diff --git a/config/electron-builder.config.cjs b/config/electron-builder.config.cjs
index e9a3bb6b9..e731cb7f1 100644
--- a/config/electron-builder.config.cjs
+++ b/config/electron-builder.config.cjs
@@ -12,10 +12,13 @@ const {
   verifyPackagedMainRuntimeDeps
 } = require('./packaged-runtime-node-modules.cjs')
 const { verifyLinuxGlibcFloor } = require('./scripts/verify-linux-glibc-floor.cjs')
+const { writeMacBuildCompatibility } = require('./scripts/mac-build-compatibility.cjs')
 const { verifyPackagedPluginResources } = require('./scripts/verify-packaged-plugin-resources.cjs')
 
 const isMacRelease = process.env.ORCA_MAC_RELEASE === '1'
 const isLinuxArm64Release = process.env.ORCA_LINUX_ARM64_RELEASE === '1'
+const localBuildVersion = isMacRelease ? undefined : process.env.ORCA_LOCAL_BUILD_VERSION
+const appId = 'com.stablyai.orca'
 const featureWallResources = {
   from: 'resources/onboarding/feature-wall',
   to: 'onboarding/feature-wall'
@@ -59,8 +62,9 @@ const winSpeechNativeResource = {
 
 /** @type {import('electron-builder').Configuration} */
 module.exports = {
-  appId: 'com.stablyai.orca',
+  appId,
   productName: 'Orca',
+  ...(localBuildVersion ? { extraMetadata: { version: localBuildVersion } } : {}),
   directories: {
     buildResources: 'resources/build'
   },
@@ -171,6 +175,25 @@ module.exports = {
     if (!existsSync(resourcesDir)) {
       return
     }
+    if (context.electronPlatformName === 'darwin') {
+      const architectureByEnum = { 1: 'x64', 3: 'arm64' }
+      const architecture = architectureByEnum[context.arch]
+      if (!architecture) {
+        throw new Error(`Unsupported local-build compatibility architecture: ${context.arch}`)
+      }
+      const version = context.packager.appInfo.version
+      let commit = process.env.ORCA_BUILD_COMMIT || process.env.GITHUB_SHA || 'unknown'
+      if (commit === 'unknown') {
+        try {
+          commit = execFileSync('git', ['rev-parse', '--short=12', 'HEAD'], {
+            encoding: 'utf8'
+          }).trim()
+        } catch {
+          // Source archives can still produce a signed build with an explicit version.
+        }
+      }
+      writeMacBuildCompatibility(resourcesDir, { version, commit, architecture })
+    }
     prunePackagedRuntimeNodeModules(resourcesDir, context.electronPlatformName, context.arch)
     verifyPackagedMainRuntimeDeps(resourcesDir)
     // Why: boot the packaged daemon-entry under plain Node, but only for the
diff --git a/config/scripts/build-mac-local.mjs b/config/scripts/build-mac-local.mjs
new file mode 100644
index 000000000..d0426a946
--- /dev/null
+++ b/config/scripts/build-mac-local.mjs
@@ -0,0 +1,46 @@
+import { execFileSync } from 'node:child_process'
+import { readFileSync } from 'node:fs'
+import { resolve } from 'node:path'
+
+export function createLocalBuildVersion(baseVersion, timestamp, commit) {
+  if (!/^\d+\.\d+\.\d+(?:-[0-9A-Za-z.-]+)?$/.test(baseVersion)) {
+    throw new Error(`Package version is not valid semver: ${baseVersion}`)
+  }
+  if (!Number.isSafeInteger(timestamp) || timestamp <= 0) {
+    throw new Error('Local build timestamp is invalid.')
+  }
+  const sanitizedCommit = commit.replace(/[^0-9A-Za-z-]/g, '').slice(0, 12)
+  if (!sanitizedCommit) {
+    throw new Error('Git commit identity is empty.')
+  }
+  const suffix = `local.${timestamp}.${sanitizedCommit}`
+  return baseVersion.includes('-') ? `${baseVersion}.${suffix}` : `${baseVersion}-${suffix}`
+}
+
+export function getLocalBuildIdentity() {
+  const packageJson = JSON.parse(readFileSync(resolve('package.json'), 'utf8'))
+  const commit = execFileSync('git', ['rev-parse', '--short=12', 'HEAD'], {
+    encoding: 'utf8'
+  }).trim()
+  return {
+    commit,
+    version: createLocalBuildVersion(packageJson.version, Date.now(), commit)
+  }
+}
+
+if (process.argv[1] && resolve(process.argv[1]) === resolve(import.meta.filename)) {
+  const identity = getLocalBuildIdentity()
+  console.log(`[build:mac] local update version ${identity.version}`)
+  execFileSync(
+    process.platform === 'win32' ? 'pnpm.cmd' : 'pnpm',
+    ['exec', 'electron-builder', '--config', 'config/electron-builder.config.cjs', '--mac'],
+    {
+      env: {
+        ...process.env,
+        ORCA_BUILD_COMMIT: identity.commit,
+        ORCA_LOCAL_BUILD_VERSION: identity.version
+      },
+      stdio: 'inherit'
+    }
+  )
+}
diff --git a/config/scripts/build-mac-local.test.mjs b/config/scripts/build-mac-local.test.mjs
new file mode 100644
index 000000000..21c587432
--- /dev/null
+++ b/config/scripts/build-mac-local.test.mjs
@@ -0,0 +1,15 @@
+import { describe, expect, it } from 'vitest'
+import { createLocalBuildVersion } from './build-mac-local.mjs'
+
+describe('createLocalBuildVersion', () => {
+  it('creates unique valid prerelease versions without changing the release base', () => {
+    expect(createLocalBuildVersion('1.4.159-rc.0', 123456, 'abc123')).toBe(
+      '1.4.159-rc.0.local.123456.abc123'
+    )
+    expect(createLocalBuildVersion('1.4.159', 123456, 'abc123')).toBe('1.4.159-local.123456.abc123')
+  })
+
+  it('sanitizes commit identifiers', () => {
+    expect(createLocalBuildVersion('1.0.0', 1, 'abc/def')).toBe('1.0.0-local.1.abcdef')
+  })
+})
diff --git a/config/scripts/electron-builder-config.test.mjs b/config/scripts/electron-builder-config.test.mjs
index 4d492d68c..0d4c7dd71 100644
--- a/config/scripts/electron-builder-config.test.mjs
+++ b/config/scripts/electron-builder-config.test.mjs
@@ -19,6 +19,12 @@ const {
 } = require('../packaged-runtime-node-modules.cjs')
 
 describe('electron-builder config', () => {
+  it('keeps the packaged app identity aligned with local-build validation', () => {
+    expect(electronBuilderConfig.appId).toBe(
+      require('../../src/shared/local-build-compatibility-contract.json').appId
+    )
+  })
+
   it('excludes repo-only source trees from app.asar', () => {
     expect(electronBuilderConfig.files).toEqual(
       expect.arrayContaining([
@@ -173,6 +179,58 @@ describe('electron-builder config', () => {
     }
   })
 
