Prompt Templates

Every prompt that Overdeck sends to Claude — the work agent that implements a feature, the review specialist that audits the diff, the merge agent that lands a PR, the planning agent that generates an xBRIEF — is built from a versioned Markdown template under src/lib/cloister/prompts/. A single loader, renderPrompt at src/lib/cloister/prompts.ts, is the only sanctioned way to turn one of those templates into a finished prompt string. Every specialist, every handoff, every resume call goes through it. This page is the authoritative guide to that system: what the templates are, how the loader works, the frontmatter contract, the full template catalogue, and how to add, edit, or migrate a prompt without breaking production.

Why templates at all

Before the unified loader, prompts were assembled a dozen different ways — inline template literals in TypeScript, readFileSync of raw Markdown files, ad-hoc String.replace passes, and a pair of home-grown processIfBlocks / processEnvBlocks helpers. Each specialist invented its own variable syntax and its own idea of what an “optional” section looked like. That sprawl produced three recurring failures:

Silent typos. A variable like {{issueId}} referenced in the template but named issue_id at the call site rendered as the literal string {{issueId}} in the prompt sent to Claude. No error, no warning — the specialist just got a broken prompt and ran on bad context.
Drift between similar templates. The merge-agent prompt used by the full-push path and the wake-time validation path were two separate string builders that were supposed to stay in sync and didn’t.
No way to see what a prompt expects. Finding the variables a template depended on meant reading the TypeScript call site line by line.

The template system fixes all three. Every template declares its variables in YAML frontmatter; the loader validates them on every render; missing or unknown variables throw a PromptError with the exact template path and the list of offending keys.

Core principles

Keep these five rules in mind when you touch any prompt template.

1. Fail loud, fail early

Missing a required variable is a programming error, not a runtime condition to recover from. The loader throws PromptError with the template path and the list of missing keys. There is no silent fallback, no empty-string substitution, no “render partial output and hope nobody notices”. If you see a PromptError in a log, it means a call site is wrong and needs to be fixed — not that the loader needs a guard.

2. One template, one API

Templates are read only via renderPrompt({ name, vars }). There is no readFileSync on a prompt file anywhere in the codebase. If you find one, that’s a bug — migrate it to renderPrompt.

3. Composition happens in TypeScript

Mustache is deliberately a small, logic-less templating language. The loader disables HTML escaping globally (Mustache.escape = String) because we’re generating prompts for an LLM, not HTML — but everything else is vanilla Mustache with its usual section syntax. Any non-trivial composition — choosing between two instruction variants, joining an array of file paths, formatting a table of tasks — happens in TypeScript. The TypeScript builds a string, then passes that string to the template as a single variable. This keeps templates readable and keeps business logic in a place where tsc and your tests can see it.

4. Variables are declared, not discovered

Every variable used by the template’s body must appear in the frontmatter as either requires or optional. Undeclared variables are rejected by the loader. Undefined required variables are rejected by the loader. Both errors point at the template path and name the offending keys. This means reading the frontmatter tells you exactly what a template expects — you never have to grep the body to reconstruct the contract.

5. Prompts are not docstrings

A prompt template is production code that steers an LLM’s behavior. Treat it accordingly: prefer explicit instructions over implicit assumptions, prefer concrete examples over abstract rules, and when you change a template, think about what’s going to happen the first time an agent runs it against a real workspace.

The `renderPrompt` API

import { renderPrompt } from './prompts.js';

const prompt = renderPrompt({
  name: 'work',
  vars: {
    ISSUE_ID: 'PAN-742',
    BRANCH: 'feature/pan-742',
    // ...every required variable declared in work.md
  },
});

Signature

export function renderPrompt(options: RenderPromptOptions): string;

export interface RenderPromptOptions {
  name: string;                          // template basename without .md
  vars: Record<string, unknown>;         // values for required + optional vars
}

The name is the filename under src/lib/cloister/prompts/ without the .md extension. renderPrompt({ name: 'work' }) loads work.md.

