Claude Code History & Codex History Viewer

Read, search and export your local Claude Code history and Codex history in VS Code, with tool calls, file edit diffs and token totals, without ever changing a session file.

The screenshot is the real session view, rendered by the extension's own webview code from a synthetic demo session in test/fixtures (no real transcript). scripts/screenshot/shot.js makes it in a headless browser.

Why use it

1. One view for both tools. Claude Code sessions from ~/.claude/projects and Codex sessions from ~/.codex/sessions sit in one tree, grouped by project folder.
2. You see what the agent changed. Edit, MultiEdit, Write and apply_patch calls show as red and green diffs, and every tool call keeps its input and output one click away.
3. Read-only and offline. The extension only reads session files. It never writes, moves or deletes them, makes no network calls and sends no telemetry.

Quick start

1. Install the extension and click the Agent Sessions icon in the activity bar.
2. Click a session. To find something across all sessions, click the search icon at the top of the view.

What the session view shows

• A header with the tool, model, project folder, git branch, start time, duration, turn count, token totals (input, output, cache read, cache write, reasoning) and the cost when the file records it. Claude Code writes the cost, Codex does not.
• User and assistant turns, in file order.
• Tool calls, collapsed, with their input and output. Failed calls get a red mark.
• File edits as diffs. Edit calls show the changed lines with context, Write shows the new file and apply_patch shows each file in the patch.
• Thinking (Claude Code) and reasoning summaries (Codex), collapsed.
• Subagent turns, indented under the call that started them.
• Notes for record types it does not know and for lines that are not valid JSON. It skips them and keeps going.

Search across sessions

Run "Agent Sessions: Search Sessions". The search reads each file line by line in the extension host, so the editor stays responsive. A progress message shows how many files are done, and Cancel stops it and keeps the results found so far. Pick a result to open the session at that spot.

Export and resume

• Export Markdown writes a .md file where you choose. Before it writes, it reminds you that transcripts can hold secrets, and it offers Export without tool outputs, which leaves out command output and file contents.
• Copy resume command copies claude --resume <id> or codex resume <id>, with a cd into the project folder first. Turn the cd off with agentSessionViewer.resumeWithCd.

Both actions sit in the session toolbar and in the right-click menu of the tree.

Open a session file directly

Files under .claude/projects and .codex/sessions open in the viewer by default. For a session file somewhere else (one a teammate sent you, say), right-click it, pick Open With and choose Agent Session Viewer. The viewer checks the first 20 records and tells you if the file is not a session. Open as text opens the raw file in a read-only editor.

Settings

Large files

Files are streamed, never read in one piece. The first turns appear while the rest is still loading, and the view adds more as you scroll. Very long tool outputs are cut to 40,000 characters in the view. The tree reads the first 256 KB of each file for its label, then counts turns in the background.

Privacy

Session transcripts hold your prompts, code, paths and sometimes secrets. Agent Session Viewer reads them on your machine and keeps what it reads in memory only. The webview runs under a strict Content Security Policy with no remote scripts, and all file content is inserted as text, never as HTML.

Limits

• Session formats change often. Unknown record types are counted and skipped, so a new release of either tool may show less detail until this extension catches up.
• Codex usually stores reasoning encrypted. Only the reasoning summaries it writes in plain text can be shown.
• Search matches plain text, not regular expressions, and stops at 300 results.
• The cost shown is the figure the file records. The extension does not price tokens itself.

Agent Session Viewer is not made by or affiliated with Anthropic or OpenAI. Claude Code and Codex are named only to say which session files it reads.

Using it with JSONL Viewer

If you also have JSONL Viewer installed, VS Code asks which editor should open session files. Pick "Configure Default" once and choose Agent Session Viewer. The sidebar tree always opens sessions here.

Support

Zovo extensions have no ads and no tracking, and sponsors pay for the time that goes into fixes and new viewers. You can sponsor the work on GitHub Sponsors.

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Coming soon to the Marketplace, with the code on GitHub now.

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