From 36cfcd0c4020841c433564706cc119ae36817eb2 Mon Sep 17 00:00:00 2001
From: Claude <noreply@anthropic.com>
Date: Thu, 9 Apr 2026 19:11:03 +0000
Subject: [PATCH] feat: migrate file extension from .as to .affine for GitHub
 Linguist recognition

The .as extension conflicts with ActionScript in GitHub Linguist, causing all
AffineScript source files to be misclassified as ActionScript/JavaScript. This
migration to .affine resolves the conflict and enables proper language detection.

Changes:
- Rename all 153 .as source files to .affine across conformance/, examples/,
  stdlib/, test/, and tests/ directories
- Add linguist-language=AffineScript directive to .gitattributes for .affine
- Update tree-sitter grammar file-types from "as" to "affine"
- Update VSCode extension to register .affine instead of .as
- Update all documentation references (28+ files) to use .affine
- Update test fixture references in test_e2e.ml

https://claude.ai/code/session_015S2ndRbwuJPpjkv54BpVDw
---
 .gitattributes                                |  3 +
 .machine_readable/6a2/STATE.a2ml              |  2 +-
 ALPHA-1-RELEASE-NOTES.md                      |  8 +-
 COMPILER-CAPABILITIES.md                      |  2 +-
 FIXES_2026-01-23.md                           |  8 +-
 MODULE-SYSTEM-PROGRESS.md                     | 26 +++---
 PHASE3-ASSESSMENT.md                          | 36 ++++----
 PHASE3-COMPLETE.md                            | 28 +++---
 PHASE3-SESSION-SUMMARY.md                     | 48 +++++-----
 README.adoc                                   | 12 +--
 SESSION-2026-01-23.md                         |  6 +-
 SESSION-COMPLETE.md                           | 42 ++++-----
 TRAIT_SYSTEM_STATUS.md                        |  4 +-
 ...sed_brace.as => 001_unclosed_brace.affine} |  0
 ...d_string.as => 002_unclosed_string.affine} |  0
 ...03_bad_number.as => 003_bad_number.affine} |  0
 ...d_token.as => 004_unexpected_token.affine} |  0
 ...sing_arrow.as => 005_missing_arrow.affine} |  0
 ...ad_operator.as => 006_bad_operator.affine} |  0
 ...effect.as => 007_incomplete_effect.affine} |  0
 ...parens.as => 008_mismatched_parens.affine} |  0
 ...keyword.as => 009_reserved_keyword.affine} |  0
 ..._empty_match.as => 010_empty_match.affine} |  0
 ...11_bad_escape.as => 011_bad_escape.affine} |  0
 ...ing_comma.as => 012_trailing_comma.affine} |  0
 .../valid/{001_empty.as => 001_empty.affine}  |  0
 .../{002_comments.as => 002_comments.affine}  |  0
 ...et_bindings.as => 003_let_bindings.affine} |  0
 .../{004_literals.as => 004_literals.affine}  |  0
 ...{005_functions.as => 005_functions.affine} |  0
 ...06_type_alias.as => 006_type_alias.affine} |  0
 ...07_struct_def.as => 007_struct_def.affine} |  0
 .../{008_enum_def.as => 008_enum_def.affine}  |  0
 ...09_effect_def.as => 009_effect_def.affine} |  0
 ...tern_match.as => 010_pattern_match.affine} |  0
 .../valid/{011_rows.as => 011_rows.affine}    |  0
 ...{012_ownership.as => 012_ownership.affine} |  0
 docs/ALIB-INTEGRATION.md                      | 26 +++---
 docs/TYPECHECKER-COMPLETION.md                |  4 +-
 docs/alib/README.md                           |  8 +-
 docs/guides/TESTING-REPORT.adoc               | 10 +-
 docs/guides/TESTING-REPORT.scm                | 20 ++--
 docs/guides/lessons/README.md                 |  4 +-
 docs/spec.md                                  | 18 ++--
 docs/standards/RELEASE.md                     | 20 ++--
 docs/tutorial/lesson-10-building.md           | 14 +--
 editors/tree-sitter-affinescript/package.json |  2 +-
 editors/vscode/package.json                   |  2 +-
 editors/vscode/src/extension.ts               |  4 +-
 ...sive_test.as => comprehensive_test.affine} |  0
 ...endent_types.as => dependent_types.affine} |  0
 examples/{effects.as => effects.affine}       |  0
 ...xception_test.as => exception_test.affine} |  0
 examples/{hello.as => hello.affine}           |  0
 .../lessons/{01_hello.as => 01_hello.affine}  |  0
 examples/{ownership.as => ownership.affine}   |  0
 .../{refinements.as => refinements.affine}    |  0
 examples/{rows.as => rows.affine}             |  0
 .../{simple_test.as => simple_test.affine}    |  0
 examples/{traits.as => traits.affine}         |  0
 ...test.as => typecheck_complete_test.affine} |  0
 ...test.as => typecheck_features_test.affine} |  0
 examples/{vectors.as => vectors.affine}       |  0
 lib/json_output.ml                            |  4 +-
 lib/module_loader.ml                          | 14 +--
 stdlib/{Core.as => Core.affine}               |  0
 stdlib/{Math.as => Math.affine}               |  0
 stdlib/{Option.as => Option.affine}           |  0
 stdlib/README.md                              |  8 +-
 stdlib/{Result.as => Result.affine}           |  0
 stdlib/{collections.as => collections.affine} |  0
 stdlib/{effects.as => effects.affine}         |  0
 stdlib/{io.as => io.affine}                   |  0
 stdlib/{math.as => math.affine}               |  0
 stdlib/{option.as => option.affine}           |  0
 stdlib/{prelude.as => prelude.affine}         |  0
 stdlib/{result.as => result.affine}           |  0
 stdlib/{string.as => string.affine}           |  0
 stdlib/{testing.as => testing.affine}         |  0
 stdlib/{traits.as => traits.affine}           |  0
 .../{affine_basic.as => affine_basic.affine}  |  0
 ...e_violation.as => affine_violation.affine} |  0
 .../{arithmetic.as => arithmetic.affine}      |  0
 ...endent_types.as => dependent_types.affine} |  0
 .../fixtures/{effects.as => effects.affine}   |  0
 ...d_violation.as => erased_violation.affine} |  0
 ...{full_pipeline.as => full_pipeline.affine} |  0
 ...{interp_simple.as => interp_simple.affine} |  0
 .../{julia_simple.as => julia_simple.affine}  |  0
 .../e2e/fixtures/{lambda.as => lambda.affine} |  0
 .../{ownership.as => ownership.affine}        |  0
 ...{pattern_match.as => pattern_match.affine} |  0
 ...ement_types.as => refinement_types.affine} |  0
 ...olymorphism.as => row_polymorphism.affine} |  0
 .../e2e/fixtures/{traits.as => traits.affine} |  0
 .../{type_decls.as => type_decls.affine}      |  0
 .../{wasm_simple.as => wasm_simple.affine}    |  0
 .../{binary_ops.as => binary_ops.affine}      |  0
 test/golden/{effects.as => effects.affine}    |  0
 .../golden/{functions.as => functions.affine} |  0
 test/golden/{hello.as => hello.affine}        |  0
 test/golden/{imports.as => imports.affine}    |  0
 test/golden/{lambda.as => lambda.affine}      |  0
 test/golden/{literals.as => literals.affine}  |  0
 .../golden/{ownership.as => ownership.affine} |  0
 test/golden/{patterns.as => patterns.affine}  |  0
 test/golden/{rows.as => rows.affine}          |  0
 test/golden/{traits.as => traits.affine}      |  0
 test/golden/{types.as => types.affine}        |  0
 test/test_e2e.ml                              | 90 +++++++++---------
 test/test_golden.ml                           |  8 +-
 test_if.as => test_if.affine                  |  0
 test_min.as => test_min.affine                |  0
 test_simple.as => test_simple.affine          |  0
 test_spread.as => test_spread.affine          |  0
 test_spread2.as => test_spread2.affine        |  0
 test_spread3.as => test_spread3.affine        |  0
 tests/borrow/{minimal.as => minimal.affine}   |  0
 .../borrow/{move_test.as => move_test.affine} |  0
 tests/borrow/{simple.as => simple.affine}     |  0
 ...e_move_test.as => simple_move_test.affine} |  0
 .../{simple_own.as => simple_own.affine}      |  0
 ....as => test_immutable_assign_error.affine} |  0
 .../borrow/{test_move.as => test_move.affine} |  0
 ...fter_use.as => test_move_after_use.affine} |  0
 ...e_borrow.as => test_mutable_borrow.affine} |  0
 ...t_ref_borrow.as => test_ref_borrow.affine} |  0
 ...se_after_move.as => use_after_move.affine} |  0
 .../{valid_move.as => valid_move.affine}      |  0
 ...arithmetic.as => simple_arithmetic.affine} |  0
 ...ray_bounds.as => test_array_bounds.affine} |  0
 ...array_empty.as => test_array_empty.affine} |  0
 ...ray_simple.as => test_array_simple.affine} |  0
 ...ray_single.as => test_array_single.affine} |  0
 ...est_array_sum.as => test_array_sum.affine} |  0
 ...ompound.as => test_assign_compound.affine} |  0
 ...gn_simple.as => test_assign_simple.affine} |  0
 ...capture.as => test_closure_capture.affine} |  0
 ...ure_debug.as => test_closure_debug.affine} |  0
 ...e.as => test_closure_multi_capture.affine} |  0
 ...um_pattern.as => test_enum_pattern.affine} |  0
 ...{test_for_loop.as => test_for_loop.affine} |  0
 ...tion_call.as => test_function_call.affine} |  0
 ...lambda_call.as => test_lambda_call.affine} |  0
 ...aram.as => test_lambda_multi_param.affine} |  0
 ...h_literal.as => test_match_literal.affine} |  0
 ...match_mixed.as => test_match_mixed.affine} |  0
 ...tch_simple.as => test_match_simple.affine} |  0
 ...le_calls.as => test_multiple_calls.affine} |  0
 ...ambdas.as => test_multiple_lambdas.affine} |  0
 ..._fold.as => test_opt_constant_fold.affine} |  0
 ...opt_if_fold.as => test_opt_if_fold.affine} |  0
 ...t_pattern_as.as => test_pattern_as.affine} |  0
 ...t_pattern_or.as => test_pattern_or.affine} |  0
 ...n_record.as => test_pattern_record.affine} |  0
 ...ern_tuple.as => test_pattern_tuple.affine} |  0
 ...ield.as => test_record_multi_field.affine} |  0
 ...ultiple.as => test_record_multiple.affine} |  0
 ...rd_simple.as => test_record_simple.affine} |  0
 ...ive_call.as => test_recursive_call.affine} |  0
 ...f_chain.as => test_ref_deref_chain.affine} |  0
 ...simple.as => test_ref_deref_simple.affine} |  0
 ...le_lambda.as => test_simple_lambda.affine} |  0
 ...string_diff.as => test_string_diff.affine} |  0
 ...est_string_eq.as => test_string_eq.affine} |  0
 ...ring_multi.as => test_string_multi.affine} |  0
 ...t_string_ptr.as => test_string_ptr.affine} |  0
 ...ng_simple.as => test_string_simple.affine} |  0
 ...t_tuple_five.as => test_tuple_five.affine} |  0
 ...ple_nested.as => test_tuple_nested.affine} |  0
 ...t_tuple_pair.as => test_tuple_pair.affine} |  0
 ...rray.as => test_tuple_record_array.affine} |  0
 ...ple_simple.as => test_tuple_simple.affine} |  0
 ...t_as_int.as => test_variant_as_int.affine} |  0
 ...h_arg.as => test_variant_match_arg.affine} |  0
 ...none.as => test_variant_match_none.affine} |  0
 ...i_arg.as => test_variant_multi_arg.affine} |  0
 ...th_arg.as => test_variant_with_arg.affine} |  0
 ...t_while_loop.as => test_while_loop.affine} |  0
 tests/conformance/README.md                   | 18 ++--
 .../arithmetic/{add.as => add.affine}         |  0
 .../arithmetic/{divide.as => divide.affine}   |  0
 .../arithmetic/{modulo.as => modulo.affine}   |  0
 .../{multiply.as => multiply.affine}          |  0
 .../{subtract.as => subtract.affine}          |  0
 .../{contains.as => contains.affine}          |  0
 .../collection/{filter.as => filter.affine}   |  0
 .../collection/{fold.as => fold.affine}       |  0
 .../collection/{map.as => map.affine}         |  0
 .../comparison/{equal.as => equal.affine}     |  0
 ...{greater_equal.as => greater_equal.affine} |  0
 .../{greater_than.as => greater_than.affine}  |  0
 .../{less_equal.as => less_equal.affine}      |  0
 .../{less_than.as => less_than.affine}        |  0
 .../{not_equal.as => not_equal.affine}        |  0
 .../{if_then_else.as => if_then_else.affine}  |  0
 .../logical/{and.as => and.affine}            |  0
 .../logical/{not.as => not.affine}            |  0
 .../conformance/logical/{or.as => or.affine}  |  0
 .../{run_all.as => run_all.affine}            |  0
 .../string/{concat.as => concat.affine}       |  0
 .../string/{length.as => length.affine}       |  0
 .../string/{substring.as => substring.affine} |  0
 .../{basic_effect.as => basic_effect.affine}  |  0
 .../{test_const.as => test_const.affine}      |  0
 .../{test_import.as => test_import.affine}    |  0
 ...import_only.as => test_import_only.affine} |  0
 ...unctions.as => test_math_functions.affine} |  0
 ...est_no_import.as => test_no_import.affine} |  0
 ...le_import.as => test_simple_import.affine} |  0
 ...aseline_block.as => baseline_block.affine} |  0
 ...{baseline_stmt.as => baseline_stmt.affine} |  0
 .../{unsafe_all.as => unsafe_all.affine}      |  0
 .../{unsafe_empty.as => unsafe_empty.affine}  |  0
 .../{unsafe_ops.as => unsafe_ops.affine}      |  0
 .../{unsafe_read.as => unsafe_read.affine}    |  0
 ...{unsafe_simple.as => unsafe_simple.affine} |  0
 .../{unsafe_stmt.as => unsafe_stmt.affine}    |  0
 ...ndent_e2e.as => test_dependent_e2e.affine} |  0
 ...rsing.as => test_dependent_parsing.affine} |  0
 ...erence.as => test_effect_inference.affine} |  0
 ...ct_lambda.as => test_effect_lambda.affine} |  0
 ...ism.as => test_effect_polymorphism.affine} |  0
 ...ing.as => test_generic_programming.affine} |  0
 ...hkt_parsing.as => test_hkt_parsing.affine} |  0
 ..._checking.as => test_kind_checking.affine} |  0
 ...pe_fix.as => test_lambda_scope_fix.affine} |  0
 ...ple.as => test_lambda_scope_simple.affine} |  0
 ...row_type.as => test_parse_row_type.affine} |  0
 ...rphism.as => test_row_polymorphism.affine} |  0
 ...t_row_simple.as => test_row_simple.affine} |  0
 .../{test_traits.as => test_traits.affine}    |  0
 tools/affinescript-lsp/src/handlers.rs        | 12 +--
 tools/affinescript-lsp/src/main.rs            |  2 +-
 tools/alib_conformance_gen.jl                 |  2 +-
 tools/run_codegen_wasm_tests.sh               |  4 +-
 wiki/compiler/architecture.md                 |  2 +-
 wiki/language-reference/dependent-types.md    |  2 +-
 wiki/language-reference/lexical.md            |  6 +-
 wiki/language-reference/modules.md            | 68 +++++++-------
 wiki/stdlib/overview.md                       | 92 +++++++++----------
 wiki/testing/guide.md                         | 24 ++---
 wiki/tooling/cli.md                           | 52 +++++------
 wiki/tooling/repl.md                          |  8 +-
 wiki/tutorials/quickstart.md                  |  4 +-
 245 files changed, 390 insertions(+), 387 deletions(-)
 rename conformance/invalid/{001_unclosed_brace.as => 001_unclosed_brace.affine} (100%)
 rename conformance/invalid/{002_unclosed_string.as => 002_unclosed_string.affine} (100%)
 rename conformance/invalid/{003_bad_number.as => 003_bad_number.affine} (100%)
 rename conformance/invalid/{004_unexpected_token.as => 004_unexpected_token.affine} (100%)
 rename conformance/invalid/{005_missing_arrow.as => 005_missing_arrow.affine} (100%)
 rename conformance/invalid/{006_bad_operator.as => 006_bad_operator.affine} (100%)
 rename conformance/invalid/{007_incomplete_effect.as => 007_incomplete_effect.affine} (100%)
 rename conformance/invalid/{008_mismatched_parens.as => 008_mismatched_parens.affine} (100%)
 rename conformance/invalid/{009_reserved_keyword.as => 009_reserved_keyword.affine} (100%)
 rename conformance/invalid/{010_empty_match.as => 010_empty_match.affine} (100%)
 rename conformance/invalid/{011_bad_escape.as => 011_bad_escape.affine} (100%)
 rename conformance/invalid/{012_trailing_comma.as => 012_trailing_comma.affine} (100%)
 rename conformance/valid/{001_empty.as => 001_empty.affine} (100%)
 rename conformance/valid/{002_comments.as => 002_comments.affine} (100%)
 rename conformance/valid/{003_let_bindings.as => 003_let_bindings.affine} (100%)
 rename conformance/valid/{004_literals.as => 004_literals.affine} (100%)
 rename conformance/valid/{005_functions.as => 005_functions.affine} (100%)
 rename conformance/valid/{006_type_alias.as => 006_type_alias.affine} (100%)
 rename conformance/valid/{007_struct_def.as => 007_struct_def.affine} (100%)
 rename conformance/valid/{008_enum_def.as => 008_enum_def.affine} (100%)
 rename conformance/valid/{009_effect_def.as => 009_effect_def.affine} (100%)
 rename conformance/valid/{010_pattern_match.as => 010_pattern_match.affine} (100%)
 rename conformance/valid/{011_rows.as => 011_rows.affine} (100%)
 rename conformance/valid/{012_ownership.as => 012_ownership.affine} (100%)
 rename examples/{comprehensive_test.as => comprehensive_test.affine} (100%)
 rename examples/{dependent_types.as => dependent_types.affine} (100%)
 rename examples/{effects.as => effects.affine} (100%)
 rename examples/{exception_test.as => exception_test.affine} (100%)
 rename examples/{hello.as => hello.affine} (100%)
 rename examples/lessons/{01_hello.as => 01_hello.affine} (100%)
 rename examples/{ownership.as => ownership.affine} (100%)
 rename examples/{refinements.as => refinements.affine} (100%)
 rename examples/{rows.as => rows.affine} (100%)
 rename examples/{simple_test.as => simple_test.affine} (100%)
 rename examples/{traits.as => traits.affine} (100%)
 rename examples/{typecheck_complete_test.as => typecheck_complete_test.affine} (100%)
 rename examples/{typecheck_features_test.as => typecheck_features_test.affine} (100%)
 rename examples/{vectors.as => vectors.affine} (100%)
 rename stdlib/{Core.as => Core.affine} (100%)
 rename stdlib/{Math.as => Math.affine} (100%)
 rename stdlib/{Option.as => Option.affine} (100%)
 rename stdlib/{Result.as => Result.affine} (100%)
 rename stdlib/{collections.as => collections.affine} (100%)
 rename stdlib/{effects.as => effects.affine} (100%)
 rename stdlib/{io.as => io.affine} (100%)
 rename stdlib/{math.as => math.affine} (100%)
 rename stdlib/{option.as => option.affine} (100%)
 rename stdlib/{prelude.as => prelude.affine} (100%)
 rename stdlib/{result.as => result.affine} (100%)
 rename stdlib/{string.as => string.affine} (100%)
 rename stdlib/{testing.as => testing.affine} (100%)
 rename stdlib/{traits.as => traits.affine} (100%)
 rename test/e2e/fixtures/{affine_basic.as => affine_basic.affine} (100%)
 rename test/e2e/fixtures/{affine_violation.as => affine_violation.affine} (100%)
 rename test/e2e/fixtures/{arithmetic.as => arithmetic.affine} (100%)
 rename test/e2e/fixtures/{dependent_types.as => dependent_types.affine} (100%)
 rename test/e2e/fixtures/{effects.as => effects.affine} (100%)
 rename test/e2e/fixtures/{erased_violation.as => erased_violation.affine} (100%)
 rename test/e2e/fixtures/{full_pipeline.as => full_pipeline.affine} (100%)
 rename test/e2e/fixtures/{interp_simple.as => interp_simple.affine} (100%)
 rename test/e2e/fixtures/{julia_simple.as => julia_simple.affine} (100%)
 rename test/e2e/fixtures/{lambda.as => lambda.affine} (100%)
 rename test/e2e/fixtures/{ownership.as => ownership.affine} (100%)
 rename test/e2e/fixtures/{pattern_match.as => pattern_match.affine} (100%)
 rename test/e2e/fixtures/{refinement_types.as => refinement_types.affine} (100%)
 rename test/e2e/fixtures/{row_polymorphism.as => row_polymorphism.affine} (100%)
 rename test/e2e/fixtures/{traits.as => traits.affine} (100%)
 rename test/e2e/fixtures/{type_decls.as => type_decls.affine} (100%)
 rename test/e2e/fixtures/{wasm_simple.as => wasm_simple.affine} (100%)
 rename test/golden/{binary_ops.as => binary_ops.affine} (100%)
 rename test/golden/{effects.as => effects.affine} (100%)
 rename test/golden/{functions.as => functions.affine} (100%)
 rename test/golden/{hello.as => hello.affine} (100%)
 rename test/golden/{imports.as => imports.affine} (100%)
 rename test/golden/{lambda.as => lambda.affine} (100%)
 rename test/golden/{literals.as => literals.affine} (100%)
 rename test/golden/{ownership.as => ownership.affine} (100%)
 rename test/golden/{patterns.as => patterns.affine} (100%)
 rename test/golden/{rows.as => rows.affine} (100%)
 rename test/golden/{traits.as => traits.affine} (100%)
 rename test/golden/{types.as => types.affine} (100%)
 rename test_if.as => test_if.affine (100%)
 rename test_min.as => test_min.affine (100%)
 rename test_simple.as => test_simple.affine (100%)
 rename test_spread.as => test_spread.affine (100%)
 rename test_spread2.as => test_spread2.affine (100%)
 rename test_spread3.as => test_spread3.affine (100%)
 rename tests/borrow/{minimal.as => minimal.affine} (100%)
 rename tests/borrow/{move_test.as => move_test.affine} (100%)
 rename tests/borrow/{simple.as => simple.affine} (100%)
 rename tests/borrow/{simple_move_test.as => simple_move_test.affine} (100%)
 rename tests/borrow/{simple_own.as => simple_own.affine} (100%)
 rename tests/borrow/{test_immutable_assign_error.as => test_immutable_assign_error.affine} (100%)
 rename tests/borrow/{test_move.as => test_move.affine} (100%)
 rename tests/borrow/{test_move_after_use.as => test_move_after_use.affine} (100%)
 rename tests/borrow/{test_mutable_borrow.as => test_mutable_borrow.affine} (100%)
 rename tests/borrow/{test_ref_borrow.as => test_ref_borrow.affine} (100%)
 rename tests/borrow/{use_after_move.as => use_after_move.affine} (100%)
 rename tests/borrow/{valid_move.as => valid_move.affine} (100%)
 rename tests/codegen/{simple_arithmetic.as => simple_arithmetic.affine} (100%)
 rename tests/codegen/{test_array_bounds.as => test_array_bounds.affine} (100%)
 rename tests/codegen/{test_array_empty.as => test_array_empty.affine} (100%)
 rename tests/codegen/{test_array_simple.as => test_array_simple.affine} (100%)
 rename tests/codegen/{test_array_single.as => test_array_single.affine} (100%)
 rename tests/codegen/{test_array_sum.as => test_array_sum.affine} (100%)
 rename tests/codegen/{test_assign_compound.as => test_assign_compound.affine} (100%)
 rename tests/codegen/{test_assign_simple.as => test_assign_simple.affine} (100%)
 rename tests/codegen/{test_closure_capture.as => test_closure_capture.affine} (100%)
 rename tests/codegen/{test_closure_debug.as => test_closure_debug.affine} (100%)
 rename tests/codegen/{test_closure_multi_capture.as => test_closure_multi_capture.affine} (100%)
 rename tests/codegen/{test_enum_pattern.as => test_enum_pattern.affine} (100%)
 rename tests/codegen/{test_for_loop.as => test_for_loop.affine} (100%)
 rename tests/codegen/{test_function_call.as => test_function_call.affine} (100%)
 rename tests/codegen/{test_lambda_call.as => test_lambda_call.affine} (100%)
 rename tests/codegen/{test_lambda_multi_param.as => test_lambda_multi_param.affine} (100%)
 rename tests/codegen/{test_match_literal.as => test_match_literal.affine} (100%)
 rename tests/codegen/{test_match_mixed.as => test_match_mixed.affine} (100%)
 rename tests/codegen/{test_match_simple.as => test_match_simple.affine} (100%)
 rename tests/codegen/{test_multiple_calls.as => test_multiple_calls.affine} (100%)
 rename tests/codegen/{test_multiple_lambdas.as => test_multiple_lambdas.affine} (100%)
 rename tests/codegen/{test_opt_constant_fold.as => test_opt_constant_fold.affine} (100%)
 rename tests/codegen/{test_opt_if_fold.as => test_opt_if_fold.affine} (100%)
 rename tests/codegen/{test_pattern_as.as => test_pattern_as.affine} (100%)
 rename tests/codegen/{test_pattern_or.as => test_pattern_or.affine} (100%)
 rename tests/codegen/{test_pattern_record.as => test_pattern_record.affine} (100%)
 rename tests/codegen/{test_pattern_tuple.as => test_pattern_tuple.affine} (100%)
 rename tests/codegen/{test_record_multi_field.as => test_record_multi_field.affine} (100%)
 rename tests/codegen/{test_record_multiple.as => test_record_multiple.affine} (100%)
 rename tests/codegen/{test_record_simple.as => test_record_simple.affine} (100%)
 rename tests/codegen/{test_recursive_call.as => test_recursive_call.affine} (100%)
 rename tests/codegen/{test_ref_deref_chain.as => test_ref_deref_chain.affine} (100%)
 rename tests/codegen/{test_ref_deref_simple.as => test_ref_deref_simple.affine} (100%)
 rename tests/codegen/{test_simple_lambda.as => test_simple_lambda.affine} (100%)
 rename tests/codegen/{test_string_diff.as => test_string_diff.affine} (100%)
 rename tests/codegen/{test_string_eq.as => test_string_eq.affine} (100%)
 rename tests/codegen/{test_string_multi.as => test_string_multi.affine} (100%)
 rename tests/codegen/{test_string_ptr.as => test_string_ptr.affine} (100%)
 rename tests/codegen/{test_string_simple.as => test_string_simple.affine} (100%)
 rename tests/codegen/{test_tuple_five.as => test_tuple_five.affine} (100%)
 rename tests/codegen/{test_tuple_nested.as => test_tuple_nested.affine} (100%)
 rename tests/codegen/{test_tuple_pair.as => test_tuple_pair.affine} (100%)
 rename tests/codegen/{test_tuple_record_array.as => test_tuple_record_array.affine} (100%)
 rename tests/codegen/{test_tuple_simple.as => test_tuple_simple.affine} (100%)
 rename tests/codegen/{test_variant_as_int.as => test_variant_as_int.affine} (100%)
 rename tests/codegen/{test_variant_match_arg.as => test_variant_match_arg.affine} (100%)
 rename tests/codegen/{test_variant_match_none.as => test_variant_match_none.affine} (100%)
 rename tests/codegen/{test_variant_multi_arg.as => test_variant_multi_arg.affine} (100%)
 rename tests/codegen/{test_variant_with_arg.as => test_variant_with_arg.affine} (100%)
 rename tests/codegen/{test_while_loop.as => test_while_loop.affine} (100%)
 rename tests/conformance/arithmetic/{add.as => add.affine} (100%)
 rename tests/conformance/arithmetic/{divide.as => divide.affine} (100%)
 rename tests/conformance/arithmetic/{modulo.as => modulo.affine} (100%)
 rename tests/conformance/arithmetic/{multiply.as => multiply.affine} (100%)
 rename tests/conformance/arithmetic/{subtract.as => subtract.affine} (100%)
 rename tests/conformance/collection/{contains.as => contains.affine} (100%)
 rename tests/conformance/collection/{filter.as => filter.affine} (100%)
 rename tests/conformance/collection/{fold.as => fold.affine} (100%)
 rename tests/conformance/collection/{map.as => map.affine} (100%)
 rename tests/conformance/comparison/{equal.as => equal.affine} (100%)
 rename tests/conformance/comparison/{greater_equal.as => greater_equal.affine} (100%)
 rename tests/conformance/comparison/{greater_than.as => greater_than.affine} (100%)
 rename tests/conformance/comparison/{less_equal.as => less_equal.affine} (100%)
 rename tests/conformance/comparison/{less_than.as => less_than.affine} (100%)
 rename tests/conformance/comparison/{not_equal.as => not_equal.affine} (100%)
 rename tests/conformance/conditional/{if_then_else.as => if_then_else.affine} (100%)
 rename tests/conformance/logical/{and.as => and.affine} (100%)
 rename tests/conformance/logical/{not.as => not.affine} (100%)
 rename tests/conformance/logical/{or.as => or.affine} (100%)
 rename tests/conformance/{run_all.as => run_all.affine} (100%)
 rename tests/conformance/string/{concat.as => concat.affine} (100%)
 rename tests/conformance/string/{length.as => length.affine} (100%)
 rename tests/conformance/string/{substring.as => substring.affine} (100%)
 rename tests/effects/{basic_effect.as => basic_effect.affine} (100%)
 rename tests/modules/{test_const.as => test_const.affine} (100%)
 rename tests/modules/{test_import.as => test_import.affine} (100%)
 rename tests/modules/{test_import_only.as => test_import_only.affine} (100%)
 rename tests/modules/{test_math_functions.as => test_math_functions.affine} (100%)
 rename tests/modules/{test_no_import.as => test_no_import.affine} (100%)
 rename tests/modules/{test_simple_import.as => test_simple_import.affine} (100%)
 rename tests/parser/{baseline_block.as => baseline_block.affine} (100%)
 rename tests/parser/{baseline_stmt.as => baseline_stmt.affine} (100%)
 rename tests/parser/{unsafe_all.as => unsafe_all.affine} (100%)
 rename tests/parser/{unsafe_empty.as => unsafe_empty.affine} (100%)
 rename tests/parser/{unsafe_ops.as => unsafe_ops.affine} (100%)
 rename tests/parser/{unsafe_read.as => unsafe_read.affine} (100%)
 rename tests/parser/{unsafe_simple.as => unsafe_simple.affine} (100%)
 rename tests/parser/{unsafe_stmt.as => unsafe_stmt.affine} (100%)
 rename tests/types/{test_dependent_e2e.as => test_dependent_e2e.affine} (100%)
 rename tests/types/{test_dependent_parsing.as => test_dependent_parsing.affine} (100%)
 rename tests/types/{test_effect_inference.as => test_effect_inference.affine} (100%)
 rename tests/types/{test_effect_lambda.as => test_effect_lambda.affine} (100%)
 rename tests/types/{test_effect_polymorphism.as => test_effect_polymorphism.affine} (100%)
 rename tests/types/{test_generic_programming.as => test_generic_programming.affine} (100%)
 rename tests/types/{test_hkt_parsing.as => test_hkt_parsing.affine} (100%)
 rename tests/types/{test_kind_checking.as => test_kind_checking.affine} (100%)
 rename tests/types/{test_lambda_scope_fix.as => test_lambda_scope_fix.affine} (100%)
 rename tests/types/{test_lambda_scope_simple.as => test_lambda_scope_simple.affine} (100%)
 rename tests/types/{test_parse_row_type.as => test_parse_row_type.affine} (100%)
 rename tests/types/{test_row_polymorphism.as => test_row_polymorphism.affine} (100%)
 rename tests/types/{test_row_simple.as => test_row_simple.affine} (100%)
 rename tests/types/{test_traits.as => test_traits.affine} (100%)

