diff --git a/shared/src/messages.test.ts b/shared/src/messages.test.ts
index b6f4de141a..80df94903c 100644
--- a/shared/src/messages.test.ts
+++ b/shared/src/messages.test.ts
@@ -1,8 +1,11 @@
 import { describe, expect, test } from 'bun:test'
 import {
+    collapseRepeats,
     extractAssistantPlainText,
     extractNotifySummary,
     isRedundantGoalStatusEventContent,
+    matchNotifySummaryLine,
+    NOTIFY_SUMMARY_TOKEN,
     type NotifySummary
 } from './messages'
 
@@ -207,6 +210,60 @@ describe('extractNotifySummary + extractAssistantPlainText (integration)', () =>
     })
 })
 
+describe('collapseRepeats (corruption normalizer)', () => {
+    test('collapses runs of a repeated character to one', () => {
+        expect(collapseRepeats('SUMMARY')).toBe('SUMARY')
+        expect(collapseRepeats('aaa-bb-c')).toBe('a-b-c')
+        expect(collapseRepeats('')).toBe('')
+        expect(collapseRepeats('abc')).toBe('abc')
+    })
+
+    test('the correct token and the Cursor dup-drop collapse to the same form', () => {
+        // AGENT_NOTIFY_SUMMARY -> AGENT_NOTIFY_SUMARY (drop one M);
+        // both must normalize equal so a corrupted line still matches.
+        expect(collapseRepeats(NOTIFY_SUMMARY_TOKEN)).toBe(collapseRepeats('AGENT_NOTIFY_SUMARY'))
+    })
+})
+
+describe('matchNotifySummaryLine (corruption-tolerant detector)', () => {
+    test('matches the correct token line and returns the JSON', () => {
+        expect(matchNotifySummaryLine('AGENT_NOTIFY_SUMMARY {"status":"done"}')).toBe('{"status":"done"}')
+    })
+
+    test('matches the Cursor dup-dropped token (SUMARY)', () => {
+        expect(matchNotifySummaryLine('AGENT_NOTIFY_SUMARY {"status":"done"}')).toBe('{"status":"done"}')
+    })
+
+    test('tolerates trailing/leading whitespace on the line', () => {
+        expect(matchNotifySummaryLine('  AGENT_NOTIFY_SUMMARY {"a":1}  ')).toBe('{"a":1}')
+    })
+
+    test('rejects a token embedded in prose (not a bare token)', () => {
+        expect(matchNotifySummaryLine('see the AGENT_NOTIFY_SUMMARY {"x":1}')).toBeNull()
+    })
+
+    test('rejects lines with no JSON or no leading token', () => {
+        expect(matchNotifySummaryLine('AGENT_NOTIFY_SUMMARY not json')).toBeNull()
+        expect(matchNotifySummaryLine('{"x":1}')).toBeNull()
+        expect(matchNotifySummaryLine('')).toBeNull()
+    })
+
+    test('rejects a non-dup deletion (NOTFY) - acceptable residual loss', () => {
+        // Non-adjacent-duplicate corruption is not recoverable by collapse-norm;
+        // observed rate in the wild is ~2 in 5800. Documented as acceptable.
+        expect(matchNotifySummaryLine('AGENT_NOTFY_SUMMARY {"x":1}')).toBeNull()
+    })
+})
+
+describe('extractNotifySummary (corruption-tolerant end-to-end)', () => {
+    test('parses a corrupted (SUMARY) trailing line into a summary object', () => {
+        const text = 'Did the thing.\n\nAGENT_NOTIFY_SUMARY {"version":1,"status":"blocked","summary":"needs key"}'
+        const r = extractNotifySummary(text)
+        expect(r?.status).toBe('blocked')
+        expect(r?.summary).toBe('needs key')
+    })
+})
+
 describe('isRedundantGoalStatusEventContent (regression-guard for messages.ts edits)', () => {
     test('still detects goal-active events', () => {
         const value = {
diff --git a/shared/src/messages.ts b/shared/src/messages.ts
index 551b308207..65ddfcd4f5 100644
--- a/shared/src/messages.ts
+++ b/shared/src/messages.ts
@@ -117,7 +117,7 @@ export function extractAssistantPlainText(content: unknown): string | null {
     return null
 }
 
