Merge branch 'codex/simp-prune-llm-contract' into codex/simp-hide-llm-adapter-helpers

packages/llm/llm-pi-ai/README.md

@@ -35,10 +35,28 @@ Every request carries the shared attribution header from dsh-llm's `attributionH
 
 pi-ai declares the openai/anthropic/google/mistral/AWS SDKs as install-time dependencies. They are lazy-loaded — only the openai SDK actually loads for this adapter — but they do land in `node_modules`. Accepted for a package whose purpose is design verification.
 
-## Limitations
-
-Same MVP contract as llm-deepseek: `tool_choice` is not mapped.
-
 ## Testing
 
 Unit suites run against a local `node:http` mock SSE server (pi-ai's openai SDK happily talks to any base URL). Real-API coverage in `tests/adapter.e2e.ts` (`pnpm run test:e2e`, key-gated): V4 Flash + V4 Pro across all exposed reasoning levels (off/high/xhigh), the thinking+tools round trip, and a cross-adapter structural-equivalence check against llm-deepseek.
+
+## Model Experience
+
+### DeepSeek request through pi-ai
+
+**What the model sees**: The selected model receives the same logical system prompt, history, tools, stop sequences, and raw replayed tool arguments as the hand-written adapter. This package adds no prompt prose and removes pi-ai's own per-tool `strict` default to preserve that contract.
+
+**Token effect**: Provider tokenization governs exact input. Reasoning level changes generated and passback content; pi-ai reports reasoning inside output usage rather than as a separate count.
+
+### DeepSeek response
+
+**What the model sees**: pi-ai events become harness reasoning, text, tool-call, usage, and finish chunks; parsed tool arguments are restored to raw JSON strings at the harness boundary.
+
+**Token effect**: Generated content affects later inputs only after the loop records it; adapter conversion adds no model-visible text.
+
+## Known Limitations and Deferred Work
+
+- **`tool_choice` is not mapped** — same MVP contract as llm-deepseek.
+- **In-history `system`-role messages fold into `user`-role wire messages** — pi-ai exposes a single `systemPrompt` slot, diverging from the hand-rolled twin's `role: 'system'` passthrough.
+- **`LlmError.status` is never set** — pi-ai reports failures as in-stream events with no HTTP status, so error codes are regex-classified from the error text.
+- **`buildModel` hardcodes descriptor metadata** — `contextWindow: 128000`, `maxTokens: 64000`, zero cost, identically for every registered model name; not configurable.
+- **pi-ai's built-in retries are disabled (`maxRetries: 0`)** — failures surface immediately; retry policy belongs to `llm/stream` listeners.