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ProbeLabs36 findings · 123 requirements
SYS-REQ-061SystemApproved

When ParseString encounters a UTF-16 high surrogate escape (e.g., '\uD800') that is not followed by a valid low surrogate escape, the parser shall substitute U+FFFD (replacement character) for the lone surrogate and continue parsing, matching encoding/json behavior, rather than producing corrupted output or synthesizing a bogus code point.

PriorityshallTypeguaranteeCategoryfunctionalComponentparserAssuranceEFindingsHighworst open

Specification

The requirement exactly as authored — its complete prose text and, where present, the formal FRETish sentence it compiles to.

Description

When ParseString encounters a UTF-16 high surrogate escape (e.g., '\uD800') that is not followed by a valid low surrogate escape, the parser shall substitute U+FFFD (replacement character) for the lone surrogate and continue parsing, matching encoding/json behavior, rather than producing corrupted output or synthesizing a bogus code point.

FRETish formula
the parser shall always satisfy !raw_string_has_missing_low_surrogate | substitutes_replacement_for_missing_low_surrogate

Rationale & tags

Why this requirement exists, and how it is categorised.

Surrogate pair handling in decodeUnicodeEscape requires both high and low surrogates. A missing or invalid low surrogate exercises a distinct failure path.

parsestringunicodesurrogate

Verification & provenance

How this requirement was checked: the review trail, edit history, and the machine-analysis status terms (each ⓘ explains what it means).

Assurance levelE
Formalizationvalid
Realizabilityrealizable
Vacuitychecked_ok
Strategyfretish

Review

Status
approved
Reviewer
human:buger · lead_engineer
Reviewed
Jul 27, 2026, 12:22 UTC
Aligned FRETish with U+FFFD substitution behavior (DEFECT-260727-SNGT fix)

History

Created
Apr 14, 2026, 18:00 UTC · agent:claude
Modified
Jul 27, 2026, 12:22 UTC · human:buger

Obligations

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No obligations recorded for this requirement

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Formula evidence

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FRETish formula

the parser shall always satisfy !raw_string_has_missing_low_surrogate | substitutes_replacement_for_missing_low_surrogate

Variables

NameTypeDirectionDescription
raw_string_has_missing_low_surrogateTrue when ParseString encounters a UTF-16 high surrogate escape not followed by a valid low surrogate escape.
substitutes_replacement_for_missing_low_surrogateTrue when ParseString substitutes U+FFFD for a lone high surrogate, matching encoding/json behavior.

Witnesses· 2 scenarios total

  • TestMissingSurrogateLow
    deep_spec_test.go:617
  • TestMCDC_SYS_REQ_061_Row1_TriggerFalse
    mcdc_spec_witnesses_test.go:2802exercises 1 condition scenario
  • TestMCDC_SYS_REQ_061_Row3_MissingLowSurrogateError
    mcdc_spec_witnesses_test.go:2815exercises 1 condition scenario

Its place

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Trace evidence

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No implementation linked

No source files are traced to this requirement yet.

Impact

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If you change this

Requirements
0
Files
0
Tests
2
At-risk contracts
0

Tests to re-run (2)

  • deep_spec_test.godeep_spec_test.go
  • mcdc_spec_witnesses_test.gomcdc_spec_witnesses_test.go

What this rests on

Discussions

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