Adopt native env-var credential support from google-antigravity 0.1.7 and remove the sidecar override

[joycel-github]

Background

The antigravity harness sidecar (python/antigravity/harness_server.py) currently carries a temporary override, _vertex_kwargs_from_env(), that reads the standard GenAI environment variables (GOOGLE_GENAI_USE_VERTEXAI / GOOGLE_GENAI_USE_ENTERPRISE + GOOGLE_CLOUD_{PROJECT,LOCATION}) and threads them into LocalAgentConfig explicitly.

This override existed because older google-antigravity releases (through 0.1.5, which we pin) did not read those env vars natively: a user following the documented recipe (export env vars, construct a bare LocalAgentConfig) would fall through to the AI Studio path and hit a misleading "A Gemini API key is required" error instead of routing to Vertex.

The upstream SDK has since been fixed to read these env vars natively (LocalAgentConfig.__init__ hydrates vertex; VertexEndpoint hydrates project/location via a model_validator). That fix shipped in google-antigravity==0.1.7 (published 2026-07-16), verified present in the published wheel.

The override is now redundant and marked TODO: remove once AGY reads these env vars natively.

Plan

Tracked as two small, sequenced PRs:

• PR 1 — Bump google-antigravity 0.1.5 → 0.1.7. Just python/antigravity/requirements.txt. Independently valuable; with the override still present, behavior is unchanged (explicit kwargs from the override simply win, same result).
• PR 2 — Remove the _vertex_kwargs_from_env override. Depends on PR 1. Deletes the override + VertexKwargs, simplifies _build_default_config() to a bare LocalAgentConfig(system_instructions=...), and updates _has_credentials() to read GOOGLE_CLOUD_{PROJECT,LOCATION} from env (the SDK now hydrates those onto the VertexEndpoint, not the LocalAgentConfig, so the startup precheck must consult env rather than config.{project,location}). Includes the corresponding harness_server_test.py updates.

Ordering matters: PR 1 must merge first. Removing the override while still pinned to 0.1.5 would regress to the original bug.

Notes on the 0.1.5 → 0.1.7 jump

ax inherits both 0.1.6 and 0.1.7. Reviewed the SDK diff scoped to ax's surface (Agent, AgentConfig, LocalAgentConfig, types.{Text,Thought,ToolCall}, conversation.chat) — no breaking changes. New LocalAgentConfig params (env, subagents, session_continuation_mode) are additive/optional. DEFAULT_IMAGE_GENERATION_MODEL was renamed but ax doesn't reference it.

[joycel-github]

Validation (PR 1 — bump): Installed google-antigravity==0.1.7 and ran the sidecar test suite — 32/32 pass, no regressions. Version bump is compatible with the override still in place.

[joycel-github]

Deeper validation: Ran real google-antigravity==0.1.7 locally — a bare LocalAgentConfig() + env vars routes to Vertex with project/location hydrated (also via USE_ENTERPRISE alias); AI Studio path unchanged. Confirms 0.1.7 natively does what the override forced, so the override is redundant.

[joycel-github]

PR 1 (bump) opened as draft: #326

[joycel-github]

SDK delta 0.1.5 → 0.1.7 (bump spans 0.1.6 + 0.1.7)

Reviewed the full diff scoped to ax's surface. No breaking changes to Agent, LocalAgentConfig, types.{Text,Thought,ToolCall}, or conversation.chat.

Relevant to ax

Change	Ver	Relevance
Native env hydration — SDK reads GOOGLE_GENAI_USE_VERTEXAI / _USE_ENTERPRISE + GOOGLE_CLOUD_{PROJECT,LOCATION}	0.1.7	🎯 The reason for this bump; unblocks the override removal
Config inheritance cleanup + None-init pydantic fixes	0.1.7	✅ Part of the same env-hydration work
Vertex validation error message cleanup (dropped misleading "API key" ref)	0.1.6	✅ Sibling of the env fix; cleaner error on Vertex misconfig
Python 3.14 compatibility	0.1.6	✅ Future-proofs the sidecar
Local WebSocket retries localhost and 127.0.0.1	0.1.7	🎯 The reason for this bump; unblocks the override removal - SDK now does what ax's _resolve_localhost() hack does

Not used by ax (additive features, no impact)

Custom subprocess env=, multi-threaded tool/hook state (ctx.lock()), "extra_high" thinking level, LiteRT + LocalOpenAI backends, MCP/subagents for local models, multimodal tool outputs (supplemental_media), read_url_content tool, default image model rename. New exports (LiteRTAgentConfig, LocalOpenAIAgentConfig, SessionContinuationMode, LocalAgentConfig(env=, subagents=, session_continuation_mode=)) are additive.

Follow-up candidate

• _resolve_localhost() hack in harness_server.py may be removable now that 0.1.7 retries localhost/127.0.0.1 internally. Needs verification on substrate before removing — tracking separately, not in scope for the bump/override PRs.

[joycel-github]

_resolve_localhost cleanup opened for review: #328 (local verified; substrate check delegated).

[joycel-github]

#328 (_resolve_localhost cleanup) merged. Remaining: credential-override removal.

[joycel-github]

Credential-override removal opened for review: #331 (local verified; substrate delegated).