+  it('overrides packaged semver only for local macOS builds', () => {
+    const configPath = require.resolve('../electron-builder.config.cjs')
+    const original = process.env.ORCA_LOCAL_BUILD_VERSION
+    const originalMacRelease = process.env.ORCA_MAC_RELEASE
+    try {
+      delete require.cache[configPath]
+      delete process.env.ORCA_MAC_RELEASE
+      process.env.ORCA_LOCAL_BUILD_VERSION = '1.4.159-rc.0.local.123.abc'
+      expect(require('../electron-builder.config.cjs').extraMetadata).toEqual({
+        version: '1.4.159-rc.0.local.123.abc'
+      })
+    } finally {
+      if (originalMacRelease === undefined) {
+        delete process.env.ORCA_MAC_RELEASE
+      } else {
+        process.env.ORCA_MAC_RELEASE = originalMacRelease
+      }
+      if (original === undefined) {
+        delete process.env.ORCA_LOCAL_BUILD_VERSION
+      } else {
+        process.env.ORCA_LOCAL_BUILD_VERSION = original
+      }
+      delete require.cache[configPath]
+      require('../electron-builder.config.cjs')
+    }
+  })
+
+  it('never applies local semver to release packaging', () => {
+    const configPath = require.resolve('../electron-builder.config.cjs')
+    const originalLocalVersion = process.env.ORCA_LOCAL_BUILD_VERSION
+    const originalMacRelease = process.env.ORCA_MAC_RELEASE
+    try {
+      delete require.cache[configPath]
+      process.env.ORCA_LOCAL_BUILD_VERSION = '1.4.159-local.123.abc'
+      process.env.ORCA_MAC_RELEASE = '1'
+      expect(require('../electron-builder.config.cjs').extraMetadata).toBeUndefined()
+    } finally {
+      if (originalLocalVersion === undefined) {
+        delete process.env.ORCA_LOCAL_BUILD_VERSION
+      } else {
+        process.env.ORCA_LOCAL_BUILD_VERSION = originalLocalVersion
+      }
+      if (originalMacRelease === undefined) {
+        delete process.env.ORCA_MAC_RELEASE
+      } else {
+        process.env.ORCA_MAC_RELEASE = originalMacRelease
+      }
+      delete require.cache[configPath]
+      require('../electron-builder.config.cjs')
+    }
+  })
+
   it('uses Orca native rebuild hook instead of electron-builder default rebuild', () => {
     expect(electronBuilderConfig.beforeBuild).toBe(electronBuilderNativeRebuild)
     expect(electronBuilderConfig.npmRebuild).toBe(true)
diff --git a/config/scripts/mac-build-compatibility.cjs b/config/scripts/mac-build-compatibility.cjs
new file mode 100644
index 000000000..4df85d4fe
--- /dev/null
+++ b/config/scripts/mac-build-compatibility.cjs
@@ -0,0 +1,34 @@
+const { writeFileSync } = require('node:fs')
+const { join } = require('node:path')
+const compatibilityContract = require('../../src/shared/local-build-compatibility-contract.json')
+
+const MAC_BUILD_COMPATIBILITY_FILENAME = 'orca-local-build.json'
+
+function createMacBuildCompatibility({ version, commit, architecture }) {
+  if (architecture !== 'arm64' && architecture !== 'x64') {
+    throw new Error(`Unsupported macOS build architecture: ${architecture}`)
+  }
+  return {
+    ...compatibilityContract,
+    buildId: `${version}-${commit}-${architecture}`,
+    version,
+    commit,
+    platform: 'darwin',
+    architecture
+  }
+}
+
+function writeMacBuildCompatibility(resourcesDir, identity) {
+  const compatibility = createMacBuildCompatibility(identity)
+  writeFileSync(
+    join(resourcesDir, MAC_BUILD_COMPATIBILITY_FILENAME),
+    `${JSON.stringify(compatibility, null, 2)}\n`,
+    'utf8'
+  )
+}
+
+module.exports = {
+  MAC_BUILD_COMPATIBILITY_FILENAME,
+  createMacBuildCompatibility,
+  writeMacBuildCompatibility
+}
diff --git a/config/scripts/mac-build-compatibility.test.mjs b/config/scripts/mac-build-compatibility.test.mjs
new file mode 100644
index 000000000..81b642c50
--- /dev/null
+++ b/config/scripts/mac-build-compatibility.test.mjs
@@ -0,0 +1,36 @@
+import { createRequire } from 'node:module'
+import { describe, expect, it } from 'vitest'
+
+const require = createRequire(import.meta.url)
+const { createMacBuildCompatibility } = require('./mac-build-compatibility.cjs')
+
+describe('mac build compatibility metadata', () => {
+  it('binds version, commit, and architecture into the packaged contract', () => {
+    expect(
+      createMacBuildCompatibility({
+        version: '1.2.3-local.1',
+        commit: 'abc123',
+        architecture: 'arm64'
+      })
+    ).toMatchObject({
+      formatVersion: 1,
+      appId: 'com.stablyai.orca',
+      buildId: '1.2.3-local.1-abc123-arm64',
+      version: '1.2.3-local.1',
+      commit: 'abc123',
+      stateSchemaVersion: 1,
+      platform: 'darwin',
+      architecture: 'arm64'
+    })
+  })
+
+  it('rejects unsupported architecture metadata', () => {
+    expect(() =>
+      createMacBuildCompatibility({
+        version: '1.2.3',
+        commit: 'abc123',
+        architecture: 'universal'
+      })
+    ).toThrow('Unsupported macOS build architecture')
+  })
+})
diff --git a/package.json b/package.json
index b68b1a2b8..1df039081 100644
--- a/package.json
+++ b/package.json
@@ -77,7 +77,7 @@
     "build:unpack": "pnpm run build && pnpm run ensure:electron-runtime && electron-builder --config config/electron-builder.config.cjs --dir",
     "build:win": "pnpm run build:desktop && pnpm run ensure:electron-runtime && electron-builder --config config/electron-builder.config.cjs --win",
     "build:icons": "bash resources/icon-source/generate.sh",
-    "build:mac": "pnpm run build:desktop && pnpm run build:computer-macos && pnpm run build:notification-status-macos && pnpm run ensure:electron-runtime && electron-builder --config config/electron-builder.config.cjs --mac",
+    "build:mac": "pnpm run build:desktop && pnpm run build:computer-macos && pnpm run build:notification-status-macos && pnpm run ensure:electron-runtime && node config/scripts/build-mac-local.mjs",
     "build:mac:release": "node config/scripts/verify-macos-release-env.mjs && ORCA_MAC_RELEASE=1 pnpm run build:desktop && ORCA_MAC_RELEASE=1 pnpm run build:computer-macos && ORCA_MAC_RELEASE=1 pnpm run build:notification-status-macos && pnpm run ensure:electron-runtime && ORCA_MAC_RELEASE=1 electron-builder --config config/electron-builder.config.cjs --mac",
     "build:linux": "pnpm run build:desktop && pnpm run ensure:electron-runtime && electron-builder --config config/electron-builder.config.cjs --linux AppImage deb",
     "test:e2e": "pnpm run ensure:electron-runtime && npx playwright test --config tests/playwright.config.ts --project=electron-headless",
diff --git a/src/main/local-builds/local-build-candidate.test.ts b/src/main/local-builds/local-build-candidate.test.ts
new file mode 100644
index 000000000..2807164ed
--- /dev/null
+++ b/src/main/local-builds/local-build-candidate.test.ts
@@ -0,0 +1,172 @@
+import { createHash } from 'node:crypto'
+import { execFile } from 'node:child_process'
+import { mkdir, mkdtemp, readFile, rename, rm, symlink, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { promisify } from 'node:util'
+import { afterEach, describe, expect, it } from 'vitest'
+import { stringify } from 'yaml'
+import type { LocalBuildCompatibility } from '../../shared/local-build-compatibility'
+import { loadLocalBuildCandidate } from './local-build-candidate'
+import { startLocalBuildFeed } from './local-build-feed-server'
+
+const tempDirectories: string[] = []
+const execFileAsync = promisify(execFile)
+
+function compatibility(): LocalBuildCompatibility {
+  return {
+    formatVersion: 1,
+    appId: 'com.stablyai.orca',
+    buildId: '1.2.3-local.1-abc-arm64',
+    version: '1.2.3-local.1',
+    commit: 'abc',
+    stateSchemaVersion: 1,
+    readableStateSchemaVersions: [1],
+    daemonProtocolVersion: 28,
+    attachableDaemonProtocolVersions: [28],
+    platform: 'darwin',
+    architecture: 'arm64'
+  }
+}
+
+async function fixture(options: { sha512?: string; url?: string } = {}) {
+  const directory = await mkdtemp(join(tmpdir(), 'orca-local-build-'))
+  tempDirectories.push(directory)
+  const artifactName = 'orca-macos-arm64.zip'
+  const artifactPath = join(directory, artifactName)
+  const content = Buffer.from('signed-zip-placeholder')
+  await writeFile(artifactPath, content)
+  const manifestPath = join(directory, 'latest-mac.yml')
+  await writeFile(
+    manifestPath,
+    stringify({
+      version: compatibility().version,
+      files: [
+        {
+          url: options.url ?? artifactName,
+          sha512: options.sha512 ?? createHash('sha512').update(content).digest('base64'),
+          size: content.length
+        },
+        {
+          url: 'orca-macos-arm64.dmg',
+          sha512: Buffer.alloc(64).toString('base64'),
+          size: 1
+        }
+      ]
+    })
+  )
+  return { artifactPath, directory, manifestPath }
+}
+
+afterEach(async () => {
+  await Promise.all(
+    tempDirectories.splice(0).map((directory) => rm(directory, { recursive: true, force: true }))
+  )
+})
+
+describe('loadLocalBuildCandidate', () => {
+  it('returns a sanitized, architecture-specific feed after hash validation', async () => {
+    const { manifestPath } = await fixture()
+    const candidate = await loadLocalBuildCandidate(manifestPath, 'arm64', {
+      readCompatibility: async () => compatibility()
+    })
+
+    expect(candidate.version).toBe('1.2.3-local.1')
+    expect([...candidate.artifacts.keys()]).toEqual(['orca-macos-arm64.zip'])
+    expect(candidate.manifestContent).toContain('orca-macos-arm64.zip')
+    await candidate.close()
+  })
+
+  it('rejects mismatched hashes and traversal paths', async () => {
+    const badHash = await fixture({ sha512: Buffer.alloc(64).toString('base64') })
+    await expect(
+      loadLocalBuildCandidate(badHash.manifestPath, 'arm64', {
+        readCompatibility: async () => compatibility()
+      })
+    ).rejects.toThrow('SHA-512 verification failed')
+
+    const traversal = await fixture({ url: '../orca-macos-arm64.zip' })
+    await expect(
+      loadLocalBuildCandidate(traversal.manifestPath, 'arm64', {
+        readCompatibility: async () => compatibility()
+      })
+    ).rejects.toThrow('invalid file entry')
+  })
+
+  it('rejects symlinked artifacts', async () => {
+    const { artifactPath, directory, manifestPath } = await fixture()
+    const realArtifact = join(directory, 'real.zip')
+    await writeFile(realArtifact, 'signed-zip-placeholder')
+    await rm(artifactPath)
+    await symlink(realArtifact, artifactPath)
+
+    await expect(
+      loadLocalBuildCandidate(manifestPath, 'arm64', {
+        readCompatibility: async () => compatibility()
+      })
+    ).rejects.toThrow('regular files, not links')
+  })
+
+  it('serves the same artifact descriptor that passed validation', async () => {
+    const { artifactPath, directory, manifestPath } = await fixture()
+    const movedArtifactPath = join(directory, 'validated.zip')
+    const candidate = await loadLocalBuildCandidate(manifestPath, 'arm64', {
+      readCompatibility: async () => {
+        await rename(artifactPath, movedArtifactPath)
+        await writeFile(artifactPath, 'replacement')
+        return compatibility()
+      }
+    })
+    const feed = await startLocalBuildFeed(candidate)
+    try {
+      await expect(
+        fetch(`${feed.url}orca-macos-arm64.zip`).then((response) => response.text())
+      ).resolves.toBe('signed-zip-placeholder')
+    } finally {
+      await feed.close()
+    }
+  })
+
+  it.runIf(process.platform === 'darwin')(
+    'reads signed compatibility metadata through the held artifact descriptor',
+    async () => {
+      const directory = await mkdtemp(join(tmpdir(), 'orca-local-build-zip-'))
+      tempDirectories.push(directory)
+      const zipRoot = join(directory, 'zip-root')
+      const resources = join(zipRoot, 'Orca.app', 'Contents', 'Resources')
+      await mkdir(resources, { recursive: true })
+      await writeFile(join(resources, 'orca-local-build.json'), JSON.stringify(compatibility()))
+      const artifactName = 'orca-macos-arm64.zip'
+      const artifactPath = join(directory, artifactName)
+      await execFileAsync('/usr/bin/zip', ['-qry', artifactPath, 'Orca.app'], { cwd: zipRoot })
+      const artifact = await readFile(artifactPath)
+      const manifestPath = join(directory, 'latest-mac.yml')
+      await writeFile(
+        manifestPath,
+        stringify({
+          version: compatibility().version,
+          files: [
+            {
+              url: artifactName,
+              sha512: createHash('sha512').update(artifact).digest('base64'),
+              size: artifact.length
+            }
+          ]
+        })
+      )
+
+      const candidate = await loadLocalBuildCandidate(manifestPath, 'arm64')
+      expect(candidate.compatibility).toEqual(compatibility())
+      await candidate.close()
+    }
+  )
+
+  it('requires exactly one ZIP for the running architecture', async () => {
+    const { manifestPath } = await fixture()
+    await expect(
+      loadLocalBuildCandidate(manifestPath, 'x64', {
+        readCompatibility: async () => compatibility()
+      })
+    ).rejects.toThrow('exactly one x64 Orca ZIP')
+  })
+})
diff --git a/src/main/local-builds/local-build-candidate.ts b/src/main/local-builds/local-build-candidate.ts
new file mode 100644
index 000000000..772a17bb7
--- /dev/null
+++ b/src/main/local-builds/local-build-candidate.ts
@@ -0,0 +1,279 @@
+import { createHash } from 'node:crypto'
+import { spawn } from 'node:child_process'
+import { constants } from 'node:fs'
+import { lstat, open, realpath, type FileHandle } from 'node:fs/promises'
+import { basename, dirname, join } from 'node:path'
+import { parse, stringify } from 'yaml'
+import {
+  LOCAL_BUILD_COMPATIBILITY_FILENAME,
+  ORCA_APP_ID,
+  parseLocalBuildCompatibility,
+  type LocalBuildCompatibility
+} from '../../shared/local-build-compatibility'
+import { isValidAppVersion } from '../../shared/app-version'
+
+const MAX_MANIFEST_BYTES = 256 * 1024
+const MAX_COMPATIBILITY_BYTES = 64 * 1024
+const MAX_UPDATE_FILES = 8
+const MAX_ZIP_BYTES = 8 * 1024 * 1024 * 1024
+const SAFE_ARTIFACT_NAME = /^[A-Za-z0-9][A-Za-z0-9._ ()+-]*\.zip$/
+
+type ManifestFile = {
+  url: string
+  sha512: string
+  size?: number
+}
+
+export type LocalBuildCandidate = {
+  version: string
+  compatibility: LocalBuildCompatibility
+  manifestContent: string
+  artifacts: Map<string, { file: FileHandle; size: number }>
+  close: () => Promise<void>
+}
+
+type LocalBuildCandidateLoaderOptions = {
+  readCompatibility?: (zipFile: FileHandle) => Promise<LocalBuildCompatibility>
+}
+
+function parseManifestFile(value: unknown): ManifestFile {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) {
+    throw new Error('The local update manifest contains an invalid file entry.')
+  }
+  const record = value as Record<string, unknown>
+  if (
+    typeof record.url !== 'string' ||
+    !SAFE_ARTIFACT_NAME.test(record.url) ||
+    basename(record.url) !== record.url ||
+    typeof record.sha512 !== 'string' ||
+    !/^[A-Za-z0-9+/]{86}==$/.test(record.sha512) ||
+    (record.size !== undefined && (!Number.isSafeInteger(record.size) || Number(record.size) <= 0))
+  ) {
+    throw new Error('The local update manifest contains an invalid file entry.')
+  }
+  return {
+    url: record.url,
+    sha512: record.sha512,
+    ...(record.size === undefined ? {} : { size: Number(record.size) })
+  }
+}
+
+function isZipManifestFile(value: unknown): boolean {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) {
+    return false
+  }
+  const url = (value as Record<string, unknown>).url
+  return typeof url === 'string' && url.toLowerCase().endsWith('.zip')
+}
+
+function parseManifest(value: unknown): { version: string; files: ManifestFile[] } {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) {
+    throw new Error('The selected file is not a valid macOS update manifest.')
+  }
+  const record = value as Record<string, unknown>
+  if (
+    typeof record.version !== 'string' ||
+    record.version.length === 0 ||
+    record.version.length > 100 ||
+    !isValidAppVersion(record.version) ||
+    !Array.isArray(record.files) ||
+    record.files.length === 0 ||
+    record.files.length > MAX_UPDATE_FILES
+  ) {
+    throw new Error('The selected file is not a valid macOS update manifest.')
+  }
+  const zipFiles = record.files.filter(isZipManifestFile)
+  if (zipFiles.length === 0) {
+    throw new Error('The selected macOS update manifest does not contain a ZIP.')
+  }
+  return { version: record.version, files: zipFiles.map(parseManifestFile) }
+}
+
+async function hashFile(file: FileHandle): Promise<string> {
+  const hash = createHash('sha512')
+  await new Promise<void>((resolve, reject) => {
+    const stream = file.createReadStream({ autoClose: false, start: 0 })
+    stream.on('data', (chunk) => hash.update(chunk))
+    stream.on('error', reject)
+    stream.on('end', resolve)
+  })
+  return hash.digest('base64')
+}
+
+async function assertContainedRegularFile(rootPath: string, filePath: string): Promise<void> {
+  const fileInfo = await lstat(filePath)
+  if (!fileInfo.isFile() || fileInfo.isSymbolicLink()) {
+    throw new Error('Local update artifacts must be regular files, not links.')
+  }
+  const [resolvedRoot, resolvedFile] = await Promise.all([realpath(rootPath), realpath(filePath)])
+  if (dirname(resolvedFile) !== resolvedRoot) {
+    throw new Error('Local update artifacts must stay beside latest-mac.yml.')
+  }
+}
+
+function extractCompatibility(zipFile: FileHandle): Promise<string> {
+  return new Promise((resolve, reject) => {
+    const child = spawn(
+      '/usr/bin/unzip',
+      ['-p', '/dev/fd/3', `Orca.app/Contents/Resources/${LOCAL_BUILD_COMPATIBILITY_FILENAME}`],
+      { stdio: ['ignore', 'pipe', 'ignore', zipFile.fd] }
+    )
+    const chunks: Buffer[] = []
+    let outputBytes = 0
+    let outputError: Error | null = null
+    const stdout = child.stdout
+    if (!stdout) {
+      child.kill()
+      reject(new Error('Could not read compatibility metadata.'))
+      return
+    }
+    stdout.on('data', (chunk: Buffer) => {
+      outputBytes += chunk.length
+      if (outputBytes > MAX_COMPATIBILITY_BYTES) {
+        outputError = new Error('Compatibility metadata is too large.')
+        child.kill()
+        return
+      }
+      chunks.push(chunk)
+    })
+    child.on('error', reject)
+    child.on('close', (code) => {
+      if (outputError) {
+        reject(outputError)
+      } else if (code !== 0) {
+        reject(new Error(`unzip exited with status ${code ?? 'unknown'}.`))
+      } else {
+        resolve(Buffer.concat(chunks).toString('utf8'))
+      }
+    })
+  })
+}
+
+async function readCompatibility(zipFile: FileHandle): Promise<LocalBuildCompatibility> {
+  let stdout: string
+  try {
+    stdout = await extractCompatibility(zipFile)
+  } catch (error) {
+    console.warn('[local-build] Could not read compatibility metadata:', error)
+    throw new Error(
+      'This build predates local switching or is missing its signed compatibility metadata.'
+    )
+  }
+  try {
+    return parseLocalBuildCompatibility(JSON.parse(stdout))
+  } catch (error) {
+    if (error instanceof SyntaxError) {
+      throw new Error('The selected build has malformed compatibility metadata.')
+    }
+    throw error
+  }
+}
+
+async function validateArtifact(
+  rootPath: string,
+  manifestFile: ManifestFile,
+  manifestVersion: string,
+  compatibilityReader: (zipFile: FileHandle) => Promise<LocalBuildCompatibility>
+): Promise<{ compatibility: LocalBuildCompatibility; file: FileHandle; size: number }> {
+  const filePath = join(rootPath, manifestFile.url)
+  await assertContainedRegularFile(rootPath, filePath)
+  const file = await open(
+    filePath,
+    constants.O_RDONLY | (typeof constants.O_NOFOLLOW === 'number' ? constants.O_NOFOLLOW : 0)
+  )
+  try {
+    const fileStats = await file.stat()
+    if (!fileStats.isFile() || fileStats.size <= 0 || fileStats.size > MAX_ZIP_BYTES) {
+      throw new Error('The selected local build ZIP has an invalid size.')
+    }
+    if (manifestFile.size !== undefined && fileStats.size !== manifestFile.size) {
+      throw new Error(`Size verification failed for ${manifestFile.url}.`)
+    }
+    if ((await hashFile(file)) !== manifestFile.sha512) {
+      throw new Error(`SHA-512 verification failed for ${manifestFile.url}.`)
+    }
+    const compatibility = await compatibilityReader(file)
+    if (compatibility.appId !== ORCA_APP_ID || compatibility.version !== manifestVersion) {
+      throw new Error('The selected ZIP does not match its update manifest.')
+    }
+    return { compatibility, file, size: fileStats.size }
+  } catch (error) {
+    await file.close()
+    throw error
+  }
+}
+
+export async function loadLocalBuildCandidate(
+  manifestPath: string,
+  architecture: NodeJS.Architecture,
+  options: LocalBuildCandidateLoaderOptions = {}
+): Promise<LocalBuildCandidate> {
+  if (basename(manifestPath) !== 'latest-mac.yml') {
+    throw new Error('Select the latest-mac.yml generated by pn build:mac.')
+  }
+  await assertContainedRegularFile(dirname(manifestPath), manifestPath)
+  const manifestFile = await open(
+    manifestPath,
+    constants.O_RDONLY | (typeof constants.O_NOFOLLOW === 'number' ? constants.O_NOFOLLOW : 0)
+  )
+  let manifestText: string
+  try {
+    const manifestStats = await manifestFile.stat()
+    if (
+      !manifestStats.isFile() ||
+      manifestStats.size <= 0 ||
+      manifestStats.size > MAX_MANIFEST_BYTES
+    ) {
+      throw new Error('The selected update manifest is too large.')
+    }
+    manifestText = await manifestFile.readFile('utf8')
+  } finally {
+    await manifestFile.close()
+  }
+  const manifest = parseManifest(parse(manifestText, { maxAliasCount: 0 }))
+  const rootPath = dirname(manifestPath)
+  const compatibilityReader = options.readCompatibility ?? readCompatibility
+  const validationResults = await Promise.allSettled(
+    manifest.files.map((file) =>
+      validateArtifact(rootPath, file, manifest.version, compatibilityReader)
+    )
+  )
+  const validated = validationResults
+    .filter((result) => result.status === 'fulfilled')
+    .map((result) => result.value)
+  const failed = validationResults.find((result) => result.status === 'rejected')
+  if (failed?.status === 'rejected') {
+    await Promise.all(validated.map((entry) => entry.file.close()))
+    throw failed.reason
+  }
+  const matching = validated
+    .map((entry, index) => ({ ...entry, manifestFile: manifest.files[index] }))
+    .filter((entry) => entry.compatibility.architecture === architecture)
+  if (matching.length !== 1) {
+    await Promise.all(validated.map((entry) => entry.file.close()))
+    throw new Error(`The manifest must contain exactly one ${architecture} Orca ZIP.`)
+  }
+  const target = matching[0]
+  await Promise.all(
+    validated.filter((entry) => entry.file !== target.file).map((entry) => entry.file.close())
+  )
+  const sanitizedFile = {
+    url: target.manifestFile.url,
+    sha512: target.manifestFile.sha512,
+    ...(target.manifestFile.size === undefined ? {} : { size: target.manifestFile.size })
+  }
+  return {
+    version: manifest.version,
+    compatibility: target.compatibility,
+    manifestContent: stringify({
+      version: manifest.version,
+      files: [sanitizedFile],
+      path: sanitizedFile.url,
+      sha512: sanitizedFile.sha512
+    }),
+    artifacts: new Map([[target.manifestFile.url, { file: target.file, size: target.size }]]),
+    close: async () => {
+      await target.file.close()
+    }
+  }
+}
diff --git a/src/main/local-builds/local-build-compatibility-contract.test.ts b/src/main/local-builds/local-build-compatibility-contract.test.ts
new file mode 100644
index 000000000..dc2e2af54
--- /dev/null
+++ b/src/main/local-builds/local-build-compatibility-contract.test.ts
@@ -0,0 +1,21 @@
+import { describe, expect, it } from 'vitest'
+import { SCHEMA_VERSION } from '../../shared/constants'
+import compatibilityContract from '../../shared/local-build-compatibility-contract.json'
+import { LOCAL_BUILD_COMPATIBILITY_CONTRACT } from '../../shared/local-build-compatibility-contract'
+import {
+  PREVIOUS_DAEMON_PROTOCOL_VERSIONS,
+  PROTOCOL_VERSION
+} from '../daemon/daemon-protocol-version'
+
+describe('packaged local build compatibility contract', () => {
+  it('stays aligned with runtime state and daemon constants', () => {
+    expect(LOCAL_BUILD_COMPATIBILITY_CONTRACT).toEqual(compatibilityContract)
+    expect(compatibilityContract).toMatchObject({
+      appId: 'com.stablyai.orca',
+      stateSchemaVersion: SCHEMA_VERSION,
+      readableStateSchemaVersions: [SCHEMA_VERSION],
+      daemonProtocolVersion: PROTOCOL_VERSION,
+      attachableDaemonProtocolVersions: [...PREVIOUS_DAEMON_PROTOCOL_VERSIONS, PROTOCOL_VERSION]
+    })
+  })
+})
diff --git a/src/main/local-builds/local-build-compatibility.ts b/src/main/local-builds/local-build-compatibility.ts
new file mode 100644
index 000000000..015377f9d
--- /dev/null
+++ b/src/main/local-builds/local-build-compatibility.ts
@@ -0,0 +1,71 @@
+import { SCHEMA_VERSION } from '../../shared/constants'
+import {
+  getLocalBuildCompatibilityError,
+  type LocalBuildCompatibility
+} from '../../shared/local-build-compatibility'
+import type { DaemonPtyAdapter } from '../daemon/daemon-pty-adapter'
+import { DaemonPtyRouter } from '../daemon/daemon-pty-router'
+import { DegradedDaemonPtyProvider } from '../daemon/degraded-daemon-pty-provider'
+import { getDaemonProvider } from '../daemon/daemon-init'
+import { getLocalPtyProvider } from '../ipc/pty'
+import { LocalPtyProvider } from '../providers/local-pty-provider'
+
+export type LocalBuildCompatibilityResult = {
+  liveTerminalCount: number
+  liveDaemonProtocols: number[]
+}
+
+async function getLiveDaemonProtocols(): Promise<{
+  count: number
+  protocols: number[]
+}> {
+  const provider = getDaemonProvider()
+  if (!provider) {
+    const localProvider = getLocalPtyProvider()
+    if (!(localProvider instanceof LocalPtyProvider)) {
+      throw new Error('Could not verify terminal preservation. Restart Orca and try again.')
+    }
+    const localProcesses = await localProvider.listProcesses()
+    if (localProcesses.length > 0) {
+      throw new Error(
+        'Local build switching is blocked while non-persistent fallback terminals are running.'
+      )
+    }
+    throw new Error('The terminal service is still starting. Try again in a moment.')
+  }
+  if (provider instanceof DegradedDaemonPtyProvider) {
+    throw new Error(
+      'Local build switching is blocked while the terminal service is in fallback mode. Restart Orca first.'
+    )
+  }
+  const adapters =
+    provider instanceof DaemonPtyRouter ? provider.getAllAdapters() : [provider as DaemonPtyAdapter]
+  const sessions = await Promise.all(
+    adapters.map(async (adapter) => ({
+      protocol: adapter.protocolVersion,
+      count: (await adapter.listSessions()).length
+    }))
+  )
+  return {
+    count: sessions.reduce((sum, entry) => sum + entry.count, 0),
+    protocols: sessions.filter((entry) => entry.count > 0).map((entry) => entry.protocol)
+  }
+}
+
+export async function assertLocalBuildCompatibility(
+  target: LocalBuildCompatibility
+): Promise<LocalBuildCompatibilityResult> {
+  const stateCompatibilityError = getLocalBuildCompatibilityError(target, SCHEMA_VERSION, [])
+  if (stateCompatibilityError) {
+    throw new Error(stateCompatibilityError)
+  }
+  const live = await getLiveDaemonProtocols()
+  const compatibilityError = getLocalBuildCompatibilityError(target, SCHEMA_VERSION, live.protocols)
+  if (compatibilityError) {
+    throw new Error(compatibilityError)
+  }
+  return {
+    liveTerminalCount: live.count,
+    liveDaemonProtocols: [...new Set(live.protocols)].sort((left, right) => left - right)
+  }
+}
diff --git a/src/main/local-builds/local-build-feed-server.test.ts b/src/main/local-builds/local-build-feed-server.test.ts
new file mode 100644
index 000000000..6c020c10f
--- /dev/null
+++ b/src/main/local-builds/local-build-feed-server.test.ts
@@ -0,0 +1,37 @@
+import { mkdtemp, open, rm, writeFile } from 'node:fs/promises'
+import { tmpdir } from 'node:os'
+import { join } from 'node:path'
+import { describe, expect, it } from 'vitest'
+import type { LocalBuildCandidate } from './local-build-candidate'
+import { startLocalBuildFeed } from './local-build-feed-server'
+
+describe('startLocalBuildFeed', () => {
+  it('serves only tokenized manifest and validated artifact routes', async () => {
+    const directory = await mkdtemp(join(tmpdir(), 'orca-local-feed-'))
+    const artifactPath = join(directory, 'orca-macos-arm64.zip')
+    await writeFile(artifactPath, 'zip')
+    const artifactFile = await open(artifactPath, 'r')
+    const candidate = {
+      version: '1.2.3-local.1',
+      manifestContent: 'version: 1.2.3-local.1\n',
+      artifacts: new Map([['orca-macos-arm64.zip', { file: artifactFile, size: 3 }]]),
+      close: () => artifactFile.close()
+    } as LocalBuildCandidate
+    const feed = await startLocalBuildFeed(candidate)
+    try {
+      await expect(
+        fetch(`${feed.url}latest-mac.yml`).then((response) => response.text())
+      ).resolves.toContain('1.2.3-local.1')
+      await expect(
+        fetch(`${feed.url}orca-macos-arm64.zip`).then((response) => response.text())
+      ).resolves.toBe('zip')
+      const baseUrl = new URL(feed.url)
+      await expect(
+        fetch(`${baseUrl.origin}/latest-mac.yml`).then((response) => response.status)
+      ).resolves.toBe(404)
+    } finally {
+      await feed.close()
+      await rm(directory, { recursive: true, force: true })
+    }
+  })
+})
diff --git a/src/main/local-builds/local-build-feed-server.ts b/src/main/local-builds/local-build-feed-server.ts
new file mode 100644
index 000000000..443cf17bf
--- /dev/null
+++ b/src/main/local-builds/local-build-feed-server.ts
@@ -0,0 +1,92 @@
+import { randomBytes } from 'node:crypto'
+import { createServer, type Server } from 'node:http'
+import type { LocalBuildCandidate } from './local-build-candidate'
+
+export type LocalBuildFeed = {
+  url: string
+  close: () => Promise<void>
+}
+
+function closeServer(server: Server): Promise<void> {
+  return new Promise((resolve) => {
+    server.close(() => resolve())
+  })
+}
+
+export async function startLocalBuildFeed(candidate: LocalBuildCandidate): Promise<LocalBuildFeed> {
+  const token = randomBytes(24).toString('hex')
+  const prefix = `/${token}/`
+  const server = createServer((request, response) => {
+    if (request.method !== 'GET' || !request.url) {
+      response.writeHead(404).end()
+      return
+    }
+    let pathname: string
+    try {
+      pathname = decodeURIComponent(new URL(request.url, 'http://127.0.0.1').pathname)
+    } catch {
+      response.writeHead(400).end()
+      return
+    }
+    if (!pathname.startsWith(prefix)) {
+      response.writeHead(404).end()
+      return
+    }
+    const filename = pathname.slice(prefix.length)
+    if (filename === 'latest-mac.yml') {
+      response.writeHead(200, {
+        'Cache-Control': 'no-store',
+        'Content-Type': 'application/yaml; charset=utf-8'
+      })
+      response.end(candidate.manifestContent)
+      return
+    }
+    const artifact = candidate.artifacts.get(filename)
+    if (!artifact) {
+      response.writeHead(404).end()
+      return
+    }
+    response.writeHead(200, {
+      'Cache-Control': 'no-store',
+      'Content-Type': 'application/zip'
+    })
+    const stream = artifact.file.createReadStream({
+      autoClose: false,
+      start: 0,
+      end: artifact.size - 1
+    })
+    stream.on('error', () => response.destroy())
+    response.on('error', () => stream.destroy())
+    response.on('close', () => stream.destroy())
+    stream.pipe(response)
+  })
+  await new Promise<void>((resolve, reject) => {
+    server.once('error', reject)
+    server.listen(0, '127.0.0.1', () => {
+      server.off('error', reject)
+      server.on('error', (error) => console.warn('[updater] Local build feed error:', error))
+      resolve()
+    })
+  }).catch(async (error) => {
+    await candidate.close()
+    throw error
+  })
+  const address = server.address()
+  if (!address || typeof address === 'string') {
+    await closeServer(server)
+    await candidate.close()
+    throw new Error('Could not start the local update feed.')
+  }
+  let closed = false
+  return {
+    url: `http://127.0.0.1:${address.port}${prefix}`,
+    close: async () => {
+      if (closed) {
+        return
+      }
+      closed = true
+      await closeServer(server)
+      await candidate.close()
+    }
+  }
+}
diff --git a/src/main/local-builds/local-build-switch.ts b/src/main/local-builds/local-build-switch.ts
new file mode 100644
index 000000000..2f1982c72
--- /dev/null
+++ b/src/main/local-builds/local-build-switch.ts
@@ -0,0 +1,59 @@
+import { app, dialog, type BrowserWindow } from 'electron'
+import { SCHEMA_VERSION } from '../../shared/constants'
+import { compareAppVersions } from '../../shared/app-version'
+import { assertLocalBuildCompatibility } from './local-build-compatibility'
+import { loadLocalBuildCandidate, type LocalBuildCandidate } from './local-build-candidate'
+
+export async function chooseLocalBuild(
+  window: BrowserWindow | null
+): Promise<LocalBuildCandidate | null> {
+  const openDialogOptions: Electron.OpenDialogOptions = {
+    title: 'Choose a Local Orca Build',
+    buttonLabel: 'Choose Build',
+    properties: ['openFile'],
+    filters: [{ name: 'Orca update manifest', extensions: ['yml'] }]
+  }
+  const selection = await (window
+    ? dialog.showOpenDialog(window, openDialogOptions)
+    : dialog.showOpenDialog(openDialogOptions))
+  const manifestPath = selection.filePaths[0]
+  if (selection.canceled || !manifestPath) {
+    return null
+  }
+  const candidate = await loadLocalBuildCandidate(manifestPath, process.arch)
+  try {
+    if (compareAppVersions(candidate.version, app.getVersion()) === 0) {
+      throw new Error(
+        'This build has the same version as the running app. Run pn build:mac again to create a uniquely versioned build.'
+      )
+    }
+    const compatibility = await assertLocalBuildCompatibility(candidate.compatibility)
+    const terminalSummary =
+      compatibility.liveTerminalCount === 0
+        ? 'No live terminals need to reconnect.'
+        : `${compatibility.liveTerminalCount} live terminal${
+            compatibility.liveTerminalCount === 1 ? '' : 's'
+          } will reconnect after restart.`
+    const messageBoxOptions: Electron.MessageBoxOptions = {
+      type: 'question',
+      title: 'Use Local Orca Build?',
+      message: `${app.getVersion()} → ${candidate.version}`,
+      detail: `${terminalSummary}\nWorkspace cards and settings are compatible with state schema ${SCHEMA_VERSION}.\n\nThe build must have the same valid code signature as Orca or installation will stop.`,
+      buttons: ['Use Local Build', 'Cancel'],
+      defaultId: 0,
+      cancelId: 1,
+      noLink: true
+    }
+    const confirmation = await (window
+      ? dialog.showMessageBox(window, messageBoxOptions)
+      : dialog.showMessageBox(messageBoxOptions))
+    if (confirmation.response === 0) {
+      return candidate
+    }
+  } catch (error) {
+    await candidate.close()
+    throw error
+  }
+  await candidate.close()
+  return null
+}
diff --git a/src/main/menu/register-app-menu.test.ts b/src/main/menu/register-app-menu.test.ts
index fa636e862..8433fd93e 100644
--- a/src/main/menu/register-app-menu.test.ts
+++ b/src/main/menu/register-app-menu.test.ts
@@ -171,6 +171,11 @@ describe('registerAppMenu', () => {
       undefined as never,
       (isMac ? { ctrlKey: true } : { metaKey: true }) as Electron.KeyboardEvent
     )
+    item?.click?.(
+      {} as never,
+      undefined as never,
+      { altKey: true, shiftKey: true } as Electron.KeyboardEvent
+    )
     item?.click?.(
       {} as never,
       undefined as never,
@@ -187,6 +192,13 @@ describe('registerAppMenu', () => {
       [{ includePrerelease: true, includePerfPrerelease: true }],
       [{ includePrerelease: false, includePerfPrerelease: true }],
       [{ includePrerelease: false, includePerfPrerelease: false }],
+      [
+        {
+          includePrerelease: !isMac,
+          includePerfPrerelease: false,
+          ...(isMac ? { localBuild: true } : {})
+        }
+      ],
       [{ includePrerelease: false, includePerfPrerelease: false }]
     ])
   })
diff --git a/src/main/menu/register-app-menu.ts b/src/main/menu/register-app-menu.ts
index 2f3a3d70a..d1e43d4fb 100644
--- a/src/main/menu/register-app-menu.ts
+++ b/src/main/menu/register-app-menu.ts
@@ -96,10 +96,15 @@ function buildAndApplyMenu(options: RegisterAppMenuOptions): void {
     event
   ) => {
     const modifierClick = !event.triggeredByAccelerator
+    const localBuild = isMac && modifierClick && event.altKey === true
     const includePerfPrerelease =
-      modifierClick && (isMac ? event.metaKey === true : event.ctrlKey === true)
-    const includePrerelease = modifierClick && event.shiftKey === true
-    onCheckForUpdates({ includePrerelease, includePerfPrerelease })
+      !localBuild && modifierClick && (isMac ? event.metaKey === true : event.ctrlKey === true)
+    const includePrerelease = !localBuild && modifierClick && event.shiftKey === true
+    onCheckForUpdates({
+      includePrerelease,
+      includePerfPrerelease,
+      ...(localBuild ? { localBuild: true } : {})
+    })
   }
 
