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You can hand off coding work between Claude Code and Codex, but treat it as a transfer of project state—not a transfer of conversation history. Keep both tools pointed at the same repository, record the current branch, changes, decisions, checks, and next step in a concise handoff note, then ask the receiving tool to inspect that state before it edits.
What transfers—and what does not
Claude Code and Codex each document ways to resume their own saved conversations: Claude Code provides claude --continue, claude --resume, and in-session /resume; Codex CLI provides codex resume. These are tool-specific session features, not evidence that one product can import the other’s conversation. The official documentation cited here does not describe a supported, lossless conversion between their transcripts.
The dependable bridge is the shared repository plus explicit task notes. The repository carries code and committed artifacts, but not every decision or instruction from a conversation. Claude also describes its JSONL transcript format as internal and subject to change, and points users to supported export or script interfaces rather than parsing transcript internals. See Claude Code session management and Codex CLI documentation.
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Prepare the repository before switching
Before leaving either tool, make the working state legible to someone who has not seen the conversation. These checks are practical workflow advice, not a guarantee supplied by either product.
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- Identify the repository, current branch, and worktree.
- Inspect
git statusand the relevant diff. Name uncommitted changes and distinguish intentional work from unrelated edits. - If you commit or stash changes, record the commit or stash reference. Do not assume the other tool has the same session state just because it can access the repository.
- Record verification precisely: the command run and its actual result. Mark checks that were not run as “not run.”
- State what remains, any blocker, and the single most useful next action.
Keep project instructions separate from the task handoff
Use project instruction files for recurring conventions and a task note for transient progress. Codex documents AGENTS.md discovery across global, project, and nested scopes; Anthropic documents CLAUDE.md as project context Claude Code reads for the applicable directory. These conventions are not interchangeable by default: the cited documentation does not establish that Claude Code automatically reads AGENTS.md or that Codex automatically reads CLAUDE.md.
Codex can be configured to use fallback instruction filenames, but that does not mean Claude Code recognizes those names. If both instruction files are needed, keep shared guidance aligned and place tool-specific directions in the relevant file. Details are in Codex’s AGENTS.md instructions and Anthropic’s CLAUDE.md and prompting guidance.
Create a concise HANDOFF.md (or another clearly named task note) with:
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- Current state: completed, in-progress, and blocked work.
- Decisions: choices that affect the implementation and rejected approaches the next tool should not repeat.
- Files and locations: changed files and the relevant areas to inspect.
- Branch and worktree: where the work lives and any commit or stash reference.
- Checks: exact commands and actual results, including checks not run.
- Risks and constraints: compatibility, security, scope, permissions, and files that must not change.
- Next action: the next useful step, stated plainly.
Hand off from Claude Code to Codex
- Review Claude Code’s work. Inspect the branch, status, and relevant diff; record the completed work and verification results in the handoff note.
- Open Codex in the same repository. Point it to
HANDOFF.mdand any relevant files. Codex’s CLI documentation describes working against a local repository and using project instructions. - Ask for an inspection before edits. For example:
Continue the task in
HANDOFF.md. First inspect the current branch, working tree, and relevant diff. Summarize the goal, decisions already made, checks actually run, and proposed next step. Do not repeat completed work. If the repository state conflicts with the handoff note, report the conflict and ask before overwriting changes. Then continue within the stated scope and report files changed and verification results. - Resolve discrepancies before proceeding. If the actual files or Git state do not match the note, have Codex report the mismatch rather than overwrite uncertain work.
Hand work back from Codex to Claude Code
- Update the same handoff note. Record Codex’s changes, the current diff, checks actually run, outstanding work, and any changed assumptions.
- Return to Claude Code in the same repository. Resume the relevant Claude conversation if useful, or start a fresh one and provide the handoff note and relevant files.
- Have Claude verify the current state first. Ask it to inspect the branch and diff, compare them with the note, and identify the next action before editing.
To return to a Claude Code conversation, its session documentation lists claude --continue for the most recent conversation in the current directory, claude --resume for a session picker, claude --resume <name> for a named conversation, and /resume within a session. It also documents /export for saving a readable transcript. To return to a Codex chat, Codex CLI documents codex resume for saved-chat resumption. These commands resume the respective tool’s own session; they do not replace checking the current repository state.
Choose between resuming and starting fresh
| Situation | Useful approach | What to verify |
|---|---|---|
| Returning to the same tool and its earlier discussion is relevant | Use that tool’s own session-resumption feature. | Check that the branch, working tree, and diff still match the conversation. |
| Switching to the other tool | Use the repository and a written handoff note to reconstruct task context. | Confirm the receiving tool understands the goal, current changes, constraints, and next step. |
| Starting a fresh session in either tool | Provide the project instructions, handoff note, and relevant files. | Ask for an inspection and summary before authorizing edits. |
A resumed conversation can provide useful history, but it may no longer describe the current files. A fresh session can work well when the task note is complete and the receiving tool checks the repository before acting.
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