## Description
Adding an extension to the spec that exposes the turn_id to hook
scripts. This is a codex-specific mechanic that allows connecting the
hook runs with particular turns
## Testing
hooks config / sample hooks to use. Extract this, rename codex ->
.codex, and place this into a repo or your home folder. It includes:
config.toml that enables hooks, hooks.json, and sample python hooks:
[codex.zip](https://github.com/user-attachments/files/26102671/codex.zip)
example run (note the turn_ids change between turns):
```
› hello
• Running SessionStart hook: lighting the observatory
SessionStart hook (completed)
warning: Hi, I'm a session start hook for wizard-tower (startup).
hook context: Startup context: A wimboltine stonpet is an exotic cuisine from hyperspace
• Running UserPromptSubmit hook: lighting the observatory lanterns
UserPromptSubmit hook (completed)
warning: wizard-tower UserPromptSubmit demo inspected: hello for turn: 019d036d-c7fa-72d2-b6fd-
78878bfe34e4
hook context: Wizard Tower UserPromptSubmit demo fired. For this reply only, include the exact
phrase 'observatory lanterns lit' near the end.
• Aloha! Grateful to be here and ready to build with you. Show me what you want to tackle in wizard-
tower, and we’ll surf the next wave together. observatory lanterns lit
• Running Stop hook: back to shore
Stop hook (completed)
warning: Wizard Tower Stop hook reviewed the completed reply (170 chars) for turn: 019d036d-c7fa-
72d2-b6fd-78878bfe34e4
› what's a stonpet?
• Running UserPromptSubmit hook: lighting the observatory lanterns
UserPromptSubmit hook (completed)
warning: wizard-tower UserPromptSubmit demo inspected: what's a stonpet? for turn: 019d036e-3164-
72c3-a170-98925564c4fc
hook context: Wizard Tower UserPromptSubmit demo fired. For this reply only, include the exact
phrase 'observatory lanterns lit' near the end.
• A stonpet isn’t a standard real-world word, brah. In our shared context here, a wimboltine stonpet
is an exotic cuisine from hyperspace, so “stonpet” sounds like the dish or food itself.
If you want, we can totally invent the lore for it next. observatory lanterns lit
• Running Stop hook: back to shore
Stop hook (completed)
warning: Wizard Tower Stop hook reviewed the completed reply (271 chars) for turn: 019d036e-3164-
72c3-a170-98925564c4fc
```
- 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())
```
Stop hooks now receive `stop_hook_active` and enable stop hooks to loop
forever if they'd like to. In the initial hooks PR, we implemented a
simpler mechanic that the stop-blocking could only happen once in a row
- support stop hook adding a continuation prompt to add a further task
- if multiple stop-blocks happen that have continuation prompts, they
are concatenated
example run:
```
› hey :)
• Running SessionStart hook: lighting the observatory
SessionStart hook (completed)
warning: Hi, I'm a session start hook for wizard-tower (startup).
hook context: Startup context: A wimboltine stonpet is an exotic cuisine from hyperspace
• Aloha :) Happy to jam with you. What are we building today?
• Running Stop hook: updating the guards
Stop hook (blocked)
warning: Wizard Tower Stop hook continuing conversation
feedback: cook the stonpet
• Aloha, here’s the hyperspace move for cooking a wimboltine stonpet:
1. Sear the stonpet in a hot pan with moon-oil until the edges shimmer.
2. Add star-lime, black salt, and a little fermented nebula paste.
3. Lower the heat and let it braise for 8 cosmic minutes with a splash of comet broth.
4. Finish with sky herbs and serve over warm asteroid rice.
The vibe: crispy outside, tender center, deep interdimensional savor.
• Running Stop hook: updating the guards
Stop hook (completed)
warning: Wizard Tower Stop hook saw a second pass and stayed calm to avoid a loop.
```
.codex/config.toml
```
[features]
codex_hooks = true
```
.codex/hooks.json
```
{
"hooks": {
"SessionStart": [
{
"matcher": "startup|resume",
"hooks": [
{
"type": "command",
"command": "/usr/bin/python3 .codex/hooks/session_start_demo.py",
"timeoutSec": 10,
"statusMessage": "lighting the observatory"
}
]
}
],
"Stop": [
{
"hooks": [
{
"type": "command",
"command": "/usr/bin/python3 .codex/hooks/stop_demo_block.py",
"timeoutSec": 10,
"statusMessage": "updating the guards"
}
]
}
]
}
}
```
.codex/hooks/session_start_demo.py
```
#!/usr/bin/env python3
import json
import sys
from pathlib import Path
def main() -> int:
payload = json.load(sys.stdin)
cwd = Path(payload.get("cwd", ".")).name or "wizard-tower"
source = payload.get("source", "startup")
source_label = "resume" if source == "resume" else "startup"
source_prefix = (
"Resume context:"
if source == "resume"
else "Startup context:"
)
output = {
"systemMessage": (
f"Hi, I'm a session start hook for {cwd} ({source_label})."
),
"hookSpecificOutput": {
"hookEventName": "SessionStart",
"additionalContext": (
f"{source_prefix} A wimboltine stonpet is an exotic cuisine from hyperspace"
),
},
}
print(json.dumps(output))
return 0
if __name__ == "__main__":
raise SystemExit(main())
```
.codex/hooks/stop_demo_block.py
```
#!/usr/bin/env python3
import json
import sys
def main() -> int:
payload = json.load(sys.stdin)
stop_hook_active = payload.get("stop_hook_active", False)
last_assistant_message = payload.get("last_assistant_message") or ""
char_count = len(last_assistant_message.strip())
if stop_hook_active:
system_message = (
"Wizard Tower Stop hook saw a second pass and stayed calm to avoid a loop."
)
print(json.dumps({"systemMessage": system_message}))
else:
system_message = (
f"Wizard Tower Stop hook continuing conversation"
)
print(json.dumps({"systemMessage": system_message, "decision": "block", "reason": "cook the stonpet"}))
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)
Andrei Eternal