## Summary

Adds an in-depth guide for message reactions covering outbound
add/remove and inbound `messageReaction` handling, plus links the
existing "Reactions" section in the Sending Messages essentials page to
the new guide.

## What's covered in the guide

- Public-developer-preview banner
- Adding and removing reactions (`api.reactions.add` /
`api.reactions.delete` / `Reactions.AddAsync` / `Reactions.DeleteAsync`)
- Receiving reactions: `messageReaction` activity handlers across all
three SDKs, plus the .NET-only `OnMessageReactionAdded` /
`OnMessageReactionRemoved` sub-handlers
- Available reaction types — the modern set of 6 (`like`, `heart`,
`1f440_eyes`, `2705_whiteheavycheckmark`, `launch`, `1f4cc_pushpin`)
- Skin tone variants (`-tone1` … `-tone5`)
- Rate limits (2 reactions/sec, 429 + Retry-After)
- Best practices and differences from Feedback

## What's intentionally omitted

- **Custom reactions section** — aligned with the Microsoft Learn agent
reactions PR
([msteams-docs#13991](MicrosoftDocs/msteams-docs#13991)),
which is omitting custom reaction examples due to a known client-side
rendering issue. A commented-out link to the Learn reactions reference
remains in the source for restoration once that PR lands.
- **Advanced API client usage** — the previous draft's example
referenced an `ApiClient` constructor that doesn't exist in the current
SDK; removed rather than rewritten.

## Coordination

- C# samples follow the project convention from #2735 (cancellationToken
in handler signatures, threaded through `Send`, `Task.Delay`, and
reaction API calls).
- The TypeScript include uses `api.reactions.delete()` ahead of
[microsoft/teams.ts#567](microsoft/teams.ts#567),
which renames `remove()` → `delete()` to align with teams.py and
teams.net.

## Test plan

- [x] `npm start` regenerates docs cleanly with no content gaps
- [x] Per-language renders (TS / Python / C#) verified in the dev server
- [x] Cross-link from `essentials/sending-messages` → in-depth guide
resolves correctly
- [ ] Visual review on the deployed preview

---------

Co-authored-by: Corina Gum <[email protected]>
Co-authored-by: Claude Opus 4.7 (1M context) <[email protected]>

## Summary

Brings `origin/main` into `release` for the **2.0.12** release. **No
carve-outs this time** — Quoted Replies is included.

`version.json`: `2.0.12-preview.{height}` → `2.0.12`.

Aligns with teams.py 2.0.12 (PR #442 already on PyPI / pending publish).

## What's in this release (delta from 2.0.11)

**Features**
- Quoted Replies + new quotes features — previously held back via the
2.0.11 carve-out (#576)
- SuggestedActionSubmitActivity for `suggestedAction/submit` invoke
(#591)
- Default targeted replies for targeted inbound messages (#592)
- Filter colliding keys before `Object.assign` in `ActivityContext`
(#596)
- Prompt Preview support (#536)
- A2A sample (#584)
- AI/MCPClient (#572)
- Allow passing custom HTTP client via `AppOptions`-equivalent
- Reactions API marked GA (#575), Rename `ReactionClient.remove()` →
`delete()` (#567)

**Security & fixes**
- Security hardening: tighten cross-origin policies (#595)
- Lock JsonWebToken trust-boundary contract (#586)
- `fix(deps)`: npm audit fix — clears all high-severity advisories
(#599)
- `fix(apps)`: log inbound activities at info, warn on missing
Authorization (#568)
- `fix`: App user-agent merging (#573)
- `fix`: Add null checks in `local-memory.ts` to prevent role crash
(#438)
- `fix`: `@microsoft/teams.client` import error in webpack 5 (#566)
- Switch to named imports without subpaths (#561)

**Deprecations / package changes**
- Deprecate `DevtoolsPlugin` in favor of Microsoft 365 Agents Playground
(#593)
- Remove in-repo Teams CLI package (#580) — moved to
`teams-sdk/packages/cli`
- Deprecate AI Libraries (#588)
- Correct imports + return types in misc. packages (#589)

**Dependency bumps**
- turbo 2.8.11 → 2.9.14 (#587)
- qs 6.15.0 → 6.15.2 (#594)
- hono 4.12.14 → 4.12.16 (#562)
- npm audit fix bundle (#599): axios 1.13.5 → 1.16.1, fast-uri 3.1.0 →
3.1.2, ws 8.19.0 → 8.21.0, @azure/msal-node hoisted 5.2.2, uuid 11.1.0 →
11.1.1, @azure/identity 4.13.0 → 4.13.1, express-rate-limit, ip-address,
brace-expansion, etc.

## Quoted Replies inclusion notes

- Teams client rendering is in-sync with the wire format as of
2026-05-06.
- APX QR rollout completed: Public 2026-04-10, GCCH/DoD/Gallatin
2026-04-14.
- No SDK-side carve-outs needed; this matches the teams.py 2.0.12 (PR
#442) decision.

## Branch structure note

`prep-release/2.0.12` is reset to `origin/main` + a one-line
`version.json` bump. Diff against `release` (this PR) shows the full
delta from 2.0.11. We deliberately did not use a 2-parent merge commit —
the auto-merge tried to interleave non-overlapping hunks from main's QR
additions with release's QR carve-outs in `activity.ts`, producing a
semantically broken file. Reset-to-main + version bump is the clean way
to express "release should equal main."

## Test plan

- [x] `npm install` clean (post-audit-fix lockfile)
- [x] `npm run build` — 33/33 targets clean
- [x] `npm test` — 14/14 task targets, 279+ tests pass
- [x] E2E echo bot smoke test against `cg-test-bot-py` via canary ABS —
done on `cg/audit-deps-ts` (now merged); covers axios + msal-node code
paths
- [ ] Pipeline Build + Test stages green on `release` after merge
- [ ] Publish pipeline run with **Public** → ESRP → npm
`@microsoft/teams.*@2.0.12`
- [ ] Smoke install: `npm view @microsoft/teams[email protected]` after
publish