Summary

• Problem: retainPreviewOnCleanupByLane could stay true after an archived-preview retain and leak into a later transient final on the same lane.
• Why it matters: when that later final fell back to sendPayload, cleanup skipped stream.clear() and left a stale partial preview next to the fallback-sent final message.
• What changed: clear the retain flag only when a lane is still in the transient preview lifecycle, then let the current final attempt set it back if it really retains the preview.
• What did NOT change (scope boundary): no new fallback behavior, no new preview-state model, no changes outside Telegram final-preview cleanup.

Change Type (select all)

• Bug fix
• Feature
• Refactor
• 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 #
• Related fix(telegram): prevent duplicate messages when preview edit times out #41662

User-visible / Behavior Changes

• Telegram multi-message draft streams no longer leave a stale partial preview visible when an earlier archived preview was retained but a later transient final falls back to a normal send.

Security Impact (required)

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

Repro + Verification

Environment

• OS: macOS
• Runtime/container: local repo checkout
• Model/provider: n/a
• Integration/channel (if any): Telegram
• Relevant config (redacted): streamMode partial

Steps

1. Stream message A so its preview is archived.
2. Retain that archived preview path via message to edit not found, then send message B as the active preview.
3. Make B's final edit fail pre-connect so it falls back to sendPayload.

Expected

• Cleanup clears B's stale active preview before exit.

Actual

• Before this fix, the stale retain flag skipped cleanup and left the partial preview visible beside the fallback-sent final.

Evidence

• 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: targeted Vitest coverage for src/telegram/lane-delivery.test.ts, src/telegram/bot-message-dispatch.test.ts, and src/telegram/network-errors.test.ts; pnpm tsgo.
• Edge cases checked: existing regression that finalized previews stay visible when extra final payloads are sent still passes; new regression covers archived retain followed by transient fallback-send cleanup.
• What you did not verify: live Telegram delivery.

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.

Compatibility / Migration

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

Failure Recovery (if this breaks)

• How to disable/revert this change quickly: revert commit 87bf43145.
• Files/config to restore: src/telegram/lane-delivery-text-deliverer.ts, src/telegram/bot-message-dispatch.test.ts
• Known bad symptoms reviewers should watch for: stale Telegram preview bubbles surviving after a fallback-sent final, or finalized previews being cleared by later extra final payloads.

Risks and Mitigations

• Risk: the retain reset could clear protection for already-finalized previews.
  • Mitigation: reset is gated to activePreviewLifecycleByLane === "transient", and the existing finalized-preview regression still passes.