# What
`SubagentStart` runs once when Codex creates a thread-spawned subagent,
before that child sends its first model request. Thread-spawned
subagents use `SubagentStart` instead of the normal root-agent
`SessionStart` hook.
Configured handlers match on the subagent `agent_type`, using the same
value passed to `spawn_agent`. When no agent type is specified, Codex
uses the default agent type.
Hook input includes the normal session-start fields plus:
- `agent_id`: the child thread id.
- `agent_type`: the resolved subagent type.
`SubagentStart` may return `hookSpecificOutput.additionalContext`. That
context is added to the child conversation before the first model
request.
# Lifecycle Scope
Only thread-spawned subagents run `SubagentStart`.
Internal/system subagents such as Review, Compact, MemoryConsolidation,
and Other do not run normal `SessionStart` hooks and do not run
`SubagentStart`. This avoids exposing synthetic matcher labels for
internal implementation paths.
Also the `SessionStart` hook no longer fires for subagents, this matches
behavior with other coding agents' implementation
# Stack
1. This PR: add `SubagentStart`.
2. #22873: add `SubagentStop`.
3. #22882: add subagent identity to normal hook inputs.
## Why
The legacy `AfterToolUse` hook path was still wired through core tool
dispatch even though the hooks registry never populated any handlers for
it. The supported hook surface is `PostToolUse`, so the old
infrastructure was dead code on the hot path.
## What changed
- Removed the legacy `AfterToolUse` dispatch from `codex-core` tool
execution.
- Removed the unused legacy hook payload types and exports from
`codex-hooks`.
- Simplified legacy notify handling now that `HookEvent` only carries
`AfterAgent`.
## Validation
- `cargo test -p codex-hooks`
- `cargo test -p codex-core registry`
Supersedes the abandoned #19859, rebuilt on latest `main`.
# Why
PR #19705 adds discovery for hooks bundled with plugins, but `/plugins`
still only shows skills, apps, and MCP servers. This follow-up makes
bundled hooks visible in the same plugin detail view so users can
inspect the full plugin surface in one place.
We also need `PluginHookSummary` to populate Plugin Hooks in the app;
`hooks/list` is not enough there because plugin detail needs to show
hooks for disabled plugins too.
# What
- extend `plugin/read` with `PluginHookSummary` entries for bundled
hooks
- summarize plugin hooks while loading plugin details
- render a `Hooks` row in the `/plugins` detail popup
<img width="3456" height="848" alt="CleanShot 2026-04-27 at 11 45 34@2x"
src="https://github.com/user-attachments/assets/fe3a38d6-a260-4351-8513-fb04c93d725b"
/>
Based on work from Vincent K -
https://github.com/openai/codex/pull/19060
<img width="1836" height="642" alt="CleanShot 2026-04-29 at 20 47 40@2x"
src="https://github.com/user-attachments/assets/b647bb89-65fe-40c8-80b0-7a6b7c984634"
/>
## Why
Compaction rewrites the conversation context that future model turns
receive, but hooks currently have no deterministic lifecycle point
around that rewrite. This adds compact lifecycle hooks so users can
audit manual and automatic compaction, surface hook messages in the UI,
and run post-compaction follow-up without overloading tool or prompt
hooks.
## What Changed
- Added `PreCompact` and `PostCompact` hook events across hook config,
discovery, dispatch, generated schemas, app-server notifications,
analytics, and TUI hook rendering.
- Added trigger matching for compact hooks with the documented `manual`
and `auto` matcher values.
- Wired `PreCompact` before both local and remote compaction, and
`PostCompact` after successful local or remote compaction.
- Kept compact hook command input to lifecycle metadata: session id,
Codex turn id, transcript path, cwd, hook event name, model, and
trigger.
- Made compact stdout handling consistent with other hooks: plain stdout
is ignored as debug output, while malformed JSON-looking stdout is
reported as failed hook output.
- Added integration coverage for compact hook dispatch, trigger
matching, post-compact execution, and the audited behavior that
`decision:"block"` does not block compaction.
