Senior Engineering Agent

🇪🇸 Versión en español: README.es.md — 🇬🇧 This file is the English version (same content, English wording; the normative core stays in Spanish).

A portable specification of an agent that embodies the role of Senior Software Engineer and Senior Information Technology Architect: identity, rules and workflows defined once, able to materialize in Claude Code, OpenAI Codex, Cursor, Gemini CLI, ChatGPT Projects and Gemini Gems without rewriting the behavior for each platform.

Language note. The normative core (core/, modules/) is written in Spanish and is the source of truth. Since 1.2.0 the Claude Code plugin has a language selector (es | en): in en mode the agent answers in English, states its role in English and uses English labels. See Language selector.

What it is and what problem it solves

Writing "a good senior-engineer prompt" for a single platform is easy. Keeping the same behavior — security rules, judgment about when to ask, scope discipline — consistent across six platforms, each with its own instruction format, size limits and loading mechanism, is not. This project separates:

• What the agent must do (identity, rules, judgment) — written once, in core/ and modules/.
• How each platform is told — lives in adapters/, one directory per runtime, which translates (never duplicates) the above into that platform's native mechanism.
• What it knows about YOUR project — never lives here. It lives in PROJECT_CONTEXT.md / ARCHITECTURE.md / DECISIONS.md inside each real repository where you deploy the agent (templates in project-knowledge-templates/).

See SPECIFICATION.md (Spanish) for the full architecture and the evidence-based rationale of each design decision.

Requirements

• To use the agent (load it in Claude Code, Codex, Cursor, Gemini CLI, ChatGPT Projects or Gemini Gems): nothing besides the runtime itself — it is plain text (Markdown/YAML/TOML) that the runtime consumes directly. The Claude Code plugin needs Claude Code ≥ v2.1.271 (it declares userConfig.options; older versions cannot load it) and Python 3.8+ for the hooks.
• To run the tests or rebuild the ZIP (only if you modify the agent): Python 3.11+ with pyyaml (pip install pyyaml --break-system-packages) and the system utilities zip/unzip. With Python 3.10 also install tomli so the TOML validation is not skipped.
• On Windows: the Claude Code plugin runs its hooks with Git Bash (plugins/claude-code/senior-engineering-agent/scripts/sea-python.sh is a bash script). The repository ships a .gitattributes (* text=auto eol=lf) that forces LF line endings even with core.autocrlf=true; without it the .sh files would get CRLF and fail with "$'\r': command not found". If you cloned earlier, run git add --renormalize . && git checkout -- . (or clone again).

Installation

With Claude Code (recommended: install as a plugin)

The repository itself is the marketplace (.claude-plugin/marketplace.json). Inside Claude Code:

/plugin marketplace add JhonnyAdriZambrano/senior-engineering-agent
/plugin install senior-engineering-agent@senior-engineering-agent

(On Claude Code 2.1.275 or later this also works in one step: /plugin install senior-engineering-agent --marketplace JhonnyAdriZambrano/senior-engineering-agent.)

The plugin ships 7 Skills, 2 read-only subagents, the core (injected at session start by one SessionStart hook per core/ file) and the deterministic hooks (SessionStart, PreToolUse and Stop); you do not need to touch CLAUDE.md or copy anything. It is a generated view (plugins/claude-code/senior-engineering-agent/, python3 scripts/generate_plugin.py), not a second source of truth. The Python hooks go through a launcher that tries python3, python and py -3 and forces UTF-8 (PYTHONUTF8=1, PYTHONIOENCODING=utf-8); hooks read stdin as UTF-8 and emit ASCII JSON, and NN-08 asks for confirmation (fail-closed) if it cannot parse the command. Hooks of the same event run in parallel and the documentation does not guarantee their order: each core part carries the header "[Núcleo SEA — parte X de 6 (orden canónico 00→05)]". Details and limits: adapters/claude-code/CLAUDE.md.

Alternative: manual copy (no plugin; do not combine both in the same project).

