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mode, the wrap-up keeps the tools and runs no call, a withdrawn tool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>

src/acp/agent.ts

@@ -42,6 +42,7 @@ import type { Message } from "../provider/types.ts"
 import type { Hub } from "./hub.ts"
 import { INVALID_PARAMS, METHOD_NOT_FOUND, RpcError, type Peer } from "./rpc.ts"
 import { jobList, jobOutput, jobSend, jobStop, jobTranscript, storedJobs } from "./jobs.ts"
+import { isNote } from "../session/prefix.ts"
 
 export const ACP_VERSION = 1
 /** The link's version (LLeMbas `services/device_link.py:PROTOCOL`, harness/acp.md *Versions*). 3:
@@ -369,7 +370,9 @@ export function planReplyFrom(answer: any, maxMode?: Mode): PlanReply {
 }
 
 /** Text the expander added to a user message (an @file, an image, a listing, a `!` command's output). */
-const ATTACHMENT = /^<(file|directory|shell|image) /
+// What the model was given beside the words typed — attachments, and a session note
+// (session/prefix.ts) — is not shown as typed.
+const ATTACHMENT = { test: (t: string) => /^<(file|directory|shell|image) /.test(t) || isNote(t) }
 
 /** A stored session as turns the web UI can draw: each person's message, then what the
  *  model said, thought and ran in answer, up to the next one. A message's attachments are chips,