feat(opencode-v2): OpenCode 2.x host adapter (reuses the existing core)

[Vladimir-Human]

Title

Add an OpenCode 2.x host adapter (reuses the existing core, no changes to the 1.x package)

Background

OpenCode 2.x (@opencode-ai/cli@0.0.0-beta-*, binary opencode2) replaced the plugin surface:

• no fetch() patching; instead session.hook("http.request" | "http.response");
• providers are declared with native packages in config, e.g.
  "package": "@opencode-ai/ai/providers/google";
• OAuth methods are registered through integration.transform, tools through tool.transform;
• the existing @cortexkit/opencode-antigravity-auth declares
  engines.opencode: ">=1.17.13 <2" and cannot load on 2.x (neither the TUI sidebar nor the
  fetch patch exist there).

So 2.x users currently have no Antigravity access. I wrote the host adapter; all logic still
comes from @cortexkit/antigravity-auth-core@2.1.0 — OAuth, transport, account pool, quota and
the model registry are untouched.

Implementation

1. session.hook("http.request") intercepts Antigravity model calls and rewrites the URL to a
   loopback server owned by the plugin.
   Why a loopback server: 2.x sends whatever event.request the hook leaves behind through its
   own HTTP client, and http.response only runs after that request succeeded, so a custom
   Response cannot be returned from the hook. The loopback keeps the core's
   fetchWithAgyCliTransport (agy header order, proxy support) while the host still sees a
   plain, streamable, cancellable SSE.
2. Inside the loopback: getCurrentOrNextForFamily (hybrid) → refreshAntigravityToken →
   ensureProjectContext → buildAgyAgentRequestMetadata +
   orderAgyRequestPayloadInPlace → ANTIGRAVITY_ENDPOINT_FALLBACKS.
   429/403 cools the account down via markRateLimitedWithReason and rotates, 401 forces a
   refresh, and an empty-candidate STOP is retried up to three times.
3. The native @opencode-ai/ai/providers/google package stays the codec, so image, PDF and
   tool-call handling comes from the host rather than a hand-written adapter.

Four issues found and worked around (may matter for 1.x / pi too)

1. GPT-OSS tool schemas — the AGY GPT bridge re-encodes protobuf numeric constraints as
   strings, so minLength: 1 returns 400 INVALID_ARGUMENT. Fixed with
   normalizeGeminiTools(request, { moveNumericConstraintsToDescription: true }) for gpt-*
   wire models (the flag already exists in core; it just needs to be enabled for that family).
2. Strict native event schema — GPT-OSS opens a turn with content and no parts, and
   Claude sometimes uses role assistant; 2.x rejects both with
   Invalid google/gemini stream event. Frames must be normalised before forwarding.
3. gzip header — the core transport already inflates the body, so copying upstream
   content-encoding: gzip to the host makes it inflate twice and fail.
4. PDF attachments — the 2.x CLI drops PDF attachments before the provider sees them (no
   inlineData in the request). I therefore register an antigravity_read_document tool that
   loads the local PDF/image itself and asks a multimodal model. Images pasted into chat work
   natively. Generated images are written to disk and returned as a text path, because the 2.x
   native parser only renders text and tool calls.

Verified (Windows 11 / Node 24 / OpenCode 0.0.0-beta-17595 / two-account pool)

• all eight selectors answered live requests, every reasoning tier included:
  Gemini 3.7 / 3.6 / 3.5 Flash, Gemini 3.1 Pro, Gemini 3.1 Flash Image,
  Claude Sonnet 4.6 Thinking, Claude Opus 4.6 Thinking, GPT-OSS 120B;
• tool calling works end to end; PNG attachment recognised; PDF text extracted through the
  tool; image generation written to disk; disabling account #0 failed over to #1.

Privacy and credentials

• No accounts, e-mail addresses, tokens, project ids or local paths appear in the code or docs.
• Logs contain only #<account index>, upstream status codes and routing — no prompts, tokens
  or e-mail addresses.
• Credentials stay in the core-owned antigravity-accounts.json (v4 schema + fenced lock),
  shared with the 1.x plugin and the standalone CLI.
• Testing was done locally with my own accounts; no test data is included.

How you may want to take it

1. I can shape it into packages/opencode-v2 (or any name you prefer) and open a PR, including
   the bilingual README, an example config and the MIT licence;
2. or you take only the fixes (GPT-OSS schema flag, frame normalisation, gzip header) and I
   split them into small PRs;
3. or I publish it as a separate repository crediting and linking your core.

Whatever suits you. Thanks for the core — its transport and account-pool design made this
adapter straightforward.

