diff --git a/apps/cli/src/commands/share-resume.test.ts b/apps/cli/src/commands/share-resume.test.ts
index 16134a5c..207ead89 100644
--- a/apps/cli/src/commands/share-resume.test.ts
+++ b/apps/cli/src/commands/share-resume.test.ts
@@ -11,7 +11,11 @@ import {
 import { tmpdir } from 'node:os'
 import { join, sep } from 'node:path'
 
-import { sequenceRoot, serializePortableSession } from '@spool-lab/session-kit'
+import {
+  parseSummaryFrontMatter,
+  sequenceRoot,
+  serializePortableSession,
+} from '@spool-lab/session-kit'
 import Database from 'better-sqlite3'
 import { describe, expect, it } from 'vite-plus/test'
 
@@ -621,6 +625,139 @@ describe('spool share local Agent Summary flow', () => {
     expect(events).toContain('select:Which local Agent should generate the Summary?')
   })
 
+  it('uploads a Summary whose only defect is an overlong title', async () => {
+    const hub = makeHub()
+    const workspace = mkdtempSync(join(tmpdir(), 'spool-summary-long-title-'))
+    const home = mkdtempSync(join(tmpdir(), 'spool-summary-long-title-home-'))
+    const filePath = writeFixtureSession(workspace)
+    const share = shareDeps(hub, workspace, filePath, home)
+    const events: string[] = []
+    const overlong = `Rename alpha to beta across the demo workspace ${'and every downstream caller '.repeat(4)}`
+
+    const exit = await handleShareCommand(
+      `${SESSION_UUID}@2`,
+      {},
+      {
+        ...share.deps,
+        ui: interactiveUi({ selected: 'claude', events }),
+        detectSummaryAgents: async () => [
+          { id: 'claude', name: 'Claude Code', path: '/bin/claude' },
+        ],
+        generateSummary: async () =>
+          BILINGUAL_SUMMARY.replace('title: Rename alpha to beta', `title: ${overlong}`),
+      },
+    )
+
+    expect(exit).toBe(0)
+    const stored = hub.sessions.get(`claude_${SESSION_UUID}`)?.summaryMd as string
+    const titles = parseSummaryFrontMatter(stored).titles
+    expect(Array.from(titles?.en ?? '').length).toBeLessThanOrEqual(96)
+    expect(titles?.en).toMatch(/^Rename alpha to beta across the demo workspace .*…$/)
+    expect(titles?.zh).toBe('将 alpha 重命名为 beta')
+    expect(stored).toContain('The demo now uses the requested beta name.')
+    expect(events).toContain('info:Shortened `title` to the 96-character Session title limit.')
+    expect(events.some((event) => event.startsWith('spinner:error:'))).toBe(false)
+  })
+
+  it('rejects an Agent Summary that exceeded 64 KiB before title repair', async () => {
+    const hub = makeHub()
+    const workspace = mkdtempSync(join(tmpdir(), 'spool-summary-too-large-'))
+    const home = mkdtempSync(join(tmpdir(), 'spool-summary-too-large-home-'))
+    const filePath = writeFixtureSession(workspace)
+    const share = shareDeps(hub, workspace, filePath, home)
+    const events: string[] = []
+    const generated = BILINGUAL_SUMMARY.replace(
+      'title: Rename alpha to beta',
+      `title: ${'a'.repeat(64 * 1024)}`,
+    )
+
+    const exit = await handleShareCommand(
+      `${SESSION_UUID}@2`,
+      {},
+      {
+        ...share.deps,
+        ui: interactiveUi({ selected: 'claude', events }),
+        detectSummaryAgents: async () => [
+          { id: 'claude', name: 'Claude Code', path: '/bin/claude' },
+        ],
+        generateSummary: async () => generated,
+      },
+    )
+
+    expect(exit).toBe(1)
+    expect(hub.sessions.get(`claude_${SESSION_UUID}`)?.summaryMd).toBeNull()
+    expect(events).toContain(
+      'error:Claude Code returned an invalid bilingual Summary: the UTF-8 document exceeds 64 KiB',
