v0.9.0

Changes

• Adapt mstack to T3 Code. docs/t3code.md explains how each T3 provider finds
  skills, the install commands per provider, $name invocation, worktrees, a
  t3.json setup recipe and T3's own safety rules. docs/session-context/T3-CODE.md
  is an opt-in routing note for sessions that have the t3-code MCP tools.
• Add T3 host bindings. skills/meta-mode, recall and create-verification-skill
  gain references/hosts/t3code.md, and the playbooks point to it in neutral
  wording. Where T3 provides the primitive, the references bind delegation to
  delegate_task, PR watching to watch_pull_request, scheduling to
  schedule_task, thread history to t3_thread_search and t3_thread_read, and
  runtime evidence to preview_* and device_*. Shipping keeps a bounded
  merge-confirmation task because T3 does not wake a thread on merge. npm test
  now fails when a T3-only tool name appears under skills/ outside
  skills/*/references/hosts/.
• Add antigravity and grok harnesses. Antigravity installs to
  ~/.gemini/antigravity-cli/skills (override HARNESS_SKILLS_ANTIGRAVITY_DIR)
  and Grok shares ~/.agents/skills (override HARNESS_SKILLS_GROK_DIR). Both
  have run-role and smoke-harnesses runtimes; runtime.promptArgs places
  flags that take the prompt as their value. Cursor needs no target because it
  reads ~/.agents/skills.
• Add project-scope install: --project <repo> copies skills into each
  harness's project root (.agents/skills, .claude/skills). It refuses
  artifacts, --migrate and --environment, rejects project paths that
  resolve into a user skill root, the package, an enclosing discovery root or
  installer storage (symlinks, junctions and case variants included), and keeps
  --replace backups beside the skill roots.
• Add provider instances and effort options to model roles. overrides.t3code
  and budgets.t3code accept <provider>/<model> (<effort>) strings or
  { provider, model, effort } objects, and model-budget sets the effort from
  a catalog's explicit option list. Harness role strings stay opaque. Reserved
  keys such as __proto__ are rejected and budget writes use own properties.
  setup-mstack reads the T3 reference on a host that lists provider instances.
• Add the mstack-help entry skill (54 skills) for install, setup and "which
  skill fits" questions. profiles/local-skills.json lets skill-baseline
  record a wholly local skill, and --check derives upstream ownership from the
  profiles so a manifest cannot reclassify an upstream file as local.
• Reject skill frontmatter that Cursor and Antigravity silently drop: a plain
  name or description that is invalid YAML (: , #, a leading
  indicator, malformed quoted or block scalars) or a name outside T3's chip
  pattern. A # in a plain scalar is rejected on purpose, since YAML would
  truncate the value there.
• Detect filesystem case sensitivity for installer path keys instead of
  lowercasing on macOS, so a case-sensitive volume no longer reports distinct
  paths as overlapping.

Upgrade notes

Reinstall skills to receive mstack-help and the updated playbooks.
--harness all now also covers antigravity and grok: Antigravity gets its
own copy in ~/.gemini/antigravity-cli/skills, and Grok joins the shared
~/.agents/skills copy, so a rerun on an existing machine adds the Antigravity
copy. --project installs skills only, and a
fresh T3 worktree contains only committed files, so commit the project copy or
use the user-level install. Existing models.json files stay valid.
Contributors with skills whose plain-scalar description contains : or #
must quote it. docs/guide/07-overnight.md now mentions schedule_task.

Verification

Seven of the eight pull requests (all but the case-sensitivity fix) were
reviewed with pi (provider relay-gpt, model GPT-6.1-SOL) until the last round
returned no blocker or major findings, and every one passed Node 18/22 CI on
Linux, macOS and Windows with the package and pinned-source checks. The T3 behavior described here was checked against the T3
Code source at commit 8f75697, not against a running T3 Code session. The
merge-confirmation task, delegate_task targets and effort option resolution
were not exercised live. The agy and grok read-only arguments and
run-role calls were run against agy 1.2.16 and Grok CLI 1.0.46; agy's
--mode plan is an agent mode, not a tool restriction.