hyperhive/docs/turn-loop/claude-invocation.md

# The claude invocation

```
claude --print --verbose --output-format stream-json --model <name> \
  --effort <level> --resume <title>   # or --name <title> on first use \
  --system-prompt-file /run/hive/claude-system-prompt.md \
  --mcp-config /run/hive/claude-mcp-config.json --strict-mcp-config \
  --tools <builtins> --allowedTools <builtins+mcp>
# wake prompt piped over stdin
```

**Crate split.** The generic subprocess mechanics — spawning
`claude --print`, streaming + classifying stream-json, session
lookup/archive, and the durable-session compaction loop — live in the
reusable **`hive-claude`** crate (`hive_claude::{Claude, InfiniteSession,
Attach, CompactionPolicy, PercentPolicy, Telemetry, Sink, SessionStore}`;
see `hive-claude/README.md`). `hive_ag3nt::turn` is the hyperhive **policy
layer** on top: it builds the per-turn config from the bus, bridges the
output stream onto the event bus (`BusSink`), and owns the compaction /
auto-reset / retry decisions in `drive_turn`. The lib returns everything it
parsed from a turn (usage, cost, context window, resolved model) as
`Telemetry`, which the policy layer applies to the bus.

Hive-enforced settings ship at `/etc/claude-code/managed-settings.json`
(claude-code's canonical managed-settings path — precedence #1,
read-only, un-overridable), wired in `nix/templates/harness-base.nix`
from the `prompts/claude-settings.json` asset. `effortLevel` is
deliberately not in that file — effort is controlled live via the
`--effort` flag (`HIVE_DEFAULT_EFFORT` / the per-agent UI slider), which
managed scope would otherwise lock.

`<name>` is read from `Bus::model()` on each turn. The initial
default is set by `hyperhive.model` in the agent's `agent.nix`
(NixOS option; propagates via `HIVE_DEFAULT_MODEL` env var; falls
back to `"haiku"` if unset). The operator can flip it at runtime
with `/model <name>` in the web terminal — the next turn picks it
up. The choice is persisted to `/harness/hyperhive-model` so it
survives restart; override path: `HYPERHIVE_MODEL_FILE` env var
for tests.

Context-window size is looked up per-model via
`events::context_window_tokens(model)`. Resolution order (first
match wins):

1. `HIVE_CONTEXT_WINDOW_TOKENS_<KEY>` env var, where `KEY`
   (lowercased) is a substring of the active model name. Injected
   by the meta flake from `services.hyperhive.c0re.contextWindowTokens`
   (host-level NixOS option, defaults: haiku=200k, sonnet=1M,
   opus=1M). Override these for all agents at once without a
   per-agent config change.
2. `HIVE_CONTEXT_WINDOW_TOKENS` — single global override for any
   model (useful in dev / test).
3. Hard fallback: `200_000` (conservative; only reached outside
   NixOS where the env vars aren't set).

The effective window drives watermarks and is exposed at runtime
via `/api/state.context_window_tokens` so the UI can show a
percentage-of-window ctx badge.

**Session identity — a constant title.** Every turn keys on one fixed,
harness-owned session title (`turn::session_title()`, default
`hive-session`, override `HIVE_SESSION_TITLE`). The durable
`hive_claude::InfiniteSession` (built once by the serve loop via
`turn::make_session`, then reused) `--resume <title>`s it; the *first* use
(bootstrap, post-archive, post-purge) misses and the session re-runs the
same prompt once with `--name <title>` to mint it. That single self-heal
rule is the whole identity system — there is **no** scraped session-id
file. Because the
title is constant, `/compact` and its post-compact retry provably target
the same session (killing the old "compact ran on a different/empty
session" bug), and a `choom` invocation in the same cwd can't hijack the
context (it won't carry our title). claude stores sessions in
`~/.claude/projects/<cwd-slug>/<uuid>.jsonl` (bind-mounted persistently);
`--name` writes the title into the file as a `custom-title` event, which
is what `--resume <title>` resolves against. We never pass bare
`--continue` (it resumes the *latest* session in the cwd — the hijack
vector). Auto-compact and auto-memory are disabled via the managed
settings at `/etc/claude-code/managed-settings.json` because hyperhive
owns compaction — see [Compaction](#compaction) below.