1. Copy the whole senior-engineering-agent/ folder to the root of your repository.
2. In your project's CLAUDE.md, add one line: @senior-engineering-agent/adapters/claude-code/CLAUDE.md
3. Copy each folder of adapters/skills/ to .claude/skills/ in your project (.claude/skills/<name>/SKILL.md) so Claude Code loads them only when the task calls for it.
4. Optional: copy adapters/claude-code/agents/*.md to .claude/agents/ to enable the 2 read-only subagents (reviewer and bootstrap research).
5. Recommended: copy adapters/claude-code/settings.hooks.json to .claude/settings.json (or merge it) to enable the deterministic hooks: missing-knowledge notice at session start (SessionStart), mandatory confirmation of destructive operations (PreToolUse, on Bash and PowerShell) and a validation requirement at the end of the turn (Stop). Requires Python 3.8+.
6. Copy project-knowledge-templates/*.md to your project root (removing [Nombre del proyecto] and filling them in), or let project-knowledge-bootstrap help you generate them after /init.

With OpenAI Codex

1. Copy the whole senior-engineering-agent/ folder to your repository root (Codex has no import mechanism; the content must be copied verbatim).
2. Copy the content of adapters/codex/AGENTS.md (from "Identidad" to the end, without the installation section) into your real AGENTS.md.
3. Copy each folder of adapters/skills/ to .agents/skills/ in your project — Codex discovers them natively (so do Cursor and Gemini CLI).
4. Optional: copy adapters/codex/agents/*.toml to .codex/agents/ to enable the read-only subagents.
5. Recommended: copy adapters/codex/hooks.json to .codex/hooks.json (deterministic hooks; in Codex destructive operations are blocked, because Codex cannot yet ask for confirmation from a hook).

With Cursor, Gemini CLI, ChatGPT Projects or Gemini Gems

Each adapter in adapters/ includes its own installation section at the top of its file. Cursor and Gemini CLI also use the Skills from adapters/skills/, installed in .agents/skills/, and the deterministic hooks (adapters/cursor/hooks.json → .cursor/hooks.json; adapters/gemini-cli/settings.hooks.json → .gemini/settings.json). Loading differs by platform (real import, verbatim copy, or compression + attached file) — see the compatibility matrix in SPECIFICATION.md §7.

To add a runtime that is not listed, see docs/ADDING_A_RUNTIME.md.

Language selector (es / en)

Since 1.2.0 the plugin declares a language option in userConfig (plugin.json): values es (default) and en. It appears as a picker in /config → senior-engineering-agent (manifest reference, "User configuration": options is shown as a picker in /config and requires Claude Code ≥ v2.1.271).

• es (default): nothing changes — the output of the session-start and pre-tool hooks is byte-for-byte identical to 1.1.2 (verified by a deterministic test against the frozen 1.1.2 code).
• en: session-start adds a directive generated from manifest.yaml (answer in English, state the role literally as "Senior Software Engineer and Senior Information Technology Architect", and the label table below). The Spanish core stays the source of truth. The hook messages (NN-08 dialog, NN-06b alerts, knowledge report and Stop notices) also come out in English, and Stop recognizes "could not validate"-style statements in both languages.
• How the value reaches the hooks: as CLAUDE_PLUGIN_OPTION_LANGUAGE. Precedence: CLAUDE_PLUGIN_OPTION_LANGUAGE → SEA_LANGUAGE → es; an unknown value is treated as es. Other runtimes (Codex, Cursor, Gemini CLI) stay in es unless you export SEA_LANGUAGE=en.
• Verified behavior (Claude Code 2.1.296): a plugin hook receives CLAUDE_PLUGIN_OPTION_LANGUAGE only when a value is stored in pluginConfigs; the manifest default is not exported. Until you pick a value the hooks behave as es. Change the value and start a new session.

Label table (single source: manifest.yaml > i18n; the test suite checks it covers every bracketed label defined in core/ and modules/):

Deterministic guarantees (hooks)

Behavior rules in a prompt are a request; the hooks below are code that runs regardless of what the model decides. Shared logic: adapters/hooks/sea_hooks.py.

