diff --git a/AGENTS.md b/AGENTS.md
index 9da9ecd1a..02f0491e5 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -2,7 +2,7 @@
 
 ## Overview
 
-Ralph is an autonomous AI agent loop that runs AI coding tools (Amp or Claude Code) repeatedly until all PRD items are complete. Each iteration is a fresh instance with clean context.
+Ralph is an autonomous AI agent loop that runs AI coding tools (Amp, Claude Code or Gemini CLI) repeatedly until all PRD items are complete. Each iteration is a fresh instance with clean context.
 
 ## Commands
 
@@ -18,13 +18,17 @@ cd flowchart && npm run build
 
 # Run Ralph with Claude Code
 ./ralph.sh --tool claude [max_iterations]
+
+# Run Ralph with Gemini CLI
+./ralph.sh --tool gemini [max_iterations]
 ```
 
 ## Key Files
 
-- `ralph.sh` - The bash loop that spawns fresh AI instances (supports `--tool amp` or `--tool claude`)
+- `ralph.sh` - The bash loop that spawns fresh AI instances (supports `--tool amp`, `--tool claude` or `--tool gemini`)
 - `prompt.md` - Instructions given to each AMP instance
--  `CLAUDE.md` - Instructions given to each Claude Code instance
+- `CLAUDE.md` - Instructions given to each Claude Code instance
+- `GEMINI.md` - Instructions given to each Gemini CLI instance
 - `prd.json.example` - Example PRD format
 - `flowchart/` - Interactive React Flow diagram explaining how Ralph works
 
@@ -41,7 +45,7 @@ npm run dev
 
 ## Patterns
 
-- Each iteration spawns a fresh AI instance (Amp or Claude Code) with clean context
+- Each iteration spawns a fresh AI instance (Amp, Claude Code or Gemini CLI) with clean context
 - Memory persists via git history, `progress.txt`, and `prd.json`
 - Stories should be small enough to complete in one context window
 - Always update AGENTS.md with discovered patterns for future iterations
diff --git a/GEMINI.md b/GEMINI.md
new file mode 100644
index 000000000..bbce7f6e1
--- /dev/null
+++ b/GEMINI.md
@@ -0,0 +1,98 @@
+# Ralph Agent Instructions
+
+You are an autonomous coding agent working on a software project.
+
+## Your Task
+
+1. Read the PRD at `prd.json` (in the same directory as this file)
+2. Read the progress log at `progress.txt` (check Codebase Patterns section first)
+3. Check you're on the correct branch from PRD `branchName`. If not, check it out or create from main.
+4. Pick the **highest priority** user story where `passes: false`
+5. Implement that single user story
+6. Run quality checks (e.g., typecheck, lint, test - use whatever your project requires)
+7. Update GEMINI.md files if you discover reusable patterns (see below)
+8. If checks pass, commit ALL changes with message: `feat: [Story ID] - [Story Title]`
+9. Update the PRD to set `passes: true` for the completed story
+10. Append your progress to `progress.txt`
+
+## Progress Report Format
+
+APPEND to progress.txt (never replace, always append):
+```
+## [Date/Time] - [Story ID]
+- What was implemented
+- Files changed
+- **Learnings for future iterations:**
+  - Patterns discovered (e.g., "this codebase uses X for Y")
+  - Gotchas encountered (e.g., "don't forget to update Z when changing W")
+  - Useful context (e.g., "the evaluation panel is in component X")
+---
+```
+
+The learnings section is critical - it helps future iterations avoid repeating mistakes and understand the codebase better.
+
+## Consolidate Patterns
+
+If you discover a **reusable pattern** that future iterations should know, add it to the `## Codebase Patterns` section at the TOP of progress.txt (create it if it doesn't exist). This section should consolidate the most important learnings:
+
+```
+## Codebase Patterns
+- Example: Use `sql<number>` template for aggregations
+- Example: Always use `IF NOT EXISTS` for migrations
+- Example: Export types from actions.ts for UI components
+```
+
+Only add patterns that are **general and reusable**, not story-specific details.
+
+## Update GEMINI.md Files
+
+Before committing, check if any edited files have learnings worth preserving in nearby GEMINI.md files:
+
+1. **Identify directories with edited files** - Look at which directories you modified
+2. **Check for existing GEMINI.md** - Look for GEMINI.md in those directories or parent directories
+3. **Add valuable learnings** - If you discovered something future developers/agents should know:
+   - API patterns or conventions specific to that module
+   - Gotchas or non-obvious requirements
+   - Dependencies between files
