diff --git a/src/main/orcad/orcad-bun-launcher.integration.test.ts b/src/main/orcad/orcad-bun-launcher.integration.test.ts
index 82272700f16..8ee18d53293 100644
--- a/src/main/orcad/orcad-bun-launcher.integration.test.ts
+++ b/src/main/orcad/orcad-bun-launcher.integration.test.ts
@@ -1,5 +1,5 @@
 import { build } from 'esbuild'
-import { existsSync } from 'node:fs'
+import { existsSync, readFileSync } from 'node:fs'
 import { copyFile, mkdtemp, readFile, writeFile } from 'node:fs/promises'
 import { tmpdir } from 'node:os'
 import { join, resolve } from 'node:path'
@@ -23,6 +23,22 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
     await copyFile(runtimePath, join(directory, orcadBunRuntimeFilename(process.platform)))
     await writeFile(join(directory, '.build-target'), `${process.platform}-${process.arch}\n`)
     await build({
+      // Record entry before imports without relying on either process's stdout.
+      banner: {
+        js: `
+          function traceLauncherPhase(phase) {
+            const runtime = process.versions.bun ? 'bun' : 'node'
+            try {
+              require('node:fs').appendFileSync(process.env.ORCA_TEST_PHASES + '.' + runtime,
+                JSON.stringify({ at: Date.now(), phase, pid: process.pid, runtime, arch: process.arch }) + '\\n')
+            } catch (error) {
+              console.error('launcher fixture trace failed:', error)
+            }
+          }
+          traceLauncherPhase('entry')
+          process.once('exit', code => traceLauncherPhase('exit:' + code))
+        `
+      },
       stdin: {
         contents: `
           import {handoffToBundledOrcad, OrcadBundledRuntimeError} from './src/main/orcad/orcad-bundled-runtime'
@@ -30,12 +46,16 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
           import {resolveOrcadExitCode} from './src/main/orcad/orcad-exit-code'
           import {writeFile} from 'node:fs/promises'
           if (!process.versions.bun) {
+            traceLauncherPhase('before-handoff')
             if (!handoffToBundledOrcad()) throw new Error('Missing bundled runtime')
+            traceLauncherPhase('after-handoff')
             process.on('message', signal => process.emit(signal))
           } else {
+            traceLauncherPhase('before-booting')
             console.log('booting:' + process.pid)
             console.log('runtime:' + process.versions.bun)
             console.log('channel-env:' + (process.env.ORCA_BUNDLED_LAUNCHER_CHANNEL ?? 'absent'))
+            traceLauncherPhase('booting-written')
             process.on('exit', code => console.log('runtime-exit:' + code))
             const keepalive = setInterval(() => {}, 1_000)
             const install = async () => {
@@ -99,6 +119,13 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
     const runtime = options.direct
       ? join(directory, orcadBunRuntimeFilename(process.platform))
       : nodePath
+    const startedAt = Date.now()
+    const events: { at: number; event: string }[] = []
+    const record = (event: string): void => {
+      if (events.length < 16) {
+        events.push({ at: Date.now(), event })
+      }
+    }
     const child = spawnProcess({
       program: options.nohup ? 'nohup' : runtime,
       args: [...(options.nohup ? [runtime] : []), join(directory, 'orcad.js')],
@@ -106,6 +133,7 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
         ...process.env,
         ORCA_BACKGROUND_LAUNCH: '1',
         ORCA_TEST_DONE: join(directory, 'done'),
+        ORCA_TEST_PHASES: join(directory, 'phases'),
         ORCA_TEST_DELAY_INSTALL: options.delay ? '1' : '0',
         ORCA_TEST_STALL: options.stall ? '1' : '0',
         ORCA_TEST_FAIL_STARTUP: options.failStartup ? '1' : '0'
@@ -114,8 +142,10 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
       stdio: ['ignore', 'pipe', 'pipe', 'ipc']
     })
     children.add(child)
+    child.once('spawn', () => record('spawn'))
     let closed = false
     child.once('close', () => {
+      record('close')
       closed = true
     })
     let output = ''
@@ -128,18 +158,57 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
         runtimes.delete(Number(pid))
       }
     }
-    child.stdout.on('data', capture)
-    child.stderr.on('data', capture)
+    const streams = [
+      ['stdout', child.stdout],
+      ['stderr', child.stderr]
+    ] as const
+    for (const [name, stream] of streams) {
+      stream.on('data', capture)
+      stream.once('data', () => record(`${name}:data`))
+      stream.once('end', () => record(`${name}:end`))
+      stream.once('close', () => record(`${name}:close`))
+    }
     const exit = new Promise<{ code: number | null; signal: NodeJS.Signals | null }>(
       (resolve, reject) => {
-        child.once('error', reject)
+        child.once('error', (error) => {
+          record(`error:${error.message}`)
+          reject(error)
+        })
         child.once('exit', (code, signal) => {
+          record(`exit:${code}:${signal}`)
           children.delete(child)
           resolve({ code, signal })
         })
       }
     )
-    return { child, output: () => output, exit, isClosed: () => closed }
+    const diagnostics = () => ({
+      startedAt,
+      elapsedMs: Date.now() - startedAt,
+      events,
+      pid: child.pid,
+      exitCode: child.exitCode,
+      signalCode: child.signalCode,
+      connected: child.connected,
+      closed,
+      streams: streams.map(([name, stream]) => ({
+        name,
+        ended: stream.readableEnded,
+        destroyed: stream.destroyed,
+        error: stream.errored?.message,
+        bufferedBytes: stream.readableLength
+      })),
+      phases: ['node', 'bun'].map((runtime) => {
+        try {
+          return {
+            runtime,
+            trace: readFileSync(join(directory, `phases.${runtime}`), 'utf8').slice(0, 4096)
+          }
+        } catch (error) {
+          return { runtime, error: String(error) }
+        }
+      })
+    })
+    return { child, output: () => output, exit, isClosed: () => closed, diagnostics }
   }
 
   it.each([false, true])(
@@ -214,7 +283,12 @@ describe.skipIf(!existsSync(runtimePath))('real Bun launcher lifecycle', () => {
 
   it('preserves a startup configuration verdict after early launcher loss', async () => {
     const h = launch({ delay: true, failStartup: true })
-    await vi.waitFor(() => expect(h.output()).toContain('booting:'), { timeout: 5_000 })
+    try {
+      await vi.waitFor(() => expect(h.output()).toContain('booting:'), { timeout: 5_000 })
+    } catch (error) {
+      console.error('Bun launcher startup diagnostics:', JSON.stringify(h.diagnostics()))
+      throw error
+    }
     h.child.kill('SIGKILL')
     await h.exit
     await vi.waitFor(() => expect(h.output()).toContain('runtime-exit:78'), { timeout: 5_000 })