Source launcher (pnpm dsh) fails every tool call after pnpm run build on Windows

[jpmailoa]

Summary

Tool calls fail with Cannot read properties of undefined (reading 'prepare') when the harness is launched through the documented source entry (pnpm dsh → node --import tsx/esm apps/cli/src/bin.ts) on a repository that has been built, as the docs require. The same profile works through the built entry (node apps/cli/lib/bin.js).

Cause: two module planes load in one process. @deepseek-ai/dsh-tools is evaluated twice — once from src/index.ts (tsx applying tsconfig paths) and once from lib/index.js (Node exports resolution) — so TOOL_RUNTIME_SCHEDULER, a unique symbol, ends up with two identities. ctx.tools is constructed by the lib/ copy while dsh-agent-loop looks the symbol up from the src/ copy, yielding undefined.prepare. This violates the "source plane vs artifact plane, never mixed" rule in AGENTS.md.

Reproduction

pnpm install
pnpm run build
pnpm dsh --profile headless "Use the pwsh shell tool to print the cwd, then reply DONE."

Fails on the first tool call. The shipped headless profile reproduces it, so no user profile, patch, or preset is involved, and any tool fails — not just pwsh.

Current behavior

The turn ends with {"kind":"error","error":{"message":"Cannot read properties of undefined (reading 'prepare')","code":"UNKNOWN"}} persisted in the session log. No stack is recorded, so the cause is not diagnosable from the Session.

Module-resolution hook output, same process:

[RESOLVE] @deepseek-ai/dsh-tools
   -> packages/core/tools/lib/index.js
   from apps/cli/node_modules/@deepseek-ai/dsh-agent-instructions/package.json

[RESOLVE] @deepseek-ai/dsh-tools
   -> packages/core/tools/src/index.ts
   from packages/core/agent-loop/lib/index.js

The split traces to a package tsconfig.json whose extends chain breaks when the package is reached through the profile's on-disk module link (apps/cli/node_modules/@deepseek-ai/*), so tsx finds no paths for that importer and falls back to Node resolution:

Importer path seen by tsx	../../../tsconfig.base.json
apps/cli/node_modules/@deepseek-ai/dsh-agent-instructions/	missing → no paths → lib/index.js
packages/context/agent-instructions/	resolves → paths → src/index.ts

Expected behavior

Both documented launchers dispatch tool calls. The source-execution reference supports both: pnpm run build then pnpm dsh <args...>, and "the installed form launches the built apps/cli/lib/bin.js without rebuilding the repository."

Environment

• Windows 11 (NT 10.0.26200), Node v26.8.2, pnpm 11.7.0, tsx ^4.22.4, repo 0.1.6-alpha.2
• Verified on Windows only. Linux/macOS use symlinks rather than junctions for the on-disk module links, so the scope may be narrower — a maintainer can confirm with the two commands above.

Coverage gap

apps/cli/tests/source-launch.compat.spec.ts is the source-launcher gate, and it only asserts the --profile <name> is required diagnostic. It never boots a profile or dispatches a tool, so a dual-evaluation regression passes CI silently. I did not find another gate that boots a profile from source and dispatches a tool call.

[jpmailoa]

As a consequence, after installing on Windows using the recommended pathway, my sessions can boot up. But it will soon get stuck because of a failed tool call (the DSH session error message does not explain why). It took a long time for me to debug and find the root cause.

I managed to fix it and get sessions working again after launching the built artifact plane instead (plain Node, no tsx):

cd path_to_dsh\deepseek-harness
node apps/cli/lib/bin.js web --port 3080 --no-open