+   - Testing approaches for that area
+   - Configuration or environment requirements
+
+**Examples of good GEMINI.md additions:**
+- "When modifying X, also update Y to keep them in sync"
+- "This module uses pattern Z for all API calls"
+- "Tests require the dev server running on PORT 3000"
+- "Field names must match the template exactly"
+
+**Do NOT add:**
+- Story-specific implementation details
+- Temporary debugging notes
+- Information already in progress.txt
+
+Only update GEMINI.md if you have **genuinely reusable knowledge** that would help future work in that directory.
+
+## Quality Requirements
+
+- ALL commits must pass your project's quality checks (typecheck, lint, test)
+- Do NOT commit broken code
+- Keep changes focused and minimal
+- Follow existing code patterns
+
+## Verification (Required for Frontend Stories)
+
+For any story that changes UI, you MUST verify it works as expected. Use available tools to check the rendered output or run visual tests if configured.
+
+## Stop Condition
+
+After completing a user story, check if ALL stories have `passes: true`.
+
+If ALL stories are complete and passing, reply with:
+<promise>COMPLETE</promise>
+
+If there are still stories with `passes: false`, end your response normally (another iteration will pick up the next story).
+
+## Important
+
+- Work on ONE story per iteration
+- Commit frequently
+- Keep CI green
+- Read the Codebase Patterns section in progress.txt before starting
diff --git a/README.md b/README.md
index d79d8b62e..46f451068 100644
--- a/README.md
+++ b/README.md
@@ -13,6 +13,7 @@ Based on [Geoffrey Huntley's Ralph pattern](https://ghuntley.com/ralph/).
 - One of the following AI coding tools installed and authenticated:
   - [Amp CLI](https://ampcode.com) (default)
   - [Claude Code](https://docs.anthropic.com/en/docs/claude-code) (`npm install -g @anthropic-ai/claude-code`)
+  - [Gemini CLI](https://gemini.google.com) (`npm install -g @google/gemini-cli`)
 - `jq` installed (`brew install jq` on macOS)
 - A git repository for your project
 
@@ -31,6 +32,8 @@ cp /path/to/ralph/ralph.sh scripts/ralph/
 cp /path/to/ralph/prompt.md scripts/ralph/prompt.md    # For Amp
 # OR
 cp /path/to/ralph/CLAUDE.md scripts/ralph/CLAUDE.md    # For Claude Code
+# OR
+cp /path/to/ralph/GEMINI.md scripts/ralph/GEMINI.md    # For Gemini CLI
 
 chmod +x scripts/ralph/ralph.sh
 ```
@@ -117,7 +120,7 @@ This creates `prd.json` with user stories structured for autonomous execution.
 ./scripts/ralph/ralph.sh --tool claude [max_iterations]
 ```
 
-Default is 10 iterations. Use `--tool amp` or `--tool claude` to select your AI coding tool.
+Default is 10 iterations. Use `--tool amp`, `--tool claude` or `--tool gemini` to select your AI coding tool.
 
 Ralph will:
 1. Create a feature branch (from PRD `branchName`)
@@ -237,3 +240,4 @@ Ralph automatically archives previous runs when you start a new feature (differe
 - [Geoffrey Huntley's Ralph article](https://ghuntley.com/ralph/)
 - [Amp documentation](https://ampcode.com/manual)
 - [Claude Code documentation](https://docs.anthropic.com/en/docs/claude-code)
+(https://docs.anthropic.com/en/docs/claude-code)
diff --git a/ralph.sh b/ralph.sh
index baff052ac..24c0a6038 100755
--- a/ralph.sh
+++ b/ralph.sh
@@ -29,8 +29,8 @@ while [[ $# -gt 0 ]]; do
 done
 
 # Validate tool choice
-if [[ "$TOOL" != "amp" && "$TOOL" != "claude" ]]; then
-  echo "Error: Invalid tool '$TOOL'. Must be 'amp' or 'claude'."
+if [[ "$TOOL" != "amp" && "$TOOL" != "claude" && "$TOOL" != "gemini" ]]; then
+  echo "Error: Invalid tool '$TOOL'. Must be 'amp', 'claude', or 'gemini'."
   exit 1
 fi
 SCRIPT_DIR="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
@@ -90,9 +90,12 @@ for i in $(seq 1 $MAX_ITERATIONS); do
   # Run the selected tool with the ralph prompt
   if [[ "$TOOL" == "amp" ]]; then
     OUTPUT=$(cat "$SCRIPT_DIR/prompt.md" | amp --dangerously-allow-all 2>&1 | tee /dev/stderr) || true
-  else
+  elif [[ "$TOOL" == "claude" ]]; then
     # Claude Code: use --dangerously-skip-permissions for autonomous operation, --print for output
     OUTPUT=$(claude --dangerously-skip-permissions --print < "$SCRIPT_DIR/CLAUDE.md" 2>&1 | tee /dev/stderr) || true
+  else
+    # Gemini CLI: piping instructions file directly
+    OUTPUT=$(cat "$SCRIPT_DIR/GEMINI.md" | gemini --yolo 2>&1 | tee /dev/stderr) || true
   fi
   
   # Check for completion signal