document reading and editing an agent's agents.md through the swarm

docs/swarm/README.md gets the routes, the revision, the apply semantics
and the stopped-agent behaviour; the persistence doc points there from
the AGENTS.md entry. The swarm-controller, swarm-controller-api and
swarmctl READMEs and the repo map in AGENTS.md list the new bodies and
routes. docs/tools/swarmctl-cli.md is regenerated for
`swarmctl agent agents-md`, whose help text loses two passive phrasings
vale flags.

AGENTS.md

@@ -118,11 +118,11 @@ Swarm-level:
   **the socket's directory is its access control**; the crate README has
   the constraint and a unit test pins the path.
 - **`swarm-controller-api/`** — serde-only request and response bodies of
-  the controller's HTTP API, shared with `swarmctl` (forge, schedules and
-  the agent-create and forge-token responses).
+  the controller's HTTP API, shared with `swarmctl` (forge, schedules,
+  `AGENTS.md` edits, and the agent-create and forge-token responses).
 - **`swarmctl/`** — swarm operator CLI; runs as **root and acts directly**
-  (README says why). Doesn't link `swarm-controller`: the forge and
-  schedule bodies and the agent responses come from
+  (README says why). Doesn't link `swarm-controller`: the forge, schedule
+  and `AGENTS.md` bodies and the agent responses come from
   `swarm-controller-api`; the agent-create request, inference and
   permissions ones are a local mirror. ⚠️ Edits authelia's
   **`users.yml` in place**, shared with `swarm-authelia-bridge`; that

docs/agent-lifecycle/persistence.md

@@ -276,7 +276,10 @@ Under `/var/lib/hyperhive/agents/<name>/`:
   `agents_md_migrate::run` renames a `state/CLAUDE.md` to `AGENTS.md`
   when no `AGENTS.md` exists. When both exist it renames neither and
   logs an error naming both paths: claude loads only `CLAUDE.md` while
-  one exists in its cwd or above.
+  one exists in its cwd or above. The harness also publishes the file
+  to the swarm, which reads that copy, and applies the git diffs the
+  swarm sends to edit it. This file stays the only copy that counts:
+  [`docs/swarm/README.md`](../swarm/README.md#an-agents-agentsmd).
 - `harness/` — harness-internal ephemeral state; not intended for
   agent consumption. Bind-mounted to `/agents/<name>/harness`
   inside the container (`$HYPERHIVE_HARNESS_DIR`). Contents:

docs/swarm/README.md

@@ -278,13 +278,19 @@ The third thing an agent publishes is its **icon**, the same SVG its own
 `GET /icon` serves. It goes into the `agent-icons` KV bucket under the key
 `<agent>`, with no hive in it, so the swarm can show the icon of an agent that's
 stopped or has moved hives. The queue grants the agent's own credential
-`$KV.agent-icons.<agent>` and no other key. The harness writes once per start,
-because a config change reaches an agent by restarting its container. An agent
-with no icon deletes its key. Swarm-side, `GET /api/agents/<name>/icon` serves
+`$KV.agent-icons.<agent>` and no other key of that bucket. The harness writes
+once per start, because a config change reaches an agent by restarting its
+container. An agent with no icon deletes its key. Swarm-side,
+`GET /api/agents/<name>/icon` serves
 the stored bytes, and 404 means the agent has no icon. swarm-ui's agent cards
 load it as an `<img>` and show the dimmed hyperhive mark for an agent without
 one, as the hive dashboard does.
 
+The fourth is its **`AGENTS.md`**, which goes into the `agents-md` bucket under
+the key `<agent>`, writable by the agent's own credential alone
+(`$KV.agents-md.<agent>`). The swarm reads that copy and edits the file through
+the agent; [An agent's AGENTS.md](#an-agents-agentsmd) has the details.
+
 The queue also limits what an agent may **subscribe** to, because agents are the
 least trusted clients on the queue. An agent's own queue credential, which its
 subagent daemon also presents, may subscribe to its reply inbox
@@ -309,6 +315,41 @@ no replies, so every request it makes times out.
 
