feat: select between Codex and Claude

.github/homebrew/git-aicommit.rb

@@ -5,7 +5,7 @@
 #   ruby -c .github/homebrew/git-aicommit.rb
 #   brew style .github/homebrew/git-aicommit.rb
 class GitAicommit < Formula
-  desc "Generate git commit messages from staged diffs using Claude"
+  desc "Generate git commit messages using Codex or Claude"
   homepage "https://github.com/getkono/git-aicommit"
   version "__VERSION__"
   license any_of: ["MIT", "Apache-2.0"]
@@ -38,12 +38,17 @@ def install
 
   def caveats
     <<~EOS
-      git-aicommit shells out to two tools this formula does NOT install:
-        * git           (brew install git, or use your system git)
-        * claude        the Claude Code CLI, which is not available in Homebrew.
-                        Install and authenticate it per:
+      git-aicommit shells out to git and one supported agent CLI. This formula
+      does NOT install them:
+        * git           brew install git, or use your system git
+        * codex         install and authenticate OpenAI Codex:
+                        https://developers.openai.com/codex/cli/
+        * claude        install and authenticate Claude Code:
                         https://docs.claude.com/en/docs/claude-code
 
+      Only one agent CLI is required. When both are installed, Codex is used by
+      default; pass --agent claude to override it.
+
       Invoke it as a git subcommand once installed:  git aicommit
     EOS
   end

Cargo.toml

@@ -14,11 +14,12 @@ homepage = "https://github.com/getkono/git-aicommit"
 
 [workspace.dependencies]
 aicommit-core = { version = "0.2.0", path = "crates/aicommit-core" }
-agent-text = { version = "0.1.0", default-features = false }
+agent-text = { version = "0.1.1", default-features = false }
 clap = { version = "4", features = ["derive"] }
 indicatif = "0.17"
 thiserror = "2"
 tokio = { version = "1", features = ["macros", "rt"] }
+which = "8"
 
 # Must live at the workspace root: a `[profile.*]` table in a member manifest is
 # ignored (with only a warning), which would silently drop these from releases.

README.md

@@ -1,17 +1,19 @@
 # git-aicommit
 
 A tiny Rust CLI that drafts a commit message from your staged changes using
+[OpenAI Codex](https://developers.openai.com/codex/cli/) or
 [Claude Code](https://docs.claude.com/en/docs/claude-code), then opens
 `git commit` with the message pre-filled so you can review, edit, or abort.
-The model is picked automatically from the diff size — Haiku for everyday
-commits, Sonnet for large ones — or pinned with `--model`.
+When both agent CLIs are installed, Codex is preferred; use `--agent` to choose
+explicitly. The model is picked automatically from the diff size or pinned with
+`--model`.
 
 ## How it works
 
 1. Parses standard `git commit` flags (see [Supported flags](#supported-flags)) to decide what to diff and how to prompt.
 2. Checks you're in a git repo and that there's something to commit.
 3. For plain and `--amend` commits, runs the `pre-commit` hook as an early check (`git hook run` on Git ≥ 2.36, executing the hook script directly on older git) — if it fails, the tool aborts before making any API call. (For `-a` and pathspec commits the staged index isn't what gets committed, so hooks run at commit time instead.)
-4. Picks a model from the diff size (Haiku by default; Sonnet with higher effort for large or many-file diffs, announced on its own line) unless you pin one with `--model`, then feeds the relevant diff to `claude -p` over stdin.
+4. Selects Codex first when available, otherwise Claude, unless you pin one with `--agent`. It picks a provider-specific model from the diff size (Luna/Terra for Codex, Haiku/Sonnet for Claude) unless you pin one with `--model`, then sends the relevant diff to that local agent CLI.
 5. Cleans up the response and runs `git commit -e -m "<message>" …`, inheriting your terminal so `$EDITOR` opens normally.
 
 Large diffs are truncated at 60KB to keep the prompt sane.
@@ -20,8 +22,10 @@ Large diffs are truncated at 60KB to keep the prompt sane.
 
