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## Summary `session/new` and switching models via `configOptions` regressed to ~15s each in v0.59.0. This removes the blocking call responsible and seeds the context window synchronously instead, restoring sub-second behavior on both paths. ## Root cause v0.59.0 added an inline `await query.getContextUsage()` on the session-creation and model-switch paths. That SDK control request is not serviced by the CLI until the session's first prompt turn has run — before then it stalls ~15s. And because SDK control requests are serialized over a single stdin/stdout channel, an awaited `setModel` queued behind the wedged `getContextUsage` inherited the full stall. So both paths blocked ~15s before returning. Verified with the real CLI (setModel alone pre-prompt: ~1ms; getContextUsage alone pre-prompt: ~16s; getContextUsage-then-setModel: both resolve together at ~16s, confirming the serialization). ## Fix Drop `getContextUsage` from both hot paths. The context window is seeded synchronously by `immediateContextWindow(...)`: 1. an authoritative value from a per-(provider, model) cache, if learned; else 2. a synchronous text heuristic (`\b1m\b` → 1,000,000); else 3. `DEFAULT_CONTEXT_WINDOW` (200,000). The authoritative window is learned the moment it's actually available — from each turn's `result.modelUsage` — and written into the cache, so later sessions/switches to the same model seed the correct window immediately with no IPC. A model that has never run a turn shows the heuristic/default window until its first response, matching pre-0.59.0 behavior. ### Cache design - **Keyed on `(provider, resolved model id)`.** The resolved id (`ModelInfo.resolvedModel`, e.g. `claude-sonnet-5[1m]`) matches the `result.modelUsage` keys, so the write key and the read keys line up. Keying on the resolved id (not the picker value) dedups aliases that resolve to the same model; keying on the provider keeps two providers that reuse an id string for different windows from crossing wires (per-session provider config, #853). The provider is captured at session creation, since the effective provider can change process-wide over the adapter's lifetime. - **Non-positive/NaN windows are ignored** — they neither overwrite the session's learned window nor enter the cache. ## Impact (measured, real CLI) | Path | Before | After | | --- | --- | --- | | `session/new` | ~17.4s | ~0.9s | | model switch (before first prompt) | ~15s | ~3ms | | model switch (after a turn) | ~14.7s | <1ms | ## Tests - New end-to-end cache test: a turn's authoritative window (learned under the resolved id even when the assistant message reports the bare id) is served on a later switch with no `getContextUsage`. - New provider-isolation test: the same resolved id on a different provider does not read another provider's cached window; the same provider does. - New non-positive-window test: a nonsensical `contextWindow` is ignored and never poisons the cache. - Rewrote the existing context-window tests to the new contract (assert no `getContextUsage` on session/new and switch; window from cache/inference/default). Closes #886 Closes #880 🤖 Generated with [Claude Code](https://claude.com/claude-code) --------- Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com> Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>
ACP adapter for the Claude Agent SDK
Use Claude Agent SDK from ACP-compatible clients!
This tool implements an ACP agent by using the official Claude Agent SDK, supporting:
- Context @-mentions
- Images
- Tool calls (with permission requests)
- Following
- Edit review
- TODO lists
- Interactive (and background) terminals
- Custom Slash commands
- Client MCP servers
Learn more about the Agent Client Protocol.
Contribution Policy
This project does not require a Contributor License Agreement (CLA). Instead, contributions are accepted under the following terms:
By contributing to this project, you agree that your contributions will be licensed under the Apache License, Version 2.0. You affirm that you have the legal right to submit your work, that you are not including code you do not have rights to, and that you understand contributions are made without requiring a Contributor License Agreement (CLA).