 </details>
 
+### An agent's AGENTS.md
+
+The file in the agent's state dir, `state/AGENTS.md`, is the only copy that
+counts, and only the agent writes it: itself, or its harness applying an edit
+from the swarm. No hive is in either path.
+
+**Reading.** The harness publishes the file's text and its revision, the git
+blob id that `git hash-object` prints for it, at start, within ten seconds of
+any change, and straight after an edit it applied. An agent with no `AGENTS.md`
+publishes `""`. `GET /api/agents/<name>/agents-md` answers `{content, revision}`
+from that copy, so it works while the agent isn't running. A 404 means the agent
+hasn't published one: its harness hasn't run since it began to.
+
+**Editing.** `PUT /api/agents/<name>/agents-md` takes `{base_revision, diff}`.
+The diff is a unified diff that names `a/AGENTS.md` and `b/AGENTS.md`, made
+against the text at `base_revision`. swarm-controller sends it as a request on
+the agent's command subject `$SWARM.control.<name>`, as it sends a cancel. The
+harness refuses it when the file isn't at `base_revision`. Otherwise it runs
+`git apply --check` and then `git apply` on a copy of the file, and writes the
+result over the file only when both pass:
+
+| Status | Meaning                                                                                                                                 |
+| ------ | --------------------------------------------------------------------------------------------------------------------------------------- |
+| 200    | applied; the body is `{revision}`, the file's new revision                                                                              |
+| 409    | the file isn't at `base_revision` any more; nothing applied, and `revision` in the body is the one it's at                              |
+| 422    | `git apply` refused the diff, or it touches a file other than `AGENTS.md`; `detail` carries git's message, and the file stays as it was |
+| 503    | the agent isn't running or isn't connected to the queue                                                                                 |
+| 504    | the harness didn't answer within ten seconds, so whether the edit applied is unknown                                                    |
+| 500    | the harness couldn't read or write the file or run git, or the queue failed the request                                                 |
+
+An edit needs the agent running, and a read of a stopped agent shows the text
+it last published. A harness older than this route doesn't know the command and
+drops it unanswered, which reads as a 504. `swarmctl agent agents-md get` and
+`apply` call the two routes.
+
 ### Swarm-wide forge objects
 
 The controller also keeps the forge objects that are one per swarm, not

docs/tools/swarmctl-cli.md

@@ -16,6 +16,9 @@ This document contains the help content for the `swarmctl` command-line program.
 * [`swarmctl agent permissions get`↴](#swarmctl-agent-permissions-get)
 * [`swarmctl agent permissions set`↴](#swarmctl-agent-permissions-set)
 * [`swarmctl agent permissions clear`↴](#swarmctl-agent-permissions-clear)
+* [`swarmctl agent agents-md`↴](#swarmctl-agent-agents-md)
+* [`swarmctl agent agents-md get`↴](#swarmctl-agent-agents-md-get)
+* [`swarmctl agent agents-md apply`↴](#swarmctl-agent-agents-md-apply)
 * [`swarmctl schedule`↴](#swarmctl-schedule)
 * [`swarmctl schedule add`↴](#swarmctl-schedule-add)
 * [`swarmctl schedule list`↴](#swarmctl-schedule-list)
@@ -71,6 +74,7 @@ Manage agents across the swarm
 * `mint-forge-token` — Check one agent's forge token, and mint it if it's missing or stale
 * `inference` — Show the model, effort, subagent models and subagent cap the swarm sets for an agent, or change the model, effort and subagent models
 * `permissions` — Show or change the permissions the swarm grants an agent
+* `agents-md` — Show an agent's AGENTS.md, or edit it with a diff
 
 
 
@@ -274,6 +278,61 @@ Clear the agent's permissions, so the default applies again
 
 
 
