Cannot read properties of undefined (reading 'prepare') in DSH

Match the exact symptom first

This guide applies when a Headless turn reaches the model normally and fails only as tool execution begins. If DSH fails before the model responds, or the deepest error names storage, a missing package, or a provider request, use that signal instead.

dsh: UNKNOWN: Cannot read properties of undefined (reading 'prepare')

Use a text-only turn as the control

Run the same profile and provider with a prompt that explicitly requires a short text response and forbids tools. If that succeeds while a deterministic read-tool call fails, the model and provider path are probably healthy and the fault is narrowed to the tool path.

Check for a second dsh-tools copy

The reproducible community case places another @deepseek-ai/dsh-tools under the Headless profile node_modules. The agent loop and live tool runtime then import different module copies. Because the scheduler key is created with a plain Symbol, the identities do not match and the lookup returns undefined.

node -v
dsh --version
npm ls @deepseek-ai/dsh-tools --all

Inspect the profile without deleting anything

Look specifically inside the profile that reproduces the error. On Windows the reported default path is under the user profile .dsh directory; on other systems use the DSH home you actually configured. Record every resolved dsh-tools path before changing the installation.

• Confirm that the extra directory is inside the failing profile rather than the launcher installation.
• Record the package versions and resolved paths for both copies.
• Preserve the profile manifest and lockfile before changing node_modules.
• Prefer moving a confirmed duplicate aside for one controlled test over deleting it permanently.

Retest the same two controls

After isolating only the confirmed duplicate copy, repeat the original text-only prompt and the deterministic tool prompt under the same DSH, Node, provider, and profile. The community reproduction reports that removing the second copy restored tool calls; if your failure remains, restore the backup and continue diagnosis rather than deleting more packages.

Evidence status

The original question remains unanswered by maintainers. The Symbol-identity explanation includes a clean reproduction and reversible control in the discussion, but it is still community analysis rather than an official root-cause statement or released patch.