Track Antigravity SDK support for model-specific agents

[cbusillo]

Objective

Track Google's Antigravity SDK / AGY CLI evolution until Every Code can support model-specific Google/Antigravity agents without mutating shared settings.json state.

Finish Line

Every Code has a supported way to call specific Google/Antigravity models for agent runs after the consumer Gemini CLI cutoff, either through a documented AGY CLI model override, an Antigravity SDK integration, or a clearly documented decision that only the configured AGY default is supported.

Current Status

State: Waiting on Google-supported per-run model selection surface.
Next action: Periodically re-check Antigravity SDK and AGY CLI docs/releases for a noninteractive model override or programmatic agent-run API.
Blocked by: None.
Waiting for: Google to document and ship an SDK/CLI surface that can select a model per invocation without mutating ~/.gemini/antigravity-cli/settings.json.
Last verified: 2026-05-24. Local agy 1.0.2 has no --model, --config-file, or settings-file override; current selected AGY model is Gemini 3.5 Flash (Medium).

Scope

• In: Antigravity SDK research, AGY CLI release/docs checks, model selector mapping, Every Code agent defaults, docs, and validation harness updates.
• Out: continuing to depend on consumer Gemini CLI as the long-term model-specific path.

Acceptance Criteria

• Verify whether AGY CLI adds a documented per-run model flag or config override.
• Verify whether Antigravity SDK exposes programmatic model selection suitable for Every Code agent runs.
• Decide whether to add model-specific AGY/SDK selectors, keep only antigravity as configured-default, or ship a guarded settings-mutation fallback.
• Update docs/agents.md and docs/config.md to explain the supported Google/Antigravity model-selection behavior.
• Add tests or a fake-command harness for any new invocation path.
• Run ./build-fast.sh for implementation changes.

Evidence / Context

Local findings on 2026-05-24:

• agy --help exposes --print, --add-dir, --sandbox, --dangerously-skip-permissions, and --log-file, but no model-selection flag.
• Probes for --model, -m, --config-file, --settings-file, --app-data-dir, and --gemini-dir were rejected by agy when used for a real invocation.
• Antigravity persists the selected model in ~/.gemini/antigravity-cli/settings.json as a display label.
• Mutating settings.json before spawning agy is likely possible but unsupported shared-state behavior and should not be the preferred long-term integration.

Relationships

Related: #97, #48

Validation

Use local agy --help / harmless print-mode probes and official Google Antigravity docs or release notes as evidence before changing Every Code behavior. For repo changes, validate with ./build-fast.sh.