Agent Note: Collapse tool-owned UI presentation

Status: rejected — TUI and the Web host/client runtime consume the tagged render-intent union, so tool-owned presentation remains current even though ACP no longer projects it.

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Problem

The optional-field bag and ACP editor mapping below were the proposal-time context for this rejection. The current contracts live in the tagged render-intent union and automation-only ACP.

Tools could define presentCall() and presentResult() callbacks that returned ToolCallPresentation, ToolResultPresentation, and optional ToolTerminal fields. The code itself flagged the design as muddy: title, kind, raw input, content, terminal cwd, terminal output, exit code, and signal had grown incrementally into a bag of optional fields. ACP then maintained pending call state to pair a result with the original args, created replay-only presenters on session/load, and mapped terminal subfields into Zed-specific _meta. dsh-tool-bash even parsed exit status back out of rendered text because the pure replay-safe presenter no longer had the structured BashRunResult.

The real first-party use was bash presentation for ACP. That was too little evidence to freeze a cross-package UI presentation API.

Proposal

Remove tool-owned UI presentation callbacks for now. The canonical tool events already carry the tool name, raw argument string, result content, and error state. UIs render a generic tool card from those fields. Tool-specific rich rendering can return later as a tagged render-intent union after there are at least two real tools and two real consumers to validate the vocabulary.

Alternatives considered

As a smaller alternative, replace the current optional-field bag with one explicit union in a single PR; but if the goal is simplification, the stronger move is to delete the callbacks and keep the generic path.

Acceptance criteria

ToolDefinition drops presentCall and presentResult.
ToolCallPresentation, ToolResultPresentation, ToolTerminal, and ToolCallKind disappear unless a minimal generic UI type still needs one.
ACP no longer keeps presenter pending state or calls tool callbacks during live streaming/load replay.
dsh-tool-bash no longer parses rendered text to recover exit status for a UI pill.
Snapshot expected outputs show generic tool cards and text results.

What we give up

Under this proposal, Bash would lose its custom terminal-looking card and model-written description placement. The fallback would remain reasonable: the command would appear as tool input, and the output as text. Rich rendering would be designed when the product had enough UI/tool variety to justify a stable presentation contract.

The later tagged render-intent union implements the smaller alternative once multiple producer and consumer families provide enough evidence for the vocabulary. Automation-only ACP removes ACP's editor projection without removing tool-owned presentation from TUI or the Web host/client runtime.

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