v1.0.0 — Three-adapter scope; Codex dropped; 1.0.0 commitment

BREAKING: Codex adapter removed. Supported hosts narrow from four (Claude Code, Antigravity, Codex, Gemini CLI) to three (Claude Code, Antigravity, Gemini CLI). Anyone running agentic-harness through Codex must migrate to one of the three remaining adapters — the phase-gated workflow itself is host-agnostic, so migration is install + relearn the host-specific invocation surface.

The version bump from 0.9.x to 1.0.0 reflects the breaking change plus a commitment: the harness has had enough churn (v0.1.0 → v0.9.0) to feel stable, and semver becomes firm going forward — major = breaking, minor = additive, patch = fixes. Future host removals, fundamental shape changes, or invariant inversions become explicit major-version events. Additive changes (new skills, the planned agent-toolkit repo split, ContextVault, design skill) become clear minor bumps. See ADR 0005 for the full decision narrative.

Removed

• Codex adapter (adapters/codex/, 15 files: README, 4 sub-agents in TOML, 10 skill dirs — 7 harness- prefixed phase-commands-as-skills + 4 shared skills).
• Codex adapter research note (harness/agents/codex-adapter-research.md, 294-line deep-dive on Codex-specific design — dead weight once the adapter is gone).
• Codex-specific code in scripts: scripts/check-parity.sh's == codex == block + divergence comments; scripts/check-references.py's CODEX_PHASE_PREFIX constant + codex branch in expected_canonical_for; scripts/validate-adapters.py's validate_codex_agents() function + codex skills-dir entry; codex expected-files lines in scripts/smoke-install-{bash,pwsh} and scripts/check-integrity-{bash,pwsh}.

Added

• ADR 0005 — Drop Codex support; three-adapter scope: documents Context (5 reasons codex was dropped), Decision (7 concrete actions including the v1.0.0 framing), Consequences (5 positive + 4 negative), and load-bearing re-audit assumptions.
• True-sync --update semantics. install.sh and install.ps1 now wipe twelve fully-harness-authored subdirs before recreating from source on --update. Orphan paths from previous versions (e.g. .codex/ for users upgrading from v0.9.0) are automatically removed and reported as removed legacy <path>/. User state files at .harness/ root, merged settings.json files, wiki/**, and root AGENTS.md/CLAUDE.md are deliberately preserved. The generalized mechanism means future host or skill removals also clean up automatically — codex is the first user, not a special case. Documented in Update-Installed-Harness.
• no-Co-Authored-By convention added to AGENTS.md + CLAUDE.md. Host-agnostic rule: agents do not append Co-Authored-By: trailers naming the model or host. Sole-author-of-intent framing.

Changed

• Adapter parity narrows to three hosts. check-parity.sh enforces the new canonical set; no more harness- prefix divergence (was only needed for Codex's collision with built-in /plan and /review). Removing the prefix requirement simplifies the parity invariant.
• Shared-skill delivery becomes explicit. .agents/skills/ (read by Gemini per the Agent Skills standard) was previously delivered by the Codex install block as a side effect. Now install.sh explicitly enumerates the four shared skills (dependabot-fixer, doctor, migrate-to-diataxis, ship-release) and sources them from adapters/claude-code/skills/ (parity-enforced identical content; cleanest source — antigravity/skills/ would over-deliver because it mixes sub-agents-as-skills).
• Repo-public surfaces scrubbed of Codex mentions. README "works with" chip row drops Codex (now 3 chips); intro paragraph drops Codex from host list; Mermaid Host node collapses to single-line three-host listing; AGENTS.md intro tool-list and Co-Authored-By convention examples drop Codex; harness/skills/doctor.md and ship-release.md adapter tables drop Codex; adapters/gemini/README.md reframes 5 Codex-block references to actual install.sh/Agent Skills standard delivery; harness/agents/gemini-adapter-research.md 10 codex-comparison phrasings reframed to current state.
• Wiki updated to three-adapter shape. 9 wiki pages scrubbed across explanation/ (Product-Intent, GitHub-Projects-Integration, How-The-Pieces-Fit including 2 ASCII diagrams), how-to/ (Cut-A-Release, Install-Into-Project, Update-Installed-Harness with new v1.0.0 sync semantics section), tutorials/01-First-Install.md, and reference/ (Repo-Layout with rewritten three-adapters table + Quick Reference + tree diagram, Installer-CLI with v1.0.0 sync details). Home.md and _Sidebar.md gain ADR 0005 row in Decisions section. Historical entries in CHANGELOG.md and wiki/reference/Completed-Features.md past-release sections deliberately preserved as history.
• README polish (multi-commit run). Mirrored install commands across MacOS/Linux and Windows sections; eliminated redundant license callout; QoL updates (badges, "works with" chip row, Mermaid architecture diagram); intro paragraph framing tightened around production-quality engineering posture.

Internal

• 5-task Codex-removal sweep plan completed. Tracked in .harness/PLAN.md: task 1 (adapter dir + canonical specs + scripts cleanup with the codex-adapter-research.md deletion decision); task 2 (installers + smoke tests — flagged Gemini's shared-skill delivery as the load-bearing risk and resolved it by sourcing from claude-code/skills/); task 2 amendment (true-sync --update generalized beyond codex cleanup per user direction "github is SoT for my personal setup"); task 3 (README + CONTRIBUTING + AGENTS + CLAUDE + adapter READMEs scrub); task 4 (wiki + ADR 0005); task 5 (release).
• Stats: 26 files changed task 1 (25 ins, 1204 del). 2 files changed task 2 (25 ins, 19 del). 2 files changed task 2 amendment (96 ins). 4 files changed task 3 (12 ins, 13 del). 12 files changed task 4 (99 ins, 27 del). Net: ~46 files touched, ~1300 lines removed.
• CI green across all three per-OS workflows on every commit in the range. Smoke tests intentionally not run as a gate during task 1 (install.sh was inconsistent post-adapter-removal); reintroduced as a gate in task 2 where the installer fix landed.