Antigravity CLI and UHP

Use direct automation when there is no verified gateway adapter

The current Antigravity CLI repository and latest 1.2.16 release remain a native product surface. HarnessRouter’s stable entrypoint lists twenty backend names and does not include Antigravity CLI. Do not substitute an Antigravity provider route or an Oh My Pi model connection for an Antigravity complete-harness backend.

For a script, begin with the documented headless shape rather than an imagined UHP endpoint:

agy -p "Summarize README.md without changing files."

Install and authenticate the native CLI first, select a trusted/disposable project, and configure actual command/tool permissions independently of the prompt. This is source-shaped and unexecuted; it can call a model. For structured output and print-timeout options, use the official headless guide matching the installed release.

Observed state	What the wrapper needs to decide
Final text arrives	Check completion/error state rather than assuming all background work ended
Partial output then timeout	Preserve the partial result and report unresolved work
A queued message is accepted	Distinguish admission from its later execution/result
Remote Control connects	Identify the owning host and service; connection is not a sandbox

A useful first integration records native process/result evidence and checks that a denied operation remains denied. If your product later adds an adapter, explicitly map cancellation, continuation, progress and errors and test those mappings. Remote harness execution explains the host boundary; UHP clients lists separately established protocol implementations. None of the current release’s terminal or queue fixes establishes native UHP adoption.

Release check — 4 October 2026

The latest stable release observed in the upstream GitHub release API is 1.2.16, published 2026-10-03. The release notes describe terminal responsiveness and selection improvements, queued-message ordering/recovery and refined allow suggestions for Go subcommands. These are upstream CLI behaviors, not evidence of UHP adoption.

Evidence scope: the integration details, commands, measurements and development-head references below preserve the 11 Sep 2026 source snapshot. They are not presented as a fresh test of this newer release. For the current UHP protocol, HarnessRouter release and suite coordinates, use the release tracker and conformance guide. Adapter support does not establish upstream-native UHP adoption.

Source snapshot — 11 Sep 2026

Antigravity CLI is a distinct coding-agent harness surface, not a UHP implementation. Google describes the CLI as the terminal-first interface to Antigravity agents. Its README states that the CLI and Antigravity 2.0 share the same core agent engine, while the CLI focuses on keyboard-driven and remote/SSH workflows with multi-step reasoning, multi-file editing, tool calling and persistent history.

The latest stable release observed at this cutoff is 1.2.0, published 10 September 2026 at 01:43:29 UTC. Tag 1.2.0 points to 34406bef8e87fc103783c0c9715e5e2cce3c3e1b, and checked upstream main is the same commit.

Caution

No native UHP adoption is established. Reviewed first-party Antigravity sources do not expose a UHP endpoint, UHP version declaration or UHP conformance result. HarnessRouter v0.15.10 does not list Antigravity CLI among its ten released backends. The same reviewed sources do not establish a native ACP or A2A-protocol interface for Antigravity CLI.

Why Antigravity CLI matters to harness architecture

Antigravity CLI is more than an interactive model shell. Its first-party documentation and changelog expose a complete harness surface around the shared agent engine:

• interactive and headless (-p) execution;
• persistent conversations and resumable history;
• background Remote Control service lifecycle for a reachable machine;
• multi-step tool-using turns and multi-file edits;
• custom agents and subagent delegation;
• Agent Skills, rules, plugins and hooks;
• first-party MCP server integration;
• a fine-grained permission engine for files, commands, URLs and tools;
• sandbox controls for supported non-interactive execution;
• structured JSON and streaming-JSON output for automation.

Those are harness/runtime semantics. UHP standardizes a different outer boundary: client → UHP server → configured complete harness. A UHP implementation could theoretically wrap Antigravity CLI, but no reviewed first-party source establishes such an adapter today.

Boundary map

Layer	Primary job	Verified Antigravity CLI relationship
Antigravity CLI	Terminal/headless agent loop, tools, files, history, model selection and approvals	Native harness surface.
Antigravity Remote Control	Background service registered with the operating-system service manager	Native runtime/host capability in stable 1.2.0.
Antigravity 2.0	Rich GUI using the same core agent engine	Shared engine; separate interface.
Subagents/custom agents	Delegated agent work and reusable agent definitions	Native harness capability.
Plugins / Skills / hooks / rules	Package reusable tools, agents, instructions and policy hooks	Native customization surface.
MCP	Tool-server interoperability	First-party supported. Local stdio and remote server configurations are documented.
ACP	Editor/client-to-agent protocol	Not established by reviewed first-party sources.
A2A protocol	Standard agent-to-agent interoperability	Not established by reviewed first-party sources.
UHP	Client → UHP server → complete configured harness	No native adoption established.
HarnessRouter	UHP reference implementation → backend adapters	Antigravity CLI is not in the released ten-backend set at this cutoff.

Headless mode is an automation surface

Antigravity CLI documents headless execution with agy -p, including text, JSON and streaming-JSON output. The same surface supports explicit model/effort selection, custom agents, continued conversations, permission controls and sandbox options, making it suitable for scripts and CI rather than only an interactive TUI.

The preceding stable 1.1.28 line established an important automation-finality detail: when --print-timeout expires during a turn, the CLI returns the partial output collected so far, exits successfully and emits a warning on stderr instead of treating the timeout itself as a failed run. Interrupts such as Ctrl+C remain non-zero exits.

