## Why
This PR expands the migration path so Codex can detect and import MCP
server config, hooks, commands, and subagents configs in a Codex-native
shape.
## What changed
- Added a `codex-external-agent-migration` crate that owns conversion
logic for external-agent MCP servers, hooks, commands, and subagents.
- Extended the app-server external-agent config detection/import API
with migration item types for MCP server config, hooks, commands, and
subagents.
## Migration strategy
The migration is intentionally conservative: Codex only imports
external-agent config that can be represented safely in Codex today.
Unsupported or ambiguous config is skipped instead of being partially
translated into behavior that may not match the source system.
- **MCP servers**: import supported stdio and HTTP MCP server
definitions into `mcp_servers`. Disabled servers and servers filtered
out by source `enabledMcpjsonServers` / `disabledMcpjsonServers` are
skipped. Project-scoped MCP entries from `.claude.json` are included
when they match the repo path.
- **Hooks**: import only supported command hooks into
`.codex/hooks.json`. Unsupported hook features such as conditional
groups, async handlers, prompt/http hooks, or unknown fields are
skipped. Referenced hook scripts are copied into `.codex/hooks/`,
preserving any existing target scripts.
- **Commands**: import supported external commands as Codex skills under
`.agents/skills/source-command-*`. Commands that rely on source runtime
expansion such as `$ARGUMENTS`, `$1`, `@file` references, shell
interpolation, or colliding generated names are skipped.
- **Subagents**: import valid subagent Markdown files into
`.codex/agents/*.toml` when they have the minimum Codex agent fields.
Source model names are not migrated, so imported agents keep the user’s
Codex default model; compatible reasoning effort and sandbox mode are
migrated when present.
- **Skills and project guidance**: copy missing skill directories into
`.agents/skills` and migrate `CLAUDE.md` guidance into `AGENTS.md`,
rewriting source-agent terminology to Codex terminology where
appropriate.
- **Detection details**: detected migration items include lightweight
details for UI preview, such as MCP server names, hook event names,
generated command skill names, and subagent names. Import still
recomputes from disk instead of trusting details as the source of truth.
- Adds focused coverage for the new migration behavior and app-server
import flow.
## Verification
- `cargo test -p codex-external-agent-migration`
- `cargo test -p codex-hooks`
- `cargo test -p codex-app-server external_agent_config`
- `just bazel-lock-check`
## Summary
This extends external agent detection/import beyond config artifacts so
Codex can detect recent sessions files from the external agent home and
import them into Codex rollout history.
## What changed
- Added a focused `external_agent_sessions` module for:
- session discovery
- source-record parsing
- rollout construction
- import ledger tracking
- Wired session detection/import into the app-server external agent
config API.
- Added compaction handling so large imported sessions can be resumed
safely before the first follow-up turn.
## Testing
Added coverage for:
- recent-session detection
- custom-title handling
- recency filtering
- dedupe and re-detect-after-source-change behavior
- visible imported turn construction
- backward-compatible import payload deserialization
- end-to-end RPC import flow
- rejection of undetected session paths
- repeat-import behavior
- large-session compaction before first follow-up
Ran:
- `cargo test -p codex-app-server external_agent_config_import_ --test
all`
Migration Behavior
* Config
* Migrates settings.json into config.toml
* Only adds fields when config.toml is missing, or when those fields are
missing from the existing file
* Supported mappings:
env -> shell_environment_policy
sandbox.enabled = true -> sandbox_mode = "workspace-write"
* Skills
* Copies home and repo .claude/skills into .agents/skills
* Existing skill directories are not overwritten
* SKILL.md content is rewritten from Claude-related terms to Codex
* AgentsMd
* Repo only
* Migrates CLAUDE.md into AGENTS.md
* Detect/import only proceed when AGENTS.md is missing or present but
empty
* Content is rewritten from Claude-related terms to Codex
