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Slingshot

Maintainer Notes

Notes lane for rough ideas, investigation breadcrumbs, and hand-written reminders.

Open questions

Section titled “Open questions”
  • Prompt-cache minimum is a per-model fact, not a per-provider one. It lives on ProviderCapabilities.promptCacheMinTokens today, which is right for Anthropic (4096 on Opus) but will need a per-model table if a provider ever varies it across its own models.
  • estimateTokens is chars/4. Good enough for the pre-flight spend estimate and the cache-minimum guard, but it is an estimate. An adapter that implements countTokens() should be preferred where precision matters.
  • Response-cache coalescing is per-process. Fine for a single home server; a multi-process deployment would want the shared store F4 adds.

Tool calling — breadcrumbs

Section titled “Tool calling — breadcrumbs”
  • Gemini has no tool-call id. functionCall carries {name, args} only, and functionResponse is matched by function NAME. The adapter synthesizes call_<part index> so the neutral seam has an id to carry, and AiToolResultPart.name exists so the adapter has something to match on. Two concurrent calls to the SAME tool in one turn are indistinguishable on that wire — Gemini’s limitation, documented rather than papered over.
  • Gemini’s parameters rejects additionalProperties, while sanitizeJsonSchema adds additionalProperties: false to every object node because the strict providers require it. Directly opposed requirements, so the strip lives in gemini.ts rather than weakening the shared sanitizer.
  • finish_reason: 'stop' with populated tool_calls is real, and common on local servers. Every adapter normalizes to stopReason: 'tool_use' when tool calls are present. Without it the loop silently stops one iteration early — green tests, no error, an answer that just isn’t grounded.
  • AiTool.execute is declared as a METHOD, not a readonly property. Under strictFunctionTypes a property-style function is contravariant in its argument, so AiTool<{lift: string}> would not be assignable to AiTool<unknown> and readonly AiTool[] could not be built without an any (engineering rule #4 forbids one). Method-shorthand declarations are checked bivariantly. If someone “tidies” this into a property, every consumer’s tool array stops compiling.
  • Not yet supported: tools on generateStructured (throws, deliberately — see CLAUDE.md), and a tool result carrying an image part. The latter is a real vendor feature (Anthropic accepts image blocks in tool_result) and would slot in as a change to toolResultBody plus a per-adapter render.