waleedlatif1 · Nov 13, 2026 · Nov 13, 2026 · Nov 13, 2026
diff --git a/apps/sim/lib/knowledge/mcp/read-budget.test.ts b/apps/sim/lib/knowledge/mcp/read-budget.test.ts
@@ -0,0 +1,73 @@
+/**
+ * @vitest-environment node
+ */
+import { describe, expect, it } from 'vitest'
+import { shareReadBudget } from '@/lib/knowledge/mcp/read-budget'
+
+const read = (characters: number, text = 'x') => ({
+  documentId: `doc-${characters}`,
+  chunks: [
+    {
+      chunkIndex: 0,
+      content: text.repeat(characters),
+      startOffset: 0,
+      endOffset: characters,
+      totalCharacters: characters * 2,
+    },
+  ],
+  hasMore: false,
+  next: null,
+})
+
+const lengths = (reads: { chunks: { content: string }[] }[]) =>
+  reads.map((entry) => entry.chunks[0]?.content.length)
+
+describe('shareReadBudget', () => {
+  it('returns every read whole when the call fits its budget', () => {
+    const reads = [read(20_000), read(15_000), read(4_000)]
+    expect(shareReadBudget(reads)).toEqual(reads)
+  })
+
+  it('gives the budget short documents leave unused to the long one', () => {
+    const shared = shareReadBudget([read(20_000), read(20_000), ...Array(4).fill(read(1_000))])
+    expect(lengths(shared)).toEqual([18_000, 18_000, 1_000, 1_000, 1_000, 1_000])
+  })
+
+  it('cuts long documents to an equal share and continues each where it stops', () => {
+    const [first] = shareReadBudget([read(20_000), read(20_000), read(20_000), read(20_000)])
+    expect(first?.chunks[0]).toMatchObject({ endOffset: 10_000 })
+    expect(first?.chunks[0]?.content).toHaveLength(10_000)
+    expect(first).toMatchObject({
+      hasMore: true,
+      next: { startChunkIndex: 0, startOffset: 10_000 },
+    })
+  })
+
+  it('never cuts a document below the standard page', () => {
+    expect(lengths(shareReadBudget(Array(6).fill(read(20_000))))).toEqual(Array(6).fill(8_000))
+  })
+
+  it('counts text as JSON encodes it', () => {
+    const [quoted] = shareReadBudget([read(30_000, '"'), read(1_000), read(1_000)])
+    const content = quoted?.chunks[0]?.content ?? ''
+    expect(JSON.stringify(content).length - 2).toBeLessThanOrEqual(38_000)
+    expect(content.length).toBeGreaterThan(18_000)
+  })
+
+  it('keeps the call within budget when a standard page encodes beyond its share', () => {
+    const shared = shareReadBudget([read(10_000, '"'), read(20_000), read(20_000), read(20_000)])
+    const encoded = shared.reduce(
+      (total, entry) => total + JSON.stringify(entry.chunks[0]?.content ?? '').length - 2,
+      0
+    )
+    expect(encoded).toBeLessThanOrEqual(40_000)
+    expect(lengths(shared)).toEqual([8_000, 8_000, 8_000, 8_000])
+  })
+
+  it('passes a failed read through and leaves its share to the others', () => {
+    const failed = { documentId: 'missing', error: 'Not found' }
+    const shared = shareReadBudget([failed, read(20_000), read(20_000), read(20_000)])
+    expect(shared[0]).toBe(failed)
+    expect(lengths(shared.slice(1) as ReturnType<typeof read>[])).toEqual([13_333, 13_333, 13_333])
+  })
+})
diff --git a/apps/sim/lib/knowledge/mcp/read-budget.ts b/apps/sim/lib/knowledge/mcp/read-budget.ts
@@ -0,0 +1,79 @@
+import { encodedWindowEnd, READ_WINDOW_CHARACTERS } from '@/lib/sim-search/live/read-window'
+
+/**
+ * Characters of document text one batched read call returns. With about a thousand characters of
+ * metadata per document, it keeps the call under the 50,000-character size at which MCP clients
+ * such as Claude Code save a tool result to a file rather than show it. A call whose standard
+ * pages alone exceed it returns those pages, as a read without sharing would.
+ */
+const READ_CALL_CHARACTERS = 40_000
+
+interface WindowedRead {
