fix(chat): enforce legacy import byte budget during reading

docs/audits/legacy-import-source-budget/README.md

@@ -0,0 +1,68 @@
+# Legacy import source byte budget
+
+The production importer accepted a transcript larger than its existing 16 MiB
+quota when the file grew between `stat()` and reading it. The fix applies that
+same quota to consumed raw bytes and rejects the entire import before replacing
+the journal. It does not import a truncated prefix.
+
+## Reproduce
+
+From the repository root, with dependencies installed:
+
+```sh
+ORCA_BACKGROUND_LAUNCH=1 node --max-old-space-size=256 docs/audits/legacy-import-source-budget/reproduce.mjs
+```
+
+The script bundles the actual production importer and decoder twice. The baseline
+restores the importer's UTF-8 stream and omits the new consumed-byte quota in
+memory; the second run uses the current source. All other dependencies are
+identical. Explicit file paths bypass discovery; a stub fails if discovery is
+unexpectedly called. No historical checkout or local-only commit is required.
+
+Each run creates one real temporary file containing a valid Claude message.
+The controlled `stat` seam captures its original size, appends spaces until the
+file is exactly 17 MiB, then returns the original stat. The production importer
+reads the grown file. A journal spy records replacement attempts and its epoch;
+no SQLite database or user transcript is touched. Temporary files are removed.
+
+`results.json` records source hashes, actual consumed bytes, stream closure,
+and replacement attempts. Before the fix the importer consumes all 17 MiB,
+returns success, and replaces the journal with the decoded prefix. Afterward it
+refuses on the first chunk crossing 16 MiB, destroys the stream, and leaves the
+prior epoch untouched. Read buffering permits one chunk of overshoot.
+
+## Process and version attribution
+
+This importer runs in the host runtime through structured-session adoption,
+handoff, transcript catch-up, and journal recovery. On desktop that runtime is
+Electron main; a remote runtime imports its own host-local source. The stat-only
+quota and unrestricted stream already existed in `v1.4.198`, release commit
+`e0826956fcfc532f5a1e55b5e081f2e57e553c43`.
+
+The reproduction establishes a quota bypass, not the cause of #19768 or #19831.
+It requires an import and source growth/replacement after the size check;
+neither incident provides that evidence. This fix is independent of #20963's
+resumable JSONL record limit.
+
+## Other whole-document audit results
+
+- `ai-vault/session-transcript-reader.ts:152` routes rewritten JSON documents
+  through whole-file `readFile` and `JSON.parse`. Gemini JSON, Hermes, Devin,
+  Cline, Grok metadata, Kimi state, Rovo, and OpenCode file readers lack a source
+  byte quota. These are allocation peaks; the parse cache retains summaries,
+  not the full documents.
+- The production default, including v1.4.198, places those scans in the forked
+  AI Vault service with a 384 MiB V8 old-space limit. That is not a total RSS
+  limit. `ORCA_AI_VAULT_SERVICE_PROCESS=0` instead puts scans in a worker thread
+  sharing main's PID; its first-prompt fallback runs directly in main.
+- Existing remote whole-document streaming parsers offer a reuse path, but
+  local conversion must preserve message-sink delivery for search indexing.
+  Streaming also needs an explicit policy for an individually oversized JSON
+  value; arbitrary history truncation was not introduced.
+- The older `native-chat/transcript-reader.ts` and `transcript-read-cache.ts`
+  have whole-history behavior, including a newest-entry cache exemption, but
+  the current production source has no external call sites for those exports.
+
+Validation: 50 targeted tests passed, including a regression that failed before
+the fix, UTF-8 and raw-byte limits, exact-boundary acceptance, and stream cleanup.
+Node typecheck, targeted lint, formatting, and diff checks passed.

