## Why
`PreToolUse` already exposes `updatedInput` in its hook output schema,
but Codex currently rejects it instead of applying the rewrite. That
leaves hook authors unable to make the documented pre-execution
adjustment to a tool call before it runs.
## What
- Accept `updatedInput` from `PreToolUse` hooks when paired with
`permissionDecision: "allow"`.
- Apply the rewritten input before dispatch so the tool executes the
updated payload, not the original one.
- Preserve the stable hook-facing compatibility shapes that
participating tool handlers expose:
- Bash-like tools (`shell`, `container.exec`, `local_shell`,
`shell_command`, `exec_command`) use `{ "command": ... }`.
- `apply_patch` exposes its patch body through the same command-shaped
hook contract.
- MCP tools expose their JSON argument object directly.
- Keep each participating tool handler responsible for translating
hook-facing `updatedInput` back into its concrete invocation shape.
## Verification
Direct Bash-like rewrite coverage:
- `pre_tool_use_rewrites_shell_before_execution`
- `pre_tool_use_rewrites_container_exec_before_execution`
- `pre_tool_use_rewrites_local_shell_before_execution`
- `pre_tool_use_rewrites_shell_command_before_execution`
- `pre_tool_use_rewrites_exec_command_before_execution`
These cases assert that each supported Bash-like surface runs only the
rewritten command while the hook still observes the original `{
"command": ... }` input.
`pre_tool_use_rewrites_apply_patch_before_execution`
- Model emits one patch.
- Hook swaps in a different patch.
- Asserts only the rewritten file is created, and the hook saw the
original patch.
`pre_tool_use_rewrites_code_mode_nested_exec_command_before_execution`
- Model runs one nested shell command from code mode.
- Hook rewrites it.
- Asserts only the rewritten command runs, and the hook saw the original
nested input.
`pre_tool_use_rewrites_mcp_tool_before_execution`
- Model calls the RMCP echo tool.
- Hook rewrites the MCP arguments.
- Asserts the MCP server receives and returns the rewritten message, not
the original one.
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>
AbhinavandGitHub
