feat: add session resumption to codex (#506)

## Description

Add continue variable, and logic for resuming task sessions 
<!-- Briefly describe what this PR does and why -->

## Type of Change

- [ ] New module
- [ ] New template
- [ ] Bug fix
- [X] Feature/enhancement
- [ ] Documentation
- [ ] Other

## Module Information

<!-- Delete this section if not applicable -->

**Path:** `registry/coder-labs/modules/codex`  
**New version:** `v3.1.0`  
**Breaking change:** [ ] Yes [X] No

## Testing & Validation

- [X] Tests pass (`bun test`)
- [X] Code formatted (`bun fmt`)
- [X] Changes tested locally

## Related Issues

<!-- Link related issues or write "None" if not applicable -->

Author: DevelopmentCats

registry/coder-labs/modules/codex/README.md

@@ -13,7 +13,7 @@ Run Codex CLI in your workspace to access OpenAI's models through the Codex inte
 ```tf
 module "codex" {
   source         = "registry.coder.com/coder-labs/codex/coder"
-  version        = "3.0.0"
+  version        = "3.1.0"
   agent_id       = coder_agent.example.id
   openai_api_key = var.openai_api_key
   workdir        = "/home/coder/project"
@@ -33,7 +33,7 @@ module "codex" {
 module "codex" {
   count          = data.coder_workspace.me.start_count
   source         = "registry.coder.com/coder-labs/codex/coder"
-  version        = "3.0.0"
+  version        = "3.1.0"
   agent_id       = coder_agent.example.id
   openai_api_key = "..."
   workdir        = "/home/coder/project"
@@ -61,7 +61,7 @@ module "coder-login" {
 
 module "codex" {
   source         = "registry.coder.com/coder-labs/codex/coder"
-  version        = "3.0.0"
+  version        = "3.1.0"
   agent_id       = coder_agent.example.id
   openai_api_key = "..."
   ai_prompt      = data.coder_parameter.ai_prompt.value
@@ -84,6 +84,7 @@ module "codex" {
 - **System Prompt**: If `codex_system_prompt` is set, writes the prompt to `AGENTS.md` in the `~/.codex/` directory
 - **Start**: Launches Codex CLI in the specified directory, wrapped by AgentAPI
 - **Configuration**: Sets `OPENAI_API_KEY` environment variable and passes `--model` flag to Codex CLI (if variables provided)
+- **Session Continuity**: When `continue = true` (default), the module automatically tracks task sessions in `~/.codex-module/.codex-task-session`. On workspace restart, it resumes the existing session with full conversation history. Set `continue = false` to always start fresh sessions.
 
 ## Configuration
 
@@ -107,7 +108,7 @@ For custom Codex configuration, use `base_config_toml` and/or `additional_mcp_se
 ```tf
 module "codex" {
   source  = "registry.coder.com/coder-labs/codex/coder"
-  version = "3.0.0"
+  version = "3.1.0"
   # ... other variables ...
 
