docs: add Phase 0.5 — spike tmux control mode

Phase 0 found that tmux pipe-pane is unreliable across alternate-screen
transitions. Before Phase 1 commits to a streaming primitive, a short
follow-up spike evaluates tmux control mode (`tmux -CC`) as an
alternative to pipe-pane + watchdog. Verdict drives T-1.1 design.

docs/PHASE-0.5-spike-tmux-control-mode.md

@@ -0,0 +1,135 @@
+# Phase 0.5 — Spike: tmux Control Mode
+
+> **Status:** ready to start.
+> **Owner:** single agent, end-to-end.
+> **Branch:** `feat/spike-tmux-cc`.
+> **Estimated effort:** ~2 hours.
+> **Trigger:** Phase 0 found that `tmux pipe-pane` is not reliable across
+> alternate-screen transitions. This phase evaluates the alternative.
+
+## Background
+
+Phase 0 (`PHASE-0-spike-stream.md`, report at
+`docs/reference/PHASE-0-report.md`) validated the high-level design:
+pi-in-tmux works, ANSI streaming over WebSocket works, latency is
+excellent, SSH and WS stay in sync.
+
+**But:** `tmux pipe-pane` is fragile. After alternate-screen usage
+(`/settings`, full-screen menus) the pipe can detach silently; the
+client sees a frozen stream. This is a Phase-1-blocker for the
+`tmux/pipe.ts` task.
+
+Two known alternatives:
+- **(A)** Keep pipe-pane, add a watchdog that polls `#{pane_pipe}` and
+  re-arms when it falls to `0`. Simple but races: bytes produced
+  between detach and detection are lost.
+- **(B)** Use **tmux control mode** (`tmux -CC`). tmux exposes a
+  structured event stream to a control client; pane output arrives as
+  framed events. This is the protocol iTerm2 uses for its tmux
+  integration. Multi-client attach still works for normal SSH users.
+
+This spike decides between A and B with evidence.
+
+## Goal
+
+Verify that tmux control mode can reliably deliver pane bytes to a Node
+client across the conditions where pipe-pane fails. Produce a short
+report and a Go decision for one of the two paths.
+
+## Acceptance Criteria
+
+- A new branch `feat/spike-tmux-cc` with throwaway PoC code.
+- A Node script that:
+  - Spawns a tmux session running `pi`.
+  - Connects to that session as a control client (`tmux -CC`).
+  - Parses the control-mode protocol enough to extract `%output`
+    events from the pi pane.
+  - Streams those bytes to stdout (no WebSocket needed for the spike —
+    raw stdout is fine).
+- A test session that triggers the Phase-0 failure mode:
+  1. Pi running normally → bytes flow.
+  2. User runs `/settings` (alternate-screen) → bytes still flow.
+  3. User exits settings → bytes still flow.
+  4. Run for ≥5 minutes with mixed interactions.
+- Report `docs/reference/PHASE-0.5-report.md` answering:
+  - **R-CC-1.** Does control mode deliver pane output reliably across
+    alternate-screen transitions?
+  - **R-CC-2.** Latency compared to pipe-pane (rough — same order of
+    magnitude is enough)?
+  - **R-CC-3.** Does a parallel `tmux attach` SSH client still work
+    while a control-mode client is connected? (P-2 critical.)
+  - **R-CC-4.** Is the control-mode protocol parser non-trivial? Order
+    of complexity estimate.
+  - **R-CC-5.** Verdict: **Path B (control mode)** or **Path A
+    (pipe-pane + watchdog)** for Phase 1, with reasoning.
+
+## Out of Scope
+
+- No WebSocket layer (raw stdout suffices to prove the streaming).
+- No reconnect, sequence, snapshot, buffer.
+- No send-keys.
+- No reuse of Phase-0 spike code — start clean.
+- No production-quality parser — minimal viable parser for `%output`
+  events is enough.
+
+## Implementation Notes
+
+- tmux control mode launch:
+  ```bash
+  tmux -CC new-session -s pi-cc 'pi'
+  ```
+  or attach to an existing detached session:
+  ```bash
+  tmux new-session -d -s pi-cc 'pi'
+  tmux -CC attach -t pi-cc
+  ```
+- Control-mode protocol overview (consult `man tmux`, search
+  "CONTROL MODE"):
+  - Server emits lines like `%output %1 <octal-escaped-bytes>` for
+    pane output.
+  - Other events: `%session-changed`, `%window-add`, `%begin`/`%end`,
+    `%layout-change`, etc. — most can be ignored for the spike.
+  - Client sends regular tmux commands as plain text; replies are
+    framed by `%begin <ts> <num> <flags>` … `%end <ts> <num> <flags>`.
+- Parse just `%output` lines, decode the octal escapes (`\NNN` in tmux's
+  output → bytes), write bytes to stdout.
+- Spawn tmux as a child process from Node, talk via stdin/stdout pipes.
+
+## File Plan
+
+- New: `extensions/remote-control/spike-cc.ts` (or `.js`, whichever is
+  faster). ~100–200 lines.
+- New: `docs/reference/PHASE-0.5-report.md`.
+- No changes to Phase-0 spike files.
+
+## Test Protocol (the spike's own QA)
+
+Run for ≥ 5 minutes, in parallel:
+1. Terminal A: `npm run spike-cc` (your spike runner).
+2. Terminal B: `tmux attach -t pi-cc` — verify normal SSH-style attach
+   still works alongside the control client.
+3. Terminal A side: confirm bytes keep flowing through these events:
+   - Type a prompt and let pi respond.
+   - Run `/settings`, navigate around, exit.
+   - Run a longer pi tool call.
+   - Resize Terminal B and observe whether the stream stays clean.
+
+If at any point bytes stop flowing without an obvious tmux process
+exit: the spike failed for Path B and the verdict is Path A.
+
+## Exit / Handover
+
+- Push branch, push report.
+- Update `docs/SYNC.md`:
+  - Remove your active claim.
+  - History entry.
+  - Phase Gate Table: Phase 0.5 → `done`, with verdict noted.
+- Based on verdict:
+  - **If Path B:** open follow-up note in SYNC about updating
+    `PHASE-1-sidecar.md` T-1.1 to specify tmux control mode in
+    `tmux/pipe.ts`.
+  - **If Path A:** same, but specifying pipe-pane + watchdog.
+
+In either case, do **not** modify `PHASE-1-sidecar.md` yourself —
+that's an orchestrator-level edit and triggers a contract change
+review.