   const checkForUpdatesItem: Electron.MenuItemConstructorOptions = {
diff --git a/src/main/updater-events.ts b/src/main/updater-events.ts
index 516416185..411bb1a71 100644
--- a/src/main/updater-events.ts
+++ b/src/main/updater-events.ts
@@ -30,7 +30,8 @@ type UpdaterHandlerContext = {
   getUserInitiatedCheck: () => boolean
   handleQuitAndInstallFailure: () => boolean
   isQuitAndInstallHandoffActive: () => boolean
-  hasNewerDownloadedVersion: () => boolean
+  hasInstallableDownloadedVersion: () => boolean
+  isLocalBuildCheck: () => boolean
   shouldHandleUpdaterErrorEvent: () => boolean
   clearUpdateAvailableEventPending: (attemptId: number | null) => void
   isActiveUpdateCheckAttempt: (attemptId: number) => boolean
@@ -40,6 +41,7 @@ type UpdaterHandlerContext = {
   performQuitAndInstall: () => void | Promise<void>
   shouldDeferMacQuitForInstall: () => boolean
   recordCompletedUpdateCheck: () => void
+  restoreReleaseUpdateSource: () => void
   sendCheckFailureStatus: (
     message: string,
     userInitiated?: boolean,
@@ -70,7 +72,8 @@ export function registerAutoUpdaterHandlers({
   getUserInitiatedCheck,
   handleQuitAndInstallFailure,
   isQuitAndInstallHandoffActive,
-  hasNewerDownloadedVersion,
+  hasInstallableDownloadedVersion,
+  isLocalBuildCheck,
   shouldHandleUpdaterErrorEvent,
   clearUpdateAvailableEventPending,
   isActiveUpdateCheckAttempt,
@@ -80,6 +83,7 @@ export function registerAutoUpdaterHandlers({
   performQuitAndInstall,
   shouldDeferMacQuitForInstall,
   recordCompletedUpdateCheck,
+  restoreReleaseUpdateSource,
   sendCheckFailureStatus,
   sendErrorStatus,
   sendStatus,
@@ -93,9 +97,9 @@ export function registerAutoUpdaterHandlers({
   // Why: electron-updater fires 'update-downloaded' before Squirrel.Mac finishes; track readiness to avoid a premature "ready".
   if (process.platform === 'darwin') {
     nativeUpdater.on('update-downloaded', () => {
-      const hasNewerVersion = hasNewerDownloadedVersion()
-      handleMacInstallerReady(hasNewerVersion, performQuitAndInstall, () => {
-        // Send the held 'downloaded' status now, only if the staged version is newer.
+      const hasInstallableVersion = hasInstallableDownloadedVersion()
+      handleMacInstallerReady(hasInstallableVersion, performQuitAndInstall, () => {
+        // Send the held status only while its staged build is still installable.
         sendStatus({
           state: 'downloaded',
           version: getPendingInstallVersion(),
@@ -121,7 +125,7 @@ export function registerAutoUpdaterHandlers({
     if (
       deferMacQuitUntilInstallerReady(
         getCurrentStatus(),
-        hasNewerDownloadedVersion(),
+        hasInstallableDownloadedVersion(),
         getPendingInstallVersion,
         sendStatus
       )
@@ -158,8 +162,8 @@ export function registerAutoUpdaterHandlers({
     const wasUserInitiated = missingManifestFallback?.userInitiated ?? getUserInitiatedCheck()
     setUserInitiatedCheck(false)
 