## Out of Scope
- Hook-specific compaction blocking is not implemented;
`decision:"block"` and exit-code-2 blocking semantics are intentionally
unsupported for `PreCompact`.
- Custom compaction instructions are not exposed to compact hooks in
this PR.
- Compact summaries, summary character counts, and summary previews are
not exposed to compact hooks in this PR.
## Verification
- `cargo test -p codex-hooks`
- `cargo test -p codex-core
manual_pre_compact_block_decision_does_not_block_compaction`
- `cargo test -p codex-app-server hooks_list`
- `cargo test -p codex-core config_schema_matches_fixture`
- `cargo test -p codex-tui hooks_browser`
## Docs
The developer documentation for Codex hooks should be updated alongside
this feature to document `PreCompact` and `PostCompact`, the
`manual`/`auto` matcher values, and the compact hook payload fields.
---------
Co-authored-by: Vincent Koc <vincentkoc@ieee.org>
## Why
Large hook outputs can enter model-visible context through hook-specific
paths such as `additionalContext` and `Stop` continuation prompts.
Without a dedicated cap, one hook can inject a large blob directly into
conversation history instead of leaving a bounded preview for the model
and preserving the full text elsewhere.
## What
- spill hook text once it exceeds a fixed `2_500`-token budget,
preserving the full output on disk and leaving a head/tail preview plus
saved path in context
- add shared hook-output spilling under
`CODEX_HOME/hook_outputs/<thread_id>/<uuid>.txt`
- apply the cap to both `additionalContext`, `feedback_message`, and
`Stop` continuation fragments
## Why
After `hooks/list` exposes the hook inventory, clients need a way to
persist user hook preferences, make those changes effective in
already-open sessions, and distinguish user-controllable hooks from
managed requirements without adding another bespoke app-server write
API.
## What
- Extends `hooks/list` entries with effective `enabled` state.
- Persists user-level hook state under `hooks.state.<hook-id>` so the
model can grow beyond a single boolean over time.
- Uses the existing `config/batchWrite` path for hook state updates
instead of introducing a dedicated hook write RPC.
- Refreshes live session hook engines after config writes so
already-open threads observe updated enablement without a restart.
## Stack
1. openai/codex#19705
2. openai/codex#19778
3. This PR - openai/codex#19840
4. openai/codex#19882
## Reviewer Notes
The generated schema files account for much of the raw diff. The core
behavior is in:
- `hooks/src/config_rules.rs`, which resolves per-hook user state from
the config layer stack.
- `hooks/src/engine/discovery.rs`, which projects effective enablement
into `hooks/list` from source-derived managedness.
- `config/src/hook_config.rs`, which defines the new `hooks.state`
representation.
- `core/src/session/mod.rs`, which rebuilds live hook state after user
config reloads.
---------
Co-authored-by: Codex <noreply@openai.com>
## Why
We need a way to list the available hooks to expose via the TUI and App
so users can view and manage their hooks
## What
- Adds `hooks/list` for one or more `cwd` values that returns discovered
hook metadata
## Stack
1. openai/codex#19705
2. This PR - openai/codex#19778
3. openai/codex#19840
4. openai/codex#19882
## Review Notes
The generated schema files account for most of the raw diff, these files
have the core change:
- `hooks/src/engine/discovery.rs` builds the inventory entries during
hook discovery while leaving runtime handlers focused on execution.
- `app-server/src/codex_message_processor.rs` wires `hooks/list` into
the app-server flow for each requested `cwd`.
- `app-server-protocol/src/protocol/v2.rs` defines the new v2
request/response payloads exposed on the wire.
### Core Changes
`core/src/plugins/manager.rs` adds `plugins_for_layer_stack(...)` so
`skills/list` and `hooks/list`can resolve plugin state for each
requested `cwd`
---------
Co-authored-by: Codex <noreply@openai.com>
## 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`
## Why
We need `PermissionRequest` hook support!