docs/README.md

@@ -6,8 +6,9 @@ its sidecar. Background / spec / audit material lives in
 
 | File | Purpose |
 |---|---|
-| [`PHASE-0-spike-stream.md`](./PHASE-0-spike-stream.md) | Stream PoC — verify tmux + pipe-pane + WebSocket. ~1 day, single agent. |
-| [`PHASE-1-sidecar.md`](./PHASE-1-sidecar.md) | Sidecar production-ready: all S-features, multi-agent parallel work. |
+| [`PHASE-0-spike-stream.md`](./PHASE-0-spike-stream.md) | Stream PoC — verify tmux + pipe-pane + WebSocket. ~1 day, single agent. **Done**, see `reference/PHASE-0-report.md`. |
+| [`PHASE-0.5-spike-tmux-control-mode.md`](./PHASE-0.5-spike-tmux-control-mode.md) | Follow-up spike: tmux control mode (`-CC`) vs pipe-pane + watchdog. Decides Phase 1 streaming path. ~2h, single agent. |
+| [`PHASE-1-sidecar.md`](./PHASE-1-sidecar.md) | Sidecar production-ready: all S-features, multi-agent parallel work. Blocked on Phase 0.5. |
 | [`PHASE-2-ios-mvp.md`](./PHASE-2-ios-mvp.md) | iOS app MVP — Groups A, B, C-01/02, D, E, F. Multi-agent parallel. |
 | [`PHASE-3-ios-augmentation.md`](./PHASE-3-ios-augmentation.md) | iOS feature polish — slash palette, voice, thumbnails, search, etc. |
 | [`SYNC.md`](./SYNC.md) | Live multi-agent coordination — claims, file ownership, contract changes. |

docs/SYNC.md

@@ -36,8 +36,9 @@ The point: no central scheduler is required. A short structured edit on
 
 | Phase | Status | Notes |
 |---|---|---|
-| Phase 0 — Spike Stream | done | ✅ GREEN LIGHT. See `reference/PHASE-0-report.md`. pipe-pane reliability issue noted. |
-| Phase 1 — Sidecar | ready to start | Recommend node-pty over pipe-pane based on Phase 0 findings. |
+| Phase 0 — Spike Stream | done | ✅ GREEN LIGHT with caveat: pipe-pane unreliable. See `reference/PHASE-0-report.md`. |
+| Phase 0.5 — Spike tmux Control Mode | ready to start | Decides streaming path before Phase 1. See `PHASE-0.5-spike-tmux-control-mode.md`. |
+| Phase 1 — Sidecar | blocked on Phase 0.5 | Streaming path must be decided before T-1.1 starts. |
 | Phase 2 — iOS MVP | blocked on Phase 1 | Sidecar must be reachable and stable. |
 | Phase 3 — iOS Augmentation | blocked on Phase 2 | Continuous after MVP ships. |