---

^{Need help on this PR? Tag @codesmith-bot with what you need. Autofix is disabled.}

---

Summary by cubic

Adds @cortexkit/opencode-v2-antigravity-auth, a native OpenCode 2.x adapter that restores Antigravity access by rerouting Google model calls to a loopback that reuses the shared core. 2.x previously had no Antigravity support; 1.x behavior is unchanged. Non‑stream generateContent now returns a merged JSON response, and generated images are saved to disk.

• Intercepts /models/*:(stream)generateContent via session.hook("http.request"), forwards to 127.0.0.1, unwraps SSE frames, normalizes events for the strict 2.x schema, retries bare STOP up to 3 times, and merges non‑stream calls into one JSON response.
• Keeps @opencode-ai/ai/providers/google as the codec; enables normalizeGeminiTools(..., { moveNumericConstraintsToDescription: true }) for GPT‑OSS tool schemas.
• Transport and pool: hybrid rotation; 401 forces one refresh then excludes the account; 429/403 cools and rotates (honors retry-after); endpoint fallbacks via ANTIGRAVITY_ENDPOINT_FALLBACKS.
• Adds antigravity_read_document for PDFs/images; by default only files under the user’s home directory are readable, sensitive paths are always denied, the boundary is enforced on the real path (prevents symlink/junction escape), and readDocumentRoots are canonicalized and can narrow access.
• OAuth “Google Antigravity (add account)” appends to the shared pool (antigravity-accounts.json, v4). Callback listens on 127.0.0.1:51121/oauth-callback; the callback page only acknowledges receipt.
• Logs to <state dir>/antigravity-v2.log without prompts/tokens. Adds example config and tests; includes the package in the publish matrix and scripts/version-sync.mjs; typechecks both plugin and callback with node --check; tests use bun test --isolate.
• Fix: import resolve explicitly in the path allowlist to avoid a runtime ReferenceError.

Rollout

• Requires OpenCode 2.x and @cortexkit/antigravity-auth-core@2.1.0.
• Add the plugin to opencode.json pointing to src/plugin.mjs (absolute path or node_modules/@cortexkit/opencode-v2-antigravity-auth/src/plugin.mjs), and declare models under the google provider using @opencode-ai/ai/providers/google.
• To add accounts: connect the google integration and select “Google Antigravity (add account)”; allow localhost access and port 51121.
• Optional: override the pool path with ANTIGRAVITY_ACCOUNTS_FILE; set readDocumentRoots to restrict document access.

^{Written for commit ccd60d9. Summary will update on new commits.}

[cubic-dev-ai]

1 issue found across 8 files

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name="packages/opencode-v2/package.json">

<violation number="1" location="packages/opencode-v2/package.json:30">
P3: This new package ships no `scripts` and is not wired into the root workspace scripts: root `build`/`typecheck`/`test` cover only `packages/core`, `packages/opencode`, and `packages/pi`. As a result nothing builds, lints, or tests the opencode-v2 source in CI, even though the `packages/*` workspace glob pulls it into `bun install`. If this stays in the monorepo, add at least a `lint`/`build`/`test` script and reference it from the root; if it is meant to be a standalone package, that is fine, but the decision should be explicit rather than leaving a workspace member with zero CI coverage.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P3: This new package ships no scripts and is not wired into the root workspace scripts: root build/typecheck/test cover only packages/core, packages/opencode, and packages/pi. As a result nothing builds, lints, or tests the opencode-v2 source in CI, even though the packages/* workspace glob pulls it into bun install. If this stays in the monorepo, add at least a lint/build/test script and reference it from the root; if it is meant to be a standalone package, that is fine, but the decision should be explicit rather than leaving a workspace member with zero CI coverage.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At packages/opencode-v2/package.json, line 30:

<comment>This new package ships no `scripts` and is not wired into the root workspace scripts: root `build`/`typecheck`/`test` cover only `packages/core`, `packages/opencode`, and `packages/pi`. As a result nothing builds, lints, or tests the opencode-v2 source in CI, even though the `packages/*` workspace glob pulls it into `bun install`. If this stays in the monorepo, add at least a `lint`/`build`/`test` script and reference it from the root; if it is meant to be a standalone package, that is fine, but the decision should be explicit rather than leaving a workspace member with zero CI coverage.</comment>

<file context>
@@ -0,0 +1,45 @@
+    "node": ">=20.0.0",
+    "opencode": ">=2 <3"
+  },
+  "main": "./src/plugin.mjs",
+  "exports": {
+    ".": "./src/plugin.mjs",
</file context>

[Vladimir-Human]

Fixed in 0660034: the package ships lint/format:check/typecheck/test scripts plus a smoke test (packages/opencode-v2/test/plugin.test.mjs), and is wired into the root typecheck (node --check) and test chains. bun.lock is regenerated. Note: this package is plain ESM by design — the typecheck step is node --check rather than tsc.

[cubic-dev-ai]

1 issue found across 12 files (changes from recent commits).

