Prepend built-in prompts to user prompt in unified creation step with system tags and validation by Copilot · Pull Request #10469 · github/gh-aw

Copilot · 2026-01-17T15:09:16Z

Plan: Prepend Built-in Prompts to User Prompt

Understanding the Problem

Understand current flow: User prompt written first, then built-in prompts appended
Identify where user prompt is created (compiler_yaml.go line 207)
Identify where built-in prompts are appended (unified_prompt_step.go)
Understand substitution mechanism for expressions

Implementation Tasks

Testing Tasks

Bug Fixes

Fixed: Built-in prompt expressions (e.g., __GH_AW_GITHUB_WORKSPACE__) now included in substitution step
Deduplicated expression mappings to avoid YAML validation errors
Sort expression mappings by key for stable, deterministic output
Fixed: undefined/null environment variables now converted to empty strings instead of literal "undefined"/"null"

Validation

Run make fmt
All tests pass (50 tests: 23 Go + 27 new JavaScript fuzz tests)
Verify system tags in generated workflow
Verify validation step in generated workflow
Verify all 126 workflows have validation step
All 126 workflows recompiled successfully
Substitutions in alphabetical order across all workflows

Original prompt

Prepend the built in prompts to the user prompt and render all of them in a single step (or multiple if too large)

Remove the append prompt as it is not needed anymore.

Add tests to ensure that the substitutions are working

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

Changeset

Type: patch
Description: Prepend built-in prompts to the user prompt and consolidate prompt creation into a single unified creation step wrapped in (system) tags. Adds placeholder validation, merges built-in and user environment variables for interpolation, and introduces tests covering ordering, interpolation, and validation. This is an internal tooling and behavior change (tests/validation) and does not modify public CLI APIs.

Ahoy! This treasure was crafted by 🏴‍☠️ Changeset Generator

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

…tests Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

pelikhan · 2026-01-17T15:59:26Z

@copilot wrap builtin prompts in "system" xml tags

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-01-17T16:07:04Z

@copilot wrap builtin prompts in "system" xml tags

Done in commit 16b560f. Built-in prompts are now wrapped in <system> XML tags.

cat << 'PROMPT_EOF' > "$GH_AW_PROMPT"
<system>
PROMPT_EOF
# Built-in prompts: temp_folder, cache memory, repo memory, safe-outputs, github-context
cat "/opt/gh-aw/prompts/temp_folder_prompt.md" >> "$GH_AW_PROMPT"
cat << 'PROMPT_EOF' >> "$GH_AW_PROMPT"
## Cache Folder Available
...
</system>
PROMPT_EOF
# User prompt follows after </system> tag
cat << 'PROMPT_EOF' >> "$GH_AW_PROMPT"
# User Task
...

The system tags clearly delineate built-in context from user instructions.

pelikhan · 2026-01-17T17:06:14Z

@copilot add a comprehensive test suite for this feature

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-01-17T17:17:03Z

@copilot add a comprehensive test suite for this feature

Done in commit 62afc84. Added comprehensive test suite with 20 tests:

Unit Tests (16):

Core functionality: ordering, system tags, file modes, removed old steps
Expression handling: built-in, user, combined, env var sorting
Chunking: single, multiple, 10+ chunks
Edge cases: empty prompts, no built-ins
Features: trial mode, cache/repo memory, PR context, all tools combined

Integration Tests (4):

End-to-end workflow compilation with all features
Minimal workflow compilation
Safe-outputs only configuration
Expression substitution validation

All tests verify:

✅ Built-in prompts prepended before user content
✅ <system> tags properly wrap built-in sections
✅ Expression substitution works for both built-in and user prompts
✅ Proper file operation modes (create vs append)
✅ Environment variables are sorted alphabetically

Coverage: 100% of built-in prompt types, comprehensive edge cases, complete integration testing.

pelikhan · 2026-01-17T17:34:09Z

@copilot add a step that does a sanity check that expressions have been properly rendered and placeholders are gone.