• NN-08 — destructive operations (PreToolUse). Before a shell command that can destroy work (forced git push, git reset --hard, git clean -f, git checkout -- ., git branch -D, history rewrites, rm -rf, PowerShell Remove-Item -Recurse -Force and aliases), the hook requires explicit human confirmation (ask) where the runtime supports it, and blocks it (deny) where it does not (Codex, Gemini CLI). Fail-closed: if the hook input cannot be read or parsed, it asks (or denies) instead of staying silent. Covers the Bash and PowerShell tools.
• NN-06b — knowledge files are data, not orders (SessionStart + Stop). At session start the hook checks PROJECT_CONTEXT.md / ARCHITECTURE.md / DECISIONS.md for lines shaped like an instruction addressed to the agent (heuristic) and reports them; at the end of the turn Stop blocks once if no assistant message pointed the embedded instruction out to the user.
• Stop — validate before finishing (Stop, Claude Code only). If the turn edited files (Edit/Write/MultiEdit or shell edits such as sed -i, redirection, tee, PowerShell Set-Content) and there is no evidence of validation (a test, build or lint command, or running an edited file or one that imports it) nor an explicit "I could not validate", it blocks once and asks to validate or say why not. Documentation exception (1.2.0): if all edited files are .md, .markdown, .txt, .rst or .adoc, no validation is required; one unknown target or any other file type keeps the old behavior. Limit: the extension does not prove the content is documentation (a .txt a program reads as data still counts as documentation).
• Project-knowledge check at session start. If PROJECT_CONTEXT.md / ARCHITECTURE.md are missing or still the template, the agent is told — only when the task works on that repository — to mention it in one line and offer to generate them.

Hooks never break the session: they always exit with 0 (a failure only warns).

Measured results

Full tables, provenance and limitations: docs/MEASUREMENTS.md (in Spanish; figures are language-independent). All runs: model claude-sonnet-5-5, Claude Code CLI 2.1.296.

Limitations of these figures: n = 3 runs per case and a single execution per measurement; a single model; 8 of the 11 ablation cases are at the ceiling; capability measurements are partial; raw results are not versioned (tests/results/ is local). 1.2.0 session (plugin 1.2.0, WITH arm only, one execution each, ≈ 4.22 USD in total; details in docs/MEASUREMENTS.md, section 6):

Same limits apply (n = 3, one model, one execution).

Context cost

SessionStart injects 19,622 characters per event (startup, clear and compact; core 19,291 + hook report) ≈ 4,900–5,600 tokens ESTIMATED (characters / 3.5–4, no tokenizer). claude plugin details reports ≈ 1,087 tokens and does not count hook output. Always-on cost ≈ 6k tokens per session event [estimate]. en mode adds a short directive (1,425 characters ≈ 0.4k tokens, estimate).

Validation status per runtime (version 1.2.0)

Known limitations (read before assuming full portability)

• Real conditional loading of modules is offered, via Skills, by Claude Code, Codex, Cursor and Gemini CLI: the runtime loads the Skill when its description matches the task (the model decides from that description). In ChatGPT Projects and Gemini Gems there is no such mechanism: modules are uploaded as attachments and using them is a behavioral convention.
• No instruction architecture changes the host product's visible name in its UI (Claude Code remains Claude Code), and this agent does not override the platform's native security/approval policies — it is an additional behavioral floor, not a ceiling that replaces them.
• The normative core is Spanish. en mode is a directive on top of it, not a translation of the core: a model may still occasionally echo a Spanish term; the test suite and the English evals (regression-en) measure this, they do not guarantee it.
• options raises the minimum version: declaring a picker means Claude Code versions before v2.1.271 cannot load the plugin.
• Hooks are heuristic: NN-06b detection and the Stop validation/edit criteria are pattern-based (documented limits in sea_hooks.py); NN-08 matches a fixed list of destructive commands.
• Stop exists only in Claude Code; Codex, Cursor and Gemini CLI have no Stop equivalent here (pending verification against a primary source).
• Measurements are small: n = 3 per case, one model, one execution each (see above).
• See SPECIFICATION.md §6 and §7 for what is portable, adaptable or platform-dependent.

