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jason.woltje c216f47dbb plugins, cli, bus, business, webui: harness, model and thinking from the instance vars, a fallback route, and a harness plug-in kind (row 65, #1558 )

Adds the harness plug-in kind (interface 1). packages/plugins/harness/pi
and claude-code hold what core branched on: the adapter, thinking levels,
preflight, version probe, sandbox mounts, builtins line, typed tool names,
gate timeout, bundle files, adapter env, turn end and session-files path.
Core reaches a module only through the loader.

A session's route is the instance's harness, model and thinking vars, or
the three fallback. vars; a missing one refuses no-route, and the system
file's execution keys are never read for a session. The launcher checks
the primary route, then the fallback: harness-off, harness-refused,
thinking-unsupported, then preflight. A failed preflight falls back when
a fallback is set, and any refusal of the fallback names the primary's
failure too. Account checks run
only when the route's module counts an account. The manifest records
route, routeReason and harnessVersion, replacing piVersion and
claudeVersion. pi gets --thinking, Claude Code --effort, both from
MOSAIC_THINKING.

The business file refuses a partial fallback. routes and routes.set are
human-only bus verbs outside ORGANIZATION_KEYS; checkRoutes is shared by
routes.set, instances.set and limits.set and checks only changed routes.
The chief of staff changes an instance's model, and the assistant's whole
vars (Q169), through limits.set, so its route write runs the same checks.
A model outside launch.models refuses unknown-model, primary or fallback,
and routes.set passes that code through.
A new run binds only on a switched-on harness module name and records
its transcript path, which the usage reader uses. Settings gains a
Routing table with six selects per instance and loses the Role models
fieldset; it posts changed rows to /api/routes. webui/src/bus.mjs is
unchanged.

Until Jason's `mosaic plugins set` adds "harness": ["claude-code"], a new
launch refuses harness-off.

2026-10-19 11:27:19 -05:00

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Mosaic runtime adapters

An adapter is the entire harness-specific surface of the system. Everything upstream of an adapter — configuration, contracts, missions, tasks, run records — is harness-agnostic; everything inside an adapter may assume one specific agent runtime.

Contract

An adapter lives at:

/opt/mosaic/adapters/<name>/adapter.sh

and must be executable. The dispatcher (/opt/mosaic/src/run-agent.sh) selects it via MOSAIC_ADAPTER (default: pi) and execs it after the system prompt has been generated.

Inputs (environment):

Variable	Meaning
`MOSAIC_SYSTEM_PROMPT_FILE`	Absolute path to the generated system prompt (contracts + optional mission section). Read it; do not modify it.
`MOSAIC_REQUEST`	The exact user request text (may contain newlines).
`MOSAIC_PROVIDER`	Configured provider name.
`MOSAIC_MODEL`	Configured model id.

Optional, adapter-specific (documented per adapter):

Variable	Meaning
`MOSAIC_MOCK_RESPONSE`	mock only: the verbatim response to emit

Outputs:

stdout: the model response text — the only channel the orchestrator captures
stderr: diagnostics (never credentials)
exit 0: success; nonzero: failure

Rules

Adapters print ONLY the response on stdout. Status lines go to stderr.
Adapters never read configuration files; the resolved settings arrive via environment.
Adapters never write outside /var/lib/mosaic.
Adding a worker adapter requires: a new directory, the contract implementation, and adding the name to the allowlist in scripts/mosaic-config.mjs. A managed-session adapter (below) is selected by the launch bundle, not by execution.adapter, and is not on that allowlist unless it also works as a worker adapter.

Included adapters

pi — the pinned @earendil-works/pi-coding-agent CLI in noninteractive print mode (-p), ambient discovery disabled, stdin detached.
mock — deterministic echo of MOSAIC_MOCK_RESPONSE. Test-only: never use it where a real model response is required.
claude — the host's claude CLI, for managed sessions only (below): MOSAIC_CLAUDE_BIN when set, else claude on PATH. Not a worker adapter: the image has no claude, and the adapter refuses without the bundle's hook and MCP files.

Managed sessions (slice 1 S6)

The session runner (packages/harness/src/runner.mjs) runs one adapter call per turn on the host, as /bin/sh <adapters/<name>/adapter.sh> (the repository keeps adapters 0644; only the image sets the mode), in the session's workspace and its own process group. Same contract, plus:

Variable	Meaning
`MOSAIC_WORKSPACE`	The session's workspace; the adapter runs there.
`MOSAIC_SESSION_DIR`	The session's persistent directory; later turns resume the session kept there.
`MOSAIC_TOOLS`	The built-in tool limit (pi names for `pi`, Claude Code names for `claude`), comma-separated.
`MOSAIC_POLICY_FILE`, `MOSAIC_TOOLS_FILE`	The bundle's gate policy and typed tools.
`MOSAIC_TOOL_SOCKET`	The runner's tool socket, which the typed tools call.
`MOSAIC_TURN_MARKER`	`pi`: the extension writes it at `agent_end`; a pi turn that exits 0 without it failed.
`MOSAIC_EXTENSIONS`	`pi` only: extension files loaded with `-e`; a missing one exits 2.
`MOSAIC_CLAUDE_SETTINGS`, `MOSAIC_CLAUDE_MCP_CONFIG`	`claude` only: the bundle's gate hook and MCP server; required.
`MOSAIC_THINKING`	The route's thinking level (row 65), which the harness module's `levels()` already checked. `pi` passes `--thinking` (`off`, `minimal`, `low`, `medium`, `high`, `xhigh`, `max`) and omits it when unset, as for `run-task.sh` workers. `claude` passes `--effort` (`low`, `medium`, `high`, `xhigh`, `max`) and requires it; unset exits 2.
`MOSAIC_CLAUDE_BIN`	`claude` only: absolute path of the CLI to run, from the host's environment (the bus unit pins it). Unset or empty runs `claude` from `PATH`; a relative path or a non-executable file exits 2.

The layers each adapter relies on, and what they don't cover, are in packages/harness/README.md.

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