TUI is an in-process ACP client

docs/adr/0041-tui-is-an-acp-client.md

@@ -0,0 +1,30 @@
+# 0041. The fullscreen TUI is an in-process ACP client
+
+Status: accepted 2026-08-27
+
+## Context
+
+`graff acp` and `apps/native` already share one mid-turn protocol (ADR 0032):
+`session/prompt` in, `session/update` thought / tool / text out. The TUI was
+a sibling frontend on the same agent loop (`tui_sink` typed events), so a
+tool row or thought chunk had two translations. Spawning `graff acp` from
+the pager would fork a second Agent and drop the in-process seams (images,
+`/debug`, idle wake, shared conversation).
+
+## Decision
+
+`graff tui` (and TTY `graff repl`) is an ACP **client in the same process**.
+It speaks initialize / session/new / session/prompt / session/cancel through
+`acp_engine` and renders thought, tools, and answer text from `session/update`.
+No child `graff acp`. Live coding still uses the existing `ReplCtx` turn
+(`replTurnCb`); the ACP envelopes are the client wire, not a second runtime.
+
+TUI-only extras ACP does not name — meters, notices, raw bash tail, failover
+— stay on `tui_sink`. Local slashes (`/theme`, `/model` picker, `/rewind`)
+stay local. `session/request_permission` is still off (`--yolo` / unattended).
+
+## Consequences
+
+Zed, the native app, and the pager share one session/update vocabulary.
+Do not spawn a child agent to "make the TUI use ACP." Revisit a subprocess
+only if the pager and the agent must be separate binaries.

docs/adr/README.md

@@ -49,6 +49,7 @@ record only when you need the evidence or the edge cases.
 | [0036](0036-computer-use-keeps-the-signed-codex-bridge.md) | Codex Computer Use keeps its authenticated node_repl process chain: Graff launches it through the signed Codex sandbox wrapper, never embeds V8 or spoofs the service. |
 | [0037](0037-experiment-pool-is-opt-in.md) | `--experiment N` / `/experiment N` pre-mints a child worktree pool; default isolation stays `shared_cwd`. 279 continuation — not on main until a later cut. |
 | [0038](0038-in-process-acp-core.md) | Same-process embed is `libgraff` + `graff-core.wasm` + `createGraffAgent()` (ACP core, echo turn). Live coding stays `graff acp`. 279 continuation — not on main until a later cut. |
+| [0041](0041-tui-is-an-acp-client.md) | The fullscreen TUI is an in-process ACP client: session/prompt in, session/update thought/tool/text out. No child `graff acp`. |
 
 ## When to write one
 

src/test_hooks.zig

@@ -334,4 +334,5 @@ test {
     _ = @import("commands_experiment.zig");
     _ = @import("acp_engine.zig");
     _ = @import("libgraff.zig");
+    _ = @import("tui_acp.zig");
 }