   # Override default configuration

registry/coder-labs/modules/codex/main.test.ts

@@ -368,4 +368,90 @@ describe("codex", async () => {
     expect(prompt.exitCode).not.toBe(0);
     expect(prompt.stderr).toContain("No such file or directory");
   });
+
+  test("codex-continue-capture-new-session", async () => {
+    const { id } = await setup({
+      moduleVariables: {
+        continue: "true",
+        ai_prompt: "test task",
+      },
+    });
+
+    const workdir = "/home/coder";
+    const expectedSessionId = "019a1234-5678-9abc-def0-123456789012";
+    const sessionsDir = "/home/coder/.codex/sessions";
+    const sessionFile = `${sessionsDir}/${expectedSessionId}.jsonl`;
+
+    await execContainer(id, ["mkdir", "-p", sessionsDir]);
+    await execContainer(id, [
+      "bash",
+      "-c",
+      `echo '{"id":"${expectedSessionId}","cwd":"${workdir}","created":"2024-10-24T20:00:00Z","model":"gpt-4-turbo"}' > ${sessionFile}`,
+    ]);
+
+    await execModuleScript(id);
+
+    await expectAgentAPIStarted(id);
+
+    const trackingFile = "/home/coder/.codex-module/.codex-task-session";
+    const maxAttempts = 30;
+    let trackingFileContents = "";
+    for (let attempt = 0; attempt < maxAttempts; attempt++) {
+      const result = await execContainer(id, [
+        "bash",
+        "-c",
+        `cat ${trackingFile} 2>/dev/null || echo ""`,
+      ]);
+      if (result.stdout.trim().length > 0) {
+        trackingFileContents = result.stdout;
+        break;
+      }
+      await new Promise((resolve) => setTimeout(resolve, 500));
+    }
+
+    expect(trackingFileContents).toContain(`${workdir}|${expectedSessionId}`);
+
+    const startLog = await readFileContainer(
+      id,
+      "/home/coder/.codex-module/agentapi-start.log",
+    );
+    expect(startLog).toContain("Capturing new session ID");
+    expect(startLog).toContain("Session tracked");
+    expect(startLog).toContain(expectedSessionId);
+  });
+
+  test("codex-continue-resume-existing-session", async () => {
+    const { id } = await setup({
+      moduleVariables: {
+        continue: "true",
+        ai_prompt: "test prompt",
+      },
+    });
+
+    const workdir = "/home/coder";
+    const mockSessionId = "019a1234-5678-9abc-def0-123456789012";
+    const trackingFile = "/home/coder/.codex-module/.codex-task-session";
+
+    await execContainer(id, ["mkdir", "-p", "/home/coder/.codex-module"]);
+    await execContainer(id, [
+      "bash",
+      "-c",
+      `echo "${workdir}|${mockSessionId}" > ${trackingFile}`,
+    ]);
+
+    await execModuleScript(id);
+
+    const startLog = await execContainer(id, [
+      "bash",
+      "-c",
+      "cat /home/coder/.codex-module/agentapi-start.log",
+    ]);
+    expect(startLog.stdout).toContain("Found existing task session");
+    expect(startLog.stdout).toContain(mockSessionId);
+    expect(startLog.stdout).toContain("Resuming existing session");
+    expect(startLog.stdout).toContain(
+      `Starting Codex with arguments: --model gpt-4-turbo resume ${mockSessionId}`,
+    );
+    expect(startLog.stdout).not.toContain("test prompt");
+  });
 });

registry/coder-labs/modules/codex/main.tf

@@ -137,6 +137,12 @@ variable "ai_prompt" {
   default     = ""
 }
 
+variable "continue" {
+  type        = bool
+  description = "Automatically continue existing sessions on workspace restart. When true, resumes existing conversation if found, otherwise runs prompt or starts new session. When false, always starts fresh (ignores existing sessions)."
+  default     = true
+}
+
 variable "codex_system_prompt" {
   type        = string
   description = "System instructions written to AGENTS.md in the ~/.codex directory"
@@ -187,8 +193,9 @@ module "agentapi" {
      ARG_OPENAI_API_KEY='${var.openai_api_key}' \
      ARG_REPORT_TASKS='${var.report_tasks}' \
      ARG_CODEX_MODEL='${var.codex_model}' \
-     ARG_CODEX_START_DIRECTORY='${var.workdir}' \
+     ARG_CODEX_START_DIRECTORY='${local.workdir}' \
      ARG_CODEX_TASK_PROMPT='${base64encode(var.ai_prompt)}' \
+     ARG_CONTINUE='${var.continue}' \
      /tmp/start.sh
    EOT
 
@@ -206,7 +213,7 @@ module "agentapi" {
     ARG_BASE_CONFIG_TOML='${base64encode(var.base_config_toml)}' \
     ARG_ADDITIONAL_MCP_SERVERS='${base64encode(var.additional_mcp_servers)}' \
     ARG_CODER_MCP_APP_STATUS_SLUG='${local.app_slug}' \
-    ARG_CODEX_START_DIRECTORY='${var.workdir}' \
+    ARG_CODEX_START_DIRECTORY='${local.workdir}' \
     ARG_CODEX_INSTRUCTION_PROMPT='${base64encode(var.codex_system_prompt)}' \
     /tmp/install.sh
   EOT