-const NOTIFY_SUMMARY_PREFIX = 'AGENT_NOTIFY_SUMMARY '
+export const NOTIFY_SUMMARY_TOKEN = 'AGENT_NOTIFY_SUMMARY'
 
 export type NotifySummary = {
     version?: number
@@ -128,20 +128,57 @@ export type NotifySummary = {
     summary?: string
 }
 
+/**
+ * Collapse every run of a repeated character down to a single instance
+ * (`"SUMMARY"` -> `"SUMARY"`, `"aaa-bb"` -> `"a-b"`).
+ *
+ * This is the corruption-normalizer for the notify contract. Observed in
+ * the wild (354k stored messages): Cursor drops one of a doubled letter in
+ * roughly 1 of 7 turns, mangling `AGENT_NOTIFY_SUMMARY` -> `AGENT_NOTIFY_SUMARY`
+ * (Claude/Codex: 0 occurrences). Matching on the collapse-normalized form
+ * makes the correct and dup-dropped tokens compare equal, so a corrupted
+ * line is still detected (and therefore both stripped from the human view
+ * and parsed into an inbox event) instead of double-failing.
+ */
+export function collapseRepeats(value: string): string {
+    return value.replace(/(.)\1+/g, '$1')
+}
+
+const NOTIFY_SUMMARY_TOKEN_NORM = collapseRepeats(NOTIFY_SUMMARY_TOKEN)
+
+/**
+ * If `line` is a notify-summary line, return the raw JSON substring `{...}`;
+ * otherwise `null`. `line` is expected to already be the last non-empty line
+ * of a message (callers enforce the end-anchor).
+ *
+ * Corruption-tolerant: the leading token is matched by collapse-normalized
+ * equality (see `collapseRepeats`), so Cursor's `SUMMARY`->`SUMARY` dup-drop
+ * still matches. The JSON must start with `{` and end with `}`; a token that
+ * is embedded in prose (`"see the AGENT_NOTIFY_SUMMARY {..}"`) fails because
+ * its collapse-normalized prefix will not equal the bare token.
+ */
+export function matchNotifySummaryLine(line: string): string | null {
+    const trimmed = line.trim()
+    const braceIdx = trimmed.indexOf('{')
+    if (braceIdx <= 0) return null
+    const token = trimmed.slice(0, braceIdx).trim()
+    if (!token || collapseRepeats(token) !== NOTIFY_SUMMARY_TOKEN_NORM) return null
+    const jsonPart = trimmed.slice(braceIdx).trim()
+    if (!jsonPart.startsWith('{') || !jsonPart.endsWith('}')) return null
+    return jsonPart
+}
+
 /**
  * Look for an `AGENT_NOTIFY_SUMMARY {...json...}` line as the **last
  * non-empty line** of an agent's plain-text message.
  *
- * Strict end-anchor: anything below the JSON line (even whitespace) is
- * fine, but if the agent wrote prose AFTER the line we treat it as
- * non-compliant and return null. This also makes false positives from
+ * Strict end-anchor: trailing whitespace-only lines are fine, but prose
+ * AFTER the JSON line is treated as non-compliant. This also makes a
  * `AGENT_NOTIFY_SUMMARY` quoted inside an earlier paragraph harmless,
  * because such a quote is never the last line.
  *
- * Returns the parsed object on success, `null` on any deviation. The
- * shape is intentionally loose - we only trust `summary`, `action`, and
- * `status` for notification rendering, but the full object is forwarded
- * onto the meta-event bus when Phase 2 lands.
+ * The token match is corruption-tolerant (see `matchNotifySummaryLine`).
+ * Returns the parsed object on success, `null` on any deviation.
  */
 export function extractNotifySummary(text: unknown): NotifySummary | null {
     if (typeof text !== 'string' || text.length === 0) return null
@@ -151,11 +188,8 @@ export function extractNotifySummary(text: unknown): NotifySummary | null {
     while (lastIdx >= 0 && lines[lastIdx].trim() === '') lastIdx -= 1
     if (lastIdx < 0) return null
 
