dsh-in-convo-mode-change

Switch the agent preset of a conversation mid-session in the DeepSeek
Harness web UI. The presets are the "conversation modes" shipped with the
harness — Standard mode, Code mode (PTC), Minimal mode, and
Creator mode, plus any custom presets you have authored.

By default the session header's preset icon is a read-only label: a session's
composition is fixed when it starts, and the built-in picker only exists on
the new-session hero screen. This plugin turns the header icon into a real
mode switcher that works on a conversation that has already started.

How it works

• Client half (lib/client.js) replaces the built-in agent-preset cell
  in conversation.session.header.actions with a menu button. Picking a mode
  asks for confirmation, then POSTs { sessionId, agentPreset } to the host
  route.
• Host half (lib/index.js) registers the POST /change-convo-mode/switch
  route on the web server. It uses the host's own
  agentPresets.recompose() — the same machinery the built-in blank-session
  picker uses — without the "no turn has ever run" restriction, and records
  the switch in the session log as an agent-preset/selected event so the
  transcript stays honest.
• Picking is disabled while the session is running a turn; the host refuses
  anyway (defense in depth), because re-parenting the agent's scope chain
  mid-call could strand an in-flight tool invocation.

Caveats

Switching modes mid-conversation is deliberately not offered by the host,
and this plugin bypasses that gate on purpose:

• The switch applies from the next turn. The current transcript is
  untouched, but tool calls made under the previous mode may render
  differently in the chat afterwards, because the UI resolves tool views
  through the session's current preset.
• Don't switch while a turn is running — the menu is disabled during a run.

Install

From a local checkout:

dsh plugin --profile web add /path/to/dsh-in-convo-mode-change

Or straight from GitHub (the dsh.bundle.patch manifest field makes the
dependency join the profile's plugin layers automatically):

dsh plugin --profile web add github:jiangr100/dsh-in-convo-mode-change

Then restart the web server (stop the dsh web process and run dsh web
again) so the loader picks up the new plugin row and the client bundle.

After restart, the header of any conversation shows the mode switcher where
the read-only preset label used to be.

Uninstall

dsh plugin --profile web remove dsh-in-convo-mode-change

and restart dsh web. Sessions that already switched modes keep running on
the preset they switched to.

Development notes

• The client bundle is a hand-written module-loader bundle (no build step),
  following the same pattern as dsh-rewind.
• The host row injects webServer, agentPresets, and agents; it imports
  error classes from @deepseek-ai/dsh-agent-presets, resolved by the
  harness loader at mount time.
• The client replaces the built-in label by registering the SAME id
  (agent-preset) in conversation.session.header.actions at a lower
  priority (the built-in sits at the default 0). The slots registry keys
  list cells by (id, priority): a duplicate id at the same priority throws
  and fails the whole plugin entry at load; the lowest priority wins the
  cell. test/slots.test.mjs drives the real SlotCore to lock this in.
  Do not remove the priority: -10 option.