Also addresses:
- https://github.com/openai/codex/issues/16301
- run a script on Hook to do things like play a sound to draw attention
but actually no-op so user can still approve
- can omit the `decision` object from output or just have the script
exit 0 and print nothing
- https://github.com/openai/codex/issues/15311
- let the script approve/deny on its own
- external UI what will run on Hook and relay decision back to codex
## Reviewer Note
There's a lot of plumbing for the new hook, key files to review are:
- New hook added in `codex-rs/hooks/src/events/permission_request.rs`
- Wiring for network approvals
`codex-rs/core/src/tools/network_approval.rs`
- Wiring for tool orchestrator `codex-rs/core/src/tools/orchestrator.rs`
- Wiring for execve
`codex-rs/core/src/tools/runtimes/shell/unix_escalation.rs`
## What
- Wires shell, unified exec, and network approval prompts into the
`PermissionRequest` hook flow.
- Lets hooks allow or deny approval prompts; quiet or invalid hooks fall
back to the normal approval path.
- Uses `tool_input.description` for user-facing context when it helps:
- shell / `exec_command`: the request justification, when present
- network approvals: `network-access <domain>`
- Uses `tool_name: Bash` for shell, unified exec, and network approval
permission-request hooks.
- For network approvals, passes the originating command in
`tool_input.command` when there is a single owning call; otherwise falls
back to the synthetic `network-access ...` command.
<details>
<summary>Example `PermissionRequest` hook input for a shell
approval</summary>
```json
{
"session_id": "<session-id>",
"turn_id": "<turn-id>",
"transcript_path": "/path/to/transcript.jsonl",
"cwd": "/path/to/cwd",
"hook_event_name": "PermissionRequest",
"model": "gpt-5",
"permission_mode": "default",
"tool_name": "Bash",
"tool_input": {
"command": "rm -f /tmp/example"
}
}
```
</details>
<details>
<summary>Example `PermissionRequest` hook input for an escalated
`exec_command` request</summary>
```json
{
"session_id": "<session-id>",
"turn_id": "<turn-id>",
"transcript_path": "/path/to/transcript.jsonl",
"cwd": "/path/to/cwd",
"hook_event_name": "PermissionRequest",
"model": "gpt-5",
"permission_mode": "default",
"tool_name": "Bash",
"tool_input": {
"command": "cp /tmp/source.json /Users/alice/export/source.json",
"description": "Need to copy a generated file outside the workspace"
}
}
```
</details>
<details>
<summary>Example `PermissionRequest` hook input for a network
approval</summary>
```json
{
"session_id": "<session-id>",
"turn_id": "<turn-id>",
"transcript_path": "/path/to/transcript.jsonl",
"cwd": "/path/to/cwd",
"hook_event_name": "PermissionRequest",
"model": "gpt-5",
"permission_mode": "default",
"tool_name": "Bash",
"tool_input": {
"command": "curl http://codex-network-test.invalid",
"description": "network-access http://codex-network-test.invalid"
}
}
```
</details>
## Follow-ups
- Implement the `PermissionRequest` semantics for `updatedInput`,
`updatedPermissions`, `interrupt`, and suggestions /
`permission_suggestions`
- Add `PermissionRequest` support for the `request_permissions` tool
path
---------
Co-authored-by: Codex <noreply@openai.com>
## Summary
- reduce public module visibility across Rust crates, preferring private
or crate-private modules with explicit crate-root public exports
- update external call sites and tests to use the intended public crate
APIs instead of reaching through module trees
- add the module visibility guideline to AGENTS.md
## Validation
- `cargo check --workspace --all-targets --message-format=short` passed
before the final fix/format pass
- `just fix` completed successfully
- `just fmt` completed successfully
- `git diff --check` passed
CHAINED PR - note that base is eternal/hooks-pretooluse-bash, not main
-- so the following PR should be first
Matching post-tool hook to the pre-tool functionality here:
https://github.com/openai/codex/pull/15211
So, PreToolUse calls for plain shell calls, allows blocking. This
PostToolUse call runs after the command executed
example run:
```
› as a test, run in parallel the following commands:
- echo 'one'
- echo '[block-pre-tool-use]'
- echo '[block-post-tool-use]'
⚠ MCP startup incomplete (failed: notion, linear)
• Cruising through those three commands in parallel now, and I’ll share the exact outputs right after
they land.
