docs: add instructions for coding agents

AGENTS.md

@@ -0,0 +1,62 @@
+# Instructions for coding agents
+
+These instructions apply throughout the Network UPS Tools (NUT) repository.
+They supplement, but do not replace, the project's authoritative guidance.
+
+## Read the project guidance
+
+Before proposing a change, read the parts relevant to it:
+
+- `docs/developers.txt` for coding style, portability, build and contribution
+  requirements.
+- `docs/developer-guide.txt` for NUT architecture, design and data flow.
+- `.github/pull_request_template.md` for the current contribution checklist.
+- `SECURITY.md` before investigating or reporting a possible vulnerability.
+
+Follow more specific guidance in those files if this summary differs from it.
+
+## Work from evidence
+
+- Verify claims against the current source and applicable specifications,
+  consulting relevant history where needed. Trace affected callers, consumers
+  and data flow, then change the layer which owns the behaviour.
+- Reuse established NUT helpers, types, probes and patterns before adding new
+  code. Check nearby code for applicable precedent.
+
+## Keep changes focused and portable
+
+- Keep each change narrow and cohesive. Exclude unrelated cleanup, formatting
+  and speculative refactoring.
+- Follow affected-file style and the portability requirements in
+  `docs/developers.txt`, including plain ASCII in source comments and AsciiDoc
+  where ASCII suffices.
+- When adding, removing or renaming files, or changing templates, update the
+  applicable `Makefile.am`, `configure.ac`, distribution lists and generation
+  rules. Update source templates rather than generated files unless project
+  practice requires a generated artefact to be tracked.
+- Update manuals, compatibility data, version markers, `NEWS.adoc`,
+  `UPGRADING.adoc` and acknowledgements only where required by the affected
+  change.
+
+## Validate the affected behaviour
+
+- Run affected tests and builds, and run `make distcheck-light` before
+  upstreaming. Include relevant documentation and distribution checks when
+  their inputs or metadata change.
+- Report expected compatibility, what was actually tested, material failures
+  and untested limitations. Do not claim hardware, platform or runtime
+  acceptance from CI jobs which did not exercise it.
+- Diagnose the first relevant CI failure before changing code, distinguishing
+  the proposed change from baseline or CI-environment failures.
+
+## Preserve human responsibility
+
+- A human contributor must review and take responsibility for every proposed
+  change and for the right to submit it under the project's licence.
+- Do not add a `Signed-off-by` trailer on the contributor's behalf. The human
+  contributor must consciously provide the required DCO sign-off for each
+  commit.
+- Disclose AI or coding-helper use as required by the current pull-request
+  template, identifying the exact tool and model actually used where
+  available. This does not prescribe a tool or model and does not replace
+  human review.

Makefile.am

@@ -260,7 +260,7 @@ libtool: $(LIBTOOL_DEPS)
 # by automake. Note that the INSTALL file is (re-)imposed by autotools
 # runs and is essentially a manual on configure script general usage, so
 # NUT's actual installation notes have had to use a different filename.
-EXTRA_DIST = LICENSE-GPL2 LICENSE-GPL3 LICENSE-DCO MAINTAINERS
+EXTRA_DIST = AGENTS.md LICENSE-GPL2 LICENSE-GPL3 LICENSE-DCO MAINTAINERS
 
 # Since the renaming of documentation to `*.adoc` extension to help IDE
 # and GitHub UIs to render the source files in a pretty fashion, we need

NEWS.adoc

@@ -471,6 +471,10 @@ https://github.com/networkupstools/nut/milestone/13
       with insecure start-up like it could do before). [issue #3331, PR #3435]
 
  - Recipes, CI and helper script updates not classified above:
+    * Introduced `AGENTS.md` for AI agents to help in a consistent manner with
+      minimal friction. [#3608]
+    * Introduced `SECURITY.md` for rules about responsible disclosure of
+      potentially exploitable bugs. [#3470]
     * Introduced `ci_build.sh` settings and respective CI workflow settings
       to optionally re-use a `config.cache` file from older runs, and similar
       logic for NIT `nit.sh` to re-use generated certificate and private key

docs/developers.txt

@@ -4,6 +4,10 @@ Information for developers
 This document is intended to explain some of the more useful things
 within the tree, and provide a standard for working on the code.
 
+NOTE: Contributors using a coding agent should ensure it reads `AGENTS.md` in
+the repository root. Tools which do not detect that file automatically should
+be pointed to it explicitly.
+
 General stuff -- common subdirectory
 ------------------------------------