Emacs UI (rpc-edn)

The repository includes an Emacs frontend at components/emacs-ui/ that runs psi in a dedicated process buffer over rpc-edn.

Install (straight.el)

Install directly from GitHub with straight.el:

(straight-use-package
 '(psi-emacs
   :type git
   :host github
   :repo "hugoduncan/psi"
   :files ("components/emacs-ui/*.el")))

(require 'psi)

This installs the Emacs frontend files from the repo and makes M-x psi-emacs-start / M-x psi-emacs-project available.

Start

1. Install the canonical psi launcher so psi is available on PATH.
2. In Emacs, add components/emacs-ui to load-path and load psi.el.
3. Run one of:
   • M-x psi-emacs-start for the default/global buffer.
     • Use C-u M-x psi-emacs-start to force a fresh buffer name (*psi*<2>, etc.).
   • M-x psi-emacs-project for a project-scoped buffer in the current project.
     • Buffer naming style: *psi:<project>* (for example *psi:psi-main*).
     • C-u M-x psi-emacs-project forces a fresh generated project buffer name.
     • C-u N M-x psi-emacs-project opens/uses slot N (N<=1 => *psi:<project>*, N>=2 => *psi:<project>*<N>).

This opens a dedicated psi buffer (default *psi*, or project-scoped *psi:<project>*) and starts one owned subprocess per dedicated buffer using:

• psi --rpc-edn

By default, the subprocess runs in the directory where psi-emacs-start is invoked. Override explicitly via psi-emacs-working-directory if needed.

Customizing psi-emacs-command

psi-emacs-command controls the exact subprocess command used by the frontend. Default:

("psi" "--rpc-edn")

Customize interactively:

• M-x customize-variable RET psi-emacs-command RET

Or set in init:

(setq psi-emacs-command '("psi" "--rpc-edn"))

Example with explicit model:

(setq psi-emacs-command
      '("psi" "--rpc-edn" "--model" "sonnet-4.6"))

Requirement: command must launch psi in rpc-edn mode (include --rpc-edn).

Streaming stall detection defaults to 600 seconds (10 minutes) in Emacs. Customize psi-emacs-stream-timeout-seconds to change the frontend watchdog.

Developer checks

From repo root:

• bb emacs:test (loads the split frontend suites, including psi-buffer-lifecycle-test.el, psi-dispatch-test.el, psi-streaming-transcript-test.el, psi-tool-output-mode-test.el, psi-extension-ui-test.el, psi-capf-test.el, and psi-session-tree-test.el)
• bb emacs:e2e (live end-to-end harness against psi --rpc-edn)
• bb emacs:byte-compile
• bb emacs:check

Compose and keybindings

In psi-emacs-mode:

• RET inserts newline (never sends)
• C-c RET send prompt
  • slash-prefixed input always uses backend command
  • while streaming, non-slash input uses steer (prompt_while_streaming with behavior=steer)
• C-u C-c RET queue override for non-slash streaming input
• C-c C-q queue while streaming for non-slash input; slash-prefixed input still uses backend command; fallback to normal send when idle
• C-c C-k abort active streaming (abort)
• C-c C-r reconnect (prompts before clearing edited buffer)
• C-c C-t toggle tool-output view mode (collapsed ↔ expanded); also available as M-x psi-emacs-toggle-tool-output-view
• C-c m m set model (M-x psi-emacs-set-model)
• C-c m n cycle model next (M-x psi-emacs-cycle-model-next)
• C-c m p cycle model previous (M-x psi-emacs-cycle-model-prev)
• C-c m t set thinking level (M-x psi-emacs-set-thinking-level)
• C-c m c cycle thinking level (M-x psi-emacs-cycle-thinking-level)

Compose source rules:

• Active region sends region text (for both C-c RET and C-c C-q).
• Without a region, psi sends the tail draft block from the draft anchor marker to end-of-buffer.
• Normal editing keeps the anchor at the start of the current draft tail, so transcript text above the anchor is not resent unless you explicitly select it as a region.
• Reconnect clear (C-c C-r after confirmation) resets the buffer and repositions the draft anchor at the new buffer end; after reconnect, sends come only from text typed after that reset point.