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jason.woltjeandClaude Opus 5.5 11dae0c7d8 feat(bus): the bus host runs an explicit Claude Code binary (#1561 , row 68)

MOSAIC_CLAUDE_BIN names the claude binary by absolute path instead of
finding it on PATH. scripts/bus-service.sh render|install --claude PATH
writes it into the unit (default: command -v claude in the installing
shell); the claude adapter, the launcher's version read and the seat
session environment all use it. Mos's Q18 ask: the unit's PATH found
/usr/bin/claude 2.1.259, which refuses claude-opus-5-5.

Candidate: round 2 manifest 21c1ab05, round 1 (a2008d8b) rebased onto
f2f2861b after row 55 changed docs/TOOLS.md and packages/cli/README.md;
the changed lines are byte-identical. Approved by Filbert (27349, 27374)
and Dewey (27350, 27375). Sage's gate on f2f2861b plus the patch: cli
112, seat 27, harness 57, nine scripts/test-*.sh 0 failed, Docker on.

Co-Authored-By: Claude Opus 5.5 <[email protected]>

2026-10-11 16:42:23 -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_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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