Summary

• Problem: iMessage reflected copies can miss dedupe when they arrive after the 4 second text fallback window or when the reflected text starts with replacement/control garbage.
• Why it matters: missed echo suppression can re-ingest the assistant's own outbound reply as a fresh inbound message and create duplicate or looping replies.
• What changed: extended the iMessage text fallback TTL to 30 seconds and normalized leading replacement/control characters in both the sent-message echo cache and the self-chat reflection cache.
• What did NOT change (scope boundary): message ID matching, routing, outbound send behavior, and non-iMessage channels were not changed.

Change Type (select all)

• Bug fix
• Feature
• Refactor required for the fix
• Docs
• Security hardening
• Chore/infra

Scope (select all touched areas)

• Gateway / orchestration
• Skills / tool execution
• Auth / tokens
• Memory / storage
• Integrations
• API / contracts
• UI / DX
• CI/CD / infra

Linked Issue/PR

• Closes iMessage DM echo: corrupted prefix breaks text-based dedup (v2026.3.31+) #59973
• Related iMessage DM echo: corrupted prefix breaks text-based dedup (v2026.3.31+) #59973
• This PR fixes a bug or regression

Root Cause / Regression History (if applicable)

• Root cause: extensions/imessage/src/monitor/echo-cache.ts only normalized CRLF plus trim and expired text fallback entries after 4 seconds, so delayed or prefix-corrupted reflected copies failed exact-text matching.
• Missing detection / guardrail: coverage preserved the short TTL behavior instead of locking in delayed and corrupted-prefix echoes as dedupe cases.
• Prior context (git blame, prior PR, issue, or refactor if known): existing iMessage echo-cache tests documented the 4 second text fallback assumption; the linked issue showed reflected text arriving 5 to 10 seconds later with leading U+FFFD characters.
• Why this regressed now: the current iMessage reflection path can deliver slower or text-corrupted reflected copies than the original fallback assumptions allowed for.
• If unknown, what was ruled out: ruled out a current fix in the active iMessage cache and inbound-processing paths; the issue behavior still reproduced against the current cache logic.

Regression Test Plan (if applicable)

• Coverage level that should have caught this:
  • Unit test
  • Seam / integration test
  • End-to-end test
  • Existing coverage already sufficient
• Target test or file: extensions/imessage/src/monitor/monitor-provider.echo-cache.test.ts, extensions/imessage/src/monitor/self-chat-cache.test.ts, and extensions/imessage/src/monitor/self-chat-dedupe.test.ts.
• Scenario the test should lock in: delayed 5 second reflections and reflected copies with leading replacement/control characters should still dedupe in both normal and self-chat flows.
• Why this is the smallest reliable guardrail: the failure is inside the two normalization and TTL caches, so focused cache tests cover the bug directly without requiring live iMessage infrastructure.
• Existing test that already covers this (if any): existing iMessage echo-cache tests covered the same caches but encoded the old 4 second miss behavior.
• If no new test is added, why not: N/A.

User-visible / Behavior Changes

• iMessage now suppresses delayed reflected echoes for longer and also matches reflected copies whose text starts with replacement/control characters.

Diagram (if applicable)

N/A

Security Impact (required)

• New permissions/capabilities? (Yes/No) No
• Secrets/tokens handling changed? (Yes/No) No
• New/changed network calls? (Yes/No) No
• Command/tool execution surface changed? (Yes/No) No
• Data access scope changed? (Yes/No) No
• If any Yes, explain risk + mitigation: N/A

Repro + Verification

Environment

• OS: macOS 25.3.0
• Runtime/container: pnpm workspace, Bun/Node repo defaults
• Model/provider: N/A
• Integration/channel (if any): iMessage
• Relevant config (redacted): default test config

Steps

1. Cache a recently sent iMessage text in the iMessage echo cache.
2. Advance time by 5 seconds and query the cache with the same text, or with the same text prefixed by replacement/control characters.
3. Observe whether the reflected copy is dropped as an echo.

Expected

• Delayed reflected copies still match the text fallback window.
• Leading replacement/control garbage does not break text dedupe.

Actual

• Before this change, the 5 second text-only reflection missed the cache and prefix-corrupted text failed normalization.

Evidence

Attach at least one:

• Failing test/log before + passing after
• Trace/log snippets
• Screenshot/recording
• Perf numbers (if relevant)

Human Verification (required)

What you personally verified (not just CI), and how:

• Verified scenarios: ran pnpm test -- extensions/imessage/src/monitor/monitor-provider.echo-cache.test.ts extensions/imessage/src/monitor/self-chat-cache.test.ts extensions/imessage/src/monitor/self-chat-dedupe.test.ts extensions/imessage/src/monitor/inbound-processing.test.ts; ran pnpm test:extension imessage; ran pnpm build; also sanity-checked the cache behavior directly before the fix and confirmed 5 second text-only and corrupted-prefix matches failed on the old logic.
• Edge cases checked: self-chat dedupe uses the same normalization fix; message ID retention still outlives the shorter text fallback window.
• What you did not verify: a live local iMessage roundtrip on macOS.

Review Conversations

• I replied to or resolved every bot review conversation I addressed in this PR.
• I left unresolved only the conversations that still need reviewer or maintainer judgment.

If a bot review conversation is addressed by this PR, resolve that conversation yourself. Do not leave bot review conversation cleanup for maintainers.

Compatibility / Migration

• Backward compatible? (Yes/No) Yes
• Config/env changes? (Yes/No) No
• Migration needed? (Yes/No) No
• If yes, exact upgrade steps: N/A

Risks and Mitigations

• Risk: a longer text fallback window could suppress a legitimate repeated identical text message if no message ID is available and it lands inside the same 30 second scope window.
  • Mitigation: the cache stays conversation-scoped, the longer-lived message ID path is unchanged, and the new normalization is limited to leading replacement/control garbage that should not be semantically meaningful for reflected copies.

Notes

• pnpm check currently fails in unrelated pre-existing extensions/diffs/src/language-hints.test.ts type assertions on this tree; the iMessage-focused tests, extension lane, and pnpm build passed for this PR.
• AI assistance: used an LLM coding agent for implementation and drafting, then reviewed the touched code paths and validation results before opening this PR.

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