diff --git a/src/doctor.ts b/src/doctor.ts
index 02974da4..818da52a 100644
--- a/src/doctor.ts
+++ b/src/doctor.ts
@@ -1,8 +1,10 @@
 import { existsSync } from 'fs'
-import { dirname } from 'path'
+import { readFile } from 'fs/promises'
+import { dirname, join } from 'path'
 
 import { Chalk } from 'chalk'
 
+import { getClaudeConfigDirs } from './providers/claude.js'
 import { getAllProviders } from './providers/index.js'
 import type { Provider } from './providers/types.js'
 import {
@@ -56,9 +58,23 @@ export type DoctorProviderReport = {
   error?: string
 }
 
+export type ClaudeRetentionNote = {
+  /// Effective transcript retention in days. Claude Code deletes session
+  /// files older than cleanupPeriodDays at startup; 30 is its default when
+  /// the setting is absent.
+  effectiveDays: number
+  /// True when cleanupPeriodDays is explicitly set in settings.json.
+  configured: boolean
+  settingsPath: string
+}
+
 export type DoctorReport = {
   generatedAt: string
   providers: DoctorProviderReport[]
+  /// Present when the Claude provider is in the report and a config dir was
+  /// found. Surfaced because deleted transcripts are unrecoverable: daily
+  /// totals survive in CodeBurn's cache, but per-session detail does not.
+  claudeRetention?: ClaudeRetentionNote
 }
 
 export type CollectDoctorOptions = {
@@ -283,13 +299,48 @@ export async function collectDoctorReport(
     }
     providers.sort((a, b) => (a.displayName < b.displayName ? -1 : a.displayName > b.displayName ? 1 : 0))
 
-    return { generatedAt: new Date().toISOString(), providers }
+    const report: DoctorReport = { generatedAt: new Date().toISOString(), providers }
+    if (providers.some(p => p.provider === 'claude')) {
+      const retention = await collectClaudeRetention()
+      if (retention) report.claudeRetention = retention
+    }
+    return report
   } finally {
     if (prevSuppress === undefined) delete process.env['CODEBURN_SUPPRESS_CACHE_WRITES']
     else process.env['CODEBURN_SUPPRESS_CACHE_WRITES'] = prevSuppress
   }
 }
 
+// Claude Code's documented default when cleanupPeriodDays is absent.
+const CLAUDE_DEFAULT_CLEANUP_DAYS = 30
+// Below this, long-horizon views depend entirely on CodeBurn's daily cache;
+// the doctor line turns into a warning.
+const CLAUDE_RETENTION_WARN_DAYS = 365
+
+async function collectClaudeRetention(): Promise<ClaudeRetentionNote | undefined> {
+  for (const dir of await getClaudeConfigDirs()) {
+    const settingsPath = join(dir, 'settings.json')
+    let raw: string
+    try {
+      raw = await readFile(settingsPath, 'utf-8')
+    } catch {
+      continue
+    }
+    try {
+      const parsed: unknown = JSON.parse(raw)
+      const days = (parsed as Record<string, unknown> | null)?.['cleanupPeriodDays']
+      if (typeof days === 'number' && Number.isFinite(days)) {
+        return { effectiveDays: days, configured: true, settingsPath }
+      }
+      return { effectiveDays: CLAUDE_DEFAULT_CLEANUP_DAYS, configured: false, settingsPath }
+    } catch {
+      // Unparseable settings: report the default; Claude Code would apply it too.
+      return { effectiveDays: CLAUDE_DEFAULT_CLEANUP_DAYS, configured: false, settingsPath }
+    }
+  }
+  return undefined
+}
+
 // ── Render ────────────────────────────────────────────────────────────────
 
 export function renderDoctorJson(report: DoctorReport): string {
@@ -364,6 +415,22 @@ export function renderDoctorTable(
     }
   }
 
