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https://github.com/NousResearch/hermes-agent.git
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emozilla
4b30db1f85
The canonical install flow
irm https://raw.githubusercontent.com/.../scripts/install.ps1 | iex
fails on PowerShell 5.1 with a cascade of 'The assignment expression
is not valid' errors at every param() default value:
[string]$Branch = 'main',
~~~~~~
The assignment expression is not valid. The input to an assignment
operator must be an object that is able to accept assignments...
Root cause: scripts/install.ps1 carries a UTF-8 BOM (0xEF 0xBB 0xBF)
as its first three bytes. 'irm' returns the response body as a string;
on PS 5.1 the BOM survives into that string as a leading \ufeff
character. 'iex' then evaluates the string and PS's parser chokes
on the invisible character before param() -- error recovery proceeds
into the body but every assignment is reported as broken.
This was the exact failure mode the install.ps1 hardening pass (PR
#27224) deliberately fixed by stripping the BOM and ensuring the
file body is pure ASCII. Commit 4279da4db ('fix(windows): make
PowerShell installer parse in 5.1') re-introduced the BOM later,
unintentionally undoing the irm|iex compatibility fix; the merge
that brought it into bb/gui carried it forward.
Fix: strip the three BOM bytes. File body is verified pure ASCII
(any-byte > 127 returns false), so PS 5.1 with no BOM falls back to
Windows-1252 decoding which is identical to ASCII for our content.
Both install paths now work:
- 'irm ... | iex' (canonical CLI)
- 'powershell -File install.ps1' (programmatic / desktop bootstrap)