diff --git a/.gitattributes b/.gitattributes
index 7bbe6d5..523fe27 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -3,6 +3,9 @@
 
 * text=auto eol=lf
 
+# AffineScript source
+*.affine text eol=lf linguist-language=AffineScript
+
 # Source
 *.rs    text eol=lf diff=rust
 *.ex    text eol=lf diff=elixir
diff --git a/.machine_readable/6a2/STATE.a2ml b/.machine_readable/6a2/STATE.a2ml
index 487f828..5f87278 100644
--- a/.machine_readable/6a2/STATE.a2ml
+++ b/.machine_readable/6a2/STATE.a2ml
@@ -19,7 +19,7 @@ parser = "complete (1245 conflicts; block_terminator rule added for self-delimit
 type-checker = "99% (Never/bottom type handling fixed; block divergence propagation added)"
 borrow-checker = "95%"
 interpreter = "95%"
-wasm-codegen = "92% (real-world game compiles: airborne-submarine-squadron/src/main.as → 8KB WASM)"
+wasm-codegen = "92% (real-world game compiles: airborne-submarine-squadron/src/main.affine → 8KB WASM)"
 wasm-gc-codegen = "70% (WasmGC proposal target: struct.new/struct.get/array.new_fixed/array.get; --wasm-gc CLI flag)"
 julia-codegen = "exists"
 lsp-phase-a = "complete"
diff --git a/ALPHA-1-RELEASE-NOTES.md b/ALPHA-1-RELEASE-NOTES.md
index 444da95..c69c80e 100644
--- a/ALPHA-1-RELEASE-NOTES.md
+++ b/ALPHA-1-RELEASE-NOTES.md
@@ -95,13 +95,13 @@ dune build
 ### Try the Examples
 ```bash
 # Type check a game example
-dune exec affinescript -- check examples/hello.as
+dune exec affinescript -- check examples/hello.affine
 
 # Run with interpreter
-dune exec affinescript -- eval examples/hello.as
+dune exec affinescript -- eval examples/hello.affine
 
 # Compile to WebAssembly
-dune exec affinescript -- compile examples/hello.as -o hello.wasm
+dune exec affinescript -- compile examples/hello.affine -o hello.wasm
 ```
 
 ---
@@ -217,7 +217,7 @@ git clone --branch v0.1.0-alpha.1 https://github.com/hyperpolymath/affinescript
 
 # Build and run
 dune build
-dune exec affinescript -- eval examples/hello.as
+dune exec affinescript -- eval examples/hello.affine
 
 # Start building your bug-free game!
 ```
diff --git a/COMPILER-CAPABILITIES.md b/COMPILER-CAPABILITIES.md
index c00aa90..6447995 100644
--- a/COMPILER-CAPABILITIES.md
+++ b/COMPILER-CAPABILITIES.md
@@ -206,7 +206,7 @@ WebAssembly.instantiate(wasmBuffer).then(wasmModule => {
 ### Native Deployment (Future)
 ```bash
 # Future: Compile to native binary
-affinescript compile --target native --arch arm64 program.as
+affinescript compile --target native --arch arm64 program.affine
 ./program
 ```
 
diff --git a/FIXES_2026-01-23.md b/FIXES_2026-01-23.md
index ba9664e..475a3bc 100644
--- a/FIXES_2026-01-23.md
+++ b/FIXES_2026-01-23.md
@@ -189,7 +189,7 @@ and check_block (ctx : context) (blk : block) (expected : ty) : eff result =
 
 ### Created Tests
 
-**tests/borrow/use_after_move.as** - Should fail:
+**tests/borrow/use_after_move.affine** - Should fail:
 ```affinescript
 fn consume(own x: Int) -> Int { return x; }
 fn test_use_after_move() -> Int {
@@ -200,7 +200,7 @@ fn test_use_after_move() -> Int {
 }
 ```
 
-**tests/borrow/valid_move.as** - Should pass:
+**tests/borrow/valid_move.affine** - Should pass:
 ```affinescript
 fn consume(own x: Int) -> Int { return x; }
 fn test_valid_move() -> Int {
@@ -257,8 +257,8 @@ fn test_valid_move() -> Int {
 - `STATE.scm` - Updated completion %, blockers, accomplishments
 
 ### Tests Created
-- `tests/borrow/use_after_move.as` - Negative test
-- `tests/borrow/valid_move.as` - Positive test
+- `tests/borrow/use_after_move.affine` - Negative test
+- `tests/borrow/valid_move.affine` - Positive test
 
 ## Next Steps
 
diff --git a/MODULE-SYSTEM-PROGRESS.md b/MODULE-SYSTEM-PROGRESS.md
index 067314b..35700d7 100644
--- a/MODULE-SYSTEM-PROGRESS.md
+++ b/MODULE-SYSTEM-PROGRESS.md
@@ -29,9 +29,9 @@
 - bin/main.ml (integrated module loader)
 
 **Tests Passing:**
-- ✅ test_simple_import.as - Single function import
-- ✅ test_import.as - Multiple imports (Core + Math)
-- ✅ test_math_functions.as - Complex math operations
+- ✅ test_simple_import.affine - Single function import
+- ✅ test_import.affine - Multiple imports (Core + Math)
+- ✅ test_math_functions.affine - Complex math operations
 
 **Commit:** `a1b2c3d` "fix: Transfer type information during module imports"
 
@@ -53,9 +53,9 @@
 - lib/codegen.ml (~30 lines added)
 
 **Tests Passing:**
-- ✅ test_function_call.as - Simple helper function (returns 42)
-- ✅ test_recursive_call.as - Factorial recursion (returns 120)
-- ✅ test_multiple_calls.as - Multiple functions + composition (returns 135)
+- ✅ test_function_call.affine - Simple helper function (returns 42)
+- ✅ test_recursive_call.affine - Factorial recursion (returns 120)
+- ✅ test_multiple_calls.affine - Multiple functions + composition (returns 135)
 - All tests verified with Node.js WASM execution
 
 **Commit:** `31a60c5` "feat: Implement function calls in WASM codegen (Phase 2 complete)"
@@ -110,7 +110,7 @@
 **File:** `lib/module_loader.ml` (272 lines)
 
 **Features:**
-- Module path to file path resolution (`Math.Geometry` → `stdlib/Math/Geometry.as`)
+- Module path to file path resolution (`Math.Geometry` → `stdlib/Math/Geometry.affine`)
 - Configurable search paths (stdlib, current dir, additional paths)
 - Module file parsing and caching
 - Circular dependency detection
@@ -139,13 +139,13 @@
 
 ### 3. Standard Library Fixed ✅
 
-**Core.as:**
+**Core.affine:**
 - Removed underscore-prefixed parameters
 - Removed lambdas (parser limitation)
 - Added explicit `return` statements
 - Status: ✅ Working
 
-**Math.as:**
+**Math.affine:**
 - Converted `const` to functions
 - Removed float operations (type checker limitation)
 - Added explicit `return` statements
@@ -194,9 +194,9 @@ type context = {
 
 | Test | Feature | Expected | Result |
 |------|---------|----------|--------|
-| test_function_call.as | Simple call | 42 | ✅ PASS |
-| test_recursive_call.as | Recursion | 120 | ✅ PASS |
-| test_multiple_calls.as | Composition | 135 | ✅ PASS |
+| test_function_call.affine | Simple call | 42 | ✅ PASS |
+| test_recursive_call.affine | Recursion | 120 | ✅ PASS |
+| test_multiple_calls.affine | Composition | 135 | ✅ PASS |
 
 ## Module System Features Status
 
@@ -308,7 +308,7 @@ type context = {
 3. Integrate effects with borrow checker
 
 ### Short-term
-1. Fix Option.as and Result.as (explicit returns)
+1. Fix Option.affine and Result.affine (explicit returns)
 2. Add more stdlib modules
 3. Improve error messages
 
diff --git a/PHASE3-ASSESSMENT.md b/PHASE3-ASSESSMENT.md
index 088f512..31ce977 100644
--- a/PHASE3-ASSESSMENT.md
+++ b/PHASE3-ASSESSMENT.md
@@ -60,9 +60,9 @@ Phase 3 infrastructure is **surprisingly complete**! The type system (lib/types.
 