-    // Guard: don't show an update that isn't actually newer than what's running.
-    if (compareVersions(info.version, app.getVersion()) <= 0) {
+    // Release checks remain newer-only; validated local builds may intentionally downgrade.
+    if (!isLocalBuildCheck() && compareVersions(info.version, app.getVersion()) <= 0) {
       clearAvailableUpdateContext()
       if (missingManifestFallback || publishingWindowLastGoodCheck) {
         // Why: a current-version fallback manifest means the primary is transiently missing; keep the short retry cadence.
@@ -178,7 +182,9 @@ export function registerAutoUpdaterHandlers({
     markUpdateAvailableEventPending(attemptId)
     void (async () => {
       try {
-        const changelog = await fetchChangelog(info.version, app.getVersion()).catch(() => null)
+        const changelog = isLocalBuildCheck()
+          ? null
+          : await fetchChangelog(info.version, app.getVersion()).catch(() => null)
 
         // Why: async fetch may take seconds; bail if a newer event superseded this attempt to avoid a stale 'available' broadcast.
         if (!isActiveUpdateCheckAttempt(attemptId)) {
@@ -191,13 +197,15 @@ export function registerAutoUpdaterHandlers({
         // Why: side effects must run after the guard so a concurrent 'error' during the fetch can't leave orphaned state.
         setAvailableVersion(info.version)
         setAvailableReleaseUrl(null)
-        if (missingManifestFallback || publishingWindowLastGoodCheck) {
-          // Why: last-good release is a temporary fallback; keep probing so users can move to the newest tag once it publishes.
-          scheduleAutomaticUpdateCheck(AUTO_UPDATE_RETRY_INTERVAL_MS)
-        } else {
-          recordCompletedUpdateCheck()
-          if (!wasUserInitiated) {
-            scheduleAutomaticUpdateCheck(AUTO_UPDATE_CHECK_INTERVAL_MS)
+        if (!isLocalBuildCheck()) {
+          if (missingManifestFallback || publishingWindowLastGoodCheck) {
+            // Why: last-good release is a temporary fallback; keep probing so users can move to the newest tag once it publishes.
+            scheduleAutomaticUpdateCheck(AUTO_UPDATE_RETRY_INTERVAL_MS)
+          } else {
+            recordCompletedUpdateCheck()
+            if (!wasUserInitiated) {
+              scheduleAutomaticUpdateCheck(AUTO_UPDATE_CHECK_INTERVAL_MS)
+            }
           }
         }
 
@@ -217,18 +225,24 @@ export function registerAutoUpdaterHandlers({
     const missingManifestFallback = consumeMissingManifestPrereleaseFallbackResult()
     const publishingWindowLastGoodCheck = getPublishingWindowLastGoodCheck()
     const wasUserInitiated = missingManifestFallback?.userInitiated ?? getUserInitiatedCheck()
+    const localBuildCheck = isLocalBuildCheck()
     setUserInitiatedCheck(false)
     clearAvailableUpdateContext()
-    if (missingManifestFallback || publishingWindowLastGoodCheck) {
-      // Why: last-good not-available is a transient release-transition outcome; keep the short retry, don't suppress for 24h.
-      scheduleAutomaticUpdateCheck(AUTO_UPDATE_RETRY_INTERVAL_MS)
-    } else {
-      recordCompletedUpdateCheck()
-      if (!wasUserInitiated) {
-        scheduleAutomaticUpdateCheck(AUTO_UPDATE_CHECK_INTERVAL_MS)
+    if (!localBuildCheck) {
+      if (missingManifestFallback || publishingWindowLastGoodCheck) {
+        // Why: last-good not-available is a transient release-transition outcome; keep the short retry, don't suppress for 24h.
+        scheduleAutomaticUpdateCheck(AUTO_UPDATE_RETRY_INTERVAL_MS)
+      } else {
+        recordCompletedUpdateCheck()
+        if (!wasUserInitiated) {
+          scheduleAutomaticUpdateCheck(AUTO_UPDATE_CHECK_INTERVAL_MS)
+        }
       }
     }
     sendStatus({ state: 'not-available', userInitiated: wasUserInitiated || undefined })
+    if (localBuildCheck) {
+      restoreReleaseUpdateSource()
+    }
   })
 
   autoUpdater.on('download-progress', (progress) => {
@@ -242,8 +256,8 @@ export function registerAutoUpdaterHandlers({
 
   autoUpdater.on('update-downloaded', (info) => {
     clearBackgroundCheckLaunchPending()
-    // Skip the banner for non-newer versions (same-version or stale cached updates).
-    if (compareVersions(info.version, app.getVersion()) <= 0) {
+    // Release downloads remain newer-only; the local source was validated before checking.
+    if (!isLocalBuildCheck() && compareVersions(info.version, app.getVersion()) <= 0) {
       clearAvailableUpdateContext()
       sendStatus({ state: 'not-available' })
       return
@@ -288,5 +302,8 @@ export function registerAutoUpdaterHandlers({
       return
     }
     sendErrorStatus(message, wasUserInitiated || undefined)
+    if (isLocalBuildCheck()) {
+      restoreReleaseUpdateSource()
+    }
   })
 }
diff --git a/src/main/updater-fallback.ts b/src/main/updater-fallback.ts
index 411ddbd0a..d91cdf75e 100644
--- a/src/main/updater-fallback.ts
+++ b/src/main/updater-fallback.ts
@@ -10,6 +10,9 @@ export const isPrereleaseVersion = isPrereleaseAppVersion
 export const isValidVersion = isValidAppVersion
 
 export function statusesEqual(left: UpdateStatus, right: UpdateStatus): boolean {
+  if (left.source !== right.source) {
+    return false
+  }
   switch (left.state) {
     case 'idle':
       return right.state === 'idle'
diff --git a/src/main/updater.test.ts b/src/main/updater.test.ts
index b09c727ee..730dd5be9 100644
--- a/src/main/updater.test.ts
+++ b/src/main/updater.test.ts
@@ -50,6 +50,8 @@ const {
     autoUpdaterMock.setFeedURL.mockClear()
     autoUpdaterMock.updateConfigPath = undefined
     autoUpdaterMock.allowPrerelease = false
+    autoUpdaterMock.allowDowngrade = false
+    autoUpdaterMock.disableDifferentialDownload = false
     autoUpdaterMock.autoRunAppAfterInstall = true
     delete (autoUpdaterMock as Record<string, unknown>).verifyUpdateCodeSignature
   }
@@ -59,6 +61,8 @@ const {
     autoInstallOnAppQuit: false,
     autoRunAppAfterInstall: true,
     allowPrerelease: false,
+    allowDowngrade: false,
+    disableDifferentialDownload: false,
     on,
     checkForUpdates: vi.fn(),
     downloadUpdate: vi.fn(),
@@ -146,6 +150,14 @@ const { fetchNewerReleaseTagsMock } = vi.hoisted(() => ({
   fetchNewerReleaseTagsMock: vi.fn()
 }))
 