+  chunks: { content: string; startOffset: number; endOffset: number }[]
+  hasMore: boolean
+  next: { startChunkIndex: number; startOffset: number } | null
+}
+
+const encodedLength = (text: string) => JSON.stringify(text).length - 2
+
+const isWindowedRead = (document: object): document is WindowedRead => 'chunks' in document
+
+/**
+ * A read's text as JSON encodes it, and the part of that it always keeps: its standard page, or
+ * all of it when it is not a single chunk this budget can shorten.
+ */
+function encodedSize(read: object): { length: number; kept: number } {
+  if (!isWindowedRead(read)) return { length: 0, kept: 0 }
+  const length = read.chunks.reduce((total, chunk) => total + encodedLength(chunk.content), 0)
+  const [chunk] = read.chunks
+  if (!chunk || read.chunks.length !== 1) return { length, kept: length }
+  return { length, kept: encodedLength(chunk.content.slice(0, READ_WINDOW_CHARACTERS)) }
+}
+
+/**
+ * Shares one call's text budget across the documents it read; an entry without text, such as a
+ * failed read, passes through. Every document keeps its standard page, and the budget those pages
+ * leave is shared as further text: documents needing less than an even share keep all theirs and
+ * leave the rest to the longer ones, which are cut to an equal share and continue through `next`.
+ */
+export function shareReadBudget<T extends object>(reads: readonly T[]): T[] {
+  const sizes = reads.map(encodedSize)
+  if (sizes.reduce((total, size) => total + size.length, 0) <= READ_CALL_CHARACTERS)
+    return [...reads]
+  const extras = sizes.map((size) => size.length - size.kept)
+  let remaining = READ_CALL_CHARACTERS - sizes.reduce((total, size) => total + size.kept, 0)
+  let left = reads.length
+  let cap = 0
+  for (const extra of [...extras].sort((a, b) => a - b)) {
+    const share = Math.max(0, Math.floor(remaining / left))
+    if (extra > share) {
+      cap = share
+      break
+    }
+    remaining -= extra
+    left--
+  }
+  return reads.map((read, index) =>
+    isWindowedRead(read) && extras[index] > cap ? cut(read, sizes[index].kept + cap) : read
+  )
+}
+
+/** A single-chunk read shortened so its text encodes within `budget`, continuing where it stops. */
+function cut<T extends WindowedRead>(read: T, budget: number): T {
+  const [chunk] = read.chunks
+  if (!chunk || read.chunks.length !== 1) return read
+  const end = encodedWindowEnd(
+    chunk.content,
+    0,
+    budget,
+    Math.min(chunk.content.length, READ_WINDOW_CHARACTERS)
+  )
+  if (end >= chunk.content.length) return read
+  const endOffset = chunk.startOffset + end
+  return {
+    ...read,
+    chunks: [{ ...chunk, content: chunk.content.slice(0, end), endOffset }],
+    hasMore: true,
+    next: { startChunkIndex: 0, startOffset: endOffset },
+  }
+}
diff --git a/apps/sim/lib/knowledge/mcp/server.protocol.test.ts b/apps/sim/lib/knowledge/mcp/server.protocol.test.ts
@@ -100,7 +100,7 @@ describe('Search MCP protocol', () => {
       expect(read.isError).not.toBe(true)
       expect(mocks.liveRead.mock.lastCall?.[0].input).toMatchObject({
         limit: 8,
-        scaledWindow: { documentsInCall: 1 },
+        scaledWindow: true,
       })
       expect(read.content).toEqual([
         { type: 'text', text: expect.stringContaining('Read evidence') },
@@ -112,7 +112,7 @@ describe('Search MCP protocol', () => {
       expect(batchRead.isError).not.toBe(true)
       expect(mocks.liveRead.mock.lastCall?.[0].input).toMatchObject({
         limit: 8,
-        scaledWindow: { documentsInCall: 2 },
+        scaledWindow: true,
       })
       const offsetless = await client.callTool({
         name: 'search',

