diff --git a/publish/src/core/log.ts b/publish/src/core/log.ts
new file mode 100644
index 0000000..6cc4201
--- /dev/null
+++ b/publish/src/core/log.ts
@@ -0,0 +1,106 @@
+export type RunMode = 'diff' | 'force-all' | 'post-single'
+
+export interface PostLog {
+  slug: string
+  status: 'success' | 'failed' | 'skipped-draft'
+  action?: 'new' | 'update'
+  event_id?: string
+  relays_ok?: string[]
+  relays_failed?: string[]
+  blossom_servers_ok?: string[]
+  images_uploaded?: number
+  duration_ms?: number
+  error?: string
+}
+
+export interface RunLog {
+  run_id: string
+  started_at: string
+  ended_at: string
+  mode: RunMode
+  posts: PostLog[]
+  exit_code: number
+}
+
+export interface SuccessArgs {
+  slug: string
+  action: 'new' | 'update'
+  eventId: string
+  relaysOk: string[]
+  relaysFailed: string[]
+  blossomServersOk: string[]
+  imagesUploaded: number
+  durationMs: number
+}
+
+export interface FailedArgs {
+  slug: string
+  error: string
+  durationMs: number
+}
+
+export interface LoggerOptions {
+  mode: RunMode
+  runId: string
+  print?: (line: string) => void
+  now?: () => Date
+}
+
+export interface Logger {
+  postSuccess(args: SuccessArgs): void
+  postFailed(args: FailedArgs): void
+  postSkippedDraft(slug: string): void
+  finalize(exitCode: number): RunLog
+  writeJson(path: string, summary: RunLog): Promise<void>
+}
+
+export function createLogger(opts: LoggerOptions): Logger {
+  const print = opts.print ?? ((line: string) => console.log(line))
+  const now = opts.now ?? (() => new Date())
+  const posts: PostLog[] = []
+  const startedAt = now().toISOString()
+  return {
+    postSuccess(a) {
+      posts.push({
+        slug: a.slug,
+        status: 'success',
+        action: a.action,
+        event_id: a.eventId,
+        relays_ok: a.relaysOk,
+        relays_failed: a.relaysFailed,
+        blossom_servers_ok: a.blossomServersOk,
+        images_uploaded: a.imagesUploaded,
+        duration_ms: a.durationMs,
+      })
+      print(
+        `✓ ${a.slug} (${a.action}) — relays:${a.relaysOk.length}ok/${a.relaysFailed.length}fail — ${a.durationMs}ms`,
+      )
+    },
+    postFailed(a) {
+      posts.push({
+        slug: a.slug,
+        status: 'failed',
+        error: a.error,
+        duration_ms: a.durationMs,
+      })
+      print(`✗ ${a.slug} — ${a.error}`)
+    },
+    postSkippedDraft(slug) {
+      posts.push({ slug, status: 'skipped-draft' })
+      print(`- ${slug} (draft, skipped)`)
+    },
+    finalize(exitCode) {
+      return {
+        run_id: opts.runId,
+        started_at: startedAt,
+        ended_at: now().toISOString(),
+        mode: opts.mode,
+        posts,
+        exit_code: exitCode,
+      }
+    },
+    writeJson(path, summary) {
+      return Deno.writeTextFile(path, JSON.stringify(summary, null, 2))
+    },
+  }
+}
diff --git a/publish/tests/log_test.ts b/publish/tests/log_test.ts
new file mode 100644
index 0000000..dbc3868
--- /dev/null
+++ b/publish/tests/log_test.ts
@@ -0,0 +1,50 @@
+import { assertEquals } from '@std/assert'
+import { createLogger } from '../src/core/log.ts'
+
+Deno.test('logger: sammelt post-einträge und schreibt summary', () => {
+  const sink: string[] = []
+  const logger = createLogger({
+    mode: 'force-all',
+    runId: 'run-1',
+    print: (line) => sink.push(line),
+    now: () => new Date('2026-04-16T10:00:00Z'),
+  })
+  logger.postSuccess({
+    slug: 's1',
+    action: 'new',
+    eventId: 'ev1',
+    relaysOk: ['wss://r1'],
+    relaysFailed: [],
+    blossomServersOk: [],
+    imagesUploaded: 0,
+    durationMs: 10,
+  })
+  logger.postSkippedDraft('s2')
+  const summary = logger.finalize(0)
+  assertEquals(summary.run_id, 'run-1')
+  assertEquals(summary.mode, 'force-all')
+  assertEquals(summary.posts.length, 2)
+  assertEquals(summary.posts[0].status, 'success')
+  assertEquals(summary.posts[1].status, 'skipped-draft')
+  assertEquals(summary.exit_code, 0)
+  assertEquals(sink.some((s) => s.includes('s1')), true)
+})
+
+Deno.test('logger: writeJson schreibt datei', async () => {
+  const tmp = await Deno.makeTempDir()
+  try {
+    const logger = createLogger({
+      mode: 'diff',
+      runId: 'run-2',
+      print: () => {},
+      now: () => new Date('2026-04-16T10:00:00Z'),
+    })
+    const summary = logger.finalize(0)
+    await logger.writeJson(`${tmp}/out.json`, summary)
+    const text = await Deno.readTextFile(`${tmp}/out.json`)
+    const parsed = JSON.parse(text)
+    assertEquals(parsed.run_id, 'run-2')
+  } finally {
+    await Deno.remove(tmp, { recursive: true })
+  }
+})