junegunn/fzf

Can another program use it through a documented, machine-readable surface?

• next: [cli] L3 Machine-readable output (--json/--format) and documented exit statuses. (no --json/--format option)
• next: [library] L4 An API reference is generated from the code (autodoc, mkdocstrings, typedoc, …). (no generated API reference)

cli ladder · level 2

• ✓ L1 Invocable non-interactively: no prompts, or prompts guarded by a TTY check or a --yes/--no-input option. src/options.go 3 matchessrc/util/util.go 1 match
• ✓ L2 --help documents every option (at least 90% of options have help text). src/core.go 3 matches
• ✗ L3 Machine-readable output (--json/--format) and documented exit statuses. no --json/--format option
• ✗ L4 The output format is specified by a JSON Schema. no JSON Schema for the output

library ladder · level 3

• ✓ L1 An importable, packaged API exists. go.mod Go module with exported packages
• ✓ L2 The public API is delimited (__all__, an exports map, exported identifiers). go.mod exported identifiers
• ✓ L3 The public API is statically typed (py.typed, type declarations, a typed language). go.mod statically typed language
• ✗ L4 An API reference is generated from the code (autodoc, mkdocstrings, typedoc, …). no generated API reference

Can integrators rely on it not changing under them?

• next: L3 A deprecation mechanism is used in code (warnings, @deprecated, Deprecation/Sunset headers) or the API is versioned. (no deprecation mechanism or API versioning)

all ladder · level 2

• ✓ L1 Releases are versioned (semver tags or versioned changelog sections). 180 semver tags, latest v0.74.5
• ✓ L2 A changelog exists and marks breaking changes. CHANGELOG.md marks breaking changes
• ✗ L3 A deprecation mechanism is used in code (warnings, @deprecated, Deprecation/Sunset headers) or the API is versioned. no deprecation mechanism or API versioning
• ✓ L4 Across tagged releases, no OpenAPI operation, CLI option or __all__ symbol was removed without first being deprecated. 20 tagged releases compared

Can others react to state changes without polling?

Can a machine act with its own revocable, least-privilege identity?

• next: [cli] L4 Several profiles or scoped credentials per target. (no credential profiles)
• next: [library] L4 Several profiles or scoped credentials per target. (no credential profiles)

cli ladder · level 3

• ✓ L1 Credentials can be supplied non-interactively (environment variables). src/server.go 1 match
• ✓ L2 Credentials never need to be on the command line, and their environment variables are documented. CHANGELOG.md 5 matches
• ✓ L3 No output or log statement includes a credential. no credential in print/log statements
• ✗ L4 Several profiles or scoped credentials per target. no credential profiles

library ladder · level 3

• ✓ L1 Credentials can be supplied non-interactively (environment variables). src/server.go 1 match
• ✓ L2 The credential environment variables are documented. CHANGELOG.md 5 matches
• ✓ L3 No output or log statement includes a credential. no credential in print/log statements
• ✗ L4 Several profiles or scoped credentials per target. no credential profiles

Can its data get in and out, in bulk, in open formats, with an explicit schema?

Can an automated caller use it without guessing, and recover from failure?

• next: [cli] L3 Documented exit statuses distinguish error classes, errors are JSON in JSON mode, and color is off when not a TTY. (errors aren't JSON in JSON mode)
• next: [library] L1 Errors are specific exception types, and library code never calls sys.exit. (no exception classes)

cli ladder · level 2

• ✓ L1 Never blocks on a prompt when stdin is not a TTY. src/options.go 3 matchessrc/util/util.go 1 match
• ✓ L2 Data on stdout, diagnostics on stderr, non-zero exit on failure. src/options_pprof.go 3 matchessrc/util/util_windows.go 2 matches
• ✗ L3 Documented exit statuses distinguish error classes, errors are JSON in JSON mode, and color is off when not a TTY. errors aren't JSON in JSON mode
• ✗ L4 --dry-run, limits for long or costly operations (timeouts, budgets), and agent docs. no --dry-run

library ladder · level 0

• ✗ L1 Errors are specific exception types, and library code never calls sys.exit. no exception classes
• ✗ L2 Inputs are validated with messages naming the bad argument. no input validation errors
• ✓ L3 Timeouts and retries are configurable. src/tui/light_windows.go 2 matchessrc/tui/light.go 6 matches
• ✗ L4 Agent docs, and examples that run as tests (doctests). no agent docs

Can another system run and compose it without a human?