+const { chooseLocalBuildMock, startLocalBuildFeedMock, closeLocalBuildFeedMock } = vi.hoisted(
+  () => ({
+    chooseLocalBuildMock: vi.fn(),
+    startLocalBuildFeedMock: vi.fn(),
+    closeLocalBuildFeedMock: vi.fn()
+  })
+)
+
 vi.mock('./updater-prerelease-feed', () => ({
   fetchNewerReleaseTagsWithReadiness: async (...args: unknown[]) => {
     const result = await fetchNewerReleaseTagsMock(...args)
@@ -157,6 +169,14 @@ vi.mock('./updater-prerelease-feed', () => ({
     `https://github.com/stablyai/orca/releases/download/${tag}`
 }))
 
+vi.mock('./local-builds/local-build-switch', () => ({
+  chooseLocalBuild: chooseLocalBuildMock
+}))
+
+vi.mock('./local-builds/local-build-feed-server', () => ({
+  startLocalBuildFeed: startLocalBuildFeedMock
+}))
+
 describe('updater', () => {
   beforeEach(() => {
     vi.resetModules()
@@ -177,6 +197,12 @@ describe('updater', () => {
     shouldApplyNudgeMock.mockReset().mockReturnValue(false)
     fetchChangelogMock.mockReset().mockResolvedValue(null)
     fetchNewerReleaseTagsMock.mockReset().mockResolvedValue([])
+    chooseLocalBuildMock.mockReset()
+    closeLocalBuildFeedMock.mockReset()
+    startLocalBuildFeedMock.mockReset().mockResolvedValue({
+      url: 'http://127.0.0.1:1234/token/',
+      close: closeLocalBuildFeedMock
+    })
     vi.unstubAllGlobals()
     vi.useRealTimers()
   })
@@ -196,6 +222,184 @@ describe('updater', () => {
     expect(powerMonitorOnMock).not.toHaveBeenCalled()
   })
 
+  it.runIf(process.platform === 'darwin')(
+    'allows a validated local build to downgrade through the normal updater lifecycle',
+    async () => {
+      chooseLocalBuildMock.mockResolvedValue({
+        version: '0.9.0-local.1',
+        manifestContent: 'version: 0.9.0-local.1',
+        artifacts: new Map()
+      })
+      autoUpdaterMock.checkForUpdates.mockImplementation(() => {
+        autoUpdaterMock.emit('checking-for-update')
+        autoUpdaterMock.emit('update-available', { version: '0.9.0-local.1' })
+        return Promise.resolve(undefined)
+      })
+      const send = vi.fn()
+      const { setupAutoUpdater, checkForUpdatesFromMenu } = await import('./updater')
+      setupAutoUpdater({ webContents: { send } } as never, {
+        getLastUpdateCheckAt: () => Date.now()
+      })
+
+      checkForUpdatesFromMenu({ localBuild: true })
+
+      await vi.waitFor(() => {
+        expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(1)
+      })
+      expect(autoUpdaterMock.allowDowngrade).toBe(true)
+      expect(autoUpdaterMock.disableDifferentialDownload).toBe(true)
+      expect(autoUpdaterMock.setFeedURL).toHaveBeenLastCalledWith({
+        provider: 'generic',
+        url: 'http://127.0.0.1:1234/token/'
+      })
+      await vi.waitFor(() => {
+        expect(send).toHaveBeenCalledWith(
+          'updater:status',
+          expect.objectContaining({
+            state: 'available',
+            version: '0.9.0-local.1',
+            source: 'local'
+          })
+        )
+      })
+
+      setupAutoUpdater({ webContents: { send } } as never, {
+        getLastUpdateCheckAt: () => Date.now()
+      })
+      expect(autoUpdaterMock.setFeedURL).toHaveBeenLastCalledWith({
+        provider: 'generic',
+        url: 'http://127.0.0.1:1234/token/'
+      })
+      expect(autoUpdaterMock.allowDowngrade).toBe(true)
+
+      autoUpdaterMock.checkForUpdates.mockResolvedValue(undefined)
+      checkForUpdatesFromMenu()
+      await vi.waitFor(() => {
+        expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(2)
+      })
+      expect(closeLocalBuildFeedMock).toHaveBeenCalledTimes(1)
+      expect(autoUpdaterMock.allowDowngrade).toBe(false)
+      expect(autoUpdaterMock.disableDifferentialDownload).toBe(false)
+    }
+  )
+
+  it.runIf(process.platform === 'darwin')(
+    'restores ordinary release checks after local build selection fails',
+    async () => {
+      chooseLocalBuildMock.mockRejectedValue(new Error('invalid local build'))
+      const send = vi.fn()
+      const { setupAutoUpdater, checkForUpdates, checkForUpdatesFromMenu } =
+        await import('./updater')
+      setupAutoUpdater({ webContents: { send } } as never, {
+        getLastUpdateCheckAt: () => Date.now()
+      })
+
+      checkForUpdatesFromMenu({ localBuild: true })
+      await vi.waitFor(() => {
+        expect(send).toHaveBeenCalledWith('updater:status', {
+          state: 'error',
+          message: 'invalid local build',
+          userInitiated: true,
+          source: 'local'
+        })
+      })
+
+      checkForUpdates()
+      await vi.waitFor(() => {
+        expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(1)
+      })
+      expect(autoUpdaterMock.allowDowngrade).toBe(false)
+      expect(autoUpdaterMock.disableDifferentialDownload).toBe(false)
+      expect(autoUpdaterMock.setFeedURL).toHaveBeenLastCalledWith({
+        provider: 'generic',
+        url: 'https://github.com/stablyai/orca/releases/latest/download'
+      })
+    }
+  )
+
+  it.runIf(process.platform === 'darwin')(
+    'restores ordinary release checks after a local build is unavailable',
+    async () => {
+      chooseLocalBuildMock.mockResolvedValue({
+        version: '0.9.0-local.1',
+        manifestContent: 'version: 0.9.0-local.1',
+        artifacts: new Map()
+      })
+      autoUpdaterMock.checkForUpdates.mockImplementationOnce(() => {
+        autoUpdaterMock.emit('checking-for-update')
+        autoUpdaterMock.emit('update-not-available')
+        return Promise.resolve(undefined)
+      })
+      const send = vi.fn()
+      const { setupAutoUpdater, checkForUpdates, checkForUpdatesFromMenu } =
+        await import('./updater')
+      setupAutoUpdater({ webContents: { send } } as never, {
+        getLastUpdateCheckAt: () => Date.now()
+      })
+
+      checkForUpdatesFromMenu({ localBuild: true })
+      await vi.waitFor(() => {
+        expect(closeLocalBuildFeedMock).toHaveBeenCalledTimes(1)
+      })
+      expect(send).toHaveBeenCalledWith('updater:status', {
+        state: 'not-available',
+        userInitiated: true,
+        source: 'local'
+      })
+      expect(autoUpdaterMock.allowDowngrade).toBe(false)
+      expect(autoUpdaterMock.disableDifferentialDownload).toBe(false)
+
+      checkForUpdates()
+      await vi.waitFor(() => {
+        expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(2)
+      })
+      expect(autoUpdaterMock.setFeedURL).toHaveBeenLastCalledWith({
+        provider: 'generic',
+        url: 'https://github.com/stablyai/orca/releases/latest/download'
+      })
+    }
+  )
+
+  it.runIf(process.platform === 'darwin')(
+    'restores ordinary release checks after a local updater failure',
+    async () => {
+      chooseLocalBuildMock.mockResolvedValue({
+        version: '0.9.0-local.1',
+        manifestContent: 'version: 0.9.0-local.1',
+        artifacts: new Map()
+      })
+      autoUpdaterMock.checkForUpdates.mockRejectedValueOnce(new Error('local feed failed'))
+      const send = vi.fn()
+      const { setupAutoUpdater, checkForUpdates, checkForUpdatesFromMenu } =
+        await import('./updater')
+      setupAutoUpdater({ webContents: { send } } as never, {
+        getLastUpdateCheckAt: () => Date.now()
+      })
+
+      checkForUpdatesFromMenu({ localBuild: true })
+      await vi.waitFor(() => {
+        expect(send).toHaveBeenCalledWith('updater:status', {
+          state: 'error',
+          message: 'local feed failed',
+          userInitiated: true,
+          source: 'local'
+        })
+      })
+      expect(closeLocalBuildFeedMock).toHaveBeenCalledTimes(1)
+      expect(autoUpdaterMock.allowDowngrade).toBe(false)
+      expect(autoUpdaterMock.disableDifferentialDownload).toBe(false)
+
+      checkForUpdates()
+      await vi.waitFor(() => {
+        expect(autoUpdaterMock.checkForUpdates).toHaveBeenCalledTimes(2)
+      })
+      expect(autoUpdaterMock.setFeedURL).toHaveBeenLastCalledWith({
+        provider: 'generic',
+        url: 'https://github.com/stablyai/orca/releases/latest/download'
+      })
+    }
+  )
+
   it('deduplicates identical check errors from the event and rejected promise', async () => {
     autoUpdaterMock.checkForUpdates.mockImplementation(() => {
       autoUpdaterMock.emit('checking-for-update')
diff --git a/src/main/updater.ts b/src/main/updater.ts
index a1373af8a..34067e03b 100644
--- a/src/main/updater.ts
+++ b/src/main/updater.ts
@@ -44,6 +44,7 @@ import {
   hasServeUpdateSupervisor,
   requestServeUpdateHandoff
 } from './serve-update-handoff'
+import type { LocalBuildFeed } from './local-builds/local-build-feed-server'
 
 type CheckFailureSource = 'event' | 'promise' | 'fallback-promise'
 type MissingManifestPrereleaseFallbackResult = { userInitiated: boolean }
@@ -128,6 +129,9 @@ let downloadInFlight = false
 /** Guards the macOS `activate` handler from reopening the old version while ShipIt replaces the .app bundle. */
 let quittingForUpdate = false
 let autoUpdater: ElectronAutoUpdater | null = null
+let activeUpdateSource: 'release' | 'local' = 'release'
+let activeLocalBuildFeed: LocalBuildFeed | null = null
+let localBuildSelectionInProgress = false
 
 function getAutoUpdater(): ElectronAutoUpdater {
   if (!autoUpdater) {
@@ -141,6 +145,36 @@ function clearAvailableUpdateContext(): void {
   availableReleaseUrl = null
 }
 
+function closeLocalBuildFeed(): void {
+  const feed = activeLocalBuildFeed
+  activeLocalBuildFeed = null
+  if (feed) {
+    void feed.close()
+  }
+}
+
+function restoreReleaseUpdateSource(): void {
+  closeLocalBuildFeed()
+  activeUpdateSource = 'release'
+  if (autoUpdater) {
+    autoUpdater.allowDowngrade = false
+    autoUpdater.disableDifferentialDownload = false
+  }
+}
+
+function sendLocalBuildErrorAndRestore(message: string, userInitiated?: boolean): void {
+  clearAvailableUpdateContext()
+  if (
+    currentStatus.state !== 'error' ||
+    currentStatus.message !== message ||
+    currentStatus.userInitiated !== userInitiated ||
+    currentStatus.source !== 'local'
+  ) {
+    sendStatus({ state: 'error', message, userInitiated, source: 'local' })
+  }
+  restoreReleaseUpdateSource()
+}
+
 function clearPrereleaseFallbackContext(): void {
   pendingPrereleaseFallback = null
 }
@@ -219,7 +253,9 @@ function sendStatus(status: UpdateStatus): void {
     }
   }
 
-  const decoratedStatus = decorateStatusWithActiveNudge(status)
+  const sourcedStatus: UpdateStatus =
+    activeUpdateSource === 'local' ? { ...status, source: 'local' } : status
+  const decoratedStatus = decorateStatusWithActiveNudge(sourcedStatus)
 
   if (isUpdateCheckResultState(status.state)) {
     finishActiveUpdateCheckAttempt()
@@ -523,8 +559,11 @@ function getKnownReleaseUrl(): string | undefined {
   return availableReleaseUrl ?? undefined
 }
 
-function hasNewerDownloadedVersion(): boolean {
-  return availableVersion !== null && compareVersions(availableVersion, app.getVersion()) > 0
+function hasInstallableDownloadedVersion(): boolean {
+  return (
+    availableVersion !== null &&
+    (activeUpdateSource === 'local' || compareVersions(availableVersion, app.getVersion()) > 0)
+  )
 }
 
 function getPendingInstallVersion(): string {
@@ -769,6 +808,10 @@ async function sendCheckFailureStatus(
   source: CheckFailureSource = 'promise',
   sourceError?: unknown
 ): Promise<void> {
+  if (activeUpdateSource === 'local') {
+    sendLocalBuildErrorAndRestore(message, userInitiated)
+    return
+  }
   const failureKey = getCheckFailureKey(message, userInitiated)
   if (
     source === 'promise' &&
@@ -1172,6 +1215,9 @@ function retryPrereleaseFallbackAfterMissingManifest(
 function runBackgroundUpdateCheck(
   nudgeId: string | null = getPersistedPendingUpdateNudgeId()
 ): void {
+  if (activeUpdateSource === 'local' || localBuildSelectionInProgress) {
+    return
+  }
   if (backgroundCheckLaunchPending || currentStatus.state === 'checking') {
     return
   }
@@ -1238,6 +1284,20 @@ export function checkForUpdatesFromMenu(options?: UpdateCheckOptions): void {
     sendStatus({ state: 'not-available', userInitiated: true })
     return
   }
+  if (options?.localBuild) {
+    void checkForLocalBuildFromMenu()
+    return
+  }
+  if (localBuildSelectionInProgress) {
+    return
+  }
+  if (
+    activeUpdateSource === 'local' &&
+    (currentStatus.state === 'checking' || currentStatus.state === 'downloading')
+  ) {
+    return
+  }
+  restoreReleaseUpdateSource()
 
   const checkVariant = getUpdateCheckVariant(options)
   if (checkVariant === 'prerelease') {
@@ -1303,12 +1363,63 @@ export function checkForUpdatesFromMenu(options?: UpdateCheckOptions): void {
     })
 }
 