What happens on every call

Load + cache. The file is read from disk once and cached in an in-memory Map keyed by name. Subsequent calls reuse the parsed ParsedPrompt (frontmatter + body + resolved path).
Parse frontmatter. The leading --- YAML block is extracted via js-yaml. Missing frontmatter, invalid YAML, or a missing name / description field all throw PromptError.
Validate requires. Every key listed in requires must be present in vars and not undefined/null. Missing keys are collected and reported in one error message.
Validate unknown keys. Every key in vars must be listed in either requires or optional. Undeclared keys are collected and reported in one error message.
Render. The body is passed to Mustache.render(body, vars) with HTML escaping disabled.

Error handling

Everything throws PromptError — a subclass of Error exported from the module. Typical messages:

Prompt "work" (.../prompts/work.md) requires variables that are missing: BRANCH, DIFFICULTY.
Provided: ISSUE_ID, XBRIEF_PATH

Prompt "review" (.../prompts/review.md) was passed unknown variables: DEBUG_MODE.
Declare them in the template's "requires" or "optional" frontmatter, or remove them from the call site.

Prompt template "work" at .../prompts/work.md is missing YAML frontmatter (expected "---\n<yaml>\n---\n<body>" header).

Failed to load prompt template "work" from .../prompts/work.md: ENOENT: no such file or directory

Do not catch these. They indicate bugs in call sites or templates that must be fixed, not runtime conditions. The fail-loud posture is deliberate — if a call site is allowed to silently skip a required variable, the resulting prompt silently loses context and the agent silently does the wrong thing.

Cache invalidation

clearPromptCache() is exported for test isolation. Production code never calls it — templates are bundled at build time and don’t change during a dashboard’s lifetime.

Prompts directory resolution

resolvePromptsDir() looks for prompts/ in two places, in order:

join(__dirname, 'prompts') — the expected location in both dev (src/lib/cloister/prompts) and production (dist/dashboard/prompts).
If __dirname contains /src/, the resolver strips everything from /src/ onward and re-anchors to <package>/src/lib/cloister/prompts. This is the tsx dev-mode fallback for cases where the module is imported from a nested path that has been re-exported through multiple barrel files.

See BUILD.md for how the build pipeline copies *.md from source to dist/dashboard/prompts/.

Frontmatter contract

Every template starts with a YAML frontmatter block delimited by ---. The loader enforces this structure — a missing or malformed block throws PromptError before a single byte of the body is read.

---
name: work
description: Work-agent prompt — implementation-phase instructions, per-task workflow, finalization steps.
requires:
  - ISSUE_ID
  - ISSUE_TITLE
  - BRANCH
  - XBRIEF_PATH
  - DIFFICULTY
optional:
  - SPEC_SECTION
  - POLYREPO_HEADER
  - TRACKER_CONTEXT
---
Body of the prompt starts here...

Fields

Field	Type	Required	Purpose
`name`	string	yes	Must match the filename (without `.md`). Used for error messages and cross-references.
`description`	string	yes	One-line summary shown in catalogues and reference docs. Write it for the reader who’s scanning a list of templates, not for the one already inside the file.
`requires`	string array	no (defaults to `[]`)	Variables that MUST be provided in `vars`. A missing or `undefined`/`null` value throws `PromptError`.
`optional`	string array	no (defaults to `[]`)	Variables that MAY be provided. Rendering with an optional variable omitted is fine — the corresponding Mustache section simply renders empty.

`requires` vs `optional`

The rule of thumb:

If the template’s output would be broken or misleading without the variable, list it as requires.
If the variable is genuinely a “fill this in if you have it, leave the section out otherwise” case, list it as optional.

requires is stricter than you might think: passing an empty string ("") satisfies the check — only undefined and null fail. This is intentional. An empty-string CURRENT_PHASE in the resume prompt means “STATE.md had no phase”, not “the caller forgot to compute one”. The caller is the one who decides whether “empty” is a legitimate value.

Unknown keys are an error

If vars contains a key that isn’t listed in requires or optional, the loader refuses to render. This catches two classes of bug:

You renamed a template variable and forgot to update the call site.
You added a new variable to the call site and forgot to declare it in the frontmatter.

Both show up as a single clear error message with the offending keys.

Mustache syntax reference

We use Mustache.js v4. HTML escaping is disabled globally, so {{VAR}} and {{&VAR}} behave identically and you never need to worry about < or & showing up in prompts.

