Match claude-agent-acp / codex-acp: the bash tool_call title IS the command (an execute card hides rawInput), the model description rides as a content text block above the card, and the completed card carries an exit-status pill via _meta.terminal_exit. Bridge fixes found in review of the prior terminal-card commit: - tool_call_update.content is OMITTED in terminal mode (an ACP update.content REPLACES the call's content collection in Zed, so the fenced ```console block would clobber the terminal content block). - terminal.output preserves RAW newlines (terminal renderers rely on exact bytes); only the fenced fallback trims trailing blank lines. - a relative workdir is resolved against the session cwd for the card header, matching where the command actually ran. - result-side terminal output is gated on the pending call having registered a terminal (no orphan _meta.terminal_output for a terminal Zed never made). The exit pill is recovered by parsing renderResult's status markers (the pure presentResult seam sees only content blocks); a round-trip test pins the parse to the marker emission. Neutral ToolTerminal gains exitCode/signal; widened ToolCallPresentation with a content block. Docs (RFC + 3 READMEs) updated; with-key e2e verifies the card + exit pill against the real model.
RFCs
One kind of design doc lives here. An RFC records a decision or proposal that shapes this codebase — the why and what we gave up, the parts code and docs can't carry. (Earlier this split into separate "ADR" and "RFC" trees; they were unified, since most ADRs were simply implemented RFCs.)
Layout and naming
Files are grouped by lifecycle into three folders, and an RFC moves between them as its status changes:
proposed/— proposals reviewed before implementation; not yet built (or only partly).implemented/— the decision shipped. The file records what was decided and what was rejected.rejected/— the proposal was considered and declined. Kept for the record so the rejection isn't re-litigated.
Each file is named yyyy-mm-dd-topic-title.md, where the date is when the topic was first proposed (per git history). Cross-references between RFCs use relative markdown links ([topic](../implemented/2026-…-….md)) — never bare prose or numbers — so they are mechanically checkable and survive moves between folders.
When to write one
Write an RFC when a decision is durable (it shapes the codebase beyond a single function or package), contested (there was a real alternative a reasonable engineer might have chosen), and surprising (a future reader would otherwise ask "why on earth is it done this way?"). A proposal for substantial future work starts in proposed/; a decision already made starts in implemented/.
Do NOT write one for a mechanical or local choice (a variable name, a one-file refactor), for anything already enforced and explained by a gate or a convention in AGENTS.md, or for a still-provisional decision tagged TODO(...) in the code — record those as TODOs and promote to an RFC only once they settle. An RFC is never edited into a different decision: supersede it with a new one and cross-link.
Proposed
| Title | First proposed |
|---|---|
| Mutation testing as the coverage counterweight | 2026-06-11 |
| Deterministic tests, the replay invariant fixture, and race stress | 2026-06-11 |
| Architectural conformance — dependency rules and the adapter kit | 2026-06-11 |
| API extractor reports | 2026-06-11 |
| Supply chain checks and vendor drift verification | 2026-06-11 |
| Agent Client Protocol (ACP) support for external editors | 2026-06-14 |
| Multiplex concurrent ACP sessions over one connection | 2026-06-14 |
| Optional Code Mode — model writes TypeScript against an SDK of all tools | 2026-06-15 |
| Runtime schemas for the event vocabulary (Zod vs the merge-extensible-map pattern) | 2026-06-16 |
Implemented
Rejected
| Title | First proposed |
|---|---|
| Deep-readonly public surfaces | 2026-06-11 |