-    const lastLine = lines[lastIdx].trim()
-    if (!lastLine.startsWith(NOTIFY_SUMMARY_PREFIX)) return null
-
-    const jsonPart = lastLine.slice(NOTIFY_SUMMARY_PREFIX.length).trim()
-    if (!jsonPart.startsWith('{') || !jsonPart.endsWith('}')) return null
+    const jsonPart = matchNotifySummaryLine(lines[lastIdx])
+    if (!jsonPart) return null
 
     try {
         const parsed: unknown = JSON.parse(jsonPart)
diff --git a/shared/src/overseerEvents.test.ts b/shared/src/overseerEvents.test.ts
index 94956fdd8d..147eca8621 100644
--- a/shared/src/overseerEvents.test.ts
+++ b/shared/src/overseerEvents.test.ts
@@ -15,8 +15,10 @@ import {
     normalizeUrlIdempotencyKey,
     OVERSEER_EVENT_TYPES,
     HAPI_EVENTS_BEGIN,
-    HAPI_EVENTS_END
+    HAPI_EVENTS_END,
+    stripAgentContract
 } from './overseerEvents'
+import { extractNotifySummary } from './messages'
 
 describe('overseerEvents mapping', () => {
     test('maps notify status to event_type', () => {
@@ -113,3 +115,45 @@ describe('overseerEvents mapping', () => {
         expect(normalizeUrlIdempotencyKey('https://Example.COM/path/#frag')).toBe('https://example.com/path')
     })
 })
+
+describe('stripAgentContract (render-only, human-facing)', () => {
+    test('strips a correct trailing summary line + the blank line above it', () => {
+        const text = 'Here is the answer.\n\nAGENT_NOTIFY_SUMMARY {"status":"done","summary":"ok"}'
+        expect(stripAgentContract(text)).toBe('Here is the answer.')
+    })
+
+    test('strips a corrupted (SUMARY) trailing summary line', () => {
+        const text = 'Here is the answer.\nAGENT_NOTIFY_SUMARY {"status":"done"}'
+        expect(stripAgentContract(text)).toBe('Here is the answer.')
+    })
+
+    test('strips the leading inline-contract prefix block (historical stored msgs)', () => {
+        const text = `${AGENT_NOTIFY_CONTRACT_INLINE_PREFIX}please do the thing`
+        expect(stripAgentContract(text)).toBe('please do the thing')
+    })
+
+    test('strips both leading prefix and trailing summary in one pass', () => {
+        const text = `${AGENT_NOTIFY_CONTRACT_INLINE_PREFIX}real content\nAGENT_NOTIFY_SUMMARY {"status":"done"}`
+        expect(stripAgentContract(text)).toBe('real content')
+    })
+
+    test('leaves a quoted-but-not-last token untouched', () => {
+        const text = 'I emit AGENT_NOTIFY_SUMMARY {json} at the end.\nThen more prose.'
+        expect(stripAgentContract(text)).toBe(text)
+    })
+
+    test('no-ops on clean text and empty input', () => {
+        expect(stripAgentContract('just a normal reply')).toBe('just a normal reply')
+        expect(stripAgentContract('')).toBe('')
+    })
+
+    test('round-trip invariant: overseer still parses raw, human view has no marker', () => {
+        const raw = 'Work done.\nAGENT_NOTIFY_SUMARY {"status":"done","summary":"shipped"}'
+        // overseer reads the RAW text and still gets the event (corruption-tolerant)
+        expect(extractNotifySummary(raw)?.summary).toBe('shipped')
+        // the human render is stripped clean and can no longer parse a marker
+        const human = stripAgentContract(raw)
+        expect(human).toBe('Work done.')
+        expect(extractNotifySummary(human)).toBeNull()
+    })
+})
diff --git a/shared/src/overseerEvents.ts b/shared/src/overseerEvents.ts
index b9f44a895f..6c5a8654bd 100644
--- a/shared/src/overseerEvents.ts
+++ b/shared/src/overseerEvents.ts
@@ -1,4 +1,5 @@
 import type { NotifySummary } from './messages'
+import { matchNotifySummaryLine } from './messages'
 
 export const NOTIFY_SUMMARY_STATUSES = [
     'done',
@@ -21,6 +22,41 @@ export const AGENT_NOTIFY_CONTRACT_INLINE_PREFIX = [
     ''
 ].join('\n')
 
