• [varLib] Support decreasing design-space axis mappings, via a new keyword-only allow_decreasing argument to models.normalizeValue (#3970, #4217, #4243).
• [designspaceLib] Allow partial DesignSpace v5 axis subsets: omitted range attributes on an <axis-subset> are taken from the parent axis, as the spec says (#4205).
• [designspaceLib] Fix DesignSpaceDocument.normalize() for mapped axes: axis bounds and rule conditions are now normalized from their original values (#4218).
• [designspaceLib] splitInterpolable and splitVariableFonts now warn when a source or instance is dropped because it lies outside the document's own axes, instead of silently discarding it (#4244).
• [varLib.instancer] Add support for instancing variable COLRv1 fonts (#2699, #4279).
• [varLib.instancer] Apply VVAR vertical-origin deltas to VORG, and use OpenType rounding for instanced advances and vertical origins (#4221).
• [varLib.instancer] Keep a universal FeatureVariations record when pinning removes its last condition but other axes remain (#4247).
• [varLib.instancer] Preserve ppem Device corrections in GDEF, BASE, GPOS and JSTF instead of asserting on them (#4290).
• [varLib.instancer] Allow requesting an axis's original range on VARC fonts (#4280).
• [varLib.instancer, subset] Fold, remove or remap MATH VariationIndex devices when instancing, subsetting the GDEF store or optimizing it (#4288).
• [varLib] Raise ValueError: Missing required table fvar from varLib.mutator and the instancer CLI on a static font, instead of a bare KeyError (#3751, #4300).
• [featureVars] When adding rvrn, also shift lookup indices inside existing FeatureVariations (#4233). Handle null ConditionSet and FeatureTableSubstitution offsets when building, subsetting and instancing (#4234, #4235). Keep FeatureTableSubstitution records sorted after merging new ones into an existing record (#4248).
• [ttLib] Fix FeatureParams (size, ssXX, cvXX) in FeatureVariations alternate feature tables, which failed to compile and round-trip (#3623, #4278).
• [ttLib] Fully decode lazily loaded ligatures, SinglePos and PairPos arrays during recursive decompilation, so reorderGlyphs() on a lazy font no longer corrupts or asserts on them (#4231, #4232).
• [VARC] Update the variation-store binary format to follow harfbuzz/boring-expansion-spec#175: SparseVarRegionList.RegionCount is uint32, sparse axes use Offset32 and MultiVarData items are stored in an INDEX. VARC fonts built with earlier fontTools versions must be rebuilt (#4219).
• [VARC] Several fixes: derive component conditions from conditionIndex (#4237), set the implicit scaleY when importing XML (#4238), report the font's current coordinates for components that reset unspecified axes (#4239), and keep inherited coordinates when drawing CFF2 VARC components (#4236).
• [varLib] buildMultiVarData accepts flattened per-region vector tuples (#4245).
• [otConverters] Bounds-check CFF2 INDEX count and offSize on read, raising TTLibError instead of allocating huge lazy lists (#4220).
• [ttLib] Handle empty packed deltas when OPTIMIZE_FONT_SPEED is set (#4241).
• [scaleUpem] Scale per-glyph VORG origins (#4222); fix VARC scaling for static fonts and condition variations (#4223); don't mutate the shared default CFF FontMatrix (#4251, #4252).
• [cmap] Fix format 2 compilation when all codes are single-byte (#1524, #4211) or all single-byte codes map to .notdef (#4215). Formats 2 and 4 now reject glyph IDs above 65535 instead of wrapping them (#4226). Split format 14 default UVS ranges longer than 256 codepoints (#4229). Empty format 12 and 13 subtables round-trip (#4246).
• [glyf] Use unsigned instruction lengths, so programs of 32768-65535 bytes compile and decompile correctly (#4227). Keep instructions in zero-contour glyphs (#4228).
• [pens] Fix cubic off-curve detection in TTGlyphPointPen across contour starts (#4224). Glyph.drawPoints() now raises NotImplementedError for an all-off-curve cubic contour, which the point pen protocol cannot express (#3191, #4225). RoundingPen passes the all-off-curve None sentinel through (#4311, #4312).
• [CFF2] Preserve operands when a blend has zero regions (#4240).
• [cffLib] Read CFF font names as Latin-1, matching how they are written (#4253). Deleting a CFF dict attribute now actually removes it (#2725, #4264).
• [CFF2ToCFF] Fix conversion of fonts with local subroutines (#4258). A CFF2 table with a single FontDict is now converted to a name-keyed CFF font that keeps its glyph names (#3890, #4265).
• [subset] Handle a null GDEF variation store (#4230).
• [merge] Support merging fonts that both have a MATH table (#3823, #4257).
• [feaLib] Reject the same mark class used twice in one anchor list (#3628, #4255). Don't crash on value records whose devices are all NULL (#2396, #4261). Pad a short OS/2 Vendor with spaces (#4259).
• [feaLib] Raise FeatureLibError with a location, instead of a bare Python error, for: a BASE script list without a matching tag list (#4263), a UnicodeRange bit outside 0-127 (#4266), a name string that cannot be decoded (#4267), a STAT axis location with no or too many values (#4268), and a non-ASCII OS/2 Vendor (#4269).
• [name] Fix the BCP 47 tags of some Mac and Windows language IDs, e.g. es was mapped to Mac Estonian (#3733, #4256). getDebugName prefers the Windows English name over the Mac one (#3969, #4273).
• [post] Don't crash on a format 2.0 table with numGlyphs set to 0 (#3060, #4274).
• [VDMX] Recompute numRecs and numRatios when compiling (#4293).
• [Silf] Fix compiling a Silf table that was decompiled from binary (#4294).
• [woff2] Preserve minorVersion when copying flavor data (#4249, #4250).
• [ttGlyphSet] Compute glyph width lazily for glyf variable fonts without HVAR, so .width is correct before drawing (#3964, #4260).
• [varLib.interpolatable] Respect designspace source layers (#3951, #4275); fix --json output with SciPy (#3870, #4276).
• [misc.psLib] Fix tokenizing of escaped parentheses in PostScript strings (#4207).
• [svgLib] Raise ValueError instead of IndexError on a truncated path command (#4254).
• [misc.transform] Preserve the direction of the remaining axis when decomposing a transform whose first column is zero (#4242).
• [misc.textTools] Tag.__ne__ returns NotImplemented for unsupported types (#4305, #4306).
• [misc.dictTools] hashdict rejects in-place union (|=) (#4313, #4314).
• [misc.xmlReader] Close owned input streams when parsing fails (#4298).
• [misc.filesystem] WriteZipFS.close() can be called more than once (#4309, #4310).
• [EBDT] Keep EBDT/CBDT glyph metrics after probing a missing attribute (#3806, #4216).