Best possible solution:

Close this duplicate draft and continue review, live Telegram proof, and any landing work on #53762.

Do we have a high-confidence way to reproduce the issue?

Yes. Source inspection and both PR tests show the path: a final payload split into reasoning and answer segments can leave reasoning only hinted, buffer the answer, and return from the segment branch before flushing; I did not execute tests because this review is read-only.

Is this the best way to solve the issue?

No for this PR as the merge vehicle. The code shape is plausible, but the same fix is already represented by the older canonical PR with the linked bug and fuller regression scenario.

Security review:

Security review cleared: The diff touches Telegram dispatch logic and a test only; it does not change dependencies, workflows, permissions, secrets handling, or package execution paths.

What I checked:

• Current PR diff: The PR adds an info.kind === "final" guard that calls flushBufferedFinalAnswer() before the segmented-delivery early return, plus a mocked regression test for a skipped reasoning segment followed by a visible final answer. (extensions/telegram/src/bot-message-dispatch.ts:1383, f1b425034912)
• Current main behavior: On current main, final payload segments can buffer an answer after a reasoning segment stays only hinted, then the segments.length > 0 branch returns before the later flush paths run. (extensions/telegram/src/bot-message-dispatch.ts:1313, 35cd2af159f4)
• Buffered state contract: The reasoning coordinator buffers a final answer when reasoning is only hinted and exposes takeBufferedFinalAnswer(), making the proposed flush consistent with the existing state contract. (extensions/telegram/src/reasoning-lane-coordinator.ts:118, 35cd2af159f4)
• Canonical duplicate found: GitHub search found the older open PR fix(telegram): flush buffered final answer when reasoning delivery is skipped [AI-assisted] #53762 with the same Telegram buffered-final fix and linked root bug [Bug]: streaming: partial drops text block when assistant turn contains [thinking, text] #53384.
• Canonical PR carries the same remaining work: The older PR adds the same final-kind flush before the segmented early return, a more specific two-turn regression test, and a changelog entry, so this draft does not carry unique merge-critical work. (extensions/telegram/src/bot-message-dispatch.ts:693, b25e563bcb94)
• Telegram proof expectation: Maintainer notes say Telegram behavior PRs touching transport or streaming need real Telegram proof rather than synthetic-only validation. (.agents/maintainer-notes/telegram.md:37, 35cd2af159f4)

Likely related people:

• Peter Steinberger: Current-main blame/log show the reasoning split, buffered-final helper, and adjacent Telegram dispatch paths were introduced or recently carried through commits 57c952f and 1ba9f5d. (role: recent area contributor; confidence: high; commits: 57c952f67985, 1ba9f5ded325; files: extensions/telegram/src/bot-message-dispatch.ts, extensions/telegram/src/reasoning-lane-coordinator.ts, extensions/telegram/src/bot-message-dispatch.test.ts)
• amitgaur: The older open canonical PR and the linked root bug are both by this contributor, and the PR commits carry the same flush plus a more detailed regression test. (role: canonical reporter and fix contributor; confidence: high; commits: 10046fb66ccc, b25e563bcb94; files: extensions/telegram/src/bot-message-dispatch.ts, extensions/telegram/src/bot-message-dispatch.test.ts, CHANGELOG.md)

Codex review notes: model gpt-5.5, reasoning high; reviewed against 35cd2af159f4.