docs/audits/legacy-import-source-budget/reproduce.mjs

@@ -0,0 +1,170 @@
+import assert from 'node:assert/strict'
+import { createHash } from 'node:crypto'
+import * as fs from 'node:fs'
+import * as fsPromises from 'node:fs/promises'
+import Module, { createRequire } from 'node:module'
+import { tmpdir } from 'node:os'
+import { join, relative, resolve } from 'node:path'
+import { fileURLToPath } from 'node:url'
+import { build } from 'esbuild'
+
+if (process.env.ORCA_BACKGROUND_LAUNCH !== '1') {
+  throw new Error('Run with ORCA_BACKGROUND_LAUNCH=1')
+}
+
+const root = fileURLToPath(new URL('../../../', import.meta.url))
+const require = createRequire(import.meta.url)
+const sourcePaths = [
+  'src/main/native-chat/agent-session-journal/journal-legacy-import.ts',
+  'src/main/native-chat/transcript-stream-lines.ts'
+]
+const limit = 16 * 1024 * 1024
+const grownBytes = 17 * 1024 * 1024
+
+function sourceAt(version, path) {
+  const source = fs.readFileSync(resolve(root, path), 'utf8')
+  if (version !== 'before' || path !== sourcePaths[0]) {
+    return source
+  }
+  const stream = 'const stream = createReadStream(input.filePath)'
+  const budget = 'true,\n    MAX_LEGACY_IMPORT_SOURCE_BYTES'
+  assert.ok(source.includes(stream) && source.includes(budget), 'Review changed baseline transform')
+  return source
+    .replace(stream, "const stream = createReadStream(input.filePath, { encoding: 'utf-8' })")
+    .replace(budget, 'true')
+}
+
+async function run(version) {
+  const sources = new Map(sourcePaths.map((path) => [path, sourceAt(version, path)]))
+  const built = await build({
+    absWorkingDir: root,
+    entryPoints: [sourcePaths[0]],
+    bundle: true,
+    platform: 'node',
+    format: 'cjs',
+    packages: 'external',
+    write: false,
+    plugins: [
+      {
+        name: 'select-production-version',
+        setup(bundler) {
+          bundler.onLoad(
+            { filter: /(?:journal-legacy-import|transcript-stream-lines)\.ts$/ },
+            (args) => {
+              const path = relative(root, args.path).split('\\').join('/')
+              const contents = sources.get(path)
+              return contents === undefined ? undefined : { contents, loader: 'ts' }
+            }
+          )
+          bundler.onResolve({ filter: /session-file-resolver$/ }, () => ({
+            path: 'unused',
+            namespace: 'probe'
+          }))
+          bundler.onLoad({ filter: /.*/, namespace: 'probe' }, () => ({
+            contents:
+              'export function resolveSessionFilePath() { throw new Error("Unexpected path discovery") }'
+          }))
+        }
+      }
+    ]
+  })
+  const directory = await fsPromises.mkdtemp(join(tmpdir(), 'orca-legacy-source-budget-'))
+  const filePath = join(directory, 'growing.jsonl')
+  const initial = `${JSON.stringify({
+    type: 'assistant',
+    uuid: 'valid-prefix',
+    message: {
+      role: 'assistant',
+      content: [{ type: 'text', text: 'Existing journal must survive refusal' }]
+    }
+  })}\n`
+  let consumedBytes = 0
+  let observedStatBytes
+  let stream
+  let replaceCalls = 0
+  let journalEpoch = 'prior-epoch'
+  const compiled = new Module(join(root, 'legacy-import-budget-probe.cjs'))
+  compiled.filename = join(root, 'legacy-import-budget-probe.cjs')
+  compiled.paths = Module._nodeModulePaths(root)
+  compiled.require = (id) => {
+    if (id === 'node:fs/promises') {
+      return {
+        ...fsPromises,
+        stat: async (...args) => {
+          const snapshot = await fsPromises.stat(...args)
+          if (args[0] === filePath) {
+            observedStatBytes = snapshot.size
+            await fsPromises.appendFile(filePath, Buffer.alloc(grownBytes - snapshot.size, 0x20))
+          }
+          return snapshot
+        }
+      }
+    }
+    if (id === 'node:fs') {
+      return {
+        ...fs,
+        createReadStream: (...args) => {
+          stream = fs.createReadStream(...args)
+          stream.on('data', (chunk) => {
+            consumedBytes += Buffer.isBuffer(chunk)
+              ? chunk.byteLength
+              : Buffer.byteLength(chunk, 'utf8')
+          })
+          return stream
+        }
+      }
+    }
+    return require(id)
+  }
+  compiled._compile(built.outputFiles[0].text, compiled.filename)
+  try {
+    await fsPromises.writeFile(filePath, initial)
+    const result = await compiled.exports.importLegacyTranscriptIntoJournal({
+      agent: 'claude',
+      sessionId: 'source-budget-probe',
+      fence: 0,
+      options: { filePath },
+      journal: {
+        cursor: () => ({ epoch: journalEpoch, sequence: 0 }),
+        replaceEpochItems: async () => {
+          replaceCalls++
+          journalEpoch = 'replacement-epoch'
+          return { epoch: journalEpoch, sequence: 1 }
+        }
+      }
+    })
+    assert.equal(observedStatBytes, Buffer.byteLength(initial))
+    assert.equal(stream.destroyed, true)
+    assert.equal(result.ok, version === 'before')
+    assert.equal(replaceCalls, version === 'before' ? 1 : 0)
+    return {
+      source: version === 'before' ? 'working tree without consumed-byte quota' : 'working tree',
+      sourceSha256: Object.fromEntries(
+        [...sources].map(([path, source]) => [
+          path,
+          createHash('sha256').update(source).digest('hex')
+        ])
+      ),
+      observedStatBytes,
+      sourceBytesAfterGrowth: (await fsPromises.stat(filePath)).size,
+      consumedBytes,
+      limitBytes: limit,
+      streamDestroyed: stream.destroyed,
+      result,
+      journalReplaceCalls: replaceCalls,
+      journalEpoch
+    }
+  } finally {
+    stream?.destroy()
+    await fsPromises.rm(directory, { recursive: true, force: true })
+  }
+}
+
+const results = {
+  node: process.version,
+  platform: process.platform,
+  architecture: process.arch,
+  before: await run('before'),
+  after: await run('after')
+}
+process.stdout.write(`${JSON.stringify(results, null, 2)}\n`)

