instructions: Windows lowercase drive letter in workspace path causes stack overflow, blocking all sessions #50857

Summary

On Windows, launching opencode from a directory whose drive letter is lowercase (e.g. d:\workspace\repo) makes the built-in instruction source core/instructions fail activation with RangeError: Maximum call stack size exceeded. Every session in that location then fails with:

Session failed
Instruction initialization blocked by unavailable sources: core/instructions

Launching the exact same workspace with an uppercase drive letter (D:\workspace\repo) works fine. cmd.exe preserves the drive-letter case the user types, so whether a workspace works depends purely on how you cd into it.

Environment

• opencode version: v2.0.14 (also observed on 2.0.12 running as opencode serve --service)
• OS: Windows 10 22H2 (10.0.19045), win32 x64
• Terminal: Windows console
• Shell: cmd.exe
• Install/channel: npm global @opencode/cli 2.0.14, latest channel
• Active plugins: none configured

Reproduction

1. Open cmd.exe
2. cd /d d:\workspace\some-git-repo - note the lowercase drive letter (cmd preserves typed case)
3. Run opencode
4. Create a new session

Repeating the exact same steps with cd /d D:\workspace\some-git-repo (uppercase D) works every time.

This is 100% deterministic in my logs: every location boot with a lowercase drive letter failed instruction activation; every boot of the same workspace with an uppercase drive letter succeeded.

Expected Behavior

Drive-letter case should not matter on Windows. Sessions should start normally regardless of the case of the workspace path.

Actual Behavior

Instruction source activation dies with a stack overflow, and every new session in that location fails with Instructions.InitializationBlocked: Instruction initialization blocked by unavailable sources: core/instructions.

Additional Context

Root cause analysis (log correlation + binary inspection of 2.0.14)

The instruction source activation (ConfigInstructionPlugin) computes:

p = resolve(location.directory)        // preserves typed case -> "d:\workspace\repo"
g = resolve(project.directory)         // from `git rev-parse --show-toplevel`, which always
                                       // returns an UPPERCASE drive on Windows ("D:/workspace/repo")
f = contains(home, p) ? home : g       // workspace not under HOME -> f = g = "D:\workspace\repo"
sources = [...global, ...chain(p, f)]  // chain() walks p upward via dirname() until it === f

The chain walk terminates on strict equality e === a. Because p is d:\... and f is D:\..., equality never holds. At the drive root, dirname("d:\") === "d:\" is a fixed point, so the recursion never terminates -> stack overflow.

The guard that admits execution into this branch, contains(g, p), is case-insensitive (path.relative-based), which is why the mismatched-case walk is reached at all:

path.win32.resolve('d:\\workspace\\repo')                         // 'd:\\workspace\\repo'  (case preserved)
path.win32.resolve('D:/workspace\\repo')                          // 'D:\\workspace\\repo'
path.win32.dirname('d:\\')                                        // 'd:\\'                 (fixed point!)
path.win32.relative('D:\\workspace\\repo', 'd:\\workspace\\repo') // ''                     (case-insensitive)

Log evidence

# lowercase drive letter -> failure (~270ms after location boot)
message="location services booted" directory="d:\\workspace\\lab-emc\\lab-emc"
message="failed to activate instruction source" cause="Cause([Die(RangeError: Maximum call stack size exceeded.)])"
message="Failed to drain Session" cause="Instructions.InitializationBlocked: Instruction initialization blocked by unavailable sources: core/instructions"

# same workspace, uppercase drive letter -> success
message="location services booted" directory="D:\\workspace\\lab-emc\\lab-emc"
message="watcher subscribe" path="C:\\Users\\<user>\\.config\\opencode\\AGENTS.md" type=file
message="watcher subscribe" path="D:\\workspace\\lab-emc\\lab-emc\\AGENTS.md" type=file

The activation error handler marks the source unavailable for the process lifetime ("failed to activate instruction source", WARN); each subsequent session then throws Instructions.InitializationBlocked ("Failed to drain Session", ERROR).

Suggested fix

• Terminate the chain walk when dirname(e) === e (root fixed point), and/or
• Compare the walk target case-insensitively on win32 (consistent with the contains guard).

Workaround

Always launch with an uppercase drive letter: cd /d D:\workspace\repo before opencode.