Repository structure

senior-engineering-agent/
├── README.md                    this file (English)
├── README.es.md                 Spanish README (linked with this file)
├── CHANGELOG.md                 version history and versioning policy
├── SPECIFICATION.md             full architecture, agent contract
├── LICENSE                      Apache-2.0 (full official text)
├── NOTICE                       copyright and license notice
├── manifest.yaml                identity, version, module index, i18n (languages, English role, label table)
├── capabilities.yaml            abstract capabilities -> per-runtime binding
├── .gitattributes               LF line endings (Windows portability)
├── .gitignore                   Git hygiene (secrets, builds, results)
├── .env.example                 documents that the project needs no variables of its own
├── .github/
│   └── workflows/
│       └── structural-tests.yml CI: structural suite and --check on Linux and Windows (no LLM)
├── .claude-plugin/
│   └── marketplace.json         the repo is the Claude Code plugin marketplace
├── core/                        6 always-loaded files + compact.md
│                                (DERIVED summary for runtimes without @import)
├── modules/                     7 conditionally loaded modules
├── adapters/                    one directory per supported runtime
│   ├── skills/                  7 Skills (SKILL.md) GENERATED from modules/
│   ├── hooks/
│   │   ├── sea_hooks.py         shared hook logic (Claude Code, Codex, Cursor, Gemini CLI)
│   │   └── i18n.json            languages, English role and es->en labels (GENERATED from manifest.yaml > i18n)
│   ├── claude-code/             CLAUDE.md + agents/ (2 read-only subagents) + settings.hooks.json
│   ├── codex/                   AGENTS.md + hooks.json + agents/ (3 read-only subagents)
│   ├── cursor/                  hooks.json + rules/ (alwaysApply rule with the compact core)
│   ├── gemini-cli/              GEMINI.md + settings.hooks.json
│   └── chatgpt-and-gems/        compressed instructions + attached files
├── plugins/
│   └── claude-code/
│       └── senior-engineering-agent/   GENERATED Claude Code plugin (scripts/generate_plugin.py)
│           ├── .claude-plugin/
│           │   └── plugin.json  name, version and the language userConfig (from manifest.yaml)
│           ├── LICENSE          license copy
│           ├── NOTICE           notice copy
│           ├── core/            copy of core/00-05
│           ├── skills/          copy of adapters/skills/
│           ├── agents/          copy of adapters/claude-code/agents/
│           ├── hooks/
│           │   └── hooks.json   one SessionStart per core/ file, plus PreToolUse and Stop
│           ├── adapters/
│           │   └── hooks/
│           │       ├── sea_hooks.py  same relative path as in the source
│           │       └── i18n.json     copy of adapters/hooks/i18n.json
│           ├── project-knowledge-templates/  templates the SessionStart hook needs
│           ├── scripts/
│           │   └── sea-python.sh  Python launcher (python3 | python | py -3)
│           └── evals/           `claude plugin eval` cases (hand-written, versioned)
│               └── README.md    what is automated and criterion -> grader
├── project-knowledge-templates/ templates you copy into YOUR real project
├── docs/
│   ├── ADDING_A_RUNTIME.md      contract for building a new adapter
│   └── MEASUREMENTS.md          audited measurements (E7a, E3d and 1.2.0): tables, provenance, limitations
├── tests/                       structural validation + behavior evaluation
│   ├── test_agent.py            structural validation (level 1, no LLM)
│   ├── run_tests.sh             entry point of test_agent.py
│   ├── BENCHMARK.md             14 formal tests, PASS/PARTIAL/FAIL criteria
│   ├── GUIA_BENCHMARK.md        HOW to run all the tests (start here)
│   ├── MANUAL_SCENARIOS.md      narrative manual verification scenarios
│   ├── acceptance/              hooks_practice.sh: practical acceptance of the hooks with the real launcher (no LLM)
│   ├── fixtures/                sea_hooks_1.1.2.py: frozen copy of the 1.1.2 hook (byte-for-byte identity test of `es` mode)
│   ├── behavioral/              heuristic harness run_scenarios.sh (OBSOLETE: scripts/eval.sh replaces it)
│   ├── sandbox/                 creates the benchmark sandbox (states A/B/C)
│   └── results/                 run records (template _TEMPLATE.md)
└── scripts/
    ├── build_zip.sh             deterministic packaging (dist | repo)
    ├── generate_skills.py       modules/ -> adapters/skills/ (--check only checks)
    ├── generate_compact.py      core/compact.md -> adapters without @import (--check)
    ├── generate_plugin.py       core/, adapters/ and manifest.yaml -> Claude Code plugin (--check)
    ├── eval.sh                  automated evaluation with `claude plugin eval` (smoke|regression|capability|regression-en|all)
    ├── ablate_core.sh           core ablation (D-17): without core/02…05 over 11 cases (`completo|sin-02|sin-03|sin-04|sin-05`)
    ├── eval_report.py           report of an eval.sh run (WITH / W/OUT / Δ)
    ├── eval_summary.py          per-case summary of one or more result.json (excludes `arm: with-only` graders; no model cost)
    ├── check_results.py         summarizes tests/results/ and the gate status (manual 1.0.0 benchmark)
    └── new_result.sh            creates the prefilled record of a benchmark run