+    )
+  })
+
+  it('rejects a repeated first H1 even when its overlong title is repaired', async () => {
+    const hub = makeHub()
+    const workspace = mkdtempSync(join(tmpdir(), 'spool-summary-repeated-long-title-'))
+    const home = mkdtempSync(join(tmpdir(), 'spool-summary-repeated-long-title-home-'))
+    const filePath = writeFixtureSession(workspace)
+    const share = shareDeps(hub, workspace, filePath, home)
+    const events: string[] = []
+    const overlong = `Rename alpha to beta across the demo workspace ${'and every downstream caller '.repeat(4)}`
+    const generated = BILINGUAL_SUMMARY.replace(
+      'title: Rename alpha to beta',
+      `title: ${overlong}`,
+    ).replace('<!-- spool:summary:en -->\n', `<!-- spool:summary:en -->\n# ${overlong}\n\n`)
+
+    const exit = await handleShareCommand(
+      `${SESSION_UUID}@2`,
+      {},
+      {
+        ...share.deps,
+        ui: interactiveUi({ selected: 'claude', events }),
+        detectSummaryAgents: async () => [
+          { id: 'claude', name: 'Claude Code', path: '/bin/claude' },
+        ],
+        generateSummary: async () => generated,
+      },
+    )
+
+    expect(exit).toBe(1)
+    expect(hub.sessions.get(`claude_${SESSION_UUID}`)?.summaryMd).toBeNull()
+    expect(events).toContain(
+      'error:Claude Code returned an invalid bilingual Summary: Summary bodies must not repeat the Session title as their first H1',
+    )
+  })
+
+  it('rejects a first H1 that repeats the repaired Session title', async () => {
+    const hub = makeHub()
+    const workspace = mkdtempSync(join(tmpdir(), 'spool-summary-repeated-repaired-title-'))
+    const home = mkdtempSync(join(tmpdir(), 'spool-summary-repeated-repaired-title-home-'))
+    const filePath = writeFixtureSession(workspace)
+    const share = shareDeps(hub, workspace, filePath, home)
+    const events: string[] = []
+    const overlong = 'a'.repeat(120)
+    const repairedTitle = `${'a'.repeat(95)}…`
+    const generated = BILINGUAL_SUMMARY.replace(
+      'title: Rename alpha to beta',
+      `title: ${overlong}`,
+    ).replace('<!-- spool:summary:en -->\n', `<!-- spool:summary:en -->\n# ${repairedTitle}\n\n`)
+
+    const exit = await handleShareCommand(
+      `${SESSION_UUID}@2`,
+      {},
+      {
+        ...share.deps,
+        ui: interactiveUi({ selected: 'claude', events }),
+        detectSummaryAgents: async () => [
+          { id: 'claude', name: 'Claude Code', path: '/bin/claude' },
+        ],
+        generateSummary: async () => generated,
+      },
+    )
+
+    expect(exit).toBe(1)
+    expect(hub.sessions.get(`claude_${SESSION_UUID}`)?.summaryMd).toBeNull()
+    expect(events).toContain(
+      'error:Claude Code returned an invalid bilingual Summary: Summary bodies must not repeat the Session title as their first H1',
+    )
+  })
+
   it('does not prompt or invoke an Agent when non-interactive visibility is acknowledged', async () => {
     const hub = makeHub()
     const workspace = mkdtempSync(join(tmpdir(), 'spool-summary-nontty-'))
diff --git a/apps/cli/src/commands/share.ts b/apps/cli/src/commands/share.ts
index 8ddf0c59..3833a3b4 100644
--- a/apps/cli/src/commands/share.ts
+++ b/apps/cli/src/commands/share.ts
@@ -16,9 +16,12 @@ import {
   isResumableSessionProvider,
   parseSummaryFrontMatter,
   parseSessionText,
+  repairOverlongSummaryTitles,
   sessionRecordData,
   SESSION_PROVIDERS,
+  SUMMARY_TITLE_CHAR_LIMIT,
   type SessionProvider,
+  type SummaryTitleRepair,
 } from '@spool-lab/session-kit'
 import { Command } from 'commander'
 