Variable substitution

Issue: {{ISSUE_ID}}
Branch: {{BRANCH}}

Truthy sections

Render the enclosed block if the variable is truthy (non-empty string, true, a non-empty array, an object). Empty strings and false hide the block.

{{#USER_MESSAGE}}
## Operator Message

{{USER_MESSAGE}}
{{/USER_MESSAGE}}

Note the pattern {{#VAR}}{{VAR}}{{/VAR}} — that’s Mustache context fall-through: inside a truthy section, the variable itself is still accessible in the parent scope and gets substituted normally. This is how the resume prompt hides entire headings when their content is empty.

Inverted sections

Render if the variable is falsy/empty.

{{^DO_PUSH}}
Do NOT push to main — you are validating only.
{{/DO_PUSH}}

The merge template uses inverted sections extensively to toggle between validation-only and full-push flows from a single DO_PUSH boolean.

Boolean flags

renderPrompt({
  name: 'merge',
  vars: {
    // ...
    DO_PUSH: true,
    DO_BUILD: true,
    SKIP_DONE_REPORT: false,
  },
});

Booleans work as expected inside {{#VAR}} and {{^VAR}}. They are the cleanest way to toggle whole sections of a template based on a flow decision made in TypeScript.

No partials, no lambdas, no custom helpers

Mustache supports partials and lambdas; we don’t use them. Composing from smaller template fragments would push the contract across multiple files; lambdas would put logic back into the template. Both defeat the point of having a declared contract per file. If you find yourself reaching for a helper, the right move is almost always to do the work in TypeScript and pass the result in as a pre-built string variable.

Template catalogue

The ten templates currently under src/lib/cloister/prompts/, grouped by the role they play in the pipeline.

Work agent templates

Templates that drive the work agent — the specialist that implements xBRIEF checklist items.

Template	Used by	Purpose
`work.md`	Work agent (`spawnSpecialist`, `buildWorkAgentPrompt`)	Implementation instructions: claim one xBRIEF item, implement it, commit and push, run `pan task done`, then continue through quality gates and finalization.
`resume-work.md`	`buildResumePrompt`	Context-rich restart message sent when a stopped work agent resumes. Includes continue state, open xBRIEF items, pending feedback, and next-step instructions.
`handoff-to-work.md`	`buildHandoffPrompt`	Model-to-model handoff: wraps serialized git state, xBRIEF item state, continue state, and summaries with a preamble explaining who took over and why.

Planning agent templates

Templates for the planning agent, the discovery-phase agent that converts a PRD or raw issue into an xBRIEF plan.

Template	Used by	Purpose
`planning.md`	Planning agent (`buildPlanningPrompt`)	Discovery session: explore the codebase, ask questions through AskUserQuestion, write the legacy-compatible workspace draft named by `PAN_SPEC_FILENAME` plus `.pan/continue.json`, then run `pan plan finalize` to create the canonical `specs/*.xbrief.json`. Never implements code.

Specialist agent templates

Templates for the post-work pipeline specialists (review → test → merge) that run automatically after a work agent signals completion.

Template	Used by	Purpose
`review.md`	Review specialist (wake path)	Strict code review against xBRIEF acceptance criteria; pass/fail decision posted back to the dashboard.
`test.md`	Test specialist (wake path)	Runs the project’s test suite, compares against baseline, posts pass/fail with structured markers.
`merge.md`	Merge specialist (wake path) and `spawnMergeAgentForBranches` (full push flow)	Unified merge template. `DO_PUSH`/`DO_BUILD`/`SKIP_DONE_REPORT` booleans toggle between validation-only and full push + build + report flows.
`sync-main.md`	`syncMainIntoWorkspace` (via merge specialist)	Sync latest main into the workspace’s feature branch; abort on conflict and hand back to work agent.

Bootstrap templates

Short templates used during specialist initialization — not part of any per-issue workflow.

Template	Used by	Purpose
`identity-wake.md`	`initializeSpecialist`	Short identity prompt — tells a newly-initialized specialist who it is and to wait for tasks.

Legacy (ad-hoc) templates

Templates still on the pre-loader ad-hoc pattern. They work, but new edits should migrate to renderPrompt — see the Legacy templates section below for migration guidance.

