diff --git a/docs/ADRs/0049-agent-configuration-env-var-convention.md b/docs/ADRs/0049-agent-configuration-env-var-convention.md new file mode 100644 index 0000000000..3c61f41aa3 --- /dev/null +++ b/docs/ADRs/0049-agent-configuration-env-var-convention.md @@ -0,0 +1,186 @@ +--- +title: "49. Agent configuration environment variable convention" +status: Accepted +relates_to: + - agent-architecture + - agent-infrastructure +topics: + - configuration + - harness + - agents + - conventions +--- + +# 49. Agent configuration environment variable convention + +Date: 2026-06-16 + +## Status + +Accepted + +## Context + +Agents need behavioral knobs — settings that tune *how* they work without +changing the agent definition itself. Issue +[#2333](https://github.com/fullsend-ai/fullsend/issues/2333) surfaced +a concrete case: the review agent should let repo owners set a minimum +severity threshold for reported findings. More knobs will follow for other +agents. + +The harness already delivers environment variables into the sandbox via `.env` +files with `expand: true` +([ADR 0024](0024-harness-definitions.md)), and pre/post scripts read env vars +from `runner_env` ([ADR 0045](0045-forge-portable-harness-schema.md)). The +infrastructure for carrying configuration exists. What is missing is a +**naming convention** that establishes a consistent pattern for every agent +going forward. + +This ADR covers only **agent configuration** env vars — behavioral knobs that +tune agent behavior. It does not retroactively rename existing context vars +(event data like `GITHUB_PR_URL`, `ISSUE_NUMBER`) or infrastructure vars +(tokens, paths, credentials). Those remain as they are. + +## Decision + +Agent configuration environment variables follow a single convention: + +### Naming + +``` +{AGENT}_{SETTING_NAME} +``` + +- `{AGENT}` is the agent's **name** in uppercase, derived from the harness + filename: `REVIEW`, `CODE`, `TRIAGE`, `FIX`, `PRIORITIZE`, `RETRO`, etc. +- `{SETTING_NAME}` is `SCREAMING_SNAKE_CASE` describing the setting. +- Examples: `REVIEW_SEVERITY_THRESHOLD`, `CODE_MAX_FILE_SIZE`, + `REVIEW_POST_INLINE`, `TRIAGE_SKIP_DUPLICATE_CHECK`. +- A setting that applies to multiple agents gets separate vars per agent + (e.g., `CODE_MAX_FILE_SIZE` and `REVIEW_MAX_FILE_SIZE`), keeping each + agent's configuration independent. + +The agent name prefix prevents collisions when multiple agents share an +execution environment or when env files are sourced together. Existing context +vars (e.g., `PRIOR_REVIEW_SHA`) and credential vars (e.g., `FIX_GH_TOKEN`) +already use agent-name prefixes — the `{AGENT}_` prefix alone does not +distinguish config vars from those. The distinction is by purpose and +documentation: config vars are behavioral knobs listed in +`docs/agents/.md`. + +### Where config vars live in the harness + +Config vars are carried the same way as other agent env vars — no new schema +fields are needed. The `.env` file and `runner_env` serve different +audiences: the `.env` file delivers vars into the sandbox for the agent at +inference time, while `runner_env` makes vars available to pre/post scripts +on the host. A config var needed by both must appear in both places. + +1. **For sandbox access (inference time):** Add the variable to the agent's + `.env` file (e.g., `env/review.env`) with `${VAR}` expansion. The harness + `host_files` entry with `expand: true` resolves the value from the host + environment before copying into the sandbox. The agent reads it at runtime. + +2. **For pre/post scripts (host side):** Add the variable to the harness's + `runner_env` or the forge-specific `runner_env` block. Scripts read it + from the environment. This is independent of the `.env` file — `runner_env` + controls the host-side environment, not the sandbox. + +3. **For CI workflow injection:** The CI workflow sets the value from org + secrets, repo variables, or hardcoded defaults. This is the same mechanism + used for all other env vars — no change needed. + +### Defaults + +Default values live in the **canonical harness** (the scaffold's +`harness/.yaml`). Downstream layers — the org `.fullsend` repo or a +per-repo `.fullsend/` — override them via `base` composition +([ADR 0045](0045-forge-portable-harness-schema.md)). Defaults are also +**documented** in `docs/agents/.md` so users can discover them without +reading harness YAML. + +**For agent prompts,** the agent treats an unset or empty variable the same as +"use the default." The `.env` file's `expand: true` mechanism resolves unset +host vars to an empty string, not an absent var — so agents and scripts must +handle both cases. + +**For pre/post scripts,** use standard shell defaulting, which already handles +both empty and unset: `${REVIEW_SEVERITY_THRESHOLD:-low}`. + +### Documentation + +Each agent's user-facing documentation (`docs/agents/.md`) includes a +**Variables** subsection under the existing "Configuration and extension" +section: + +```markdown +## Configuration and extension + +See [Customizing with AGENTS.md](../guides/user/customizing-with-agents-md.md) and +[Customizing with Skills](../guides/user/customizing-with-skills.md). + +### Variables + +| Variable | Description | Default | Valid values | +|----------|-------------|---------|--------------| +| `REVIEW_SEVERITY_THRESHOLD` | Minimum severity for reported findings | `low` | `info`, `low`, `medium`, `high`, `critical` | +| `REVIEW_POST_INLINE` | Post inline comments on individual findings | `true` | `true`, `false` | +``` + +This is the single place a user looks to discover what knobs an agent +supports. Every agent doc includes this subsection for consistency — agents +that accept no configuration vars state "None" in the section. The agent's +system prompt (`agents/.md`) references config vars wherever they are +naturally needed in the instructions — no prescribed section structure. + +### Using config vars at inference time + +The agent's system prompt references config vars in context where the +behavior is conditioned. For example, in the review agent: + +```markdown +## Severity filtering + +If `$REVIEW_SEVERITY_THRESHOLD` is set, suppress findings below that level. +The severity order is: info < low < medium < high < critical. Suppressed +findings do not appear in the output — they are dropped entirely, not +downgraded. +``` + +The agent reads the value from its sandbox environment (e.g., via +`printenv REVIEW_SEVERITY_THRESHOLD` or by referencing it in tool calls) +and conditions its behavior accordingly. This is no different from how +agents already read `$GITHUB_PR_URL` or `$ISSUE_NUMBER`. + +### Precedence + +Config var values follow the existing harness layering from +[ADR 0045](0045-forge-portable-harness-schema.md) and +[ADR 0003](0003-org-config-repo-convention.md): fullsend defaults (scaffold) +can be overridden by the org `.fullsend` repo, which can be overridden by +per-repo `.fullsend/`. This layering already applies to `.env` files and +`runner_env` — config vars inherit it for free. + +## Consequences + +- **No runner changes required.** The convention uses existing env var + delivery mechanisms (`host_files` with `expand: true`, `runner_env`, + CI workflow `env:`). Agents start accepting config vars immediately by + documenting them and referencing them in their prompts and scripts. +- **Discoverability is centralized.** Users check `docs/agents/.md` + to see what knobs an agent supports. Agent authors document new config + vars there when adding them. +- **Collision-free by convention.** The `{AGENT}_` prefix scopes config vars + to the agent that owns them. +- **Agent system prompts stay flexible.** There is no required section + structure for how `agents/.md` references config vars. Agent + authors place references where they make sense in the prompt flow. +- **Each new config var may require updates in several places:** + 1. Agent `.env` file (sandbox delivery) + 2. Harness `runner_env` (host-side script access) + 3. Agent system prompt (behavioral conditioning) + 4. Pre/post scripts (host-side logic) + 5. `docs/agents/.md` (user documentation) + + Not every var needs all five — a var used only at inference time skips 2 + and 4; a var used only in scripts skips 1 and 3. diff --git a/docs/architecture.md b/docs/architecture.md index f23a64f19f..cb6a422519 100644 --- a/docs/architecture.md +++ b/docs/architecture.md @@ -91,6 +91,11 @@ The harness draws its configuration from the adopting organization's **`.fullsen runner_env) from platform-neutral fields. Forge blocks inherit from top-level defaults and override only deltas ([ADR 0045](ADRs/0045-forge-portable-harness-schema.md)). +- Agent configuration env vars: behavioral knobs use `{AGENT}_{SETTING_NAME}` + naming (e.g., `REVIEW_SEVERITY_THRESHOLD`), delivered via existing env var + mechanisms (`.env` files, `runner_env`). Each agent documents its config + vars in `docs/agents/.md` + ([ADR 0049](ADRs/0049-agent-configuration-env-var-convention.md)). **Open questions:**