diff --git a/apps/sim/lib/knowledge/mcp/server.ts b/apps/sim/lib/knowledge/mcp/server.ts
@@ -22,6 +22,7 @@ import {
   recordOrganizationSearchMcpActivity,
   type SearchMcpActivityInput,
 } from '@/lib/knowledge/mcp/activity'
+import { shareReadBudget } from '@/lib/knowledge/mcp/read-budget'
 import {
   KNOWLEDGE_MCP_READ_ONLY,
   type KnowledgeMcpToolRunner,
@@ -298,7 +299,7 @@ export function createKnowledgeMcpServer(context: KnowledgeMcpContext): McpServe
                 ...options,
                 documentId: id,
                 organizationId,
-                scaledWindow: { documentsInCall: documentId ? 1 : batch.length },
+                scaledWindow: true,
                 resultSecretRegistry: registry,
                 signal,
               },
@@ -327,7 +328,7 @@ export function createKnowledgeMcpServer(context: KnowledgeMcpContext): McpServe
               }
             }
           )
-          return projectResult({ documents }, registry)
+          return projectResult({ documents: shareReadBudget(documents) }, registry)
         },
         Math.max(1, batch.length)
       )

diff --git a/apps/sim/lib/sim-search/live/application.test.ts b/apps/sim/lib/sim-search/live/application.test.ts
@@ -1214,62 +1214,29 @@ describe('authorized live retrieval', () => {
       }
     }
 
-    const scaled = (documentsInCall: number) => ({ scaledWindow: { documentsInCall } })
-
-    it('returns a proportionally longer window when a scaling caller asks for more chunks', async () => {
-      const { length, next } = await readWindow({ limit: 8, ...scaled(1) })
-      expect(length).toBe(21_333)
-      expect(next).toEqual({ startChunkIndex: 0, startOffset: 21_333 })
+    it('returns a longer window to a scaling caller, whatever its chunk limit', async () => {
+      for (const limit of [1, 3, 8]) {
+        const { length, next } = await readWindow({ limit, scaledWindow: true })
+        expect(length).toBe(20_000)
+        expect(next).toEqual({ startChunkIndex: 0, startOffset: 20_000 })
+      }
     })
 
     it('continues a longer window from where the previous one ended', async () => {
-      const { length, next } = await readWindow({ limit: 8, ...scaled(1), startOffset: 21_333 })
-      expect(length).toBe(30_000 - 21_333)
+      const { length, next } = await readWindow({ scaledWindow: true, startOffset: 20_000 })
+      expect(length).toBe(10_000)
       expect(next).toBeNull()
     })
 
-    it.each([
-      [5, 1, 13_333],
-      [8, 2, 20_000],
-      [8, 3, 13_333],
-      [8, 4, 10_000],
-    ])(
-      'shares one call budget: limit %i across %i documents reads %i characters each',
-      async (limit, documentsInCall, expected) => {
-        expect((await readWindow({ limit, ...scaled(documentsInCall) })).length).toBe(expected)
-      }
-    )
-
-    it.each([
-      [1, 21_333],
-      [2, 20_000],
-    ])(
-      'keeps a quote-heavy window within its share once JSON-encoded, across %i documents',
-      async (documentsInCall, share) => {
-        const quotes = '"'.repeat(30_000)
-        const { length, encoded, next } = await readWindow(
-          { limit: 8, ...scaled(documentsInCall) },
-          quotes
-        )
-        expect(encoded).toBeLessThanOrEqual(share)
-        expect(length).toBeGreaterThanOrEqual(8_000)
-        expect(next).toEqual({ startChunkIndex: 0, startOffset: length })
-      }
-    )
-
-    it('keeps the standard window for quote-heavy text at the default limit', async () => {
-      const { length } = await readWindow({ limit: 3, ...scaled(1) }, '"'.repeat(30_000))
-      expect(length).toBe(8_000)
+    it('keeps a quote-heavy window within its size once JSON-encoded', async () => {
+      const { length, encoded, next } = await readWindow({ scaledWindow: true }, '"'.repeat(30_000))
+      expect(encoded).toBeLessThanOrEqual(20_000)
+      expect(length).toBeGreaterThanOrEqual(8_000)
+      expect(next).toEqual({ startChunkIndex: 0, startOffset: length })
     })
 