docs/audits/legacy-import-source-budget/results.json

@@ -0,0 +1,47 @@
+{
+  "node": "v26.6.0",
+  "platform": "darwin",
+  "architecture": "arm64",
+  "before": {
+    "source": "working tree without consumed-byte quota",
+    "sourceSha256": {
+      "src/main/native-chat/agent-session-journal/journal-legacy-import.ts": "da799f8f34e6c28516b4ac98102b9d1fb76edebefafbdf0ca17d18a06cb79535",
+      "src/main/native-chat/transcript-stream-lines.ts": "5f3a0a1e5b3d003076452fa22234af00502808ed6463672c0e58aa49ae5b6aa1"
+    },
+    "observedStatBytes": 149,
+    "sourceBytesAfterGrowth": 17825792,
+    "consumedBytes": 17825792,
+    "limitBytes": 16777216,
+    "streamDestroyed": true,
+    "result": {
+      "ok": true,
+      "epoch": "replacement-epoch",
+      "cursor": {
+        "epoch": "replacement-epoch",
+        "sequence": 1
+      },
+      "imported": 1,
+      "replaced": true
+    },
+    "journalReplaceCalls": 1,
+    "journalEpoch": "replacement-epoch"
+  },
+  "after": {
+    "source": "working tree",
+    "sourceSha256": {
+      "src/main/native-chat/agent-session-journal/journal-legacy-import.ts": "88c007b4fb83eba6ec5fdf21c50b4c4aff35199cc4eed92abe3a1c29addfc5f3",
+      "src/main/native-chat/transcript-stream-lines.ts": "5f3a0a1e5b3d003076452fa22234af00502808ed6463672c0e58aa49ae5b6aa1"
+    },
+    "observedStatBytes": 149,
+    "sourceBytesAfterGrowth": 17825792,
+    "consumedBytes": 16842752,
+    "limitBytes": 16777216,
+    "streamDestroyed": true,
+    "result": {
+      "ok": false,
+      "error": "Input exceeds 16777216 byte limit (16842752 bytes received)"
+    },
+    "journalReplaceCalls": 0,
+    "journalEpoch": "prior-epoch"
+  }
+}

src/main/native-chat/agent-session-journal/journal-legacy-import-source-bound.test.ts

@@ -0,0 +1,60 @@
+import { createReadStream } from 'node:fs'
+import { appendFile, mkdtemp, rm, stat, writeFile } from 'node:fs/promises'
+import type * as FsPromises from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { afterEach, describe, expect, it, vi } from 'vitest'
+import { prepareLegacyTranscriptImport } from './journal-legacy-import'
+
+vi.mock(import('node:fs'), async (importOriginal) => {
+  const original = await importOriginal()
+  return { ...original, createReadStream: vi.fn(original.createReadStream) }
+})
+
+vi.mock(import('node:fs/promises'), async (importOriginal) => {
+  const original = await importOriginal()
+  return { ...original, stat: vi.fn() }
+})
+
+const SOURCE_LIMIT_BYTES = 16 * 1024 * 1024
+const roots: string[] = []
+
+afterEach(async () => {
+  vi.clearAllMocks()
+  await Promise.all(roots.splice(0).map((root) => rm(root, { recursive: true, force: true })))
+})
+
+describe('legacy import source byte bound', () => {
+  it('refuses a source that grows past the limit after stat and closes the stream', async () => {
+    const root = await mkdtemp(join(tmpdir(), 'orca-legacy-import-bound-'))
+    roots.push(root)
+    const filePath = join(root, 'growing.jsonl')
+    await writeFile(
+      filePath,
+      `${JSON.stringify({
+        type: 'assistant',
+        uuid: 'first-message',
+        message: { role: 'assistant', content: [{ type: 'text', text: 'Keep the prior journal' }] }
+      })}\n`
+    )
+    const actualFs = await vi.importActual<typeof FsPromises>('node:fs/promises')
+    const beforeGrowth = await actualFs.stat(filePath)
+    vi.mocked(stat).mockImplementationOnce(async () => {
+      await appendFile(filePath, Buffer.alloc(SOURCE_LIMIT_BYTES, 0x20))
+      return beforeGrowth
+    })
+
+    const result = await prepareLegacyTranscriptImport({
+      agent: 'claude',
+      sessionId: 'source-bound',
+      options: { filePath }
+    })
+
+    expect(result).toEqual({
+      ok: false,
+      error: expect.stringContaining(`${SOURCE_LIMIT_BYTES} byte limit`)
+    })
+    expect(createReadStream).toHaveBeenCalledOnce()
+    expect(vi.mocked(createReadStream).mock.results[0]?.value.destroyed).toBe(true)
+  })
+})

