msd-core/docs/adr/0011-skill-surface-budget-module.md

Skill Surface Budget Module owns install-time profile staging and runtime surface control

• Status: Accepted
• Date: 2026-05-12
• Decision date: 2026-05-12
• Supersedes: ADR-0010 (Skill Surface Budget Module — earlier draft, install-time skill listing curation)
• Subsumed by: ADR-857 (Capability system) — generalizes this module; this seam remains live at src/surface.cts:348 (applySurface)
• Implementation: feat/3408-skills-description-dropped-due-to-size, PR

Every installed msd-* skill costs eager system-prompt tokens: runtimes (Claude Code, opencode, and others) enumerate all skill descriptions in <available_skills> on every turn. With 66 skills and 33 agents, MSD alone consumes roughly 60% of the default 1%-of-context skill-listing budget, causing descriptions to drop when users stack multiple plugins (#3408).

The root problem is an absence of a profile/surface seam: the installer wrote every skill unconditionally, and no runtime-side control existed for enabling or disabling a cohesive group of skills without a full reinstall.

Decision

• Add a Skill Surface Budget Module under msd-core/bin/lib/install-profiles.cjs as the single owner for which skills and agents are written to runtime config directories.
• Define three named profiles: core (six skills covering the main loop), standard (core + phase management and workspace skills), and full (all skills — the previous default).
• Compute each profile's effective skill set as the transitive closure over the requires: dependency graph extracted from skill frontmatter, so partial installs never break cross-skill dependencies.
• Persist the chosen profile in a .msd-profile marker file in each runtime config directory; msd update reads the marker to honor the profile on re-install.
• When multiple runtimes are configured, resolve disagreement to the most-restrictive profile (smallest effective skill set).
• Allow profile composition: --profile=core,audit resolves to union(closure(core), closure(audit)).
• Preserve back-compat aliases: --minimal and --core-only map to --profile=core; MINIMAL_SKILL_ALLOWLIST, isMinimalMode, shouldInstallSkill, and stageSkillsForMode remain exported for existing callers.
• Add a CI gate (scripts/lint-skill-deps.cjs, wired into pretest) that verifies every skill's requires: entries resolve against real skill stems — prevents the profile closure from silently over-installing or breaking.

Phase 2 — Runtime Surface Module

The Phase 2 decision, previously listed as an open question, is recorded here as an amendment to this ADR.

Decision

• Add a /msd:surface slash command with the following sub-commands:
  • list — show all clusters and their enabled/disabled status for the active runtime
  • status — show the active profile, effective skill count, and any dropped-description warnings
  • profile <name> — switch the active profile and re-stage skills/agents for the current runtime
  • disable <cluster> — mark a cluster disabled; re-stage to remove its skills from the runtime config dir
  • enable <cluster> — mark a cluster enabled; re-stage to add its skills back
  • reset — clear surface state and re-apply the active profile from .msd-profile
• Implement the runtime surface engine in msd-core/bin/lib/surface.cjs, consuming stageSkillsForProfile and stageAgentsForProfile from the Phase 1 module without duplicating staging logic.
• Persist per-runtime surface state in <runtimeConfigDir>/.msd-surface.json, independent from .msd-profile. The profile marker owns install-time identity; the surface JSON owns session-scope cluster toggles.
• Source cluster taxonomy from the research memo §3.2 (2026-05-12-skill-surface-budget.md). Define clusters in msd-core/bin/lib/clusters.cjs — a separate module so the surface engine and future SDK callers can import cluster definitions without loading the full profile module.
• Cluster taxonomy: core_loop, audit_review, milestone, research_ideate, workspace_state, docs, ui, ai_eval, ns_meta, utility. Membership may overlap; every installed skill stem must appear in at least one cluster (enforced by tests/surface-clusters.test.cjs).
• Relationship to Anthropic platform asks: Asks D (native per-skill toggle API) and E (budget-fraction negotiation) remain filed separately. The /msd:surface command is a unilateral MSD-side workaround that does not depend on those platform changes.

Status — Phase 1 shipped

Phase 1 artifacts landed on feat/3408-skills-description-dropped-due-to-size:

• msd-core/bin/lib/install-profiles.cjs — PROFILES map, resolveProfile, loadSkillsManifest, stageSkillsForProfile, stageAgentsForProfile, readActiveProfile, writeActiveProfile, mostRestrictiveProfile, resolveEffectiveProfile
• requires: frontmatter added to 64 skills in commands/msd/*.md
• scripts/lint-skill-deps.cjs — CI gate for requires: integrity, wired into pretest
• bin/install.js — --profile=<name> flag (composable); --minimal/--core-only as aliases; .msd-profile marker write on install; msd update re-reads marker
• Tests: tests/install-profiles-manifest.test.cjs, tests/install-profiles-marker.test.cjs, tests/install-profiles-resolve.test.cjs, tests/install-profiles-stage.test.cjs, tests/lint-skill-deps.test.cjs

Phase 2 shipped on the same branch:

• commands/msd/surface.md — /msd:surface slash command runbook (sub-commands: list, status, profile <name>, disable <cluster>, enable <cluster>, reset)
• msd-core/bin/lib/surface.cjs — runtime engine (readSurface, writeSurface, resolveSurface, applySurface, listSurface); reuses stageSkillsForProfile / stageAgentsForProfile from Phase 1
• msd-core/bin/lib/clusters.cjs — 10-cluster taxonomy covering all installed skill stems
• Tests: tests/surface-state.test.cjs, tests/surface-clusters.test.cjs, tests/surface-resolve.test.cjs, tests/surface-apply.test.cjs, tests/surface-list.test.cjs
• Persistent surface state: <runtimeConfigDir>/.msd-surface.json (independent from .msd-profile)

Open questions

• Whether the requires: field should also be consumed by /msd:help to annotate dependency chains in help output (follow-up).
• Whether telemetry (per-profile install counts, cluster-disable events) should be added to the surface engine or deferred.
• Whether Anthropic platform asks D and E (native skill toggle API, budget-fraction negotiation) should block any future work in this module.

Consequences

• Users with constrained context budgets can install --profile=core and expand incrementally via /msd:surface enable <cluster> without a full reinstall.
• The requires: closure ensures partial installs never silently break skill cross-references.
• Future skills must declare requires: dependencies to participate in profile resolution; the lint gate enforces this at CI time.
• CONTEXT.md gains a canonical Skill Surface Budget Module entry; future architecture reviews should treat out-of-seam skill staging as drift.
• Cluster definitions in clusters.cjs are the authoritative taxonomy for runtime surface control; additions must be reflected there and in tests.

References

• Feature issue: #3408
• Research memo: docs/research/2026-05-12-skill-surface-budget.md (§3.2 cluster taxonomy)
• See 0008-installer-migration-module.md
• See 0009-shell-command-projection-module.md
• See 0010-file-operation-engine-module.md