coliseum.md

Coliseum

One prompt fans out across multiple entrants, while the parent task stays untouched until you pick a winner.

Run the same prompt across 2-4 entrants in parallel, compare the results side by side, and promote one answer back into the parent task when you are ready.

Summary

• Coliseum is Stave's side-by-side model comparison flow.
• You choose a lineup of (provider, model) entrants, send one shared prompt, and watch each branch stream independently inside the arena.
• Nothing is written into the parent task until you explicitly pick a champion.
• After a winner is picked, you can still review, re-pick, merge ideas from other branches, or finish the arena.

When To Use It

Use Coliseum when:

• You want to compare how different models solve the same request before committing anything to the main task.
• You are testing whether Claude, Codex, or stave-auto produces the clearest result for a prompt.
• You want a reviewer model to compare multiple drafts and recommend a winner.
• You need a strong final answer assembled from several branches rather than trusting one model run.

Skip Coliseum when:

• You already know which model you want and a normal single-model turn is enough.
• The parent task is still streaming, waiting on approval, or otherwise busy.
• The task is externally managed and Stave cannot take over the turn lifecycle.
• You want a multi-turn branch conversation. Coliseum is a single fan-out round, not a long-lived branch workspace.

Before You Start

• Coliseum supports 2 to 4 entrants.
• Every entrant is a real provider turn, so total cost and token usage scale with the number of branches you run.
• The parent task must be idle before you can launch the arena.
• Shared prompt text, attached files, and attached images are copied into every branch's first user message.
• When Claude is selected inside Coliseum, new Claude rows default to Opus 4.7.

Quick Start

1. Open a task and look above the composer for the Coliseum button.

   

   The launcher lives in the composer control strip and is only available when the parent task is idle.

2. Click Coliseum to open the launcher dialog.

   

   A new run starts with two entrants by default. You can add a third or fourth row before starting.

3. Pick the entrants you want to compare. Each row has a provider picker and a model picker.

4. Type the one prompt every entrant should run. Optionally attach files.

5. Click Start Coliseum.

6. Compare the live columns in the arena, optionally open Review & compare, then either:

   • pick a winner and Finish arena
   • or Discard run to throw everything away

Interface Walkthrough

Entry Point

• The Coliseum button appears above the composer for the active task.
• If the task is streaming, the button stays disabled until the current turn finishes or you stop it.
• If a run is minimized, the same spot changes into Reopen arena so you can jump back into the comparison.

Launcher Dialog

• Entrant rows: each row is one (provider, model) pair.
• Provider picker: switching providers resets the row to that provider's Coliseum default model.
• Model picker: choose the exact model variant for that row.
• Add entrant: expands the lineup up to four branches.
• Remove entrant: drops a row, but never below two entrants.
• Prompt: the shared request every branch receives.
• Attach files: sends the same file context to every entrant.
• Start shortcut: Cmd/Ctrl + Enter.
• Validation: the start button stays disabled until every row is valid, every provider is available, and the prompt is non-empty.

Arena Header

• Status badge: shows whether the run is still Running, fully Ready, or already Promoted.
• Focus / Grid: switches between all-columns view and single-branch focus mode.
• Review & compare: launches or reopens the reviewer flow once at least one branch has finished.
• Minimize: hides the arena and returns you to the normal task view without ending the run.
• Discard run: aborts every branch and removes the arena if you have not promoted a winner.
• Finish arena: appears after a champion is picked and closes the arena while keeping the promoted answer on the parent task.
• Unpick: appears after promotion and rolls the parent task back to its pre-fan-out state so you can choose a different branch.
• Use ideas from: appears after promotion and stages a follow-up draft that pulls ideas from non-winning branches into the parent task.

Branch Columns

• Column header: shows the branch's provider, exact model, live activity state, and column index.
• Pick champion: promotes that branch immediately. If other branches are still running, they stay alive so you can keep comparing.
• Focus this branch: expands one branch and collapses the others into a rail.
• Close this branch: drops just that branch. If only one branch would remain, the whole Coliseum is discarded.
• Prior conversation: when the parent already had messages before fan-out, each branch can show the copied pre-fan-out context in a collapsible section.
• Prompt card: shows the shared fan-out request at the top of the column.
• File changes: lists touched files when the branch produced edit or diff output.
• Latest answer: renders the branch's most recent assistant output with the same trace UI used in normal task chat.