 - Rust (stable)
 - `git` (any reasonably recent version; the pre-commit pre-check uses `git hook run` on ≥ 2.36 and falls back to running the hook script directly on older git)
-- [`claude`](https://docs.claude.com/en/docs/claude-code) CLI, installed and authenticated
-  (tested with Claude Code 2.x; requires a version that supports `--output-format json` and `--disable-slash-commands`)
+- At least one supported agent CLI installed and authenticated:
+  - [`codex`](https://developers.openai.com/codex/cli/) 0.146.0 or newer
+  - [`claude`](https://docs.claude.com/en/docs/claude-code) 2.x with
+    `--output-format json` and `--disable-slash-commands` support
 
 ## Install
 
@@ -31,8 +35,9 @@ Large diffs are truncated at 60KB to keep the prompt sane.
 brew install getkono/tap/git-aicommit
 ```
 
-`git-aicommit` calls the [`claude`](https://docs.claude.com/en/docs/claude-code) CLI (not in Homebrew) and
-`git` at runtime — see [Requirements](#requirements). `brew info getkono/tap/git-aicommit` repeats this.
+`git-aicommit` calls `git` and one of the supported agent CLIs at runtime; the
+formula does not install those tools. See [Requirements](#requirements).
+`brew info getkono/tap/git-aicommit` repeats this.
 
 **From crates.io** (requires Rust):
 
@@ -67,7 +72,13 @@ git aicommit
 
 Your editor opens with the AI-generated message. Save to commit, or quit with an empty message to abort.
 
-`git aicommit` aims to be a drop-in for `git commit`: it understands the common flags and forwards anything else straight through. By default it auto-selects the model from the diff size (`haiku`, or `sonnet` with higher effort for large/many-file diffs, announced when it isn't haiku); pass `--model <name>` to pin one (before any git flags). Run `git aicommit --help` for a summary, or `git aicommit --version` to print the version, build metadata, and binary path.
+`git aicommit` aims to be a drop-in for `git commit`: it understands the common
+flags and forwards anything else straight through. It uses Codex when `codex`
+is on `PATH`, otherwise Claude when `claude` is available. Pass
+`--agent codex|claude` to override that choice. By default it selects
+`gpt-5.6-luna` or `gpt-5.6-terra` for Codex and `haiku` or `sonnet` for Claude,
+escalating on large or many-file diffs. Pass `--model <name>` to pin a model for
+the selected agent. `--agent` and `--model` must come before any Git flags.
 
 ### Supported flags
 
@@ -83,6 +94,8 @@ git aicommit --amend           # regenerate the message from the previous messag
 **Steer the AI:**
 
 ```sh
+git aicommit --agent claude                       # override Codex-first detection
+git aicommit --agent codex --model gpt-5.6-terra # pin both agent and model
 git aicommit -m "call out the perf fix"     # an instruction, NOT a literal message (repeatable)
 git aicommit -t .gitmessage                 # make the output follow a template file
 ```
@@ -137,7 +150,9 @@ git aicommit -- --weird-filename
 - The prompt asks for Conventional Commits style (`feat:`, `fix:`, etc.), imperative subject ≤72 chars, optional body explaining the *why*.
 - When a commit bundles several unrelated changes, the message leads with the primary one in the subject and itemizes the rest as body bullets. A `git diff --stat` inventory of every changed file is sent alongside the diff so small or buried changes aren't dropped.
 - By default the editor opens so you can review before committing; quit with an empty message to abort. `-y`/`--yes` (or `--no-edit`) commits the generated message directly, and `--dry-run` never commits.
-- No API key handling here; auth is delegated entirely to the `claude` CLI.
+- No API key handling here; auth is delegated entirely to the selected local
+  `codex` or `claude` CLI. If neither executable is installed, generation exits
+  with an actionable error.
 
 ## Using it from your own application
 
@@ -147,7 +162,9 @@ editor wanting an AI-drafted message for its commit box, say. Hand it a diff and
 it hands you a string; what you do with that string is yours. It never invokes
 `git`, and it accepts any async
 [`agent_text::Agent`](https://docs.rs/agent-text/latest/agent_text/trait.Agent.html).
-The application chooses the concrete adapter; this CLI uses
+The application chooses the concrete adapter; this CLI selects between
+[`agent_text::Codex`](https://docs.rs/agent-text/latest/agent_text/struct.Codex.html)
+and
 [`agent_text::ClaudeCode`](https://docs.rs/agent-text/latest/agent_text/struct.ClaudeCode.html).
 