Template	Used by	Purpose
`inspect-agent.md`	Inspect specialist (`buildInspectPrompt`)	Per-task spec verification mid-implementation. Still uses the legacy `readFileSync` + `String.replace` path.

Deleted (replaced by the loader)

These files used to live under prompts/ or were built inline by dead code. They no longer exist:

merge-agent.md → replaced by merge.md with DO_PUSH/DO_BUILD flags
review-agent.md → replaced by review.md
test-agent.md → replaced by test.md
uat-agent.md → uat specialist was removed from the pipeline
work-agent.md → replaced by work.md

If you find references to any of those paths in comments, PRD docs, or old commits, they are stale.

Legacy templates

inspect-agent.md still uses the pre-loader pattern: inspect-agent.ts reads it via readFileSync and does ad-hoc String.replace for a fixed set of {{variable}} placeholders. It also wraps its output in the orchestration markers that the dashboard uses to collapse context. It works and it’s in active use, so it hasn’t been migrated. If you’re editing it, either:

Keep using the ad-hoc pattern (add your new variable, update the replace chain in inspect-agent.ts), or
Migrate it to renderPrompt, wire the migration into buildInspectPrompt, and delete the ad-hoc replace chain.

Option 2 is strongly preferred for any non-trivial change, but a small one-line tweak can stay on the legacy path.

Orchestration markers

Two templates wrap their output in HTML comments:

<!-- overdeck:orchestration-context-start -->
...template body...
<!-- overdeck:orchestration-context-end -->

planning.md — marks the orchestration-context block so that session summarizers and the dashboard know which part of the planning prompt is Overdeck setup vs. the agent’s actual work.
inspect-agent.ts — wraps its rendered prompt in the same markers via a wrapping template literal.

Do not add these markers to new templates unless you have a specific dashboard-display reason and you’ve checked the code that consumes them. For the vast majority of prompts, unmarked Markdown is the right shape.

Composition pattern

Most non-trivial templates use a pattern we call pre-built blocks: the TypeScript call site composes a multi-line Markdown string based on runtime state, and passes that string in as a single optional variable. The template then conditionally renders the block via a Mustache section.

Example: `resume-work.md`

{{#PENDING_FEEDBACK_BLOCK}}
{{PENDING_FEEDBACK_BLOCK}}
{{/PENDING_FEEDBACK_BLOCK}}

And the call site:

const pendingFeedbackBlock = ctx.pendingFeedback.length > 0
  ? `## Pending Feedback (ACTION REQUIRED)\n\nThese feedback files exist in \`.planning/feedback/\` — read and address them:\n${ctx.pendingFeedback.map(f => `- \`.planning/feedback/${f}\``).join('\n')}`
  : '';

return renderPrompt({
  name: 'resume-work',
  vars: {
    // ...
    PENDING_FEEDBACK_BLOCK: pendingFeedbackBlock,
    // ...
  },
});

When pendingFeedbackBlock is non-empty, the section renders; when it’s empty, the section disappears entirely. The template stays readable (no nested conditionals, no formatting logic) and the TypeScript stays honest about what the block looks like.

When to use in-template conditionals vs pre-built blocks

In-template sections ({{#VAR}}...{{/VAR}}) are right when the block is a fixed, static chunk of instructions that’s either present or absent based on a boolean flag. The merge.md push/no-push toggles are a good example: the alternative paths are both long, both fully specified in the template, and both known at template-authoring time.
Pre-built blocks are right when the block’s content is dynamic — it joins a list, formats a table, runs git commands, reads STATE.md — and the template’s job is just to decide whether to include it. The resume-work feedback list is a good example: the TypeScript knows how to format it, the template just needs to show or hide it.

If you’re torn, default to pre-built blocks. It’s always easier to read a template that delegates dynamic content to the call site than one that tries to be clever.

Testing prompts

Prompt tests live in src/lib/cloister/__tests__/prompts.test.ts. They fall into three categories:

1. Loader contract tests

These test the loader itself against small inline fixture templates created in a temp directory: missing frontmatter, invalid YAML, missing requires, unknown vars, empty strings as requires, Mustache section rendering, etc. They exercise every error path in renderPrompt and every branch of the frontmatter parser.