 **Test Cases Passing:**
 ```bash
-✓ tests/types/test_row_simple.as       # Basic row polymorphism
-✓ tests/types/test_parse_row_type.as   # Parser validation
-✓ tests/types/test_row_polymorphism.as # Complex multi-call test
+✓ tests/types/test_row_simple.affine       # Basic row polymorphism
+✓ tests/types/test_parse_row_type.affine   # Parser validation
+✓ tests/types/test_row_polymorphism.affine # Complex multi-call test
 ```
 
 **Example Working Code:**
@@ -246,7 +246,7 @@ fn apply[F: Type -> Type, G: Type -> Type, A](f: F[A], g: G[A]) -> F[A] {
 }
 ```
 
-**Test File:** tests/types/test_hkt_parsing.as ✅ PASSES
+**Test File:** tests/types/test_hkt_parsing.affine ✅ PASSES
 
 **What's Needed:**
 1. ❌ Integrate kind checking into type definitions
@@ -368,9 +368,9 @@ fn apply[F: Type -> Type, G: Type -> Type, A](f: F[A], g: G[A]) -> F[A] {
 
 **Test Cases Passing:**
 ```bash
-✓ tests/types/test_effect_inference.as  # Pure function composition
-✓ tests/types/test_row_polymorphism.as  # Still works with effect changes
-✓ tests/types/test_row_simple.as        # Still works
+✓ tests/types/test_effect_inference.affine  # Pure function composition
+✓ tests/types/test_row_polymorphism.affine  # Still works with effect changes
+✓ tests/types/test_row_simple.affine        # Still works
 ```
 
 **Known Limitation:**
@@ -438,31 +438,31 @@ fn take_positive(x: Int where (x > 0)) -> Int { return x; }
 fn dep_with_eff(f: (x: Int) -{IO}-> Int) -> Int { return 0; }
 ```
 
-**Test File:** tests/types/test_dependent_parsing.as ✅ PASSES
+**Test File:** tests/types/test_dependent_parsing.affine ✅ PASSES
 
 ## Testing Strategy
 
 ### ✅ Row Polymorphism Tests (COMPLETE)
-- ✅ tests/types/test_row_simple.as - Basic usage
-- ✅ tests/types/test_parse_row_type.as - Parser validation
-- ✅ tests/types/test_row_polymorphism.as - Complex scenarios
+- ✅ tests/types/test_row_simple.affine - Basic usage
+- ✅ tests/types/test_parse_row_type.affine - Parser validation
+- ✅ tests/types/test_row_polymorphism.affine - Complex scenarios
 
 ### ✅ Effect System Tests (COMPLETE)
-- ✅ tests/types/test_effect_inference.as - Pure function composition
+- ✅ tests/types/test_effect_inference.affine - Pure function composition
 
 ### ✅ Dependent Types Tests (PARSING COMPLETE)
-- ✅ tests/types/test_dependent_parsing.as - Parser validation for dependent arrows and refinements
+- ✅ tests/types/test_dependent_parsing.affine - Parser validation for dependent arrows and refinements
 
 ### ✅ Higher-Kinded Types Tests (COMPLETE)
-- ✅ tests/types/test_hkt_parsing.as - Parser validation for kind annotations and type applications
-- ✅ tests/types/test_kind_checking.as - Kind checking integration
+- ✅ tests/types/test_hkt_parsing.affine - Parser validation for kind annotations and type applications
+- ✅ tests/types/test_kind_checking.affine - Kind checking integration
 
 ### ✅ Generic Programming Tests (COMPLETE)
-- ✅ tests/types/test_traits.as - Trait definitions with higher-kinded types
-- ✅ tests/types/test_generic_programming.as - Functor, Applicative, Monad traits
+- ✅ tests/types/test_traits.affine - Trait definitions with higher-kinded types
+- ✅ tests/types/test_generic_programming.affine - Functor, Applicative, Monad traits
 
 ### ✅ End-to-End Tests (COMPLETE)
-- ✅ tests/types/test_dependent_e2e.as - Dependent types with refinements in practice
+- ✅ tests/types/test_dependent_e2e.affine - Dependent types with refinements in practice
 
 ## Conclusion
 
diff --git a/PHASE3-COMPLETE.md b/PHASE3-COMPLETE.md
index 804cdc9..8a6e18c 100644
--- a/PHASE3-COMPLETE.md
+++ b/PHASE3-COMPLETE.md
@@ -32,7 +32,7 @@ Implemented save-restore pattern for variable bindings:
 - Modified ExprLambda handling in `synth` function (lib/typecheck.ml:626-646)
 - Modified ExprLambda handling in `check` function (lib/typecheck.ml:982-997)
 
-**Test:** tests/types/test_lambda_scope_simple.as ✓ Passes
+**Test:** tests/types/test_lambda_scope_simple.affine ✓ Passes
 
 ### 1. Row Polymorphism (100%)
 **Implementation:** Extensible record types with row variables
@@ -208,19 +208,19 @@ fn fmap_twice[F: Type -> Type, A, B, C](
 | Generic Programming | 2 | ✅ |
 
 **Test Files:**
-1. ✅ test_lambda_scope_simple.as (Lambda scope fix)
-2. ✅ test_row_simple.as
-3. ✅ test_parse_row_type.as
-4. ✅ test_row_polymorphism.as
-5. ✅ test_effect_inference.as
-6. ✅ test_effect_lambda.as
-7. ✅ test_effect_polymorphism.as
-8. ✅ test_dependent_parsing.as
-9. ✅ test_dependent_e2e.as
-10. ✅ test_hkt_parsing.as
-11. ✅ test_kind_checking.as
-12. ✅ test_traits.as
-13. ✅ test_generic_programming.as
+1. ✅ test_lambda_scope_simple.affine (Lambda scope fix)
+2. ✅ test_row_simple.affine
+3. ✅ test_parse_row_type.affine
+4. ✅ test_row_polymorphism.affine
+5. ✅ test_effect_inference.affine
+6. ✅ test_effect_lambda.affine
+7. ✅ test_effect_polymorphism.affine
+8. ✅ test_dependent_parsing.affine
+9. ✅ test_dependent_e2e.affine
+10. ✅ test_hkt_parsing.affine
+11. ✅ test_kind_checking.affine
+12. ✅ test_traits.affine
+13. ✅ test_generic_programming.affine
 
 ## 📈 Progress Timeline
 
diff --git a/PHASE3-SESSION-SUMMARY.md b/PHASE3-SESSION-SUMMARY.md
index b597c85..133211e 100644
--- a/PHASE3-SESSION-SUMMARY.md
+++ b/PHASE3-SESSION-SUMMARY.md
@@ -21,9 +21,9 @@
 **Time:** 3.5 hours
 
 **Tests:**
-- ✓ tests/types/test_row_simple.as
-- ✓ tests/types/test_parse_row_type.as
-- ✓ tests/types/test_row_polymorphism.as
+- ✓ tests/types/test_row_simple.affine
+- ✓ tests/types/test_parse_row_type.affine
+- ✓ tests/types/test_row_polymorphism.affine
 
 ### 2. ✅ Effect Inference (85% Complete)
 
@@ -40,9 +40,9 @@
 **Time:** 2 hours
 
 **Tests:**
-- ✓ tests/types/test_effect_inference.as
-- ✓ tests/types/test_effect_lambda.as
-- ✓ tests/types/test_effect_polymorphism.as
+- ✓ tests/types/test_effect_inference.affine
+- ✓ tests/types/test_effect_lambda.affine
+- ✓ tests/types/test_effect_polymorphism.affine
 
 **Known Limitation:** Lambda parameter scope bug (pre-existing, separate issue)
 
@@ -81,7 +81,7 @@ Works with both pure and effectful functions!
 - Type checker integration ✓
 
 **Tests:**
-- ✓ tests/types/test_dependent_parsing.as
+- ✓ tests/types/test_dependent_parsing.affine
 
 **Example:**
 ```affinescript
@@ -114,7 +114,7 @@ fn take_positive(x: Int where (x > 0)) -> Int { return x; }
 **Time:** 0.5 hours
 
 **Tests:**
-- ✓ tests/types/test_hkt_parsing.as
+- ✓ tests/types/test_hkt_parsing.affine
 
 **Example:**
 ```affinescript
@@ -155,14 +155,14 @@ Much of Phase 3 infrastructure was **already implemented** but not integrated:
 **All 8 Phase 3 tests passing:**
 
 ```
-✓ tests/types/test_row_simple.as
-✓ tests/types/test_parse_row_type.as
-✓ tests/types/test_row_polymorphism.as
-✓ tests/types/test_effect_inference.as
-✓ tests/types/test_effect_lambda.as
-✓ tests/types/test_effect_polymorphism.as
-✓ tests/types/test_dependent_parsing.as
-✓ tests/types/test_hkt_parsing.as
+✓ tests/types/test_row_simple.affine
+✓ tests/types/test_parse_row_type.affine
+✓ tests/types/test_row_polymorphism.affine
+✓ tests/types/test_effect_inference.affine
+✓ tests/types/test_effect_lambda.affine
+✓ tests/types/test_effect_polymorphism.affine
+✓ tests/types/test_dependent_parsing.affine
+✓ tests/types/test_hkt_parsing.affine
 ```
 
 ## Phase 3 Status Breakdown
@@ -250,14 +250,14 @@ Row types created 20 shift/reduce conflicts. Solution was to write explicit recu
 - `lib/unify.ml` - Already complete (no changes needed)
 
 ### Tests Created:
-- `tests/types/test_row_simple.as`
-- `tests/types/test_parse_row_type.as`
-- `tests/types/test_row_polymorphism.as`
-- `tests/types/test_effect_inference.as`
-- `tests/types/test_effect_lambda.as`
-- `tests/types/test_effect_polymorphism.as`
-- `tests/types/test_dependent_parsing.as`
-- `tests/types/test_hkt_parsing.as`
+- `tests/types/test_row_simple.affine`
+- `tests/types/test_parse_row_type.affine`
+- `tests/types/test_row_polymorphism.affine`
+- `tests/types/test_effect_inference.affine`
+- `tests/types/test_effect_lambda.affine`
+- `tests/types/test_effect_polymorphism.affine`
+- `tests/types/test_dependent_parsing.affine`
+- `tests/types/test_hkt_parsing.affine`
 
 ### Documentation:
 - `PHASE3-ASSESSMENT.md` - Comprehensive progress tracking
diff --git a/README.adoc b/README.adoc
index 9b8a3df..d4516e9 100644
--- a/README.adoc
+++ b/README.adoc
@@ -299,22 +299,22 @@ total fn append[n: Nat, m: Nat, T](
 dune build
 
 # Type check a file
-dune exec affinescript -- check examples/hello.as
+dune exec affinescript -- check examples/hello.affine
 
 # Run with interpreter
-dune exec affinescript -- eval examples/factorial.as
+dune exec affinescript -- eval examples/factorial.affine
 
 # Compile to WebAssembly
-dune exec affinescript -- compile examples/hello.as -o hello.wasm
+dune exec affinescript -- compile examples/hello.affine -o hello.wasm
 
 # Format code
-dune exec affinescript -- fmt examples/hello.as
+dune exec affinescript -- fmt examples/hello.affine
 
 # Lint for code quality
-dune exec affinescript -- lint examples/hello.as
+dune exec affinescript -- lint examples/hello.affine
 
 # JSON diagnostics (for editors/CI)
-dune exec affinescript -- check --json examples/hello.as
+dune exec affinescript -- check --json examples/hello.affine
 ----
 
 == Project Status
diff --git a/SESSION-2026-01-23.md b/SESSION-2026-01-23.md
index 12e66f1..4f435f4 100644
--- a/SESSION-2026-01-23.md
+++ b/SESSION-2026-01-23.md
@@ -101,7 +101,7 @@ fn main() -> Int {
 - Multiple sequential effects don't work correctly
 
 **Documentation:** `docs/EFFECTS-IMPLEMENTATION.md`
-**Test:** `tests/effects/basic_effect.as`
+**Test:** `tests/effects/basic_effect.affine`
 
 ### 3. WebAssembly Code Generation Infrastructure 🔄
 
@@ -168,7 +168,7 @@ Created complete WASM code generation infrastructure:
 - **Files added:**
   - `docs/EFFECTS-IMPLEMENTATION.md`
   - `docs/tutorial/lesson-{02-10}-*.md` (9 files)
-  - `tests/effects/basic_effect.as`
+  - `tests/effects/basic_effect.affine`
 - **Files modified:**
   - `lib/value.ml`: Add PerformEffect error type
   - `lib/interp.ml`: Implement effect handlers
@@ -281,7 +281,7 @@ Created complete WASM code generation infrastructure:
 - `docs/tutorial/lesson-09-modules.md`
 - `docs/tutorial/lesson-10-building.md`
 - `docs/EFFECTS-IMPLEMENTATION.md`
-- `tests/effects/basic_effect.as`
+- `tests/effects/basic_effect.affine`
 - `lib/wasm.ml`
 - `lib/codegen.ml`
 - `SESSION-2026-01-23.md` (this file)
diff --git a/SESSION-COMPLETE.md b/SESSION-COMPLETE.md
index 31d5117..29c0782 100644
--- a/SESSION-COMPLETE.md
+++ b/SESSION-COMPLETE.md
@@ -46,7 +46,7 @@ This extended session completed all four priorities requested by the user:
 
 **Example:**
 ```bash
-affinescript eval program.as
+affinescript eval program.affine
 ```
 
 ## Priority 2: WebAssembly Codegen ✅ WORKING
@@ -91,7 +91,7 @@ affinescript eval program.as
 
 **End-to-End Pipeline:**
 ```
-AffineScript source (.as)
+AffineScript source (.affine)
     ↓ parse
 AST
     ↓ resolve names
@@ -106,7 +106,7 @@ Result
 
 ### Verified Working
 
-**Test Program:** `simple_arithmetic.as`
+**Test Program:** `simple_arithmetic.affine`
 ```affinescript
 fn main() -> Int {
   let a = 10;
@@ -118,7 +118,7 @@ fn main() -> Int {
 
 **Compilation:**
 ```bash
-affinescript compile simple_arithmetic.as -o test.wasm
+affinescript compile simple_arithmetic.affine -o test.wasm
 ```
 
 **Execution with Node.js:**
@@ -151,7 +151,7 @@ Still TODO for complete WASM support:
 
 ### Modules Created
 
-**1. Core.as** - Basic utilities (~100 lines)
+**1. Core.affine** - Basic utilities (~100 lines)
 ```affinescript
 pub fn min(a: Int, b: Int) -> Int
 pub fn max(a: Int, b: Int) -> Int
@@ -161,7 +161,7 @@ pub fn compose[A, B, C](f, g)  // Function composition
 pub fn flip[A, B, C](f)         // Flip arguments
 ```
 
-**2. Result.as** - Error handling (~120 lines)
+**2. Result.affine** - Error handling (~120 lines)
 ```affinescript
 pub fn unwrap[T, E](own r: Result[T, E]) -> T
 pub fn unwrap_or[T, E](own r: Result[T, E], default: T) -> T
@@ -169,7 +169,7 @@ pub fn map[T, U, E](own r: Result[T, E], f: fn(T) -> U) -> Result[U, E]
 pub fn and_then[T, U, E](own r: Result[T, E], f: fn(T) -> Result[U, E]) -> Result[U, E]
 ```
 
-**3. Option.as** - Optional values (~150 lines)
+**3. Option.affine** - Optional values (~150 lines)
 ```affinescript
 pub fn unwrap[T](own opt: Option[T]) -> T
 pub fn unwrap_or[T](own opt: Option[T], default: T) -> T
@@ -178,7 +178,7 @@ pub fn and_then[T, U](own opt: Option[T], f: fn(T) -> Option[U]) -> Option[U]
 pub fn filter[T](own opt: Option[T], pred: fn(ref T) -> Bool) -> Option[T]
 ```
 
-**4. Math.as** - Mathematical functions (~150 lines)
+**4. Math.affine** - Mathematical functions (~150 lines)
 ```affinescript
 pub const PI: Float = 3.141592653589793;
 pub const E: Float = 2.718281828459045;
@@ -318,14 +318,14 @@ pub fn area(radius: Float) -> Float {
 - `lib/wasm.ml` - WASM IR definitions
 - `lib/codegen.ml` - Code generator
 - `lib/wasm_encode.ml` - Binary encoder
-- `stdlib/Core.as` - Core utilities
-- `stdlib/Result.as` - Result error handling
-- `stdlib/Option.as` - Option optional values
-- `stdlib/Math.as` - Mathematical functions
+- `stdlib/Core.affine` - Core utilities
+- `stdlib/Result.affine` - Result error handling
+- `stdlib/Option.affine` - Option optional values
+- `stdlib/Math.affine` - Mathematical functions
 
 ### Tests
-- `tests/effects/basic_effect.as` - Effect handler test
-- `tests/codegen/simple_arithmetic.as` - WASM codegen test
+- `tests/effects/basic_effect.affine` - Effect handler test
+- `tests/codegen/simple_arithmetic.affine` - WASM codegen test
 
 ## Working Examples
 
@@ -348,7 +348,7 @@ fn main() -> Int {
 
 **Run:**
 ```bash
-affinescript eval effect_test.as
+affinescript eval effect_test.affine
 # Output: Program executed successfully
 ```
 
@@ -366,8 +366,8 @@ fn main() -> Int {
 
 **Compile:**
 ```bash
-affinescript compile arithmetic.as -o output.wasm
-# Output: Compiled arithmetic.as -> output.wasm
+affinescript compile arithmetic.affine -o output.wasm
+# Output: Compiled arithmetic.affine -> output.wasm
 ```
 
 **Execute:**
@@ -424,14 +424,14 @@ let local_count = ctx_final.next_local - param_count in
 
 ### Interpreter Tests
 ```bash
-affinescript eval tests/effects/basic_effect.as
-affinescript eval tests/borrow/valid_move.as
-affinescript eval tests/borrow/use_after_move.as  # Should fail
+affinescript eval tests/effects/basic_effect.affine
+affinescript eval tests/borrow/valid_move.affine
+affinescript eval tests/borrow/use_after_move.affine  # Should fail
 ```
 
 ### Codegen Tests
 ```bash
-affinescript compile tests/codegen/simple_arithmetic.as -o test.wasm
+affinescript compile tests/codegen/simple_arithmetic.affine -o test.wasm
 file test.wasm  # Should show: WebAssembly (wasm) binary module
 node run_wasm.js  # Should output: 42
 ```
diff --git a/TRAIT_SYSTEM_STATUS.md b/TRAIT_SYSTEM_STATUS.md
index 06b17f5..b8afc19 100644
--- a/TRAIT_SYSTEM_STATUS.md
+++ b/TRAIT_SYSTEM_STATUS.md
@@ -191,7 +191,7 @@ Known failures/limitations:
 
 **Example Output:**
 ```
-/tmp/test_type_mismatch.as:9:26: Type mismatch
+/tmp/test_type_mismatch.affine:9:26: Type mismatch
   Expected: Bool
   Actual: Int
   Cannot mix Int and Bool types.
@@ -331,7 +331,7 @@ The effect system core is **substantially complete** (95%). Effects:
 4. Mark builtin operations with appropriate effects
 
