jj-guide

jj Guide for AI Agents

Critical Rules

• NEVER run git commands in a jj repo. Use jj equivalents exclusively.
• ALWAYS use -m flags for commit/describe. Without -m, editors open and hang the agent.
• NEVER use -i flags. Interactive TUI hangs in agent environments.
• After jj commit -m "msg": content is in @- (parent). New @ is empty. Target @- for bookmarks and pushes.
• Use change IDs (letters, e.g. nmwwolux) over commit IDs (hex). Change IDs are stable across rewrites.

Mental Model

• Working copy IS a commit (@). File edits auto-amend into @.
• No staging area. No git add. All file changes are tracked automatically.
• Commits are mutable until pushed.
• Conflicts are stored in commits — resolve later, not at merge time.
• Operation log records everything. jj undo reverts any operation.

Multi-Agent Bookmark Model

Each agent operates on its own named bookmark, branched from main. Isolation is structural — one bookmark per concern, not reactive splitting after the fact.

Start work (one bookmark per agent/feature)

Use /jj-workspace to create an isolated workspace with GIT_DIR wiring, or manually:

jj new main -m "feat: description"
jj bookmark create <feature-name> -r @   # bookmark tracks this change ID
# ... work ... (auto-tracked)
jj commit -m "feat: description"
# bookmark already points at @- (the content) — no set needed
jj git push -b <feature-name>

Why @ not @- on create?

The bookmark tracks the change ID, not the graph position. After jj commit, the change (with content) becomes @- and the bookmark still points at it.

Bookmark lifecycle

• Create before work: jj bookmark create <name> -r @ — gives agent context immediately
• After commit: verify with jj bookmark list — bookmark should point at @-
• After PR merges: clean up with jj bookmark delete <feature-name>
• Fix mispointed bookmark: jj bookmark set <name> -r <change-id>

Workspaces in colocated repos

Secondary workspaces created by jj workspace add lack a .git/ directory. The WorktreeCreate hook handles this automatically by writing a .envrc that sets $GIT_DIR. If gh CLI is not working in a worktree, verify direnv is installed and run direnv allow (or source .envrc) in that directory.

Common Workflows

Amend current change

jj describe -m "better message"     # change message only
jj squash                           # fold @ into parent

Address PR review (rewrite)

jj edit <change-id>                 # make it working copy
# ... fix ...
jj new                              # done editing
jj git push                         # auto force-push

Address PR review (additive)

jj new <bookmark-tip>
# ... fix ...
jj commit -m "address review"
jj bookmark set <name> -r @-
jj git push -b <name>

Sync after PR merge (fast-forward)

jj git fetch
jj bookmark set main -r main@origin   # advance local bookmark

Sync with local commits on top

jj git fetch
jj bookmark set main -r main@origin
jj rebase -d main@origin               # rebase YOUR commits, not main

Never jj rebase -s main — main is an immutable tracked bookmark. Target the commit above it.

Selective operations with filesets

# Commit only some files:
jj commit -m "msg" file1.rs file2.rs

# Commit by glob pattern:
jj commit -m "msg" 'glob:src/**/*.rs'

# Restore specific files:
jj restore --from @- file.txt

# Split a change (non-interactive):
jj split 'glob:tests/**'            # tests go to first commit, rest stays

Advanced operations

# Auto-route hunks to correct ancestor commits:
jj absorb

# Compare how a change evolved across rewrites:
jj interdiff --from <rev1> --to <rev2>

Git → jj Quick Reference

Task	git	jj
Status	git status	jj st
Diff	git diff	jj diff
Log	git log	jj log
Show commit	git show <ref>	jj show <rev>
Stage + commit	git add . && git commit -m "msg"	jj commit -m "msg"
Amend	git commit --amend	jj squash or jj describe -m "msg"
Push	git push	jj git push
Fetch	git fetch	jj git fetch
Pull (fast-forward)	git pull	jj git fetch && jj bookmark set main -r main@origin
Pull (rebase local)	git pull --rebase	jj git fetch && jj rebase -d main@origin
Switch branch	git checkout <branch>	jj new <rev> or jj edit <rev>
Create branch	git checkout -b <name>	jj new main -m "desc" (+ bookmark later)
List branches	git branch	jj bookmark list
Stash	git stash	jj new (old work stays in parent)
Stash pop	git stash pop	jj edit <prev-change-id>
Cherry-pick	git cherry-pick	jj duplicate <rev>
Revert	git revert	jj revert -r <rev>
Rebase	git rebase <base>	jj rebase -d <dest>
Blame	git blame	jj file annotate
Worktree	git worktree add	jj workspace add
Undo last	(complex)	jj undo

Full mapping: see references/git-to-jj.md

Revset Quick Reference

Expression	Meaning
@	Current working copy
@-	Parent of working copy
@--	Grandparent of working copy
trunk()	Main/master branch tip
mine()	Changes authored by you
bookmarks()	All bookmark tips
remote_bookmarks()	All remote bookmark tips
x::y	DAG range: ancestors of y that are descendants of x
::x	All ancestors of x
x..y	Set difference: (::y) ~ (::x) — commits in y but not x
heads(x)	Commits in x with no children in x
roots(x)	Commits in x with no parents in x
description(pat)	Commits whose description matches pattern
file(path)	Commits that modified the given path
present(x)	x if it exists, empty set otherwise
empty()	Commits with no diff
conflicts()	Commits with unresolved conflicts
x | y	Union
x & y	Intersection
~x	Complement (not in x)

Workspace Model

• Colocated: both .jj/ and .git/ exist. Git tools read .git/ naturally.
• Claude Code: WorktreeCreate hook → jj workspace add + .envrc for $GIT_DIR. Automatic.
• Codex: built-in worktree toggle uses git worktrees; jj auto-imports changes.
• Multi-agent isolation: one bookmark per agent/feature (see above) + workspace per agent for filesystem isolation.

Common Pitfalls

1. Bookmarks don't auto-advance after commit. bookmark create tracks the change ID (stays correct). bookmark set on named bookmarks like main needs -r @- explicitly.
2. @ after jj commit is empty. Content is in @-. Don't push @ — push @-.
3. jj new ≠ git commit. jj new = new empty change. jj commit = finalize @.
4. :: is DAG range, .. is set difference. They are NOT interchangeable.
5. Empty commits are normal — they mean "ready to work here."
6. Forgot to describe? Use jj describe -m "msg" on @ or jj describe -m "msg" -r <rev> on any mutable commit.
7. Commit is immutable error — you targeted a tracked bookmark (e.g. main) directly in a rebase. Target the commit above it, or use main@origin as the destination instead.

Troubleshooting

• Undo anything: jj undo
• See operation history: jj op log
• Restore to past state: jj op restore <op-id>
• Stale workspace: jj workspace update-stale
• Complex issues (Claude Code): invoke jj-doctor
• Complex issues (Codex): describe problem, check jj op log, try jj undo