LLeMbas-CLI/harness

The harness spec

LLeMbas CLI (a terminal coding agent, TypeScript) and LLeMbas (a self-hosted web UI, Python) are two independent projects that share one harness design: the same tools, the same permission design, the same prompt texts, the same model quirks and model metadata. This directory writes that design down as data. Each project implements it in its own language; neither ever runs the other. LLeMbas CLI embeds these files at build time; LLeMbas vendors a pinned, hash-checked copy.

The concept-by-concept map of the two implementations, and where they still differ, is the wiki page Harness-parity.

What is here

Path	What
VERSION	The spec's own version, apart from LLeMbas CLI's
purpose.json	The purpose argument added to a tool whose calls say what they are for
tools/<name>.json	One tool each: name, scope, sessions, risk, exclusive, block (how a call is shown: shell, edit, read, search, web, task, plan — not drawn, the plan card refreshes — hidden, tool), purpose, former names (aliases, per project), renamed arguments, variables, what a project offers of the parameters (narrow, per project), offered (subagent: given to subagents only, never to the main agent — report), requires and unavailable (when it can be offered, and what a call answers when that has gone), confirm (always: the person is asked in every mode), the description and the JSON Schema of its parameters — exactly what a model is sent
prompts/	The prompt texts; prompts/index.json says which are shared, which LLeMbas fragment each one is, and what each {{variable}} in a text means. prompts/personality/ holds the personality presets both offer
permission/hardline.json	The floor: commands refused in every mode, protected paths, and how a command is spelled plainly before it is checked again
permission/arity.json	How much of a command an "always allow" covers
permission/defaults.json	The rules every session starts from
permission/modes.json	The four modes — manual, edit, auto, plan — as what each does with each risk class
models/schema.json	Model metadata: context, output limit, efforts, vision, tools, notes, capacity
loop.json	How one prompt runs: the step backstop, budgets, wrap-up, nudges, parallel calls, capacity; jobs — background work, its marks and limits; context — result ids, stubs, the output cap, the compaction table
filesystem.md	The file system a session works in: paths, node kinds, the four access levels, errors, listings, search and indexing by tokens, stacked instruction files, skills, memory
context.md	Context hygiene: what happens to a tool result when it is inserted, and never afterwards
quirks.json	What real servers do, and how both harnesses cope
conformance/<area>.json	Cases with their expected results, run by both test suites
acp.md	The link between them: ACP plus every _lembas/* method, field and capability

Vocabulary

• Risk classes: read, write, execute, interact. Reading and writing are never one tool among the shared ones, so a read-only helper is given exactly the readers.
• Modes: manual, edit, auto, plan (unrestricted is read as auto).
• Scopes: shared — both projects implement it; cli or llembas — only that one. The same two names key what is per project elsewhere: a tool's aliases, loop.json's budgets, a protected path's scope.
• Sessions (a tool's sessions, spec 3.0.0): where a tool is offered — chat, a conversation on the server, working in the server's file system (filesystem.md); agent, a session on a device (the CLI's own, Desktop's agent — which is the CLI — or an agent chat the web UI runs on a linked device), working on that machine's disk; both. The two say different things: read is shared and both (each project implements it for its own world); bash is cli and agent; mkdir is llembas and chat.
• Requires (spec 3.0.0): what must hold for a tool to be offered at all — page: a browser page of the chat is open and attached (not a schedule, not a background job); display: the session is shown somewhere a file can be opened (the web UI, Desktop; not a bare terminal); forge: the session's view holds a repository mounted from a forge. A requirement that goes away between the offer and the call makes the call answer the tool's unavailable text, word for word, as its result.
• Confirm (spec 3.0.0): always — the call is put to the person before it runs, in every mode, auto included, and runs on a yes only; nothing remembers the answer (permission/modes.json).
• A tool's other names, per project, are listed in its aliases and work as the tool. A former name may have taken different arguments; the project converts them. The one such case: todo → plan_write, todos[] becoming one phase called "Work" (pending → todo, in_progress → doing, completed → done, cancelled → dropped; conformance/plan.json).
• The plan (plan_write, plan_update, plan_submit) is one structure both keep per session — title, summary, findings, objectives, phases of tasks with a status each, ids given by the implementation and never by the model — shown as a card in every UI and put into the prompt ({{plan_context}}) on every step while it exists. plan_write and plan_update are offered in every mode; plan_submit only in plan mode, where it is the approval. Their permission key is plan (permission/defaults.json), which a rule written for the former todo key still reaches.