-    it.each([
-      ['at the default limit', { limit: 3, ...scaled(1) }],
-      ['below the default limit', { limit: 1, ...scaled(1) }],
-      ['when the call budget is spread over five documents', { limit: 8, ...scaled(5) }],
-      ['when the call budget is spread over ten documents', { limit: 8, ...scaled(10) }],
-      ['for a caller that does not scale', { limit: 8 }],
-    ])('keeps the standard window %s', async (_, extra) => {
-      expect((await readWindow(extra)).length).toBe(8_000)
+    it('keeps the standard window for a caller that does not scale', async () => {
+      expect((await readWindow({ limit: 8 })).length).toBe(8_000)
     })
   })
   it('refuses a chunk index other than zero before reading the document from its provider', async () => {

diff --git a/apps/sim/lib/sim-search/live/application.ts b/apps/sim/lib/sim-search/live/application.ts
@@ -75,6 +75,7 @@ import { loadLiveSearchPolicies } from '@/lib/sim-search/live/policy-store'
 import { LIVE_SEARCH_PROVIDER_IDS } from '@/lib/sim-search/live/provider-catalog'
 import { liveSearchGuidance } from '@/lib/sim-search/live/providers'
 import { LiveReadError } from '@/lib/sim-search/live/read-error'
+import { encodedWindowEnd, READ_WINDOW_CHARACTERS } from '@/lib/sim-search/live/read-window'
 import {
   encodeLiveReference,
   includesLiveDocument,
@@ -287,44 +288,25 @@ export const LIVE_NOT_STARTED_MESSAGE =
 export const LIVE_OVER_ACCOUNT_LIMIT_MESSAGE = `Not searched: one search covers at most ${MAX_ACCOUNTS} accounts. Search this source or account alone.`
 /** Previews center on the query's longest matching term, like indexed passages. */
 const PREVIEW_CHARACTERS = 1800
-/** Characters one read returns at the default limit, the page budget indexed document reads use. */
-const READ_WINDOW_CHARACTERS = 8000
-/** The read limit {@link READ_WINDOW_CHARACTERS} is sized for, which is the default limit. */
-const READ_WINDOW_LIMIT = 3
 /**
- * Characters the documents of one scaled read call share. Through four documents it keeps the
- * call's result, with about a thousand characters of metadata per document, under the
- * 50,000-character size at which MCP clients such as Claude Code save a tool result to a file
- * rather than show it. From five documents the standard page per document is the larger, so
- * those calls read exactly what they read without scaling.
+ * Characters a scaled read returns for one document. Two documents at this size, with about a
+ * thousand characters of metadata each, stay under the 50,000-character size at which MCP clients
+ * such as Claude Code save a tool result to a file rather than show it; a call of more documents
+ * shares that budget, as the MCP server's batched read sizes it.
  */
-const SCALED_READ_CALL_CHARACTERS = 40_000
+const SCALED_READ_DOCUMENT_CHARACTERS = 20_000
 
