feat!: AIR tool call contract, exact diff patches, and fixes for every client

.gitattributes

@@ -0,0 +1 @@
+src/__tests__/scenarios/data/** linguist-generated=true

CHANGELOG.md

@@ -39,7 +39,6 @@
 ### Performance Improvements
 
 * derive file change reports from turn diffs ([#518](https://github.com/agentclientprotocol/codex-acp/issues/518)) ([caddefe](https://github.com/agentclientprotocol/codex-acp/commit/caddefe56ff55a3f0827aa8ad60d03779f168425))
-* supply validated diff statistics to ACP clients ([#501](https://github.com/agentclientprotocol/codex-acp/issues/501)) ([989a8f1](https://github.com/agentclientprotocol/codex-acp/commit/989a8f1735f2465f3db2e8acfa00a4da8f352c00))
 
 ## [1.11.0](https://github.com/agentclientprotocol/codex-acp/compare/v1.10.0...v1.11.0) (2026-09-09)
 

README.md

@@ -10,13 +10,17 @@ Use [OpenAI Codex](https://github.com/openai/codex) from [Agent Client Protocol]
 
 - ChatGPT, API key, and client-provided custom gateway authentication.
 - Model, reasoning effort, fast mode, approval, and sandbox mode configuration.
-- Concrete recommended model and reasoning-effort values through the opt-in [AIR recommended config values](docs/recommended-config-values-extension.md) capability.
+- Concrete recommended model and reasoning-effort values through the opt-in [AIR recommended config values](docs/air-extensions.md#recommended-config-values) capability.
 - Text prompts, embedded context, images, resource links, and additional workspace directories.
-- Shell command, file change, [permission request](docs/permission-extension.md), MCP tool call, terminal output, reasoning, plan, web search, image generation, image view, token usage, and review events.
+- Shell command, file change, [permission request](docs/air-extensions.md#permission-presentation), MCP tool call, terminal output, reasoning, plan, web search, image generation, image view, token usage, and review events.
+- Compact file changes through the negotiated [AIR diff patch extension](docs/air-extensions.md#diff-patch).
+- For AIR, one tool call shape with each fact in one field, as the [tool call contract](docs/air-extensions.md#tool-call-contract) defines. Other clients keep the earlier fields.
 - [Native ACP subagent sessions](docs/subagent-sessions.md) (after capability negotiation) with separate child histories and root-routed permissions; a legacy tool-call fallback otherwise.
-- [Background terminal tasks](docs/async-tasks.md) in AIR, with task status and targeted stop support after capability negotiation.
-- Session-scoped long-running goals through the provider-neutral [goal extension](docs/goal-extension.md).
-- A per-turn [agent file-change report](docs/agent-file-change-report.md) after capability negotiation.
+- [Background terminal tasks](docs/air-extensions.md#async-tasks) in AIR, with task status and targeted stop support after capability negotiation.
+- Session-scoped long-running goals in AIR through the [goal extension](docs/air-extensions.md#goal).
+- Typed warnings and errors through the opt-in [AIR session failure extension](docs/air-extensions.md#session-failure).
+- All AIR extensions, capabilities, and `_meta` keys: [AIR extensions](docs/air-extensions.md).
+- A per-turn [agent file-change report](docs/air-extensions.md#agent-file-change-report) after capability negotiation.
 - Client-provided MCP servers over command-based stdio config and HTTP transport.
 - Slash commands: `/status`, `/mcp`, `/skills`, `/goal`, `/review`, `/review-branch`, `/review-commit`, `/compact`, and `/logout`, as well as configured skills.
 
@@ -98,7 +102,7 @@ See [docs/subagent-sessions.md](docs/subagent-sessions.md) for the negotiation,
 
 Codex can keep a shell command running after a turn continues. AIR clients can show this work in the Async Tasks panel and stop one command.
 
-See [docs/async-tasks.md](docs/async-tasks.md) for the capability, lifecycle events, and stop request.
+See [AIR extensions](docs/air-extensions.md#async-tasks) for the capability, lifecycle events, and stop request.
 
 ## License