[BUG] Session history / resume list is silently empty on Windows when the workspace is on a `subst` drive

Preflight Checklist

• [x] I have searched existing issues and this hasn't been reported yet
• [x] This is a single bug report (please file separate reports for different bugs)
• [x] I am using the latest version of Claude Code

What's Wrong?

The extension resolves the workspace path with two different realpath implementations that disagree on Windows subst drives. Transcripts are written under a project key derived from the unresolved path (x--myproject), but the session lister reads from a key derived from the natively-resolved path (C--Apache2-htdocs-myproject). That second directory never exists, readdir throws, the error is swallowed, and listSessions() returns zero sessions.

Every past conversation becomes invisible in the UI. No error is shown or logged. The transcripts are intact on disk the whole time and resume correctly via claude.exe --resume <id>, so this is purely a listing bug — but it reads to the user as "my sessions were never saved".

subst is common in Apache/PHP/XAMPP setups, where a drive letter is mapped to the docroot.

What Should Happen?

Past conversation should show in the UI.

Error Messages/Logs

Steps to Reproduce

1. subst X: C:\Apache2\htdocs (any target works; an Apache docroot is the common real-world case).
2. mkdir C:\Apache2\htdocs\myproject
3. Open X:\myproject as the workspace folder in VS Code.
4. Start a Claude Code conversation and send at least one message.
5. Confirm the transcript exists at %USERPROFILE%\.claude\projects\x--myproject\<uuid>.jsonl.
6. Confirm %USERPROFILE%\.claude\projects\C--Apache2-htdocs-myproject does not exist.
7. Reload the window (or start a new conversation).
8. Open the Session history list.

Expected: the conversation from step 4 is listed and resumable.
Actual: only the live conversation is listed. The step-4 session never appears, with no error.

Claude Model

Opus

Is this a regression?

No, this never worked

Last Working Version

_No response_

Claude Code Version

2.1.212

Platform

Anthropic API

Operating System

Windows

Terminal/Shell

VS Code integrated terminal

Additional Information

Note: All below written by Claude - problem identified.

Environment

| Component | Version |
|---|---|
| VS Code | 1.128.1 |
| Claude Code extension | anthropic.claude-code 2.1.212 (win32-x64) |
| Bundled CLI (resources/native-binary/claude.exe) | 2.1.212 |
| Claude Agent SDK (CLAUDE_AGENT_SDK_VERSION in bundle) | 0.3.212 |
| OS | Windows 10 Pro 22H2 (10.0.19045) |
| Node used for the standalone repro | v22.16.0 |
| Drive mapping | subst X: C:\Apache2\htdocs |

Symptom

• The Session history list shows only the currently-active conversation.
• All previous sessions for the workspace are missing, permanently.
• No error, no entry in the extension output channel.
• The transcripts exist and are valid: %USERPROFILE%\.claude\projects\x--myproject\<uuid>.jsonl
• claude.exe --resume <uuid> resumes them correctly — so the data layer is fine and only the listing path is broken.

Root cause

The writer keeps the subst drive letter; the reader resolves it away.

Identifiers below are the minified names in extension.js as shipped in 2.1.212, with their semantics, since the mapping to source names isn't public.

Writer (observed behaviour): transcripts are persisted under the project key derived from the unresolved cwd — x:\myproject → %USERPROFILE%\.claude\projects\x--myproject\.

this.cwd — in the webview view provider (resolveWebviewView), the workspace root is resolved with the JS implementation, which preserves the subst drive:

let o = fs.realpathSync(workspaceFolders[0].uri.fsPath || os.homedir()).normalize("NFC");
// -> 'x:\myproject'

Reader — listSessions() passes that value as dir:

async listSessions() {
  let e = await xme({
    dir: this.cwd,                                    // 'x:\myproject'
    includeWorktrees: false,
    includeProgrammatic: this.includeProgrammaticSessions
  });
  ...
}

xme → mRt → pRt, which resolves dir a second time, via Zpe:

async function Zpe(e) {
  try { return Hd(await fs.promises.realpath(e)) } catch { return Hd(e) }
}

fs.promises.realpath is the native binding (uv_fs_realpath → GetFinalPathNameByHandle on Windows), not the JS implementation used above. It resolves the subst mapping to C:\Apache2\htdocs\myproject.

That resolved path is then slugged and joined to the projects directory:

function dx(e)  { return e.replace(/[^a-zA-Z0-9]/g, "-") }        // path -> project key
function px()   { return path.join(configDir(), "projects") }
function UAt(e) { return path.join(px(), dx(e)) }

async function wb(e) {
  let t = UAt(e), r = [];
  try { await fs.promises.readdir(t), r.push(t) } catch {}          // <-- ENOENT swallowed
  let n = dx(e);
  if (n.length <= 200) return r;                                    // returns []
  ...
}

So the lister looks in %USERPROFILE%\.claude\projects\C--Apache2-htdocs-myproject, which has never existed. readdir throws ENOENT, the catch {} discards it, wb returns [], no transcript files are discovered, and listSessions() returns an empty array.

