Summary

After the msteams SDK rebase (#76262), Teams streaming double-posts replies longer than ~4000 chars: the streamed preview persists AND the full final text is re-sent via chunked/block fallback. Short replies collapse correctly. This is a regression of #59297 (which fixed the same >4000-char duplicate on the pre-rebase pipeline).

Environment

• OpenClaw: 2026.6.1
• Channel: channels.msteams, streaming.mode=partial
• Provider: bifrost-claude/claude-opus-4-8 via Bifrost -> Azure AI Foundry Anthropic
• Install: openshell sandbox image (K3s on Docker)

Steps to reproduce

1. channels.msteams.streaming.mode=partial
2. Send a prompt that yields a >4000-char reply in a DM
3. Observe: the streamed preview AND a second full copy of the reply (chunked block delivery) both persist as separate bubbles. Replies under 4000 chars collapse correctly (single bubble).

Root cause (from PR history + source)

• TEAMS_MAX_CHARS = 4000. When a streamed reply exceeds it, the finalize path falls through to resolveTextChunksWithFallback -> chunked block send.
• fix(msteams): prevent duplicate text when stream exceeds 4000 char limit #59297 (merged 2026-04-02, fixes msteams: streaming + block delivery duplicate text when response exceeds 4000 chars #58601) solved this on the OLD pipeline: it added stream-failure metadata (failed flag + streamed length) and trimmed the already-streamed prefix from the fallback payload, suppressing fallback entirely when the streamed prefix already covered the full text.
• fix(msteams): rebase TeamsSDK patterns to simplify Teams Integration #76262 (merged 2026-05-28) rebased the plugin onto @microsoft/teams.apps and replaced the custom streaming pipeline with ctx.stream. The fix(msteams): prevent duplicate text when stream exceeds 4000 char limit #59297 streamed-prefix suppression/trim logic was not carried into the new SDK finalize path, so the over-limit fallback now re-sends the full text.

Expected

When a streamed reply exceeds the limit and falls back to block delivery, the fallback should trim the already-streamed prefix (or be suppressed entirely if the prefix covered the full text), as #59297 did. No duplicate.

Related

• Regresses fix(msteams): prevent duplicate text when stream exceeds 4000 char limit #59297 (fix) / msteams: streaming + block delivery duplicate text when response exceeds 4000 chars #58601 (original bug)
• [Bug]: Teams streaming delivers normal-length replies twice in 2026.5.28 #90398 (open) - normal-length double-post on 5.28; fix(msteams): rebase TeamsSDK patterns to simplify Teams Integration #76262 fixed the normal-length half, this is the remaining long-reply half
• Introduced by fix(msteams): rebase TeamsSDK patterns to simplify Teams Integration #76262 (SDK rebase)

Workaround

channels.msteams.streaming.mode: "off" (loses streaming UX).