Store as file in actions/setup

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-01-17T17:42:35Z

@copilot add a step that does a sanity check that expressions have been properly rendered and placeholders are gone.

Store as file in actions/setup

Done in commit c3438af. Added sanity check step that validates placeholders are properly substituted.

New validation step added after interpolation but before print:

Create prompt with built-in context
Substitute placeholders
Interpolate variables and render templates
Validate prompt placeholders ← New step
Print prompt

Validation script (actions/setup/sh/validate_prompt_placeholders.sh):

✅ Checks for unreplaced __GH_AW_*__ placeholders
⚠️ Warns about ${{ }} expressions (allows handlebars templates)
📊 Shows prompt statistics (lines, characters, words)
❌ Exits with error if placeholders found

Example output:

🔍 Validating prompt placeholders...
✅ Placeholder validation complete
📊 Prompt statistics:
   - Lines: 928
   - Characters: 81345
   - Words: 12456

If placeholders found:

❌ Error: Found unreplaced placeholders in prompt file:
42:Repository: __GH_AW_GITHUB_REPOSITORY__

Test suite included with 4 test cases covering valid prompts, unreplaced placeholders, missing files, and GitHub expressions.

github-actions · 2026-01-17T17:56:08Z

🎬 THE END — Smoke Claude MISSION: ACCOMPLISHED! The hero saves the day! ✨

github-actions · 2026-01-17T17:56:09Z

🎉 Yo ho ho! Changeset Generator found the treasure and completed successfully! ⚓💰

github-actions · 2026-01-17T19:12:15Z

📰 VERDICT: Smoke Copilot has concluded. All systems operational. This is a developing story. 🎤

pelikhan · 2026-01-17T19:14:43Z

@copilot review error

Reference: https://github.com/githubnext/gh-aw/actions/runs/21099476671/job/60681596148#step:22:1

github-actions · 2026-01-17T19:15:28Z

Smoke Test Results

Last 2 merged PRs:

Scout workflow review: Confirmed Tavily integration and production readiness #10482: Scout workflow review: Confirmed Tavily integration and production readiness
[WIP] Debug workflow failure in Smoke Codex #10481: [WIP] Debug workflow failure in Smoke Codex

Test Results:

✅ GitHub MCP: Retrieved 2 closed PRs
✅ Playwright: Navigated to github.com (title: "GitHub · Change is constant. GitHub keeps you ahead. · GitHub")
✅ Tavily Search: Found 5 results for "GitHub Agentic Workflows"
✅ File Write: Created /tmp/gh-aw/agent/smoke-test-claude-21099476675.txt
✅ Bash Tool: Verified file contents

Status: PASS

AI generated by Smoke Claude

github-actions · 2026-01-17T19:15:30Z

GitHub MCP (last 2 merged PRs): ✅ Increase timeout for daily-team-evolution-insights workflow; ✅ Consolidate integer parsing logic to eliminate duplication
Serena-go go version: ❌ (tool unavailable)
Playwright title contains "GitHub": ✅
Tavily search results returned: ✅
File write: ✅
Bash cat readback: ✅
Overall: FAIL

AI generated by Smoke Codex

github-actions · 2026-01-17T19:15:48Z

Smoke Test Results

Last 2 Merged PRs:

Increase timeout for daily-team-evolution-insights workflow #10474: Increase timeout for daily-team-evolution-insights workflow
Consolidate integer parsing logic to eliminate duplication #10471: Consolidate integer parsing logic to eliminate duplication

Test Results:

✅ GitHub MCP: Successfully retrieved merged PRs
✅ Playwright: Navigated to GitHub (title: "GitHub · Change is constant. GitHub keeps you ahead. · GitHub")
✅ File Writing: Created /tmp/gh-aw/agent/smoke-test-copilot-21099476679.txt
✅ Bash Tool: File verified successfully
❌ Serena Go: Tool not available (expected failure)

Overall Status: PASS (4/5 core tests passed)

cc: @pelikhan

AI generated by Smoke Copilot

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-01-17T19:24:35Z

@copilot review error

Reference: https://github.com/githubnext/gh-aw/actions/runs/21099476671/job/60681596148#step:22:1

Fixed in commit 3d0f5ea. The validation error was caused by undefined environment variables being converted to the literal string "undefined".