Reviewer Dialog

The reviewer compares branch outputs, recommends a winner, and can queue a merged follow-up draft on the parent task.

• Available after first completion: the review button stays disabled until at least one branch has produced an answer.
• Reviewer provider + model: choose which model should compare the branches. When the reviewer is Claude, Coliseum defaults it to Opus 4.7.
• Live verdict stream: reviewer output streams into the dialog like a normal turn.
• Re-run review: runs a fresh comparison against the current branch outputs.
• Clear review: removes the current verdict without affecting the branches.
• Draft merged answer: creates a parent-task draft that uses the reviewer verdict plus branch outputs to synthesize one stronger final answer.

Common Workflows

Compare Models Before Choosing One

1. Start a Coliseum with 2-4 entrants.
2. Watch the branches stream in parallel.
3. Open focus mode if one branch deserves closer inspection.
4. Compare the prompt card, file changes, and final answer in each column.

Promote, Re-Pick, And Finish

1. Click Pick champion on the branch you want to keep.
2. Stave grafts that branch's post-fan-out messages into the parent task.
3. If you change your mind, click Unpick and select a different branch.
4. When you are satisfied, click Finish arena to leave comparison mode.

Review Branches And Draft A Merged Answer

1. Wait until at least one branch finishes.
2. Click Review & compare.
3. Let the reviewer recommend the best branch and call out trade-offs.
4. Use Draft merged answer if you want the parent task to synthesize one final response from several branches instead of promoting a single winner unchanged.

Pause The Arena Without Losing It

1. Click Minimize.
2. Continue browsing the parent task normally while branches keep running.
3. Click Reopen arena above the composer to restore the comparison view.

Throw The Run Away

1. Click Discard run before finishing.
2. Stave aborts every remaining branch and removes the arena.
3. The parent task returns to the exact state it had before Coliseum started.

How It Works

• Stave creates one hidden child task per entrant.
• Each child task receives the same prompt payload, attachments, and inherited runtime mode settings from the parent.
• Branch tasks stay hidden from the task list, sidebar previews, and task tabs. You interact with them only through the arena.
• The parent task remains unchanged while the run is active.
• When you promote a winner, Stave appends only that branch's post-fan-out tail back into the parent task.
• If you discard the run, close branches, or reload a workspace with stale branch records, Stave reaps the ephemeral tasks automatically.

Limitations And Advanced Options

• Coliseum is a one-round comparison. You cannot chat back and forth inside individual branches.
• The layout is capped at four entrants to keep the arena readable.
• Shared attachments are copied once at launch. Branches do not re-read files automatically after the run has started.
• Nested Coliseums are blocked.
• Managed tasks cannot launch Coliseum until Stave owns the task again.
• Running large or expensive models in every branch can multiply cost quickly. Use smaller models or stave-auto when you want a cheaper exploratory pass.

Troubleshooting

The Coliseum button is missing

• Symptom: the control strip above the composer does not show Coliseum.
• Cause: no active task is selected, or the task view is still hydrating.
• Fix: select a task and wait for the task view to finish loading.

The Coliseum button is disabled

• Symptom: hovering the button says you must wait for the current turn to finish.
• Cause: the parent task still has a running turn.
• Fix: wait for the turn to end or stop it, then reopen the launcher.

Start Coliseum stays disabled

• Symptom: the dialog never enables Start Coliseum.
• Cause: one row is incomplete, the prompt is empty, or a selected provider is unavailable.
• Fix: verify every row has a valid provider and model, enter a prompt, and confirm provider availability in the task controls.

Review & compare is disabled

• Symptom: the arena header shows Review & compare, but it cannot be clicked yet.
• Cause: no branch has finished producing an answer.
• Fix: wait for the first completed branch, then open the reviewer.

One branch looks stuck

• Symptom: one column keeps showing a live state without useful output.
• Cause: that provider or model may have failed, stalled, or been rate-limited.
• Fix: close just that branch and continue with the remaining entrants, or rerun the whole Coliseum with a different lineup.

A branch task shows up after reload

• Symptom: you briefly see a duplicated task title or a stale hidden branch.
• Cause: a stale runtime branch survived until workspace bootstrap.
• Fix: reload the workspace. Stave reaps orphan Coliseum tasks on load.

Related Docs

• Provider Sandbox and Approval
• Stave Model Router
• Attachments