@@ -420,12 +423,18 @@ export async function handleShareCommand(
       const prompt =
         dependencies.buildSummaryPrompt?.(target, prepared) ??
         buildPreparedSummaryPrompt(target, prepared)
-      const summary = (await summarize(agent, prompt)).trim()
-      if (!summary) throw new Error(`${agent.name} returned an empty Summary.`)
-      const invalidSummary = bilingualSummaryValidationError(summary)
+      const generated = (await summarize(agent, prompt)).trim()
+      if (!generated) throw new Error(`${agent.name} returned an empty Summary.`)
+      const oversizedSummary = summaryDocumentSizeValidationError(generated)
+      if (oversizedSummary) {
+        throw new Error(`${agent.name} returned an invalid bilingual Summary: ${oversizedSummary}`)
+      }
+      const repaired = repairOverlongSummaryTitles(generated)
+      const invalidSummary = repairedBilingualSummaryValidationError(repaired)
       if (invalidSummary) {
         throw new Error(`${agent.name} returned an invalid bilingual Summary: ${invalidSummary}`)
       }
+      const { summary, shortened } = repaired
       generation.message('Uploading generated Summary')
       await publishPreparedShare(client, prepared, {
         card,
@@ -436,6 +445,11 @@ export async function handleShareCommand(
           generation.message(`Uploading Summary objects ${uploaded}/${total}`),
       })
       generation.stop(`Summary generated by ${agent.name} and uploaded`)
+      if (shortened.length > 0) {
+        ui.info(
+          `Shortened ${shortened.map((key) => `\`${key}\``).join(' and ')} to the ${SUMMARY_TITLE_CHAR_LIMIT}-character Session title limit.`,
+        )
+      }
       ui.outro('Summary uploaded.')
       return 0
     } catch (cause) {
@@ -457,13 +471,15 @@ export async function handleShareCommand(
   }
 }
 
+const SUMMARY_REPEATED_TITLE_HEADING_ERROR =
+  'Summary bodies must not repeat the Session title as their first H1'
+
 export function bilingualSummaryValidationError(summary: string): string | null {
-  if (Buffer.byteLength(summary, 'utf8') > 64 * 1024) {
-    return 'the UTF-8 document exceeds 64 KiB'
-  }
+  const oversizedSummary = summaryDocumentSizeValidationError(summary)
+  if (oversizedSummary) return oversizedSummary
   const parsed = parseSummaryFrontMatter(summary)
   if (parsed.titleOverflow) {
-    return '`title` and `title_zh` must each be at most 96 characters'
+    return `\`title\` and \`title_zh\` must each be at most ${SUMMARY_TITLE_CHAR_LIMIT} characters`
   }
   if (!parsed.titles?.en || !parsed.titles.zh) {
     return 'both `title` and `title_zh` are required in leading front-matter'
@@ -475,11 +491,31 @@ export function bilingualSummaryValidationError(summary: string): string | null
     repeatsTitleAsFirstHeading(parsed.summaries.en, parsed.titles.en) ||
     repeatsTitleAsFirstHeading(parsed.summaries.zh, parsed.titles.zh)
   ) {
-    return 'Summary bodies must not repeat the Session title as their first H1'
+    return SUMMARY_REPEATED_TITLE_HEADING_ERROR
   }
   return null
 }
 
+function repairedBilingualSummaryValidationError(repaired: SummaryTitleRepair): string | null {
+  const invalidSummary = bilingualSummaryValidationError(repaired.summary)
+  if (invalidSummary || !repaired.sourceTitles) return invalidSummary
+  const parsed = parseSummaryFrontMatter(repaired.summary)
+  if (!parsed.summaries?.en || !parsed.summaries.zh) return null
+  if (
+    (repaired.sourceTitles.en &&
+      repeatsTitleAsFirstHeading(parsed.summaries.en, repaired.sourceTitles.en)) ||
+    (repaired.sourceTitles.zh &&
+      repeatsTitleAsFirstHeading(parsed.summaries.zh, repaired.sourceTitles.zh))
+  ) {
+    return SUMMARY_REPEATED_TITLE_HEADING_ERROR
+  }
+  return null
+}
+
+function summaryDocumentSizeValidationError(summary: string): string | null {
+  return Buffer.byteLength(summary, 'utf8') > 64 * 1024 ? 'the UTF-8 document exceeds 64 KiB' : null
+}
+
 function repeatsTitleAsFirstHeading(markdown: string, title: string): boolean {
   const first = markdown.split(/\r?\n/).find((line) => line.trim() !== '')
   if (!first || !/^\s{0,3}#\s+/.test(first)) return false
diff --git a/packages/session-kit/src/index.ts b/packages/session-kit/src/index.ts
index cb15a5c9..4a2f9732 100644
--- a/packages/session-kit/src/index.ts
+++ b/packages/session-kit/src/index.ts
@@ -95,7 +95,17 @@ export {
   isSessionProvider,
 } from './types.js'
 
