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feat(types): multi-chat sessions (ahp-chat: channel)#197

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feat(types): multi-chat sessions (ahp-chat: channel)#197
sandy081 wants to merge 15 commits into
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@sandy081 sandy081 commented Jun 5, 2026

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Implements the multi-chat sessions proposal (design discussion, approved).

Splits the AHP session model: a session becomes a shared coordination scope (workspace, project, model/agent defaults, tools, config), and a session can hold multiple chats, each its own independently subscribable conversation over the shared scope.

What ships in this PR (Phase 1: protocol types)

  • New ahp-chat: channel. types/channels-chat/{state,commands,actions,reducer}.ts.
  • ChatState carries the turn / input / pending-message state today living on SessionState.
  • ChatSummary with optional per-chat model / agent overrides and an origin?: ChatOrigin provenance field.
  • ChatOrigin discriminated union: User / Fork / Tool (per-call discussion with @connor4312 — Tool carries { chat, toolCallId } so tool-spawned chats reference their spawning tool call).
  • SessionState changes:
    • Removed: turns, activeTurn, steeringMessage, queuedMessages, inputRequests.
    • Added: chats: ChatSummary[], defaultChat?: URI (UI input-routing hint — not a hierarchy marker).
  • New commands: createChat (with optional ChatForkSource { chat, turnId }), disposeChat.
  • Retargeted commands: fetchTurns / completions now take an ahp-chat: channel URI.
  • Reducer split: turn / input / pending-message handling moved to the chat reducer; session reducer gains chats[] / defaultChat handling.
  • Version bump: PROTOCOL_VERSION 0.3.0 → 0.4.0 (allowed pre-1.0 per versioning.md).
  • CHANGELOGs: root + every client.

Subsequent phases (will land in follow-up commits on this branch)

  • Phase 2: regenerate JSON schema.
  • Phase 3: per-client codegen + manual updates (rust / kotlin / swift / typescript / go).
  • Phase 4: docs (chat-channel reference, session↔chat relationship, URI scheme) + integration tests.
  • Phase 5: address surviving open implementation questions from the proposal; finalize release notes.

Verification

  • npm run test passes: 241/241, 100% branch coverage on types/reducers.ts.

Notes for reviewers

  • Proposal lives at docs/proposals/multi-chat-sessions.md on PR docs: add multi-chat sessions proposal #184; design discussion is captured there.
  • Doc updates (chat-channel reference, session↔chat docs) intentionally deferred to Phase 4 so this PR stays a clean type-shape diff.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

sandy081 and others added 7 commits June 5, 2026 15:39
@sandy081
Add chat channel protocol types
80e2f65 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
feat(schema): regenerate for multi-chat types
bcc3181 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
wip(clients): start multi-chat codegen
d360bde 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
feat(swift): port reducers to chat/session split
bdf5d9c 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
feat(kotlin): port reducers to chat/session split
6a3fe92 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
fix(codegen): regenerate Go/Kotlin and add Chat actions to Go generator
32a200d 
The Go generator was missing the ChatToolCallApproved/Denied/Confirmed
discriminated union variants and the ChatAction top-level union from its
explicit-skip list, causing exhaustiveness warnings during codegen.
Kotlin regeneration picked up trivial drift in State.generated.kt.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
fix(swift): update SessionState test fixtures for chats split
1bf40ab 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
connor4312
connor4312 reviewed Jun 5, 2026
View reviewed changes
Comment thread types/channels-chat/state.ts
connor4312
connor4312 reviewed Jun 5, 2026
View reviewed changes
Comment thread types/channels-session/actions.ts Outdated
connor4312
connor4312 reviewed Jun 5, 2026
View reviewed changes
Comment thread types/channels-chat/state.ts Outdated
connor4312
connor4312 reviewed Jun 5, 2026
View reviewed changes
Comment thread types/channels-session/state.ts
connor4312
connor4312 reviewed Jun 5, 2026
View reviewed changes
Comment thread types/channels-chat/state.ts
sandy081 and others added 8 commits June 7, 2026 21:59
@sandy081
docs(multi-chat): add chat channel reference + spec
729818b 
Adds the user-facing documentation for the new `ahp-chat:` channel
introduced by the multi-chat session split: chat-channel.md
specification page and updates the per-client CHANGELOG entries.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
docs(multi-chat): chat reference + sidebar entries + session spec sli…
a81c2fa 
…mming

- New generateChatChannelPage in scripts/generate-markdown.ts emits the
  ahp-chat:/ reference page from types/channels-chat/{state,actions,commands}.ts.
- Session spec doc slimmed: turn lifecycle moves to chat-channel.md;
  fetchTurns/completions removed from session command table; validation
  table reduced to session-scoped actions only; new 'Chat aggregation'
  section spelling out how SessionSummary.status/activity/modifiedAt
  derive from chats.
- Sidebar: add 'Chat Channel' entries to both /specification/ and
  /reference/ sidebars.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
feat(go): port reducers to chat/session split
b7e77ac 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
feat(rust): port to chat/session split + update generator
4d1e7cf 
Update the Rust generator to split session-scoped and chat-scoped
protocol surfaces: rename `SessionInput*` types to `ChatInput*`, add
`ChatState`/`ChatSummary`/`ChatOrigin` state types and chat commands,
partition the action map into `session/*` and `chat/*`, and add a
merged chat tool-call-confirmed helper.