+## `swarmctl agent agents-md`
+
+Show an agent's AGENTS.md, or edit it with a diff.
+
+`get` shows the copy the agent last published, so it works while the agent isn't running. `apply` hands the diff to the agent, which applies it to the file with `git apply`; it needs the agent running.
+
+**Usage:** `swarmctl agent agents-md <COMMAND>`
+
+###### **Subcommands:**
+
+* `get` — Print an agent's AGENTS.md on stdout, and its revision on stderr
+* `apply` — Apply a unified diff to an agent's AGENTS.md
+
+
+
+## `swarmctl agent agents-md get`
+
+Print an agent's AGENTS.md on stdout, and its revision on stderr
+
+**Usage:** `swarmctl agent agents-md get [OPTIONS] <AGENT>`
+
+###### **Arguments:**
+
+* `<AGENT>` — Agent name
+
+###### **Options:**
+
+* `--controller-socket <PATH>` — swarm-controller's unix socket.
+
+   Supplied by the nix module that installs this binary, from the same `socketPath` option the daemon binds; falls back to `SWARM_CONTROLLER_SOCKET`.
+
+
+
+## `swarmctl agent agents-md apply`
+
+Apply a unified diff to an agent's AGENTS.md.
+
+The diff names `a/AGENTS.md` and `b/AGENTS.md`, as `diff -u a/AGENTS.md b/AGENTS.md` writes it. The agent refuses it when the file is no longer at `--base`, or when it doesn't apply, and leaves the file as it was.
+
+**Usage:** `swarmctl agent agents-md apply [OPTIONS] --base <REVISION> <AGENT> <DIFF_FILE>`
+
+###### **Arguments:**
+
+* `<AGENT>` — Agent name
+* `<DIFF_FILE>` — The file holding the diff
+
+###### **Options:**
+
+* `--base <REVISION>` — The revision you made the diff against, as `get` printed it. It's the git blob id of that text, so `git hash-object` of the unedited file prints it too
+* `--controller-socket <PATH>` — swarm-controller's unix socket.
+
+   Supplied by the nix module that installs this binary, from the same `socketPath` option the daemon binds; falls back to `SWARM_CONTROLLER_SOCKET`.
+
+
+
 ## `swarmctl schedule`
 
 Manage scheduled prompts.

swarm-controller-api/README.md

@@ -17,7 +17,8 @@ controller's `OpenAPI` spec. `swarmctl` leaves it off.
 ## What's here
 
 One module per endpoint family: `agents` (the responses of `POST /api/agents`
-and `POST /api/agents/{name}/forge-token`), `forge`
+and `POST /api/agents/{name}/forge-token`), `agents_md`
+(`/api/agents/{name}/agents-md`), `forge`
 (`POST /api/forge/users/{name}/admin`) and `schedules` (`/api/schedules`).
 The agent-create request, inference and permissions bodies are still mirrored
 by hand in `swarmctl`.

swarm-controller/README.md

@@ -58,6 +58,12 @@ The swarm's control plane. The swarm UI and `swarmctl` are its clients.
   (`GET`/`PUT`/`DELETE /api/agents/{name}/limits`); the hive running the
   agent reads it, and each cap replaces the hive's own answer for that field →
   [`docs/scheduler/coordinator.md`](../docs/scheduler/coordinator.md#container-resource-limits).
+- **Agent instructions** — each agent's `AGENTS.md` as its harness last
+  published it into the `agents-md` KV bucket
+  (`GET /api/agents/{name}/agents-md`), and edits to it as git diffs, which
+  this daemon hands to the agent's harness to apply
+  (`PUT /api/agents/{name}/agents-md`) →
+  [`docs/swarm/README.md`](../docs/swarm/README.md#an-agents-agentsmd).
 - **Review classifier** — try-outs from the swarm UI and reviews on review
   requests, and the newest 100 finished runs, one document in the
   `review-classifier-runs` KV bucket, which this daemon alone writes

swarmctl/README.md

@@ -7,8 +7,9 @@ that talk to the controller, from anywhere as your own SSO account (see
 
 Distinct from `hivectl`, which drives one hive's `hive-c0re` over its
 admin socket. This crate doesn't link `swarm-controller`, for the same
-reason `hivectl` doesn't link `hive-c0re`; the forge and schedule bodies
-and the agent responses both sides speak come from `swarm-controller-api`,
+reason `hivectl` doesn't link `hive-c0re`; the forge, schedule and
+`AGENTS.md` bodies and the agent responses both sides speak come from
+`swarm-controller-api`,
 as `hivectl`'s come from `hive-host-sock`.
 
 ## Why root, and why no socket

swarmctl/src/main.rs

@@ -306,7 +306,7 @@ enum AgentVerb {
     /// Show an agent's AGENTS.md, or edit it with a diff.
     ///
     /// `get` shows the copy the agent last published, so it works while the
-    /// agent is stopped. `apply` hands the diff to the agent, which applies
+    /// agent isn't running. `apply` hands the diff to the agent, which applies
     /// it to the file with `git apply`; it needs the agent running.
     AgentsMd {
         #[command(subcommand)]
@@ -333,7 +333,7 @@ struct AgentsMdApplyArgs {
     agent: String,
     /// The file holding the diff.
     diff_file: PathBuf,
-    /// The revision the diff was made against, as `get` printed it. It is
+    /// The revision you made the diff against, as `get` printed it. It's
     /// the git blob id of that text, so `git hash-object` of the unedited
     /// file prints it too.
     #[arg(long, value_name = "REVISION")]