[Feature]: Add per-commit views to the Diff pane

[dain]

Before submitting

• I searched existing issues and did not find a duplicate.
• I am describing a concrete problem or use case, not just a vague idea.

Area

apps/web

Problem or use case

The Diff pane currently lets me inspect Working tree, Branch changes, Latest turn, or individual Turns.

Branch changes is cumulative, while Turns are based on T3 checkpoints. Neither option lets me review the actual Git commits on the current branch one at a time.

When an agent creates several commits, I want to inspect the exact diff introduced by each commit without leaving T3. Today I have to use git show, GitHub, or another Git client, losing the integrated Diff pane workflow.

Proposed solution

Add a “Commits” submenu to the existing diff-source picker, parallel to the existing “Turns” submenu. This is similar to the design in Codex.

The submenu should list the commits included in the current Branch changes range, showing at least each commit’s subject and age. Selecting a commit should display only the changes introduced by that commit — its parent-to-commit diff — using the existing Diff pane renderer and controls.

The other sources, such as Working tree, Branch changes, Latest turn, and Turns, should remain available as they are today.

Why this matters

Agents frequently produce a stack of commits, and reviewing only the cumulative branch diff can hide whether changes were divided into coherent commits.

A commit-by-commit view would make it easier to review history before opening a PR, understand why a change was introduced, and catch commits that contain unrelated or incomplete work. Codex has a similar view, and it is especially useful when reviewing agent-generated changes.

Smallest useful scope

List the commits in the existing Branch changes range and allow selecting one to view its parent-to-commit diff in the web Diff pane and desktop wrapper.

It should fetch the selected commit’s patch on demand rather than loading every commit’s patch up front.

Alternatives considered

The only alternative is to use an external tool.

Risks or tradeoffs

• The commit list should be limited to the relevant branch range so large repository histories are not loaded unnecessarily. Maybe cap the commit list to not consume too much memory if there is a massive list.
• Merge commits need a defined comparison parent; using the first parent would match common git show behavior.
• Rebasing or otherwise rewriting the branch can invalidate the selected commit, so the pane should fall back gracefully.
• Commit patches should be loaded only when selected to avoid unnecessary server, WebSocket, and rendering cost.

Examples or references

Codex provides a commit-by-commit diff view with a commit selector.

Related but not duplicate T3 work:

• PR feat: multi-provider pull requests page with in-app reviews #4849 adds per-commit selection to the Pull Requests Code view:
  feat: multi-provider pull requests page with in-app reviews #4849
• PR feat(vcs): add actionable Version Control to web and mobile #3177 adds commit history and details in a separate Version Control panel:
  feat(vcs): add actionable Version Control to web and mobile #3177
• PR feat(web): add a since-fork diff scope #5193 proposes a cumulative “Since fork” scope rather than individual commit diffs:
  feat(web): add a since-fork diff scope #5193

Contribution

• I would be open to helping implement this.

[dain]

I had codex do an implementation of this and it took about 20m, but I'm not a front end dev, so I figured it would be easier to post an issue then asking for a code review. If you want, I can post the changes as a PR.

[Bil0000]

This & more is already implemented in #4849

It will be merged to nightly soon

[xixixao]

@Bil0000 the changes did not implement the ability to review a single local commit.

[Bil0000]

Will get a PR up soon

[Kameleon21]

+1. Agents often produce a stack of commits, and reading them one at a time is the natural way to review that work.

An idea on top of this: once the Commits picker exists, each commit could get a short AI-generated title and summary, such as "Update X so it does Y", with the files and folders it changed listed beneath. Many agent-written commit subjects are vague, and a one-line summary makes it easy to pick the commit you want. A small or cheap model is enough for this, ideally the guide model already configured for review guides (#18124).

The same per-commit grouping could also drive a "group by commit" mode for review guides in the PR sidebar. I've added more detail in #16824.

[sssilvar]

Follow-up for reviewing a stack of commits one at a time: #31564 proposes ‹ sha⌄ › controls in the diff header to step to the previous or next commit, with an implementation in #31505.