 **Testing:**
-- ✅ Basic trait method calls compile correctly (/tmp/test_effects.as)
+- ✅ Basic trait method calls compile correctly (/tmp/test_effects.affine)
 - ⚠️ Need tests for effect violations (pure calling impure)
 - ⚠️ Need tests with explicit effect annotations
 
diff --git a/conformance/invalid/001_unclosed_brace.as b/conformance/invalid/001_unclosed_brace.affine
similarity index 100%
rename from conformance/invalid/001_unclosed_brace.as
rename to conformance/invalid/001_unclosed_brace.affine
diff --git a/conformance/invalid/002_unclosed_string.as b/conformance/invalid/002_unclosed_string.affine
similarity index 100%
rename from conformance/invalid/002_unclosed_string.as
rename to conformance/invalid/002_unclosed_string.affine
diff --git a/conformance/invalid/003_bad_number.as b/conformance/invalid/003_bad_number.affine
similarity index 100%
rename from conformance/invalid/003_bad_number.as
rename to conformance/invalid/003_bad_number.affine
diff --git a/conformance/invalid/004_unexpected_token.as b/conformance/invalid/004_unexpected_token.affine
similarity index 100%
rename from conformance/invalid/004_unexpected_token.as
rename to conformance/invalid/004_unexpected_token.affine
diff --git a/conformance/invalid/005_missing_arrow.as b/conformance/invalid/005_missing_arrow.affine
similarity index 100%
rename from conformance/invalid/005_missing_arrow.as
rename to conformance/invalid/005_missing_arrow.affine
diff --git a/conformance/invalid/006_bad_operator.as b/conformance/invalid/006_bad_operator.affine
similarity index 100%
rename from conformance/invalid/006_bad_operator.as
rename to conformance/invalid/006_bad_operator.affine
diff --git a/conformance/invalid/007_incomplete_effect.as b/conformance/invalid/007_incomplete_effect.affine
similarity index 100%
rename from conformance/invalid/007_incomplete_effect.as
rename to conformance/invalid/007_incomplete_effect.affine
diff --git a/conformance/invalid/008_mismatched_parens.as b/conformance/invalid/008_mismatched_parens.affine
similarity index 100%
rename from conformance/invalid/008_mismatched_parens.as
rename to conformance/invalid/008_mismatched_parens.affine
diff --git a/conformance/invalid/009_reserved_keyword.as b/conformance/invalid/009_reserved_keyword.affine
similarity index 100%
rename from conformance/invalid/009_reserved_keyword.as
rename to conformance/invalid/009_reserved_keyword.affine
diff --git a/conformance/invalid/010_empty_match.as b/conformance/invalid/010_empty_match.affine
similarity index 100%
rename from conformance/invalid/010_empty_match.as
rename to conformance/invalid/010_empty_match.affine
diff --git a/conformance/invalid/011_bad_escape.as b/conformance/invalid/011_bad_escape.affine
similarity index 100%
rename from conformance/invalid/011_bad_escape.as
rename to conformance/invalid/011_bad_escape.affine
diff --git a/conformance/invalid/012_trailing_comma.as b/conformance/invalid/012_trailing_comma.affine
similarity index 100%
rename from conformance/invalid/012_trailing_comma.as
rename to conformance/invalid/012_trailing_comma.affine
diff --git a/conformance/valid/001_empty.as b/conformance/valid/001_empty.affine
similarity index 100%
rename from conformance/valid/001_empty.as
rename to conformance/valid/001_empty.affine
diff --git a/conformance/valid/002_comments.as b/conformance/valid/002_comments.affine
similarity index 100%
rename from conformance/valid/002_comments.as
rename to conformance/valid/002_comments.affine
diff --git a/conformance/valid/003_let_bindings.as b/conformance/valid/003_let_bindings.affine
similarity index 100%
rename from conformance/valid/003_let_bindings.as
rename to conformance/valid/003_let_bindings.affine
diff --git a/conformance/valid/004_literals.as b/conformance/valid/004_literals.affine
similarity index 100%
rename from conformance/valid/004_literals.as
rename to conformance/valid/004_literals.affine
diff --git a/conformance/valid/005_functions.as b/conformance/valid/005_functions.affine
similarity index 100%
rename from conformance/valid/005_functions.as
rename to conformance/valid/005_functions.affine
diff --git a/conformance/valid/006_type_alias.as b/conformance/valid/006_type_alias.affine
similarity index 100%
rename from conformance/valid/006_type_alias.as
rename to conformance/valid/006_type_alias.affine
diff --git a/conformance/valid/007_struct_def.as b/conformance/valid/007_struct_def.affine
similarity index 100%
rename from conformance/valid/007_struct_def.as
rename to conformance/valid/007_struct_def.affine
diff --git a/conformance/valid/008_enum_def.as b/conformance/valid/008_enum_def.affine
similarity index 100%
rename from conformance/valid/008_enum_def.as
rename to conformance/valid/008_enum_def.affine
diff --git a/conformance/valid/009_effect_def.as b/conformance/valid/009_effect_def.affine
similarity index 100%
rename from conformance/valid/009_effect_def.as
rename to conformance/valid/009_effect_def.affine
diff --git a/conformance/valid/010_pattern_match.as b/conformance/valid/010_pattern_match.affine
similarity index 100%
rename from conformance/valid/010_pattern_match.as
rename to conformance/valid/010_pattern_match.affine
diff --git a/conformance/valid/011_rows.as b/conformance/valid/011_rows.affine
similarity index 100%
rename from conformance/valid/011_rows.as
rename to conformance/valid/011_rows.affine
diff --git a/conformance/valid/012_ownership.as b/conformance/valid/012_ownership.affine
similarity index 100%
rename from conformance/valid/012_ownership.as
rename to conformance/valid/012_ownership.affine
diff --git a/docs/ALIB-INTEGRATION.md b/docs/ALIB-INTEGRATION.md
index 2262e5a..aca1b87 100644
--- a/docs/ALIB-INTEGRATION.md
+++ b/docs/ALIB-INTEGRATION.md
@@ -43,7 +43,7 @@ From `aggregate-library/`:
 **Action:** Implement aLib conformance test runner for AffineScript
 
 ```affinescript
-// stdlib/alib_conformance.as
+// stdlib/alib_conformance.affine
 fn run_collection_map_tests() -> TestResult {
   // Load test vectors from aggregate-library/specs/collection/map.md
   // Execute against AffineScript stdlib implementation
@@ -137,14 +137,14 @@ benchmarks:
 ```
 alib-for-affinescript/
 ├── src/
-│   ├── arithmetic.as      # Conformant arithmetic operations
-│   ├── collection.as      # Conformant collection operations
-│   ├── comparison.as      # Conformant comparison operations
-│   ├── string.as          # Conformant string operations
+│   ├── arithmetic.affine      # Conformant arithmetic operations
+│   ├── collection.affine      # Conformant collection operations
+│   ├── comparison.affine      # Conformant comparison operations
+│   ├── string.affine          # Conformant string operations
 │   └── ...
 ├── tests/
 │   └── conformance/       # aLib test vectors
-│       ├── runner.as
+│       ├── runner.affine
 │       └── vectors/       # Imported from aggregate-library
 ├── docs/
 │   └── affine-semantics.md  # AffineScript-specific notes
@@ -187,10 +187,10 @@ alib-for-affinescript/
 
 | AffineScript Module | aLib Spec | Conformance Status |
 |---------------------|-----------|-------------------|
-| `stdlib/prelude.as` | collection/{map,filter,fold} | Partial (needs testing) |
-| `stdlib/math.as` | arithmetic/* | Good (basic ops) |
-| `stdlib/string.as` | string/* | Partial (missing ops) |
-| `stdlib/collections.as` | collection/* | Good (comprehensive) |
+| `stdlib/prelude.affine` | collection/{map,filter,fold} | Partial (needs testing) |
+| `stdlib/math.affine` | arithmetic/* | Good (basic ops) |
+| `stdlib/string.affine` | string/* | Partial (missing ops) |
+| `stdlib/collections.affine` | collection/* | Good (comprehensive) |
 
 **Actions:**
 1. Add conformance attributes to stdlib functions:
@@ -252,7 +252,7 @@ All elements consumed exactly once.
 **Add to AffineScript test suite:**
 
 ```affinescript
-// tests/alib_conformance_test.as
+// tests/alib_conformance_test.affine
 
 // Auto-generated from aggregate-library/specs/collection/map.md
 fn test_map_conformance() -> TestResult {
@@ -314,7 +314,7 @@ Preserves order, only includes elements where predicate returns true
 ### 2. Implement in AffineScript (Affine Semantics)
 
 ```affinescript
-// stdlib/collections.as
+// stdlib/collections.affine
 
 /// Conforms to aLib collection/filter v1.0
 /// Affine semantics: Predicate borrows, source moved
@@ -333,7 +333,7 @@ fn filter<T: affine>(arr: [T], pred: &T -> Bool) -> [T] {
 ### 3. Run Conformance Tests
 
 ```affinescript
-// tests/conformance/collection_filter.as
+// tests/conformance/collection_filter.affine
 
 fn test_alib_filter_conformance() -> TestResult {
   // From aLib test vectors
diff --git a/docs/TYPECHECKER-COMPLETION.md b/docs/TYPECHECKER-COMPLETION.md
index 162ab3e..f10b096 100644
--- a/docs/TYPECHECKER-COMPLETION.md
+++ b/docs/TYPECHECKER-COMPLETION.md
@@ -308,8 +308,8 @@ Type checker completion tested via:
 
 ### Example Programs
 Created test files demonstrating new features:
-- `examples/typecheck_complete_test.as` - Full feature demonstration
-- `examples/typecheck_features_test.as` - Parseable subset
+- `examples/typecheck_complete_test.affine` - Full feature demonstration
+- `examples/typecheck_features_test.affine` - Parseable subset
 
 **Note:** Parser may not yet support all syntax (e.g., `unsafe` blocks), but type checker is ready when parser is completed.
 
diff --git a/docs/alib/README.md b/docs/alib/README.md
index db132fe..e3809b5 100644
--- a/docs/alib/README.md
+++ b/docs/alib/README.md
@@ -73,12 +73,12 @@ AffineScript stdlib aligns with these aLib categories:
 
 | aLib Category | AffineScript Module | Status |
 |---------------|---------------------|--------|
-| `arithmetic` | `stdlib/math.as` | ✓ Good |
-| `collection` | `stdlib/collections.as` + `prelude.as` | ⚠ Needs affine semantics docs |
-| `comparison` | `stdlib/prelude.as` | ✓ Good |
+| `arithmetic` | `stdlib/math.affine` | ✓ Good |
+| `collection` | `stdlib/collections.affine` + `prelude.affine` | ⚠ Needs affine semantics docs |
+| `comparison` | `stdlib/prelude.affine` | ✓ Good |
 | `conditional` | Built-in (if/match) | ✓ Good |
 | `logical` | Built-in (&&, \|\|, !) | ✓ Good |
-| `string` | `stdlib/string.as` | ⚠ Partial |
+| `string` | `stdlib/string.affine` | ⚠ Partial |
 
 ## Affine Semantics Examples
 
diff --git a/docs/guides/TESTING-REPORT.adoc b/docs/guides/TESTING-REPORT.adoc
index f898a6a..382dafd 100644
--- a/docs/guides/TESTING-REPORT.adoc
+++ b/docs/guides/TESTING-REPORT.adoc
@@ -210,7 +210,7 @@ Menhir resolves by preferring shift (continue parsing statement), which breaks t
 
 == Example Files
 
-=== hello.as
+=== hello.affine
 
 Fixed syntax for effect annotations:
 
@@ -221,7 +221,7 @@ The parser uses `-{Eff}->` syntax, not `-> T / Eff`.
 
 === Other Examples
 
-The example files (`effects.as`, `ownership.as`, `traits.as`, etc.) use aspirational syntax that is not yet supported:
+The example files (`effects.affine`, `ownership.affine`, `traits.affine`, etc.) use aspirational syntax that is not yet supported:
 
 * `-> T / Eff` effect syntax (parser uses `-{Eff}-> T`)
 * GADT-style enum variants (`| Nil : Vec[0, T]`)
@@ -237,10 +237,10 @@ The compiler CLI works correctly:
 $ affinescript --help
 # Shows help for: check, compile, lex, parse commands
 
-$ affinescript lex examples/hello.as
+$ affinescript lex examples/hello.affine
 # Successfully tokenizes the file
 
-$ affinescript parse examples/hello.as
+$ affinescript parse examples/hello.affine
 # Successfully parses (after syntax fix)
 ----
 
@@ -274,4 +274,4 @@ $ affinescript parse examples/hello.as
 * `lib/ast.ml` - Added trd_where field
 * `lib/parse.ml` - Removed WITH token
 * `test/test_parser.ml` - Fixed pattern matching
-* `examples/hello.as` - Fixed effect syntax
+* `examples/hello.affine` - Fixed effect syntax
diff --git a/docs/guides/TESTING-REPORT.scm b/docs/guides/TESTING-REPORT.scm
index 7b05e84..d291eec 100644
--- a/docs/guides/TESTING-REPORT.scm
+++ b/docs/guides/TESTING-REPORT.scm
@@ -205,49 +205,49 @@
 
   (cli-testing
     (command "affinescript --help" (status pass))
-    (command "affinescript lex examples/hello.as" (status pass))
-    (command "affinescript parse examples/hello.as" (status pass)
+    (command "affinescript lex examples/hello.affine" (status pass))
+    (command "affinescript parse examples/hello.affine" (status pass)
       (note "After fixing effect syntax")))
 
   (example-files
     (file
-      (name "hello.as")
+      (name "hello.affine")
       (status fixed)
       (issue "Effect syntax mismatch")
       (fix "Changed `-> () / IO` to `-{IO}-> ()`"))
 
     (file
-      (name "effects.as")
+      (name "effects.affine")
       (status needs-update)
       (issues
         "Uses aspirational syntax not yet implemented"))
 
     (file
-      (name "ownership.as")
+      (name "ownership.affine")
       (status needs-update)
       (issues
         "Uses aspirational syntax not yet implemented"))
 
     (file
-      (name "traits.as")
+      (name "traits.affine")
       (status needs-update)
       (issues
         "Uses aspirational syntax not yet implemented"))
 
     (file
-      (name "refinements.as")
+      (name "refinements.affine")
       (status needs-update)
       (issues
         "Uses aspirational syntax not yet implemented"))
 
     (file
-      (name "rows.as")
+      (name "rows.affine")
       (status needs-update)
       (issues
         "Uses aspirational syntax not yet implemented"))
 
     (file
-      (name "vectors.as")
+      (name "vectors.affine")
       (status needs-update)
       (issues
         "Uses aspirational syntax not yet implemented")))
@@ -283,5 +283,5 @@
       (changes "Removed WITH token mapping"))
     (file "test/test_parser.ml"
       (changes "Fixed pattern matching issues"))
-    (file "examples/hello.as"
+    (file "examples/hello.affine"
       (changes "Fixed effect annotation syntax"))))
diff --git a/docs/guides/lessons/README.md b/docs/guides/lessons/README.md
index 13d796b..513db14 100644
--- a/docs/guides/lessons/README.md
+++ b/docs/guides/lessons/README.md
@@ -40,14 +40,14 @@ Each lesson is a markdown file you can read on GitHub.
 
 ### Option 2: Interactive Playground
 1. Open the [Playground](../../../playground/test.html)
-2. Load the lesson example (e.g., `examples/lessons/01_hello.as`)
+2. Load the lesson example (e.g., `examples/lessons/01_hello.affine`)
 3. Follow along by running code as you read
 
 ### Option 3: Clone and Experiment
 ```bash
 git clone https://github.com/hyperpolymath/affinescript
 cd affinescript
-./affinescript examples/lessons/01_hello.as
+./affinescript examples/lessons/01_hello.affine
 ```
 
 ---
diff --git a/docs/spec.md b/docs/spec.md
index 7939a62..b2456e9 100644
--- a/docs/spec.md
+++ b/docs/spec.md
@@ -1644,7 +1644,7 @@ tests/
 
 ```
 error[E0501]: cannot use `file` after move
-  --> src/main.as:10:5
+  --> src/main.affine:10:5
    |
  8 |     close(file);
    |           ---- value moved here
@@ -1657,7 +1657,7 @@ error[E0501]: cannot use `file` after move
 
 ```
 error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immutable
-  --> src/main.as:5:10
+  --> src/main.affine:5:10
    |
  4 |     let r = ref x;
    |             ----- immutable borrow occurs here
@@ -1671,7 +1671,7 @@ error[E0502]: cannot borrow `x` as mutable because it is also borrowed as immuta
 
 ```
 error[E0308]: mismatched types
-  --> src/main.as:5:12
+  --> src/main.affine:5:12
    |
  5 |     head(empty)
    |          ^^^^^ expected `Vec[n + 1, T]`, found `Vec[0, T]`
@@ -1682,7 +1682,7 @@ error[E0308]: mismatched types
 
 ```
 error[E0309]: refinement predicate not satisfied
-  --> src/main.as:8:15
+  --> src/main.affine:8:15
    |
  8 |     safeGet(arr, 10)
    |                  ^^ cannot prove `10 < 5`
@@ -1694,7 +1694,7 @@ error[E0309]: refinement predicate not satisfied
 
 ```
 error[E0601]: effect not handled
-  --> src/main.as:3:5
+  --> src/main.affine:3:5
    |
  3 |     println("hello")
    |     ^^^^^^^^^^^^^^^^ this has effect `IO`
@@ -1705,7 +1705,7 @@ error[E0601]: effect not handled
 
 ```
 warning[W0602]: owned resource may leak on exception
-  --> src/main.as:8:5
+  --> src/main.affine:8:5
    |
  7 |     let file = open(path)?;
    |         ---- owned resource acquired here
@@ -1722,7 +1722,7 @@ warning[W0602]: owned resource may leak on exception
 
 ```
 error[E0401]: no implementation of trait `Show` for type `MyType`
-  --> src/main.as:5:5
+  --> src/main.affine:5:5
    |
  5 |     println(x.show())
    |             ^^^^^^^^ `Show` is not implemented for `MyType`
@@ -1740,7 +1740,7 @@ error[E0401]: no implementation of trait `Show` for type `MyType`
 
 ```
 error[E0701]: cannot find `Vec` in this scope
-  --> src/main.as:3:10
+  --> src/main.affine:3:10
    |
  3 |     let v: Vec[3, Int] = Nil;
    |            ^^^ not found in this scope
@@ -1750,7 +1750,7 @@ error[E0701]: cannot find `Vec` in this scope
 
 ```
 error[E0702]: function `helper` is private
-  --> src/main.as:5:5
+  --> src/main.affine:5:5
    |
  5 |     Utils.helper()
    |     ^^^^^^^^^^^^^^ private function
diff --git a/docs/standards/RELEASE.md b/docs/standards/RELEASE.md
index 43c4a51..390aaf3 100644
--- a/docs/standards/RELEASE.md
+++ b/docs/standards/RELEASE.md
@@ -15,13 +15,13 @@ This is the first public release of AffineScript, featuring a complete specifica
 - **Error Handling** - Structured diagnostics with source locations
 
 ### Examples
-- `examples/hello.as` - Hello World with effects
-- `examples/vectors.as` - Dependent types with length-indexed vectors
-- `examples/ownership.as` - Ownership and borrowing patterns
-- `examples/rows.as` - Row polymorphism
-- `examples/effects.as` - Effect handling and state
-- `examples/traits.as` - Traits and type classes
-- `examples/refinements.as` - Refinement types
+- `examples/hello.affine` - Hello World with effects
+- `examples/vectors.affine` - Dependent types with length-indexed vectors
+- `examples/ownership.affine` - Ownership and borrowing patterns
+- `examples/rows.affine` - Row polymorphism
+- `examples/effects.affine` - Effect handling and state
+- `examples/traits.affine` - Traits and type classes
+- `examples/refinements.affine` - Refinement types
 
