perf(workflow): default to inline execution for small plans (#1979)

Plans with 1-2 tasks now execute inline (Pattern C) instead of spawning
a subagent (Pattern A). This avoids ~14K token subagent spawn overhead
and preserves the orchestrator's prompt cache for small plans.

The threshold is configurable via workflow.inline_plan_threshold
(default: 2). Set to 0 to always spawn subagents. Plans above the
threshold continue to use checkpoint-based routing as before.

Closes #1979

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

get-shit-done/bin/lib/config.cjs

@@ -28,6 +28,7 @@ const VALID_CONFIG_KEYS = new Set([
   'git.branching_strategy', 'git.base_branch', 'git.phase_branch_template', 'git.milestone_branch_template', 'git.quick_branch_template',
   'planning.commit_docs', 'planning.search_gitignored',
   'workflow.subagent_timeout',
+  'workflow.inline_plan_threshold',
   'hooks.context_warnings',
   'features.thinking_partner',
   'context',

get-shit-done/references/planning-config.md

@@ -35,6 +35,7 @@ Configuration options for `.planning/` directory behavior.
 | `git.quick_branch_template` | `null` | Optional branch template for quick-task runs |
 | `workflow.use_worktrees` | `true` | Whether executor agents run in isolated git worktrees. Set to `false` to disable worktrees — agents execute sequentially on the main working tree instead. Recommended for solo developers or when worktree merges cause issues. |
 | `workflow.subagent_timeout` | `300000` | Timeout in milliseconds for parallel subagent tasks (e.g. codebase mapping). Increase for large codebases or slower models. Default: 300000 (5 minutes). |
+| `workflow.inline_plan_threshold` | `2` | Plans with this many tasks or fewer execute inline (Pattern C) instead of spawning a subagent. Avoids ~14K token spawn overhead for small plans. Set to `0` to always spawn subagents. |
 | `manager.flags.discuss` | `""` | Flags passed to `/gsd-discuss-phase` when dispatched from manager (e.g. `"--auto --analyze"`) |
 | `manager.flags.plan` | `""` | Flags passed to plan workflow when dispatched from manager |
 | `manager.flags.execute` | `""` | Flags passed to execute workflow when dispatched from manager |
@@ -259,6 +260,7 @@ Set via `workflow.*` namespace in config.json (e.g., `"workflow": { "research":
 | `workflow.skip_discuss` | boolean | `false` | `true`, `false` | Skip discuss phase entirely |
 | `workflow.use_worktrees` | boolean | `true` | `true`, `false` | Run executor agents in isolated git worktrees |
 | `workflow.subagent_timeout` | number | `300000` | Any positive integer (ms) | Timeout for parallel subagent tasks (default: 5 minutes) |
+| `workflow.inline_plan_threshold` | number | `2` | `0`–`10` | Plans with ≤N tasks execute inline instead of spawning a subagent |
 | `workflow.code_review` | boolean | `true` | `true`, `false` | Enable built-in code review step in the ship workflow |
 | `workflow.code_review_depth` | string | `"standard"` | `"light"`, `"standard"`, `"deep"` | Depth level for code review analysis in the ship workflow |
 | `workflow._auto_chain_active` | boolean | `false` | `true`, `false` | Internal: tracks whether autonomous chaining is active |

get-shit-done/workflows/execute-plan.md

@@ -61,10 +61,18 @@ PLAN_START_EPOCH=$(date +%s)
 
 <step name="parse_segments">
 ```bash
+TASK_COUNT=$(grep -c "^<task" .planning/phases/XX-name/{phase}-{plan}-PLAN.md 2>/dev/null || echo "0")
+INLINE_THRESHOLD=$(node "$HOME/.claude/get-shit-done/bin/gsd-tools.cjs" config-get workflow.inline_plan_threshold --default 2 2>/dev/null || echo "2")
 grep -n "type=\"checkpoint" .planning/phases/XX-name/{phase}-{plan}-PLAN.md
 ```
 
-**Routing by checkpoint type:**
+**Primary routing: task count threshold (#1979)**
+
+If `TASK_COUNT <= INLINE_THRESHOLD`: Use Pattern C (inline) regardless of checkpoint type. Small plans execute faster inline — avoids ~14K token subagent spawn overhead and preserves prompt cache. Configure threshold via `workflow.inline_plan_threshold` (default: 2).
+
+If `TASK_COUNT > INLINE_THRESHOLD`: Apply checkpoint-based routing below.
+
+**Checkpoint-based routing (plans with > threshold tasks):**
 
 | Checkpoints | Pattern | Execution |
 |-------------|---------|-----------|