3.0.0 (draft)

VERSION says 3.0.0-draft while the spec is written ahead of both implementations: a SemVer pre-release, ordered below 3.0.0, which no stable release of either project carries. It becomes 3.0.0 when both implement it. Two worlds, one harness: a chat works in the server's file system, an agent session on its device's disk, and neither sees the other's files; what is shared is this design.

• sessions, requires, unavailable, confirm — new fields on a tool (Vocabulary). Every tool says its sessions.
• New tools. mkdir, mv, rm (to the trash) and search (meaning and words over the files this session can see, filtered by its view after scoring) — LLeMbas, chat. show (a file in the user's viewer: Markdown, code, text, HTML in a sandboxed frame) — shared, requires: display: a chat in the web UI, an agent session through the link to the web UI or Desktop (acp.md _lembas/show), never a bare terminal. python (Pyodide in the user's browser) — LLeMbas, chat, requires: page; with no page it answers Python cannot run now: no open browser page is attached to this chat. The forge verbs commit, branch, pr, merge, tag, release — LLeMbas, chat, requires: forge; merge, tag and release confirm: always. recall — shared, both (context.md). An agent session keeps git through bash, as before.
• The file tools are shared. read, write, edit, glob, grep and list are shared and offered in both: on the device's disk, and over the server's tree in a chat. multiedit, apply_patch and bash stay the agent's. A chat's listing marks a mount and a read-only entry (filesystem.md, told to the model in blocks/workspace.md). skills_list, skill_view and skill_manage work over skill files on both sides; memory is the same tool on both, and its records are the server's for both (filesystem.md, Memory; acp.md, The HTTP API). session_search is shared.
• Removed from chat (LLeMbas): knowledge_search, knowledge_get, notes_search, note_view, note_manage — now cli and agent only: the CLI keeps its local library — and LLeMbas's own report_*, scratch_write, the prototype tools and the canvas, which were never in the spec. Notes, reports and knowledge become files; prototypes become show. blocks/library.md and blocks/prototypes.md are the CLI's alone.
• filesystem.md — the file system as a contract: paths, the kinds dir, file, mount, the levels none, ro, stage, commit, grants and floors, the exact error texts, and the rule that a granted path under one that is not is reached only by its full path, its ancestor denied for reading and writing and never listed. Search results and indexing by tokens (at most 480 tokens a piece, 64 repeated; a piece the embedder refuses is split, never dropped). Instruction files stack from the boundary down to the start directory, outermost first, one per directory (AGENTS.md, else CLAUDE.md), none from a directory the session cannot read — the CLI took only the nearest one before. blocks/workspace.md (LLeMbas) tells a chat's model its view.
• context.md — context hygiene, insert-time only, nothing sent ever rewritten: every result has an id (#a3f2); a read carries its lines and content hash; an unchanged re-read, or a range inside an earlier unchanged read, is a stub; output over 400 lines or 40,000 characters keeps its head and tail with [N lines elided, full output #id]; recall shows any stored result; edits answer with their diff; the same listing or search with the same result is a stub; compaction adds a table of reads and empties the dedupe table; earlier reasoning is left to the chat template. loop.json context holds the texts and numbers, blocks/context.md tells the model.
• acp.md: session/new's result carries instance; a session the client opened runs on the chat's model and no other — refused rather than answered on the device's own, so the "answered on its own model" notice is gone; capability show with _lembas/show; memory through the instance; a 3.0.0 instance sends neither library nor prototypes.
• Permissions: default rules for the new tools (search, recall, show, python allowed; the forge verbs asked); modes.json confirm.
• Conformance: fs_access, instructions, context, chunk_tokens — new, their answers written from a reference model of the rules, not recorded from either implementation (neither has them yet). chunk stays, noted as the character rule.