• Running PreToolUse hook: checking the observatory runes
• Running PreToolUse hook: checking the observatory runes
• Running PreToolUse hook: checking the observatory runes
PreToolUse hook (blocked)
warning: wizard-tower PreToolUse demo blocked a Bash command on purpose.
feedback: PreToolUse demo blocked the command. Remove [block-pre-tool-use] to continue.
PreToolUse hook (completed)
warning: wizard-tower PreToolUse demo inspected Bash: echo 'one'
PreToolUse hook (completed)
warning: wizard-tower PreToolUse demo inspected Bash: echo '[block-post-tool-use]'
• Ran echo '[block-post-tool-use]'
└ [block-post-tool-use]
• Ran echo 'one'
└ one
• Running PostToolUse hook: reading the observatory aftermath
• Running PostToolUse hook: reading the observatory aftermath
PostToolUse hook (blocked)
warning: wizard-tower PostToolUse demo blocked the Bash follow-through on purpose.
feedback: PostToolUse demo blocked the result after execution. Remove [block-post-tool-use] to
continue.
PostToolUse hook (completed)
warning: wizard-tower PostToolUse demo inspected Bash: echo 'one'
hook context: PostToolUse demo saw the Bash result. Response preview: one
──────────────────────────────────────────────────────────────────────────────────────────────────────
• Ran them in parallel. Little wave report:
- echo 'one' completed and returned one.
- echo '[block-pre-tool-use]' was blocked before execution by the PreToolUse hook.
- echo '[block-post-tool-use]' ran, but its result was blocked afterward by the PostToolUse hook.
The hook messages were:
- PreToolUse demo blocked the command. Remove [block-pre-tool-use] to continue.
- PostToolUse demo blocked the result after execution. Remove [block-post-tool-use] to continue.
› for the blocked messages (correctly blocked in this test) did the tool output land back into
context?
• Yeah, from this run:
- PreToolUse block: the command itself did not execute, so no command output landed in context. Only
the block message did.
- PostToolUse block: the command did execute, but the actual stdout did not come back into context.
Only the post-tool block message did.
So the blocked notifications landed in context, but the blocked command payloads themselves did not.
Nice clean guardrail, aloha.
```
- add `PreToolUse` hook for bash-like tool execution only at first
- block shell execution before dispatch with deny-only hook behavior
- introduces common.rs matcher framework for matching when hooks are run
example run:
```
› run three parallel echo commands, and the second one should echo "[block-pre-tool-use]" as a test
• Running the three echo commands in parallel now and I’ll report the output directly.
• Running PreToolUse hook: name for demo pre tool use hook
• Running PreToolUse hook: name for demo pre tool use hook
• Running PreToolUse hook: name for demo pre tool use hook
PreToolUse hook (completed)
warning: wizard-tower PreToolUse demo inspected Bash: echo "first parallel echo"
PreToolUse hook (blocked)
warning: wizard-tower PreToolUse demo blocked a Bash command on purpose.
feedback: PreToolUse demo blocked the command. Remove [block-pre-tool-use] to continue.
PreToolUse hook (completed)
warning: wizard-tower PreToolUse demo inspected Bash: echo "third parallel echo"
• Ran echo "first parallel echo"
└ first parallel echo
• Ran echo "third parallel echo"
└ third parallel echo
• Three little waves went out in parallel.
1. printed first parallel echo
2. was blocked before execution because it contained the exact test string [block-pre-tool-use]
3. printed third parallel echo
There was also an unrelated macOS defaults warning around the successful commands, but the echoes
themselves worked fine. If you want, I can rerun the second one with a slightly modified string so
it passes cleanly.
