
Over nine months, Tom Swadell engineered core features and infrastructure across google/cel-go and google/cel-java, focusing on policy evaluation, cost analysis, and AI integration. He enhanced CEL’s runtime with extensible cost tracking, robust environment configuration, and YAML serialization, using Go and Java to improve API usability and cross-language consistency. Tom refactored testing frameworks for flexibility, introduced observable evaluation for performance, and expanded macro and type system support. His work addressed build reliability, conformance, and documentation, while also integrating AI prompt templating and policy source builders. These contributions deepened CEL’s reliability, configurability, and developer experience across multiple repositories and environments.

July 2025 performance summary: Delivered significant features and bug fixes across three repositories, with clear business impact in cost visibility, policy construction, and AI model integration. In google/cel-go, three features were delivered to strengthen correctness and usability: alias resolution test coverage for container imports, cost tracking for common list operations, and AI prompt template support for variable descriptions. In kubernetes/kubernetes, a cost estimation bug fix for nil targets improved cost accuracy across functions. In google/cel-java, added a string-based CelPolicySource builder API to simplify policy construction from raw CEL content. These contributions enhance cost transparency, policy ergonomics, and AI integration, while expanding test coverage and reliability across the codebase.
July 2025 performance summary: Delivered significant features and bug fixes across three repositories, with clear business impact in cost visibility, policy construction, and AI model integration. In google/cel-go, three features were delivered to strengthen correctness and usability: alias resolution test coverage for container imports, cost tracking for common list operations, and AI prompt template support for variable descriptions. In kubernetes/kubernetes, a cost estimation bug fix for nil targets improved cost accuracy across functions. In google/cel-java, added a string-based CelPolicySource builder API to simplify policy construction from raw CEL content. These contributions enhance cost transparency, policy ergonomics, and AI integration, while expanding test coverage and reliability across the codebase.
May 2025 (google/cel-go) monthly summary: Key feature delivered: Cel-go Testing Framework Refactor for Config via Options. This work decouples test configuration from direct CLI flags, introducing option-based configuration and new helpers (TestExpression, TestCompiler) to manage test setup more flexibly and robustly. Flags are parsed only when needed, resulting in a cleaner testing framework and reduced setup complexity. Implemented in commit f6d3c92171c2c8732a8d0a4b24d6729df4261520.
May 2025 (google/cel-go) monthly summary: Key feature delivered: Cel-go Testing Framework Refactor for Config via Options. This work decouples test configuration from direct CLI flags, introducing option-based configuration and new helpers (TestExpression, TestCompiler) to manage test setup more flexibly and robustly. Flags are parsed only when needed, resulting in a cleaner testing framework and reduced setup complexity. Implemented in commit f6d3c92171c2c8732a8d0a4b24d6729df4261520.
April 2025 highlights across google/cel-go, grpc/bazel-central-registry, and google/cel-java. Delivered core features to improve developer experience, performance, and cross-repo reliability. Key outcomes include documentation enhancements, observable CEL evaluation to boost throughput, enhanced expression unparsing with macro tracking, type-parameter formatting adjustments, and cross-repo integrations with registry updates and YAML serialization support.
April 2025 highlights across google/cel-go, grpc/bazel-central-registry, and google/cel-java. Delivered core features to improve developer experience, performance, and cross-repo reliability. Key outcomes include documentation enhancements, observable CEL evaluation to boost throughput, enhanced expression unparsing with macro tracking, type-parameter formatting adjustments, and cross-repo integrations with registry updates and YAML serialization support.
March 2025 monthly summary focusing on stabilizing the build and release workflow for google/cel-go by addressing conformance and tooling gaps. Upgraded the Bazel and Go toolchains, refreshed Go modules, and updated build rules to resolve conformance breakage, enhancing compatibility and stability in Cloud Build. Implemented Bzlmod configuration fixes to ensure reliable module resolution and reproducible builds.
March 2025 monthly summary focusing on stabilizing the build and release workflow for google/cel-go by addressing conformance and tooling gaps. Upgraded the Bazel and Go toolchains, refreshed Go modules, and updated build rules to resolve conformance breakage, enhancing compatibility and stability in Cloud Build. Implemented Bzlmod configuration fixes to ensure reliable module resolution and reproducible builds.
February 2025 monthly summary — CEL Go and CEL Java Key accomplishments: - Delivered extensive CEL environment configurability and serialization enhancements in google/cel-go, enabling FromConfig/ToConfig, env.Config with feature flags/validators, time zone handling, canonical environment descriptions, library subsetting, and Activation aliases to simplify API usage. - Introduced function overload-based exposure control in CEL, enabling subsettable function declarations to be selectively exposed or hidden for safer API surface and governance. - Fixed evaluation correctness for unknown attributes in CEL, ensuring proper identification of unknown patterns and correct propagation of partial activation to dependent rules. - Advanced policy AST optimization and unnesting, including splitting nested branching operators, separating unnest optimization from the composer to preserve type information, and expanding tests for comprehension pruning. - Updated documentation and branding to reflect CEL as an official Google product, across both Go and Java repositories (Go: removal of non-official disclaimer; Java: branding update). Overall impact and accomplishments: - Business value: stronger configurability and governance of CEL deployments, safer exposure of function implementations, and clearer product status communications, enabling broader adoption with confidence in correctness and interoperability across languages. - Technical impact: unified cross-language improvements in API usability, evaluation correctness, and AST optimization, with documented product alignment to support stakeholders. Technologies/skills demonstrated: - Go and Java codebase familiarity, configuration modeling, AST optimization patterns, exposure control design, test expansion, and release-ready documentation and branding.
