Land the agent bridge sidecar so Claude and Antigravity agents work from stock Codex

[shiny-code-app]

Objective

Make Claude and Antigravity agents usable from stock Codex through the MCP agent bridge that spike #949 proved, maintained as a sidecar on main like tools/account-router. The owner decided on 2026-09-26 that this bridge is the route for other providers' agents.

other providers' agents work through sidecars or small patches

The owner's bar from #964 is a richer experience "with callbacks and turns… to make it feel like a real codex agent", not just calling a helper through a CLI.

Finish Line

tools/agent-bridge is on main with tests and an install step. From an ordinary stock Codex CLI session the owner can hand a task to a Claude agent and an Antigravity agent and get their results back as progress and a final report, and can cancel them. The orchestrating model uses the bridge without being told to. The number of upstream files changed is recorded, and stays zero if possible.

Current Status

State: Active; this is the first item for other-provider agents in "Other needs on the fresh start".
Next action: bring tools/agent-bridge from spike branch work/spike-agent-bridge-20260919 (commit b9318ef) to main as a maintained Python sidecar with tests, then run the unprompted-delegation check.
Blocked by: none.
Last verified: 2026-09-26. The spike passed PONG from both providers through stock Codex 0.155.1 and through Claude Code, and cancel was verified (#949).

Scope

• In: the MCP tools spawn, wait, cancel and list, plus progress reporting; the providers claude and agy; bounded output; cleanup of the whole process group; read-only and write modes; install and config (default_tools_approval_mode="approve" for non-interactive use); tests.
• Out: engine patches unless a measured gap requires one; TUI rendering; usage accounting; account handling.

Acceptance Criteria

• tools/agent-bridge is on main with tests, runnable with uv.
• A PONG check passes for both providers through stock Codex.
• Cancel kills the provider's whole process tree and leaves no orphans.
• An empty provider result is reported as a failure, never as success (carried over from Handle recurrent true-empty Antigravity review results #839).
• Progress and the final result reach the orchestrating session in a way that feels like a Codex agent turn, with the gap to native subagents written down.
• From an ordinary task, the orchestrating model delegates through the bridge without being told to, or the missing guidance is written down.
• The number of upstream files changed is recorded.

Relationships

• Follows spike Spike: deliver Claude and Antigravity agents through a standalone MCP bridge #949 (closed as completed) and thin-fork decision Explore a thin-fork path: stock Codex engine with Lab features moved to plugin, MCP bridge, and a minimal patch series #926.
• Criteria carried over from Handle recurrent true-empty Antigravity review results #839 and Make spawned-agent source snapshots explicit and freshness-aware #598.

Validation

• The bridge's tests.
• A PONG check from stock Codex for claude and agy, recorded with the exact commands.
• One real delegated task from an ordinary session.

Decisions

• 2026-09-26, owner: the MCP bridge sidecar is the route for other providers' agents.

Open Questions

• Can MCP progress notifications or elicitation give the "callbacks and turns" feel, or does that need a small patch?

[shiny-code-app]

Direction reconciliation, 2026-09-26 (against the owner's overall DIRECTION.md)

Owner decision, 2026-09-26: parked. Under the overall Order, codex-lab is other tooling (the "lab" in the own-projects list is the owner's work room and workbench). This bridge adds a capability rather than removing a repeated stop, and it is not on a listed milestone's path.

Parked until a stop that the missing bridge causes has happened twice with both occurrences linked here, or a listed milestone names this work. #93 and #925 stay parked with it.