Harness spec 3.1.0: the prefix stays still, in the CLI

The system prompt is made once per session (start, compaction, model
switch), kept in session_meta and resent byte for byte; it holds no
date. What changes mid-session -- the date, a mode the person chose, a
plan or memory or instruction file they edited, a personality, MCP
instructions that arrived later -- is a <session-note> on the next user
message, stored with it. The tool list is fixed for the session:
plan_submit is always offered and answers unavailable outside plan
mode, the wrap-up keeps the tools and runs no call, a withdrawn tool
stays listed and answers its refusal; the first request waits up to
mcp_wait_ms for MCP servers. Compaction asks for its summary as the
next turn of the same conversation. Cached input tokens are parsed
(incl. llama.cpp timings), stored per request and shown in /context.

Spec: context.md §7/§10, loop.json context.note (+ plan_ended,
plan_own, personal, empty, mcp_wait_ms), modes.json plan.refused,
compact.md without the transcript heading. Conformance area prefix.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CHANGELOG.md

@@ -6,6 +6,34 @@ All notable changes to LLeMbas CLI. The format follows
 
 ## [Unreleased]
 
+Harness spec 3.1.0 (draft): what the model has already read stays exactly as it was, so its server
+can reuse it instead of reading the whole session again.
+
+### Changed
+
+- **The system prompt is made once per session** — at the start, after a compaction, on a model
+  switch — kept with the session and sent byte for byte on every request; a resumed session sends
+  the one it kept. It holds no date any more.
+- **What changes during a session is said in a note** after your words on your next message: the
+  date (on the first message, and when it changes), a permission mode you chose, a plan you
+  changed, memory or an instruction file you edited, a personality you picked, an MCP server's
+  instructions that arrived later. The model's own changes (its plan, its edits, a plan approval)
+  are not said again. Notes are not shown as your words.
+- **The tool list is the same for the whole session.** `plan_submit` is offered in every mode and
+  answers that it works only in plan mode; `show` is offered from the start where the session can
+  have a viewer; knowledge search is decided as the session starts. The tools stay listed when a
+  step limit or budget winds a prompt up (a call in that answer is not run), and a tool refused
+  for good stays listed and answers that refusal. The first request waits up to 3 seconds for the
+  configured MCP servers, so their tools are in the first list.
+- **Compaction asks for its summary as the next turn of the same conversation** instead of a
+  separate request with a pasted transcript, so it reuses what the server has read and no longer
+  loses the middle of a long session. A tool call in the summary's reply is not run.
+
+### Added
+
+- **Cached input tokens are recorded for every request** (the usage's own count, or llama.cpp's
+  `timings` and progress), kept with the session, and shown by `/context` for the last request.
+
 ## [2.0.0-beta.1] — 2026-11-03
 
 LLeMbas CLI 2.0 works with LLeMbas 2.0 and nothing else: it uses the server it is logged in to,