 ```rust,no_run

crates/aicommit-core/README.md

@@ -38,6 +38,10 @@ println!("{}", generated.message);
 # }
 ```
 
+`auto_select` preserves the default Claude model tiers. Frontends selecting a
+different provider can call `auto_select_with_models` with model names that
+provider understands while reusing the same diff thresholds and effort policy.
+
 See `examples/editor.rs` for a runnable version.
 
 `CommitRequest` also carries a template, steering instructions, a changed-file

crates/aicommit-core/src/lib.rs

@@ -48,7 +48,7 @@ pub use agent_text::{Agent, GenerationRequest, Usage};
 pub use error::{CoreError, Result};
 pub use model::{
     ESCALATE_DIFF_BYTES, ESCALATE_FILE_COUNT, Effort, LARGE_DIFF_MODEL, ModelChoice,
-    SMALL_DIFF_MODEL, auto_select,
+    SMALL_DIFF_MODEL, auto_select, auto_select_with_models,
 };
 pub use prompt::{
     DEFAULT_MAX_DIFF_BYTES, build_prompt, build_prompt_with_max, build_system_prompt, truncate_diff,

crates/aicommit-core/src/model.rs

@@ -38,14 +38,27 @@ pub const LARGE_DIFF_MODEL: &str = "sonnet";
 /// secondary changes aren't lost in the summary. Pass the *full* diff length,
 /// before any truncation.
 pub fn auto_select(diff_len: usize, file_count: usize) -> ModelChoice {
+    auto_select_with_models(diff_len, file_count, SMALL_DIFF_MODEL, LARGE_DIFF_MODEL)
+}
+
+/// Choose between caller-supplied small- and large-diff models.
+///
+/// This keeps the selection thresholds and effort policy provider-neutral while
+/// allowing a frontend to supply model names understood by its chosen agent.
+pub fn auto_select_with_models(
+    diff_len: usize,
+    file_count: usize,
+    small_model: &str,
+    large_model: &str,
+) -> ModelChoice {
     if diff_len >= ESCALATE_DIFF_BYTES || file_count >= ESCALATE_FILE_COUNT {
         ModelChoice {
-            model: LARGE_DIFF_MODEL.to_string(),
+            model: large_model.to_string(),
             effort: Some(Effort::Medium),
         }
     } else {
         ModelChoice {
-            model: SMALL_DIFF_MODEL.to_string(),
+            model: small_model.to_string(),
             effort: None,
         }
     }
@@ -78,9 +91,24 @@ mod tests {
         assert_eq!(auto_select(100, ESCALATE_FILE_COUNT), large());
     }
 
+    #[test]
+    fn auto_select_accepts_provider_model_names() {
+        assert_eq!(
+            auto_select_with_models(0, 1, "gpt-small", "gpt-large"),
+            ModelChoice::new("gpt-small")
+        );
+        assert_eq!(
+            auto_select_with_models(ESCALATE_DIFF_BYTES, 1, "gpt-small", "gpt-large",),
+            ModelChoice {
+                model: "gpt-large".to_string(),
+                effort: Some(Effort::Medium),
+            }
+        );
+    }
+
     #[test]
     fn effort_wire_form() {
-        // Agent adapters pass this through; "medium" is what Claude expects.
+        // Bundled agent adapters pass these stable wire names through.
         assert_eq!(Effort::Medium.as_str(), "medium");
         assert_eq!(Effort::Low.to_string(), "low");
         assert_eq!(Effort::High.to_string(), "high");

crates/git-aicommit/Cargo.toml

@@ -1,9 +1,9 @@
 [package]
 name = "git-aicommit"
 version = "1.4.0"
-description = "Generate git commit messages from staged diffs using Claude."
+description = "Generate git commit messages from staged diffs using local AI agent CLIs."
 readme = "../../README.md"
-keywords = ["git", "commit", "ai", "claude", "cli"]
+keywords = ["git", "commit", "ai", "claude", "codex"]
 categories = ["command-line-utilities", "development-tools"]
 edition.workspace = true
 rust-version.workspace = true
@@ -14,8 +14,9 @@ homepage.workspace = true
 
 [dependencies]
 aicommit-core.workspace = true
-agent-text = { workspace = true, features = ["claude-code"] }
+agent-text = { workspace = true, features = ["claude-code", "codex"] }
 clap.workspace = true
 indicatif.workspace = true
 thiserror.workspace = true
 tokio.workspace = true
+which.workspace = true