Prompt for AI agents (unresolved issues)

Check if these issues are valid — if so, understand the root cause of each and fix them. If appropriate, use sub-agents to investigate and fix each issue separately.


<file name=".github/workflows/release.yml">

<violation number="1" location=".github/workflows/release.yml:82">
P2: Adding `@cortexkit/opencode-v2-antigravity-auth` to the publish matrix breaks the release because its version is never synchronized. The workflow's `Sync version` step runs `scripts/version-sync.mjs <tag-version>`, whose `packageJsonPaths` array only covers `packages/{core,opencode,pi}/package.json` and omits `packages/opencode-v2/package.json`. So opencode-v2 always publishes its hardcoded `2.1.0`, which diverges from the release tag and, on the second release, collides with the already-published version and fails the `npm publish` job (which blocks the downstream `github-release`). Add the opencode-v2 path to `version-sync.mjs` alongside this matrix entry.</violation>
</file>

<sub>Reply with feedback, questions, or to request a fix.

Re-trigger cubic</sub>

[cubic-dev-ai]

P2: Adding @cortexkit/opencode-v2-antigravity-auth to the publish matrix breaks the release because its version is never synchronized. The workflow's Sync version step runs scripts/version-sync.mjs <tag-version>, whose packageJsonPaths array only covers packages/{core,opencode,pi}/package.json and omits packages/opencode-v2/package.json. So opencode-v2 always publishes its hardcoded 2.1.0, which diverges from the release tag and, on the second release, collides with the already-published version and fails the npm publish job (which blocks the downstream github-release). Add the opencode-v2 path to version-sync.mjs alongside this matrix entry.

Prompt for AI agents

Check if this issue is valid — if so, understand the root cause and fix it. At .github/workflows/release.yml, line 82:

<comment>Adding `@cortexkit/opencode-v2-antigravity-auth` to the publish matrix breaks the release because its version is never synchronized. The workflow's `Sync version` step runs `scripts/version-sync.mjs <tag-version>`, whose `packageJsonPaths` array only covers `packages/{core,opencode,pi}/package.json` and omits `packages/opencode-v2/package.json`. So opencode-v2 always publishes its hardcoded `2.1.0`, which diverges from the release tag and, on the second release, collides with the already-published version and fails the `npm publish` job (which blocks the downstream `github-release`). Add the opencode-v2 path to `version-sync.mjs` alongside this matrix entry.</comment>

<file context>
@@ -79,6 +79,8 @@ jobs:
             workspace: "@cortexkit/opencode-antigravity-auth"
           - package: "@cortexkit/pi-antigravity-auth"
             workspace: "@cortexkit/pi-antigravity-auth"
+          - package: "@cortexkit/opencode-v2-antigravity-auth"
+            workspace: "@cortexkit/opencode-v2-antigravity-auth"
     steps:
</file context>

[Vladimir-Human]

Fixed in b9136d9: scripts/version-sync.mjs now includes packages/opencode-v2/package.json in packageJsonPaths, so release tags bump the adapter version together with core/opencode/pi and the publish matrix cannot collide with a stale hardcoded version.

[Vladimir-Human]

All eight review comments are addressed in 0660034 (push e58698a..0660034), with replies on each thread:

• P1 — at most one forced refresh per account/request; repeated 401 excludes the account and pool selection continues.
• P2 — requestSessions.completeExecution() is called after terminal streams, collected tool responses, and non-stream answers.
• P2 — non-streaming generateContent calls now get a single JSON GenerateContentResponse (frames merged) instead of an SSE body.
• P2 — antigravity_read_document refuses well-known credential/secret paths (.ssh, .config, .local, AppData, .env, *.key/*.pem/*.p12/*.pfx, id_rsa, auth.json, antigravity-accounts.json, …), defaults to the user's home directory, and can be narrowed via the readDocumentRoots plugin option; the exfiltration risk is documented in both READMEs (EN + zh-CN).
• P2 — the OAuth callback page reports only that the authorization was received; the result is reported by OpenCode after exchange + persistence.
• P2 — Install instructions fixed (adapter package, not just core) incl. plugin-path resolution.
• P3 — root README package-count references fixed; release publish matrix now includes @cortexkit/opencode-v2-antigravity-auth.
• P3 — the package ships lint/format:check/typecheck/test scripts and a smoke test, wired into the root typecheck and test chains; bun.lock regenerated.

Verified locally before pushing: biome check clean (repo-wide), node --check clean, package smoke test passes, and a live request through the adapted plugin answered (gemini-3.6-flash, PDF through antigravity_read_document).

[cubic-dev-ai]

All reported issues were addressed across 4 files (changes from recent commits).

<sub>Tip: Review your code locally with the cubic CLI to iterate faster.

Re-trigger cubic</sub>