 ## Building from Source
 
@@ -70,7 +70,7 @@ dune build
 ### Lex a File
 
 ```bash
-dune exec affinescript -- lex examples/hello.as
+dune exec affinescript -- lex examples/hello.affine
 ```
 
 Output:
@@ -85,7 +85,7 @@ FN @ 2:3-2:5
 ### Parse a File
 
 ```bash
-dune exec affinescript -- parse examples/hello.as
+dune exec affinescript -- parse examples/hello.affine
 ```
 
 Output:
@@ -100,7 +100,7 @@ Output:
 ### Check a File (WIP)
 
 ```bash
-dune exec affinescript -- check examples/hello.as
+dune exec affinescript -- check examples/hello.affine
 ```
 
 Note: Type checking is not yet implemented in this release.
diff --git a/docs/tutorial/lesson-10-building.md b/docs/tutorial/lesson-10-building.md
index f71816d..345d86f 100644
--- a/docs/tutorial/lesson-10-building.md
+++ b/docs/tutorial/lesson-10-building.md
@@ -5,11 +5,11 @@
 ```
 my-project/
 ├── src/
-│   ├── main.as
-│   ├── lib.as
-│   └── util.as
+│   ├── main.affine
+│   ├── lib.affine
+│   └── util.affine
 ├── tests/
-│   └── test_main.as
+│   └── test_main.affine
 └── affinescript.toml
 ```
 
@@ -27,13 +27,13 @@ fn test_addition() -> TestResult {
 
 ```bash
 # Check types and borrow checker
-affinescript check src/main.as
+affinescript check src/main.affine
 
 # Compile to WebAssembly
-affinescript compile src/main.as -o output.wasm
+affinescript compile src/main.affine -o output.wasm
 
 # Run with interpreter
-affinescript eval src/main.as
+affinescript eval src/main.affine
 ```
 
 ## Next Steps
diff --git a/editors/tree-sitter-affinescript/package.json b/editors/tree-sitter-affinescript/package.json
index 19c5c03..bf0146f 100644
--- a/editors/tree-sitter-affinescript/package.json
+++ b/editors/tree-sitter-affinescript/package.json
@@ -23,7 +23,7 @@
   "tree-sitter": [
     {
       "scope": "source.affinescript",
-      "file-types": ["as"],
+      "file-types": ["affine"],
       "highlights": "queries/highlights.scm"
     }
   ]
diff --git a/editors/vscode/package.json b/editors/vscode/package.json
index afe2589..33d0082 100644
--- a/editors/vscode/package.json
+++ b/editors/vscode/package.json
@@ -38,7 +38,7 @@
           "affinescript"
         ],
         "extensions": [
-          ".as"
+          ".affine"
         ],
         "configuration": "./language-configuration.json",
         "icon": {
diff --git a/editors/vscode/src/extension.ts b/editors/vscode/src/extension.ts
index 2a9e5f7..816c2bd 100644
--- a/editors/vscode/src/extension.ts
+++ b/editors/vscode/src/extension.ts
@@ -64,7 +64,7 @@ async function startLsp(context: vscode.ExtensionContext) {
   const clientOptions: LanguageClientOptions = {
     documentSelector: [{ scheme: 'file', language: 'affinescript' }],
     synchronize: {
-      fileEvents: vscode.workspace.createFileSystemWatcher('**/*.as')
+      fileEvents: vscode.workspace.createFileSystemWatcher('**/*.affine')
     }
   };
 
@@ -125,7 +125,7 @@ async function compileCurrentFile() {
   }
 
   const filePath = editor.document.uri.fsPath;
-  const outputPath = filePath.replace(/\.as$/, '.wasm');
+  const outputPath = filePath.replace(/\.affine$/, '.wasm');
 
   const terminal = vscode.window.createTerminal('AffineScript Compile');
   terminal.show();
diff --git a/examples/comprehensive_test.as b/examples/comprehensive_test.affine
similarity index 100%
rename from examples/comprehensive_test.as
rename to examples/comprehensive_test.affine
diff --git a/examples/dependent_types.as b/examples/dependent_types.affine
similarity index 100%
rename from examples/dependent_types.as
rename to examples/dependent_types.affine
diff --git a/examples/effects.as b/examples/effects.affine
similarity index 100%
rename from examples/effects.as
rename to examples/effects.affine
diff --git a/examples/exception_test.as b/examples/exception_test.affine
similarity index 100%
rename from examples/exception_test.as
rename to examples/exception_test.affine
diff --git a/examples/hello.as b/examples/hello.affine
similarity index 100%
rename from examples/hello.as
rename to examples/hello.affine
diff --git a/examples/lessons/01_hello.as b/examples/lessons/01_hello.affine
similarity index 100%
rename from examples/lessons/01_hello.as
rename to examples/lessons/01_hello.affine
diff --git a/examples/ownership.as b/examples/ownership.affine
similarity index 100%
rename from examples/ownership.as
rename to examples/ownership.affine
diff --git a/examples/refinements.as b/examples/refinements.affine
similarity index 100%
rename from examples/refinements.as
rename to examples/refinements.affine
diff --git a/examples/rows.as b/examples/rows.affine
similarity index 100%
rename from examples/rows.as
rename to examples/rows.affine
diff --git a/examples/simple_test.as b/examples/simple_test.affine
similarity index 100%
rename from examples/simple_test.as
rename to examples/simple_test.affine
diff --git a/examples/traits.as b/examples/traits.affine
similarity index 100%
rename from examples/traits.as
rename to examples/traits.affine
diff --git a/examples/typecheck_complete_test.as b/examples/typecheck_complete_test.affine
similarity index 100%
rename from examples/typecheck_complete_test.as
rename to examples/typecheck_complete_test.affine
diff --git a/examples/typecheck_features_test.as b/examples/typecheck_features_test.affine
similarity index 100%
rename from examples/typecheck_features_test.as
rename to examples/typecheck_features_test.affine
diff --git a/examples/vectors.as b/examples/vectors.affine
similarity index 100%
rename from examples/vectors.as
rename to examples/vectors.affine
diff --git a/lib/json_output.ml b/lib/json_output.ml
index ce35c03..1946c20 100644
--- a/lib/json_output.ml
+++ b/lib/json_output.ml
@@ -16,7 +16,7 @@
             "severity": "error" | "warning" | "hint" | "info",
             "code": "E0001",
             "message": "...",
-            "file": "path/to/file.as",
+            "file": "path/to/file.affine",
             "start_line": 1,
             "start_col": 1,
             "end_line": 1,
@@ -342,7 +342,7 @@ let of_lint_diagnostic (d : Linter.diagnostic) : diagnostic =
             "id": 0,
             "name": "foo",
             "kind": "function",
-            "file": "path/to/file.as",
+            "file": "path/to/file.affine",
             "start_line": 1, "start_col": 4,
             "end_line": 1, "end_col": 7,
             "type": "Int -> Int" | null,
diff --git a/lib/module_loader.ml b/lib/module_loader.ml
index d9fb292..b5f9559 100644
--- a/lib/module_loader.ml
+++ b/lib/module_loader.ml
@@ -63,19 +63,19 @@ let default_config () : config =
 (** Convert module path to file path candidates
 
     For module path ["Math", "Geometry"], try:
-    1. Math/Geometry.as (nested module)
-    2. Math.as (check if it exports Geometry)
+    1. Math/Geometry.affine (nested module)
+    2. Math.affine (check if it exports Geometry)
 *)
 let path_to_candidates (mod_path : string list) : string list =
   match mod_path with
   | [] -> []
-  | [name] -> [name ^ ".as"]
+  | [name] -> [name ^ ".affine"]
   | _ ->
-    (* Try nested path: A/B/C.as *)
-    let nested = String.concat "/" mod_path ^ ".as" in
-    (* Try parent with submodule: A/B.as (if B declares module C) *)
+    (* Try nested path: A/B/C.affine *)
+    let nested = String.concat "/" mod_path ^ ".affine" in
+    (* Try parent with submodule: A/B.affine (if B declares module C) *)
     let parent_parts = List.rev mod_path |> List.tl |> List.rev in
-    let parent = String.concat "/" parent_parts ^ ".as" in
+    let parent = String.concat "/" parent_parts ^ ".affine" in
     [nested; parent]
 
 (** Search for a module file in search paths *)
diff --git a/stdlib/Core.as b/stdlib/Core.affine
similarity index 100%
rename from stdlib/Core.as
rename to stdlib/Core.affine
diff --git a/stdlib/Math.as b/stdlib/Math.affine
similarity index 100%
rename from stdlib/Math.as
rename to stdlib/Math.affine
diff --git a/stdlib/Option.as b/stdlib/Option.affine
similarity index 100%
rename from stdlib/Option.as
rename to stdlib/Option.affine
diff --git a/stdlib/README.md b/stdlib/README.md
index b8bc1d3..1ec68a9 100644
--- a/stdlib/README.md
+++ b/stdlib/README.md
@@ -166,8 +166,8 @@ To add new stdlib functions:
 Test standard library functions:
 
 ```bash
-affinescript eval tests/stdlib/test_core.as
-affinescript eval tests/stdlib/test_result.as
-affinescript eval tests/stdlib/test_option.as
-affinescript eval tests/stdlib/test_math.as
+affinescript eval tests/stdlib/test_core.affine
+affinescript eval tests/stdlib/test_result.affine
+affinescript eval tests/stdlib/test_option.affine
+affinescript eval tests/stdlib/test_math.affine
 ```
diff --git a/stdlib/Result.as b/stdlib/Result.affine
similarity index 100%
rename from stdlib/Result.as
rename to stdlib/Result.affine
diff --git a/stdlib/collections.as b/stdlib/collections.affine
similarity index 100%
rename from stdlib/collections.as
rename to stdlib/collections.affine
diff --git a/stdlib/effects.as b/stdlib/effects.affine
similarity index 100%
rename from stdlib/effects.as
rename to stdlib/effects.affine
diff --git a/stdlib/io.as b/stdlib/io.affine
similarity index 100%
rename from stdlib/io.as
rename to stdlib/io.affine
diff --git a/stdlib/math.as b/stdlib/math.affine
similarity index 100%
rename from stdlib/math.as
rename to stdlib/math.affine
diff --git a/stdlib/option.as b/stdlib/option.affine
similarity index 100%
rename from stdlib/option.as
rename to stdlib/option.affine
diff --git a/stdlib/prelude.as b/stdlib/prelude.affine
similarity index 100%
rename from stdlib/prelude.as
rename to stdlib/prelude.affine
diff --git a/stdlib/result.as b/stdlib/result.affine
similarity index 100%
rename from stdlib/result.as
rename to stdlib/result.affine
diff --git a/stdlib/string.as b/stdlib/string.affine
similarity index 100%
rename from stdlib/string.as
rename to stdlib/string.affine
diff --git a/stdlib/testing.as b/stdlib/testing.affine
similarity index 100%
rename from stdlib/testing.as
rename to stdlib/testing.affine
diff --git a/stdlib/traits.as b/stdlib/traits.affine
similarity index 100%
rename from stdlib/traits.as
rename to stdlib/traits.affine
diff --git a/test/e2e/fixtures/affine_basic.as b/test/e2e/fixtures/affine_basic.affine
similarity index 100%
rename from test/e2e/fixtures/affine_basic.as
rename to test/e2e/fixtures/affine_basic.affine
diff --git a/test/e2e/fixtures/affine_violation.as b/test/e2e/fixtures/affine_violation.affine
similarity index 100%
rename from test/e2e/fixtures/affine_violation.as
rename to test/e2e/fixtures/affine_violation.affine
diff --git a/test/e2e/fixtures/arithmetic.as b/test/e2e/fixtures/arithmetic.affine
similarity index 100%
rename from test/e2e/fixtures/arithmetic.as
rename to test/e2e/fixtures/arithmetic.affine
diff --git a/test/e2e/fixtures/dependent_types.as b/test/e2e/fixtures/dependent_types.affine
similarity index 100%
rename from test/e2e/fixtures/dependent_types.as
rename to test/e2e/fixtures/dependent_types.affine
diff --git a/test/e2e/fixtures/effects.as b/test/e2e/fixtures/effects.affine
similarity index 100%
rename from test/e2e/fixtures/effects.as
rename to test/e2e/fixtures/effects.affine
diff --git a/test/e2e/fixtures/erased_violation.as b/test/e2e/fixtures/erased_violation.affine
similarity index 100%
rename from test/e2e/fixtures/erased_violation.as
rename to test/e2e/fixtures/erased_violation.affine
diff --git a/test/e2e/fixtures/full_pipeline.as b/test/e2e/fixtures/full_pipeline.affine
similarity index 100%
rename from test/e2e/fixtures/full_pipeline.as
rename to test/e2e/fixtures/full_pipeline.affine
diff --git a/test/e2e/fixtures/interp_simple.as b/test/e2e/fixtures/interp_simple.affine
similarity index 100%
rename from test/e2e/fixtures/interp_simple.as
rename to test/e2e/fixtures/interp_simple.affine
diff --git a/test/e2e/fixtures/julia_simple.as b/test/e2e/fixtures/julia_simple.affine
similarity index 100%
rename from test/e2e/fixtures/julia_simple.as
rename to test/e2e/fixtures/julia_simple.affine
diff --git a/test/e2e/fixtures/lambda.as b/test/e2e/fixtures/lambda.affine
similarity index 100%
rename from test/e2e/fixtures/lambda.as
rename to test/e2e/fixtures/lambda.affine
diff --git a/test/e2e/fixtures/ownership.as b/test/e2e/fixtures/ownership.affine
similarity index 100%
rename from test/e2e/fixtures/ownership.as
rename to test/e2e/fixtures/ownership.affine
diff --git a/test/e2e/fixtures/pattern_match.as b/test/e2e/fixtures/pattern_match.affine
similarity index 100%
rename from test/e2e/fixtures/pattern_match.as
rename to test/e2e/fixtures/pattern_match.affine
diff --git a/test/e2e/fixtures/refinement_types.as b/test/e2e/fixtures/refinement_types.affine
similarity index 100%
rename from test/e2e/fixtures/refinement_types.as
rename to test/e2e/fixtures/refinement_types.affine
diff --git a/test/e2e/fixtures/row_polymorphism.as b/test/e2e/fixtures/row_polymorphism.affine
similarity index 100%
rename from test/e2e/fixtures/row_polymorphism.as
rename to test/e2e/fixtures/row_polymorphism.affine
diff --git a/test/e2e/fixtures/traits.as b/test/e2e/fixtures/traits.affine
similarity index 100%
rename from test/e2e/fixtures/traits.as
rename to test/e2e/fixtures/traits.affine
diff --git a/test/e2e/fixtures/type_decls.as b/test/e2e/fixtures/type_decls.affine
similarity index 100%
rename from test/e2e/fixtures/type_decls.as
rename to test/e2e/fixtures/type_decls.affine
diff --git a/test/e2e/fixtures/wasm_simple.as b/test/e2e/fixtures/wasm_simple.affine
similarity index 100%
rename from test/e2e/fixtures/wasm_simple.as
rename to test/e2e/fixtures/wasm_simple.affine
diff --git a/test/golden/binary_ops.as b/test/golden/binary_ops.affine
similarity index 100%
rename from test/golden/binary_ops.as
rename to test/golden/binary_ops.affine
diff --git a/test/golden/effects.as b/test/golden/effects.affine
similarity index 100%
rename from test/golden/effects.as
rename to test/golden/effects.affine
diff --git a/test/golden/functions.as b/test/golden/functions.affine
similarity index 100%
rename from test/golden/functions.as
rename to test/golden/functions.affine
diff --git a/test/golden/hello.as b/test/golden/hello.affine
similarity index 100%
rename from test/golden/hello.as
rename to test/golden/hello.affine
diff --git a/test/golden/imports.as b/test/golden/imports.affine
similarity index 100%
rename from test/golden/imports.as
rename to test/golden/imports.affine
diff --git a/test/golden/lambda.as b/test/golden/lambda.affine
similarity index 100%
rename from test/golden/lambda.as
rename to test/golden/lambda.affine
diff --git a/test/golden/literals.as b/test/golden/literals.affine
similarity index 100%
rename from test/golden/literals.as
rename to test/golden/literals.affine
diff --git a/test/golden/ownership.as b/test/golden/ownership.affine
similarity index 100%
rename from test/golden/ownership.as
rename to test/golden/ownership.affine
diff --git a/test/golden/patterns.as b/test/golden/patterns.affine
similarity index 100%
rename from test/golden/patterns.as
rename to test/golden/patterns.affine
diff --git a/test/golden/rows.as b/test/golden/rows.affine
similarity index 100%
rename from test/golden/rows.as
rename to test/golden/rows.affine
diff --git a/test/golden/traits.as b/test/golden/traits.affine
similarity index 100%
rename from test/golden/traits.as
rename to test/golden/traits.affine
diff --git a/test/golden/types.as b/test/golden/types.affine
similarity index 100%
rename from test/golden/types.as
rename to test/golden/types.affine
diff --git a/test/test_e2e.ml b/test/test_e2e.ml
index 367c017..652a861 100644
--- a/test/test_e2e.ml
+++ b/test/test_e2e.ml
@@ -155,33 +155,33 @@ let run_interp_pipeline path =
 *)
 
 let test_parse_arithmetic () =
-  match parse_fixture (fixture "arithmetic.as") with
+  match parse_fixture (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check int) "declaration count" 6 (List.length prog.prog_decls)
 
 let test_parse_affine_basic () =
-  match parse_fixture (fixture "affine_basic.as") with
+  match parse_fixture (fixture "affine_basic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check int) "declaration count" 4 (List.length prog.prog_decls)
 
 let test_parse_dependent_types () =
-  match parse_fixture (fixture "dependent_types.as") with
+  match parse_fixture (fixture "dependent_types.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     (* 1 type decl + 3 functions *)
     Alcotest.(check int) "declaration count" 4 (List.length prog.prog_decls)
 
 let test_parse_refinement_types () =
-  match parse_fixture (fixture "refinement_types.as") with
+  match parse_fixture (fixture "refinement_types.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check bool) "has declarations" true
       (List.length prog.prog_decls > 0)
 
 let test_parse_traits () =
-  match parse_fixture (fixture "traits.as") with
+  match parse_fixture (fixture "traits.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     (* Count trait decls, impls, struct, enum, and functions *)
@@ -195,7 +195,7 @@ let test_parse_traits () =
     Alcotest.(check bool) "has impls" true has_impl
 
 let test_parse_effects () =
-  match parse_fixture (fixture "effects.as") with
+  match parse_fixture (fixture "effects.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     let has_effect = List.exists (fun d ->
@@ -204,27 +204,27 @@ let test_parse_effects () =
     Alcotest.(check bool) "has effects" true has_effect
 
 let test_parse_ownership () =
-  match parse_fixture (fixture "ownership.as") with
+  match parse_fixture (fixture "ownership.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check bool) "has declarations" true
       (List.length prog.prog_decls > 0)
 
 let test_parse_row_polymorphism () =
-  match parse_fixture (fixture "row_polymorphism.as") with
+  match parse_fixture (fixture "row_polymorphism.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check int) "declaration count" 3 (List.length prog.prog_decls)
 
 let test_parse_pattern_match () =
-  match parse_fixture (fixture "pattern_match.as") with
+  match parse_fixture (fixture "pattern_match.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check bool) "has declarations" true
       (List.length prog.prog_decls > 0)
 
 let test_parse_type_decls () =
-  match parse_fixture (fixture "type_decls.as") with
+  match parse_fixture (fixture "type_decls.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     let has_type = List.exists (fun d ->
@@ -233,14 +233,14 @@ let test_parse_type_decls () =
     Alcotest.(check bool) "has type decls" true has_type
 
 let test_parse_lambda () =
-  match parse_fixture (fixture "lambda.as") with
+  match parse_fixture (fixture "lambda.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     Alcotest.(check bool) "has declarations" true
       (List.length prog.prog_decls > 0)
 
 let test_parse_full_pipeline () =
-  match parse_fixture (fixture "full_pipeline.as") with
+  match parse_fixture (fixture "full_pipeline.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     (* struct Vec2, enum Shape, 4 functions + main *)
@@ -271,7 +271,7 @@ let parse_tests = [
 *)
 
 let test_resolve_arithmetic () =
-  match parse_fixture (fixture "arithmetic.as") with
+  match parse_fixture (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -282,7 +282,7 @@ let test_resolve_arithmetic () =
         (Symbol.lookup ctx.symbols "add" <> None)
 
 let test_resolve_traits () =
-  match parse_fixture (fixture "traits.as") with
+  match parse_fixture (fixture "traits.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -292,7 +292,7 @@ let test_resolve_traits () =
       ()
 
 let test_resolve_effects () =
-  match parse_fixture (fixture "effects.as") with
+  match parse_fixture (fixture "effects.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -300,7 +300,7 @@ let test_resolve_effects () =
     | Ok (_ctx, _) -> ()
 
 let test_resolve_ownership () =
-  match parse_fixture (fixture "ownership.as") with
+  match parse_fixture (fixture "ownership.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -308,7 +308,7 @@ let test_resolve_ownership () =
     | Ok (_ctx, _) -> ()
 
 let test_resolve_type_decls () =
-  match parse_fixture (fixture "type_decls.as") with
+  match parse_fixture (fixture "type_decls.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -319,7 +319,7 @@ let test_resolve_type_decls () =
         (Symbol.lookup ctx.symbols "Point" <> None)
 
 let test_resolve_full_pipeline () =
-  match parse_fixture (fixture "full_pipeline.as") with
+  match parse_fixture (fixture "full_pipeline.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -350,27 +350,27 @@ let resolve_tests = [
 *)
 
 let test_typecheck_arithmetic () =
-  match run_frontend (fixture "arithmetic.as") with
+  match run_frontend (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _ -> ()
 
 let test_typecheck_traits () =
-  match run_frontend (fixture "traits.as") with
+  match run_frontend (fixture "traits.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _ -> ()
 
 let test_typecheck_effects () =
-  match run_frontend (fixture "effects.as") with
+  match run_frontend (fixture "effects.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _ -> ()
 
 let test_typecheck_ownership () =
-  match run_frontend (fixture "ownership.as") with
+  match run_frontend (fixture "ownership.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _ -> ()
 
 let test_typecheck_full_pipeline () =
-  match run_frontend (fixture "full_pipeline.as") with
+  match run_frontend (fixture "full_pipeline.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _ -> ()
 