+async function checkForLocalBuildFromMenu(): Promise<void> {
+  if (process.platform !== 'darwin') {
+    sendLocalBuildErrorAndRestore(
+      'Local build switching is currently available only on macOS.',
+      true
+    )
+    return
+  }
+  if (currentStatus.state === 'checking' || currentStatus.state === 'downloading') {
+    return
+  }
+  if (localBuildSelectionInProgress) {
+    return
+  }
+  localBuildSelectionInProgress = true
+  try {
+    const [{ chooseLocalBuild }, { startLocalBuildFeed }] = await Promise.all([
+      import('./local-builds/local-build-switch'),
+      import('./local-builds/local-build-feed-server')
+    ])
+    const candidate = await chooseLocalBuild(mainWindowRef)
+    if (!candidate) {
+      return
+    }
+    closeLocalBuildFeed()
+    const feed = await startLocalBuildFeed(candidate)
+    activeLocalBuildFeed = feed
+    activeUpdateSource = 'local'
+    clearPrereleaseFallbackContext()
+    clearPublishingWindowLastGoodCheck()
+    clearAvailableUpdateContext()
+    activeUpdateNudgeId = null
+    userInitiatedCheck = true
+    sendStatus({ state: 'checking', userInitiated: true })
+
+    const updater = getAutoUpdater()
+    updater.allowDowngrade = true
+    updater.disableDifferentialDownload = true
+    updater.setFeedURL({ provider: 'generic', url: feed.url })
+    const attemptId = beginUpdateCheckAttempt()
+    markUpdateCheckLaunched(attemptId)
+    await updater.checkForUpdates()
+    handleSettledUpdateCheckPromise(attemptId)
+  } catch (error) {
+    userInitiatedCheck = false
+    sendLocalBuildErrorAndRestore(String((error as Error)?.message ?? error), true)
+  } finally {
+    localBuildSelectionInProgress = false
+  }
+}
+
 export function isQuittingForUpdate(): boolean {
   return quittingForUpdate
 }
 
 export function quitAndInstall(): void {
-  if (pendingQuitAndInstallTimer || quitAndInstallInProgress) {
+  if (localBuildSelectionInProgress || pendingQuitAndInstallTimer || quitAndInstallInProgress) {
     return
   }
 
@@ -1319,7 +1430,7 @@ export function quitAndInstall(): void {
   if (
     deferMacQuitUntilInstallerReady(
       currentStatus,
-      hasNewerDownloadedVersion(),
+      hasInstallableDownloadedVersion(),
       getPendingInstallVersion,
       sendStatus
     )
@@ -1441,6 +1552,10 @@ export function setupAutoUpdater(
 
   const autoUpdater = getAutoUpdater()
   autoUpdater.autoDownload = false
+  if (activeUpdateSource === 'release') {
+    autoUpdater.allowDowngrade = false
+    autoUpdater.disableDifferentialDownload = false
+  }
   // Why: supervised serve installs require an explicit handoff; ordinary service quits must never install implicitly.
   autoUpdater.autoInstallOnAppQuit = updateInstallMode === 'interactive'
   // Why: MacUpdater ignores quitAndInstall arguments; the surviving CLI supervisor must be the only serve relaunch owner.
@@ -1457,10 +1572,12 @@ export function setupAutoUpdater(
   // Security: never re-add a verifyUpdateCodeSignature override — a no-op disables electron-updater's built-in Authenticode check and accepts any installer.
 
   // Why: generic provider avoids the native GitHub provider's RC-channel filtering; per-check repinning to a concrete /releases/download/<tag>/ URL avoids /latest redirect drift between check and download.
-  autoUpdater.setFeedURL({
-    provider: 'generic',
-    url: 'https://github.com/stablyai/orca/releases/latest/download'
-  })
+  if (activeUpdateSource === 'release') {
+    autoUpdater.setFeedURL({
+      provider: 'generic',
+      url: 'https://github.com/stablyai/orca/releases/latest/download'
+    })
+  }
 
   if (autoUpdaterInitialized) {
     return
@@ -1480,7 +1597,8 @@ export function setupAutoUpdater(
     getUserInitiatedCheck: () => userInitiatedCheck,
     handleQuitAndInstallFailure,
     isQuitAndInstallHandoffActive,
-    hasNewerDownloadedVersion,
+    hasInstallableDownloadedVersion,
+    isLocalBuildCheck: () => activeUpdateSource === 'local',
     shouldHandleUpdaterErrorEvent,
     performQuitAndInstall,
     clearUpdateAvailableEventPending,
@@ -1494,6 +1612,7 @@ export function setupAutoUpdater(
     shouldSuppressMissingManifestPrereleaseFallbackEvent,
     suppressMissingManifestPrereleaseFallbackPromiseFailure,
     recordCompletedUpdateCheck,
+    restoreReleaseUpdateSource,
     sendStatus,
     scheduleAutomaticUpdateCheck,
     clearBackgroundCheckLaunchPending,
@@ -1544,13 +1663,13 @@ export function setupAutoUpdater(
 }
 
 export function downloadUpdate(): void {
-  if (downloadInFlight) {
+  if (localBuildSelectionInProgress || downloadInFlight) {
     return
   }
   // Why: allow retry from 'error' (availableVersion stays cached) so the error card's Retry Download button works.
   const canStart =
     currentStatus.state === 'available' ||
-    (currentStatus.state === 'error' && hasNewerDownloadedVersion())
+    (currentStatus.state === 'error' && hasInstallableDownloadedVersion())
   if (!canStart) {
     return
   }
@@ -1562,6 +1681,7 @@ export function downloadUpdate(): void {
     return
   }
   downloadInFlight = true
+  const localBuildDownload = activeUpdateSource === 'local'
   beginMacUpdateDownload()
   // Why: setup can take seconds before progress emits; surface acceptance now so the action never looks inert.
   sendStatus({ state: 'downloading', percent: 0, version })
@@ -1569,6 +1689,11 @@ export function downloadUpdate(): void {
     .downloadUpdate()
     .catch((err) => {
       downloadInFlight = false
-      sendErrorStatus(String(err?.message ?? err))
+      const message = String(err?.message ?? err)
+      if (localBuildDownload) {
+        sendLocalBuildErrorAndRestore(message)
+      } else {
+        sendErrorStatus(message)
+      }
     })
 }
diff --git a/src/renderer/src/components/UpdateCard.error-card.test.tsx b/src/renderer/src/components/UpdateCard.error-card.test.tsx
index cbe84536b..e440729f2 100644
--- a/src/renderer/src/components/UpdateCard.error-card.test.tsx
+++ b/src/renderer/src/components/UpdateCard.error-card.test.tsx
@@ -6,6 +6,7 @@ import { UpdateCard } from './UpdateCard'
 
 const openUrl = vi.fn()
 const download = vi.fn()
+const check = vi.fn()
 
 function renderAfterAvailableStatus(): void {
   useAppStore.setState({
@@ -26,6 +27,7 @@ beforeEach(() => {
   useAppStore.setState(useAppStore.getInitialState(), true)
   openUrl.mockReset()
   download.mockReset()
+  check.mockReset()
   Object.defineProperty(window, 'api', {
     configurable: true,
     value: {
@@ -34,7 +36,7 @@ beforeEach(() => {
       shell: { openUrl },
       ui: { set: vi.fn().mockResolvedValue(undefined) },
       updater: {
-        check: vi.fn(),
+        check,
         dismissNudge: vi.fn(),
         download,
         quitAndInstall: vi.fn().mockResolvedValue(undefined)
@@ -94,3 +96,37 @@ describe('UpdateCard Windows signature failures', () => {
     )
   })
 })
+
+describe('UpdateCard local builds', () => {
+  it('does not link local versions to GitHub release downloads', () => {
+    useAppStore.setState({
+      updateStatus: {
+        state: 'available',
+        version: '1.4.100-local.1.abc',
+        changelog: null,
+        source: 'local'
+      },
+      updateChangelog: null,
+      dismissedUpdateVersion: null,
+      updateCardCollapsed: false,
+      updateReassuranceSeen: true
+    })
+    render(<UpdateCard />)
+
+    expect(screen.queryByText('Release notes')).toBeNull()
+    fireEvent.click(screen.getByRole('button', { name: 'Update' }))
+    expect(download).toHaveBeenCalledTimes(1)
+
+    act(() =>
+      useAppStore.getState().setUpdateStatus({
+        state: 'error',
+        message: 'signature rejected',
+        source: 'local'
+      })
+    )
+    expect(screen.getByText('Local Build Error')).toBeTruthy()
+    expect(screen.queryByRole('button', { name: 'Download Manually' })).toBeNull()
+    fireEvent.click(screen.getByRole('button', { name: 'Choose Another Build' }))
+    expect(check).toHaveBeenCalledWith({ localBuild: true })
+  })
+})
diff --git a/src/renderer/src/components/UpdateCard.tsx b/src/renderer/src/components/UpdateCard.tsx
index 0612c91fd..1e04d8df2 100644
--- a/src/renderer/src/components/UpdateCard.tsx
+++ b/src/renderer/src/components/UpdateCard.tsx
@@ -53,7 +53,7 @@ type ErrorCardModel = {
   explainer?: string
   /** Raw error text, shown only when the user expands "Show details". */
   detail?: string
-  releaseUrl: string
+  releaseUrl?: string
   /** Overrides the secondary button label (defaults to "Download Manually"). */
   manualLabel?: string
   primaryAction?: {
@@ -137,6 +137,7 @@ export function UpdateCard() {
   // Tracks card exit so the fade-out animation plays before unmount.
   const [exiting, setExiting] = useState(false)
   const changelog: ChangelogData | null = storeChangelog
+  const isLocalBuild = status.source === 'local'
 
   // Why: the 'error' variant carries no version, but the card needs it for the fallback URL and dismiss; cache from states that have it.
   const versionRef = useRef<string | null>(null)
@@ -324,79 +325,104 @@ export function UpdateCard() {
     status.state === 'error' && isWindowsSignatureCheckUnavailableFailure(status.message)
   const errorCard: ErrorCardModel | null =
     status.state === 'error'
-      ? isHttp2UpdateError
+      ? isLocalBuild
         ? {
-            variant: 'http1Compatibility',
-            title: translate('auto.components.UpdateCard.1339b82cee', 'HTTP/2 Download Blocked'),
-            summary: 'Orca can retry through HTTP/1.1 compatibility mode.',
-            explainer: translate(
-              'auto.components.UpdateCard.90559b14e3',
-              'This turns on a process-wide Electron networking switch after restart. Use it for corporate VPNs or proxies that reject HTTP/2 update downloads.'
-            ),
-            detail: compatibilitySetupError ?? status.message,
-            releaseUrl: releaseUrlForVersion(cachedVersion),
+            title: cachedVersion
+              ? translate('auto.components.UpdateCard.8cf17b10af', 'Local Build Error')
+              : translate('auto.components.UpdateCard.a4650b0dc4', 'Could Not Use Local Build'),
+            summary: cachedVersion
+              ? translate(
+                  'auto.components.UpdateCard.b1e390250d',
+                  'Could not complete the local build switch.'
+                )
+              : translate(
+                  'auto.components.UpdateCard.d29740d175',
+                  'The selected build could not be used.'
+                ),
+            detail: status.message,
             primaryAction: {
-              label: translate('auto.components.UpdateCard.933c6fdf5b', 'Enable & Restart'),
-              pendingLabel: 'Restarting...',
-              isPending: compatibilityRelaunching,
-              onClick: handleEnableHttp1Compatibility
+              label: translate('auto.components.UpdateCard.37d45c9ec1', 'Choose Another Build'),
+              onClick: () => {
+                void window.api.updater.check({ localBuild: true })
+              }
             }
           }
-        : isSignatureMismatchError
+        : isHttp2UpdateError
           ? {
-              // Security stop: installer signed by the wrong publisher — no retry, only a verified-download path.
-              variant: 'security',
-              title: translate('auto.components.UpdateCard.5b309b19f3', "Update Wasn't Installed"),
-              summary: translate(
-                'auto.components.UpdateCard.092f09fc14',
-                "The installer's publisher doesn't match Orca, so we stopped the update. Don't install this download; check official releases for a corrected version."
+              variant: 'http1Compatibility',
+              title: translate('auto.components.UpdateCard.1339b82cee', 'HTTP/2 Download Blocked'),
+              summary: 'Orca can retry through HTTP/1.1 compatibility mode.',
+              explainer: translate(
+                'auto.components.UpdateCard.90559b14e3',
+                'This turns on a process-wide Electron networking switch after restart. Use it for corporate VPNs or proxies that reject HTTP/2 update downloads.'
               ),
-              detail: status.message,
-              // Why: linking the rejected version would let users bypass the publisher check by re-running it.
-              releaseUrl: releaseUrlForVersion(null),
-              manualLabel: translate(
-                'auto.components.UpdateCard.c9ff9b9ec2',
-                'Check official releases'
-              )
+              detail: compatibilitySetupError ?? status.message,
+              releaseUrl: releaseUrlForVersion(cachedVersion),
+              primaryAction: {
+                label: translate('auto.components.UpdateCard.933c6fdf5b', 'Enable & Restart'),
+                pendingLabel: 'Restarting...',
+                isPending: compatibilityRelaunching,
+                onClick: handleEnableHttp1Compatibility
+              }
             }
-          : isSignatureCheckBlockedError
+          : isSignatureMismatchError
             ? {
+                // Security stop: installer signed by the wrong publisher — no retry, only a verified-download path.
+                variant: 'security',
                 title: translate(
-                  'auto.components.UpdateCard.e944c2de43',
-                  'Update Verification Blocked'
+                  'auto.components.UpdateCard.5b309b19f3',
+                  "Update Wasn't Installed"
                 ),
                 summary: translate(
-                  'auto.components.UpdateCard.a05992a26b',
-                  "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases."
+                  'auto.components.UpdateCard.092f09fc14',
+                  "The installer's publisher doesn't match Orca, so we stopped the update. Don't install this download; check official releases for a corrected version."
                 ),
                 detail: status.message,
-                releaseUrl: releaseUrlForVersion(cachedVersion),
-                primaryAction: {
-                  label: translate('auto.components.UpdateCard.48565a32bc', 'Retry Download'),
-                  onClick: handleUpdate
+                // Why: linking the rejected version would let users bypass the publisher check by re-running it.
+                releaseUrl: releaseUrlForVersion(null),
+                manualLabel: translate(
+                  'auto.components.UpdateCard.c9ff9b9ec2',
+                  'Check official releases'
+                )
+              }
+            : isSignatureCheckBlockedError
+              ? {
+                  title: translate(
+                    'auto.components.UpdateCard.e944c2de43',
+                    'Update Verification Blocked'
+                  ),
+                  summary: translate(
+                    'auto.components.UpdateCard.a05992a26b',
+                    "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases."
+                  ),
+                  detail: status.message,
+                  releaseUrl: releaseUrlForVersion(cachedVersion),
+                  primaryAction: {
+                    label: translate('auto.components.UpdateCard.48565a32bc', 'Retry Download'),
+                    onClick: handleUpdate
+                  }
                 }
-              }
-            : {
-                // Why: title is scoped to the failed operation so check-time (GitHub-side) failures don't read as an Orca bug.
-                title: cachedVersion ? 'Update Error' : 'Update Check Failed',
-                summary: cachedVersion
-                  ? 'Could not complete the update.'
-                  : 'Could not check for updates.',
-                detail: status.message,
-                releaseUrl: releaseUrlForVersion(cachedVersion),
-                // Why: check-time failures are often transient, so offer a Re-check instead of forcing manual download.
-                primaryAction: cachedVersion
-                  ? {
-                      label: translate('auto.components.UpdateCard.48565a32bc', 'Retry Download'),
-                      onClick: handleUpdate
-                    }
-                  : {
-                      label: translate('auto.components.UpdateCard.6b0085010d', 'Re-check'),
-                      onClick: () => {
-                        void window.api.updater.check({ includePrerelease: false })
+              : {
+                  // Why: title is scoped to the failed operation so check-time (GitHub-side) failures don't read as an Orca bug.
+                  title: cachedVersion ? 'Update Error' : 'Update Check Failed',
+                  summary: cachedVersion
+                    ? 'Could not complete the update.'
+                    : 'Could not check for updates.',
+                  detail: status.message,
+                  releaseUrl: releaseUrlForVersion(cachedVersion),
+                  // Why: check-time failures are often transient, so offer a Re-check instead of forcing manual download.
+                  primaryAction: cachedVersion
+                    ? {
+                        label: translate('auto.components.UpdateCard.48565a32bc', 'Retry Download'),
+                        onClick: handleUpdate
                       }
-                    }
-              }
+                    : {
+                        label: translate('auto.components.UpdateCard.6b0085010d', 'Re-check'),
+                        onClick: () => {
+                          void window.api.updater.check({ includePrerelease: false })
+                        }
+                      }
+                }
       : installError
         ? {
             title: translate('auto.components.UpdateCard.4cf109845a', 'Update Error'),
@@ -558,6 +584,7 @@ export function UpdateCard() {
           onMediaError={() => setMediaFailed(true)}
           onMediaLoad={() => setMediaLoaded(true)}
           onCollapse={handleCollapseWithAnimation}
+          showReleaseNotes={!isLocalBuild}
         />
       )
     }
@@ -568,9 +595,10 @@ export function UpdateCard() {
       return null
     }
 
