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Bohdan Triapitsyn 28f0736d69 feat: small-model utility calls on existing OpenCode providers (#2049 )

Adds a server-side "small model" capability: direct, cheap LLM calls that
reuse the user's existing OpenCode provider logins — the mechanism OpenCode
uses internally for titles and summaries but does not expose through the
SDK or plugins. Zero new dependencies; plain fetch with per-provider wire
formats, credentials never leave the server.

Core (packages/web/server/lib/small-model):
- Resolution mirrors OpenCode's session scoping: explicit settings override
  → small_model from the OpenCode config → family scan within the session's
  provider → the session's own model. The global provider scan only serves
  callers without a session context, and background callers forbid it
  entirely (restrictToPreferredProvider), so conversation content never
  reaches a provider the user didn't pick — explicit choices excepted.
- Per-provider auth replicating OpenCode's plugin loaders: GitHub Copilot
  (device token as bearer, no exchange), ChatGPT plan via the codex
  Responses API (single-flight OAuth refresh written back to auth.json),
  Anthropic messages, Google generateContent, generic OpenAI-compatible.
- OpenCode's free models (opencode/big-pickle, *-free) are never called
  directly; unauthenticated providers are skipped by design.
- Prompt clamping to the model's catalog context limit; thinking disabled
  where a wire switch exists (Z.AI/GLM, MiniMax-M3, Gemini Flash); robust
  content parsing with a clear error when a thinking model spends its whol
  budget on reasoning.
- Settings → Sessions gains a Small Model group: use-default checkbox plus
  an override picker limited to authenticated providers, persisted with
  web/desktop/VS Code sanitization parity.

Consumers:
- Session assist: a server-side watcher on the global SSE hub generates a
  short recap and one suggested follow-up after a session idles quietly fo
  a minute, stored on session metadata (openchamber.assist). Freshness is
  keyed to the last assistant message id, so new activity invalidates the
  payload everywhere with no extra writes. The chat shows the recap under
  the last message after five quiet minutes and the suggestion as a
  dismissible chip above the composer (tap fills the input, never sends).
  Gated by a new Chat setting (default on) that is a hard generation
  switch. Language is anchored to the conversation itself, with a
  script-mismatch guard against model/backend language hallucination.
- TTS: a third input mode, summarized — long replies are condensed to
  spoken prose before playback on any TTS engine.
- Git: commit-message and PR generation moved off the active chat session
  onto the small model fed with real diffs and the commit list (bodies
  included), with a session-transport fallback for free-model-only setups.
- Notes: Add to notes distills long selections into 1-3 dense sentences
  preserving exact identifiers, with verbatim fallback on failure.

Fixes along the way:
- The global event watcher now starts unconditionally; it was gated behind
  the desktop-notify env, leaving the server-side event hub dead in
  packaged apps.
- OpenCode re-emits message.updated for old user messages after idle; the
  watcher no longer mistakes those for new activity.
- Session metadata merges from a fresh read right before the PATCH, so
  writes made during the generation window (suggestion dismissals, review
  links) are preserved; the assist runtime stops during graceful shutdown.

2026-07-05 23:19:10 +03:00

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Small Model

Server-side direct LLM calls that reuse the user's existing OpenCode provider logins (~/.local/share/opencode/auth.json). OpenCode uses a "small model" internally (titles, summaries) but does not expose it through the SDK or plugins — this module replicates that mechanism as an OpenChamber runtime API.

Security boundary

Credentials never leave the server process. The client sends only a prompt; auth resolution, OAuth refresh, and provider dispatch all happen server-side. Routes live under /api/* and are gated by the ui-auth middleware like every other runtime API.

Files

index.js — orchestration: generateSmallModelText() / describeSmallModel().
resolve.js — model selection, mirroring OpenCode's getSmallModel chain: 0. OpenChamber's own settings override (Settings → Sessions → Small Model): when smallModelUseDefault is false, smallModelOverride (provider/model) outranks everything below. Sanitized in settings-helpers.js (server), persistence.ts (client), and bridge-settings-runtime.ts (VS Code).
1. small_model from the merged OpenCode config layers (provider/model).
2. Family-priority scan (gemini-flash → gpt-nano → claude-haiku) within the session's provider first (preferredProviderID, like OpenCode resolves within the current provider), then over the other providers with a usable auth entry, newest release_date first.
3. GitHub Copilot hidden utility models (gpt-*-nano/mini) — these never appear in the catalog, so they participate as the gpt-nano family entry and as a final utility fallback.
4. Last resort: the session's own model (preferredModelID) when no small model resolves anywhere — costlier, but always valid.
Input clamp: the prompt is truncated to the resolved model's catalog limit.context (minus an output reserve, ~4 chars/token estimate; conservative default when the model is not in the catalog). Truncation is reported as inputTruncated: true in the response.
call.js — wire formats and per-provider auth, replicating OpenCode's plugin auth loaders:
- GitHub Copilot: OpenAI-compatible /chat/completions on https://api.githubcopilot.com (or copilot-api.<enterprise>) with the stored device-OAuth token as the bearer — no token exchange, no expiry.
- OpenAI OAuth (ChatGPT plan): streaming Responses API on https://chatgpt.com/backend-api/codex/responses with ChatGPT-Account-Id; expired tokens are refreshed against auth.openai.com (single-flight) and written back to auth.json.
- Anthropic (type: api): /v1/messages with x-api-key.
- Google (type: api): generateContent with x-goog-api-key.
- Everything else: OpenAI-compatible /chat/completions against the provider's models.dev base URL with Authorization: Bearer <key>.
catalog.js — models.dev catalog via the shared in-process cache (../opencode/models-metadata.js, also serving /api/openchamber/models-metadata).
routes.js — GET /api/small-model (resolution preview) and POST /api/small-model/generate ({ prompt, system?, maxOutputTokens?, model?, directory? } → { text, providerID, modelID, source }).

Registration

Mounted lazily from feature-routes-runtime.js (same pattern as quota): the module is imported on first request, not at server startup.

Known limitations

OpenCode's free models (opencode/big-pickle, *-free) work without a token only through OpenCode's own server — direct calls are rejected, and piggybacking on their subsidized infra is out of bounds by design. Every resolution step therefore requires a usable auth entry for the provider: a session on an unauthenticated opencode provider falls through to the global scan (or a clean 404 on a vanilla setup with no logins).
Anthropic OAuth (Claude Pro/Max) entries are not supported — OpenCode itself keeps those outside auth.json in this generation; only type: api keys work for Anthropic.
Amazon Bedrock, GitLab, Azure and other credential-chain providers are out of scope; they need more than a key/token (regions, resource names).
Responses from the codex backend are collected from the SSE stream; the endpoint itself is non-streaming by design (small utility calls).

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