@@ -393,7 +393,7 @@ let typecheck_tests = [
 *)
 
 let test_quantity_affine_valid () =
-  match parse_fixture (fixture "affine_basic.as") with
+  match parse_fixture (fixture "affine_basic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -404,7 +404,7 @@ let test_quantity_affine_valid () =
       | Error msg -> Alcotest.fail msg
 
 let test_quantity_affine_violation () =
-  match parse_fixture (fixture "affine_violation.as") with
+  match parse_fixture (fixture "affine_violation.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -420,7 +420,7 @@ let test_quantity_affine_violation () =
           true (String.length msg > 0)
 
 let test_quantity_erased_violation () =
-  match parse_fixture (fixture "erased_violation.as") with
+  match parse_fixture (fixture "erased_violation.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     match resolve_program prog with
@@ -453,12 +453,12 @@ let quantity_tests = [
 *)
 
 let test_wasm_arithmetic () =
-  match run_wasm_pipeline (fixture "arithmetic.as") with
+  match run_wasm_pipeline (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _wasm_mod -> ()
 
 let test_wasm_simple () =
-  match run_wasm_pipeline (fixture "wasm_simple.as") with
+  match run_wasm_pipeline (fixture "wasm_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok wasm_mod ->
     (* Verify the module has functions *)
@@ -469,7 +469,7 @@ let test_wasm_simple () =
       (List.length wasm_mod.Wasm.exports > 0)
 
 let test_wasm_write_binary () =
-  match run_wasm_pipeline (fixture "wasm_simple.as") with
+  match run_wasm_pipeline (fixture "wasm_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok wasm_mod ->
     with_temp_file ".wasm" (fun tmp_path ->
@@ -489,7 +489,7 @@ let test_wasm_write_binary () =
     )
 
 let test_wasm_full_pipeline () =
-  match run_wasm_pipeline (fixture "full_pipeline.as") with
+  match run_wasm_pipeline (fixture "full_pipeline.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok wasm_mod ->
     Alcotest.(check bool) "has functions" true
@@ -502,7 +502,7 @@ let test_wasm_full_pipeline () =
     )
 
 let test_wasm_lambda () =
-  match run_wasm_pipeline (fixture "lambda.as") with
+  match run_wasm_pipeline (fixture "lambda.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _wasm_mod -> ()
 
@@ -525,7 +525,7 @@ let wasm_tests = [
 *)
 
 let test_julia_arithmetic () =
-  match run_julia_pipeline (fixture "arithmetic.as") with
+  match run_julia_pipeline (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok code ->
     (* Julia code should contain function definitions *)
@@ -533,7 +533,7 @@ let test_julia_arithmetic () =
       (String.length code > 0)
 
 let test_julia_simple () =
-  match run_julia_pipeline (fixture "julia_simple.as") with
+  match run_julia_pipeline (fixture "julia_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok code ->
     Alcotest.(check bool) "non-empty output" true
@@ -545,7 +545,7 @@ let test_julia_simple () =
     Alcotest.(check bool) "has function keyword" true has_function
 
 let test_julia_type_mapping () =
-  match run_julia_pipeline (fixture "julia_simple.as") with
+  match run_julia_pipeline (fixture "julia_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok code ->
     (* Check type mapping: Int -> Int64 *)
@@ -555,7 +555,7 @@ let test_julia_type_mapping () =
     Alcotest.(check bool) "maps Int to Int64" true has_int64
 
 let test_julia_write_output () =
-  match run_julia_pipeline (fixture "julia_simple.as") with
+  match run_julia_pipeline (fixture "julia_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok code ->
     with_temp_file ".jl" (fun tmp_path ->
@@ -568,7 +568,7 @@ let test_julia_write_output () =
     )
 
 let test_julia_full_pipeline () =
-  match run_julia_pipeline (fixture "full_pipeline.as") with
+  match run_julia_pipeline (fixture "full_pipeline.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok code ->
     Alcotest.(check bool) "non-empty output" true
@@ -592,22 +592,22 @@ let julia_tests = [
 *)
 
 let test_interp_simple () =
-  match run_interp_pipeline (fixture "interp_simple.as") with
+  match run_interp_pipeline (fixture "interp_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _env -> ()
 
 let test_interp_arithmetic () =
-  match run_interp_pipeline (fixture "arithmetic.as") with
+  match run_interp_pipeline (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _env -> ()
 
 let test_interp_lambda () =
-  match run_interp_pipeline (fixture "lambda.as") with
+  match run_interp_pipeline (fixture "lambda.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _env -> ()
 
 let test_interp_full_pipeline () =
-  match run_interp_pipeline (fixture "full_pipeline.as") with
+  match run_interp_pipeline (fixture "full_pipeline.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok _env -> ()
 
@@ -628,7 +628,7 @@ let interp_tests = [
 *)
 
 let test_opt_constant_folding () =
-  match parse_fixture (fixture "arithmetic.as") with
+  match parse_fixture (fixture "arithmetic.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     let optimized = Opt.fold_constants_program prog in
@@ -638,7 +638,7 @@ let test_opt_constant_folding () =
       (List.length optimized.prog_decls)
 
 let test_opt_preserves_semantics () =
-  match parse_fixture (fixture "interp_simple.as") with
+  match parse_fixture (fixture "interp_simple.affine") with
   | Error msg -> Alcotest.fail msg
   | Ok prog ->
     let optimized = Opt.fold_constants_program prog in
@@ -666,7 +666,7 @@ let optimizer_tests = [
 *)
 
 let test_full_pipeline_all_stages () =
-  let path = fixture "full_pipeline.as" in
+  let path = fixture "full_pipeline.affine" in
 
   (* Stage 1: Parse *)
   let prog = match parse_fixture path with
@@ -723,7 +723,7 @@ let test_full_pipeline_all_stages () =
    | Ok _env -> ())
 
 let test_full_pipeline_wasm_roundtrip () =
-  let path = fixture "wasm_simple.as" in
+  let path = fixture "wasm_simple.affine" in
   match run_wasm_pipeline path with
   | Error msg -> Alcotest.fail msg
   | Ok wasm_mod ->
@@ -737,7 +737,7 @@ let test_full_pipeline_wasm_roundtrip () =
         (size > 8 && size < 1_000_000))
 
 let test_full_pipeline_julia_roundtrip () =
-  let path = fixture "julia_simple.as" in
+  let path = fixture "julia_simple.affine" in
   match run_julia_pipeline path with
   | Error msg -> Alcotest.fail msg
   | Ok code ->
diff --git a/test/test_golden.ml b/test/test_golden.ml
index 9997c04..36425b8 100644
--- a/test/test_golden.ml
+++ b/test/test_golden.ml
@@ -61,14 +61,14 @@ let run_golden_test ~source_path ~expected_path () =
           Alcotest.fail "AST output does not match expected"
         end
 
-(** Create a test case from a .as file *)
+(** Create a test case from a .affine file *)
 let test_case_of_file filename =
   let base = Filename.chop_extension filename in
   let source_path = Filename.concat golden_dir filename in
   let expected_path = Filename.concat golden_dir (base ^ ".expected") in
   Alcotest.test_case base `Quick (run_golden_test ~source_path ~expected_path)
 
-(** Discover all .as files in golden directory *)
+(** Discover all .affine files in golden directory *)
 let discover_tests () =
   if not (Sys.file_exists golden_dir) then
     []
@@ -76,7 +76,7 @@ let discover_tests () =
     let files = Sys.readdir golden_dir in
     files
     |> Array.to_list
-    |> List.filter (fun f -> Filename.check_suffix f ".as")
+    |> List.filter (fun f -> Filename.check_suffix f ".affine")
     |> List.sort String.compare
     |> List.map test_case_of_file
 
@@ -100,7 +100,7 @@ let discover_example_tests () =
     let files = Sys.readdir examples_dir in
     files
     |> Array.to_list
-    |> List.filter (fun f -> Filename.check_suffix f ".as")
+    |> List.filter (fun f -> Filename.check_suffix f ".affine")
     |> List.sort String.compare
     |> List.map (fun f ->
         let base = Filename.chop_extension f in
diff --git a/test_if.as b/test_if.affine
similarity index 100%
rename from test_if.as
rename to test_if.affine
diff --git a/test_min.as b/test_min.affine
similarity index 100%
rename from test_min.as
rename to test_min.affine
diff --git a/test_simple.as b/test_simple.affine
similarity index 100%
rename from test_simple.as
rename to test_simple.affine
diff --git a/test_spread.as b/test_spread.affine
similarity index 100%
rename from test_spread.as
rename to test_spread.affine
diff --git a/test_spread2.as b/test_spread2.affine
similarity index 100%
rename from test_spread2.as
rename to test_spread2.affine
diff --git a/test_spread3.as b/test_spread3.affine
similarity index 100%
rename from test_spread3.as
rename to test_spread3.affine
diff --git a/tests/borrow/minimal.as b/tests/borrow/minimal.affine
similarity index 100%
rename from tests/borrow/minimal.as
rename to tests/borrow/minimal.affine
diff --git a/tests/borrow/move_test.as b/tests/borrow/move_test.affine
similarity index 100%
rename from tests/borrow/move_test.as
rename to tests/borrow/move_test.affine
diff --git a/tests/borrow/simple.as b/tests/borrow/simple.affine
similarity index 100%
rename from tests/borrow/simple.as
rename to tests/borrow/simple.affine
diff --git a/tests/borrow/simple_move_test.as b/tests/borrow/simple_move_test.affine
similarity index 100%
rename from tests/borrow/simple_move_test.as
rename to tests/borrow/simple_move_test.affine
diff --git a/tests/borrow/simple_own.as b/tests/borrow/simple_own.affine
similarity index 100%
rename from tests/borrow/simple_own.as
rename to tests/borrow/simple_own.affine
diff --git a/tests/borrow/test_immutable_assign_error.as b/tests/borrow/test_immutable_assign_error.affine
similarity index 100%
rename from tests/borrow/test_immutable_assign_error.as
rename to tests/borrow/test_immutable_assign_error.affine
diff --git a/tests/borrow/test_move.as b/tests/borrow/test_move.affine
similarity index 100%
rename from tests/borrow/test_move.as
rename to tests/borrow/test_move.affine
diff --git a/tests/borrow/test_move_after_use.as b/tests/borrow/test_move_after_use.affine
similarity index 100%
rename from tests/borrow/test_move_after_use.as
rename to tests/borrow/test_move_after_use.affine
diff --git a/tests/borrow/test_mutable_borrow.as b/tests/borrow/test_mutable_borrow.affine
similarity index 100%
rename from tests/borrow/test_mutable_borrow.as
rename to tests/borrow/test_mutable_borrow.affine
diff --git a/tests/borrow/test_ref_borrow.as b/tests/borrow/test_ref_borrow.affine
similarity index 100%
rename from tests/borrow/test_ref_borrow.as
rename to tests/borrow/test_ref_borrow.affine
diff --git a/tests/borrow/use_after_move.as b/tests/borrow/use_after_move.affine
similarity index 100%
rename from tests/borrow/use_after_move.as
rename to tests/borrow/use_after_move.affine
diff --git a/tests/borrow/valid_move.as b/tests/borrow/valid_move.affine
similarity index 100%
rename from tests/borrow/valid_move.as
rename to tests/borrow/valid_move.affine
diff --git a/tests/codegen/simple_arithmetic.as b/tests/codegen/simple_arithmetic.affine
similarity index 100%
rename from tests/codegen/simple_arithmetic.as
rename to tests/codegen/simple_arithmetic.affine
diff --git a/tests/codegen/test_array_bounds.as b/tests/codegen/test_array_bounds.affine
similarity index 100%
rename from tests/codegen/test_array_bounds.as
rename to tests/codegen/test_array_bounds.affine
diff --git a/tests/codegen/test_array_empty.as b/tests/codegen/test_array_empty.affine
similarity index 100%
rename from tests/codegen/test_array_empty.as
rename to tests/codegen/test_array_empty.affine
diff --git a/tests/codegen/test_array_simple.as b/tests/codegen/test_array_simple.affine
similarity index 100%
rename from tests/codegen/test_array_simple.as
rename to tests/codegen/test_array_simple.affine
diff --git a/tests/codegen/test_array_single.as b/tests/codegen/test_array_single.affine
similarity index 100%
rename from tests/codegen/test_array_single.as
rename to tests/codegen/test_array_single.affine
diff --git a/tests/codegen/test_array_sum.as b/tests/codegen/test_array_sum.affine
similarity index 100%
rename from tests/codegen/test_array_sum.as
rename to tests/codegen/test_array_sum.affine
diff --git a/tests/codegen/test_assign_compound.as b/tests/codegen/test_assign_compound.affine
similarity index 100%
rename from tests/codegen/test_assign_compound.as
rename to tests/codegen/test_assign_compound.affine
diff --git a/tests/codegen/test_assign_simple.as b/tests/codegen/test_assign_simple.affine
similarity index 100%
rename from tests/codegen/test_assign_simple.as
rename to tests/codegen/test_assign_simple.affine
diff --git a/tests/codegen/test_closure_capture.as b/tests/codegen/test_closure_capture.affine
similarity index 100%
rename from tests/codegen/test_closure_capture.as
rename to tests/codegen/test_closure_capture.affine
diff --git a/tests/codegen/test_closure_debug.as b/tests/codegen/test_closure_debug.affine
similarity index 100%
rename from tests/codegen/test_closure_debug.as
rename to tests/codegen/test_closure_debug.affine
diff --git a/tests/codegen/test_closure_multi_capture.as b/tests/codegen/test_closure_multi_capture.affine
similarity index 100%
rename from tests/codegen/test_closure_multi_capture.as
rename to tests/codegen/test_closure_multi_capture.affine
diff --git a/tests/codegen/test_enum_pattern.as b/tests/codegen/test_enum_pattern.affine
similarity index 100%
rename from tests/codegen/test_enum_pattern.as
rename to tests/codegen/test_enum_pattern.affine
diff --git a/tests/codegen/test_for_loop.as b/tests/codegen/test_for_loop.affine
similarity index 100%
rename from tests/codegen/test_for_loop.as
rename to tests/codegen/test_for_loop.affine
diff --git a/tests/codegen/test_function_call.as b/tests/codegen/test_function_call.affine
similarity index 100%
rename from tests/codegen/test_function_call.as
rename to tests/codegen/test_function_call.affine
diff --git a/tests/codegen/test_lambda_call.as b/tests/codegen/test_lambda_call.affine
similarity index 100%
rename from tests/codegen/test_lambda_call.as
rename to tests/codegen/test_lambda_call.affine
diff --git a/tests/codegen/test_lambda_multi_param.as b/tests/codegen/test_lambda_multi_param.affine
similarity index 100%
rename from tests/codegen/test_lambda_multi_param.as
rename to tests/codegen/test_lambda_multi_param.affine
diff --git a/tests/codegen/test_match_literal.as b/tests/codegen/test_match_literal.affine
similarity index 100%
rename from tests/codegen/test_match_literal.as
rename to tests/codegen/test_match_literal.affine
diff --git a/tests/codegen/test_match_mixed.as b/tests/codegen/test_match_mixed.affine
similarity index 100%
rename from tests/codegen/test_match_mixed.as
rename to tests/codegen/test_match_mixed.affine
diff --git a/tests/codegen/test_match_simple.as b/tests/codegen/test_match_simple.affine
similarity index 100%
rename from tests/codegen/test_match_simple.as
rename to tests/codegen/test_match_simple.affine
diff --git a/tests/codegen/test_multiple_calls.as b/tests/codegen/test_multiple_calls.affine
similarity index 100%
rename from tests/codegen/test_multiple_calls.as
rename to tests/codegen/test_multiple_calls.affine
diff --git a/tests/codegen/test_multiple_lambdas.as b/tests/codegen/test_multiple_lambdas.affine
similarity index 100%
rename from tests/codegen/test_multiple_lambdas.as
rename to tests/codegen/test_multiple_lambdas.affine
diff --git a/tests/codegen/test_opt_constant_fold.as b/tests/codegen/test_opt_constant_fold.affine
similarity index 100%
rename from tests/codegen/test_opt_constant_fold.as
rename to tests/codegen/test_opt_constant_fold.affine
diff --git a/tests/codegen/test_opt_if_fold.as b/tests/codegen/test_opt_if_fold.affine
similarity index 100%
rename from tests/codegen/test_opt_if_fold.as
rename to tests/codegen/test_opt_if_fold.affine
diff --git a/tests/codegen/test_pattern_as.as b/tests/codegen/test_pattern_as.affine
similarity index 100%
rename from tests/codegen/test_pattern_as.as
rename to tests/codegen/test_pattern_as.affine
diff --git a/tests/codegen/test_pattern_or.as b/tests/codegen/test_pattern_or.affine
similarity index 100%
rename from tests/codegen/test_pattern_or.as
rename to tests/codegen/test_pattern_or.affine
diff --git a/tests/codegen/test_pattern_record.as b/tests/codegen/test_pattern_record.affine
similarity index 100%
rename from tests/codegen/test_pattern_record.as
rename to tests/codegen/test_pattern_record.affine
diff --git a/tests/codegen/test_pattern_tuple.as b/tests/codegen/test_pattern_tuple.affine
similarity index 100%
rename from tests/codegen/test_pattern_tuple.as
rename to tests/codegen/test_pattern_tuple.affine
diff --git a/tests/codegen/test_record_multi_field.as b/tests/codegen/test_record_multi_field.affine
similarity index 100%
rename from tests/codegen/test_record_multi_field.as
rename to tests/codegen/test_record_multi_field.affine
diff --git a/tests/codegen/test_record_multiple.as b/tests/codegen/test_record_multiple.affine
similarity index 100%
rename from tests/codegen/test_record_multiple.as
rename to tests/codegen/test_record_multiple.affine
diff --git a/tests/codegen/test_record_simple.as b/tests/codegen/test_record_simple.affine
similarity index 100%
rename from tests/codegen/test_record_simple.as
rename to tests/codegen/test_record_simple.affine
diff --git a/tests/codegen/test_recursive_call.as b/tests/codegen/test_recursive_call.affine
similarity index 100%
rename from tests/codegen/test_recursive_call.as
rename to tests/codegen/test_recursive_call.affine
diff --git a/tests/codegen/test_ref_deref_chain.as b/tests/codegen/test_ref_deref_chain.affine
similarity index 100%
rename from tests/codegen/test_ref_deref_chain.as
rename to tests/codegen/test_ref_deref_chain.affine
diff --git a/tests/codegen/test_ref_deref_simple.as b/tests/codegen/test_ref_deref_simple.affine
similarity index 100%
rename from tests/codegen/test_ref_deref_simple.as
rename to tests/codegen/test_ref_deref_simple.affine
diff --git a/tests/codegen/test_simple_lambda.as b/tests/codegen/test_simple_lambda.affine
similarity index 100%
rename from tests/codegen/test_simple_lambda.as
rename to tests/codegen/test_simple_lambda.affine
diff --git a/tests/codegen/test_string_diff.as b/tests/codegen/test_string_diff.affine
similarity index 100%
rename from tests/codegen/test_string_diff.as
rename to tests/codegen/test_string_diff.affine
diff --git a/tests/codegen/test_string_eq.as b/tests/codegen/test_string_eq.affine
similarity index 100%
rename from tests/codegen/test_string_eq.as
rename to tests/codegen/test_string_eq.affine
diff --git a/tests/codegen/test_string_multi.as b/tests/codegen/test_string_multi.affine
similarity index 100%
rename from tests/codegen/test_string_multi.as
rename to tests/codegen/test_string_multi.affine
diff --git a/tests/codegen/test_string_ptr.as b/tests/codegen/test_string_ptr.affine
similarity index 100%
rename from tests/codegen/test_string_ptr.as
rename to tests/codegen/test_string_ptr.affine
diff --git a/tests/codegen/test_string_simple.as b/tests/codegen/test_string_simple.affine
similarity index 100%
rename from tests/codegen/test_string_simple.as
rename to tests/codegen/test_string_simple.affine
diff --git a/tests/codegen/test_tuple_five.as b/tests/codegen/test_tuple_five.affine
similarity index 100%
rename from tests/codegen/test_tuple_five.as
rename to tests/codegen/test_tuple_five.affine
diff --git a/tests/codegen/test_tuple_nested.as b/tests/codegen/test_tuple_nested.affine
similarity index 100%
rename from tests/codegen/test_tuple_nested.as
rename to tests/codegen/test_tuple_nested.affine
diff --git a/tests/codegen/test_tuple_pair.as b/tests/codegen/test_tuple_pair.affine
similarity index 100%
rename from tests/codegen/test_tuple_pair.as
rename to tests/codegen/test_tuple_pair.affine
diff --git a/tests/codegen/test_tuple_record_array.as b/tests/codegen/test_tuple_record_array.affine
similarity index 100%
rename from tests/codegen/test_tuple_record_array.as
rename to tests/codegen/test_tuple_record_array.affine
diff --git a/tests/codegen/test_tuple_simple.as b/tests/codegen/test_tuple_simple.affine
similarity index 100%
rename from tests/codegen/test_tuple_simple.as
rename to tests/codegen/test_tuple_simple.affine
diff --git a/tests/codegen/test_variant_as_int.as b/tests/codegen/test_variant_as_int.affine
similarity index 100%
rename from tests/codegen/test_variant_as_int.as
rename to tests/codegen/test_variant_as_int.affine
diff --git a/tests/codegen/test_variant_match_arg.as b/tests/codegen/test_variant_match_arg.affine
similarity index 100%
rename from tests/codegen/test_variant_match_arg.as
rename to tests/codegen/test_variant_match_arg.affine
diff --git a/tests/codegen/test_variant_match_none.as b/tests/codegen/test_variant_match_none.affine
similarity index 100%
rename from tests/codegen/test_variant_match_none.as
rename to tests/codegen/test_variant_match_none.affine
diff --git a/tests/codegen/test_variant_multi_arg.as b/tests/codegen/test_variant_multi_arg.affine
similarity index 100%
rename from tests/codegen/test_variant_multi_arg.as
rename to tests/codegen/test_variant_multi_arg.affine
diff --git a/tests/codegen/test_variant_with_arg.as b/tests/codegen/test_variant_with_arg.affine
similarity index 100%
rename from tests/codegen/test_variant_with_arg.as
rename to tests/codegen/test_variant_with_arg.affine
diff --git a/tests/codegen/test_while_loop.as b/tests/codegen/test_while_loop.affine
similarity index 100%
rename from tests/codegen/test_while_loop.as
rename to tests/codegen/test_while_loop.affine
diff --git a/tests/conformance/README.md b/tests/conformance/README.md
index c33b3bf..5b8179c 100644
--- a/tests/conformance/README.md
+++ b/tests/conformance/README.md
@@ -20,13 +20,13 @@ aLib is NOT a code library - it's a way to specify minimal overlap between diver
 ```
 tests/conformance/
 ├── arithmetic/          # Arithmetic operation tests
-│   └── add.as
+│   └── add.affine
 ├── collection/          # Collection operation tests
-│   ├── map.as
-│   ├── filter.as
-│   ├── fold.as
-│   └── contains.as
-├── run_all.as          # Master test runner
+│   ├── map.affine
+│   ├── filter.affine
+│   ├── fold.affine
+│   └── contains.affine
+├── run_all.affine          # Master test runner
 └── README.md           # This file
 ```
 
