[ACP] session/new never sends available_commands_update, so ACP clients show an empty command/skill palette

[apple-ouyang]

Summary. dsh's ACP bridge never advertises slash commands. ACP clients learn an agent's commands from a session/update notification carrying sessionUpdate: "available_commands_update", sent after session/new (and after session/load / session/resume). @deepseek-ai/dsh-acp does not send it at any point, so the command palette of every ACP client is empty for dsh. Paseo 0.8.0 shows No commands found when the user types /.

Where. packages/acp/acp/src/index.ts — the bridge's only update emitters are agent_message_chunk (≈577), agent_message_chunk/agent_thought_chunk (≈566), tool_call (≈593), tool_call_update (≈618), usage_update (≈631) and config_option_update (≈776). available_commands_update does not appear in the package at all. session/new returns only:

return { sessionId, configOptions };

Measured (dsh 0.1.5-rc.1, macOS, dsh --profile acp over stdio). A minimal ACP client sends initialize, then session/new, then waits 3 s while recording every session/update:

INIT agentCapabilities: {"mcpCapabilities":{"http":true},
  "promptCapabilities":{"image":true,"audio":false,"embeddedContext":false},
  "sessionCapabilities":{"close":{},"list":{},"resume":{}}}
SESSION: {"sessionId":"c849b340-…","configOptions":[{"id":"model",…}]}
SESSION UPDATE KINDS: []

Zero updates on the whole connection, not merely zero commands. The count does not change with a longer wait or a second session/new, so this is not a timing race — the notification is never produced.

Why the registries are unreachable from this path. The bridge's cordis context dependencies are ctx.agents, ctx.effect, ctx.get, ctx.llm, ctx.logger, ctx.on, ctx.sessionPersistence and ctx.sessions. There is no ctx.skills and no ctx.commands, so the skill and command registries that the rest of dsh populates are never consulted when a session is opened for an ACP client.

Impact. Skills remain fully functional for the model in a dsh ACP session — skill, skill-filesystem and tool-skill are mounted by dsh-base (skill-badge is the only disabled row), roots are ~/.agents/skills, ~/.dsh/skills and the project's .dsh/skills / .agents/skills, and the agent invokes them through the skill tool. What is missing is human-facing discovery: a user driving dsh from an ACP client cannot browse or invoke what is installed, and gets an empty palette with no indication that anything is wrong. This is a visible asymmetry against sibling providers in the same client — Codex surfaces its skills through the skills/list app-server RPC and Claude through the Agent SDK, so the same UI is populated for them and empty for dsh.

Request. After a session is established (session/new, loadSession, unstable_resumeSession), emit one session/update with sessionUpdate: "available_commands_update", listing the currently resolvable model- and user-invocable skills together with any other user-invocable commands, read from ctx.skills / ctx.commands. Re-emit on registry change so an already-open client picks up newly installed skills without reconnecting.

[apple-ouyang]

Local patch, verified. The same fork branch now also emits available_commands_update.

• Branch: https://github.com/apple-ouyang/deepseek-harness/tree/feat/acp-session-load-replay
• Commit: 5ad7ce301 feat(acp): emit available_commands_update from the skill catalog

After session/new (and resume/load), the bridge lists user-invocable ctx.skills entries and sends:

sessionUpdate: "available_commands_update"

Measured (dsh --profile acp, stdio, session/new):

updates { available_commands_update: 1 }
commands n=43 sample [agent-history-search, browse, commit, find-docs, …]

The skills registry is optional (ctx.get("skills")); a missing service still emits an empty list so clients waiting on the notification can settle. Refresh on skills/change.

This is stacked on the loadSession replay work tracked in #6393. CONTRIBUTING.md still blocks PRs against this repo, so the source is the fork for cherry-pick.

[apple-ouyang]

Update (Paseo slash palette). Emitting available_commands_update from dsh is necessary but not sufficient: Paseo's generic ACP client (extends: "acp") was calling listCommands() as soon as session/new returned, dropping the notification (session id not bound yet) and caching an empty palette for 60s.

Fix on the Paseo side: wait for that first available_commands_update, same as Cursor/Kiro/Trae.

• Issue: Generic ACP providers show an empty slash palette when commands arrive after session/new getpaseo/paseo#4759
• PR: fix(acp): wait for available_commands_update on generic ACP providers getpaseo/paseo#4760

dsh ACP source for the emit + session/load replay remains on the fork: https://github.com/apple-ouyang/deepseek-harness/tree/feat/acp-session-load-replay