## Why
`execpolicy` currently keys `prefix_rule()` matching off the literal
first token. That works for rules like `["/usr/bin/git"]`, but it means
shared basename rules such as `["git"]` do not help when a caller passes
an absolute executable path like `/usr/bin/git`.
This PR lays the groundwork for basename-aware matching without changing
existing callers yet. It adds typed host-executable metadata and an
opt-in resolution path in `codex-execpolicy`, so a follow-up PR can
adopt the new behavior in `unix_escalation.rs` and other call sites
without having to redesign the policy layer first.
## What Changed
- added `host_executable(name = ..., paths = [...])` to the execpolicy
parser and validated it with `AbsolutePathBuf`
- stored host executable mappings separately from prefix rules inside
`Policy`
- added `MatchOptions` and opt-in `*_with_options()` APIs that preserve
existing behavior by default
- implemented exact-first matching with optional basename fallback,
gated by `host_executable()` allowlists when present
- normalized executable names for cross-platform matching so Windows
paths like `git.exe` can satisfy `host_executable(name = "git", ...)`
- updated `match` / `not_match` example validation to exercise the
host-executable resolution path instead of only raw prefix-rule matching
- preserved source locations for deferred example-validation errors so
policy load failures still point at the right file and line
- surfaced `resolvedProgram` on `RuleMatch` so callers can tell when a
basename rule matched an absolute executable path
- preserved host executable metadata when requirements policies overlay
file-based policies in `core/src/exec_policy.rs`
- documented the new rule shape and CLI behavior in
`execpolicy/README.md`
## Verification
- `cargo test -p codex-execpolicy`
- added coverage in `execpolicy/tests/basic.rs` for parsing, precedence,
empty allowlists, basename fallback, exact-match precedence, and
host-executable-backed `match` / `not_match` examples
- added a regression test in `core/src/exec_policy.rs` to verify
requirements overlays preserve `host_executable()` metadata
- verified `cargo test -p codex-core --lib`, including source-rendering
coverage for deferred validation errors
In a [recent PR](https://github.com/openai/codex/pull/9182), I made some
improvements to config error messages so errors didn't leave app server
clients in a dead state. This is a follow-on PR to make these error
messages more readable and actionable for both TUI and GUI users. For
example, see #9668 where the user was understandably confused about the
source of the problem and how to fix it.
The improved error message:
1. Clearly identifies the config file where the error was found (which
is more important now that we support layered configs)
2. Provides a line and column number of the error
3. Displays the line where the error occurred and underlines it
For example, if my `config.toml` includes the following:
```toml
[features]
collaboration_modes = "true"
```
Here's the current CLI error message:
```
Error loading config.toml: invalid type: string "true", expected a boolean in `features`
```
And here's the improved message:
```
Error loading config.toml:
/Users/etraut/.codex/config.toml:43:23: invalid type: string "true", expected a boolean
|
43 | collaboration_modes = "true"
| ^^^^^^
```
The bulk of the new logic is contained within a new module
`config_loader/diagnostics.rs` that is responsible for calculating the
text range for a given toml path (which is more involved than I would
have expected).
In addition, this PR adds the file name and text range to the
`ConfigWarningNotification` app server struct. This allows GUI clients
to present the user with a better error message and an optional link to
open the errant config file. This was a suggestion from @.bolinfest when
he reviewed my previous PR.
Adds an optional `justification` parameter to the `prefix_rule()`
execpolicy DSL so policy authors can attach human-readable rationale to
a rule. That justification is propagated through parsing/matching and
can be surfaced to the model (or approval UI) when a command is blocked
or requires approval.
When a command is rejected (or gated behind approval) due to policy, a
generic message makes it hard for the model/user to understand what went
wrong and what to do instead. Allowing policy authors to supply a short
justification improves debuggability and helps guide the model toward
compliant alternatives.
Example:
```python
prefix_rule(
pattern = ["git", "push"],
decision = "forbidden",
justification = "pushing is blocked in this repo",
)
```
If Codex tried to run `git push origin main`, now the failure would
include:
```
`git push origin main` rejected: pushing is blocked in this repo
```
whereas previously, all it was told was:
```
execpolicy forbids this command
```
Some effects of this change:
- New formatting changes across many files. No functionality changes
should occur from that.
- Calls to `set_env` are considered unsafe, since this only happens in
tests we wrap them in `unsafe` blocks
As described in detail in `codex-rs/execpolicy/README.md` introduced in
this PR, `execpolicy` is a tool that lets you define a set of _patterns_
used to match [`execv(3)`](https://linux.die.net/man/3/execv)
invocations. When a pattern is matched, `execpolicy` returns the parsed
version in a structured form that is amenable to static analysis.
The primary use case is to define patterns match commands that should be
auto-approved by a tool such as Codex. This supports a richer pattern
matching mechanism that the sort of prefix-matching we have done to
date, e.g.:
5e40d9d221/codex-cli/src/approvals.ts (L333-L354)
Note we are still playing with the API and the `system_path` option in
particular still needs some work.