• next: [library] L4 Optional features behind extras/features. (no optional extras)

cli ladder · level 4

• ✓ L1 Runnable from source (a declared entry point). main.go go main
• ✓ L2 Installable as a package that provides the command. main.go go main
• ✓ L3 Published to a public registry and run non-interactively in CI. .github/workflows/release.yml 3 matches.github/workflows/linux.yml 1 match
• ✓ L4 Also shipped as a container image or a single binary. Dockerfile.goreleaser.yml

library ladder · level 3

• ✓ L1 Importable from source. go.mod Go module with exported packages
• ✓ L2 Installable as a package (a package manifest). go.mod package manifest
• ✓ L3 Published to a public registry, with at most 10 runtime dependencies. .github/workflows/release.yml 3 matches unknown number of runtime dependencies
• ✗ L4 Optional features behind extras/features. no optional extras

Can behaviour be added without modifying the code?

• next: L1 Internal seams: a registry, registration function or plugin manager. (no registry or registration function)

all ladder · level 0

• ✗ L1 Internal seams: a registry, registration function or plugin manager. no registry or registration function
• ✗ L2 The docs show how to add behaviour through those seams (even in-tree). no registration functions to document
• ✗ L3 Out-of-tree extensions are discovered (entry points, a plugin directory, configuration) without editing the package. extensions must be added inside the package
• ✗ L4 The extension API is versioned, has lifecycle hooks, and has example extensions. the extension API isn't versioned

Can an operator, or an orchestrating agent, tell whether it works and why not?

• next: [cli] L2 Verbosity control for diagnostics (--quiet, --log-level, --debug). (no --quiet or log-level control)
• next: [library] L1 Logs through a standard logger namespace and never prints from library code. (no standard logger)

cli ladder · level 1

• ✓ L1 Meaningful exit statuses, and errors on stderr. src/options_pprof.go 3 matchessrc/util/util_windows.go 2 matches
• ✗ L2 Verbosity control for diagnostics (--quiet, --log-level, --debug). no --quiet or log-level control
• ✗ L3 Structured logs (e.g. --log-format json) or a machine-readable run summary. no structured diagnostics
• ✗ L4 Tracing hooks (OpenTelemetry). no tracing hooks

library ladder · level 0

• ✗ L1 Logs through a standard logger namespace and never prints from library code. no standard logger
• ✗ L2 Log levels are used meaningfully (at least two levels). fewer than two log levels used
• ✗ L3 Optional metrics or tracing hooks. no metrics or tracing hooks
• ✗ L4 OpenTelemetry instrumentation available. no OpenTelemetry instrumentation

Can an agent change it safely with limited context?

• next: L3 At least 90% of modules fit 32k tokens and no file exceeds 12k; test/source token ratio at least 0.3; at least 70% of the code is typed. (75% of modules fit 32k tokens; 2 files over 12k)

all ladder · level 2

• ✓ L1 A README and some tests. README.mdsrc/algo/algo_test.go 42 test files
• ✓ L2 CI runs the tests; applications pin dependencies (libraries and zero-dependency projects are exempt). .github/workflows/codeql-analysis.yml.github/workflows/depsreview.yaml
• ✗ L3 At least 90% of modules fit 32k tokens and no file exceeds 12k; test/source token ratio at least 0.3; at least 70% of the code is typed. 75% of modules fit 32k tokens; 2 files over 12k
• ✗ L4 No import cycles, and agent docs (AGENTS.md, CLAUDE.md, llms.txt). no agent docs (AGENTS.md, CLAUDE.md, llms.txt)