Felix FaerberandClaude Opus 4.8
5601dfe8d6
Fully hiding the caller's AGENTS.md dropped repo-specific operational knowledge agents need (e.g. homelab's migration mechanism: deleting a service requires a matching migrations/*.sh, else the old service keeps running in prod). Separate the two concerns: - Platform golden rules stay authoritative (scripts/agent-rules.md), un-overridable. - The caller's AGENTS.md / CLAUDE.md text is captured before quarantine and injected into the prompt as explicitly SUBORDINATE context — usable for repo mechanics, but unable to change behavior, grant permissions, or override the rules. - opencode.json / .opencode remain fully blocked (config + RCE), never re-injected. Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
45 lines
2.3 KiB
Markdown
45 lines
2.3 KiB
Markdown
# Security model — agent behavior isolation
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Agent behavior — which models run, what skills / permissions / MCP servers they get, and the golden
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rules they follow — is defined **only** by this `agents` repository. A caller repository must not be
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able to change it.
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## For caller repos
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Call the shared workflow pinned to this repo's `main`:
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```yaml
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uses: ffaerber/agents/.gitea/workflows/agent.yml@main
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secrets: inherit
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```
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Do **not** point `uses:` at a fork or a non-`main` ref. The trigger gate, the agent registry, and the
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isolation controls all live here on `main`; a caller that repoints it opts out of these protections.
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## How isolation is enforced at runtime
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The agent runs inside the caller repo's checkout, and opencode auto-discovers project-level config
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from the working tree. Because opencode has **no flag to disable that discovery**, the run
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(`scripts/run-agent.sh`) quarantines the caller-controlled behavior files for the duration of each
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run so they cannot override the agent's configuration or execute code on the runner (which holds the
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workflow secrets):
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- `opencode.json` / `opencode.jsonc` — provider, model, permission, `mcp`
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- `.opencode/` — plugins, skills, agents, commands, tools
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- `AGENTS.md` / `CLAUDE.md` — instructions
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They are moved aside before opencode starts and restored after it exits, so the committed tree is
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unchanged. The authoritative configuration comes from `~/.config/opencode/` (written by
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`scripts/install-opencode.sh`), and the authoritative golden rules from `scripts/agent-rules.md`,
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injected into the agent prompt.
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**`opencode.json` / `.opencode/` are fully blocked** — never re-introduced — because they can change
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config or execute code.
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**`AGENTS.md` / `CLAUDE.md` are treated as repo notes, not rules.** A caller repo legitimately uses
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its `AGENTS.md` to document repo-specific mechanics (build/deploy/migration conventions) the agent
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needs. So its text is captured and injected into the prompt as explicitly **subordinate** context —
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useful for how the repo works, but unable to change agent behavior, grant permissions, or override
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the golden rules. It is never auto-loaded by opencode as top-level instructions.
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**Consequence:** an agent cannot durably edit these quarantined files *during a run* — its changes to
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them are not persisted. Change them via a normal human PR instead.
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