core: gitbash() fails when git resolves to mingw64/bin (e.g. inside Git Bash), shell falls back to pwsh #57310

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1. opencode-agent commented on Oct 20, 2026

   

   opencode-agentBot

   on Oct 20, 2026 – with OpenCode Agent

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   Thanks for the detailed report. I confirmed this on the latest dev (9d90d892), and select.ts is the same in v2.0.32.

   There was no Windows machine available, so I recreated the Git for Windows folder layout on Linux (Git/cmd/git, Git/mingw64/bin/git, Git/bin/bash.exe) and made ShellSelect take its Windows branch. The script below does this.

   • With Git/cmd first on PATH, ShellSelect.gitbash() returns Git/bin/bash.exe.
   • With Git/mingw64/bin first on PATH, as inside Git Bash, it returns undefined.

   The cause is path.join(git, "..", "..", "bin", "bash.exe"), which only works when git is the one in Git\cmd. I didn't run the full resolve() path. From the code, though, once gitbash() fails, SHELL=/usr/bin/bash and "shell": "bash" fall back as you describe.

   Related: #22054 reported the same guess failing for MSYS2's ucrt64/bin/git.exe (on v1).

   Reproduction script (gitbash-sim.ts)

   // Copy into <checkout>/packages/core/ and run there with bun (module resolution needs the workspace).
   // Simulates the Git for Windows directory layout on Linux and makes ShellSelect take its
   // win32 branch (process.platform is overridden after imports), to exercise gitbash()'s
   // path derivation. Run from a checkout's packages/core:  bun /workspace/repro/gitbash-sim.ts
   import { mkdirSync, writeFileSync, chmodSync, mkdtempSync } from "fs"
   import path from "path"
   import os from "os"
   const { ShellSelect } = await import("@opencode/core/shell/select")
   
   const root = path.join(mkdtempSync(path.join(os.tmpdir(), "gfw-")), "Git")
   for (const f of ["cmd/git", "mingw64/bin/git", "bin/bash.exe"]) {
     const p = path.join(root, f)
     mkdirSync(path.dirname(p), { recursive: true })
     writeFileSync(p, "#!/bin/sh\n")
     chmodSync(p, 0o755)
   }
   Object.defineProperty(process, "platform", { value: "win32" })
   
   process.env.PATH = `${root}/cmd:/usr/bin:/bin` // like cmd.exe / PowerShell: Git\cmd on PATH
   console.log("git on PATH = Git/cmd/git         -> gitbash():", ShellSelect.gitbash())
   process.env.PATH = `${root}/mingw64/bin:${root}/cmd:/usr/bin:/bin` // inside Git Bash: /mingw64/bin first
   console.log("git on PATH = Git/mingw64/bin/git -> gitbash():", ShellSelect.gitbash())
   console.log("expected in both cases:", path.join(root, "bin", "bash.exe"))

   Run it: bun gitbash-sim.ts
2. opencode-agent

   added

   reproduced

   on Oct 20, 2026