-export { parseSummaryFrontMatter } from './summary.js'
-export type { ParsedSummary, SessionSummaries, SessionTitles } from './summary.js'
+export {
+  parseSummaryFrontMatter,
+  repairOverlongSummaryTitles,
+  SUMMARY_TITLE_CHAR_LIMIT,
+} from './summary.js'
+export type {
+  ParsedSummary,
+  SessionSummaries,
+  SessionTitles,
+  SummaryTitleKey,
+  SummaryTitleRepair,
+} from './summary.js'
 export { costForUsage, MODEL_PRICING } from './pricing.js'
 export type { ModelPricing, SessionCost } from './pricing.js'
diff --git a/packages/session-kit/src/summary.test.ts b/packages/session-kit/src/summary.test.ts
index 97c8f02a..b9035178 100644
--- a/packages/session-kit/src/summary.test.ts
+++ b/packages/session-kit/src/summary.test.ts
@@ -1,7 +1,7 @@
 import { describe, expect, it } from 'vite-plus/test'
 
 import { costForUsage } from './pricing.js'
-import { parseSummaryFrontMatter } from './summary.js'
+import { parseSummaryFrontMatter, repairOverlongSummaryTitles } from './summary.js'
 
 describe('parseSummaryFrontMatter', () => {
   it('parses bilingual titles and strips the block from the body', () => {
@@ -106,6 +106,96 @@ describe('parseSummaryFrontMatter', () => {
   })
 })
 
+describe('repairOverlongSummaryTitles', () => {
+  it('shortens English and Chinese titles without changing the bodies', () => {
+    const source = [
+      '---',
+      'title: Rename alpha to beta',
+      'title_zh: 将 alpha 重命名为 beta',
+      '---',
+      '',
+      '<!-- spool:summary:en -->',
+      'The demo now uses the requested beta name.',
+      '<!-- /spool:summary -->',
+      '',
+      '<!-- spool:summary:zh -->',
+      '演示项目现在使用要求的 beta 名称。',
+      '<!-- /spool:summary -->',
+    ].join('\n')
+    const longEnglish =
+      'Fix the daemon reconnect loop that keeps retrying after macOS sleep and wake, and add regression coverage for the backoff'
+
+    const repairedEnglish = repairOverlongSummaryTitles(
+      source.replace('title: Rename alpha to beta', `title: ${longEnglish}`),
+    )
+
+    expect(repairedEnglish.shortened).toEqual(['title'])
+    expect(repairedEnglish.sourceTitles?.en).toBe(longEnglish)
+    expect(parseSummaryFrontMatter(repairedEnglish.summary).titles?.en).toBe(
+      'Fix the daemon reconnect loop that keeps retrying after macOS sleep and wake, and add…',
+    )
+    expect(repairedEnglish.summary.slice(repairedEnglish.summary.indexOf('\n---\n'))).toBe(
+      source.slice(source.indexOf('\n---\n')),
+    )
+
+    const longChinese = '修'.repeat(120)
+    const repairedChinese = repairOverlongSummaryTitles(
+      source.replace('title_zh: 将 alpha 重命名为 beta', `title_zh: ${longChinese}`),
+    )
+    expect(repairedChinese.shortened).toEqual(['title_zh'])
+    expect(parseSummaryFrontMatter(repairedChinese.summary).titles?.zh).toBe(`${'修'.repeat(95)}…`)
+
+    expect(repairOverlongSummaryTitles(source)).toEqual({
+      summary: source,
+      shortened: [],
+      sourceTitles: { en: 'Rename alpha to beta', zh: '将 alpha 重命名为 beta' },
+    })
+    const legacy = '# Legacy summary\n\nA single-language body.'
+    expect(repairOverlongSummaryTitles(legacy)).toEqual({
+      summary: legacy,
+      shortened: [],
+      sourceTitles: null,
+    })
+  })
+
+  it('measures the word-boundary floor in Unicode codepoints', () => {
+    const source = [
+      '---',
+      `title: ${'😀'.repeat(30)} ${'a'.repeat(70)}`,
+      'title_zh: 中文标题',
+      '---',
+      'Body.',
+    ].join('\n')
+
+    const repaired = repairOverlongSummaryTitles(source)
+
+    expect(parseSummaryFrontMatter(repaired.summary).titles?.en).toBe(
+      `${'😀'.repeat(30)} ${'a'.repeat(64)}…`,
+    )
+  })
+
+  it('preserves mixed LF and CRLF outside repaired title lines', () => {
+    const source = [
+      '---\r\n',
+      `title: ${'a'.repeat(120)}\n`,
+      'title_zh: 中文标题\r\n',
+      '---\n',
+      '\r\n',
+      '<!-- spool:summary:en -->\r\n',
+      'English body.\n',
+      '<!-- /spool:summary -->\r\n',
+      '\n',
+      '<!-- spool:summary:zh -->\r\n',
+      '中文正文。\n',
+      '<!-- /spool:summary -->',
+    ].join('')
+
+    const repaired = repairOverlongSummaryTitles(source)
+
+    expect(repaired.summary).toBe(source.replace('a'.repeat(120), `${'a'.repeat(95)}…`))
+  })
+})
+
 describe('costForUsage', () => {
   it('prices by longest model prefix and reports totals', () => {
     const cost = costForUsage({
diff --git a/packages/session-kit/src/summary.ts b/packages/session-kit/src/summary.ts
index 418b7fc2..0dcde678 100644
--- a/packages/session-kit/src/summary.ts
+++ b/packages/session-kit/src/summary.ts
@@ -22,7 +22,26 @@ export interface ParsedSummary {
   titleOverflow?: boolean
 }
 