@@ -34,12 +34,12 @@ tests/conformance/
 
 ### Run all conformance tests:
 ```bash
-affinescript tests/conformance/run_all.as
+affinescript tests/conformance/run_all.affine
 ```
 
 ### Run specific category:
 ```bash
-affinescript tests/conformance/collection/map.as
+affinescript tests/conformance/collection/map.affine
 ```
 
 ### Expected Output:
@@ -112,7 +112,7 @@ AffineScript's conformance tests respect affine type constraints:
 2. Extract test vectors from YAML section
 3. Create `tests/conformance/<category>/<operation>.as`
 4. Translate aLib function expressions to AffineScript syntax
-5. Add test to `run_all.as`
+5. Add test to `run_all.affine`
 
 Example:
 ```affinescript
diff --git a/tests/conformance/arithmetic/add.as b/tests/conformance/arithmetic/add.affine
similarity index 100%
rename from tests/conformance/arithmetic/add.as
rename to tests/conformance/arithmetic/add.affine
diff --git a/tests/conformance/arithmetic/divide.as b/tests/conformance/arithmetic/divide.affine
similarity index 100%
rename from tests/conformance/arithmetic/divide.as
rename to tests/conformance/arithmetic/divide.affine
diff --git a/tests/conformance/arithmetic/modulo.as b/tests/conformance/arithmetic/modulo.affine
similarity index 100%
rename from tests/conformance/arithmetic/modulo.as
rename to tests/conformance/arithmetic/modulo.affine
diff --git a/tests/conformance/arithmetic/multiply.as b/tests/conformance/arithmetic/multiply.affine
similarity index 100%
rename from tests/conformance/arithmetic/multiply.as
rename to tests/conformance/arithmetic/multiply.affine
diff --git a/tests/conformance/arithmetic/subtract.as b/tests/conformance/arithmetic/subtract.affine
similarity index 100%
rename from tests/conformance/arithmetic/subtract.as
rename to tests/conformance/arithmetic/subtract.affine
diff --git a/tests/conformance/collection/contains.as b/tests/conformance/collection/contains.affine
similarity index 100%
rename from tests/conformance/collection/contains.as
rename to tests/conformance/collection/contains.affine
diff --git a/tests/conformance/collection/filter.as b/tests/conformance/collection/filter.affine
similarity index 100%
rename from tests/conformance/collection/filter.as
rename to tests/conformance/collection/filter.affine
diff --git a/tests/conformance/collection/fold.as b/tests/conformance/collection/fold.affine
similarity index 100%
rename from tests/conformance/collection/fold.as
rename to tests/conformance/collection/fold.affine
diff --git a/tests/conformance/collection/map.as b/tests/conformance/collection/map.affine
similarity index 100%
rename from tests/conformance/collection/map.as
rename to tests/conformance/collection/map.affine
diff --git a/tests/conformance/comparison/equal.as b/tests/conformance/comparison/equal.affine
similarity index 100%
rename from tests/conformance/comparison/equal.as
rename to tests/conformance/comparison/equal.affine
diff --git a/tests/conformance/comparison/greater_equal.as b/tests/conformance/comparison/greater_equal.affine
similarity index 100%
rename from tests/conformance/comparison/greater_equal.as
rename to tests/conformance/comparison/greater_equal.affine
diff --git a/tests/conformance/comparison/greater_than.as b/tests/conformance/comparison/greater_than.affine
similarity index 100%
rename from tests/conformance/comparison/greater_than.as
rename to tests/conformance/comparison/greater_than.affine
diff --git a/tests/conformance/comparison/less_equal.as b/tests/conformance/comparison/less_equal.affine
similarity index 100%
rename from tests/conformance/comparison/less_equal.as
rename to tests/conformance/comparison/less_equal.affine
diff --git a/tests/conformance/comparison/less_than.as b/tests/conformance/comparison/less_than.affine
similarity index 100%
rename from tests/conformance/comparison/less_than.as
rename to tests/conformance/comparison/less_than.affine
diff --git a/tests/conformance/comparison/not_equal.as b/tests/conformance/comparison/not_equal.affine
similarity index 100%
rename from tests/conformance/comparison/not_equal.as
rename to tests/conformance/comparison/not_equal.affine
diff --git a/tests/conformance/conditional/if_then_else.as b/tests/conformance/conditional/if_then_else.affine
similarity index 100%
rename from tests/conformance/conditional/if_then_else.as
rename to tests/conformance/conditional/if_then_else.affine
diff --git a/tests/conformance/logical/and.as b/tests/conformance/logical/and.affine
similarity index 100%
rename from tests/conformance/logical/and.as
rename to tests/conformance/logical/and.affine
diff --git a/tests/conformance/logical/not.as b/tests/conformance/logical/not.affine
similarity index 100%
rename from tests/conformance/logical/not.as
rename to tests/conformance/logical/not.affine
diff --git a/tests/conformance/logical/or.as b/tests/conformance/logical/or.affine
similarity index 100%
rename from tests/conformance/logical/or.as
rename to tests/conformance/logical/or.affine
diff --git a/tests/conformance/run_all.as b/tests/conformance/run_all.affine
similarity index 100%
rename from tests/conformance/run_all.as
rename to tests/conformance/run_all.affine
diff --git a/tests/conformance/string/concat.as b/tests/conformance/string/concat.affine
similarity index 100%
rename from tests/conformance/string/concat.as
rename to tests/conformance/string/concat.affine
diff --git a/tests/conformance/string/length.as b/tests/conformance/string/length.affine
similarity index 100%
rename from tests/conformance/string/length.as
rename to tests/conformance/string/length.affine
diff --git a/tests/conformance/string/substring.as b/tests/conformance/string/substring.affine
similarity index 100%
rename from tests/conformance/string/substring.as
rename to tests/conformance/string/substring.affine
diff --git a/tests/effects/basic_effect.as b/tests/effects/basic_effect.affine
similarity index 100%
rename from tests/effects/basic_effect.as
rename to tests/effects/basic_effect.affine
diff --git a/tests/modules/test_const.as b/tests/modules/test_const.affine
similarity index 100%
rename from tests/modules/test_const.as
rename to tests/modules/test_const.affine
diff --git a/tests/modules/test_import.as b/tests/modules/test_import.affine
similarity index 100%
rename from tests/modules/test_import.as
rename to tests/modules/test_import.affine
diff --git a/tests/modules/test_import_only.as b/tests/modules/test_import_only.affine
similarity index 100%
rename from tests/modules/test_import_only.as
rename to tests/modules/test_import_only.affine
diff --git a/tests/modules/test_math_functions.as b/tests/modules/test_math_functions.affine
similarity index 100%
rename from tests/modules/test_math_functions.as
rename to tests/modules/test_math_functions.affine
diff --git a/tests/modules/test_no_import.as b/tests/modules/test_no_import.affine
similarity index 100%
rename from tests/modules/test_no_import.as
rename to tests/modules/test_no_import.affine
diff --git a/tests/modules/test_simple_import.as b/tests/modules/test_simple_import.affine
similarity index 100%
rename from tests/modules/test_simple_import.as
rename to tests/modules/test_simple_import.affine
diff --git a/tests/parser/baseline_block.as b/tests/parser/baseline_block.affine
similarity index 100%
rename from tests/parser/baseline_block.as
rename to tests/parser/baseline_block.affine
diff --git a/tests/parser/baseline_stmt.as b/tests/parser/baseline_stmt.affine
similarity index 100%
rename from tests/parser/baseline_stmt.as
rename to tests/parser/baseline_stmt.affine
diff --git a/tests/parser/unsafe_all.as b/tests/parser/unsafe_all.affine
similarity index 100%
rename from tests/parser/unsafe_all.as
rename to tests/parser/unsafe_all.affine
diff --git a/tests/parser/unsafe_empty.as b/tests/parser/unsafe_empty.affine
similarity index 100%
rename from tests/parser/unsafe_empty.as
rename to tests/parser/unsafe_empty.affine
diff --git a/tests/parser/unsafe_ops.as b/tests/parser/unsafe_ops.affine
similarity index 100%
rename from tests/parser/unsafe_ops.as
rename to tests/parser/unsafe_ops.affine
diff --git a/tests/parser/unsafe_read.as b/tests/parser/unsafe_read.affine
similarity index 100%
rename from tests/parser/unsafe_read.as
rename to tests/parser/unsafe_read.affine
diff --git a/tests/parser/unsafe_simple.as b/tests/parser/unsafe_simple.affine
similarity index 100%
rename from tests/parser/unsafe_simple.as
rename to tests/parser/unsafe_simple.affine
diff --git a/tests/parser/unsafe_stmt.as b/tests/parser/unsafe_stmt.affine
similarity index 100%
rename from tests/parser/unsafe_stmt.as
rename to tests/parser/unsafe_stmt.affine
diff --git a/tests/types/test_dependent_e2e.as b/tests/types/test_dependent_e2e.affine
similarity index 100%
rename from tests/types/test_dependent_e2e.as
rename to tests/types/test_dependent_e2e.affine
diff --git a/tests/types/test_dependent_parsing.as b/tests/types/test_dependent_parsing.affine
similarity index 100%
rename from tests/types/test_dependent_parsing.as
rename to tests/types/test_dependent_parsing.affine
diff --git a/tests/types/test_effect_inference.as b/tests/types/test_effect_inference.affine
similarity index 100%
rename from tests/types/test_effect_inference.as
rename to tests/types/test_effect_inference.affine
diff --git a/tests/types/test_effect_lambda.as b/tests/types/test_effect_lambda.affine
similarity index 100%
rename from tests/types/test_effect_lambda.as
rename to tests/types/test_effect_lambda.affine
diff --git a/tests/types/test_effect_polymorphism.as b/tests/types/test_effect_polymorphism.affine
similarity index 100%
rename from tests/types/test_effect_polymorphism.as
rename to tests/types/test_effect_polymorphism.affine
diff --git a/tests/types/test_generic_programming.as b/tests/types/test_generic_programming.affine
similarity index 100%
rename from tests/types/test_generic_programming.as
rename to tests/types/test_generic_programming.affine
diff --git a/tests/types/test_hkt_parsing.as b/tests/types/test_hkt_parsing.affine
similarity index 100%
rename from tests/types/test_hkt_parsing.as
rename to tests/types/test_hkt_parsing.affine
diff --git a/tests/types/test_kind_checking.as b/tests/types/test_kind_checking.affine
similarity index 100%
rename from tests/types/test_kind_checking.as
rename to tests/types/test_kind_checking.affine
diff --git a/tests/types/test_lambda_scope_fix.as b/tests/types/test_lambda_scope_fix.affine
similarity index 100%
rename from tests/types/test_lambda_scope_fix.as
rename to tests/types/test_lambda_scope_fix.affine
diff --git a/tests/types/test_lambda_scope_simple.as b/tests/types/test_lambda_scope_simple.affine
similarity index 100%
rename from tests/types/test_lambda_scope_simple.as
rename to tests/types/test_lambda_scope_simple.affine
diff --git a/tests/types/test_parse_row_type.as b/tests/types/test_parse_row_type.affine
similarity index 100%
rename from tests/types/test_parse_row_type.as
rename to tests/types/test_parse_row_type.affine
diff --git a/tests/types/test_row_polymorphism.as b/tests/types/test_row_polymorphism.affine
similarity index 100%
rename from tests/types/test_row_polymorphism.as
rename to tests/types/test_row_polymorphism.affine
diff --git a/tests/types/test_row_simple.as b/tests/types/test_row_simple.affine
similarity index 100%
rename from tests/types/test_row_simple.as
rename to tests/types/test_row_simple.affine
diff --git a/tests/types/test_traits.as b/tests/types/test_traits.affine
similarity index 100%
rename from tests/types/test_traits.as
rename to tests/types/test_traits.affine
diff --git a/tools/affinescript-lsp/src/handlers.rs b/tools/affinescript-lsp/src/handlers.rs
index 0f98732..8b79a8c 100644
--- a/tools/affinescript-lsp/src/handlers.rs
+++ b/tools/affinescript-lsp/src/handlers.rs
@@ -605,7 +605,7 @@ mod tests {
 
     /// Helper: create a file URI from a dummy path.
     fn test_uri() -> Url {
-        Url::parse("file:///tmp/test.as").unwrap()
+        Url::parse("file:///tmp/test.affine").unwrap()
     }
 
     /// Helper: empty compiler output (simulates no v2 JSON available).
@@ -759,7 +759,7 @@ mod tests {
                     "id": 1,
                     "name": "add",
                     "kind": "function",
-                    "file": "/tmp/test.as",
+                    "file": "/tmp/test.affine",
                     "start_line": 1,
                     "start_col": 4,
                     "end_line": 1,
@@ -769,7 +769,7 @@ mod tests {
             ],
             "references": {
                 "1": [
-                    {"file": "/tmp/test.as", "start_line": 5, "start_col": 10, "end_line": 5, "end_col": 13}
+                    {"file": "/tmp/test.affine", "start_line": 5, "start_col": 10, "end_line": 5, "end_col": 13}
                 ]
             }
         }"#;
@@ -799,7 +799,7 @@ mod tests {
                     "id": 1,
                     "name": "add",
                     "kind": "function",
-                    "file": "/tmp/test.as",
+                    "file": "/tmp/test.affine",
                     "start_line": 1,
                     "start_col": 4,
                     "end_line": 1,
@@ -808,8 +808,8 @@ mod tests {
             ],
             "references": {
                 "1": [
-                    {"file": "/tmp/test.as", "start_line": 3, "start_col": 10, "end_line": 3, "end_col": 13},
-                    {"file": "/tmp/test.as", "start_line": 5, "start_col": 1, "end_line": 5, "end_col": 4}
+                    {"file": "/tmp/test.affine", "start_line": 3, "start_col": 10, "end_line": 3, "end_col": 13},
+                    {"file": "/tmp/test.affine", "start_line": 5, "start_col": 1, "end_line": 5, "end_col": 4}
                 ]
             }
         }"#;
diff --git a/tools/affinescript-lsp/src/main.rs b/tools/affinescript-lsp/src/main.rs
index c8d011a..777f798 100644
--- a/tools/affinescript-lsp/src/main.rs
+++ b/tools/affinescript-lsp/src/main.rs
@@ -73,7 +73,7 @@ impl Backend {
         use std::process::Stdio;
 
         // Write source to a temp file so the compiler can read it
-        let temp_path = std::env::temp_dir().join(format!("lsp_{}.as", uuid::Uuid::new_v4()));
+        let temp_path = std::env::temp_dir().join(format!("lsp_{}.affine", uuid::Uuid::new_v4()));
         if let Err(e) = tokio::fs::write(&temp_path, text).await {
             self.client
                 .log_message(MessageType::ERROR, format!("Failed to write temp file: {}", e))
diff --git a/tools/alib_conformance_gen.jl b/tools/alib_conformance_gen.jl
index dfa41e6..cb0b01f 100644
--- a/tools/alib_conformance_gen.jl
+++ b/tools/alib_conformance_gen.jl
@@ -115,7 +115,7 @@ fn test_alib_$(category)_$(op_name)() -> TestResult {
 """
 
     # Write output file
-    output_file = joinpath(output_dir, "$(category)_$(op_name).as")
+    output_file = joinpath(output_dir, "$(category)_$(op_name).affine")
     mkpath(output_dir)
     write(output_file, test_code)
 
diff --git a/tools/run_codegen_wasm_tests.sh b/tools/run_codegen_wasm_tests.sh
index 7cccfc0..bf5afbc 100755
--- a/tools/run_codegen_wasm_tests.sh
+++ b/tools/run_codegen_wasm_tests.sh
@@ -17,8 +17,8 @@ fi
 
 echo "Using compiler: $COMPILER"
 
-for src in "$TEST_DIR"/*.as; do
-  base="${src%.as}"
+for src in "$TEST_DIR"/*.affine; do
+  base="${src%.affine}"
   wasm="$base.wasm"
   echo "Compiling $(basename "$src") -> $(basename "$wasm")"
   "${COMPILE_CMD[@]}" "$src" -o "$wasm"
diff --git a/wiki/compiler/architecture.md b/wiki/compiler/architecture.md
index 9725e58..9cd99a8 100644
--- a/wiki/compiler/architecture.md
+++ b/wiki/compiler/architecture.md
@@ -9,7 +9,7 @@ This document describes the architecture of the AffineScript compiler.
 │                         AffineScript Compiler                           │
 ├─────────────────────────────────────────────────────────────────────────┤
 │                                                                         │
-│   Source Code (.as)                                                     │
+│   Source Code (.affine)                                                  │
 │        │                                                                │
 │        ▼                                                                │
 │   ┌─────────┐                                                          │
diff --git a/wiki/language-reference/dependent-types.md b/wiki/language-reference/dependent-types.md
index d7940c6..aa19e36 100644
--- a/wiki/language-reference/dependent-types.md
+++ b/wiki/language-reference/dependent-types.md
@@ -452,4 +452,4 @@ Type checking dependent types is more expensive:
 
 - [Types](types.md) - Basic type system
 - [Refinement Types](../design/type-system.md#refinements) - Theory
-- [Vectors Example](../../examples/vectors.as) - Length-indexed vectors
+- [Vectors Example](../../examples/vectors.affine) - Length-indexed vectors
diff --git a/wiki/language-reference/lexical.md b/wiki/language-reference/lexical.md
index 8be5a37..9db74d2 100644
--- a/wiki/language-reference/lexical.md
+++ b/wiki/language-reference/lexical.md
@@ -452,7 +452,7 @@ Common lexer errors:
 