 /**
- * Where one read's window ends. A live document is one chunk, so a caller that scales the window
- * gets a longer one when it asks for more chunks than the default, bounded by an even share of the
- * call's budget across the documents it reads. The share counts the window as the result encodes
- * it, since JSON escapes quotes, backslashes and line breaks, so a longer window is shortened until
- * its encoded text fits. The window is never shorter than the standard page, which is also what a
- * read at or below the default limit, or from any other caller, returns.
+ * Where one read's window ends: the standard page, or for a caller that scales its window, up to
+ * {@link SCALED_READ_DOCUMENT_CHARACTERS} as the result encodes it. A live document is one chunk,
+ * so its window is sized by characters, not by the chunk limit. The window is never shorter than
+ * the standard page.
  */
-function readWindowEnd(
-  content: string,
-  start: number,
-  { limit, scaledWindow }: Pick<LiveReadInput, 'limit' | 'scaledWindow'>
-): number {
+function readWindowEnd(content: string, start: number, scaledWindow: boolean | undefined): number {
   const standardEnd = Math.min(content.length, start + READ_WINDOW_CHARACTERS)
-  if (!scaledWindow || limit <= READ_WINDOW_LIMIT) return standardEnd
-  const scaled = Math.floor((READ_WINDOW_CHARACTERS * limit) / READ_WINDOW_LIMIT)
-  const share = Math.floor(SCALED_READ_CALL_CHARACTERS / Math.max(1, scaledWindow.documentsInCall))
-  const budget = Math.min(scaled, share)
-  let end = Math.min(content.length, start + budget)
-  for (let attempt = 0; attempt < 3 && end > standardEnd; attempt++) {
-    const encoded = JSON.stringify(content.slice(start, end)).length - 2
-    if (encoded <= budget) return end
-    end = start + Math.floor(((end - start) * budget) / encoded)
-  }
-  return standardEnd
+  return scaledWindow
+    ? encodedWindowEnd(content, start, SCALED_READ_DOCUMENT_CHARACTERS, standardEnd)
+    : standardEnd
 }
 
 /**
@@ -1017,11 +999,8 @@ export type LiveReadInput = ResourceOwner & {
   documentId: string
   filters?: WorkspaceSearchFilters
   limit: number
-  /**
-   * Lengthens the window for a limit above the default, sharing one call's budget across the
-   * documents it reads, as {@link readWindowEnd} sizes it.
-   */
-  scaledWindow?: { documentsInCall: number }
+  /** Lengthens the window past the standard page, as {@link readWindowEnd} sizes it. */
+  scaledWindow?: boolean
   startChunkIndex?: number
   startOffset?: number
   resultSecretRegistry: ResolvedSecretTraceRegistry
@@ -1167,7 +1146,7 @@ export const readLiveDocument = defineAuthorizedKnowledgeUseCase({
         'validation',
         'This document changed. Read again from the beginning'
       )
-    const end = readWindowEnd(content, start, input)
+    const end = readWindowEnd(content, start, input.scaledWindow)
     return {
       documentId: input.documentId,
       knowledgeBaseId: '',

diff --git a/apps/sim/lib/sim-search/live/read-window.ts b/apps/sim/lib/sim-search/live/read-window.ts
@@ -0,0 +1,22 @@
+/** Characters one standard read returns, the page budget indexed document reads use. */
+export const READ_WINDOW_CHARACTERS = 8000
+
+/**
+ * Where a window of `content` from `start` ends so its text, as JSON encodes it, fits `budget`
+ * characters. JSON escapes quotes, backslashes and line breaks, so a window is shortened until its
+ * encoded text fits. It never ends before `minimumEnd`.
+ */
+export function encodedWindowEnd(
+  content: string,
+  start: number,
+  budget: number,
+  minimumEnd: number
+): number {
+  let end = Math.min(content.length, start + budget)
+  for (let attempt = 0; attempt < 3 && end > minimumEnd; attempt++) {
+    const encoded = JSON.stringify(content.slice(start, end)).length - 2
+    if (encoded <= budget) return end
+    end = start + Math.floor(((end - start) * budget) / encoded)
+  }
+  return minimumEnd
+}
diff --git a/apps/sim/lib/sim-search/live/term-fallback.test.ts b/apps/sim/lib/sim-search/live/term-fallback.test.ts
@@ -14,7 +14,7 @@ import type { NativeDocument, NativePage, NativeSearchInput } from '@/lib/sim-se
 const input: NativeSearchInput = { query: 'contractor offboarding runbook', limit: 4, scopes: [] }
 
 /** The any-term search's own budget, which a slow provider must not outlast. */
-const BUDGET_MS = 4000
+const BUDGET_MS = 2000
 
 /** A caller that never cancels. */
 const live = new AbortController().signal