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Record the Runtime Install Policy Module decision and ownership boundary: install policy projects a pure, typed install plan by composing artifact placements (ADR-3660) and command text (ADR-0009) plus per-runtime config intentions, with no filesystem IO; runtime adapters consume the plan and execute concrete file mutations and format-specific config rendering. Explicitly records what stays outside the policy module (TOML/JSON/Markdown serialization, merge semantics, filesystem effects). Adds the ADR index row in docs/adr/README.md and a glossary entry in CONTEXT.md. Leads the installer-refactor chain (#58 -> #60 -> #56). Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>
57 lines
4.2 KiB
Markdown
57 lines
4.2 KiB
Markdown
# Runtime Install Policy Module owns the typed install-plan projection
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- **Status:** Accepted
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- **Date:** 2026-06-07
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- **Issue:** #58
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## Context
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Runtime install logic is currently spread across one-off helper functions. `getGlobalDir(runtime, explicitDir)` in `bin/install.js` switch-dispatches to per-runtime helpers (`getOpencodeGlobalDir`, `getKiloGlobalDir`), and `getAgentsDir` lives separately in `src/core.cts`. These helpers resolve directories at ~11 call sites and are free to drift from the behavior that install and runtime-query paths actually expect, because nothing owns the *composition* of an install decision as a single value.
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Two adjacent seams already exist:
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- **ADR-3660 (Runtime Artifact Layout Module)** owns *where* per-runtime artifacts (commands, agents, skills) are placed.
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- **ADR-0009 (Shell Command Projection Module)** owns runtime-aware *command text* rendering (quoting, path style, wrapper prefixes).
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But no ADR owns composing those — placements + command text + per-runtime config intentions — into one unified, typed install-plan projection. That missing seam is why directory/config logic re-derives itself ad hoc at each call site.
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## Decision
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Introduce a **Runtime Install Policy Module** as the seam that, given a runtime and an install context, **projects a pure, typed `InstallPlan` value** describing everything that should happen for that runtime. The projection:
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- composes artifact placements by delegating to the Runtime Artifact Layout Module (ADR-3660),
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- composes command text by delegating to the Shell Command Projection Module (ADR-0009),
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- declares config *intentions* (which config files need which keys/values for that runtime),
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- performs **no filesystem IO** and **no format-specific serialization** while resolving the plan.
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Concrete execution is owned by runtime-specific **adapters** (made explicit as a registry in #60). Adapters consume the `InstallPlan` and perform the effectful work: file mutations, directory creation, and rendering format-specific config (TOML, JSON, Markdown) for their runtime.
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This follows the repository's established pure-policy-projects / thin-adapters-execute pattern (ADR-0001, Dispatch Policy Module): the `InstallPlan` is the narrow waist, resolution stays free of IO, and callers become thin adapters over a stable interface rather than re-deriving directory logic.
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## What stays OUTSIDE the policy module
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To keep the abstraction honest about the filesystem boundary, the following are explicitly **not** the policy module's responsibility and remain in the runtime adapters:
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- Concrete TOML / JSON / Markdown read-modify-write and serialization.
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- Merge semantics for pre-existing config files (preserving user keys, ordering, formatting).
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- Filesystem effects: directory creation, atomic write/rename, existence/permission checks.
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- Any path resolution that requires touching the disk.
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The policy module resolves *intent* as data; adapters turn that intent into bytes on disk.
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## Consequences
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- Install logic becomes testable as pure data: assert the projected `InstallPlan` for a runtime without a filesystem.
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- The scattered directory helpers (`getGlobalDir`, `getOpencodeGlobalDir`, `getKiloGlobalDir`, `getAgentsDir`) gain a single projection to migrate onto, retiring or narrowing them (tracked in #56).
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- The plan/adapter contract becomes a stability surface that must be held narrow; drift there reintroduces the very divergence this seam removes.
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- Rollout is incremental, not big-bang: this ADR establishes the boundary (#58); the explicit Runtime Adapter Registry lands next (#60); legacy helper retirement follows (#56); downstream cleanup in #57.
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## References
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- ADR-0001 — Dispatch Policy Module (pure-policy-projects / thin-adapters-execute precedent).
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- ADR-3660 — Runtime Artifact Layout Module (per-runtime artifact placement; delegated to by this projection).
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- ADR-0009 — Shell Command Projection Module (runtime-aware command text; delegated to by this projection).
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- ADR-0008 — Installer Migration Module (adjacent installer seam).
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- `CONTEXT.md` § Glossary — Domain modules and seams (the architecture seam map / glossary this module is registered in).
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- Installer-refactor chain: #58 (this ADR) → #60 (explicit adapter registry) → #56 (retire legacy directory helpers) → #57.
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