**Session reset** is available via `POST /api/new-session` (or
`/new-session` slash command). It does *not* touch the session inline —
that would race a mid-write claude process. Instead `Bus::request_session_reset()`
sets a one-shot flag consumed at the next turn boundary by `drive_turn`,
which **archives** the current session: the backing `<uuid>.jsonl` is
renamed to `<uuid>.jsonl.archived` (dropped out of claude's `*.jsonl`
resolution glob, history preserved on disk, only the file carrying *our*
title — any `choom` session sharing the cwd is left alone). The next
turn's `--resume <title>` then misses and self-heals into a fresh session.

## Compaction

claude's own in-session auto-compact is off (via the managed settings
at `/etc/claude-code/managed-settings.json`); hyperhive owns it. The
`hive_claude::InfiniteSession` keeps the session alive across the context
window with two triggers baked into its `run`:

- **Reactive** — claude-code prints `Prompt is too long`. The session is
  *already* past the window, so no turn can run on it — the session
  `/compact`s straight away and retries the same wake-up prompt once. No
  notes-checkpoint turn is possible here: the detail is gone. If the retry
  *still* overflows, `run` surfaces `Error::PromptTooLong`; `drive_turn`
  then archives the session (session lifecycle stays hive-side) and the
  serve loop requeues the message so it redelivers into a fresh session
  (see [Turn outcomes](../turn-loop.md#turn-outcomes) — the wake prompt itself is tiny, so
  the overflow was the accumulated context the archive clears).
- **Proactive** — a turn finishes cleanly but the last inference's context
  size crossed the policy watermark. While the session is still healthy it
  runs one synthetic *notes-checkpoint* turn (`CHECKPOINT_PROMPT` —
  "context is filling up, flush durable state into `/state` now") and
  *then* `/compact`s, so the agent can persist in-flight state before the
  detail collapses into a summary.

The **when** is a `hive_claude::CompactionPolicy` injected by the harness:
`turn::make_session` builds a `PercentPolicy` that compacts once the
model-reported context fill reaches `HIVE_COMPACT_WATERMARK_PERCENT`
(default **75%**), falling back to `events::context_window_tokens(model)`
for the window on turns the model didn't report one. `0` disables proactive
compaction (the reactive path always applies). The proactive path is
best-effort — a failed checkpoint or `/compact` never fails the turn that
already succeeded.

The operator can force a compaction any time via `POST /api/compact`. It's
**deferred**: the handler sets `Bus::request_compact()` and returns
immediately; the harness runs the `/compact` at the next turn boundary
(end of the in-flight turn in `drive_turn`, or — when the agent is idle —
in `turn::run_pending_compact` on the serve loop's next empty poll). This
lets `/api/compact` work mid-turn instead of only when idle, without racing
a live claude process.

To disable proactive compaction for a specific agent, use the nix option:

```nix
hyperhive.autoCompact = false;  # default true
```

Setting `autoCompact = false` sets `HIVE_COMPACT_WATERMARK_TOKENS=0`, which
the percent resolver still honours as a disable. Useful for large-context
models (sonnet/opus) where the 75% heuristic fires before the session is
actually full — the reactive path (compact-on-overflow at the hard limit)
still applies.

- **Auto session-reset** — a third path (`turn::maybe_auto_reset`,
  pre-turn) that fires when both conditions hold: context is ≥ a watermark
  (`HIVE_AUTO_RESET_WATERMARK_TOKENS`, default **50% of
  `context_window_tokens(model)`**) AND the time since the last turn
  exceeds the assumed prompt-cache TTL (`HIVE_CACHE_TTL_SECS`, default
  `3600`). Claude's prompt cache goes cold after a while; once it's cold,
  `--resume`-ing a large session pays the full re-upload cost with no
  benefit over starting fresh. So `drive_turn` **archives** the current
  session (same mechanism as the operator reset — rename `<uuid>.jsonl` →
  `.archived`) so the next turn's `--resume <title>` misses and starts
  fresh. Unlike proactive compaction the session is dropped entirely, not
  compacted — and *no* preceding checkpoint turn runs, because any turn
  before the reset would just re-warm the cache and defeat the purpose.
  Set `HIVE_AUTO_RESET_WATERMARK_TOKENS=0` to disable. Auto-reset and the
  operator reset are mutually exclusive per turn (both archive → fresh
  turn), so an explicit operator reset short-circuits the heuristic.

