fix: merge duplicate build log steps before reading output

src/build-logs.ts

@@ -7,7 +7,7 @@ export type BuildLogPage = {
   state: 'ready' | 'pending' | 'unsupported' | 'unavailable'
   buildState: string
   error?: string
-  steps: Array<{ digest: string; name: string; error?: string; hasLogs: boolean }>
+  steps: Array<{ digest: string; name: string; error?: string; hasLogs: boolean; completedAt?: string }>
   entries: Array<{ timestamp: string; message: string; occurrence?: number }>
   nextCursor?: string
 }
@@ -21,6 +21,12 @@ type FollowState = { tails: Map<string, LogTail>; emit: (snapshot: BuildLogSnaps
 const entryKey = (step: string, entry: BuildLogPage['entries'][number]) => createHash('sha256').update(JSON.stringify([step, entry.timestamp, entry.message])).digest('hex')
 class LogsNotReady extends Error {}
 
+// Compute emits UTC RFC3339Nano; Date.parse discards submillisecond ordering.
+function completionKey(value: string): string {
+  const [seconds, fraction = ''] = value.slice(0, -1).split('.')
+  return `${seconds}.${fraction.padEnd(9, '0')}`
+}
+
 export async function readBuildLogs(api: Api, projectId: string, source: BuildSource, buildId: string, signal = AbortSignal.timeout(30_000), follow?: FollowState): Promise<BuildLogSnapshot> {
   let bytes = 0
   let requests = 0
@@ -62,7 +68,15 @@ export async function readBuildLogs(api: Api, projectId: string, source: BuildSo
   const stepPages = await pages()
   const first = stepPages[0]!
   if (stepPages.some((page) => page.state !== first.state)) throw new LogsNotReady('build steps are temporarily unavailable')
-  const steps = stepPages.flatMap((page) => page.steps)
+  const byDigest = new Map<string, BuildLogPage['steps'][number]>()
+  for (const step of stepPages.flatMap((page) => page.steps)) {
+    const previous = byDigest.get(step.digest)
+    if (!previous) { byDigest.set(step.digest, step); continue }
+    const [older, newer] = previous.completedAt && (!step.completedAt || completionKey(previous.completedAt) > completionKey(step.completedAt))
+      ? [step, previous] : [previous, step]
+    byDigest.set(step.digest, { ...older, ...newer, hasLogs: older.hasLogs || newer.hasLogs, error: newer.error })
+  }
+  const steps = [...byDigest.values()]
   follow?.emit({ ...first, steps, output: [] })
   const output: BuildLogSnapshot['output'] = []
   for (const step of steps) {

test/build-logs.test.ts

@@ -8,6 +8,22 @@ const entry = (message: string) => ({ timestamp: '2026-09-17T00:00:00Z', message
 const apiWith = (read: (path: string) => unknown): Pick<ApiClient, 'rawRequest'> => ({ rawRequest: vi.fn(async (_method, path) => ({ status: 200, body: read(path) })) })
 
 describe('build logs', () => {
+  it.each([[false, false, false, false], [true, false, false, false], [false, true, false, false], [true, true, false, false], [false, true, true, false], [true, true, true, false], [false, true, true, true], [true, true, true, true]])('merges duplicate steps across pages (terminal first: %s, older completion: %s, sub-ms: %s, success: %s)', async (terminalFirst, olderCompletion, subMillisecond, success) => {
+    const finished = { digest: 'step1', name: 'RUN test', hasLogs: false, completedAt: subMillisecond ? '2026-09-17T00:00:00.000000002Z' : '2026-09-17T00:00:01Z', ...(success ? {} : { error: 'exit 17' }) }
+    const running = { digest: 'step1', name: 'RUN test', hasLogs: true, ...(olderCompletion ? { completedAt: subMillisecond ? '2026-09-17T00:00:00.000000001Z' : '2026-09-17T00:00:00Z', error: 'older error' } : {}) }
+    const records = terminalFirst ? [finished, running] : [running, finished]
+    const api = apiWith(path => {
+      const q = new URL('http://local' + path).searchParams
+      if (!q.has('step')) return { ...base, steps: [records[q.has('cursor') ? 1 : 0]], ...(q.has('cursor') ? {} : { nextCursor: 'steps2' }) }
+      return { ...base, steps: [], entries: [entry('same\n'), entry('same\n')] }
+    })
+    const snapshot = await readBuildLogs(api, 'p', 'archive', 'b')
+    expect(snapshot.steps).toEqual([{ ...finished, hasLogs: true }])
+    expect(snapshot.output).toHaveLength(1)
+    expect(snapshot.output[0]!.entries).toEqual([entry('same\n'), entry('same\n')])
+    expect(api.rawRequest).toHaveBeenCalledTimes(3)
+  })
+
   it('follows step and output pagination, preserving repeated records and API order', async () => {
     const api = apiWith((path) => {
       const q = new URL('http://local' + path).searchParams