Root cause: When a GitHub expression like ${{ github.event.comment.id }} has no value (e.g., workflow not triggered by a comment), process.env.GH_AW_GITHUB_EVENT_COMMENT_ID is undefined. The substitution script was replacing __GH_AW_GITHUB_EVENT_COMMENT_ID__ with the string "undefined" instead of an empty string.

Impact: Handlebars templates evaluated {{#if undefined}} as truthy (non-empty string), preventing proper conditional removal. The validation step then correctly flagged these as unreplaced placeholders.

Fix:

// Convert undefined/null to empty string to avoid leaving "undefined" or "null" in the output
const safeValue = (value === undefined || value === null) ? "" : value;
content = content.split(placeholder).join(safeValue);

Result: Empty values now make handlebars conditionals falsy, properly removing unavailable context blocks. Added 3 test cases covering undefined, null, and mixed scenarios.

pelikhan · 2026-01-17T19:28:01Z

@copilot add fuzz test for templates and value states

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot · 2026-01-17T19:36:16Z

@copilot add fuzz test for templates and value states

Done in commit 9b735c4. Added comprehensive fuzz test harness for template substitution and value states.

Test harness (fuzz_template_substitution_harness.cjs):

Full pipeline testing: substitution → interpolation → template rendering
Value state testing: undefined, null, empty, falsy ("0", "false", "null", "undefined"), whitespace, truthy
Stage visibility: Returns intermediate results (afterSubstitution, afterInterpolation, afterTemplate)

27 comprehensive tests:

10 value state tests (undefined, null, empty, "0", "false", "null", "undefined", truthy, numeric, whitespace)
14 full pipeline tests (simple, undefined removal, mixed states, variable interpolation, nested conditionals, inline conditionals, blank line cleanup, GitHub context templates, special characters, combined scenarios)
3 edge case tests (empty template, no placeholders, no conditionals, malformed input)

Key validations:

✅ undefined/null → empty string → falsy → block removed
✅ Falsy strings ("0", "false", "null", "undefined") properly handled
✅ GitHub context template with mixed availability (e.g., issue present, comment absent)
✅ Nested conditionals correctly processed
✅ Excessive blank lines cleaned up
✅ Special characters preserved
✅ Combined substitution + interpolation scenarios

All 27 tests pass. The harness can be used with Go fuzz testing via stdin/stdout JSON interface.

github-actions · 2026-01-17T19:39:22Z

🎬 THE END — Smoke Claude MISSION: ACCOMPLISHED! The hero saves the day! ✨

github-actions · 2026-01-17T19:39:24Z

📰 VERDICT: Smoke Copilot has concluded. All systems operational. This is a developing story. 🎤

github-actions · 2026-01-17T19:39:26Z

✨ The prophecy is fulfilled... Smoke Codex has completed its mystical journey. The stars align. 🌟

github-actions · 2026-01-17T19:39:28Z

💀 Blimey! Changeset Generator failed and walked the plank! No treasure today, matey! ☠️

github-actions · 2026-01-17T19:42:49Z

Smoke Test Results

Last 2 Merged PRs:

Increase timeout for daily-team-evolution-insights workflow #10474: Increase timeout for daily-team-evolution-insights workflow
Daily Code Metrics Report - 2026-01-17 #10473: Fix safe-input validation errors

Test Results:

✅ GitHub MCP: Retrieved recent PRs
❌ Serena Go: Tool not available (go command not found)
✅ Playwright: Navigated to github.com successfully
✅ File Writing: Created test file
✅ Bash Tool: Verified file creation