The child runs with `cwd = /state` (when the bind exists; falls
back to the parent's cwd in dev), so any relative path in a tool
call (`Read foo.md`, `Bash ls`, `Write notes.md`) lands in the
agent's durable bind-mounted dir. CLAUDE.md auto-load walks
upward from `/state` — drop a per-agent CLAUDE.md there if you
want long-term hints that survive destroy/recreate.

The wake prompt is intentionally minimal: the popped message's
`from`/`body`, prefixed with a `[msg #<id>]` broker-row-id marker
(so the agent knows what id to pass to `ack_until` for bulk triage;
transient pings show no marker because their sentinel id 0 has nothing
to ack), plus an inline `({unread} more pending — drain via …)` hint
when `unread > 0`. Claude drives any further `recv`/`send` itself via
the embedded MCP server.

Whenever hive-c0re starts / restarts / rebuilds a container, it
also drops a `system` message into the agent's inbox via
`Coordinator::kick_agent` — a one-line "you were just (re)started,
check /state/ for your notes, your session is intact". The
next turn picks it up like any other inbox message.

## On-boot files

`hive_ag3nt::turn::write_*` writes two files next to the per-agent
socket at `/run/hive/` once at startup:

- `claude-mcp-config.json` — by default re-invokes the running binary
  as `mcp` stdio child (so the same binary serves as harness + MCP
  server per turn). When `hyperhive.mcp.httpPort` is set in the
  agent's NixOS config, the config instead points claude at the
  persistent `hive-mcp-http` daemon (`http://127.0.0.1:{port}/mcp`)
  — no stdio child per turn; trades the per-turn re-registration race
  for a hard dependency on the daemon's uptime (`Restart=always`).
- `claude-system-prompt.md` — rendered from
  `hive-ag3nt/prompts/system.md` by `hive_ag3nt::prompt::render`:
  HTML-comment markers (`<!-- role:agent -->...<!-- /role:agent -->`,
  same for `role:manager`) gate the role-specific blocks; everything
  else is shared. Five placeholders are then
  substituted: `{label}` (short agent name), `{qualified_label}`
  (hive-qualified `name@domain` form), `{operator_pronouns}`,
  `{hive_identity}` (e.g. `` on hive `pr1ma` ``; empty when
  `hyperhive.hiveName` is unset), and `{swarm_identity}` (same
  shape for the swarm). Pronouns come from `HIVE_OPERATOR_PRONOUNS`
  env (set by the meta flake from
  `services.hyperhive.c0re.operatorPronouns`, default `she/her`).
  When `hyperhive.docs.enable` is set, `HIVE_DOCS_DIR` is present
  in the environment and `render()` appends a one-sentence pointer
  telling the agent the docs are mounted at that path (in lieu of
  the old CLAUDE.md-in-docs-dir approach, which was dropped in
  favour of this direct injection).
  Passed via `--system-prompt-file`.

  **Marker grammar.** `<!-- role:X -->` opens a block; any
  `<!-- /role:X -->` closes the current block. The renderer always uses
  role `agent`, so blocks with other role tags are elided. Nesting is NOT
  supported — a stray opener with no closer runs until end of file.
  Whitespace inside markers is tolerated (`<!--role:foo-->` parses the
  same as `<!-- role:foo -->`). Content outside any marker is always
  included. Today's `system.md` carries no markers (single agent role) —
  the grammar stays wired for a future manager / multi-role prompt.

  **`hive_identity` / `swarm_identity` shape.** Each carries a
  leading space + backticked name (` on hive \`pr1ma\``,
  ` in swarm \`constellat1on\``) when the corresponding env var
  is set, otherwise empty string. The independence lets the
  template drop one or both into the opener prose without
  breaking single-hive deployments that never set the option;
  the renderer also treats `Some("")` from a caller as `None` so
  empty-string env vars and missing env vars round-trip the
  same way.

The per-turn plumbing lives in `hive_ag3nt::turn`: `write_mcp_config` /
`write_system_prompt` (on-boot files), `make_session` (builds the durable
`InfiniteSession`, once), `drive_turn` (the policy state machine —
reset/auto-reset, the turn, 401-retry, deferred-compact-at-turn-end),
`run_pending_compact` (idle operator compact), `BusSink` (stream → bus +
`Telemetry` applied via `apply_telemetry`), `emit_turn_end`, `session_title`
/ `session_store` / `archive_session` (identity + turn-boundary reset). The
actual claude spawn, stream classification, and the reactive/proactive
compaction loop are in the `hive-claude` crate. Login-wait
(`wait_for_login`) lives in `hive_ag3nt::login`.