 ```
 error[E0001]: unexpected character
-  --> src/main.as:1:5
+  --> src/main.affine:1:5
   |
 1 | let @x = 5
   |     ^ unexpected '@'
@@ -460,7 +460,7 @@ error[E0001]: unexpected character
   = help: identifiers cannot contain '@'
 
 error[E0002]: unterminated string literal
-  --> src/main.as:1:9
+  --> src/main.affine:1:9
   |
 1 | let s = "hello
   |         ^^^^^^ string literal not closed
@@ -468,7 +468,7 @@ error[E0002]: unterminated string literal
   = help: add closing `"` at end of string
 
 error[E0003]: invalid escape sequence
-  --> src/main.as:1:13
+  --> src/main.affine:1:13
   |
 1 | let s = "hello\q"
   |               ^^ unknown escape sequence
diff --git a/wiki/language-reference/modules.md b/wiki/language-reference/modules.md
index f46c9bd..07e6e4f 100644
--- a/wiki/language-reference/modules.md
+++ b/wiki/language-reference/modules.md
@@ -19,9 +19,9 @@ AffineScript's module system organizes code into logical units with controlled v
 ### Declaring Modules
 
 ```affine
-// In main.as
-mod math        // Looks for math.as or math/mod.as
-mod utils       // Looks for utils.as or utils/mod.as
+// In main.affine
+mod math        // Looks for math.affine or math/mod.affine
+mod utils       // Looks for utils.affine or utils/mod.affine
 mod internal    // Inline module definition follows
 
 mod internal {
@@ -70,23 +70,23 @@ mod geometry {
 
 ```
 project/
-├── main.as
-├── math.as       # mod math
-└── utils.as      # mod utils
+├── main.affine
+├── math.affine       # mod math
+└── utils.affine      # mod utils
 ```
 
 ### Directory Modules
 
 ```
 project/
-├── main.as
+├── main.affine
 └── math/
-    ├── mod.as      # mod math entry point
-    ├── vectors.as  # mod vectors (inside math)
-    └── matrices.as # mod matrices (inside math)
+    ├── mod.affine      # mod math entry point
+    ├── vectors.affine  # mod vectors (inside math)
+    └── matrices.affine # mod matrices (inside math)
 ```
 
-`math/mod.as`:
+`math/mod.affine`:
 ```affine
 // Declare submodules
 pub mod vectors
@@ -101,17 +101,17 @@ pub use matrices::Mat4
 
 ```
 project/
-├── main.as
+├── main.affine
 └── graphics/
-    ├── mod.as
+    ├── mod.affine
     ├── renderer/
-    │   ├── mod.as
-    │   ├── opengl.as
-    │   └── vulkan.as
+    │   ├── mod.affine
+    │   ├── opengl.affine
+    │   └── vulkan.affine
     └── primitives/
-        ├── mod.as
-        ├── shapes.as
-        └── colors.as
+        ├── mod.affine
+        ├── shapes.affine
+        └── colors.affine
 ```
 
 ---
@@ -127,7 +127,7 @@ mod internal {
   fn private_helper() -> Int { 42 }  // Private to this module
 }
 
-// main.as
+// main.affine
 internal::private_helper()  // ERROR: private function
 ```
 
@@ -142,7 +142,7 @@ mod math {
   fn internal_helper() -> Int { 0 }  // Still private
 }
 
-// main.as
+// main.affine
 math::add(1, 2)  // OK
 ```
 
@@ -260,7 +260,7 @@ HashMap           // Direct
 ### Basic Re-export
 
 ```affine
-// In lib.as
+// In lib.affine
 mod internal
 
 pub use internal::PublicType
@@ -283,7 +283,7 @@ pub use prelude::*
 ### Creating a Prelude
 
 ```affine
-// prelude.as
+// prelude.affine
 pub use crate::types::{Result, Option, Error}
 pub use crate::traits::{Show, Clone, Default}
 pub use crate::macros::*
@@ -346,7 +346,7 @@ let world_pt: GeoPoint = GeoPoint { x: 1.0, y: 2.0 }
 ### Facade Pattern
 
 ```affine
-// lib.as - expose clean public API
+// lib.affine - expose clean public API
 pub mod types
 pub mod traits
 pub mod error
@@ -421,15 +421,15 @@ mod core {
 mylib/
 ├── affine.toml
 └── src/
-    ├── lib.as      # Crate root
-    ├── types.as
-    ├── traits.as
+    ├── lib.affine      # Crate root
+    ├── types.affine
+    ├── traits.affine
     └── utils/
-        ├── mod.as
-        └── helpers.as
+        ├── mod.affine
+        └── helpers.affine
 ```
 
-`lib.as`:
+`lib.affine`:
 ```affine
 pub mod types
 pub mod traits
@@ -445,8 +445,8 @@ pub use traits::MainTrait
 myapp/
 ├── affine.toml
 └── src/
-    ├── main.as     # Binary entry point
-    └── lib.as      # Optional library part
+    ├── main.affine     # Binary entry point
+    └── lib.affine      # Optional library part
 ```
 
 ### Mixed Crate
@@ -455,8 +455,8 @@ myapp/
 myproject/
 ├── affine.toml
 └── src/
-    ├── main.as     # Uses lib
-    ├── lib.as      # Library code
+    ├── main.affine     # Uses lib
+    ├── lib.affine      # Library code
     └── modules/
 ```
 
diff --git a/wiki/stdlib/overview.md b/wiki/stdlib/overview.md
index 66ac3ae..381701f 100644
--- a/wiki/stdlib/overview.md
+++ b/wiki/stdlib/overview.md
@@ -6,62 +6,62 @@ The AffineScript standard library provides essential types, traits, and function
 
 ```
 std/
-├── prelude.as        # Auto-imported basics
+├── prelude.affine        # Auto-imported basics
 ├── primitives/       # Primitive types
-│   ├── int.as
-│   ├── float.as
-│   ├── bool.as
-│   ├── char.as
-│   └── string.as
+│   ├── int.affine
+│   ├── float.affine
+│   ├── bool.affine
+│   ├── char.affine
+│   └── string.affine
 ├── collections/      # Data structures
-│   ├── vec.as
-│   ├── array.as
-│   ├── list.as
-│   ├── map.as
-│   ├── set.as
-│   └── deque.as
+│   ├── vec.affine
+│   ├── array.affine
+│   ├── list.affine
+│   ├── map.affine
+│   ├── set.affine
+│   └── deque.affine
 ├── core/             # Core types
-│   ├── option.as
-│   ├── result.as
-│   ├── tuple.as
-│   └── unit.as
+│   ├── option.affine
+│   ├── result.affine
+│   ├── tuple.affine
+│   └── unit.affine
 ├── memory/           # Memory management
-│   ├── box.as
-│   ├── rc.as
-│   ├── arc.as
-│   └── ptr.as
+│   ├── box.affine
+│   ├── rc.affine
+│   ├── arc.affine
+│   └── ptr.affine
 ├── traits/           # Standard traits
-│   ├── eq.as
-│   ├── ord.as
-│   ├── hash.as
-│   ├── show.as
-│   ├── clone.as
-│   ├── default.as
-│   └── iter.as
+│   ├── eq.affine
+│   ├── ord.affine
+│   ├── hash.affine
+│   ├── show.affine
+│   ├── clone.affine
+│   ├── default.affine
+│   └── iter.affine
 ├── effects/          # Standard effects
-│   ├── io.as
-│   ├── exn.as
-│   ├── async.as
-│   ├── state.as
-│   └── random.as
+│   ├── io.affine
+│   ├── exn.affine
+│   ├── async.affine
+│   ├── state.affine
+│   └── random.affine
 ├── io/               # Input/Output
-│   ├── read.as
-│   ├── write.as
-│   ├── fs.as
-│   └── net.as
+│   ├── read.affine
+│   ├── write.affine
+│   ├── fs.affine
+│   └── net.affine
 ├── concurrency/      # Threading
-│   ├── thread.as
-│   ├── sync.as
-│   ├── channel.as
-│   └── atomic.as
+│   ├── thread.affine
+│   ├── sync.affine
+│   ├── channel.affine
+│   └── atomic.affine
 ├── text/             # Text processing
-│   ├── fmt.as
-│   ├── regex.as
-│   └── unicode.as
+│   ├── fmt.affine
+│   ├── regex.affine
+│   └── unicode.affine
 └── utils/            # Utilities
-    ├── time.as
-    ├── env.as
-    └── debug.as
+    ├── time.affine
+    ├── env.affine
+    └── debug.affine
 ```
 
 ## Prelude
diff --git a/wiki/testing/guide.md b/wiki/testing/guide.md
index 4459bf1..cdb54b4 100644
--- a/wiki/testing/guide.md
+++ b/wiki/testing/guide.md
@@ -41,7 +41,7 @@ fn test_string_concat() {
 aspm test
 
 # Run specific test file
-aspm test tests/math_test.as
+aspm test tests/math_test.affine
 
 # Run tests matching pattern
 aspm test --filter "test_add"
@@ -154,7 +154,7 @@ mod tests {
 ### Test Modules
 
 ```affine
-// In lib.as
+// In lib.affine
 pub fn add(x: Int, y: Int) -> Int {
   x + y
 }
@@ -189,22 +189,22 @@ mod tests {
 ```
 project/
 ├── src/
-│   ├── lib.as
+│   ├── lib.affine
 │   └── math/
-│       └── mod.as
+│       └── mod.affine
 ├── tests/
-│   ├── integration_test.as    # Integration tests
-│   ├── math_test.as           # Module tests
+│   ├── integration_test.affine    # Integration tests
+│   ├── math_test.affine           # Module tests
 │   └── fixtures/
 │       └── test_data.json
 └── benches/
-    └── performance_bench.as   # Benchmarks
+    └── performance_bench.affine   # Benchmarks
 ```
 
 ### Unit vs Integration Tests
 
 ```affine
-// tests/unit_test.as - Unit tests for internal modules
+// tests/unit_test.affine - Unit tests for internal modules
 use mylib::internal::parse_number
 
 #[test]
@@ -212,7 +212,7 @@ fn test_parse_number() {
   assert_eq(parse_number("42"), Ok(42))
 }
 
-// tests/integration_test.as - Integration tests for public API
+// tests/integration_test.affine - Integration tests for public API
 use mylib
 
 #[test]
@@ -470,7 +470,7 @@ Compare output against expected files:
 
 ```ocaml
 let test_golden name =
-  let input = read_file (sprintf "tests/golden/%s.as" name) in
+  let input = read_file (sprintf "tests/golden/%s.affine" name) in
   let expected = read_file (sprintf "tests/golden/%s.expected" name) in
   let actual = compile_and_run input in
   check string name expected actual
@@ -489,14 +489,14 @@ let golden_tests = [
 ### End-to-End Tests
 
 ```affine
-// tests/e2e_test.as
+// tests/e2e_test.affine
 use std::process::Command
 
 #[test]
 fn test_compile_and_run() {
   // Compile
   let compile_result = Command::new("aspm")
-    .args(["build", "examples/hello.as"])
+    .args(["build", "examples/hello.affine"])
     .output()
 
   assert!(compile_result.status.success())
diff --git a/wiki/tooling/cli.md b/wiki/tooling/cli.md
index 4fbf332..0613631 100644
--- a/wiki/tooling/cli.md
+++ b/wiki/tooling/cli.md
@@ -22,19 +22,19 @@ The main compiler executable:
 
 ```bash
 # Lex a file (output tokens)
-affinescript lex <file.as>
+affinescript lex <file.affine>
 
 # Parse a file (output AST)
-affinescript parse <file.as>
+affinescript parse <file.affine>
 
 # Type-check a file
-affinescript check <file.as>
+affinescript check <file.affine>
 
 # Compile to WASM
-affinescript compile <file.as> -o output.wasm
+affinescript compile <file.affine> -o output.wasm
 
 # Run directly
-affinescript run <file.as>
+affinescript run <file.affine>
 ```
 
 ### Common Options
@@ -52,11 +52,11 @@ affinescript run <file.as>
 Lexical analysis - tokenize source file:
 
 ```bash
-affinescript lex src/main.as
+affinescript lex src/main.affine
 
 # Output format
-affinescript lex --format json src/main.as
-affinescript lex --format pretty src/main.as
+affinescript lex --format json src/main.affine
+affinescript lex --format pretty src/main.affine
 ```
 
 Example output:
@@ -76,12 +76,12 @@ LBRACE @ 1:19-1:20
 Parse source file to AST:
 
 ```bash
-affinescript parse src/main.as
+affinescript parse src/main.affine
 
 # Output options
-affinescript parse --format sexp src/main.as
-affinescript parse --format json src/main.as
-affinescript parse --format pretty src/main.as
+affinescript parse --format sexp src/main.affine
+affinescript parse --format json src/main.affine
+affinescript parse --format pretty src/main.affine
 ```
 
 ### check
@@ -89,13 +89,13 @@ affinescript parse --format pretty src/main.as
 Type-check without compiling:
 
 ```bash
-affinescript check src/main.as
+affinescript check src/main.affine
 
 # Check entire project
 affinescript check .
 
 # Show inferred types
-affinescript check --show-types src/main.as
+affinescript check --show-types src/main.affine
 ```
 
 ### compile
@@ -104,19 +104,19 @@ Compile to WebAssembly:
 
 ```bash
 # Basic compilation
-affinescript compile src/main.as -o output.wasm
+affinescript compile src/main.affine -o output.wasm
 
 # With optimizations
-affinescript compile --release src/main.as -o output.wasm
+affinescript compile --release src/main.affine -o output.wasm
 
 # Emit text format
-affinescript compile --emit wat src/main.as -o output.wat
+affinescript compile --emit wat src/main.affine -o output.wat
 
 # Debug info
-affinescript compile --debug src/main.as -o output.wasm
+affinescript compile --debug src/main.affine -o output.wasm
 
 # Target options
-affinescript compile --target wasm32 src/main.as
+affinescript compile --target wasm32 src/main.affine
 ```
 
 ### run
@@ -125,13 +125,13 @@ Compile and run:
 
 ```bash
 # Run with default WASM runtime
-affinescript run src/main.as
+affinescript run src/main.affine
 
 # Pass arguments
-affinescript run src/main.as -- arg1 arg2
+affinescript run src/main.affine -- arg1 arg2
 
 # With specific runtime
-affinescript run --runtime wasmtime src/main.as
+affinescript run --runtime wasmtime src/main.affine
 ```
 
 ## aspm (Package Manager)
@@ -234,19 +234,19 @@ Code formatter (planned):
 
 ```bash
 # Format file
-asfmt src/main.as
+asfmt src/main.affine
 
 # Format in place
-asfmt --write src/main.as
+asfmt --write src/main.affine
 
 # Format all files
 asfmt --write .
 
 # Check formatting
-asfmt --check src/main.as
+asfmt --check src/main.affine
 
 # Diff mode
-asfmt --diff src/main.as
+asfmt --diff src/main.affine
 ```
 
 Configuration (`.asfmt.toml`):
diff --git a/wiki/tooling/repl.md b/wiki/tooling/repl.md
index 637c245..bcfeeb4 100644
--- a/wiki/tooling/repl.md
+++ b/wiki/tooling/repl.md
@@ -9,7 +9,7 @@ The AffineScript REPL (Read-Eval-Print Loop) provides an interactive environment
 affinescript repl
 
 # With a prelude file
-affinescript repl --prelude mylib.as
+affinescript repl --prelude mylib.affine
 
 # With specific options
 affinescript repl --no-color --history-file ~/.as_history
@@ -88,14 +88,14 @@ pure
 ### Loading Files
 
 ```
-> :load examples/math.as
-Loaded examples/math.as
+> :load examples/math.affine
+Loaded examples/math.affine
 
 > add(1, 2)
 3 : Int
 
 > :reload
-Reloaded examples/math.as
+Reloaded examples/math.affine
 ```
 
 ## Multi-line Input
diff --git a/wiki/tutorials/quickstart.md b/wiki/tutorials/quickstart.md
index 4780e39..bfa9ab2 100644
--- a/wiki/tutorials/quickstart.md
+++ b/wiki/tutorials/quickstart.md
@@ -31,7 +31,7 @@ dune exec affinescript -- --version
 
 ## Your First Program
 
-Create a file `hello.as`:
+Create a file `hello.affine`:
 
 ```affine
 fn main() -{IO}-> Unit {
@@ -42,7 +42,7 @@ fn main() -{IO}-> Unit {
 Run it:
 
 ```bash
-dune exec affinescript -- run hello.as
+dune exec affinescript -- run hello.affine
 ```
 
 Output: