MCP Session Context — Vision

Mirrored from docs/design/mcp-session-context/3_vision.md. Edit the source document in the repository, not this generated page.

Session context should stay small and deliberate: fields belong here only when they are session-scoped, trusted by the transport boundary, and safer than repeating low-signal inputs on every tool call.

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1. Open Questions

1. Should future MCP transports store context by transport session id rather than by server instance?
2. Should workspace context eventually accept a workspace id as well as a path, or should the path remain the only MCP address and .orbit/config.yaml remain the binding source?
3. Which additional low-noise fields, if any, are safe enough for session context rather than tool input?

2. Prior Work

Task Artifacts

[ADR-0149] established that .orbit/config.yaml stores the load-bearing workspace_id binding and that defaulting task writes from cwd can silently route to the wrong workspace.

MCP Schema Trimming

[ORB-00255] motivated reducing repetitive tool fields, but workspace could not become optional until MCP had a deliberate ambient channel.

3. What May Be Distinctive

Orbit treats session context as a safety mechanism rather than a convenience cache. The resolver deliberately refuses to use process cwd, even when cwd would appear to work, because worktree and non-default binding cases are exactly where an implicit fallback is most dangerous.

4. References

• [ADR-0149] records the task-artifact workspace binding invariant.
• [ADR-0181] records the MCP ambient workspace session context decision.
• [ORB-00256] implemented the first session context field.
• [ORB-00255] motivated the schema trimming pressure that made a safe default useful.

Task References

• [ORB-00255] motivated reducing repetitive workspace boilerplate.
• [ORB-00256] implemented the session context channel.

Resolve any task above with orbit task show <ID> or git log --grep=<ID>.