Testing

python3 tests/test_agent.py
bash tests/acceptance/hooks_practice.sh

tests/test_agent.py is a structural (static) suite plus deterministic hook tests (no LLM): manifest/capabilities consistency, no broken references, no leaked secrets, YAML/TOML validity, Skill and compact-core sync, canonical role, version and count coherence, packaging determinism, generated-plugin sync, hook behavior (NN-08, NN-06b, Stop, UTF-8/cp1252, language es/en, documentation exception) and tool tests. Checks that cannot run are reported as [SKIP] with a reason, never as passed. Behavior is evaluated separately with scripts/eval.sh (claude plugin eval, with a no-plugin baseline) and the manual benchmark (tests/BENCHMARK.md, tests/GUIA_BENCHMARK.md).

Contributing / changing the agent

See README.es.md (Spanish), section "Actualizar el agente", for the full checklist: edit core/ or modules/, regenerate Skills / compact core / plugin (python3 scripts/generate_skills.py, generate_compact.py, generate_plugin.py; each with --check), run the suite, bump manifest.yaml > agent.version per CHANGELOG.md, and rebuild the ZIPs.

Authorship

Designed, directed and validated by Jhonny Adrian Zambrano Gonzalez (architecture, decisions, benchmark criteria and test execution). Developed with the assistance of Claude (Anthropic) for drafting, script implementation and audits.

License

Apache License 2.0 since version 1.2.1 (LICENSE holds the full official text, NOTICE the copyright notice). It allows use, modification and redistribution, including commercial use, as long as the license and notice are kept. Versions up to and including 1.2.0 were released under CC BY-NC 4.0 and keep that license.

Support

The project is free and open. On request I offer services to adapt the agent to enterprise stacks, plus support and training. Contact: open an Issue in the repository.

Sponsor the project on GitHub Sponsors.

{
  "name": "senior-engineering-agent",
  "description": "Senior Engineering Agent marketplace: Claude Code plugin generated from this repository's portable specification. / Marketplace del Senior Engineering Agent: plugin de Claude Code generado desde la especificación portable de este repositorio.",
  "owner": {
    "name": "Jhonny Adrian Zambrano Gonzalez"
  },
  "plugins": [
    {
      "name": "senior-engineering-agent",
      "source": "./plugins/claude-code/senior-engineering-agent",
      "description": "Senior Software Engineer and Senior IT Architect: core loaded by SessionStart hooks, language selector (es/en), 7 Skills, 2 read-only agents and deterministic hooks (NN-08, project knowledge, validation at stop). / Ingeniero de Software Senior y Arquitecto de TI Senior: núcleo por hooks SessionStart, selector de idioma (es/en), 7 Skills, 2 subagentes de solo lectura y hooks deterministas (NN-08, conocimiento del proyecto, validación al terminar).",
      "category": "development",
      "tags": [
        "engineering",
        "code-review",
        "architecture",
        "security"
      ]
    }
  ]
}