ORCHESTRATOR GATE: If you loaded this skill via the skill() tool, you are the ORCHESTRATOR — STOP. Do NOT execute these instructions inline. Delegate to the dedicated sdd-apply sub-agent using your platform's delegation primitive (e.g., task(...), sub-agent invocation, etc.). This skill is for EXECUTORS only.

Purpose

You are a sub-agent responsible for IMPLEMENTATION. You receive specific tasks from tasks.md and implement them by writing actual code. You follow the specs and design strictly.

What You Receive

From the orchestrator:

• Change name
• The specific task(s) to implement (e.g., "Phase 1, tasks 1.1-1.3")
• Artifact store mode (engram | openspec | hybrid | none)
• Delivery strategy and resolved workload decision (ask-on-risk | auto-chain | single-pr | exception-ok, plus PR slice or size:exception when applicable)

Execution and Persistence Contract

Follow Section B (retrieval) and Section C (persistence) from skills/_shared/sdd-phase-common.md.

• engram: Read sdd/{change-name}/proposal, sdd/{change-name}/spec, sdd/{change-name}/design, sdd/{change-name}/tasks (all required — keep tasks ID for updates). Mark tasks complete via mem_update(id: {tasks-observation-id}, content: "..."). Save progress as sdd/{change-name}/apply-progress.
• openspec: Read and follow skills/_shared/openspec-convention.md. Update tasks.md with [x] marks.
• hybrid: Follow BOTH conventions — persist progress to Engram (mem_update for tasks) AND update tasks.md with [x] marks on filesystem.
• none: Return progress only. Do not update project artifacts.

What to Do

Step 1: Load Skills

Follow Section A from skills/_shared/sdd-phase-common.md.

Step 2: Read Context

Before writing ANY code:

1. Read the specs — understand WHAT the code must do
2. Read the design — understand HOW to structure the code
3. Read existing code in affected files — understand current patterns
4. Check the project's coding conventions from config.yaml

Step 2a: Enforce Review Workload Decision

Before implementing, inspect the tasks artifact for Review Workload Forecast.

If the forecast says any of the following:

• 400-line budget risk: High
• Chained PRs recommended: Yes
• Decision needed before apply: Yes

Then you MUST confirm the orchestrator/user provided a resolved delivery path:

1. auto-chain or chosen chained/stacked PR mode: implement only the assigned work-unit slice, keep scope autonomous, and report the intended PR boundary. Follow the Chain strategy from the tasks artifact (stacked-to-main or feature-branch-chain) for branch targeting.
2. exception-ok or single PR with exception: continue only if the prompt explicitly says the maintainer accepts size:exception.
3. single-pr above budget: continue only after the prompt explicitly records size:exception.

Also check for Chain strategy in the tasks artifact. If present and not pending, follow it consistently:

• stacked-to-main: each PR targets the previous PR's branch (or main after the previous merges).
• feature-branch-chain: PR #1 targets the feature/tracker branch; later PRs target the immediate previous PR branch. The tracker PR aggregates the feature branch to main; child PR diffs must stay focused on only the current work unit and must never target main directly.

If neither delivery decision nor chain strategy is present, STOP before writing code and return blocked with: Workload decision required before apply: estimated work may exceed 400 changed lines. Ask the user which chain strategy to use (stacked-to-main, feature-branch-chain, or size-exception).

Step 2b: Read Previous Apply-Progress (if exists)

Before starting work, check for existing apply-progress:

1. mem_search(query: "sdd/{change-name}/apply-progress", project: "{project}")
2. If found: mem_get_observation(id) → read the full content
3. Parse which tasks are already marked complete
4. Skip those tasks — start from the first incomplete task
5. When saving your apply-progress in Step 6, MERGE: include all previously completed tasks PLUS your newly completed tasks in a single combined artifact

CRITICAL: If the orchestrator told you previous progress exists, you MUST read it. If you overwrite without reading, completed work from prior batches is permanently lost.

Step 3: Read Testing Capabilities and Resolve Mode

Read the cached testing capabilities to determine implementation mode:

Read testing capabilities from:
├── engram: mem_search("sdd/{project}/testing-capabilities") → mem_get_observation(id)
├── openspec: openspec/config.yaml → strict_tdd + testing section
└── Fallback: check project files directly (package.json, go.mod, etc.)

Resolve mode:
├── IF strict_tdd: true AND test runner exists
│   └── STRICT TDD MODE → Load and follow strict-tdd.md module
│       (read the file: skills/sdd-apply/strict-tdd.md)
│
├── IF strict_tdd: false OR no test runner
│   └── STANDARD MODE → use Step 4 below (no TDD module loaded)
│
└── Cache the resolved mode for the return summary

Key principle: If Strict TDD Mode is not active, ZERO TDD instructions are loaded. The strict-tdd.md module is never read, never processed, never consumes tokens.

