diff --git a/src/main/orcad/orcad-health.test.ts b/src/main/orcad/orcad-health.test.ts
index 70e02b37e87..f21ea22f92e 100644
--- a/src/main/orcad/orcad-health.test.ts
+++ b/src/main/orcad/orcad-health.test.ts
@@ -1,4 +1,6 @@
-import { mkdtempSync, writeFileSync } from 'node:fs'
+import { mkdirSync, mkdtempSync, rmSync, writeFileSync } from 'node:fs'
+import { createHash } from 'node:crypto'
+import { computeLocalOrcadBuildHash } from '../ssh/orcad-local-build-hash'
 import { tmpdir } from 'node:os'
 import { join } from 'node:path'
 import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'
@@ -172,3 +174,48 @@ describe('computeOrcadBuildHash', () => {
     expect(computeOrcadBuildHash('')).toBe('unknown')
   })
 })
+
+describe('shared orcad build identity', () => {
+  let directory: string
+  beforeEach(() => {
+    directory = mkdtempSync(join(tmpdir(), 'orcad-build-identity-'))
+  })
+  afterEach(() => rmSync(directory, { recursive: true, force: true }))
+
+  it('changes matching host and client hashes when only the application changes', () => {
+    const entry = join(directory, 'orcad.js')
+    writeFileSync(entry, 'import("./orcad-app")')
+    writeFileSync(join(directory, 'orcad-app.js'), 'application-a')
+    const first = computeLocalOrcadBuildHash(directory)
+    expect(computeOrcadBuildHash(entry)).toBe(first)
+    writeFileSync(join(directory, 'orcad-app.js'), 'application-b')
+    const second = computeLocalOrcadBuildHash(directory)
+    expect(second).not.toBe(first)
+    expect(computeOrcadBuildHash(entry)).toBe(second)
+    writeFileSync(entry, '// launcher changed\nimport("./orcad-app")')
+    expect(computeLocalOrcadBuildHash(directory)).not.toBe(second)
+    expect(computeOrcadBuildHash(entry)).toBe(computeLocalOrcadBuildHash(directory))
+  })
+
+  it('preserves the original single-bundle hash for older deployments', () => {
+    const entry = join(directory, 'orcad.js')
+    const legacy = 'original single-bundle application'
+    writeFileSync(entry, legacy)
+    const expected = createHash('sha256').update(legacy).digest('hex').slice(0, 16)
+    expect(computeLocalOrcadBuildHash(directory)).toBe(expected)
+    expect(computeOrcadBuildHash(entry)).toBe(expected)
+  })
+
+  it.each(['missing', 'unreadable'])(
+    'refuses a %s application instead of hashing only the launcher',
+    (kind) => {
+      const entry = join(directory, 'orcad.js')
+      writeFileSync(entry, 'import("./orcad-app")')
+      if (kind === 'unreadable') {
+        mkdirSync(join(directory, 'orcad-app.js'))
+      }
+      expect(() => computeLocalOrcadBuildHash(directory)).toThrow()
+      expect(computeOrcadBuildHash(entry)).toBe('unknown')
+    }
+  )
+})
diff --git a/src/main/orcad/orcad-health.ts b/src/main/orcad/orcad-health.ts
index 0c3a3525171..2517d4f37fa 100644
--- a/src/main/orcad/orcad-health.ts
+++ b/src/main/orcad/orcad-health.ts
@@ -8,8 +8,7 @@
  * to cross the process boundary: orcad drives it, the daemon performs it, and the verdict
  * travels back over the daemon's socket.
  */
-import { createHash } from 'node:crypto'
-import { readFileSync } from 'node:fs'
+import { readOrcadBuildHash } from '../../shared/orcad-build-hash'
 import process from 'node:process'
 import { checkDaemonHealth, type DaemonHealth } from '../daemon/daemon-health'
 import {
@@ -81,7 +80,7 @@ export function computeOrcadBuildHash(entryPath = process.argv[1]): string {
     return 'unknown'
   }
   try {
-    return createHash('sha256').update(readFileSync(entryPath)).digest('hex').slice(0, 16)
+    return readOrcadBuildHash(entryPath)
   } catch {
     return 'unknown'
   }
diff --git a/src/main/ssh/orcad-local-build-hash.ts b/src/main/ssh/orcad-local-build-hash.ts
index 3740ea6d55c..6de7dc211be 100644
--- a/src/main/ssh/orcad-local-build-hash.ts
+++ b/src/main/ssh/orcad-local-build-hash.ts
@@ -1,22 +1,9 @@
-/**
- * The build identity the deploy expects the host to answer with.
- *
- * It must be computed the same way `computeOrcadBuildHash` computes it on the host —
- * sha256 of `orcad.js`, first 16 hex characters — or the activation gate would reject every
- * healthy candidate. Keeping the two in one comment is deliberate: they are one contract
- * split across a network, and the version string cannot stand in for it, because
- * `ORCA_VERSION` is whatever the launch command exported and two builds can carry one value.
- */
-import { createHash } from 'node:crypto'
-import { readFileSync } from 'node:fs'
 import { join } from 'node:path'
+import { readOrcadBuildHash } from '../../shared/orcad-build-hash'
 
-export const ORCAD_BUILD_HASH_LENGTH = 16
+export { ORCAD_BUILD_HASH_LENGTH } from '../../shared/orcad-build-hash'
 
+/** The activation gate compares this with the host's hash of the same installed bytes. */
 export function computeLocalOrcadBuildHash(localOrcadDir: string): string {
-  const entry = join(localOrcadDir, 'orcad.js')
-  return createHash('sha256')
-    .update(readFileSync(entry))
-    .digest('hex')
-    .slice(0, ORCAD_BUILD_HASH_LENGTH)
+  return readOrcadBuildHash(join(localOrcadDir, 'orcad.js'))
 }
diff --git a/src/shared/orcad-build-hash.ts b/src/shared/orcad-build-hash.ts
new file mode 100644
index 00000000000..1e8d50ad74a
--- /dev/null
+++ b/src/shared/orcad-build-hash.ts
@@ -0,0 +1,32 @@
+import { createHash } from 'node:crypto'
+import { readFileSync } from 'node:fs'
+import { dirname, join } from 'node:path'
+
+export const ORCAD_BUILD_HASH_LENGTH = 16
+const APPLICATION_FILENAME = 'orcad-app.js'
+
+/** Keep legacy identities stable; split builds must identify the application as well. */
+export function readOrcadBuildHash(entryPath: string): string {
+  const entry = readFileSync(entryPath)
+  let application: Buffer
+  try {
+    application = readFileSync(join(dirname(entryPath), APPLICATION_FILENAME))
+  } catch (error) {
+    if (
+      error instanceof Error &&
+      'code' in error &&
+      error.code === 'ENOENT' &&
+      !entry.includes('orcad-app')
+    ) {
+      return createHash('sha256').update(entry).digest('hex').slice(0, ORCAD_BUILD_HASH_LENGTH)
+    }
+    throw error
+  }
+  return createHash('sha256')
+    .update(`orcad-split-build\0${entry.length}\0`)
+    .update(entry)
+    .update(`\0${application.length}\0`)
+    .update(application)
+    .digest('hex')
+    .slice(0, ORCAD_BUILD_HASH_LENGTH)
+}