src/main/native-chat/agent-session-journal/journal-legacy-import.ts

@@ -194,7 +194,8 @@ async function decodeWithIdentities(input: {
   const identities: AgentJournalItemIdentity[] = []
   let lineIndex = 0
 
-  const stream = createReadStream(input.filePath, { encoding: 'utf-8' })
+  // Count raw bytes while reading: the source can grow after the stat check.
+  const stream = createReadStream(input.filePath)
   const { messages } = await decodeTranscriptStream(
     stream,
     input.filePath,
@@ -217,7 +218,8 @@ async function decodeWithIdentities(input: {
       }
       return message
     },
-    true
+    true,
+    MAX_LEGACY_IMPORT_SOURCE_BYTES
   )
   return { messages, identities }
 }

src/main/native-chat/transcript-stream-lines.test.ts

@@ -11,6 +11,35 @@ const decode = (line: string, id: string) => ({
 })
 
 describe('decodeTranscriptStream', () => {
+  it('accepts the exact source limit with split UTF-8 bytes and preserves order', async () => {
+    const bytes = Buffer.from('é\n😀\n')
+    const result = await decodeTranscriptStream(
+      Readable.from([bytes.subarray(0, 1), bytes.subarray(1, 5), bytes.subarray(5)]),
+      '/chat.jsonl',
+      0,
+      decode,
+      true,
+      bytes.length
+    )
+    expect(result.messages.map((message) => message.blocks[0])).toEqual([
+      { type: 'text', text: 'é' },
+      { type: 'text', text: '😀' }
+    ])
+  })
+
+  it.each([Buffer.from('é'), 'é', Buffer.from([0xff, 0xff])])(
+    'counts source bytes before decoding an oversized chunk %j',
+    async (chunk) => {
+      const stream = Readable.from([chunk])
+      const trackedDecode = vi.fn(decode)
+      await expect(
+        decodeTranscriptStream(stream, '/chat.jsonl', 0, trackedDecode, true, 1)
+      ).rejects.toThrow('exceeds 1 byte limit')
+      expect(trackedDecode).not.toHaveBeenCalled()
+      expect(stream.destroyed).toBe(true)
+    }
+  )
+
   it.each([true, false])('preserves chunked record offsets with trailing=%s', async (trailing) => {
     const first = `${'long record '.repeat(10_000)}😀`
     const prefix = `\r\n${first}\r\n\n`

src/main/native-chat/transcript-stream-lines.ts

@@ -1,6 +1,7 @@
 import type { Readable } from 'node:stream'
 import { StringDecoder } from 'node:string_decoder'
 import type { NativeChatMessage } from '../../shared/native-chat-types'
+import { NodeReadableTextTooLargeError } from '../../shared/node-readable-text'
 import { transcriptFallbackId } from './transcript-fallback-id'
 
 type TranscriptDecoder = (line: string, fallbackId: string) => NativeChatMessage | null
@@ -10,10 +11,12 @@ export async function decodeTranscriptStream(
   filePath: string,
   start: number,
   decode: TranscriptDecoder,
-  includeTrailingLine: boolean
+  includeTrailingLine: boolean,
+  maxSourceBytes = Infinity
 ): Promise<{ messages: NativeChatMessage[]; consumedBytes: number }> {
   const messages: NativeChatMessage[] = []
   let consumedBytes = 0
+  let sourceBytes = 0
   const framer = createTranscriptLineFramer((line, byteLength, terminated) => {
     if (terminated || includeTrailingLine) {
       decodeLine(line, consumedBytes)
@@ -21,6 +24,12 @@ export async function decodeTranscriptStream(
     }
   })
   for await (const chunk of stream) {
+    if (maxSourceBytes !== Infinity) {
+      sourceBytes += Buffer.isBuffer(chunk) ? chunk.byteLength : Buffer.byteLength(chunk, 'utf8')
+      if (sourceBytes > maxSourceBytes) {
+        throw new NodeReadableTextTooLargeError(sourceBytes, maxSourceBytes)
+      }
+    }
     framer.write(chunk)
   }
   framer.end()