+/**
+ * Strip the machine-only notify contract from text destined for HUMAN eyes.
+ *
+ * The `AGENT_NOTIFY_SUMMARY` contract rides fully in-band so it works across
+ * every agent flavor, but it must never reach the human render. Two removals:
+ *   1. The trailing `AGENT_NOTIFY_SUMMARY {...}` line (collapse-normalized, so
+ *      Cursor's corrupted `SUMARY` variant strips too) plus any blank lines it
+ *      leaves behind.
+ *   2. A leading inline-contract prefix block - only present on historical
+ *      operator messages stored before input-side decoupling (the hub now
+ *      injects the prefix into the agent-bound copy only, never the stored one).
+ *
+ * Overseer event capture and notification builders MUST read the raw text, not
+ * this - stripping is render-only so the machine signal survives in the store.
+ */
+export function stripAgentContract(text: string): string {
+    if (typeof text !== 'string' || text.length === 0) return text
+    let out = text
+
+    if (out.startsWith(AGENT_NOTIFY_CONTRACT_INLINE_PREFIX)) {
+        out = out.slice(AGENT_NOTIFY_CONTRACT_INLINE_PREFIX.length)
+    }
+
+    const lines = out.split('\n')
+    let lastIdx = lines.length - 1
+    while (lastIdx >= 0 && lines[lastIdx].trim() === '') lastIdx -= 1
+    if (lastIdx >= 0 && matchNotifySummaryLine(lines[lastIdx])) {
+        const kept = lines.slice(0, lastIdx)
+        while (kept.length > 0 && kept[kept.length - 1].trim() === '') kept.pop()
+        out = kept.join('\n')
+    }
+
+    return out
+}
+
 export const HAPI_EVENTS_BEGIN = '<!--HAPI_EVENTS_BEGIN-->'
 export const HAPI_EVENTS_END = '<!--HAPI_EVENTS_END-->'
 
diff --git a/web/src/lib/assistant-runtime.ts b/web/src/lib/assistant-runtime.ts
index 7769ead3c2..8400fe766a 100644
--- a/web/src/lib/assistant-runtime.ts
+++ b/web/src/lib/assistant-runtime.ts
@@ -4,7 +4,7 @@ import type { AppendMessage, AttachmentAdapter, ThreadMessageLike } from '@assis
 import { useExternalMessageConverter, useExternalStoreRuntime } from '@assistant-ui/react'
 import type { PendingSchedule } from '@/components/AssistantChat/ScheduleTimePicker'
 import { resolvePendingSchedule } from '@/components/AssistantChat/ScheduleTimePicker'
-import { safeStringify } from '@hapi/protocol'
+import { safeStringify, stripAgentContract } from '@hapi/protocol'
 import { renderEventLabel } from '@/chat/presentation'
 import type { ChatBlock, CliOutputBlock, CodexReview, UsageData } from '@/chat/types'
 import type { AgentEvent, ToolCallBlock } from '@/chat/types'
@@ -324,7 +324,11 @@ function toThreadMessageLike(block: VisibleChatBlock, threadMessageId: string):
             role: 'user',
             id: threadMessageId,
             createdAt: new Date(block.createdAt),
-            content: [{ type: 'text', text: block.text }],
+            // Strip the machine-only notify contract from the human render. On
+            // non-Cursor flavors the hub prepends an inline contract prefix to
+            // the stored operator message (#20); stripAgentContract removes that
+            // leading block. No-op when absent.
+            content: [{ type: 'text', text: stripAgentContract(block.text) }],
             metadata: {
                 custom: {
                     kind: 'user',
@@ -343,7 +347,12 @@ function toThreadMessageLike(block: VisibleChatBlock, threadMessageId: string):
             role: 'assistant',
             id: threadMessageId,
             createdAt: new Date(block.createdAt),
-            content: [{ type: 'text', text: block.text }],
+            // Strip the trailing AGENT_NOTIFY_SUMMARY line (collapse-normalized,
+            // so Cursor's corrupted SUMARY variant strips too) so the human never
+            // sees the machine contract. The raw text stays in the store for the
+            // overseer event/inbox pipeline. copyText derives from this content,
+            // so the clipboard is clean too.
+            content: [{ type: 'text', text: stripAgentContract(block.text) }],
             metadata: {
                 custom: {
                     kind: 'assistant',