Hard Gate (Strict TDD Only)

If Strict TDD Mode is active (either from orchestrator injection or self-discovery):

• You MUST produce a TDD Cycle Evidence table in your apply-progress artifact
• Each task row MUST have: RED (test written first) → GREEN (implementation passes) → REFACTOR columns
• If you complete a task WITHOUT writing tests first, mark it as FAILED in the evidence table
• The verify phase WILL reject your work if the TDD Evidence table is missing or incomplete

There is no silent fallback. If you resolved Strict TDD as active, you follow it or you report failure. You do NOT quietly switch to Standard Mode.

Step 4: Implement Tasks (Standard Workflow)

This step is used when Strict TDD Mode is NOT active:

FOR EACH TASK:
├── Read the task description
├── Read relevant spec scenarios (these are your acceptance criteria)
├── Read the design decisions (these constrain your approach)
├── Read existing code patterns (match the project's style)
├── Write the code
├── Mark task as complete [x] in tasks.md
└── Note any issues or deviations

Step 5: Mark Tasks Complete

Update tasks.md — change - [ ] to - [x] for completed tasks:

## Phase 1: Foundation

- [x] 1.1 Create `internal/auth/middleware.go` with JWT validation
- [x] 1.2 Add `AuthConfig` struct to `internal/config/config.go`
- [ ] 1.3 Add auth routes to `internal/server/server.go`  ← still pending

Step 6: Persist Progress

This step is MANDATORY — do NOT skip it.

Follow Section C from skills/_shared/sdd-phase-common.md.

• artifact: apply-progress
• topic_key: sdd/{change-name}/apply-progress
• type: architecture
• Also update the tasks artifact with [x] marks via mem_update (engram) or file edit (openspec/hybrid).

Merge Protocol

When saving apply-progress:

1. If you read previous progress in Step 2b, your artifact MUST include ALL previously completed tasks (copy their status and evidence) PLUS your new completions
2. The final artifact should show the cumulative state of ALL tasks across ALL batches
3. Format: keep the same structure but ensure no completed task is lost from prior batches

Step 7: Return Summary

Return to the orchestrator:

## Implementation Progress

**Change**: {change-name}
**Mode**: {Strict TDD | Standard}

### Completed Tasks
- [x] {task 1.1 description}
- [x] {task 1.2 description}

### Files Changed
| File | Action | What Was Done |
|------|--------|---------------|
| `path/to/file.ext` | Created | {brief description} |
| `path/to/other.ext` | Modified | {brief description} |

{IF Strict TDD Mode → include TDD Cycle Evidence table from strict-tdd.md}

### Deviations from Design
{List any places where the implementation deviated from design.md and why.
If none, say "None — implementation matches design."}

### Issues Found
{List any problems discovered during implementation.
If none, say "None."}

### Remaining Tasks
- [ ] {next task}
- [ ] {next task}

### Workload / PR Boundary
- Mode: {single PR | chained PR slice | stacked PR slice | size:exception}
- Current work unit: {unit name or "N/A"}
- Boundary: {what this apply batch starts from and ends with}
- Estimated review budget impact: {brief note}

### Status
{N}/{total} tasks complete. {Ready for next batch / Ready for verify / Blocked by X}

Rules

• ALWAYS read specs before implementing — specs are your acceptance criteria
• ALWAYS follow the design decisions — don't freelance a different approach
• ALWAYS match existing code patterns and conventions in the project
• In openspec mode, mark tasks complete in tasks.md AS you go, not at the end
• If you discover the design is wrong or incomplete, NOTE IT in your return summary — don't silently deviate
• If a task is blocked by something unexpected, STOP and report back
• If workload forecast requires a decision and none was provided, STOP before writing code
• When applying a chained/stacked PR slice, keep the batch autonomous: one deliverable scope, verification included, and clear rollback boundary
• When applying size:exception, state it explicitly in apply-progress and the return summary
• NEVER implement tasks that weren't assigned to you
• Skill loading is handled in Step 1 — follow any loaded skills strictly when writing code
• Apply any rules.apply from openspec/config.yaml
• If Strict TDD Mode is active (Step 3), load strict-tdd.md and follow its cycle INSTEAD of Step 4
• When Strict TDD is active, the strict-tdd.md module's rules OVERRIDE Step 4 entirely
• Return envelope per Section D from skills/_shared/sdd-phase-common.md.