-    const releaseUrl =
-      ('releaseUrl' in status ? status.releaseUrl : undefined) ??
-      releaseUrlForVersion(status.version)
+    const releaseUrl = isLocalBuild
+      ? undefined
+      : (('releaseUrl' in status ? status.releaseUrl : undefined) ??
+        releaseUrlForVersion(status.version))
 
     if (isRichMode && changelog) {
       return (
@@ -750,7 +778,7 @@ function SimpleCardContent({
   onClose
 }: {
   version: string
-  releaseUrl: string
+  releaseUrl?: string
   onUpdate: () => void
   onClose: () => void
 }) {
@@ -781,12 +809,14 @@ function SimpleCardContent({
         {translate('auto.components.UpdateCard.fdd4a364fa', "Sessions won't be interrupted.")}
       </p>
 
-      <button
-        className="text-xs text-muted-foreground underline underline-offset-2 hover:text-foreground self-start"
-        onClick={() => void window.api.shell.openUrl(releaseUrl)}
-      >
-        {translate('auto.components.UpdateCard.44324ef542', 'Release notes')}
-      </button>
+      {releaseUrl && (
+        <button
+          className="text-xs text-muted-foreground underline underline-offset-2 hover:text-foreground self-start"
+          onClick={() => void window.api.shell.openUrl(releaseUrl)}
+        >
+          {translate('auto.components.UpdateCard.44324ef542', 'Release notes')}
+        </button>
+      )}
 
       <Button
         variant="default"
@@ -811,7 +841,8 @@ function DownloadingContent({
   mediaLoaded,
   onMediaError,
   onMediaLoad,
-  onCollapse
+  onCollapse,
+  showReleaseNotes
 }: {
   version: string
   percent: number
@@ -822,6 +853,7 @@ function DownloadingContent({
   onMediaError: () => void
   onMediaLoad: () => void
   onCollapse: () => void
+  showReleaseNotes: boolean
 }) {
   const release = changelog?.release
   const showMedia =
@@ -877,18 +909,20 @@ function DownloadingContent({
             })}
       </p>
 
-      <button
-        className="text-xs text-muted-foreground underline hover:text-foreground self-start"
-        onClick={() =>
-          void window.api.shell.openUrl(
-            release ? release.releaseNotesUrl : releaseUrlForVersion(version)
-          )
-        }
-      >
-        {release
-          ? translate('auto.components.UpdateCard.aad383aecc', 'Read the full release notes')
-          : translate('auto.components.UpdateCard.44324ef542', 'Release notes')}
-      </button>
+      {showReleaseNotes && (
+        <button
+          className="text-xs text-muted-foreground underline hover:text-foreground self-start"
+          onClick={() =>
+            void window.api.shell.openUrl(
+              release ? release.releaseNotesUrl : releaseUrlForVersion(version)
+            )
+          }
+        >
+          {release
+            ? translate('auto.components.UpdateCard.aad383aecc', 'Read the full release notes')
+            : translate('auto.components.UpdateCard.44324ef542', 'Release notes')}
+        </button>
+      )}
 
       <div className="flex flex-col gap-2 mt-1">
         <Progress value={percent} className="h-1.5" />
@@ -918,7 +952,7 @@ function ErrorCardContent({
   summary: string
   explainer?: string
   detail?: string
-  releaseUrl: string
+  releaseUrl?: string
   manualLabel?: string
   primaryAction?: {
     label: string
@@ -1018,14 +1052,16 @@ function ErrorCardContent({
               : primaryAction.label}
           </Button>
         )}
-        <Button
-          variant="outline"
-          size="sm"
-          onClick={() => void window.api.shell.openUrl(releaseUrl)}
-          className="flex-1"
-        >
-          {manualLabel ?? translate('auto.components.UpdateCard.47126bcf57', 'Download Manually')}
-        </Button>
+        {releaseUrl && (
+          <Button
+            variant="outline"
+            size="sm"
+            onClick={() => void window.api.shell.openUrl(releaseUrl)}
+            className="flex-1"
+          >
+            {manualLabel ?? translate('auto.components.UpdateCard.47126bcf57', 'Download Manually')}
+          </Button>
+        )}
       </div>
     </div>
   )
diff --git a/src/renderer/src/components/settings/GeneralUpdateSettingsSection.tsx b/src/renderer/src/components/settings/GeneralUpdateSettingsSection.tsx
index 0e4b16752..b9e6635f3 100644
--- a/src/renderer/src/components/settings/GeneralUpdateSettingsSection.tsx
+++ b/src/renderer/src/components/settings/GeneralUpdateSettingsSection.tsx
@@ -168,20 +168,22 @@ export function GeneralUpdateSettingsSection(): React.JSX.Element {
                 'auto.components.settings.GeneralUpdateSettingsSection.8311da27ba',
                 'is available. Click "Install Update" to download and install it.'
               )}{' '}
-              <a
-                href={
-                  updateStatus.releaseUrl ??
-                  `https://github.com/stablyai/orca/releases/tag/v${updateStatus.version}`
-                }
-                target="_blank"
-                rel="noopener noreferrer"
-                className="underline hover:text-foreground"
-              >
-                {translate(
-                  'auto.components.settings.GeneralUpdateSettingsSection.8a52ca1d02',
-                  'Release notes'
-                )}
-              </a>
+              {updateStatus.source !== 'local' && (
+                <a
+                  href={
+                    updateStatus.releaseUrl ??
+                    `https://github.com/stablyai/orca/releases/tag/v${updateStatus.version}`
+                  }
+                  target="_blank"
+                  rel="noopener noreferrer"
+                  className="underline hover:text-foreground"
+                >
+                  {translate(
+                    'auto.components.settings.GeneralUpdateSettingsSection.8a52ca1d02',
+                    'Release notes'
+                  )}
+                </a>
+              )}
             </>
           )}
           {updateStatus.state === 'not-available' &&
@@ -206,20 +208,22 @@ export function GeneralUpdateSettingsSection(): React.JSX.Element {
                 'auto.components.settings.GeneralUpdateSettingsSection.d89806cc89',
                 'is ready to install.'
               )}{' '}
-              <a
-                href={
-                  updateStatus.releaseUrl ??
-                  `https://github.com/stablyai/orca/releases/tag/v${updateStatus.version}`
-                }
-                target="_blank"
-                rel="noopener noreferrer"
-                className="underline hover:text-foreground"
-              >
-                {translate(
-                  'auto.components.settings.GeneralUpdateSettingsSection.8a52ca1d02',
-                  'Release notes'
-                )}
-              </a>
+              {updateStatus.source !== 'local' && (
+                <a
+                  href={
+                    updateStatus.releaseUrl ??
+                    `https://github.com/stablyai/orca/releases/tag/v${updateStatus.version}`
+                  }
+                  target="_blank"
+                  rel="noopener noreferrer"
+                  className="underline hover:text-foreground"
+                >
+                  {translate(
+                    'auto.components.settings.GeneralUpdateSettingsSection.8a52ca1d02',
+                    'Release notes'
+                  )}
+                </a>
+              )}
             </>
           )}
           {updateStatus.state === 'error' &&
diff --git a/src/renderer/src/components/sidebar/SidebarSettingsHelpMenu.tsx b/src/renderer/src/components/sidebar/SidebarSettingsHelpMenu.tsx
index 1c6e282be..9fee62dde 100644
--- a/src/renderer/src/components/sidebar/SidebarSettingsHelpMenu.tsx
+++ b/src/renderer/src/components/sidebar/SidebarSettingsHelpMenu.tsx
@@ -40,7 +40,12 @@ const CHANGELOG_URL = 'https://onorca.dev/changelog'
 const GITHUB_URL = 'https://github.com/stablyai/orca'
 const DISCORD_URL = 'https://discord.gg/fzjDKHxv8Q'
 const X_URL = 'https://x.com/orca_build'
-const NO_UPDATE_CHECK_MODIFIERS = { ctrlKey: false, metaKey: false, shiftKey: false }
+const NO_UPDATE_CHECK_MODIFIERS = {
+  altKey: false,
+  ctrlKey: false,
+  metaKey: false,
+  shiftKey: false
+}
 
 function openExternalUrl(url: string): void {
   void window.api.shell.openUrl(url)
@@ -154,6 +159,7 @@ export function SidebarSettingsHelpMenu(): React.JSX.Element {
 
   const handleCheckForUpdatesPointerDown = (event: React.PointerEvent): void => {
     updateCheckModifiersRef.current = {
+      altKey: event.altKey,
       ctrlKey: event.ctrlKey,
       metaKey: event.metaKey,
       shiftKey: event.shiftKey
diff --git a/src/renderer/src/i18n/locales/en.json b/src/renderer/src/i18n/locales/en.json
index f5cf363fb..44b4124a0 100644
--- a/src/renderer/src/i18n/locales/en.json
+++ b/src/renderer/src/i18n/locales/en.json
@@ -1900,7 +1900,12 @@
         "c9ff9b9ec2": "Check official releases",
         "a05992a26b": "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases.",
         "5194358929": "Hide details",
-        "8bc9e17d8f": "Show details"
+        "8bc9e17d8f": "Show details",
+        "8cf17b10af": "Local Build Error",
+        "a4650b0dc4": "Could Not Use Local Build",
+        "b1e390250d": "Could not complete the local build switch.",
+        "d29740d175": "The selected build could not be used.",
+        "37d45c9ec1": "Choose Another Build"
       },
       "WorktreeJumpPalette": {
         "ac037cfac2": "Move",
diff --git a/src/renderer/src/i18n/locales/es.json b/src/renderer/src/i18n/locales/es.json
index e8158d266..8e6783cf3 100644
--- a/src/renderer/src/i18n/locales/es.json
+++ b/src/renderer/src/i18n/locales/es.json
@@ -1877,7 +1877,12 @@
         "c9ff9b9ec2": "Check official releases",
         "a05992a26b": "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases.",
         "5194358929": "Hide details",
-        "8bc9e17d8f": "Show details"
+        "8bc9e17d8f": "Show details",
+        "8cf17b10af": "Local Build Error",
+        "a4650b0dc4": "Could Not Use Local Build",
+        "b1e390250d": "Could not complete the local build switch.",
+        "d29740d175": "The selected build could not be used.",
+        "37d45c9ec1": "Choose Another Build"
       },
       "WorktreeJumpPalette": {
         "ac037cfac2": "Mover",
diff --git a/src/renderer/src/i18n/locales/ja.json b/src/renderer/src/i18n/locales/ja.json
index 26922f91d..1448421ca 100644
--- a/src/renderer/src/i18n/locales/ja.json
+++ b/src/renderer/src/i18n/locales/ja.json
@@ -1877,7 +1877,12 @@
         "c9ff9b9ec2": "Check official releases",
         "a05992a26b": "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases.",
         "5194358929": "Hide details",
-        "8bc9e17d8f": "Show details"
+        "8bc9e17d8f": "Show details",
+        "8cf17b10af": "Local Build Error",
+        "a4650b0dc4": "Could Not Use Local Build",
+        "b1e390250d": "Could not complete the local build switch.",
+        "d29740d175": "The selected build could not be used.",
+        "37d45c9ec1": "Choose Another Build"
       },
       "WorktreeJumpPalette": {
         "ac037cfac2": "移動",
diff --git a/src/renderer/src/i18n/locales/ko.json b/src/renderer/src/i18n/locales/ko.json
index e80c196ab..22a54ebb5 100644
--- a/src/renderer/src/i18n/locales/ko.json
+++ b/src/renderer/src/i18n/locales/ko.json
@@ -1877,7 +1877,12 @@
         "c9ff9b9ec2": "Check official releases",
         "a05992a26b": "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases.",
         "5194358929": "Hide details",
-        "8bc9e17d8f": "Show details"
+        "8bc9e17d8f": "Show details",
+        "8cf17b10af": "Local Build Error",
+        "a4650b0dc4": "Could Not Use Local Build",
+        "b1e390250d": "Could not complete the local build switch.",
+        "d29740d175": "The selected build could not be used.",
+        "37d45c9ec1": "Choose Another Build"
       },
       "WorktreeJumpPalette": {
         "ac037cfac2": "이동",
diff --git a/src/renderer/src/i18n/locales/zh.json b/src/renderer/src/i18n/locales/zh.json
index b88d6bf99..390037d42 100644
--- a/src/renderer/src/i18n/locales/zh.json
+++ b/src/renderer/src/i18n/locales/zh.json
@@ -1877,7 +1877,12 @@
         "c9ff9b9ec2": "Check official releases",
         "a05992a26b": "The signature check couldn't run — usually because antivirus software blocked it. Retry the download, or get the installer from our official releases.",
         "5194358929": "Hide details",
-        "8bc9e17d8f": "Show details"
+        "8bc9e17d8f": "Show details",
+        "8cf17b10af": "Local Build Error",
+        "a4650b0dc4": "Could Not Use Local Build",
+        "b1e390250d": "Could not complete the local build switch.",
+        "d29740d175": "The selected build could not be used.",
+        "37d45c9ec1": "Choose Another Build"
       },
       "WorktreeJumpPalette": {
         "ac037cfac2": "移动",
diff --git a/src/renderer/src/lib/update-check-click-options.test.ts b/src/renderer/src/lib/update-check-click-options.test.ts
index 02f664013..3bb19ea15 100644
--- a/src/renderer/src/lib/update-check-click-options.test.ts
+++ b/src/renderer/src/lib/update-check-click-options.test.ts
@@ -1,13 +1,16 @@
 import { describe, expect, it } from 'vitest'
 import { getUpdateCheckClickOptions, getUpdateCheckHint } from './update-check-click-options'
 