-const MAX_TITLE_CHARS = 96
+export const SUMMARY_TITLE_CHAR_LIMIT = 96
+export type SummaryTitleKey = 'title' | 'title_zh'
+
+export interface SummaryTitleRepair {
+  summary: string
+  shortened: SummaryTitleKey[]
+  /** Normalized, unbounded titles from the source document. */
+  sourceTitles: SessionTitles | null
+}
+
+interface SummarySourceLine {
+  content: string
+  ending: string
+}
+
+interface LeadingSummaryFrontMatter {
+  lines: SummarySourceLine[]
+  closing: number
+}
+
 const SUMMARY_SECTION_START_RE = /^<!--\s*spool:summary:(en|zh)\s*-->$/
 const SUMMARY_SECTION_END = '<!-- /spool:summary -->'
 
@@ -43,40 +62,94 @@ const SUMMARY_SECTION_END = '<!-- /spool:summary -->'
  */
 export function parseSummaryFrontMatter(summaryMd: string | null | undefined): ParsedSummary {
   const source = summaryMd ?? ''
-  const lines = source.split(/\r?\n/)
-  if (lines[0]?.trim() !== '---') return withParsedSummaries(null, source, false)
-
-  let closing = -1
-  for (let i = 1; i < lines.length; i++) {
-    if (lines[i]!.trim() === '---') {
-      closing = i
-      break
-    }
-  }
-  if (closing === -1) return withParsedSummaries(null, source, false)
+  const frontMatter = leadingSummaryFrontMatter(source)
+  if (!frontMatter) return withParsedSummaries(null, source, false)
 
   const titles: SessionTitles = {}
   let titleOverflow = false
-  for (const line of lines.slice(1, closing)) {
-    const match = /^([A-Za-z0-9_-]+)\s*:\s*(.*)$/.exec(line.trim())
-    if (!match) continue
-    const locale = match[1] === 'title' ? 'en' : match[1] === 'title_zh' ? 'zh' : null
-    if (locale === null) continue
-    const normalized = normalizeTitle(match[2]!)
-    if (Array.from(normalized).length > MAX_TITLE_CHARS) titleOverflow = true
-    const value = boundTitle(normalized)
+  for (const line of frontMatter.lines.slice(1, frontMatter.closing)) {
+    const title = parseSummaryTitleLine(line.content)
+    if (!title) continue
+    const locale = title.key === 'title' ? 'en' : 'zh'
+    if (Array.from(title.value).length > SUMMARY_TITLE_CHAR_LIMIT) titleOverflow = true
+    const value = boundTitle(title.value)
     if (!value) continue
     titles[locale] = value
   }
 