2. Live-template smoke tests

These render the real templates against realistic vars fixtures and assert that key strings appear (or don’t appear) in the output. The merge.md tests are a good example: four tests covering the push+build flow, the validation-only flow, the SKIP_DONE_REPORT branch, and the polyrepo header. Smoke tests are load-bearing — they catch cases where someone edits a template in a way that looks fine to Mustache but breaks a downstream specialist’s expectations.

3. Caller-side tests

Tests that verify TypeScript call sites pass the right variables, live alongside the calling module (e.g., build-test-prompt.test.ts for the test-specialist dispatch path). These catch the “call site got out of sync with the frontmatter” class of bug.

Writing a new smoke test

When you add a template, add at least one smoke test that:

Renders the template with a realistic set of vars.
Asserts the presence of fixed strings that the template always produces.
Asserts the presence / absence of conditional blocks for each branch the template can take.

Keep the fixture vars small and local to the test — no shared state, no global setup. The loader is pure, so tests can be dead simple.

Authoring workflow

Adding a new template

Create src/lib/cloister/prompts/<name>.md.
Write the frontmatter first. List every variable you’ll reference in the body under requires (if it must be provided) or optional (if it’s fine to omit). Write a one-line description.
Write the body using {{VAR}} for substitution and {{#VAR}}...{{/VAR}} for optional sections.

Add a caller in TypeScript:

import { renderPrompt } from './prompts.js';

const prompt = renderPrompt({
  name: '<name>',
  vars: { /* every required variable */ },
});

Add at least one smoke test in prompts.test.ts.
Run npx vitest run src/lib/cloister/__tests__/prompts.test.ts and npx tsc --noEmit.
Run npm run build — the build pipeline copies *.md from src/lib/cloister/prompts/ to dist/dashboard/prompts/. If you skip this step, the production dashboard will throw a PromptError at runtime.

Editing an existing template

Decide whether the change is contract-breaking: does it add a new required variable, remove one, or change the meaning of an existing one? If yes, update every call site in the same commit.
Update the frontmatter. Adding a new variable means adding it to requires or optional — the loader will refuse to render until you do.
Update the body.
Update or add smoke tests.
Run typecheck + prompts tests.

Migrating a legacy ad-hoc prompt

If you find a call site that builds a prompt via template literals, readFileSync + ad-hoc replace, or any other pre-loader pattern, the migration path is:

Create the new prompts/<name>.md template with frontmatter that matches the variables the ad-hoc code was substituting.
Replace the ad-hoc builder with a single renderPrompt({ name, vars }) call.
If the old code had conditional logic (e.g., “if foo, include bar”), decide per case: simple toggles become Mustache sections, dynamic content becomes a pre-built block variable.
Delete the ad-hoc builder, the old template file if there was one, and any helper functions that existed only to support it.
Add smoke tests.
Run typecheck + prompts tests.

The typical commit layout is: template + loader call + tests + deletion of the old code, all in one PR. The loader’s fail-loud validation makes it very hard to leave a half-migrated path in place — either the call site works or it throws.

Troubleshooting

”requires variables that are missing”

Prompt "merge" (.../prompts/merge.md) requires variables that are missing: TARGET_BRANCH.
Provided: ISSUE_ID, SOURCE_BRANCH, PROJECT_PATH, DO_PUSH, DO_BUILD, API_URL

The call site isn’t passing a variable the template declares as required. Fix the call site — don’t “fix” the template by moving the variable to optional, unless the template genuinely works with it absent.

”was passed unknown variables”

Prompt "review" (.../prompts/review.md) was passed unknown variables: DEBUG_MODE.
Declare them in the template's "requires" or "optional" frontmatter, or remove them from the call site.

Either the call site is passing a variable that the template no longer uses (delete it from the call site), or the variable is new and hasn’t been declared yet (add it to the frontmatter).

“missing YAML frontmatter”

Prompt template "<name>" at .../<name>.md is missing YAML frontmatter (expected "---\n<yaml>\n---\n<body>" header).

