Quest: Observe and interact with multiple coding-agent sessions #785

Story

As a person coordinating coding agents, I want XMD surfaces for viewing, interacting with, and arranging their sessions, so I can move between roles and issues without depending on each provider's native interface for every task.

XMD provides three distinct experiences:

• xmd tail and <Session.Tail> read an existing conversation from provider files.
• A linear XMD REPL interacts with sessions through ACP.
• <Grid> and <Pane> arrange Tail, REPL, ordinary output, or native terminal content through a selected run provider.

Tmux presents Grid panes today. A later XMD-owned provider can present the same document. Provider files remain observation only, ACP remains the reliable interaction boundary, and native terminal input remains owned by its pane.

Example

<Grid columns={2}>
  <Pane title="Architect · #785">
    <Agent name="codex">
      <Session.Tail nativeSession="existing-session-id" />
    </Agent>
  </Pane>
  <Pane title="Implementor · #785">
    <Agent name="claude">
      <Session.Launch session="implementor">...</Session.Launch>
    </Agent>
  </Pane>
</Grid>

Role and current issue are ordinary document props used in pane titles. They do not become provider, pane, or Agent identity.

Current gap

The unmerged #717 stack supplies provider-neutral Grid/Pane structure and a tmux run provider. It does not supply a session viewer, a linear XMD REPL, configurable conversation presentation, or a first-party multiplexer.

#774 established the safe black-box boundary. Provider session files can supply passive conversation observation. Generic tmux input cannot close the race between the last provider-file sample and terminal delivery, so it cannot authorize messaging.

Product contract

Tail and REPL share normalized conversation entries and Markdown presentation, not transport or lifecycle:

• Tail rebuilds a disposable read-only view from an exact provider file on each invocation.
• REPL evaluates one XMD block at a time in a long-lived scope, receives live updates from its own ACP work, and journals only committed execution and final normalized Prompt snapshots.
• Grid presents each content source without merging stores, opening competing connections, or acquiring session control.

Presentation is live and ephemeral. Streaming snapshots replace stable per-entry regions and coalesce when rendering is slower than ingestion. Repository-local Markdown components configure each message kind. Terminal frames and viewer state are not journaled.

Tmux remains a run-only Grid provider and is never used as a workflow mechanism. Bombshell TTY supplies structured rendering and input parsing. It is not a PTY manager or terminal emulator; native TUI support in the XMD-owned provider remains gated on separate evidence.

Dependency-ordered child map

1. Test black-box REPL messaging through xmd run terminal panes #774 — Test black-box REPL messaging through xmd run terminal panes

   • Status: VIEW_ONLY architecture outcome recorded; disposable evidence remains in draft PR 🔒 Terminal REPL POC (#774) — VIEW_ONLY evidence #779.
   • Supplies exact read-only observation findings and rejects terminal delivery as interaction capability.

2. Make executable document grids use <Grid> and <Pane> #781 — Make executable document grids use <Grid> and <Pane>

   • Status: implemented by merged stacked PR 🚚 Name executable document grids <Grid> and <Pane> (#781) #797 inside open delivery PR ♻️ Extract terminal providers into workspace packages (#717) #771; issue remains open until the stack delivers.
   • Supplies the provider-neutral Grid/Pane vocabulary and package boundary.

3. Test incremental Agent session rendering with Markdown components #799 — Test incremental Agent session rendering with Markdown components

   • Status: implemented on open PR ✅ Prove one session view renders from source and a binary (#799) #805 at exact head 9a3cf24; architecture evidence accepted.
   • Finite synthetic proof of XMD generator updates, stable regions, local components, coalescing, Bombshell viewport behavior, and deno compile.

4. Render Agent session entries with Markdown components #800 — Render Agent session entries with Markdown components

   • Status: open and ready for architecture; Test incremental Agent session rendering with Markdown components #799 evidence is accepted.
   • Owns normalized entries and live, ephemeral Markdown presentation without owning files, ACP, REPL, or Grid.