-  const body = lines
-    .slice(closing + 1)
+  const body = frontMatter.lines
+    .slice(frontMatter.closing + 1)
+    .map((line) => line.content)
     .join('\n')
     .replace(/^\s*\n/, '')
 
   return withParsedSummaries(titles.en || titles.zh ? titles : null, body, titleOverflow)
 }
 
+/**
+ * Shorten only overlong leading front-matter titles while preserving every
+ * other source byte, including mixed LF/CRLF line endings and both bodies.
+ */
+export function repairOverlongSummaryTitles(summary: string): SummaryTitleRepair {
+  const frontMatter = leadingSummaryFrontMatter(summary)
+  if (!frontMatter) return { summary, shortened: [], sourceTitles: null }
+
+  const shortened: SummaryTitleKey[] = []
+  const sourceTitles: SessionTitles = {}
+  for (const line of frontMatter.lines.slice(1, frontMatter.closing)) {
+    const title = parseSummaryTitleLine(line.content)
+    if (!title) continue
+    sourceTitles[title.key === 'title' ? 'en' : 'zh'] = title.value
+    if (Array.from(title.value).length <= SUMMARY_TITLE_CHAR_LIMIT) continue
+    line.content = `${title.key}: ${shortenSummaryTitle(title.value)}`
+    shortened.push(title.key)
+  }
+
+  return {
+    summary:
+      shortened.length === 0
+        ? summary
+        : frontMatter.lines.map((line) => `${line.content}${line.ending}`).join(''),
+    shortened,
+    sourceTitles: sourceTitles.en || sourceTitles.zh ? sourceTitles : null,
+  }
+}
+
+function leadingSummaryFrontMatter(source: string): LeadingSummaryFrontMatter | null {
+  const lines = splitSummarySourceLines(source)
+  if (lines[0]?.content.trim() !== '---') return null
+  const closing = lines.findIndex((line, index) => index > 0 && line.content.trim() === '---')
+  return closing === -1 ? null : { lines, closing }
+}
+
+function splitSummarySourceLines(source: string): SummarySourceLine[] {
+  const lines: SummarySourceLine[] = []
+  let start = 0
+  while (start <= source.length) {
+    const newline = source.indexOf('\n', start)
+    if (newline === -1) {
+      lines.push({ content: source.slice(start), ending: '' })
+      break
+    }
+    const contentEnd = newline > start && source[newline - 1] === '\r' ? newline - 1 : newline
+    lines.push({
+      content: source.slice(start, contentEnd),
+      ending: source.slice(contentEnd, newline + 1),
+    })
+    start = newline + 1
+  }
+  return lines
+}
+
+function parseSummaryTitleLine(line: string): { key: SummaryTitleKey; value: string } | null {
+  const trimmed = line.trim()
+  const separator = trimmed.indexOf(':')
+  if (separator === -1) return null
+  const candidate = trimmed.slice(0, separator).trimEnd()
+  if (candidate !== 'title' && candidate !== 'title_zh') return null
+  return { key: candidate, value: normalizeTitle(trimmed.slice(separator + 1)) }
+}
+
 /**
  * Canonical bilingual bodies are delimited with invisible Markdown comments:
  *
@@ -143,5 +216,13 @@ function normalizeTitle(raw: string): string {
 }
 
 function boundTitle(value: string): string {
-  return Array.from(value).slice(0, MAX_TITLE_CHARS).join('')
+  return Array.from(value).slice(0, SUMMARY_TITLE_CHAR_LIMIT).join('')
+}
+
+function shortenSummaryTitle(value: string): string {
+  const budget = SUMMARY_TITLE_CHAR_LIMIT - 1
+  const clipped = Array.from(value).slice(0, budget)
+  const lastSpace = clipped.lastIndexOf(' ')
+  const bounded = lastSpace >= Math.floor(budget / 2) ? clipped.slice(0, lastSpace) : clipped
+  return `${bounded.join('').replace(/[\s\p{P}]+$/u, '')}…`
 }