```
- this allows blocking the user's prompts from executing, and also
prevents them from entering history
- handles the edge case where you can both prevent the user's prompt AND
add n amount of additionalContexts
- refactors some old code into common.rs where hooks overlap
functionality
- refactors additionalContext being previously added to user messages,
instead we use developer messages for them
- handles queued messages correctly
Sample hook for testing - if you write "[block-user-submit]" this hook
will stop the thread:
example run
```
› sup
• Running UserPromptSubmit hook: reading the observatory notes
UserPromptSubmit hook (completed)
warning: wizard-tower UserPromptSubmit demo inspected: sup
hook context: Wizard Tower UserPromptSubmit demo fired. For this reply only, include the exact
phrase 'observatory lanterns lit' exactly once near the end.
• Just riding the cosmic wave and ready to help, my friend. What are we building today? observatory
lanterns lit
› and [block-user-submit]
• Running UserPromptSubmit hook: reading the observatory notes
UserPromptSubmit hook (stopped)
warning: wizard-tower UserPromptSubmit demo blocked the prompt on purpose.
stop: Wizard Tower demo block: remove [block-user-submit] to continue.
```
.codex/config.toml
```
[features]
codex_hooks = true
```
.codex/hooks.json
```
{
"hooks": {
"UserPromptSubmit": [
{
"hooks": [
{
"type": "command",
"command": "/usr/bin/python3 .codex/hooks/user_prompt_submit_demo.py",
"timeoutSec": 10,
"statusMessage": "reading the observatory notes"
}
]
}
]
}
}
```
.codex/hooks/user_prompt_submit_demo.py
```
#!/usr/bin/env python3
import json
import sys
from pathlib import Path
def prompt_from_payload(payload: dict) -> str:
prompt = payload.get("prompt")
if isinstance(prompt, str) and prompt.strip():
return prompt.strip()
event = payload.get("event")
if isinstance(event, dict):
user_prompt = event.get("user_prompt")
if isinstance(user_prompt, str):
return user_prompt.strip()
return ""
def main() -> int:
payload = json.load(sys.stdin)
prompt = prompt_from_payload(payload)
cwd = Path(payload.get("cwd", ".")).name or "wizard-tower"
if "[block-user-submit]" in prompt:
print(
json.dumps(
{
"systemMessage": (
f"{cwd} UserPromptSubmit demo blocked the prompt on purpose."
),
"decision": "block",
"reason": (
"Wizard Tower demo block: remove [block-user-submit] to continue."
),
}
)
)
return 0
prompt_preview = prompt or "(empty prompt)"
if len(prompt_preview) > 80:
prompt_preview = f"{prompt_preview[:77]}..."
print(
json.dumps(
{
"systemMessage": (
f"{cwd} UserPromptSubmit demo inspected: {prompt_preview}"
),
"hookSpecificOutput": {
"hookEventName": "UserPromptSubmit",
"additionalContext": (
"Wizard Tower UserPromptSubmit demo fired. "
"For this reply only, include the exact phrase "
"'observatory lanterns lit' exactly once near the end."
),
},
}
)
)
return 0
if __name__ == "__main__":
raise SystemExit(main())
```
(Experimental)
This PR adds a first MVP for hooks, with SessionStart and Stop
The core design is:
- hooks live in a dedicated engine under codex-rs/hooks
- each hook type has its own event-specific file
- hook execution is synchronous and blocks normal turn progression while
running
- matching hooks run in parallel, then their results are aggregated into
a normalized HookRunSummary
On the AppServer side, hooks are exposed as operational metadata rather
than transcript-native items:
- new live notifications: hook/started, hook/completed
- persisted/replayed hook results live on Turn.hookRuns
- we intentionally did not add hook-specific ThreadItem variants
Hooks messages are not persisted, they remain ephemeral. The context
changes they add are (they get appended to the user's prompt)
Summary
- move `core/src/hooks` implementation into a new `codex-hooks` crate
with its own manifest
- update `codex-rs` workspace and `codex-core` crate to depend on the
extracted `hooks` crate and wire up the shared APIs
- ensure references, modules, and lockfile reflect the new crate layout
Testing
- Not run (not requested)