The template file doesn’t start with a --- frontmatter block. This happens when someone deletes the frontmatter by accident, or pastes a body-only template from an old pattern. Add the frontmatter.

”Failed to load prompt template”

Failed to load prompt template "work" from .../prompts/work.md: ENOENT: no such file or directory

Three likely causes:

Typo in name. renderPrompt({ name: 'work-agent' }) when the file is work.md.
Missing build copy. You edited or added a template but didn’t run npm run build, so dist/dashboard/prompts/ is stale. Rebuild.
Wrong working directory. The dashboard server resolves prompts relative to dist/dashboard/ — if you’re running a script from some other location and it imports the loader, double-check that the prompts/ directory actually exists where the loader expects it.

A template renders the literal `{{VAR}}` instead of a value

Mustache left the variable in place because nothing in vars matched that name. The loader would normally throw an “unknown variables” error if the variable was passed but undeclared — if you’re seeing literal braces in the output, the variable isn’t being passed at all and the template doesn’t list it in requires. Either add the variable to requires (to force the call site to provide it) or fix the call site to pass it.

A Mustache section renders when it shouldn’t

Check whether the value you’re passing is actually falsy by Mustache’s rules. Empty string: falsy. 0: falsy. false: falsy. null / undefined: falsy. An empty array: falsy. An empty object: truthy — the section will render. This trips people up when they pass { some: 'object' } expecting the section to hide. If you want a section to hide on “nothing to say”, pass an empty string, not an empty object.

​Prompt Templates

​Why templates at all

​Core principles

​1. Fail loud, fail early

​2. One template, one API

​3. Composition happens in TypeScript

​4. Variables are declared, not discovered

​5. Prompts are not docstrings

​The renderPrompt API

​Signature

​What happens on every call

​Error handling

​Cache invalidation

​Prompts directory resolution

​Frontmatter contract

​Fields

​requires vs optional

​Unknown keys are an error

​Mustache syntax reference

​Variable substitution

​Truthy sections

​Inverted sections

​Boolean flags

​No partials, no lambdas, no custom helpers

​Template catalogue

​Work agent templates

​Planning agent templates

​Specialist agent templates

​Bootstrap templates

​Legacy (ad-hoc) templates

​Deleted (replaced by the loader)

​Legacy templates

​Orchestration markers

​Composition pattern

​Example: resume-work.md

​When to use in-template conditionals vs pre-built blocks

​Testing prompts

​1. Loader contract tests

​2. Live-template smoke tests

​3. Caller-side tests

​Writing a new smoke test

​Authoring workflow

​Adding a new template

​Editing an existing template

​Migrating a legacy ad-hoc prompt

​Troubleshooting

​”requires variables that are missing”

​”was passed unknown variables”

​“missing YAML frontmatter”

​”Failed to load prompt template”

​A template renders the literal {{VAR}} instead of a value

​A Mustache section renders when it shouldn’t

​Further reading

Prompt Templates

Why templates at all

Core principles

1. Fail loud, fail early

2. One template, one API

3. Composition happens in TypeScript

4. Variables are declared, not discovered

5. Prompts are not docstrings

The `renderPrompt` API

Signature

What happens on every call

Error handling

Cache invalidation

Prompts directory resolution

Frontmatter contract

Fields

`requires` vs `optional`

Unknown keys are an error

Mustache syntax reference

Variable substitution

Truthy sections

Inverted sections

Boolean flags

No partials, no lambdas, no custom helpers

Template catalogue

Work agent templates

Planning agent templates

Specialist agent templates

Bootstrap templates

Legacy (ad-hoc) templates

Deleted (replaced by the loader)

Legacy templates

Orchestration markers

Composition pattern

Example: `resume-work.md`

When to use in-template conditionals vs pre-built blocks

Testing prompts

1. Loader contract tests

2. Live-template smoke tests

3. Caller-side tests

Writing a new smoke test

Authoring workflow

Adding a new template

Editing an existing template

Migrating a legacy ad-hoc prompt

Troubleshooting

”requires variables that are missing”

”was passed unknown variables”

“missing YAML frontmatter”

”Failed to load prompt template”

A template renders the literal `{{VAR}}` instead of a value

A Mustache section renders when it shouldn’t

Further reading