedByBytes: false }
 }
 
 function truncateLine(line: string, maxLineLength: number): string {
@@ -77,13 +76,12 @@ function lineByteSize(line: string, currentLineCount: number): number {
 
 function consumeLine(acc: WindowAccumulator, rawLine: string, request: ReadWindow): void {
   acc.totalLines += 1
-  if (acc.totalLines < request.offset || acc.lines.length >= request.limit) return
+  if (acc.truncatedByBytes || acc.totalLines < request.offset || acc.lines.length >= request.limit) return
 
   const text = truncateLine(rawLine, request.maxLineLength)
   const bytes = lineByteSize(text, acc.lines.length)
   if (acc.outputBytes + bytes > request.maxBytes) {
     acc.truncatedByBytes = true
-    acc.done = true
     return
   }
   acc.outputBytes += bytes
@@ -102,8 +100,9 @@ function finish(acc: WindowAccumulator, request: ReadWindow, displayPath: string
 }
 
 /**
- * Build one window from streamed or whole-file chunks, enforcing line and byte caps and throwing
- * `FS_NOT_FOUND` when the requested offset is past EOF.
+ * Build one window from streamed or whole-file chunks, enforcing line and byte caps while still
+ * scanning to an exact total line count, and throwing `FS_NOT_FOUND` when the requested offset is
+ * past EOF.
  * @param chunks - decoded text chunks in file order; chunk boundaries carry no meaning.
  * @param request - the resolved window; the caller has already applied its defaults and caps.
  * @param displayPath - the caller-facing path used in the offset-out-of-range error.
@@ -137,7 +136,6 @@ export async function buildWindow(
       appendToLineBuffer(chunk.slice(startPos, newlinePos))
       flushLine()
       startPos = newlinePos + 1
-      if (acc.done) return finish(acc, request, displayPath)
     }
     appendToLineBuffer(chunk.slice(startPos))
   }

packages/fs/tool-fs/tests/read-render.spec.ts

@@ -86,6 +86,7 @@ describe('buildWindow', () => {
     it('caps output at a custom maxBytes', async () => {
       const result = await buildWindow(whole('aaaa\nbbbb\ncccc'), { offset: 1, limit: 10, maxLineLength: 2000, maxBytes: 9 }, 'f')
       expect(result.lines.map(l => l.text)).toEqual(['aaaa', 'bbbb'])
+      expect(result.totalLines).toBe(3)
       expect(result.truncatedByBytes).toBe(true)
     })
   })
@@ -105,6 +106,7 @@ describe('buildWindow', () => {
     it('caps output bytes mid-stream', async () => {
       const big = Array.from({ length: 2000 }, () => 'y'.repeat(100)).join('\n')
       const result = await buildWindow(chunked(big, 512), READ_ALL, 'f')
+      expect(result.totalLines).toBe(2000)
       expect(result.truncatedByBytes).toBe(true)
     })
 

packages/fs/tool-fs/tests/tools.spec.ts

@@ -572,6 +572,9 @@ describe('read caps are plugin config', () => {
     const { ctx, fs } = await setupWith({ readMaxBytes: 9 })
     fs.files.set('key:a.txt', 'aaaa\nbbbb\ncccc')
     const result = await call(ctx, 'read', { file_path: 'a.txt' })
+    expect(result.isError).toBe(false)
+    if (result.isError) throw new Error('expected read success')
+    expect(result.value).toMatchObject({ totalLines: 3 })
     expect(text(result)).toContain('Output capped.')
     expect(text(result)).not.toContain('cccc')
   })