Split the reducer into a slimmed session reducer (lifecycle, metadata,
customizations, chats catalogue) and a new `apply_action_to_chat`
chat reducer (turn lifecycle, tool calls, input requests, pending
messages). Track chat state in `MultiHostStateMirror` and update
fixtures/tests for the new state shapes.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
Merge remote-tracking branch 'origin/main' into sandy081/multi-chat-impl
d867bcf 
# Conflicts:
#	CHANGELOG.md
#	clients/go/CHANGELOG.md
#	clients/go/ahptypes/version.generated.go
#	clients/go/examples/reducers_demo/main.go
#	clients/go/release-metadata.json
#	clients/kotlin/CHANGELOG.md
#	clients/kotlin/release-metadata.json
#	clients/kotlin/src/main/kotlin/com/microsoft/agenthostprotocol/generated/Version.generated.kt
#	clients/rust/CHANGELOG.md
#	clients/rust/crates/ahp-types/src/version.rs
#	clients/rust/release-metadata.json
#	clients/swift/AgentHostProtocol/Sources/AgentHostProtocol/Generated/Version.generated.swift
#	clients/swift/CHANGELOG.md
#	clients/swift/release-metadata.json
#	clients/typescript/CHANGELOG.md
#	clients/typescript/release-metadata.json
#	types/version/registry.ts
@sandy081
fix(go): regenerate with gofmt formatting
10f6e2a 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
fix(go): gofmt reducers.go
70e83e2 
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
@sandy081
Address review feedback on multi-chat sessions
41ab532 
Addresses connor4312's five inline review comments on PR #197:

1. Denormalize ChatSummary into ChatState - flatten the summary nesting
   so ChatState exposes resource/title/status/activity/modifiedAt/origin
   directly. ChatSummary stays as the lightweight session-catalog view.

2. Add upsert/partial semantics for chat catalog mutations: replace
   SessionChatsChangedAction (full-replacement) with three targeted
   actions: SessionChatAddedAction (upsert by summary.resource),
   SessionChatRemovedAction (clears defaultChat if removed),
   SessionChatUpdatedAction (Partial<ChatSummary> merge).

3. Change modifiedAt from epoch millis (number) to ISO-8601 string on
   both ChatSummary and ChatState. Reducers emit
   new Date(Date.now()).toISOString() so existing Date.now mocks remain
   deterministic.

4. Document SessionSummary aggregate derivation rules - status promotion
   (InputNeeded > InProgress > Idle), activity, modifiedAt as max of
   chat modifiedAts, workingDirectory as the default-chat fallback.

5. Add optional workingDirectory to ChatState/ChatSummary so harnesses
   can support agent-swarm worktree patterns where cooperating chats
   pin to different working directories.

Codegen + clients:
- Fix Rust/Kotlin/Swift generators to emit Partial<T> structs that are
  referenced only from actions (previously only notification-side
  partials were emitted).
- Regenerate all clients (Rust, Kotlin, Swift, TypeScript, Go).
- Port hand-written reducers in Rust, Go, Kotlin, Swift to match the
  new action shape and ISO timestamps.
- Migrate all 87 chat reducer fixtures to the flat ChatState shape with
  ISO modifiedAt; replace 3 old chatsChanged fixtures with 6 fixtures
  covering chatAdded upsert, chatRemoved + defaultChat clearing, and
  chatUpdated partial merge (plus no-op cases).

Docs: update chat-channel.md and session-channel.md with the
denormalized shape, per-chat workingDirectory, catalog mutation
actions, and the full session aggregation rules.

Changelogs: updated root + all 5 client CHANGELOGs under Unreleased.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
connor4312
connor4312 reviewed Jun 8, 2026
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I think this overall is looking good. Feel free to promote to 'ready for review' when you're happy with it. We should avoid merging until we have a PR ready on the VS Code side of things too, just so we don't block other people getting stuff into AHP main while adoption happens.

@sandy081

sandy081 commented Jun 8, 2026

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@connor4312 thanks for the review — all five points are addressed in 41ab532 and the threads are resolved.

Summary of changes:

  1. Denormalized ChatSummary into ChatState — ChatState is now flat (resource/title/status/activity/modifiedAt/origin/workingDirectory live directly on it). ChatSummary remains the standalone lightweight session-catalog view, no longer embedded.

  2. Upsert + partial update semantics — replaced SessionChatsChangedAction with three targeted actions mirroring the session pattern: SessionChatAddedAction (upsert by summary.resource), SessionChatRemovedAction (clears defaultChat when needed), and SessionChatUpdatedAction carrying Partial<ChatSummary>. Fixtures 170–175 cover the new semantics including no-ops.

  3. ISO-8601 modifiedAt — now a timestamp string on both ChatSummary and ChatState.

  4. SessionSummary derivation documented — status promotion (InputNeeded > InProgress > Idle), activity from the primary chat, modifiedAt as max across chats, workingDirectory from the default chat. Also expanded in the spec docs.

  5. Per-chat workingDirectory — added as optional on ChatState/ChatSummary (inherits session default when unset) to model the agent-swarm worktree pattern.

Codegen/clients: fixed the Rust/Kotlin/Swift generators to emit Partial<T> structs referenced only from actions, regenerated all clients, and ported the hand-written reducers in Rust/Go/Kotlin/Swift. TS (248 ✓, 100% coverage), Rust (cargo test ✓), and Go (go test ✓) all pass; Swift swift build ✓. All six CHANGELOGs updated under Unreleased.

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