Harness spec 2.0.0: background work is a job — commands and subagents alike, seen and steered

One registry per process, every job owned by a session: bash's background commands (and a command
still running at its timeout, which now goes to the background instead of being killed) and
subagents started with task background: true. job_list, job_output, job_stop (the former
bash_list, bash_output, bash_kill) and the new job_send and report; a finished job wakes the owning
session in every front end with its marked note. The TUI counts jobs, lists them (/jobs), opens a
command's output, enters a subagent and messages it, moves a command to the background (ctrl+b)
and asks before quitting with jobs running. The link gains the jobs capability. Subagents get a
session row of their own, the spec's preamble and agent texts, and their errors reach the report.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

harness/tools/bash.json

@@ -14,7 +14,7 @@
   "argument_aliases": {
     "workdir": "cwd"
   },
-  "description": "Run a shell command (bash) and return its combined output and exit status.\n\n- Each call is a fresh shell: `cd` and variables do not carry over. Use `cwd` instead of `cd`.\n- Use the dedicated tools for files: read, not cat; edit/write, not sed or heredocs; grep and glob, not find.\n- Quote paths that contain spaces.\n- Commands time out (default {{timeout}}, `timeout` up to {{timeout_max}}).{{background}}\n- Git: do not commit, amend, push or change git config unless asked. Before a commit, check `git status` and `git diff`, stage files by name, never commit secrets.",
+  "description": "Run a shell command (bash) and return its combined output and exit status.\n\n- Each call is a fresh shell: `cd` and variables do not carry over. Use `cwd` instead of `cd`.\n- Use the dedicated tools for files: read, not cat; edit/write, not sed or heredocs; grep and glob, not find.\n- Quote paths that contain spaces.\n- A command still running when `timeout` passes (default {{timeout}}, up to {{timeout_max}}) is not killed: it goes on in the background as a job, and the call returns what it had printed with the job id.{{background}}\n- Git: do not commit, amend, push or change git config unless asked. Before a commit, check `git status` and `git diff`, stage files by name, never commit secrets.",
   "parameters": {
     "type": "object",
     "properties": {
@@ -31,13 +31,13 @@
         "type": "string"
       },
       "timeout": {
-        "description": "Milliseconds",
+        "description": "Milliseconds to wait for the command before it goes on in the background",
         "type": "integer",
         "exclusiveMinimum": 0,
         "maximum": 600000
       },
       "background": {
-        "description": "Run in the background and return a job id at once",
+        "description": "Run in the background from the start and return a job id at once",
         "type": "boolean"
       }
     },
@@ -46,8 +46,8 @@
     ]
   },
   "variables": {
-    "timeout": "how long a command may run when the call names no timeout, in words (\"2 minutes\")",
+    "timeout": "how long a command may run before it goes on in the background when the call names no timeout, in words (\"2 minutes\")",
     "timeout_max": "the longest timeout a call may ask for, in words (\"10 minutes\")",
-    "background": "where commands may run in the background: \" For a server, a watcher or anything long, set `background: true`: it returns at once with a job id; read its output with bash_output, list jobs with bash_list, stop one with bash_kill.\" — otherwise empty, and the `background` parameter is not sent"
+    "background": "where commands may run in the background: \" For a server, a watcher or anything long, set `background: true`: it returns at once with a job id. Read a job's output with job_output, list jobs with job_list, stop one with job_stop; you are told when one ends.\" — otherwise empty, and the `background` parameter is not sent"
   }
 }

harness/tools/bash_list.json

@@ -1,19 +0,0 @@
-{
-  "name": "bash_list",
-  "scope": "cli",
-  "risk": "read",
-  "exclusive": false,
-  "block": "tool",
-  "purpose": false,
-  "aliases": {
-    "cli": [],
-    "llembas": [
-      "job_list"
-    ]
-  },
-  "description": "The background jobs of this session: id, state, how long each has run, and its command.",
-  "parameters": {
-    "type": "object",
-    "properties": {}
-  }
-}

harness/tools/job_list.json

@@ -0,0 +1,19 @@
+{
+  "name": "job_list",
+  "scope": "shared",
+  "risk": "read",
+  "exclusive": false,
+  "block": "tool",
+  "purpose": false,
+  "aliases": {
+    "cli": [
+      "bash_list"
+    ],
+    "llembas": []
+  },
+  "description": "The background jobs of this session — commands started with bash `background: true` (or moved there when their timeout passed) and subagents started with task `background: true`: id, kind, state, how long each has run, whether it has output you have not read, and its command or description.",
+  "parameters": {
+    "type": "object",
+    "properties": {}
+  }
+}