5. View coding-agent sessions with <Session.Tail> and xmd tail #782 — View coding-agent sessions with <Session.Tail> and xmd tail

   • Status: open; production integration depends on Render Agent session entries with Markdown components #800.
   • Owns exact read-only provider-file observation and a disposable full-history interactive viewer.
   • Its native observation substrate and provider adapters may be developed in parallel with Test incremental Agent session rendering with Markdown components #799 and Render Agent session entries with Markdown components #800.

6. Run and reopen a linear multi-Agent XMD REPL #783 — Run and reopen a linear multi-Agent XMD REPL

   • Status: open; depends on Render Agent session entries with Markdown components #800 and may proceed in parallel with View coding-agent sessions with <Session.Tail> and xmd tail #782.
   • Owns one-at-a-time scope evaluation, bindings and resources, ACP interaction, committed replay, interrupted-block behavior, and final Prompt snapshots.

7. Test native TUI hosting with an XMD-owned PTY and terminal emulator #801 — Test native TUI hosting with an XMD-owned PTY and terminal emulator

   • Status: open and parallel with Test incremental Agent session rendering with Markdown components #799–Run and reopen a linear multi-Agent XMD REPL #783.
   • Selects and tests the missing native terminal boundary without a real Agent.

8. Present Agent session grids without an external multiplexer #784 — Present Agent session grids without an external multiplexer

   • Status: open; depends on Make executable document grids use <Grid> and <Pane> #781, View coding-agent sessions with <Session.Tail> and xmd tail #782, Run and reopen a linear multi-Agent XMD REPL #783, and the accepted Test native TUI hosting with an XMD-owned PTY and terminal emulator #801 result.
   • Owns the first-party run provider while preserving tmux as an alternative.

#774 ───────────────────────────────► #782 ───┐
                                               │
#799 ─► #800 ────────────────┬──────► #782 ───┤
                              └──────► #783 ───┼──► #784
                                               │
#781 ──────────────────────────────────────────┤
#801 ──────────────────────────────────────────┘

#782's observer work and #783's linear REPL work can proceed independently once their shared #800 boundary is available. #801 can proceed at the same time.

Completion

• Test incremental Agent session rendering with Markdown components #799 establishes that the Markdown/Bombshell presentation model works from source and a compiled executable.
• Standard normalized entries render through default and repository-local Markdown components without exposing raw provider records.
• xmd tail and <Session.Tail> open exact Claude and Codex sessions, reconstruct complete history, and follow live files without gaining interaction capability.
• The linear REPL evaluates one block at a time, retains committed work and scope-bound resources, interacts through ACP, and never automatically resends an interrupted block.
• Grid and Pane remain the authored vocabulary, and tmux remains run-only rather than Workflow behavior.
• Test native TUI hosting with an XMD-owned PTY and terminal emulator #801 establishes an owned PTY and emulator boundary before the XMD provider hosts native TUIs or shells.
• One Grid document runs under tmux or the XMD provider without changing its syntax, identities, permissions and ownership, or teardown guarantees.
• No surface claims that ACP messages synchronize into a provider-native UI.
• Provider files, terminal pixels, and tmux convergence never authorize prompts, cancellation, permissions, ownership, or completion.

Relationships

• Quest: Add interactive grids to executable documents #717 owns the initial Grid/Pane lifecycle and tmux delivery stack.
• PR ♻️ Extract terminal providers into workspace packages (#717) #771 contains the Grid/Pane package extraction; PR ✨ Launch Codex sessions with <Session.Launch> (#755) #764 remains the separate Codex native-launch certification above it.
• Make Claude native-to-ACP continuation preserve the exact conversation #770 governs native Claude-to-ACP continuation identity where required.
• Test black-box REPL messaging through xmd run terminal panes #774 and draft PR 🔒 Terminal REPL POC (#774) — VIEW_ONLY evidence #779 remain evidence rather than production code.

Out of scope

• Adding Grid, Tail, terminal observation, or the interactive REPL to Workflow.
• Synchronizing an independently open native Agent UI with ACP.
• Provider-file writes, hooks, plugins, or provider-specific input automation.
• Durable terminal frames or viewer UI state.