-function clickEvent(overrides: Partial<Pick<MouseEvent, 'ctrlKey' | 'metaKey' | 'shiftKey'>>) {
+function clickEvent(
+  overrides: Partial<Pick<MouseEvent, 'altKey' | 'ctrlKey' | 'metaKey' | 'shiftKey'>>
+) {
   return {
+    altKey: false,
     ctrlKey: false,
     metaKey: false,
     shiftKey: false,
     ...overrides
-  } as Pick<MouseEvent, 'ctrlKey' | 'metaKey' | 'shiftKey'>
+  } as Pick<MouseEvent, 'altKey' | 'ctrlKey' | 'metaKey' | 'shiftKey'>
 }
 
 describe('getUpdateCheckClickOptions', () => {
@@ -42,9 +45,19 @@ describe('getUpdateCheckClickOptions', () => {
     })
   })
 
+  it('gives local build selection precedence over release channel modifiers', () => {
+    expect(
+      getUpdateCheckClickOptions(clickEvent({ altKey: true, shiftKey: true, metaKey: true }), true)
+    ).toEqual({ localBuild: true })
+    expect(getUpdateCheckClickOptions(clickEvent({ altKey: true }), false)).toEqual({
+      includePrerelease: false,
+      includePerfPrerelease: false
+    })
+  })
+
   it('formats the tooltip hint by platform', () => {
     expect(getUpdateCheckHint(true)).toBe(
-      '⇧+click checks the latest RC; ⌘+click checks the latest perf build.'
+      '⇧+click checks the latest RC; ⌘+click checks the latest perf build. ⌥+click chooses a local macOS build.'
     )
     expect(getUpdateCheckHint(false)).toBe(
       'Shift+click checks the latest RC; Ctrl+click checks the latest perf build.'
diff --git a/src/renderer/src/lib/update-check-click-options.ts b/src/renderer/src/lib/update-check-click-options.ts
index 2ee4191c3..1734c4f19 100644
--- a/src/renderer/src/lib/update-check-click-options.ts
+++ b/src/renderer/src/lib/update-check-click-options.ts
@@ -1,7 +1,7 @@
 import type { UpdateCheckOptions } from '../../../shared/types'
 import { getShortcutPlatform } from './shortcut-platform'
 
-type UpdateCheckClickEvent = Pick<MouseEvent, 'ctrlKey' | 'metaKey' | 'shiftKey'>
+type UpdateCheckClickEvent = Pick<MouseEvent, 'altKey' | 'ctrlKey' | 'metaKey' | 'shiftKey'>
 
 function isMacShortcutPlatform(): boolean {
   return getShortcutPlatform() === 'darwin'
@@ -10,13 +10,17 @@ function isMacShortcutPlatform(): boolean {
 export function getUpdateCheckHint(isMac = isMacShortcutPlatform()): string {
   const rcClickLabel = isMac ? '⇧+click' : 'Shift+click'
   const perfClickLabel = isMac ? '⌘+click' : 'Ctrl+click'
-  return `${rcClickLabel} checks the latest RC; ${perfClickLabel} checks the latest perf build.`
+  const releaseHints = `${rcClickLabel} checks the latest RC; ${perfClickLabel} checks the latest perf build.`
+  return isMac ? `${releaseHints} ⌥+click chooses a local macOS build.` : releaseHints
 }
 
 export function getUpdateCheckClickOptions(
   event: UpdateCheckClickEvent,
   isMac = isMacShortcutPlatform()
 ): UpdateCheckOptions {
+  if (isMac && event.altKey) {
+    return { localBuild: true }
+  }
   return {
     includePrerelease: event.shiftKey,
     includePerfPrerelease: isMac ? event.metaKey : event.ctrlKey
diff --git a/src/shared/local-build-compatibility-contract.json b/src/shared/local-build-compatibility-contract.json
new file mode 100644
index 000000000..8c2bb743b
--- /dev/null
+++ b/src/shared/local-build-compatibility-contract.json
@@ -0,0 +1,11 @@
+{
+  "formatVersion": 1,
+  "appId": "com.stablyai.orca",
+  "stateSchemaVersion": 1,
+  "readableStateSchemaVersions": [1],
+  "daemonProtocolVersion": 28,
+  "attachableDaemonProtocolVersions": [
+    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
+    27, 28
+  ]
+}
diff --git a/src/shared/local-build-compatibility-contract.ts b/src/shared/local-build-compatibility-contract.ts
new file mode 100644
index 000000000..f05be487d
--- /dev/null
+++ b/src/shared/local-build-compatibility-contract.ts
@@ -0,0 +1,11 @@
+export const LOCAL_BUILD_COMPATIBILITY_CONTRACT = {
+  formatVersion: 1,
+  appId: 'com.stablyai.orca',
+  stateSchemaVersion: 1,
+  readableStateSchemaVersions: [1],
+  daemonProtocolVersion: 28,
+  attachableDaemonProtocolVersions: [
+    1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26,
+    27, 28
+  ]
+} as const
diff --git a/src/shared/local-build-compatibility.test.ts b/src/shared/local-build-compatibility.test.ts
new file mode 100644
index 000000000..45f9a21ae
--- /dev/null
+++ b/src/shared/local-build-compatibility.test.ts
@@ -0,0 +1,45 @@
+import { describe, expect, it } from 'vitest'
+import {
+  getLocalBuildCompatibilityError,
+  parseLocalBuildCompatibility,
+  type LocalBuildCompatibility
+} from './local-build-compatibility'
+
+function target(overrides: Partial<LocalBuildCompatibility> = {}): LocalBuildCompatibility {
+  return {
+    formatVersion: 1,
+    appId: 'com.stablyai.orca',
+    buildId: '1.2.3-abc-arm64',
+    version: '1.2.3-local.1.abc',
+    commit: 'abc',
+    stateSchemaVersion: 1,
+    readableStateSchemaVersions: [1],
+    daemonProtocolVersion: 28,
+    attachableDaemonProtocolVersions: [27, 28],
+    platform: 'darwin',
+    architecture: 'arm64',
+    ...overrides
+  }
+}
+
+describe('local build compatibility', () => {
+  it('rejects state and live-terminal protocol incompatibilities', () => {
+    expect(
+      getLocalBuildCompatibilityError(target({ readableStateSchemaVersions: [2] }), 1, [])
+    ).toContain('cannot read Orca workspace state schema')
+    expect(getLocalBuildCompatibilityError(target(), 1, [26])).toContain(
+      'cannot reconnect terminal daemon protocol 26'
+    )
+    expect(getLocalBuildCompatibilityError(target(), 1, [27, 28])).toBeNull()
+  })
+
+  it('parses only bounded Orca compatibility contracts', () => {
+    expect(parseLocalBuildCompatibility(target())).toEqual(target())
+    expect(() => parseLocalBuildCompatibility(target({ appId: 'other.app' }))).toThrow(
+      'invalid compatibility metadata'
+    )
+    expect(() =>
+      parseLocalBuildCompatibility(target({ attachableDaemonProtocolVersions: [] }))
+    ).toThrow('invalid compatibility metadata')
+  })
+})
diff --git a/src/shared/local-build-compatibility.ts b/src/shared/local-build-compatibility.ts
new file mode 100644
index 000000000..203ffe464
--- /dev/null
+++ b/src/shared/local-build-compatibility.ts
@@ -0,0 +1,90 @@
+import { LOCAL_BUILD_COMPATIBILITY_CONTRACT } from './local-build-compatibility-contract'
+
+export const LOCAL_BUILD_COMPATIBILITY_FILENAME = 'orca-local-build.json'
+export const LOCAL_BUILD_COMPATIBILITY_FORMAT_VERSION =
+  LOCAL_BUILD_COMPATIBILITY_CONTRACT.formatVersion
+export const ORCA_APP_ID = LOCAL_BUILD_COMPATIBILITY_CONTRACT.appId
+
+export type LocalBuildArchitecture = 'arm64' | 'x64'
+
+export type LocalBuildCompatibility = {
+  formatVersion: number
+  appId: string
+  buildId: string
+  version: string
+  commit: string
+  stateSchemaVersion: number
+  readableStateSchemaVersions: number[]
+  daemonProtocolVersion: number
+  attachableDaemonProtocolVersions: number[]
+  platform: 'darwin'
+  architecture: LocalBuildArchitecture
+}
+
+function isIntegerArray(value: unknown): value is number[] {
+  return (
+    Array.isArray(value) &&
+    value.length > 0 &&
+    value.length <= 64 &&
+    value.every((entry) => Number.isSafeInteger(entry) && entry > 0)
+  )
+}
+
+export function parseLocalBuildCompatibility(value: unknown): LocalBuildCompatibility {
+  if (!value || typeof value !== 'object' || Array.isArray(value)) {
+    throw new Error('The selected build has invalid compatibility metadata.')
+  }
+  const record = value as Record<string, unknown>
+  const architecture = record.architecture
+  if (
+    record.formatVersion !== LOCAL_BUILD_COMPATIBILITY_FORMAT_VERSION ||
+    record.appId !== ORCA_APP_ID ||
+    typeof record.buildId !== 'string' ||
+    record.buildId.length === 0 ||
+    record.buildId.length > 200 ||
+    typeof record.version !== 'string' ||
+    record.version.length === 0 ||
+    record.version.length > 100 ||
+    typeof record.commit !== 'string' ||
+    record.commit.length === 0 ||
+    record.commit.length > 100 ||
+    !Number.isSafeInteger(record.stateSchemaVersion) ||
+    Number(record.stateSchemaVersion) <= 0 ||
+    !isIntegerArray(record.readableStateSchemaVersions) ||
+    !Number.isSafeInteger(record.daemonProtocolVersion) ||
+    Number(record.daemonProtocolVersion) <= 0 ||
+    !isIntegerArray(record.attachableDaemonProtocolVersions) ||
+    record.platform !== 'darwin' ||
+    (architecture !== 'arm64' && architecture !== 'x64')
+  ) {
+    throw new Error('The selected build has invalid compatibility metadata.')
+  }
+  if (
+    !(record.readableStateSchemaVersions as number[]).includes(
+      record.stateSchemaVersion as number
+    ) ||
+    !(record.attachableDaemonProtocolVersions as number[]).includes(
+      record.daemonProtocolVersion as number
+    )
+  ) {
+    throw new Error('The selected build has inconsistent compatibility metadata.')
+  }
+  return record as LocalBuildCompatibility
+}
+
+export function getLocalBuildCompatibilityError(
+  target: LocalBuildCompatibility,
+  currentStateSchemaVersion: number,
+  liveDaemonProtocols: readonly number[]
+): string | null {
+  if (!target.readableStateSchemaVersions.includes(currentStateSchemaVersion)) {
+    return `This build cannot read Orca workspace state schema ${currentStateSchemaVersion}. Your workspace was not changed.`
+  }
+  const unsupportedProtocols = liveDaemonProtocols.filter(
+    (protocol) => !target.attachableDaemonProtocolVersions.includes(protocol)
+  )
+  if (unsupportedProtocols.length > 0) {
+    return `This build cannot reconnect terminal daemon protocol ${unsupportedProtocols.join(', ')}. Close those terminals or choose a compatible build.`
+  }
+  return null
+}
diff --git a/src/shared/types.ts b/src/shared/types.ts
index e34ed5bc2..cb63444b4 100644
--- a/src/shared/types.ts
+++ b/src/shared/types.ts
@@ -2340,9 +2340,12 @@ export type ChangelogData = {
 export type UpdateCheckOptions = {
   includePrerelease?: boolean
   includePerfPrerelease?: boolean
+  localBuild?: boolean
 }
 
-export type UpdateStatus =
+export type UpdateSource = 'local'
+
+export type UpdateStatus = (
   | { state: 'idle' }
   | { state: 'checking'; userInitiated?: boolean }
   | {
@@ -2365,6 +2368,7 @@ export type UpdateStatus =
   | { state: 'downloading'; percent: number; version: string; activeNudgeId?: string }
   | { state: 'downloaded'; version: string; releaseUrl?: string; activeNudgeId?: string }
   | { state: 'error'; message: string; userInitiated?: boolean; activeNudgeId?: string }
+) & { source?: UpdateSource }
 
 // ─── Settings ────────────────────────────────────────────────────────
 export type NotificationSettings = {