Playback machine: support party-line sessions — multi-entity, multi-model conversations

[koad]

Context

We now have party-line conversations — multi-entity shared sessions where different entities take turns in one workspace. Each entity brings their own model, API key, and provider. The session accumulates in opencode's DB, exportable as JSON.

This is a new content format for the playback machine.

What's different from single-entity sessions

Aspect	Current (single)	Party-line
Entities	1 per session	Multiple, turn-based
Models	1 per session	Different per turn (Opus, Grok, big-pickle, etc.)
Identity	Fixed assistant	Rotates — each turn has a different entity
Signing	None	Provenance: --- entity @ time | host:user | model ---
Files	Entity writes files	Multiple entities write/modify same files
Session format	Claude Code JSONL	opencode JSON export

What the playback machine needs

1. Multi-avatar rendering — different entity avatars appear as they take turns. Entry/exit animations per entity.
2. Provenance display — show the signed provenance line (entity, host, user, model) as a badge on each turn.
3. Model indicator — visual indicator of which model/provider is active (e.g., Opus = purple, big-pickle = green, Grok = blue).
4. Turn transitions — visual "passing of the conch" animation between entities.
5. File collaboration view — show which entity touched which files, maybe a git-blame-style coloring.
6. Party metadata — pull from .koad-io/parties/<name>/PRIMER.md for title, topic, participants.

Demo proof

Working example at ~/Workbench/test-new-convo-thing/:

• 4 entities (Juno, Iris, Alice, Vesta)
• 7 turns in one shared session
• 6 files written collaboratively
• Session: ses_28bcfffedffe1xS0YyL4FnAsIG
• Export: opencode export ses_28bcfffedffe1xS0YyL4FnAsIG

Party-line commands (for reference)

<entity> spawn party <name> [topic]   # start
<entity> respond "message"            # pass the conch
<entity> party check                  # find protocol violators

Priority

This expands the content inventory significantly. Every party-line session is a multi-personality collaboration video. The talent pool goes from "one entity working" to "a team collaborating." That's the demo that sells the platform.

Filed by Juno.