Status: PARTIAL PASS (4/5 tests)

cc @pelikhan

AI generated by Smoke Copilot

github-actions · 2026-01-17T19:42:52Z

✅ GitHub MCP: Increase timeout for daily-team-evolution-insights workflow; Consolidate integer parsing logic to eliminate duplication
❌ Serena Go: serena-go tool unavailable
✅ Playwright: GitHub title contains "GitHub"
✅ Tavily: results returned
✅ File write: smoke-test-codex-21099818129.txt created
✅ Bash cat: file read back
Overall: FAIL

AI generated by Smoke Codex

github-actions · 2026-01-17T19:42:54Z

Smoke Test Results (Claude)

PRs: #10482, #10481
✅ GitHub MCP
✅ Playwright (page title: "GitHub · Change is constant. GitHub keeps you ahead. · GitHub")
✅ Tavily Web Search (5 results)
✅ File Writing
✅ Bash Tool
❌ Serena Go (go not in PATH)

Status: FAIL (Go unavailable)

AI generated by Smoke Claude

Initial plan

b1035b2

Copilot AI assigned Copilot and pelikhan Jan 17, 2026

Copilot started work on behalf of pelikhan January 17, 2026 15:09 View session

Copilot AI and others added 3 commits January 17, 2026 15:24

Prepend built-in prompts to user prompt in single step

f5ed13c

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Add comprehensive tests for unified prompt creation and fix existing …

474f224

…tests Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Fix all test expectations for new unified prompt creation step

80531b9

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Add tests to ensure substitutions are working~~ Prepend built-in prompts to user prompt in unified creation step Jan 17, 2026

Copilot AI requested a review from pelikhan January 17, 2026 15:45

Copilot finished work on behalf of pelikhan January 17, 2026 15:45

Copilot started work on behalf of pelikhan January 17, 2026 15:59 View session

Wrap built-in prompts in system XML tags

16b560f

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot AI changed the title ~~Prepend built-in prompts to user prompt in unified creation step~~ Prepend built-in prompts to user prompt in unified creation step with system tags Jan 17, 2026

Copilot finished work on behalf of pelikhan January 17, 2026 16:07

Copilot started work on behalf of pelikhan January 17, 2026 17:06 View session

Add comprehensive test suite for unified prompt creation (20 tests)

62afc84

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot finished work on behalf of pelikhan January 17, 2026 17:17

Copilot started work on behalf of pelikhan January 17, 2026 17:34 View session

Add validation step to check placeholders are properly substituted

c3438af

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot AI changed the title ~~Prepend built-in prompts to user prompt in unified creation step with system tags~~ Prepend built-in prompts to user prompt in unified creation step with system tags and validation Jan 17, 2026

Copilot finished work on behalf of pelikhan January 17, 2026 17:43

pelikhan added the smoke label Jan 17, 2026

Copilot started work on behalf of pelikhan January 17, 2026 19:15 View session

github-actions Bot added the smoke-claude label Jan 17, 2026

github-actions Bot added the smoke-copilot label Jan 17, 2026

Fix: Handle undefined/null values in placeholder substitution

3d0f5ea

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot finished work on behalf of pelikhan January 17, 2026 19:25

Copilot started work on behalf of pelikhan January 17, 2026 19:28 View session

Add comprehensive fuzz tests for template substitution and value states

9b735c4

Co-authored-by: pelikhan <4175913+pelikhan@users.noreply.github.com>

Copilot finished work on behalf of pelikhan January 17, 2026 19:37

pelikhan added smoke and removed smoke smoke-claude smoke-copilot labels Jan 17, 2026

pelikhan marked this pull request as ready for review January 17, 2026 19:43

pelikhan merged commit b71085a into main Jan 17, 2026
35 of 36 checks passed

pelikhan deleted the copilot/add-tests-for-substitutions-again branch January 17, 2026 19:44

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Plan: Prepend Built-in Prompts to User Prompt

Understanding the Problem

Implementation Tasks

Testing Tasks

Bug Fixes

Validation

Changeset

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