Skill Nix Implementation

Nix Implementation Skill

Thin wrapper that delegates Nix configuration implementation to nix-implementation-agent subagent.

Trigger Conditions

This skill activates when:

• Task type is "nix"
• /implement command targets a Nix task
• NixOS modules, Home Manager configs, or flake changes need to be created using Nix

Execution Flow

Stage 1: Input Validation

Validate task_number exists, task_type is "nix", and an implementation plan is present.

Stage 2 + Stage 3: Preflight Status Update and Postflight Marker

Source skill-base.sh once, then follow @.claude/context/patterns/skill-preflight-flow.md in full for Stage 2 (preflight status update) and Stage 3 (marker creation):

source .claude/scripts/skill-base.sh
padded_num=$(printf "%03d" "$task_number")
skill_name="skill-nix-implementation"
operation="implement"

Intentional behavior fix: this skill previously wrote no .postflight-pending marker at all — zero premature-termination protection. This import gives it one.

Stage 4a: Memory Retrieval and Literature Detection

Skip memory retrieval if: clean_flag is true (from --clean).

if [ "$clean_flag" != "true" ]; then
  memory_context=$(bash .claude/scripts/memory-retrieve.sh "$description" "$task_type" "" 2>/dev/null) || memory_context=""
fi

Follow @.claude/context/patterns/lit-stage4a-flow.md in full to resolve --lit and set lit_context, exactly as skill-implementer does. This skill supplies the shared block's preconditions: lit_flag, description, orchestrator_mode (default "false" when unset).

Stage 4: Prepare Delegation Context

Domain-specific context for the nix-implementation-agent:

• Nix style guide from .claude/extensions/nix/context/
• MCP-NixOS for package/option validation (when available)
• Verification: nix flake check, nixos-rebuild build --flake .#hostname

{
  "session_id": "sess_{timestamp}_{random}",
  "delegation_depth": 1,
  "delegation_path": ["orchestrator", "implement", "skill-nix-implementation"],
  "timeout": 7200,
  "task_context": {
    "task_number": N,
    "task_name": "{project_name}",
    "description": "{description}",
    "task_type": "nix"
  },
  "plan_path": "specs/{NNN}_{SLUG}/plans/MM_{short-slug}.md",
  "metadata_file_path": "specs/{NNN}_{SLUG}/.return-meta.json"
}

If memory_context and/or lit_context from Stage 4a are non-empty, include them in the prompt (memory context first, then literature briefing), after the delegation context and before task-specific instructions. Do NOT inject an empty block for either.

Stage 5: Invoke Subagent

Use Agent tool with subagent_type: "nix-implementation-agent".

Stage 5b: Self-Execution Fallback

Follow @.claude/context/patterns/skill-self-execution-fallback.md in full. This skill's success status value for that block's write obligation is "implemented".

Postflight (ALWAYS EXECUTE)

The following stages MUST execute after work is complete, whether the work was done by a subagent or inline (Stage 5b). Do NOT skip these stages for any reason.

Stage 6: Parse Subagent Return

Read the metadata file from specs/{N}_{SLUG}/.return-meta.json.

metadata_file="specs/${padded_num}_${project_name}/.return-meta.json"

if [ -f "$metadata_file" ] && jq empty "$metadata_file" 2>/dev/null; then
    status=$(jq -r '.status' "$metadata_file")
    artifact_path=$(jq -r '.artifacts[0].path // ""' "$metadata_file")
    artifact_type=$(jq -r '.artifacts[0].type // ""' "$metadata_file")
    artifact_summary=$(jq -r '.artifacts[0].summary // ""' "$metadata_file")
    memory_candidates=$(jq -c '.memory_candidates // []' "$metadata_file")
    # Schema: .claude/context/formats/return-metadata-file.md
    completion_summary=$(jq -r '.completion_data.completion_summary // ""' "$metadata_file")
    roadmap_items=$(jq -c '.completion_data.roadmap_items // []' "$metadata_file")
else
    echo "Error: Invalid or missing metadata file"
    status="failed"
fi

Stage 7, 7a, 8, 8a, 9: Postflight Status, Memory Candidates, Artifact Linking, Notify, Cleanup

Follow @.claude/context/patterns/skill-postflight-flow.md in full:

field_name='**Summary**'
next_field='**Description**'

Not covered by the shared block: completion_summary/roadmap_items propagation via skill_propagate_completion_summary, preserved from before this conversion (already routed through skill-base.sh, which is now sourced once at Stage 2 + Stage 3 above rather than re-sourced here):

if [ "$status" = "implemented" ] || [ "$status" = "completed" ]; then
    # Literal "nix" (deliberate): this skill's Trigger Conditions hardcode a single task_type.
    skill_propagate_completion_summary "$task_number" "$completion_summary" "$roadmap_items" "nix"
fi

Error Handling

Input Validation Errors

Return immediately if task not found.

Metadata File Missing

Keep status as "implementing", report error.

Subagent Returns Partial/Failed

Do not attempt to continue, complete, or "fill in" the subagent's work. Report the status and let the user re-run /implement to resume.

Git Commit Failure

Non-blocking: Log failure but continue.

MUST NOT (Postflight Boundary)

After the agent returns, this skill MUST NOT:

1. Edit .nix files - All Nix config work is done by agent
2. Run nix flake check - Verification is done by agent
3. Analyze or grep source - Analysis is agent work
4. Write summary/reports - Artifact creation is agent work

PROHIBITION: If the subagent returned partial or failed status, the lead skill MUST NOT attempt to continue, complete, or "fill in" the subagent's work. Report the partial/failed status and let the user re-run /implement to resume.

The postflight phase is LIMITED TO:

• Reading agent metadata file
• Updating state.json via jq
• Updating TODO.md status marker via Edit
• Linking artifacts in state.json
• Git commit
• Cleanup of temp/marker files

Reference: @.claude/context/standards/postflight-tool-restrictions.md

Return Format

Brief text summary (NOT JSON).