February 2025 monthly summary — CEL Go and CEL Java Key accomplishments: - Delivered extensive CEL environment configurability and serialization enhancements in google/cel-go, enabling FromConfig/ToConfig, env.Config with feature flags/validators, time zone handling, canonical environment descriptions, library subsetting, and Activation aliases to simplify API usage. - Introduced function overload-based exposure control in CEL, enabling subsettable function declarations to be selectively exposed or hidden for safer API surface and governance. - Fixed evaluation correctness for unknown attributes in CEL, ensuring proper identification of unknown patterns and correct propagation of partial activation to dependent rules. - Advanced policy AST optimization and unnesting, including splitting nested branching operators, separating unnest optimization from the composer to preserve type information, and expanding tests for comprehension pruning. - Updated documentation and branding to reflect CEL as an official Google product, across both Go and Java repositories (Go: removal of non-official disclaimer; Java: branding update). Overall impact and accomplishments: - Business value: stronger configurability and governance of CEL deployments, safer exposure of function implementations, and clearer product status communications, enabling broader adoption with confidence in correctness and interoperability across languages. - Technical impact: unified cross-language improvements in API usability, evaluation correctness, and AST optimization, with documented product alignment to support stakeholders. Technologies/skills demonstrated: - Go and Java codebase familiarity, configuration modeling, AST optimization patterns, exposure control design, test expansion, and release-ready documentation and branding.
Month 2025-01 focused on CEL cost estimation enhancements in google/cel-go. Delivered extended cost tracking for two-variable comprehensions and bindings, consolidated local variable cost tracking, and refactored cost computation to be extensible while preserving backward compatibility. Implemented new tests covering the extended cost model and ordering scenarios to ensure reliable cost analysis for complex expressions. These changes improve precision of cost estimation for complex CEL expressions and establish a foundation for future extensibility, contributing to more predictable pricing and resource planning for users of CEL-powered expressions.
Month 2025-01 focused on CEL cost estimation enhancements in google/cel-go. Delivered extended cost tracking for two-variable comprehensions and bindings, consolidated local variable cost tracking, and refactored cost computation to be extensible while preserving backward compatibility. Implemented new tests covering the extended cost model and ordering scenarios to ensure reliable cost analysis for complex expressions. These changes improve precision of cost estimation for complex CEL expressions and establish a foundation for future extensibility, contributing to more predictable pricing and resource planning for users of CEL-powered expressions.
December 2024 monthly summary for google/cel-go: Focused on reliability, extensibility, and correctness. Delivered key features including versioning support for extension functions and policy composition enhancements, along with substantial fixes to comprehension pruning, partial evaluation, and Unicode handling. These changes improve backward compatibility, evaluation accuracy, and developer control, delivering business value by reducing risk in extension loading, enabling more robust policy definitions, and improving overall resilience of the CEL-go runtime.
December 2024 monthly summary for google/cel-go: Focused on reliability, extensibility, and correctness. Delivered key features including versioning support for extension functions and policy composition enhancements, along with substantial fixes to comprehension pruning, partial evaluation, and Unicode handling. These changes improve backward compatibility, evaluation accuracy, and developer control, delivering business value by reducing risk in extension loading, enabling more robust policy definitions, and improving overall resilience of the CEL-go runtime.
November 2024 monthly summary for google/cel-go and google/cel-java focused on advancing policy expressiveness, runtime safety, and build reliability, with notable cross-repo collaboration.
November 2024 monthly summary for google/cel-go and google/cel-java focused on advancing policy expressiveness, runtime safety, and build reliability, with notable cross-repo collaboration.
October 2024 monthly summary: Delivered measurable business value and technical stability across google/cel-java and google/cel-go. Focused on conformance reliability, build-system modernization, and broader code reuse. Key outcomes include fixes to proto import paths for conformance tests, a Bazel-mod upgrade with module support and dependency harmonization, a string indexing bug fix, dependency version alignment for cel.dev/expr, and an expanded visibility for parser/gen packages to enable reuse across subpackages. These efforts reduce test fragility, simplify migration paths, and improve consistency of expression evaluation across CEL implementations.
October 2024 monthly summary: Delivered measurable business value and technical stability across google/cel-java and google/cel-go. Focused on conformance reliability, build-system modernization, and broader code reuse. Key outcomes include fixes to proto import paths for conformance tests, a Bazel-mod upgrade with module support and dependency harmonization, a string indexing bug fix, dependency version alignment for cel.dev/expr, and an expanded visibility for parser/gen packages to enable reuse across subpackages. These efforts reduce test fragility, simplify migration paths, and improve consistency of expression evaluation across CEL implementations.
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