The realpath divergence, isolated

This reproduces with plain Node and no VS Code involved:

const fs = require('fs');
const p = 'x:\\myproject';               // subst X: C:\Apache2\htdocs

fs.realpathSync(p);                      // 'x:\myproject'                    <- writer / this.cwd
fs.realpathSync.native(p);               // 'C:\Apache2\htdocs\myproject'
fs.promises.realpath(p);                 // 'C:\Apache2\htdocs\myproject'     <- Zpe / reader

fs.realpathSync is a JS path-walk and preserves the subst drive letter. fs.promises.realpath and fs.realpathSync.native both call the native binding and resolve it. The two call sites therefore derive two different project keys from the same workspace.

Why the active conversation still shows (and masks the bug)

In the webview's doListSessions(), results from listSessions() are merged into an existing list, while the active session object exists independently of that call:

for (let a of i.sessions) {
  if (!a.isCurrentWorkspace) continue;
  ...
}

An empty listSessions() therefore renders as "only the current conversation" rather than an empty list or an error. This is what makes the failure so hard to diagnose from the UI — it looks like an over-aggressive filter rather than a read from a non-existent directory.

For the record, these are not involved, though they look like plausible culprits:

• isCurrentWorkspace (Jjt) only special-cases .claude/worktrees/<name> paths and returns true for all ordinary paths.
• includeProgrammatic: false only excludes entrypoints sdk-cli / sdk-ts / sdk-py; affected sessions record claude-vscode.
• hiddenSessionIds in globalState is unset.

Steps to reproduce

1. subst X: C:\Apache2\htdocs (any target works; an Apache docroot is the common real-world case).
2. mkdir C:\Apache2\htdocs\myproject
3. Open X:\myproject as the workspace folder in VS Code.
4. Start a Claude Code conversation and send at least one message.
5. Confirm the transcript exists at %USERPROFILE%\.claude\projects\x--myproject\<uuid>.jsonl.
6. Confirm %USERPROFILE%\.claude\projects\C--Apache2-htdocs-myproject does not exist.
7. Reload the window (or start a new conversation).
8. Open the Session history list.

Expected: the conversation from step 4 is listed and resumable.
Actual: only the live conversation is listed. The step-4 session never appears, with no error.

Confirm the data is intact and only listing is broken:

"%USERPROFILE%\.vscode\extensions\anthropic.claude-code-2.1.212-win32-x64\resources\native-binary\claude.exe" --resume <uuid>

This resumes the session correctly.

Impact

• All session history is invisible for every workspace on a subst drive.
• Completely silent — no error surfaced, nothing in the output channel.
• Users reasonably conclude sessions aren't being saved or that resume is broken. Recovery requires knowing that --resume exists and digging the UUID out of ~/.claude/projects.
• Likely under-reported: subst is standard practice for Apache/PHP/XAMPP docroots, and the "only the current conversation shows" presentation doesn't look like a path bug.

Workaround

A directory junction that makes both keys resolve to the same real directory:

mklink /J "%USERPROFILE%\.claude\projects\C--Apache2-htdocs-myproject" "%USERPROFILE%\.claude\projects\x--myproject"

Verified working. Needed per project, survives extension updates, and remains harmless whichever way the bug is fixed (reader and writer meet in the same directory either way).

Suggested fix

1. Use one resolver for both write and read. The specific choice matters less than consistency — but note that changing only the writer to the native resolver would orphan every existing transcript on affected machines.
2. Don't swallow the readdir error in wb(). The bare catch {} is what turned a path mismatch into a silent empty list. Even a debug-level log naming the directory it tried would have made this self-diagnosing.
3. Consider a fallback for existing installs: if the resolved project directory is missing or empty, retry with the key derived from the unresolved path. That would auto-heal affected users without requiring a junction.
4. Consider distinguishing "no sessions found" from "project directory not found" in the UI, so a broken read can't render as a normal-looking list.

Verification performed

The shipped functions (Zpe, wb, fb, dRt, Ype, Xpe, RAt) were extracted from extension.js 2.1.212 and executed directly against a real project directory containing four valid transcripts:

• Before the junction: wb() returned [] → listSessions() returned 0 sessions.
• After the junction: four transcripts discovered → listSessions() returned 4 sessions, each with the correct title.

Confirming the mismatch is the sole cause, and that every other filter in the path (isCurrentWorkspace, includeProgrammatic, the title/parse drop, hiddenSessionIds) passes the sessions through cleanly.

function gx(e){let t=e.replace(/[^a-zA-Z0-9]/g,"-"); ...}                        // dx  in 2.1.212
function _x(){return tp.join(th(),"projects")}                                   // px
function iIt(e){return tp.join(_x(),gx(e))}                                      // UAt
async function ife(e){try{return Wd(await Lo.realpath(e))}catch{return Wd(e)}}   // Zpe
async function kb(e){let t=iIt(e),r=[];try{await Lo.readdir(t),r.push(t)}catch{} ...}   // wb
async function DIt(e,t,r){let n=await ife(e); ... for(let d of await kb(n)) ...}

~/.claude/projects/
  P--MyApp/                       31 transcripts   (VS Code extension + CLI, cwd "P:\MyApp")
  C--Users-me-work-code-MyApp/     1 transcript    (Claude Desktop, cwd "C:\Users\me\work\code\MyApp")

mklink /J "%USERPROFILE%\.claude\projects\C--Users-me-work-code-MyApp" "%USERPROFILE%\.claude\projects\P--MyApp"