That means downstream automation should not interpret a zero process exit alone as proof that the intended agent turn completed in full; stderr/truncation state remains part of the result boundary. This is Antigravity CLI runtime behavior, not a UHP finality rule.

The same 1.1.28 line also improved headless shutdown by waiting for running background tasks and scheduled timers, bounded by --print-timeout, while leaving daemon background processes such as development servers running. Fatal headless errors use a stable error: stderr marker, and previously silent no-output failures report why they ended.

Stable 1.2.0 adds durable Remote Control lifecycle

The most architectural addition in 1.2.0 is a first-party background-service lifecycle:

• remote-control start registers the CLI with the operating system’s service manager so the machine can remain reachable across logouts and reboots;
• remote-control status reports the service state;
• remote-control stop removes/stops the managed service;
• remote-control start --name <label> assigns a custom machine label;
• --session scopes the service to the active login session instead of the broader persistent service lifecycle.

The release also fixes the macOS service exiting shortly after service-manager startup, cleans up legacy installer-script background services during start/stop, and restores the Remote Control setting for access supplied through a paid Google Cloud project.

This is an Antigravity host/runtime lifecycle, not a new remote-execution protocol. It does not create a UHP transport, ACP interface or A2A binding, and it does not change the UHP 2026-08-11 task/session contract.

MCP and customization composition

Antigravity’s plugin model can bundle plugin.json, MCP configuration, hooks, skills, custom agents and rules. First-party MCP documentation supports local stdio servers and remote server configurations, with management through the CLI’s MCP surface.

Stable 1.2.0 fixes two additional MCP interoperability defects:

• MCP servers bundled inside globally installed plugins now initialize at CLI startup and update their running status when plugins are enabled or disabled;
• third-party MCP server tools whose input schemas omit additionalProperties no longer fail the CLI’s schema validation solely for that omission.

The preceding 1.1.28 line fixed plugin-defined MCP servers resolving relative or missing working directories against the wrong location and removed a startup race where subagents could fail to discover MCP tools while servers were still initializing. 1.1.27 separately began rejecting tool-call arguments the MCP server’s own schema never declared instead of silently dropping invented parameters.

These are harness/tool compatibility and lifecycle safeguards. They do not change the MCP protocol specification and do not establish UHP support.

Permissions are part of the harness boundary

Antigravity CLI documents a fine-grained permission model whose effective order gives deny precedence over ask, and ask over allow. Stable 1.1.28 changed URL fetching from always allowed to ask by default, so external reads require approval unless an applicable grant already exists.

That line also made approval prompts name the concrete action being approved and can surface a reason when the request was escalated by a hook or because a file belongs to another project. These controls belong to the Antigravity harness/policy layer; UHP does not prescribe Antigravity’s permission syntax or approval UI.

1.2.0 also improves run finality and compatibility

Beyond Remote Control and MCP composition, stable 1.2.0:

• surfaces a clear content-filter stop reason instead of a spurious no candidate found, empty turn or repeated retry of rejected input;
• prevents temporary agent scratch/ files from recursively triggering filesystem watchers and polluting artifact/checkpoint review;
• avoids unnecessary filesystem customization discovery on every user message when no slash command is invoked;
• removes a spurious logging prefix from ordinary CLI/daemon output;
• fixes older conversations failing to resume with unknown step type;
• improves half-page navigation across scrollable views.

The preceding stable 1.1.28 remains the automation-hardening baseline for longer transient-model retry/backoff, headless completion/failure/partial-output semantics, model-resolution audit logging, stricter URL-fetch approval defaults, exact plugin reinstall replacement, subagent completion cleanup and long-session terminal-state memory use.

These are upstream Antigravity CLI harness/runtime changes. They do not change UHP 2026-08-11, MCP wire semantics, HarnessRouter’s backend set or UHP conformance evidence.

Evidence boundaries

• Stable: 1.2.0, published 10 Sep 2026 at 01:43:29 UTC.
• Tag target: 34406bef8e87fc103783c0c9715e5e2cce3c3e1b.
• Checked main: the same 34406bef commit at this cutoff.
• Shared Antigravity engine: established by the first-party CLI README.
• Headless automation: established by first-party CLI documentation and stable changelog.
• Background Remote Control service: established by the 1.2.0 release/changelog.
• MCP: established by first-party documentation and changelog evidence.
• Subagents / plugins / skills / hooks / rules: established by first-party documentation and changelog evidence.
• ACP: not established by reviewed first-party sources.
• A2A protocol: not established by reviewed first-party sources.
• Native UHP: not established.
• HarnessRouter backend: not present in v0.15.10’s ten released backends.
• UHP conformance evidence: none attributed to Antigravity CLI.

Related pages

Read Gemini CLI for Google’s separate HarnessRouter-backed CLI, harness composition for delegation topology, remote harness execution for non-local execution boundaries, Skills Over MCP for the emerging skills-distribution standard, UHP vs MCP for the tool-protocol boundary, and ecosystem for adoption classifications.

Primary sources

• Antigravity CLI repository
• Antigravity CLI 1.2.0
• Antigravity CLI tag/current-main commit 34406bef
• Antigravity CLI README at 1.2.0
• Antigravity CLI changelog at 1.2.0
• Official Antigravity CLI overview
• Official headless-mode documentation
• Official MCP documentation
• Official plugins documentation
• Official permissions documentation
• HarnessRouter v0.15.10