harness/tools/job_output.json

@@ -1,17 +1,17 @@
 {
-  "name": "bash_output",
-  "scope": "cli",
+  "name": "job_output",
+  "scope": "shared",
   "risk": "read",
   "exclusive": false,
-  "block": "shell",
+  "block": "tool",
   "purpose": false,
   "aliases": {
-    "cli": [],
-    "llembas": [
-      "job_output"
-    ]
+    "cli": [
+      "bash_output"
+    ],
+    "llembas": []
   },
-  "description": "New output from a background job since you last looked, and whether it is still running. `wait` (seconds, up to 60) waits for more first.",
+  "description": "New output from a background job since you last looked, and whether it is still running: a command's output; a subagent's progress — its tool calls and what it has written so far. `wait` (seconds, up to 60) waits for more first.",
   "parameters": {
     "type": "object",
     "properties": {

harness/tools/job_send.json

@@ -0,0 +1,29 @@
+{
+  "name": "job_send",
+  "scope": "shared",
+  "risk": "interact",
+  "exclusive": false,
+  "block": "tool",
+  "purpose": false,
+  "aliases": {
+    "cli": [],
+    "llembas": []
+  },
+  "description": "Send a message to a subagent running as a background job — an answer to something it reported, a correction, more to do. It is given to it at its next step. To a subagent that has finished, the message starts it again with its context intact, under the same job id; its new report comes to you when it ends.",
+  "parameters": {
+    "type": "object",
+    "properties": {
+      "id": {
+        "type": "string"
+      },
+      "text": {
+        "type": "string",
+        "minLength": 1
+      }
+    },
+    "required": [
+      "id",
+      "text"
+    ]
+  }
+}

harness/tools/job_stop.json

@@ -1,17 +1,17 @@
 {
-  "name": "bash_kill",
-  "scope": "cli",
+  "name": "job_stop",
+  "scope": "shared",
   "risk": "execute",
   "exclusive": false,
   "block": "tool",
   "purpose": false,
   "aliases": {
-    "cli": [],
-    "llembas": [
-      "job_stop"
-    ]
+    "cli": [
+      "bash_kill"
+    ],
+    "llembas": []
   },
-  "description": "Stop a background job started with bash background: true.",
+  "description": "Stop a background job. A command is terminated; a subagent is stopped where it is, and what it had worked out comes to you as its report.",
   "parameters": {
     "type": "object",
     "properties": {

harness/tools/report.json

@@ -0,0 +1,26 @@
+{
+  "name": "report",
+  "scope": "shared",
+  "risk": "interact",
+  "exclusive": false,
+  "block": "tool",
+  "purpose": false,
+  "aliases": {
+    "cli": [],
+    "llembas": []
+  },
+  "offered": "subagent",
+  "description": "Send a message to the main agent now, before your final reply: a finding it should act on at once, or a question you cannot settle yourself. It reaches the main agent as a message; an answer, if one comes, arrives as a message to you. Your final reply still goes to it when you finish.",
+  "parameters": {
+    "type": "object",
+    "properties": {
+      "text": {
+        "type": "string",
+        "minLength": 1
+      }
+    },
+    "required": [
+      "text"
+    ]
+  }
+}

harness/tools/task.json

@@ -11,7 +11,7 @@
       "subagent_run"
     ]
   },
-  "description": "Hand a self-contained piece of work to a subagent, which works on its own and returns only its final report — keeping the searching and reading out of your context.\n\n- Use it for broad research (\"where is X handled, and what calls it?\") or a separable job. For one file you already know, just read it.\n- `prompt` must stand on its own: the subagent sees nothing of this conversation. Say what to find or do, and what to report back.\n- Independent tasks can run in the same turn. Subagents that change files at the same time should each have `worktree: true`, so they work on separate branches.\n- Agents: {{agents}}",
+  "description": "Hand a self-contained piece of work to a subagent, which works on its own and returns only its final report — keeping the searching and reading out of your context.\n\n- Use it for broad research (\"where is X handled, and what calls it?\") or a separable job. For one file you already know, just read it.\n- `prompt` must stand on its own: the subagent sees nothing of this conversation. Say what to find or do, and what to report back.\n- `background: true` returns at once with a job id and you carry on; the report comes to you as a message when it ends. Meanwhile job_output shows its progress, job_send gives it a message, job_stop stops it. Without it, the call waits for the report.\n- Independent tasks can run in the same turn. Subagents that change files at the same time should each have `worktree: true`, so they work on separate branches.\n- Agents: {{agents}}",
   "parameters": {
     "type": "object",
     "properties": {
@@ -32,6 +32,10 @@
         "description": "Work in a separate git checkout on a new branch, apart from yours — for changes made alongside other work; the result says how to merge it",
         "type": "boolean"
       },
+      "background": {
+        "description": "Run it as a background job: return its id at once, get its report as a message when it ends",
+        "type": "boolean"
+      },
       "model": {
         "description": "Run it on another configured model (connection/model, from the list in your instructions) — a second opinion, or a model better at this kind of work. Default: the agent's own model, else yours.",
         "type": "string"