modelcontextprotocol / modelcontextprotocol/python-sdk

raise without from discards exception chain in 12 remaining sites

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bug P3
Dominant language
Python
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Description

Initial Checks
Description

Follow-up to #2541 (fixed in #2542). The same pattern exists in 12 additional sites across 7 files. Each catches an exception and re-raises a new one without from, discarding the original traceback and __cause__.

Sites:

File Line Caught Raised
client/session.py 346 ValidationError RuntimeError
client/session.py 348 SchemaError RuntimeError
client/auth/utils.py 246 ValidationError OAuthRegistrationError
client/auth/utils.py 339 ValidationError OAuthTokenError
server/auth/middleware/client_auth.py 83 ValueError/UnicodeDecodeError/binascii.Error AuthenticationError
server/mcpserver/resources/types.py 75 Exception ValueError
server/mcpserver/resources/types.py 151 Exception ValueError
server/mcpserver/resources/types.py 196 Exception ValueError
server/mcpserver/resources/types.py 205 Exception ValueError
server/mcpserver/resources/resource_manager.py 96 Exception ValueError
server/mcpserver/resources/templates.py 133 Exception ValueError
server/mcpserver/prompts/base.py 185, 189 Exception ValueError
Impact

Same as #2541: without from, Python shows "During handling of the above exception, another exception occurred" instead of "The above exception was the direct cause of the following exception." Callers cannot inspect __cause__ to determine the root cause programmatically.

The codebase already uses from correctly in server.py:451, server.py:459, server.py:1112, func_metadata.py:216,265, and tools/base.py:119. These 12 sites are the remaining inconsistencies.

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start by inspecting the 12 listed sites in client/session.py, client/auth/utils.py, server/auth/middleware/client_auth.py, server/mcpserver/resources/types.py, resource_manager.py, templates.py, and prompts/base.py. Compare them with the existing uses in server.py, func_metadata.py, and tools/base.py. Done means each re-raised exception preserves the original as its direct cause and the relevant client and server behavior remains passing.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
backend
Issue type
Bug
Difficulty
3/5
Estimated time
1-2 days
Activity status
Quiet
Clarity
Clearly specified
Newbie friendliness
74/100

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