2.0.0

Background work is one thing in both projects: a job, owned by a session, is a command run in the background (bash background: true, or one still running when its timeout passed — it is no longer killed) or a subagent run in the background (task background: true, new). One id sequence per session; job_list, job_output, job_stop (renamed from bash_list, bash_output, bash_kill — the CLI's former names, read for one minor) now cover both kinds and are shared; job_send (new, shared) messages a running subagent or starts a finished one again with its context; report (new, shared, offered: subagent) lets a subagent message the main agent before its final reply. A job that ends wakes the session that owns it with a marked message (loop.json jobs.marks, conformance/jobs.json): at the next step while a prompt runs, else as a turn of its own marked machine. The subagent's preamble and the two built-in agents' texts are prompt texts now (blocks/subagent.md, agents/*.md). acp.md: capability jobs — the job and job_note events, _lembas/jobs, _lembas/job/output|stop|send|transcript, jobs in status, job on an approval, machine on a prompt. The capacity rule counts the subagents already running.

1.2.0

The library's tools fit both projects: memory, notes_search, note_view, note_manage, skills_list, skill_view and skill_manage say the CLI's facts (files, projects, supporting files, sessions) through variables, so LLeMbas sends the same tools with its own facts; filled with the CLI's values, every description is word for word what 1.1.0 said. Tool descriptions are filled by the prompt texts' rules, including the descriptions inside the parameters. A tool's narrow says what a project offers of its parameters where it offers less (LLeMbas: one memory target, no note scope, no skill categories, supporting files or project skills). Note and knowledge-document ids are strings on both sides. Three conformance areas: fill, narrow, memory (one change or a batch, applied together, against the size limit).

1.1.0

Planning as one shared structure: plan_write and plan_update (new, shared, in every mode) and plan_submit now shared; todo folded into plan_write as a former name. The shared system text (system/default.md) is now one text for both projects, with variables for what differs; modes/*.md shared; blocks/prototypes.md and blocks/library.md new and shared. acp.md: the client hands the device what only it knows (context, library, prototypes), the plan travels as a structure (plan_state), the device scopes library calls to the chat (_meta.lembas.scope), and a client may rewind a session (rewind). loop.json says its numbers as numbers. Four conformance areas: plan, prototype, library_scope, toolcall_index.

1.0.1

acp.md: a device links even with remote work off or no roots, saying limits.roots: [] and refusing every session, directory and terminal; and one whose limits change dials the link again so the client hears the new ones. No change for a client: it already takes empty roots and a link that drops and comes back.

1.0.0

The spec as described here: the shared tools with their scopes, risk classes, call blocks and aliases; the prompt texts and the six personality presets; the permission floor, arity table, default rules and the four modes; model metadata; the loop; the quirks of real servers; the conformance cases; and acp.md, the link between the two projects (_lembas protocol 2, every feature beyond protocol 1 gated on its capability string).

Variables in a description, and in a prompt text

A description may hold {{name}} where the two projects differ in a fact, not in design — a timeout's default, whether commands may run in the background, which subagents exist, where a skill's supporting files are. The tool's variables says what each one means; each project fills them before sending the description — and the description of every parameter, which may hold them too — and none may reach a model unfilled.

A prompt text may hold them too, declared in prompts/index.json under its entry. The same rules for both, and one more: a line that is nothing but a bullet and a variable (- {{name}}) disappears when the variable is empty, so one text serves a project that has the fact and one that does not (conformance/fill.json).

Offering less of a shared tool

A project that does not have part of a shared tool says so in the tool's narrow.<project> rather than in a different tool: drop leaves out optional properties, enum keeps some of a property's values (a.b is b inside a; a[].b is b inside the items of the array a). It offers a subset and nothing else — never a property the spec does not have, never another type — so a call valid for the narrower tool is valid for the whole one (conformance/narrow.json). The description says the narrower tool's facts through its variables.

Changing it

1. Change the spec first, and bump VERSION: patch for a text or a new conformance case, minor for a new tool, rule or field, major for a rename or a removed tool — removed from either project. A spec written ahead of its implementations carries a pre-release suffix (3.0.0-draft) until both have it. A tool folded into another, its name kept as an alias that still runs, is minor: nothing stored or trained breaks.
2. A fix comes with a conformance case that fails without it. In LLeMbas CLI, bun run harness record fills in the expected result of a new case from the implementation, and bun run harness record --all shows every case whose result would change.
3. Implement it in both projects — in the same session, or with an open item recorded against the other. A bug found in one is searched for in the other.
4. Nothing here names a host, a path on a server or anybody's setup: both projects are public.

Licence: MIT, as LLeMbas CLI. Files that came from elsewhere say so in their source field (Hermes Agent's hardline patterns, OpenCode's arity table) or in an HTML comment (prompt texts).