+  if (report.claudeRetention) {
+    const r = report.claudeRetention
+    const source = r.configured ? 'cleanupPeriodDays' : 'cleanupPeriodDays not set; Claude Code default'
+    const line = `Claude Code deletes transcripts after ${r.effectiveDays} day${r.effectiveDays === 1 ? '' : 's'} (${source}).`
+    out.push('')
+    if (r.effectiveDays < CLAUDE_RETENTION_WARN_DAYS) {
+      out.push(
+        c.yellow(line) + ' ' +
+        `Daily totals survive in CodeBurn's cache, but per-session detail older than that is gone for good. ` +
+        `To keep it, set "cleanupPeriodDays": 3650 in ${r.settingsPath}.`,
+      )
+    } else {
+      out.push(c.dim(line + ' Long transcript retention: per-session detail is preserved.'))
+    }
+  }
+
   out.push('')
   const broken = report.providers.filter(r => r.status === 'error' || r.status === 'errors')
   const empty = report.providers.filter(r => r.status === 'empty')
diff --git a/tests/doctor.test.ts b/tests/doctor.test.ts
index ce4c15da..d8ca4113 100644
--- a/tests/doctor.test.ts
+++ b/tests/doctor.test.ts
@@ -328,3 +328,57 @@ describe('doctor is inert', () => {
     }
   })
 })
+
+// ── Claude transcript retention note ───────────────────────────────────────
+describe('collectDoctorReport - claude retention note', () => {
+  async function withClaudeConfig(settings: string | null, fn: () => Promise<void>): Promise<void> {
+    const prev = process.env['CLAUDE_CONFIG_DIR']
+    const prevMulti = process.env['CLAUDE_CONFIG_DIRS']
+    delete process.env['CLAUDE_CONFIG_DIRS']
+    const dir = join(tmpDir, 'claude-config')
+    await mkdir(dir, { recursive: true })
+    if (settings !== null) await writeFile(join(dir, 'settings.json'), settings)
+    process.env['CLAUDE_CONFIG_DIR'] = dir
+    try {
+      await fn()
+    } finally {
+      if (prev === undefined) delete process.env['CLAUDE_CONFIG_DIR']
+      else process.env['CLAUDE_CONFIG_DIR'] = prev
+      if (prevMulti !== undefined) process.env['CLAUDE_CONFIG_DIRS'] = prevMulti
+    }
+  }
+
+  it('reports an explicit cleanupPeriodDays and renders it as preserved when long', async () => {
+    await withClaudeConfig(JSON.stringify({ cleanupPeriodDays: 3650 }), async () => {
+      const provider = fakeProvider({ name: 'claude' })
+      const report = await collectDoctorReport('all', { providers: [provider], cache: emptyCache() })
+      expect(report.claudeRetention).toMatchObject({ effectiveDays: 3650, configured: true })
+      const table = renderDoctorTable(report, { color: false })
+      expect(table).toContain('deletes transcripts after 3650 days')
+      expect(table).toContain('per-session detail is preserved')
+    })
+  })
+
+  it('reports the 30-day default and renders a warning with the settings path', async () => {
+    await withClaudeConfig(JSON.stringify({ theme: 'dark' }), async () => {
+      const provider = fakeProvider({ name: 'claude' })
+      const report = await collectDoctorReport('all', { providers: [provider], cache: emptyCache() })
+      expect(report.claudeRetention).toMatchObject({ effectiveDays: 30, configured: false })
+      const table = renderDoctorTable(report, { color: false })
+      expect(table).toContain('deletes transcripts after 30 days')
+      expect(table).toContain('cleanupPeriodDays not set')
+      expect(table).toContain('"cleanupPeriodDays": 3650')
+      expect(table).toContain(report.claudeRetention!.settingsPath)
+    })
+  })
+
+  it('emits no note when claude is not in the report or has no settings file', async () => {
+    await withClaudeConfig(null, async () => {
+      const claudeless = await collectDoctorReport('all', { providers: [fakeProvider({ name: 'codex' })], cache: emptyCache() })
+      expect(claudeless.claudeRetention).toBeUndefined()
+      const noSettings = await collectDoctorReport('all', { providers: [fakeProvider({ name: 'claude' })], cache: emptyCache() })
+      expect(noSettings.claudeRetention).toBeUndefined()
+      expect(renderDoctorTable(noSettings, { color: false })).not.toContain('deletes transcripts')
+    })
+  })
+})